Activation of focal adhesion kinase via M1 muscarinic acetylcholine receptor is required in restitution of intestinal barrier function after epithelial injury

AbstractImpairment of epithelial barrier is observed in various intestinal disorders including inflammatory bowel diseases (IBD). Numerous factors may cause temporary damage of the intestinal epithelium. A complex network of highly divergent factors regulates healing of the epithelium to prevent inflammatory response. However, the exact repair mechanisms involved in maintaining homeostatic intestinal barrier integrity remain to be clarified.In this study, we demonstrate that activation of M1 muscarinic acetylcholine receptor (mAChR) augments the restitution of epithelial barrier function in T84 cell monolayers after ethanol-induced epithelial injury, via ERK-dependent phosphorylation of focal adhesion kinase (FAK). We have shown that ethanol injury decreased the transepithelial electrical resistance (TER) along with the reduction of ERK and FAK phosphorylation. Carbachol (CCh) increased ERK and FAK phosphorylation with enhanced TER recovery, which was completely blocked by either MT-7 (M1 antagonist) or atropine. The CCh-induced enhancement of TER recovery was also blocked by either U0126 (ERK pathway inhibitor) or PF-228 (FAK inhibitor). Treatment of T84 cell monolayers with interferon-γ (IFN-γ) impaired the barrier function with the reduction of FAK phosphorylation. The CCh-induced ERK and FAK phosphorylation were also attenuated by the IFN-γ treatment. Immunological and binding experiments exhibited a significant reduction of M1 mAChR after IFN-γ treatment. The reduction of M1 mAChR in inflammatory area was also observed in surgical specimens from IBD patients, using immunohistochemical analysis. These findings provide important clues regarding mechanisms by which M1 mAChR participates in the maintenance of intestinal barrier function under not only physiological but also pathological conditions

Functional analysis of the a-defensin disulfide array in mouse cryptdin-4

The alpha-defensin antimicrobial peptide family is defined by a unique tridisulfide array. To test whether this invariant structural feature determines alpha-defensin bactericidal activity, mouse cryptdin-4 (Crp4) tertiary structure was disrupted by pairs of site-directed Ala for Cys substitutions. In a series of Crp4 disulfide variants whose cysteine connectivities were confirmed using NMR spectroscopy and mass spectrometry, mutagenesis did not induce loss of function. To the contrary, the in vitro bactericidal activities of several Crp4 disulfide variants were equivalent to or greater than those of native Crp4. Mouse Paneth cell alpha-defensins require the proteolytic activation of precursors by matrix metalloproteinase-7 (MMP-7), prompting an analysis of the relative sensitivities of native and mutant Crp4 and proCrp4 molecules to degradation by MMP-7. Although native Crp4 and the alpha-defensin moiety of proCrp4 resisted proteolysis completely, all disulfide variants were degraded extensively by MMP-7. Crp4 bactericidal activity was eliminated by MMP-7 cleavage. Thus, rather than determining alpha-defensin bactericidal activity, the Crp4 disulfide arrangement confers essential protection from degradation by this critical activating proteinase

Natural immunologic function of Paneth cells in small intestine of patients with Crohn's disease

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Long-term effectiveness and safety of infliximab-biosimilar: A multicenter Phoenix retrospective cohort study.

BackgroundInfliximab (IFX) effectively treats patients with inflammatory bowel disease (IBD). IFX-biosimilar (IFX-BS) has the same amino acid sequence as that of the IFX originator, and its increasing use is expected to reduce national healthcare costs. Long-term efficacy and safety of IFX-BS in patients with Crohn's disease (CD) and ulcerative colitis (UC) have not been completely investigated.MethodsWe conducted a retrospective, multicenter observational study of patients with IBD who received IFX-BS treatment at three hospitals between October 2016 and April 2022. Clinical data were collected from electronic medical records and evaluated for achieving clinical remission (CR) using Crohn's disease activity index (CDAI) and partial Mayo (pMayo) score, persistency of long-term IFX-BS administration, and clinical response rate in the bio-naïve and bio-failure groups.ResultsA total of 117 patients with IBD (90 CD and 27 UC) were included. The study findings indicated that both bio-naïve and bio-failure groups of patients with UC showed similar effectiveness of IFX-BS. The treatment persistence rate in patients with CD was significantly higher in the bio-naïve (P = 0.042) and switch (P = 0.010) groups than in the bio-failure group. In the former two groups, the treatment persistence rate was high at two years after administration (more than 80%). In patients with UC, the findings indicated higher treatment persistence rate in the switch group than in the bio-naïve group. Univariable and multivariable analyses for treatment persistence rate showed that the albumin level at the initial IFX-BS administration and groups (bio-naïve, bio-failure and switch) were effective factors for patients with CD. Adverse events were reported in 18 patients (15.4%).ConclusionThe present study demonstrates the long-term effectiveness and safety of IFX-BS. In addition to the favorable remission induction in the bio-naïve and bio-failure groups, we demonstrated remission maintenance and treatment persistence rates beyond two years. Albumin level and groups were associated with better treatment persistence in patients with CD

Isoleucine, an Essential Amino Acid, Induces the Expression of Human β Defensin 2 through the Activation of the G-Protein Coupled Receptor-ERK Pathway in the Intestinal Epithelia

AuthorAnti-microbial peptides are essential for the intestinal innate immunity that protects the intestinal epithelia from attacks by foreign pathogens. Human β-defensin (HBD) is one of the pivotal anti-microbial peptides that are expressed in the colonic epithelia. This study investigated the effect and the signaling mechanism of inducible β-defensin HBD2 by an essential amino acid, isoleucine (Ile) in colonic epithelial cells. Here we examined the expression level of HBD2 on induction of Ile in epithelial cells, and checked this pathway. HBD2 mRNA was induced by co-incubation with IL-1α and Ile in Caco2 cells, but not by Ile alone. An inhibitor of either ERK or Gi, a subunit of G-proteins, reduced the in- duction of HBD2 mRNA by Ile. The treatment with Ile also increased the intracellular calcium ion concentration, thus suggesting that the GPCR and ERK signaling pathway mediate the effects of Ile. These results indicate that an essential amino acid, Ile, enhances the expression of an inducible β-defensin, namely HBD2, by IL-1α through the activation of GPCRs and ERK signaling pathway. The administration of Ile may therefore represent a possible option to safely treat intestinal inflammation