title: Fatty acids induce apoptosis in human smooth muscle cells depending on chain length, saturation, and duration of exposure.
abstract: OBJECTIVE
  Plasma free fatty acid (FFA) concentrations are increased in states of insulin resistance. Therefore, this study evaluated apoptosis and underlying mechanisms induced by selected nutritional FFAs, a defined FFA-mix, and human plasma containing high FFA concentrations in human smooth muscle cells (HSMCs).
  
  
  METHODS
  HSMCs were incubated (24-72 h) with selected FFAs (100-300 micromol/l), an FFA-mix (palmitic-/stearic-/oleic-/linoleic-/alpha-linolenic acid=2.6/1/3.6/9/1; 300-900 micromol/l), or with high FFA-plasma (600 micromol/l) versus respective control cultures. Apoptosis, caspase activation, and protein expression were determined by DNA-fragmentation assays, flow cytometry, and Western blots, respectively.
  
  
  RESULTS
  Exposure (24h) of HSMCs to 300 micromol/l stearic-, oleic-, linoleic-, alpha-linolenic-, and arachidonic acid induced apoptosis, correlating (p<0.01) with the FFAs' chain length (r=0.602) and number of FFA double bonds (r=0.956). After 48 h, 100 micromol/l of all tested FFAs - including palmitic acid - were already sufficient to trigger HSMCs' cell death. FFA-exposure resulted in activation of caspases and apoptosis was completely abolished by co-incubation with caspase inhibitors and negatively correlated (p<0.01) with the base-excision repair protein XRCC1 (r=-0.765) and with c-myc's antagonist mad (r=-0.916), whereas positive correlations (p<0.01) were found for protein expression of the proto-oncogene c-myc (r=0.972) and the transcription factor E2F-1 (r=0.971). Exposure of HSMCs to the defined FFA-mix and to plasma samples from individuals with elevated plasma FFAs supported the results obtained by defined FFA stimulation.
  
  
  CONCLUSIONS
  Since smooth muscle cells surround the macrophage/foam cell/lipid-laden artheromatous core of atherosclerotic lesions with a protective fibrous cap, their FFA-induced HSMC apoptosis could contribute to progression of atherosclerosis by thinning of the fibrous cap and subsequent plaque destabilization.
authors.affiliation: Department of Internal Medicine III, Clinical Division of Endocrinology and Metabolism, Medical University of Vienna, Währinger Gürtel 18-20, A-1090 Vienna, Austria. michaela.artwohl@meduniwien.ac.at
authors.forename: Michaela
authors.initials: M
authors.lastname: Artwohl
authors.forename: Andrea
authors.initials: A
authors.lastname: Lindenmair
authors.forename: Michael
authors.initials: M
authors.lastname: Roden
authors.forename: Werner-Klaus
authors.initials: WK
authors.lastname: Waldhäusl
authors.forename: Angelika
authors.initials: A
authors.lastname: Freudenthaler
authors.forename: Gabriele
authors.initials: G
authors.lastname: Klosner
authors.forename: Aysegül
authors.initials: A
authors.lastname: Ilhan
authors.forename: Anton
authors.initials: A
authors.lastname: Luger
authors.forename: Sabina M
authors.initials: SM
authors.lastname: Baumgartner-Parzer
mesh_terms: D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology*; D016718:Arachidonic Acid / Q000494:pharmacology; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors / Q000378:metabolism; D020169:Caspases / Q000378:metabolism; D002478:Cells, Cultured; D045304:Cytochromes c / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D050687:E2F1 Transcription Factor / Q000378:metabolism; D005230:Fatty Acids, Nonesterified / Q000494:pharmacology*; D006801:Humans; D019787:Linoleic Acid / Q000494:pharmacology; D009131:Muscle, Smooth, Vascular / Q000166:cytology* / Q000187:drug effects*; D032389:Myocytes, Smooth Muscle / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D019301:Oleic Acid / Q000494:pharmacology; D019308:Palmitic Acid / Q000494:pharmacology; D000090063:Proto-Oncogene Mas; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism; D013229:Stearic Acids / Q000494:pharmacology; D014470:Umbilical Cord / Q000166:cytology; D000076105:X-ray Repair Cross Complementing Protein 1; D017962:alpha-Linolenic Acid / Q000494:pharmacology
chemical_list: D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D004268:DNA-Binding Proteins; D050687:E2F1 Transcription Factor; C493753:E2F1 protein, human; D005230:Fatty Acids, Nonesterified; C000715470:MAS1 protein, human; C079439:MXD1 protein, human; C489427:MYC protein, human; D000090063:Proto-Oncogene Mas; D016271:Proto-Oncogene Proteins c-myc; D012097:Repressor Proteins; D013229:Stearic Acids; D000076105:X-ray Repair Cross Complementing Protein 1; C000619371:XRCC1 protein, human; D017962:alpha-Linolenic Acid; D016718:Arachidonic Acid; D019301:Oleic Acid; D019308:Palmitic Acid; C031183:stearic acid; D045304:Cytochromes c; D019787:Linoleic Acid; D020169:Caspases