Membrane-damaging and cytotoxic effects on human fibroblasts of alpha- and beta-hemolysins from Aeromonas hydrophila

Abstract

The effects of two hemolysins (α and β) from Aeromonas hydrophila on human lung fibroblasts were investigated. The toxins differed distinctly in regard to the morphological changes they produced. The α-hemolysin caused rounding of the cells. The β-hemolysin caused a striking vacuolization of the cytoplasm in cells which remained spread out on the growth surface. The toxins also differed as to relative size of the intial lesions they induced in the fibroblast membrane, scored by leakage of different-sized cytoplasmic markers. The α-hemolysin induced larger lesions than did the β-hemolysin. It was indirectly demonstrated that the α-hemolysin did not bind, or bound only transiently, to the fibroblasts. By contrast, the β-hemolysin bound rapidly and firmly. The cytopathogenic response to the α-hemolysin was reversible, whereas cells treated with small amounts of the β-hemolysin for only 1 min invariably died within a few hours. Thus, the two hemolysins from A. hydrophila, despite many biochemical similarities, show essential dissimilarities in their interactions with cultured cells.