GFP assay as a sensitive eukaryotic screening model to detect toxic and genotoxic activity of azaarenes

Azaarenes are nitrogen-containing polyaromatic heterocyclic compounds (NPAHs). The majority of the azaarenes found in the environment originate from anthropogenic sources. Concentrations of NPAHs found in the environment are reported to be one to two orders of magnitude lower than polycyclic aromatic hydrocarbons (PAHs) concentrations, yet their biological effects can be of similar magnitude. Very few studies on the genotoxicity of azaarenes are available in the literature. In the present study, a preliminary profile of both the toxic and genotoxic potential of 5 PAHs and their 20 aza-analogues were investigated. To assess the toxic and genotoxic activity, a green fluorescent protein (GFP) assay based on the yeast Saccharomyces cerevisiae was selected. To compare the sensitivity of this eukaryotic short-term assay with bacterial screening tests, the Toxi-Chromotest for toxicity and SOS-Chromotest for genotoxicity assessment were also performed. This comparison indicates that in most cases, the yeast GFP assay is apparently of comparable specificity to the bacterial toxicity or genotoxicity tests with respect to the correlation of positive/negative responses, but much more sensitive with respect to the effective concentration values. In the cases of phenazine, phenanthridine, 1,10-phenanthroline, or 4,7-phenanthroline, one to two orders of magnitude lower IC20 and minimum genotoxic concentration values in the yeast GFP assay were observed. In this study, the authors present evidence that genotoxicity assessment using the yeast GFP assay can provide a simple system to monitor the activity of these environmental pollutants that could possess mutagenic potential at low concentrations.