NITRIC-OXIDE MEDIATES ANGIOGENESIS IN-VIVO AND ENDOTHELIAL-CELL GROWTH AND MIGRATION IN-VITRO PROMOTED BY SUBSTANCE-P

We evaluated the effects of nitric oxide (NO) generators and endogenou s production of NO elicited by substance P (SP) in the angiogenesis pr ocess. Angiogenesis was monitored in the rabbit cornea in vivo and in vitro by measuring the growth and migration of endothelial cells isola ted from coronary postcapillary venules. The angiogenesis promoted in the rabbit cornea by [Sar(9)]-SP-sulfone, a stable and selective agoni st for the tachykinin NK, receptor, and by prostaglandin E(1) (PGE(1)) , was potentiated by sodium nitroprusside (SNP). Conversely, the NO sy nthase inhibitor N-omega-nitro-Larginine methyl ester (L-NAME), given systemically, inhibited angiogenesis elicited by [Sar(9)]-SP-sulfone a nd by PGE(1). Endothelial cells exposed to SNP exhibited an increase i n thymidine incorporation and in total cell number. Exposure of the ce lls to NO generating drugs, such as SNP, isosorbide dinitrate, and gly ceryl trinitrate, produced a dose-dependent increase in endothelial ce ll migration. Capillary endothelial cell proliferation and migration p roduced by SP were abolished by pretreatment with the NO synthase inhi bitors N-omega-mono-methyl-L-arginine (L-NMMA), N-omega-nitro-L-argini ne (L-NNA), and L-NAME. Exposure of the cells to SP activated the calc ium-dependent NO synthase. Angiogenesis and endothelial cell growth an d migration induced by basic fibroblast growth factor were not affecte d by NO synthase inhibitors. These data indicate that NO production in duced by vasoactive agents, such as SP, functions as an autocrine regu lator of the microvascular events necessary for neovascularization and mediates angiogenesis.