Baicalein Protects Cardiomyocytes Against Mitochondrial Oxidant Injury Associated with JNK Inhibition and Mitochondrial Akt Activation

Baicalein, a flavonoid derived from Scutellaria baicalensis Georgi, possesses cardioprotection against oxidant injury by scavenging reactive oxygen species (ROS). Few studies investigate whether baicalein protection is mediated by attenuating mitochondrial ROS and modulating the prosurvival and proapoptotic signaling. Primary cultured chick cardiomyocytes were used to study the role of baicalein in mitochondrial superoxide (O-2(center dot-)) generation and signaling of Akt and JNK. Cells were exposed to H2O2 for 2 h and baicalein was given 2 h prior to and during 2 h of H2O2 exposure. Cell viability was assessed by propidium iodide and DNA fragmentation. H2O2 (500 mu M) significantly induced 45: 3 +/- 6: 2% of cell death compared to the control (p < 0: 001) and resulted in DNA laddering. Baicalein (10, 25 or 50 mu M) dose-dependently reduced the cell death to 38: 7 +/- 5: 6% (p < 0: 226); 31: 2 +/- 3: 9% (p < 0: 01); 30: 3 +/- 5: 3% (p < 0: 01), respectively. It also attenuated DNA laddering. Further, baicalein decreased intracellular ROS and mitochondrial O-2(center dot-) generation that was confirmed by superoxide dismutase PEG-SOD and mitochondria electron transport chain complex III inhibitor stigmatellin. In addition, baicalein increased Akt phosphorylation and decreased JNK phosphorylation in H2O2-exposed cells. Moreover, baicalein augmented mitochondrial phosphorylation of Akt Thr308 and GSK3 beta Ser9, and prevented mitochondrial cytochrome c release assessed by cellular fractionation. Our results suggest that baicalein cardioprotection may involve an attenuation of mitochondrial O-2(center dot-) and an increase in mitochondrial phosphorylation of Akt and GSK3 beta while decreasing JNK activation.