Role of TLR4 and MAPK in the local effect of LPS on intestinal contractility

Objectives Lipopolysaccharide (LPS) has been shown to alter intestinal contractility. Toll-like receptor 4 (TLR4), K+ channels and mitogen-activated protein kinases (MAPKs) have been proposed to be involved in the mechanism of action of LPS. The aim of this study was to determine the role of TLR4, K+ channels and MAPKs (p38, JNK and MEK1/2) in the local effect of LPS on the acetylcholine (ACh)-induced contractions in rabbit small intestine in vitro. Methods Segments of rabbit duodenum were suspended in the direction of longitudinal or circular smooth muscle fibres in a thermostatically controlled organ bath. Key findings LPS (0.3 mu g/ml) reduced the contractions induced by ACh (100 mu m) in the longitudinal and circular smooth muscle of the duodenum after 90 min of incubation. Polymyxin (TLR4 inhibitor), SB203580 (p38 MAPK inhibitor), SP600125 (JNK1/2 inhibitor) and U0126 (MEK1/2 inhibitor) antagonized the effects of the LPS on ACh-induced contractions in duodenal smooth muscle. Incubation with the blockers of K+ channels, TEA, apamin, charybdotoxin, iberiotoxin, glibenclamide or quinine, did not reverse the effect of LPS on ACh-induced contractions. Conclusions These results suggest that the effect of LPS on ACh-induced contractions in the rabbit duodenum might be mediated by TLR4 and p38, JNK1/2 and MEK1/2 MAPKs.