Limonoids, a novel type of inhibitors of sphingomyelin biosynthesis to study the membrane dynamics of sphingolipid domains

鞘脂是膜脂双分子层形成的重要细胞成分，也是细胞生长、凋亡和炎症的重要组成部分。利用选择性的高通量显微镜筛选，我们最近分离了天然化合物，柠檬类化合物，作为真核生物膜中主要鞘磷脂生物合成的新抑制剂。为了明确其治疗作用，我们建立了实验条件，分析其对各种鞘脂依赖性事件的影响：1)柠檬黄酮皂荚素预处理对鞘脂含量的调节提高了一些抗癌药物（阿霉素而不是紫杉醇）在HeLa细胞中的效率；2)红细胞中疟原虫的鞘脂依赖性生长和HeLa细胞中弓形虫的鞘脂依赖性生长均受到柠檬黄酮预处理的抑制，但其本身具有毒性作用；3)由于柠檬素有利于在膜上形成富含神经酰胺的结构域，我们尝试用新型神经酰胺的巯基类似物分析神经酰胺在体外单层囊泡中的跨双层运动；4)鞘磷脂的膜分布对控制二酰基甘油跨双分子层运动等各种事件起重要作用。

Sphingolipids are important cell components for the formation of membrane lipid bilayers as well as for cell growth, apoptosis and inflammation. Using a selective high-throughput microscopy-based screening, we recently isolated natural compounds, Limonoids as new inhibitor type of the biosynthesis of sphingomyelin, the major sphingolipid in eukaryotic membranes. In order to precise their therapeutic properties, we set up the experimental conditions to analyze their effects on various sphingolipid-dependent events: 1) modulation of sphingolipid content by limonoid Gedunin pretreatment improved the efficiency of some anticancer drugs (doxorubicin but not Paclitaxel) in HeLa cells; 2) sphingolipid-dependent growth of Plasmodium malaria parasite in erythrocytes and Toxoplasma parasite in HeLa cells was decreased by limonoid Gedunin pretreatment of the cells but had a toxic effect by itself; 3) since Limonoids favored the formation of ceramide-rich domains in the membrane, we tried to analyse the ceramide transbilayer movement in vitro in unilamellar vesicles with new type of sulhydryl analogs of ceramides; 4) the membrane distribution of sphingomyelin is important to control various events as diacylglycerol transbilayer movement .