[en] Because of their deep penetration in human lungs, fine airborne particulate matter were described as mainly responsible for the deleterious effects of exposure to air pollution on health. Organic constituents are adsorbed on particles surface and, after inhalation, some (polycyclic aromatic hydrocarbons, PAHs) can be activated into reactive metabolites and can bind to DNA. The formation of bulky DNA adducts has been researched after exposure of mono-and co-cultures of alveolar macrophages (AM) and human embryonic human lung epithelial (L132), to fine air pollution particulate matter Air samples have been collected with cascade impactor and characterized: size distribution (92.15% < 2.5μ.m), specific surface area (1 m2/g), inorganic (Fe, AI, Ca, Na, K, Mg, Pb, etc.) and organic compounds (PAHs, etc.). 32P post-labeling method was applied to detect bulky DNA adducts in AM and L132, in mono-and co-cultures, 72 h after their exposure to atmospheric particles at their Lethals and Effects concentrations or (LC or CE) to 50% (i.e. MA: EC50 = 74.63 μg/mL and L132: LC-5-0 = 75.36 μg/mL). Exposure to desorbed particles (MA: C1= 61.11 μg/mL and L132 : C2 = 61.71 μg/mL) and B[a]P (1 μM) were included. Bulky PAH-DNA adducts were detected in AM in mono-culture after exposure to total particles (Pt), to B[a]P and desorbed particles (Pd). Whatever the exposure, no DNA adduct was detected in L132 in mono-culture. These results are coherent with the enzymatic activities of cytochrome P450 l Al in AM and L132. Exposure of co-culture to Pt, or Pd induced bulky adducts to DNA in AM but not in L132. Exposure to B[a]P alone has altered the DNA of AM and L132, in co-culture. Exposure to Pt is closer to the environmental conditions, but conferred an exposure to amounts of genotoxic agents compared to studies using organic extracts. The formation of bulky DNA adducts was nevertheless observed in AM exposed to Pt, in mono- or co-culture, indicating that they were competent in terms of metabolic activation of PAHs. The DNA damage in the L132 in co-culture following exposure to B[a]P have suggested that some PAH metabolites generated by the MA could be have a genotoxic action on L132. (authors)
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[en] Environmental exposure to fine airborne particulate matter (PM 2.5) is thought to be responsible for cardiopulmonary diseases, including lung cancer. However, the mechanisms of action potentially involved in PM2.5 toxicity are not yet fully described. Mutations in the TP53 gene are the most common alterations in human solid tumors. TP53 mutational patterns have sometimes been linked to carcinogen exposure. The purpose of this study was to determine the mutations that alter the functionality of this transcription factor in a model of human epithelial lung cells (A549) exposed to the fine particulate fraction (PM2.5) of an atmospheric aerosol sampled under urban and industrial influences. PM2.5 was collected in Dunkerque City by cascade impaction. Its physicochemical characterization revealed the presence of many inorganic and organic compounds, including some that are known for their toxicity. The search for mutations altering the functionality of the P53 protein was performed 72 h after exposure of A549 cells to PM2.5 at its lethal concentration at 50% (LC50, 118.60 μg/mL = 31.63 μg/cm2 ), using the Functional Analysis of Separated Alleles in Yeast (FASAY). Sixteen mutations altering P53 function were detected after A549 cells exposure to the collected PM2.5: eight deletions of one or two nucleotides and eight nucleotide substitutions, mainly transitions A > G and G > A. These mutations are described in the literature as possibly caused by endogenous mechanisms, such as oxidative stress. This kind of alteration can be induced by metal content of the PM2.5, as well as by metabolic activation of the organic compounds coated onto its surface. Involvement of oxidative stress in TP53 mutations was confirmed by the detection of an oxidative DNA adduct, 8-hydroxy-2'-deoxyguanosine (8-OHdG), in A549 cells exposed to the collected PM. (authors)
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[en] Epidemiological studies associate air pollution, especially particulate, increased morbidity and mortality from respiratory and cardiovascular origin . Africa, which has an urbanization rate among the highest in the world, is particularly exposed. The 'Initiative on the air quality in Sub-Saharan Africa' showed the importance of atmospheric concentrations of certain pollutants such as nitrogen oxides, sulfur dioxide and particulate matter (PM10). Like the great capitals of Africa, Abidjan, economic capital and most industrialized city of Ivory Coast is facing an air pollution from industrial-urban and health consequences for its population of nearly 6 million inhabitants. To better understand the mechanisms of action resulting from pulmonary exposure to particulate atmospheric aerosols, we proposed: (i) to collect atmospheric particles (PM2.5) using high volume cascade impaction in the District of Abidjan in three influences (rural, urban or industrial), (ii) to determine their main physicochemical, (iii) assess their cytotoxicity and their role in the induction of oxidative damage in a model of human lung cells (A549) in culture. The chemical composition of the atmospheric particles revealed their heterogeneity, and many inorganic (e.g. Al, Ca, Fe, Mn, Zn, Ni, Cr, Cu, Pb, Mg) and organic compounds (e.g. paraffins) were quantified at the three sites. Their effect concentrations (EC) to 10 and 50% on the A549 were as follows: influence rural: EC10 = 5.91 μg/cm2 and EC50 29.55 μg/cm2, urban influence: EC10 = 5 .45 μg/cm2 and EC50 = 27.23 μg/cm2, and industrial influence: EC10 = 6.86 μg/cm2 and EC50 = 34.29 μg/cm2. Exposure of A549 cells to Abidjan city's PM samples for 24, 48 or 72 hours to their EC10 or EC50 induced oxidative damage, as demonstrated by the formation of malon-dialdehyde, changes in enzyme activity of superoxide dismutase and alteration of glutathione status. (authors)
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[en] Epidemiological studies have associated the increase of respiratory and cardiovascular mortality and morbidity with high levels of air pollution particulate matter (PM). However, the underlying mechanisms of actions by which PM induce adverse health effects are still unclear. We have recently undertaken an extensive investigation of the adverse health effects of air pollution PM2.5, and shown that in vitro short-term exposure to PM2.5 induced oxidative stress and inflammation in human lung epithelial cells (L132). Hence, it was convenient to complete the physical and chemical characterization of PM and to investigate whether in vitro short-term exposure to PM could be imply in the activation of apoptosis. Accordingly, we found that 92.15% of PM were equal or smaller than 2.5 μm and their specific surface area was 1 m2/g. Inorganic (i.e. Fe, Al, Ca, Na, K, Mg, Pb, etc.) and organic (i.e. polycyclic aromatic hydrocarbons) chemicals were found in PM, suggesting that much of them derived from wind-borne dust from the industrial complex and the heavy motor vehicle traffic. In other respects, we showed that PM exposure induced apoptosis by activating not only the tumor necrosis factor-alpha (TNF-α)-induced pathway (i.e. TNF-α secretion, caspase-8 and -3 activation), but also the mitochondrial pathway (i.e. 8-hydroxy-2'-desoxyguanosine formation, cytochrome c release from mitochondria, caspase-9 and -3 activation). Moreover, changes in the transcription rates of p53, bcl-2, and bax genes, on the one hand, and DNA fragmentation, on the other hand, were reported in PM-exposed proliferating L132 cells, revealing the occurrence of apoptotic events. Taken together, these findings suggested that in vitro short-term exposure to PM2.5 induced apoptosis in L132 cells
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