Studies of pathogenesis in Farber disease-cloning of the DNA and study of signal transduction system

法伯氏病是一种罕见的常染色体隐性遗传性鞘氨醇脂肪病，由酸性神经酰胺酶缺乏引起。酸性神经酰胺酶是一种溶酶体酶，通常催化神经酰胺水解成鞘氨醇和游离脂肪酸。该病的临床特征是关节肿胀，活动受限，弥漫性皮下结节，尤其是关节和压力点过大，声音嘶哑，最近，神经酰胺作为细胞内效应分子在细胞凋亡中的作用引起了人们的极大关注。在Farber病中，至少有一些病理事件与第二信使功能有关。我们最近诊断了两例II型Farber病，原因是摄取放射性标记的丝氨酸后，神经酰胺酶活性降低和神经酰胺堆积。这些患者的cDNA分析分别揭示了V369I/V97E和V96 del的同型突变。这些突变在COS I细胞中的表达研究中得到证实。这些突变包括IL-2、-6、IL-2和IL-6等细胞因子的分泌增加对照组和Farber病患者皮肤成纤维细胞中未检测到肿瘤坏死因子α，神经酰胺不能诱导细胞因子的产生。切除的结节中神经酰胺和巨噬细胞浸润增加，而Fas、bcl2和IL-6免疫染色呈阴性。TUNEL法未见明显阳性染色，从结节提取的DNA中未检测到DNA梯状条带。

Farber disease is a rare autosomal recessive sphingolipidosis caused by a deficiency of acid ceramidase, a lysosomal enzyme that normally catalyzes the hydrolysis of ceramide to sphingosine and free fatty acids.The disease is clinically characterized by swollen joints with limitation of movements, disseminated subcutaneous nodules, particularly in the joints and over pressured points, hoarseness, and progressive cachexia.Recently the mode of ceramide action and the regulation of its production have attracted great attention impart due to the emerging role of ceramide as an intracellular effector molecule in apoptosis.It is possible that at least some of the pathologic events in Farber disease are related to second messenger functions.We have recently diagnosed two patients with type II Farber disease due to the reduced enzymatic activity of ceramidase and accumulation of ceramide after feeding of radiolabelled serin.cDNA analysis of these patients disclosed V369I/V97E and homogygous mutation of V96 del, respectively.These mutations were confirmed in expression studies in COS I cells.Increased secreations of cytokins including IL-2, -6, and TNF- alpha, not detected in skin fibroblasts from control and Farber disease, and ceramide did not induced cytokin productions.The removed nodules showed increased level of ceramide and macrophage infiltrations.However, immunostainig of Fas, bcl-2, and IL-6 showed negative.Tunel method did not show significant positive staining and no DNA ladder was not detected in extracted DNA from nodules.These evidence suggest that apoptosis did not occur in the nodules.