Flap Necrosis as an Ischemia-Reperfusion Injury Model and its Pharmacological Control

在许多缺血性疾病和器官移植中观察到的缺血/再灌注损伤都伴随着活性氧（ROS）的形成。本研究的目的是利用合适的皮瓣模型探讨这种类型损伤的机制和预防。缺血时，ATP被分解为次黄嘌呤（黄嘌呤氧化酶的底物），黄嘌呤脱氢酶被钙蛋白酶（钙活化的中性蛋白酶）转化为氧化酶。当组织被再氧化时，超氧化物和过氧化氢的爆发会导致组织损伤。取大鼠岛状皮瓣和随机皮瓣，注射脂质体SOD （L-SOD）、E-64-c（半胱氨酸蛋白酶特异性抑制剂，包括钙蛋白酶）或别嘌呤醇（黄嘌呤氧化酶抑制剂）后，测定其血流量、皮肤超氧化物歧化酶（SOD）活性和存活率。这三种药物可改善结扎10小时后岛状皮瓣的存活率。血流量和SOD活性明显降低。然而，只有L-SOD能提高随机皮瓣的存活长度，而E-64-c或别嘌呤醇不能。这些发现提示黄嘌呤氧化酶系统产生的活性氧对缺血/再灌注损伤有重要作用。此外，使用三种药物的不同结果表明，在这两种模型中，可能涉及与中性粒细胞依赖性炎症有关的不同机制。我们建立的简单定量的皮瓣模型可用于缺血性心脑血管疾病和器官移植的药理学评价和筛选。

Ischemia/reperfusion injury observed in many ischemic diseases and organ transplantation is accompanied by the formation of reactive oxygen species (ROS). The purpose of the present study is to investigate the mechanism and prevention of this type injury using suitable skin flap models. During ischemia, ATP is broken down to hypoxanthine, a substrate of xanthine oxidase, and xanthine dehydrogenase is converted to oxidase by calpain, a calcium activated neutral proteinase. When the tissue is reoxygenated, a burst of superoxide and hydrogen peroxide occurs with resultant tissue damage. Two kinds of skin flaps, island and random, were lifted in rats, and the blood flow, cutaneous superoxide dismutase (SOD) activity, survival rates were measured after injection of liposomal SOD (L-SOD), E-64-c (specific inhibitor of cysteine proteinases including calpain) or allopurinol (xanthine oxidase inhibitor). Improved survival of island skin flaps after 10hr ligation was observed by these three agents. Remarkably reduced blood flow and SOD activity were confirmed. However, only L-SOD, but not E-64-c or allopurinol, improved the survival length in random skin flaps. These findings suggest the significant contribution of ROS generated in xanthine oxidase system to ischemia/reperfusionn injury. Also the discrepant results using three agents indicate the involvement of different mechanisms presumably linking to neutrophil-dependent inflammation in these two models. Our simple and quantitati ve skin flap models are useful in pharmacological evaluation and screening of any possible agent for the treatment of ischemic heart and cerebrovascular diseases as well as organ transplantation.