Xanthine oxidoreductase in impaired diabetic wound healing.

 描述(由申请人提供)： 糖尿病及其并发症是美国医疗体系的重大负担，2012年美国在这些患者的护理上花费了近2500亿美元。这在退伍军人管理局的医疗系统中更加明显，那里的糖尿病发病率是前者的三倍。糖尿病患者容易因神经病变、感染易感性和微血管疾病而导致足部和腿部溃疡。不幸的是，糖尿病患者治愈这些溃疡的能力明显受损，通常会进行轻微或重大的肢体截肢。这些事件会导致生产力下降以及相关的发病率和死亡率。糖尿病患者创面愈合不良的原因之一是产生过多的活性氧(ROS)和不足的一氧化氮(NO)。已有研究表明，糖尿病创面减少ROS或释放NO可提高治愈率，减少感染。然而，NO的传递受到分子的短半衰期及其高活性状态的阻碍。黄嘌呤氧化还原酶(XOR)是一种能够产生ROS的酶，我们发现它在皮肤和伤口中高度表达。异或因能将稳定的化合物亚硝酸盐转化为NO而在过去几年中引起了人们的极大关注。XOR已被证明在各种疾病模型中利用饮食中的亚硝酸盐来介导NO的有益影响。在伤口中，初步数据表明，XOR在正常的伤口修复中起着至关重要的作用，但它在糖尿病伤口中的作用仍不确定。糖尿病患者全身抑制XOR似乎可以促进伤口愈合，而局部抑制则进一步推迟愈合。此外，全身或局部使用滴眼剂也能促进伤口修复。异或的一个吸引人的性质是，当在低氧环境下提供亚硝酸盐时，它有利于NO的产生。当产生NO时，XOR介导的ROS产生减少。这些特性在慢性创面的环境中是非常有利的，在慢性创面中，血管因导致的缺血而减少。在这种情况下，服用亚硝酸盐不仅可能诱导异或产生NO，而且还可能减少ROS的产生。该提案的目的是研究XOR及其产物在糖尿病创面修复过程中的确切作用。研究将检测XOR产生的NO和ROS在糖尿病伤口中的作用。我们将研究XOR在伤口新生血管中的作用，以确定XOR函数来源的重要性。这些研究将通过使用内皮细胞特异的XOR基因敲除小鼠来辅助。该提案将最终检查不同原因的人类伤口，以量化异或活性，通过补充亚硝酸盐来增加局部NO产生的能力，以及其他亚硝酸盐还原酶在这种NO产生中的影响。这项建议的最终目标是为开发局部亚硝酸盐作为糖尿病创面愈合受损的治疗方法奠定基础。这种疗法的极具吸引力的方面是它的简单、低成本，以及利用人体自身的机械来产生治疗剂的能力。如果有效，局部亚硝酸盐疗法也可以应用于其他原因的伤口，如静脉淤血和缺血性伤口。

 DESCRIPTION (provided by applicant): Diabetes and its complications are a significant burden on the healthcare system in the United States with nearly $250 billion spent on the care of these patients in 2012. This is even more significant in the VA Healthcare System where the incidence of diabetes is three times as high. Diabetic patients are prone to develop foot and leg ulcers resulting from neuropathy, susceptibility to infection, and microvascular disease. Unfortunately, diabetics have a significantly impaired ability to heal these ulcers and often go on to minor or major limb amputations. These events lead to loss of productivity and associated morbidity and mortality. One of the deficits associated with impaired wound healing in diabetic patients is the excessive production of reactive oxygen species (ROS) and insufficient nitric oxide (NO) production. It has been demonstrated that reduction of ROS or delivery of NO to diabetic wounds can improve healing rates and reduce infection. However, NO delivery is hampered by the short half-life of the molecule and its highly reactive state. Xanthine oxidoreductase (XOR) is an enzyme known for its ability to produce ROSs and we identified that it is highly expressed in skin and wounds. XOR has attracted a great deal of attention in the past few years because it can convert the stable compound nitrite back to NO. XOR has been shown to utilize dietary nitrite to mediate the beneficial effects of NO in a variety of disease models. In the wound, preliminary data indicate that XOR plays an essential role in normal wound repair but its role in diabetic wounds remains uncertain. The systemic inhibition of XOR in diabetes appears to improve wound healing while local inhibition further delays healing. In addition, the administration of systemic or topical nitite also improves wound repair. An attractive property of XOR is that it favors the production of NO when nitrite is provided in the setting of hypoxia. When producing NO, XOR mediated ROS production is reduced. These properties are extremely favorable in the setting of chronic wounds where vascularity is diminished with resulting ischemia. In such a setting, administering nitrite may not only induce XOR to generate NO but it may also reduce ROS production. The goal of this proposal is to investigate the precise role of XOR and its products in the diabetic wound repair process. Studies will examine the function of XOR generated NO and ROS in diabetic wounds. The role of XOR in wound neovascularization will be examined to define the importance of the source of the XOR function. These studies will be aided by the use of endothelial cell specific XOR knockout mice. The proposal will culminate in examination of human wounds of different etiologies to quantify XOR activity, the ability to augment local NO production through nitrite supplementation, and the impact of other nitrite reductases in this NO production. The ultimate goal of this proposal is to establish the foundation for developing topical nitrite as a treatment for impaired diabetic wound healing. The extremely attractive aspect of such a therapy is its simplicity, low cost, and the ability to harness the body's own machinery to produce the therapeutic agent. If effective, topical nitrite therapy may also be applied to wounds of other etiologies such as venous stasis and ischemic wounds.