title: Stearic acid accumulation in macrophages induces toll-like receptor 4/2-independent inflammation leading to endoplasmic reticulum stress-mediated apoptosis.
abstract: OBJECTIVE
  Elevated serum free fatty acid levels are associated with an increased risk of cardiovascular disease and type 2 diabetes mellitus. Macrophages are recruited to atherosclerotic plaques and metabolic tissues during obesity and accumulate lipids, including free fatty acids. We investigated the molecular consequences of intracellular saturated free fatty acid accumulation in macrophages.
  
  
  RESULTS
  Previously, we demonstrated that cotreatment of mouse peritoneal macrophages (MPMs) with stearic acid and triacsin C (an inhibitor of long-chain acyl coenzyme A synthetases) results in intracellular free fatty acid accumulation and apoptosis. Here, we used Western blotting analysis, real-time reverse transcription polymerase chain reaction, and terminal deoxynucleotidyl transferase dUTP nick-end labeling staining to assess endoplasmic reticulum (ER) stress, inflammation, and apoptosis in MPMs. Intracellular stearic acid accumulation induces Toll-like receptor 4/2-independent inflammation that results in ER stress-mediated apoptosis of MPMs. Polarization of MPMs to a proinflammatory M1 phenotype increases their susceptibility to inflammation and ER stress, but not apoptosis, in response to cotreatment with stearic acid and triacsin C.
  
  
  CONCLUSIONS
  Intracellular accumulation of stearic acid in MPMs activates inflammatory signaling, leading to ER stress-mediated apoptosis. M1 macrophages are more prone to stearic acid-induced inflammation and ER stress. These same pathways may be activated in macrophages residing in atherosclerotic plaques and metabolic tissues during conditions of obesity and hyperlipidemia.
authors.affiliation: Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232-0615, USA.
authors.forename: Emily K
authors.initials: EK
authors.lastname: Anderson
authors.forename: Andrea A
authors.initials: AA
authors.lastname: Hill
authors.forename: Alyssa H
authors.initials: AH
authors.lastname: Hasty
mesh_terms: D000818:Animals; D017209:Apoptosis; D016764:Cell Polarity; D059865:Endoplasmic Reticulum Stress / Q000502:physiology*; D007249:Inflammation / Q000209:etiology*; D008264:Macrophages / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D013229:Stearic Acids / Q000378:metabolism*; D051195:Toll-Like Receptor 2 / Q000502:physiology; D051197:Toll-Like Receptor 4 / Q000502:physiology
chemical_list: D013229:Stearic Acids; C493486:Tlr2 protein, mouse; C493487:Tlr4 protein, mouse; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; C031183:stearic acid