Epigallocatechin gallate (EGCG) inhibits lipopolysaccharide‐induced inflammation in RAW 264.7 macrophage cells via modulating nuclear factor kappa‐light‐chain enhancer of activated B cells (NF‐κB) signaling pathway

Epigallocatechin‐3‐gallate (EGCG) is a major bioactive compound in tea polyphenol extract. After ingestion, EGCG reaches the intestine and may commence anti‐inflammation in the intestinal organ. Thus, in this paper, the anti‐inflammatory effect of EGCG was studied using lipopolysaccharide (LPS)‐induced inflammation in RAW 264.7 cells. LPS induction instigated morphological deformation extensively which was normalized by EGCG. In LPS‐induced macrophage cells, EGCG was found to lower cellular nitric oxide (32% of LPS group) and intercellular ROS level (45.4% of LPS group). It also suppressed the expression of IL‐1β (LPS 132.6 ± 14.6, EGCG 10.67 ± 3.65), IL‐6 (LPS 2994.44 ± 178.5, EGCG 408.33 ± 52.34), TNF‐α (LPS 27.11 ± 2.84, EGCG 1.22 ± 0.03), and iNOS (LPS 40.45 ± 11.17, EGCG 10.24 ± 0.89). The GO function analysis identified that these differential genes involved 24 biological processes, 18 molecular functions, and 19 cellular component‐related processes. KEGG pathway enrichment analysis revealed that LPS significantly affects NF‐κB, TNF, and TLR signaling pathways. Western blotting revealed that EGCG diminished P‐IκB/IκB ratio by 75% and p‐p65/p65 by 50% compared to the LPS group. Finally, Arg‐1 and CD‐206 mRNA expression were determined by RT‐PCR, which was consistent with the RNA‐Seq result. These findings indicate that EGCG exerts an anti‐inflammatory effect by reducing NO and ROS production, suppressing TLR4 protein expression, and inhibiting IκB and p65 phosphorylation.