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Keel venom: Rhabdophis subminiatus (red-necked keelback) venom pathophysiologically affects diverse blood clotting pathways.

Chowdhury, Abhinandan, Lewin, Matthew R, Carter, Rebecca W, Casewell, Nicholas ORCID: and Fry, Bryan G (2022) 'Keel venom: Rhabdophis subminiatus (red-necked keelback) venom pathophysiologically affects diverse blood clotting pathways.'. Toxicon, Vol 218, pp. 19-24.

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Venoms are evolutionary novelties that have real-world implications due to their impact upon human health. However, relative to the abundant studies of elapid and viperid snake venoms, fewer investigations have been undertaken on those of rear-fanged snakes as they are more problematic for obtaining venom. While most rear-fanged venomous snakes are not considered to be of great medical importance, several species are capable of producing fatalities. Most notable among these are snakes from the genus Rhabdophis, the Asian "keelback" snakes. Prior work have described potent procoagulant toxicity suggesting Factor X and prothrombin activation, but did not investigate the ability to activate other clotting factors. Here we show that in addition to activating both Factor X and prothrombin (with prothrombin twice that of FX), the venom of Rhabdophis subminiatus is able to more potently activate Factor VII (ten times that of prothrombin), while also activating FXII and FIX equipotently to prothrombin, and with FXI also activated but at a much lower level. The ability to activate FVII represents a third convergent evolution of this trait. The Australian elapid clade of [Oxyuranus (taipans) + Pseudonaja (brown snakes)] was the first identified to have evolved this trait. and only recently was it shown to be independently present in another lineage (the Central American viperid species Porthidium volcanicum). In addition, the abilities to activate FXI and FXII are also convergent between R. subminiatus and P. volcanicum, but with R. subminiatus being much more potent. By testing across amphibian, avian, and mammalian plasmas we demonstrate that the venom is potently procoagulant across diverse plasma types. However, consistent with dietary preference, R. subminiatus venom was most potent upon amphibian plasma. While a Rhabdophis antivenom is produced in Japan to treat R. tigrinus envenomings, it is scarce even within Japan and is not exported. As this genus is very wide-ranging in Asia, alternate treatment options are in need of development. Hence we tested the ability of candidate, broad-spectrum enzyme inhibitors to neutralize R. subminiatus venom: marimastat was more effective than prinomastat but both marimastat and prinomastat were significantly more effective than DMPS (2,3-Dimercapto-1-propanesulfonic acid). The findings of this study shed light on the evolution of these fascinating rear-fanged snakes as well as explored their systemic effects upon blood coagulation and point to potential treatment options for the rare, but potentially lethal encounters.

Item Type: Article
Subjects: QV Pharmacology > Toxicology > General Toxicology > QV 600 General works
QY Clinical Pathology > Blood. Blood Chemistry > QY 410 Coagulation
WD Disorders of Systemic, Metabolic or Environmental Origin, etc > Animal Poisons > WD 400 General works
WD Disorders of Systemic, Metabolic or Environmental Origin, etc > Animal Poisons > WD 410 Reptiles
Faculty: Department: Biological Sciences > Department of Tropical Disease Biology
Digital Object Identifer (DOI):
SWORD Depositor: JISC Pubrouter
Depositing User: JISC Pubrouter
Date Deposited: 15 Dec 2022 09:44
Last Modified: 31 Aug 2023 03:12


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