Joshua Uhlorn's Abstracts
Joshua Uhlorn
Ph.D. Candidate
Physiological Sciences
Hypertension 2019 Scientific Sessions
New Orleans, LA
September 5-8, 2019
T cells are involved in hypertension pathogenesis in both males and postmenopausal females while premenopausal females are resistant to T cell-mediated Ang II-induced hypertension. The goals of this study were (1) to identify T cell specific proteomic pathways associated with postmenopausal susceptibility to hypertension (2) to identify T cell specific transcriptomic changes associated with premenopausal protection from hypertension. Proteomic analysis was performed on splenic CD4+ T cells isolated from premenopausal and postmenopausal females (VCD, 160 mg/kg/day i.p. 20d) following Ang II infusion (800 ng/kg/min 14d). 384 proteins from CD4+ T cells were identified as differentially expressed following Ang II infusion in premenopausal females. 285 proteins from CD4+ T cells were identified as differentially expressed between premenopausal and postmenopausal females following Ang II infusion. Gene ontology (GO) analysis of pre vs. postmenopausal proteins identified enriched pathways associated with RNA binding, chaperone activity and cellular stress responses. Transcriptomic changes were analyzed, via RNAseq, on isolated splenic CD4+ T cells from premenopausal females, with and without Ang II infusion. Thirty-four genes were identified as differentially expressed in CD4+ T cells following Ang II infusion. GO analysis of Ang II upregulated genes revealed an enrichment of five distinct molecular functions, including antioxidant activity. In a subsequent study to validate the RNAseq, we confirmed that Ang II increased CD4+ T cell mRNA expression of calprotectin (S100a8/S100a9), a calcium and zinc binding protein complex that contributes to antioxidant defense (S100a8: Con 1.0 ± 0.4 vs Ang II 5.0 ± 0.8*; S100a9: Con 1.0 ± 0.4 vs Ang II 6.0 ± 0.8*, *P<0.05 vs Con). Furthermore, we determined that Ang II did not increase calprotectin expression in mice lacking estrogen receptor a (ERKO) (S100a8 ERKO 0.1 ± 0.4 vs ERKO/Ang II 0.3 ± 0.7; S100a9: ERKO 0.2 ± 0.5 vs ERKO/Ang II 0.3 ± 0.6). The current studies demonstrate a role for estrogen in Ang II-induced T cell gene expression and signal transduction, and begin to elucidate the molecular mechanisms of female protection from T cell-mediated hypertension.
Abstract for Lay Audience
We typically associate the development of high blood pressure in adults with poor diet, aging or the damage and failure of organs, such as the heart and kidneys. The current most commonly prescribed drugs to treat hypertension all target the kidney to lower blood pressure, however they have all been tested in men. Recent studies have shown that they do not work as well in women. In addition we know that women are protected from high blood pressure, until menopause. Once women enter menopause we know that blood pressure increases rapidly and yet the drugs do not work as well. Our group aims to identify the sex differences in these responses. Recent discoveries in males indicate that the immune system is involved in the development of large increases in blood pressure and in cardiovascular organ damage. We have shown that premenopausal females are resistant and protected from experimentally induced blood pressure increases. Once we induce menopause this resistance is lost and similar to males, blood pressure increases and the immune system is activated and involved in this blood pressure increase. We hypothesize that the loss of estrogen, associated with the transition into menopause, is responsible for loss of protection to immune-mediated increases in blood pressure. To address this hypothesis, we sought to determine the effect of estrogen on a specific immune cell, the T lymphocyte (T cell), whose presence is necessary for large blood pressure increases in males. We first analyzed T cell protein expression differences between premenopausal postmenopausal females with and without hypertension, using large scale quantitative approaches. We identified 285 proteins that were differentially expressed between the pre and post menopausal groups. Analysis of the cellular pathways for the 285 proteins suggest that the ability of the T cells to respond to stress is different between premenopausal and menopausal mice. To further determine why premenopausal females are resistant to immune-mediated blood pressure increases we investigated which T cell genes were either turned off or on in the presence of a high blood pressure stimulant (Angiotensin II). We identified 34 genes that were differentially expressed between control premenopausal mice and premenopausal mice given a hypertensive stimulant. Pathway analysis of the T cell gene differences revealed premenopausal females upregulate genes involved in antioxidant activity. This antioxidant associated gene upregulation was validated in studies in knockout mice lacking estrogen receptors. In isolating the effect of estrogen on the cells involved in the development of high blood pressure and determining the mechanisms behind its protection, we can work towards identifying the major pathways that abruptly become impaired after the onset of menopause; the goal being to distinguish possible treatments to combat the increased risk of high blood pressure in menopause and the decreased effectiveness of current medications.