Aging and Hepatic Microvascular Dysfunction

描述(由申请人提供)：肝脏的老化与其质量的减少以及30%-50%的血流减少有关，并伴随着新陈代谢受损和潜在的临床影响，包括药物不良反应、对毒素的敏感性和动脉粥样硬化。这种与年龄相关的肝脏血流量减少的原因尚不清楚。然而，与年龄相关的肝窦内皮细胞(SEC)窗口的显著减少以及Disse间隙内细胞外基质、基底膜和结缔组织的沉积增加，导致SEC的“假毛细血管化”，被认为影响了包括氧、乳糜粒残留、毒素和药物在内的底物在血液和肝实质细胞之间的转移。伴发“假毛细血管形成”的SEC中的哪些功能改变尚不清楚，但可能在年龄相关性血流减少中起重要作用。晚期糖基化终末产物(AGEs)的积聚也会随着SEC的年龄增长而发生，但其对SEC和微血管功能的影响尚不清楚。我们推测，AGE相关的肝血流量和SEC形态的减少是由于AGE在这些细胞中积聚，导致结构性一氧化氮(NO)的产生减少和/或内皮素-1(ET-1)的产生增加，可能伴随着肝脏微血管炎症反应。为了验证这一假设，将在0.8、3.3、14和27个月龄时对小鼠的肝脏进行研究。活体显微镜将被用来确定肝脏微血管功能障碍的动态时空发展。对固定标本和分离的SEC进行光镜和电子显微镜检查，将评估无法在体内观察到的结构变化。这些指标将与SEC中AGE的积聚以及SEC和肝脏中NO、eNOS、ET-1、促炎细胞因子和超氧化物歧化的变化相关联，以获得解释显微镜下观察到的反应的线索。这一结果应该会为肝脏老化提供新的、新的信息。

DESCRIPTION (provided by applicant): Aging of the liver is associated with reductions in its mass as well as a 30-50% reduction in blood flow accompanied by an impaired metabolism and potential clinical implications including adverse drug reactions, susceptibility to toxins, and atherosclerosis. The reason for this age related reduction in hepatic blood flow is not known. However, significant age associated reductions in the fenestration of hepatic sinusoidal endothelial cells (SEC) and increased deposition of extracellular matrix, basal lamina, and connective tissue in the Space of Disse leading to "pseudocapillarization" of the SEC are thought to affect the transfer of substrates including oxygen, chylomicron remnants, toxins, and drugs between the blood and hepatic parenchymal cells. What functional alterations in SEC accompany "pseudocapillarization" are not clear but may play a significant role in the age related diminished blood flow. Accumulation of advanced glycation end-products (AGEs) also occurs with aging in SEC, but its effects on SEC and microvascular function are unknown. We hypothesize that age associated reductions in hepatic blood flow and SEC morphology are due the accumulation of AGE in these cells causing reduced production of constitutive nitric oxide (NO) and/or enhanced production of endothelin-1 (ET-1) and sinusoid constriction perhaps accompanied by an hepatic microvascular inflammatory response. To validate this hypothesis, the livers of mice will be studied at 0.8, 3.3,14, and 27 months of age. In vivo microscopy will be used to determine the dynamic spatial and temporal development of hepatic microvascular dysfunction. Light and electron microscopic examination of fixed specimens and isolated SEC will evaluate structural alterations that can not be visualized in vivo. These will be correlated with measurements of the accumulation of AGE in SEC and changes in NO, eNOS, ET-1, proinflammatory cytokines, and superoxide in SEC and liver to gain clues to explain the responses observed microscopically. The results should provide novel, new information about the aging liver.