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

• Published in: Molecules (Basel, Switzerland) Vol. 22; no. 10; p. 1754
• Main Authors: Dai, Jian-Ping, Wang, Qian-Wen, Su, Yun, Gu, Li-Ming, Zhao, Ying, Chen, Xiao-Xua, Chen, Cheng, Li, Wei-Zhong, Wang, Ge-Fei, Li, Kang-Sheng
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 18.10.2017; MDPI
• Subjects: Animals; Cytokines; Disease Models, Animal; Edema; Emodin; Emodin - administration & dosage; Enzyme-linked immunosorbent assay; Humans; Immune system; Infections; Inflammation; Influenza; Influenza A; influenza A virus; 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; Inhibition; Interleukin 6; JNK protein; Lungs; MAP kinase; MAPK; Mice; MyD88 protein; Myeloid Differentiation Factor 88 - genetics; NF-E2-Related Factor 2 - genetics; NF-κB; NF-κB protein; Nrf2; Nuclear transport; p38 Mitogen-Activated Protein Kinases - genetics; Pneumonia; Pneumonia - drug therapy; Pneumonia - etiology; Pneumonia - pathology; Pneumonia - virology; Proteins; Replication; RNA, Small Interfering - administration & dosage; Rodents; Signal Transduction - drug effects; siRNA; TLR2 protein; TLR4 protein; TNF Receptor-Associated Factor 6 - genetics; Toll-Like Receptor 4 - genetics; Toll-like receptors; toll-like receptors (TLRs); TRAF6 protein; Transcription Factor RelA - genetics; Translocation; Virus Replication - drug effects; Viruses; Western blotting; NF-κB; MAPK; Nrf2; toll-like receptors (TLRs); emodin; influenza A virus
• ISSN: 1420-3049; 1420-3049
• DOI: 10.3390/molecules22101754

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.