(-)Epigallocatechin gallate and quercetin enhance survival signaling in response to oxidant-induced human endothelial apoptosis.
We reported recently that (-)epigallocatechin gallate and quercetin inhibited H2O2-induced apoptosis through modulation of the expression of apoptosis-related Bcl-2 and Bax in endothelial cells. This study attempted to identify possible regulatory sites and mechanisms of antiapoptotic flavonoids, focusing on ROS-mediated signaling in HUVEC. The effects of apigenin on the signaling pathway downstream were compared. Submillimolar H2O2 caused >30% cell killing with intracellular oxidant generation. H2O2-induced oxidant generation markedly decreased total intracellular glutathione (GSH) levels. Micromolar (-)epigallocatechin gallate and quercetin partially eliminated the dichlorodihydrofluorescein (DCF) and phospho-p53 staining, suggesting that these flavonoids inhibited the accumulation of intracellular oxidants and nuclear transactivation of p53 in H2O2-exposed cells. In contrast, cells treated with apigenin remained DCF and phospho-p53 staining positive in response to H2O2. (-)Epigallocatechin gallate significantly raised the total GSH level that had been depleted by H2O2. Caspase-3 activity was enhanced by H2O2, and this increase was inhibited by (-)epigallocatechin gallate and quercetin. Additionally, the upregulation of caspase-3 activation was reversed by these flavonoids at > or =10 micromol/L; these inhibitory effects were dose dependent. Western blot data revealed that H2O2 upregulated phosphorylation of c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (MAPK), which was rapidly reversed by quercetin within 30 min; H2O2 activation of c-Jun was downregulated. (-)Epigallocatechin gallate inhibited H2O2-induced phosphorylation of JNK and p38 MAPK after 60 min. These results reveal that quercetin blocks JNK- and p38 MAPK-related signaling triggered by the oxidant and may regulate expression of apoptotic downstream genes, preventing apoptosis and promoting cell survival. (-)Epigallocatechin gallate may function as an antiapoptotic agent through other antiapoptotic pathways.
Choi
Yean-Jung
YJ
Division of Life Sciences and Silver Biotechnology Research Center, Hallym University, Chuncheon, Korea.
Jeong
Yu-Jin
YJ
Lee
Yong-Jin
YJ
Kwon
Hyang-Mi
HM
Kang
Young-Hee
YH
D017209:Apoptosis / Q000187:drug effects*; D002392:Catechin / Q000031:analogs & derivatives* / Q000494:pharmacology*; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects*; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D005978:Glutathione / Q000378:metabolism; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D048670:MAP Kinase Kinase 4; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D016877:Oxidants / Q000633:toxicity; D010766:Phosphorylation; D011794:Quercetin / Q000494:pharmacology*; D017382:Reactive Oxygen Species / Q000494:pharmacology; D014471:Umbilical Veins
D016877:Oxidants; D017382:Reactive Oxygen Species; D002392:Catechin; D011794:Quercetin; D006861:Hydrogen Peroxide; C045651:epigallocatechin gallate; D048031:JNK Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases; D005978:Glutathione