Varanid Lizard Venoms Disrupt the Clotting Ability of Human Fibrinogen through Destructive Cleavage
Venom Evolution Lab, School of Biological Sciences, University of Queensland, St Lucia, QLD 4072, Australia
Alphabiotoxine Laboratory sprl, Barberie 15, 7911 Montroeul-au-bois, Belgium
Department of Earth and Biological Sciences, Loma Linda University, Loma Linda, CA 92350, USA
Author to whom correspondence should be addressed.
Toxins 2019, 11(5), 255; https://doi.org/10.3390/toxins11050255
Received: 11 March 2019 / Revised: 30 April 2019 / Accepted: 1 May 2019 / Published: 7 May 2019
(This article belongs to the Special Issue Assessment of Animal Toxin Function with Novel Viscoelastic Methods)
The functional activities of Anguimorpha lizard venoms have received less attention compared to serpent lineages. Bite victims of varanid lizards often report persistent bleeding exceeding that expected for the mechanical damage of the bite. Research to date has identified the blockage of platelet aggregation as one bleeding-inducing activity, and destructive cleavage of fibrinogen as another. However, the ability of the venoms to prevent clot formation has not been directly investigated. Using a thromboelastograph (TEG5000), clot strength was measured after incubating human fibrinogen with Heloderma and Varanus lizard venoms. Clot strengths were found to be highly variable, with the most potent effects produced by incubation with Varanus venoms from the Odatria and Euprepriosaurus clades. The most fibrinogenolytically active venoms belonged to arboreal species and therefore prey escape potential is likely a strong evolutionary selection pressure. The results are also consistent with reports of profusive bleeding from bites from other notably fibrinogenolytic species, such as V. giganteus. Our results provide evidence in favour of the predatory role of venom in varanid lizards, thus shedding light on the evolution of venom in reptiles and revealing potential new sources of bioactive molecules useful as lead compounds in drug design and development.