DNA damage in lung epithelial cells isolated from rats exposed to quartz: role of surface reactivity and neutrophilic inflammation.
Respirable quartz has been classified as a human lung carcinogen (IARC, 1997). However, the mechanisms involved in quartz-induced carcinogenesis remain unclear. The aim of the present study was to investigate acute DNA damage in epithelial lung cells from rats exposed to quartz. Since surface reactivity is considered to play a crucial role in the toxicity of quartz, the effect of surface modifying agents polyvinylpyridine-N-oxide (PVNO) and aluminium lactate (AL) was evaluated. Therefore, rats were instilled with quartz (DQ12, 2 mg/rat) or quartz treated with PVNO or AL. After 3 days animals were killed and brochoalveolar lavage (BAL) was performed to evaluate inflammatory cell influx. BAL-fluid levels of lactate dehydrogenase (LDH), alkaline phosphatase (AP) and total protein were used as lung damage markers. Neutrophil activation was assessed by myeloperoxidase (MPO) measurement, and total antioxidant capacity of the BAL-fluid was determined using the TEAC (trolox equivalent antioxidant capacity) assay. Lung epithelial cells were isolated and DNA strand breakage was determined by single cell gel electrophoresis (comet assay). DNA damage was significantly increased in epithelial cells from rats instilled with DQ12, whereas no enhanced DNA strand breakage was observed when quartz was treated with PVNO or AL. Total protein, LDH and TEAC were increased in rats treated with native quartz, and this was inhibited by both coatings. A significant correlation between neutrophil numbers and MPO levels was observed, indicating neutrophil activation. Inhibition of DNA damage by both coatings was paralleled by a reduction of neutrophil influx as well as MPO activity. In this study we provide evidence that modification of the particle surface prevents DNA strand breakage in epithelial lung cells from quartz-exposed rats. Furthermore, the present data show the feasibility of our in vivo model to evaluate the role of inflammation, antioxidant status, and cytotoxicity in particle-induced DNA damage.
Institut für umweltmedizinische Forschung at the University of Düsseldorf, Department of Particle Toxicology, Auf'm Hennekamp 50, 40225 Düsseldorf, Germany.
Ad M
AM
Knaapen
Catrin
C
Albrecht
Andrea
A
Becker
Doris
D
Höhr
Astrid
A
Winzer
Guido R
GR
Haenen
Paul J A
PJ
Borm
Roel P F
RP
Schins
D000469:Alkaline Phosphatase / Q000378:metabolism; D017607:Aluminum Compounds / Q000494:pharmacology; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D001992:Bronchoalveolar Lavage Fluid / Q000166:cytology; D002478:Cells, Cultured; D002839:Chromans / Q000494:pharmacology; D020552:Comet Assay; D004249:DNA Damage / Q000187:drug effects*; D004847:Epithelial Cells / Q000187:drug effects / Q000201:enzymology; D006801:Humans; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D007773:Lactates / Q000494:pharmacology; D008168:Lung / Q000187:drug effects* / Q000201:enzymology; D009504:Neutrophils / Q000502:physiology; D011144:Polyvinylpyridine N-Oxide / Q000494:pharmacology; D011791:Quartz / Q000633:toxicity*; D051381:Rats; D017208:Rats, Wistar; D013499:Surface Properties; D014810:Vitamin E / Q000031:analogs & derivatives
D017607:Aluminum Compounds; D000975:Antioxidants; D002839:Chromans; D007773:Lactates; D014810:Vitamin E; D011791:Quartz; D011144:Polyvinylpyridine N-Oxide; D007770:L-Lactate Dehydrogenase; D000469:Alkaline Phosphatase; C010643:6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid; C104223:aluminum lactate