In vitro assessment of enzymatic activities, haemolytic potential, and cytotoxic effects of Mangshan pit viper (Protobothrops mangshanensis) venom

The Mangshan pit viper (Protobothrops mangshanensis) is a medically relevant venomous snake endemic to China. Owing to its popularity in the pet trade, an increasing number of envenomations by this species have been reported, typically presenting with localised cytotoxicity and severe coagulopathy. However, the functional properties of P. mangshanensis venom have yet to be comprehensively characterised. In this study, we conducted an in-depth analysis of its biochemical activities using a broad panel of in vitro assays. We evaluated protease, phospholipase A2, Factor Xa-like, thrombin-like, and plasmin-like activities, alongside assessments of haemolytic and cytotoxic effects. The venom exhibited pronounced Factor Xa-like, thrombin-like, and plasmin-like activities (maximum 66.7 %, 112.1 %, and 51.9 %, respectively), but moderate protease activity (maximum 46.7 %) and low phospholipase A2 activity (maximum 9.9 %). In contrast, haemolytic activity was virtually absent. Cytotoxicity was assessed in two epithelial cell lines, MDCK II and Calu-3, with a response observed only in Calu-3 cells, which remained low (<19 %). Overall, our findings are consistent with the severe haemotoxicity reported following envenomation by the Mangshan pit viper, and highlight the venom's disruptive effects on the blood coagulation cascade. This characterisation enhances our understanding of the functioning of P. mangshanensis venom, and may support the development of more effective treatment for envenomation by this species.