Central and peripheral effects of Dihydrotestosterone (DHT) in females: a preclinical perspective

Background. The underpinning mechanisms of the beneficial effects of androgens on female sexual behavior and on the integrity and functionality of genital tissues have not been elucidated. 1st study. Ovariectomized (OVX) Long-Evans rats were treated with oil (O) + O, 10 mcg Estradiol Benzoate (EB) + O, 10 mcg EB + 500 mcg Progesterone (P), O + 500 mcg Dihydrotestosterone (DHT) or 10 mcg EB + 500 mcg DHT (n = 12 per group). EB was administered 48 h, while P and DHT 4 h, prior to 4 sexual behavioral testing sessions in bisected unilevel pacing chambers. Appetitive behaviors (the frequencies of hops/darts and solicitations) were considered as the main outcome measure. Sexual receptivity indexes [lordosis magnitude, expressed as lordosis rating (LR), and lordosis quotient (LQ)], rejection responses, as well as mounts, intromissions and ejaculations received from the male were also coded. The probability of transition among sexual behaviors was evaluated by Transition Matrices; T-Pattern analysis was performed to detect hidden repeated temporal behavioral sequences. Preliminary analyses found no statistically significant differences between the O+O and EB+O groups, therefore we excluded the EB+O group from further analyses. Rats treated with EB+DHT displayed significantly more appetitive behaviors compared to negative controls (O+O and O+DHT), whereas no difference was observed between EB+DHT rats and positive controls (EB+P); noteworthy, a higher number of appetitive behaviors was observed in the O + DHT group compared to the O + O group. Furthermore, rats treated with EB+DHT showed significantly higher receptivity measures (LR and LQ) and received more mounts, intromissions and ejaculations compared to negative controls (O+O and O+DHT), to levels equivalent to EB+P. No differences were detected in female-male mounts or rejection responses among the 4 groups. Under a qualitative perspective, full solicitation was found exclusively in T-patterns of the EB+DHT group, which was also the only one to display T-patterns of higher order encompassing appetitive behaviors-only events. 2nd study. Chronic inflammation plays an important role in the onset of Genitourinary Syndrome of Menopause (GSM). Following preliminary experiments in the rat, the potential involvement of human vagina smooth muscle cells (hSMCs) in the immune and inflammatory response and the immunomodulatory effect of in vitro treatment with DHT were investigated. RT-PCR for the evaluation of mRNA expression of sex steroids receptors and of several pro-inflammatory markers, immunofluorescence studies for NF-κB nuclear translocation, a bead-based immunoassay to measure cytokines/chemokines concentrations in cell culture supernatants and flow cytometry studies were performed in hSMCs stimulated with lipopolysaccharide (LPS) or IFN (interferon)γ. The mRNA expression of androgen receptor (AR) was significantly higher compared to estrogens receptors. After LPS stimulation, DHT pre-treatment inhibited the mRNA expression of pro-inflammatory mediators COX2, IL6, IL12A and IFNγ, an effect significantly blunted by AR antagonist bicalutamide. DHT also significantly reduced the secretion of pro-inflammatory markers IL1RA, IL2, IL5, IL15, FGF, VEGF and TNFα. LPS-induced NF-κB nuclear translocation was significantly inhibited by DHT, counteracted by bicalutamide co-treatment. DHT pre-treatment significantly decreased IFNγ-induced expression of HLA-DR. Finally, in IFNγ-stimulated hSMCs, DHT significantly reduced the mRNA expression of proinflammatory mediators iNOS, COX2 and MCP1, IL12A and IP10. Overall, androgen signaling plays a suppressive role in the inflammatory response in the vagina, reducing the potential of hSMCs to be involved in the initiation and maintaining of inflammation. Conclusions. The selective activation of the AR in the brain and in the genital tissues represents a potential therapeutic strategy for common clinical conditions characterized by a strong negative impact on quality of life in women, including Hypoactive Sexual Desire Disorder and Genitourinary Syndrome of Menopause.