Purpose: The purpose of this study was to investigate the expression of antiviral cytokines and interferon-stimulated genes (ISGs) against human norovirus surrogates, murine norovirus (MNV) by the treatment of flavonoids.
Methods: According to the previous study, six antiviral flavonoids were selected as candidates. In order to examine the expression of antiviral cytokines, 150 μM of EGCG, 100 μM of ECG, fisetin, and quercetin, 50 μM of fisetin and daidzein were pretreated on RAW264.7 cells for 24 h and challenged with MNV. The cells and cell supernatant were harvested in 48 h. The mRNA expression of interferon-α (IFN-α), interferon- λ (IFN-λ), Interleukin-1 (IL-1), Interleukin-6 (IL-6), Tumor necrosis factor-α (TNF-α), zinc finger antiviral protein shorter isoform (ZAPS), Mx, 2'-5'-oligo (A) synthetase (OAS), and inducible nitric oxide synthases (iNOS) were analyzed with measured using quantitative real-time RT-PCR. For the cell supernatant, IFN-α, IFN-β, IL-1, IL-6, TNF-α protein were assayed with ELISA kit.
Results: In mRNA level, IFN-α and TNF-α were increased in of MNV-infected group treated with 50 μM of fisetin or daidzein or 100 μM of quercetin than group infected with MNV alone. IFN-λ and Mx was only highly expressed in MNV-infected group treated with 50 μM of daidzein and 100 μM of quercetin, respectively. Especially, IFN-α protein level showed the significant induction in MNV-infected group treated with 100 μM of fisetin or quercetin.
Significance: IFN-α, IFN-λ, TNF-α, Mx contribute to inhibit the replication of MNV on RAW264.7 cells pretreated with 50 μM of fisetin and daidzein and 100 μM of quercetin and fisetin.