Fatty acids induce apoptosis in human smooth muscle cells depending on chain length, saturation, and duration of exposure

Atherosclerosis. 2009 Feb;202(2):351-62. doi: 10.1016/j.atherosclerosis.2008.05.030. Epub 2008 May 28.

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).

Research design and 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.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Apoptosis / drug effects*
  • Apoptosis / physiology*
  • Arachidonic Acid / pharmacology
  • Basic Helix-Loop-Helix Leucine Zipper Transcription Factors / metabolism
  • Caspases / metabolism
  • Cells, Cultured
  • Cytochromes c / metabolism
  • DNA-Binding Proteins / metabolism
  • E2F1 Transcription Factor / metabolism
  • Fatty Acids, Nonesterified / pharmacology*
  • Humans
  • Linoleic Acid / pharmacology
  • Muscle, Smooth, Vascular / cytology*
  • Muscle, Smooth, Vascular / drug effects*
  • Myocytes, Smooth Muscle / cytology
  • Myocytes, Smooth Muscle / drug effects
  • Myocytes, Smooth Muscle / metabolism
  • Oleic Acid / pharmacology
  • Palmitic Acid / pharmacology
  • Proto-Oncogene Mas
  • Proto-Oncogene Proteins c-myc / metabolism
  • Repressor Proteins / metabolism
  • Stearic Acids / pharmacology
  • Umbilical Cord / cytology
  • X-ray Repair Cross Complementing Protein 1
  • alpha-Linolenic Acid / pharmacology

Substances

  • Basic Helix-Loop-Helix Leucine Zipper Transcription Factors
  • DNA-Binding Proteins
  • E2F1 Transcription Factor
  • E2F1 protein, human
  • Fatty Acids, Nonesterified
  • MAS1 protein, human
  • MXD1 protein, human
  • MYC protein, human
  • Proto-Oncogene Mas
  • Proto-Oncogene Proteins c-myc
  • Repressor Proteins
  • Stearic Acids
  • X-ray Repair Cross Complementing Protein 1
  • XRCC1 protein, human
  • alpha-Linolenic Acid
  • Arachidonic Acid
  • Oleic Acid
  • Palmitic Acid
  • stearic acid
  • Cytochromes c
  • Linoleic Acid
  • Caspases