Chloride secretion induced by thermostable direct haemolysin of Vibrio parahaemolyticus depends on colonic cell maturation.

Vibrio parahaemolyticus produces a thermostable direct haemolysin (TDH) that has been implicated in the pathogenesis of diarrhoeal disease caused by this organism. In previous work, TDH induced Cl- secretion in human colonic epithelial cells that was dependent on the intracellular Ca2+ concentration, [Ca2+]in. This study investigated whether Cl- secretion induced by TDH is influenced by the stage of maturation of intestinal epithelial cells. Two different human colonic cell lines, villus cell-like Caco-2 cells and crypt cell-like T84 cells, cultured by different methods to obtain differentiated samples, were used. When these cells were exposed to butyrate, a transcriptional regulator of differentiation genes, or co-cultured with 18Co cells, a human colonic fibroblast cell line, they showed increased trans-epithelial resistance and villus cell marker enzyme activity. In Caco-2 cells, exposure to butyrate or co-culturing with 18Co cells resulted in increased TDH binding, higher short-circuit currents (Isc) and greater [Ca2+]in. These results suggest that sensitivity to TDH is affected by the stage of cellular differentiation of cultured intestinal epithelial cells.