Habu coagulotoxicity: Clinical implications of the functional diversification of Protobothrops snake venoms upon blood clotting factors

Abstract

Venom can affect any part of the body reachable via the bloodstream. Toxins which specifically act upon the coagulation cascade do so either by anticoagulant or procoagulant mechanisms. Here we investigated the coagulotoxic effects of six species within the medically important pit viper genus Protobothrops (Habu) from the Chinese mainland and Japanese islands, a genus known to produce hemorrhagic shock in envenomed patients. Differential coagulotoxicity was revealed: P. jerdonii and P. mangshanensis produced an overall net anticoagulant effect through the pseudo-procoagulant clotting of fibrinogen; P. flavoviridis and P. tokarensis exhibit a strong anticoagulant activity through the destructive cleavage of fibrinogen; and while P. elegans and P. mucrosquamatus both cleaved the Aalpha and B-beta chains of fibrinogen they did not exhibit strong anticoagulant activity.

A blood bond: evolutionary, pathophysiological and biodiscovery implications of coagulotoxic snake venoms

“…In contrast, the transient, weak fibrin clots shown in this study for D. acutus venom, consistent with previous reports would have a short half-life due to their inherent instability. Thus the effects upon both prey and humans envenomated by D. acutus venoms would therefore be similar: a rapid decrease in fibrinogen levels leading to an anticoagulant state (Cheng et al, 2017;Teng, 1976, 1978), with death resulting from haemorrhagic shock, like has been shown for the Protobothrops genus (Debono et al, 2019c). Both D. acutus and H. hypnale venoms displayed similar biochemistry for their pseudo-procoagulant action, which required calcium for full action (Nielsen, 2016b;Nielsen and Bazzell, 2017).…”

“…The functional variation extended to the patterns of fibrinogen chain cleavage as revealed in the SDS PAGE gels ( Just as the neurotoxicity exhibited by some species in this clade of snakes are unique, so too is the thrombin generating activity of C. rhodostoma. In contrast, D. acutus was more like the typical Asian pit-viper, which are broadly known for their haemorrhagic-shock inducing venoms (Cheng et al, 2017;Debono et al, 2019c;Hutton et al, 1990;Joseph et al, 2007;Maduwage et al, 2013a;Rojnuckarin et al, 1998;Warrell et al, 1986;Withana et al, 2014). Haemorrhagic effects are a result of anticoagulation mechanisms, or a net anticoagulant outcome.…”

“…Various enzymatic assays were performed to investigate activity on specific artificial substrates, as well as PLA2, plasminogen activation, prothrombin activation and FX activation. Investigation followed that described by (Debono et al, 2019c). Phytools heat mapping followed that of .…”

“…Procoagulant snake venoms produce endogenous thrombin through the activation of Factor X or prothrombin, resulting in strong, stable fibrin clots while anticoagulant venoms effect upon fibrinogen is either through destructive cleavage of fibrinogen or the pseudo-procoagulant mechanism of cleaving fibrinogen to form abnormal, short-lived fibrin clots (thus having a net anticoagulant effect) (Dambisya et al, 1994;Debono et al, 2019c;Fry et al, 2009a;Isbister, 2009).…”

“…Haemorrhagic effects are potentiated by fibrinogenolytic enzymes which may act upon fibrinogen to either directly produce anticoagulation, by destructively cleaving fibrinogen, or to indirectly produce anticoagulation by cleaving fibrinogen to form short-lived, weak clots in a pseudo-procoagulant manner Debono et al, 2019c;Dobson et al, 2018;Esnouf and Tunnah, 1967;Huang et al, 1992;Levy and Del Zoppo, 2006;Nielsen, 2016a;Premawardena et al, 1998;Trookman et al, 2009;Zulys et al, 1989).…”