Characteristics of catechin- and theaflavin-mediated cardioprotection.
Catechins and theaflavins-the main polyphenolic substances of green and black tea, respectively-exert a plethora of beneficial effects on the cardiovascular system. In a model of H(2)O(2)-mediated oxidative stress, we investigated the effects of epigallocatechin-3-gallate (EGCG) and theaflavin-3,3'-digallate (TF3) on neonatal rat cardiomyocytes. Pretreatment with EGCG or TF3 1 hr prior to induction of oxidative stress by H(2)O(2) effectively protected cardiac myocytes as determined by measuring release of lactate dehydrogenase after 24 hrs. Longer pre-incubation times resulted in significant loss of protection. To enable further mechanistic insight, we investigated expression of antioxidative enzymes and activation of prosurvival signaling cascades. Whereas mRNA levels of glutathione peroxidase 3, superoxide dismutase 1, and catalase were not influenced by both polyphenols, heme oxygenase (HO-1) was selectively upregulated by EGCG-but not by TF3. However, inhibition of HO-1 did not diminish polyphenol-mediated cardioprotection. While EGCG and TF3 activated Akt, extracellular signal-regulated kinase 1/2, and p38 mitogen-activated protein kinase, inhibition of these kinases did not attenuate polyphenol-mediated protection. Loading of cardiomyocytes with dichlorofluorescein revealed that intracellular levels of reactive oxygen species were significantly reduced after treatment with EGCG or TF3 as early as 30 mins after induction of oxidative stress. In conclusion, activation of prosurvival signaling kinases and upregulation of antioxidative enzymes do not play a major role in tea polyphenol-mediated cardioprotection.
Dreger
Henryk
H
Medizinische Klinik m. S. Kardiologie und Angiologie (CCM), Charité - Universitätsmedizin Berlin, Charitéplatz 1, D - 10117 Berlin, Germany.
Lorenz
Mario
M
Kehrer
Alexandra
A
Baumann
Gert
G
Stangl
Karl
K
Stangl
Verena
V
D000818:Animals; D000831:Animals, Newborn; D000975:Antioxidants / Q000378:metabolism*; D044946:Biflavonoids / Q000378:metabolism*; D002316:Cardiotonic Agents / Q000378:metabolism*; D002392:Catechin / Q000031:analogs & derivatives* / Q000378:metabolism; D002478:Cells, Cultured; D005707:Gallic Acid / Q000031:analogs & derivatives* / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism; D032383:Myocytes, Cardiac / Q000166:cytology / Q000378:metabolism; D016877:Oxidants / Q000378:metabolism; D018384:Oxidative Stress; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D013662:Tea / Q000737:chemistry; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
D000975:Antioxidants; D044946:Biflavonoids; D002316:Cardiotonic Agents; D016877:Oxidants; D017382:Reactive Oxygen Species; D013662:Tea; C088983:theaflavine gallate; D005707:Gallic Acid; D002392:Catechin; D006861:Hydrogen Peroxide; C045651:epigallocatechin gallate; D051057:Proto-Oncogene Proteins c-akt; D048051:p38 Mitogen-Activated Protein Kinases