M. LEPRAE-INDUCED CONTACT-DEPENDENT DEMYELINATION

描述(申请人提供)：脱髓鞘，导致长期的神经功能障碍，是麻风和许多原因不明的神经退行性疾病共同的中央病理条件之一，如多发性硬化症(MS)和格林-巴利综合征(GBS)。然而，脱髓鞘的分子基础在很大程度上是未知的。我们认为，在这些经典的和传染性的神经退行性疾病中，脱髓鞘过程的开始有共同的主题。众所周知，周围神经脱髓鞘的传染性神经退行性疾病的一个例子是麻风，它是由无毒细菌麻风分枝杆菌引起的。我们最近的研究表明，麻风杆菌可以作为一个模型来剖析脱髓鞘的早期分子事件。我们发现麻风杆菌或其细胞壁成分与髓鞘雪旺细胞轴突单位的结合足以以接触依赖的方式诱导显著的脱髓鞘，这不需要免疫反应。然而，这种髓鞘损伤的机制尚不清楚，它代表了脱髓鞘的最初事件。为了研究这些，我们分别使用了先前建立的大鼠髓鞘雪旺细胞-神经元共培养体系和RAG-1-/-基因敲除小鼠作为体外和体内模型。我们使用Affymetrix大鼠和小鼠GeneChips和髓鞘雪旺细胞-神经元共培养制备的cRNA以及感染麻风杆菌的Rag-1/-基因敲除小鼠的坐骨神经进行微阵列分析，结果表明：(1)主要信号蛋白基因显著上调，(2)髓鞘、突触蛋白和电压门控离子通道基因下调。我们认为麻风杆菌附着在雪旺细胞-轴突单位的受体/分子上，迅速诱导强烈的信号，影响下游转录因子的激活和基因表达，最终导致髓鞘损伤。为了调查这些问题，我们将进行以下研究： (1)在苔藓分枝杆菌诱导的脱髓鞘开始和期间的时间基因表达， (2)早期脱髓鞘中信号通路和转录激活的特征，以及(3)非层粘连蛋白受体作为麻风杆菌诱导信号和脱髓鞘靶标的鉴定和特征。这些研究将在受体、信号、转录和基因水平为早期脱髓鞘和神经元功能障碍的分子事件提供新的见解，并将有助于开发新的神经损伤诊断和治疗方法，包括麻风和其他神经退行性疾病，如MS和GBS。

DESCRIPTION (provided by applicant): Demyelination, which leads to prolonged neurological disability, is one of the central pathologic conditions that is shared by leprosy and many neurodegenerative diseases with unknown etiology, such as multiple sclerosis (MS) and Guillain-Barr syndrome {GBS). However, molecular basis of demyelination is largely unknown. We propose that there are common themes at the onset of demyelination process among these classical and infectious neurodegenerative diseases. One of the well-known examples of infectious neurodegenerative diseases with peripheral nerve demyelination is leprosy, which is caused by the non-toxic bacterium, Mycobacterium leprae. Our recent studies have shown that M. leprae can be used as a model to dissect the early molecular events of demyelination. We found that the binding of M. leprae or its cell wall components to myelinating Schwann cell-axon units is sufficient to induce significant demyelination in a contact-dependent manner, which does not require immune responses. However, the mechanism of such myelin damage, which represents initial events of demyelination, is unknown. To study these, we used previously established rat myelinating Schwann cell-neuron co-culture system and Rag-1 -/- knockout mice as in vitro and in vivo models respectively. Microarray analysis using Affymetrix rat and mouse GeneChips with cRNA prepared from myelinating Schwann cell-neuron-co-cultures and the Sciatic nerves iromRag-1-/- knockout mice infected with M. leprae, we showed (i) significant up-regulation of genes for major signaling proteins, and (ii) down-regulation of genes for myelin and synaptic proteins and voltage-gated ion channels. We propose that the attachment of M. leprae to the receptors/molecules on Schwann cell-axon units rapidly induce strong signaling that influence the activation of downstream transcription factors and gene expression that eventually lead to myelin damage. To investigate these, we will study the following: (1) Temporal gene expression at the onset of and during M. teprae-induced demyelination, (2) Characterization of signaling pathways and transcriptional activation in early demyelination, and (3) Identification and characterization of non-laminin receptors as M. leprae targets for induction of signaling and demyelination. These studies will provide novel insights into the early molecular events of demyelination and neuronal dysfunctions at receptor, signaling, transcriptional and gene levels, and will aid in developing new diagnostics and therapeutics for nerve injuries both in leprosy and other neurodegenerative diseases such as MS and GBS.