Monodansylcadaverine inhibits cytotoxicity of Vibrio parahaemolyticus thermostable direct hemolysin on cultured rat embryonic fibroblast cells

The mechanism of action of Vibrio parahaemolyticus thermostable direct hemo lysin (TDH) on cultured cells still remains unclear. We show that addition of osmotic stabilizers, such as polyethylene glycol and dextran, could not protect cultured rat embryonic fibroblast cells (Rat-l) against cytotoxicit y induced by TDH, unlike their protection against the hemolytic activity of TDH. By contrast, 100 muM monodansylcadaverine, as well as the presence of 1 mM ethylene glycol-bis(beta -aminoethyl ether)-N,N,N',N'-tetraacetic aci d (EGTA) in medium, protected the cells against cytotoxicity of TDH. Bindin g of TDH to Rat-1 cells and intracellular localization of TDH were affected by monodansylcadaverine and EGTA as analyzed by flow cytometry and confoca l microscopy. On the hemolytic activity of TDH, monodansylcadaverine and EG TA had no effect. These results suggest that the mechanism of cytotoxicity of TDH on Rat-1 cells was different from that of hemolytic activity of TDH on red blood cells. (C) 2001 Federation of European Microbiological Societi es. Published by Elsevier Science B.V. All rights reserved.