Antiviral activity of baicalin against influenza virus H1N1-pdm09 is due to modulation of NS1-mediated cellular innate immune responses

Mukti Kant Nayak, Anurodh S. Agrawal, Sudeshna Bose, Shaon Naskar, Rahul Bhowmick, Saikat Chakrabarti, Sagartirtha Sarkar, Mamta Chawla-Sarkar

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44 Scopus citations

Abstract

Objectives: Baicalin, a flavonoid, has been shown to have antiviral and anti-inflammatory activities, although the mechanism of action has been unknown. Therefore, attempts were made to analyse the mechanism behind the antiviral effects of baicalin using an influenza A virus (IAV) model in vitro and in vivo. Methods: Baicalin's anti-influenza activity was elucidated (in vitro and in vivo) utilizing pandemic influenza strain A/H1N1/Eastern India/66/pdm09 (H1N1-pdm09). Anti-influenza activity was measured by plaque inhibition, fluorescent focus-forming units (ffu) and quantifying viral transcripts using quantitative real-time PCR following treatment with baicalin in a dose-and time-dependent manner. The role of the IAV non-structural protein 1 (NS1) gene in modulating host responses was measured by immunoblotting, co-immunoprecipitation and molecular docking. Results: Baicalin treatment following IAV infection revealed up-regulation of interferon (IFN)-induced antiviral signalling and decreased phosphoinositide 3-kinase/Akt (PI3K/Akt) activation compared with infected, untreated controls. Baicalin exerts its antiviral effects by modulating the function of the IAV-encoded NS1 protein. NS1 has been shown to counteract cellular antiviral responses by down-regulating IFN induction and up-regulating PI3K/ Akt signalling. Baicalin disrupted NS1-p85b binding. Molecular docking predicted the binding site of baicalin in the RNA binding domain (RBD) of NS1. Site-directed mutagenesis within the RBD region of NS1 and the difference in the fluorescence quenching pattern of full-length NS1 and mutant NS1 proteins in the presence of baicalin confirmed the interaction of baicalin with the NS1 RBD. Amino acid residues 39-43 of the NS1 RBD were found to be crucial for the baicalin-NS1 interaction Conclusions: Overall, this study highlights that baicalin exerts its anti-influenza virus activity by modulati g viral protein NS1, resulting in up-regulation of IFN-induced antiviral signalling and a decrease in PI3K/Akt signalling in cells

Original languageEnglish (US)
Article numberdkt534
Pages (from-to)1298-1310
Number of pages13
JournalJournal of Antimicrobial Chemotherapy
Volume69
Issue number5
DOIs
StatePublished - May 2014

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Keywords

  • Anti-influenza virus
  • Flavonoids
  • Interferons
  • Non-structural protein 1
  • PI3K/Akt

ASJC Scopus subject areas

  • Pharmacology
  • Microbiology (medical)
  • Infectious Diseases
  • Pharmacology (medical)

Cite this

Nayak, M. K., Agrawal, A. S., Bose, S., Naskar, S., Bhowmick, R., Chakrabarti, S., Sarkar, S., & Chawla-Sarkar, M. (2014). Antiviral activity of baicalin against influenza virus H1N1-pdm09 is due to modulation of NS1-mediated cellular innate immune responses. Journal of Antimicrobial Chemotherapy, 69(5), 1298-1310. [dkt534]. https://doi.org/10.1093/jac/dkt534