A PHOSPHOLIPASE A(2)-RELATED SNAKE-VENOM (FROM CROTALUS-DURISSUS-TERRIFICUS) STIMULATES NEUROENDOCRINE AND IMMUNE FUNCTIONS - DETERMINATIONOF DIFFERENT SITES OF ACTION

Immune neuroendocrine interactions are vital for the individual's surv ival in certain physiopathological conditions, such as sepsis and tiss ular injury. It is known that several animal venoms, such as those fro m different snakes, are potent neurotoxic compounds and that their mai n component is a specific phospholipase A type 2 (PLA(2)). It has been described recently that the venom from Crotalus durissus terrificus [ snake venom (SV), in the present study] possesses some cytotoxic effec t in different in vitro and in vivo animal models. In the present stud y, we investigated whether SV and its main component, PLA(2) (obtained from the same source), are able to stimulate both immune and neuroend ocrine functions in mice, thus characterizing this type of neurotoxic shock. For this purpose, several in vivo and in vitro designs were use d to further determine the sites of action of SV-PLA(2) on the hypotha lamo-pituitary-adrenal (HPA) axis function and on the release of the p athognomonic cytokine, tumor necrosis factor alpha (TNF alpha), of dif ferent types of inflammatory stress. Our results indicate that SV (25 mu g/animal) and PLA(2) (5 mu g/animal), from the same origin, stimula te the HPA and immune axes when administered (ip) to adult mice; both preparations were able to enhance plasma glucose, ACTH, corticosterone (B), and TNF alpha plasma levels in a time-related fashion. SV was fo und to activate CRH- and arginine vasopressin-ergic functions in vivo and, in vitro, SV and PLA(2) induced a concentration-related (0.05-10 mu g/ml) effect on the release of both neuropeptides. SV also was effe ctive in changing anterior pituitary ACTH and adrenal B contents, also in a time-dependent fashion. Direct effects of SV and PLA(2) on anter ior pituitary ACTH secretion also were found to function in a concentr ation-related fashion (0.001-1 mu g/ml), and the direct corticotropin- releasing activity of PLA(2) was additive to those of CRH and arginine vasopressin; the corticotropin-releasing activity of both SV and PLA( 2) were partially reversed by the specific PLA(2) inhibitor, manoalide . On the other hand, neither preparation was able to directly modify s pontaneous and ACTH-stimulated adrenal B output. The stimulatory effec t of SV and PLA(2) on in vivo TNF alpha release was confirmed by in vi tro experiments on peripheral mononuclear cells; in fact, both PLA2 (0 .001-1 mu g/ml) and SV (0.1-10 mu g/ml), as well as concavalin A (1-10 0 mu g/ml), were able to stimulate TNF alpha output in the incubation medium. Our results clearly indicate that PLA(2)-dependent mechanisms are responsible for several symptoms of inflammatory stress induced du ring neurotoxemia. In fact, we found that this particular PLA(2)-relat ed SV is able to stimulate both HPA axis and immune functions during t he acute phase response of the inflammatory processes.