Effect of Low Androgen Status on the Expression of P2Y Receptors in the Corpus Cavernosum of Rats

Androgens and erectile dysfunction: from androgen deficiency to treatment

INTRODUCTION

Androgens play important roles in regulating the growth and development of the male reproductive system and maintaining libido and erectile function. The specific mechanisms by which androgen deficiency leads to erectile dysfunction (ED) are not yet fully understood.

OBJECTIVES

To understand the mechanisms and treatment of androgen deficiency-related ED.

METHODS

A literature search in the past 10 years was conducted in PubMed and Google Scholar to determine the effects of androgen deficiency on erectile function and the treatment of androgen deficiency.

RESULTS

Androgen deficiency can be caused by hypothalamic-pituitary lesions and injuries, testicular-related diseases and injuries, endocrine and metabolic disorders, the side effects of medication, and age. Androgen deficiency can lead to ED by inhibiting the NOS/NO/cGMP pathway (nitric oxide synthase/nitric oxide/cyclic guanosine monophosphate) and altering the expression of ion channel proteins, as well as by inducing oxidative stress, death, and fibrosis in penile corpus cavernosum cells. Testosterone replacement therapy is effective at improving the serum testosterone levels and erectile function in patients with androgen deficiency. For patients who need to maintain a low androgenic state, erectile function can be improved by lifestyle changes, treatment with phosphodiesterase type 5 inhibitors, low-intensity extracorporeal shock wave therapy, and stem cell therapy.

CONCLUSIONS

Androgen deficiency can affect the structure and function of the penile corpus cavernosum, leading to ED. Areas of further study include how androgen replacement therapy can improve erectile function and how to improve the maintenance of erectile function in patients with hypoandrogenic status.

P2 purinergic receptor dysregulation in urologic disease

P2 purinergic receptors are involved in the normal function of the kidney, bladder, and prostate via signaling that occurs in response to extracellular nucleotides. Dysregulation of these receptors is common in pathological states and often associated with disease initiation, progression, or aggressiveness. Indeed, P2 purinergic receptor expression is altered across multiple urologic disorders including chronic kidney disease, polycystic kidney disease, interstitial cystitis, urinary incontinence, overactive bladder syndrome, prostatitis, and benign prostatic hyperplasia. P2 purinergic receptors are likewise indirectly associated with these disorders via receptor-mediated inflammation and pain, a common characteristic across most urologic disorders. Furthermore, select P2 purinergic receptors are overexpressed in urologic cancer including renal cell carcinoma, urothelial carcinoma, and prostate adenocarcinoma, and pre-clinical studies depict P2 purinergic receptors as potential therapeutic targets. Herein, we highlight the compelling evidence for the exploration of P2 purinergic receptors as biomarkers and therapeutic targets in urologic cancers and other urologic disease. Likewise, there is currently optimism for P2 purinergic receptor-targeted therapeutics for the treatment of inflammation and pain associated with urologic diseases. Further exploration of the common pathways linking P2 purinergic receptor dysregulation to urologic disease might ultimately help in gaining new mechanistic insight into disease processes and therapeutic targeting.

Effect of Late Androgen Replacement Therapy on Erectile Function Through Structural Changes in Castrated Rats

Background

Because androgen replacement therapy (ART) is not performed immediately after the onset of androgen deficiency, the treatment is considered to be late.

Aim

To investigate the effects of late ART, starting 4 weeks after castration of rats, on erectile function and structural changes in the corpus cavernosum.

Methods

Rats were subjected to ART for 4 (Late-ART [4w]) or 8 (Late-ART [8w]) weeks. In either case, rats were assigned to the following groups: castrated (Cast), castrated with subcutaneous administration of testosterone (3 mg/kg/day; Cast+T), and sham (Sham). Cast + T rats received daily subcutaneous doses of testosterone starting 4 weeks after castration for 4 or 8 weeks whereas Sham and Cast rats received only the vehicle.

Outcomes

Erectile function was assessed by evaluating intracavernosal pressure (ICP) and mean arterial pressure (MAP) after electrical stimulation of the cavernous nerve, corporal veno-occlusive function using dynamic infusion cavernosometry, and histology using Masson's trichrome staining.

Results

No increase in the ICP was observed in Cast+T rats in the Late-ART (4w) group (0.47 ± 0.02, P > .05), whereas, in Cast+T rats in the Late-ART (8w) group, there was a significant increase in the ICP/MAP ratio (0.60 ± 0.02, P < .05), drop rate, and smooth muscle/collagen ratio.

Clinical Translation

The present study provides scientific evidence for the effect of late ART on erectile function.

Strengths and Limitations

This study provides insights into the influence of late ART on erectile function through improvements in the structure of corpus cavernosum. The major limitation of this study is the difference in the time required for healing between the humans and rats, which might have a bearing on the translational relevenace of the results.

Conclusions

Late ART could improve erectile function. However, as improvement requires a considerable time period, it is necessary to persist with therapy patiently for optimal results.

Kataoka T, Hotta Y, Yamamoto Y, et al. Effect of Late Androgen Replacement Therapy on Erectile Function Through Structural Changes in Castrated Rats. Sex Med 2021;XX:XX–XXX.

Icariin modulates eNOS activity via effect on post-translational protein-protein interactions to improve erectile function of spontaneously hypertensive rats

BACKGROUND

Type 5 phosphodiesterase inhibitor (PDE5I) has become the first-line treatment for erectile dysfunction (ED). However, its effective rate for hypertension ED is only 60%-70%. How to improve the efficacy of ED treatment is the focus of current research.

OBJECTIVE

To explore whether icariin can improve the erectile function of spontaneously hypertensive rats (SHR) by affecting post-translational protein-protein interactions to regulate endothelial nitric oxide synthetase (eNOS) activity.

METHOD

Twelve-week-old healthy male SHR rats and Wistar-Kyoto rats (WKY) were randomly divided into four groups: SHR control group, SHR + icariin (10 mg/kg·d gavage) treatment group, WKY control group, and WKY + icariin (10 mg/kg·d gavage) treatment group (n = 5). After 4 weeks, the maximum penile intracavernous pressure/mean arterial pressure (ICPmax/MAP), the expression of heat-shock protein 90 (Hsp90), caveolin-1, calmodulin, p-eNOS, and eNOS in penile cavernous tissue and the content of nitric oxide (NO) and cGMP were measured. The interaction between eNOS and Hsp90, caveolin-1, and calmodulin were detected by immunoprecipitation.

RESULT

The ICPmax/MAP in the SHR + icariin treatment group (0.08 ± 0.01, 0.23 ± 0.07, 0.40 ± 0.05) was significantly higher than the SHR group (0.03 ± 0.01, 0.13 ± 0.03, 0.21 ± 0.02) under 3V and 5V electrical stimulations (P < .05). Compared with the SHR group, the expression of HSP90, calmodulin, P-eNOS, eNOS, and P-eNOS/eNOS in the penile cavernous tissue of rats in the WKY group and the SHR + icariin treatment group were significantly increased (P < .05), and the expression of caveolin-1 was significantly decreased (P < .05). The NO content (2.16 ± 0.22 μmol/g) and cGMP concentration (3.69 ± 0.12 pmol/mg) in the SHR + icariin treatment group were significantly higher than those in the SHR group (1.01 ± 0.14 μmol/g, 2.31 ± 0.22 pmol/mg) (P < .05). Compared with the SHR group, the interaction between eNOS and HSP90 in the cavernosa of the rats in the SHR + icariin treatment group was significantly increased (P < .05), the interaction between eNOS and caveolin-1 was significantly decreased (P < .01), and the interaction between eNOS and calmodulin did not significantly change.

DISCUSSION AND CONCLUSION

Up-regulating the expression of HSP90 and calmodulin and inhibiting caveolin-1 in SHR corpus cavernosum, promoting the interaction between eNOS and HSP90, inhibiting the interaction between eNOS and caveolin-1, increasing p-eNOS/eNOS, may be the mechanism of icariin that improves SHR erectile function.

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.

Low androgen status inhibits erectile function by up-regulating the expression of P2X receptors in rat corpus cavernosum

The aim of our study was to investigate whether low androgen level inhibits the erectile function of rats by regulating the expression of P2X receptors. Thirty-six 8-week-old male SD rats were randomly divided into six groups: sham-operated groups (4w-sham, 8w-sham), castration groups (4w-cast, 8w-cast) and androgen replacement after castration groups (4w-cast + T, 8w-cast + T). The maximum intracavernous pressure/mean arterial pressure (ICPmax/MAP), the levels of serum testosterone (T) and nitric oxide (NO), and the expression of P2X1, P2X2, P2X3, eNOS, p-eNOS, ROCK1 and ROCK2 in the cavernous tissue of rats were determined. The serum T, ICPmax/MAP and NO levels in penile corpus cavernosum in the castration groups were significantly lower than those in other groups (p < .01). The protein expression of P2X1, P2X2, P2X3, ROCK1 and ROCK2 in the castration groups was significantly higher than those in other groups (p < .01). P-eNOS/eNOS of the castration groups were significantly lower than those of other groups (p < .01). The serum T level was negatively correlated with the expression of P2X1, P2X2 and P2X3 in the corpus cavernosum. Low androgen level inhibits erectile function by up-regulating the expression of P2X1, P2X2, P2X3 and RhoA/Rho-kinase resulting in reducing the ratio of p-eNOS/eNOS and the level of NO in corpus cavernosum of rats.

Effect of low androgen status on the expression of adenosine A2A and A2B receptors in rat penile corpus cavernosum

To investigate whether low androgen status affects erectile function by regulating the expression of adenosine A_2A and A_2B receptors in rat penile corpus cavernosum. Thirty-six 8-week-old male Sprague-Dawley rats were randomly divided into six groups: sham-operated group (4w-sham, 8w-sham), castration group (4w-cast, 8w-cast) and androgen replacement group (4w-cast+T, 8w-cast+T). The rats in the androgen replacement groups were subcutaneously injected with testosterone propionate (3 mg/kg) every other day after castration. The maximum intracavernous pressure/mean arterial pressure (ICPmax/MAP), the expression of A_2A , A_2B , AKT and eNOS and the concentrations of cAMP and cGMP in the corpus cavernosum were detected at the 4th and 8th weeks after the operation. The serum testosterone level and the ratio of ICPmax/MAP decreased significantly in the castration group as compared to other groups (p < 0.01). There was no significant difference in the expression of A_2A receptor among groups, while the expression of A_2B , AKT and eNOS and the concentrations of cAMP and cGMP in the castration group were significantly lower than in other groups (p < 0.01). Low androgen status inhibits the AKT/eNOS/cGMP signalling pathways and the production of cAMP in the corpus cavernosum of castrated rats by down-regulating the expression of A_2B receptor, and results in decreased of ICPmax/MAP.