Guanylate cyclase C signaling pathway regulates intestinal inflammatory injury and epithelial barrier function in Caco 2 cells
Background: Guanylate cyclase C (GC C) signaling pathway via guanylin (Gn) and uroguanylin (Ugn) activation regulates intestinal fluid and electrolyte homeostasis. It is down regulated in the patients of inflammatory bowel diseases (IBD) However, studies on the role of GC C signaling in murine models of colitis are controversial. Here, we investigated the effect of GC C on intestinal inflammation using Caco 2 cells. Methods: Caco 2 monolayers grown on Transwell filters were stimulated with IL 1b to model the inflammatory cells of intestine. The activity of GC C signaling was regulated by transfection with Gn overexpression vector or GC C shRNA plasmid. After different treatment with cells, the levels of Gn, Ugn, GC C, paracellular permeability, superoxide dismutase (SOD) pro inflammatory cytokines (IL 8 and TNF a) and tight junction proteins (occludin, claudin 1 and ZO 1) were detected. Results: The expression of Gn, Ugn and GC C was all significantly reduced after stimulation with IL 1b. Relative to the empty vector controls, IL 1b treated cells transfected with Gn overexpression vector had significantly increased levels of Gn, GC C, SOD, claudin 1 and ZO 1 as well as decreased levels of IL 8, TNF a and permeability. Conversely, GC C silencing cells had significantly increased levels of IL 8, TNF a and permeability as well as decreased levels of Gn, Ugn, GC C, SOD, claudin 1 and ZO 1 induced by IL 1b compared with the corresponding empty plasmid controls. Conclusions: GC C signaling pathway plays a protective role in the intestinal inflammatory injury and epithelial barrier function in Caco 2 cells. These observations further support the possible pathogenetic role of GC C and clinical therapeutic potential of GC C agonists in IBD.