Inflammation in Salt-Sensitive Hypertension and Renal Damage

We have shown previously that T cells are required for the full development of angiotensin II-induced hypertension. However, the specific subsets of T cells that are important in this process are unknown. T helper 17 cells represent a novel subset that produces the proinflammatory cytokine interleukin 17 (IL-17). We found that angiotensin II infusion increased IL-17 production from T cells and IL-17 protein in the aortic media. To determine the effect of IL-17 on blood pressure and vascular function, we studied IL-17(-/-) mice. The initial hypertensive response to angiotensin II infusion was similar in IL-17(-/-) and C57BL/6J mice. However, hypertension was not sustained in IL-17(-/-) mice, reaching levels 30-mm Hg lower than in wild-type mice by 4 weeks of angiotensin II infusion. Vessels from IL-17(-/-) mice displayed preserved vascular function, decreased superoxide production, and reduced T-cell infiltration in response to angiotensin II. Gene array analysis of cultured human aortic smooth muscle cells revealed that IL-17, in conjunction with tumor necrosis factor-alpha, modulated expression of >30 genes, including a number of inflammatory cytokines/chemokines. Examination of IL-17 in diabetic humans showed that serum levels of this cytokine were significantly increased in those with hypertension compared with normotensive subjects. We conclude that IL-17 is critical for the maintenance of angiotensin II-induced hypertension and vascular dysfunction and might be a therapeutic target for this widespread disease.

The skin interstitium sequesters excess Na+ and Cl- in salt-sensitive hypertension. Mononuclear phagocyte system (MPS) cells are recruited to the skin, sense the hypertonic electrolyte accumulation in skin, and activate the tonicity-responsive enhancer-binding protein (TONEBP, also known as NFAT5) to initiate expression and secretion of VEGFC, which enhances electrolyte clearance via cutaneous lymph vessels and increases eNOS expression in blood vessels. It is unclear whether this local MPS response to osmotic stress is important to systemic blood pressure control. Herein, we show that deletion of TonEBP in mouse MPS cells prevents the VEGFC response to a high-salt diet (HSD) and increases blood pressure. Additionally, an antibody that blocks the lymph-endothelial VEGFC receptor, VEGFR3, selectively inhibited MPS-driven increases in cutaneous lymphatic capillary density, led to skin Cl- accumulation, and induced salt-sensitive hypertension. Mice overexpressing soluble VEGFR3 in epidermal keratinocytes exhibited hypoplastic cutaneous lymph capillaries and increased Na+, Cl-, and water retention in skin and salt-sensitive hypertension. Further, we found that HSD elevated skin osmolality above plasma levels. These results suggest that the skin contains a hypertonic interstitial fluid compartment in which MPS cells exert homeostatic and blood pressure-regulatory control by local organization of interstitial electrolyte clearance via TONEBP and VEGFC/VEGFR3-mediated modification of cutaneous lymphatic capillary function.

Angiotensin (Ang) II induces hypertension by mechanisms mediated in part by adaptive immunity and T effector lymphocytes. T regulatory lymphocytes (Tregs) suppress T effector lymphocytes. We questioned whether Treg adoptive transfer would blunt Ang II-induced hypertension and vascular injury. Ten- to 12-week-old male C57BL/6 mice were injected IV with 3 ×10(5) Treg (CD4(+)CD25(+)) or T effector (CD4(+)CD25(-)) cells, 3 times at 2-week intervals, and then infused or not with Ang II (1 μg/kg per minute, SC) for 14 days. Ang II increased systolic blood pressure by 43 mm Hg (P<0.05), NADPH oxidase activity 1.5-fold in aorta and 1.8-fold in the heart (P<0.05), impaired acetylcholine vasodilatory responses by 70% compared with control (P<0.05), and increased vascular stiffness (P<0.001), mesenteric artery vascular cell adhesion molecule expression (2-fold; P<0.05), and aortic macrophage and T-cell infiltration (P<0.001). All of the above were prevented by Treg but not T effector adoptive transfer. Ang II caused a 43% decrease in Foxp3(+) cells in the renal cortex, whereas Treg adoptive transfer increased Foxp3(+) cells 2-fold compared with control. Thus, Tregs suppress Ang II-mediated vascular injury in part through anti-inflammatory actions. Immune mechanisms modulate Ang II-induced blood pressure elevation, vascular oxidative stress, inflammation, and endothelial dysfunction.