CpG oligonucleotide activates Toll-like receptor 9 and causes lung inflammation in vivo

Respir Res. 2007 Oct 9;8(1):72. doi: 10.1186/1465-9921-8-72.


Background: Bacterial DNA containing motifs of unmethylated CpG dinucleotides (CpG-ODN) initiate an innate immune response mediated by the pattern recognition receptor Toll-like receptor 9 (TLR9). This leads in particular to the expression of proinflammatory mediators such as tumor necrosis factor (TNF-alpha) and interleukin-1beta (IL-1beta). TLR9 is expressed in human and murine pulmonary tissue and induction of proinflammatory mediators has been linked to the development of acute lung injury. Therefore, the hypothesis was tested whether CpG-ODN administration induces an inflammatory response in the lung via TLR9 in vivo.

Methods: Wild-type (WT) and TLR9-deficient (TLR9-D) mice received CpG-ODN intraperitoneally (1668-Thioat, 1 nmol/g BW) and were observed for up to 6 hrs. Lung tissue and plasma samples were taken and various inflammatory markers were measured.

Results: In WT mice, CpG-ODN induced a strong activation of pulmonary NFkappaB as well as a significant increase in pulmonary TNF-alpha and IL-1beta mRNA/protein. In addition, cytokine serum levels were significantly elevated in WT mice. Increased pulmonary content of lung myeloperoxidase (MPO) was documented in WT mice following application of CpG-ODN. Bronchoalveolar lavage (BAL) revealed that CpG-ODN stimulation significantly increased total cell number as well as neutrophil count in WT animals. In contrast, the CpG-ODN-induced inflammatory response was abolished in TLR9-D mice.

Conclusion: This study suggests that bacterial CpG-ODN causes lung inflammation via TLR9.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Bronchoalveolar Lavage Fluid / cytology
  • Cytokines / blood
  • Cytokines / genetics
  • Cytokines / metabolism*
  • DNA, Bacterial
  • Disease Models, Animal
  • Gene Expression Regulation
  • Interleukin-1beta / metabolism
  • Interleukin-6 / metabolism
  • Leukocyte Count
  • Lung / enzymology
  • Lung / metabolism*
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • NF-kappa B / metabolism
  • Oligodeoxyribonucleotides
  • Peroxidase / metabolism
  • Pneumonia / blood
  • Pneumonia / chemically induced
  • Pneumonia / metabolism*
  • RNA, Messenger / metabolism
  • Signal Transduction* / genetics
  • Time Factors
  • Toll-Like Receptor 9 / deficiency
  • Toll-Like Receptor 9 / genetics
  • Toll-Like Receptor 9 / metabolism*
  • Tumor Necrosis Factor-alpha / metabolism


  • CPG-oligonucleotide
  • Cytokines
  • DNA, Bacterial
  • IL6 protein, human
  • Interleukin-1beta
  • Interleukin-6
  • NF-kappa B
  • Oligodeoxyribonucleotides
  • RNA, Messenger
  • Tlr9 protein, mouse
  • Toll-Like Receptor 9
  • Tumor Necrosis Factor-alpha
  • Peroxidase