ABSTRACT
The cytochromes P450 (CYP450) represent a major enzyme family operating mostly in the first step of xenobiotic detoxification in aquatic organisms. The ability to measure these CYP450 enzymes' activities provides a crucial tool to understand organisms' response to chemical stressors. However, research on CYP450 activity measurement is still limited and has had variable success. In the present study, we optimize, compile, and compare existing scientific information and techniques for a series of CYP450 biomarkers (EROD, MROD, ECOD, APND, and ERND) used on Daphnia magna. Additionally, we explored these CYP450 biomarkers' activities through the first 5 days of life of daphnids, providing a link between their age and sensitivity to chemicals. In the experiment, daphnids were exposed to an organophosphate pesticide (diazinon) from birth to measure the molecular response of the detoxification process. Our results suggest EROD as the most applicable biomarker for organisms such as D. magna, with a higher organophosphate detoxification rate in daphnids that are 2 and 5 days old. Additionally, a larger body size allowed a more accurate EROD measurement; hence, we emphasize the use of 5-day-old daphnids when analyzing their detoxification response.
ABSTRACT
As the smallest environmental microplastics (EMPs), even at nanoscale, are increasingly present in the environment, their availability and physical and chemical effects on marine organisms are poorly documented. In the present study, we primarily investigated the uptake and accumulation of a mixture of environmental microplastics (EMPs) obtained during an artificial degradation process in early-juvenile sea bass (Dicentrarchus labrax). Moreover, we evaluated their hazardous effects using biochemical markers of cytotoxicity. Polymer distribution and composition in gill, gut, and liver were analyzed using polarized light microscopy (PLM) and Raman microspectroscopy (RMS). Our findings revealed the size-dependent ingestion and accumulation of smaller MPs (0.45-3 µm) in fish tissues even after a short-term exposure (3 and 5 days). In addition to MPs, our results showed the presence of plastic additives including plasticizers, flame retardants, curing agents, heat stabilizers, and fiber-reinforced plastic materials in fish tissues, which contributed mostly to the larger-sized range (≥ 1.2 µm). Our data showed that significant oxidative alterations were highly correlated with MPs size range. Our results emphasized that the toxicity of smaller EMPs (≤ 3 µm) was closely related to different factors, including the target tissue, exposure duration, size range of MPs, and their chemical properties.
