Relationship between Reactive Oxygen Species (ROS) activity and Cytotoxicity of Ambient Particles

摘要

Associations of particulate matter (PM) concentration with cardiopulmonary disease and mortality have been reported in several studies. Threat of PM to public health is likely due to reactive oxygen species (ROS) generation by PM. However, only a handful of studies could demonstrate a consistent correlation between biological toxicity endpoints and ROS formation measured in acellular assays. In this study, we targeted to investigate these associations by measuring the acellular ROS generation and cytotoxicity of ambient particulate matter (PM) samples collected from an urban site. The cytotoxicity of water-soluble PM is assessed by exposing aerosol extracts to Chinese hamster ovary (CHO) cells. Two methods were used to assess the ROS generation ability -1. dithiothreitol (DTT) loss (conventional DTT assay); and 2. hydroxyl radical generation through redox cycling in the DTT system. Inhibition of CHO cells by soluble PM was observed, and half maximal inhibitory concentrations (IC_(50)) were calculated for the PM samples, which range from 43.6% to 74.0% (percentage of soluble PM extract). Interestingly, we found strong and significant correlation between ROS generation in the DTT system and IC_(50)(R~2 = 0.60, p<0.05). To further understand the chemical components, which might drive the response of both DTT and cytotoxicity assays, we measured the concentrations of metals and water-soluble organic carbon (WSOC) in PM extracts. Fe, Cu, Zn and WSOC were significantly correlated with both IC_(50) and ROS generation in DTT assay. Further chemical analysis of the collected samples in underway and would be presented in this talk. However, Our preliminary results indicate that measuring the ROS generation from PM could be used as a biologically relevant metric to assess the toxicity and health impacts from ambient aerosol pollution.