Mud in the blood: Novel potent anticoagulant coagulotoxicity in the venoms of the Australian elapid snake genus Denisonia (mud adders) and relative antivenom efficacy

An Appetite for Destruction: Detecting Prey-Selective Binding of α-Neurotoxins in the Venom of Afro-Asian Elapids

“…Regarding toxin diversification and evolution, the Red Queen hypothesis [1] would suggest that an arms race between predator and prey would provide a positive selection pressure for predatory venom toxins to evolve prey specificity and, reciprocally, for toxin resistance to evolve in prey and predators of venomous animals. Evidence for prey driving toxin specificity has been suggested by the discovery of taxon-specific crude venoms [2][3][4][5][6] and individual toxins [7][8][9][10][11][12][13] across the animal kingdom. Molecular evidence likewise suggests that some venom toxins are under high positive selection pressure, causing rapid diversification through mutations that alter protein structure and function [14][15][16].…”

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

“…ii) incubation with plasma followed by addition of FXa to determine effects on prothrombinase complex formation (with the site of action determined by comparison with iii and iv, whereby if a strong effect was noted here but corresponding strong effects were not noted in iii or iv, then this indicated inhibition of the formation of the prothrombinase complex, as previously validated by us (Youngman et al, 2018); iii) incubation with thrombin followed by addition of fibrinogen to determine direct inhibition of thrombin; and iv) incubation with fibrinogen followed by addition of thrombin to determine the ability to degrade fibrinogen. Results were as follows ( Figure 6.3 brevicaudus, G. tsushimaensis, and G. ussuriensis) or inactive in this assay (O. okinavensis) ( Figure 6.3A); ii) incubation with plasma followed by addition of FXa did not produce a relative strong effect for any of the venoms (Figure 6.3B); iii) incubation with thrombin also revealed negligible effects in this inhibitory function ( Figure 6.3C); iv) incubation with fibrinogen revealed a very strong nonclotting, destructive fibrinogenolytic effect for G. brevicaudus, a lower but still strong effect for on G. ussuriensis male venom sample, but only moderate to low for all other samples (Figure 6.3D).…”

“…Additional procoagulation (Factor X and prothrombin activation) or anticoagulation (inhibition of FXa, prothrombinase complex formation, thrombin, or fibrinogen cleavage, Table 6.2) assays were also conducted, using methods previously validated by us (Debono et al, 2019a;Debono et al, 2019c;Youngman et al, 2018). To identify the possible target in the clotting cascade which the venom was acting upon, inhibition assays were performed in which either plasma or individual clotting factors were incubated with the sample venom, as shown in (Youngman et al, 2018). Data was analysed using GraphPad PRISM 8.0 (GraphPad Prism Inc., La Jolla, CA, USA).…”

“…by Trimeresurus venoms were performed using previously validated methods (Debono et al, 2019a;Debono et al, 2019b;Debono et al, 2019c;Youngman et al, 2018). All species were subjected to these assays.…”

“…Procoagulant venoms are known to activate Factor X or prothrombin, resulting in the generation of endogenous thrombin and subsequent stable fibrin clots (Joseph and Kini, 2002;Kini, 2005aKini, , 2006Kornalik and Blombäck, 1975;Lister et al, 2017;Oulion et al, 2018;Rogalski et al, 2017;Rosing and Tans, 1991;Rosing and Tans, 1992;Rosing and Tans, 2010;Sousa et al, 2018;Tans and Rosing, 2002;Yamada et al, 1996;Zdenek et al, 2019). Anticoagulant effects can be accomplished through the inhibition of clotting enzymes, such as Factors Xa, XIa, IXa or thrombin, or through fibrinogenolytic effects (Youngman et al, 2018). Fibrinogen cleavage occurs either in a non-clotting, destructive manner, or results in the formation of aberrant fibrin clots that are short lived and rapidly degraded Debono et al, 2019c).…”