Abstract/Summary

Snakebite envenoming is a propriety neglected tropical disease that annually claims a life of around 150,000 and is responsible for 500,000 disabilities. Skeletal muscle damage is a primary factor for snake venom-induced permanent disabilities. The only treatment available for snakebite envenoming is anti-venoms produced against venomous snake species. These anti-venoms are raised against the geographical venom variant and effectively treat the systemic effects of envenoming. However, they fail to treat local tissue damage. Most research in the snake venom field is focused on improving anti-venom understanding of venom chemistry and physiology. Studies on local effects, pathologies, and treatment of local tissue damage are limited. This thesis investigates skeletal muscle pathologies inflicted by snake venom, especially snake venom metalloprotease-rich viper venoms. The viper venoms and some species of elapids can cause local tissue damage and tissue necrosis. These venoms are rich in snake venom metalloproteases (SVMP), three-finger toxins (3FTxs), and phospholipase A2, which can induce local damaging effects on the skeletal muscle of the bite victim. The elapid venom-mediated damage is often self-resolved; however, in the case of viper envenoming, the muscle damage is often permanent. Here, we aim to narrow down niche areas in skeletal muscle regeneration affected by viper envenomation. We can use innovative methods to target and eliminate the hindrance in the normal regeneration of skeletal muscle damage. The factors contributing to impaired muscle regeneration in the case of SBE are: 1. The venom proteins are present in the muscle tissue and cause persistent damage. 2. The impaired muscle regeneration often results in fibrotic/scar tissue formation that hampers muscle regeneration. 3. The snake venom toxins, especially SVMPs, can affect the function of muscle stem cells and alter the immune response post-muscle injury, which then dysregulated the muscle regeneration process. We selected different approaches to target each problem area. We used small molecular inhibitors marimastat and varespladib specific for SVMPs and PLA2s to inhibit the initial trigger of active venom proteins. These inhibitor molecules improved muscle regeneration, reduced venom pathological effects and restored immune response balance. Secondly, we tested the effect of a known anti-fibrotic molecule soluble activin receptor IIB to minimise muscle fibrosis, which improved muscle regeneration and reduced fibrosis with persistent dosing. Lastly, we have used stem cell-derived condition media to boost the innate regeneration mechanism and restore the dysregulation of the immune response. The presence of secretome was found effective in enhancing myoblast proliferation, differentiation and maturation of muscle cells. All the individual approaches achieved effective muscle regeneration. However, there is a possibility of gaining more benefits from the combination of these molecules. The Circulatory system also plays a vital role in wound healing and regeneration. Hence, we studied the effects of P-III metalloprotease from Crotalus atrox (CAMP) venom and a cardiotoxin -I (CTX) from Naja pallida concerning intramuscular bleeding and microthrombus formation in the tissue. CAMP affected αIIbβ3 integrin-mediated thrombus formation, whereas CTX exhibited effects on extrinsic and intrinsic clotting pathways. All the approaches tested and validated in this thesis target specific areas of muscle regeneration. The small molecule inhibitors target particular proteins in the whole venom, soluble activin receptor IIB, target the specific pathological outcome and condition media targeted modulation of immune response and muscle stem cells. Hence, these treatment molecules may have global application and potential to tackle the crucial pathological outcome of envenoming: SBE-induced muscle damage.