Abstract 15: Baicalein Protects Cardiomyocytes Against H2O2-induced Mitochondrial Injury
Introduction: Baicalein is a flavonoid compound extracted from Scutellaria baicalensis root that scavenges reactive oxygen species (ROS) and protects against cardiomyocyte ischemia/reperfusion (I/R) injury. Our prior work suggests that flavonoids can induce Akt-mediated cardioprotection. Akt and JNK, ROS-sensitive signaling pathways, play opposing roles during I/R that may affect mitochondrial function. In addition, optimal cardioprotection may require mitochondrial Akt localization. We hypothesized that baicalein protects cardiomyocytes against ROS-induced mitochondrial injury by decreasing JNK activation and increasing Akt activation with mitochondrial localization.
Methods: Primary chick embryonic ventricular cardiomyocytes (4–5 days) were exposed to severe oxidant stress using H2O2 500 μM for 2 h. Bailcalein (25 μM) was administered 2 h prior to and during H2O2 exposure. Intracellular ROS was measured by 6-carboxy-2′,7′-dichlorodihydrofluorescein diacetate (DCF) and the mitochondrial superoxide indicator Mito-SOXTM red. Viability was assessed by propidium iodide and apoptosis was measured by DNA fragmentation. Phosphorylation of Akt (p-Akt) and JNK (p-JNK) was analyzed by western blot. Cellular fractionation was used to assess mitochondrial cytotchrome c release, Akt localization and phosphorylation of its target GSK 3β.
Results: Baicalein significantly reduced cell death (31.2 ± 3.9% vs. 45.3 ± 6.2% in control, n=8, p<0.01) and DNA fragmentation caused by H2O2. It attenuated ROS generation as measured by DCF (679 ± 83 vs. 903 ± 93 a.u., n=6, p<0.05) and mitochondrial superoxide as measured by Mito-SOXTM red (1.14 ± 0.03 vs. 1.38 ± 0.04, n=4, p<0.05). Baicalein increased p-Akt (Thr308 and Ser473) and decreased p-JNK during H2O2 exposure. Furthermore, baicalein increased mitochondrial p-Akt (Thr308) and p-GSK 3β (Ser9), and decreased mitochondrial cytochrome c release.
Conclusions: Baicalein protected cardiomyocytes against severe oxidative injury by attenuating ROS, DNA fragmentation and cell death. This cardioprotection was associated with increased p-Akt and decreased p-JNK. The antioxidant properties of baicalein may preserve mitochondrial function by increasing mitochondrial Akt localization.
- © 2010 by American Heart Association, Inc.