DIETARY SODIUM-INDUCED BLOOD PRESSURE RISE IS ASSOCIATED WITH A PRO-INFLAMMATORY PHENOTYPE OF CLASSICAL MONOCYTES – A RANDOMIZED CONTROLLED TRIAL IN HEALTHY HUMAN SUBJECTS

Abstract

Objective: High salt intake is associated with hypertension and cardiovascular disease. The mechanisms behind this are not fully elucidated, and may extend beyond the kidney. Proposedly, inflammation is involved. We investigated the effect of high salt intake on circulating monocytes and skin macrophages of healthy human subjects. Design and method: We performed a randomized cross-over trial in healthy males. All subjects pursued a 2-week low salt diet (LSD: < 3 grams NaCl/day) and high salt diet (HSD: > 12 grams NaCl/day) in randomized order. After each diet, body weight and blood pressure were measured, and blood and urine samples were obtained. Flow cytometry was used for phenotypic characterization of monocytes into classical (CD14+CD16-), intermediate (CD14+CD16+) and non-classical (CD14-CD16+) subtypes. We examined the expression of pro-inflammatory chemokine receptors (CCR2, CCR5, CCR7, CXCR1), anti-inflammatory chemokine receptors (CD206, CD200R) and molecules associated with migration (CD62L, CD49d, CD29, CD11b, CD11c, CD18). In addition, LPS-induced cytokine secretion (IL-6, IL-8, IL-10, IL-12, TNF) in whole blood was investigated. Furthermore, after each diet, skin biopsies were taken, to investigate skin macrophage density (CD163) and macrophages expression of the M1 marker HLA-DR and the M2 marker CD206. Results: Eleven subjects were included in this study. HSD increased body weight and systolic blood pressure, whereas CRP and monocyte number did not differ between LSD and HSD (Table 1). HSD increased CCR2 expression on classical monocytes (Figure 1A) and induced a trend towards decreased CD206 expression (Figure 1B). There was no effect on the other chemokine receptors or on the molecules associated with migration. Furthermore, HSD increased LPS-induced IL-6 secretion (Figure 1C) without any effect on the other cytokines. Macrophage density significantly increased after HSD (Figure 1D) and showed increased HLA-DR expression but decreased CD206 expression (Figure 1E+1F). Conclusions: In healthy human subjects, HSD-induced BP rise associates with a pro-inflammatory state of macrophages and of monocytes, including increased CCR2 expression and IL-6 secretion. Both factors have been shown to play a role in hypertension and cardiovascular disease in animal models, and may provide a link between salt and these deleterious outcomes in humans. (Figure Presented) .