Neuropeptide Y, an orexigenic hormone, regulates phagocytic activity of lizard splenic phagocytes

Present in vitro study in the wall lizard Hemidactylus flaviviridis, for the first time in ectothermic vertebrates, demonstrated the immunoregulatory role of neuropeptide Y (NPY) and its receptor-coupled downstream signaling cascade. NPY inhibited the percentage phagocytosis and phagocytic index of splenic phagocytes. The inhibitory effect of NPY on phagocytosis was completely antagonized by Y-2 and Y-5 receptor antagonists. This suggests that NPY mediated its effect on phagocytosis through Y2 and Y-5 receptors. Further, NPY receptor-coupled downstream signaling cascade for NPY effect on phagocytosis was explored using the inhibitors of adenylate cyclase (SQ 22536) and protein kinase A (H-89). The SQ 22536/H-89 in a concentration-related manner decreased the inhibitory effect of NPY on phagocytosis. Further, an increase in intracellular cAMP level was observed in response to NPY. Taken together, it can be concluded that NPY via Y-2 and Y-5 receptor-coupled AC-cAMP-PKA pathway downregulated the phagocytic activity of lizard splenic phagocytes. (C) 2011 Elsevier Inc. All rights reserved.