Journal
TOXICOLOGY AND APPLIED PHARMACOLOGY
Volume 329, Issue -, Pages 112-120Publisher
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.taap.2017.05.016
Keywords
Green tea; Catechins; Inflammation; Rheumatoid arthritis; EGCG; EGC
Categories
Funding
- Robber's Research Award (WSU College of Pharmacy) [17A293059836]
- NIH [AR063104]
- Arthritis Foundation Innovative Research Grant
- Washington State University
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In this study, we found that catechins found in green tea (EGCG, EGC, and EC) differentially interfere with the IL-1 beta signaling pathway which regulates the expression of pro-inflammatory mediators (IL-6 and IL-8) and Cox-2 in primary human rheumatoid arthritis synovial fibroblasts (RASFs). EGCG and EGC inhibited IL-6, IL-8, and MMP-2 production and selectively inhibited Cox-2 expression. EC did not exhibit any inhibitory effects. When we looked at the expression of key signaling proteins in the IL-1 beta signaling pathway, we found all the tested catechins could inhibit TAK-1 activity. Therefore, the consumption of green tea offers an overall anti-inflammatory effect. Molecular docking analysis confirms that EGCG, EGC, and EC all occupy the active site of the TAK1 kinase domain. However, EGCG occupies the majority of the TAK1 active site. In addition to TAK1 inhibition, EGCG can also inhibit P38 and nuclear NF-kappa B expression whereas EC and EGC were not effective inhibitors. Our findings suggest one of the main health benefits associated with the consumption of green tea are due to the activity of EGCG and EGC which are both present at higher amounts. Although EGCG is the most effective catechin at inhibiting downstream inflammatory signaling, its effectiveness could be hindered by the presence of EC. Therefore, varying EC content in green tea may reduce the anti-inflammatory effects of other potential catechins in green tea. (C) 2017 Published by Elsevier Inc.
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