ORF3 of Hepatitis E Virus Inhibits the Expression of Proinflammatory Cytokines and Chemotactic Factors in LPS-Stimulated Human PMA-THP1 Cells by Inhibiting NF-κB Pathway

Viral Immunol. 2016 Mar;29(2):105-11. doi: 10.1089/vim.2015.0107. Epub 2016 Jan 15.

Abstract

Hepatitis E virus (HEV) is one of the primary causative agents of acute hepatitis. It is noteworthy that HEV can develop chronic infection and even lead to liver cirrhosis; however, the mechanism has not been revealed. In this study, the ELISA assay was used to detect protein levels, and we found that HEV open reading frame 3 (ORF3) protein inhibited the expression of proinflammatory cytokines (tumor necrosis factor-alpha [TNF-α], interleukin [IL]-1β, IL-6, IL-8, IL-12p40, and IL-18) and chemotactic factors (nitric oxide [NO], interferon-inducible protein-10 (IP-10), macrophage inflammatory protein (MIP)-1α, monocyte chemoattractant protein-1 (MCP-1), granulocyte colony-stimulating factor (G-CSF), granulocyte macrophage colony-stimulating factor (GM-CSF)] in lipopolysaccharide (LPS)-stimulated human PMA-THP1 cells. Further study showed that mRNA and protein levels of pattern recognition receptors (PRRs), such as Toll-like receptor 4 (TLR4), TNF receptor-associated factor 6 (TRAF6), and nucleotide-binding oligomerization domain containing 2 (NOD2), decreased after infection of pLL3.7-ORF3 (pORF3); moreover, the inhibition produced corresponding upregulation of IκBα and downregulation of phosphorylated IκB kinase IKKɛ (p-IKKɛ) and phosphorylated nuclear factor (NF)-κB (p-NF-κB), but little variation was found in the concentration of IKKɛ and NF-κB. Taken together, our results demonstrated that HEV ORF3 attenuated LPS-induced cytokine production and chemotactic factors, predominantly by inhibiting various PRRs-mediated NF-κB signaling pathways. The anti-inflammatory properties might be of great importance to clarify the role and mechanism of macrophages in chronic HEV infection and cirrhosis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Line
  • Chemotactic Factors / antagonists & inhibitors*
  • Cytokines / antagonists & inhibitors*
  • Gene Expression Profiling
  • Hepatitis E virus / immunology*
  • Hepatitis E virus / pathogenicity*
  • Humans
  • Immune Evasion*
  • Lipopolysaccharides / immunology
  • NF-kappa B / antagonists & inhibitors*
  • Proteome / analysis
  • Viral Proteins / metabolism*

Substances

  • Chemotactic Factors
  • Cytokines
  • Lipopolysaccharides
  • NF-kappa B
  • ORF3 protein, Hepatitis E virus
  • Proteome
  • Viral Proteins