Possible roles of neuropeptide Y [Y.sub.3]-receptor subtype in rat aortic endothelial cell proliferation under hypoxia, and its specific signal transduction

The present study was undertaken to determine whether neuropeptide Y (NPY) induces proliferation of rat aortic endothelial cells (RAECs). Since NPY increased the permeability of RAEC monolayers to large molecules via the NPY [Y.sub.3] receptor, RAEC proliferation has been evaluated in terms of NPY-receptor subtypes and also intracellular mechanisms. RAECs were incubated with gases containing 20, 15, or 10% [O.sub.2] and a certain amount of [N.sub.2], depending on the [O.sub.2] content in 5% C[O.sub.2] incubators. NPY ([10.sup.-9]-[10.sup.-6] M) increased the RAEC numbers under hypoxic conditions, such as 15 or 10% [O.sub.2]. Peptide YY elicited no proliferative effect on RAEC, and NPY-(18-36) inhibited the NPY-induced increase in cell number, suggesting that NPY increases the RAEC count through the NPY [Y.sub.3] receptor. Pertussis toxin, U-73122, GF-109203X, myristorylated autocamtide-2-related inhibitory peptide, and wortmannin inhibited the NPY-induced proliferation of RAEC concentration dependently. DY9760e little affected the proliferation caused by NPY. ML-9 and imatinib actually enhanced the NPY-induced proliferation of cells. These results indicated that the NPY [Y.sub.3] receptor is coupled with [G.sub.i] protein, and that NPY-induced increases in RAEC proliferation are mediated by phospholipase C-protein kinase C and/or phosphatidylinositol 3-kinase pathways. In intracellular [Ca.sup.2+]-calmodulin-dependent pathways, calmodulin-dependent protein kinase II partly participates in the NPY-induced cell proliferation. Regarding the previously reported effect of NPY on the permeability of RAEC monolayers to large molecules, it is probable that protein kinase C and phosphatidylinositol 3-kinase pathways are activated for both permeability and cell proliferation induced by NPY under hypoxia, relevant to new insights into the roles of NPY in ischemia-hypoxia. protein kinase C; phosphatidylinositol 3-kinase; phospholipase C; calmodulin-dependent protein kinase