Sex Differences in Renal T cells in DOCA‐salt Hypertension are not Blood Pressure Dependent.

Background There is increasing evidence implicating T cells in the development and maintenance of hypertension. Our lab has previously shown that there is a sex difference in renal T cells in deoxycorticosterone acetate salt (DOCA) hypertension, with females having greater T regulatory cells than males. Moreover, Tregs attenuate DOCA‐induced increases in blood pressure (BP) only in female rats. Therefore, the goal of the current study was to test the hypothesis that the sex difference in renal Tregs in DOCA‐salt rats is BP dependent. Methods At 10 wks of age, male and female Sprague‐Dawley rats were anesthetized, a right uni‐nephrectomy was performed, and all rats were implanted with telemetry devices for the continuous measurement of BP. After one week of recovery, all rats received a subcutaneous 21‐day slow‐release DOCA pellet (200 mg) with 0.9% saline water to drink. To prevent DOCA‐salt induced increases in BP, a subset of rats (N=9–12/group) were randomized to receive hydrochlorothiazide (HCTZ; 55 mg/kg/day) and reserpine (4.5 mg/kg/day) combined with 0.9% saline in the drinking water for 3 weeks. Rats were individually housed throughout the study. Water intake and body weights were measured every two days and the dose of drugs were altered, as needed, to maintain baseline BP levels. After 3 wks of treatment, the remaining kidney was isolated for flow cytometric analysis of T cells. Results After 3 wks of DOCA‐treatment, males had a higher BP than females (179 ± 3 mmHg vs. 157 ± 4 mmHg; n=6–7; P sex =0.0001). Treatment with HCTZ and reserpine prevented DOCA‐induced increases in BP in both males (110 ± 5 mmHg) and females (101 ± 5 mmHg; P treatment <0.0001; P interaction =0.307). With DOCA‐salt induced hypertension, males had more renal CD4 + T cells (expressed as %CD3 + T cells: 63 ± 2 vs 60 ± 1) and Th17 (expressed as %CD3 + CD4 + cells: 14 ± 1 vs 11 ±1) than females (P sex =0.04). HCTZ and reserpine decreased both CD4 + cells (expressed as %CD3 + T cells: 61 ± 3.9 vs 60 ±2.9; P treatment <0.0001) and Th17 cells (expressed as %CD3 + CD4 + cells: 5.15 ±0.93 vs 5.1 ± 1.3; P treatment <0.0001) and the decrease was comparable between sexes (CD4 + : P interaction =0.86; Th17: P interaction =0.55). With DOCA alone, females had a higher number of Tregs than males (expressed as %CD3 + CD4 + cells: 3.9 ±0.21 vs 2.6 ±0.2; P sex <0.0001). Preventing DOCA‐salt induced increases in BP with HCTZ and reserpine did not significantly change renal Tregs in either sex (P treatment =0.11; P interaction =0.38). Discussion Our data suggests that while preventing DOCA‐salt induced increases in BP attenuates the increase in renal pro‐inflammatory T cells, sex differences in renal T cells is not dependent on hypertension.