Melatonin (N-acetyl-5-methoxytryptamine) is an efficient
free radical scavenger and
antioxidant, both in vitro and in vivo. The role of
melatonin as an
immunomodulator is, in some cases, contradictory. In this study we have investigated the therapeutic efficacy of
melatonin in rats subjected to Pelagia noctiluca crude
venom (of the familia Pelaguiidae; and genus Pelagia) induced acute paw
inflammation. In particular, injection of the
venom into the paw of rats elicited an acute inflammatory response characterized by accumulation of fluid containing a large number of polymorphonuclear neutrophils in the paw and subsequent lipid peroxidation. Furthermore, the
venom promoted an expression of iNOS,
nitrotyrosine and the activation of the nuclear
enzyme poly (ADP-ribose) polymerase as determined by immunohistochemical analysis of paw tissues. Administration of
melatonin 30 min, 1 and 6 hr after the challenge with the
venom, caused a significant reduction in all the parameters of
inflammation measured. Thus, based on these findings we propose that
melatonin may be useful a treatment of local acute
inflammation induced by P. noctiluca crude
venom.