ADENOVIRAL TRANSFER OF THE INDUCIBLE NITRIC-OXIDE SYNTHASE GENE BLOCKS ENDOTHELIAL-CELL APOPTOSIS

Background, We have previously reported that vascular inducible nitric oxide synthase (iNOS) gene transfer inhibits injury-induced intimal h yperplasia in vitro and in vivo. One mechanism by which NO may prevent intimal hyperplasia is by preserving the endothelium or promoting its regeneration. To study this possibility toe examined the effect of iN OS gene transfer on endothelial cell (EC) proliferation and viability. Methods. An adenoviral vector (AdiNOS) containing the human iNOS cDNA was constructed and used to infect cultured sheep arterial ECs. NO pr oduction was measured, and the effects of continuous NO exposure on EC proliferation, viability, and apoptosis were evaluated. Results. AdiN OS-infected ECs Produced 25- to 100-fold more NO than control (AdlacZ) infected cells as measured by nitrite accumulation. This increased NO synthesis did not inhibit EC proliferation as reflected by tritiated thymidine incorporation. Chromium 51 release assay revealed that EC vi ability was also unaffected by AdiNOS infection and NO synthesis. In a ddition prolonged exposure to NO synthesis did not induce EC apoptosis , instead, NO inhibited lipopolysaccharide-induced apoptosis in these cells by reducing caspase-3-like protease activity. Conclusions, Vascu lar iNOS gene transfer, while inhibiting smooth muscle cell proliferat ion, does not impair EC mitogenesis or viability. Augmented NO synthes is may also protect ECs against apogenic stimuli such as lipopolysacch aride. Therefore iNOS gene transfer may promote endothelial regenerati on and can perhaps accelerate vascular healing.