oxidative potential

Oxidative potential (OP) has been proposed as a useful descriptor for the ability of particulate matter (PM) to generate reactive oxygen species (ROS) and consequently induce oxidative stress in biological systems, which has been recognized as one of the most important mechanisms responsible for PM toxicity. The dithiothreitol (DTT) assay is one of the most frequently used techniques to quantify OP because it is low-cost, easy-to-operate, and has high repeatability. With two thiol groups, DTT has been used as a surrogate of biological sulfurs that can be oxidized when exposed to ROS. Within the DTT measurement matrix, OP is defined as the DTT consumption rate. Often, the DTT consumption can be attributed to the presence of transition metals and quinones in PM as they can catalyze the oxidation of DTT through catalytic redox reactions. However, the DTT consumption by non-catalytic PM components has not been fully investigated. In addition, weak correlations between DTT consumption, ROS generation, and cellular responses have been observed in several studies, which also reveal the knowledge gaps between DTT-based OP measurements and their implication on health effects. In this review, we critically assessed the current challenges and limitations of DTT measurement, highlighted the understudied DTT consumption mechanisms, elaborated the necessity to understand both PM-bound and PM-induced ROS, and concluded with research needs to bridge the existing knowledge gaps.

Abstract The chemical composition and oxidative potential (OP) of particulate matter (PM10) samples were investigated at an industrial (Ala) and a background (TN) site in northern Italy. Three emission sources of airborne metals were identified by Positive Matrix Factorization (PMF) analysis, i.e., the zinc coating facility located in the area, the traffic on the nearby motorway and the pesticides normally used in the extensive vineyard cultivation. PM10 redox activity was measured using dithiothreitol (OPDTTV) and ascorbic acid (OPAAV) cell-free assays. Similar OPDTTV responses were obtained at the two sites (0.60 ± 0.23 mmol min−1 m−3), while higher (OPAAV) values were measured at Ala (1.4 ± 1.1 nmol min−1 m−3) than at TN (0.7 ± 0.4 nmol min−1 m−3). Overall, both OPDTTV and OPAAV responses were found to be broadly correlated with several inorganic species, namely ions and soluble metals, and organic components. In particular, OPAAV responses are mainly affected by Zn directly emitted from the zinc factory and Cu used in the vineyard cultivation. Therefore, the higher OPAAV values measured at Ala can be explained by the higher concentration of these metals at the industrial site.