title: Acute acidic exposure induces p53-mediated oxidative stress and DNA damage in tilapia (Oreochromis niloticus) blood cells.
abstract: Acid rain and inputs of acidic effluent can result in increased acidity in aquatic ecosystems, where it is known to have a significant impact and possibly, to cause the decline of some populations of aquatic organisms. In previous studies, intracellular acid-induced oxidative stress has been shown to cause DNA damage, and cooperatively activate the expression of the p53 gene. The acute effects of acidic environments on shrimp and fish have been widely studied. However, the molecular mechanism of acid-induced injury remains largely unknown. In this study, we examined the cellular responses of tilapia to acidic exposure-induced oxidative stress and antioxidant enzyme gene expression. Furthermore, we determined how acute acid stress activates the ATM-p53 signal pathway. We measured the upregulation of reactive oxygen species (ROS) production, the intracellular Ca(2)(+) concentration ([Ca(2)(+)](i)), the tail DNA values, the malondialdehyde (MDA) level in the blood cells and the percentage of dead and damaged blood cells. Our results suggest that oxidative stress and DNA damage occurred in tilapia in conditions where the pH was 5.3. Apoptosis was detected by Hoechst staining, which was mainly associated with changes in cell viability. The parameters that we measured were related to acid-induced DNA damage, and all parameters changed in the blood cells through time. The effects of acute acid exposure (pH 5.3) on the expression of ATM, p53, p21, Bax, manganese superoxide dismutase (MnSOD), glutathione peroxidase (GPx) were investigated in tilapia blood cells. The results showed that acute acid stress induced upregulation of ATM, p53 and p21, associated with increasing of DNA damage and apoptosis in blood cells. Additionally, the expression of Bax was slightly increased. Moreover, consensus p53-binding sequences were identified in tilapia MnSOD and GPx gene promoter regions and increased levels of ROS in the blood cells coincided with increased mRNA expression of p53, MnSOD and GPx. Therefore, it suggests that acid exposure-induced oxidative stress may cause DNA damage or apoptosis, and cooperatively activate ATM-p53 pathway, which may lead to the activation of p21 and regulate transcription of MnSOD and GPx.
authors.affiliation: Key Laboratory of Ecology and Environment Science in Guangdong Higher Education & Guangdong Provincial Key Laboratory for Healthy and Safe Aquaculture, College of Life Science, South China Normal University, Guangzhou 510631, China. mwj9876@yahoo.com.cn
authors.forename: Wei-jun
authors.initials: WJ
authors.lastname: Mai
authors.forename: Jun-lun
authors.initials: JL
authors.lastname: Yan
authors.forename: Lei
authors.initials: L
authors.lastname: Wang
authors.forename: Ying
authors.initials: Y
authors.lastname: Zheng
authors.forename: Yu
authors.initials: Y
authors.lastname: Xin
authors.forename: Wei-na
authors.initials: WN
authors.lastname: Wang
mesh_terms: D015258:Acid Rain; D000143:Acids / Q000633:toxicity*; D000818:Animals; D001773:Blood Cells / Q000187:drug effects* / Q000378:metabolism; D023681:Cichlids / Q000502:physiology*; D004249:DNA Damage; D005979:Glutathione Peroxidase / Q000378:metabolism; D018384:Oxidative Stress; D012333:RNA, Messenger / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013482:Superoxide Dismutase / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D015258:Acid Rain; D000143:Acids; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D016159:Tumor Suppressor Protein p53; D014874:Water Pollutants, Chemical; D005979:Glutathione Peroxidase; D013482:Superoxide Dismutase