title: Green tea epigallocatechin gallate binds to and inhibits respiratory complexes in swelling but not normal rat hepatic mitochondria.
abstract: Epigallocatechin gallate (EGCG), the major flavonoid in green tea, is consumed via tea products and dietary supplements, and has been tested in clinical trials. However, EGCG can cause hepatotoxicity in humans and animals by unknown mechanisms. Here EGCG effects on rat liver mitochondria were examined. EGCG showed negligible effects on oxidative phosphorylation at 7.5-100μM in normal mitochondria. However, respiratory chain complexes (RCCs) were profoundly inhibited by EGCG in mitochondria undergoing Ca(2+) overload-induced mitochondrial permeability transition (MPT). As RCCs are located in mitochondrial inner membranes (IM) and matrix, it was reasoned that EGCG could not readily pass through IM to affect RCCs in normal mitochondria but may do so when IM integrity is compromised. This speculation was substantiated in three ways. (1) Purified EGCG-bound proteins were barely detectable in normal mitochondria and contained no RCCs as determined by Western blotting, but swelling mitochondria contained about 1.5-fold more EGCG-bound proteins which included four RCC subunits together with cyclophilin D that locates in mitochondrial matrix. (2) Swelling mitochondria consumed more EGCG than normal ones. (3) The MPT blocker cyclosporine A diminished the above-mentioned difference. Among four subunits of RCC II, only SDHA and SDHB which locate in mitochondrial matrix, but not SDHC or SDHD which insert into the IM, were found to be EGCG targets. Interestingly, EGCG promoted Ca(2+) overload-induced MPT only when moderate MPT already commenced. This study identified hepatic RCCs as targets for EGCG in swelling but not normal mitochondria, suggesting EGCG may trigger hepatotoxicity by worsening pre-existing mitochondria abnormalities.
authors.affiliation: Division of Systems Biology, National Center for Toxicological Research, Food and Drug Administration, 3900 NCTR Road, Jefferson, AR 72079, USA.
authors.forename: Zuquan
authors.initials: Z
authors.lastname: Weng
authors.affiliation: Division of Systems Biology, National Center for Toxicological Research, Food and Drug Administration, 3900 NCTR Road, Jefferson, AR 72079, USA.
authors.forename: Peng
authors.initials: P
authors.lastname: Zhou
authors.affiliation: Division of Systems Biology, National Center for Toxicological Research, Food and Drug Administration, 3900 NCTR Road, Jefferson, AR 72079, USA.
authors.forename: William F
authors.initials: WF
authors.lastname: Salminen
authors.affiliation: Division of Systems Biology, National Center for Toxicological Research, Food and Drug Administration, 3900 NCTR Road, Jefferson, AR 72079, USA.
authors.forename: Xi
authors.initials: X
authors.lastname: Yang
authors.affiliation: Department of Occupational and Environmental Health, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA.
authors.forename: Alison H
authors.initials: AH
authors.lastname: Harrill
authors.affiliation: Division of Systems Biology, National Center for Toxicological Research, Food and Drug Administration, 3900 NCTR Road, Jefferson, AR 72079, USA.
authors.forename: Zhijun
authors.initials: Z
authors.lastname: Cao
authors.affiliation: PharmPoint Consulting, 17014 Hersperger Lane, Poolesville, MD 20837, USA.
authors.forename: William B
authors.initials: WB
authors.lastname: Mattes
authors.affiliation: Division of Systems Biology, National Center for Toxicological Research, Food and Drug Administration, 3900 NCTR Road, Jefferson, AR 72079, USA.
authors.forename: Donna L
authors.initials: DL
authors.lastname: Mendrick
authors.affiliation: Division of Systems Biology, National Center for Toxicological Research, Food and Drug Administration, 3900 NCTR Road, Jefferson, AR 72079, USA. Electronic address: Qiang.Shi@fda.hhs.gov.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Shi
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002392:Catechin / Q000031:analogs & derivatives* / Q000494:pharmacology; D045222:Electron Transport Chain Complex Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D008297:Male; D008930:Mitochondria, Liver / Q000187:drug effects* / Q000378:metabolism*; D033681:Mitochondrial Membrane Transport Proteins / Q000378:metabolism; D000083162:Mitochondrial Permeability Transition Pore; D008933:Mitochondrial Swelling / Q000187:drug effects*; D010085:Oxidative Phosphorylation / Q000187:drug effects; D011485:Protein Binding / Q000187:drug effects; D021122:Protein Subunits / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D016622:Silver Staining; D013662:Tea / Q000737:chemistry*
chemical_list: D045222:Electron Transport Chain Complex Proteins; D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; D021122:Protein Subunits; D013662:Tea; D002392:Catechin; C045651:epigallocatechin gallate
keywords: ATP; CsA; DS; EGCG; Epigallocatechin gallate; FDA; GTE; Green tea; HPLC; IC(50); IM; Liver; MGST1; MPT; MT-CO1; Mitochondria; NADH dehydrogenase [ubiquinone] iron-sulfur protein 3; NADH dehydrogenase [ubiquinone] iron-sulfur protein 8; NDUFS3; NDUFS8; RCCs; Rat; Respiratory chain complexes; SDHA; SDHB; SDHC; SDHD; U.S. Food and Drug Administration; UQCRC1; UQCRC2; adenosine triphosphate; cyclosporine A; dietary supplements; epigallocatechin gallate; green tea extract; half maximal inhibitory concentration; high-performance liquid chromatography; inner membranes; microsomal glutathione S-transferase 1; mitochondrial permeability transition; mitochondrially encoded cytochrome c oxidase I; respiratory chain complexes; succinate dehydrogenase complex, subunit A; succinate dehydrogenase complex, subunit B; succinate dehydrogenase complex, subunit C; succinate dehydrogenase complex, subunit D; ubiquinol-cytochrome c reductase core protein I; ubiquinol-cytochrome c reductase core protein II