Aging and Hepatic Microvascular Dysfunction

描述（由申请人提供）：肝脏老化与肝脏质量减少以及血流减少30-50%相关，并伴有代谢受损和潜在的临床影响，包括药物不良反应、毒素易感性和动脉粥样硬化。这种年龄相关的肝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）开窗减少和细胞外基质、基底膜和结缔组织在病变间隙的沉积增加，导致SEC的“假毛细血管化”，被认为会影响底物的转移，包括氧气、乳糜微粒残留物、毒素和药物在血液和肝实质细胞之间的转移。SEC伴随“假毛细血管化”的哪些功能改变尚不清楚，但可能在与年龄相关的血流减少中起重要作用。晚期糖基化终产物（AGEs）的积累也会随着年龄的增长而发生，但其对SEC和微血管功能的影响尚不清楚。我们假设，与年龄相关的肝血流和SEC形态减少是由于age在这些细胞中的积累，导致组成型一氧化氮（NO）的产生减少和/或内皮素-1 （ET-1）的产生增强，并且可能伴随肝微血管炎症反应的鼻窦收缩。为了验证这一假设，将对0.8个月、3.3个月、14个月和27个月大的小鼠肝脏进行研究。体内显微镜将用于确定肝微血管功能障碍的动态空间和时间发展。固定标本和分离的SEC的光镜和电镜检查将评估在体内无法可视化的结构变化。这些将与SEC中AGE的积累以及SEC和肝脏中NO、eNOS、ET-1、促炎细胞因子和超氧化物的变化相关联，以获得解释显微镜下观察到的反应的线索。这一结果将为肝脏衰老提供新的信息。

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.