Baicalin inhibits TLR7/MYD88 signaling pathway activation to suppress lung inflammation in mice infected with influenza A virus

The present study aimed to investigate the protective effects and underlying mechanisms of baicalin on imprinting control region mice infected with influenza A/FM/1/47 (H1N1) virus. Oral administration of baicalin into mice infected with H1N1 prevented death, increased the mean time to death and inhibited lung index and lung consolidation. Subsequently, fluorescence quantitative polymerase chain reaction was used to assess the mRNA expression of toll-like receptor 7 (TLR7) and myeloid differentiation primary response gene 88 (MYD88), and western blot analysis was used to determine the expression of phosphorylated nuclear factor κB (NF-κB)-P65 and c-jun/activator protein 1 (AP-1). An enzyme-linked immunosorbent assay was applied to test for the inflammatory cytokines, tumor necrosis factor (TNF)-α and interleukin (IL)-1β and IL-6, in the lung tissue. The findings indicated that baicalin downregulated the mRNA expression of TLR7 and MYD88, significantly downregulated the protein expression of NF-κB-P65 and AP-1 and also inhibited the secretion of TNF-α, IL-1β and IL-6. In conclusion, baicalin effectively reduced the pathological damage and inflammation of the lungs by downregulating the TLR7/MYD88-mediated signaling pathway.