CARBON-MONOXIDE AND NITRIC-OXIDE SUPPRESS THE HYPOXIC INDUCTION OF VASCULAR ENDOTHELIAL GROWTH-FACTOR GENE VIA THE 5'-ENHANCER

Vascular endothelial growth factor (VEGF) plays an important role in a ngiogenesis and blood vessel remodeling. Its expression is up-regulate d in vascular smooth muscle cells by a number of conditions, including hypoxia. Hypoxia increases the transcriptional rate of VEGF via a 28- base pair enhancer located in the 5'-upstream region of the gene. The gas molecules nitric oxide (NO) and carbon monoxide (CO) are important vasodilating agents. We report here that these biological molecules c an suppress the hypoxia-induced production of VEGF mRNA and protein in smooth muscle cells. In transient expression studies, both NO and CO inhibited the ability of the hypoxic enhancer we have previously ident ified to activate gene transcription. Furthermore, electrophoretic mob ility shift assays indicated decreased binding of hypoxia-inducible fa ctor 1 (HIF-1) to this enhancer by nuclear proteins isolated from CO-t reated cells, although HIF-1 protein levels were unaffected by CO, Giv en that both CO and NO activate guanylyl cyclase to produce cGMP and t hat a cGMP analog (8-Br-cGMP) showed a similar suppressive effect on t he hypoxic induction of the VEGF enhancer, we speculate that the suppr ession of VEGF by these two gas molecules occurs via a cyclic GMP-medi ated pathway.