Cytotoxicity of Vibrio vulnificus cytolysin on pulmonary endothelial cells

The cytolysin produced by V. vulnificus has been known to cause lethality by increasing pulmonary vascular permeability in mice. In the present study, its cytotoxic mechanism on CPAE cell, a cell line of pulmonary endothelial cell, has been investigated. The cytolysin rapidly bound on CPAE cells and killed approximately 80% of the cells at 1.0 HU as determined by trypan blue exclusion test. The death of CPAE cells was associated with the formation of transmembrane pore evidenced by rapid flow of monovalent ions in patch clamp of CPAE cell membrane. The cytolysin decreased cellular ATP levels to less than 30% of control at 0.25 HU. The incubation of cytolysin in the presence of cholesterol completely inhibited its cytotoxic effect on CPAE cells, suggesting that cholesterol on CPAE cell membrane is the probable binding site for cytolysin. These results suggest that the death of CPAE cell induced by cytolysin is due to the depletion of cellular ATP levels by the formation of small transmembrane pores, which are permeable to monovalent ions, but not to LDH.