Iron regulation at the CNS vascular barriers and aging

描述（由申请人提供）：虽然铁（Fe）是正常脑功能所必需的，但其在老化脑中的积累与神经变性有关。积累的机制尚不清楚。 我们最近的研究表明，转铁蛋白（Tf）结合和游离铁进入中枢神经系统是由（i）由脑毛细血管（BBB）和脉络丛（CP）的初始快速隔离，和（ii）随后从血管结构到脑间质液（ISF）和脑脊液（CSF）的控制和缓慢释放。 此外，我们的初步数据表明，铁是迅速清除从大脑进入血液，通过血脑屏障主要是由Tf介导的机制。 基于这些初步的数据，我们假设，铁的流入跨越血脑屏障和CP是一个两步的过程，需要Tf受体（TfR）和DMT 1（二价金属转运蛋白1）与DMT 1是一个限速步骤，而铁从中枢神经系统的流出是一个一步的过程，取决于Tf的路线，并需要TfR在血脑屏障。 我们进一步假设，铁CNS流入和流出运输机制之间的不平衡，主要是由于减少清除在血管CNS屏障导致其在老化的大脑中的积累。 有两个目标。 1.在选择年龄的bold型和DMT 1突变型Belgrade大鼠中，确定Tf介导的和非Tf途径对铁从CNS流出的作用以及铁在CNS中的保留机制。 2. 在选择的年龄段，测定野生型和贝尔格莱德大鼠Tf和非Tf介导的铁离子穿过血脑屏障和CP的动力学。 这些目的将通过使用脑灌注和清除技术以及贝尔格莱德大鼠（B/B）来实现，因为它是DNT 1的生理敲除。 将在B/B/和对照大鼠中测定Tf和非Tf结合的Fe的动力学参数，以确定DMT 1在血脑屏障和CP处Fe的流入和流出中的作用。 在选定年龄的对照大鼠中进行的类似研究将确定年龄相关的变化。 将通过标准分子技术测定血脑屏障和CP处TfR和DMT 1的相对水平，以补充转运研究。 这项研究将有助于我们了解DMT 1和TfR在BBB和CP中与脑中铁积累相关的作用，相关的神经退行性作用，并确定未来开发脑铁降低策略的潜在目标。

DESCRIPTION (provided by applicant): While iron (Fe) is essential for normal brain function its accumulation in the aging brain is associated with neurodegeneration. The mechanism of accumulation is still unclear. Our recent studies indicated that entry of transferrin (Tf)-bound and free iron into the CNS is determined by (i) initial rapid sequestration by brain capillaries (BBB) and choroid plexus (CP), and (ii) subsequent controlled and slow release from vascular structures into brain interstitial fluid (ISF) and cerebrospinal fluid (CSF). In addition, our pilot data suggest that iron is rapidly cleared from brain into blood across the blood-brain barrier mainly by a Tf-medicated mechanism. Based on these preliminary data, we hypothesize that influx of iron across the blood-brain barrier and CP is a two-step process that requires both Tf receptor (TfR) and DMT1 (divalent metal transporter 1) with DMT1 being a rate limiting step, while efflux of Fe from the CNS is a one-step process that depends on Tf route and requires TfR at the blood-brain barrier. We further hypothesize that imbalance between iron CNS influx and efflux transport mechanisms, due mainly to reduced clearance at the vascular CNS barriers leads to its accumulation in the aging brain. There are two Aims. 1. To determine the role of Tf-mediated and non-Tf route for Fe efflux from CNS and the retention mechanism for Fe in CNS in bold type and DMT1 mutant Belgrade rats at selective ages. 2. To determine the kinetics of Tf and non-Tf mediated Fe influx across blood-brain barrier and CP in wild type and Belgrade rats at selective ages. These Aims will be achieved by using the brain perfusion and clearance techniques and the Belgrade rat (b/b) since it is a physiological knock out for DNT1. The kinetic parameters of Tf and non Tf bound Fe will be determined in b/b/ and control rats to establish the role of DMT1 in the influx and efflux of Fe at the blood-brain barrier and CP. Similar studies in control rats at selected ages will determine age related changes. Relative levels of TfR and DMT1 at blood-brain barrier and CP will be determined by standard molecular techniques to complement the transport studies. This study will help us understand the roles of DMT1 and TfR at the BBB and CP with respect to iron accumulation in the brain, associated neurodegenerative effects, and identify potential targets for future development of brain iron lowering strategies.