Greater T Regulatory Cells in Females Attenuate DOCA-Salt-Induced Increases in Blood Pressure Versus Males

Abstract

Hypertension is the most common risk factor for cardiovascular disease, causing over 18 million deaths a year. Although the mechanisms controlling blood pressure (BP) in either sex remain largely unknown, T cells play a critical role in the development of hypertension. Further evidence supports a role for the immune system in contributing to sex differences in hypertension. The goal of the current study was to first, determine the impact of sex on the renal T-cell profiles in DOCA-salt hypertensive males and females and second, test the hypothesis that greater numbers of T regulatory cells (Tregs) in females protect against DOCA-salt-induced increases in BP and kidney injury. Male rats displayed greater increases in BP than females following 3 weeks of DOCA-salt treatment, although increases in renal injury were comparable between the sexes. DOCA-salt treatment resulted in an increase in proinflammatory T cells in both sexes; however, females had more anti-inflammatory Tregs than males. Additional male and female DOCA-salt rats were treated with anti-CD25 to decrease Tregs. Decreasing Tregs significantly increased BP only in females, thereby abolishing the sex difference in the BP response to DOCA-salt. This data supports the hypothesis that Tregs protect against the development of hypertension and are particularly important for the control of BP in females.

Keywords: blood pressure; cardiovascular disease; hypertension; inflammation; kidney.

Figure 1:

24 hour mean arterial pressure (MAP) was measured via telemetry in male (M) and female (F) Sprague-Dawley (SD) rats (n=11–12). After 1 week of baseline MAP measurements, rats were treated with DOCA-salt for 21 days. Data within each sex were analyzed using repeated measures ANOVA with Tukey’s multiple comparisons test and between group comparisons were made using a t-test. # indicates p<0.05 vs. baseline MAP; * indicates p<0.05 vs. male.

Figure 2:

Renal T cell profiles were measured via flow cytometric analysis in male and female rats following 1 week of UNX control or DOCA-salt treatment (n=12). Shown are percentages of (A) total CD3⁺ T cells expressed as a percentage of total renal cells: P_interaction = 0.96; P_treatment = 0.10; P_sex = 0.02, (B) CD4⁺ T cells expressed as a percentage of total CD3⁺ T cells: P_interaction = 0.72; P_treatment = 0.10; P_sex = 0.08, (C) Foxp3⁺ T regulatory cells (Tregs) expressed as a percentage of CD3⁺CD4⁺ T cells: P_interaction = 0.37; P_treatment = 0.08; P_sex = 0.002, and (D) IL-17⁺ T helper (Th)17 cells expressed as a percentage of CD3⁺CD4⁺ T cells: P_interaction = 0.99; P_treatment = 0.013; P_sex < 0.0001. Data were analyzed using two-way ANOVA.

Figure 3:

Renal T cell profile measured via flow cytometric analysis in male and female rats following 3 weeks of UNX control or DOCA-salt treatment (n=12). Shown are percentages of (A) total CD3⁺ T cells expressed as a percentage of total renal cells: P_interaction = 0.94; P_treatment = 0.03; P_sex = 0.89, (B) CD4⁺ T cells expressed as a percentage of total CD3⁺ T cells: P_interaction = 0.44; P_treatment = 0.04; P_sex = 0.04, (C) Foxp3⁺ T regulatory cells (Tregs) expressed as a percentage of CD3⁺CD4⁺ T cells: P_interaction = 0.03; P_treatment = 0.02; P_sex < 0.0001, (D) IL-17⁺ T helper (Th)17 cells expressed as a percentage of CD3⁺CD4⁺ T cells: P_interaction = 0.72; P_treatment = 0.03; P_sex = 0.007. Data were analyzed using two-way ANOVA.

Figure 4:

24 hour mean arterial pressure (MAP) was measured via telemetry in male (M; A and B) and female (F; A and C) Sprague-Dawley (SD) rats (n=6–8). After 4 days of baseline MAP measurements, rats were treated with DOCA-salt plus weekly control IgG or anti-CD25 injections and MAP was measured for 21 days. At the end of the treatment, blood (D) and the remaining kidney (E) were isolated to measure Tregs by flow cytometric analysis. MAP data within each sex were analyzed using repeated measures ANOVA with Tukey’s multiple comparisons test and between group comparisons were made using a t-test. * indicates p<0.05 vs. DOCA controls. Flow cytometric data were analyzed using two-way ANOVA.