The androgen receptor inhibits transcription of GPER1 by preventing Sp1 and Sp3 from binding to the promoters in prostate cancer cells

Dihydrotestosterone induces arterial stiffening in female mice

BACKGROUND

Androgens are important sex hormones in both men and women and are supplemented when endogenous levels are low, for gender transitioning, or to increase libido. Androgens also circulate at higher levels in women with polycystic ovarian syndrome, a condition that increases the risk for cardiovascular diseases including hypertension and arterial stiffness. Since our previous work shows an important role for the G protein-coupled estrogen receptor (GPER) in arterial stiffness, we hypothesized that other hormones including androgens may impact arterial stiffness in female mice via downregulation of GPER.

METHODS

The impact of the non-aromatizable androgen dihydrotestosterone (DHT), the glucocorticoid dexamethasone, and the progestin medroxyprogesterone acetate (all 100 nM for 24 h) on GPER and ERα expression was assessed in cultured vascular smooth muscle cells using droplet digital PCR (ddPCR). To assess the in vivo impact of the DHT-induced downregulation of GPER, female ovary-intact C57Bl/6 mice at 15-16 weeks of age were treated with silastic capsules containing DHT for 4 weeks, one with a dosage expected to mimic human male DHT levels and another to double the expected human concentration (n = 8-9/group).

RESULTS

In cultured vascular smooth muscle cells, GPER mRNA was decreased by DHT (P = 0.001) but was not impacted by dexamethasone or medroxyprogesterone. In contrast, ERα expression in cultured cells was significantly suppressed by all three hormones (P < 0.0001). In control mice or mice treated with a single or double dose of DHT, a dose-dependent increase in body weight was observed (control 22 ± 2 g, single dose 24 ± 2 g, double dose 26 ± 2 g; P = 0.0002). Intracarotid stiffness measured via pulse wave velocity showed a more than two-fold increase in both DHT-treated groups (control 1.9 ± 0.3 m/s, single dose 4.3 ± 0.8 m/s, double dose 4.8 ± 1.0 m/s). This increase in arterial stiffness occurred independent of changes in blood pressure (P = 0.59). Histological analysis of aortic sections using Masson's trichrome showed a significant decrease in collagen between the control group (24 ± 5%) and the double dose group (17 ± 3%, P = 0.007), despite no changes in aortic wall thickness or smooth muscle content. Lastly, ddPCR showed that in vivo DHT treatment decreased aortic expression of both GPER (control 20 ± 5, single dose 10.5 ± 5.6, double dose 10 ± 4 copies/ng; P = 0.001) and ERα (control 54 ± 2, single dose 24 ± 13, and double dose 23 ± 12 copies/ng; P = 0.003).

CONCLUSIONS

These findings indicate that androgen promotes arterial stiffening and cardiovascular damage in female mice and is associated with decreased estrogen receptor expression. These data are important for transgender men, women using testosterone for fitness or reduced libido, as well as patients with polycystic ovarian syndrome.

GPER1 Activation Exerts Anti-Tumor Activity in Multiple Myeloma

G protein-coupled estrogen receptor 1 (GPER1) activation is emerging as a promising therapeutic strategy against several cancer types. While GPER targeting has been widely studied in the context of solid tumors, its effect on hematological malignancies remains to be fully understood. Here, we show that GPER1 mRNA is down-regulated in plasma cells from overt multiple myeloma (MM) and plasma cell leukemia patients as compared to normal donors or pre-malignant conditions (monoclonal gammopathy of undetermined significance and smoldering MM); moreover, lower GPER1 expression associates with worse overall survival of MM patients. Using the clinically applicable GPER1-selective agonist G-1, we demonstrate that the pharmacological activation of GPER1 triggered in vitro anti-MM activity through apoptosis induction, also overcoming the protective effects exerted by bone marrow stromal cells. Noteworthy, G-1 treatment reduced in vivo MM growth in two distinct xenograft models, even bearing bortezomib-resistant MM cells. Mechanistically, G-1 upregulated the miR-29b oncosuppressive network, blunting an established miR-29b-Sp1 feedback loop operative in MM cells. Overall, this study highlights the druggability of GPER1 in MM, providing the first preclinical framework for further development of GPER1 agonists to treat this malignancy.

Dihydrotestosterone Induces Arterial Stiffening in Female Mice

Background

Testosterone is the predominant sex hormone in men and is increased in women with polycystic ovarian syndrome. These patients also experience an increased risk for cardiovascular diseases including hypertension and arterial stiffness. Since our previous work shows an important role for the G protein-coupled estrogen receptor (GPER) in arterial stiffness, we hypothesized that other hormones including androgens may impact arterial stiffness in female mice via regulation of GPER.

Methods

The impact of the non-aromatizable androgen dihydrotestosterone (DHT), the glucocorticoid dexamethasone, and the progestin medroxyprogesterone acetate (all 100 nM for 24 h) on GPER and ERα expression was assessed in cultured vascular smooth muscle cells using droplet digital PCR (ddPCR). To assess the in vivo impact of the DHT-induced downregulation of GPER, female ovary-intact C57Bl/6 mice were treated with silastic capsules containing DHT for 4 weeks, one with a dosage expected to mimic human male DHT levels and another to double the expected human concentration (n=8-9/group).

Results

GPER mRNA was only decreased by DHT (P=0.001), while ERα expression was significantly suppressed by all hormones (P<0.0001). While blood pressure was not different between groups (P= 0.59), there was a dose-dependent increase in body weight (control 22±2 g, single dose 24±2 g, double dose 26±2 g; P=0.0002). Intracarotid stiffness measured via pulse wave velocity showed a more than two-fold increase in both DHT-treated groups (control 1.9±0.3 m/s, single dose 4.3±0.8 m/s, double dose 4.8±1.0 m/s). Histological analysis of aortic sections using Masson's trichrome showed a significant decrease in collagen between the control group (24 ± 5%) and the double dose group (17 ± 3%, P=0.007), despite no changes in aortic wall thickness or smooth muscle content. Lastly, ddPCR showed that in vivo DHT treatment decreased aortic expression of both GPER (control 20±5, single dose 10.5 ± 5.6, double dose 10±4 copies/ng; P=0.001) and ERα (control 54±2, single dose 24±13, and double dose 23 ± 12 copies/ng; P=0.003).

Conclusions

These findings indicate that testosterone promotes arterial stiffening and cardiovascular damage in female mice and is associated with decreased estrogen receptor expression. These data are important not only for polycystic ovarian syndrome patients but also women using testosterone for fitness, gender transitioning, or reduced libido.