BLOOD BRAIN BARRIER CHANGES INDUCED BY PAIN

慢性疼痛在美国每年影响近7000万人，花费数十亿美元用于医疗和生产力损失。迄今为止，所有关于血脑屏障（BBB）和镇痛剂递送的研究均在未处理的无疼痛动物中进行。越来越清楚的是，血脑屏障不是一个静态的屏障，而是可以通过免疫，神经元和激素系统的许多因素进行调节。 在疼痛时，这三个系统都被激活。本研究的假设是疼痛激活免疫、神经元和激素系统，导致血脑屏障的分子和功能特性发生改变。这种改变将导致物质穿过血脑屏障的运输发生变化，并可能在慢性疼痛的病因学中发挥作用。 在初步研究中，我们已经观察到在三种外周疼痛模型（福尔马林、A-角叉菜胶、弗氏完全佐剂）期间大鼠血脑屏障对[S14 C]蔗糖的渗透性增加，如果紧密连接受损，[S14 C]蔗糖仅会穿过血脑屏障。在平行的蛋白质印迹研究中，我们观察到occiudin（一种完整的BBB紧密连接蛋白）的减少和ZO-1和肌动蛋白（分别为辅助蛋白和细胞骨架蛋白）的增加。这表明疼痛改变了BBB紧密连接。ELISA和核糖核酸酶保护测定显示，在A-角叉菜胶诱导的疼痛期间，外周血中TNF-α的水平和CNS中TNF-α、IFN-γ和白细胞介素5和6的水平以时间依赖性方式改变。所有这些物质以前都被证明可以改变紧密连接蛋白。因此，本研究拟综合运用生理学、分子生物学和药理学等多种手段，进一步探讨疼痛引起的变化及促进这些变化的机制。我们的长期目标是确定可以治疗血脑屏障中这些改变的药理学药物。

DESCRIPTION (provided by applicant): Chronic pain affects nearly 70 million people a year in the United States and costs billions of dollars in medical treatment and lost productivity. To date, all investigations concerning the blood-brain barrier (BBB) and the delivery of analgesics have been performed in naive non-pained animals. It is becoming increasingly clear that the blood-brain barrier is not a static barrier but can be modulated by a number of factors from the immune, neuronal and hormonal systems. During pain all three of these systems are activated. The hypothesis of this study is that pain activates the immune, neuronal and hormonal systems leading to an alteration in the molecular and functional properties in the blood-brain barrier. This alteration will lead to a change in the transport of substances across the blood-brain barrier and may have a role in the etiology of chronic pain. In preliminary studies, we have seen an increase in the permeability of the rat blood-brain barrier during three models of peripheral pain (Formalin, A-carrageenan, Complete Freunds Adjuvant) to [S14C] Sucrose which will only cross the blood-brain barrier if the tight junctions have been compromised. In parallel Western blot studies we observed a reduction in occiudin (an integral BBB tight junction protein) and an increase in ZO-1 and actin (an accessory and cytoskeletal protein respectively). This indicates that the pain has altered BBB tight junctions. ELISA and ribonuclease protection assays, show that levels of TNF-a in peripheral blood and TNF-a, IFN-gamma, and interleukins 5 and 6 are altered in the CNS in a time dependent manner during A-carrageenan induced pain. All of these substances have previously been shown to alter tight junction proteins. Therefore, this proposal is designed to further investigate the changes induced by pain and the mechanisms that promote these changes by utilizing the tools of physiology, molecular biology and pharmacology in an integrative manner. It is our long-term aim to identify pharmacological agents that can treat these alterations in the blood-brain barrier.