Development of stable HSPA1A promoter-driven luciferase reporter HepG2 cells for assessing the toxicity of organic pollutants present in air

Abstract

HSPA1A (HSP70-1) is a highly inducible heat shock gene up-regulated in response to environmental stresses and pollutants. The aim of our study was to evaluate the sensitivity of the stable metabolically competent HepG2 cells containing a human HSPA1A promoter-driven luciferase reporter (HepG2-luciferase cells) for assessing the toxicity of organic pollutants present in air. The HepG2-luciferase cells were validated by heat shock treatment and testing three organic compounds (pyrene, benzo[a]pyrene, and formaldehyde) that are ubiquitous in the air. The maximal level of HSPA1A (HSP70-1) and relative luciferase activity induced by heat shock were over three and nine times the control level, respectively. Pyrene, benzo[a]pyrene, and formaldehyde all induced significantly elevated levels of relative luciferase activity in a dose-dependent manner. Extractable organic matter (EOM) from urban traffic and coke oven emissions in ambient air were tested on the HepG2-luciferase cells. The traffic EOM induced significant increase in relative luciferase activity at concentrations of picogram per liter. The coke oven EOM produced a strong dose-dependent induction of relative luciferase activity up to six times the control value. Significant increases in relative luciferase activity were observed at concentrations that were as low, or lower than the concentrations that the tested organic pollutants decreased cell viability, and increased malondialdehyde concentration, Olive tail moment, and micronuclei frequency. Therefore, we conclude that the HepG2-luciferase cells are a valuable tool for rapid screening of the overall toxicity of organic pollutants present in air.