ABSTRACT
AIM: To investigate the role and signal mechanism of PPAR-α in the pathogenesis of cardiac hypertrophy. METHODS: Small interfering RNA (siRNA) was applied to efficiently silence the gene expression of PPAR-α in cardiac myocytes. [~3H] leucine incorporation assay was performed to measure protein synthesis. Reverse transcription-polymerase chain reaction (RT-PCR) was used to analyze the mRNA level of atrial natriuretic factor (ANF) and PPAR-α. Western blotting analysis was performed to investigate the levels of phosphorylation of protein kinase B (PKB/Akt) and glycogen synthase kinase 3β (GSK3β). Immunofluorescence analysis was used to examine the cellular localization of NFATc4. RESULTS: (1)RSS304168 was the most efficient stealth RNAi duplex to specifically inhibit PPAR-α expression. (2)RSS304168 significantly potentiated the ET-1-induced cardiomyocyte hypertrophy and enhanced ET-1-induced protein synthesis and ANF mRNA expression in cardiomyocytes. Moreover, RSS304168 completely reversed the inhibitory effects of fenofibrate on ET-1-induced protein synthesis and ANF mRNA expression. (3)RSS304168 enhanced ET-1-induced phosphorylation of Akt at Ser473 and GSK3β at Ser9. The effects of ET-1 or ET-1 combined with RSS304168 on phosphorylation of Akt/GSK3β were completely blocked by LY294002, a PI3K specific inhibitor. Fenofibrate markedly inhibited ET-1-induced phosphorylation of Akt/GSK3β while RSS304168 abolished these effects of fenofibrate. (4)Fenofibrate prevented the nuclear translocation of NFATc4 induced by ET-1 while RSS304168 abolished this effect of fenofibrate. CONCLUSION: Activation of PPAR-α inhibits ET-1-induced cardiomyocyte hypertrophy through blocking Akt/GSK3β-NFATc4 signaling pathways.