Nitroxides as Protectors Against Oxidative Stress

我们实验室的广泛研究表明，氮氧化物（如Tempol）是有效的抗氧化剂和电离辐射损伤的保护剂。我们以前已经证明，氮氧化物介导的保护氧化应激的潜在机制（S）包括超氧化物歧化酶和过氧化氢酶样活性和自由基-自由基反应。然而，最近的研究集中在氮氧化物处理是否影响基因表达。用无毒浓度的几种不同的氮氧化物类似物处理的细胞;包括不能进入细胞（和保护）的氮氧化物，都表现出类似的基因表达模式。氮氧化物处理上调的突出基因包括热休克蛋白（HSP）家族、还原酶基因和与Wnt/β-连环蛋白途径相关的基因。我们目前正在比较一氧化氮介导的基因表达谱与其他形式的氧化应激，包括过氧化氢，超氧化物和电离辐射。此外，我们正在对从食物中使用Tempol的动物中提取的选定组织进行基因表达研究。我们已经表明，长期给予Tempol（在食物或饮用水中）导致小鼠体重显著减轻和自发肿瘤发病率降低。这些研究将使我们能够更好地了解复杂的细胞/分子机制的氮氧化物，触发重要的反应，氮氧化物的抗氧化性能，以及那些相关的重量和肿瘤发病率的下降。我们最近表明，氮氧化物可以防止雌二醇介导的细胞毒性和致突变性使用的体外模型提供了强有力的证据，氮氧化物抗氧化剂可以用作新的化学预防剂。最后，我们正在继续研究Tempol对正常组织和肿瘤的差异辐射保护作用。最近的研究表明，分次放疗前10分钟给予Tempol不能保护SCC和HT-29肿瘤生长。我们最近的研究表明，放射治疗前给予氮氧化物可以保护唾液腺免受损伤。正在进行的研究，以评估氮氧化物的能力，以防止辐射诱导的粘膜炎。我们的临床前研究支持氮氧化物如Tempol将提供正常组织的选择性辐射保护的概念。由于氮氧自由基很容易穿透细胞膜，是有效的抗氧化剂，它们可以用于医学研究的其他领域，如缺血/再灌注损伤研究，预防白内障，炎症过程和衰老。

Extensive studies in our laboratory have demonstrated that nitroxides (such as Tempol) are effective antioxidants and protectors against ionizing radiation damage. We have previously demonstrated that the potential mechanism(s) for nitroxide-mediated protection against oxidative stress include superoxide dismutase- and catalase-like activity and radical-radical reactions. However, more recent studies have focused on whether nitroxide treatment impacts 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. Prominent genes up-regulated by nitroxide treatment include the heat shock protein (HSP) family, reductive enzyme genes, and genes associated with the Wnt/beta-catenin pathway. We are currently comparing nitroxide-mediated gene expression profiles with other forms of oxidative stress including hydrogen peroxide, superoxide, and ionizing radiation. Additionally we are conducting gene expression studies of selected tissues taken from animals maintained on Tempol in the food. We have shown that 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. 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 decreases in tumor incidence. We have recently shown that nitroxides can protect against estradiol-mediated cytotoxicity and mutagenicity using an in vitro model providing strong evidence that nitroxide antioxidants can be used as novel chemopreventative agents. Lastly, we are continuing our studies on the differential radioprotection of Tempol toward normal tissues as opposed to tumor. Recent studies indicate that Tempol administered 10 min prior to fractionated radiation treatment does not protect SCC and HT-29 tumor growth. We have recently shown that nitroxides administered prior to radiation protects against salivary gland damage. Studies underway to evaluate the ability of nitroxides to protect against radiation-induced mucositis. Our pre-clinical studies support the concept that nitroxides such as Tempol will provide selective radioprotection of normal tissues. Since nitroxides readily penetrate cell membranes and are potent antioxidants, they may be of use in other areas of medical research such as ischemia/reperfusion injury studies, prevention of cataracts, inflammatory processes, and aging.