Decreased MAPK- and PGE2-dependent IL-11 production in Giα2−/− colonic myofibroblasts

Abstract

Mice deficient in the G-protein alpha subunit Giα2 spontaneously develop colitis and colon cancer. IL-11 is a pleiotropic cytokine known to protect the intestinal epithelium from injury in animal models of colitis and is produced by subepithelial myofibroblasts in response to inflammatory mediators including TGF-β, IL-1β, and PGE2. Arachidonic acid release and subsequent PGE2 production is significantly decreased in the colonic mucosa of Giα2−/− mice, and we hypothesized that this would affect mucosal IL-11 production. Mucosal levels of IL-11 were found to be significantly decreased in Giα2−/− mice despite the presence of mild colitis. Primary cultures of Giα2−/− intestinal and colonic myofibroblasts (IMF and CMF, respectively) produced less basal and TGF-β or IL-1β-stimulated IL-11 mRNA and protein than wild-type cells. Inhibitors of ERK or p38 MAPK activation dose dependently inhibited IMF and CMF IL-11 production in response to TGF-β stimulation, whereas 16,16 dimethyl-PGE2 and prostanoid receptor subtype-selective agonists induced IL-11 production. Treatment of animals with the EP4-specific agonist ONO-AE1-329 resulted in enhanced mucosal levels of IL-11, and increased IL-11 production by ex vivo cultured CMF. Modulation of cAMP levels produced diverging results, with enhancement of TGF-β-induced IL-11 release in IMF pretreated with 8-Br-cAMP and inhibition in cells treated either with pertussis toxin or the PKA inhibitor H-89. These data suggest a physiological role for prostaglandins, MAPK signaling, and cAMP signaling for the production of myofibroblast-derived IL-11 in the mouse intestinal mucosa.