Goodrum J F
Brain and Development Research Center, University of North Carolina, Chapel Hill 27599.
J Neurochem. 1991 Jun;56(6):2082-6. doi: 10.1111/j.1471-4159.1991.tb03469.x.
Apolipoprotein E is synthesized and secreted by rat sciatic nerve consequent to several types of injury. It has been proposed that endoneurial apolipoprotein E, in analogy to its role in systemic cholesterol transport, is involved in the salvage and reutilization of myelin cholesterol during degeneration and regeneration. To test this hypothesis, nerve lipids were prelabeled via intraneural injection of [3H]acetate. Four weeks later the nerves were crushed. From 1 to 12 weeks later, crushed nerves were examined for extracellular lipoprotein-bound cholesterol label. By 2 weeks after injury, 10% of the endoneurial lipid label was in a soluble form that was releasable into incubation medium. This released fraction was enriched in labeled cholesterol, and its labeled lipid composition was constant, in contrast to the changing distribution of label in the nerve with time after injury. On a KBr gradient, the released lipid label cofractionated with the released apolipoprotein E at densities similar to that of lipoproteins. These data indicate that at least some myelin cholesterol in injured nerve becomes associated with apolipoprotein E-containing lipoproteins and thus is available for reutilization via the hypothesized model.
载脂蛋白E由大鼠坐骨神经在几种损伤后合成并分泌。有人提出，神经内膜载脂蛋白E与其在全身胆固醇转运中的作用类似，在变性和再生过程中参与髓鞘胆固醇的挽救和再利用。为了验证这一假设，通过神经内注射[3H]醋酸盐对神经脂质进行预标记。四周后对神经进行挤压。在损伤后1至12周，检查挤压后的神经细胞外脂蛋白结合胆固醇标记。损伤后2周，10%的神经内膜脂质标记呈可溶形式，可释放到培养液中。与损伤后神经中标记随时间变化的分布情况相反，这个释放部分富含标记胆固醇，其标记脂质组成恒定。在KBr梯度上，释放的脂质标记与释放的载脂蛋白E在类似于脂蛋白的密度下共分离。这些数据表明，损伤神经中的至少一些髓鞘胆固醇与含载脂蛋白E的脂蛋白结合，因此可通过假设模型进行再利用。
