Protective effect of heme oxygenase-1 gene transfer against oxyhemoglobin-induced endothelial

The current study was designed to determine the effect of recombinant heme oxygenase-1 (HO-1) gene expression on endothelial function in cerebral arte ries. Isolated canine basilar arteries were exposed ex vivo (30 minutes at 37 degreesC) to an adenoviral vector (10(10) PFU/mL, total volume 300 muL) encoding either the HO-1 gene (AdCMVHO-1) or the beta -galactosidase (beta -Gal) reporter gene (AdCMV beta -Gal). Twenty-four hours after transduction , arterial rings were suspended in organ chamber for isometric force record ing. Endothelium-dependent relaxations were obtained in response to bradyki nin (10(-10) to 10(-6) mol/L) during contraction to uridine-5'-triphosphate (UTP; 3 x 10(-6) to 3 x 10(-5) mol/L). Certain rings were incubated with o xyhemoglobin (OxyHb; 10(-5) mol/L) overnight (16 to 18 hours of 24 hours). Expression and localization of recombinant protein were shown by Western bl ot analysis and immunohistochemistry. Endothelium-dependent relaxation to b radykinin and endothelium-independent relaxation to forskolin (10(-9) to 10 (-5) mol/L) and DEA-NONOate (10(-10) to 10(-5) mol/L) were identical in bet a -Gal- and HO-1-transduced arteries. Exposure to OxyHb caused impairment o f endothelium-dependent relaxation to bradykinin (P < 0.01). In contrast, O xyHb did not affect endothelium-dependent relaxation in arteries expressing recombinant HO-1 (P > 0.05). This protective effect of HO-1 was reversed b y coincubation with tin protoporphyrin (SnPP9; 10(-5) mol/L), a selective i nhibitor of HO-1 (P < 0.01). Basal levels of 3',5'-cyclic monophosphate (cG MP) in HO-1-transduced vessels were not significantly different from those in beta -Gal-transduced vessels. Pretreatment with OxyHb significantly redu ced cGMP level in beta -Gal-transduced rings (P < 0.01), whereas it had no effect in HO-1-transduced rings. These results demonstrate that HO-1 gene t ransfer does not affect endothelial and smooth muscle function of normal ar teries, and that expression of recombinant HO-1 in cerebral arteries protec ts vasomotor function against OxyHb-induced injury.