The Guanosine-Adenosine Mechanism

鸟苷-腺苷机制

• 批准号: 8369704
• 负责人: EDWIN Kerry JACKSON
• 金额: $ 38.13万
• 依托单位: UNIVERSITY OF PITTSBURGH AT PITTSBURGH
• 依托单位国家: 美国
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-07-01 至 2016-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8369704
• 关键词: Adenosine; Biological; Biological Models; Blood Vessels; Blushing; Brain; Cell Surface Receptors; Cell physiology; Cells; Cellular Stress; Cyclic AMP; Cyclic GMP; Data; Enzymes; Evolution; Guanine; Guanosine; Heart; High Pressure Liquid Chromatography; Immune system; Injury; Kidney Diseases; Lung; Measures; Mediating; Metabolism; Physiological; Physiological Processes; Play; Purines; Role; Smooth Muscle Myocytes; Stress; Testing; Tissues; Vasodilation; analog; cell type; extracellular; in vivo; kidney cell; liquid chromatography mass spectrometry; purine; receptor; research study; response; response to injury; uptake

DESCRIPTION (provided by applicant): Adenosine and guanosine are naturally-occurring and structurally similar purines. Moreover, naturally- occurring cyclic analogues of adenosine and guanosine are involved in similar physiological processes (e.g., both cAMP and cGMP mediate vasodilation). Strangely, at first blush it would seem that evolution broke the symmetry between adenosine and guanosine by bestowing cells with adenosine, but not guanosine, receptors. Thus the standard view is that adenosine serves as a physiological regulator of cellular function via activation of its own cell-surface receptors, while guanosine is merely an idle bystander. The purpose of this application is to challenge this received view by proposing that guanosine also plays an important role in cellular physiology, not via its own receptors but rather by engaging a powerful collaborative mechanism involving adenosine. In this regard, we hypothesize that extracellular guanosine is THE major physiological determinant of extracellular levels of adenosine because guanosine blocks the disposition of adenosine from the extracellular compartment allowing greater activation of adenosine cell-surface receptors due to increased extracellular adenosine levels. We refer to this guanosine-adenosine interaction as the GUANOSINE- ADENOSINE MECHANISM. Our pilot experiments strongly suggest that our hypothesis is correct. In preglomerular vascular smooth muscle cells (a model system for microvascular smooth muscle cells) we observe that for any given amount of adenosine added to cells, the extracellular concentrations of adenosine [as measured by high performance liquid chromatography-mass spectrometry (LC-MS/MS)] are more than 10- fold higher when guanosine is also added to the cells. We also find that cellular stress/injury increases extracellular levels of BOTH guanosine and adenosine. Moreover, we find that guanosine PROFOUNDLY augments the biological effects of adenosine in vivo! These findings suggest that extracellular guanosine, by blocking the disposition of extracellular adenosine, is the most important physiological determinant of extracellular levels of adenosine yet discovered. We propose to test the existence of, the mechanism of and the importance of the Guanosine-Adenosine Mechanism with the following six Specific Aims: Aim 1 - To determine the existence of the Guanosine-Adenosine Mechanism in vascular and renal cell types; Aim 2 - To determine whether the Guanosine-Adenosine Mechanism is mediated directly by guanosine or indirectly by conversion of guanosine to guanine; Aim 3 - To determine whether the Guanosine-Adenosine Mechanism involves inhibition by guanosine of enzymes involved in adenosine metabolism; Aim 4 - To determine whether the Guanosine-Adenosine Mechanism involves inhibition by guanosine of transporters involved in adenosine uptake; Aim 5 - To determine whether the Guanosine-Adenosine Mechanism importantly contributes to elevated extracellular levels of adenosine following cellular stress with energy depletion; and Aim 6 - To determine whether the Guanosine-Adenosine Mechanism amplifies the effects of adenosine in vivo. PUBLIC HEALTH RELEVANCE: Adenosine is a critical "retaliatory" metabolite. During cellular/tissue stress and injury, extracellular adenosine levels are elevated and activate cell surface receptors that mediate tissue/cellular protection (or in some cases participate in adverse responses). Our pilot experiments show that cellular stress/injury increases extracellular levels of guanosine as much as or more than extracellular levels of adenosine and that extracellular guanosine elevates the levels of extracellular adenosine by interfering with the disposition of adenosine from the extracellular compartment. Manipulation of this mechanism, which we call this the "Guanosine-Adenosine Mechanism," can be exploited to treat diseases of the kidneys, heart, blood vessels, lungs, brain and immune system.

描述（由申请人提供）： 腺苷和鸟苷是天然存在且结构相似的嘌呤。此外，天然存在的腺苷和鸟苷的环状类似物参与相似的生理过程（例如，cAMP和cGMP均介导血管舒张）。奇怪的是，乍一看，进化似乎通过赋予细胞腺苷受体而不是鸟苷受体来打破腺苷和鸟苷之间的对称性。因此，标准观点是腺苷通过激活其自身的细胞表面受体而充当细胞功能的生理调节剂，而鸟苷只是一个无所事事的旁观者。本申请的目的是挑战这一公认的观点，提出鸟苷在细胞生理学中也发挥着重要作用，不是通过其自身的受体，而是通过涉及腺苷的强大协作机制。在这方面，我们假设细胞外鸟苷是细胞外腺苷水平的主要生理决定因素，因为鸟苷阻止腺苷从细胞外区室的处置，从而由​​于细胞外腺苷水平增加而允许更大程度地激活腺苷细胞表面受体。我们将这种鸟苷-腺苷相互作用称为鸟苷-腺苷机制。我们的试点实验强烈表明我们的假设是正确的。在肾小球前血管平滑肌细胞（微血管平滑肌细胞的模型系统）中，我们观察到，对于添加到细胞中的任何给定量的腺苷，腺苷的细胞外浓度[通过高效液相色谱-质谱法（LC-MS/当鸟苷也添加到细胞中时，MS)]高出10倍以上。我们还发现细胞应激/损伤会增加细胞外鸟苷和腺苷的水平。此外，我们发现鸟苷极大地增强了腺苷在体内的生物效应！这些发现表明，细胞外鸟苷通过阻断细胞外腺苷的处置，是迄今为止发现的细胞外腺苷水平最重要的生理决定因素。我们建议通过以下六个具体目标来测试鸟苷-腺苷机制的存在、机制和重要性： 目标 1 - 确定鸟苷-腺苷机制在血管和肾细胞类型中的存在；目标 2 - 确定鸟苷-腺苷机制是由鸟苷直接介导还是由鸟苷转化为鸟嘌呤间接介导；目标 3 - 确定鸟苷-腺苷机制是否涉及鸟苷对参与腺苷代谢的酶的抑制；目标 4 - 确定鸟苷-腺苷机制是否涉及鸟苷对参与腺苷摄取的转运蛋白的抑制；目标 5 - 确定鸟苷-腺苷机制是否对细胞应激和能量消耗后细胞外腺苷水平升高有重要贡献；目标 6 - 确定鸟苷-腺苷机制是否放大腺苷在体内的作用。 公共健康相关性：腺苷是一种重要的“报复性”代谢物。在细胞/组织应激和损伤期间，细胞外腺苷水平升高并激活介导组织/细胞保护（或在某些情况下参与不良反应）的细胞表面受体。我们的初步实验表明，细胞应激/损伤增加的细胞外鸟苷水平与细胞外腺苷水平一样多或更多，并且细胞外鸟苷通过干扰细胞外区室中腺苷的处置来提高细胞外腺苷水平。操纵这种机制，我们称之为“鸟苷-腺苷机制”，可用于治疗肾脏、心脏、血管、肺、大脑和免疫系统的疾病。