title: Oxidative stress intensity-related effects of cadmium (Cd) and paraquat (PQ) on UV-damaged-DNA binding and excision repair activities in zebrafish (Danio rerio) embryos.
abstract: Our earlier studies showed the inhibitory effects of cadmium (Cd) and paraquat (PQ) on the gene expression of DNA mismatch recognition proteins in zebrafish (Danio rerio) embryos. This study explored the effects of Cd and PQ on nucleotide excision repair (NER) capacity in zebrafish embryos. Exposure of embryos at 1 h post fertilization (hpf) to 3-5 μM Cd or 30-100 μM PQ for 9 h induced a 2-3-fold increase of oxidative stress, while a 6.5-fold increase of oxidative stress was induced by 200 μM PQ. Real-time RT-PCR detected a down-regulated xeroderma pigmentosum C (XPC) and an up-regulated UV-DDB2 gene expression in mildly-stressed embryos, whereas 8-oxoguanine DNA glycosylase (OGG1) gene expression increased with PQ exposure levels. NER of UV-damaged DNA was enhanced in weakly oxidant-stressed embryos as shown by a transcription-based DNA repair assay, yet repair activities of both UV and cisplatin-damaged DNA were inhibited in embryos exposed to 200 μM PQ. Band shift assay showed a suppression of cyclobutane pyrimidine dimer (CPD) binding activity in all stressed embryos. In contrast, (6-4) photoproduct (6-4PP) recognition activity was weakly stimulated except in embryos exposed to 200 μM PQ, revealing a link of NER capacity to 6-4PP binding. Our results showed that Cd and PQ imposed similar inducing effects on UV-DDB2 gene expression, NER of UV-damaged DNA and 6-4PP binding activity in zebrafish embryo under low levels of oxidative stress and NER capacity could be inhibited if the intensity of oxidative stress increased to a critical level.
authors.affiliation: Department of Bioscience and Biotechnology and Center of Excellence for the Oceans, National Taiwan Ocean University, No.2, Pei-Ning Rd., Keelung 20224, Taiwan, Republic of China.
authors.forename: Li-Bin
authors.initials: LB
authors.lastname: Ling
authors.affiliation: Department of Bioscience and Biotechnology and Center of Excellence for the Oceans, National Taiwan Ocean University, No.2, Pei-Ning Rd., Keelung 20224, Taiwan, Republic of China.
authors.forename: Yung
authors.initials: Y
authors.lastname: Chang
authors.affiliation: Department of Bioscience and Biotechnology and Center of Excellence for the Oceans, National Taiwan Ocean University, No.2, Pei-Ning Rd., Keelung 20224, Taiwan, Republic of China.
authors.forename: Chia-Wei
authors.initials: CW
authors.lastname: Liu
authors.affiliation: Department of Bioscience and Biotechnology and Center of Excellence for the Oceans, National Taiwan Ocean University, No.2, Pei-Ning Rd., Keelung 20224, Taiwan, Republic of China.
authors.forename: Po-Ling
authors.initials: PL
authors.lastname: Lai
authors.affiliation: Department of Bioscience and Biotechnology and Center of Excellence for the Oceans, National Taiwan Ocean University, No.2, Pei-Ning Rd., Keelung 20224, Taiwan, Republic of China. Electronic address: toddhsu@mail.ntou.edu.tw.
authors.forename: Todd
authors.initials: T
authors.lastname: Hsu
mesh_terms: D000818:Animals; D002104:Cadmium / Q000633:toxicity*; D004247:DNA / Q000378:metabolism; D004249:DNA Damage; D004260:DNA Repair / Q000187:drug effects; D004625:Embryo, Nonmammalian / Q000187:drug effects / Q000378:metabolism; D005260:Female; D015870:Gene Expression / Q000187:drug effects / Q000528:radiation effects; D006540:Herbicides / Q000633:toxicity*; D008297:Male; D018384:Oxidative Stress / Q000187:drug effects; D010269:Paraquat / Q000633:toxicity*; D011740:Pyrimidine Dimers / Q000378:metabolism; D014466:Ultraviolet Rays / Q000009:adverse effects*; D014874:Water Pollutants, Chemical / Q000633:toxicity*; D015027:Zebrafish / Q000235:genetics / Q000378:metabolism
chemical_list: D006540:Herbicides; D011740:Pyrimidine Dimers; D014874:Water Pollutants, Chemical; D002104:Cadmium; D004247:DNA; D010269:Paraquat
keywords: Cadmium; Nucleotide excision repair; Oxidative stress; Paraquat; UV; Zebrafish