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[摘要]：Peroxisome proliferator-activated receptors (PPAR alpha and -gamma) are nuclear receptors involved in transcriptional regulation of lipid and energy metabolism. Since the energy demand increases when cardiac progenitor cells are developing rhythmic contractile activity, PPAR activation may play a critical role during cardiomyogenesis of embryonic stem (ES) cells. It is shown that ES cells express PPAR alpha, -beta, and -gamma mRNA during differentiation of ES cells towards cardiac cells. Treatment with PPAR alpha agonists (WY14643, GW7647, and ciprofibrate) significantly increased cardiomyogenesis and expression of the cardiac genes MLC2a, ANP, MHC-beta, MLC2v, and cardiac alpha-actin. Furthermore, WY14643 increased PPAR alpha gene expression and the expression of the cardiogenic transcription factors GATA-4, Nkx2.5, DTEF-1, and MEF 2C. In contrast, the PPAR alpha antagonist MK886 decreased cardiomyogenesis, whereas the PPAR beta agonist L-165,041 as well as the PPAR gamma agonist GW1929 were without effects. Treatment with PPAR alpha, but not PPAR beta, and PPAR gamma agonists and MK886, resulted in generation of reactive oxygen species (ROS), which was inhibited in the presence of the NADPH oxidase inhibitors diphenylen iodonium (DPI) and apocynin and the free radical scavengers vitamin E and N-(2-mercapto-propionyl)-glycine (NMPG), whereas the mitochondrial complex I inhibitor rotenone was without effects. The effect of PPAR alpha agonists on cardiomyogenesis of ES cells was abolished upon preincubation with free radical scavengers and NADPH oxidase inhibitors, indicating involvement of ROS in PPAR alpha, mediated cardiac differentiation. In summary, our data indicate that stimulation of PPAR alpha but not PPAR beta and -gamma enhances cardiomyogenesis in ES cells using a pathway that involves ROS and NADPH oxidase activity. |
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