INHIBITION OF ENDOTHELIAL-CELL PROLIFERATION AND BFGF-INDUCED PHENOTYPIC MODULATION BY NITRIC-OXIDE

S-nitroso-N-acetyl-D,L-acetylpenicillamine (SNAP), a chemical donor of NO, inhibited serum- and basic fibroblast growth factor (bFGF)-stimul ated cultured endothelial cell (EC) proliferation in a dose-dependent manner. The inhibitory effect of NO was reversible after washoff of SN AP-containing media. Measurement of nitrate and nitrite in the media o f SNAP-treated EC indicated that decomposition of SNAP into NO reached a stable level at or before 24 h; proliferation of EC was significant ly inhibited for another 48 h and recovered thereafter if no additiona l SNAP was added. The level of NO produced by inhibitory concentration s of SNAP was comparable to NO levels produced by the induction of ind ucible nitric oxide synthase (iNOS) in smooth muscle cells or retinal pigmented epithelial cells. The growth-inhibitory effect of NO was unl ikely to be due to cytotoxicity since 1) cells never completely lost t heir proliferative capacity even after 10 days of exposure to repeated additions of SNAP, 2) the inhibitory effect was reversible upon remov al of NO and with the passage of time, and 3) NO did not reduce the nu mber of cells that were growth-arrested with TGF-beta 1. In addition t o its mitogenic effect, bFGF induced pronounced phenotypic changes, in cluding suppression of contact inhibition, altered cell morphology, an d scattering of the cells, in BPAEC cultures, whereas cells treated si multaneously with bFGF and NO did not exhibit these changes. These obs ervations suggest that NO contributes to the regulation of angiogenesi s and reendothelialization, processes that require EC proliferation, m igration, and differentiation. (C) 1996 Wiley-Liss, Inc.