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

Abstract

Nitric oxide (NO) is the principal mediator of penile erection. NO is synthesized by a variety of nitric oxide synthases (NOS). It has been demonstrated that a decrease in NOS activity, as observed in aging, is associated with a diminished erectile response. The objective of this study was to determine if adenoviral-mediated gene transfer of eNOS could reverse age-related erectile dysfunction in the rat. Two groups of animals were transfected with adenoviruses: (1) aged rats (60 weeks) with AdRSVbgal; and (2) aged rats (60 weeks) with AdRSVeNOS. Five days after transfection, these study animals underwent cavernosal nerve stimulation (CNS) to assess erectile function 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 ef®ciency of b-galactosidase reporter gene was measured by a galacto-light chemiluminescent reporter gene assay in cavernosal tissues of rats administered AdRSVbgal. The transgene expression of eNOS was examined by RT-PCR in rats transfected with AdRSVbgal and AdRSVeNOS. eNOS and iNOS protein levels were measured by Western blot analysis, and cGMP levels were assessed in cavernosal tissue by enzyme immunoassay. Adenoviral expression of the b-galactosidase reporter gene was observed in cavernosal tissue for up to 30 days, with peak expression registered at 5 days after intracavernosal administration of AdRSVbgal. Cross-sections of the rat penises transfected with the AdRSVeNOS revealed no pathological (morphological or histological) changes. Five days after administration of AdRSVeNOS, eNOS protein, mRNA and cGMP levels in the corpora cavernosa were signi®cantly increased (P`0.05), while iNOS protein levels remained unchanged (P b 0.05). In conclusion, enhanced expression of eNOS employing an adenoviral vector signi®cantly 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 adenoviral gene transfer of eNOS can physiologically improve erectile function in the aged rat.

Effect of combination endothelial nitric oxide synthase gene therapy and sildenafil on erectile function in diabetic rats

“…Several groups have demonstrated that adenoviral gene therapy can be used to restore NO production in the rat corpus cavernosum to improve erectile function. [18][19][20]38 Recently, adenovirus-mediated gene transfer of eNOS to diabetic rabbit aorta augmented vascular reactivity and partially restored impaired smooth muscle relaxation. 39 Therefore, a gene transfer approach can be used to restore impaired cavernosal smooth muscle relaxation seen in diabetic corpus cavernosum.…”

“…These procedures have been described previously. 18,23 The Tulane University School of Medicine Animal Care and Use Committee has approved all procedures used in the present study.…”

“…The samples were assayed for cGMP using an enzyme immunoassay kit (Cayman Chemical, Ann Arbor, MI, USA), as previously described. 18 Cavernosal cGMP levels are expressed as picomoles per milligram of protein.…”

“…Recent reports have shown that in vivo gene transfer with adenoviral vectors encoding eNOS and nNOS can reverse age-related ED in experimental animal models. [17][18][19][20] Additionally, overexpression of eNOS in the aged penis results in an increase in both cavernosal NOS activity and cGMP formation. 17,18,21 In the present study, we used the streptozotocin (STZ)-diabetic rat model that represents a model of type I DM.…”

Gene and stem cell therapy for erectile dysfunction

“…These data suggest that in vivo adenoviral gene transfer of eNOS driven by the RSV promoter can physiologically improve erectile function in the aged rat for a relatively longer period of time. 18 The major contributing factor to diabetes-related ED is the reduced production of NO caused by the significant decrease in both nNOS and eNOS protein expression and activity in the penis. [19][20][21] To determine whether adenoviral gene transfer of eNOS to the penis of streptozotocin (STZ)-induced diabetic rats with ED 22 could improve the impaired erectile function, rats were intracavernosally injected with adenovirus.…”