Acid Sphingomyelinase and Niemann-Pick Disease

描述(由申请人提供)： 这项研究的总体目标是使用我们独特的A和B型尼曼-皮克病(NPD)小鼠模型来开发这种疾病的新疗法，并揭示新的致病机制。提出了两个目标。目的1：两种新疗法的临床前评价。在第一组研究中，我们将评估一种使用热休克蛋白Hsp70的新的酶增强方法。这些实验是基于最近发表的一篇文章，该文章显示，Hsp70增强了A型和B型NPD患者细胞中残留的ASM活性，并减少了溶酶体病理，这一发现得到了自上次提交以来获得的新的体内数据的支持。第二组研究将继续我们的工作，旨在利用ICAM-1改善ASM到肺的输送。利用AAV8载体在NPD小鼠肝脏中表达ASM/ICAM-1融合蛋白，将进行“原则证明”基因转移实验。将研究融合酶在肺和其他临床重要器官中的摄取和疗效。还获得了新的活体数据来证明这种方法的可行性。目的2：探讨ERT相关肝毒性的新致病机制。ASM基因敲除(ASMKO)小鼠的临床前ERT研究表明，剂量超过5 mg/kg的重组ASM会导致肝脏出血、肝酶释放和死亡。我们最近发现，在这些小鼠的肝脏中积累脂质的主要是鞘氨醇，而不是鞘磷脂，并假设鞘氨醇的储存至少部分地导致了ERT相关的毒性。我们将通过评估神经酰胺酶、鞘氨醇激酶和鞘氨醇-1-磷酸裂解酶在ASMKO小鼠中的表达来确定神经鞘氨醇的积累来源，并将这些动物饲养到缺乏鞘氨醇激酶-1的小鼠身上，以确定其对ERT相关肝脏毒性的影响。这些结果将为小鼠的临床观察提供机制基础，也可能导致克服这种毒性的新策略。

DESCRIPTION (provided by applicant): The overall goal of this research is to use our unique mouse models of Types A & B Niemann-Pick disease (NPD) to develop new therapies for this disorder and to uncover novel pathogenic mechanisms. Two aims are proposed. Aim 1: Preclinical Evaluation of Two New Therapies. In the first set of studies we will evaluate a novel enzyme enhancement approach using the heat shock protein, Hsp70. These experiments are based on a recent publication showing that Hsp70 enhanced residual ASM activity and reduced lysosomal pathology in cells from Type A and B NPD patients, a finding that has been supported by new in vivo data obtained since the previous submission. The second set of studies will continue our work aimed at improved delivery of ASM to the lung using ICAM-1. A "proof-of-principle" gene transfer experiment will be undertaken that will use AAV8 vectors to express ASM/ICAM-1 fusion proteins in the livers of NPD mice. Uptake and efficacy of the fusion enzymes in the lung and other clinically important organs will be studied. New in vivo data also has been obtained to demonstrate the feasibility of this approach. Aim 2: Investigation of Novel Pathogenic Mechanisms Leading to ERT-Related Liver Toxicity. Preclinical ERT studies in ASM knockout (ASMKO) mice have shown that administration of recombinant ASM at doses above 5 mg/Kg results in liver bleeding, the release of liver enzymes, and death. We have recently found that sphingosine, not sphingomyelin, is the major accumulating lipid in the livers of these mice, and hypothesize that sphingosine storage is responsible, at least in part, for the ERT-associated toxicity. We will determine the source of accumulating sphingosine by evaluating the expression of ceramidases, sphingosine kinases and sphingosine-1-phosphate lyase in the ASMKO mice, and breed these animals to mice lacking sphingosine kinase-1 to determine the effects on ERT- associated liver toxicity. These results should provide a mechanistic basis for the clinical observations in the mice, and also may lead to new strategies to overcome this toxicity.