Transcriptomic Analysis in Renal T Lymphocytes Exposes Sodium-Independent Dietary Differences in Dahl Salt-Sensitive Rats

Background. The Dahl salt-sensitive (SS) rat is an established model of salt-sensitive hypertension and renal damage. Recently, sodium-independent dietary effects were shown to be important in the development of the SS hypertensive phenotype. Compared to Dahl SS/JrHsdMcwi (SS/MCW) rats fed a purified diet (AIN-76A), grain-fed Dahl SS/JrHsdMcwiCrl rats (SS/CRL; Teklad 5L2F) were less susceptible to salt-induced hypertension and renal damage. Methods. With the known role of the immune system in hypertension, the present study characterized the immune cells infiltrating SS/MCW and SS/CRL kidneys. To further identify distinct molecular pathways between SS/MCW and SS/CRL, transcriptomic analysis was performed via RNA sequencing in T-cells isolated from the blood and kidneys of low and high salt-fed rats. Results. Following a 3-week high salt (4.0% NaCl) challenge, SS/CRL rats were protected from salt-induced hypertension (116.5±1.2 vs 141.9±14.4 mmHg) and albuminuria (21.7±3.5 vs 162.9±22.2 mg/day) compared to SS/MCW. Additionally, the absolute number of immune cells infiltrating the kidney was significantly reduced in SS/CRL. RNA-seq revealed >50% of all annotated genes in the entire transcriptome to be significantly differentially expressed in T-cells isolated from blood versus kidney. Pathway analysis of significant differentially expressed genes between SS/MCW and SS/CRL renal and circulating T-cells demonstrated salt-induced changes in genes related to inflammation in SS/MCW compared to metabolism-related pathways in SS/CRL. Conclusions. These functional and transcriptomic T-cell differences between SS/MCW and SS/CRL show that sodium-independent dietary effects may influence the immune response and infiltration of immune cells into the kidney, ultimately impacting susceptibility to salt-induced hypertension and renal damage. Overall design: 5 experimental groups; 4 pools/experimental group; 3 rats/pool