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Int. J. Mol. Sci. 2012, 13(6), 7174-7185; doi:10.3390/ijms13067174

Pu-erh Tea Reduces Nitric Oxide Levels in Rats by Inhibiting Inducible Nitric Oxide Synthase Expression through Toll-Like Receptor 4

1
Key Laboratory for Molecular Enzymology and Engineering, the Ministry of Education, College of Life Science, Jilin University, Changchun 130012, China
2
Yunnan Research Centre for Advance Tea Processing, Yunnan Agricultural University, Kunming 650201, China
*
Authors to whom correspondence should be addressed.
Received: 7 May 2012 / Revised: 28 May 2012 / Accepted: 28 May 2012 / Published: 11 June 2012
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Abstract

Pu-erh tea undergoes a unique fermentation process and contains theabrownins, polysaccharides and caffeine; although it is unclear about which component is associated with the down regulation of nitric oxide levels or how this process is mediated. To address this question we examined the effects of pu-erh tea on nitric oxide synthase (NOS) genes. Cohorts of rats were separately given four-week treatments of water as control, pu-erh tea, or the tea components: theabrownins, caffeine or polysaccharides. Five experimental groups were injected with lipopolysaccharides (LPS) to induce nitric oxide (NO) production, while the corresponding five control groups were injected with saline as a negative control. The serum and liver NO concentrations were examined and the NOS expression of both mRNA and protein was measured in liver. The results showed that the rats which were fed pu-erh tea or polysaccharides had lower levels of NO which corresponded with the down-regulation of inducible nitric oxide synthase (iNOS) expression. We further demonstrate that this effect is mediated through reduction of Toll-like receptor 4 (TLR4) signaling. Thus we find that the polysaccharide components in pu-erh tea reduce NO levels in an animal model by inhibiting the iNOS expression via signaling through TLR4.
Keywords: pu-erh tea; nitric oxide; inducible nitric oxide synthase; polysaccharides; Toll-like receptor 4 pu-erh tea; nitric oxide; inducible nitric oxide synthase; polysaccharides; Toll-like receptor 4
This is an open access article distributed under the Creative Commons Attribution License (CC BY 3.0).

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MDPI and ACS Style

Xu, Y.; Wang, G.; Li, C.; Zhang, M.; Zhao, H.; Sheng, J.; Shi, W. Pu-erh Tea Reduces Nitric Oxide Levels in Rats by Inhibiting Inducible Nitric Oxide Synthase Expression through Toll-Like Receptor 4. Int. J. Mol. Sci. 2012, 13, 7174-7185.

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