Influence of the geographical variability on the neurotoxic potential and cross-reactivity with comercial antivenom of venoms from Crotalus durissus subspecies (Viperidae-Crotalinae) distributed in Brazil

• Grant number: 24/01800-5
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: August 01, 2024
• End date: July 31, 2025
• Field of knowledge: Biological Sciences - Pharmacology - Toxicology
• Principal Investigator: Francis Lopes Pacagnelli
• Grantee: Sofia Nicole da Silva Azevedo
• Host Institution: Pró-Reitoria de Pesquisa e Pós-Graduação. Universidade do Oeste Paulista (UNOESTE). Presidente Prudente , SP, Brazil

Abstract

Envenomations by snakes comprise the group of neglected tropical diseases, according to the World Health Organization (WHO), resulting in more than 2.5 million cases and 150,000 deaths every year worldwide. In Brazil, accidents caused by rattlesnakes (Crotalus durissus spp.) represent an important public health problem due to the severity of these envenomations. Crotalic accidents are characterized by inducing a potent neurotoxic and myotoxic effects mostly mediated by crotoxin, phospholipase A2 (PLA2) toxin which comprises 70-90% of the composition of these venoms. Recent studies have evidenced the influence of geographic variability on the PLA2 compositional profile of C. d. terrificus and C. d. collilineatus venoms, indicating greater complexity of their isoforms in specimens from the southern and southeastern regions of Brazil. In this study, we propose to evaluate the influence of the geographic variability on the neuromuscular activity of the venoms of Crotalus durissus cascavella, C. d. collilineatus, C. d. ruruima and C. d. terrificus (Brazilian rattlesnakes) and on the cross-reactivity of these venoms with commercial anti-Crotalus serum. Initially, we will perform an enzymatic kinetics protocol to determine the minimum inhibitory concentration of varespladib on the PLA2 activity of C. durissus spp. venoms, using a colorimetric method in a spectrophotometer. Afterwards, we will determine the levels of cross-reactivity of C. durissus spp. venoms with commercial anti-Crotalus serum by Western blotting. In a mouse phrenic nerve-diaphragm (PND) preparation, we will compare variations in the neurotoxic potential of C. durissus spp. venoms and then compare the influence of crotoxin (PLA2) on the neuromuscular activity after inhibition with varespladib (selective PLA2 inhibitor). In addition, we will also evaluate the residual neuromuscular response to C. durissus spp. venoms after exposure to commercial antivenom. Finally, using diaphragm muscle samples preserved from neuromuscular protocols, we will evaluate the levels of morphological changes caused by C. durissus spp. venoms. This study represents an investigation that has not been carried out before and the results will contribute to the understanding of the influence of geographic variability on the profile of neuromuscular action of Crotalus durissus cascavella, C. d. collilineatus, C. d. ruruima and C. d. terrificus venoms, guiding better strategies for the treatment of envenomations by these subspecies.