Carbon Monoxide Signaling in Promoting Angiogenesis in Human Microvessel Endothelial Cells

Abstract

Heme oxygenase isoforms (HO-1/HO-2) catalyze the conversion of heme to carbon monoxide (CO) and bilirubin. In this study, HO-1-deficient endothelial cells were transduced with HO-1 in the antisense orientation to determine whether supplementation with CO or bilirubin would regulate cell proliferation and angiogenesis. Western blotting, enzyme activity, CO and prostaglandin E₂ (PGE₂) production, and cell-cycle analysis were used to assess transgenic expression and functionality of the recombinant protein. AMatrigel matrix was used for assessment of in vitro capillary formation. Transduction with HO-1 antisense resulted in decreased capillary formation, cell proliferation, and cell-cycle progression, and increased PGE₂ production compared with control. HO-1 deficiency was also associated with increased expression of p21 and p27, but had no significant effect on p16 and p53. We also compared two different CO donors for their ability to rescue angiogenesis. Compared with control, HO-1-deficient endothelial cells showed increased angiogenesis following tricarbonyldichlororuthenium( II) dimer ([Ru(CO)₃Cl₂]₂) (CORM-1) starting at 50 μM, whereas tricarbonylchloro(glycinato) ruthenium(II) (CORM-3), starting at 25 μM, was a potent enhancer of angiogenesis. The addition of bilirubin did not restore angiogenesis. These data suggest that HO-mediated angiogenesis and cell proliferation were dependent on HO-1- and not HO-2-derived CO.Antioxid. Redox Signal. 7, 704–710.