Nicotine exaggerates LPS-induced airway hyperreactivity via JNK-mediated up-regulation of Toll-like receptor 4

Am J Respir Cell Mol Biol. 2014 Sep;51(3):370-9. doi: 10.1165/rcmb.2013-0409OC.


Tobacco smokers often display increased airway hyperreactivity (AHR) when faced with bacterial infections. The present study uses a murine organ-culture model to dissect the mechanisms involved in this exaggerated smooth muscle response. Nicotine simulates the effects of smoking, and LPS represents bacterial infection. Contractile responses of isolated murine tracheal segments were analyzed in myographs after organ culture with increasing concentrations of LPS and/or nicotine for 4 days with or without specific MAPK inhibitors. Nicotine's effect on the expression of cell surface Toll-like receptors (TLRs), MCP-1, COX-2, and TNF-α were examined by real-time PCR. Increased protein expression was verified by immunohistochemistry. LPS concentration-dependently increased contractile responses to bradykinin and des-Arg(9)-bradykinin. A combination of nicotine and low-dose LPS caused powerful synergistic contractions along with increased kinin receptor expression. Specific kinin B1 and B2 receptor inhibitors blocked this reaction. Nicotine increased mRNA and protein expression of TLR4 and -6 in the epithelium and smooth muscle layer, with MCP-1 and COX-2 mRNA increasing in parallel. Specific inhibition of JNK attenuated nicotine's effects. In conclusion, long-term exposure to nicotine up-regulated the expression of TLR4 and -6 via a JNK-related pathway, causing an exaggeration of the LPS-induced local airway inflammation and increased AHR. This might offer a mechanistic explanation to the increased AHR seen in tobacco smokers confronted with bacterial infections.

Keywords: Toll-like receptor; airway hyperreactivity; nicotine; smoking.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Bradykinin / analogs & derivatives
  • Bradykinin / chemistry
  • Chemokine CCL2 / metabolism
  • Cyclooxygenase 2 / metabolism
  • Gene Expression Regulation
  • In Vitro Techniques
  • Lipopolysaccharides / chemistry
  • MAP Kinase Kinase 4 / metabolism*
  • MAP Kinase Signaling System
  • Male
  • Mice
  • Mice, Inbred BALB C
  • Nicotine / chemistry*
  • Nicotinic Agonists / chemistry*
  • Respiratory Mucosa / metabolism
  • Smoking
  • Toll-Like Receptor 4 / metabolism*
  • Toll-Like Receptor 6 / metabolism
  • Trachea / metabolism*


  • Ccl2 protein, mouse
  • Chemokine CCL2
  • Lipopolysaccharides
  • Nicotinic Agonists
  • Tlr4 protein, mouse
  • Tlr6 protein, mouse
  • Toll-Like Receptor 4
  • Toll-Like Receptor 6
  • bradykinin, des-Arg(9)-
  • Nicotine
  • Ptgs2 protein, mouse
  • Cyclooxygenase 2
  • MAP Kinase Kinase 4
  • Bradykinin