Opioid and non-opioid receptor-mediated immunoregulatory role of leucine-enkephalin in teleost Channa punctatus.
Leucine-enkephalin (Leu-enk) is an endogenous opioid peptide and highly conserved throughout the vertebrates. Despite its conserved nature, the immunoregulatory property of Leu-enk is explored only in mammals. The present study describes the immunomodulatory role of Leu-enk in a lower vertebrate, spotted murrel Channa punctatus. Leu-enk increased the percentage phagocytosis and phagocytic index, though its stimulatory effect on phagocytosis markedly decreased at concentrations higher than 10(-9) M. Moreover, it had bell-shaped stimulatory effect also on the superoxide production by phagocytes. On the other hand, Leu-enk showed bimodal effects on nitrite release. The lower concentrations of Leu-enk produced inhibitory effect, while higher concentrations had stimulatory effect on nitrite release. Interestingly, the Leu-enk-induced increase in nitrite release was unaltered by non-selective opioid receptor antagonist though the same completely antagonized the inhibitory effect of Leu-enk on nitrite release and the stimulatory effect on phagocytosis and superoxide production. This suggests that the stimulatory effect of Leu-enk on nitrite production is mediated by the non-opioid receptor. Further, delta-opioid receptor was precisely seen involved in mediating the stimulatory effect of Leu-enk on phagocytosis and superoxide production, or inhibitory effect on nitrite release. It can be concluded that Leu-enk regulates the innate immune response of splenic phagocytes acting via both opioid and non-opioid receptor in the fish C. punctatus.
Department of Zoology, University of Delhi, Delhi-110007, India.
Rajeev
R
Singh
Umesh
U
Rai
D000818:Animals; D002478:Cells, Cultured; D004743:Enkephalin, Leucine / Q000037:antagonists & inhibitors / Q000276:immunology* / Q000494:pharmacology; D008297:Male; D009271:Naltrexone / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D018377:Neurotransmitter Agents / Q000494:pharmacology; D009573:Nitrites / Q000276:immunology; D010473:Perciformes / Q000276:immunology*; D010587:Phagocytosis / Q000187:drug effects / Q000276:immunology; D013154:Spleen / Q000187:drug effects / Q000276:immunology; D013481:Superoxides / Q000276:immunology
D009292:Narcotic Antagonists; D018377:Neurotransmitter Agents; D009573:Nitrites; D013481:Superoxides; D004743:Enkephalin, Leucine; D009271:Naltrexone