title: Effects of EGCG content in green tea extract on pharmacokinetics, oxidative status and expression of inflammatory and apoptotic genes in the rat ocular tissues.
abstract: Green tea extract (GTE) exerts antioxidative activities in ocular tissues of rats, but high levels of (-)-epigallocatechin gallate (EGCG) can induce oxidative stress. In this study, pharmacokinetics, diurnal variation of oxidative status, antioxidation and transcription factors changes in ocular tissues of rats were investigated. Rats were fed intragastrically with GTE and catechin mixtures containing different amounts of EGCG. Plasma and various ocular tissues were taken for pharmacokinetic analysis, oxidation marker testings and gene expression assays. Effects of EGCG on ocular oxidation status were assessed by 8-isoprostane level and reduced/oxidized glutathione ratio. Oxidation, inflammation and apoptosis regulations in retina were evaluated by real-time polymerase chain reaction. Epicatechin, epigallocatechin and EGCG were dominant in various ocular tissues except vitreous humor, where gallocatechin was predominant. Diurnal variation of oxidative status was found in some compartments. GTE caused oxidative stress increase in the plasma, aqueous humor, vitreous humor, cornea and retina but decrease in the lens and choroid-sclera. Catechins mixture containing half dose of EGCG lowered 8-isoprostane in the retina and lens. GTE treatment induced superoxide dismutase 1 and glutathione peroxidase-3 expressions but suppressed catalase in the retina. Our results reveal pro-oxidation of GTE with high EGCG content to the ocular tissues. Optimal EGCG level is needed for protection.
authors.affiliation: Department of Ophthalmology and Visual Sciences, the Chinese University of Hong Kong; Department of Obstetrics and Gynaecology, the Chinese University of Hong Kong.
authors.forename: Kai On
authors.initials: KO
authors.lastname: Chu
authors.affiliation: Department of Ophthalmology and Visual Sciences, the Chinese University of Hong Kong.
authors.forename: Kwok Ping
authors.initials: KP
authors.lastname: Chan
authors.affiliation: Department of Ophthalmology and Visual Sciences, the Chinese University of Hong Kong.
authors.forename: Ya Ping
authors.initials: YP
authors.lastname: Yang
authors.affiliation: Department of Ophthalmology and Visual Sciences, the Chinese University of Hong Kong.
authors.forename: Yong Jie
authors.initials: YJ
authors.lastname: Qin
authors.affiliation: Department of Ophthalmology and Visual Sciences, the Chinese University of Hong Kong.
authors.forename: Wai Ying
authors.initials: WY
authors.lastname: Li
authors.affiliation: School of Biomedical Sciences, The Chinese University of Hong Kong.
authors.forename: Sun On
authors.initials: SO
authors.lastname: Chan
authors.affiliation: Department of Obstetrics and Gynaecology, the Chinese University of Hong Kong.
authors.forename: Chi Chiu
authors.initials: CC
authors.lastname: Wang
authors.affiliation: Department of Ophthalmology and Visual Sciences, the Chinese University of Hong Kong. Electronic address: cppang@cuhk.edu.hk.
authors.forename: Chi Pui
authors.initials: CP
authors.lastname: Pang
mesh_terms: D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology; D000975:Antioxidants / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics*; D002392:Catechin / Q000031:analogs & derivatives* / Q000097:blood / Q000493:pharmacokinetics / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D009877:Endophthalmitis / Q000178:diet therapy / Q000235:genetics*; D005123:Eye / Q000187:drug effects / Q000503:physiopathology; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D018384:Oxidative Stress / Q000187:drug effects; D010936:Plant Extracts / Q000737:chemistry; D017207:Rats, Sprague-Dawley; D013662:Tea / Q000737:chemistry*; D014822:Vitreous Body / Q000187:drug effects
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D000975:Antioxidants; D010936:Plant Extracts; D013662:Tea; D002392:Catechin; C045651:epigallocatechin gallate
keywords: Dosage effect; Epigallocatechin gallate; Green tea extract; Ocular tissue; Oxidative stress