Oxidative damage in human epithelial alveolar cells exposed in vitro to oil fly ash transition metals.
Among particulate matter emissions from combustion processes, oil fly ash (OFA) displays a marked oxidative and inflammogenic reactivity, due to the high content of bioavailable transition metals. In the present study, we evaluated the biological effects of an OFA water solution, composed of the transition metals Fe (57.5%), V (32.4%), and Ni (10.1%), in human epithelial alveolar cells (A549 line). The fluorimetric analysis by 2',7'-dichlorofluorescein showed a significant, dose- and time-dependent induction of intracellular reactive oxygen species (ROS) triggered by OFA metal components at subtoxic doses. The metal chelator deferoxamine and the radical scavenger dimethylsulfoxide attenuated the metal-induced generation of ROS. Confocal microscopy observations strengthened these findings and showed an intense cytoplasmic fluorescence with perinuclear thickenings in A549 cells, in the absence of morphological damage. Metal-induced generation of ROS was significantly correlated with a dose- and time-dependent DNA damage, as assessed by single cell gel electrophoresis (comet assay). Catalase was able to decrease dramatically DNA damage. Fluorimetric analyses by diphenyl-1-pyrenylphosphine showed a parallelism between generation of ROS and formation of lipid peroxides. The results obtained in the experiments evaluating the effects of individual metal solutions did not show any significant difference in DNA damage between Fe(III) and V(IV), but highlighted the higher capability of V(IV) to increase ROS in the cytoplasmic compartment. The different behavior of these two elements, confirmed by the weak Fe-induced lipid peroxidation, may be ascribed to the presence of Fe-binding proteins, such as ferritin, in the cytoplasm. Finally, Ni(II) had negligible effects on ROS production. On the whole, the results obtained in this study show the strong capability of transition metals adsorbed to OFA to cause widespread damage to biological macromolecules, and suggest potential health effects resulting from exposure to power plant emissions in industrialized sites.
Di Pietro
Angela
A
Department of Hygiene, Public Health and Preventive Medicine, University of Messina, I-98100 Messina, Italy.
Visalli
Giuseppa
G
Munaò
Fortunato
F
Baluce
Barbara
B
La Maestra
Sebastiano
S
Primerano
Patrizia
P
Corigliano
Francesco
F
De Flora
Silvio
S
D000393:Air Pollutants / Q000009:adverse effects; D002244:Carbon / Q000009:adverse effects*; D002374:Catalase / Q000494:pharmacology; D045744:Cell Line, Tumor; D060729:Coal Ash; D004249:DNA Damage; D004847:Epithelial Cells / Q000187:drug effects* / Q000473:pathology; D005452:Fluoresceins; D006801:Humans; D007501:Iron / Q000009:adverse effects; D015227:Lipid Peroxidation / Q000187:drug effects; D009532:Nickel / Q000009:adverse effects; D010084:Oxidation-Reduction / Q000187:drug effects; D018384:Oxidative Stress / Q000187:drug effects*; D052638:Particulate Matter / Q000009:adverse effects*; D011650:Pulmonary Alveoli / Q000187:drug effects* / Q000473:pathology; D017382:Reactive Oxygen Species / Q000009:adverse effects* / Q000032:analysis; D028561:Transition Elements / Q000009:adverse effects*; D014639:Vanadium / Q000009:adverse effects
D000393:Air Pollutants; D060729:Coal Ash; D005452:Fluoresceins; D052638:Particulate Matter; D017382:Reactive Oxygen Species; D028561:Transition Elements; D014639:Vanadium; C037631:2',7'-dichlorofluorescein; D002244:Carbon; D009532:Nickel; D007501:Iron; D002374:Catalase