PROJECT SUMMARY/ABSTRACT Nearly half of the ~116 million Americans with hypertension are salt-sensitive and confer a 3-fold higher risk of developing cardiovascular disease. Only 26% of hypertensive patients reach blood pressure (BP) control, which may be due to lack of studies in females despite the growing evidence for sex differences in hypertensive mechanisms. It is known that the gut microbiota and immune system are critical in hypertension in males; this is largely unknown in females. The objective of this grant is to address this knowledge gap regarding the role of the gut microbiota and immune system to mediate sex differences in salt-sensitive hypertension. Mechanistic studies will be performed in male and female Dahl Salt-Sensitive (SS) rats, with translational studies performed in samples from opposite-sex twin pairs where the males have hypertension compared to females. Dahl SS rats, a model consistent with human salt-sensitive hypertension, exhibit a greater degree of salt- sensitivity and associated end-organ damage in males compared to females. We have observed stark sex differences in gut microbiota composition and gut-derived metabolites. Through microbiota transfer studies, we know the gut microbiota plays a causal role in the regulation of BP and renal damage. Linking the microbiota to immunity, microbiota transfer also influences renal T cell infiltration. Genetic deletion of T cells (SSCD247–/–) eliminates sex differences in salt-sensitive hypertension, highlighting the role of T cells to mediate BP sex differences. Since the gut microbiota influences renal T cell infiltration, and T cells amplify salt-sensitive hypertension, we have strong rationale for studying how sex-specific microbiota impact T cell function and salt- sensitivity. We will test the central hypothesis that gut microbiota-dependent T cell activation determines the extent of salt-sensitive hypertension and mediates the sex differences in disease severity. Our hypothesis will be rigorously tested with three aims: Aim 1 will test the hypothesis that the gut microbiota drives sex differences in salt-sensitive hypertension. Sex-specific microbiota transfer and gonadectomy studies will reveal whether the gut microbiota sex- and hormone-dependently contributes to salt-sensitive hypertension in SS rats. Aim 2 will test the hypothesis that the male versus female gut microbiota influences sex differences in T cell function and activation. Microbiota transfer in SSCD247–/– rats lacking T cells will assess the impact of sex and gut microbiota on T cell bioenergetics and cytokine production, and will address whether T cells are required for gut microbiota-dependent salt-sensitive hypertension. Aim 3 will determine whether the sex-specific observations in gut microbiota, gut metabolites, and T cell function in the SS rat similarly parallel humans from a longitudinal opposite-sex twin cohort, where the males exhibit hypertension compared to their female twin pair. These studies will reveal key mechanisms related to gut microbiota-immune-kidney crosstalk and provide the preclinical and human basis for developing novel, sex-specific targets to improve BP control and kidney disease.

PROJECT NARRATIVE Hypertension is the number one risk factor for cardiovascular disease, which is the leading cause of death worldwide; salt-sensitive hypertensive patients have a 3-fold higher risk of developing cardiovascular disease. We know that the gut microbiota and the immune system are linked and play critical roles in salt-sensitive hypertension in males, but this is largely understudied in females. The present studies will address this significant knowledge gap in our understanding of sex differences in salt-sensitive hypertension by investigating previously unrecognized gut microbiota- and immune-related mechanisms in both salt-sensitive rats and human samples, aiding in the development of more effective, sex-specific therapeutics for the control of blood pressure and kidney disease.