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SUMMARY Sodium accumulates in the interstitium and promotes inflammation through poorly defined mechanisms. We describe a pathway by which sodium enters dendritic cells (DCs) through amiloride-sensitive channels including the alpha and gamma subunits of the epithelial sodium channel and the sodium hydrogen exchanger 1. This leads to calcium influx via the sodium calcium exchanger, activation of protein kinase C (PKC), phosphorylation of p47phox, and association of p47phox with gp91phox. The assembled NADPH oxidase produces superoxide with subsequent formation of immunogenic isolevuglandin (IsoLG)-protein adducts. DCs activated by excess sodium produce increased interleukin-1β (IL-1β) and promote T cell production of cytokines IL-17A and interferon gamma (IFN-γ). When adoptively transferred into naive mice, these DCs prime hypertension in response to a sub-pressor dose of angiotensin II. These findings provide a mechanistic link between salt, inflammation, and hypertension involving increased oxidative stress and IsoLG production in DCs.

Rationale Inflammation and adaptive immunity plays a crucial role in the development of hypertension. Angiotensin II and likely other hypertensive stimuli activate the central nervous system and promote T cell activation and end-organ damage in peripheral tissues. Objective To determine if renal sympathetic nerves mediate renal inflammation and T cell activation in hypertension. Methods and Results Bilateral renal denervation (RDN) using phenol application to the renal arteries reduced renal norepinephrine (NE) levels and blunted angiotensin II induced hypertension. Bilateral RDN also reduced inflammation, as reflected by decreased accumulation of total leukocytes, T cells and both CD4+ and CD8+ T cells in the kidney. This was associated with a marked reduction in renal fibrosis, albuminuria and nephrinuria. Unilateral RDN, which partly attenuated blood pressure, only reduced inflammation in the denervated kidney, suggesting that this effect is pressure independent. Angiotensin II also increased immunogenic isoketal-protein adducts in renal dendritic cells (DCs) and increased surface expression of costimulation markers and production of IL-1α, IL-1β, and IL-6 from splenic dendritic cells. NE also dose dependently stimulated isoketal formation in cultured DCs. Adoptive transfer of splenic DCs from angiotensin II-treated mice primed T cell activation and hypertension in recipient mice. RDN prevented these effects of hypertension on DCs. In contrast to these beneficial effects of ablating all renal nerves, renal afferent disruption with capsaicin had no effect on blood pressure or renal inflammation. Conclusions Renal sympathetic nerves contribute to dendritic cell activation, subsequent T cell infiltration and end-organ damage in the kidney in the development of hypertension.

Recent studies have emphasized a role of adaptive immunity, and particularly T cells, in the genesis of hypertension. We sought to determine the T cell subtypes that contribute to hypertension and renal inflammation in angiotensin II-induced hypertension. Using T cell receptor (TCR) spectratyping to examine TCR usage we demonstrated that CD8+ cells, but not CD4+ cells, in the kidney exhibited altered TCR transcript lengths in Vβ3, 8.1 and 17 families in response to angiotensin II-induced hypertension. Clonality was not observed in other organs. The hypertension caused by angiotensin II in CD4−/− and MHCII−/− mice was similar to that observed in WT mice, while CD8−/− mice and OT1xRAG-1−/− mice, which have only one TCR, exhibited a blunted hypertensive response to angiotensin II. Adoptive transfer of pan-T cells and CD8+ T cells but not CD4+/CD25− cells conferred hypertension to RAG-1−/− mice. In contrast, transfer of CD4+/CD25+ cells to wild type mice receiving angiotensin II decreased blood pressure. Mice treated with angiotensin II exhibited increased numbers of kidney CD4+ and CD8+ T cells. In response to a sodium/volume challenge, wild type and CD4−/− mice infused with angiotensin II retained water and sodium whereas CD8−/− mice did not. CD8−/− mice were also protected against angiotensin-induced endothelial dysfunction and vascular remodeling in the kidney. These data suggest that in the development of hypertension, an oligoclonal population of CD8+ cells accumulate in the kidney and likely contribute to hypertension by contributing to sodium and volume retention and vascular rarefaction.