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

法伯病是一种罕见的常染色体隐性神经鞘脂病，由酸性神经酰胺酶缺乏引起，该酶是一种溶酶体酶，通常催化神经酰胺水解为鞘氨醇和游离脂肪酸。该疾病的临床特征是关节肿胀，活动受限，播散性皮下结节，特别是在关节和受压点，声音嘶哑，近年来，神经酰胺作为细胞内效应分子在细胞凋亡中的作用越来越受到人们的重视，神经酰胺的作用方式及其产生的调节可能与法伯病的某些病理事件有关，我们最近诊断了两名II型法伯病患者，这两名患者由于喂食放射性标记的丝氨酸后神经酰胺酶的酶活性降低和神经酰胺的积累。对这些患者的cDNA分析分别揭示了V369 I/V97 E和V96 del的同源突变。这些突变在COS I细胞中的表达研究中得到证实。细胞因子包括IL-2，-6，神经酰胺不能诱导细胞因子的产生，切除的结节显示神经酰胺和巨噬细胞浸润水平增加，但Fas，bcl-2，和IL-TUNEL法未检测到明显阳性染色，提取的DNA中未检测到DNA梯状条带，提示细胞凋亡可能与细胞凋亡有关。不会发生在结节上。

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.