The edematogenic effect of Micrurus lemniscatus venom is dependent on venom phospholipase A₂ activity and modulated by non-neurogenic factors

Coral snakes mainly cause neurotoxic symptoms in human envenomation, but experimental studies have already demonstrated several pharmacological activities in addition to these effects. This investigation was carried out with the aim of evaluating (1) non-neurogenic mechanisms involved in the inflammatory response induced by Micrurus lemniscatus venom (MLV) in rat hind paws, (2) participation of PLA2 in this response, and (3) neutralizing efficiency of commercial anti-elapid antivenom on edema. MLV promoted a rapid, significant in-crease in vascular permeability, influx of leukocytes, and disorganization of collagen bundles, as demonstrated by histological analysis. Several pretreatments were applied to establish the involvement of inflammatory me-diators in MLV-induced edema (5 mu g/paw). Treatment of animals with chlorpromazine reduced MLV-induced edema, indicating participation of TNF-alpha. However, the inefficiency of other pharmacological treatments sug-gests that eicosanoids, leukotrienes, and nitric oxide have no role in this type of edema formation. In contrast, PAF negatively modulates this venom-induced effect. MLV was recognized by anti-elapid serum, but this anti -venom did not neutralize edema formation. Chemical modification of MLV with p-bromophenacyl bromide abrogated the phospholipase activity and markedly reduced edema, demonstrating PLA2 participation in MLV-induced edema. In conclusion, the non-neurogenic inflammatory profile of MLV is characterized by TNF-alpha-mediated edema, participation of PLA2 activity, and down-regulation by PAF. MLV induces an influx of leu-kocytes and destruction of collagen fibers at the site of its injection.