Dietary salt and endothelin A receptor activation regulates T cell responses in a tissue‐dependent manner

Abstract

Numerous studies have investigated the role of high salt diet (HSD) by utilizing salt‐sensitive animal models or co‐administration with pro‐hypertensive insult. HSD is implicated in altering tissue‐dependent immunologic responses. Endothelin (ET‐1) is a major vasoconstrictor peptide synthesized in response to HSD. The ET‐1/endothelin A (ETA) receptor pathway has been implicated in regulating inflammatory responses, and to blunt the immunologic response with pro‐hypertensive conditions. However, the singular role of HSD on renal, colonic and splenic T cells is not fully understood. Therefore, we hypothesized that ETA receptor activation blunts T cell responses with HSD. Utilizing flow cytometry, we immunophenotyped renal, colonic, and splenic T cells in 12‐wk old male C57BL6/J mice provided normal salt diet (NSD, 0.4% NaCl food), ETA blockade (atrasentan, 10mg/kg/day) with NSD, HSD (4% NaCl food plus 1% NaCl drinking water), or co‐administration of atrasentan and HSD for 5 weeks. Kidneys, colons and spleens were collected for single cell suspensions. Isolated cells were stimulated followed by fluorescent antibody staining for flow cytometric analysis. Data are expressed as cell number means SEM (n=4/group) with statistical differences calculated by two‐way ANOVA with Tukey’s correction for multiple comparisons. HSD significantly blunted the total number of renal CD4+T cells mice compared to NSD as well as atrasentan treatment without further suppression of CD4+T cells under co‐administration of both HSD and atrasentan (NSD: 5217 619; Atrasentan: 1.8 0.15*; HSD: 2.4 0.32*; Atrasentan/HSD: 1.8 0.15*, x103, *p<0.001). Colonic CD4+T cells were similarly blunted under Atrasentan‐only and HSD‐only administration, without further reduction under co‐administration. However, splenic CD4+T cells were significantly expanded under chronic atrasentan administration (NSD: 2.66 1.45; Atrasentan: 7.63 0.61#; HSD: 6.63 0.69#; Atrasentan/HSD: 6.46 0.96#, x106, #p<0.05). We next examined IL‐17A production by CD4+T cells, which allows us to determine TH17 cells. Compared to NSD, HSD or atrasentan significantly blunted the total number of renal TH17 cells (NSD: 65 9; Atrasentan: 22 5*; HSD: 26 4*; Atrasentan/HSD: 20 3*, *p<0.001). Colonic TH17cells were similarly blunted. However, splenicTH17cells were seemingly unaffected under chronic atrasentan administration with similar results under HSD and combination of HSD/Atrasentan (NSD: 2.9 1.4; Atrasentan: 8.6 1.6; HSD: 7.6 2.8; Atrasentan/HSD: 5.5 1.6, x104, p>0.05). These findings suggest that HSD or ETA receptor activation may regulate T cell responsiveness in a tissue‐dependent manner.Support or Funding InformationU01HL117684, P01HL69999, AHA SFRN 24450002, P01HL136267, 1 F31 HL151264‐01