Mitogen-activated protein kinase pathways contribute to hypercontractility and increased Ca2+ sensitization in murine experimental colitis.

Inflammatory bowel disease (IBD) is associated with intestinal smooth muscle dysfunction. Many smooth muscle contractile events are associated with alterations in Ca(2+)-sensitizing pathways. The aim of the present study was to assess the effect of colitis on Ca(2+) sensitization and the signaling pathways responsible for contractile dysfunction in murine experimental colitis. Colitis was induced in BALB/c mice by providing 5% dextran sulfate sodium (DSS) in drinking water for 7 days. Contractile responses of colonic circular smooth muscle strips to 118 mM K(+) and carbachol (CCh) were assessed. DSS induced a T(H)2 colitis [increased interleukin (IL)-4 and IL-6] with no changes in T(H)1 cytokines. Animals exposed to DSS had increased CCh-induced contraction (3.5-fold) and CCh-induced Ca(2+)-sensitization (2.2-fold) responses in intact and alpha-toxin permeabilized colonic smooth muscle, respectively. The contributions of extracellular signal-regulated kinase (ERK) and p38 mitogen-activated protein kinase (MAPK) to CCh-induced contractions were significantly increased during colitis. Ca(2+)-independent contraction induced by microcystin was potentiated (1.5-fold) in mice with colitis. ERK and p38MAPK (but not Rho-associated kinase) contributed to this potentiation. ERK1/2 and p38MAPK expression were increased in the muscularis propria of colonic tissue from both DSS-treated mice and patients with IBD (ulcerative colitis >> Crohn's disease). Murine T(H)2 colitis resulted in colonic smooth muscle hypercontractility with increased Ca(2+) sensitization. Both ERK and p38MAPK pathways contributed to this contractile dysfunction, and expression of these molecules was altered in patients with IBD.