Background: 3,4,5-tri-O-caffeoylquinic acid (3,4,5-TCQA), a natural polyphenolic acid, has been shown to be effective against influenza A virus (IAV) infection. Although it was found to inhibit the neuraminidase of IAV, it may also perturb other cellular functions, as polyphenolic acids have shown antioxidant, anti-inflammatory and other activities.
Purpose: This study aimed to investigate the effect of 3,4,5-TCQA at a cell level, which is critical for protecting host cell from IAV infection.
Study design and methods: We explored the effect of 3,4,5-TCQA on H292 cells infected or un-infected with Pr8 IAV. The major genes and related pathway were identified through RNA sequencing. The pathway was confirmed by qRT-PCR and western blot analysis. The anti-inflammatory activity was evaluated using nitric oxide measurement assay.
Results: We showed that 3,4,5-TCQA downregulated the immune response in H292 cells, and reduced the cytokine production in Pr8-infected cells, through Toll-like receptor (TLR) signaling pathway. In addition, 3,4,5-TCQA showed anti-inflammatory activity in LPS-activated RAW264.7 cells.
Conclusion: Collectively, our results indicated that 3,4,5-TCQA suppressed inflammation caused by IAV infection through TLR3/7 signaling pathway. This provides a new insight into the antiviral mechanism of 3,4,5-TCQA.
Keywords: 3,4,5-TCQA; Anti-inflammation; Anti-influenza; TLR3/7.
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