Effect of PACAP on Bacterial Adherence and Cytokine Expression in Intestinal Cell Cultures

Bacterial adhesion is a crucial event of intestinal pathological conditions evoked by bacterial infections. Pituitary adenylate cyclase activating polypeptide (PACAP) is an endogenous neuropeptide having a widespread distribution throughout the entire body including the digestive tract. It has diverse physiological functions in the gastrointestinal system, including protective effects in several models of intestinal inflammatory conditions. However, its effects on bacterial adherence and the inflammatory reactions as a result of that have not been elucidated yet. The aim of our study was therefore to investigate the effect of PACAP on bacterial adherence and cytokine expression upon lipopolysaccharide (LPS) exposure. Small intestinal INT407 and colonic Caco-2 cells were treated with PACAP prior to exposure to bacteria (Escherichia coli, Salmonella Typhimurium, Klebsiella pneumoniae, Enterococcus faecalis) and colonies were counted. PACAP had no significant influence on bacterial adhesion, as it did not change the number of colonies of investigated bacteria. However, PACAP was able to counteract the LPS-induced increases in the expression of the cytokines IL-8 and CXCL-1 in INT407 cells, as assessed by cytokine array. These results indicate that while PACAP has no direct effect on bacterial adherence, it can influence the cytokine expression of intestinal cells upon endotoxin-induced exposure, possibly contributing to the known anti-inflammatory actions of PACAP in the intestinal system.