Thursday, February 24, 2011

Snakes Venom a Neglected Resource

In a forth coming article Freek Vonk and colleagues (2011) note that snake venoms are a grossly under explored resource in pharmacological prospecting and that recent discoveries in snake systematics demonstrate that former taxonomic bias in research has led to the neglect of thousands of species of potential medical use. Recent discoveries suggest an unexpected degree of variation in venom composition among snakes, variation that differs not only from species to species, but during the life of an individual. The molecular mechanisms underlying this diversity are only beginning to be understood. However, Vonk and colleagues note the enormous potential of snake venom as resource for pharmacological prospecting give new the methods of finding potentially useful molecules. This discovery comes at a time when snake populations are threatened with extinction from human degradation of the environment. Many venom proteins affect the hemostatic system and have been used as defibrinogenating agents for several clinical conditions including deep vein thrombosis, myocardial infarction, and pulmonary embolus. Drugs already derived from snake venoms include Ancrod (Arvin) from the venom of the Malayan Pitviper (Calloselasma rhodostoma), batroxobin (Reptilase) from the lancehead (Bothrops atrox), and crotalase from the Eastern Diamondback Rattlesnake (Crotalus adamanteus). Aggrastat (tirobifan) was developed from the venom of the Saw-scaled Viper (Echis carinatus), and is used as an antiplatelet drug for unstable angina. Venoms with procoagulant properties are useful for the diagnosis of clotting abnormalities. ‘‘Ecarin’’ (E. carinatus) and ‘‘taipan time’’ (Oxyuranus scutellatus) are used for assays for phrothrombin, and Russell’s viper (Daboia russelii) venom assays for factor X and for monitoring anticoagulant therapy. Angiotensin-converting enzyme (ACE) inhibitors were developed from an enzyme isolated from the venom of the Brazilian Pitviper (Bothrops jararaca) to treat high-blood pressure and heart disease. Many venoms have analgesic properties, Hannalgesin is derived from the venom of the King Cobra (Ophiophagus hannah) is now in clinical trials. Promising molecules for pain relief have been isolated from the Tropical Rattlesnake (Crotalus durissus terrificus) as well as related species. The anticancer properties of venoms are also being explored. Malignant brain and spinal-cord tumors (gliomas) are not curable by surgery because they invade the surrounding brain tissue without clear boundaries, making removal impossible. Disintegrins, like contortrostatin from American Copperhead (Agkistrodon contortrix) venom, prevent cells from sticking together, and inhibit their interaction with surrounding tissue, resulting in a blockage of cell motility and invasiveness. Most of the exploration of snake venoms to date have focused on vipers and elapids, but there are many other families of snakes that produce valuable venom molecules - and this resource is only starting to be recognized. In order to keep these valuable molecules available for humans it is necessary to conserve snakes.

Citation: Vonk, F. J., K. Jackson, R. Doley, F. Madaras, P. J. Mirtschin, and N. Vidal. 2011. Snake venom: From fieldwork to the clinic. Bioessays, DOI 10.1002/bies.201000117

No comments:

Post a Comment