Salt increases monocyte CCR2 expression and inflammatory responses in humans
Eliane F.E. Wenstedt, Sanne G.S. Verberk, Jeffrey Kroon, Annette E. Neele, Jeroen Baardman, Nike Claessen, Özge T. Pasaoglu, Emma Rademaker, Esmee M. Schrooten, Rosa D. Wouda, Menno P.J. de Winther, Jan Aten, Liffert Vogt, Jan Van den Bossche
Eliane F.E. Wenstedt, Sanne G.S. Verberk, Jeffrey Kroon, Annette E. Neele, Jeroen Baardman, Nike Claessen, Özge T. Pasaoglu, Emma Rademaker, Esmee M. Schrooten, Rosa D. Wouda, Menno P.J. de Winther, Jan Aten, Liffert Vogt, Jan Van den Bossche
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Research Article Clinical trials Inflammation

Salt increases monocyte CCR2 expression and inflammatory responses in humans

Abstract

Inflammation may play a role in the link between high salt intake and its deleterious consequences. However, it is unknown whether salt can induce proinflammatory priming of monocytes and macrophages in humans. We investigated the effects of salt on monocytes and macrophages in vitro and in vivo by performing a randomized crossover trial in which 11 healthy human subjects adhered to a 2-week low-salt and high-salt diet. We demonstrate that salt increases monocyte expression of CCR2, a chemokine receptor that mediates monocyte infiltration in inflammatory diseases. In line with this, we show a salt-induced increase of plasma MCP-1, transendothelial migration of monocytes, and skin macrophage density after high-salt diet. Macrophages demonstrate signs of an increased proinflammatory phenotype after salt exposure, as represented by boosted LPS-induced cytokine secretion of IL-6, TNF, and IL-10 in vitro, and by increased HLA-DR expression and decreased CD206 expression on skin macrophages after high-salt diet. Taken together, our data open up the possibility for inflammatory monocyte and macrophage responses as potential contributors to the deleterious effects of high salt intake.

Authors

Eliane F.E. Wenstedt, Sanne G.S. Verberk, Jeffrey Kroon, Annette E. Neele, Jeroen Baardman, Nike Claessen, Özge T. Pasaoglu, Emma Rademaker, Esmee M. Schrooten, Rosa D. Wouda, Menno P.J. de Winther, Jan Aten, Liffert Vogt, Jan Van den Bossche

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Figure 5

HSD increases skin macrophage content with signs of a more proinflammatory and less antiinflammatory phenotype.

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HSD increases skin macrophage content with signs of a more proinflammato...
(A and B) To assess total skin macrophage content, sections were stained with anti-CD163 (red). Quantification of total macrophage content was expressed as the percentage of the total dermal area of the section that was positively stained for anti-CD163 (A). Anti-CD163 was favored above anti-CD68, since our pilot experiments showed that CD163 proved to be a more consistent macrophage marker than CD68 (Supplemental Figure 1), which is in line with the observations of 2 other research groups (51, 52). (C–H) To assess expression of proinflammatory and antiinflammatory macrophage markers, sections were stained with anti-CD163 (red) and either anti–HLA-DR (blue) (C and D), anti-CD206 (blue) (E and F), or anti-CCR2 (blue) (G and H). Since HLA-DR, CD206, and CCR2 can be expressed by other cells than macrophages, we only took into account the positively stained area of the concerning marker that was also positive for the macrophage marker anti-CD163. Quantification of the total expression of the several markers by macrophages was expressed as the percentage of positively stained area for anti-CD163 that was also positively stained for the concerning marker. (I and J) To assess skin expression of MCP-1, section were stained with anti–MCP-1 (blue) and anti-CD163 (red). Quantification of skin expression of MCP-1 was expressed as the total dermal area of the section that was positively stained for MCP-1 (I). LSD, low-salt diet. HSD, high-salt diet. Scale bar: 200 μm. Values represent mean ± SEM of n = 9–11 healthy male volunteers. Data are tested using a paired t test. *P < 0.05.