Hypercholesterolemia and Human Skin Blood Flow

描述（由申请人提供）：皮肤循环是一个可接近的，具有代表性的血管床，用于体内检查导致血管功能障碍的机制。这一建议是我们之前研究皮肤血流控制中与年龄相关的变化的神经血管机制的合理延伸。提出的研究扩展了我们之前的研究，以检查高胆固醇血症（HC）人群的皮肤血管舒张（VD）信号机制。HC损伤VD信号的特征是氧化应激的增加加上内皮一氧化氮（NO）的损失；这些事件共同导致与动脉粥样硬化发病机制相关的内皮功能障碍。介导内皮NO降低的确切机制尚不清楚。HC可能导致NO减少的推测位点包括：1)氧化低密度脂蛋白（ox-LDL）诱导的血管精氨酸酶活性上调，其优先将常见NO合成酶（NOS）底物L-精氨酸（L-arg）代谢为L-鸟氨酸和尿素；2)内皮(e)NOS解偶联，其中eNOS由于底物（L-arg）或必需辅助因子（四氢生物蝶呤）缺乏而产生超氧化物，从而增加氧化应激。此外，ox- ldl诱导的血管精氨酸酶活性增强与动脉粥样硬化的发病机制之间存在机制联系，多胺和脯氨酸前体l -鸟氨酸的增加有助于内膜增厚。为此，拟议的研究将利用最先进的体内皮肤特异性技术（局部加热和皮内微透析）与经典的皮肤活检体外生化分析相结合，系统地探索影响HC损害NO依赖性皮肤VD的机制。具体目的1和2将分别考察精氨酸酶和氧化应激在eNOS解偶联背景下的作用，以澄清与年龄匹配的正常胆固醇水平对照组相比，它们在HC患者VD功能障碍中的作用。特异性目的3将补充目的1和目的2，对eNOS和精氨酸酶基因表达、酶活性和蛋白质浓度进行体外生化分析。特异性Aim 4检查了Aims 1-3中所研究的机制，在他汀类药物与阿托伐他汀治疗干预前后。

DESCRIPTION (provided by applicant): The cutaneous circulation is an accessible, representative vascular bed for in vivo examination of mechanisms that contribute to vascular dysfunction. This proposal is a logical extension of our previous work investigating the neurovascular mechanisms underlying age-related changes in the control of skin blood flow. The proposed studies expand our previous research to examine cutaneous vasodilatory (VD) signaling mechanisms in a hypercholesterolemic (HC) population. Impaired VD signaling with HC is characterized by an increase in oxidant stress coupled with the loss of endothelial nitric oxide (NO); together these events contribute to endothelial dysfunction associated with the pathogenesis of atherosclerosis. The precise mechanisms mediating decreased endothelial NO remain unclear. Putative sites through which NO may be decreased with HC include 1) oxidized low density lipoprotein (ox-LDL)-induced upregulation of vascular arginase activity, which preferentially metabolizes the common NO-synthase (NOS) substrate L- arginine (L-arg) to L-ornithine and urea and 2) endothelial (e)NOS uncoupling where eNOS contributes to increased oxidant stress by producing superoxide as a result of substrate (L-arg) or essential cofactor (tetrahydrobiopterin) deficiency. Additionally, there is a mechanistic link between ox-LDL-induced augmented vascular arginase activity and the pathogenesis of atherosclerosis through an increase in the polyamine and proline precursor L-ornithine which contributes to intimal thickening. To this end, the proposed investigations will systematically explore mechanisms affecting impaired NO- dependent cutaneous VD with HC using state-of-the-art in vivo skin specific techniques (local heating and intradermal microdialysis) paired with classic in vitro biochemical analysis of cutaneous biopsies. Specific Aims 1 and 2 will mechanistically examine the roles of arginase, and oxidant stress in the context of eNOS uncoupling, respectively, to clarify their contributions to VD dysfunction with HC compared to an age- matched normocholesterolemic control group. Specific Aim 3 will complement Aims 1 and 2 with in vitro biochemical analysis of eNOS and arginase gene expression, enzyme activity, and protein concentration. Specific Aim 4 examines the mechanisms investigated in Aims 1-3 before and after a statin therapy intervention with atrovastatin.