Adenoviral gene transfer of endothelial nitric oxide synthase (eNOS) to the penis improves age-related erectile dysfunction in the rat

Nitric oxide (NO) is the principal mediator of penile erection. NO is synth esized by a variety of nitric oxide synthases (NOS). It has been demonstrat ed that a decrease in NOS activity, as observed in aging, is associated wit h a diminished erectile response. The objective of this study was to determ ine if adenoviral-mediated gene transfer of eNOS could reverse age-related erectile dysfunction in the rat. Two groups of animals were transfected wit h adenoviruses: (1) aged rats (60 weeks) with AdRSV beta gal; and (2) aged rats (60 weeks) with AdRSVeNOS. Five days after transfection, these study a nimals underwent cavernosal nerve stimulation (CNS) to assess erectile func tion and their responses were compared with young (20 weeks) control rats, Cross-sections of the rat penises transfected with AdRSVeNOS were examined after trichrome staining. Adenoviral transduction efficiency of beta-galact osidase reporter gene was measured by a galacto-light chemiluminescent repo rter gene assay in cavernosal tissues of rats administered AdRSV beta gal, The transgene expression of eNOS was examined by RT-PCR in rats transfected with AdRSV beta gal and AdRSVeNOS. eNOS and iNOS protein levels were measu red by Western blot analysis, and cGMP levels were assessed in cavernosal t issue by enzyme immunoassay. Adenoviral expression of the P-galactosidase r eporter gene was observed in cavernosal tissue for up to 30 days, with peak expression registered at 5 days after intracavernosal administration of Ad RSV beta gal. Cross-sections of the rat penises transfected with the AdRSVe NOS revealed no pathological (morphological or histological) changes. Five days after administration of AdRSVeNOS, eNOS protein, mRNA and cGMP levels in the corpora cavernosa were significantly increased (P < 0.05), while iNO S protein levels remained unchanged (P > 0.05). In conclusion, enhanced exp ression of eNOS employing an adenoviral vector significantly increased the erectile response to cavernosal nerve stimulation in the aged rat, similar to the response observed in younger rats. These data suggest that in vivo a denoviral gene transfer of eNOS can physiologically improve erectile functi on in the aged rat.