Hemolytic activity and platelet aggregation inhibitory effect of vipoxin's basic sPLA(2) subunit

In the present study we evaluated the effect of secreted phospholipase A(2) (sPLA(2)) (the toxic subunit of the heterodimeric neurotoxin vipoxin, isolated from the Bulgarian long-nosed viper Vipera ammodytes meridionalis) on hemolysis, erythrocyte morphology and platelet aggregation. Hemolytic activity of sPLA(2) was examined in the presence of saturated (palmitic) and unsaturated (oleic) fatty acids and it was found that oleic acid increased the hemolytic activity of sPLA(2) in a concentration-dependent manner, compared to the effect of palmitic acid and controls. The addition of heparin to red blood cells (RBC) suspension containing sPLA(2) or mixture of sPLA(2) and the corresponding fatty acid led to an inhibition of hemolytic activity. The effect of sPLA(2) on RBC morphology resulted in formation of echinocytes (spherocyte subtype), suggesting that RBC could be the possible targets attacked by sPLA(2). Vipoxin sPLA(2) inhibited (in a dose-dependent manner) platelet aggregation when arachidonic acid and collagen were used as inducers, while in the case of ADP its inhibitory effect was inappreciable.