Chronic waterborne zinc and cadmium exposures induced different responses towards oxidative stress in the liver of zebrafish.
Based on the same toxic level of 0.6% LC50 for 96-h and the severe situation of water pollution, we compared effects of chronic Zn (180μgL(-1)) and Cd exposures (30μgL(-1)) on growth, survival, histology, ultrastructure, and oxidative stress in the liver of zebrafish for 5 weeks. Growth performance and survival rate remained relatively constant under Zn stress, but was reduced under Cd exposure. Cd exposure also induced severe pyknotic nuclei, evident ultrastructure damage, and considerable lipid inclusions in the hepatocytes. However, these phenomena were not pronounced under Zn exposure. The negative effects caused by Cd may be explained by an increase in hepatic oxidative damage, as reflected by the enhanced levels of lipid peroxidation (LPO) and protein carbonylation (PC). The reduced activity of Cu/Zn-superoxide dismutase (Cu/Zn-SOD) and catalase (CAT) may result in the enhanced hepatic oxidative damage, though the mRNA and protein levels of both genes increased and remained unchanged respectively. On the contrary, Zn up-regulated the levels of mRNA, protein and activity of Cu/Zn-SOD, which may contribute to the decreased LPO levels. Nonetheless, the sharply up-regulated mRNA levels of CAT did not induce an increase in the protein and activity levels of CAT under Zn stress. Furthermore, transcription factor NF-E2-related factor 2 (Nrf2) expression parelleled with its target genes, suggesting that Nrf2 is required for the protracted induction of antioxidant genes. In conclusion, our data demonstrated that essential and non-essential metals induced some differences in oxidative damage in fish. The differences were not caused by the transcriptional level of related genes but depended on post-transcriptional modifications.
National Engineering Research Center of Marine Facilities Aquaculture, Zhejiang Ocean University, Zhoushan 316022, PR China. Electronic address: zhengjialang@aliyun.com.
Jia-Lang
JL
Zheng
National Engineering Research Center of Marine Facilities Aquaculture, Zhejiang Ocean University, Zhoushan 316022, PR China.
Shuang-Shuang
SS
Yuan
National Engineering Research Center of Marine Facilities Aquaculture, Zhejiang Ocean University, Zhoushan 316022, PR China.
Chang-Wen
CW
Wu
Zhoushan fisheries research institute, Zhoushan 316022, PR China.
Wei-Ye
WY
Li
D000818:Animals; D000975:Antioxidants / Q000378:metabolism; D015415:Biomarkers / Q000378:metabolism; D002104:Cadmium / Q000633:toxicity*; D005786:Gene Expression Regulation / Q000187:drug effects; D007928:Lethal Dose 50; D015227:Lipid Peroxidation / Q000187:drug effects; D008099:Liver / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology / Q000648:ultrastructure; D018384:Oxidative Stress / Q000187:drug effects* / Q000502:physiology; D036401:Toxicity Tests, Chronic; D014874:Water Pollutants, Chemical / Q000633:toxicity*; D015027:Zebrafish / Q000502:physiology*; D015032:Zinc / Q000633:toxicity*
D000975:Antioxidants; D015415:Biomarkers; D014874:Water Pollutants, Chemical; D002104:Cadmium; D015032:Zinc
Fish; Gene regulation; Metal exposure; Nrf2; Oxidative stress