Effects of myonecrotic snake venom phospholipase A2 toxins on cultured muscle cells.

We have attempted to establish a cell culture model suitable for molecular mechanism of action studies of necrotic phospholipases A2 (PLA2). Three myonecrotic PLA2 were purified, one basic PLA2 from Naja nigricollis venom and two basic PLA2 (VRV-PL-V and VRV-PL-VIIIa) from Vipera russelli venom. The effects of these PLA2 on several established muscle cell lines were evaluated. As judged by light microscopy, some, but not all, cell lines detached from the culture plate in a time- and concentration-related fashion. Naja nigricollis PLA2 was the most potent at eliciting this effect, followed by VRV-PL-V and VRV-PL-VIIIa. The two most sensitive cell lines, 1447 and 1456, were chosen for further study using N. nigricollis PLA2. Cellular protein and nucleic acid syntheses were inhibited by the toxin in a time- and dose-related manner. However, it appeared that most, if not all, of the inhibition was due to toxin-induced reduction of precursor uptake, suggesting effects at the plasma membrane level. The putative membrane effects were specific, in that uptake of calcium, choline or glucose was not inhibited by the toxin. Moreover, treating the cells with toxin failed to significantly increase lactate dehydrogenase release into the medium. Polyclonal antiserum prepared against N. nigricollis basic PLA2 neutralized the toxicity completely with 1456 cells, but only partially with the 1447 cell line. Both the 1447 and 1456 lines appear to be suitable as cell culture models for necrotizing PLA2 molecular mechanism of action studies.