Bifenazate is a novel acaricide for selective foliar spraying and is widely used to control mites in agricultural production. However, its toxicity to aquatic organisms is unknown. Here, a zebrafish model was used to study bifenazate toxicity to aquatic organisms. Exposure to bifenazate was found to cause severe cardiotoxicity in zebrafish embryos, along with disorders in the gene expression related to heart development. Bifenazate also caused oxidative stress. Cardiotoxicity caused by bifenazate was partially rescued by astaxanthin (an antioxidant), accompanied by cardiac genes and oxidative stress-related indicators becoming normalized. Our results showed that exposure to bifenazate can significantly change the ATPase activity and gene expression levels of the calcium signaling pathway. These led to heart failure, in which the blood accumulated outside the heart without entering it, eventually leading to death. The results indicated that bifenazate exposure caused cardiotoxicity in zebrafish embryos through the induction of oxidative stress and inhibition of the calcium signaling pathway.

Diclofop-methyl (DM) is one of the most widely used herbicides in agriculture production and has been frequently detected in both freshwater and environments, even agricultural products. However, the potential toxic effects of DM on organisms and the underlying mechanisms are still poorly understood. In this study, we utilized zebrafish to evaluate the toxicity of DM during the cardiovascular developmental process. Exposure of zebrafish embryos to 0.75, 1.0 and 1.25 mg/L DM induced cardiac defects, such as pericardial edema, slow heart rate and long SV-BA distance but the vascular development in zebrafish larvae was not influenced by DM treatment. The expression of cardiac-related genes were disordered and DM exposure initiated disordering cardiogenesis from the period of precardiac mesoderm formation. Moreover, the apoptosis and proliferation of cardiomyocytes were not influenced but the levels of oxidative stress were upregulated by DM exposure. Fullerenes and astaxanthin was able to rescue cardiac defects caused by DM via downregulating oxidative stress. Wnt signaling was downregulated after DM treatment and activation of Wnt signaling could rescue cardiac defects. Therefore, our results suggest that DM has the potential to induce cardiac developmental toxicity through upregulation of Wnt-Mediated (reactive oxygen species) ROS generation in zebrafish larvae.

Oxadiazon-Butachlor (OB) is a widely used herbicide for controlling most annual weeds in rice fields. However, its potential toxicity in aquatic organisms has not been evaluated so far. We used the zebrafish embryo model to assess the toxicity of OB, and found that it affected early cardiac development and caused extensive cardiac damage. Mechanistically, OB significantly increased oxidative stress in the embryos by inhibiting antioxidant enzymes that resulted in excessive production of reactive oxygen species (ROS), eventually leading to cardiomyocyte apoptosis. In addition, OB also inhibited the WNT signaling pathway and downregulated its target genes includinglef1, axin2 and β-catenin. Reactivation of this pathway by the Wnt activator BML-284 and the antioxidant astaxanthin rescued the embryos form the cardiotoxic effects of OB, indicating that oxidative stress, and inhibition of WNT target genes are the mechanistic basis of OB-induced damage in zebrafish. Our study shows that OB exposure causes cardiotoxicity in zebrafish embryos and may be potentially toxic to other aquatic life and even humans.

Copper (Cu) is one of the toxic elements that cause environmental pollution. As a result of excessive accumulation of copper in the organism, it causes damage in various organs and tissues and hemolysis in erythrocytes. Astaxanthin (ATX) is a pigment belonging to the xanthophyll family, which is an oxygenated derivative of carotenoids. Thanks to its powerful antioxidant properties, ATX has an extraordinary potential to protect the organism against various diseases, especially cancer. The main objective of this study was to investigate the toxic effect of copper ions on the glucose 6-phosphate dehydrogenase (G6PD), 6-phospho-gluconate dehydrogenase (6PGD), glutathione reductase (GR), glutathione S-transferase (GST), and thioredoxin reductase (TrxR) enzymes and the role of astaxanthin in reducing this effect. In in vivo study, Wistar Albino male rats (n=28) were randomly divided into 4 groups: the control group, copper (Cu2+) group, astaxanthin (ATX) group, and copper + astaxanthin (Cu2++ATX) group. The results show that G6PD enzyme activity in Cu2+ group was strongly inhibited (p ˂ 0.05), while in other groups, there were no significant effects compared to the control group (p ⩾ 0.05). 6PGD enzyme activity was significantly reduced in Cu2+ group compared to that in the control group (p ˂ 0.05), and GR enzyme activity was lower in Cu2+ group compared to that in the control group (p ˂ 0.05). Similarly, when GST enzyme activity was evaluated, a strong decrease was observed in the Cu2+ group compared to that in the control group (p ˂ 0.05), while the enzyme activity in the Cu2++ATX group approached the control group (p ⩾ 0.05). When TrxR enzyme activity level was examined, a statistically significant decrease was observed in the Cu2+ and Cu2++ATX groups (p ˂ 0.05), and the enzyme activity in the ATX group was found to be close to that in the control group. When in vitro results were evaluated, it was observed that copper ions inhibited G6PD enzyme purified from rat erythrocyte tissues with IC50=1.90 μM value and Ki = 0.97 μM ± 0.082 value and the inhibition was non-competitive. From the results, it can be concluded that Cu2+ ions have an inhibitory effect on rat erythrocyte pentose phosphate pathway and antioxidant system enzymes both in vivo and in vitro, and astaxanthin reduces this effect.

Purpose This paper analyses the presence of polychlorinated biphenyls (PCBs) in escaped: farmed and wild salmons in southern Chile, analysing their concentrations and congener profiles in two species (Oncorhynchus kisutch and Oncorhynchus mykiss). Methods Muscle samples from both farmed and escaped fish of two species, O. mykiss (rainbow trout) and O. kisutch (coho salmon), were analysed for PCBs (42 congeners). To differentiate between the wild salmon and the salmon that have escaped from fish farms, the astaxanthin content in the muscular tissue was analysed with a high-performance liquid chromatography -diode array detector method. PCBs were measured by gas chromatography with an electron capture detector. Results The levels of astaxanthin can be used to differentiate between farmed, escaped and wild-borne salmons with statistically different concentrations. When comparing the total PCB concentrations for both trout and salmon samples, it can be determined that a separate analysis for farmed, escaped and wild-borne fish more accurately describes the real differences in the concentrations; these differences are hidden when separate analyses are not performed. The congener profiles are similar in both trout and coho salmon, where the tri-, tetra- and penta-CB congeners are the most abundant. Conclusion This study is the first report of PCBs in wild-borne, farmed and escaped salmons for the Southern Hemisphere, considering that Chile is actually one of the principal world producers of salmon.

Developing a use for the inedible parts of citrus, mainly peel, would have great environmental and economic benefits worldwide. Astaxanthin is a value-added fine chemical that affects fish pigmentation and has recently been used in healthcare products for humans, resulting in an increased demand. This study aimed to produce astaxanthin from a citrus, ponkan, peel extract using the yeast Xanthophyllomyces dendrorhous, which has the ability to use both pentose and hexose. Feeding on only ponkan peel extract enhanced X. dendrorhous growth and the concomitant astaxanthin production. Additionally, we determined that pectin and its arabinose content were the main substrate and sole carbon source, respectively, for X. dendrorhous growth and astaxanthin production. Thus, ponkan peel extract could become a valuable resource for X. dendrorhous–based astaxanthin production. Using citrus peel extract for microbial fermentation will allow the development of processes that produce value-added chemicals from agricultural byproducts.