Oxidative potential, cytotoxicity, and intracellular oxidative stress generating capacity of PM10 at an urban background site in Italy

Maria Giulia Lionetto

It is widely recognized that long and short-term exposure to atmospheric particulate matter (PM) has detrimental effects on human health, in particular on pulmonary and cardiovascular systems. Recent studies suggest that several effects of atmospheric PM on human health may be mediated by the induction of oxidative stress, which has been considered as an important underlying mechanism of action for the outcome of adverse health effects. The aim of the study was to investigate the toxicological properties of PM10 sampled at an urban background site (the Environmental-Climate Observatory of ISAC-CNR in Lecce, Southern Italy) focusing on the intrinsic oxidative potential (OP), measured with the acellular dithiothreitol (DTT) assay test, and on health-related cellular outcomes such as the induction of intracellular oxidative stress, assessed by the ROS sensitive fluorescent probe CM-H2DCFDA, cytotoxicity (measured as reduced cell viability by the MTT assay), and genotoxicity (measured by comet test). In particular, the study wanted to assess whether the PM10 intrinsic OP is correlated with cellular endpoints, and whether cellular and acellular endpoints are correlated with chemical properties of atmospheric PM10 such as concentration and carbon content. The cellular endpoints were investigated on A549 cell line, representative of the Alveolar Type II pneumocytes of the human lung, and widely used as a cellular model.
The obtained results showed a detectable intrinsic OP, cytotoxicity, and intracellular oxidative stress generating capacity (OSGC) in aqueous extracts of PM10 samples. A statistically significant correlation was observed between OP, cytotoxicity, and OSGC with the carbon content of PM10. This suggests that combustion sources at this site play an important role in determining cellular oxidative stress and cytotoxicity of PM10. The OP was correlated to OSCG, suggesting that the ability of PM10 to generate intracellular oxidative stress conditions is related to its intrinsic oxidative potential depending on the physico-chemical properties of the particles. The OSGC results are well correlated with cell mortality and, a lower, but still statistically significant correlation is observed between intrinsic OP and reduced cellular viability, suggesting that the prooxidant properties of PM10 play a key role in the multiple mechanisms underlying PM10 cytotoxicity. Genotoxicity results, although limited to a subset of samples, are well correlated with OSGC, cytotoxicity and OP and this also suggest the relationship between the prooxidant properties of PM and genotoxic effects. In conclusions, obtained results demonstrate the correlation between the intrinsic oxidative potential of particulate matter and health related cellular outcomes.

 

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