Quinoxyfen 1995-2019 is the story's end? Evaluation of its adverse effects on head size and nervous system genes involved in synaptic maturation

In 2013 quinoxyfen (QXY) was included in the list of priority hazard pollutants of the European Water Framework Directive due to its toxicity to aquatic organisms. The use of products formulated containing QXY was banned from all commercials starting from 27th June of 2019. QXY is an organic pollutant with potential persistence, bioaccumulation and this must not lower attention to this pollutant. To date the effects of this compound on development are not completely clear, thus this research tries to elucidate the adverse effects of QXY on zebrafish development. The study aims to understand the toxicological effects of QXY using the zebrafish as in vivo model and performing toxicological and molecular investigations. Considering the FET test results two sublethal concentrations, 0.4 mg/L and 0.8 mg/L were chosen for subsequent analysis. The expression of the gad1b, cyp19a1b, shank3a, nrxn1a and c-fos genes, involved in the development of the nervous system and the regulation of synaptic transmission, were evaluated. To confirm the potential neurotoxic effects of the treatment on the development of the central nervous system, both a transgenic Tg(neuroD:gfp ia50) line was used for confocal microscopy and Orange Acridine was used on wild type larvae to assess the presence of neuronal apoptosis. The results showed sub-lethal alterations, particularly affecting craniofacial and brain development highlighting as QXY may represent a possible endocrine disruptor able to induce severe cartilage defects, small head and tremor phenotype in zebrafish larvae and a strong modulation of the selected genes.