title: Black tea protects against hypertension-associated endothelial dysfunction through alleviation of endoplasmic reticulum stress.
abstract: Hypertensive patients have been found to be associated with elevated levels of homocysteine, known as hyperhomocysteinemia. Homocysteine (Hcy) can induce endoplasmic reticulum (ER) stress in endothelial cells. This study aims to investigate whether black tea (BT) protects against hypertension-associated endothelial dysfunction through alleviation of ER stress. Rat aortae and cultured rat aortic endothelial cells were treated with Hcy, BT extract, and theaflavin-3,3'-digallate (TF3). Male Sprague Dawley rats were infused with angiotensin II (Ang II) to induce hypertension and orally administrated with BT extract at 15 mg/kg/day for 2 weeks. Hcy impaired endothelium-dependent relaxations of rat aortae and led to ER stress in endothelial cells, which were ameliorated by co-incubation of BT extract and TF3. The blood pressure of Ang II-infused rats and plasma Hcy level were normalized by BT consumption. Impaired endothelium-dependent relaxations in renal arteries, carotid arteries and aortae, and flow-mediated dilatations in third-order mesenteric resistance arteries were improved. Elevations of ER stress markers and ROS level, plus down-regulation of Hcy metabolic enzymes in aortae from Ang II-infused rats were prevented by BT treatment. Our data reveal the novel cardiovascular benefits of BT in ameliorating vascular dysfunctions, providing insight into developing BT into beneficial dietary supplements in hypertensive patients.
authors.affiliation: Institute of Vascular Medicine and Li Ka Shing Institute of Health Sciences, Chinese University of Hong Kong, Hong Kong, China.
authors.forename: Wai
authors.initials: W
authors.lastname: San Cheang
authors.affiliation: Institute of Vascular Medicine and Li Ka Shing Institute of Health Sciences, Chinese University of Hong Kong, Hong Kong, China.
authors.forename: Ching
authors.initials: C
authors.lastname: Yuen Ngai
authors.affiliation: Institute of Vascular Medicine and Li Ka Shing Institute of Health Sciences, Chinese University of Hong Kong, Hong Kong, China.
authors.forename: Ye
authors.initials: Y
authors.lastname: Yen Tam
authors.affiliation: Department of Cardiovascular Sciences, Methodist Research Institute, Houston, TX, USA.
authors.forename: Xiao
authors.initials: X
authors.lastname: Yu Tian
authors.affiliation: Department of Cardiovascular Sciences, Methodist Research Institute, Houston, TX, USA.
authors.forename: Wing
authors.initials: W
authors.lastname: Tak Wong
authors.affiliation: Institute of Vascular Medicine and Li Ka Shing Institute of Health Sciences, Chinese University of Hong Kong, Hong Kong, China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Institute of Vascular Medicine and Li Ka Shing Institute of Health Sciences, Chinese University of Hong Kong, Hong Kong, China.
authors.forename: Chi
authors.initials: C
authors.lastname: Wai Lau
authors.affiliation: School of Life Sciences, Chinese University of Hong Kong, Hong Kong, China.
authors.forename: Zhen Yu
authors.initials: ZY
authors.lastname: Chen
authors.affiliation: Clinical Division, School of Chinese Medicine, Hong Kong Baptist University, Hong Kong, China.
authors.forename: Zhao-Xiang
authors.initials: ZX
authors.lastname: Bian
authors.affiliation: Institute of Vascular Medicine and Li Ka Shing Institute of Health Sciences, Chinese University of Hong Kong, Hong Kong, China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Huang
authors.affiliation: Clinical Division, School of Chinese Medicine, Hong Kong Baptist University, Hong Kong, China.
authors.forename: Fung
authors.initials: F
authors.lastname: Ping Leung
mesh_terms: D000804:Angiotensin II; D000818:Animals; D001011:Aorta / Q000166:cytology; D044946:Biflavonoids / Q000494:pharmacology*; D001794:Blood Pressure / Q000187:drug effects*; D028241:Camellia sinensis / Q000378:metabolism; D002200:Capillary Resistance / Q000187:drug effects*; D002392:Catechin / Q000031:analogs & derivatives* / Q000494:pharmacology; D002478:Cells, Cultured; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects*; D042783:Endothelial Cells; D004730:Endothelium, Vascular / Q000378:metabolism; D006710:Homocysteine / Q000494:pharmacology; D020138:Hyperhomocysteinemia / Q000188:drug therapy; D006973:Hypertension / Q000473:pathology; D008297:Male; D018384:Oxidative Stress / Q000187:drug effects; D010936:Plant Extracts / Q000627:therapeutic use; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism; D013662:Tea / Q000378:metabolism*; D014664:Vasodilation / Q000187:drug effects
chemical_list: D044946:Biflavonoids; D010936:Plant Extracts; D017382:Reactive Oxygen Species; D013662:Tea; C585473:theaflavin-3,3'-digallate; D006710:Homocysteine; D000804:Angiotensin II; D002392:Catechin