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Neutrophils cause oxidative DNA damage in alveolar epithelial cells
A M Knaapen1, F Seiler, P A Schilderman
1Department of Health Risk Analysis and Toxicology, Maastricht University, The Netherlands.
Abstract:
Inflammation has been recognized as a contributing factor in the pathogenesis of some cancers. In the lung, inflammation is characterized by an influx of polymorphonuclear leukocytes (PMN) that release a variety of reactive oxygen species (ROS). The aim of the present study was to investigate the direct effect of PMN on oxidative DNA damage in lung target cells. Therefore, rat alveolar epithelial cells (RLE) were coincubated with PMN or hydrogen peroxide. Known to be correlated with the incidence of cancer, 7-hydro-8-oxo-2'deoxyguanosine (8-oxodG) was used as an effect marker for oxidative damage. Viability of the RLE, when coincubated with PMN, decreased to 43%, dependent on the ratio between PMN and RLE. After washing off PMN, 8-oxodG levels were significantly increased in RLE, but the highest levels were observed in the washed off PMN fraction. In addition, to avoid washing off procedures, immunohistochemical analysis was used to measure the 8-oxodG levels specifically in the RLE and similar results were obtained. In addition, inhibitor experiments showed that antioxidants ameliorated oxidative DNA damage. Our data provide evidence that ROS released by PMN as well as H2O2, cause oxidative DNA damage in epithelial cells.
Insights
Inflammation involves polymorphonuclear leukocytes (PMN) releasing reactive oxygen species (ROS), causing DNA damage in lung cells. Antioxidants can reduce this oxidative DNA damage, suggesting a link between inflammation and cancer pathogenesis.
Area of Science:
- Cell Biology
- Molecular Biology
- Cancer Research
Background:
- Inflammation is implicated in cancer development.
- Lung inflammation involves polymorphonuclear leukocytes (PMN) releasing reactive oxygen species (ROS).
- Oxidative DNA damage, marked by 8-hydro-7-oxo-2'-deoxyguanosine (8-oxodG), is linked to cancer incidence.
Purpose of the Study:
- To investigate the direct impact of PMN on oxidative DNA damage in lung epithelial cells.
- To determine if ROS from PMN contribute to DNA damage in lung cells.
Main Methods:
- Coincubation of rat alveolar epithelial cells (RLE) with PMN or hydrogen peroxide (H2O2).
- Measurement of 8-oxodG levels as a marker of oxidative DNA damage.
- Immunohistochemical analysis to assess 8-oxodG in RLE.
- Inhibitor experiments using antioxidants.
Main Results:
- PMN significantly reduced RLE viability.
- 8-oxodG levels increased in RLE and PMN after coincubation.
- Immunohistochemistry confirmed increased 8-oxodG in RLE.
- Antioxidants mitigated PMN-induced oxidative DNA damage.
Conclusions:
- ROS released by PMN cause oxidative DNA damage in lung epithelial cells.
- Hydrogen peroxide also induces oxidative DNA damage in epithelial cells.
- This study provides evidence for a mechanism linking inflammation-driven ROS to DNA damage, a factor in cancer pathogenesis.