Abstract
BackgroundH9N2 avian influenza viruses (AIVs) infect avian and mammalian hosts and provide internal genes for new emerging highly pathogenic avian viruses that cause severe pneumonia with high mortality, for which few medications are available. Arctiin, a bioactive lignan glycoside, has been reported to possess multiple pharmacological properties. However, the effect of arctiin on H9N2 virus infection is unclear. In the current study, we analyzed the effect of arctiin on H9N2 virus infection and the underlying molecular mechanism in vitro.MethodsThe antiviral effect against H9N2 virus was determined by plaque reduction assay (PRA) and progeny virus reduction assay. We employed MTT assay, qRT-PCR, ELISA, immunofluorescence and Western blotting to better understand the anti-inflammatory effect and corresponding mechanism of arctiin on H9N2 virus-infected cells.ResultsThe results showed that arctiin had antiviral activity against H9N2 virus. Arctiin treatment reduced H9N2 virus-triggered proinflammatory cytokines, such as IL-6, and TNF-α. Moreover, arctiin significantly suppressed H9N2 virus-mediated expression of COX-2 and PGE2. Furthermore, we found that arctiin inhibited H9N2 virus-mediated activation of RIG-I/JNK MAPK signaling. Interestingly, arctiin treatment obviously reversed H9N2 virus-induced reduction of Nrf2, increased the nuclear translocation of Nrf2, and upregulated Nrf2 signaling target genes (HO-1 and SOD2). Zinc protoporphyrin (Znpp)—an HO-1 inhibitor—weakened the inhibitory effect of arctiin on H9N2 virus-induced RIG-I/JNK MAPK and proinflammatory mediators.ConclusionTaken together, these results suggested that the anti-inflammatory effects of arctiin on H9N2 virus infection may be due to the activation of Nrf2/HO-1 and blocked RIG-I/JNK MAPK signaling; thus, arctiin may be a promising agent for prevention and treatment of H9N2 virus infections.
Highlights
H9N2 avian influenza virus (AIV) was initially isolated in 1966 from turkeys in the United States [1]
Cytotoxicity and antiviral effects of arctiin Arctiin isolated from Arctium lappa L. was confirmed by NMR spectroscopy
The results showed that the increased mRNA levels of proinflammatory cytokines upon H9N2 virus infection were significantly suppressed by arctiin treatment (Fig. 2A)
Summary
H9N2 avian influenza virus (AIV) was initially isolated in 1966 from turkeys in the United States [1]. It contains eight segments of single-stranded negative-sense RNA wrapped by a lipid bilayer envelope [1]. It is remarkable that highly pathogenic avian influenza (e.g., H5N1 and H7N9) has acquired gene segments from H9N2 viruses, resulting in fatal respiratory diseases in humans [5, 6]. H9N2 avian influenza viruses (AIVs) infect avian and mammalian hosts and provide internal genes for new emerging highly pathogenic avian viruses that cause severe pneumonia with high mortality, for which few medications are available. The effect of arctiin on H9N2 virus infection is unclear. We analyzed the effect of arctiin on H9N2 virus infection and the underlying molecular mechanism in vitro
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