HYPOXIC REGULATION OF ENDOTHELIAL GLYCERALDEHYDE-3-PHOSPHATE DEHYDROGENASE

The glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is induced by hypoxia in endothelial cells (EC). To define the mechan isms by which GAPDH is regulated by hypoxia, EC were exposed to cobalt , other transition metals, carbon monoxide (CO), deferoxamine, or cycl oheximide in the presence or absence of hypoxia for 24 h, and GAPDH pr otein and mRNA levels were measured. GAPDH was induced in cells by the transition metals cobalt, nickel, and manganese and by deferoxamine, and GAPDH mRNA induction by hypoxia was blocked by cycloheximide. GAPD H induction by hypoxia, unlike that of other hypoxia-regulated genes, was not inhibited by CO or by 4,6-dioxoheptanoic acid, an inhibitor of heme synthesis. GAPDH induction was not altered by mediators of prote in phosphorylation, a calcium channel blocker, a calcium ionophore, or alterations in redox state. GAPDH induction by hypoxia or transitiona l metals was partially blocked by sodium nitroprusside but was not alt ered by the inhibitor of nitric oxide synthase N-omega-nitro-L-arginin e. These findings suggest that GAPDH induction by hypoxia in EC occurs via mechanisms other than those involved in other hypoxia-responsive systems.