Docosahexaenoic acid, a peroxisome proliferator-activated receptor-alpha ligand, induces apoptosis in vascular smooth muscle cells by stimulation of p38 mitogen-activated protein kinase.
Omega-3 fatty acids (n-3 FAs) have been shown to exert a blood pressure-lowering effect in hypertension, possibly in part by influencing vascular structure. We previously demonstrated that n-3 FAs induce vascular smooth muscle cell (VSMC) apoptosis, which could exert an effect on the structure of blood vessels. In the present study, we investigated signaling pathways through which n-3 FAs mediate apoptosis in VSMCs. Cultured mesenteric VSMCs from Sprague-Dawley rats were stimulated with docosahexaenoic acid (DHA), a representative n-3 FAs. Morphological changes in apoptosis and DNA fragmentation were examined with phase-contrast microscopy and fluorescence microscopy with Hoechst 33342 staining. To clarify possible pathways of apoptosis, we evaluated the expression of phosphorylated p38 mitogen-activated protein kinases, bax, bcl-2, cytochrome c, and peroxisome proliferator-activated receptor-alpha (PPAR-alpha) with Western blot analysis. DHA treatment induced cell shrinkage, cell membrane blebbing, and apoptotic bodies in VSMCs. DHA time-dependently activated p38 mitogen-activated protein kinases, bax, PPAR-alpha, and cytochrome c, with maximal effects obtained after 5 and 30 minutes and 1 and 3 hours, respectively. SB-203580 and SB-202190, selective p38 inhibitors, reduced DHA-elicited apoptosis and expression of PPAR-alpha but had no effect on the expression of bax or cytochrome c. The present results indicate that DHA induces apoptosis in VSMCs through >/=2 distinct mechanisms: (1) a p38-dependent pathway that regulates PPAR-alpha and (2) a p38-independent pathway via dissipation of mitochondrial membrane potential and cytochrome c release. The death-signaling pathway stimulated by DHA may involve an integration of these multiple pathways. By triggering VSMC apoptosis, DHA may play a pathophysiological role in vascular remodeling in cardiovascular disease.
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MRC Multidisciplinary Research Group on Hypertension, Clinical Research Institute of Montreal, University of Montreal, Montreal, Quebec, Canada.
Touyz
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Schiffrin
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D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D015153:Blotting, Western; D002478:Cells, Cultured; D053938:DNA Fragmentation / Q000187:drug effects; D004281:Docosahexaenoic Acids / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D020928:Mitogen-Activated Protein Kinases / Q000187:drug effects / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000166:cytology* / Q000187:drug effects* / Q000378:metabolism; D020025:Peroxisome Proliferators / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018160:Receptors, Cytoplasmic and Nuclear / Q000187:drug effects / Q000502:physiology*; D014157:Transcription Factors / Q000187:drug effects / Q000502:physiology*; D048051:p38 Mitogen-Activated Protein Kinases
D020025:Peroxisome Proliferators; D018160:Receptors, Cytoplasmic and Nuclear; D014157:Transcription Factors; D004281:Docosahexaenoic Acids; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases