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Molecular mechanism of glucocorticoid resistance in inflammatory bowel disease

Natural and synthetic glucocorticoids (GCs) are widely employed in a number of inflammatory, autoimmune and neoplastic diseases, and, despite the introduction of novel therapies, remain the first-line treatment for inducing remission in moderate to severe active Crohns disease and ulcerative colitis. Despite their extensive therapeutic use and the proven effectiveness, considerable clinical evidence of wide inter-individual differences in GC efficacy among patients has been reported, in particular when these agents are used in inflammatory diseases. In recent years, a detailed knowledge of the GC mechanism of action and of the genetic variants affecting GC activity at the molecular level has arisen from several studies. GCs interact with their cytoplasmic receptor, and are able to repress inflammatory gene expression through several distinct mechanisms. The glucocorticoid receptor (GR) is therefore crucial for the effects of these agents: mutations in the GR gene (NR3C1, nuclear receptor subfamily 3, group C, member 1) are the primary cause of a rare, inherited form of GC resistance; in addition, several polymorphisms of this gene have been described and associated with GC response and toxicity. However, the GR is not self-standing in the cell and the receptor-mediated functions are the result of a complex interplay of GR and many other cellular partners. The latter comprise several chaperonins of the large cooperative hetero-oligomeric complex that binds the hormone-free GR in the cytosol, and several factors involved in the transcriptional machinery and chromatin remodeling, that are critical for the hormonal control of target genes transcription in the nucleus. Furthermore, variants in the principal effectors of GCs (e.g. cytokines and their regulators) have also to be taken into account for a comprehensive evaluation of the variability in GC response. Polymorphisms in genes involved in the transport and/or metabolism of these hormones have also been suggested as other possible candidates of interest that could play a role in the observed inter-individual differences in efficacy and toxicity. The best-characterized example is the drug efflux pump P-glycoprotein, a membrane transporter that extrudes GCs from cells, thereby lowering their intracellular concentration. This protein is encoded by the ABCB1/MDR1 gene; this gene presents different known polymorphic sites that can influence its expression and function. This editorial reviews the current knowledge on this topic and underlines the role of genetics in predicting GC clinical response. The ambitious goal of pharmacogenomic studies is to adapt therapies to a patients specific genetic background, thus improving on efficacy and safety rates.

Effect of Thalidomide on Clinical Remission in Children and Adolescents With Refractory Crohn Disease: A Randomized Clinical Trial

IMPORTANCE Pediatric-onset Crohn disease is more aggressive than adult-onset disease, has high rates of resistance to existing drugs, and can lead to permanent impairments. Few trials have evaluated new drugs for refractory Crohn disease in children. OBJECTIVE To determine whether thalidomide is effective in inducing remission in refractory pediatric Crohn disease. DESIGN, SETTING, AND PATIENTS Multicenter, double-blind, placebo-controlled, randomized clinical trial of 56 children with active Crohn disease despite immunosuppressive treatment, conducted August 2008-September 2012 in 6 pediatric tertiary care centers in Italy. INTERVENTIONS Thalidomide, 1.5 to 2.5 mg/kg per day, or placebo once daily for 8 weeks. In an open-label extension, nonresponders to placebo received thalidomide for an additional 8 weeks. All responders continued to receive thalidomide for an additional minimum 52 weeks. MAIN OUTCOMES AND MEASURES Primary outcomes were clinical remission at week 8, measured by Pediatric Crohn Disease Activity Index (PCDAI) score and reduction in PCDAI by ≥25% or ≥75% at weeks 4 and 8. Primary outcomes during the open-label follow-up were clinical remission and 75% response. RESULTS Twenty-eight children were randomized to thalidomide and 26 to placebo. Clinical remission was achieved by significantly more children treated with thalidomide (13/28 [46.4%] vs 3/26 [11.5%]; risk ratio [RR], 4.0 [95% CI, 1.2-12.5]; P = .01; number needed to treat [NNT], 2.86). Responses were not different at 4 weeks, but greater improvement was observed at 8 weeks in the thalidomide group (75% response, 13/28 [46.4%] vs 3/26 [11.5%]; RR, 4.0 [95% CI, 1.2-12.5]; NNT = 2.86; P = .01; and 25% response, 18/28 [64.2%] vs 8/26 [30.8%]; RR, 2.1 [95% CI, 1.1-3.9]; NNT = 2.99; P = .01). Of the nonresponders to placebo who began receiving thalidomide, 11 of 21 (52.4%) subsequently reached remission at week 8 (RR, 4.5 [95% CI, 1.4-14.1]; NNT = 2.45; P = .01). Overall, 31 of 49 children treated with thalidomide (63.3%) achieved clinical remission, and 32 of 49 (65.3%) achieved 75% response. Mean duration of clinical remission in the thalidomide group was 181.1 weeks (95% CI, 144.53-217.76) vs 6.3 weeks (95% CI, 3.51-9.15) in the placebo group (P < .001). Cumulative incidence of severe adverse events was 2.1 per 1000 patient-weeks, with peripheral neuropathy the most frequent severe adverse event. CONCLUSIONS AND RELEVANCE In children and adolescents with refractory Crohn disease, thalidomide compared with placebo resulted in improved clinical remission at 8 weeks of treatment and longer-term maintenance of remission in an open-label follow-up. These findings require replication to definitively determine clinical utility of this treatment. TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT00720538.

Association of BclI polymorphism of the glucocorticoid receptor gene locus with response to glucocorticoids in inflammatory bowel disease

Glucocorticoids (GCs) are immunosuppressive drugs used for the acute treatment of patients with moderate to severe inflammatory bowel disease (IBD),1 but interindividual variability in the response to these agents is frequently observed.2 GCs diffuse freely into cells and bind to an intracellular receptor (hGR/NR3C1), so the sensitivity to these drugs may depend on the receptor number and affinity or on their availability to the receptors, and transport proteins (including P-glycoprotein (Pgp) encoded by the MDR1/ABCB1 gene) can modify their intracellular concentration.3,4 Polymorphisms in the hGR and MDR1 genes have been described in different populations and may contribute to the variability in sensitivity to GCs observed in the clinical setting.3,4 A study was conducted to estimate the impact of genetic variations in hGR and MDR1 genes on the efficacy and individual response to GCs in young patients with IBD. Polymorphisms of the hGR gene ( Bcl I and N363S which are related to GC hypersensitivity and ER22/23EK which is associated with relative resistance to GCs5) and the MDR1 gene (C3435T and G2677T which are associated with changes in Pgp expression and activity6) were studied in 119 young patients …

Genetic predictors of glucocorticoid response in pediatric patients with inflammatory bowel diseases

Background Glucocorticoids (GCs) are used in moderate-to-severe inflammatory bowel diseases (IBD) but their effect is often unpredictable. Aim To determine the influence of 4 polymorphisms in the GC receptor [nuclear receptor subfamily 3, group C, member 1 (NR3C1)], interleukin-1&bgr; (IL-1&bgr;), and NACHT leucine-rich-repeat protein 1 (NALP1) genes, on the clinical response to steroids in pediatric patients with IBD. Methods One hundred fifty-four young IBD patients treated with GCs for at least 30 days and with a minimum follow-up of 1 year were genotyped. The polymorphisms considered are the BclI in the NR3C1 gene, C-511T in IL-1&bgr; gene, and Leu155His and rs2670660/C in NALP1 gene. Patients were grouped as responder, dependant, and resistant to GCs. The relation between GC response and the genetic polymorphisms considered was examined using univariate, multivariate, and Classification and Regression Tree (CART) analysis. Results Univariate analysis showed that BclI polymorphism was more frequent in responders compared with dependant patients (P=0.03) and with the combined dependant and resistant groups (P=0.02). Moreover, the NALP1 Leu155His polymorphism was less frequent in the GC responsive group compared with resistant (P=0.0059) and nonresponder (P=0.02) groups. Multivariate analysis comparing responders and nonresponders confirmed an association between BclI mutated genotype and steroid response (P=0.030), and between NALP1 Leu155His mutant variant and nonresponders (P=0.033). An association between steroid response and male sex was also observed (P=0.034). In addition, Leu155His mutated genotype was associated with steroid resistance (P=0.034). Two CART analyses supported these findings by showing that BclI and Leu155His polymorphisms had the greatest effect on steroid response (permutation P value=0.046). The second CART analysis also identified age of disease onset and male sex as important variables affecting response. Conclusions These results confirm that genetic and demographic factors may affect the response to GCs in young patients with IBD and strengthen the importance of studying high-order interactions for predicting response.

MicroRNAs as tools to predict glucocorticoid response in inflammatory bowel diseases

In spite of the introduction in therapy of highly effective biological agents, glucocorticoids (GCs) are still employed to induce remission in moderate to severe inflammatory bowel diseases (IBD), but considerable inter-individual differences in their efficacy and side effects have been reported. The effectiveness of these drugs is indeed very variable and side effects, particularly severe in pediatric patients, are common and often unpredictable: the understanding of the complex gene regulation mediated by GCs could shed light on the causes of this variability. In this context, microRNAs (miRNAs) represent a new and promising field of research. miRNAs are small non-coding RNA molecules that suppress gene expression at post-transcriptional level, and are fine-tuning regulators of diverse biological processes, including the development and function of the immune system, apoptosis, metabolism and inflammation. Emerging data have implicated the deregulated expression of certain miRNA networks in the pathogenesis of autoimmune and inflammatory diseases, such as IBD. There is a great interest in the identification of the role of miRNAs in the modulation of pharmacological response; however, the association between miRNA and GC response in patients with IBD has not yet been evaluated in a prospective clinical study. The identification of miRNAs differently expressed as a consequence of GC treatment in comparison to diagnosis, represents an important innovative approach that could be translated into clinical practice. In this review we highlight the altered regulation of proteins involved in GC molecular mechanism by miRNAs, and their potential role as molecular markers useful for predicting in advance GC response.

Association between BclI polymorphism in the NR3C1 gene and in vitro individual variations in lymphocyte responses to methylprednisolone

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT In vitro lymphocyte steroid sensitivity has been suggested as a useful tool to predict in vivo response to glucocorticoid treatment in different inflammatory chronic diseases. A correlation between genetic polymorphisms and clinical response to glucocorticoids has been demonstrated in these patients. WHAT THIS STUDY ADDS The BclI polymorphism in the glucocorticoid receptor (NR3C1) gene is associated with higher methylprednisolone potency in vitro. The combined evaluation of the in vitro sensitivity to methylprednisolone and BclI polymorphism could represent an aid for physicians to adjust therapy a priori. AIM To evaluate the association between the in vitro sensitivity of peripheral blood mononuclear cells (PBMCs) to methylprednisolone (MP) and the presence of genetic polymorphisms involved in glucocorticoid (GC) response. METHODS In vitro MP inhibition of the proliferation of lymphocytes stimulated with concanavalin A was determined. Non linear regression of dose-response data was performed computing the MP concentration required to reduce proliferation to 50% (IC(50) ). The maximum inhibition achievable at the highest MP concentration (I(max) ) was also calculated. Moreover, the Taqman technique was used to analyze the BclI polymorphism in the NR3C1 gene and the Leu155His polymorphism in the NALP1 gene. RESULTS A significant association between the BclI mutated genotype and an increased in vitro sensitivity to GCs was observed. CONCLUSIONS The a priori evaluation of the BclI polymorphism, associated with a lymphocyte proliferation assay, could represent a useful diagnostic tool for the optimization of steroid treatment.

Deletion of glutathione-s-transferase m1 reduces azathioprine metabolite concentrations in young patients with inflammatory bowel disease.

Goals: To investigate, in young patients with inflammatory bowel disease (IBD) treated with azathioprine, the association between genetic polymorphisms of thiopurine-S-methyl-transferase (TPMT), inosine-triphosphate-pyrophosphatase (ITPA), and glutathione-S-transferases (GST), involved in azathioprine metabolism, the concentration of the main metabolites of azathioprine, thioguanine nucleotides (TGNs) and the methylated nucleotides (MMPN), and the dose of the medication. Background: Azathioprine is widely used in IBD as an immunosuppressive agent, particularly to maintain remission in patients with steroid refractory disease. Azathioprine is a prodrug and requires conversion to its active form mercaptopurine, which has no intrinsic activity, and is activated by the enzymes of the purine salvage pathway to TGNs. Polymorphisms in genes of enzymes involved in azathioprine metabolism influence the efficacy and toxicity of treatment. Study: Seventy-five young patients with IBD treated with azathioprine at least for 3 months were enrolled and genotyped for the selected genes; for these patients, TGN and MMPN metabolites were measured by high performance liquid chromatography in erythrocytes. Results: GST-M1 deletion was associated with lower TGN/dose ratio (P=0.0030), higher azathioprine dose requirement (P=0.022), and reduced response to therapy (P=0.0022). TPMT variant genotype was associated with lower MMPN concentration (P=0.0064) and increased TGN/dose ratio (P=0.0035). ITPA C94A polymorphism resulted in an increased MMPN concentration (P=0.037). Conclusions: This study describes the effect of candidate genetic polymorphisms in TPMT, ITPA, and GST-M1 on azathioprine pharmacokinetics in IBD patients, showing, for the first time, relevant effects of GST-M1 genotype on azathioprine metabolites concentration.

Pharmacogenetics of azathioprine in inflammatory bowel disease: A role for glutathione-S-transferase?

Azathioprine is a purine antimetabolite drug commonly used to treat inflammatory bowel disease (IBD). In vivo it is active after reaction with reduced glutathione (GSH) and conversion to mercaptopurine. Although this reaction may occur spontaneously, the presence of isoforms M and A of the enzyme glutathione-S-transferase (GST) may increase its speed. Indeed, in pediatric patients with IBD, deletion of GST-M1, which determines reduced enzymatic activity, was recently associated with reduced sensitivity to azathioprine and reduced production of azathioprine active metabolites. In addition to increase the activation of azathioprine to mercaptopurine, GSTs may contribute to azathioprine effects even by modulating GSH consumption, oxidative stress and apoptosis. Therefore, genetic polymorphisms in genes for GSTs may be useful to predict response to azathioprine even if more in vitro and clinical validation studies are needed.

Glutathione-S-transferase-P1 I105V polymorphism and response to antenatal betamethasone in the prevention of respiratory distress syndrome.

PurposeThe aim of this pilot study was to assess the association between polymorphisms in genes that encode for proteins involved in the pharmacokinetics/pharmacodynamics of glucocorticoids and the occurrence of respiratory distress syndrome (RDS) in preterm infants born to mothers treated with a complete course of betamethasone.MethodsSixty-two preterm infants were enrolled. The C1236T, G2677T, and C3435T polymorphisms in the ABCB1 gene, BclI, N363S and ER22/23EK in the NR3C1 gene, I105V in the GST-P1 gene and GST-M1 and GST-T1 deletions were analyzed, and their association with the occurrence of RDS was assessed.ResultsIn univariate analysis, the heterozygous and homozygous presence of the I105V variant in the GST-P1 gene seemed to confer protection against the occurrence of RDS (P = 0.032), while no association for all other polymorphisms was observed. In multivariate analysis, selection from the reference model of independent variables based on AIC (Akaike information criteria) maintained three variables in the model: gestation, C3435T, and GST-P1 genotype.ConclusionsPolymorphisms of the GST-P1 gene may influence the effect of antenatal steroids on the newborn lung.

Failure of interferon-γ pre-treated mesenchymal stem cell treatment in a patient with Crohn's disease.

Mesenchymal stem cells (MSC) are cells of stromal origin which exhibit unlimited self-renewal capacity and pluripotency in vitro. It has recently been observed that MSC may also exert a profound immunosuppressive and anti-inflammatory effect both in vitro and in vivo with consequent potential use in autoimmune disorders. We present the case of a patient suffering from childhood-onset, multidrug resistant and steroid-dependent Crohns disease who underwent systemic infusions of MSC, which led to a temporary reduction in CCR4, CCR7 and CXCR4 expression by T-cells, and a temporary decrease in switched memory B-cells, In addition, following MSC infusion, lower doses of steroids were needed to inhibit proliferation of the patients peripheral blood mononuclear cells. Despite these changes, no significant clinical benefit was observed, and the patient required rescue therapy with infliximab and subsequent autologous hematopoietic stem cell transplantation. The results of biological and in vitro observations after MSC use and the clinical effects of infusion are discussed, and a brief description is provided of previous data on MSC-based therapy in autoimmune disorders.