The inflammatory bowel diseases (IBD) such as Crohn’s disease and ulcerative colitis are immunological dysfunctions of the gastrointestinal tract that develop because of multifactorial processes, including genetic predisposition, gut dysbiosis, and excessive inflammation in susceptible subjects. These pathologies affect millions of people worldwide, with substantial impact on healthcare systems and patients’ quality of life. Considering the chronic inflammation that underlies the IBD presentation, the main treatment options are related to the control of patients’ inflammatory response, through immunosuppressor and modulatory therapies. Therefore, in this chapter we reviewed the main mechanisms associated with the treatments that are aimed at suppressing mucosal immunity and the effects of corticosteroid therapies in Crohn’s disease and ulcerative colitis.
- inflammatory bowel disease
- Crohn’s disease
- ulcerative colitis
The treatment of Crohn’s disease and ulcerative colitis has central purposes such as to induce and maintain the patients’ remission, while restraining the disease’s secondary effects and improving the quality of life of the affected subjects. Pharmacological therapy against these pathologies converges on controlling the exacerbation of immune response, either with systemic agents, such as corticosteroids, azathioprine (AZA), aminosalicylates, and methotrexate, or topical anti-inflammatory drugs. Traditionally, the treatment for CD and UC follows a “step-up” approach. However, in the last years, a “top-down” strategy was implemented in IBD therapy, beginning to treat patients with biological agents, especially for more aggressive diseases . After the main control of the inflammation, biologicals can be withdrawn, and weaker immunosuppressor medicines can be used, such as AZA, aminosalicylates, or other drug alternatives for maintenance of disease remission , with different mechanisms of action, as discussed in the following section.
2. Mechanisms of action of IBD’s therapies: from corticosteroids to immunosuppressor drugs
Corticosteroids, a type of steroid hormones, are lipophilic molecules derived from cholesterol. Glucocorticoids, whose major representative is cortisol, play a role in the metabolism of lipids and carbohydrates and in the immune response, through immunosuppressive mechanisms. These hormones are synthesized by the adrenal glands in response to psychological or physiological stressful stimuli, such as excessive inflammation. The synthesis of glucocorticoids occurs after hypothalamic production of corticotropin-releasing hormone (CRH), which activates the pituitary secretion of corticotropin (ACTH) that, in turn, leads to adrenal release of cortisol, in a fine-tuned circadian rhythm .
Many of the immunosuppressive and anti-inflammatory functions of glucocorticoids occur after the binding of this hormone to the glucocorticoid receptor (GR). This molecule was described in the 1970s  and presents two isoforms of GR, GRα and GRβ, which differ in the C-terminal domain, being that the α forms the most prevalent in many human cells .
Glucocorticoids may exert their effects by non-genomic and mainly by the genomic signaling pathways . One of the first evidences on the formation of a glucocorticoid-GR complex dated from 1972 in a study, which showed that free glucocorticoids penetrate hepatoma cells and bind to a cytoplasmic receptor, forming a complex which migrates to the nucleus shortly thereafter . In the nucleus, the glucocorticoid/receptor complex binds to specific DNA sequences, named
Cortisol was first synthesized around 1937/1938 by Tadeusz Reichstein, who won the Nobel Prize about 10 years later for his work . The first use of corticosteroids as an immunosuppressive and anti-inflammatory treatment occurred in the 1940s for rheumatoid arthritis in a study by Hench et al., who showed a decrease in symptoms when patients were treated with these hormones, besides disease relapse when treatment was stopped . Since then, corticosteroids have been effective in treating other diseases, including intestinal inflammation .
Today, corticosteroid therapy is one of the most widely used and most effective drugs in the treatment of IBD, especially in acute inflammation, to induce disease remission . However, there are important limitations regarding their long-term use, because of the drug’s side effects. In line with that, despite the anti-inflammatory role in experimental colitis, budesonide worsens the general status of the mice, leading to endotoxemia and impaired epithelial repair in the gut, which are findings that could partially explain the fails in long-term glucocorticoid therapy for intestinal inflammation . In contrast, mice exposed to dextran sodium sulfate for colitis development and treated for short term with the glucocorticoid dexamethasone had decreased intestinal inflammation, with reduced expression of pro-inflammatory cytokines such as IFN-γ and IL-1, diminishment of IFN- γ-producing CD4+ T cells and augmented frequency of anti-inflammatory cytokine-producing cells such as IL-10. Moreover, the increase in the frequency of regulatory markers such as GITR, CTLA-4, PD-1, CD73, and FoxP3 in treated mice pointed to a relevant role for this short-term therapy in the induction of immune regulation , despite the long-term adverse effects of these drugs. These findings corroborate the relevance of this hormone in the regulation of mucosal immunity. In fact, regulatory T cells deficient for glucocorticoid receptor fail to control intestinal inflammatory diseases, in vivo. In addition, these knockout regulatory T cells acquire Th1 phenotype and secrete IFN-γ, with a consequent failure to inhibit the proliferation of CD4+ T cells. Then, not only the synthetic glucocorticoid is important to inflammation control, but the glucocorticoid receptor is critical for regulatory T cell functions neither .
Regarding the pivotal role of microbiota in the development of gut inflammation , it is known that the commensal intestinal bacteria may be involved in the mechanisms of action of glucocorticoid and mediate the anti-inflammatory effects of dexamethasone in the colon . Indeed, the evaluation of mucosa transcriptomics of ulcerative colitis patients pointed to a corticosteroid-response gene signature that could predict response to this therapy, together with notable changes in gut microbiota . In Crohn’s disease or ulcerative colitis, the bacteria translocation in the gut is originally restrained by local phagocytic cells such as neutrophils, which in turn may contribute to tissue damage due to their excessive inflammation triggered in an attempt to control microbial invasion. Then, the mechanisms and efficacy of corticosteroids in IBD also involve the reduction in the chemokines responsible for the recruitment of neutrophils, besides natural killer cells and activated T lymphocytes to the gut, during ulcerative colitis . There is also a decrease in adhesion and chemotaxis of these cells to the intestinal mucosa .
Although the efficacy of corticosteroid for the treatment of autoimmune and inflammatory diseases has been demonstrated, prolonged utilization of these drugs is associated with an increased risk of developing eye diseases such as glaucoma or cataract, hyperglycemia or insulin resistance, dermatological affections, and purpura . Moreover, there is an increased risk of gastrointestinal problems such as peptic ulcer with perforations, bleeding, and acute pancreatitis . The use of corticosteroids can also cause psychiatric and cognitive disorders , psychosis, and also sleep-related disorders . Moreover, because of its immunosuppressive and anti-inflammatory effects, many patients who use corticosteroids may suffer from reduced effectiveness of the immune system and are at risk for opportunistic infections .
The aminosalicylates (5-aminosalicylic acid, 5-ASA, or mesalazine) are one of the most used therapeutic choices to control mild to moderate inflammatory bowel diseases (IBD). Sulfasalazine (SASP), balsalazide, and olsalazine are prodrugs in which an azo bond is added to the structure to connect the 5-ASA moiety to carrier molecules. Sulfasalazine was the first aminosalicylate used for IBD and provided the basis for this class of medications. It was developed in the late 1930s, by the Swedish physician Nanna Svartz for the treatment of patients with rheumatic polyarthritis. Interestingly, some of the patients who were treated with SASP had ulcerative colitis too, and, surprisingly, their condition became more stable . Therefore, SASP was soon being chosen as a treatment option for patients with IBD. Later, metabolic studies revealed that when this drug reaches the colon, the azo bond is cleaved by bacterial azoreductase, liberating 5-ASA and sulfapyridine, which is responsible for most of the usual adverse effects related to sulfasalazine . In fact, in earlier elegant studies from the 70–80 decades, 5-ASA was shown to be the therapeutically active compound in sulfasalazine, while sulfapyridine plays a role as a carrier molecule, not required for clinical efficacy of the drug. These works were very important to drive the development of pure 5-ASA preparations useful for the treatment of IBD. Therefore, since aminosalicylates are among the most common therapeutic agents for these diseases, many studies have been performed in an attempt to discover the mechanisms of action of these drugs in the gut inflammation.
When the initial triggers break the mucosal tolerance in IBD, there is a vast infiltration of leukocytes in the intestine, with consequent production of soluble mediators of inflammation such as cytokines, chemokines, and eicosanoids. Some of these mediators are significantly elevated in the inflamed mucosa of IBD individuals, corroborating the pathogenesis of the disease, due to their pro-inflammatory impacts upon the bowel. In fact, the increased levels of seven eicosanoids, including prostaglandin (PG)E2, PGD2, thromboxane (TBX)B2, 5-HETE, 11-HETE, 12-HETE, and 15-HETE are found on mucosal biopsies from patients with ulcerative colitis, being correlated with the severity of inflammation . Similarly, prostacyclin I2, PGE2, and TBXA2 are increased in cultured gut biopsies of active colitis patients, and, notably, the levels of these inflammatory mediators are reduced in the presence of 5-ASA. In fact, the activated leucocytes in patients’ mucosa release toxic reactive oxygen metabolites and harmful eicosanoids such as LTB4, which seems to be an essential chemotactic agent in these diseases . Therefore, considering the therapy mechanisms, sulfasalazine can effectively repress LTB4 and 5-HETE production by human polymorphonuclear leukocytes , while sulfasalazine, 5-ASA, and olsalazine (a 5-ASA dimer) potently inhibit colonic macrophage chemotaxis toward LTB4 . These data suggested that one of the mechanisms of action of these drugs could be the inhibition of eicosanoids and then it is plausible to infer that the therapeutic inhibition of LOX or COX pathways could be useful in both ulcerative colitis and Crohn’s disease.
Platelet-activating factor (PAF) is another phospholipid mediator released early in inflammation by a diversity of cell types, playing important roles in inflammatory conditions, including IBD. In active Crohn’s disease, PAF levels are significantly higher and more elevated in inflamed than in noninflamed areas . In parallel, PAF is increased in the colon and ileum from Crohn’s disease patients , while biopsies of inflamed areas taken from ulcerative colitis subjects produce PAF spontaneously . In this context, sulfasalazine and 5-ASA greatly reduce the synthesis of this mediator when incubated with mucosal biopsy specimens, indicating that these drugs exert beneficial effects in the inhibition of inflammation induced by PAF .
Chronic gut inflammation is also related to enhanced production of reactive metabolites of oxygen and nitrogen, since both reactive oxygen species (ROS) and nitric oxide (NO) deeply modulate the inflammatory responses. The generation of these reactive species can be attenuated by sulfasalazine, as it inhibits the binding of N-formyl-methionyl-leucyl-phenyl-alanine (fMLP) to its receptor on neutrophils  and also the superoxide production . Interestingly, olsalazine and sulfasalazine are both potent inhibitors of superoxide production and degranulation of human neutrophils stimulated with fMLP, in contrast to 5-ASA and sulfapyridine, which do not have this ability . On the other hand, 5-ASA can be converted to the oxidation products salicylate and gentisate, when the drug is incubated with activated human mononuclear cells and neutrophils, indicating that 5-ASA may scavenge toxic oxygen and nitrogen metabolites . Similarly, evidences from an in vivo study pointed once more to a scavenge role of sulfasalazine as a mechanism of action, thus reducing experimental intestinal inflammation induced by acetic acid . In humans, 5-ASA oxidation products can be found in the stools of IBD patients using sulfasalazine, suggesting that this drug indeed plays a role as scavenger for ROS and NO in these diseases .
A series of studies have demonstrated that sulfasalazine and its metabolites, at clinically relevant concentrations, also inhibit the release of cytokines produced by multiple cell types, including T cell mediators such as interleukin (IL)-2  and those produced by monocytes or macrophages, like IL-12 , IL-1β, and tumor necrosis factor (TNF) . Precisely, how sulfasalazine represses the release of cytokines has not been fully elucidated yet, but some studies have shown, for example, that sulfasalazine inhibits TNF expression in macrophages by inducing apoptosis  or inhibiting nuclear factor kappa B (NF-KB), a transcription factor crucial to the production of inflammatory mediators . In the last years, the effects of sulfasalazine have been extensively studied in experimental models of intestinal inflammation. The chemically treated animals develop inflammation signs similar to those of human IBD, such as severe bloody diarrhea, body weight loss, colon length shortening, and gut pathological changes. In general, sulfasalazine treatment is able to reduce these signs and the colitis severity. Moreover, the drug significantly decreases the levels of inflammatory markers such as ROS , NF-KB, COX-2 , IL-6, TNF, IL-1 , NO , inducible nitric oxide synthase (iNOS) , myeloperoxidase (MPO) , monocyte chemoattractant protein-1 (MCP-1) , intercellular adhesion molecule-1 (ICAM-1) , and LTB4 , which are frequently overexpressed in IBD and widely known to be involved in chronic inflammatory disorders. Taken together, these experimental findings pointed to different mechanisms of action of sulfasalazine in the control of innate inflammatory reactions in gut mucosa, with outstanding relevance to the disease outcome.
Regarding adaptive and regulatory responses, it is known that a close relationship exists between colonic inflammation and T helper 1 (Th1) or Th17 immune reactions, which are related to the severity of inflammation in both human and experimental IBD . In accordance, in a colitis model, mesalazine is able to inhibit Th1 and Th17 responses in contrast to an induction of regulatory immune profile, as observed by the disease amelioration, reduced expression neutrophil activity, IL-1β, TNF, IL-12, IFNγ, IL-17, IL-6, and RORγt, along with an augment in the suppressive cytokines IL-10 and TGF-β and in the transcription factor Foxp3 . These data indicate that another mechanism of action of aminosalicylate drugs could be by decreasing pathogenic while increasing regulatory responses in intestinal inflammation.
The peroxisome proliferator-activated receptor ligand-γ (PPARγ) plays a significant role in the immune control through its capacity to repress the expression of inflammatory cytokines and induce the differentiation of leukocytes toward anti-inflammatory phenotypes. Importantly, by using experimental approaches with epithelial colon cell lines and human biopsies, Rousseaux et al. showed that 5-ASA activates PPARγ, pointing to the receptor as an important drug’s target for the control of intestinal inflammation . In line with that, regulatory T cells (Tregs) play an indispensable role in suppressing exacerbated inflammatory immune responses that can be harmful to the host, such as in IBD . Recently, Oh-Oka et al. proposed a new anti-inflammatory mechanism for mesalamine (5-ASA) in colitis, involving colonic Tregs. The oral treatment with this drug leads to the accumulation of Tregs in the colon lamina propria associated with increased levels of the active form of the anti-inflammatory cytokine TGF-β. These alterations attributed to mesalamine are dependent on the activation of aryl hydrocarbon receptor (AhR), a transcription factor that regulates several immune processes, including Treg activation and differentiation .
Altogether, these studies show that aminosalicylates play an important role in the regulation of IBD responses.
One of the most prescribed strategies for IBD therapy is the use of thiopurines, mainly azathioprine (AZA) and 6-mercaptopurine (6-MP). AZA is a prodrug that is metabolized by nonenzymatic mechanisms to be converted to 6-MP and other metabolites. Therefore, patients could be treated with AZA or directly with 6-MP, but the final metabolites produced from the thiopurines are the same. Also, both drugs generate endogenously active products able to interfere on DNA and RNA synthesis .
The discovery of AZA and 6-MP yielded a Nobel Prize in Medicine in 1988 for Gertrude B. Elion and George Hitchings. At first, the thiopurines were used in cancer therapy, in order to stop cell proliferation. Nonetheless, the immunosuppressive effect of thiopurines was evident as well as their efficiency in prolonging renal allograft transplant survival . Thereafter, AZA and 6-MP began to be used in the clinics for inflammatory and rheumatic diseases. Since then, many mechanisms of action of thiopurines were proposed, mainly involving immunological axis in an attempt to unravel their immunosuppressive effects.
Some thiopurine metabolites, such as deoxyguanosine triphosphate (dGTP) and 6-thioguanine (6-TG), can be incorporated to DNA, replacing the natural purines adenine (A) and guanine (G). Then, during the DNA replication, a high level of substitution 6-TG could be particularly cytotoxic . These DNA modifications are not restricted to cancer cells, and lymphocytes can be affected by the purine analogue 6-TG as well . Besides that, some evidences point to the inhibition of de novo synthesis, which produce purines, by the thiopurine therapy. Then, the lack of abundant nitrogenous bases impairs the lymphocyte replication either, which contributes to the immunosuppression .
The thiopurines have the capacity to downregulate the expression of inflammatory genes in activated T lymphocytes . One of these genes is the TNF-related apoptosis-inducing ligand (TRAIL), which is important to induce apoptosis and is upregulated in activated T lymphocytes. Despite being apparently contradictory, TRAIL could increase T cell proliferation and IFN-γ production , a phenomenon that is pathogenic for Crohn’s disease patients. It is important to state that IFN-γ is a cytokine that accompanies the Th1 response, which increases gut inflammation. Also, CD27, which is a member of TNF superfamily, is downregulated by AZA . This receptor is required to T cell maintenance and for B cell activation. Consequently, a low expression of CD27 could facilitate the lymphocyte death . Besides, CD27 is involved in the NF-κB activation and IFN-γ production . In fact, the 6-TG incorporation into T cell DNA is correlated to the decreased IFN-γ production in CD patients . Lastly, the thiopurines could reduce the expression of the α4-integrin as well . This integrin is mandatory to the lymphocyte accumulation in the gut and the chronic inflammation .
It is clear that the accumulation of T lymphocytes in the gut mucosa is one of the main hallmarks for the exacerbated inflammation and disease worsening. Accordingly, thiopurines also reduce T cell proliferation and the consequent excessive inflammatory mediators produced by this population. Indeed, 6-MP that impairs the A and T purine integration into the replicant DNA and replaces them for mimetic purines compromises the cell cycle and T cell proliferation. 6-MP interferes in the G1 to S phase transition and progression through S phase in cell cycle, with consequent increase in lymphocyte death . Thereby, it is unquestionable that the thiopurine metabolites incorporate into the genetic material and negatively influence the DNA integrity or stability, which causes cellular death. In the last decade, the first conclusive and detailed studies about the thiopurines’ molecular mechanism of action in T lymphocytes explained better the delayed effects of these drugs, besides the incorporation of mimetic purines, as described above.
The Ras-related C3 botulinum toxin substrate 1 (Rac1) is a GTPase protein that activates MEKK/IκB/NF-κB (mitogen-activated protein kinase kinase/IKK/nuclear factor kappa-light-chain-enhancer of activated B cells) and signal transducer and activator of transcripition-3 (STAT-3) pathways, both of which lead to the accumulation of B-cell lymphoma-extra large (Bcl-xL) in the mitochondria. The enhancement of this protein results in an anti-apoptotic effect to cell survival. However, AZA and the 6-MP metabolite 6-thioguanine triphosphate (6-Thio-GTP) bind to Rac1, which impairs MEKK and STAT-3 phosphorylation, and consequently the anti-apoptotic effect by Bcl-xL is lost. Instead of that, there is an enhancement of Caspase-9, an apoptotic pathway of human cells involving mitochondria . Interestingly, these mechanisms require the co-stimulation by CD28 in T cells.
The bind of CD28 by costimulatory molecules leads to lymphocyte’s lamellipodia formations, which are projections of the cytoskeletal protein actin, necessary for T cell movement and membrane readjustment to make contact with antigen-presenting cells (APC). GTPase Rac1 also mediates this process . Later, it was observed that thiopurines also bind to and block Rac2 activation, while the treatment with these drugs impairs the lamellipodia formation. Additionally, upon binding to Rac proteins, AZA and its metabolites reduce ezrin-radixin-moesin protein (ERM) desphosphorylation and subsequently the formation of APC-T cell conjugates, necessary for an effective immune adaptive response. Likewise, that was dependent on CD28 activation too . Taken together, these results suggested that AZA and its metabolites binding Rac1 promote T cell apoptosis, by decreasing Bcl-xL and increasing caspase-9, but also interfere in T cell function or activation. Recently, a Bcl-2 inhibitor was suggested as a novel therapy to patients refractory to AZA treatment, despite Bcl-2, as a biomarker, cannot predict AZA treatment response in IBD patients .
In 2009 a study confirmed that 6-MP and 6-TG decrease the lymphoproliferative capacity of T cells, but in a physiological concentration (5 μM) . The thiopurine therapy causes, in vivo, specifically depletion of T CD4 memory cells, thus reducing the capacity of response to a recurrent antigen. Considering that in IBD there is continuous microbial translocation and antigen presentation , this should explain, at least in part, the delayed onset of the drug’s effect on the disease.
Thiopurine metabolites are also capable to inhibit the inflammatory response of macrophages and epithelial cells. These drugs significantly reduce the activity of c-Jun N-terminal kinase (JNK) and STAT3, as well IL-6, IL-8, CCL2, and CCL5 and inducible nitric oxide synthase (iNOS) expression. However, only iNOS in macrophages and IL-8 in epithelial cells are decreased dependent on Rac1 . In fact, AZA restores the paracellular permeability after TNF-induced apoptosis. The treatment improves the expression of tight junctions and adherens junctions, such as occludin and E-cadherin . Thus, the reduction of Rac1 is proposed as a biomarker for effectiveness of thiopurine treatment in patients with IBD .
It seems that the use of thiopurines can modulate the frequency of diverse immune cell populations, even by an indirect pathway. For example, patients treated with AZA have increased CCR5 expression in circulating monocytes. These CCR5+ cells are considered to have an anti-inflammatory profile, with increased CD163 and diminished TLR4-induced TNF and IL-6 secretion, probably in an attempt to achieve immunoregulation under AZA treatment . Moreover, thiopurine therapy decreases CD160 expression , as well as natural killer (NK) cells and the population of B lymphocytes in the peripheral blood of IBD patients . Indeed, the reduction in B cells is one of the reasons for using combo therapy with AZA plus infliximab (IFX), instead of IFX alone. AZA diminishes the antibody formation against IFX and then improves the patients’ responsiveness to the biological treatment .
The presence of variant Tγδ cells, specifically the TCR Vδ2, in the gut mucosa of Crohn’s disease patients is associated with worse clinical prognosis and inflammation . However, AZA is able to ablate this population in the blood and mucosa of patients treated with this drug, suggesting other potential mechanisms of action of AZA in the control of intestinal inflammation .
Besides the cellular changes, thiopurines are also capable of modulating soluble mediators, by decreasing IL-1β, TNF, and IFN-γ or increasing IL-10
Finally, a last mechanism of immune regulation was recently described involving AZA’s use. This drug can induce autophagy, which is a natural mechanism to recycle cellular components and to promote cell survival, depending on PERK sensor and mTORC1 in lymphocytes. Hence, modulation of autophagy could represent an additional mechanism of inflammation control through AZA treatment in IBD .
Methotrexate (MTX), originally known as amethopterin, is a folate antagonist. Its history and clinical use refers to Faber and Diamond , who reported the utilization of aminopterin, the first folic acid antagonist, as a treatment for acute leukemia in children. MTX, which is a derivative of aminopterin and is distinguished by having an additional methyl in its structure, subsequently replaced aminopterin after a study reported its lower toxicity in an experimental model of acute leukemia in rats . The idea behind the use of antifolates for the treatment of neoplasias was based on the knowledge that folates function as cofactors for DNA biosynthesis. Subsequently, the ability of MTX to interfere in DNA synthesis was proven experimentally , and years later lower doses of MTX also began to be studied for other conditions such as psoriasis  and rheumatoid arthritis .
For IBD, Kozarek et al.  were the first to report the ability of this drug to induce clinical and histological remission in patients with Crohn’s disease, but it was only after two randomized controlled trials (RCTs) of the North American Crohn’s Study Group (NACSG) that MTX was formally established as a possible therapy for this disease . On the other hand, there is no strong scientific basis for recommending the use of MTX as a monotherapy for UC. Nevertheless, the utilization of high or low doses of MTX in combination with anti-TNF has been shown to be effective in disease control at the same extent in both Crohn’s disease and ulcerative colitis patients . In summary, because of these and other results, MTX is usually recommended in specific conditions, especially depending on disease outcome and response to other therapies .
MTX acts as an antineoplastic drug when used at high doses and as immunosuppressive at low doses . This led to the investigation of other possible mechanisms capable of inducing immunosuppression, in addition to interfering in cell proliferation. In line with that, there is a lack of specific investigation unraveling the exact mechanisms of action of MTX in IBD, but this drug is capable of inducing apoptosis in activated T cells , inhibiting IL-8 production by peripheral blood mononuclear cells , and increasing extracellular adenosine levels. This metabolite has potent anti-inflammatory properties  in patients with rheumatoid arthritis  and potentially in IBD . Clearly, more experimental studies are needed to better understand the action of MTX in IBD, but those mentioned above represent possible mechanisms that could explain the relative success of MTX as an immunomodulatory therapy, especially for Crohn’s disease.
The cyclosporine A (CsA) is an immunosuppressor drug initially used for organ transplantation on the late 70 and 80 decades . Some years later, it was utilized as an alternative treatment for ulcerative colitis (UC) patients refractory to glucocorticoids, because of its strong immune regulatory effects .
CsA is a lipophilic cyclic peptide that is metabolized by hepatic enzymes of cytochrome P450 pathway . Its immunosuppressor activity depends on the intracellular binding to cyclophilins with further inhibition of the calcium-calcineurin pathway and the resulting blockage of the nuclear activated T cell factor (NFAT) translocation to the nucleus , thus avoiding cellular activation. Consequently, there is reduction in the transcription of genes related to cytokine production such as IL-2, IL-4, and IFN-γ , inhibition of CD4 expression, cell proliferation , and activation of CD8 lymphocytes . Therefore, the blockage of NFAT is considered one of the main effects of this immunosuppressor drug .
Upon in vitro treatment of peripheral blood mononuclear cells (PBMCs), from ulcerative colitis or Crohn’s disease patients with CsA, there is reduction of TNF, IL-17, and IL-10 in samples from all donors, besides an exclusive significant IL-13 decrease in subjects with UC. Also, CsA stimulates the cellular apoptosis of PBMC from patients with UC, though not by the mitochondrial route . In an experimental colitis model, the treatment with CsA reduces the clinical activity of the disease and mRNA expression of several inflammatory cytokines such as IL-1β, IL-6, and TNF .
Hence, though the therapy with CsA has shown to be beneficial, the systemic treatment can be limited due to its side effects such as nephrotoxicity, hypertension, seizures, production of ROS or hydrogen peroxide, and opportunistic infections .
Tacrolimus (Tac) was isolated in 1984 from the fungus strain
The Tac, compared to CsA, has a more potent inhibitory action against T cell activation, leading to immunosuppression. It binds to FKBP-12, with further inhibition of the calmodulin-dependent phosphatase activity of calcineurin . Thus, it inhibits the action of activated nuclear T cell factor (NFAT), reducing the production of IL-2. In line with that, Tac can also decrease the activity of NF-κB . Therefore, besides IL-2, Tac is a calcineurin inhibitor that leads to reduced production of IL-3, TNF, IFN-γ, and IL-17, as well as the release of histamine from mast cells and proliferation of CD4+ or CD8+ T cells in a variety of inflammatory processes . Tac treatment in bone marrow-derived macrophages also leads to reduced IL-12p40, IL-12p70, and IL-23 during LPS stimuli .
As described, in vitro treatment with Tac inhibits the activity of leukocytes such as T lymphocytes, NKT, and antigen-presenting cells, usually present on colon tissue. Moreover, the administration of Tac in trinitrobenzene sulfonic acid (TNBS) colitis results in the reduction of neutrophil infiltrate in the intestinal mucosa associated with inhibition of T cell activation, as well as decreased expression of CXCL1 and CXCL2 chemokines . Most interestingly, Tac is able to inhibit the expression of IL-17 and TNF , suggesting that this drug could assume therapeutic effect on diseases mediated by Th17 responses, such as IBD. Furthermore, the rectal treatment in mice leads to better results than oral administration of the drug .
In experimental granulomatous colitis, treatment with Tac results in the reduction of intestinal permeability, neutrophil activity, as well as extra-intestinal manifestations of the disease, such as hepatic and splenic granulomas, caused by the colitis-inducing agent . On the other scenario, myofibroblasts isolated from normal gut tissues and stimulated in vitro with TNF show increased phosphorylation of the p38 subunit of MAP kinase, leading to augmented CCL2 and CXCL10 expression. However, in vitro treatment with Tac suppresses the expression of CCL2 and CXCL10 mRNA by inhibiting phosphorylation of MAP kinase, indicating that these effects could be one of the mechanisms of therapeutic action of Tac on intestinal inflammation .
Hence, although this therapy may result in satisfactory IBD outcome, research has pointed that after mucosal healing, it is desirable to change this therapeutic intervention to other immunosuppressor drugs, in order to reduce the long-term adverse effects caused by Tac, such as nephrotoxicity .
The introduction of pharmacological therapies for IBD is of high importance to achieve remission and maintenance of quiescent disease in affected patients. Nonetheless, although these drugs act by diverse mechanisms, all of them are relevant in constraining the activation and perpetuation of the exacerbated immune-inflammatory responses that underline the gut inflammation in Crohn’s disease and ulcerative colitis. Then, the balance between adequate control of inflammatory responses and drugs’ adverse effects dictates the efficiency of corticosteroid and suppressor treatments in IBD.
The authors would like to thank Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP), for the financial support 2017/08651.1 and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), 310174/2016-3.
Khanna R, Bressler B, Levesque BG, Zou G, Stitt LW, Greenberg GR, et al. Early combined immunosuppression for the management of Crohn’s disease (REACT): A cluster randomised controlled trial. Lancet. 2015; 386(10006):1825-1834
Casanova MJ, Chaparro M, Garcia-Sanchez V, Nantes O, Leo E, Rojas-Feria M, et al. Evolution after anti-TNF discontinuation in patients with inflammatory bowel disease: A multicenter long-term follow-up study. The American Journal of Gastroenterology. 2017; 112(1):120-131
Ramamoorthy S, Cidlowski JA. Corticosteroids: Mechanisms of action in health and disease. Rheumatic Diseases Clinics of North America. 2016; 42(1):15-31. vii
Wira C, Munck A. Specific glucocorticoid receptors in thymus cells. Localization in the nucleus and extraction of the cortisol-receptor complex. The Journal of Biological Chemistry. 1970; 245(13):3436-3438
Hollenberg SM, Weinberger C, Ong ES, Cerelli G, Oro A, Lebo R, et al. Primary structure and expression of a functional human glucocorticoid receptor cDNA. Nature. 1985; 318(6047):635-641
Panettieri RA, Schaafsma D, Amrani Y, Koziol-White C, Ostrom R, Tliba O. Non-genomic effects of glucocorticoids: An updated view. Trends in Pharmacological Sciences. 2019; 40(1):38-49
Baxter JD, Rousseau GG, Benson MC, Garcea RL, Ito J, Tomkins GM. Role of DNA and specific cytoplasmic receptors in glucocorticoid action. Proceedings of the National Academy of Sciences of the United States of America. 1972; 69(7):1892-1896
Dostert A, Heinzel T. Negative glucocorticoid receptor response elements and their role in glucocorticoid action. Current Pharmaceutical Design. 2004; 10(23):2807-2816
Curtin NM, Boyle NT, Mills KH, Connor TJ. Psychological stress suppresses innate IFN-gamma production via glucocorticoid receptor activation: Reversal by the anxiolytic chlordiazepoxide. Brain, Behavior, and Immunity. 2009; 23(4):535-547
Ballegeer M, Van Looveren K, Timmermans S, Eggermont M, Vandevyver S, Thery F, et al. Glucocorticoid receptor dimers control intestinal STAT1 and TNF-induced inflammation in mice. The Journal of Clinical Investigation. 2018; 128(8):3265-3279
Cronstein BN, Kimmel SC, Levin RI, Martiniuk F, Weissmann G. A mechanism for the antiinflammatory effects of corticosteroids: The glucocorticoid receptor regulates leukocyte adhesion to endothelial cells and expression of endothelial-leukocyte adhesion molecule 1 and intercellular adhesion molecule 1. Proceedings of the National Academy of Sciences of the United States of America. 1992; 89(21):9991-9995
Gayo A, Mozo L, Suarez A, Tunon A, Lahoz C, Gutierrez C. Glucocorticoids increase IL-10 expression in multiple sclerosis patients with acute relapse. Journal of Neuroimmunology. 1998; 85(2):122-130
Paliogianni F, Raptis A, Ahuja SS, Najjar SM, Boumpas DT. Negative transcriptional regulation of human interleukin 2 (IL-2) gene by glucocorticoids through interference with nuclear transcription factors AP-1 and NF-AT. The Journal of Clinical Investigation. 1993; 91(4):1481-1489
Stahn C, Lowenberg M, Hommes DW, Buttgereit F. Molecular mechanisms of glucocorticoid action and selective glucocorticoid receptor agonists. Molecular and Cellular Endocrinology. 2007; 275(1-2):71-78
Hench PS, Kendall EC, et al. The effect of a hormone of the adrenal cortex (17-hydroxy-11-dehydrocorticosterone; compound E) and of pituitary adrenocorticotropic hormone on rheumatoid arthritis. Proceedings of the Staff Meetings. Mayo Clinic. 1949; 24(8):181-197
Li J, Wang F, Zhang HJ, Sheng JQ , Yan WF, Ma MX, et al. Corticosteroid therapy in ulcerative colitis: Clinical response and predictors. World Journal of Gastroenterology. 2015; 21(10):3005-3015
Sales-Campos H, Basso PJ, Alves VB, Fonseca MT, Bonfa G, Nardini V, et al. Classical and recent advances in the treatment of inflammatory bowel diseases. Brazilian Journal of Medical and Biological Research. 2015; 48(2):96-107
Ocon B, Aranda CJ, Gamez-Belmonte R, Suarez MD, Zarzuelo A, Martinez-Augustin O, et al. The glucocorticoid budesonide has protective and deleterious effects in experimental colitis in mice. Biochemical Pharmacology. 2016; 116:73-88
Sales-Campos H, de Souza PR, Basso PJ, Nardini V, Silva A, Banquieri F, et al. Amelioration of experimental colitis after short-term therapy with glucocorticoid and its relationship to the induction of different regulatory markers. Immunology. 2017; 150(1):115-126
Rocamora-Reverte L, Tuzlak S, von Raffay L, Tisch M, Fiegl H, Drach M, et al. Glucocorticoid receptor-deficient Foxp3(+) regulatory T cells fail to control experimental inflammatory bowel disease. Frontiers in Immunology. 2019; 10:472
Yilmaz B, Juillerat P, Oyas O, Ramon C, Bravo FD, Franc Y, et al. Microbial network disturbances in relapsing refractory Crohn’s disease. Nature Medicine. 2019; 25(2):323-336
Huang EY, Inoue T, Leone VA, Dalal S, Touw K, Wang Y, et al. Using corticosteroids to reshape the gut microbiome: Implications for inflammatory bowel diseases. Inflammatory Bowel Diseases. 2015; 21(5):963-972
Haberman Y, Karns R, Dexheimer PJ, Schirmer M, Somekh J, Jurickova I, et al. Ulcerative colitis mucosal transcriptomes reveal mitochondriopathy and personalized mechanisms underlying disease severity and treatment response. Nature Communications. 2019; 10(1):38
Egesten A, Eliasson M, Olin AI, Erjefalt JS, Bjartell A, Sangfelt P, et al. The proinflammatory CXC-chemokines GRO-alpha/CXCL1 and MIG/CXCL9 are concomitantly expressed in ulcerative colitis and decrease during treatment with topical corticosteroids. International Journal of Colorectal Disease. 2007; 22(12):1421-1427
Wendt E, White GE, Ferry H, Huhn M, Greaves DR, Keshav S. Glucocorticoids suppress CCR9-mediated chemotaxis, calcium flux, and adhesion to MAdCAM-1 in human T cells. Journal of Immunology. 2016; 196(9):3910-3919
Hengge UR, Ruzicka T, Schwartz RA, Cork MJ. Adverse effects of topical glucocorticosteroids. Journal of the American Academy of Dermatology. 2006; 54(1):1-15. quiz 16-18
Sadr-Azodi O, Mattsson F, Bexlius TS, Lindblad M, Lagergren J, Ljung R. Association of oral glucocorticoid use with an increased risk of acute pancreatitis: A population-based nested case-control study. JAMA Internal Medicine. 2013; 173(6):444-449
Kajiyama Y, Iijima Y, Chiba S, Furuta M, Ninomiya M, Izumi A, et al. Prednisolone causes anxiety- and depression-like behaviors and altered expression of apoptotic genes in mice hippocampus. Progress in Neuro-Psychopharmacology & Biological Psychiatry. 2010; 34(1):159-165
Wang ZJ, Zhang XQ , Cui XY, Cui SY, Yu B, Sheng ZF, et al. Glucocorticoid receptors in the locus coeruleus mediate sleep disorders caused by repeated corticosterone treatment. Scientific Reports. 2015; 5:9442
Stuck AE, Minder CE, Frey FJ. Risk of infectious complications in patients taking glucocorticosteroids. Reviews of Infectious Diseases. 1989; 11(6):954-963
Wollheim FA. Nanna Svartz (1890-1986): The first female professor of medicine in Sweden. Zeitschrift für Rheumatologie. 2017; 76(9):813-819
Klotz U. Clinical pharmacokinetics of sulphasalazine, its metabolites and other prodrugs of 5-aminosalicylic acid. Clinical Pharmacokinetics. 1985; 10(4):285-302
Masoodi M, Pearl DS, Eiden M, Shute JK, Brown JF, Calder PC, et al. Altered colonic mucosal polyunsaturated fatty acid (PUFA) derived lipid mediators in ulcerative colitis: New insight into relationship with disease activity and pathophysiology. PLoS One. 2013; 8(10):e76532
Lobos EA, Sharon P, Stenson WF. Chemotactic activity in inflammatory bowel disease. Role of leukotriene B4. Digestive Diseases and Sciences. 1987; 32(12):1380-1388
Nielsen OH, Bukhave K, Elmgreen J, Ahnfelt-Ronne I. Inhibition of 5-lipoxygenase pathway of arachidonic acid metabolism in human neutrophils by sulfasalazine and 5-aminosalicylic acid. Digestive Diseases and Sciences. 1987; 32(6):577-582
Nielsen OH, Verspaget HW, Elmgreen J. Inhibition of intestinal macrophage chemotaxis to leukotriene B4 by sulphasalazine, olsalazine, and 5-aminosalicylic acid. Alimentary Pharmacology & Therapeutics. 1988; 2(3):203-211
Sobhani I, Hochlaf S, Denizot Y, Vissuzaine C, Rene E, Benveniste J, et al. Raised concentrations of platelet activating factor in colonic mucosa of Crohn’s disease patients. Gut. 1992; 33(9):1220-1225
Kald B, Olaison G, Sjodahl R, Tagesson C. Novel aspect of Crohn’s disease: Increased content of platelet-activating factor in ileal and colonic mucosa. Digestion. 1990; 46(4):199-204
Wardle TD, Hall L, Turnberg LA. Platelet activating factor: Release from colonic mucosa in patients with ulcerative colitis and its effect on colonic secretion. Gut. 1996; 38(3):355-361
Eliakim R, Karmeli F, Razin E, Rachmilewitz D. Role of platelet-activating factor in ulcerative colitis. Enhanced production during active disease and inhibition by sulfasalazine and prednisolone. Gastroenterology. 1988; 95(5):1167-1172
Stenson WF, Mehta J, Spilberg I. Sulfasalazine inhibition of binding of N-formyl-methionyl-leucyl-phenylalanine (FMLP) to its receptor on human neutrophils. Biochemical Pharmacology. 1984; 33(3):407-412
Kanerud L, Hafstrom I, Ringertz B. Effect of sulphasalazine and sulphapyridine on neutrophil superoxide production: Role of cytosolic free calcium. Annals of the Rheumatic Diseases. 1990; 49(5):296-300
Neal TM, Winterbourn CC, Vissers MC. Inhibition of neutrophil degranulation and superoxide production by sulfasalazine. Comparison with 5-aminosalicylic acid, sulfapyridine and olsalazine. Biochemical Pharmacology. 1987; 36(17):2765-2768
Dull BJ, Salata K, Van Langenhove A, Goldman P. 5-Aminosalicylate: Oxidation by activated leukocytes and protection of cultured cells from oxidative damage. Biochemical Pharmacology. 1987; 36(15):2467-2472
Keshavarzian A, Morgan G, Sedghi S, Gordon JH, Doria M. Role of reactive oxygen metabolites in experimental colitis. Gut. 1990; 31(7):786-790
Ahnfelt-Ronne I, Nielsen OH, Christensen A, Langholz E, Binder V, Riis P. Clinical evidence supporting the radical scavenger mechanism of 5-aminosalicylic acid. Gastroenterology. 1990; 98(5 Pt 1):1162-1169
Fujiwara M, Mitsui K, Yamamoto I. Inhibition of proliferative responses and interleukin 2 productions by salazosulfapyridine and its metabolites. Japanese Journal of Pharmacology. 1990; 54(2):121-131
Kang BY, Chung SW, Im SY, Choe YK, Kim TS. Sulfasalazine prevents T-helper 1 immune response by suppressing interleukin-12 production in macrophages. Immunology. 1999; 98(1):98-103
Rodenburg RJ, Ganga A, van Lent PL, van de Putte LB, van Venrooij WJ. The antiinflammatory drug sulfasalazine inhibits tumor necrosis factor alpha expression in macrophages by inducing apoptosis. Arthritis and Rheumatism. 2000; 43(9):1941-1950
Weber CK, Liptay S, Wirth T, Adler G, Schmid RM. Suppression of NF-kappaB activity by sulfasalazine is mediated by direct inhibition of IkappaB kinases alpha and beta. Gastroenterology. 2000; 119(5):1209-1218
Shin MR, Kim KJ, Kim SH, Kim SJ, Seo BI, An HJ, et al. Comparative evaluation between sulfasalazine alone and in combination with herbal medicine on DSS-induced ulcerative colitis mice. BioMed Research International. 2017; 2017:6742652
Han KH, Park JM, Jeong M, Han YM, Go EJ, Park J, et al. Heme oxygenase-1 induction and anti-inflammatory actions of Atractylodes macrocephalaand Taraxacum herbaextracts prevented colitis and was more effective than sulfasalazine in preventing relapse. Gut Liver. 2017; 11(5):655-666
Suluvoy JK, Sakthivel KM, Guruvayoorappan C, Berlin Grace VM. Protective effect of Averrhoa bilimbiL. fruit extract on ulcerative colitis in Wistar rats via regulation of inflammatory mediators and cytokines. Biomedicine & Pharmacotherapy. 2017; 91:1113-1121
Xu B, Li YL, Xu M, Yu CC, Lian MQ , Tang ZY, et al. Geniposide ameliorates TNBS-induced experimental colitis in rats via reducing inflammatory cytokine release and restoring impaired intestinal barrier function. Acta Pharmacologica Sinica. 2017; 38(5):688-698
Araujo DFS, Guerra GCB, Junior RFA, Antunes de Araujo A, Antonino de Assis PO, Nunes de Medeiros A, et al. Goat whey ameliorates intestinal inflammation on acetic acid-induced colitis in rats. Journal of Dairy Science. 2016; 99(12):9383-9394
Ito R, Kita M, Shin-Ya M, Kishida T, Urano A, Takada R, et al. Involvement of IL-17A in the pathogenesis of DSS-induced colitis in mice. Biochemical and Biophysical Research Communications. 2008; 377(1):12-16
Zou Y, Dai SX, Chi HG, Li T, He ZW, Wang J, et al. Baicalin attenuates TNBS-induced colitis in rats by modulating the Th17/Treg paradigm. Archives of Pharmacal Research. 2015; 38(10):1873-1887
Rousseaux C, Lefebvre B, Dubuquoy L, Lefebvre P, Romano O, Auwerx J, et al. Intestinal antiinflammatory effect of 5-aminosalicylic acid is dependent on peroxisome proliferator-activated receptor-gamma. The Journal of Experimental Medicine. 2005; 201(8):1205-1215
Zhu JF, Xu Y, Zhao J, Li X, Meng X, Wang TQ , et al. IL-33 protects mice against DSS-induced chronic colitis by increasing both regulatory B cell and regulatory T cell responses as well as decreasing Th17 cell response. Journal of Immunology Research. 2018; 2018:1827901
Oh-Oka K, Kojima Y, Uchida K, Yoda K, Ishimaru K, Nakajima S, et al. Induction of colonic regulatory T cells by mesalamine by activating the aryl hydrocarbon receptor. Cellular and Molecular Gastroenterology and Hepatology. 2017; 4(1):135-151
Etchevers MJ, Aceituno M, Sans M. Are we giving azathioprine too late? The case for early immunomodulation in inflammatory bowel disease. World Journal of Gastroenterology. 2008; 14(36):5512-5518
Murray JE, Merrill JP, Harrison JH, Wilson RE, Dammin GJ. Prolonged survival of human-kidney homografts by immunosuppressive drug therapy. The New England Journal of Medicine. 1963; 268:1315-1323
Yoshida S, Yamada M, Masaki S, Saneyoshi M. Utilization of 2′-deoxy-6-thioguanosine 5′-triphosphate in DNA synthesis in vitro by DNA polymerase alpha from calf thymus. Cancer Research. 1979; 39(10):3955-3958
Morley AA, Trainor KJ, Seshadri R, Ryall RG. Measurement of in vivo mutations in human lymphocytes. Nature. 1983; 302(5904):155-156
Krynetski EY, Krynetskaia NF, Yanishevski Y, Evans WE. Methylation of mercaptopurine, thioguanine, and their nucleotide metabolites by heterologously expressed human thiopurine S-methyltransferase. Molecular Pharmacology. 1995; 47(6):1141-1147
Thomas CW, Myhre GM, Tschumper R, Sreekumar R, Jelinek D, McKean DJ, et al. Selective inhibition of inflammatory gene expression in activated T lymphocytes: A mechanism of immune suppression by thiopurines. The Journal of Pharmacology and Experimental Therapeutics. 2005; 312(2):537-545
Chou AH, Tsai HF, Lin LL, Hsieh SL, Hsu PI, Hsu PN. Enhanced proliferation and increased IFN-gamma production in T cells by signal transduced through TNF-related apoptosis-inducing ligand. Journal of Immunology. 2001; 167(3):1347-1352
Croft M. The role of TNF superfamily members in T-cell function and diseases. Nature Reviews. Immunology. 2009; 9(4):271-285
Remedios KA, Meyer L, Zirak B, Pauli ML, Truong HA, Boda D, et al. CD27 promotes CD4(+) effector T cell survival in response to tissue self-antigen. Journal of Immunology. 1 Aug 2019; 203(3):639-646
Cuffari C, Li DY, Mahoney J, Barnes Y, Bayless TM. Peripheral blood mononuclear cell DNA 6-thioguanine metabolite levels correlate with decreased interferon-gamma production in patients with Crohn’s disease on AZA therapy. Digestive Diseases and Sciences. 2004; 49(1):133-137
Kurmaeva E, Lord JD, Zhang S, Bao JR, Kevil CG, Grisham MB, et al. T cell-associated alpha4beta7 but not alpha4beta1 integrin is required for the induction and perpetuation of chronic colitis. Mucosal Immunology. 2014; 7(6):1354-1365
Quemeneur L, Gerland LM, Flacher M, Ffrench M, Revillard JP, Genestier L. Differential control of cell cycle, proliferation, and survival of primary T lymphocytes by purine and pyrimidine nucleotides. Journal of Immunology. 2003; 170(10):4986-4995
Tiede I, Fritz G, Strand S, Poppe D, Dvorsky R, Strand D, et al. CD28-dependent Rac1 activation is the molecular target of azathioprine in primary human CD4+ T lymphocytes. The Journal of Clinical Investigation. 2003; 111(8):1133-1145
Salazar-Fontana LI, Barr V, Samelson LE, Bierer BE. CD28 engagement promotes actin polymerization through the activation of the small rho GTPase Cdc42 in human T cells. Journal of Immunology. 2003; 171(5):2225-2232
Weder B, Mozaffari M, Biedermann L, Mamie C, Moncsek A, Wang L, et al. BCL-2 levels do not predict azathioprine treatment response in inflammatory bowel disease, but inhibition induces lymphocyte apoptosis and ameliorates colitis in mice. Clinical and Experimental Immunology. 2018; 193(3):346-360
Ben-Horin S, Goldstein I, Fudim E, Picard O, Yerushalmi Z, Barshack I, et al. Early preservation of effector functions followed by eventual T cell memory depletion: A model for the delayed onset of the effect of thiopurines. Gut. 2009; 58(3):396-403
Chiodini RJ, Dowd SE, Galandiuk S, Davis B, Glassing A. The predominant site of bacterial translocation across the intestinal mucosal barrier occurs at the advancing disease margin in Crohn’s disease. Microbiology. 2016; 162(9):1608-1619
Marinkovic G, Hamers AA, de Vries CJ, de Waard V. 6-Mercaptopurine reduces macrophage activation and gut epithelium proliferation through inhibition of GTPase Rac1. Inflammatory Bowel Diseases. 2014; 20(9):1487-1495
Khare V, Krnjic A, Frick A, Gmainer C, Asboth M, Jimenez K, et al. Mesalamine and azathioprine modulate junctional complexes and restore epithelial barrier function in intestinal inflammation. Scientific Reports. 2842; 9(1):2019
Seinen ML, van Nieuw Amerongen GP, de Boer NK, Mulder CJ, van Bezu J, van Bodegraven AA. Rac1 as a potential pharmacodynamic biomarker for thiopurine therapy in inflammatory bowel disease. Therapeutic Drug Monitoring. 2016; 38(5):621-627
Nieto JC, Zamora C, Canto E, Garcia-Planella E, Gordillo J, Ortiz MA, et al. CSF-1 regulates the function of monocytes in Crohn’s disease patients in remission. Scientific Reports. 2017; 7(1):92
Bouma G, Baggen JM, van Bodegraven AA, Mulder CJ, Kraal G, Zwiers A, et al. Thiopurine treatment in patients with Crohn’s disease leads to a selective reduction of an effector cytotoxic gene expression signature revealed by whole-genome expression profiling. Molecular Immunology. 2013; 54(3-4):472-481
Lord JD, Shows DM. Thiopurine use associated with reduced B and natural killer cells in inflammatory bowel disease. World Journal of Gastroenterology. 2017; 23(18):3240-3251
Ben-Horin S, Waterman M, Kopylov U, Yavzori M, Picard O, Fudim E, et al. Addition of an immunomodulator to infliximab therapy eliminates antidrug antibodies in serum and restores clinical response of patients with inflammatory bowel disease. Clinical Gastroenterology and Hepatology. 2013; 11(4):444-447
McCarthy NE, Bashir Z, Vossenkamper A, Hedin CR, Giles EM, Bhattacharjee S, et al. Proinflammatory Vdelta2+ T cells populate the human intestinal mucosa and enhance IFN-gamma production by colonic alphabeta T cells. Journal of Immunology. 2013; 191(5):2752-2763
McCarthy NE, Hedin CR, Sanders TJ, Amon P, Hoti I, Ayada I, et al. Azathioprine therapy selectively ablates human Vdelta2(+) T cells in Crohn’s disease. The Journal of Clinical Investigation. 2015; 125(8):3215-3225
Quaglio AE, Castilho AC, Di Stasi LC. Experimental evidence of heparanase, Hsp70 and NF-kappaB gene expression on the response of anti-inflammatory drugs in TNBS-induced colonic inflammation. Life Sciences. 2015; 141:179-187
Makitalo L, Rintamaki H, Tervahartiala T, Sorsa T, Kolho KL. Serum MMPs 7-9 and their inhibitors during glucocorticoid and anti-TNF-alpha therapy in pediatric inflammatory bowel disease. Scandinavian Journal of Gastroenterology. 2012; 47(7):785-794
Makitalo L, Sipponen T, Karkkainen P, Kolho KL, Saarialho-Kere U. Changes in matrix metalloproteinase (MMP) and tissue inhibitors of metalloproteinases (TIMP) expression profile in Crohn’s disease after immunosuppressive treatment correlate with histological score and calprotectin values. International Journal of Colorectal Disease. 2009; 24(10):1157-1167
Hooper KM, Casanova V, Kemp S, Staines KA, Satsangi J, Barlow PG, et al. The inflammatory bowel disease drug azathioprine induces autophagy via mTORC1 and the unfolded protein response sensor PERK. Inflammatory Bowel Diseases. 2019
Farber S, Diamond LK. Temporary remissions in acute leukemia in children produced by folic acid antagonist, 4-aminopteroyl-glutamic acid. The New England Journal of Medicine. 1948; 238(23):787-793
Goldin A, Venditti JM, Humphreys SR, Dennis D, Mantel N, Greenhouse SW. A quantitative comparison of the antileukemic effectiveness of two folic acid antagonists in mice. Journal of the National Cancer Institute. 1955; 15(6):1657-1664
Skeel RT, Sawicki WL, Cashmore AR, Bertino JR. Inhibition of DNA synthesis in normal and malignant human cells by triazinate (Baker’s antifol) and methotrexate. Cancer Research. 1976; 36(10):3659-3664
Chouela EN, Mejer LI, Mom AM. Tissue immunology in psoriasis. I. Changes in the immunologic mechanism caused by methotrexate. Medicina Cutánea Ibero-Latino-Americana. 1975; 3(2):167-172
Hall GH, Jones BJ, Head AC, Jones VE. Intra-articular methotrexate. Clinical and laboratory study in rheumatoid and psoriatic arthritis. Annals of the Rheumatic Diseases. 1978; 37(4):351-356
Kozarek RA, Patterson DJ, Gelfand MD, Botoman VA, Ball TJ, Wilske KR. Methotrexate induces clinical and histologic remission in patients with refractory inflammatory bowel disease. Annals of Internal Medicine. 1989; 110(5):353-356
Feagan BG, Rochon J, Fedorak RN, Irvine EJ, Wild G, Sutherland L, et al. Methotrexate for the treatment of Crohn’s disease. The North American Crohn’s study group investigators. The New England Journal of Medicine. 1995; 332(5):292-297
Borren NZ, Luther J, Colizzo FP, Garber JG, Khalili H, Ananthakrishnan AN. Low-dose methotrexate has similar outcomes to high-dose methotrexate in combination with anti-TNF therapy in inflammatory bowel diseases. Journal of Crohn’s and Colitis. 14 Aug 2019; 13(8):990-995
Swaminath A, Taunk R, Lawlor G. Use of methotrexate in inflammatory bowel disease in 2014: A user’s guide. World Journal of Gastrointestinal Pharmacology and Therapeutics. 2014; 5(3):113-121
Malaviya AN, Sharma A, Agarwal D, Kapoor S, Garg S, Sawhney S. Low-dose and high-dose methotrexate are two different drugs in practical terms. International Journal of Rheumatic Diseases. 2010; 13(4):288-293
Genestier L, Paillot R, Fournel S, Ferraro C, Miossec P, Revillard JP. Immunosuppressive properties of methotrexate: Apoptosis and clonal deletion of activated peripheral T cells. The Journal of Clinical Investigation. 1998; 102(2):322-328
Seitz M, Dewald B, Ceska M, Gerber N, Baggiolini M. Interleukin-8 in inflammatory rheumatic diseases: Synovial fluid levels, relation to rheumatoid factors, production by mononuclear cells, and effects of gold sodium thiomalate and methotrexate. Rheumatology International. 1992; 12(4):159-164
Krump E, Lemay G, Borgeat P. Adenosine A2 receptor-induced inhibition of leukotriene B4 synthesis in whole blood ex vivo. British Journal of Pharmacology. 1996; 117(8):1639-1644
Riksen NP, Barrera P, van den Broek PH, van Riel PL, Smits P, Rongen GA. Methotrexate modulates the kinetics of adenosine in humans in vivo. Annals of the Rheumatic Diseases. 2006; 65(4):465-470
Longhi MS, Moss A, Bai A, Wu Y, Huang H, Cheifetz A, et al. Characterization of human CD39+ Th17 cells with suppressor activity and modulation in inflammatory bowel disease. PLoS One. 2014; 9(2):e87956
Calne RY, Rolles K, White DJ, Thiru S, Evans DB, McMaster P, et al. Cyclosporin a initially as the only immunosuppressant in 34 recipients of cadaveric organs: 32 kidneys, 2 pancreases, and 2 livers. Lancet. 1979; 2(8151):1033-1036
Cohen RD, Stein R, Hanauer SB. Intravenous cyclosporin in ulcerative colitis: A five-year experience. The American Journal of Gastroenterology. 1999; 94(6):1587-1592
Graham RM. Cyclosporine: Mechanisms of action and toxicity. Cleveland Clinic Journal of Medicine. 1994; 61(4):308-313
Schreiber SL, Crabtree GR. The mechanism of action of cyclosporin a and FK506. Immunology Today. 1992; 13(4):136-142
Fellman CL, Archer TM, Stokes JV, Wills RW, Lunsford KV, Mackin AJ. Effects of oral cyclosporine on canine T-cell expression of IL-2 and IFN-gamma across a 12-h dosing interval. Journal of Veterinary Pharmacology and Therapeutics. 2016; 39(3):237-244
Pallet N, Fernandez-Ramos AA, Loriot MA. Impact of immunosuppressive drugs on the metabolism of T cells. International Review of Cell and Molecular Biology. 2018; 341:169-200
Nemlander A, Hayry P. Effect of cyclosporin a on the generation of cytotoxic T lymphocytes in mouse mixed lymphocyte culture. Scandinavian Journal of Immunology. 1980; 12(6):493-498
Rao A, Luo C, Hogan PG. Transcription factors of the NFAT family: Regulation and function. Annual Review of Immunology. 1997; 15:707-747
Steiner S, Daniel C, Fischer A, Atreya I, Hirschmann S, Waldner M, et al. Cyclosporine a regulates pro-inflammatory cytokine production in ulcerative colitis. Archivum Immunologiae et Therapiae Experimentalis (Warsz). 2015; 63(1):53-63
Hoffmann M, Schwertassek U, Seydel A, Weber K, Falk W, Hauschildt S, et al. A refined and translationally relevant model of chronic DSS colitis in BALB/c mice. Laboratory Animals. 2018; 52(3):240-252
Godat S, Fournier N, Safroneeva E, Juillerat P, Nydegger A, Straumann A, et al. Frequency and type of drug-related side effects necessitating treatment discontinuation in the Swiss inflammatory bowel disease cohort. European Journal of Gastroenterology & Hepatology. 2018; 30(6):612-620
Kino T, Hatanaka H, Hashimoto M, Nishiyama M, Goto T, Okuhara M, et al. FK-506, a novel immunosuppressant isolated from a Streptomyces. I. Fermentation, isolation, and physico-chemical and biological characteristics. Journal of Antibiotics (Tokyo). 1987; 40(9):1249-1255
Staatz CE, Tett SE. Clinical pharmacokinetics and pharmacodynamics of tacrolimus in solid organ transplantation. Clinical Pharmacokinetics. 2004; 43(10):623-653
Ordonez-Robles M, Santos-Beneit F, Martin JF. Unraveling nutritional regulation of tacrolimus biosynthesis in Streptomyces tsukubaensisthrough omic approaches. Antibiotics (Basel). 2018; 7(2)
Xu J, Feng Y, Song G, Gong Q , Yin L, Hu Y, et al. Tacrolimus reverses UVB irradiation-induced epidermal langerhans cell reduction by inhibiting TNF-alpha secretion in keratinocytes via regulation of NF-kappaB/p65. Frontiers in Pharmacology. 2018; 9:67
Li Y, Guptill JT, Russo MA, Massey JM, Juel VC, Hobson-Webb LD, et al. Tacrolimus inhibits Th1 and Th17 responses in MuSK-antibody positive myasthenia gravis patients. Experimental Neurology. 2019; 312:43-50
Elloumi HZ, Maharshak N, Rao KN, Kobayashi T, Ryu HS, Muhlbauer M, et al. A cell permeable peptide inhibitor of NFAT inhibits macrophage cytokine expression and ameliorates experimental colitis. PLoS One. 2012; 7(3):e34172
van Lierop PP, de Haar C, Lindenbergh-Kortleve DJ, Simons-Oosterhuis Y, van Rijt LS, Lambrecht BN, et al. T-cell regulation of neutrophil infiltrate at the early stages of a murine colitis model. Inflammatory Bowel Diseases. 2010; 16(3):442-451
Yago T, Nanke Y, Kawamoto M, Yamanaka H, Kotake S. Tacrolimus potently inhibits human osteoclastogenesis induced by IL-17 from human monocytes alone and suppresses human Th17 differentiation. Cytokine. 2012; 59(2):252-257
van Dieren JM, Lambers ME, Kuipers EJ, Samsom JN, van der Woude CJ, Nieuwenhuis EE. Local immune regulation of mucosal inflammation by tacrolimus. Digestive Diseases and Sciences. 2010; 55(9):2514-2519
Aiko S, Conner EM, Fuseler JA, Grisham MB. Effects of cyclosporine or FK506 in chronic colitis. The Journal of Pharmacology and Experimental Therapeutics. 1997; 280(2):1075-1084
Aomatsu T, Imaeda H, Takahashi K, Fujimoto T, Kasumi E, Yoden A, et al. Tacrolimus (FK506) suppresses TNF-alpha-induced CCL2 (MCP-1) and CXCL10 (IP-10) expression via the inhibition of p38 MAP kinase activation in human colonic myofibroblasts. International Journal of Molecular Medicine. 2012; 30(5):1152-1158
Matsumoto S, Otake H, Sekine M, Uehara T, Miyatani H, Mashima H. Appropriate timing of discontinuation of tacrolimus therapy for refractory ulcerative colitis. Clinical Drug Investigation. Aug 2019; 39(8):737-744