G Protein-coupled Estrogen Receptor 1 Signaling Downregulates Epithelial Na Channel Activity in the Collecting Duct
Authors: Nasci Victoria , Mironova Elena , Rhoads Megan , Stockand James , Gohar Eman 
Published: May 2023

Hypertension is more prevalent in men than women. Sodium (Na+) homeostasis is critical for blood pressure control. Recent studies in our lab showed that activation of G-protein coupled estrogen receptor 1 (GPER1) in the renal medulla evokes natriuresis in female, but not male, Sprague Dawley (SD) rats via endothelin 1 (ET-1) signaling. ET-1 has been shown to regulate epithelial Na+ channel (ENaC) which plays a crucial role in Na+ handling in the collecting duct (CD) and thus blood pressure. Whether ENaC contributes to GPER1-evoked natriuresis is unknown. We hypothesized that GPER1 activation suppresses ENaC activity, and this interaction may play a role in promoting Na+ excretion in females. To evaluate this, we investigated the tubular mRNA expression pattern of GPER1 and αENaC by RNAscope in male and female SD rat kidneys. We also infused G1 (GPER1 agonist, 5 pmol/kg/min) and/or amiloride (AML, ENaC inhibitor, 0.67 μg/kg/min) into the renal medulla of anesthetized female SD rats then measured urinary Na+ excretion. To further identify GPER1/ENaC interaction, we generated mice with deletion of GPER1 in principal cells (PC) of the CD by crossing GPER1 floxed and aquaporin 2 cre mice. Urinary ET-1 was assessed in WT and PC-GPER1 KO mice. Finally, patch clamp electrophysiology was performed on freshly-isolated CDs to determine ENaC activity in response to G1 activation and genetic deletion of GPER1. RNAscope revealed that GPER1 colocalizes with αENaC in male and female rat kidneys. The female kidney elicited a trend towards more outer medullary tubules co-expressing αENaC and GPER1 than males (43.3 ± 2.8 vs 34.7 ± 3.5 % of tubules positive for either, respectively P=0.0826). When infused into the female rat medulla, G1 and AML increased urinary Na+ excretion to a comparable extent (69.8 ± 22.2 vs 77.6 ± 31.0 % change from baseline, respectively P=0.9765). No additional natriuretic response was observed when G1 and AML were coadministered. Urinary ET-1 excretion was greater in female WT mice compared to male WT (1.95 ± 0.27 vs 1.04 ± 0.10 pg/mg creatinine, respectively P=0.0155). Genetic deletion of GPER1 in PC reduced ET-1 excretion in female, but not male, mice (female KO; 1.08 ± 0.18 pg/mg creatinine P=0.0166). Importantly, genetic deletion of GPER1 in PC upregulated ENaC open probability (Po) compared to WT (0.280 ± 0.024 vs 0.194 ± 0.024 Po, respectively P=0.0462). Similarly, treatment of WT CDs with G1 (1 μM) downregulated ENaC Po (G1 vs control; 0.064 ± 0.017 vs 0.194 ± 0.024 Po P=0.0024). In conclusion, our data demonstrate GPER1-αENaC colocalization in renal tissues, with a trend towards higher colocalization in the outer medulla of the female kidney. CD-GPER1 is required for the greater ET-1 excretion in female mice. Further, our data uncover a direct regulatory effect for GPER1 on ENaC activity in the CD. Improving our understanding of the GPER1/ET-1/ENaC natriuretic axis could reveal future sex-specific antihypertensive therapeutics. NIH/NIDDK R00 DK119413 This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.