Direct Effects of High Sodium on Histone Deacetylases in RAW264.7 Macrophages

Abstract

Evidence demonstrates a key role of macrophage (MΦ) activation in salt‐sensitive hypertension with pro‐inflammatory (M1) phenotype transition following high salt (NaCl) exposure. Our lab has shown that high Na+ regulates histone deacetylase 1 (HDAC1) expression in the kidney and HDAC9 was previously shown to regulate the M1 phenotype. However, it is unknown whether high Na specifically regulates MΦ HDAC1 or HDAC9 expression. The MΦ cell line RAW264.7 was cultured in DMEM (10% FBS) to confluency and exposed to 40mM NaCl, sodium acetate, choline chloride or mannitol for 24 hours to determine whether the gene expression is dependent on high Na or osmolality. To determine whether this in vitro system modulates the M1 or profibrotic M2 phenotype, we determined expression of interleukin 1β (IL‐1β), interleukin 12α (IL‐12α), and nitric oxide synthase 2 (NOS2) in response to 100ng/mL lipopolysaccharide (LPS) or 10ng/mL interleukin‐4 (IL‐4). Three independent experiments were completed. Data are presented as relative expression fold difference and one‐way ANOVA utilized for statistical analysis with significance at p<0.05. LPS exposure leads to M1 MΦ phenotype with increased IL‐1β and NOS2 (1713±618 and 42±6, respectively). Traditionally, IL‐4 is thought to induce the anti‐inflammatory M2 phenotype but 24hr treatment did not demonstrate a difference in IL‐12α from control, IL‐4 or LPS treatment, supporting the requirement of additional M2‐specific stimuli in parallel with IL‐4. Additionally, to examine an effect of high salt on LPS or IL‐4, MΦ were also exposed to IL‐1β + NaCl or IL‐4 + NaCl. There were no changes in HDAC1 mRNA expression following NaCl, sodium acetate, choline chloride, mannitol, LPS, LPS+NaCl, and IL‐4. IL‐4+NaCl decreased HDAC1 expression by 59.3±3.5%. There was no change in HDAC9 mRNA expression following any treatment group. These studies suggest that high sodium does not induce HDAC1 or HDAC9 gene expression in cultured macrophages. Further studies are warranted to determine protein abundance as well as in vivo effects of high salt diets, and in particular examination of changes in resident kidney macrophages.Support or Funding InformationNIH P01 HL69999, NIH P01 HL136267, AHA SFRN, MSTP T32 GM008361This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.