Nicotine reduces TNF-α expression through a α7 nAChR/MyD88/NF-ĸB pathway in HBE16 airway epithelial cells

Cell Physiol Biochem. 2011;27(5):605-12. doi: 10.1159/000329982. Epub 2011 Jun 15.

Abstract

Aims: To explore the signaling mechanism associated with the inhibitory effect of nicotine on tumor necrosis factor (TNF)- α expression in human airway epithelial cells.

Methods: HBE16 airway epithelial cells were cultured and incubated with either nicotine or cigarette smoke extract (CE). Cells were then transfected with α1, α5, or α7 nicotinic acetylcholine receptor (nAChR)-specific small interfering RNAs (siRNAs). The effects of nicotine on the production of proinflammatory factors TNF-α, in transfected cells were analyzed. Furthermore, we assayed the expression levels of myeloid differentiation primary response gene 88 (MyD88) protein, nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) p65 protein, NF-κB activity and NF-κB inhibitor alpha (I-κBα) expression in cells after treatment with nicotine or α7 nAChR inhibitor, α -bungarotoxin (α-BTX).

Results: The production of TNF-α was lower in cells pretreated with nicotine before lipopolysaccharide (LPS) stimulation, compared with LPS-only-treated cells. In contrast, in α7 siRNA-transfected cells incubated with nicotine and LPS, TNF-α expression was higher than that in non-transfected cells or in α1 or α5 siRNA-transfected cells. Addition of MyD88 siRNA or the NF-κB inhibitor pyridine-2,6-dithiocarboxylic acid (PDTC) also reduced TNF-α expression. Furthermore, we found that nicotine decreased MyD88 protein, NF-κB p65 protein, NF-κB activity and phospho-I-κBα expression induced by CE or LPS. The inhibitor α-BTX could reverse these effects.

Conclusion: Nicotine reduces TNF-α expression in HBE16 airway epithelial cells, mainly through an α7 nAChR/MyD88/NF-κB pathway.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bungarotoxins / pharmacology
  • Cell Line, Transformed
  • Cholinergic Antagonists / pharmacology
  • Epithelial Cells / cytology
  • Epithelial Cells / metabolism*
  • Gene Expression Regulation
  • Humans
  • I-kappa B Proteins / pharmacology
  • Lipopolysaccharides / pharmacology
  • Myeloid Differentiation Factor 88 / antagonists & inhibitors*
  • Myeloid Differentiation Factor 88 / genetics
  • Myeloid Differentiation Factor 88 / metabolism
  • NF-KappaB Inhibitor alpha
  • Nicotine / pharmacology*
  • Pyrrolidines / pharmacology
  • RNA, Small Interfering / pharmacology
  • Receptors, Nicotinic / genetics
  • Receptors, Nicotinic / metabolism*
  • Respiratory System / cytology
  • Respiratory System / metabolism*
  • Signal Transduction / drug effects
  • Smoke
  • Thiocarbamates / pharmacology
  • Tobacco*
  • Transcription Factor RelA / antagonists & inhibitors*
  • Transcription Factor RelA / genetics
  • Transcription Factor RelA / metabolism
  • Tumor Necrosis Factor-alpha / antagonists & inhibitors*
  • Tumor Necrosis Factor-alpha / genetics
  • Tumor Necrosis Factor-alpha / metabolism
  • alpha7 Nicotinic Acetylcholine Receptor

Substances

  • Bungarotoxins
  • Cholinergic Antagonists
  • Chrna7 protein, human
  • I-kappa B Proteins
  • Lipopolysaccharides
  • MYD88 protein, human
  • Myeloid Differentiation Factor 88
  • NFKBIA protein, human
  • Pyrrolidines
  • RNA, Small Interfering
  • Receptors, Nicotinic
  • Smoke
  • Thiocarbamates
  • Transcription Factor RelA
  • Tumor Necrosis Factor-alpha
  • alpha7 Nicotinic Acetylcholine Receptor
  • NF-KappaB Inhibitor alpha
  • pyrrolidine dithiocarbamic acid
  • Nicotine