Effect of monosultap on notochord development in zebrafish (Danio rerio) embryos.

Monosultap (Mon) is a broad-spectrum insecticide used in agricultural production to control stem borers in rice fields. Currently, little evidence shows how Mon affects notochord development in zebrafish (Danio rerio). In our study, zebrafish embryos were exposed to 0.25, 0.5, and 0.75 mg/L Mon to determine the effects of different concentrations of Mon on notochord development. Mon exposure reduced the body length, decreased the heart rate and hatchability, and induced notochord deformity in zebrafish. The effects of Mon exposure on the internal organization of the notochord and the structural abnormalities were determined based on histological staining of paraffinized tissue sections. Quantitative polymerase chain reaction (qPCR) and in situ hybridization findings revealed that the expression levels of genes related to notochord development (shha, col2a, and ptch2) showed an increasing trend in a concentration-dependent manner. An abnormal increase of apoptosis and cell proliferation in some parts of the notochord suggested that Mon exposure could cause developmental abnormality of the notochord. This study revealed the toxicity of Mon in notochord development. Our findings provide information in assessing the risk of Mon to the ecological environment and human health.

Pentachloronitrobenzene Reduces the Proliferative Capacity of Zebrafish Embryonic Cardiomyocytes via Oxidative Stress.

Pentachloronitrobenzene (PCNB) is an organochlorine protective fungicide mainly used as a soil and seed fungicide. Currently, there are few reports on the toxicity of PCNB to zebrafish embryo. Here, we evaluated the toxicity of PCNB in aquatic vertebrates using a zebrafish model. Exposure of zebrafish embryos to PCNB at concentrations of 0.25 mg/L, 0.5 mg/L, and 0.75 mg/L from 6 hpf to 72 hpf resulted in abnormal embryonic development, including cardiac malformation, pericardial edema, decreased heart rate, decreased blood flow velocity, deposition at yolk sac, shortened body length, and increased distance between venous sinus and arterial bulb (SV-BA). The expression of genes related to cardiac development was disordered. However, due to the unstable embryo status in the 0.75 mg/L exposure concentration group, the effect of PCNB on the expression levels of cardiac-related genes was not concentration-dependent. We found that PCNB increased reactive oxygen species stress levels in zebrafish, increased malondialdehyde (MDA) content and catalase (CAT) activity, and decreased superoxide dismutase (SOD) activity. The increased level of oxidative stress reduced the proliferation ability of zebrafish cardiomyocytes, and the expressions of zebrafish proliferation-related genes such as cdk-2, cdk-6, ccnd1, and ccne1 were significantly down-regulated. Astaxanthin (AST) attenuates PCNB-induced reduction in zebrafish cardiomyocyte proliferation by reducing oxidative stress levels. Our study shows that PCNB can cause severe oxidative stress in zebrafish, thereby reducing the proliferative capacity of cardiomyocytes, resulting in zebrafish cardiotoxicity.

FGF21 alleviates acute liver injury by inducing the SIRT1-autophagy signalling pathway.

Liver injury can lead to different hepatic diseases, which are the mainly causes of high global mortality and morbidity. Autophagy and Sirtuin type 1 (SIRT1) have been shown protective effects in response to liver injury. Previous studies have showed that Fibroblast growth factor 21 (FGF21) could alleviate acute liver injury (ALI), but the mechanism remains unclear. Here, we verified the relationship among FGF21, autophagy and SIRT1 in carbon tetrachloride (CCl4 )-induced ALI. We established CCl4 -induced ALI models in C57BL/6 mice and the L02 cell line. The results showed that FGF21 was robustly induced in response to stress during the development of ALI. After exogenous FGF21 treatment in ALI models, liver damage in ALI mice was significantly reduced, as well as serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels. Consistently, FGF21 also greatly reduced the levels of ALT, AST, pro-inflammatory cytokines interleukin 6 (IL6) and tumour necrosis factor-alpha (TNFα) in ALI cell lines. Mechanistically, exogenous FGF21 treatment efficiently upregulated the expression of autophagy marker microtubule-associated protein light chain-3 beta (LC3 II) and autophagy key molecule coiled-coil myosin-like BCL2-interacting protein (Beclin1), which was accompanied by alleviating hepatotoxicity in CCl4 -treated wild-type mice. Then, we examined how FGF21 induced autophagy expression and found that SIRT1 was also upregulated by FGF21 treatment. To further verify our results, we constructed an anti-SIRT1 lentit-RNAi to inhibit SIRT1 expression in mice and L02 cells, which reversed the protective effect of FGF21 on ALI. In summary, these results indicate that FGF21 alleviates ALI by enhancing SIRT1-mediated autophagy.

Fibroblast Growth Factor 21 Augments Autophagy and Reduces Apoptosis in Damaged Liver to Improve Tissue Regeneration in Zebrafish.

Regeneration of a part of the diseased liver after surgical resection is mainly achieved by the proliferation of the remaining healthy liver cells. However, in case of extreme loss of liver cells or in the final stages of chronic liver disease, most liver cells are depleted or lose their ability to proliferate. Therefore, to foster liver regeneration, it is of great clinical and scientific significance to improve the survival and proliferation ability of residual hepatocytes. In this study, we conducted experiments on a zebrafish model of targeted ablation of liver cells to clarify the role of fibroblast growth factor 21 (FGF21). We found that FGF21 increased the regeneration area of the damaged liver and improved the survival rate of damaged liver cells by inhibiting cell apoptosis and reducing oxidative stress. Our results also showed that administration of FGF21 upregulated autophagy, and the beneficial effects of FGF21 were reversed by the well-known autophagy inhibitor chloroquine (CQ), indicating that FGF21-activated autophagy played a central role in the treatment. We further showed that the enhancement of autophagy induced by FGF21 was due to the activation of the AMPK-mTOR signaling pathway. Taken together, these data provide new evidence that FGF21 is an effective autophagy regulator that can significantly improve the survival of damaged livers.

Nitazoxanide induced myocardial injury in zebrafish embryos by activating oxidative stress response.

Nitazoxanide (NTZ) is a broad-spectrum antiparasitic and antiviral drug (thiazole). However, although NTZ has been extensively used, there are no reports concerning its toxicology in vertebrates. This study used the zebrafish as a vertebrate model to evaluate the safety of NTZ and to analyse the related molecular mechanisms. The experimental results showed that zebrafish embryos exposed to NTZ had cardiac malformation and dysfunction. NTZ also significantly inhibited proliferation and promoted apoptosis in cardiomyocytes. Transcriptomic analysis used compared gene expression levels between zebrafish embryos in the NTZ treatment and the control groups identified 200 upregulated genes and 232 downregulated genes. Analysis by Kyoto encyclopaedia of genes and genomes (KEGG) and gene ontology (GO) showed that signal pathways on cardiomyocyte development were inhibited while the oxidative stress pathways were activated. Further experiments showed that NTZ increased the content of reactive oxygen species (ROS) in the hearts of zebrafish. Antioxidant gadofullerene nanoparticles (GFNPs) significantly alleviated the developmental toxicity to the heart, indicating that NTZ activated the oxidative stress response to cause embryonic cardiomyocyte injury in zebrafish. This study provides evidence that NTZ causes developmental abnormalities in the cardiovascular system of zebrafish.

Effects of cyhalofop-butyl on the developmental toxicity and immunotoxicity in zebrafish (Danio rerio).

Cyhalofop-butyl is a kind of aromatic phenoxypropionic acid herbicide widely used in agriculture. However, studies on its immunotoxicity to aquatic organisms have not been reported. In this study paper, morphological, immunological, cytological, biochemical and molecular biology methods were used to study the effects of cyhalofop-butyl on the developmental toxicity and immunotoxicity in zebrafish. After cyhalofop-butyl exposed, the results showed that the zebrafish embryos had shorter length, yolk sac edema, significantly reduced number of immune cells, inflammatory response and immunocytes apoptosis. In addition, we found that the expression of immune-related genes and pro-apoptotic genes were up-regulated, and the JAK-STAT signaling pathway mediated the immunotoxicity induced by cyhalofop-butyl. Therefore, our results indicate that cyhalofop-butyl has developmental toxicity and immunotoxicity to zebrafish, and this study offer new contents for the effects of cyhalofop-butyl exposure on aquatic organisms.

Thiophanate-methyl induces severe hepatotoxicity in zebrafish.

Thiophanate-methyl (TM) is widely used all over the world and is a typical example of pesticide residues, which can be detected in the soil, and even in vegetables and fruits. However, the molecular mechanisms underlying the hepatotoxicity of TM are not well understood. In this study, we utilized zebrafish to comprehensively evaluate the hepatotoxicity of TM and explore how the molecular mechanisms of hepatotoxicity are induced. The zebrafish larvae were exposed in 6.25, 12.5 and 25 mg/L TM from 72 to 144 hpf, while the adults were exposed in 2, 4 and 6 mg/L TM for 28 days. Here, we found that 12.5 and 25 mg/L TM induces specifically serious hepatotoxicity but not the toxicity of other organs in zebrafish larvae and adults. Moreover, it might triggered hepatotoxicity by activating the caspase-3 through apoptotic pathways and oxidative stress in zebrafish. Subsequently, this resulted in a metabolic imbalance in the zebrafish's liver. In conclusion, our results disclosed the fact that TM may induce severe hepatotoxicity by mediating activation of caspase-3 and oxidative stress in zebrafish.