Institute of Biochemistry and Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario, Canada.
Gene. 2011 Oct 10;485(2):114-9. doi: 10.1016/j.gene.2011.06.014. Epub 2011 Jun 25.
Antioxidant defenses are an important part of adaptation to environmental stress for many organisms. This study analyzed responses to dehydration stress by manganese-dependent superoxide dismutase (MnSOD) and catalase, and the role of forkhead box class O type 1 (FoxO1) transcription factor in regulating their up-regulation, in selected tissues of the African clawed frogs, Xenopus laevis. Protein and mRNA levels of MnSOD and catalase were analyzed by immunoblotting and PCR. Analysis of FoxO1 included protein and phosphoprotein (FoxO1(ser245)) levels, nuclear versus cytoplasmic distribution, and FoxO1 binding to DNA. MnSOD protein increased significantly in the liver during dehydration whereas catalase rose in the liver and skeletal muscle. This was supported in liver by 1.5-2.2 fold increases in MnSOD and catalase mRNA levels. FoxO1 transcriptional activity was enhanced in liver of dehydrated versus control frogs as evidenced by: (a) 1.8-fold increase in FoxO1 protein in the nucleus, (b) strong decreases in inactive phosphorylated FoxO1(ser245) in total and nuclear extracts, and (c) a 57% increase in FoxO1 binding to DNA in nuclear extracts. The study documents up-regulation of MnSOD and catalase in frog organs during dehydration and indicates a role for FoxO1 in controlling expression of these genes in liver. Dehydration-rehydration has components of an ischemia-reperfusion event and the oxidative stress that this generates appears to be effectively addressed, at least in X. laevis liver, by enhanced production of antioxidant enzymes under FoxO1 regulation.
抗氧化防御系统是许多生物适应环境胁迫的重要组成部分。本研究分析了锰依赖性超氧化物歧化酶（MnSOD）和过氧化氢酶对脱水胁迫的反应，以及叉头框 O 类 1 型（FoxO1）转录因子在调节它们在非洲爪蟾（Xenopus laevis）选定组织中上调的作用。通过免疫印迹和 PCR 分析 MnSOD 和过氧化氢酶的蛋白和 mRNA 水平。FoxO1 的分析包括蛋白和磷酸化蛋白（FoxO1(ser245)）水平、核质分布以及 FoxO1 与 DNA 的结合。在脱水过程中，MnSOD 蛋白在肝脏中显著增加，而过氧化氢酶在肝脏和骨骼肌中增加。这在肝脏中得到了支持，MnSOD 和过氧化氢酶的 mRNA 水平增加了 1.5-2.2 倍。FoxO1 的转录活性在脱水蛙的肝脏中增强，证据是：（a）FoxO1 蛋白在核中的增加了 1.8 倍，（b）总核提取物中无活性磷酸化 FoxO1(ser245)的强烈减少，以及（c）核提取物中 FoxO1 与 DNA 的结合增加了 57%。本研究记录了在脱水过程中蛙器官中 MnSOD 和过氧化氢酶的上调，并表明 FoxO1 在控制这些基因在肝脏中的表达中起作用。脱水-复水有缺血再灌注事件的成分，而这种再灌注产生的氧化应激似乎在 X. laevis 肝脏中通过 FoxO1 调节下抗氧化酶的增强产生得到有效解决。
