Sex Differences in Hypertension: Contribution of DAMPs

PROJECT SUMMARY P2, SULLIVAN Hypertension affects ~33% of adults in the U.S. and regardless of sex, fewer than 40% of hypertensive patients taking medication achieve blood pressure (BP) control to recommended levels. A critical barrier to improving BP control rates is lack of knowledge regarding molecular mechanisms driving elevated BP in either sex. Therapies targeting the cause of hypertension will improve BP control rates and prevent premature death from cardiovascular disease. T cells contribute to hypertension in experimental animals, yet the mechanism(s) initiating inflammatory responses in either sex remains unresolved. High mobility group box 1 protein (HMGB1) is a damage-associated molecular pattern (DAMP) that when released by necrosis stimulates pro-inflammatory immune cells via toll-like receptor (TLR)4. In contrast, apoptosis limits HMGB1 release and promotes T regulatory cells (Treg). The objective of Project (P)2 is to determine the contributions of cell death, HMGB1, TLR4, and dendritic cells (DCs) to T cell activation, BP control, renal and vascular function in hypertension. Our central hypothesis is that cell death drives DC and T cell activation and increases in BP via HMGB1 release and TLR4 activation in both sexes. However, due to a sex difference in the type of cell death, the molecular pathway driving immune-based hypertension in females favors greater Treg formation. We will test our hypothesis via three specific aims: 1) test the hypothesis that cellular necrosis is pro-inflammatory and pro- hypertensive in male SHR, yet greater apoptosis in females attenuates the pro-inflammatory impact of cell death, 2) test the hypothesis that HMGB1 and TLR4 are pro-inflammatory and pro-hypertensive in males, while HMGB1 in females promotes Treg formation and mitigates increases in BP, and 3) test the hypothesis that mDCs in male SHR promote greater pro-inflammatory T cell activation and hypertension, while greater plasmacytoid DCs in female SHR result in more Tregs and lower BP. P2 is highly synergistic with the other projects and is dependent on all cores for the successful completion of our aims. Aim 1 of P2 is highly collaborative with aim 1 of P1 and aim 3 of P3, and data generated in P2 will inform P3 as to the inflammatory status of the renal medulla, allowing for further insight into the impact of sex and BP on renal medullary function. Proposed studies integrate physiological, pharmacological, biochemical, molecular and cellular techniques to provide mechanistic insight into BP control. For decades, basic science research has focused almost exclusively on males; mechanistic insight into disease progression and treatment that could be gained by studying females has been ignored. Our results will provide the pre-clinical foundation to support targeting specific components of the immune system in a sex-specific manner to improve BP control rates in humans.