Omic Identified T Cell Mechanisms in Hypertension

Abstract

Hypertension is the leading risk factor for global disease burden. While premenopausal females are protected from hypertension, about 40% of a woman’s lifespan is spent in a menopausal state that is associated with increased hypertension and cardiovascular disease risk. Mechanistic understanding of this shift in blood pressure regulation is inadequate and correlates to greater uncontrolled hypertension in menopausal women compared with age matched men, despite greater medication adherence. Clinical trials assessing the efficacy of hormone replacement therapy in menopausal women have identified contraindications and produced controversial results, emphasizing the need for other approaches to control blood pressure in menopausal women. Recent evidence in experimental hypertension models demonstrates that premenopausal female induction of T cell immunosuppressive pathways contributes to sex differences in hypertension development. Further evidence suggests a dominant role for estrogen in mediating this effect. However, mechanisms by which estrogen inhibits T cell-mediated inflammation during hypertension are lacking. To identify novel targets for anti-hypertensive drug development, we sought to determine the effect of estrogen signaling on T cell activation, renal inflammation, and blood pressure control during angiotensin II-induced hypertension. We hypothesized that estrogen regulates T cell-specific molecular pathways, that estrogen T cell regulation contributes to premenopausal protection against Ang II hypertension, and that dysregulation of these pathways in estrogen deplete menopausal females results in increased hypertension incidence and severity. To test the hypothesis that T cell estrogen signaling via its dominant receptor, estrogen receptor α, is necessary for premenopausal protection against hypertension, female, T cell deficient Rag-1-/- mice, received adoptive transfer of C57BL/6 or ERαKO T cells before Ang II infusion. Ang II-induced blood pressure responses remained blunted in female Rag-1-/- mice with ERαKO T cells, suggesting the importance of other estrogen receptors in T cell function and/or the importance of estrogen signaling within upstream regulators of T cell activation (i.e., dendritic cells, brain, kidney). To address the hypothesis that estrogen differentially regulates T cell protein expression, phosphorylation, and gene transcription during Ang II infusion, CD4+ T cell quantitative proteomic and transcriptomic analyses were conducted. The results support the hypothesis, demonstrating that differences in estrogen levels associate with unique T cell gene transcript, protein, and phosphorylation profiles during Ang II hypertension. To test the hypothesis that omic-identified T cell pathways contribute to premenopausal protection against hypertension, Ang II was administered to S100a9KO premenopausal female mice for 21 days. S100a9KO mice lack calprotectin, a protein product of two genes upregulated in T cells from Ang II infused premenopausal mice as determined by RNA-seq and RT-qPCR. Contrary to our hypothesis, S100a9KO females experienced blunted 7-day blood pressure responses to Ang II infusion due to a delay in T cell activation, highlighting the importance of calprotectin in innate immune cells and the need for additional refinement to isolate a T cell-specific function.