Glial uptake of dopamine after L-DOPA medication

 描述（由申请人提供）：帕金森病（PD）在美国影响超过一百万人，是第二常见的进行性神经退行性疾病。早期，运动缺陷（震颤，僵硬，运动减慢，步态改变）通常对口服左旋多巴（L-DOPA）和其他药物有反应。然而，随着疾病的进展，左旋多巴的有效性逐渐减弱，出现运动障碍和运动波动。PD的大多数症状是由于黑质中多巴胺（DA）分泌细胞的减少。在PD中，L-DOPA通过替代丢失的DA来恢复功能。内源性L-DOPA和DA浓度在很大程度上由维持细胞外稳态的星形胶质细胞调节。虽然星形胶质细胞有几个单胺摄取的转运系统，包括DA，我们已经表明，星形胶质细胞通过低亲和力，高容量Uptake 2转运蛋白摄取过量的DA。我们还证明了缠绕在血管周围的星形胶质细胞吸收左旋多巴，并含有B型单胺氧化酶（MAO），其氧化细胞吸收的DA。我们假设星形胶质细胞吸收并氧化了从左旋多巴转化而来的绝大多数DA，特别是当DA神经元由于PD而严重退化时。通过使用特异性转运蛋白阻断剂降低星形胶质细胞摄取DA的能力，可以允许使用较低剂量的L-DOPA，从而减少DA脉动性和运动波动。这一假设将在3个目标中得到检验。目标1.利用脑切片和细胞培养模型鉴定参与星形胶质细胞多巴胺再摄取的特异性转运蛋白分子。目标2.使用星形胶质细胞脑切片模型确定哪种特异性转运蛋白阻断剂可以减缓DA再摄取。目标3.确定哪种Uptake 2阻滞剂可有效降低PD整体动物模型中的L-DOPA治疗浓度。这一结果将极大地增强对星形胶质细胞在PD病因学中作用的理解，并为L-DOPA诱导的运动障碍的预防措施的发展铺平道路。

 DESCRIPTION (provided by applicant): Parkinson's disease (PD) affects more than a million persons in the U.S. and is the 2nd most common progressive, neurodegenerative disease. Early on, the movement deficits (tremor, rigidity, slowed movement, altered gait), usually respond to oral levodopa (L-DOPA) and other medications. However, with disease progression, L-DOPA's effectiveness gradually diminishes and dyskinesia and motor fluctuations emerge. Most symptoms of PD are due to a reduction of dopamine (DA)-secreting cells in the substantia nigra. In PD, L-DOPA restores function by replacing lost DA. Endogenous L-DOPA and DA concentrations are largely regulated by astrocytes, which maintain extracellular homeostasis. Although astrocytes have several transporter systems for monoamine uptake, including DA, we have shown that astrocytes take up excess of DA via low-affinity, high-capacity Uptake2 transporters. We also demonstrated that astrocytes wrapping around blood vessels take up L-DOPA and contain monoamine oxidase (MAO) type B which oxidizes DA taken up by the cell. We hypothesize that astrocytes take up and oxidize the vast majority of DA converted from L-DOPA, especially when DA neurons are severely degenerated due to PD. Reducing the ability of astrocytes to take up DA through use of specific transporter blockers may permit the use of lower doses of L-DOPA, thereby diminishing DA pulsatility and motor fluctuations. This hypothesis will be tested here in 3 Aims. Aim 1. Identify the specific transporter molecules involved in dopamine reuptake by astrocytes using brain slice and cell culture models. Aim 2. Identify which specific transporter blockers can slow DA reuptake using an astrocyte brain slice model. Aim 3. Identify which Uptake2 blockers are effective in reducing therapeutic L-DOPA concentrations in a whole animal model of PD. The results will greatly enhance the understanding of the role of astrocytes in PD etiology and pave the way to the development of preventive measures for L-DOPA-induced dyskinesia.