Figure 1

T3-dependent mitogenic signaling requires H₂O₂ and mitochondrial biogenesis. (A) Mito-TEMPO impedes the increases in media H₂O₂ levels that results due to T3 (10 nmol/L) treatment of neonatal cardiomyocytes in culture. (B) Representative immunoblots and quantitative analyses showing that T3 treatment to neonatal cardiomyocytes in culture increases phosphorylated-ERK (p-ERK1/2 T202/Y204) protein levels as well as cyclins D1, A2 and B1 in a concentration-dependent manner. (C) Inhibition of T3 (10 nmol/L)-dependent ERK1/2 activation by the ERK1/2 inhibitor (PD98059) repressed cyclin D1/B1 expression. (D) Scavenging H₂O₂ with PEG-catalase (200 U/ml) inhibited T3 (10 nmol/L)-mediated p-ERK1/2 and cyclin D1/B1 accumulation. (E) Treatment of neonatal cardiomyocytes with low concentrations of H₂O₂ (1.5–15 µmol/L) increases phosphorylated-ERK (p-ERK1/2 T202/Y204) and cyclin B1 protein levels. (F) NRF1 siRNA knockdown prevented TFAM expression and simultaneously reduced cyclin B1 accumulation as compared to treatment with scrambled siRNA. *P < 0.05; **P < 0.01; ***P < 0.001 compared to groups indicated on the graph. n = 4/group. Error bars indicate SEM.