Review article: mitogen-activated protein kinases in chronic intestinal inflammation - targeting ancient pathways to treat modern diseases

Over-production of exopolysaccharide by Lacticaseibacillus rhamnosus CNCM I-3690 strain cutbacks its beneficial effect on the host

Most lactobacilli produce extracellular polysaccharides that are considered to contribute to the probiotic effect of many strains. Lacticaseibacillus rhamnosus CNCM I-3690 is an anti-inflammatory strain able to counterbalance gut barrier dysfunction. In this study ten spontaneous variants of CNCM I-3690 with different EPS-production were generated and characterized by their ropy phenotype, the quantification of the secreted EPS and genetic analysis. Amongst them, two were further analysed in vitro and in vivo: an EPS over-producer (7292) and a low-producer derivative of 7292 (7358, with similar EPS levels than the wild type (WT) strain). Our results showed that 7292 does not have anti-inflammatory profile in vitro, and lost the capacity to adhere to the colonic epithelial cells as well as the protective effect on the permeability. Finally, 7292 lost the protective effects of the WT strain in a murine model of gut dysfunction. Notably, strain 7292 was unable to stimulate goblet cell mucus production and colonic IL-10 production, all key features for the beneficial effect of the WT strain. Furthermore, transcriptome analysis of colonic samples from 7292-treated mice showed a down-regulation of anti-inflammatory genes. Altogether, our results point out that the increase of EPS production in CNCM I-3690 impairs its protective effects and highlight the importance of the correct EPS synthesis for the beneficial effects of this strain.

Commensal fungi and their cell-wall β-glucans direct differential responses in human intestinal epithelial cells

Intestinal epithelial cells (IECs) are the first to encounter luminal antigens and play an active role in intestinal immune responses. We previously reported that β-glucans, major fungal cell-wall glycans, induced chemokine secretion by IEC lines in a Dectin-1- and Syk-dependent manner. Here, we show that in contrast to β-glucans, stimulation of IEC lines with Candida albicans and Saccharomyces cerevisiae did not induce secretion of any of the proinflammatory cytokines IL-8, CCL2, CXCL1, and GM-CSF. Commensal fungi and β-glucans activated Syk and ERK in IEC lines. However, only β-glucans activated p38, JNK, and the transcription factors NF-κB p65 and c-JUN, which were necessary for cytokine secretion. Furthermore, costimulation of IEC lines with β-glucans and C. albicans yielded decreased cytokine secretion compared to stimulation with β-glucans alone. Finally, ex vivo stimulation of human colonic mucosal explants with zymosan and C. albicans, leads to epithelial Syk and ERK phosphorylation, implying recognition of fungi and similar initial signaling pathways as in IEC lines. Lack of cytokine secretion in response to commensal fungi may reflect IECs' response to fungal glycans, other than β-glucans, that contribute to mucosal tolerance. Skewed epithelial response to commensal fungi may impair homeostasis and contribute to intestinal inflammation.

Identification and Characterization of MAPK Signaling Pathway Genes and Associated lncRNAs in the Ileum of Piglets Infected by Clostridium perfringens Type C

Clostridium perfringens type C (C. perfringens type C) is one of the main microbial pathogens responsible for piglet diarrhea worldwide, causing substantial economic losses for pig-rearing industries. The mitogen-activated protein kinase (MAPK) signaling pathway is a key regulator of inflammatory bowel disease, especially necrotic enteritis. However, whether and how the MAPK signaling pathway is involved in regulating the process of piglet diarrhea when challenged by C. perfringens type C are still unknown. Here, we screened 38 differentially expressed genes (DEGs) in piglets' ileum tissues experimentally infected with C. perfringens type C that were enriched in the Sus scrofa MAPK signaling pathway, based on our previous transcriptome data. Of these DEGs, 12 genes (TRAF2, MAPK8, and GADD45G, among others) were upregulated whereas 26 genes (MAPK1, TP53, and CHUK, among others) were downregulated in the infected group. Our results showed that MAPK1, TP53, MAPK8, MYC, and CHUK were in the core nodes of the PPI network. Additionally, we obtained 35 lncRNAs from the sequencing data, which could be trans-targeted to MAPK signaling pathway genes and were differentially expressed in the ileum tissues infected with C. perfringens. We used qRT-PCR to verify the expression levels of genes and lncRNAs related to the MAPK signaling pathway; their expression patterns were consistent with RNA sequencing data. Our results provide strong support for deeply exploring the role of the MAPK signaling pathway in diarrhea caused by C. perfringens type C.

The potential probiotic Lactobacillus rhamnosus CNCM I-3690 strain protects the intestinal barrier by stimulating both mucus production and cytoprotective response

The gut barrier plays an important role in human health. When barrier function is impaired, altered permeability and barrier dysfunction can occur, leading to inflammatory bowel diseases, irritable bowel syndrome or obesity. Several bacteria, including pathogens and commensals, have been found to directly or indirectly modulate intestinal barrier function. The use of probiotic strains could be an important landmark in the management of gut dysfunction with a clear impact on the general population. Previously, we found that Lactobacillus rhamnosus CNCM I-3690 can protect intestinal barrier functions in mice inflammation model. Here, we investigated its mechanism of action. Our results show that CNCM I-3690 can (i) physically maintain modulated goblet cells and the mucus layer and (ii) counteract changes in local and systemic lymphocytes. Furthermore, mice colonic transcriptome analysis revealed that CNCM I-3690 enhances the expression of genes related to healthy gut permeability: motility and absorption, cell proliferation; and protective functions by inhibiting endogenous proteases. Finally, SpaFED pili are clearly important effectors since an L. rhamnosus ΔspaF mutant failed to provide the same benefits as the wild type strain. Taken together, our data suggest that CNCM I-3690 restores impaired intestinal barrier functions via anti-inflammatory and cytoprotective responses.

Diet-Induced Hyperhomocysteinaemia Increases Intestinal Inflammation in an Animal Model of Colitis

BACKGROUND

Hyperhomocysteinaemia [HHcy] is a common phenomenon observed in patients with inflammatory bowel disease [IBD]. Homocysteine is a pro-inflammatory molecule and has been identified as a risk factor for cardiovascular and cerebral diseases. Whether HHcy contributes to the chronic inflammation of the colon in IBD has rarely been explored. The aim of this study was to investigate the effect of HHcy on dextran sulphate sodium [DSS]-induced colitis.

METHODS

Wistar rats were randomly divided into eight groups: [1] Control; [2] HHcy; [3] p38 inhibitor; [4] DSS; [5] HHcy + DSS; [6] HHcy + DSS+p38 inhibitor; [7] HHcy + DSS [21 days]; and [8] HHcy + DSS + folate [21 days]. Colitis was induced by 5% DSS. HHcy was induced by the normal rodent diet containing 1.7% methionine. The mRNA expression of interleukin 17 [IL-17] was detected by qRT-PCR. The protein expressions of IL-17, retinoid-related orphan nuclear receptor-γt [RORγt], p38 MAPK, phosphorylated-p38 MAPK, cytosolic phospolipaseA2 [cPLA2], phosphorylated-cPLA2, and cyclooxygenase 2 [COX2] were detected by immunoblot analysis.

RESULTS

The rats of the HHcy + DSS group had significantly higher myeloperoxidase [MPO] activity, DAI score, and histological score. HHcy significantly increased the plasma concentration, the colonic mRNA, and the protein levels of IL-17. HHcy also activated p38 MAPK and cPLA2, and increased the protein levels of COX2 and RORγt as well as the plasma level of prostaglandin E2 [PGE2]. Folate supplementation down-regulated homocysteine-induced IL-17 and RORγt expressions.

CONCLUSIONS

HHcy aggravated DSS-induced colitis by stimulating IL-17 expression via the p38/cPLA2/COX2/PGE2 signalling pathway. The folate supplementation may represent a novel approach to treating the chronic intestinal inflammation of IBD exacerbated by HHcy.

Insight into the Structural Determinants of Imidazole Scaffold-Based Derivatives as TNF-α Release Inhibitors by in Silico Explorations

Presently, 151 widely-diverse pyridinylimidazole-based compounds that show inhibitory activities at the TNF-α release were investigated. By using the distance comparison technique (DISCOtech), comparative molecular field analysis (CoMFA), and comparative molecular similarity index analysis (CoMSIA) methods, the pharmacophore models and the three-dimensional quantitative structure-activity relationships (3D-QSAR) of the compounds were explored. The proposed pharmacophore model, including two hydrophobic sites, two aromatic centers, two H-bond donor atoms, two H-bond acceptor atoms, and two H-bond donor sites characterizes the necessary structural features of TNF-α release inhibitors. Both the resultant CoMFA and CoMSIA models exhibited satisfactory predictability (with Q² (cross-validated correlation coefficient) = 0.557, R²_ncv (non-cross-validated correlation coefficient) = 0.740, R²_pre (predicted correlation coefficient) = 0.749 and Q² = 0.598, R²_ncv = 0.767, R²_pre = 0.860, respectively). Good consistency was observed between the 3D-QSAR models and the pharmacophore model that the hydrophobic interaction and hydrogen bonds play crucial roles in the mechanism of actions. The corresponding contour maps generated by these models provide more diverse information about the key intermolecular interactions of inhibitors with the surrounding environment. All these models have extended the understanding of imidazole-based compounds in the structure-activity relationship, and are useful for rational design and screening of novel 2-thioimidazole-based TNF-α release inhibitors.

β-Cryptoxanthin supplementation prevents cigarette smoke-induced lung inflammation, oxidative damage, and squamous metaplasia in ferrets

In epidemiologic studies, high intake of β-cryptoxanthin has been associated with a decreased risk of lung cancer, particularly among current smokers. However, data are not available from well-controlled animal studies to examine the effects of β-cryptoxanthin on cigarette smoke-induced lung lesions, and the biological mechanisms by which β-cryptoxanthin might affect lung carcinogenesis. We evaluated the effects of β-cryptoxanthin supplementation on cigarette smoke-induced squamous metaplasia, inflammation, and changes in protein levels of proinflammatory cytokine [tumor necrosis factor alpha (TNFα)] and transcription factors [nuclear factor kappa B (NF-κB) and activator protein-1 (AP-1)], as well as on smoke-induced oxidative DNA damage [8-hydroxy-2'-deoxyguanosine (8-OHdG)] in the lung tissue of ferrets. Thirty-six male ferrets were assigned to cigarette smoke exposure or no exposure and to low-dose, or high-dose β-cryptoxanthin, or no dose (2 × 3 factorial design) for 3 months. β-Cryptoxanthin supplementation dose-dependently increased plasma and lung β-cryptoxanthin levels in ferrets, whereas cigarette smoke exposure lowered plasma and lung β-cryptoxanthin levels. β-Cryptoxanthin at both doses significantly decreased smoke-induced lung squamous metaplasia and inflammation. β-Cryptoxanthin also substantially reduced smoke-elevated TNFα levels in alveolar, bronchial, bronchiolar, and bronchial serous/mucous gland epithelial cells and in lung macrophages. Moreover, β-cryptoxanthin decreased smoke-induced activation of NF-κB, expression of AP-1 and levels of 8-OHdG. The beneficial effects of β-cryptoxanthin were stronger for high-dose β-cryptoxanthin than for low-dose β-cryptoxanthin. Data from this study indicate that β-cryptoxanthin provides a beneficial effect against cigarette smoke-induced inflammation, oxidative DNA damage and squamous metaplasia in the lungs.

Oxidative state and IL-6 production in intestinal myofibroblasts of Crohn's disease patients

BACKGROUND

Intestinal subepithelial myofibroblasts (ISEMFs) produce inflammatory cytokines in response to certain stimuli. In the intestine of patients with Crohn's disease (CD), cytokine synthesis is modified and an increased number of myofibroblasts has been observed. The intracellular redox state influences cytokine production and oxidative stress is present in the intestinal mucosa of CD patients.

METHODS

This study was performed in ISEMFs isolated from the colon of patients with active CD and in a myofibroblast cell line derived from human colonic mucosa: 18Co cells. Cellular glutathione (GSH) levels were modulated by treatment with buthionine sulfoximine, an inhibitor of GSH synthesis, or N-acetylcysteine, a GSH precursor. GSH and oxidized glutathione (GSSG) levels were measured by high-performance liquid chromatography (HPLC) methods. Interleukin (IL)-6 production was detected by enzyme-linked immunosorbent assay (ELISA).

RESULTS

ISEMFs of CD patients exhibited an increased oxidative state due to a decrease in the GSH/GSSG ratio, which is related to an increase in basal IL-6 production or is stimulated by tumor necrosis factor alpha (TNFα) or bacterial products. This relationship was also confirmed in 18Co cells. Phosphorylation and activation of ERK1/2 and p38 MAPK, which are signaling factors involved in the IL-6 synthesis, were also increased when there is oxidative stress in ISEMFs.

CONCLUSIONS

This study shows for the first time in ISEMFs of CD patients an increased production of IL-6 synthesis related to the decrease in the GSH/GSSH ratio, suggesting redox regulation with the involvement of specific kinase activation. The present data shed light on the pathogenesis of inflammatory chronic processes and relapses that occur in this pathology.

Distinct effects of p38alpha deletion in myeloid lineage and gut epithelia in mouse models of inflammatory bowel disease

BACKGROUND & AIMS

p38Alpha is a mitogen-activated protein kinase that mediates inflammatory responses, but its role in inflammatory bowel disease is unclear. The effects of p38alpha inhibitors have been inconsistent in animal models and clinical studies of inflammatory bowel disease, possibly arising from the different functions of p38alpha in different tissues or cell types. We investigated the effects of p38alpha inhibition in myeloid versus colonic epithelium.

METHODS

We studied mice with myeloid cell-specific and intestinal epithelial cell-specific disruption of p38alpha (LtrLys(Cre)-p38alpha(Delta/Delta) mice and Villin(Cre)-p38alpha(Delta/Delta) mice), as well as p38beta, gamma, and delta knockout. Colitis was induced using dextran sodium sulfate or trinitrobenzene sulfonic acid (TNBS).

RESULTS

Mice with myeloid cell-specific deletion of p38alpha had less inflammation and an improved disease condition compared with wild-type mice, whereas mice with intestinal epithelial cell-specific deletion of p38alpha had increased progression of colitis that resulted from disrupted intestinal epithelial homeostasis. The distinct effects of p38alpha disruption in different tissue types might underlie the unsuccessful therapeutic application of p38 inhibitors to colitis. We found that a gamma-secretase inhibitor, which functions opposite that of a p38 inhibitor in the regulation of intestinal epithelial homeostasis, can significantly improve the effects of a p38 inhibitor in reducing colitis.

CONCLUSIONS

p38Alpha has distinct functions in mouse myeloid cells versus colonic epithelium; these differences should be taken into consideration in defining the role of p38alpha in inflammation and developing p38 inhibitors as therapeutics.

Dietary polyphenols can modulate the intestinal inflammatory response

Inflammatory bowel diseases (IBD) arise from multiple causes, including environmental factors, gut microflora, immunity, and genetic predispositions. In the course of IBD, immune homeostasis and intestinal mucosa barrier integrity are impaired. Among natural preventive treatments that have been identified to date, polyphenols appear as promising candidates. They have been shown to protect against several diseases, including cardiovascular diseases and cancers, and they have anti-inflammatory properties in non-intestinal models. This paper will review the literature that has described to date some effects of polyphenols on intestinal inflammation. Studies, conducted using in vivo and in vitro models, provide evidence that pure polyphenolic compounds and natural polyphenolic plant extracts can modulate intestinal inflammation.

FR167653, a p38 mitogen-activated protein kinase inhibitor, aggravates experimental colitis in mice

AIM: To investigate the effects of FR167653 on the development of dextran sulfate sodium (DSS)-induced colitis in mice.

METHODS: BALB/c mice were fed rodent chow containing 3.5% (wt/wt) DSS. The recipient mice underwent intra-peritoneal injection of vehicles or FR167653 (30 mg/kg per day). The mice were sacrificed on day 14, and the degree of colitis was assessed. Immunohistochemical analyses for CD4⁺ T cell and F4/80⁺ macrophage infiltration were also performed. Mucosal cytokine expression was analyzed by RT-PCR.

RESULTS: The body weight loss was more apparent in the FR167653-treated DSS mice than in the vehicle-treated DSS mice. The colon length was shorter in the FR167653-treated DSS mice than in the vehicle-treated DSS mice. Disease activity index and histological colitis score were significantly higher in FR167653- than in vehicle-treated DSS animals. Microscopically, mucosal edema, cellular infiltration (CD4 T cells and F4/80 macrophages), and the disruption of the epithelium were much more severe in FR167653-treated mice than in controls. Mucosal mRNA expression for interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) were found to be markedly reduced in FR167653-treated DSS mice.

CONCLUSION: Treatment with FR167653 aggravated DSS colitis in mice. This effect was accompanied by a reduction of mucosal IL-1β and TNF-α expression, suggesting a role of p38 mitogen-activated protein kinase (MAPK)-mediated proinflammatory cytokine induction in host defense mechanisms.

Role of the JNK signal transduction pathway in inflammatory bowel disease

The c-Jun NH2-terminal Kinase (JNK) pathway represents one sub-group of the mitogen-activated protein (MAP) kinases which plays an important role in various inflammatory diseases states, including inflammatory bowel disease (IBD). Significant progress towards understanding the function of the JNK signaling pathway has been achieved during the past few years. Blockade of the JNK pathway with JNK inhibitors in animal models of IBD lead to resolution of intestinal inflammation. Current data suggest specific JNK inhibitors hold promise as novel therapies in IBD.

ADOA3R as a therapeutic target in experimental colitis: proof by validated high-density oligonucleotide microarray analysis

Adenosine A3 receptors (ADOA3Rs) are emerging as novel purinergic targets for treatment of inflammatory diseases. Our goal was to assess the protective effect of the ADOA3R agonist N(6)-(3-iodobenzyl)-adenosine-5-N-methyluronamide (IB-MECA) on gene dysregulation and injury in a rat chronic model of 2,4,6-trinitrobenzene sulfonic acid (TNBS)--induced colitis. It was necessary to develop and validate a microarray technique for testing the protective effects of purine-based drugs in experimental inflammatory bowel disease. High-density oligonucleotide microarray analysis of gene dysregulation was assessed in colons from normal, TNBS-treated (7 days), and oral IB-MECA-treated rats (1.5 mg/kg b.i.d.) using a rat RNU34 neural GeneChip of 724 genes and SYBR green polymerase chain reaction. Analysis included clinical evaluation, weight loss assessment, and electron paramagnetic resonance imaging/spin-trap monitoring of free radicals. Remarkable colitis-induced gene dysregulation occurs in the most exceptional cluster of 5.4% of the gene pool, revealing 2 modes of colitis-related dysregulation. Downregulation occurs in membrane transporter, mitogen-activated protein (MAP) kinase, and channel genes. Upregulation occurs in chemokine, cytokine/inflammatory, stress, growth factor, intracellular signaling, receptor, heat shock protein, retinoid metabolism, neural, remodeling, and redox-sensitive genes. Oral IB-MECA prevented dysregulation in 92% of these genes, histopathology, gut injury, and weight loss. IB-MECA or adenosine suppressed elevated free radicals in ex vivo inflamed gut. Oral IB-MECA blocked the colitis-induced upregulation (<or=20-fold) of Bzrp, P2X1R, P2X4R, P2X7R, P2Y2R, P2Y6R, and A2aR/A2bR but not A1R or A3R genes or downregulated P2X2R, P2Y1R, and P2Y4R. Real-time SYBR green polymerase chain reaction validated gene chip data for both induction of colitis and treatment with IB-MECA for >90% of genes tested (33 of 37 genes). We conclude that our validated high-density oligonucleotide microarray analysis is a powerful technique for molecular gene dysregulation studies to assess the beneficial effects of purine-based or other drugs in experimental colitis. ADOA3R is new potential therapeutic target for inflammatory bowel disease.

Structure-driven HtL: design and synthesis of novel aminoindazole inhibitors of c-Jun N-terminal kinase activity

The design and synthesis of a new series of c-Jun N-terminal kinase inhibitors are reported. The novel series of substituted amino indazoles were designed based on a combination of hits from high-throughput screening and X-ray crystal structure information of the compounds crystallised into the JNK-1 ATP binding site.

Specific inhibition of c-Raf activity by semapimod induces clinical remission in severe Crohn's disease

There is a substantial need for novel treatment strategies in Crohn's disease (CD), a chronic relapsing inflammatory disease of the gut. In an earlier study, we reported clinical efficacy of a 2-wk treatment with semapimod (CNI-1493) in 12 patients with therapy resistant CD. The aim of this study was to identify the cellular target underlying semapimod action. In vitro experiments with murine macrophages showed impaired MAPK signaling and decreased cytokine production due to semapimod treatment. In vitro kinase assays revealed c-Raf as a direct molecular target of semapimod, and semapimod did not affect b-Raf enzymatic activity. Immunohistochemistry performed on paired colon biopsies obtained from CD patients (n = 6) demonstrated increased expression of phospho-MEK, the substrate of Raf. Strikingly, phospho-MEK levels were significantly decreased in patients with a good clinical response to semapimod, but no decrease in phospho-MEK expression was observed in a clinically nonresponsive patient. In conclusion, this study identifies c-Raf as a molecular target of semapimod action and suggests that decreased c-Raf activity correlates with clinical benefit in CD. Our observations indicate that c-Raf inhibitors are prime candidates for the treatment of CD.

Identifying and defusing weapons of mass inflammation in carcinogenesis

The continued cancer risks associated with chronic inflammation necessitate the identification of inflammatory molecules and the cancer pathways they affect. Evidence indicates that there are multiple mechanisms linking inflammation to cancer and that there are multiple targets for chemoprevention. Here, we review some of the key factors and the cancer pathways they disturb as a necessary prerequisite to the identification of targets for chemoprevention.

Inhibition of RICK/Nuclear Factor-κB and p38 Signaling Attenuates the Inflammatory Response in a Murine Model of Crohn Disease

Nuclear factor-kappaB (NF-kappaB) is the main target of anti-inflammatory therapies in human chronic inflammatory bowel diseases (IBD), Crohn disease, and ulcerative colitis. This study investigates the molecular anti-inflammatory mechanisms of SB203580, an inhibitor of the mitogen-activated protein kinase p38. The murine trinitrobenzene sulfonic acid (TNBS)-induced colitis was used as an established model of human Crohn disease. Here we show that SB203580 improved the clinical condition, reduced intestinal inflammation, and suppressed mRNA levels of pro-inflammatory cytokines elevated upon induction of colitis. Besides p38 kinase activity, the "classical" IkappaB-dependent NF-kappaB pathway was strongly up-regulated during colitis induction, whereas the "alternative" was not. SB203580 treatment resulted in a drastic down-regulation of p38 and NF-kappaB activity. The molecular analysis of NF-kappaB activation revealed that Rip-like interacting caspase-like apoptosis-regulatory protein kinase (RICK), a key component of a pathway leading to NF-kappaB induction, is also strongly inhibited by SB203580. In contrast, SB203580 had no effect on the colitis-induced activation of other potential NF-kappaB-activating kinases such as protein kinase C (PKC), mixed lineage kinase 3, and the oncogene product Cot/TPL2. Thus, the inhibitory effect of SB203580 on NF-kappaB activation is to a large extent mediated by RICK inhibition. RICK is the effector kinase of the intracellular receptor of bacterial peptidoglycan NOD. Because bacterial products are suggested to be the key pathogenic agents triggering IBD, inhibition of the NOD/RICK pathway may serve as a novel target of future therapies in human IBD.

Inhibition of p38 MAP kinase- and RICK/NF-kappaB-signaling suppresses inflammatory bowel disease

Ulcerative colitis and Crohn's disease are the two entities of chronic inflammatory bowel diseases (IBD). One of the main pathogenic mechanisms is probably a dysregulated immune response triggered by products of the enteric bacterial flora. The goal of this study was to evaluate the effects of the p38 mitogen-activated protein kinase (MAPK) inhibitor SB203580 on inflammatory responses using the DSS-induced experimental colitis model in mice reflecting human IBD. We found that SB203580 improved the clinical score, ameliorates the histological alterations, and reduces the mRNA levels of proinflammatory cytokines. In addition to p38 kinase activity, the "classical" and the "alternative" NF-kappaB pathways were also strongly activated during colitis induction. All three pathways were drastically down-regulated by SB203580 treatment. An analysis of the molecular basis of NF-kappaB activation revealed that Rip-like interacting caspase-like apoptosis-regulatory protein kinase (RICK), a key component of a pathway leading to NF-kappaB induction, is also strongly inhibited by SB203580. Since RICK is an effector kinase of NOD2, an intracellular receptor of bacterial peptidoglycan, these results support the notion that NOD signaling could play a pivotal role in the IBD pathogenesis. Thus, RICK could represent a novel target for future therapies in human IBD.

Pharmacogenetics of inflammatory bowel disease

The therapeutic efficacy and toxicity of many commonly employed drugs show interindividual variations that relate to several factors, including genetic variability in drug-metabolizing enzymes, transporters or targets. The study of the genetic determinants influencing interindividual variations in drug response is known as pharmacogenetics. The ability to identify, through preliminary genetic screening, the patients most likely to respond positively to a medication should facilitate the best choice of treatment for each patient; drugs likely to exhibit low efficacy or to give negative side-effects can be avoided. Among the medications used for inflammatory bowel disease, the best studied pharmacogenetically is azathioprine. The hematopoietic toxicity of azathioprine is due to single nucleotide polymorphisms in the thiopurine S-methyltransferase enzyme. Additionally, likely gene targets have been investigated to predict the response to glucocorticoids and infliximab, a monoclonal antibody against tumour necrosis factor that induces remission in approximately 30-40% of patients. However, no genetic predictor of response has been identified in either case.