Lipopolysaccharide Induces Inhibition of Galactose Intestinal Transport in Rabbits in vitro

Abstract

Background/Aims: Previous studies from our laboratory have revealed impaired intestinal absorption of D-galactose in lipopolysaccharide-treated rabbits. The aim of the present work was to examine the effect of LPS on D-galactose intestinal absorption in vitro. Methods: D-galactose intestinal transport was assessed employing three techniques: sugar uptake in rings of everted jejunum, transepithelial flux in Ussing-type chambers and transport assays in brush border membrane vesicles. The level of expression of the Na⁺/D-galactose cotransporter (SGLT1) was analyzed by Western blot. Results: LPS decreased the mucosal D-galactose transport in rabbit jejunum but a preexposition to the endotoxin was required. LPS affected the Na⁺-dependent transport system by increasing the apparent Km value without affecting the Vmax. It also decreased the Na⁺, K⁺-ATPase activity. However, it did not inhibit neither the uptake of D-galactose by brush border membrane vesicles nor modified the SGLT1 protein levels in the brush border, suggesting an indirect endotoxin effect. This inhibitory effect, was reduced by selective inhibitors of Ca²⁺-calmodulin (W13), protein kinase C (GF 109203X), p38 mitogen-activated protein kinase (SB 203580), c-Jun N-terminal kinase (SP 600125) and mitogen extracellular kinase (U 0126). Conclusion: LPS inhibits the mucosal Na⁺-dependent D-galactose intestinal absorption and the Na⁺, K⁺-ATPase activity when it is added to the tissue. Intracellular processes related to protein kinases seem to be implicated in the endotoxin effect.