cytochrome-c-t and stearic-acid

In this study we have tested the effect of unsaturated fatty acids on the proapoptotic effects of saturated fatty acids in the human pancreatic β-cells NES2Y.. We found that unsaturated palmitoleic and oleic acid at a concentration of 0.2 mM and higher are able to completely inhibit the proapoptotic effect of their counterpart saturated palmitic and stearic acid at a concentration of 1 mM. Apoptosis induced by stearic acid was associated with significant activation of caspase-6, -7, -9, -2 and -8, but not with significant activation of caspase-3. The activation of caspases was blocked by coincubation with oleic acid. Stearic acid treatment was not associated with a significant change in mitochondrial membrane potential, reactive oxygen species level and with cytochrome c release from mitochondria. Furthermore, stearic acid treatment was not associated with changes in p21(WAF1/CIP1), PIDD, Fas receptor and Fas ligand expression. However, we detected endoplasmic reticulum (ER) stress markers, i. e. a significant upregulation of BiP and CHOP expression as well as XBP1 mRNA splicing. These changes were inhibited by coincubation with oleic acid.. Presented data indicate that oleic acid inhibits apoptosis induction by stearic acid in NES2Y cells upstream of caspase activation and ER stress induction. It does not involve an interference with the mitochondrial pathway of apoptosis induction, with p53 activation and PIDD expression as well as with Fas receptor and Fas ligand expression.

Topics: Apoptosis; Caspases; Cell Line, Transformed; Cytochromes c; DNA-Binding Proteins; Endoplasmic Reticulum; Endoplasmic Reticulum Chaperone BiP; Enzyme Activation; Fatty Acids, Monounsaturated; Flow Cytometry; Gene Expression; Heat-Shock Proteins; Humans; Insulin-Secreting Cells; Membrane Potential, Mitochondrial; Mitochondria; Oleic Acid; Regulatory Factor X Transcription Factors; RNA Splicing; RNA, Messenger; Stearic Acids; Stress, Physiological; Transcription Factor CHOP; Transcription Factors; Up-Regulation; X-Box Binding Protein 1

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).. 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.. 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.. 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.

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