Sex Differences in Renal Sodium Handling

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SUMMARY This K99/R00 application from Eman Y. Gohar, PhD, is designed to acquire the knowledge and training necessary to transition into an independently-funded investigator leading a research program focused on sex differences in cardiovascular and renal physiology. Hypertension and kidney-related diseases are more common in men and postmenopausal women compared to premenopausal women. Renal purinergic signaling has emerged as an important system in the control of blood pressure and Na+ homeostasis. We have a recent evidence that estradiol (E2) stimulates Na+ excretion and increases the expression of renal purinergic receptors (P2Y2&4-R). Importantly, sex differences in the purinergic system has been demonstrated in non-renal tissues, however sex-related differences in renal purinergic signaling are not clear. The novel estrogen receptor, G protein-coupled estrogen receptor (GPER), is expressed in the renal medulla. GPER activation elicits cardiovascular and nephroprotective effects against salt-induced complications. However, its role in Na+ handling is not yet defined. Our preliminary data indicate that activation of GPER in the renal medulla promotes Na+ excretion via an endothelin-1 (ET-1)-dependent mechanism in female rats. In the current proposal, the overall hypothesis is that the enhanced renal Na+ handling in females is due, at least in part, to ATP/P2Y2&4-R/ phospholipase C/ epithelial Na+ channels (ENaC) and E2/GPER/ET-1/ENaC signaling within the renal medulla. This hypothesis will be tested by two specific aims. One aim will test whether female rats have enhanced P2Y2&4-R signaling in the renal medulla compared to males in response to high salt intake. The second aim will determine whether locally synthetized E2 activates GPER in the renal medulla to promote ET-1-dependent natriuresis in female rats via inhibition of ENaC. Under the mentorship of Dr. David Pollock and co-mentor, Dr. Edward Inscho, Dr. Gohar extends her current research on purinergic signaling and rapid estrogen signaling and proposes additional training that involves three major goals: i) technical development; Dr. Gohar will develop knowledge and technical expertise in the fields of calcium imaging, RNA sequencing and bioinformatics, beside refining her surgical skills, ii) professional career development in lab management, mentoring and grant writing, iii) training in translational research. This 5-year plan will prepare Dr. Gohar for an R01 submission and set her on a path for a successful independent career.