A low androgen state impairs erectile function by suppressing EPAC1 in rat penile corpus cavernosum.

Background: Exchange proteins activated by cAMP 1 (EPAC1) can promote vasodilatation by regulating endothelial nitric oxide synthase (eNOS) activity through the phosphoinositide 3-kinase/protein kinase B (PI3K/AKT) pathway and prevent vascular smooth muscle contraction by restraining the ras homolog gene family, member A/Rho-associated coiled-coil forming protein kinase (RhoA/ROCK) pathway. However, the relationship among EPAC1, androgen and erectile function is still unknown. Therefore, we attempted to investigate whether EPAC1 expresses in penile corpus cavernosum of rats and how EPAC1 affects erectile function under low androgenic conditions. Methods: Thirty 8-week-old Sprague-Dawley male rats were randomly divided into six groups (n=5): sham operation (sham), castrated, castrated + testosterone replacement (castrated + T), sham + EPAC1 over-expression lentivirus (sham + EPAC1), castrated + empty lentivirus vector (castrated + empty vector), and castrated + EPAC1. Four weeks after the operation, the lentivirus vectors carrying the EPAC1 gene were injected into the penile corpus cavernosum of the sham + EPAC1 and castrated + EPAC1 groups (1×108 TU/mL, 20 µL per rat). A week after injection, the ratio of maximum intracavernous pressure to mean arterial pressure (ICPmax/MAP) and the levels of serum testosterone (T), nitric oxide (NO), the active form of RhoA (RhoA-GTP), AKT, phospho-AKT (p-AKT), eNOS, phospho-eNOS (p-eNOS), p-AKT/AKT, p-eNOS/eNOS and EPAC1 levels were measured. Results: In comparison to the sham group, ICPmax/MAP and EPAC1 content in the castrated group were significantly reduced. EPAC1 is primarily located in the cyto-membrane and cytoplasm of endothelial cells and smooth muscle cells in the rat penile corpus cavernosum. In comparison to the sham group, the T, ICPmax/MAP and NO levels of the castrated group were significantly reduced (P<0.01). Meanwhile, the RhoA-GTP concentration in the castrated + EPAC1 group was reduced in comparison with the castrated + empty vector group (P<0.01). Compared with the castrated + empty vector group, the p-AKT/AKT, EPAC1 and p-eNOS/eNOS levels in the castrated + EPAC1 group were significantly increased (P<0.05). Conclusions: Androgen deficiency can suppress EPAC1 expression in the penile corpus cavernosum of rats, while the up-regulation of which can improve the erectile function of castrated rats.

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

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.

Downregulation of the expression of galanin impairs erectile function in hypoandrogenic rats.

Background: The relationship between galanin and erectile function under low androgen levels is still unclear. Aim: To explore whether a low testosterone level damages the erection of a rat by regulating the expression of galanin and GalR in penile cavernous tissue. Methods: Thirty-six male Sprague-Dawley rats, 8 weeks of age, were randomly grouped as follows (n = 6): control, castration, castration + testosterone replacement, control + transfection, castration + transfection, and castration + empty transfection. At 4 weeks after castration, rats in the transfection group were injected with lentivirus carrying the targeting galanin gene (2 × 108 TU/mL, 10 µL) in the corpus cavernosum. After 1 week of injection, the intracavernosal pressure (ICP), mean arterial blood pressure (MAP), nitric oxide (NO), serum testosterone concentration, galanin, GalR1-3, ROCK1, ROCK2, and p-eNOS/eNOS in the rat penile tissues were evaluated. Outcomes: ICPmax/MAP and the expression of galanin in the corpus cavernosum in castrated rats were obviously decreased as compared with those in the control rats. Results: The castrated rats showed remarkably lower ICPmax/MAP, galanin, GalR1-3, p-eNOS/eNOS, and NO content and markedly higher ROCK1 and ROCK2 in penile tissues than the control group (P < .05). The transfected rats administrated with LV Gal had obviously higher ICPmax/MAP, p-eNOS/eNOS, and NO content and less ROCK1 and ROCK2 protein expression in the corpus cavernosum when compared with the castration group (P < .05). Clinical Translation: Upregulating the expression of galanin in the penile corpus cavernosum might be a novel method of treating erectile dysfunction caused by a low androgen level. Strengths and Limitations: The conclusions obtained in the animal experiments need to be confirmed in human data. Conclusion: The erectile function of hypoandrogen rats might be inhibited by downregulating the level of galanin and GalR1-3, upregulating ROCK1 and ROCK2 levels, and inhibiting the eNOS/NO signaling pathway in penile corpus cavernosum.

Low androgen status inhibits erectile function by upregulating the expression of proteins of mitochondria-associated membranes in rat corpus cavernosum.

OBJECTIVE: To investigate the effect of low androgen status on mitochondria-associated membranes (MAMs) and its relationship with erectile function. METHODS: A total of 36 eight-week-old male Sprague-Dawley rats were randomly divided into six groups: the control (sham-operated) group, the castration group, the castration + testosterone (cast + T) group, the control + siRNA group, the cast + siRNA group, and the cast + empty vector group. Testosterone propionate (3 mg/kg) was subcutaneously injected into the rats in the cast + T group every other day starting from the second day after the surgery. Four weeks later, lentiviral vectors carrying phosphofurin acidic cluster sorting protein 2 (PACS-2) gene-specific siRNA (1 × 108 TU/ml, 10 µl) were injected into the rats in the siRNA groups. At the sixth week of castration, the ratio of the maximum intracavernous pressure/the mean arterial pressure (ICPmax/MAP), the levels of nitric oxide (NO), endothelial nitric oxide synthase (eNOS), phospho-eNOS (p-eNOS), fatty acid-CoA ligase 4 (FACL-4), PACS-2, and inositol 1,4,5-trisphosphate receptor type 1 (IP3R1) in the penile corpus cavernosum were determined. RESULTS: The FACL-4, PACS-2, and IP3R1 were primarily localized in the cytoplasm of endothelial cells and part of smooth muscle cells in the corpus cavernosum. The level of NO, the ratio of ICPmax/MAP, and p-eNOS/eNOS were decreased significantly in the castration group compared with the control group (p < 0.01). The expressions of FACL-4, PACS-2, and IP3R1 were increased significantly in the castration group compared with the control group (p < 0.01). The level of NO, the ratios of ICPmax/MAP, and the ratio of p-eNOS/eNOS were increased significantly in the cast + siRNA group compared with the castration group (p < 0.01). The expressions of FACL-4 and PACS-2 were decreased significantly in the cast + siRNA group compared with the castration group (p < 0.01). CONCLUSION: Low androgen status upregulated the expressions of patients in MAMs (FACL-4, PACS-2, and IP3R1) in the corpus cavernosum and inhibited the eNOS/NO/cGMP signaling pathway, resulting in impaired erectile function in rats. Erectile function may be improved by inhibiting the high expression of PACS-2 in the corpus cavernosum under low androgen state.

Low androgen status inhibits erectile function by inducing eNOS uncoupling in rat corpus cavernosum.

BACKGROUND: The number of erectile dysfunction (ED) patients is increasing annually. How to improve the effectiveness of ED treatment is an important issue for the field of andrology. OBJECTIVES: To investigate whether low androgen status impairs the erectile function of rats by regulated endothelial nitric oxide synthase (eNOS) uncoupling. MATERIALS AND METHODS: Thirty-six 8-week-old male Sprague Dawley (SD) rats were randomly divided into six groups as follows: 4-week sham-operated group (4w-sham), 4-week castration group (4w-cast), 4-week castration + testosterone (T) group (4w-cast + T), 8-week sham-operated group (8w-sham), 8-week castration group (8w-cast), and 8-week castration + T group (8w-cast + T). Three mg/kg of T was subcutaneously injected every other day in castration + T groups. The ratio of the maximum intracavernous pressure/the mean arterial pressure (ICPmax/MAP), the level of serum T, dihydrobiopterin(BH2 ), tetrahydrobiopterin (BH4 ), nitric oxygen(NO), 3-nitrotyrosine(3NT), dihydrofolate reductase (DHFR), guanosine triphosphate cyclohydrolase 1 (GTPCH1), nicotinamide adenine dinucleotide phosphate oxidase 2 (NOX2), and eNOS monomers/dimers in the corpus cavernosum were detected. RESULTS: The ratio of ICPmax/MAP and BH4 /BH2 , the level of serum T, NO, and GTPCH1 decreased significantly in castration groups compared with sham-operated groups and castration + T groups (P < .05) and decreased significantly in 8w-cast group compared with 4w-cast group (P < .05). The expression of 3NT and NOX2 and the ratio of eNOS monomers/dimers increased significantly in castration groups compared with sham-operated groups and castration + T groups (P < .01) and increased significantly in 8w-cast group compared with 4w-cast group (P < .01). The expression of DHFR in 4w-cast group was significantly higher than that in 4w-sham group and 4w-cast + T group (P < .01) and in 8w-cast group was significantly lower than that in 8w-sham group and 8w-cast + T group (P < .01). DISCUSSION AND CONCLUSION: Low androgen status induces eNOS uncoupling by reducing BH4 /BH2 and increasing 3NT. Due to the decreased NO production, the erectile function of the rats was impaired.

[MRI for etiological diagnosis of ED: Advances in studies].

ED is a common male sexual dysfunction clinically. An insight into its etiology and accurate diagnosis play a valuable role in its prevention and treatment. MRI has the advantages of high-resolution imaging of the pelvic structure, penis and brain tissue, no radiation damage, three-dimensional imaging, and functional imaging, which make more accurate the etiological diagnosis of ED. This paper presents an overview of the advances in the studies of MRI in the etiological diagnosis of ED.