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The antioxidant effects of green tea reduces blood pressure and sympathoexcitation in an experimental model of hypertension

Garcia, Michelle L.; Pontes, Roberto B.; Nishi, Erika E.; Ibuki, Flávia K.; Oliveira, Vanessa; Sawaya, Alexandra C.H.; Carvalho, Patrícia O.; Nogueira, Fernando N.; Franco, Maria do Carmo; Campos, Ruy R.; Oyama, Lila M.; Bergamaschi, Cássia T.

doi: 10.1097/HJH.0000000000001149
ORIGINAL PAPERS: Pathophysiological aspects
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Background: Oxidative stress is a key mediator in the maintenance of sympathoexcitation and hypertension in human and experimental models. Green tea is widely known to be potent antioxidant.

Objective: We aimed to evaluate the effects of green tea in a model of hypertension.

Methods: Hypertension was induced by the nitric oxide synthase inhibitor [N-nitro-L-arginine-methyl-ester (L-NAME); 20 mg/kg per day, orally, for 2 weeks] in male Wistar rats. After the first week of L-NAME treatment, animals received green tea ad libitum for 1 week. At the end of the treatment period, blood pressure, heart rate, baroreflex sensitivity, renal sympathetic nerve activity, and vascular and systemic oxidative stress were assessed.

Results: L-NAME-treated animals exhibited an increase in blood pressure (165 ± 2 mmHg) compared with control rats (103 ± 1 mmHg) and green tea treatment reduced hypertension (119 ± 1 mmHg). Hypertensive animals showed a higher renal sympathetic nerve activity (161 ± 12 spikes/s) than the control group (97 ± 2 spikes/s), and green tea also decreased this parameter in the hypertensive treated group (125 ± 5 spikes/s). Arterial baroreceptor function and vascular and systemic oxidative stress were improved in hypertensive rats after green tea treatment.

Conclusions: Taken together, short-term green tea treatment improved cardiovascular function in a hypertension model characterized by sympathoexcitation, which may be because of its antioxidant properties.

aDepartment of Physiology, Escola Paulista de Medicina, Universidade Federal de São Paulo

bDepartment of Biomaterials and Oral Biology, Faculdade de Odontologia, Universidade de São Paulo

cDepartment of Medicine, Universidade Federal de São Paulo, São Paulo

dDepartment of Plant Biology, Universidade Estadual de Campinas, Campina

eLaboratory of Multidisciplinary Research, Universidade São Francisco, São Paulo, Brazil

Correspondence to Cássia T. Bergamaschi, PhD, Disciplina de Fisiologia Cardiovascular, Escola Paulista de Medicina, Universidade Federal de São Paulo, Rua Botucatu, 862, CEP 04023-060, São Paulo, SP, Brazil. Tel: +55 11 5573 7820 ext. 24; fax: +55 11 5573 7820; ext. 5; e-mail: bergamaschi.cassia@unifesp.br

Abbreviations: BP, blood pressure; CAT, catalase; DAF-2, 4,5-diamino fluorescein diacetate; DHE, dihydroethidium; EGCG, epigallocatechin-3-gallate; eNOS, endothelial nitric oxide synthase; GPx, glutathione peroxidase; HR, heart rate; L-NAME, N-nitro-L-arginine-methyl-ester; MAP, mean arterial pressure; MDA, malondialdehyde; NO, nitric oxide; ROS, reactive oxygen species; rSNA, renal sympathetic nerve activity; SEM, standard error of the mean; SOD, superoxide dismutase

Received 2 June, 2016

Revised 8 August, 2016

Accepted 16 September, 2016

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