The Effect Of Rosiglitazone On Hypertrophy Of Myocyte Induced By Angiotensine Ⅱ And Its Mechanism

Objective: To observe the effect of rosiglitazone on hypertrophy and increase secreation of ANP of cultured cardiomyocyte induced by angiotensineII and the role of NF-κB in this effect . Method:Primary cardiomyocytes were isolated from Sprague-Dawley neonatal rats (1 to 3 days old) ventricles by enzymatic digestiontrypsin digestion and different paste speed of cells. The cells were not used before treated with bromodeoxyuridine (Brdu) for 48 hours. Neonatal rat ventricular myocyte(NRVM) were exposed to rosiglitazone /PDTC, AngII (1 μmol/L) , or AngII combined with rosiglitazone/PDTC treatment for 24 hours. Cardiomyocytes hypertrophy were determined by cell surface area, protein content, and protein synthesis which were assessed by semiautomatic, computer-assisted planimetry, Coomassie and 3 H-Leucine incorporation into myocytes respectively. Activation of NF-κB in the cells was examined by using quantitative confocal immunfluorescence microscopy. Radio immune assay method was used to determine ANP concentration of culture supernatants, ELISA for TNF α, and RT-PCR for TNF αmRNA. Results: (1)Compared with control group, cell surface area,incorparation of 3 H-Leucine and protein content increased by 203.5%, 77.26% and75.5% respectively of NRVM treated with AngII. PPARγagonists- rosiglitazone markedly inhibited AngII-dependent increase in cell surface area, protein content and 3 H-Leucine incorparation : 5μmol/L rosiglitazone by 19.09%, 24.02% and 40.18% respectively; 50μmol/L rosiglitazone by 47.57%, 58.56%, and 78.42% respectively. Rosiglitazone also abolished markedly AngII stimulated increase of ANP in culture supernatants: 5μmol/L by 47.88%(* without significance); 50μmol/L by 86.75%. (2)A similarly depressed of cadiomyocyte hypertrophy was also seen markedly in cells treated with PDTC combined with AngII: 10μmol/L abolished AngII-dependent increase in cell surface area, protein content ,3 H-Leucine incorparation and ANP concetration by37.00%, 37.99%. 60.18%, 81.83% respetively and 100μmol/L by 85.95%,99.96%, 109.96%, 113.34% respectively.(3)Compared with control group , AngII significantly induced increase in NF-κB expression and translocation to nucleus. The amount of NF- κB immunoreactive signal at sites of introcellular in myocytes treated with AngII combined rosiglitazone(50μmol/L) were much larger than in myocytes treated with AngII only (1837.13±328.47 versus 2712.37±344.80, respectively). PDTC also significantly abolished the AngII stimulated increase by 31.5%. (All the differences are significant except for the ANP decrease induced by 5μmol/L rosiglitazone.) ( 4 ) Compared with control group, AngII stimulation for 24h significantly increased of TNF-α concetration in supercontant. Pretreatment with rosigliatazone and PDTC markedly caused 48.93%, 95.94% decrease in TNF-α that was inducded by AngII respectively. There were barely no TNF-αmRNA expression in control group, the levels of TNF-αmRNA expression were 0.41±0.09, 0.53±0.15, 0.78±0.21 in AngⅡ, AngⅡcombined rosiglitazone, AngⅡcombined with PDTC groups(n=5).The differences among any two groups were significantly Conclusions: These results suggest that PPAR-[gamma] activationinterferes with the signaling pathway of Ang Ⅱ –induced cardiac hypertrophy through negative regulation of NF-κB binding activity, partly via inhibition of the expression of TNF-α in cultured cardiomyocytes.