Peroxisome Proliferator-Activated Receptor α Agonists Enhance Cardiomyogenesis of Mouse ES Cells by Utilization of a Reactive Oxygen Species-Dependent Mechanism

Peroxisome proliferator-activated receptors (PPARα, -β and -γ) 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 PPARα, -β, and -γ mRNA during differentiation of ES cells towards cardiac cells. Treatment with PPARα agonists (WY14643, GW7647, and ciprofibrate) significantly increased cardiomyogenesis and expression of the cardiac genes MLC2a, ANP, MHC-β, MLC2v, and cardiac α-actin. Furthermore, WY14643 increased PPARα gene expression and the expression of the cardiogenic transcription factors GATA-4, Nkx2.5, DTEF-1, and MEF 2C. In contrast, the PPARα antagonist MK886 decreased cardiomyogenesis, whereas the PPARβ agonist L-165,041 as well as the PPARγ agonist GW1929 were without effects. Treatment with PPARα, but not PPARβ, and PPARγ 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 PPARα agonists on cardiomyogenesis of ES cells was abolished upon preincubation with free radical scavengers and NADPH oxidase inhibitors, indicating involvement of ROS in PPARα, mediated cardiac differentiation. In summary, our data indicate that stimulation of PPARα but not PPARβ and -γ enhances cardiomyogenesis in ES cells using a pathway that involves ROS and NADPH oxidase activity. Disclosure of potential conflicts of interest is found at the end of this article.