Role of Cytoglobin in the Regulation of Vascular Tone

内皮源性一氧化氮（NO）是调节血管张力和血压的关键介质。没有 通过激活平滑肌中的可溶性鸟苷酸环化酶（sGC）介导血管舒张。 虽然NO由内皮中的NO合酶合成，但血管NO降解和 平滑肌中的代谢知之甚少。血管壁中的NO降解由O2-介导。 依赖性NO双加氧酶（NOD），将NO氧化为硝酸盐。细胞珠蛋白（Cytoglobin，Cgb）是新近发现的一种珠蛋白 在平滑肌中表达（但不在内皮中），具有以前未知的功能。Cgb建议 作为血管壁中O2依赖性NO代谢速率的关键调节剂，反过来调节 血管张力在先前的资助期间：1）我们证明了Cgb是主要的血红素蛋白， 调节管道和阻力平滑肌中O2依赖性NO代谢的速率 细胞色素b5（B5）/B5（B5）/B5（B5）/ B5（B5）/ B5 还原酶（B5 R）构成了支持这种NOD功能的主要Cgb还原系统; 3）我们发现 Cgb具有强大的超氧化物歧化酶（SOD）功能，这是其先前无法解释的抗氧化剂 4）最近，我们发现了新的Cgb NOD功能的选择性抑制剂，其不损害其SOD 在血管中显示增强NO介导的sGC活化。然而，主要问题 关于血管壁中NO衰变的整个过程，这在疾病中是如何变化的，以及它如何能够 被调节以改善疾病。在这个赠款计划的下一阶段，我们寻求确定如何不 Cgb在血管壁中的降解和SOD/抗氧化特性控制NO和氧化还原过程 正常和高血压血管的代谢，以及这反过来如何调节血管张力和全身血液 压力Cgb表达水平及其NOD活性的调节的关键作用将是 测定研究将首先在离体血管中进行，然后在体内心血管系统中进行， 在我们的Cgb-/-、Cgb-/+和Cgb过表达的转基因小鼠系中进行测量， 作为选择性抑制Cgb NOD功能的化合物。研究还将在我们最近的 开发了条件性平滑肌选择性Cgb-/-小鼠，以明确表征Cgb在 平滑肌研究将集中在正常非高血压小鼠中发生的生理调节 然后是血管紧张素诱发的高血压。所有获得的数据将用于支持计算 这将使我们能够预测调节Cgb表达及其NO代谢的影响 功能本研究计划的完成将阐明Cgb水平及其NOD和SOD的功能 调节O2依赖的NO代谢和血管的氧化还原状态，从而提供重要的见解 调节正常生理和心血管疾病中的血管张力。这些知识将导致 涉及治疗或逆转高血压和其他心血管疾病的新治疗方法。

Endothelium-derived nitric oxide (NO), is a key mediator regulating vascular tone and blood pressure. NO mediates vascular relaxation through activation of soluble guanylate cyclase (sGC) in the smooth muscle. While NO is synthesized by NO synthase in the endothelium, the process of vascular NO degradation and metabolism in smooth muscle is poorly understood. NO degradation in the vessel wall is mediated by an O2- dependent NO dioxygenase (NOD) that oxidizes NO to nitrate. Cytoglobin (Cgb) is a recently discovered globin expressed in smooth muscle (but not in the endothelium) with previously unknown function. Cgb is proposed to serve as a critical regulator of the rate of O2-dependent NO metabolism in the vessel wall, in turn regulating vascular tone. Over the prior grant period: 1) we demonstrated that Cgb is the major heme protein that regulates the rate of O2-dependent NO metabolism in the smooth muscle of both conduit and resistance vessels and, in turn, profoundly modulates vascular tone; 2) we identified that cytochrome b5 (B5)/ B5 reductase (B5R) constitutes the major Cgb reducing system that supports this NOD function; 3) we discovered that Cgb has potent superoxide dismutase (SOD) function accounting for its previously unexplained antioxidant effects; 4) most recently, we identified novel selective inhibitors of Cgb NOD function that do not impair its SOD function and were shown in vessels to enhance NO mediated sGC activation. However, major questions remain regarding the overall process of NO decay in the vessel wall, how this varies in disease, and how it can be modulated to ameliorate disease. In the next stage of this grant program, we seek to determine how the NO degrading and SOD/antioxidant properties of Cgb in the vessel wall control the processes of NO and redox metabolism in normal and hypertensive vessels, and how this in turn regulates vessel tone and systemic blood pressure. The critical effects of Cgb expression levels and the modulation of its NOD activity will be determined. Studies will be performed first in isolated vessels and then in the in vivo cardiovascular system, with measurements in our genetically modified mouse lines with Cgb-/-, Cgb-/+ and Cgb overexpression as well as compounds that selectively inhibit Cgb NOD function. Studies will also be performed in our recently developed conditional smooth muscle-selective Cgb-/- mouse to definitively characterize the role of Cgb in smooth muscle. Studies will focus on the physiological regulation that occurs in normal non-hypertensive mice and then on angiotensin-induced hypertension. All the data obtained will be used to support computational modeling that will enable us to predict the effects of modulating Cgb expression and its NO metabolizing function. Accomplishment of this research plan will elucidate how Cgb levels and its NOD and SOD function regulates O2-dependent NO metabolism and the redox state of the vessel, thus providing important insights into the regulation of vascular tone in normal physiology and cardiovascular disease. This knowledge will lead to new therapeutic approaches to treat or reverse hypertension and other cardiovascular disease.