Pathobiology of Diabetic Gastroenteropathy

正常的胃肠运动需要维持肠神经和Cajal间质细胞网络(ICC)。这项建议的总体目标是确定糖尿病胃肠病(DGE)的病理生物学基础的机制。我们的初步数据表明，神经元型一氧化氮合酶/一氧化氮(nNOS/NO)和血红素加氧酶/一氧化碳(HO/CO)通路在维持糖尿病的ICC网络中起着核心作用。我们做了以下关键的初步观察：HO1在糖尿病中表达上调，并作为一种保护机制来对抗糖尿病引起的氧化应激。NO上调HO1的表达。NNOS的丢失是DGE发生的早期阶段，导致NO的减少，HO1上调的丢失，以及随后ICC数量的减少。 支持这一假设的是，初步数据显示，在nNOS基因敲除的小鼠中，ICC数量减少，NOS抑制剂减少ICC数量，而NO供体增加培养中的ICC数量。此外，DGE患者nNOS表达减少，HO1上调缺失，ICC数量减少。我们还开发了DGE的动物和人类组织模型，并开发了一种非侵入性测试来确定小鼠的胃排空。基于这项工作，我们提出了一个新的假设，即活性氧上调HO1/CO途径是对抗AGE和活性氧对ICC损伤的一种初始细胞保护机制。 肠神经nNOS表达缺失导致HO1持续上调功能丧失 导致对ICC的氧化损伤。ICC的丢失会导致起搏器信号的丢失， 放大神经元信号和运动障碍。该提案有两个具体目标。在第一个目的中，我们将检验DGE的假设，即DGE是由最初nNOS表达丢失和随后ICC丢失引起的。在第二个目标中，我们将检验这一假设，即HO/CO途径对ICC具有细胞保护作用，并且HO/CO途径的异常调节会导致ICC和随后的DGE减少。这些研究将使用新开发的胃排空和ICC培养技术、电生理学、免疫组织化学和分子生物学来回答提出的问题。我们现在独一无二地准备就DGE发展的基础机制提供新的信息。由于这项工作将确定维持ICC的基本机制，它也对进一步了解许多与ICC数量和功能障碍相关的运动障碍的病理生理学有意义。

Normal gastrointestinal motility requires maintenance of enteric nerves and the networks of interstitial cells of Cajal (ICC). The overall objective of this proposal is to identify the mechanisms that underlie the pathobiology of diabetic gastroenteropathy (DGE). Our preliminary data suggest a central role for the neuronal nitric oxide synthase/nitric oxide (nNOS/NO) and the heme oxygenase/carbon monoxide (HO/CO) pathways in the maintenance of ICC networks in diabetes. We have made the following key preliminary observations: HO1 is up-regulated in diabetes and serves as a protective mechanism against diabetes-induced oxidative stress. NO up-regulates HO1. Loss of nNOS is an early step in the development of DGE resulting in decrease in NO, loss of up-regulation of HO1 and subsequent decrease in ICC numbers. Supporting the hypothesis that NO is cytoprotective to ICC are preliminary data that show that ICC numbers are decreased in nNOS knockout mice, NOS inhibitors decrease ICC numbers, and NO donors increase ICC numbers in culture. Also, nNOS expression is decreased, HO1 up-regulation is lost and ICC numbers are decreased in patients with DGE. We have also developed animal and human tissue models for DGE and developed a non-invasive test to determine gastric emptying in mice. Based on this work we have generated the novel hypothesis that up-regulation of the HO1/CO pathway by reactive oxygen species serves as an initial cytoprotective mechanism against damage to ICC by AGE and reactive oxygen species. Loss of nNOS expression from enteric nerves leads to loss of continued up-regulation of HO1 resulting in oxidative injury to ICC. Loss of ICC results in loss of the pacemaker signal, failure to amplify neuronal signals and dysmotility. The proposal has two specific aims. In the first aim we will test the hypothesis that DGE results from initial loss of nNOS expression and subsequent loss of ICC. In the second aim we will test the hypothesis that the HO/CO pathway is cytoprotective to ICC and that aberrant regulation of the HO/CO pathway results in decreased ICC and subsequent DGE. The studies will employ newly developed gastric emptying and ICC culture techniques, electrophysiology, immunohistochemistry, and molecular biology to answer the questions raised. We are now uniquely poised to provide new information on the mechanisms that underlie the development of DGE. As this work will identify basic mechanisms that underlie maintenance of ICC it also has implications for further understanding the pathophysioIogy of many of the motility disorders linked to disorders in ICC number and function.