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保健系统的重大负担，2012年花费了近2500亿美元用于这些患者的护理。这在VA医疗保健系统中更为重要，糖尿病的发病率是其三倍。糖尿病患者易于发展由神经病变、感染易感性和微血管疾病引起的足部和腿部溃疡。不幸的是，糖尿病患者治愈这些溃疡的能力明显受损，并且经常进行轻微或严重的截肢。这些事件导致生产力的丧失以及相关的发病率和死亡率。与糖尿病患者伤口愈合受损相关的缺陷之一是活性氧（ROS）的过度产生和一氧化氮（NO）产生不足。已经证明，减少ROS或向糖尿病伤口递送NO可以提高愈合率并减少感染。然而，NO递送受到分子的短半衰期及其高反应性状态的阻碍。黄嘌呤氧化还原酶（XOR）是一种已知能够产生ROS的酶，我们发现它在皮肤和伤口中高度表达。XOR在过去几年中引起了极大的关注，因为它可以将稳定的化合物亚硝酸盐转化回NO。XOR已被证明可以利用膳食亚硝酸盐来介导NO在各种疾病模型中的有益作用。在伤口中，初步数据表明XOR在正常伤口修复中起重要作用，但其在糖尿病伤口中的作用仍不确定。在糖尿病中，全身性抑制XOR似乎改善伤口愈合，而局部抑制进一步延迟愈合。此外，全身或局部给予硝石也可改善伤口修复。XOR的一个有吸引力的特性是，当在缺氧环境中提供亚硝酸盐时，它有利于NO的产生。当产生NO时，XOR介导的ROS产生减少。这些特性在血管供应减少并导致局部缺血的慢性伤口的情况下是非常有利的。在这种情况下，给予亚硝酸盐不仅可以诱导XOR产生NO，而且还可以减少ROS的产生。本提案的目标是研究XOR及其产物在糖尿病伤口修复过程中的确切作用。研究将检查XOR产生的NO和ROS在糖尿病伤口中的功能。将检查XOR在伤口新生血管形成中的作用，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性XOR敲除小鼠来辅助。该提案将最终在检查不同病因的人类伤口，以量化XOR活性，通过亚硝酸盐补充增加局部NO产生的能力，以及其他亚硝酸盐还原酶在NO产生中的影响。该提案的最终目标是为开发局部亚硝酸盐作为糖尿病伤口愈合受损的治疗方法奠定基础。这种疗法最吸引人的方面是它简单、成本低，并且能够利用人体自身的机制来产生治疗剂。如果有效，局部亚硝酸盐疗法也可以应用于其他病因的伤口，如静脉淤滞和缺血性伤口。

 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.