Xanthine Oxidase-Induced Vascular Dysfunction in Inhalation Toxicology

项目摘要 吸入二氧化钛(二氧化钛)是一个相当大的职业保健问题，因为它导致 不仅在局部引起肺部炎症反应，而且还介导全身血管功能障碍。 然而，支持肺部原发炎症事件之间联系的信号机制 全身血管后果尚不清楚；特别是如果毒物仍主要局限于 肺组织。这一过程的一个潜在贡献者可能是黄嘌呤氧化还原酶(XOR)，一种 在炎症条件下上调的酶可以释放到循环中并强烈结合 与内皮细胞表面的糖胺多聚糖(GAG)结合，并通过产生 氧化剂。我们最近已经证明，循环异或的一个关键来源是肝脏，由此 肝细胞对炎症刺激的反应是向循环释放异或。这一过程似乎是 作为肝细胞异或的遗传消融，在炎症刺激的背景下， 在没有其他器官/组织代偿的情况下，显著消耗循环中的XOR水平。 虽然肝脏似乎在控制循环中的XOR水平方面发挥了主调节作用，但信号转导 从原发的非现场损害(肺)到肝细胞仍未明确，确认有必要进一步 对这一地区的探索。为此，我们提供了初步数据，表明 小鼠吸入二氧化钛后的血浆异或反应。此外，暴露在二氧化钛下会导致 大脑中动脉和胸主动脉的内皮依赖性功能障碍可通过 使用XOR特异性抑制剂非布索他汀治疗。总而言之，这些数据激励了这样的假设 吸入二氧化钛介导了从肺到肝的信号传递，上调了XOR，随后释放到 导致血管功能障碍的血液循环。以下具体目标将检验这一假设： 1)确定XOR介导的与吸入二氧化钛相关的血管功能障碍的贡献，并建立肝脏 作为放大的循环异或的来源和2)识别从肺到肝的信号，这是中介 吸入二氧化钛后XOR上调。这些目标结合在一起，将建立一条新的途径 因此，对肺组织的原发损伤可导致XOR和下游血管的异位上调 后果。这一点意义重大，因为异或是FDA批准的化合物(非布索坦和 而其他来源的氧化剂(如线粒体、NADPH氧化酶、去偶联eNOS等) 对血管功能障碍没有贡献，因此为快速将结果转化为临床奠定了基础 通过脱离目标的应用程序。

Project Summary Exposure to titanium dioxide (TiO2) via inhalation is a considerable occupational healthcare issue as it results in not only in a local pulmonary inflammatory response but also mediates systemic vascular dysfunction. However, the signaling mechanisms underpinning the link between a primary inflammatory event in the lung with systemic vascular consequences are unclear; especially, if the toxicant remains localized primarily in the pulmonary tissue. One potential contributor to this process may be xanthine oxidoreductase (XOR), an enzyme that is upregulated under inflammatory conditions, can be released into the circulation and avidly bind to glycosaminoglycans (GAGs) on the endothelial surface and drive endothelial dysfunction via production of oxidants. We have recently demonstrated that a key source of circulating XOR is the liver whereby hepatocytes respond to inflammatory stimuli by releasing XOR to the circulation. This process seems to be specific to the liver as genetic ablation of hepatocellular XOR, in the context of inflammatory stimulus, significantly depletes circulating XOR levels in a manner absent of compensation by other organs/tissues. While the liver seems to play a master regulator role for controlling XOR levels in the circulation, the signaling from the primary off-site insult (lungs) to the hepatocyte remains undefined affirming the need for further exploration of this area. To this end, we provide preliminary data demonstrating a substantive increase in plasma XOR following inhalation exposure to TiO2 in a murine model. In addition, exposure to TiO2 results in endothelium-dependent dysfunction in both the middle cerebral artery and thoracic aorta that is restored by treatment with the XOR-specific inhibitor, febuxostat. Collectively, these data incentivize the hypothesis that inhalation of TiO2 mediates signaling from the lung to the liver upregulating XOR with subsequent release to the circulation where it contributes to vascular dysfunction. The following specific aims will test this hypothesis: 1) define XOR-mediated contributions to vascular dysfunction allied to inhalation of TiO2 and establish the liver as the source of amplified circulating XOR and 2) Identify the signaling from the lung to liver which mediates upregulation of XOR in response to TiO2 inhalation. Combined, these aims will establish a novel pathway whereby a primary insult to pulmonary tissue confers off-site upregulation of XOR and downstream vascular consequences. This is significant as XOR is targetable by FDA-approved compounds (febuxostat and allopurinol) whereas other sources of oxidants (e.g. mitochondria, NADPH oxidase, uncoupled eNOS etc.) contributory to vascular dysfunction are not and thus sets the stage for rapid translation of results to the clinic by off-target application.