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

• Published in: Atherosclerosis Vol. 202; no. 2; pp. 351 - 362
• Main Authors: Artwohl, Michaela, Lindenmair, Andrea, Roden, Michael, Waldhäusl, Werner-Klaus, Freudenthaler, Angelika, Klosner, Gabriele, Ilhan, Aysegül, Luger, Anton, Baumgartner-Parzer, Sabina M
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Ireland Ltd 01-02-2009; Elsevier
• Subjects: alpha-Linolenic Acid - pharmacology; Apoptosis; Apoptosis - drug effects; Apoptosis - physiology; Arachidonic Acid - pharmacology; Atherosclerosis (general aspects, experimental research); Basic Helix-Loop-Helix Leucine Zipper Transcription Factors - metabolism; Biological and medical sciences; Blood and lymphatic vessels; Blood vessels and receptors; c-myc; Cardiology. Vascular system; Cardiovascular; Caspases; Caspases - metabolism; Cells, Cultured; Cytochromes c - metabolism; DNA-Binding Proteins - metabolism; E2F-1; E2F1 Transcription Factor - metabolism; Fatty Acids, Nonesterified - pharmacology; Free fatty acids; Fundamental and applied biological sciences. Psychology; Human plasma; Humans; Linoleic Acid - pharmacology; mad; Medical sciences; 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 Proteins c-myc - metabolism; Repressor Proteins - metabolism; Smooth muscle cells; Stearic Acids - pharmacology; Umbilical Cord - cytology; Vertebrates: cardiovascular system; X-ray Repair Cross Complementing Protein 1; XRCC1; FFA; Human plasma; c-myc; XRCC1; phenylmethylsulfonyl fluoride; Smooth muscle cells; HSMCs; Free fatty acids; Dulbecco's Modified Eagle's Medium; DMEM; X-ray repair cross-complementing 1; mad; FITC; PMSF; free fatty acid; FCS; human smooth muscle cells; E2F-1; fetal calf serum; VSMC; vascular smooth muscle cell; Caspases; fluorescein isothiocyanate; Apoptosis; Human; Enzyme; Cysteine endopeptidases; Saturation; Lipids; Smooth muscle; Cardiovascular disease; Free fatty acid; Vascular disease; Peptidases; Atherosclerosis; Hydrolases
• ISSN: 0021-9150; 1879-1484
• DOI: 10.1016/j.atherosclerosis.2008.05.030

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 μmol/l), an FFA-mix (palmitic-/stearic-/oleic-/linoleic-/α-linolenic acid = 2.6/1/3.6/9/1; 300–900 μmol/l), or with high FFA-plasma (600 μmol/l) versus respective control cultures. Apoptosis, caspase acitvation, and protein expression were determined by DNA-fragmentation assays, flow cytometry, and Western blots, respectively. Results Exposure (24 h) of HSMCs to 300 μmol/l stearic-, oleic-, linoleic-, α-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 μmol/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.