Panagiota Tsounapi

Hormonal regulation of spermatogenesis and spermiogenesis.

Normal testicular function is dependent upon hormones acting through endocrine and paracrine pathways both in vivo and in vitro. Sertoli cells provide factors necessary for the successful progression of spermatogonia into spermatozoa. Sertoli cells have receptors for follicle stimulating hormone (FSH) and testosterone which are the main hormonal regulators of spermatogenesis. Hormones such as testosterone, FSH and luteinizing hormone (LH) are known to influence the germ cell fate. Their removal induces germ cell apoptosis. Proteins of the Bcl-2 family provide one signaling pathway which appears to be essential for male germ cell homeostasis. In addition to paracrine signals, germ cells also depend upon signals derived from Sertoli by direct membrane contact. Somatostatin is a regulatory peptide playing a role in the regulation of the proliferation of the male gametes. Activin A, follistatin and FSH play a role in germ cell maturation during the period when gonocytes resume mitosis to form the spermatogonial stem cells and differentiating germ cell populations. In vitro cultures systems have provided evidence that spermatogonia in advance stage of differentiation have specific regulatory mechanisms that control their fate. This review article provides an overview of the literature concerning the hormonal pathways regulating spermatogenesis.

Effects of phosphodiesterase 5 inhibitors on sperm parameters and fertilizing capacity

The aim of this review study is to elucidate the effects that phosphodiesterase 5 (PDE5) inhibitors exert on spermatozoa motility, capacitation process and on their ability to fertilize the oocyte. Second messenger systems such as the cAMP/adenylate cyclase (AC) system and the cGMP/guanylate cyclase (GC) system appear to regulate sperm functions. Increased levels of intracytosolic cAMP result in an enhancement of sperm motility and viability. The stimulation of GC by low doses of nitric oxide (NO) leads to an improvement or maintenance of sperm motility, whereas higher concentrations have an adverse effect on sperm parameters. Several in vivo and in vitro studies have been carried out in order to examine whether PDE5 inhibitors affect positively or negatively sperm parameters and sperm fertilizing capacity. The results of these studies are controversial. Some of these studies demonstrate no significant effects of PDE5 inhibitors on the motility, viability, and morphology of spermatozoa collected from men that have been treated with PDE5 inhibitors. On the other hand, several studies demonstrate a positive effect of PDE5 inhibitors on sperm motility both in vivo and in vitro. In vitro studies of sildenafil citrate demonstrate a stimulatory effect on sperm motility with an increase in intracellular cAMP suggesting an inhibitory action of sildenafil citrate on a PDE isoform other than the PDE5. On the other hand, tadalafils actions appear to be associated with the inhibitory effect of this compound on PDE11. In vivo studies in men treated with vardenafil in a daily basis demonstrated a significantly larger total number of spermatozoa per ejaculate, quantitative sperm motility, and qualitative sperm motility; it has been suggested that vardenafil administration enhances the secretory function of the prostate and subsequently increases the qualitative and quantitative motility of spermatozoa. The effect that PDE5 inhibitors exert on sperm parameters may lead to the improvement of the outcome of assisted reproductive technology (ART) programs. In the future PDE5 inhibitors might serve as adjunct therapeutical agents for the alleviation of male infertility.

Effects of phosphodiesterase‐5 inhibitors on Leydig cell secretory function in oligoasthenospermic infertile men: a randomized trial

Study Type – Therapy (RCT)
Level of Evidence 1b

Effect of silodosin on detrusor overactivity in the male spontaneously hypertensive rat

Whats known on the subject? and What does the study add?

Erectile function and male reproduction in men with spinal cord injury: a review

Spinal cord injury (SCI) in men results in defects in erectile function, ejaculatory process and male reproductive potential. There are alterations in the capacity of men with SCI to achieve reflexogenic, psychogenic and nocturnal erections. The sexual function in different stages after SCI and the types of erections depend mainly on the completeness of the injury and the level of neurological damage. Furthermore, most of the SCI men demonstrate defects concerning the entrance of semen into the posterior urethra and the expulsion of the semen through the penile urethra and the urethral orifice. In addition, SCI men develop defects in the secretory function of the Leydig cells, Sertoli cells and the male accessory genital glands. The overall result is a decreased quality of the semen is recovered either with penile vibratory stimulation (PVS) or with electroejaculation. Nowadays the therapeutic andrological approach of SCI men focuses on achievement of erectile function, recovery of spermatozoa and assisted reproductive technology. The first line of therapy recommended for infertility in SCI men is collection of semen via PVS with concomitant evaluation of total motile sperm yields for assisted conception which may include intravaginal insemination, intrauterine insemination, or in vitro fertilisation/intracytoplasmic sperm injection. Patients failing PVS may be referred for electroejaculation or surgical sperm retrieval.

Prostatic ischemia induces ventral prostatic hyperplasia in the SHR; possible mechanism of development of BPH

In the light of increasing evidence that benign prostatic hyperplasia is associated with cardiovascular disease, we have investigated the relationship between prostatic blood flow and prostatic hyperplasia in the spontaneously-hypertensive-rat (SHR). Twelve-week-old male SHRs were treated with nicorandil for six weeks. Wistar-Kyoto rats were used as controls. Six weeks after nicorandil treatment, blood pressure and the prostatic blood flow were estimated, and tissue levels of malondialdehyde, HIF-1α, TGF-β1, bFGF, dihydrotestosterone, and α-SMA were measured. SHRs showed significant increases in blood pressure, tissue levels of malondialdehyde, HIF-1α, TGF-β1, bFGF, α-SMA and a significant decrease in the prostatic blood flow. Although treatment with nicorandil failed to alter the blood-pressure and α-SMA, it significantly ameliorated the increased levels of malondialdehyde, HIF-1α, TGF-β1, and bFGF. There were no significant differences in tissue levels of dihydrotestosterone among any groups. These data indicate that development of prostatic hyperplasia may be associated with prostatic hypoxia, which nicorandil prevents via its effect to increase the blood flow.

Fasudil improves the endothelial dysfunction in the aorta of spontaneously hypertensive rats

We investigated the effects of fasudil, a Rho kinase inhibitor, in the endothelial dysfunction of aortas from spontaneously hypertensive rats (SHRs). SHRs were divided in three groups; intraperitoneally (i.p.) vehicle-treated SHRs (SHR), SHRs treated with fasudil 3 mg/kg i.p. (Fas3), and SHRs treated with fasudil 10 mg/kg i.p. (Fas10). Vehicle-treated Wistar rats were used as normo-tensive control group. After a six-week-treatment, blood pressure and heart rate were measured by the tail cuff method. Afterwards animals were sacrificed and aortas were examined in vitro by organ bath studies to evaluate the contraction and relaxation ability. Rho kinase activity, myosin light chain (MLC), phosphorylated MLC (phospho-MLC), eNOS, phospho-eNOS protein expression and eNOS mRNA levels were evaluated. SHR demonstrated a significant hypercontractility and impaired relaxation compared to the control. Fasudil 10mg/kg significantly corrected the hypercontractility, restored the relaxation, and significantly decreased the mean arterial blood pressure, while no change observed in the systolic blood pressure. Rho kinase activity was significantly higher in the SHR, and was significantly inhibited by the high dose of fasudil. There was a slight up-regulation in the MLC, and phospho-MLC protein levels in the SHR. eNOS and phospho-eNOS protein levels were significantly lower in the SHR, and this abnormality was significantly normalized by fasudil treatment. No significant difference was observed in the eNOS gene expression. This study suggests that fasudil by inhibiting the Rho kinase activity normalizes the eNOS expression and phosphorylation and ameliorates the endothelial dysfunction induced by hypertension in the SHR model.

Lower urinary tract symptoms, benign prostatic hyperplasia/benign prostatic enlargement and erectile dysfunction: Are these conditions related to vascular dysfunction?

Although the pathogenesis of lower urinary tract symptoms, benign prostatic hyperplasia/benign prostatic enlargement and erectile dysfunction is poorly understood and thought to be multifactorial, it has been traditionally recognized that these conditions increase with age. There is increasing evidence that there is an association between cardiovascular disease and lower urinary tract symptoms as well as benign prostatic hyperplasia/benign prostatic enlargement and erectile dysfunction in elderly patients. Age might activate systemic vascular risk factors, resulting in disturbed blood flow. Hypertension, diabetes, hyperlipidemia and atherosclerosis are also linked to the etiology of lower urinary tract symptoms, benign prostatic hyperplasia/benign prostatic enlargement and erectile dysfunction. In the present review, we discuss the relationship between decreased pelvic blood flow and lower urinary tract symptoms, benign prostatic hyperplasia/benign prostatic enlargement and erectile dysfunction. Furthermore, we suggest possible common mechanisms underlining these urological conditions.

Characterization of silodosin and naftopidil in the treatment of bladder dysfunction in the spontaneously hypertensive rat

As increasing evidence suggest that α1‐blockers prevent benign prostatic hyperplasia related overactive bladder and nocturia in the human, we investigated the effects of silodosin and naftopidil on hypertension‐related bladder dysfunction in the spontaneously hypertensive rat (SHR) model.

Hydroxyfasudil ameliorates penile dysfunction in the male spontaneously hypertensive rat

Hypertension represents a major risk factor for erectile dysfunction. Although the etiology of hypertension-induced erectile dysfunction is multifactorial and still unknown, Rho-Rho kinase pathway is one of the key factors. To investigate whether administration of hydroxyfasudil, a Rho kinase inhibitor could prevent dysfunction of NO-induced relaxation in corpus cavernosum smooth muscle in the SHR (spontaneously hypertensive rat), twelve-week-old male SHRs were treated with hydroxyfasudil (3 or 10 mg/kg, i.p.) once a day for 6 weeks. Wistar rats and SHRs treatment with vehicle were used as age-matched controls. Penile cGMP concentrations and Rho kinase activities were determined, and penile function was estimated by organ bath studies with norepinephrine-induced contractions and acetylcholine-induced relaxations. The participation mRNA levels of eNOS and participation protein levels of eNOS and phosphorylated eNOS were investigated by quantitative real-time PCR methods and immunoblot analysis, respectively. The SHR showed significantly decreased cGMP concentrations, increased Rho kinase activities, norepinephrine-induced hyper-contractions, and acetylcholine-induced hypo-relaxations in the penile tissue. Treatment with hydroxyfasudil significantly improved the decreased penile cGMP concentrations, the increased Rho kinase activities, the increased norepinephrine-induced contractions, and the decreased acetylcholine-induced relaxation in a dose-dependent manner. Although there were no significant differences in expression protein levels of eNOS among any of the groups, down-regulation of eNOS mRNAs as well as phosphorylated eNOS were significantly ameliorated after treatment with hydroxyfasudil. Our data suggest that hydroxyfasudil ameliorates hypertension-associated dysfunction of NO-induced relaxation in corpus cavernosum smooth muscle possibly via inhibition of the Rho-Rho kinase pathway and activation of NO-eNOS pathway in the SHR.