Morin Pier, Ni Zhouli, McMullen David C, Storey Kenneth B
Institute of Biochemistry and Department of Chemistry, Carleton University, 1125 Colonel By Drive, Ottawa, ON, Canada K1S 5B6.
Mol Cell Biochem. 2008 May;312(1-2):121-9. doi: 10.1007/s11010-008-9727-3. Epub 2008 Mar 10.
Mammalian hibernation is associated with wide variation in heart rate, blood flow, and oxygen delivery to tissues and is used as a model of natural ischemia/reperfusion. In non-hibernators, ischemia/reperfusion is typically associated with oxidative stress but hibernators seem to deal with potential oxidative damage by enhancing antioxidant defenses in an anticipatory manner. The present study assesses the role of the Nrf2 transcription factor in the regulation of antioxidant defenses during hibernation. Nrf2 mRNA and protein expression were enhanced in selected organs of 13-lined ground squirrels, Spermophilus tridecemlineatus during hibernation. Furthermore, Nrf2 protein in heart was elevated by 1.4-1.5 fold at multiple stages over a torpor-arousal bout including during entry, long term torpor, and early arousal. Levels returned to euthermic values when squirrels were fully aroused in interbout. Protein levels of selected downstream target genes under Nrf2 control were also measured via immunoblotting over the torpor-arousal cycle in heart. Cu/Zn superoxide dismutase and aflatoxin aldehyde reductase levels increased significantly during entry into torpor and then gradually declined falling to control levels or below in fully aroused animals. Heme oxygenase-1 also showed the same trend. This suggests a role for Nrf2 in regulating the antioxidant defenses needed for hibernation success. Heart nrf2 was amplified by PCR and sequenced. The deduced amino acid sequence showed high identity with the sequence from other mammals but with selected unique substitutions (e.g., proline residues at positions 111 and 230) that might be important for conformational stability of the protein at near 0 degrees C body temperatures in the torpid state.
哺乳动物的冬眠与心率、血流量以及组织的氧气输送的广泛变化有关，并被用作自然缺血/再灌注的模型。在非冬眠动物中，缺血/再灌注通常与氧化应激相关，但冬眠动物似乎通过以预期的方式增强抗氧化防御来应对潜在的氧化损伤。本研究评估了Nrf2转录因子在冬眠期间抗氧化防御调节中的作用。在冬眠期间，13条纹地松鼠（Spermophilus tridecemlineatus）的选定器官中，Nrf2 mRNA和蛋白质表达增强。此外，在从蛰伏到觉醒的多个阶段，包括进入蛰伏期、长期蛰伏期和早期觉醒期，心脏中的Nrf2蛋白升高了1.4 - 1.5倍。当松鼠在两次蛰伏间完全觉醒时，水平恢复到正常体温值。还通过免疫印迹法在心脏的蛰伏 - 觉醒周期中测量了Nrf2控制下选定的下游靶基因的蛋白质水平。进入蛰伏期时，铜/锌超氧化物歧化酶和黄曲霉毒素醛还原酶水平显著增加，然后逐渐下降，在完全觉醒的动物中降至对照水平或更低。血红素加氧酶 - 1也呈现相同趋势。这表明Nrf2在调节冬眠成功所需的抗氧化防御中发挥作用。通过PCR扩增并测序了心脏中的nrf2。推导的氨基酸序列与其他哺乳动物的序列具有高度同一性，但有选定的独特替代（例如，第111和230位的脯氨酸残基），这些替代可能对于在蛰伏状态下接近0摄氏度的体温时蛋白质的构象稳定性很重要。
