Guanylate cyclase C reduces invasion of intestinal epithelial cells by bacterial pathogens

The guanylate cyclase C (GC-C) receptor regulates electrolyte and water secretion into the gut following activation by the E. coli enterotoxin STa, or by weaker endogenous agonists guanylin and uroguanylin. Our previous work has demonstrated that GC-C plays an important role in controlling initial infection as well as carrying load of non-invasive bacterial pathogens in the gut. Here, we use Salmonella enterica serovar Typhimurium to determine whether GC-C signaling is important in host defense against pathogens that actively invade enterocytes. In vitro studies indicated that GC-C signaling significantly reduces Salmonella invasion into Caco2-BBE monolayers. Relative to controls, GC-C knockout mice develop severe systemic illness following oral Salmonella infection, characterized by disrupted intestinal mucus layer, elevated cytokines and organ CFUs, and reduced animal survival. In Salmonella-infected wildtype mice, oral gavage of GC-C agonist peptide reduced host/pathogen physical interaction and diminished bacterial translocation to mesenteric lymph nodes. These studies suggest that early life susceptibility to STa-secreting enterotoxigenic E. coli may be counter-balanced by a critical role of GC-C in protecting the mucosa from non-STa producing, invasive bacterial pathogens.