Contribution of T‐lymphocytes to the Sex Differences Observed in Dahl Salt‐sensitive Hypertension and Renal Damage

Field: Medicine (Health Sciences)

Previous studies in our laboratory have established a clear role for the immune system in the development of hypertension and renal damage in male Dahl salt‐sensitive (SS) rats. Far less is known about the salt‐sensitive phenotype in female Dahl SS rats and how it compares to males, especially in regard to the contribution of immune‐related mechanisms. Using radiotelemetry to measure blood pressure, urine and renal histological analysis to assess kidney damage, and flow cytometry to assess renal immune cell infiltration, the current study examined the hypertensive and kidney injury phenotype in response to a 3 week high salt challenge (HS, 4.0% NaCl, AIN‐76A) in female versus male Dahl SS rats (n>10/group). During the low‐salt (LS, 0.4% NaCl) period, there was no difference in baseline mean arterial pressure (MAP) between females and males (129.4±2.0 vs 123.7±1.9 mmHg, respectively). However, after 3 weeks of HS, females were significantly protected from developing the same extent of hypertension observed in the males (161.5±3.1 vs 176.7±6.7 mmHg). This protection in the females coincided with significantly less renal damage, evident by markedly reduced albuminuria (105.0±15.7 vs 183.2±15.6 mg/day) and medullary protein cast formation (6.96±0.72 vs 14.62±1.14%) compared to the males. There was also a significant 48.5% reduction in the number of CD45+ total leukocytes in the female versus male kidneys (3.3±.3 vs 6.3±0.5 ×10 6 cells/kidney), which was true across all immune subsets – CD3+ T‐lymphocytes (50.8% reduction), CD45R+ B‐lymphocytes (73.5% reduction), and CD11b/c+ monocytes/macrophages (46.7% reduction). To interrogate the potential contribution of adaptive immunity, specifically T‐lymphocytes, to the development of this sex difference, the same parameters were investigated in both female and male SS CD247−/− rats. The lack of functional CD3+ T‐lymphocytes in SS CD247−/− rats significantly reduced blood pressure in both females (147.1±5.9 vs 161.5±3.1 mmHg; SS CD247−/− vs SS) and males (157.2±8.1 vs 176.7±6.7 mmHg) after a 3 week salt challenge, where there was no statistical difference between female and male SS CD247−/− rats. There was a corresponding decrease in kidney damage, with reduced albuminuria in both female (37.2±12.1 vs 105.0±15.7 mg/day) and male (88.4±12.7 vs 183.2±15.6 mg/day) SS CD247−/− rats when compared to SS rats with the full complement of immune cells. Flow cytometric analysis confirmed the lack of T‐lymphocytes in all SS CD247−/− rats, and additionally, there was significantly less medullary protein cast formation in the SS CD247−/− rats compared to the SS, regardless of sex (females: 1.82±0.37 vs 6.96±0.72%; males: 9.10±0.75 vs 14.62±1.14%; SS CD247−/− vs SS). Together, our data indicate that although female SS rats are significantly protected from progressing to the same severity of disease compared to male SS rats, female SS rats do still develop salt‐induced hypertension and renal damage that is amplified by T‐lymphocytes. Support or Funding Information 19CDA34660184, HL116264, HL137748