Gene transfer of endothelial nitric oxide synthase but not Cu/Zn superoxide dismutase restores nitric oxide availability in the SHRSP.

Abstract

Objective: Previous studies from our group have shown a deficit in nitric oxide (NO) bioavailability and an excess production of the superoxide anion (O₂⁻) in the stroke prone spontaneously hypertensive rat (SHRSP) compared to the normotensive Wistar Kyoto (WKY) strain. This present study has investigated whether adenoviral-mediated gene transfer of human eNOS or Cu/ZnSOD can alter the NO/O₂⁻ balance, thereby improving endothelial function. Methods: A recombinant adenovirus, Ad/Hu/eNOS, containing the human eNOS cDNA fragment was generated by homologous recombination in 293 cells. Ad/Hu/eNOS or Ad/Cu/ZnSOD was delivered into SHRSP carotid arteries in vivo, using a titre of 2×10⁹–2×10¹⁰ plaque forming units (pfu)/ml, and the effect on gene expression was observed 24 h later. Results: Western blotting confirmed increased enzyme levels of eNOS and Cu/ZnSOD in the viral-infused vessels. Ex vivo, the pressor response to phenylephrine (PE) in the presence of l-NAME was increased in the eNOS-infused arteries relative to the contralateral controls, indicating restoration of basal NO availability to that observed in untreated control WKY rats. Infusion of the SOD virus produced a statistically insignificant increase in NO bioavailability. Conclusions: Our results support our previous findings obtained using a bovine eNOS recombinant adenovirus, that recombinant adenoviral gene transfer of human eNOS has a significant effect on NO bioavailability. In contrast, AdCu/ZnSOD gene transfer does not elicit an effect in our model. These results indicate that short-term overexpression of a recombinant eNOS, but not Cu/ZnSOD gene, in carotid arteries of the SHRSP is an effective means of locally increasing NO bioavailability to improve endothelial function.