Action of Varespladib (LY-315920), a Phospholipase A2 Inhibitor, on the Enzymatic, Coagulant and Haemorrhagic Activities of Lachesis muta rhombeata (South-American Bushmaster) Venom
Pamella G. Gutierres, Diego Roberto Pereira, Nataly L. Vieira, Lilian F. Arantes, Nelson Jorge da Silva, Kristian A. Torres-Bonilla, Stephen Hyslop, Karen de Morais-Zani, Rosa Maria Barilli Nogueira, Edward G. Rowan, Rafael Stuani Floriano
Abstract
Varespladib (VPL) was primarily developed to treat inflammatory disturbances associated with high levels of serum phospholipase A 2 (PLA 2 ). VPL has also demonstrated to be a potential antivenom support agent to prevent PLA 2 -dependent effects produced by snake venoms. In this study, we examined the action of VPL on the coagulant, haemorrhagic and enzymatic activities of Lachesis muta rhombeata (South-American bushmaster) venom. Conventional colorimetric enzymatic assays were performed for PLA 2 , caseinolytic and esterasic activities; in vitro coagulant activities for prothrombin time (PT) and activated partial thromboplastin time (aPTT) were performed in rat citrated plasma through a quick timer coagulometer, whereas the dimensions of haemorrhagic haloes obtained after i.d. injections of venom in Wistar rats were determined using ImageJ software. Venom (1 mg/ml) exhibited accentuated enzymatic activities for proteases and PLA 2 in vitro , with VPL abolishing the PLA 2 activity from 0.01 mM; VPL did not affect caseinolytic and esterasic activities at any tested concentrations (0.001–1 mM). In rat citrated plasma in vitro , VPL (1 mM) alone efficiently prevented the venom (1 mg/ml)-induced procoagulant disorder associated to extrinsic (PT) pathway, whereas its association with a commercial antivenom successfully prevented changes in both intrinsic (aPTT) and extrinsic (PT) pathways; commercial antivenom by itself failed to avoid the procoagulant disorders by this venom. Venom (0.5 mg/kg)-induced hemorrhagic activity was slightly reduced by VPL (1 mM) alone or combined with antivenom (antivenom:venom ratio 1:3 ‘v/w’) in rats, with antivenom alone producing no protective action on this parameter. In conclusion, VPL does not inhibit other major enzymatic groups of L. m. rhombeata venom, with its high PLA 2 antagonize activity efficaciously preventing the venom-induced coagulation disturbances.