Protective Effect of Heme Oxygenase-1 Gene Transfer against Oxyhemoglobin-Induced Endothelial Dysfunction

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Abstract
The current study was designed to determine the effect of recombinant heme oxygenase-1 (HO-1) gene expression on endothelial function in cerebral arteries. Isolated canine basilar arteries were exposed ex vivo (30 minutes at 37°C) to an adenoviral vector (1010 PFU/mL, total volume 300 μL) encoding either the HO-1 gene (AdCMVHO-1) or the β-galactosidase (β-Gal) reporter gene (AdCMVβ-Gal). Twenty-four hours after transduction, arterial rings were suspended in organ chamber for isometric force recording. Endothelium-dependent relaxations were obtained in response to bradykinin (10−10 to 10−6 mol/L) during contraction to uridine-5′-triphosphate (UTP; 3 × 10−6 to 3 × 10−5 mol/L). Certain rings were incubated with oxyhemoglobin (OxyHb; 10−5 mol/L) overnight (16 to 18 hours of 24 hours). Expression and localization of recombinant protein were shown by Western blot analysis and immunohistochemistry. Endothelium-dependent relaxation to bradykinin 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 β-Gal– and HO-1–transduced arteries. Exposure to OxyHb caused impairment of endothelium-dependent relaxation to bradykinin ( P < 0.01). In contrast, OxyHb did not affect endothelium-dependent relaxation in arteries expressing recombinant HO-1 ( P > 0.05). This protective effect of HO-1 was reversed by coincubation with tin protoporphyrin (SnPP9; 10−5 mol/L), a selective inhibitor of HO-1 ( P < 0.01). Basal levels of 3′,5′-cyclic monophosphate (cGMP) in HO-1–transduced vessels were not significantly different from those in β-Gal–transduced vessels. Pretreatment with OxyHb significantly reduced cGMP level in β-Gal–transduced rings ( P < 0.01), whereas it had no effect in HO-1–transduced rings. These results demonstrate that HO-1 gene transfer does not affect endothelial and smooth muscle function of normal arteries, and that expression of recombinant HO-1 in cerebral arteries protects vasomotor function against OxyHb-induced injury.

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