Open access peer-reviewed chapter

The Intratubular and Intracrine Renin-Angiotensin System in the Proximal Tubules of the Kidney and Its Roles in Angiotensin II-Induced Hypertension

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Xiao C. Li, Ana Paula de Oliveira Leite, Xu Chen, Chunling Zhao, Xiaowen Zheng, Jianfeng Zhang and Jia L. Zhuo

Submitted: 10 May 2019 Reviewed: 14 June 2019 Published: 22 August 2019

DOI: 10.5772/intechopen.88054

From the Edited Volume

Selected Chapters from the Renin-Angiotensin System

Edited by Aleksandar Kibel

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Abstract

The kidney plays a fundamental role in the physiological regulation of basal blood pressure and the development of hypertension. Although the mechanisms underlying hypertension are very complex, the renin-angiotensin system (RAS) in the kidney, especially intratubular and intracellular RAS, undoubtedly plays a critical role in maintaining basal blood pressure homeostasis and the development of angiotensin II (ANG II)-dependent hypertension. In the proximal tubules, ANG II activates two G protein-coupled receptors, AT1 and AT2, to exert powerful effects to regulate proximal tubular sodium and fluid reabsorption by activating cell surface as well as intracellular AT1 receptors. Increased production and actions of ANG II in the proximal tubules may cause salt and fluid retention, impair the pressure-natriuresis response, and consequently increase blood pressure in hypertension. The objectives of this chapter are to critically review and discuss our current understanding of intratubular and intracellular RAS in the kidney, and their contributions to basal blood pressure homeostasis and the development of ANG II-dependent hypertension. The new knowledge will likely help uncover novel renal mechanisms of hypertension, and develop kidney- or proximal tubule-specific strategies or drugs to prevent and treat hypertension in humans.

Keywords

  • angiotensin II
  • blood pressure
  • hypertension
  • kidney
  • proximal tubule

1. Introduction

According to the most recent American College of Cardiology (ACC)/American Heart Association (AHA) reports, 46% of U.S. adults now develop hypertension and take antihypertensive drugs in their lifetime [1, 2]. Prevention and treatment of hypertension and its target organ complications cost several hundreds of billion dollars a year to the U.S. economy [3, 4, 5, 6]. Although the causes of hypertension are multifactorial, the activation of circulating (endocrine), tissue (paracrine) and intracellular (intracrine) RAS via angiotensin II (ANG II) remains one of most important contributing mechanisms [1, 2, 3, 4, 5, 6, 7]. Indeed, angiotensin-converting enzyme (ACE) inhibitors, ANG II receptor blockers (ARBs), and renin inhibitors, which block the RAS at the enzymatic or receptor levels, are widely used to treat hypertension, reduce cardiovascular and renal disease risks, and prevent target organ damage [1, 2, 3, 4, 5, 6, 7]. However, clinical trials have shown that not all RAS-targeting drugs have the same efficacy of blocking the actions of ANG II and afford the same degree of cardiovascular, blood pressure and renal protection [1, 2, 3, 4, 5, 6]. Some patients continue to develop cardiovascular and renal complications despite being treated with one or more than two of these blockers [7, 8]. The underlying mechanisms responsible for these clinical observations are not well understood. One of the possibilities may be that not all ARBs have the same ability to enter the cells to block intracellular ANG II. Some, but not all, ARB(s) such as telmisartan and losartan may exert therapeutic effects beyond the classic ARBs’ properties.

There is accumulating evidence that ANG II acts not only as an endocrine or paracrine hormone activating cell surface ANG II receptors, but also as an intracellular or intracrine peptide activating intracellular ANG II receptors, though the precise roles of the latter remain largely unknown [9, 10, 11]. Indeed, in addition to activating cell surface ANG II receptors, circulating and paracrine ANG II can readily enter the cells via AT1 receptor-mediated endocytosis. The ANG II/AT1 receptor complex internalized into endosomes may continue to transmit signals from endosomes or be translocated to the nucleus to induce long-lasting genomic effects [12, 13]. Recently, we and others have used innovative in vitro cell expression system [14, 15, 16], in vivo adenoviral gene transfer of an intracellular ANG II protein selectively in proximal tubule cells of the rat and mouse kidneys [17, 18], or genetically modified mouse models to investigate the physiological roles and mechanisms of actions of intratubular and intracellular ANG II in the proximal tubules of the kidney, with a focus on basal blood pressure homeostasis and ANG II-induced hypertension [19, 20]. Specifically, we have determined whether intracellular ANG II is derived from AT1 (AT1a) receptor-mediated uptake by the proximal tubule cells, and whether proximal tubule-selective expression of an intracellular ANG II fusion protein in the rat and mouse kidney increases the expression and activity of NHE3, promotes proximal tubular sodium and fluid reabsorption, and therefore elevates arterial blood pressure [17, 18, 19, 20, 21, 22, 23]. These new studies have generated new knowledge to improve, and provided new insights into our understanding of renal mechanisms of hypertension involving both endocrine, paracrine and intracellular ANG II, and perhaps aid the development of new classes of multifunctional drugs to treat ANG II-induced hypertension and its target organ damage by blocking not only extracellular but also intracellular and nuclear actions of ANG II. Accordingly, the objectives of this chapter are to critically review, analyze, and discuss the recent developments and progresses in the studies of novel renal mechanisms of hypertension with a focus on the roles of intratubular and intracellular ANG II in the proximal tubules of the kidney.

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2. Localization of intratubular and intracellular RAS and its receptors in the proximal tubules of the kidney

2.1 Angiotensinogen

Angiotensinogen, a ∼60 kDa α2 globulin in the serpin family, is the primary, if not the only, substrate for the RAS super family. It is well-recognized that angiotensinogen is primarily expressed or produced in the liver under physiological conditions. Human angiotensinogen consists of 452 amino acids, whereas rodent’s angiotensinogen may vary in its molecular size slightly from human form [24, 25, 26, 27]. Angiotensinogen, not active in itself, is released from the liver and cleaved in the circulation by the rate-limiting enzyme renin to form the still inactive decapeptide ANG I. This is followed by the conversion of inactive ANG I to the active and potent peptide ANG II, initiating important biological and physiological actions. A second enzyme called angiotensin I-converting enzyme (ACE) acts to convert ANG I to form the biologically active ANG II, initiating an important biochemical and physiological angiotensinogen/renin/ANG I/ACE/ANG II cascade (see below section on ACE). Accordingly, the recognized and primary role of angiotensinogen is to serve as a key substrate to the production of ANG II in the circulation and tissues.

In the kidney, angiotensinogen mRNAs and proteins have been localized in the kidney, primarily in the proximal tubules [28, 29, 30]. Immunohistochemistry, immunoelectron microscopy and non-isotopic hybridization histochemistry have demonstrated the localization of angiotensinogen mRNAs and proteins in the proximal convoluted and straight tubules of the cortex, with glomerular mesangial cells and medullary vascular bundles also being immunopositive in neonatal rat kidney [29, 30]. In the adult rat kidney, however, angiotensinogen mRNA expression was localized primarily in the proximal convoluted tubules, whereas electron-microscopic immunohistochemistry localized angiotensinogen immunostaining in the apical membrane of proximal convoluted tubules [29, 30]. By contrast, few if any angiotensinogen mRNAs and proteins are localized in the glomeruli, mesangial cells, or distal nephrons under physiological conditions [29, 30].

Although most of angiotensinogen in the circulation is derived from the liver, there is evidence showing that angiotensinogen is also expressed and produced in the kidney [28, 31, 32, 33]. Kobori et al. have consistently shown that angiotensinogen mRNA expression and proteins are increased in the proximal tubules of the kidney in ANG II-infused rats [28, 31, 32, 33]. However, Matsusaka et al. have demonstrated that there were no significant differences in the levels of angiotensinogen and ANG II proteins in the kidney between wildtype mice and mice with kidney-specific angiotensinogen knockout [34]. It was further found that angiotensinogen protein and ANG II levels in the kidney were nearly abolished in mice with liver-specific knockout of angiotensinogen [34]. The studies of Kobori et al. and Matsusaka et al. suggests that liver-derived angiotensinogen is the primary source of renal angiotensinogen protein and ANG II under physiological conditions, but during the ANG II-induced hypertension, angiotensinogen mRNAs and proteins are also expressed in the kidney proximal tubules.

2.2 Renin

Renin, the rate-limiting enzyme first discovered to increase blood pressure in rabbits by Tigerstedt and Bergman in 1898 [35], is an aspartyl proteinase or angiotensinogenase. Renin plays the most critical role in the initiation of the angiotensinogen/renin/ACE/ANG II/AT1 receptor activation in the cardiovascular, kidney, and other major target tissues. Human renin precursor consists of 406 amino acids with a pre- and a pro-segment of 20 and 46 amino acids, respectively [36]. Mature human renin contains 340 amino acids and a molecular wt. of 37 kDa [36]. Renin, renin activity, and its mRNA have been localized in the kidney, submaxillary glands, blood vessels, heart, adrenal glands, and brain tissues by enzymatic assays, immunohistochemistry, in situ hybridization histochemistry etc. [37, 38, 39]. In the kidney, active renin is primarily localized in the juxtaglomerular apparatus (JGAs) in the afferent arterioles of the kidney under both physiological and diseased conditions [40, 41, 42]. For example, light and electron microscopic immunocytochemistry with an antibody to purified human renal renin localized renin in the secretion granules of the epithelioid cells of the afferent arteriole of the JGAs, in renal artery stenosis, or in Bartter’s syndrome [36, 37]. In the dog kidney, we have used an in vitro autoradiographic approach to localize active renin using radiolabeled renin inhibitors [40, 41, 42]. High resolution light microscopic autoradiography specifically localized active renin to the vascular pole of the glomeruli, or the JGAs (Figure 1) [40, 41, 42].

Figure 1.

Intrarenal localization of renin in the juxtaglomerular apparatus (A: JGA), angiotensin-converting enzyme (B: ACE), and angiotensin II AT1 receptors in the kidney (C: AT1 or AT1a) using quantitative in vitro autoradiography. C, renal cortex; G, glomerulus; IM, inner medulla; ISOM, inner stripe of the outer medulla; PCT, proximal convoluted tubule.

In the proximal tubule of the kidney, renin mRNAs have been reported [43, 44]. Renin activity and mRNAs were detectable in cultured rabbit proximal tubule cells [45], in isolated proximal convoluted and straight tubules, but not in outer medullary collecting ducts [44]. Tang et al. reported that all major components of the RAS, including angiotensinogen, angiotensin converting enzyme, and renin, were expressed in an immortalized rat proximal tubule cell line [45]. However, there is also evidence that renin localized in the proximal tubules may be due to the uptake of circulating renin after filtration [46, 47]. Taugner et al. demonstrated that the reabsorptive pinocytosis of the filtered renin was the primary source of tubular renin in the kidney [46], whereas Iwao et al. used light and electron microscopic autoradiography to localize 125I-labeled renin accumulated in the apical membranes of the proximal convoluted tubules [47]. Taken together, these studies strongly support the concept that in addition to local biosynthesis and expression, circulating or interstitial renin may be taken up by the proximal convoluted tubules in the kidney.

2.3 Angiotensin I-converting enzyme (ACE)

The 2nd key enzyme for the activation of the RAS is ACE, a dipeptidyl carboxypeptidase I, kininase II and EC 3.4.15.1 [48]. Corvol’s group first molecularly cloned ACE from human vascular endothelial cells [48], whereas Bernstein’s group cloned ACE from the mouse kidney in 1988, respectively [49]. ACE in humans consists of 1306 residues with a signal peptide of 29 amino acids [48], whereas ACE in mice contains 1278 amino acids [49]. Approximately 80% of the amino acid sequences are similar between human and mouse ACE. There are two ACE isozymes, one somatic isozyme in the lung, vascular endothelial cells, renal epithelial cells, and testicular Leydig cells, and the other germinal isoenzyme solely in sperm [50, 51, 52]. The key actions of ACE are to convert the biologically inactive ANG I to the active peptide ANG II, and to degrade the vasoactive peptide bradykinin. Thus, ACE is most critical for the generation of ANG II in the circulation and tissues.

Abundant ACE is expressed and localized in the kidney, especially in the proximal tubules and glomerular and vascular endothelial cells of intrarenal blood vessels [53, 54, 55, 56, 57]. We and others have localized ACE proteins and its mRNA expression in the kidney using quantitative in vitro autoradiography, immunohistochemistry, and in situ hybridization histochemistry (Figure 1). For example, the Mendelsohn’s group first localized ACE in the rat kidney using quantitative in vitro autoradiography with the radiolabeled ACE inhibitor lisinopril, 125I-351A [53]. ACE was localized primarily to the inner cortex, corresponding to the proximal tubules and blood vessels [53]. We found that infusion of ANG II for 2 weeks significantly increased, rather than downregulated, ACE in the proximal tubules of the rat kidney [54]. At higher resolutions, Brunevaly et al. and others showed ACE primarily in the microvilli and brush borders of the proximal tubules in the human kidney [55, 56, 57]. In the vasculature, ACE was localized to the vascular endothelial cells especially in the peritubular capillaries, but not glomerular capillaries of the kidney [53, 54, 55, 56, 57]. ACE was also localized inside the renal vascular endothelial and proximal tubular cell in endoplasmic reticulum, endosomes, and nuclear envelope, suggesting the presence of intracellular and/or nuclear ACE [53, 54, 55, 56, 57]. However, only very low levels of ACE were detected in the inner medulla.

2.4 Angiotensin II (ANG II)

Angiotensin II (ANG II) is undoubtedly the most powerful peptide in the RAS super family, playing a key role in regulating renal blood flow, glomerular filtration, and proximal tubular reabsorption of sodium and fluid, contributing to normal blood pressure and body salt and fluid homeostasis [58, 59, 60, 61, 62, 63, 64]. It is well-recognized that the levels of ANG II in the kidney, especially in the proximal tubules, are higher than in the plasma or other tissues. Indeed, local expression and biosynthesis of angiotensinogen, renin, and ACE in the proximal tubules of the kidney significantly contribute to high levels of ANG II levels in the kidneys under physiological conditions [64, 65, 66, 67, 68]. Furthermore, ANG II levels are further increased in the kidney of animal models of ANG II-dependent hypertension, even though the circulating and JGA renin and ACE are suppressed [67, 68, 69, 70, 71, 72, 73]. This is likely due to the fact that the proximal tubules express all major components of the RAS necessary for the formation of ANG II [38, 47, 54, 59, 67, 74, 75], the proximal tubules have a greater capacity to take up circulating ANG II via AT1 (AT1a) receptor-mediated mechanisms [14, 19, 20, 67], and to augmentation of the expression or generation of angiotensinogen, ACE and ANG II in ANG II-induced hypertension [54, 67, 70, 73]. Finally, ANG II is not only generated in the intratubular fluid compartment, but also localized in intracellular organelles, such as endosomes, mitochondria, and nuclei [15, 67, 71, 74, 75], where it serves as an important intracellular or intracrine peptide.

2.5 AT1 and AT2 receptors

It is now well-accepted that ANG II binds to and activates two different classes of G protein-coupled receptors (GPCRs) to induce well-recognized cardiovascular, renal and blood pressure responses, following the successful development of nonpeptide ANG II type 1 and type 2 receptor antagonists [76, 77, 78]. Molecular cloning of AT1 and AT2 receptors and studies of animal models with genetically knockout of these receptors further confirms their pharmacological characterization. Murphy et al. [79] and Sasaki et al. [80] successfully cloned the AT1 receptor in 1991, showing that the AT1 receptor shares the seven-transmembrane-region motif of the GPCR superfamily. AT1 receptors mediate the well-known actions of ANG II on vasoconstriction, cardiac hypertrophy, hypertensive, renal salt retention, as well as aldosterone biosynthesis [76, 77, 78, 81]. The AT2 receptor was cloned by Mukoyama et al. [82], Nakajima et al. [83], and Kambayashi et al. [84], respectively. The AT2 receptor was found to have 34% of the identical sequence to the AT1 receptor, sharing a seven-transmembrane domain topology of GPCRs [82, 83, 84]. However, the roles and signal transduction pathways for the AT2 receptor remain incompletely understood.

In the kidney, the AT1 receptor is widely expressed and localized in different structures or cell types, most prominent in three anatomical regions, that is, the glomerulus, proximal tubules, and the inner stripe of the outer medulla, corresponding the vasa recta blood vessels and renomedullary interstitial cells (Figure 1) [85, 86, 87]. We and others have consistently localized the AT1 receptor in the rodent and human kidneys using quantitative in vitro and in vivo autoradiography, with high levels of these receptors in the glomerulus, proximal tubules, and renomedullary interstitial cells (Figure 1) [85, 86, 87]. Other anatomical regions or renal structures may express low levels of AT1 receptor expression, detectable with RT-PCR or immunohistochemistry. AT1 receptors have also been localized in intracellular organelles, for example, endosomes, mitochondria, and nuclei in the proximal tubule cells, suggesting an important intracellular roles [67, 74, 88, 89, 90]. By contrast, the levels of AT2 receptor expression in the kidney are species-related or closely associated with the kidney development. Indeed, high levels of AT2 receptors are expressed extensively in the developing fetal and neonatal tissues, but most of them disappear before reaching the adulthood [87]. Nevertheless, the expression of AT2 receptors appears to persist in the adrenal medulla, proximal tubules, and the adventitia of human kidney blood vessels, suggesting potential roles for these receptors in these target tissues [85, 86, 87, 91, 92, 93].

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3. Intratubular and intracellular ANG II: the long-term genomic effects induced by endocrine, paracrine and intracellular ANG II

In contrast to the classic dogma that ANG II only binds to and activates cell surface GPCRs to initiate downstream signaling responses, ANG II can also bind and activate intracellular GPCRs to induce long-term genomic effects. The RAS includes an extracellular system and an intracellular system. ANG II acts as the principle effector of both extracellular and intracellular RAS. Extracellular ANG II includes circulating (endocrine) and paracrine ANG II, which plays the classical roles of the RAS through activation of cell surface GPCRs [76, 77, 78, 81, 94, 95]. Intracellular ANG II includes intracellularly formed ANG II (intracrine) and ANG II internalized through AT1 (AT1a) receptor-mediated endocytosis [96, 97, 98, 99, 100, 101]. The roles of circulating and paracrine ANG II and its GPCR-mediated signaling mechanisms via cell surface receptors have been extensively investigated. By contrast, the roles of intracellular ANG II and its mechanisms of actions remain poorly understood. This disparity in our understanding extracellular versus intracellular ANG II has led many to assume that ANG II only activates cell surface receptors to induce all of its biological and physiological responses, and that all ARBs would only block cell surface receptors to produce the same beneficial effects. Thus, an intracellular ANG II system is thought to be unnecessary in the regulation of cardiovascular, blood pressure, and renal physiology and diseases.

However, recent studies strongly suggest that these views may be revised for a number of reasons [96, 97, 98, 99, 100, 101]. First, it is well-recognized that extracellular ANG II is continuously internalized with its receptors after it activates cell surface receptors. This has long been interpreted only as required for the desensitization of cell surface receptors to repetitive stimulation by extracellular ANG II by moving the ANG II/AT1 complex into the lysosomal pathway for degradation. There is evidence, however, that the activated agonist/receptor complex internalized into the endosomes may continue to transmit ras/mitogen-activated protein kinase (MAPK) signaling [12, 13]. Ras and MAPK signaling for AT1a, vasopressin V2, and β2 adrenergic receptors (β2AR) have been reported in endosomal membranes [12, 13, 15, 16], the endoplasmic reticulum, the Golgi or the nucleus independent of cell surface receptor-initiated signaling [81, 88, 89, 102]. Second, ANG II exerts long-lasting genomic or transcriptional effects, which may be independent from the well-recognized effects induced by activation of cell surface receptors [97, 98, 99, 102, 103]. ANG II induces the expression or transcription of many growth factors and proliferative cytokines including nuclear factor-κB (NF-κB) [104, 105, 106, 107], monocyte chemoattractant protein-1 (MCP-1) [106, 108], TNF-α [107], and TGF-β1 [102, 109, 110]. While hemodynamic responses to ANG II often occur in seconds or minutes, cellular growth, mitogenic, proliferative and fibrotic responses to ANG II may last from hours to weeks and months. Since the cell surface AT1 (AT1a) receptors may be desensitized in response to sustained exposure to endocrine and paracrine ANG II, the long-term genomic effects of ANG II, as observed in cardiovascular, hypertensive, and renal diseases, are at least in part mediated by intracellular ANG II system. Third, not all ARBs, ACE or renin inhibitors are created equal to block both extracellular and intracellular ANG II systems. ARBs may differ in their lipophilic ability to enter the cells to block intracellular AT1 receptors [111, 112, 113]. Indeed, ARBs show different effects on uric acid metabolism, cell proliferation, oxidative stress, nitric oxide production and PPAR-γ activity [111, 112, 113]. We and others have shown that losartan internalized with AT1a and AT1b receptors, albeit at a slower rate than ANG II [19, 20, 67, 103, 114], and to attenuate ANG II-induced intracellular and nuclear effects [15, 88, 89, 102, 103]. Moreover, telmisartan not only blocks AT1 receptors, but also acts as a partial activator of liver-specific peroxisome proliferator-activated receptor γ (PPAR-γ) [111, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140, 141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 156, 157]. Finally, some clinical studies have shown that even treated with renin inhibitors, ACE inhibitors or ARBs, there are some patients who still progress to hypertension and suffer from cardiovascular and renal complications [111, 115, 116, 117]. These data suggest that additional mechanisms should be involved and studied accordingly. Thus, the new challenges to the field are to study whether and how intracellular ANG II may contribute to these mechanisms and design multifunctional drugs to block both extracellular and intracellular ANG II-induced effects.

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4. Intratubular and intracellular ANG II: AT1a receptor-mediated uptake of circulating and paracrine ANG II in the proximal tubules

We and others have investigated whether circulating and local paracrine ANG II is taken up by the proximal tubules of the kidney via AT1 (AT1a) receptor-mediated endocytosis [19, 20, 118, 119, 120, 121], and whether internalized ANG II and AT1a receptors are co-localized in the endosomal compartment and nucleus (Figure 2) [67, 74, 88, 89]. Our studies demonstrated that global deletion of AT1a receptors blocked the uptake of unlabeled Val5-ANG II [19] or [125I]Val5-ANG II in the kidney of AT1a-KO mice [20]. However, these studies focused only on the entire kidney, and what nephron segments involved in taking up unlabeled Val5-ANG II or [125I]Val5-ANG II could not be determined using these approaches [19, 20]. We further used cultured proximal tubules cells to test whether proximal tubule cells take up extracellular ANG II and the mechanisms involved (Figure 2) [14, 100, 122, 123, 124, 125, 126]. The advantages of using these cells for the proposed studies are that ANG II receptors are abundantly expressed and localized in both apical (AP) and basolateral (BL) membranes [127, 128, 129, 130, 131]. However, it has not been determined whether ANG II receptors in AP or BL membranes mediate ANG II uptake in the proximal tubules. In a previous study using a porcine proximal tubule cell line expressing a rabbit AT1 receptor, AT1-mediated uptake of [125I]-ANG II was found to be significantly different between AP and BL membranes [130]. AT1-mediated uptake of [125I]-ANG II was more robust and efficient in AP membranes than in BL membranes [130]. Conversely, ANG II-induced AT1 receptor internalization was reportedly much faster in BL membranes than in AP membranes of OK cells [131]. Thus these differences inAT1-mediated uptake of [125I]-ANG II or ANG II-induced AT1 receptor endocytosis or internalization may underscore the differences in the cell types used or experimental conditions.

Figure 2.

All major components of the circulating RAS, including angiotensinogen (AGT), renin, angiotensin I (ANG I), and ANG II, may be filtered by the kidney glomerulus and taken up by the proximal tubules. Alternatively, all major components of the RAS may be expressed and localized in the proximal tubules of the kidney. ACE, angiotensin-converting enzyme and APA, aminopeptidase A.

In addition to AT1 (AT1a) receptors, other factors may also regulate the uptake of extracellular ANG II by proximal tubule cells. AP membranes of proximal tubule cells express abundant endocytic receptor megalin, which plays a crucial role in mediating the uptake of low molecular weight (LMW) proteins in proximal tubule cells [132, 133, 134, 135, 136]. Deletion of megalin in mice led to the development of LMW proteinuria [135]. Interestingly, megalin also binds and internalizes ANG II in immortalized yolk sac cells (BN-16 cells) [136]. We have demonstrated that siRNA knockdown of megalin expression or caveolin 1 in proximal tubule cells significantly attenuated ANG II uptake by proximal tubule cells [122, 123]. However, the extent to which megalin- and caveolin 1-mediate ANG II uptake in proximal tubule cells is significantly smaller than that mediated by AT1 (AT1a) receptor-dependent mechanism [19, 20, 122, 123].

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5. Intratubular and intracellular ANG II: canonical versus noncanonical endocytic pathways in mediating ANG II uptake in the proximal tubules

We have mechanistically investigated that AT1 (AT1a) receptor-mediate the uptake of extracellular ANG II by proximal tubule cells in vitro and circulating ANG II in vivo [19, 20, 122, 123, 124, 125, 126]. It has been previously shown that in vascular smooth muscle cells (VSMCs), cardiomyocytes, and COS-7 cells, β2 adrenergic receptors, AT1a, epidermal growth factor receptors, and insulin receptors are internalized via the canonical clathrin-dependent pathway [137, 138, 139, 140, 141, 142, 143, 144]. Clathrin-coated pits play an important role in invaginating and pinching off the plasma membranes to form coated vesicles and targeted to endosomes [138, 140, 142]. GPCR kinases (GRKs), small GTP-binding proteins, such as Rab5, and β-arrestins are reportedly involved in clathrin-dependent AT1a endocytosis [145, 146]. However, dominant-negatives, siRNAs or knockout targeting dynamin, GRKs or β-arrestins have little effects on AT1a receptor endocytosis in some studies, suggesting that alternative (non-canonical) pathways may also be involved in AT1a receptor endocytosis [137, 138, 139, 140, 141, 142, 143, 144, 145, 146].

There is evidence to suggest that tyrosine phosphatases may be involved in ANG II-induced AT1 receptor endocytosis in AP and BL membranes, since the endocytic response was inhibited by the tyrosine phosphatases inhibitor, phenylarsine oxide (PAO), rather than by pertussis toxin [147, 148, 149, 150, 151]. Colchicine, an inhibitor of cytoskeleton microtubules [148], also appeared to inhibit AT1 receptor-mediated ANG II uptake and its effects in rat proximal tubule cells [150, 151]. The role of clathrin-coated pits in mediating AT1 receptor-mediated ANG II uptake was also investigated, but we found that deletion of clathrin-coated pits with sucrose or specific siRNAs to knock down clathrin light (LC) or high chain subunits (HC) failed to alter AT1-mediated uptake of Val5-ANG II [151]. However, AT1-mediated uptake of Val5-ANG II was significantly inhibited by colchicine or siRNA knocking down of microtubule-associated proteins, MAP-1A or MAP-1B, in proximal tubule cells [151]. Our studies therefore support the scientific premise that the noncanonical microtubule-dependent endocytic pathway may be involved in mediating the AT1-mediated uptake of ANG II in proximal tubule cells.

How ANG II and AT1 receptors are internalized into the endosomal compartments and transported to other organelles or the nucleus in proximal tubule cells remains incompletely understood. Intravenous infusion of 125I-labeled ANG II was previously detected in the nuclei of rat vascular smooth muscle cells (VSMCs) and cardiac myocytes [152] or the Golgi of adrenal cells [153]. Cook et al. showed that ANG II and its AT1a receptor were translocated to the nuclei of hepatocytes and VSMCs [154]. In AT1a receptor-expressing HEK 293 cells, internalized AT1a receptors were detected in perinuclear areas as well as in the nuclei [155, 156]. In supporting the above-mentioned studies, we also reported high levels of internalized FITC-labeled ANG II in perinuclear areas and the nucleus, which was inhibited by colchicine and siRNA knockdown of MAP-1A [14, 122, 123, 151]. Taken together, our results strongly suggest that the microtubule-dependent pathway may play an important role in mediating the nuclear translocation of internalized ANG II/AT1 receptor complex in proximal tubule cells. Indeed, a nuclear localization sequence (NLS, KKFKKY, aa307-312) has been identified within the AT1a receptor, which may mediate nuclear trafficking and activation of AT1a receptors by ANG II [155, 156].

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6. Intratubular and intracellular ANG II: intracellular versus extracellular effects and signaling mechanisms in the proximal tubules

In the proximal tubules of the kidney, extracellular ANG II has been reported to stimulate the expression of Na+/H+ exchanger 3 (NHE3) [14, 16, 102, 125], AP insertion of NHE3 [157], Na+/H+ exchanger activity [158, 159, 160, 161], or NHE3-induced 22Na+ uptake in cultured or isolated proximal tubule cells [162, 163]. The signaling mechanisms by which extracellular ANG II increases the expression and activity of NHE3 in proximal tubule cells have been well studied and documented [164, 165, 166, 167, 168, 169]. The most well-described signal mechanism is that ANG II activates cell surface receptor-coupled G proteins, with subsequent increases in IP3 and [Ca2+]i, generation of DG, and activation of PKC [164, 165, 166, 167, 168, 169]. The other well-recognized downstream signaling pathways for extracellular ANG II to induce biological or physiological responses also include activation or inhibition of calcium-dependent calcineurin [170], cAMP-dependent protein kinase A (PKA) [169, 171], Ca2+-independent PLA2 [172], PI 3-kinase [157], c-Src/MAP kinases ERK 1/2 [165], or nuclear factor-κB [173].

According to the principles of the G protein-coupled receptor pharmacology, ANG II must bind to its cell surface receptors to activate intracellular signaling mechanisms in order to induce responses [76, 77, 78, 138]. Upon internalization, however, ANG II may act as an intracellular peptide to induce biological or physiological responses. Indeed, blockade of the endocytosis of AT1 receptors is associated with inhibition of PKC, IP3 formation, and Na+ flux in proximal tubule cells [14, 16, 122, 123, 124, 125, 126, 149, 150]. Furthermore, ANG II-induced AT1 receptor endocytosis is also associated with activation of PLA2 [147, 172], inhibition of adenylyl cyclase [151, 169, 171], and increases in Na+ uptake from AP membranes [149, 150, 151]. We have recently shown that AT1-mediated uptake of extracellular Val5-ANG II was indeed associated with inhibition of basal and forskolin-stimulated cAMP accumulation [125, 151], ANG II-stimulated NHE3 expression [14, 16, 122, 123], and ANG II-induced activation of MAP Kinases ERK1/2 and nuclear factor-κB in proximal tubule cells [14, 16, 124, 126, 151].

Nevertheless, these approaches are unlikely able to distinguish the effects of ANG II mediated by cell surface or intracellular receptors. Previous studies have shown that single cell microinjection or microdialysis of ANG II directly into the cells may distinguish between the effects induced by extracellular ANG II from those induced by intracellular ANG II [15, 102, 174, 175, 176, 177]. Indeed, we have demonstrated that intracellular microinjection of ANG II directly into single rabbit proximal tubule cells induced intracellular [Ca2+]i responses (Figure 3) [10, 15, 16, 81, 177]. We further reported that microinjection of the AT1 blocker losartan abolished the [Ca2+]i response induced by microinjected ANG II, but it only partially blocked the effects of extracellular ANG II [15]. In further proof-of-the concept studies, we showed that ANG II stimulated nuclear AT1a receptors to increase in vitro transcription of mRNAs for TGF1, MCP-1 and NHE3 in isolated rat renal cortical nuclei [102]. These studies provide evidence that intracellular ANG II may activate cytoplasmic and nuclear AT1 receptor to induce important genomic effects in proximal tubule cells [15, 102, 174, 175, 176, 177].

Figure 3.

Intracellular microinjection of angiotensin II induces intracellular calcium mobilization in cultured rabbit proximal tubule cells. Adapted from Zhuo et al. with permission [15].

Whether intracellular ANG II may alter biological responses in a cell culture model has been determined by directly expressing an intracellular ANG II fusion protein [9, 11, 15, 88, 89, 90, 102]. Cook et al. overexpressed a cyan fluorescent, intracellular ANG II construct (ECFP/ANG II) with or without a rat yellow fluorescent AT1a receptor (AT1R/EYFP) in rat VSMCs or hepatocytes [9, 97, 98]. They demonstrated that intracellular ANG II induced the proliferation of VSMC via activation of cAMP response element-binding protein (CREB), p38 MAP kinase, and MAP kinases ERK 1/2 [9, 97, 98]. In another study, an intracellular ANG II (pcDNA/TO-iAng II) was expressed in CHO cells to induce cell proliferation, but none of ARBs was found to attenuate the effect of intracellular ANG II on cell proliferation [178, 179]. Nevertheless, these early proof of concept studies suggest that in vitro or in vivo expression of a cyan fluorescent intracellular ANG II fusion protein (ECFP/ANG II) in the proximal tubule cells of wild-type and AT1a-KO mice may be an innovative approach to distinguish the effects of intracellular versus extracellular ANG II.

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7. Intratubular and intracellular ANG II: physiological effects of intracellular versus extracellular ANG II on proximal tubule Na+ reabsorption and blood pressure

The physiological roles of intracellular ANG II in the regulation of proximal tubule Na+ reabsorption and normal blood pressure homeostasis remain to be determined. Whether intracellular and/or internalized ANG II may physiologically regulate proximal tubule Na+ transport and blood pressure has not been studied until recently. Indeed, this line of research has been long stymied due to the lack of suitable animal models that express an intracellular ANG II protein, which is not secreted outside the cells and only acts intracellularly. Dr. Reudelhuber’s group was the first to generate genetically modified mouse model that expresses an ANG II-producing fusion protein in the cardiomyocytes of the rat heart [180, 181]. They used the α myosin heavy chain promoter to control the expression of ANG II-releasing fusion protein in the cardiomyocytes. Cardiac specific expression of this ANG II fusion protein led to 10-fold increases in ANG II levels in the heart of these transgenic mice, but it did not elevate ANG II levels in the plasma [180, 181]. This approach is very unique to construct this cardiac-specific ANG II fusion protein with a signal peptide sequence derived from human prorenin and a furin cleavage site. Thus, the expressed ANG II fusion protein will be cleaved by furin, and released into the secretory pathway and the cardiac interstitium [180, 181]. It is expected that this cardiac-specific ANG II fusion protein activates cell surface, but not intracellular receptors. In a different study, Baker et al. expressed an intracellular ANG II peptide in the mouse cardiomyocytes using an adenoviral vector [178]. Cardiac-specific expression of this intracellular ANG II peptide in mice induced cardiac hypertrophy, but not altered blood pressure and plasma ANG II [99, 178]. Furthermore, the AT1 receptor blocker failed to block the cardiac hypertrophic effect of this peptide, suggesting that AT1 receptor may not be involved [99, 178].

In the kidney, a proximal tubule cell-specific promoter may be an ideal approach to express an intracellular ANG II protein selectively in the proximal tubules. For example, the kidney androgen-regulated protein gene (KAP) has been used to drive “proximal tubule-specific” expression of human angiotensinogen and renin in the kidney [182, 183]. It has been shown that the KAP gene is widely expressed in the kidney, with its expression reportedly confined to the proximal tubules and regulated by androgen and estrogen [184, 185]. The advantages of this approach are its usefulness for studying the sexual dimorphic regulation of angiotensinogen expression in the proximal tubules of the kidney [182, 183].

We have collaborated with Dr. Julie Cook of Ochsner Clinic and Dr. Isabelle Rubera of University of Nice-Sophia, France to develop an adenoviral construct (Ad-sglt2-ECFP/ANG II), which encodes a cyan fluorescent intracellular ANG II fusion protein (ECFP/ANG II) [17, 18]. The sodium and glucose cotransporter 2 promoter, sglt2, was used to drive the expression of ECFP/ANG II selectively in the proximal tubule cells of the rat and mouse kidneys. Sglt2 is expressed almost exclusively in S1 and S2 segments of the kidney proximal tubules [186]. Using this approach, we have determined whether intrarenal adenovirus-mediated expression of intracellular ECFP/ANG II selectively in the proximal tubules of the rat and mouse kidneys increases the expression and activity of NHE3, stimulate proximal tubule sodium reabsorption, and increase blood pressure in rats and mice. We demonstrated that expression of intracellular ECFP/ANG II selectively in the proximal tubules of rats and mice significantly increased NHE3 expression, proximal tubule sodium reabsorption, and blood pressure (Figure 4) [17, 18]. We further showed that AT1 receptor blocker losartan and deletion of AT1a receptors in mice significantly attenuated intracellular ANG II-induced NHE3 expression, proximal tubule sodium reabsorption, and blood pressure responses, suggesting an AT1 (AT1a) receptor-mediated mechanisms.

Figure 4.

Overexpression of an intracellular ECFP/ANG II fusion protein selectively in the proximal tubule of the kidney in C57BL/6J or AT1a-KO mice. ECFP/ANG II increased systolic blood pressure and had a significant antinatriuretic response in C57BL/6J but not in AT1a-KO mice. Green blue represents ECFP/ANG II expression in the proximal tubules, whereas Red represents DAPI-stained nuclei in the cortex after conversion from blue color. G, glomerulus. PT, proximal tubule. **p < 0.01 versus control, whereas ++p < 0.01 versus C57BL/6J mice. Reproduced from Zhuo et al. with permission [15].

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8. Intratubular and intracellular ANG II: role of NHE3 in maintaining normal blood pressure homeostasis and ANG II-induced hypertension

The Na+/H+ exchanger 3 (NHE3) is the most important Na+ transporter in AP membranes of the proximal tubules of the kidney [187, 188, 189, 190]. NHE3 is directly and indirectly responsible for reabsorbing approximately 50–60% of filtered load of NaCl and 70–80% of filtered load of bicarbonate (HCO3) [187, 188, 189, 190]. Indeed, nearly all of the measured Na+/H+ exchanger activity in AP membrane vesicles of proximal tubules are mediated by NHE3 [187, 188, 189, 190]. The importance of proximal tubule NHE3 in maintaining body salt and fluid balance and blood pressure homeostasis has not been well studied until recently. Overall, global deletion of the NHE3 gene in all tissues of mice (Nhe3−/−) leads to ∼50% decreases in fluid, Na+ and HCO3 absorption in proximal convoluted tubules, causes salt wasting from the digestive system, and significantly decreases basal blood pressure [191, 192, 193, 194]. One of striking phenotypes is absorptive defects in the small intestines due to intestinal NHE3 deletion [191, 192, 193, 194]. Moreover, the transgenic rescue of the NHE3 transgene in small intestines in Nhe3−/− mice, tgNhe3−/−, failed to rescue the structural and absorptive defects of global NHE3 deletion, with basal blood pressure being similar to those of Nhe3−/− mice [195, 196]. These abnormal phenotypes have been confirmed by us recently [21, 22, 23].

However, these studies using either Nhe3−/− or tgNhe3−/− mice are unable to determine the roles of NHE3 in the proximal tubules of the kidney, since NHE3 is abundantly expressed not only in the proximal tubules of the kidney, but also in small intestines of the gut. To overcome this limitation, we have generated mutant mice with deletion of NHE3 selectively in the proximal tubules of the kidney, PT-Nhe3−/−, using the state of the art Sglt2-Cre/LoxP approach [23]. We directly tested the hypothesis that deletion of NHE3 selectively in the proximal tubules of the kidney would lower basal blood pressure by inhibiting proximal tubule Na+ reabsorption and increasing the pressure natriuresis response in mice [23]. We demonstrated that under basal conditions, PT-Nhe3−/− mice had significantly lower systolic, diastolic, and mean arterial blood pressure than WT mice, accompanied by significantly greater diuretic and natriuretic responses than WT mice, without altering 24 h fecal Na+ excretion, plasma pH, Na+, and bicarbonate levels. Furthermore, we demonstrated that the pressure-natriuresis response, as well natriuretic responses to acute volume expansion and a high salt diet, were significantly augmented in PT-Nhe3−/− mice [23]. Thus, our data support the scientific premise and physiological relevance that NHE3 in the proximal tubules plays an important role in maintaining basal blood pressure homeostasis, and genetic deletion of NHE3 selectively in the proximal tubules of the kidney lowers blood pressure by increasing the pressure-natriuretic response.

Recently, we further investigated whether NHE3 in small intestines and proximal tubules of the kidney plays a key role in ANG II-induced hypertension using Nhe3−/−, tgNhe3−/−, and PT-Nhe3−/− mice [21, 22]. As expected, infusion of a pressor dose of ANG II, 1.5 mg/kg/day, i.p., via an osmotic minipump for 2 weeks markedly increased blood pressure and caused hypertension in C57BL/6J mice (Figure 5) [21, 22]. These hypertensive responses were significantly attenuated in conscious and anesthetized Nhe3−/−, tgNhe3−/−, and PT-Nhe3−/− mice [21, 22, 197]. These results strongly support an important role of NHE3 not only in small intestines, but also in the proximal tubules of the kidney in maintaining basal blood pressure homeostasis and in the development of ANG II-induced hypertension.

Figure 5.

Global (Nhe3−/−) or “kidney-selective” deletion of the Na+/H+ exchanger 3 (NHE3) (tgNhe3−/−) in mice significantly attenuates systolic blood pressure response to angiotensin II infusion for 2 weeks (ANG II), 1.5 mg/kg/day, i.p. **p < 0.01 versus their control or basal; ++p < 0.01 versus wildtype; ##p < 0.01 versus ANG II.

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9. Future perspectives and conclusions

Taken together, there is accumulating evidence to support the existence of the circulating (endocrine), local intratubular (paracrine), and intracellular RAS system in the kidney, especially in the proximal tubules. All major components of the RAS, including the substrate angiotensinogen, renin, ACE, ANG II, AT1 and AT2 receptors, have been localized in the circulation, the kidney, and in the proximal tubule. The roles of the circulating and intratubular RAS in the cardiovascular and kidney, and blood pressure regulation have been extensively studied using molecular, cellular, genetic and pharmacological approaches. It is now well-understood that AGT, prorenin, renin, ACE, ANG II and AT1 and AT2 receptors are not only expressed and localized in the proximal tubules under physiological conditions, but the levels of intratubular angiotensinogen, renin, ACE, and ANG II proteins are also significantly increased in the kidney in response to ANG II infusion in spite of suppression of the circulating RAS. Furthermore, there is also increasing evidence supporting the genomic roles of intracellular and nuclear ANG II in the regulation of proximal tubule reabsorption, blood pressure and the development of hypertension. Future studies should focus more on the long-term genomic and hypertensive roles of intracellular, mitochondrial and nuclear ANG II and the underlying signaling mechanisms in ANG II-dependent hypertension and target organ injury.

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Acknowledgments

This work was supported in part by NIH grants, 2R01DK102429-03A1, 2R01DK067299-10A1, and 1R56HL130988-01 to Dr. Zhuo. Ana Paula de Oliveira Leite was supported by scholarships from the Ministry of Education, Brazilian Federal Agency for Support and Evaluation of Graduate Education—CAPES, and Hospital do Rim, Sao Paulo, Brazil, respectively. Drs. Chunling Zhao, Xiaowen Zheng, Jianfeng Zhang were visiting scholars from the Department of Emergency Medicine, The 2nd Affiliated Hospital, Guangxi Medical University, Nanning, Guangxi, China.

Conflict of interest

The authors declare no conflict of interest.

References

  1. 1. Whelton PK, Carey RM, Aronow WS, Casey DE Jr, Collins KJ, Dennison HC, et al. 2017ACC/AHA/AAPA/ABC/ACPM/AGS/APhA/ASH/ASPC/NMA/PCNA guideline for the prevention, detection, evaluation, and management of high blood pressure in adults: Executive summary: A report of the American College Of Cardiology/American Heart Association task force on clinical practice guidelines. Circulation. 2018;138(17):e426-e483
  2. 2. Carey RM, Whelton PK. Prevention, detection, evaluation, and management of high blood pressure in adults: Synopsis of the 2017 American College of Cardiology/American Heart Association Hypertension Guideline. Annals of Internal Medicine. 2018;168(5):351-358
  3. 3. Chobanian AV, Bakris GL, Black HR, Cushman WC, Green LA, Izzo JL Jr, et al. The seventh report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure. Hypertension. 2003;42(6):1206-1252
  4. 4. Lloyd-Jones D, Adams RJ, Brown TM, Carnethon M, Dai S, De SG, et al. Heart disease and stroke statistics—2010 update: A report from the American Heart Association. Circulation. 2010;121(7):e46-e215
  5. 5. Calhoun DA, Jones D, Textor S, Goff DC, Murphy TP, Toto RD, et al. Resistant hypertension: Diagnosis, evaluation, and treatment. A scientific statement from the American Heart Association Professional Education Committee of the Council for High Blood Pressure Research. Hypertension. 2008;51(6):1403-1419
  6. 6. Sacks FM, Svetkey LP, Vollmer WM, Appel LJ, Bray GA, Harsha D, et al. Effects on blood pressure of reduced dietary sodium and the Dietary Approaches to Stop Hypertension (DASH) diet. DASH-Sodium Collaborative Research Group. The New England Journal of Medicine. 2001;344(1):3-10
  7. 7. Bomback AS, Toto R. Dual blockade of the renin-angiotensin-aldosterone system: Beyond the ACE inhibitor and angiotensin-II receptor blocker combination. American Journal of Hypertension. 2009;22(10):1032-1040
  8. 8. Jorde UP, Ennezat PV, Lisker J, Suryadevara V, Infeld J, Cukon S, et al. Maximally recommended doses of angiotensin-converting enzyme (ACE) inhibitors do not completely prevent ACE-mediated formation of angiotensin II in chronic heart failure. Circulation. 2000;101(8):844-846
  9. 9. Cook JL, Zhang Z, Re RN. In vitro evidence for an intracellular site of angiotensin action. Circulation Research. 2001;89(12):1138-1146
  10. 10. Li XC, Zhu D, Zheng X, Zhang J, Zhuo JL. Intratubular and intracellular renin-angiotensin system in the kidney: A unifying perspective in blood pressure control. Clinical Science (London, England). 2018;132(13):1383-1401
  11. 11. Kumar R, Singh VP, Baker KM. The intracellular renin-angiotensin system: Implications in cardiovascular remodeling. Current Opinion in Nephrology and Hypertension. 2008;17(2):168-173
  12. 12. Murphy JE, Padilla BE, Hasdemir B, Cottrell GS, Bunnett NW. Endosomes: A legitimate platform for the signaling train. Proceedings of the National Academy of Sciences of the United States of America. 2009;0906541106:1-8
  13. 13. Cottrell GS, Padilla BE, Amadesi S, Poole DP, Murphy JE, Hardt M, et al. Endosomal endothelin-converting enzyme-1: A regulator of beta-arrestin-dependent ERK signaling. The Journal of Biological Chemistry. 2009;284(33):22411-22425
  14. 14. Li XC, Carretero OA, Zhuo JL. Angiotensin II AT1a receptor siRNA inhibits receptor-mediated angiotensin II endocytosis and NHE3 expression in proximal tubule cells. Journal of the American Society of Nephrology. 2005;16:573A
  15. 15. Zhuo JL, Li XC, Garvin JL, Navar LG, Carretero OA. Intracellular angiotensin II induces cytosolic Ca2+ mobilization by stimulating intracellular AT1 receptors in proximal tubule cells. American Journal of Physiology. Renal Physiology. 2006;290:F1382-F1390
  16. 16. Li XC, Hopfer U, Zhuo JL. Novel signaling mechanisms of intracellular angiotensin II-induced NHE3 expression and activation in mouse proximal tubule cells. American Journal of Physiology. Renal Physiology. 2012;303(12):F1617-F1628
  17. 17. Li XC, Cook JL, Rubera I, Tauc M, Zhang F, Zhuo JL. Intrarenal transfer of an intracellular cyan fluorescent fusion of angiotensin II selectively in proximal tubules increases blood pressure in rats and mice. American Journal of Physiology. Renal Physiology. 2011;300:F1076-F1088
  18. 18. Li XC, Zhuo JL. Proximal tubule-dominant transfer of AT1a receptors induces blood pressure responses to intracellular angiotensin II in AT1a receptor-deficient mice. American Journal of Physiology. Regulatory, Integrative and Comparative Physiology. 2013;304:R588-R598
  19. 19. Li XC, Navar LG, Shao Y, Zhuo JL. Genetic deletion of AT1a receptors attenuates intracellular accumulation of angiotensin II in the kidney of AT1a receptor-deficient mice. American Journal of Physiology. Renal Physiology. 2007;293:F586-F593
  20. 20. Li XC, Zhuo JL. In vivo regulation of AT1a receptor-mediated intracellular uptake of [125I]-Val5-angiotensin II in the kidneys and adrenal glands of AT1a receptor-deficient mice. American Journal of Physiology. Renal Physiology. 2008;294:F293-F302
  21. 21. Li XC, Shull GE, Miguel-Qin E, Zhuo JL. Role of the Na+/H+ exchanger 3 in angiotensin II-induced hypertension. Physiological Genomics. 2015;47(10):479-487
  22. 22. Li XC, Shull GE, Miguel-Qin E, Chen F, Zhuo JL. Role of the Na+/H+ exchanger 3 in angiotensin II-induced hypertension in NHE3-deficient mice with transgenic rescue of NHE3 in small intestines. Physiological Reports. 2015;3(11):e12605
  23. 23. Li XC, Soleimani M, Zhu D, Rubera I, Tauc M, Zheng X, et al. Proximal tubule-specific deletion of the NHE3 (Na+/H+ exchanger 3) promotes the pressure-natriuresis response and lowers blood pressure in mice. Hypertension. 2018;72(6):1328-1336
  24. 24. Tewksbury DA, Frome WL, Dumas ML. Characterization of human angiotensinogen. The Journal of Biological Chemistry. 1978;253(11):3817-3820
  25. 25. Tewksbury DA, Dart RA, Travis J. The amino terminal amino acid sequence of human angiotensinogen. Biochemical and Biophysical Research Communications. 1981;99(4):1311-1315
  26. 26. Bouhnik J, Clauser E, Strosberg D, Frenoy JP, Menard J, Corvol P. Rat angiotensinogen and des(angiotensin I)angiotensinogen: Purification, characterization, and partial sequencing. Biochemistry. 1981;20(24):7010-7015
  27. 27. Clouston WM, Evans BA, Haralambidis J, Richards RI. Molecular cloning of the mouse angiotensinogen gene. Genomics. 1988;2(3):240-248
  28. 28. Kobori H, Nangaku M, Navar LG, Nishiyama A. The intrarenal renin-angiotensin system: From physiology to the pathobiology of hypertension and kidney disease. Pharmacological Reviews. 2007;59(3):251-287
  29. 29. Taugner R, Hackenthal E, Rix E, Nobiling R, Poulsen K. Immunocytochemistry of the renin-angiotensin system: Renin, angiotensinogen, angiotensin I, angiotensin II, and converting enzyme in the kidneys of mice, rats, and tree shrews. Kidney International Supplements. 1982;12:S33-S43
  30. 30. Darby IA, Sernia C. In situ hybridization and immunohistochemistry of renal angiotensinogen in neonatal and adult rat kidneys. Cell and Tissue Research. 1995;281(2):197-206
  31. 31. Kobori H, Harrison-Bernard LM, Navar LG. Expression of angiotensinogen mRNA and protein in angiotensin II-dependent hypertension. Journal of the American Society of Nephrology. 2001;12(3):431-439
  32. 32. Kobori H, Harrison-Bernard LM, Navar LG. Urinary excretion of angiotensinogen reflects intrarenal angiotensinogen production. Kidney International. 2002;61(2):579-585
  33. 33. Kobori H, Harrison-Bernard LM, Navar LG. Enhancement of angiotensinogen expression in angiotensin II-dependent hypertension. Hypertension. 2001;37(5):1329-1335
  34. 34. Matsusaka T, Niimura F, Shimizu A, Pastan I, Saito A, Kobori H, et al. Liver angiotensinogen is the primary source of renal angiotensin II. Journal of the American Society of Nephrology. 2012;23(7):1181-1189
  35. 35. Tigerstedt R, Bergman PG. Niere und Kreislauf. Skandinavisches Archiv Für Physiologie. 1898;8:223-271
  36. 36. Imai T, Miyazaki H, Hirose S, Hori H, Hayashi T, Kageyama R, et al. Cloning and sequence analysis of cDNA for human renin precursor. Proceedings of the National Academy of Sciences of the United States of America. 1983;80(24):7405-7409
  37. 37. Taugner R, Hackenthal E, Nobiling R, Harlacher M, Reb G. The distribution of renin in the different segments of the renal arterial tree: Immunocytochemical investigation in the mouse kidney. Histochemistry. 1981;73(1):75-88
  38. 38. Celio MR, Inagami T. Renin in the human kidney. Immunohistochemical localization. Histochemistry. 1981;72(1):1-10
  39. 39. Faraggiana T, Gresik E, Tanaka T, Inagami T, Lupo A. Immunohistochemical localization of renin in the human kidney. The Journal of Histochemistry and Cytochemistry. 1982;30(5):459-465
  40. 40. Song K, Zhuo JL, Chai SY, Mendelsohn FA. A new method to localize active renin in tissues by autoradiography: Application to dog kidney. Kidney International. 1992;42(3):639-646
  41. 41. Zhuo JL, Anderson WP, Song K, Mendelsohn FA. Autoradiographic localization of active renin in the juxtaglomerular apparatus of the dog kidney: Effects of sodium intake. Clinical and Experimental Pharmacology & Physiology. 1996;23(4):291-298
  42. 42. Zhuo JL, Song K, Chai SY, Mendelsohn FA. Anatomical localization of components of the renin-angiotensin system in different organs and tissues. In: MacGregor GA, Sever PS, editors. Inhibition of the Renin-Angiotensin System: Recent Advances. Hong Kong: Gardiner-Calwell Communications (Pacific) Ltd.; 1993
  43. 43. Moe OW, Ujiie K, Star RA, Miller RT, Widell J, Alpern RJ, et al. Renin expression in renal proximal tubule. The Journal of Clinical Investigation. 1993;91(3):774-779
  44. 44. Chen M, Harris MP, Rose D, Smart A, He XR, Kretzler M, et al. Renin and renin mRNA in proximal tubules of the rat kidney. Journal of Clinical Investigation. 1994;94(1):237-243
  45. 45. Tang SS, Jung F, Diamant D, Brown D, Bachinsky D, Hellman P, et al. Temperature-sensitive SV40 immortalized rat proximal tubule cell line has functional renin-angiotensin system. The American Journal of Physiology. 1995;268(3 Pt 2):F435-F446
  46. 46. Taugner R, Hackenthal E, Inagami T, Nobiling R, Poulsen K. Vascular and tubular renin in the kidneys of mice. Histochemistry. 1982;75(4):473-484
  47. 47. Iwao H, Nakamura N, Ikemoto F, Yamamoto K. Subcellular localization of exogenously administered renin in mouse kidney. Japanese Circulation Journal. 1983;47(10):1198-1202
  48. 48. Soubrier F, Alhenc-Gelas F, Hubert C, Allegrini J, John M, Tregear G, et al. Two putative active centers in human angiotensin I-converting enzyme revealed by molecular cloning. Proceedings of the National Academy of Sciences of the United States of America. 1988;85(24):9386-9390
  49. 49. Bernstein KE, Martin BM, Bernstein EA, Linton J, Striker L, Striker G. The isolation of angiotensin-converting enzyme cDNA. The Journal of Biological Chemistry. 1988;263(23):11021-11024
  50. 50. Esther CR, Marino EM, Howard TE, Machaud A, Corvol P, Capecchi MR, et al. The critical role of tissue angiotensin-converting enzyme as revealed by gene targeting in mice. The Journal of Clinical Investigation. 1997;99:2375-2385
  51. 51. Bernstein KE. Views of the renin-angiotensin system: Brilling, mimsy, and slithy tove. Hypertension. 2006;47(3):509-514
  52. 52. Bernstein KE, Ong FS, Blackwell WL, Shah KH, Giani JF, Gonzalez-Villalobos RA, et al. A modern understanding of the traditional and nontraditional biological functions of angiotensin-converting enzyme. Pharmacological Reviews. 2012;65(1):1-46
  53. 53. Chai SY, Allen AM, Adam WR, Mendelsohn FA. Local actions of angiotensin II: Quantitative in vitro autoradiographic localization of angiotensin II receptor binding and angiotensin converting enzyme in target tissues. Journal of Cardiovascular Pharmacology. 1986;8(Suppl 10):S35-S39
  54. 54. Harrison-Bernard LM, Zhuo JL, Kobori H, Ohishi M, Navar LG. Intrarenal AT1 receptor and ACE binding in ANG II-induced hypertensive rats. American Journal of Physiology. Renal Physiology. 2002;282(1):F19-F25
  55. 55. Bruneval P, Hinglais N, Alhenc-Gelas F, Tricottet V, Corvol P, Menard J, et al. Angiotensin I converting enzyme in human intestine and kidney. Ultrastructural immunohistochemical localization. Histochemistry. 1986;85(1):73-80
  56. 56. Danilov SM, Faerman AI, Printseva OY, Martynov AV, Sakharov IY, Trakht IN. Immunohistochemical study of angiotensin-converting enzyme in human tissues using monoclonal antibodies. Histochemistry. 1987;87(5):487-490
  57. 57. Schulz WW, Hagler HK, Buja LM, Erdos EG. Ultrastructural localization of angiotensin I-converting enzyme (EC 3.4.15.1) and neutral metalloendopeptidase (EC 3.4.24.11) in the proximal tubule of the human kidney. Laboratory Investigation. 1988;59(6):789-797
  58. 58. Navar LG, Kobori H, Prieto-Carrasquero M. Intrarenal angiotensin II and hypertension. Current Hypertension Reports. 2003;5(2):135-143
  59. 59. Navar LG, Carmines PK, Huang WC, Mitchell KD. The tubular effects of angiotensin II. Kidney International. Supplement. 1987;20:S81-S88
  60. 60. Harris PJ, Navar LG. Tubular transport responses to angiotensin II. American Journal of Physiology. Renal Physiology. 1985;248:F621-F630
  61. 61. Crowley SD, Gurley SB, Herrera MJ, Ruiz P, Griffiths R, Kumar AP, et al. Angiotensin II causes hypertension and cardiac hypertrophy through its receptors in the kidney. Proceedings of the National Academy of Sciences of the United States of America. 2006;103(47):17985-17990
  62. 62. Crowley SD, Gurley SB, Oliverio MI, Pazmino AK, Griffiths R, Flannery PJ, et al. Distinct roles for the kidney and systemic tissues in blood pressure regulation by the renin-angiotensin system. The Journal of Clinical Investigation. 2005;115(4):1092-1099
  63. 63. Carey RM, Siragy HM. Newly recognized components of the renin-angiotensin system: Potential roles in cardiovascular and renal regulation. Endocrine Reviews. 2003;24(3):261-271
  64. 64. Navar LG, Kobori H, Prieto MC, Gonzalez-Villalobos RA. Intratubular renin-angiotensin system in hypertension. Hypertension. 2011;57(3):355-362
  65. 65. Nishiyama A, Seth DM, Navar LG. Renal interstitial fluid concentrations of angiotensins I and II in anesthetized rats. Hypertension. 2002;39(1):129-134
  66. 66. Siragy HM, Howell NL, Ragsdale NV, Carey RM. Renal interstitial fluid angiotensin. Modulation by anesthesia, epinephrine, sodium depletion, and renin inhibition. Hypertension. 1995;25(5):1021-1024
  67. 67. Zhuo JL, Imig JD, Hammond TG, Orengo S, Benes E, Navar LG. Ang II accumulation in rat renal endosomes during Ang II-induced hypertension: Role of AT1 receptor. Hypertension. 2002;39(1):116-121
  68. 68. Shaltout HA, Westwood BM, Averill DB, Ferrario CM, Figueroa JP, Diz DI, et al. Angiotensin metabolism in renal proximal tubules, urine, and serum of sheep: Evidence for ACE2-dependent processing of angiotensin II. American Journal of Physiology. Renal Physiology. 2007;292(1):F82-F91
  69. 69. Prieto-Carrasquero MC, Kobori H, Ozawa Y, Gutierrez A, Seth D, Navar LG. AT1 receptor-mediated enhancement of collecting duct renin in angiotensin II-dependent hypertensive rats. American Journal of Physiology. Renal Physiology. 2005;289(3):F632-F637
  70. 70. Zou LX, Hymel A, Imig JD, Navar LG. Renal accumulation of circulating angiotensin II in angiotensin II-infused rats. Hypertension. 1996;27(3 Pt 2):658-662
  71. 71. Chappell MC. Nonclassical renin-angiotensin system and renal function. Comprehensive Physiology. 2012;2(4):2733-2752
  72. 72. Zhuo JL, Li XC. New insights and perspectives on intrarenal renin-angiotensin system: Focus on intracrine/intracellular angiotensin II. Peptides. 2011;32(7):1551-1565
  73. 73. Zou LX, Imig JD, von Thun AM, Hymel A, Ono H, Navar LG. Receptor-mediated intrarenal angiotensin II augmentation in angiotensin II-infused rats. Hypertension. 1996;28(4):669-677
  74. 74. Imig JD, Navar GL, Zou LX, O'Reilly KC, Allen PL, Kaysen JH, et al. Renal endosomes contain angiotensin peptides, converting enzyme, and AT1a receptors. The American Journal of Physiology. 1999;277(2 Pt 2):F303-F311
  75. 75. Abadir PM, Foster DB, Crow M, Cooke CA, Rucker JJ, Jain A, et al. Identification and characterization of a functional mitochondrial angiotensin system. Proceedings of the National Academy of Sciences of the United States of America. 2011;108(36):14849-14854
  76. 76. Timmermans PB, Wong PC, Chiu AT, Herblin WF, Benfield P, Carini DJ, et al. Angiotensin II receptors and angiotensin II receptor antagonists. Pharmacological Reviews. 1993;45(2):205-251
  77. 77. de Gasparo M, Catt KJ, Inagami T, Wright JW, Unger T. International union of pharmacology. XXIII. The angiotensin II receptors. Pharmacological Reviews. 2000;52(3):415-472
  78. 78. Karnik SS, Unal H, Kemp JR, Tirupula KC, Eguchi S, Vanderheyden PM, et al. International union of basic and clinical pharmacology. XCIX. Angiotensin receptors: Interpreters of pathophysiological angiotensinergic stimuli. Pharmacological Reviews. 2015;67(4):754-819
  79. 79. Murphy TJ, Alexander RW, Griendling KK, Runge MS, Bernstein KE. Isolation of a cDNA encoding the vascular type-1 angiotensin II receptor. Nature. 1991;16(351):233-236
  80. 80. Sasaki K, Yamano Y, Bardhan S, Iwai N, Murray JJ, Hasegawa M, et al. Cloning and expression of a complementary DNA encoding a bovine adrenal angiotensin II type-1 receptor. Nature. 1991;351(6323):230-233
  81. 81. Zhuo JL, Ferrao FM, Zheng Y, Li XC. New frontiers in the intrarenal renin-angiotensin system: A critical review of classical and new paradigms. Frontiers in Endocrinology (Lausanne). 2013;4:166
  82. 82. Mukoyama M, Nakajima M, Horiuchi M, Sasamura H, Pratt RE, Dzau VJ. Expression cloning of type 2 angiotensin II receptor reveals a unique class of seven-transmembrane receptors. The Journal of Biological Chemistry. 1993;268(33):24539-24542
  83. 83. Nakajima M, Mukoyama M, Pratt RE, Horiuchi M, Dzau VJ. Cloning of cDNA and analysis of the gene for mouse angiotensin II type 2 receptor. Biochemical and Biophysical Research Communications. 1993;197(2):393-399
  84. 84. Kambayashi Y, Bardhan S, Takahashi K, Tsuzuki S, Inui H, Hamakubo T, et al. Molecular cloning of a novel angiotensin II receptor isoform involved in phosphotyrosine phosphatase inhibition. The Journal of Biological Chemistry. 1993;268(33):24543-24546
  85. 85. Zhuo JL, Alcorn D, Harris PJ, Mendelsohn FA. Localization and properties of angiotensin II receptors in rat kidney. Kidney International. Supplement. 1993;42:S40-S46
  86. 86. Zhuo JL, Song K, Harris PJ, Mendelsohn FA. In vitro autoradiography reveals predominantly AT1 angiotensin II receptors in rat kidney. Renal Physiology and Biochemistry. 1992;15(5):231-239
  87. 87. Zhuo JL, Allen AM, Alcorn D, MacGregor D, Aldred GP, Mendelsohn FA. The distribution of angiotensin II receptors. In: Laragh JH, Brenner BM, editors. Hypertension: Pathology, Diagnosis & Management. 2nd ed. New York: Raven Press; 1995. pp. 1739-1762
  88. 88. Gwathmey T, Shaltout HA, Pendergrass KD, Pirro NT, Figueroa JP, Rose JC, et al. Nuclear angiotensin II—type 2 (AT2) receptors are functionally linked to nitric oxide production. American Journal of Physiology-Renal Physiology. 2009;296:F1484-F1493
  89. 89. Gwathmey TM, Westwood BM, Pirro NT, Tang L, Rose JC, Diz DI, et al. Nuclear angiotensin-(1-7) receptor is functionally coupled to the formation of nitric oxide. American Journal of Physiology. Renal Physiology. 2010;299(5):F983-F990
  90. 90. Wilson BA, Nautiyal M, Gwathmey TM, Rose JC, Chappell MC. Evidence for a mitochondrial angiotensin-(1-7) system in the kidney. American Journal of Physiology. Renal Physiology. 2016;310(7):F637-F645
  91. 91. Zhuo JL, MacGregor D, Mendelsohn FA. Comparative distribution of angiotensin II receptor subtypes in mammalian adrenal glands. In: Vinson GP, Anderson DC, editors. Vascular, Adrenal and Hypertension. London: Journal of Endocrinology Pty Ltd.; 1995. pp. 53-68
  92. 92. Ozono R, Wang ZQ, Moore AF, Inagami T, Siragy HM, Carey RM. Expression of the subtype 2 angiotensin (AT2) receptor protein in rat kidney. Hypertension. 1997;30(5):1238-1246
  93. 93. Kemp BA, Howell NL, Gildea JJ, Keller SR, Padia SH, Carey RM. AT(2) receptor activation induces natriuresis and lowers blood pressure. Circulation Research. 2014;115(3):388-399
  94. 94. Touyz RM, Schiffrin EL. Signal transduction mechanisms mediating the physiological and pathophysiological actions of angiotensin II in vascular smooth muscle cells. Pharmacological Reviews. 2000;52:639-672
  95. 95. Mehta PK, Griendling KK. Angiotensin II cell signaling: Physiological and pathological effects in the cardiovascular system. American Journal of Physiology. Cell Physiology. 2007;292(1):C82-C97
  96. 96. Baker KM, Booz GW, Dostal DE. Cardiac actions of angiotensin II: Role of an intracardiac renin-angiotensin system. Annual Review of Physiology. 1992;54:227-241
  97. 97. Re RN. On the biological actions of intracellular angiotensin. Hypertension. 2000;35(6):1189-1190
  98. 98. Re R. Intracellular renin-angiotensin system: The tip of the intracrine physiology iceberg. American Journal of Physiology-Heart and Circulatory Physiology. 2007;293(2):H905-H906
  99. 99. Kumar R, Singh VP, Baker KM. The intracellular renin-angiotensin system: A new paradigm. Trends in Endocrinology and Metabolism. 2007;18(5):208-214
  100. 100. Zhuo JL, Li XC. Novel roles of intracrine angiotensin II and signalling mechanisms in kidney cells. Journal of the Renin-Angiotensin-Aldosterone System. 2007;8(1):23-33
  101. 101. De Mello WC, Danser AH. Angiotensin II and the heart: On the intracrine renin-angiotensin system. Hypertension. 2000;35(6):1183-1188
  102. 102. Li XC, Zhuo JL. Intracellular ANG II directly induces in vitro transcription of TGF-β1, MCP-1, and NHE-3 mRNAs in isolated rat renal cortical nuclei via activation of nuclear AT1a receptors. American Journal of Physiology. Cell Physiology. 2008;294(4):C1034-C1045
  103. 103. Ferrao FM, Cardoso LHD, Drummond HA, Li XC, Zhuo JL, Gomes DS, et al. Luminal ANG II is internalized as a complex with AT1R/AT2R heterodimers to target endoplasmic reticulum in LLC-PK1 cells. American Journal of Physiology. Renal Physiology. 2017;313(2):F440-F449
  104. 104. Brasier AR, Jamaluddin M, Han Y, Patterson C, Runge MS. Angiotensin II induces gene transcription through cell-type-dependent effects on the nuclear factor-kappaB (NF-kappaB) transcription factor. Molecular and Cellular Biochemistry. 2000;212(1-2):155-169
  105. 105. Ruiz-Ortega M, Lorenzo O, Ruperez M, Konig S, Wittig B, Egido J. Angiotensin II activates nuclear transcription factor κB through AT1 and AT2 in vascular smooth muscle cells: Molecular mechanisms. Circulation Research. 2000;86(12):1266-1272
  106. 106. Li XC, Zhuo JL. Nuclear factor-κB as a hormonal intracellular signaling molecule: Focus on angiotensin II-induced cardiovascular and renal injury. Current Opinion in Nephrology and Hypertension. 2008;17(1):37-43
  107. 107. Takahashi M, Suzuki E, Takeda R, Oba S, Nishimatsu H, Kimura K, et al. Angiotensin II and tumor necrosis factor-alpha synergistically promote monocyte chemoattractant protein-1 expression: Roles of NF-κB, p38, and reactive oxygen species. American Journal of Physiology. Heart and Circulatory Physiology. 2008;294(6):H2879-H2888
  108. 108. Zhuo JL. Monocyte chemoattractant protein-1: A key mediator of angiotensin II-induced target organ damage in hypertensive heart disease? Journal of Hypertension. 2004;22(3):451-454
  109. 109. Kagami S, Border WA, Miller DE, Noble NA. Angiotensin II stimulates extracellular matrix protein synthesis through induction of transforming growth factor-beta expression in rat glomerular mesangial cells. The Journal of Clinical Investigation. 1994;93:2431-2437
  110. 110. Wolf G, Ziyadeh FN, Stahl RA. Angiotensin II stimulates expression of transforming growth factor beta receptor type II in cultured mouse proximal tubular cells. Journal of Molecular Medicine. 1999;77(7):556-564
  111. 111. Kurtz TW, Gardner DG. Transcription-modulating drugs: A new frontier in the treatment of essential hypertension. Hypertension. 1998;32:380-386
  112. 112. Kurtz TW, Pravenec M. Molecule-specific effects of angiotensin II-receptor blockers independent of the renin-angiotensin system. American Journal of Hypertension. 2008;21(8):852-859
  113. 113. Kurtz TW. Beyond the classic angiotensin-receptor-blocker profile. Nature Clinical Practice. Cardiovascular Medicine. 2008;5(Suppl 1):S19-S26
  114. 114. Conchon S, Monnot C, Teutsch B, Corvol P, Clauser E. Internalization of the rat AT1a and AT1b receptors: Pharmacological and functional requirements. FEBS Letters. 1994;349(3):365-370
  115. 115. Schupp M, Janke J, Clasen R, Unger T, Kintscher U. Angiotensin type 1 receptor blockers induce peroxisome proliferator-activated receptor-gamma activity. Circulation. 2004;109(17):2054-2057
  116. 116. Kurtz TW, Klein U. Next generation multifunctional angiotensin receptor blockers. Hypertension Research. 2009;32(10):826-834
  117. 117. Mauer M, Zinman B, Gardiner R, Suissa S, Sinaiko A, Strand T, et al. Renal and retinal effects of enalapril and losartan in type 1 diabetes. The New England Journal of Medicine. 2009;361(1):40-51
  118. 118. van Kats JP, Schalekamp MA, Verdouw PD, Duncker DJ, Danser AH. Intrarenal angiotensin II: Interstitial and cellular levels and site of production. Kidney International. 2001;60(6):2311-2317
  119. 119. von Thun AM, Vari RC, El Dahr SS, Navar LG. Augmentation of intrarenal angiotensin II levels by chronic angiotensin II infusion. The American Journal of Physiology. 1994;266(1 Pt 2):F120-F128
  120. 120. Zou LX, Imig JD, Hymel A, Navar LG. Renal uptake of circulating angiotensin II in Val5-angiotensin II infused rats is mediated by AT1 receptor. American Journal of Hypertension. 1998;11(5):570-578
  121. 121. Shao W, Seth DM, Navar LG. Augmentation of endogenous intrarenal angiotensin II levels in Val5-Ang II infused rats. American Journal of Physiology. Renal Physiology. 2009;296(5):F1067-F1071
  122. 122. Li XC, Zhuo JL. Mechanisms of AT1a receptor-mediated uptake of angiotensin II by proximal tubule cells: A novel role of the multiligand endocytic receptor megalin. American Journal of Physiology. Renal Physiology. 2014;307(2):F222-F233
  123. 123. Li XC, Gu V, Miguel-Qin E, Zhuo JL. Role of caveolin 1 in AT1a receptor-mediated uptake of angiotensin II in the proximal tubule of the kidney. American Journal of Physiology. Renal Physiology. 2014;307(8):F949-F961
  124. 124. Li XC, Carretero OA, Navar LG, Zhuo JL. AT1 receptor-mediated accumulation of extracellular angiotensin II in proximal tubule cells: Role of cytoskeleton microtubules and tyrosine phosphatases. American Journal of Physiology. Renal Physiology. 2006;291:F375-F383
  125. 125. Li XC, Zhuo JL. Selective knockdown of AT1 receptors by RNA interference inhibits Val5-Ang II endocytosis and NHE-3 expression in immortalized rabbit proximal tubule cells. American Journal of Physiology. Cell Physiology. 2007;293:C367-C378
  126. 126. Zhuo JL, Carretero OA, Li XC. Effects of AT1 receptor-mediated endocytosis of extracellular Ang II on activation of nuclear factor-κB in proximal tubule cells. Annals of the New York Academy of Sciences. 2006;1091:336-345
  127. 127. Brown GP, Douglas JG. Angiotensin II binding sites on isolated rat renal brush border membranes. Endocrinology. 1982;111(6):1830-1836
  128. 128. Douglas JG. Angiotensin receptor subtypes of the kidney cortex. The American Journal of Physiology. 1987;253(1 Pt 2):F1-F7
  129. 129. Dulin NO, Ernsberger P, Suciu DJ, Douglas JG. Rabbit renal epithelial angiotensin II receptors. The American Journal of Physiology. 1994;267(5 Pt 2):F776-F782
  130. 130. Becker BN, Cheng HF, Burns KD, Harris RC. Polarized rabbit type 1 angiotensin II receptors manifest differential rates of endocytosis and recycling. The American Journal of Physiology. 1995;269(4 Pt 1):C1048-C1056
  131. 131. Thekkumkara TJ, Cookson R, Linas SL. Angiotensin (AT1a) receptor-mediated increases in transcellular sodium transport in proximal tubule cells. The American Journal of Physiology. 1998;274:F897-F905
  132. 132. Christensen EI, Birn H. Megalin and cubilin: Synergistic endocytic receptors in renal proximal tubule. American Journal of Physiology. Renal Physiology. 2001;280(4):F562-F573
  133. 133. Zhai XY, Nielsen R, Birn H, Drumm K, Mildenberger S, Freudinger R, et al. Cubilin- and megalin-mediated uptake of albumin in cultured proximal tubule cells of opossum kidney. Kidney International. 2000;58(4):1523-1533
  134. 134. Kozyraki R, Fyfe J, Verroust PJ, Jacobsen C, Dautry-Varsat A, Gburek J, et al. Megalin-dependent cubilin-mediated endocytosis is a major pathway for the apical uptake of transferrin in polarized epithelia. Proceedings of the National Academy of Sciences of the United States of America. 2001;98(22):12491-12496
  135. 135. Leheste JR, Rolinski B, Vorum H, Hilpert J, Nykjaer A, Jacobsen C, et al. Megalin knockout mice as an animal model of low molecular weight proteinuria. The American Journal of Pathology. 1999;155(4):1361-1370
  136. 136. Gonzalez-Villalobos R, Klassen RB, Allen PL, Navar LG, Hammond TG. Megalin binds and internalizes angiotensin II. American Journal of Physiology. Renal Physiology. 2005;288:F420-F427
  137. 137. Anborgh PH, Seachrist JL, Dale LB, Ferguson SS. Receptor/beta-arrestin complex formation and the differential trafficking and resensitization of β2-adrenergic and angiotensin II type 1A receptors. Molecular Endocrinology. 2000;14(12):2040-2053
  138. 138. Ferguson SS. Evolving concepts in G protein-coupled receptor endocytosis: The role in receptor desensitization and signaling. Pharmacological Reviews. 2001;53(1):1-24
  139. 139. Zhang J, Barak LS, Anborgh PH, Laporte SA, Caron MG, Ferguson SS. Cellular trafficking of G protein-coupled receptor/beta-arrestin endocytic complexes. The Journal of Biological Chemistry. 1999;274(16):10999-11006
  140. 140. Thomas WG, Thekkumkara TJ, Baker KM. Molecular mechanisms of angiotensin II (AT1A) receptor endocytosis. Clinical and Experimental Pharmacology & Physiology. Supplement. 1996;3:S74-S80
  141. 141. Rajagopal K, Whalen EJ, Violin JD, Stiber JA, Rosenberg PB, Premont RT, et al. Beta-arrestin2-mediated inotropic effects of the angiotensin II type 1A receptor in isolated cardiac myocytes. Proceedings of the National Academy of Sciences of the United States of America. 2006;103(44):16284-16289
  142. 142. Rappoport JZ, Kemal S, Benmerah A, Simon SM. Dynamics of clathrin and adaptor proteins during endocytosis. American Journal of Physiology. Cell Physiology. 2006;291(5):C1072-C1081
  143. 143. Zhang J, Ferguson SS, Barak LS, Menard L, Caron MG. Dynamin and beta-arrestin reveal distinct mechanisms for G protein-coupled receptor internalization. The Journal of Biological Chemistry. 1996;271(31):18302-18305
  144. 144. Qian H, Pipolo L, Thomas WG. Association of beta-Arrestin 1 with the type 1A angiotensin II receptor involves phosphorylation of the receptor carboxyl terminus and correlates with receptor internalization. Molecular Endocrinology. 2001;15(10):1706-1719
  145. 145. Seachrist JL, Laporte SA, Dale LB, Babwah AV, Caron MG, Anborgh PH, et al. Rab5 association with the angiotensin II type 1A receptor promotes Rab5 GTP binding and vesicular fusion. The Journal of Biological Chemistry. 2002;277(1):679-685
  146. 146. Dale LB, Seachrist JL, Babwah AV, Ferguson SS. Regulation of angiotensin II type 1A receptor intracellular retention, degradation, and recycling by Rab5, Rab7, and Rab11 GTPases. The Journal of Biological Chemistry. 2004;279(13):13110-13118
  147. 147. Becker BN, Cheng HF, Harris RC. Apical ANG II-stimulated PLA2 activity and Na+ flux: A potential role for Ca2+-independent PLA. The American Journal of Physiology. 1997;273(4 Pt 2):F554-F562
  148. 148. Elkjaer ML, Birn H, Agre P, Christensen EI, Nielsen S. Effects of microtubule disruption on endocytosis, membrane recycling and polarized distribution of Aquaporin-1 and gp330 in proximal tubule cells. European Journal of Cell Biology. 1995;67(1):57-72
  149. 149. Schelling JR, Linas SL. Angiotensin II-dependent proximal tubule sodium transport requires receptor-mediated endocytosis. The American Journal of Physiology. 1994;266(3 Pt 1):C669-C675
  150. 150. Schelling JR, Hanson AS, Marzec R, Linas SL. Cytoskeleton-dependent endocytosis is required for apical type 1 angiotensin II receptor-mediated phospholipase C activation in cultured rat proximal tubule cells. The Journal of Clinical Investigation. 1992;90(6):2472-2480
  151. 151. Li XC, Hopfer U, Zhuo JL. AT1 receptor-mediated uptake of angiotensin II and NHE-3 expression in proximal tubule cells through the microtubule-dependent endocytic pathway. American Journal of Physiology. Renal Physiology. 2009;297(5):F1342-F1352
  152. 152. Robertson A, Khairallah P. Angiotensin II: Rapid localization in nuclei of smooth and cardiac muscle. Science. 1971;172:1138-1139
  153. 153. Bianchi C, Gutkowska J, De Lean A, Ballak M, Anand-Srivastava MB, Genest J, et al. Fate of [125I]angiotensin II in adrenal zona glomerulosa cells. Endocrinology. 1986;118:2605-2607
  154. 154. Cook JL, Mills SJ, Naquin RT, Alam J, Re RN. Cleavage of the angiotensin II type 1 receptor and nuclear accumulation of the cytoplasmic carboxy-terminal fragment. American Journal of Physiology. Cell Physiology. 2007;292(4):C1313-C1322
  155. 155. Chen R, Mukhin YV, Garnovskaya MN, Thielen TE, Iijima Y, Huang C, et al. A functional angiotensin II receptor-GFP fusion protein: Evidence for agonist-dependent nuclear translocation. American Journal of Physiology. Renal Physiology. 2000;279(3):F440-F448
  156. 156. Morinelli TA, Raymond JR, Baldys A, Yang Q, Lee MH, Luttrell L, et al. Identification of a putative nuclear localization sequence within the angiotensin II AT1a receptor associated with nuclear activation. American Journal of Physiology. Cell Physiology. 2007;292(4):C1398-C1408
  157. 157. du Cheyron D, Chalumeau C, Defontaine N, Klein C, Kellermann O, Paillard M, et al. Angiotensin II stimulates NHE3 activity by exocytic insertion of the transporter: Role of PI 3-kinase. Kidney International. 2003;64(3):939-949
  158. 158. Liu FY, Cogan MG. Angiotensin II stimulation of hydrogen ion secretion in the rat early proximal tubule. Modes of action, mechanism, and kinetics. Journal of Clinical Investigation 1988;82(2):601-607
  159. 159. Bloch RD, Zikos D, Fisher KA, Schleicher L, Oyama M, Cheng JC, et al. Activation of proximal tubular Na+-H+ exchange by angiotensin II. The American Journal of Physiology. 1992;263(1 Pt 2):F135-F143
  160. 160. Geibel J, Giebisch G, Boron WF. Angiotensin II stimulates both Na+-H+ exchange and Na+/HCO3 cotransport in the rabbit proximal tubule. Proceedings of the National Academy of Sciences of the United States of America. 1990;87(20):7917-7920
  161. 161. Reilly AM, Harris PJ, Williams DA. Biphasic effect of angiotensin II on intracellular sodium concentration in rat proximal tubules. The American Journal of Physiology. 1995;269(3 Pt 2):F374-F380
  162. 162. Jourdain M, Amiel C, Friedlander G. Modulation of Na+-H+ exchange activity by angiotensin II in opossum kidney cells. The American Journal of Physiology. 1992;263(6 Pt 1):C1141-C1146
  163. 163. Houillier P, Chambrey R, Achard JM, Froissart M, Poggioli J, Paillard M. Signaling pathways in the biphasic effect of angiotensin II on apical Na+-H+ antiport activity in proximal tubule. Kidney International. 1996;50(5):1496-1505
  164. 164. Han HJ, Park SH, Koh HJ, Taub M. Mechanism of regulation of Na+ transport by angiotensin II in primary renal cells. Kidney International. 2000;57(6):2457-2467
  165. 165. Tsuganezawa H, Preisig PA, Alpern RJ. Dominant negative c-Src inhibits angiotensin II induced activation of NHE3 in OKP cells. Kidney International. 1998;54(2):394-398
  166. 166. Du Z, Ferguson W, Wang T. Role of PKC and calcium in modulation of effects of angiotensin II on sodium transport in proximal tubule. American Journal of Physiology. Renal Physiology. 2003;284(4):F688-F692
  167. 167. Wang T, Chan YL. The role of phosphoinositide turnover in mediating the biphasic effect of angiotensin II on renal tubular transport. The Journal of Pharmacology and Experimental Therapeutics. 1991;256(1):309-317
  168. 168. Karim Z, Defontaine N, Paillard M, Poggioli J. Protein kinase C isoforms in rat kidney proximal tubule: Acute effect of angiotensin II. The American Journal of Physiology. 1995;269(1 Pt 1):C134-C140
  169. 169. Schelling JR, Singh H, Marzec R, Linas SL. Angiotensin II-dependent proximal tubule sodium transport is mediated by cAMP modulation of phospholipase C. The American Journal of Physiology. 1994;267(5 Pt 1):C1239-C1245
  170. 170. Lea JP, Jin SG, Roberts BR, Shuler MS, Marrero MB, Tumlin JA. Angiotensin II stimulates calcineurin activity in proximal tubule epithelia through AT-1 receptor-mediated tyrosine phosphorylation of the PLC-gamma1 isoform. Journal of the American Society of Nephrology. 2002;13(7):1750-1756
  171. 171. Liu FY, Cogan MG. Angiotensin II stimulates early proximal bicarbonate absorption in the rat by decreasing cyclic adenosine monophosphate. The Journal of Clinical Investigation. 1989;84(1):83-91
  172. 172. Dulin NO, Alexander LD, Harwalkar S, Falck JR, Douglas JG. Phospholipase A2-mediated activation of mitogen-activated protein kinase by angiotensin II. Proceedings of the National Academy of Sciences of the United States of America. 1998;95(14):8098-8102
  173. 173. Ruiz-Ortega M, Lorenzo O, Ruperez M, Blanco J, Egido J. Systemic infusion of angiotensin II into normal rats activates nuclear factor-kappaB and AP-1 in the kidney: Role of AT1 and AT2 receptors. The American Journal of Pathology. 2001;158(5):1743-1756
  174. 174. Haller H, Lindschau C, Erdmann B, Quass P, Luft FC. Effects of intracellular angiotensin II in vascular smooth muscle cells. Circulation Research. 1996;79(4):765-772
  175. 175. Haller H, Lindschau C, Quass P, Luft FC. Intracellular actions of angiotensin II in vascular smooth muscle cells. Journal of the American Society of Nephrology. 1999;10(Suppl 11):S75-S83
  176. 176. De Mello WC. Renin increments the inward calcium current in the failing heart. Journal of Hypertension. 2006;24(6):1181-1186
  177. 177. Zhuo JL. Intracrine renin and angiotensin II: A novel role in cardiovascular and renal cellular regulation. Journal of Hypertension. 2006;24(6):1017-1020
  178. 178. Baker KM, Kumar R. Intracellular angiotensin II induces cell proliferation independent of AT1 receptor. American Journal of Physiology. Cell Physiology. 2006;291(5):C995-C1001
  179. 179. Baker KM, Chernin MI, Schreiber T, Sanghi S, Haiderzaidi S, Booz GW, et al. Evidence of a novel intracrine mechanism in angiotensin II-induced cardiac hypertrophy. Regulatory Peptides. 2004;120(1-3):5-13
  180. 180. van Kats JP, Methot D, Paradis P, Silversides DW, Reudelhuber TL. Use of a biological peptide pump to study chronic peptide hormone action in transgenic mice. Direct and indirect effects of angiotensin II on the heart. The Journal of Biological Chemistry. 2001;276(47):44012-44017
  181. 181. Xu J, Carretero OA, Lin CX, Cavasin MA, Shesely EG, Yang JJ, et al. Role of cardiac overexpression of ANG II in the regulation of cardiac function and remodeling postmyocardial infarction. American Journal of Physiology. Heart and Circulatory Physiology. 2007;293(3):H1900-H1907
  182. 182. Ding Y, Davisson RL, Hardy DO, Zhu LJ, Merrill DC, Catterall JF, et al. The kidney androgen-regulated protein promoter confers renal proximal tubule cell-specific and highly androgen-responsive expression on the human angiotensinogen gene in transgenic mice. The Journal of Biological Chemistry. 1997;272(44):28142-28148
  183. 183. Ding Y, Sigmund CD. Androgen-dependent regulation of human angiotensinogen expression in KAP-hAGT transgenic mice. American Journal of Physiology. Renal Physiology. 2001;280(1):F54-F60
  184. 184. Soler M, Tornavaca O, Sole E, Menoyo A, Hardy D, Catterall JF, et al. Hormone-specific regulation of the kidney androgen-regulated gene promoter in cultured mouse renal proximal-tubule cells. The Biochemical Journal. 2002;366(Pt 3):757-766
  185. 185. Meseguer A, Catterall JF. Cell-specific expression of kidney androgen-regulated protein messenger RNA is under multihormonal control. Molecular Endocrinology. 1990;4(8):1240-1248
  186. 186. Hediger MA, Rhoads DB. Molecular physiology of sodium-glucose cotransporters. Physiological Reviews. 1994;74(4):993-1026
  187. 187. Weinman EJ, Shenolikar S. Regulation of the renal brush border membrane Na+-H+ exchanger. Annual Review of Physiology. 1993;55:289-304
  188. 188. Biemesderfer D, Rutherford PA, Nagy T, Pizzonia JH, Abu-Alfa AK, Aronson PS. Monoclonal antibodies for high-resolution localization of NHE3 in adult and neonatal rat kidney. The American Journal of Physiology. 1997;273(2 Pt 2):F289-F299
  189. 189. Amemiya M, Loffing J, Lotscher M, Kaissling B, Alpern RJ, Moe OW. Expression of NHE-3 in the apical membrane of rat renal proximal tubule and thick ascending limb. Kidney International. 1995;48(4):1206-1215
  190. 190. Moe OW. Acute regulation of proximal tubule apical membrane Na/H exchanger NHE-3: Role of phosphorylation, protein trafficking, and regulatory factors. Journal of the American Society of Nephrology. 1999;10:2412-2425
  191. 191. Schultheis PJ, Clarke LL, Meneton P, Miller ML, Soleimani M, Gawenis LR, et al. Renal and intestinal absorptive defects in mice lacking the NHE3 Na+/H+ exchanger. Nature Genetics. 1998;19(3):282-285
  192. 192. Wu MS, Biemesderfer D, Giebisch G, Aronson PS. Role of NHE3 in mediating renal brush border Na+/H+ exchange. Adaptation to metabolic acidosis. The Journal of Biological Chemistry. 1996;271(51):32749-32752
  193. 193. Wang T, Yang CL, Abbiati T, Schultheis PJ, Shull GE, Giebisch G, et al. Mechanism of proximal tubule bicarbonate absorption in NHE3 null mice. The American Journal of Physiology. 1999;277(2 Pt 2):F298-F302
  194. 194. Ledoussal C, Lorenz JN, Nieman ML, Soleimani M, Schultheis PJ, Shull GE. Renal salt wasting in mice lacking NHE3 Na+/H+ exchanger but not in mice lacking NHE2. American Journal of Physiology. Renal Physiology. 2001;281(4):F718-F727
  195. 195. Woo AL, Noonan WT, Schultheis PJ, Neumann JC, Manning PA, Lorenz JN, et al. Renal function in NHE3-deficient mice with transgenic rescue of small intestinal absorptive defect. American Journal of Physiology. Renal Physiology. 2003;284(6):F1190-F1198
  196. 196. Noonan WT, Woo AL, Nieman ML, Prasad V, Schultheis PJ, Shull GE, et al. Blood pressure maintenance in NHE3-deficient mice with transgenic expression of NHE3 in small intestine. American Journal of Physiology. Regulatory, Integrative and Comparative Physiology. 2005;288(3):R685-R691
  197. 197. Li XC, Zhu D, Chen X, Zheng XW, Zhao C, Zhang JF, et al. Proximal tubule-specific deletion of the NHE3 (Na+/H+ exchanger 3) in the kidney attenuates angiotensin II-induced hypertension in mice. Hypertension. 2019 (in press)

Written By

Xiao C. Li, Ana Paula de Oliveira Leite, Xu Chen, Chunling Zhao, Xiaowen Zheng, Jianfeng Zhang and Jia L. Zhuo

Submitted: 10 May 2019 Reviewed: 14 June 2019 Published: 22 August 2019