Catechin inhibiting the H1N1 influenza virus associated with the regulation of autophagy

Background: The influenza virus is a highly infectious disease, with a notably rapid transmission rate. Autophagy is triggered by viral infection and is a survival mechanism exerted to maintain cellular homeostasis. Catechin is a representative phenolic acid which exerts anti-inflammatory responses against influenza A virus infection. The aim of this study is to explore the anti–H1N1 influenza virus effects by catechin associated with the restoration of autophagy. Methods: XTT assay was used to detect cellular viability. The inhibitory effects on the H1N1 influenza virus were assessed by hemagglutination assay, neuraminidase activity, and quantitative reverse transcription-polymerase chain reaction (qRT-PCR). The protein levels of H1N1 influenza virulence and autophagic markers were detected by Western blot. Results: We herein demonstrated that catechin had no cytotoxic effect on both infected and noninfected A549 cells and exerted protective effects on infected A549 cells. The results of the hemagglutination assay, neuraminidase activity, and qRT-PCR to examine viral load demonstrated that catechin effectively inhibited the replication of the H1N1 influenza virus. The virulent M2 protein and viral nucleoprotein were also inhibited after treatment with catechin. As for the autophagic markers, the LC3B protein was notably decreased by catechin in a dose-dependent manner, while the amount of autophagic vacuoles in H1N1 influenza virus–infected cells also decreased after catechin treatment in a dose-dependent manner. Conclusion: Collectively, the autophagy activated by the H1N1 influenza virus could be reversed after catechin treatment. This study indicates that catechin effectively inhibits H1N1 viral proliferation and thus may be applied as an adjuvant in future clinical application.