Expression and distribution of key enzymes of the cyclic GMP signaling in the human clitoris: relation to phosphodiesterase type 5 (PDE5)

Preliminary Efficacy of Topical Sildenafil Cream for the Treatment of Female Sexual Arousal Disorder: A Randomized Controlled Trial

OBJECTIVE

To assess the efficacy of topical sildenafil cream, 3.6% among healthy premenopausal women with female sexual arousal disorder.

METHODS

We conducted a phase 2b, exploratory, randomized, placebo-controlled, double-blind study of sildenafil cream. Coprimary efficacy endpoints were the change from baseline to week 12 in the Arousal Sensation domain of the SFQ28 (Sexual Function Questionnaire) and question 14 of the FSDS-DAO (Female Sexual Distress Scale-Desire, Arousal, Orgasm).

RESULTS

Two hundred women with female sexual arousal disorder were randomized to sildenafil cream (n=101) or placebo cream (n=99). A total of 174 participants completed the study (sildenafil 90, placebo 84). Among the intention-to-treat (ITT) population, which included women with only female sexual arousal disorder and those with female sexual arousal disorder with concomitant sexual dysfunction diagnoses or genital pain, although the sildenafil cream group demonstrated greater improvement in the SFQ28 Arousal Sensation domain scores, there were no statistically significant differences between sildenafil and placebo cream users in the coprimary and secondary efficacy endpoints. An exploratory post hoc subset of the ITT population with an enrollment diagnosis of female sexual arousal disorder with or without concomitant decreased desire randomized to sildenafil cream reported significant increases in their SFQ28 Arousal Sensation domain score (least squares mean 2.03 [SE 0.62]) compared with placebo cream (least squares mean 0.08 [SE 0.71], P =.04). This subset achieved a larger mean improvement in the SFQ28 Desire and Orgasm domain scores. This subset population also had significantly reduced sexual distress and interpersonal difficulties with sildenafil cream use as measured by FSDS-DAO questions 3, 5, and 10 (all P ≤.04).

CONCLUSION

Topical sildenafil cream improved outcomes among women with female sexual arousal disorder, most significantly in those who did not have concomitant orgasmic dysfunction. In particular, in an exploratory analysis of a subset of women with female sexual arousal disorder with or without concomitant decreased desire, topical sildenafil cream increased sexual arousal sensation, desire, and orgasm and reduced sexual distress.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov , NCT04948151.

Analysis of hsa-miR-19a-3p and hsa-miR-19b-3p modulation and phosphodiesterase type 5 expression in the vaginal epithelium of premenopausal women with genital arousal disorder

BACKGROUND

Few studies have investigated the role of the phosphodiesterase type 5A (PDE5A) isoenzyme in female genital tissue disorders, exclusively taken from cadavers, as well as the epigenetic mechanisms responsible for the regulation of PDE5A levels.

AIM

The aim was to study the in vivo association between microRNA (miRNA) expression and the expression levels of PDE5A in women with female genital arousal disorder (FGAD) compared with healthy women.

METHODS

Premenopausal women affected by FGAD (cases) and sexually healthy women (control group) underwent microbiopsy of the periclitoral anterior vaginal wall for the collection of tissue samples. Computational analyses were preliminarily performed in order to identify miRNAs involved in the modulation of PDE5A by using miRNA-messenger RNA interaction prediction tools. Differences in the expression levels of miRNAs and PDE5A were finally investigated in cases and control subjects by using the droplet digital polymerase chain reaction amplification system and stratifying women considering their age, number of pregnancies, and body mass index.

OUTCOMES

Expression levels of miRNAs were able to target PDE5A and the tissue expression in women with FGAD compared with healthy women.

RESULTS

The experimental analyses were performed on 22 (43.1%) cases and 29 (56.9%) control subjects. Two miRNAs with the highest interaction levels with PDE5A, hsa-miR-19a-3p (miR-19a) and hsa-miR-19b-3p (miR-19b), were identified and selected for validation analyses. A reduction of the expression levels of both miRNAs was observed in women with FGAD compared with the control subjects (P < .05). Moreover, PDE5A expression levels were higher in women with FGAD and lower in women without sexual dysfunctions (P < .05). Finally, a correlation between body mass index and the expression levels of miR-19a was found (P < .01).

CLINICAL IMPLICATIONS

Women with FGAD had higher levels of PDE5 compared with control subjects; therefore, the administration of PDE5 inhibitors (PDE5 inhibitors) could be useful in women with FGAD.

STRENGTHS AND LIMITATIONS

The strength of the current study was to analyze genital tissue obtained in vivo from premenopausal women. A limitation was to not investigate other factors, including endothelial nitric oxide synthetases, nitric oxide, and cyclic guanosine monophosphate.

CONCLUSION

The results of the present study indicate that the modulation of selected miRNAs could influence PDE5A expression in genital tissues in healthy women or in those with FGAD. Such findings further suggest that treatment with PDE5 inhibitors, as a modulator of PDE5A expression, could be indicated for women with FGAD.

Testosterone positively regulates vagina NO-induced relaxation: an experimental study in rats

PURPOSE

Female sexual response involves a complex interplay between neurophysiological mechanisms and the nitric oxide (NO)-mediated relaxation of clitoris and vagina. The aim of this study was to evaluate sex steroids regulation of the relaxant pathway in vagina, using a validated animal model.

METHODS

Subgroups of OVX Sprague-Dawley rats were treated with 17β-estradiol, testosterone, or testosterone and letrozole, and compared with a group of intact animals. Masson's trichrome staining was performed for morphological evaluation of the distal vaginal wall, in vitro contractility studies investigated the effect of OVX and in vivo treatments on vaginal smooth muscle activity. RNA from vaginal tissue was analyzed by semi-quantitative RT-PCR.

RESULTS

Immunohistochemical analysis showed that OVX induced epithelial and smooth muscle structural atrophy, testosterone and testo + letrozole increased the muscle bundles content and organization without affecting the epithelium while 17β-estradiol mediated the opposite effects. In vitro contractility studies were performed on noradrenaline pre-contracted vaginal strips from each experimental group. Acetylcholine (0.001-10 µM) stimulation induced a concentration-dependent relaxation, significantly reduced by NO-synthase inhibitor L-NAME and by guanylate cyclase inhibitor ODQ. OVX resulted in a decreased responsiveness to acetylcholine, restored by testosterone, with or without letrozole, but not by 17β-estradiol. OVX sensitivity to the NO-donor SNP was higher than in the control. Vardenafil, a PDE5 inhibitor, enhanced SNP effect in OVX + testosterone as well as in control, as supported by RNA expression analysis.

CONCLUSIONS

Our study demonstrates that testosterone improves the NO-mediated smooth muscle vaginal cells relaxation confirming its role in maintaining the integrity of muscular relaxant machinery.

Differential Effects of Testosterone and Estradiol on Clitoral Function: An Experimental Study in Rats

INTRODUCTION

Female sexual response is a complex phenomenon in which psychological, neurologic, and vascular mechanisms and hormonal factors interact. During the arousal phase, they cooperate to increase genital blood flow, thus inducing engorgement of the clitoris and lubrication of the vagina. Regulation of vascular and non-vascular smooth muscle tone is the crucial event in the erectile process. Preclinical studies have suggested that nitric oxide (NO) is the main vasodilator neurotransmitter modulating, through the second messenger cyclic guanosine monophosphate (cGMP), clitoral flow vessels.

AIM

To investigate the effects of sexual steroid hormones on pro-erectile and relaxant (mediated by NO and cGMP) and anti-erectile and contractile (mediated by ras homolog gene family member A [RhoA] and Rho-associated protein kinase [ROCK]) mechanisms in the clitoris using a validated animal model of female ovariectomized Sprague-Dawley rats.

METHODS

Subgroups of ovariectomized rats were treated with 17β-estradiol, progesterone, testosterone, or testosterone and letrozole for 6 weeks. The experimental groups were compared with a control group of intact rats.

MAIN OUTCOME MEASURES

Sex steroids plasma levels were assessed and in vitro contractility studies were carried out in order to investigate the effect of ovariectomy and in vivo treatments on clitoris smooth muscle activity. Smooth muscle cells (SMCs) from rat clitoral biopsies were isolated and characterized. RhoA activity was determined in SMCs cell cultures. RNA from tissues and cells was analyzed by quantitative real-time RT-PCR.

RESULTS

Using real-time polymerase chain reaction, testosterone treatment upregulated the expression of NO-mediated pathway genes (endothelial and neuronal NO synthase, guanylate cyclase soluble subunit-α₃, guanylate cyclase soluble subunit-β₃, cGMP-dependent protein kinase 1, and phosphodiesterase type 5). Conversely, estrogen replacement upregulated the expression of calcium-sensitizing RhoA-ROCK pathway genes. In vitro contractility studies were performed on phenylephrine pre-contracted clitoris strips. Ovariectomy resulted in a decreased responsiveness to Y-27632, a ROCK inhibitor, which was fully restored by 17β-estradiol supplementation. To further examine the effect of 17β-estradiol on the RhoA-ROCK pathway, smooth muscle cells were isolated from rat clitoris and their migration capacity was evaluated.

CONCLUSION

Collectively, these data demonstrate that testosterone improves the relaxation of vascular smooth muscle cells through the NO-cGMP pathway, and that testosterone and 17β-estradiol are necessary to maintain a functional contractile and relaxant machinery in the clitoris. This new concept might provide support for the concomitant use of estrogen and testosterone during the treatment of sexual arousal disorders related to hormonal imbalance or insufficiency.

Expression and distribution of the transient receptor potential cationic channel A1 (TRPA1) in the human clitoris-comparison to male penile erectile tissue

The transient receptor potential cationic channel ankyrin 1 (TRPA1) is a channel protein assumed to act in various human tissues as mechano- and pain sensor and play a role in neurotransmission. The expression of TRPA has already been investigated in the human prostate and urethra, however, only very few studies have addressed the expression and distribution in the male and female genital tract. The present study aimed to investigate by means of immunohistochemistry (double-labeling technique, laser fluorescence microscopy) in the human clitoris and penile erectile tissue the localization of TRPA1 in relation to nNOS, the vasoactive intestinal polypeptide (VIP) and vesicular acetylcholine transporter (VAChT). In the clitoral tissue, TRPA1 was observed in basal epithelial cells and slender nNOS-positive nerve fibers transversing the subepithelial space. To a certain degree, in the clitoral epithelial cells, TRPA1 was found co-localized with vimentin. In human corpus cavernosum, immunoreactivity for TRPA1 was seen in nerves transversing the cavernous sinusoidal space and running alongside small arteries, these nerves also displayed expression of the vesicular acetylcholine transporter protein (VAChT). Varicose nerves containing nNOS or VIP were not immunoreactive for TRPA1. It seems likely that TRPA1 is involved in nitric oxide-mediated afferent sensory transmission in the clitoris while, in penile erectile tissue, a role for TRPA1 in cholinergic signaling might be assumed.

Inhibition of phosphodiesterase 4 enhances clitoral and vaginal blood flow responses to dorsal clitoral nerve stimulation or PGE1 in anesthetized female rats

INTRODUCTION.: Cyclic adenosine 3'5' monophosphate (cAMP) is produced by adenylate cyclase after activation by, e.g., vasoactive intestinal polypeptide or prostaglandin E1 (PGE1). The cAMP-degrading phosphodiesterase 4 (PDE4) is expressed in the vagina and clitoris, but no information is available on the functional role for PDE4-related signals in the female neurovascular genital response. AIM.: The aim of this study is to study the effect of inhibition of PDE4 with rolipram on nerve- and PGE1-induced vaginal and clitoral blood flow responses of rat. METHODS.: Measure of clitoral and vaginal blood flow and blood pressure in anesthetized rats during activation of the dorsal clitoral nerve (DCN) before and after intraperitoneal administration of rolipram or sildenafil (phosphodiesterase type 5 inhibitors [PDE5]) and nitro-L-arginine (L-NNA) (nitric oxide synthase inhibitor). Effect by topical administration of PGE1 on genital blood flow was also evaluated. MAIN OUTCOME MEASURE.: Blood flow was recorded as tissue perfusion units (TPU) by a Laser Doppler Flowmeter. Mean arterial blood pressure (MAP) was recorded (cmH2 O) in the carotid artery. Blood flow responses are expressed as TPU/MAP. Unpaired t-test and an analysis of variance were used. RESULTS.: Compared with control stimulations, rolipram (0.3 mg/kg) caused a twofold increase in peak blood flow (P < 0.05) and fourfold increase of the rate of clitoral blood flow during activation of the DCN (P < 0.05). Simultaneously, a twofold increase in peak blood flow and threefold increase in rate of blood flow were noted in the vagina (P < 0.05). Similar effects were noted for sildenafil (0.2 mg/kg) (P < 0.05). Inhibitory effects by L-NNA (60 mg/kg) on blood flow responses to DCN activation were significantly lower for rats treated with rolipram than with sildenafil (P < 0.05). PGE1-induced (10 μg) blood flow responses were significantly higher (P < 0.05) in rats treated with rolipram than with sildenafil. CONCLUSIONS.: These findings suggest that the cAMP/PDE4 system may be of similar functional importance as the nitric oxide/cyclic guanosine monophosphate/PDE5 pathway for neurovascular genital responses of the female rat.