Open access peer-reviewed chapter

Transcriptional Regulation and Epigenetics in Cardiovascular Cells: Role of the Mineralocorticoid Receptor

Written By

Lisa Deng, Lutz Hein and Achim Lother

Submitted: May 22nd, 2019 Reviewed: June 4th, 2019 Published: September 25th, 2019

DOI: 10.5772/intechopen.87230

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Abstract

The mineralocorticoid receptor (MR), a ligand-activated transcription factor, plays an important role in the pathophysiology of cardiovascular disease. Epigenetic mechanisms such as DNA methylation or histone modifications in addition to the DNA sequence are decisive regulators of cell type-specific transcriptional activity and gene expression by controlling chromatin accessibility. In this review, we summarise the current knowledge about the impact of MR on gene expression in cardiovascular cells. We discuss studies investigating the interaction of MR with epigenetic mechanisms or other transcription factors and their implications for the cardiovascular system. Finally, we compare mechanisms of transcriptional regulation by MR and other nuclear transcription factors. In conclusion, MR is an important regulator of gene expression in cardiovascular cells. Potential mechanisms of cell type-specific transcriptional regulation by MR include interaction with other transcription factors or co-regulators, tethering and post-translational modifications of the MR. Further studies will be needed to clarify the interplay of MR and epigenetic mechanisms.

Keywords

  • mineralocorticoid receptor
  • epigenetics
  • chromatin
  • gene expression
  • cell types

1. Introduction

Mineralocorticoid receptor (MR) antagonists are a cornerstone in the current pharmacological therapy of chronic heart failure [1, 2]. MR in renal epithelial cells plays an important role for ion homeostasis and blood pressure control, but MR is also expressed in extrarenal tissue including different cell types of the heart and the vasculature [3]. This understanding has subsequently triggered intense research on the molecular basis of MR activity in the cardiovascular system. The MR is a member of the nuclear receptor (NR) family, which consists of different DNA-binding transcription factors [4]. As a ligand-activated transcription factor, MR controls the expression of its target genes. Despite increasing evidence for rapid, non-genomic effects of MR, regulation of gene expression is still regarded as a key feature of MR action. The MR holds a unique position among steroid-activated nuclear receptors as it binds two ligands, aldosterone as the main ligand as well as cortisol (corticosterone in rodents) with similar affinity. Indeed, progesterone which acts as an antagonist at the human MR [5] and, according to recent studies, has also activating properties at chicken and zebrafish MR [6] could also be seen as a third ligand to the MR. Despite their diverse range of action, nuclear receptors share a common, highly conserved structure [7]. A ligand-induced conformational change of the ligand-binding domain (LDB) leads to the activation of the receptor. Upon translocation into the nucleus, NR modulates transcription by interacting with specific DNA sequences. Eukaryote DNA is not linear but wrapped up in a complex with histones forming the chromatin. Histones are subjected to a variety of reversible post-translational modifications, which, in turn, can change chromatin density, accessibility and high-order chromatin structure and thereby determine transcription factor binding and gene expression [8].

Epigenetics is an emerging topic in cardiovascular research. The heart and the vasculature are composed of numerous different cell types including cardiac myocytes, endothelial cells, vascular smooth muscle cells, fibroblasts, immune cells and others [9]. These different cell types show marked heterogeneity in their specific transcriptomes [10, 11, 12, 13]. Transcriptome analyses of different cell types of the heart revealed transcriptional changes during development and disease [12, 13], and these changes were associated with distinct alterations in the epigenome. For example, dysregulation of histone modifications or DNA methylation has been linked to numerous diseases of the cardiovascular system, such as atherosclerosis [14, 15, 16], hypertension [17, 18] or heart failure [19, 20, 21, 22]. Based on these findings pharmacological targeting of epigenetic modifiers has been proposed for treatment of cardiovascular disease and successfully tested in preclinical models [23, 24].

Epigenetic modifications, such as histone modifications or DNA methylation, have been identified as decisive regulators of transcription factor activity, as chromatin compaction determines the cell-specific accessibility of DNA [4]. Vice versa, NR can alter the chromatin structure through recruitment of cofactors, which act as chromatin remodelers [25]. Chromatin immunoprecipitation (ChIP) assays with subsequent deep sequencing represent a powerful technique for genome-wide analysis of histone modifications or other DNA-associated proteins [26]. The combination of different histone modifications, often referred to as the histone code, gives information on proximal and distal regulatory DNA elements, including promoters and enhancers. Promoters are often located in close proximity to the transcription start site (TSS) and associated with monomethylation of histone 3 at lysin 4 (H3K4me1), while enhancers are usually distal to TSS and marked by trimethylation of H3K4 (H3K4me3). Active promoter or enhancer sites are marked by acetylation of histone 3 at lysin 27 (H3K27ac); in contrast, H3K9me3 and H3K27me3 mark heterochromatic or repressed regions [27]. Epigenetic modifications are reversible, being recognised, established or removed by reader, writer and eraser proteins. For example, acetylation of histones is regulated by two counteracting enzymes which add (histone acetyltransferases, HAT) acetyl groups to lysine residues or remove them (histone deacetylases HDAC) [28].

DNA methylation of CpGs is the only known epigenetic mechanism directly targeting the DNA and plays an important role in gene silencing when being recognised by reader proteins such as methyl-CpG-binding protein 2 (MeCP2) that act as transcriptional repressors [29]. DNA methylation is established and maintained during mitosis by DNA methyltransferases (DNMT) [29]. Oxidation of methylcytosines to hydroxylmethylcytosines, which is an intermediate step towards demethylation, is mediated by members of the ten-eleven translocation (TET) enzyme family. This occurs predominantly in promoter and enhancer regions with low CpG density, resulting in low methylated regions and can be used to identify active regulatory regions [29, 30]. CpG-rich regions, also referred to as CpG islands, in the promoter of constitutively active genes are typically unmethylated [29]. This allows to use DNA methylation as a stable mark of cell lineage during development [31]. Analysis of the DNA methylome of murine cardiomyocytes revealed distinct DNA methylation pattern during cardiomyocyte development and disease [32]. Demethylation of cardiac gene bodies correlated with active histone marks and increased gene expression. Interestingly, by comparison of the DNA methylome of healthy and failing cardiomyocytes, the DNA methylation pattern of failing cardiomyocytes was bearing a partial resemblance to foetal cardiomyocytes; however, changes were not major [32]. A similar result could be observed in human failing cardiac myocytes. Pathological gene expression in heart failure was accompanied by changes in active histone marks, whereas the DNA methylation pattern remained mostly the same [33]. Similarly, changes in the transcriptome of cardiac myocytes following myocardial infarction were accompanied by altered accessibility of chromatin [12].

Given the important role of epigenetics in transcriptional regulation, interaction of MR with epigenetic modifications; with epigenetic reader, writer or eraser proteins; or with other transcription factors might control the cell type-specific impact of MR on gene expression and function. In this review article, we will summarise what is known about MR-dependent gene expression, epigenetic mechanisms and their interaction with MR in cardiovascular cells.

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2. Impact of aldosterone and MR on gene expression in the cardiovascular system

A series of experimental studies during the past years revealed distinct MR functions in cardiac myocytes, fibroblasts, endothelial cells, vascular smooth muscle cells and immune cells [3, 34, 35]. These studies provided evidence that the beneficial effect of MR antagonists in heart failure is directly related to MR in cardiovascular cells and independent from MR in renal epithelial cells. Several attempts have been made to understand the downstream signalling events following MR activation and to identify direct MR target genes in different cells or tissues of the cardiovascular system.

Early studies on cultured fibroblasts revealed an upregulation of collagen by aldosterone [36, 37] and by this suggested MR-dependent gene expression in cardiovascular cells. Later studies applied microarray or RNA-sequencing techniques to systematically detect MR-responsive genes. Similar to fibroblasts, aldosterone induced the expression of collagen types I and III in cultured smooth muscle cells from the coronary artery [38]. In mouse aorta, aldosterone regulated the expression of genes related to vascular function, such as oxidative stress, extracellular matrix and angiogenesis [39]. Treatment of EAhy926 endothelial cells expressing MR after retroviral transfection with aldosterone leads to regulation of only 17 transcripts [40]. In contrast, 133 genes were found up- or downregulated by aldosterone in human umbilical vein endothelial cells with naïve MR expression but not after MR knockdown [41]. These genes were associated leukocyte migration and angiogenesis. Interestingly, aldosterone treatment had opposing effects on endothelial cell gene expression when compared to treatment with vascular endothelial cell growth factor, a potent pro-angiogenic factor [41].

In a H9C2 cardiac myocyte cell line stably expressing MR, 53 transcripts were detected to be differentially regulated after treatment with aldosterone, the majority of them being upregulated [42]. Among the upregulated transcripts were genes related to extracellular matrix deposition such as Adamts1 (A disintegrin and metalloprotease with thrombospondin motifs), Pai-1 (plasminogen-activator inhibitor 1) or Tnx (tenascin-X) [42]. Studies using selective MR or GR antagonists confirmed MR-dependent expression of these genes in H9C2 cells [43, 44]. In heart tissue from untreated mice overexpressing MR in cardiac myocytes, microarray analysis revealed 24 transcripts upregulated and 22 transcripts downregulated. Again, the expression of Adamts1 and Pai-1 was induced by MR overexpression [43]. Vice versa, MR deletion from cardiac myocytes leads to differential regulation of 158 genes in heart tissue, including upregulation of Nppa (atrial natriuretic peptide type A); however, there was no clear reduction of genes related to collagen synthesis in this study [45]. In doxorubicin-treated mice, MR deletion from cardiac myocytes prevented the repressive effect of doxorubicin on gene expression, likely by a post-transcriptional mechanism [46]. One well-investigated gene that is upregulated in heart tissue by cardiac myocyte MR overexpression or aldosterone treatment is neutrophil-gelatinase-associated lipocalin (Ngal) [47]. Interestingly, Ngal was upregulated by aldosterone in endothelial cells and vascular smooth muscle cells as well [47].

Taken together, there is an overlap of several genes that were similarly regulated by MR in different cardiovascular cells or tissues including Sgk1 [41, 42, 43, 45], Tsc22d3 [40, 41], Adamts1 [41, 42, 43], Fkbp5 [40, 41, 43], Klf9 [39, 40, 41], Ngal [47] or Per1 [41, 48, 49], indicating a common signature of MR-regulated genes. Interestingly, these genes are well-related to the pathophysiological impact of MR on fibrosis and inflammation in the cardiovascular system.

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3. Regulation of MR transcriptional activity

Transcriptional activity of MR is regulated at different levels: ligand binding, nuclear translocation, chromatin state and MR-DNA interaction. The main focus of this article will be on chromatin state and MR-DNA interaction; however, some specificities of cardiovascular cell types should be noticed: First, as MR binds to aldosterone or glucocorticoids with similar affinity, different mechanisms exist that allow ligand-specificity of MR. One of them is co-expression of 11β-hydroxysteroid dehydrogenase type 2 (11βHSD2), an enzyme converting glucocorticoids to derivates that are inactive at the MR (for review, see [50]). In the cardiovascular system, 11βHSD2 is highly expressed in endothelial cells, low expressed in cardiac myocytes and smooth muscle cells and probably absent in immune cells [51]. Second, while in most cell types unliganded MR is predominantly located at the cytoplasm and shuttles into the nucleus upon ligand binding, MR has been described to be constitutively located at the nucleus in cardiac myocytes [52]. Immunohistochemical analysis of heart tissue revealed nuclear localization of the MR, and subfractional analysis showed that the vast majority of MR was chromatin-bound irrespective of plasma aldosterone or glucocorticoid levels. The subcellular distribution depended on the balance of heat shock protein 90 expression and the synergy of two nuclear localization signals. Interestingly, transcriptional activation of chromatin-bound MR nevertheless required the presence of a ligand [52].

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4. Validation of MR-responsive genes

To further elucidate the role of MR in transcriptional regulation, it has been aimed to identify genes that are direct MR targets by proofing MR binding to a corresponding regulatory region by ChIP experiments. In a human embryonic kidney cell line (HEK293) stably transfected with myc-tagged hMR, Cnksr3 was identified as a novel MR target gene containing MR binding sites (MBS) upstream of the transcription start site using ChIP in conjunction with microarray analysis (ChIP-chip). Cnksr3 was described as highly expressed in response to aldosterone, mediating ENaC activity and thereby influencing transepithelial Na+ transport in renal collecting duct cells [53]. Ueda et al. combined ChIP with high-throughput sequencing for a genome-wide analysis of MR target genes in renal distal convoluted tubular cells and identified 1113 MR binding sites associated with 1414 genes [54]. Combining data from a microarray study 186 genes were considered to be aldosterone-responsive, showing an increase in mRNA expression levels after aldosterone stimulation and a decrease in expression by inhibitory treatment with spironolactone. Interestingly, only 25 genes showed an overlap between both assays and were thus classified as MR target genes, among those the well-known target genes Sgk1, Fkbp5 and Tsc22d3 [54]. Of note, strong enrichment of MR does not necessarily translate into increased expression of target genes. In another study, analysis of renal MR target genes revealed four commonly acknowledged target of MR signalling in renal cells such as Scnn1a, Fkbp5, Zbtb16 and Per1 and nine other genes not associated with MR signalling before [55]. MR target genes could be subcategorized according to their different kinetics of MR-dependent activation of gene expression into early, intermediate and late response genes [55]. However, molecular mechanisms of MR signalling are highly cell-specific, as distinct target genes could be found in one experiment but not reproduced in another [54, 55], whereas other MR target genes seem to be independent from tissue or cell type such as Fkbp5 or Per1 [54, 55, 56, 57].

MR binding sites seem to be widespread across the genome, an equal proportion (almost 40%) of all identified peaks were located either within introns or intergenic. Surprisingly, only 40 of all approximately 1000 MBS were found within promoter regions and 11% within enhancer regions [55]. Among the 13 genes correlating to the highest MR binding peak scores in human renal cells, LINC00963 was not regulated by MR, despite high aldosterone-induced MR recruitment. As the MR binding site was located far from the nearest TSS, the involvement of this remote MBS in transcriptional regulation of another gene through long-range chromatin interactions is possible [55, 58].

For cardiovascular cells, available studies are restricted to MR binding in the promoter region of certain target genes. Cav1.2, a voltage-gated calcium channel, could be identified as an MR target in the cardiovascular system using mutational and in silico analysis. An aldosterone-dependent recruitment of MR to the alternative cardiac Cacna1c P1-promoter was observed, subsequently regulating expression of cardiac Cav1.2 transcripts in cardiac myocytes as well as in vascular smooth muscle cells, underlining the importance of aldosterone signalling in vascular reactivity and regulation of blood pressure [59]. In a similar approach, MR-dependent regulation of Icam1 in cultured endothelial cells was demonstrated using a reporter assay with different promoter fragments [60].

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5. Mineralocorticoid receptor response elements

The canonical GRE DNA motif consists of two inverted palindromic half sites, separated by a 3 bp spacer [AGAACAnnnTGTTCT (Figure 1)] [61]. Different variations of this motif exist in human renal cells with the bases C5 and G11 remaining essential for MR binding. Strong sequence degeneration of the classic consensus motif correlated with low MR enrichment and therefore disrupted MR interaction [55]. A small percentage of 7.4% MBS contained the classic consensus MRE motif; the larger part of all identified MRE consisted of half sites or a combination out of palindromic sequences and half-MREs [55]. Of note, not all MR binding sites contain an MRE consensus motif. The majority of peaks lacked the MRE implying interaction of MR with the DNA directly by binding to specific DNA sequences different from the consensus motif, indirectly via protein–protein interactions or possibly through tethering as known for GR (Figure 1) [55, 62, 63]. Indeed, an aldosterone-dependent trans-activation of AP-1 could recently be proven in human cells, underlining this hypothesis [64]. Interestingly, all MBS in rat hippocampal tissue contained an MRE [57], suggesting that the mode of MR-DNA interaction might be cell- or tissue-specific.

Figure 1.

Proposed modes of MR-DNA interaction. Mineralocorticoid receptors can directly bind to MR response elements consisting of a 15 bp palindromic DNA sequence (A) or to composite elements when interacting with a neighbouring transcription factor (B). Indirect MR-DNA interaction can be facilitated by tethering to another transcription factor (C). MR-DNA interaction is modulated by co-regulatory transcription factors or post-translational modifications of the MR (D). MR, mineralocorticoid receptor; TF, transcription factor; CR, co-regulator; ac, acetylation; P, phosphorylation.

When analysing MRE it has to be taken into account that MR and GR share a common consensus sequence. Both receptors are simultaneously expressed in various tissues and interact with each other. For example, MR and GR are able to form homodimers as well as heterodimers in rat hippocampal tissue after acute stress challenges [56]. The binding of homodimers of the respective receptors or MR/GR heterodimers seems to be gene-specific. Using a tandem ChIP approach, it could be pointed out that MR and GR mainly bind as MR/MR and GR/GR homodimers at the GRE of Sgk1, whereas MR/GR heterodimer formation could be proven for the Per1 GRE in addition to homodimers of both receptors. Notably, at the Fkbp5 GRE MR seems to bind only in a heterocomplex with GR [56], indicating distinct mechanisms controlling binding of receptors to GRE, such as local chromatin accessibility or interactions with co-regulators [65]. Interactions of MR/GR heterodimers with the Per1 promoter in response to aldosterone or cortisol stimulation could also be detected in a human renal cell line [49]. In an extensive time-course ChIP-qPCR study, the authors provide evidence for different dynamics in MR or GR recruitment to the promoter region of a given target gene. MR recruitment kinetics onto the Per1 promoter was ligand-dependent. Aldosterone induces a distinct kinetic pattern differing from MR-GR recruitment kinetics [49], suggesting different dynamics as mechanisms for receptor selectivity. MR/GR heterodimer show distinct dissociating rates differing from MR/MR or GR/GR homodimers [66], resulting in a stronger GRE binding and a synergistic effect on controlling transcriptional activity of each receptor [49, 56]. However, contrasting results have been reported. MR/GR heterodimers either enhanced [56] or inhibited [67] transcription of given target genes when compared to respective homodimers. In cardiac myocytes, Per1 was upregulated by both cortisol and aldosterone. The impact of aldosterone was enhanced in the presence of the CLOCK transcription factor, suggesting a cooperative effect of both transcription factors on Per1 expression [48]. Meinel et al. demonstrated an interaction of MR with the transcription factor specificity protein 1 (SP1) leading to the binding of an alternative MRE in the promoter region of epidermal growth factor receptor (EGFR) gene. The SP-1-dependent transactivation of EGFR through MR could also be demonstrated in cultured smooth vascular cells [68].

Comparison of GR-ChIP data with MR-ChIP data from rat hippocampal tissue revealed 918 MR-specific binding sites, 1450 GR-specific and 475 binding sites shared by MR and GR, all containing the GRE motif [57]. In all MR-exclusive binding sites, an additional motif, corresponding to the Atoh1 binding sequence, was present, and the protein was not expressed in hippocampal tissue. However, in Atoh1 belonging to the basic helix–loop–helix (bHLH) family of transcription factors, the brain-specific NeuroD family members could be identified as potential candidates for interaction with MR, thus ensuring MR specificity at MR-exclusive binding sites [57]. Different studies point at a role of differences in the nucleotide sequence of GREs in mediating distinct transcriptional activity of MR and GR [56, 59, 68], as some GRE do not enhance binding of the receptors [56], other GRE sequences favouring MR binding [69] or exclusively binding MR [68]. The ability to bind negative glucocorticoid response elements (nGRE) and therefore repressing transcription of given target genes is restricted to GR signalling and not shared with other steroid receptors [70]. Despite having a common ancestral with the capacity of binding nGRE, the ability was lost in the MR due to different mutations at independent timepoints and enhanced in the GR lineage, resulting and contributing to the capability of MR and GR to show specific and distinct transcriptional signatures even though being highly homologous. Nevertheless, repressing effects on transcriptional activities are not unique for GR as MR are likewise able to trans-repress NFκB signalling through tethering effects without interfering with DNA binding of the complex, putting an interesting angle to the pro- and antiinflammatory effects of MR and GR. However, trans-repressing effects of MR are notably weaker than those of GR [64]. Of note, in addition to the beforementioned activating protein-protein interactions of MR on inflammatory AP-1 signalling, suppressing effects on AP-1 activities in a DNA-sequence-specific manner—and therefore target gene-specific—could also be elucidated, stressing out the necessity of identifying cell type-specific target genes of MR in order to dissect augmenting effects of MR from repressing effects for the development of potential new MR antagonists [64].

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6. Co-regulators of MR activity

MR transcriptional activity in the nucleus is finely controlled by a variety of different mechanisms, including the recruitment of co-regulators, a heterogeneous group of non-receptor proteins (Figure 1) [71]. Co-regulators modulate the transcriptional activity of the receptor by either acting as coactivators or as corepressors [72]. They predominantly interact at specific regions in the NTD and at the LBD. The NTD represents the least conserved region across the steroid receptor family and thereby harbouring most potential for differential recruitment of co-regulators [73]. The LDB is conserved between different species and harbours a ligand-dependent activation function site (AF-2), which is exposed upon conformational changes induced by ligand binding of the receptor [74]. AF-2 as a docking platform is essential for co-regulator binding. Many co-regulator molecules interact via an LxxLL (L stands for a leucine, x for any other amino acid) motif with the AF-2 region [50], e.g. the first identified and well-characterised NR co-regulator steroid receptor coactivator-1 (SRC-1) [73]. Among the over 400 putative co-regulators discovered in screening assays, a few MR-specific interaction partners could be characterised such as the elongation factor eleven-nineteen lysine-rich leukaemia (ELL). ELL is able to differentially regulate MR and GR, selectively enhancing MR transcriptional activity and repressing GR-mediated transactivation [75]. GEMIN4 represents an MR corepressor, attenuating MR transcriptional activity in a cell- and gene-specific manner, as a repressive effect could be demonstrated in human embryonic kidney cells but not in a rat cardiomyocyte cell line [76]. However, GEMIN4 actions are not restricted to MR, leaving NF-YC as the only described MR-specific corepressor [77]. Just recently, a specific MR cofactor modulation has been proposed as a molecular mechanism for the differential antifibrotic properties of the novel nonsteroidal MR antagonist finerenone when compared to steroidal MR antagonists [78].

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7. Post-translational modification of the MR

Post-translational modifications such as phosphorylation, ubiquitination, sumoylation or acetylation are described to influence MR transactivation [79]. Phosphorylation of MR has contrasting effects, as it has reported early that phosphorylation of MR is necessary for aldosterone binding and enhancing the DNA-binding ability of MR [80, 81]. On the other hand, phosphorylation of MR on serine and threonine residues mediated by cyclin-dependent kinase 5 (CDK5) was shown to attenuate MR transcriptional activity, whereas nuclear receptor accumulation was not altered, suggesting impaired interaction of MR with co-regulators [82]. Recently, the ubiquitously expressed casein kinase 2 (CK2) was identified as a positive modulator of MR transcriptional activity by direct phosphorylation of the receptor and potentially by changing the phosphorylation status of other MR-co-regulators [83]. Interestingly, phosphorylation of MR is also implied as a cell type-specific mechanism, modulating MR activity. Hyperkalaemia was found to increase MR phosphorylation at S843 and subsequently prevent ligand-binding and receptor activation, a phosphorylation site specific in renal intercalated cells [84]. Intriguingly, the phosphorylation of MR can also regulate the ubiquitylation state and the subsequent degradation of the protein [85].

The epigenetic writer proteins HDACs are generally perceived as corepressors of nuclear receptors [86]. The attenuating effects on gene transcription of the earliest described corepressors, nuclear receptor corepressor (NCoR) and silencing mediator of retinoid and thyroid receptor corepressor (SMRT) rely on the subsequent recruitment of HDACs [72]. Different studies could reveal that increased acetylation of MR, induced by HDAC inhibition, interferes with MR recruitment onto the DNA and attenuates transactivation of MR target genes [87, 88]. HDAC3 is acting as a coactivator in this context, as deacetylation of MR in the hinge region restores transcriptional activities of the receptor [88]. The treatment with HDAC inhibitors has also been linked to reduced antifibrotic effects in DOCA-salt-induced hypertensive rats and decreased expression of inflammatory markers in spontaneously hypertensive rats [17, 88, 89].

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8. Summary

In summary, the distinct biological effects of MR in different cardiovascular cells are associated with changes in gene expression. Epigenetic modifications and modifying enzymes have been identified as crucial regulators of gene expression and cellular function in the cardiovascular system; however, presently available data on MR-dependent gene expression in the cardiovascular system is predominantly derived from experiments on cultured cells, in some cases after artificial overexpression of the MR, or tissue analysis. Analyses of complex tissues consisting of a dynamically changing mixture of multiple cell types can lead to ambiguous results. To date there is no ChIP-seq data published describing genome-wide MR-DNA interactions in cardiovascular cells. Studies in renal epithelial cells or brain tissue indicate that MR-DNA interaction can occur in promoter regions as well as at distal enhancer sites, but it remains speculative whether the insights from renal epithelial cells can be applied to the cardiovascular system as well.

This implies the necessity to perform cell type-specific studies from primary cardiovascular cells in homeostasis and different states of disease in order to identify distinct changes in gene expression and (epigenetic) mechanisms regulating MR activity in a given cell type (Figure 2). Utilisation of cell type-specific bulk or single-cell RNA-sequencing as well as integrated analysis of locus-specific histone modifications and DNA methylation, spatial organisation of the chromatin, MR-DNA binding and MR post-translational modification would allow a comprehensive insight into regulation of transcription by MR in cardiovascular cells and might lead to novel concepts for selective MR-targeting therapeutics.

Figure 2.

Proposed epigenetic determents of MR transcriptional activity. Transcriptional activity of the mineralocorticoid receptor is determined by DNA methylation and histone modifications governing chromatin accessibility and activation status of promoter and distal enhancer regions. Transactivation of MR-bound promoter or enhancer regions involves spatial chromatin organisation and other transcription factors. MR, mineralocorticoid receptor; TF, transcription factor; ac, acetylation; me, methylation.

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Acknowledgments

This publication is based upon work from the EU COST Action ADMIRE BM1301 in Aldosterone and Mineralocorticoid Receptor (MR) Physiology and Pathophysiology www.admirecosteu.com and was supported by the Else-Kröner-Fresenius-Stiftung (2016_ A163 to A. Lother).

References

  1. 1. Ponikowski P, Voors AA, Anker SD, Bueno H, Cleland JG, Coats AJ, et al. 2016 ESC guidelines for the diagnosis and treatment of acute and chronic heart failure: The task force for the diagnosis and treatment of acute and chronic heart failure of the european Society of Cardiology (ESC) developed with the special contribution of the heart failure association (HFA) of the ESC. European Heart Journal. 2016;37(27):2129-2200
  2. 2. Lother A, Hein L. Pharmacology of heart failure: From basic science to novel therapies. Pharmacology & Therapeutics. 2016;166:136-149
  3. 3. Lother A, Moser M, Bode C, Feldman RD, Hein L. Mineralocorticoids in the heart and vasculature: New insights for old hormones. Annual Review of Pharmacology and Toxicology. 2015;55:289-312
  4. 4. Gadaleta RM, Magnani L. Nuclear receptors and chromatin: An inducible couple. Journal of Molecular Endocrinology. 2014;52(2):13-0170
  5. 5. Fuller PJ. Novel interactions of the mineralocorticoid receptor. Molecular and Cellular Endocrinology. 2015;408:33-37
  6. 6. Katsu Y, Oka K, Baker ME. Evolution of human, chicken, alligator, frog, and zebrafish mineralocorticoid receptors: Allosteric influence on steroid specificity. Science Signaling. 2018;11(537)
  7. 7. Sever R, Glass CK. Signaling by nuclear receptors. Cold Spring Harbor Perspectives in Biology. 2013;5(3)
  8. 8. Kouzarides T. Chromatin modifications and their function. Cell. 2007;128(4):693-705
  9. 9. Pinto AR, Ilinykh A, Ivey MJ, Kuwabara JT, D'Antoni ML, Debuque R, et al. Revisiting cardiac cellular composition. Circulation Research. 2016;118(3):400-409
  10. 10. Preissl S, Schwaderer M, Raulf A, Hesse M, Gruning BA, Kobele C, et al. Deciphering the epigenetic code of cardiac myocyte transcription. Circulation Research. 2015;117(5):413-423
  11. 11. Lother A, Bergemann S, Deng L, Moser M, Bode C, Hein L. Cardiac endothelial cell transcriptome. Arteriosclerosis, Thrombosis, and Vascular Biology. 2018;38(3):566-574
  12. 12. Quaife-Ryan GA, Sim CB, Ziemann M, Kaspi A, Rafehi H, Ramialison M, et al. Multicellular transcriptional analysis of mammalian heart regeneration. Circulation. 2017;136(12):1123-1139
  13. 13. DeLaughter DM, Bick AG, Wakimoto H, McKean D, Gorham JM, Kathiriya IS, et al. Single-cell resolution of temporal gene expression during heart development. Developmental Cell. 2016;39(4):480-490
  14. 14. Dunn J, Qiu H, Kim S, Jjingo D, Hoffman R, Kim CW, et al. Flow-dependent epigenetic DNA methylation regulates endothelial gene expression and atherosclerosis. The Journal of Clinical Investigation. 2014;124(7):3187-3199
  15. 15. Jiang YZ, Jimenez JM, Ou K, McCormick ME, Zhang LD, Davies PF. Hemodynamic disturbed flow induces differential DNA methylation of endothelial kruppel-like factor 4 promoter in vitro and in vivo. Circulation Research. 2014;115(1):32-43
  16. 16. Zampetaki A, Zeng L, Margariti A, Xiao Q , Li H, Zhang Z, et al. Histone deacetylase 3 is critical in endothelial survival and atherosclerosis development in response to disturbed flow. Circulation. 2010;121(1):132-142
  17. 17. Cardinale JP, Sriramula S, Pariaut R, Guggilam A, Mariappan N, Elks CM, et al. HDAC inhibition attenuates inflammatory, hypertrophic, and hypertensive responses in spontaneously hypertensive rats. Hypertension. 2010;56(3):437-444
  18. 18. Kato N, Loh M, Takeuchi F, Verweij N, Wang X, Zhang W, et al. Trans-ancestry genome-wide association study identifies 12 genetic loci influencing blood pressure and implicates a role for DNA methylation. Nature Genetics. 2015;47(11):1282-1293
  19. 19. Cao DJ, Wang ZV, Battiprolu PK, Jiang N, Morales CR, Kong Y, et al. Histone deacetylase (HDAC) inhibitors attenuate cardiac hypertrophy by suppressing autophagy. Proceedings of the National Academy of Sciences of the United States of America. 2011;108(10):4123-4128
  20. 20. Aune SE, Herr DJ, Mani SK, Menick DR. Selective inhibition of class I but not class IIb histone deacetylases exerts cardiac protection from ischemia reperfusion. Journal of Molecular and Cellular Cardiology. 2014;72:138-145
  21. 21. Gusterson RJ, Jazrawi E, Adcock IM, Latchman DS. The transcriptional co-activators CREB-binding protein (CBP) and p300 play a critical role in cardiac hypertrophy that is dependent on their histone acetyltransferase activity. The Journal of Biological Chemistry. 2003;278(9):6838-6847
  22. 22. Zhang CL, McKinsey TA, Chang S, Antos CL, Hill JA, Olson EN. Class II histone deacetylases act as signal-responsive repressors of cardiac hypertrophy. Cell. 2002;110(4):479-488
  23. 23. van der Harst P, de Windt LJ, Chambers JC. Translational perspective on epigenetics in cardiovascular disease. Journal of the American College of Cardiology. 2017;70(5):590-606
  24. 24. McKinsey TA. Therapeutic potential for HDAC inhibitors in the heart. Annual Review of Pharmacology and Toxicology. 2012;52:303-319
  25. 25. Biddie SC, John S. Minireview: Conversing with chromatin: The language of nuclear receptors. Molecular Endocrinology. 2014;28(1):3-15
  26. 26. Pepke S, Wold B, Mortazavi A. Computation for ChIP-seq and RNA-seq studies. Nature Methods. 2009;6(11 Suppl):S22-S32
  27. 27. Shlyueva D, Stampfel G, Stark A. Transcriptional enhancers: From properties to genome-wide predictions. Nature Reviews Genetics. 2014;15(4):272-286
  28. 28. Stratton MS, McKinsey TA. Acetyl-lysine erasers and readers in the control of pulmonary hypertension and right ventricular hypertrophy. Biochemistry and Cell Biology. 2015;93(2):149-157
  29. 29. Smith ZD, Meissner A. DNA methylation: Roles in mammalian development. Nature Reviews Genetics. 2013;14(3):204-220
  30. 30. Burger L, Gaidatzis D, Schubeler D, Stadler MB. Identification of active regulatory regions from DNA methylation data. Nucleic Acids Research. 2013;41(16):e155
  31. 31. Jones PA. Functions of DNA methylation: Islands, start sites, gene bodies and beyond. Nature Reviews Genetics. 2012;13(7):484-492
  32. 32. Gilsbach R, Preissl S, Gruning BA, Schnick T, Burger L, Benes V, et al. Dynamic DNA methylation orchestrates cardiomyocyte development, maturation and disease. Nature Communications. 2014;5(5288)
  33. 33. Gilsbach R, Schwaderer M, Preissl S, Gruning BA, Kranzhofer D, Schneider P, et al. Distinct epigenetic programs regulate cardiac myocyte development and disease in the human heart in vivo. Nature Communications. 2018;9(1):017-02762
  34. 34. Cole TJ, Young MJ. 30 Years of the mineralocorticoid receptor: Mineralocorticoid receptor null mice: Informing cell-type-specific roles. The Journal of Endocrinology. 2017;234(1):T83-T92
  35. 35. Lother A, Hein L. Vascular mineralocorticoid receptors: Linking risk factors, hypertension, and heart disease. Hypertension. 2016;68(1):6-10
  36. 36. Brilla CG, Zhou G, Matsubara L, Weber KT. Collagen metabolism in cultured adult rat cardiac fibroblasts: Response to angiotensin II and aldosterone. Journal of Molecular and Cellular Cardiology. 1994;26(7):809-820
  37. 37. Bunda S, Liu P, Wang Y, Liu K, Hinek A. Aldosterone induces elastin production in cardiac fibroblasts through activation of insulin-like growth factor-I receptors in a mineralocorticoid receptor-independent manner. The American Journal of Pathology. 2007;171(3):809-819
  38. 38. Jaffe IZ, Mendelsohn ME. Angiotensin II and aldosterone regulate gene transcription via functional mineralocortocoid receptors in human coronary artery smooth muscle cells. Circulation Research. 2005;96(6):643-650
  39. 39. Newfell BG, Iyer LK, Mohammad NN, McGraw AP, Ehsan A, Rosano G, et al. Aldosterone regulates vascular gene transcription via oxidative stress-dependent and -independent pathways. Arteriosclerosis, Thrombosis, and Vascular Biology. 2011;31(8):1871-1880
  40. 40. Sekizawa N, Yoshimoto T, Hayakawa E, Suzuki N, Sugiyama T, Hirata Y. Transcriptome analysis of aldosterone-regulated genes in human vascular endothelial cell lines stably expressing mineralocorticoid receptor. Molecular and Cellular Endocrinology. 2011;341(1-2):78-88
  41. 41. Lother A, Deng L, Huck M, Fürst D, Kowalski J, Esser JS, et al. Endothelial cell mineralocorticoid receptors oppose VEGF-induced gene expression and angiogenesis. The Journal of Endocrinology. 2019;240(1):15-26
  42. 42. Fejes-Toth G, Naray-Fejes-Toth A. Early aldosterone-regulated genes in cardiomyocytes: Clues to cardiac remodeling? Endocrinology. 2007;148(4):1502-1510
  43. 43. Latouche C, Sainte-Marie Y, Steenman M, Castro Chaves P, Naray-Fejes-Toth A, Fejes-Toth G, et al. Molecular signature of mineralocorticoid receptor signaling in cardiomyocytes: From cultured cells to mouse heart. Endocrinology. 2010;151(9):4467-4476
  44. 44. Grune J, Beyhoff N, Smeir E, Chudek R, Blumrich A, Ban Z, et al. Selective mineralocorticoid receptor cofactor modulation as molecular basis for finerenone's antifibrotic activity. Hypertension. 2018;71(4):599-608
  45. 45. Lother A, Berger S, Gilsbach R, Rosner S, Ecke A, Barreto F, et al. Ablation of mineralocorticoid receptors in myocytes but not in fibroblasts preserves cardiac function. Hypertension. 2011;57(4):746-754
  46. 46. Lother A, Bergemann S, Kowalski J, Huck M, Gilsbach R, Bode C, et al. Inhibition of the cardiac myocyte mineralocorticoid receptor ameliorates doxorubicin-induced cardiotoxicity. Cardiovascular Research. 2018;114(2):282-290
  47. 47. Latouche C, El Moghrabi S, Messaoudi S, Nguyen Dinh Cat A, Hernandez-Diaz I, Alvarez de la Rosa D, et al. Neutrophil gelatinase-associated lipocalin is a novel mineralocorticoid target in the cardiovascular system. Hypertension. 2012;59(5):966-972
  48. 48. Fletcher EK, Morgan J, Kennaway DR, Bienvenu LA, Rickard AJ, Delbridge LMD, et al. Deoxycorticosterone/salt-mediated cardiac inflammation and fibrosis are dependent on functional CLOCK signaling in male mice. Endocrinology. 2017;158(9):2906-2917
  49. 49. Le Billan F, Amazit L, Bleakley K, Xue QY, Pussard E, Lhadj C, et al. Corticosteroid receptors adopt distinct cyclical transcriptional signatures. FASEB Journal: Official Publication of the Federation of American Societies for Experimental Biology. 2018;32(10):5626-5639. DOI: 10.1096/fj.201800391RR
  50. 50. Fuller PJ, Yao Y, Yang J, Young MJ. Mechanisms of ligand specificity of the mineralocorticoid receptor. The Journal of Endocrinology. 2012;213(1):15-24
  51. 51. Chapman K, Holmes M, Seckl J. 11beta-hydroxysteroid dehydrogenases: Intracellular gate-keepers of tissue glucocorticoid action. Physiological Reviews. 2013;93(3):1139-1206
  52. 52. Hernandez-Diaz I, Giraldez T, Arnau MR, Smits VA, Jaisser F, Farman N, et al. The mineralocorticoid receptor is a constitutive nuclear factor in cardiomyocytes due to hyperactive nuclear localization signals. Endocrinology. 2010;151(8):3888-3899
  53. 53. Ziera T, Irlbacher H, Fromm A, Latouche C, Krug SM, Fromm M, et al. Cnksr3 is a direct mineralocorticoid receptor target gene and plays a key role in the regulation of the epithelial sodium channel. The FASEB Journal. 2009;23(11):3936-3946
  54. 54. Ueda K, Fujiki K, Shirahige K, Gomez-Sanchez CE, Fujita T, Nangaku M, et al. Genome-wide analysis of murine renal distal convoluted tubular cells for the target genes of mineralocorticoid receptor. Biochemical and Biophysical Research Communications. 2014;445(1):132-137
  55. 55. Le Billan F, Khan JA, Lamribet K, Viengchareun S, Bouligand J, Fagart J, et al. Cistrome of the aldosterone-activated mineralocorticoid receptor in human renal cells. FASEB Journal: Official Publication of the Federation of American Societies for Experimental Biology. 2015;29(9):3977-3989
  56. 56. Mifsud KR, Reul JM. Acute stress enhances heterodimerization and binding of corticosteroid receptors at glucocorticoid target genes in the hippocampus. Proceedings of the National Academy of Sciences of the United States of America. 2016;113(40):11336-11341
  57. 57. van Weert L, Buurstede JC, Mahfouz A, Braakhuis PSM, Polman JAE, Sips HCM, et al. NeuroD factors discriminate mineralocorticoid from glucocorticoid receptor DNA binding in the male rat brain. Endocrinology. 2017;158(5):1511-1522
  58. 58. Mifsud B, Tavares-Cadete F, Young AN, Sugar R, Schoenfelder S, Ferreira L, et al. Mapping long-range promoter contacts in human cells with high-resolution capture Hi-C. Nature Genetics. 2015;47(6):598-606
  59. 59. Mesquita TR, Auguste G, Falcon D, Ruiz-Hurtado G, Salazar-Enciso R, Sabourin J, et al. Specific activation of the alternative cardiac promoter of Cacna1c by the mineralocorticoid receptor. Circulation Research. 2018;122(7):e49-e61
  60. 60. Marzolla V, Armani A, Mammi C, Moss ME, Pagliarini V, Pontecorvo L, et al. Essential role of ICAM-1 in aldosterone-induced atherosclerosis. International Journal of Cardiology. 2017;232:233-242
  61. 61. Del Monaco M, Covello SP, Kennedy SH, Gilinger G, Litwack G, Uitto J. Identification of novel glucocorticoid-response elements in human elastin promoter and demonstration of nucleotide sequence specificity of the receptor binding. The Journal of Investigative Dermatology. 1997;108(6):938-942
  62. 62. Starick SR, Ibn-Salem J, Jurk M, Hernandez C, Love MI, Chung HR, et al. ChIP-exo signal associated with DNA-binding motifs provides insight into the genomic binding of the glucocorticoid receptor and cooperating transcription factors. Genome Research. 2015;25(6):825-835
  63. 63. Ratman D, Vanden Berghe W, Dejager L, Libert C, Tavernier J, Beck IM, et al. How glucocorticoid receptors modulate the activity of other transcription factors: A scope beyond tethering. Molecular and Cellular Endocrinology. 2013;380(1-2):41-54
  64. 64. Dougherty EJ, Elinoff JM, Ferreyra GA, Hou A, Cai R, Sun J, et al. Mineralocorticoid receptor (MR) trans-activation of inflammatory AP-1 signaling: Dependence on DNA sequence, MR conformation, and AP-1 family member expression. The Journal of Biological Chemistry. 2016;291(45):23628-23644
  65. 65. Mifsud KR, Reul J. Mineralocorticoid and glucocorticoid receptor-mediated control of genomic responses to stress in the brain. Stress 2018;21(5):389-402
  66. 66. Trapp T, Rupprecht R, Castren M, Reul JM, Holsboer F. Heterodimerization between mineralocorticoid and glucocorticoid receptor: A new principle of glucocorticoid action in the CNS. Neuron. 1994;13(6):1457-1462
  67. 67. Ou XM, Storring JM, Kushwaha N, Albert PR. Heterodimerization of mineralocorticoid and glucocorticoid receptors at a novel negative response element of the 5-HT1A receptor gene. The Journal of Biological Chemistry. 2001;276(17):14299-14307
  68. 68. Meinel S, Ruhs S, Schumann K, Stratz N, Trenkmann K, Schreier B, et al. Mineralocorticoid receptor interaction with SP1 generates a new response element for pathophysiologically relevant gene expression. Nucleic Acids Research. 2013;41(17):8045-8060
  69. 69. Kolla V, Robertson NM, Litwack G. Identification of a mineralocorticoid/glucocorticoid response element in the human Na/K ATPase alpha1 gene promoter. Biochemical and Biophysical Research Communications. 1999;266(1):5-14
  70. 70. Hudson WH, Kossmann BR, de Vera IM, Chuo SW, Weikum ER, Eick GN, et al. Distal substitutions drive divergent DNA specificity among paralogous transcription factors through subdivision of conformational space. Proceedings of the National Academy of Sciences of the United States of America. 2016;113(2):326-331
  71. 71. Yang J, Young MJ. The mineralocorticoid receptor and its coregulators. Journal of Molecular Endocrinology. 2009;43(2):53-64
  72. 72. Yang J, Fuller PJ. Interactions of the mineralocorticoid receptor—Within and without. Molecular and Cellular Endocrinology. 2012;350(2):196-205
  73. 73. Fuller PJ, Yang J, Young MJ. 30 Years of the mineralocorticoid receptor: Coregulators as mediators of mineralocorticoid receptor signalling diversity. The Journal of Endocrinology. 2017;234(1):T23-T34
  74. 74. Gomez-Sanchez E, Gomez-Sanchez CE. The multifaceted mineralocorticoid receptor. Comprehensive Physiology. 2014;4(3):965-994
  75. 75. Pascual-Le Tallec L, Simone F, Viengchareun S, Meduri G, Thirman MJ, Lombes M. The elongation factor ELL (eleven-nineteen lysine-rich leukemia) is a selective coregulator for steroid receptor functions. Molecular Endocrinology. 2005;19(5):1158-1169
  76. 76. Yang J, Fuller PJ, Morgan J, Shibata H, Clyne CD, Young MJ. GEMIN4 functions as a coregulator of the mineralocorticoid receptor. Journal of Molecular Endocrinology. 2015;54(2):149-160
  77. 77. Murai-Takeda A, Shibata H, Kurihara I, Kobayashi S, Yokota K, Suda N, et al. NF-YC functions as a corepressor of agonist-bound mineralocorticoid receptor. The Journal of Biological Chemistry. 2010;285(11):8084-8093
  78. 78. Grune J, Beyhoff N, Smeir E, Chudek R, Blumrich A, Ban Z, et al. Selective mineralocorticoid receptor cofactor modulation as molecular basis for finerenone's antifibrotic activity. Hypertension. 2018;71(4):599-608
  79. 79. Faresse N. Post-translational modifications of the mineralocorticoid receptor: How to dress the receptor according to the circumstances? The Journal of Steroid Biochemistry and Molecular Biology. 2014;143:334-342
  80. 80. Galigniana MD. Native rat kidney mineralocorticoid receptor is a phosphoprotein whose transformation to a DNA-binding form is induced by phosphatases. The Biochemical Journal. 1998;333(Pt 3):555-563
  81. 81. Le Moellic C, Ouvrard-Pascaud A, Capurro C, Cluzeaud F, Fay M, Jaisser F, et al. Early nongenomic events in aldosterone action in renal collecting duct cells: PKCalpha activation, mineralocorticoid receptor phosphorylation, and cross-talk with the genomic response. Journal of the American Society of Nephrology. 2004;15(5):1145-1160
  82. 82. Kino T, Jaffe H, Amin ND, Chakrabarti M, Zheng YL, Chrousos GP, et al. Cyclin-dependent kinase 5 modulates the transcriptional activity of the mineralocorticoid receptor and regulates expression of brain-derived neurotrophic factor. Molecular Endocrinology. 2010;24(5):941-952
  83. 83. Ruhs S, Stratz N, Quarch K, Masch A, Schutkowski M, Gekle M, et al. Modulation of transcriptional mineralocorticoid receptor activity by casein kinase 2. Scientific Reports. 2017;7(1):017-15418
  84. 84. Shibata S, Rinehart J, Zhang J, Moeckel G, Castaneda-Bueno M, Stiegler AL, et al. Mineralocorticoid receptor phosphorylation regulates ligand binding and renal response to volume depletion and hyperkalemia. Cell Metabolism. 2013;18(5):660-671
  85. 85. Faresse N, Vitagliano JJ, Staub O. Differential ubiquitylation of the mineralocorticoid receptor is regulated by phosphorylation. FASEB Journal: Official Publication of the Federation of American Societies for Experimental Biology. 2012;26(10):4373-4382
  86. 86. Pascual-Le Tallec L, Lombes M. The mineralocorticoid receptor: A journey exploring its diversity and specificity of action. Molecular Endocrinology. 2005;19(9):2211-2221
  87. 87. Lee HA, Lee DY, Cho HM, Kim SY, Iwasaki Y, Kim IK. Histone deacetylase inhibition attenuates transcriptional activity of mineralocorticoid receptor through its acetylation and prevents development of hypertension. Circulation Research. 2013;112(7):1004-1012
  88. 88. Kang SH, Lee HA, Lee E, Kim M, Kim I. Histone deacetylase inhibition, but not a mineralocorticoid receptor antagonist spironolactone, attenuates atypical transcription by an activating mutant MR (MRS 810L). Clinical and Experimental Pharmacology & Physiology. 2016;43(10):995-1003
  89. 89. Iyer A, Fenning A, Lim J, Le GT, Reid RC, Halili MA, et al. Antifibrotic activity of an inhibitor of histone deacetylases in DOCA-salt hypertensive rats. British Journal of Pharmacology. 2010;159(7):1408-1417

Written By

Lisa Deng, Lutz Hein and Achim Lother

Submitted: May 22nd, 2019 Reviewed: June 4th, 2019 Published: September 25th, 2019