The Usefulness Of Bulky Dna Adduct Formation As A Biological Marker Of Exposure To Airborne Particulate Matter (Pm2.5) In In Vitro Cell Lung Models: A Comparative Study

Epidemiological evidence suggests the existence of a relationship between high environmental levels of Particulate Matter (PM) and increased incidence of both morbidity and mortality due to respiratory and/or cardiovascular diseases. The consistency among the findings of epidemiological Studies argues for a causal association, but it is still difficult to attribute acute health effects to concentration levels in light of the current knowledge. The mechanisms underlying these adverse effects are also not well understood, and major questions still remain concerning the specific size fraction, chemical composition and causative toxicological mechanisms leading to the observed health effects. Hence, to improve the knowledge of air pollution PM-induced toxicity in human lungs, with a particular interest in the crucial role played by coated organic compounds, we focused our attention on the metabolic activation of Polycyclic Aromatic Hydrocarbon (PAH)-coated onto air pollution PM and, thereafter, the formation of PAH-DNA adducts in three in vitro cell lung models. A549 cell line, 1, 132 cell line and human Alveolar Macrophages (AM). PAH, PolyChlorinated Dibenzo-p-Dioxins and -Furans (PCDD/F), Dioxin-Like PolyChlorinated Biphenyls (DLPCB) and PolyChlorinated Biphenyls (PCB) coated onto collected PM were determined (i.e., GC/MS and HRGC/HRMS, respectively). Cells were exposed to Dunkerque City's PM2.5 at its lethal concentrations at 10% and 50% (i.e., A549: LC10 = 6.33 mu g/cm(2); and LC50 = 3 1.63 mu g/cm(2); L132: LC10 = 5.02 mu g PM/cm(2); and LC50 = 20.10 mu g PM/cm(2); AM: LC10= 5.97 mu g PM/cm(2); and LC50 = 29.85 mu g PM/cm(2)). Cytochrorne P450 (CYP) 1A1 gene expression (i.e., RT-PCR) and enzymatic activity (i.e., EROD activity) and the formation of PAH-DNA adducts (i.e., P-32-postlabelling) were investigated after 24, 48 and/or 72h. Particular (i.e, desorbed PM, dPM) and PAH-positive (i.e., Benzo[a]Pyrene, B[a]P; 1 mu M) controls were included in the experimental design. A statistically significant increase in CYPIA1 gene expression was observed in the three cell lung models under study, 24, 48 and/or 72h after their exposure to dPM, suggesting thereby that the employed outgassing method was not efficient enough to remove total PAR Similarly, CYPIA1 gene expression was highly induced 24. 48 and/or 72h after lung cell exposure to PM or B[a]P. Accordingly, EROD activity was significantly increased only in A549 cells and AM, 24, 48 and/or 72h after their exposure to dPM.. PM or B[a]P. Even if B[a]P exposure caused important bulky DNA adduct formation, only very low levels of PAH-DNA adducts, which could not be reliably quantified, were reported 72h after A549 cells and AM exposure to PM and dPM. The relatively low levels of PAH, together with the presence of PCDD/F, DLPCB and PCB coated onto Dunkerque City's PM2.5 could contribute to explain this borderline detection of PAH-DNA adducts. Neither significant EROD activity nor PAH-DNA adduct formation could be measured in PM- or in B[a]P-exposed L132 cells. In contrast, A549 cells and AM seem to present higher sensibility to coated organic chemical-induced damage. We also concluded that, in the three lung cellular models we used and in the experimental conditions we chose, bulky DNA adduct formation only partly contribute to the lung toxicity arising from the exposure to Dunkerque City's PM2.5.