Role for protease activity in visceral pain in irritable bowel syndrome

Abstract

Mediators involved in the generation of symptoms in patients with irritable bowel syndrome (IBS) are poorly understood. Here we show that colonic biopsy samples from IBS patients release increased levels of proteolytic activity (arginine cleavage) compared to asymptomatic controls. This was dependent on the activation of NF-κB. In addition, increased proteolytic activity was measured in vivo, in colonic washes from IBS compared with control patients. Trypsin and tryptase expression and release were increased in colonic biopsies from IBS patients compared with control subjects. Biopsies from IBS patients (but not controls) released mediators that sensitized murine sensory neurons in culture. Sensitization was prevented by a serine protease inhibitor and was absent in neurons lacking functional protease-activated receptor-2 (PAR 2 ). Supernatants from colonic biopsies of IBS patients, but not controls, also caused somatic and visceral hyperalgesia and allodynia in mice, when administered into the colon. These pronociceptive effects were inhibited by serine protease inhibitors and a PAR 2 antagonist and were absent in PAR 2 -deficient mice. Our study establishes that proteases are released in IBS and that they can directly stimulate sensory neurons and generate hypersensitivity symptoms through the activation of PAR 2 .

Editorial: PARs for the Course: Roles of Proteases and PAR Receptors in Subtly Inflamed Irritable Bowel Syndrome

“…Th eir principal fi ndings were, fi rst, that supernatants from cultured biopsies from subjects with IBS-D, but not those with constipation-predominant IBS (IBS-C), produced a marked increase in neuronal excitability and, second, that this eff ect was mediated via the protease-activated receptor 2 (PAR2 receptor). Th e fi ndings in relation to a role for protease activity confi rm and, indeed, extend prior observations on the presence of protease or protease-like activity in fecal fl uid from IBS suff erers ( 12 ), or from more acute experiments involving supernatants from cultured IBS biopsies ( 12 -19 ). By performing more longterm experiments, Valdez-Morales and colleagues ( 11 ) were able to demonstrate that IBS supernatants were able to alter the intrinsic excitability of colonic-projecting neurons and not just their acute activation as demonstrated in the prior studies.…”

Mast Cells and Irritable Bowel Syndrome: From the Bench to the Bedside

“…The candidate drugs targeting MC maturation, development and homing to the gut as well as MC activation and major mediators are under development, some of which show benefit to IBS symptoms improvement (Table 2). [92][93][94][95][96][97][98][99][100][101][102] Disodium cromoglycate (DSCG) and ketotifen are 2 kinds of classical MC stabilizers and are available for IBS. Preliminary clinical data indicated that a 6 month of DSCG treatment significantly reduced release of tryptase from jejunal biopsies, and increased clinical improvement of bowel function in D-IBS.…”

“…Several studies also demonstrated that serine protease inhibitors and PAR2 antagonist could control the mucosal inflammation and block the pro-nociceptive effects in mice colon. 101 Accordingly, antagonizing PAR2 may be a highly compelling means for IBS treatment.…”

Immune Activation in Irritable Bowel Syndrome: Can Neuroimmune Interactions Explain Symptoms?

“…At least two subsets of macrophages have been described, M1 and M2, based on functional diff erences, but much remains to be learned regarding appropriate closer proximity to colonic nerve endings in IBS patients, a fi nding that correlated strongly with severity and frequency of pain ( 55 ). Further, supernatants from mucosal biopsies from IBS patients are more likely to activate intestinal nerves than those from healthy subjects ( 52,54,56,66,68 ). Th is nerve activation is dependent on mast cell-derived mediators, including serine proteases acting on protease-activated receptor-2, histamine acting on its H 1 receptor, and serotonin acting on its 5-HT 3 receptor ( Figure 2 ), and occurs regardless of whether changes in absolute mast cell numbers are observed or not.…”