Effect of hypoandrogenism on expression of transient receptor potential vanilloid channels in rat penile corpus cavernosum and erectile function

Abstract

Background Hypoandrogenism is a cause of erectile dysfunction (ED). Vascular smooth muscle cell contraction and relaxation are regulated by TRPV1–4 channels. However, the influence of hypoandrogenism on TRPV1–4 and its relationship with erectile function remain unclear. Aim To reveal whether hypoandrogenism affects erectile function by influencing TRPV1–4 expression in the corpus cavernosum of rats. Methods Male Sprague-Dawley rats (N = 36) aged 8 weeks were assigned to 6 groups at random (n = 6): sham operation, castrated, castrated + testosterone replacement, sham operation + transfection, castrated + transfection, and castrated + empty transfection. Four weeks after castration, 20 μL of lentiviral vector (1 × 108 TU/mL) carrying the TRPV4 gene was injected into the penile cavernous tissue of the transfection groups. One week after transfection, the maximum intracavernous pressure (ICPmax)/mean arterial pressure (MAP) and the content of TRPV1–4, phosphorylated eNOS (p-eNOS)/eNOS, and nitric oxide (NO) in penile cavernous tissue of each group were measured. Outcomes Under low androgen conditions, TRPV4 expression in endothelial cells in the rat penile cavernosum was sharply reduced, resulting in a decrease in p-eNOS/eNOS and NO content, which could inhibit erectile function. Results In rat penile cavernous tissue, TRPV1–4 was expressed in the cell membranes of endothelial cells and smooth muscle cells. The ICPmax/MAP and the content of TRPV4, p-eNOS/eNOS, and NO end product nitrite level in rat penile cavernous tissue was markedly reduced in the castrated group as compared with the sham group (P < .05). The ICPmax/MAP and the content of TRPV4, p-eNOS/eNOS, and NO end product nitrite level in rat penile cavernous tissue were markedly improved in the castrated + transfection group vs the castrated group (P < .01). Clinical Implications Upregulation of TRPV4 expression in penile cavernosum tissue might be a viable therapeutic for ED caused by hypoandrogenism. Strengths and Limitations The specific mechanism of TRPV4 in ED needs to be further verified by androgen receptor or TRPV4 gene knockout experiments. Conclusion Hypoandrogenism may cause ED by reducing the expression of TRPV4 in rat penile cavernous tissue. Upregulation of TRPV4 expression in penile cavernous tissue can increase the ratio of p-eNOS/eNOS and NO levels and ameliorate the erectile function of castrated rats.

A low androgenic state inhibits erectile function by suppressing endothelial glycosides in the penile cavernous tissue of rats

“… 20 Vascular endothelial glycocalyx protects endothelial cells by reducing blood flow impingement on endothelial cells, while it activates endothelial cells by transducing vascular mechanical shear to upregulate the expression of eNOS and the level of nitric oxide. 21 , 22 The expression of syndecan 1 and p-eNOS/eNOS was significantly lower in the castration group than the sham-operated group ( P < .05). This suggests that the vascular endothelial glycocalyx became thinner after castration and that the mechanotransduction of the vessels decreased, leading to a decrease in the number of activated endothelial cells.…”