Emodin Inhibition of Influenza A Virus Replication and Influenza Viral Pneumonia via the Nrf2, TLR4, p38/JNK and NF-kappaB Pathways

Molecules. 2017 Oct 18;22(10):1754. doi: 10.3390/molecules22101754.

Abstract

Lasting activations of toll-like receptors (TLRs), MAPK and NF-κB pathways can support influenza A virus (IAV) infection and promote pneumonia. In this study, we have investigated the effect and mechanism of action of emodin on IAV infection using qRT-PCR, western blotting, ELISA, Nrf2 luciferase reporter, siRNA and plaque inhibition assays. The results showed that emodin could significantly inhibit IAV (ST169, H1N1) replication, reduce IAV-induced expressions of TLR2/3/4/7, MyD88 and TRAF6, decrease IAV-induced phosphorylations of p38/JNK MAPK and nuclear translocation of NF-κB p65. Emodin also activated the Nrf2 pathway, decreased ROS levels, increased GSH levelss and GSH/GSSG ratio, and upregulated the activities of SOD, GR, CAT and GSH-Px after IAV infection. Suppression of Nrf2 via siRNA markedly blocked the inhibitory effects of emodin on IAV-induced activations of TLR4, p38/JNK, and NF-κB pathways and on IAV-induced production of IL-1β, IL-6 and expression of IAV M2 protein. Emodin also dramatically increased the survival rate of mice, reduced lung edema, pulmonary viral titer and inflammatory cytokines, and improved lung histopathological changes. In conclusion, emodin can inhibit IAV replication and influenza viral pneumonia, at least in part, by activating Nrf2 signaling and inhibiting IAV-induced activations of the TLR4, p38/JNK MAPK and NF-κB pathways.

Keywords: MAPK; NF-κB; Nrf2; emodin; influenza A virus; toll-like receptors (TLRs).

MeSH terms

  • Animals
  • Disease Models, Animal
  • Emodin / administration & dosage*
  • Humans
  • Influenza A virus / drug effects*
  • Influenza A virus / genetics
  • Influenza A virus / pathogenicity
  • Influenza, Human / complications
  • Influenza, Human / drug therapy*
  • Influenza, Human / genetics
  • Influenza, Human / virology
  • Mice
  • Myeloid Differentiation Factor 88 / genetics
  • NF-E2-Related Factor 2 / genetics
  • Pneumonia / drug therapy*
  • Pneumonia / etiology
  • Pneumonia / pathology
  • Pneumonia / virology
  • RNA, Small Interfering / administration & dosage
  • Signal Transduction / drug effects
  • TNF Receptor-Associated Factor 6 / genetics
  • Toll-Like Receptor 4 / genetics
  • Transcription Factor RelA / genetics
  • Virus Replication / drug effects
  • p38 Mitogen-Activated Protein Kinases / genetics

Substances

  • Myeloid Differentiation Factor 88
  • NF-E2-Related Factor 2
  • RNA, Small Interfering
  • Rela protein, mouse
  • TNF Receptor-Associated Factor 6
  • Tlr4 protein, mouse
  • Toll-Like Receptor 4
  • Transcription Factor RelA
  • p38 Mitogen-Activated Protein Kinases
  • Emodin