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Gaseous nitrogen oxides stimulate cell cycle progression by retinoblastoma phosphorylation via activation of

Jing-Hsien Chen1, Tsui-Hwa Tseng, Yung-Chyan Ho

  • 1Institute of Biochemistry, Chung Shan Medical University Hospital, Taichung, Taiwan.

Toxicological Sciences : an Official Journal of the Society of Toxicology
|September 13, 2003
PubMed

Insights

Nitrogen oxides (NOx) stimulate lung fibroblast proliferation by activating cell-cycle proteins and inhibiting cell-cycle inhibitors. This mechanism may contribute to lung fibrosis from NOx air pollution.

Area of Science:

  • Environmental Health
  • Cell Biology
  • Toxicology

Background:

  • Nitrogen oxides (NOx) are significant indoor and outdoor air pollutants.
  • NOx exposure is linked to lung tissue damage due to oxidative stress and free radicals.
  • Previous research indicated NOx induces human lung fibroblast (MRC-5) cell proliferation.

Purpose of the Study:

  • To elucidate the molecular mechanisms by which NOx gas stimulates lung fibroblast proliferation.
  • To investigate the role of retinoblastoma (Rb) phosphorylation and cyclin-cdk complexes in NOx-induced cell proliferation.

Main Methods:

  • Utilized Western blot and immunoprecipitation techniques.
  • Analyzed the expression levels of specific cyclin-cdk complexes (cyclinA/cdk2, cyclinD1/cdk4, cyclinE/cdk2).
  • Assessed the phosphorylation status of Rb and the levels of cyclin-dependent kinase inhibitors (CKIs) p27 and p16.

Main Results:

  • NOx gas exposure increased the expression of cyclinA/cdk2, cyclinD1/cdk4, and cyclinE/cdk2 complexes.
  • Phosphorylation of Rb (phospho-Rb) was elevated following NOx treatment.
  • Levels of CKIs p27 and p16 were significantly decreased.

Conclusions:

  • NOx gas stimulates MRC-5 cell proliferation by promoting cell-cycle progression.
  • This proliferation is mediated through Rb phosphorylation via activation of cyclin-cdk complexes and downregulation of CKIs.
  • NOx-induced lung fibroblast proliferation may be a contributing factor to NOx-related lung fibrosis.

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