Upregulation of Endogenous Serine Proteinases by SVMPs Contributes to Muscle Damage Induced by Bothrops atrox Venom.

In Brazil, approximately 25,000 snakebites occur annually, with Bothrops atrox responsible for most cases. Local morbidity is high, driven primarily by snake venom metalloproteases (SVMPs). The major SVMPs in B. atrox venom, Atroxlysin-Ia (ATXL) and Batroxrhagin (BATX), efficiently hydrolyze extracellular matrix proteins, inducing rapid hemorrhage and dermonecrosis. Thus, we characterized the composition of the exudate produced after SVMPs injection into the mice gastrocnemius muscle using proteomics. Muscle damage was evaluated by histological analysis. The composition of the exudate was analyzed by mass spectrometry. The SVMPs induced disorganization of muscle fibers and inflammatory cell migration. However, ATXL-induced a significantly higher neutrophil influx compared to BATX, likely triggered by an increase in CXCL16, suggesting a superior inflammatory capacity. In summary, despite being metalloproteases, these toxins exhibit distinct pathological profiles: ATXL is predominantly inflammatory, while BATX is more hemorrhagic. Interestingly, while endogenous serine proteinase levels were similar in both exudates, BATX showed significantly higher levels of proteinase inhibitors. Furthermore, identification of peptide bond cleavage sites revealed a pattern consistent with trypsin-like serine proteinases. These findings suggest that SVMPs not only damage tissue directly but also associate with the activation of host endogenous proteinases, which may contribute to the complex pathology of B. atrox envenomation, although direct causation remains to be established.