Adaptive immune response has been implicated in inflammation and fibrosis as a result of exposure to mineralocorticoids and a high-salt diet. We hypothesized that in mineralocorticoid-salt–induced hypertension, activation of the mineralocorticoid receptor alters the T-helper 17 lymphocyte (Th17)/regulatory T-lymphocyte/interleukin-17 (IL-17) pathway, contributing to cardiac and renal damage. We studied the inflammatory response and tissue damage in rats treated with deoxycorticosterone acetate and high-salt diet (DOCA–salt), with or without mineralocorticoid receptor inhibition by spironolactone. To determine whether Th17 differentiation in DOCA–salt rats is caused by hypertension per se, DOCA–salt rats received antihypertensive therapy. In addition, to evaluate the pathogenic role of IL-17 in hypertension and tissue damage, we studied the effect of IL-17 blockade with a specific antibody (anti–IL-17). We found activation of Th17 cells and downregulation of forkhead box P3 mRNA in peripheral tissues, heart, and kidneys of DOCA–salt–treated rats. Spironolactone treatment prevented Th17 cell activation and increased numbers of forkhead box P3–positive cells relative to DOCA–salt rats. Antihypertensive therapy did not ameliorate Th17 activation in rats. Treatment of DOCA–salt rats with anti–IL-17 significantly reduced arterial hypertension as well as expression of profibrotic and proinflammatory mediators and collagen deposits in the heart and kidney. We conclude that mineralocorticoid receptor activation alters the Th17/regulatory T-lymphocyte/IL-17 pathway in mineralocorticoid-dependent hypertension as part of an inflammatory mechanism contributing to fibrosis.

Excessive production of aldosterone leads to the development of hypertension and cardiovascular disease by generating an inflammatory state that can be promoted by T cell immunity. Because nature and intensity of T cell responses is controlled by dendritic cells (DCs), it is important to evaluate whether the function of these cells can be modulated by aldosterone. In this study we show that aldosterone augmented the activation of CD8+ T cells in a DC-dependent fashion. Consistently, the mineralocorticoid receptor was expressed by DCs, which showed activation of MAPK pathway and secreted IL-6 and TGF-b in response to aldosterone. In addition, DCs stimulated with aldosterone impose a Th17 phenotype to CD4+ T cells, which have recently been associated with the promotion of inflammatory and autoimmune diseases. Accordingly, we observed that aldosterone enhances the progression of experimental autoimmune encephalomyelitis, an autoimmune disease promoted by Th17 cells. In addition, blockade of the mineralocorticoid receptor prevented all aldosterone effects on DCs and attenuated experimental autoimmune encephalomyelitis development in aldosterone-treated mice. Our data suggest that modulation of DC function by aldosterone enhances CD8+ T cell activation and promotes Th17-polarized immune responses, which might contribute to the inflammatory damage leading to hypertension and cardiovascular disease.This work was supported by Fondo Nacional de Desarrollo Científico y Tecnológico Grants 1070352, 1070876, 1050265, 1050690 and 1050979; Fondo de Fomento al Desarrollo Científico y Tecnológico Grant D04I1075; INCO-CT-2006-032296; and Millennium Nucleus on Immunology and Immunotherapy (P04/030-F).A.A.H., P.A.G, and C.A.A. are fellows of Comisión Nacional de Investigación Científica y Tecnológica

A ldosterone via the activation of the mineralocorticoid receptor (MR) is a main actor of renal sodium reabsorption and water homeostasis. Extra-renal effects of the mineralocorticoid pathway have now been characterized, especially in the cardiovascular system, opening on new dimensions of the aldosterone/MR pathway in physiology, pathophysiology, and diseases. In the cardiovascular system, mineralocorticoid signaling has been shown to play an important role in the progression of cardiovascular diseases (CVDs). Previous reports using transgenic mouse models or pharmacological approaches demonstrated adverse effects of aldosterone on cardiac remodeling and fibrosis, inflammation, and hypertension.1 These features are prevented by the pharmacological blockade of the MR. In humans, several clinical studies showed the beneficial effects of MR antagonism in addition to standard care, to reduce mortality and morbidity in patients with severe 2 or mild heart failure (HF) 3 or after acute myocardial infarction. 4 Understanding the molecular mechanisms of mineralocorticoid activation pathway in cardiovascular pathophysiology remains incomplete. Indeed, a better knowledge of the underlying mechanisms may highlight novel mediators of the MR signaling cascade. These newly identified intermediates could be good candidates as biotargets for novel pharmacological approaches, especially in diseases where the aldosterone/MR pathway is involved. Moreover, these biotargets may as well be considered as potent biomarkers of MR activation, Abstract-Activation of the mineralocorticoid receptor has been shown to be deleterious in cardiovascular diseases (CVDs).We have recently shown that lipocalin 2 (Lcn2), or neutrophil gelatinase-associated lipocalin (NGAL), is a primary target of aldosterone/mineralocorticoid receptor in the cardiovascular system. Lcn2 is a circulating protein, which binds matrix metalloproteinase 9 and modulates its stability. We hypothesized that Lcn2 could be a mediator of aldosterone/ mineralocorticoid receptor profibrotic effects in the cardiovascular system. Correlations between aldosterone and profibrotic markers, such as procollagen type I N-terminal peptide, were investigated in healthy subjects and subjects with abdominal obesity. The implication of Lcn2 in the mineralocorticoid pathway was studied using Lcn2 knockout mice subjected to a nephrectomy/aldosterone/salt (NAS) challenge for 4 weeks. In human subjects, NGAL/matrix metalloproteinase 9 was positively correlated with plasma aldosterone and fibrosis biomarkers. In mice, loss of Lcn2 prevented the NAS-induced increase of plasma procollagen type I N-terminal peptide, as well as the increase of collagen fibers deposition and collagen I expression in the coronary vessels and the aorta. The lack of Lcn2 also blunted the NAS-induced increase in systolic blood pressure. Ex vivo, treatment of human fibroblasts with recombinant Lcn2 induced the expression of collagen I and the profibrotic galectin-3 and cardiotrophin-1 molecules. allowing a better selectio...