Proteinase-activated receptor 2 is an anti-inflammatory signal for colonic lamina propria lymphocytes in a mouse model of colitis

doi:10.1073/pnas.241377298

Proteinase-activated receptor 2 is an anti-inflammatory signal for colonic lamina propria lymphocytes in a mouse model of colitis

^*Clinica di Gastroenterologia ed Endoscopia Digestiva, Dipartimento di Medicina Clinica, Patologia Univesita di Perugia, Perugia 06122, Italy; ^‡Gastrointestinal and Endocrine Research Groups, Departments of Pharmacology and Therapeutics, University of Calgary, Calgary, AL, Canada T2M 4M1; and ^§Dipartimento di Farmacologia Sperimentale, Universitá di Napoli, Naples 80131, Italy

Edited by Louis J. Ignarro, University of California School of Medicine, Los Angeles, CA, and approved September 24, 2001 (received for review July 20, 2001)

Abstract

The proteinase-activated receptor 2 (PAR-2) is a member of a family of G protein-coupled receptors for proteases. Proteases cleave PARs within the extracellular N-terminal domains to expose tethered ligands that bind to and activate the cleaved receptors. PAR-2 is highly expressed in colon in epithelial and neuronal elements. In this study we show that PAR-2 activation prevents the development and induces healing of T helper cell type 1-mediated experimental colitis induced by intrarectal administration of 2,4,6-trinitrobenzene sulfonic acid (TNBS) in mice. A role for PAR-2 in the protection against colon inflammation was explored by the use of SLIGRL-NH₂, a synthetic peptide that corresponds to the mouse tethered ligand exposed after PAR-2 cleavage. TNBS-induced colitis was dose-dependently reduced by the administration of SLIGRL-NH₂, whereas the scramble control peptide, LSIGRL-NH₂, was uneffective. This beneficial effect was reflected by increased survival rates, improvement of macroscopic and histologic scores, decrease in mucosal content of T helper cell type 1 cytokines, protein, and mRNA, and a diminished myeloperoxidase activity. SLIGRL-NH₂, but not the scramble peptide, directly inhibited IFN-γ secretion and CD44 expression on lamina propria T lymphocytes. Protection exerted by PAR-2 in TNBS-treated mice was reverted by injecting mice with a truncated form of calcitonin gene-related peptide and by sensory neurons ablation with the neurotoxin capsaicin. Collectively, these studies show that PAR-2 is an anti-inflammatory receptor in the colon and suggest that PAR-2 ligands might be effective in the treatment of inflammatory bowel diseases.

Footnotes

↵ † To whom reprint requests should be addressed. E-mail: fiorucci{at}unipg.it.
This paper was submitted directly (Track II) to the PNAS office.
Abbreviations:

CGRP,

calcitonin gene-related peptide;

IBD,

inflammatory bowel disease;

iNOS,

inducible NO synthase;

LP,

lamina propria;

LPT,

LP T cells;

PAR,

proteinase-activated receptor;

PAR AP,

PAR agonistic peptide;

Th-1,

T helper cell type 1;

TNBS,

2,4,6-trinitrobenzene sulfonic acid;

TNF-α,

tumor necrosis factor α