Mark E. Gerich

Myeloid-derived miR-223 regulates intestinal inflammation via repression of the NLRP3 inflammasome

MicroRNA (miRNA)-mediated RNA interference regulates many immune processes, but how miRNA circuits orchestrate aberrant intestinal inflammation during inflammatory bowel disease (IBD) is poorly defined. Here, we report that miR-223 limits intestinal inflammation by constraining the nlrp3 inflammasome. miR-223 was increased in intestinal biopsies from patients with active IBD and in preclinical models of intestinal inflammation. miR-223-/y mice presented with exacerbated myeloid-driven experimental colitis with heightened clinical, histopathological, and cytokine readouts. Mechanistically, enhanced NLRP3 inflammasome expression with elevated IL-1&bgr; was a predominant feature during the initiation of colitis with miR-223 deficiency. Depletion of CCR2+ inflammatory monocytes and pharmacologic blockade of IL-1&bgr; or NLRP3 abrogated this phenotype. Generation of a novel mouse line, with deletion of the miR-223 binding site in the NLRP3 3′ untranslated region, phenocopied the characteristics of miR-223-/y mice. Finally, nanoparticle-mediated overexpression of miR-223 attenuated experimental colitis, NLRP3 levels, and IL-1&bgr; release. Collectively, our data reveal a previously unappreciated role for miR-223 in regulating the innate immune response during intestinal inflammation.

Towards personalized care in IBD

The expanding knowledge of the role of genetic variants involved in the susceptibility to IBD heralds an era of disease categorization beyond Crohns disease and ulcerative colitis. A more robust molecular definition of the spectrum of IBD subtypes is likely to be based on specific molecular pathways that determine not only disease susceptibility but also disease characteristics such as location, natural history and therapeutic response. Evolving diagnostic panels for IBD will include clinical variables and genetic markers as well as other indicators of gene function and interaction with environmental factors, such as the microbiome. Multimodal algorithms that combine clinical, serologic and genetic information are likely to be useful in predicting disease course. Variation in IBD-susceptibility and drug-related pathway genes seems to influence the response to anti-TNF therapy. Furthermore, gene expression signatures and composite models have both shown promise as predictors of therapeutic response. Ultimately, models based on combinations of genotype and gene expression data with clinical, biochemical, serological, and microbiome data for clinically meaningful subgroups of patients should permit the development of tools for individualized risk stratification and treatment selection.

Defective leukocyte GM-CSF receptor (CD116) expression and function in inflammatory bowel disease.

BACKGROUND & AIMSnInflammatory bowel disease (IBD) refers to 2 chronic inflammatory diseases of the intestine, ie, ulcerative colitis and Crohns disease. IBD results from environmental factors (eg, bacterial antigens) triggering a dysregulated immune response in genetically predisposed hosts. Although the basis of IBD is incompletely understood, a number of recent studies have implicated defective innate immune responses in the pathogenesis of IBD. In this regard, there is much interest in therapies that activate innate immunity (eg, recombinant granulocyte-macrophage colony-stimulating factor).nnnMETHODSnIn this study, we screened expression and function of circulating leukocyte granulocyte-macrophage colony-stimulating factor receptor (CD116) messenger RNA and surface protein in 52 IBD patients and 52 healthy controls.nnnRESULTSnOur results show that both granulocyte and monocyte CD116 levels, but not CD114 or interleukin-3Rα, were significantly decreased in IBD compared to control (P<.001) and disease controls (irritable bowel syndrome; P<.001; rheumatoid arthritis; P<.025). IBD-associated CD116 repression was more prominent in patients with ulcerative colitis compared to Crohns disease (P<.05), was independent of disease activity (P>.05), and was not influenced by current medications (P>.05). Receiver operating characteristic curve analysis revealed that leukocyte CD116 expression is a sensitive (85%) and specific (92%) biomarker for IBD. Moreover, granulocyte CD116-mediated function (phosphorylation of signal transducers and activators of transcription 3) paralleled decreased expression of CD116 in IBD granulocytes compared to control (P<.001).nnnCONCLUSIONSnThese studies identify defective expression and function of CD116 as a distinguishing feature of IBD and implicate an associated defect in innate immune responses toward granulocyte-macrophage colony-stimulating factor.

Medical Marijuana for Digestive Disorders: High Time to Prescribe?

The use of recreational and medical marijuana is increasingly accepted by the general public in the United States. Along with growing interest in marijuana use has come an understanding of marijuana’s effects on normal physiology and disease, primarily through elucidation of the human endocannabinoid system. Scientific inquiry into this system has indicated potential roles for marijuana in the modulation of gastrointestinal symptoms and disease. Some patients with gastrointestinal disorders already turn to marijuana for symptomatic relief, often without a clear understanding of the risks and benefits of marijuana for their condition. Unfortunately, that lack of understanding is shared by health-care providers. Marijuana’s federal legal status as a Schedule I controlled substance has limited clinical investigation of its effects. There are also potential legal ramifications for physicians who provide recommendations for marijuana for their patients. Despite these constraints, as an increasing number of patients consider marijuana as a potential therapy for their digestive disorders, health-care providers will be asked to discuss the issues surrounding medical marijuana with their patients.

Tryptophan metabolite activation of the aryl hydrocarbon receptor regulates IL-10 receptor expression on intestinal epithelia

IL-10 is a potent anti-inflammatory cytokine that inhibits the production of proinflammatory mediators. Signaling by IL-10 occurs through the IL-10 receptor (IL-10R), which is expressed in numerous cell types, including intestinal epithelial cells (IECs), where it is associated with development and maintenance of barrier function. Guided by an unbiased metabolomics screen, we identified tryptophan (Trp) metabolism as a major modifying pathway in interferon-γ (IFNγ)-dominant murine colitis. In parallel, we demonstrated that IFNγ induction of indoleamine 2,3-dioxygenase 1, an enzyme that catalyzes the conversion of Trp to kynurenine (Kyn), induces IL-10R1 expression. Based on these findings, we hypothesized that IL-10R1 expression on IEC is regulated by Trp metabolites. Analysis of the promoter region of IL-10R1 revealed a functional aryl hydrocarbon response element, which is induced by Kyn in luciferase-based IL-10R1 promoter assays. Additionally, this analysis confirmed that IL-10R1 protein levels were increased in response to Kyn in IEC in vitro. Studies using in vitro wounding assays revealed that Kyn accelerates IL-10-dependent wound closure. Finally, reduction of murine dextran sodium sulfate colitis through Kyn administration correlates with colonic IL-10R1 expression. Taken together, these results provide evidence on the importance of IL-10 signaling in intestinal epithelia and implicate AHR in the regulation of IL-10R1 expression in the colon.

Alpha-1-antitrypsin therapy ameliorates acute colitis and chronic murine ileitis

Background:Fecal alpha-1-antitrypsin (AAT) clearance has been a marker of clinical disease severity in inflammatory bowel diseases (IBDs) for many years. Although AAT deficiency is more often associated with lung and liver pathologies, AAT-deficient patients with concomitant IBD have been shown to develop more aggressive disease and rapid progression to surgery. Although recent studies have highlighted the pleiotropic anti-inflammatory functions of AAT, including reducing proinflammatory cytokine production and suppressing immune cell activation, its potential therapeutic role in IBD has not been described. Methods:The therapeutic potential of human AAT administration was assessed in murine models of IBD including new-onset and established chemically induced colitis and spontaneous chronic murine ileitis. Histological assessment of inflammation, cytokine secretion profiling, and flow cytometric evaluation of inflammatory infiltrate were performed in each model. The effect of AAT on intestinal barrier function was also examined both in vitro and in vivo. Results:AAT attenuated inflammation in small and large intestinal IBD models through reduced secretion of proinflammatory cytokines, inflammatory cell infiltration, and reduced tissue injury. AAT also increased intestinal restitution after chemically induced colitis. AAT significantly decreased intestinal permeability in vitro and in vivo as part of a protective mechanism for both acute and chronic models of IBD. Conclusions:Our findings describe a beneficial role for AAT in IBD models through suppression of cytokine production and enhanced intestinal barrier function. This raises the possibility that AAT supplementation, which has a long history of proven safety, may have a therapeutic effect in human IBD.

Fecal microbiota transplant in patients with Clostridium difficile infection: A systematic review.

BACKGROUND Fecal microbiota transplantation (FMT) restores a diverse bacterial profile to the gastrointestinal tract and may effectively treat patients with Clostridium difficile infection (CDI). The objective of this systematic review was to evaluate the effectiveness of FMT in the treatment of CDI. METHODS Ovid MEDLINE, EMBASE, Web of Science, and Cochrane database were used. The authors searched studies with 10 or more patients examining the resolution of symptoms after FMT in patients with CDI. Reviews, letters to the editors, and abstracts were excluded. Participants were patients with CDI. Intervention used was FMT. Quality assessment was performed using the Cochrane risk of bias assessment tool. Results were synthesized using a narrative approach. RESULTS Retrospective and uncontrolled prospective cohort studies suggest that FMT is a highly effective therapy for recurrent/refractory CDI, with clinical success rates ranging from 83% to 100%, which is similar to rates published by two randomized controlled trials. Fecal microbiota transplantation may be effectively administered via antegrade (upper gastrointestinal) or retrograde (lower gastrointestinal) routes of delivery. Fecal microbiota transplantation rarely results in major adverse events. However, diarrhea, cramping, and bloating commonly occur and are typically self-limited. Most studies were uncontrolled retrospective studies. CONCLUSION Fecal microbiota transplantation should be considered in patients with recurrent episodes of mild to moderate CDI who have failed conventional antimicrobial therapy. There is insufficient evidence to recommend FMT for the treatment of severe CDI. LEVEL OF EVIDENCE Systematic review, level III.

Long-term outcomes of thalidomide in refractory Crohn's disease

Several open‐label and retrospective studies have indicated that thalidomide may be beneficial in patients with refractory Crohns disease (CD).

Tacrolimus Salvage in Anti–Tumor Necrosis Factor Antibody Treatment-Refractory Crohn’s Disease

Background:Several small retrospective studies have reported encouraging response rates in patients with Crohn’s disease (CD) treated with tacrolimus. Methods:We conducted a retrospective study of the use of oral tacrolimus for severe CD refractory to anti–tumor necrosis factor agents. Response was defined as a clinician’s assessment of improvement after at least 7 days of treatment of one or more of the following: bowel movement frequency, fistula output, rectal bleeding, abdominal pain, extraintestinal manifestations, or well-being. Remission required all of the following: <3 stools per day, no bleeding, abdominal pain or extraintestinal manifestations, and increased well-being. Results:Twenty-four eligible patients were treated with tacrolimus for a median of 4 months. Approximately 37% were steroid dependent or steroid refractory. Response and steroid-free remission rates were 67% and 21%, respectively, and lasted for a median of 4 months. Approximately 42% of patients were able to stop steroids and 54% of patients ultimately required surgery within a median of 10 months after starting tacrolimus. Patients with mean tacrolimus trough levels of 10 to 15 ng/mL had the highest rates of response (86%) and remission (57%). Surgery seemed to be postponed in this group compared with others. An adverse event occurred in 75% of patients. Eight of these events (33%) required dose reduction and 6 (25%) led to treatment discontinuation. There were no irreversible side effects or deaths attributable to tacrolimus over a median follow-up of 56 months. Conclusions:Oral tacrolimus seems to be safe and effective in some patients with severe CD refractory to anti–tumor necrosis factor therapy, particularly at a mean trough level of 10 to 15 ng/mL.

Manipulation of the Endocannabinoid System in Colitis: A Comprehensive Review.

Background: Inflammatory bowel disease (IBD) is a lifelong disease of the gastrointestinal tract whose annual incidence and prevalence is on the rise. Current immunosuppressive therapies available for treatment of IBD offer limited benefits and lose effectiveness, exposing a significant need for the development of novel therapies. In the clinical setting, cannabis has been shown to provide patients with IBD symptomatic relief, although the underlying mechanisms of their anti-inflammatory effects remain unclear. Methods: This review reflects our current understanding of how targeting the endocannabinoid system, including cannabinoid receptors 1 and 2, endogenous cannabinoids anandamide and 2-arachidonoylglycerol, atypical cannabinoids, and degrading enzymes including fatty acid amide hydrolase and monoacylglycerol lipase, impacts murine colitis. In addition, the impact of cannabinoids on the human immune system is summarized. Results: Cannabinoid receptors 1 and 2, endogenous cannabinoids, and atypical cannabinoids are upregulated in inflammation, and their presence and stimulation attenuate murine colitis, whereas cannabinoid receptor antagonism and cannabinoid receptor deficient models reverse these anti-inflammatory effects. In addition, inhibition of endocannabinoid degradation through monoacylglycerol lipase and fatty acid amide hydrolase blockade can also attenuate colitis development, and is closely linked to cannabinoid receptor expression. Conclusions: Although manipulation of the endocannabinoid system in murine colitis has proven to be largely beneficial in attenuating inflammation, there is a paucity of human study data. Further research is essential to clearly elucidate the specific mechanisms driving this anti-inflammatory effect for the development of therapeutics to target inflammatory disease such as IBD.