Nitroxides as Protectors Against Oxidative Stress

氮氧化物作为抗氧化应激的保护剂摘要氮氧化物被证明在许多疾病过程和/或表现过度氧化应激的条件下具有广泛的用途。氮氧化物在如此广泛的条件下发挥活性的事实说明了组织中自由基反应的重要性。同样，自由基在正常分子信号通路和相关基因表达中的重要作用也越来越明显。我们已经广泛研究了氮氧化物作为抗氧化剂的化学机制，目前正在探索氮氧化物如何影响基因表达。用无毒浓度的几种不同的氮氧化物类似物处理细胞；包括不能进入（和保护）细胞的氮氧化物都表现出相似的基因表达模式。比较暴露于氮氧化物和各种形式的氧化应激（过氧化氢、超氧化物、一氧化氮和电离辐射）的MCF7细胞的基因表达谱。与炎症反应相关的一小部分基因在所有形式的氧化应激中都被上调；然而，处理氮氧化物的相同基因都被下调，这意味着氮氧化物可能在减少炎症方面非常有效。在合作研究中，对两种表现出神经变性和/或神经损伤的小鼠模型进行了长期给药（通过食物补充）的效果评估。铁调节蛋白2敲除小鼠（IRP2-/-）表现出与年龄相关的神经变性（类似于帕金森病患者）。Tempol治疗减轻了IRP2-/-小鼠神经退行性变的进展。Tempol在实验性自身免疫性脑脊髓炎（EAE）小鼠模型中也显示出高度保护作用。EAE小鼠模型是一种急性或慢性脱髓鞘性自身免疫性疾病，其临床表现为瘫痪和四肢瘫痪，与多发性硬化症患者非常相似。这些初步数据令人兴奋，可能代表了治疗这些疾病的新方法。最后，我们继续寻找长期服用Tempol（在食物或饮用水中）如何导致小鼠体重显著减轻和自发性肿瘤发生率降低的机制。在减肥方面，我们进行了广泛的基因表达阵列研究，评估了年龄匹配的对照小鼠和补充Tempol食物1个月或1年的小鼠的组织。在补充Tempol的小鼠中，已经鉴定出许多基因在肝脏和脑组织中有差异的上调或下调。最后，Tempol也显著延缓了Atm和p53缺陷小鼠以及最近的Fanconis贫血基因敲除小鼠的肿瘤发生。我们最近发现，在Tempol治疗的动物中，IGF-1的全身水平下降，与在热量限制动物中观察到的情况相似。目前正在评估对照与tempol处理小鼠的选定组织的基因表达改变。这些研究有望使我们更好地了解氮氧化物的复杂细胞/分子机制，这些机制触发了氮氧化物抗氧化性能的重要反应，以及与体重和化学预防相关的反应。

Nitroxides as Protectors against Oxidative Stress Summary Nitroxides are proving to have broad utility in a number of disease processes and/or conditions that represent excessive oxidative stress. The fact that nitroxides exert activity over such a range of conditions speaks to the importance of free radical reactions in tissue. Likewise, it is becoming apparent that free radicals are important in normal molecular signaling pathways and related gene expression. We have extensively studied the chemical mechanisms of nitroxides as antioxidants and are presently exploring how nitroxides can influence gene expression. Cells treated with non-toxic concentrations of several different nitroxide analogues; including a nitroxide incapable of cellular entry (and protection) all exhibit similar patterns of gene expression. A comparison was made of gene expression profiles for MCF7 cells exposed to nitroxides and various forms of oxidative stress (hydrogen peroxide, superoxide, nitric oxide, and ionizing radiation). A small subset of genes related to inflammatory responses was up regulated for all forms of oxidative stress; whereas, the same genes for nitroxide treatment were all down regulated, implying that nitroxides may be very effective in reducing inflammation. In collaborative studies, the effects of chronic administration of Tempol (supplemented in food) of two mouse models that exhibit neurodegeneration and/or neurological damage have been evaluated. Iron regulatory protein 2 knockout mice (IRP2-/-) exhibit age-related neurodegeneration (similar to Parkinsons disease patients). Tempol treatment attenuated the progression of neurodegeneration in IRP2-/- mice. Tempol was also shown to be highly protective in an experimental autoimmune encephalomyelitis (EAE) mouse model. The EAE mouse model is an acute or chronic demyelinating autoimmune disease whose clinical manifestations of paralysis and quadriparesis that closely resemble those observed in Multiple Sclerosis patients. These preliminary data are exciting and may represent a new approach toward treating these diseases. Lastly, we continue to search for the mechanism(s) of how long-term administration of Tempol (in the food or drinking water) results in dramatic weight reduction and a decrease in spontaneous tumor incidence in mice. With respect to weight reduction we have conducted an extensive gene expression array study evaluating tissue taken from age-matched control mice and mice on Tempol food supplementation for 1 month or 1 year. A number of genes have been identified in Tempol supplemented mice that are differentially up- or down-regulated in liver and brain tissue. Finally, Tempol administration also significantly delays the onset of tumors in Atm and p53 deficient mice and more recently in Fanconis Anemia knockout mice. We have recently found that systemic levels of IGF-1 are decreased in Tempol treated animals, similar to that observed in caloric restricted animals. Gene expression alterations selected tissues from control versus Tempol-treated mice are currently being evaluated. These studies will hopefully enable us to better understand the complex cellular/molecular mechanisms of nitroxides that trigger responses important in the antioxidant properties of nitroxides as well as those related to weight and the chemopreventive findings.