Protease signaling through protease activated receptor 1 mediate nerve activation by mucosal supernatants from irritable bowel syndrome but not from ulcerative colitis patients

Abstract

Background & aimsThe causes of gastrointestinal complaints in irritable bowel syndrome (IBS) remain poorly understood. Altered nerve function has emerged as an important pathogenic factor as IBS mucosal biopsy supernatants consistently activate enteric and sensory neurons. We investigated the neurally active molecular components of such supernatants from patients with IBS and quiescent ulcerative colitis (UC).MethodEffects of supernatants from 7 healthy controls (HC), 20 IBS and 12 UC patients on human and guinea pig submucous neurons were studied with neuroimaging techniques. We identify differentially expressed proteins with proteome analysis.ResultsNerve activation by IBS supernatants was prevented by the protease activated receptor 1 (PAR1) antagonist SCHE79797. UC supernatants also activated enteric neurons through protease dependent mechanisms but without PAR1 involvement. Proteome analysis of the supernatants identified 204 proteins, among them 17 proteases as differentially expressed between IBS, UC and HC. Of those the four proteases elastase 3a, chymotrypsin C, proteasome subunit type beta-2 and an unspecified isoform of complement C3 were significantly more abundant in IBS compared to HC and UC supernatants. Of eight proteases, which were upregulated in IBS, the combination of elastase 3a, cathepsin L and proteasome alpha subunit-4 showed the highest prediction accuracy of 98% to discriminate between IBS and HC groups. Elastase synergistically potentiated the effects of histamine and serotonin–the two other main neuroactive substances in the IBS supernatants. A serine protease inhibitor isolated from the probiotic Bifidobacterium longum NCC2705 (SERPINBL), known to inhibit elastase-like proteases, prevented nerve activation by IBS supernatants.ConclusionProteases in IBS and UC supernatants were responsible for nerve activation. Our data demonstrate that proteases, particularly those signalling through neuronal PAR1, are biomarker candidates for IBS, and protease profiling may be used to characterise IBS.

Antidepressive Mechanisms of Probiotics and Their Therapeutic Potential

“…The genome of B. longum encodes serpin, a serine protease inhibitor (Ivanov et al, 2006;Mkaouar et al, 2016). Serpin can inhibit the activation of enteric neurons by suppressing the secretion of elastase-like proteases from IECs (Ivanov et al, 2006;Buhner et al, 2018). These studies support the premise that B. longum interacts with the host via the neural pathway (similar to L. rhamnosus).…”

Serine proteases as luminal mediators of intestinal barrier dysfunction and symptom severity in IBS

“…Previous studies have shown increased protease-like activity in faecal contents18 22 40–42 and colonic biopsy supernatants from patients with IBS 16 17 19 20. The effect of proteases on barrier function has been studied mostly in vitro (predominantly basolateral exposure) or in vivo in animal models on application of exogenous proteases or biopsy supernatants from patients with IBS.…”

“…The role of proteases in mediating visceral hypersensitivity has been extensively studied over the last decade, both on administration in vivo in animals18 21 22 and ex vivo on neuronal cultures 16 17 19 20 48. Colonic mucosal biopsy supernatants were shown to activate human submucosal (mostly patients with IBS-D)19 20 and thoracic sensory neurons (all IBS subtypes)17 through PAR-1 activation. Clinically, both serine43 and cysteine18 protease activity have been correlated with abdominal pain.…”

“…An increased PA has been described in faecal and tissue supernatants from both patients with diarrhoea and constipation-predominant IBS (IBS-C) 16–20. Administration of these supernatants in mice resulted in increased intestinal permeability and development of visceral hypersensitivity 16 18 21 22.…”

Serine proteases at the cutting edge of IBD: Focus on gastrointestinal inflammation

“…Taken together, these data have lent some credence to host serine proteases as playing critical roles in controlling the homeostatic network at the mucosal surface of the intestine, while largely dismissing the effect of their bacterial counterparts. A tight regulation of such proteases is though needed since an increased proteolytic activity could be detrimental to the epithelium and impair the intestinal barrier 49,50 …”