Assessing the AhR-mediated activity of Polycyclic Aromatic Hydrocarbons (PAHs) and their Methylated Derivatives using AhR-CALUX Bioassay

Activity: Talk or presentationTalk or presentation at a conference


Polycyclic aromatic hydrocarbons (PAHs) are a group of organic compounds containing two or more fused aromatic rings. These environmental pollutants are ubiquitous and originate from the incomplete combustion of organic matter and/or mobilization by micro-organisms. Due to their hydrophobic nature, they tend to accumulate in sediments and soils, as well as in the tissues of living organisms, including humans (Goldman et al., 2001; Li et al., 2010). Meanwhile, PAHs in water are frequently detected as well (Li et al., 2010). PAHs are known to be harmful to human health and the environment, with some of them being carcinogenic and mutagenic (Goldman et al., 2001). To assess the potential toxicity of PAHs, 16 EPA PAHs are commonly monitored using instrumental analytical methods such as gas chromatography-mass spectrometry (GC-MS). While it is a highly sensitive method, it has some limitations when it comes to assessing the bio-reactivity of PAHs and their mixtures. This is because PAHs are often present in complex mixtures, and the toxicity of these mixtures is difficult to predict based on the individual components alone (Andersson and Achten, 2015). In addition, derivative forms of PAHs, such as methylated PAHs (Me-PAHs), are also of growing concern since they are frequently detected in the environment and have been shown to be more toxic than their parent compounds (Larsson et al., 2018, 2014).

To address these challenges, the Chemically Activated LUciferase gene eXpression (CALUX) bioassay was developed to screen for activation of the aryl hydrocarbon receptor (AhR) signaling pathway, which is a well-known receptor for polycyclic aromatic compounds (He et al., 2011; Pieterse et al., 2013). This bioassay consists of recombinant cell lines that have been stably transfected with AhR-responsive luciferase reporter genes (Murk et al., 1996). Upon exposure to AhR agonists, the activation of AhR leads to the production of luciferase, which is proportional to the amount and potency of the ligands that are present in the sample to which the cells are exposed (Murk et al., 1996).

Although interactions between PAHs and AhR have been investigated previously using the CALUX cell line H4IIe cells (Larsson et al., 2014; Pieterse et al., 2013), few studies have assessed the relative potencies (REP) of Me-PAHs (see however Boonen et al., 2020). The aim of this study is to optimize the CALUX assay based on H1L7.5c1 cell lines (He et al., 2011) using benzo[a]pyrene (BaP) as a reference ligand and to assess the AhR-induced activity of sixteen EPA priority PAHs and five Me-PAHs individually and in the mixture. A growing body of experimental evidence indicates that the in vitro activities of these mixtures could be predicted from the overall response of their components using the concept of the concentration addition (CA) model and/or the independent mode of action (IA). Both of these models assume an additive effect, i.e. the chemicals in the mixture act together but do not interact with each other. This is the hypothesis we tested in this study with mixtures of 2-5 constituents including PAHs and Me-PAHs.

This study presents a rapid, reliable, sensitive, and accurate method for screening the activity of PACs. The agonist activity of sixteen PAHs and 5 methylated derivatives was determined with twelve of them showing strong agonistic activity. Future analysis of antagonistic activity will provide more insight and information about mixture effects.
Period10 Sep 202314 Sep 2023
Event titleDioxin2023
Event typeConference
LocationMaastricht, Netherlands