Professor University of Reading Reading, England, United Kingdom
Background: Venom is a cocktail of bioactive compounds produced and secreted by specialised cells from venomous animals. Various components within the venom can work independently or synergistically to modulate physiological processes within target systems. These toxins can be isolated and characterised to establish their mechanisms of action and clinical applications. The blood clotting system is a common target of convergent evolution, with numerous venom toxins being able to disrupt haemostasis with high specificity. Venoms possess a high potential for bioprospecting. However, until now bioprospecting for haemostasis-modulating agents has predominantly focussed on snake venoms despite a plethora of venomous invertebrates.
Aims: In this study, we aim to investigate the impact of the venoms of two scorpion species on the modulation of blood clotting and characterise the individual toxins that exhibit haemotoxicity.
Methods: The presence of phospholipase A2, metalloprotease and serine proteases in the venoms of H. spinifer and P. viatoris was analysed using appropriate fluorogenic enzymatic assays. Then, various concentrations of these venoms were analysed in the modulation of platelet activation upon stimulation with TRAP6, ADP and U46619 as agonists in human platelet-rich plasma by measuring the levels of fibrinogen binding and P-selectin exposure using flow cytometry.
Results: High levels of PLA2 activity were observed in both venoms in a dose-dependent manner (from 50ug/ml to 3.125g/ml for H.spinifer and up to 1.56g/ml for P.viatoris) (Figure 1). However, there was no measurable activity for serine protease or metalloprotease in these venoms. Notably, both venoms inhibited TRAP6, ADP, and U46619-induced platelet activation in a dose-dependent manner (Figure 2).
Conclusion(s): The venoms of H. spinifer and P. viatoris displayed high levels of PLA2 activity although they lack proteolytic enzymes. Moreover, they potently inhibited agonist-induced platelet activation suggesting that one or more components in these venoms have the potential to be developed as anti-platelet agents to prevent/treat thrombotic diseases.
