Department of Biology and Institute of Biochemistry, Carleton University, Ottawa, ON, Canada.
Department of Biology and Institute of Biochemistry, Carleton University, Ottawa, ON, Canada; Department of Biological Sciences and Center for Environmental Epigenetics and Development, University of Toronto, Toronto, ON, Canada.
Comp Biochem Physiol B Biochem Mol Biol. 2020 Aug-Sep;246-247:110460. doi: 10.1016/j.cbpb.2020.110460. Epub 2020 May 20.
Hibernators have evolved effective mechanisms to overcome the challenges of torpor-arousal cycling. This study focuses on the antioxidant and inflammatory defenses under the control of the redox-sensitive and inflammatory-centered NFκB transcription factor in the thirteen-lined ground squirrel (Ictidomys tridecemlineatus), a well-established model of mammalian hibernation. While hibernators significantly depress oxygen consumption and overall metabolic rate during torpor, arousal brings with it a rapid increase in respiration that is associated with an influx of reactive oxygen species. As such, hibernators employ a variety of antioxidant defenses to combat oxidative damage. Herein, we used Luminex multiplex technology to examine the expression of key proteins in the NFκB transcriptional network, including NFκB, super-repressor IκBα, upstream activators TNFR1 and FADD, and downstream target c-Myc. Transcription factor DNA-binding ELISAs were also used to measure the relative degree of NFκB binding to DNA during hibernation. Analyses were performed across eight different tissues, cerebral cortex, brainstem, white and brown adipose tissue, heart, liver, kidney, and spleen, during euthermic control and late torpor to highlight tissue-specific NFκB mediated cytoprotective responses against oxidative stress experienced during torpor-arousal. Our findings demonstrated brain-specific NFκB activation during torpor, with elevated levels of upstream activators, inactive-phosphorylated IκBα, active-phosphorylated NFκB, and enhanced NFκB-DNA binding. Protein levels of downstream protein, c-Myc, also increased in the brain and adipose tissues during late torpor. The results show that NFκB regulation might serve a critical neuroprotective and cytoprotective role in hibernating brains and selective peripheral tissue.
冬眠动物已经进化出有效的机制来克服蛰伏-觉醒循环的挑战。本研究关注的是氧化还原敏感和以炎症为中心的 NFκB 转录因子控制下的抗氧化和炎症防御，这种转录因子在十三线地松鼠（Ictidomys tridecemlineatus）中得到了很好的研究，它是哺乳动物冬眠的成熟模型。虽然冬眠动物在蛰伏时显著降低氧气消耗和整体代谢率，但觉醒伴随着呼吸的快速增加，这与活性氧物质的涌入有关。因此，冬眠动物采用多种抗氧化防御机制来对抗氧化损伤。在这里，我们使用 Luminex 多重技术检测了 NFκB 转录网络中的关键蛋白的表达，包括 NFκB、超抑制型 IκBα、上游激活物 TNFR1 和 FADD，以及下游靶标 c-Myc。转录因子 DNA 结合 ELISA 也用于测量 NFκB 在冬眠期间与 DNA 的相对结合程度。分析在八个不同组织中进行，包括大脑皮层、脑干、白色和棕色脂肪组织、心脏、肝脏、肾脏和脾脏，在体温正常对照和晚期蛰伏期间进行，以突出组织特异性 NFκB 介导的对蛰伏-觉醒过程中氧化应激的细胞保护反应。我们的研究结果表明，在蛰伏期间大脑中存在特定于 NFκB 的激活，伴随着上游激活物、无活性磷酸化 IκBα、活性磷酸化 NFκB 和增强的 NFκB-DNA 结合水平的升高。在晚期蛰伏期间，大脑和脂肪组织中的下游蛋白 c-Myc 的蛋白水平也增加。结果表明，NFκB 调节可能在冬眠大脑和选择性外周组织中发挥关键的神经保护和细胞保护作用。
