Role of biological antioxidants in benzanthrone toxicity

Ligand-Specific Transcriptional Mechanisms Underlie Aryl Hydrocarbon Receptor-Mediated Developmental Toxicity of Oxygenated PAHs

Polycyclic aromatic hydrocarbons (PAHs) are priority environmental contaminants that exhibit mutagenic, carcinogenic, proinflammatory, and teratogenic properties. Oxygen-substituted PAHs (OPAHs) are formed during combustion processes and via phototoxidation and biological degradation of parent (unsubstituted) PAHs. Despite their prevalence both in contaminated industrial sites and in urban air, OPAH mechanisms of action in biological systems are relatively understudied. Like parent PAHs, OPAHs exert structure-dependent mutagenic activities and activation of the aryl hydrocarbon receptor (AHR) and cytochrome p450 metabolic pathway. Four-ring OPAHs 1,9-benz-10-anthrone (BEZO) and benz(a)anthracene-7,12-dione (7,12-B[a]AQ) cause morphological aberrations and induce markers of oxidative stress in developing zebrafish with similar potency, but only 7,12-B[a]AQ induces robust Cyp1a protein expression. We investigated the role of the AHR in mediating the toxicity of BEZO and 7,12-B[a]AQ, and found that knockdown of AHR2 rescued developmental effects caused by both compounds. Using RNA-seq and molecular docking, we identified transcriptional responses that precede developmental toxicity induced via differential interaction with AHR2. Redox-homeostasis genes were affected similarly by these OPAHs, while 7,12-B[a]AQ preferentially activated phase 1 metabolism and BEZO uniquely decreased visual system genes. Analysis of biological functions and upstream regulators suggests that BEZO is a weak AHR agonist, but interacts with other transcriptional regulators to cause developmental toxicity in an AHR-dependent manner. Identifying ligand-dependent AHR interactions and signaling pathways is essential for understanding toxicity of this class of environmentally relevant compounds.

In vivo effect confirmation of anti-androgenic compounds in sediment contact tests with Potamopyrgus antipodarum

In order to investigate the sensitivity of Potamopyrgus antipodarum to anti-androgenic compounds, three spiked sediment tests were performed. The substances benzanthrone (7H-benz[de]anthracen-7-one), traseolide (ATII) and androstenone (5α-Androst-16-en-3-one) were previously identified in an effect-directed analysis study of the river Schijn in the north of Belgium. Although, in previous studies, all of the three compounds exhibited anti-androgenic activities in vitro, only the oxy-PAH benzanthrone had significant stimulating effects on the snails' reproduction. The reproduction of P. antipodarum was significantly stimulated, following a sigmoidal dose response curve, whereby an EC(50) of 10 ng/g dry sediment was calculated. Mortality was significantly increased at the highest concentration (69 ng/g dry sediment). The results indicate different relative potencies for the in vivo test with P. antipodarum and the in vitro anti-AR-CALUX assay, performed in a previous study. This highlights the importance of combined in vitro and in vivo assays for the effect assessment of field sediments.

Identification strategy for unknown pollutants using high-resolution mass spectrometry: androgen-disrupting compounds identified through effect-directed analysis

Effect-directed analysis has been applied to a river sediment sample of concern to identify the compounds responsible for the observed effects in an in vitro (anti-)androgenicity assay. For identification after non-target analysis performed on a high-resolution LTQ-Orbitrap, we developed a de novo identification strategy including physico-chemical parameters derived from the effect-directed analysis approach. With this identification strategy, we were able to handle the immense amount of data produced by non-target accurate mass analysis. The effect-directed analysis approach, together with the identification strategy, led to the successful identification of eight androgen-disrupting compounds belonging to very diverse compound classes: an oxygenated polyaromatic hydrocarbon, organophosphates, musks, and steroids. This is one of the first studies in the field of environmental analysis dealing with the difficult task of handling the large amount of data produced from non-target analysis. The combination of bioassay activity assessment, accurate mass measurement, and the identification and confirmation strategy is a promising approach for future identification of environmental key toxicants that are not included as priority pollutants in monitoring programs.

Bio-elimination of conjugated metabolites of 3-bromobenzanthrone in urine of rats and Guinea pigs

The profile of urinary metabolites of 3-bromobenzanthrone (3-BBA), an extensively used anthraquinone dye intermediate, in rats and guinea pigs was investigated using HPTLC system. A total of 10 fluorescent metabolites were detected in the urine of guinea pigs as compared to 8 in rats including the parent compound 3-BBA. The elimination of metabolites increased in a dose dependent manner in rats. The Rf values of metabolites in rats were 0.14, 0.29, 0.42, 0.52, 0.58, 0.64, 0.77 and 0.91 while that in guinea pigs were 0.23, 0.26, 0.34, 0.37, 0.44, 0.54, 0.56, 0.68, 0.76 and 0.95. The urine of 3-BBA (50 mg/kg b.wt) treated guinea pigs when digested with acid showed the disappearance of metabolite 1, 2, 5 and 7 indicating these to be the conjugated metabolites. Further, digestion of urine of 3-BBA treated guinea pigs with glucuronidase showed disappearance of metabolite 5 and 7 suggesting these as glucuronide conjugates. Digestion of urine with sulfatase enzyme resulted in disappearance of metabolite 1 which could be a sulfate conjugate. Urinary metabolite 2 which was found to be present even after digestion with glucuronidase or sulfatase but disappeared following acid treatment appears to be glutathione conjugate(s) which resulted in formation of metabolite 3 and 6. These results suggest that conjugated fluorescent metabolites of 3-BBA are excreted in urine of rats and guinea pigs.