No abstract

The microplastic "vector effect" has received increasing attention. The aim of this study was to investigate the influence of polyethylene microplastic beads (PE MP) on accumulation and associated oxidative stress responses attributed to fluoranthene (Flu) in blue mussels, Mytilus edulis. Blue mussels were exposed for 96 h to four treatment groups: Flu-only, MP-only, Flu and MP coexposure, and Flu-incubated MP. Treatments were conducted at a low and high concentration (50 μg/L and 100  Flu μg/L and 100, and 1000 MP/mL). Results demonstrated that in both the gill and digestive gland, coexposure did not markedly affect Flu uptake, but this treatment significantly decreased tissue Flu concentrations. Antioxidant responses including activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidases (GPx), and levels of total glutathione (GSH) in both gills and digestive glands were significantly altered suggesting a perturbation of redox state induced by the exposure conditions. Although individual biomarkers varied, the biomarker profile enabled certain generalizations to be made. Antioxidant responses occurred more likely in gill tissue than in digestive gland. Individual contaminant exposures to Flu or MP led to varying responses, but coexposures and incubated exposures did not result in additive or synergistic effects. Exposure concentrations (i.e., low or high treatments) were not a consistent a predictor of response; and the internal Flu dose did not consistently predict outcome of various biomarkers. Importantly, MP-only exposure appeared to be capable of eliciting direct effects on the oxidative stress system as demonstrated by the activities of CAT and GPx. These findings warrant further investigation.

We examined the time-course stress responses in the liver of rainbow trout exposed to cuprous chloride (CuCl) and cupric chloride (CuCl). The treatment groups received a single intraperitoneal injection of CuCl or CuCl (both at a dose of 0.01 and 0.05 mg/kg); the control group received only the physiologic solution vehicle. Liver tissue samples were analyzed for total copper, superoxide dismutase, catalase, glutathione peroxidases, glutathione reductase, glutathione S-transferase, glyoxalases, and lactate dehydrogenase at 3, 6, and 9 days post-injection. Total glutathione, metallothionein, and malondialdehyde levels were also measured. The time course of metal accumulation differed between the groups; no dose-response relationship for metal load was found. Both copper species elicited significant changes in oxidative stress markers and in metal trapping. Copper underwent adaptive shifts in glutathione and metallothionein concentrations. The defense strategy primarily versus CuCl first involved glutathione, with a peak in metallothionein levels at day 6 for CuCl (at both doses) and for CuCl (0.05 mg/kg). Early stimulation of lipid peroxidation was noted after treatment with the higher copper dose and at day 9 after treatment with the lower dose of both CuCl and CuCl. Antioxidant enzyme activity was impaired due to a more or a less severe oxidative stress condition in relation to the copper species and exposure time. Copper dynamics, in terms of metal accumulation and homeostatic regulation, is noticeably complex. The present findings may advance our understanding of the effects of both copper species on the antioxidant response of rainbow trout.

Farmed trout are commonly fed carotenoid-enriched diets during the finishing period to acquire the typical red-to-pink flesh color in salmonid muscle. The aim of this study was to examine the effects of the two xanthophylls, astaxanthin (Ax) or canthaxanthin (Cx), administered individually or in combination, on oxidative stress biomarkers in kidney and liver of rainbow trout. Specimens were fed Ax and/or Cx enriched diets with 75 or 25 mg of each compound/kg for eight weeks. Changes in concentration of oxidative stress biomarkers, such as glutathione, superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, and glutathione S-transferase, were recorded in Axand Cx-dosed trout. The two carotenoids, mainly Cx, impelled antioxidant defense in rainbow trout, while lipid peroxidation process was not recorded for all Ax or Cx-dosed trout. Furthermore, both combined xanthophylls did not exert remarkable combined effects in liver and kidney. Biomarker responses were generally altered in both tissues throughout both experimental endpoints, suggesting that different time-dependent pathways may be involved in strengthening the anti-oxidative defense in Ax and/or Cx-fed trout.

A growing interest in developing and commercialization of new ecofriendly plastic polymers is 26 occurring attributed to the impact of marine plastics debris and microplastics that result from the 27 degradation of oil-based polymers as these substances adversely affect ecosystem health. Recently, polyhydroxybutyrate (PHB) has become of interest due its biodegradability and physicochemical 29 properties. However, biological consequences resulting from bioplastics exposure remains to be 30 determined. Further, few data are apparently available regarding the potential for bioplastics to act as a 31 vector for exogenous chemicals in the environment. The aim of the study was to compare the effects of 32 polyethylene (PE MPs) and polyhydroxybutyrate (PHB MPs) microplastics administered alone or in 33 combination with fluoranthene (Flu) on detoxifying enzymes in digestive glands and gills of Mytilus 34 edulis. Blue mussels were exposed for 96hr to 8 experimental groups: control, Flu-only, PE MPs-only, 35 PHB MPs-only, PE MPs-Flu co-exposure, PHB MPs-Flu co-exposure, Flu-incubated PE MPs and Flu-36 incubated PHB MPs. Superoxide dismutase (SOD), catalase (CAT), glutathione peroxidases (GPx), 37 glutathione S-transferase (GST) and glutathione reductase (GR) were found to be significantly 38 susceptible to Flu and plastics in both tissues. Interestingly, single exposure to PHB MPs led to 39 decreased levels of CAT and GST in gills, SOD in digestive glands and SeGPx in both tissues. In co-40 exposure and incubation treatments, biochemical responses were generally comparable with those 41 exerted by PE MPs or PHB MPs only, suggesting an apparent absence of combined effects with 42 pollutant. Data demonstrate the ecotoxicological impact of bioplastics materials on digestive glands 43 and gills of Mytilus edulis.