Hemolytic activity and platelet aggregation inhibitory effect of vipoxin’s basic sPLA2 subunit

In the present study we evaluated the effect of secreted phospholipase A₂ (sPLA₂) (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 sPLA₂ 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 sPLA₂ 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 sPLA₂ or mixture of sPLA₂ and the corresponding fatty acid led to an inhibition of hemolytic activity. The effect of sPLA₂ on RBC morphology resulted in formation of echinocytes (spherocyte subtype), suggesting that RBC could be the possible targets attacked by sPLA₂. Vipoxin sPLA₂ 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.