Oral Presentation Australasian Society for Immunology Annual Scientific Meeting 2014

High salt (NaCl) reduces the activation and function of IL-4 IL-13 stimulated macrophages (#128)

Katrina Binger 1 , Matthias Gebhardt 1 , Matthias Henig 2 , Carola Rintisch 2 , Agnes Schroeder 3 , Wolfgang Neuhofer 4 , Karl Hilgers 3 , Arndt Manzel 3 , Christian Schwartz 3 , Markus Kleinewietfeld 5 , Ralf Linker 3 , Florian Lang 6 , David Voehringer 3 , Mark D Wright 7 , Norbert Huebner 2 , Ralf Dechend 8 , Jonathan Jantsch 9 , Jens Titze 3 10 , Dominik N Muller 1
  1. Experimental and Clinical Research Center, institutional cooperation between the Charité Medical Faculty and the Max-Delbrueck Center for Molecular Medicine, Berlin, Germany
  2. Max-Delbrueck Center for Molecular Medicine, Berlin, Germany
  3. Friedrich-Alexander-University of Erlangen-Nuremberg, Erlangen, Germany
  4. Ludwig-Maximillian-University of Munich, Munich, Germany
  5. Dresden University of Technology, Dresden, Germany
  6. University of Tuebingen, Tuebingen, Germany
  7. Department of Immunology, Monash University, Melbourne, Australia
  8. HELIOS-Klinikum Berlin, Berlin, Germany
  9. University Hospital Regensburg, Regensburg, Germany
  10. Vanderbilt University, Nashville, TN, USA

High intake of dietary salt (sodium chloride; NaCl) has been implicated in the development of hypertension, chronic inflammation and autoimmune diseases. We have recently shown that NaCl has a pro-inflammatory effect and boosts the activation of Th17 cells in vitro, with mice fed a high salt diet having an accelerated and more severe experimental autoimmune encephalomyelitis (Kleinewietfeld et al, Nature 2013). Here, we have examined how the activation of so-called alternatively activated or M2 macrophages is affected by NaCl. In stark contrast to our study with Th17 cells, we find that high salt decreased the activation of IL-4+IL-13 stimulated bone marrow-derived mouse macrophages (M(IL-4+IL-13)). Signature genes important for M2 activation, including Mrc1, Arg1, Ym1 and Fizz1, all had a blunted induction in the presence of NaCl; an effect which was not observed in tonicity controls (mannitol or urea), implying a specific action of NaCl. When co-cultured with naïve T cells stimulated with α-CD3+α-CD28, control M(IL-4+IL-13) macrophages suppressed T cell proliferation by 88%, whilst NaCl-blunted M(IL-4+IL-13) macrophages had a reduced suppression of 35%. Additionally, mice fed a high-salt diet had a reduced wound healing capacity; collectively indicating that salt perturbs M(IL-4+IL-13) function both in vitro and in vivo. To identify the mechanism by which salt mediates this effect, we performed genome-wide epigenetic modification (ChIP-seq for H3K4me3 and H4ac) analysis, together with assessment of transcriptional changes by microarray. The results of this revealed that NaCl modulated epigenetic marks at several genes important for M(IL-4+IL-13) activation. Additionally, gene ontology analysis indicated that M(IL-4+IL-13) macrophages with NaCl blunted activation had altered metabolism. Finally, Akt, a signalling pathway important for nutrient sensing and driving metabolism, was found to be reduced by salt, providing a novel mechanism by which NaCl perturbs M(IL-4+IL-13) activation and function. This study gives further support to the notion that the modulation of immune cell function by high dietary salt is relevant to hypertension and autoimmune diseases.