INACTIVATION OF LYSOSOMAL PROTEASES BY OXIDIZED LOW-DENSITY-LIPOPROTEIN IS PARTIALLY RESPONSIBLE FOR ITS POOR DEGRADATION BY MOUSE PERITONEAL-MACROPHAGES
INACTIVATION OF LYSOSOMAL PROTEASES BY OXIDIZED LOW-DENSITY-LIPOPROTEIN IS PARTIALLY RESPONSIBLE FOR ITS POOR DEGRADATION BY MOUSE PERITONEAL-MACROPHAGES
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DOI：
10.1172/jci117490
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发表时间：
1994-10-01
影响因子：
15.9
通讯作者：
HOFF, HF
中科院分区：
文献类型：
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作者：
HOPPE, G;ONEIL, J;HOFF, HF
巨噬细胞溶酶对氧化型低密度脂蛋白(OX-LDL)中载脂蛋白B(ApoB)的处理缺陷已被证实，并归因于ApoB的修饰。我们研究了OX-LDL对溶酶体蛋白酶的直接灭活是否也是导致这种缺陷降解的原因。当小鼠腹膜巨噬细胞(MPM)在37℃下与氧化低密度脂蛋白、低密度脂蛋白或涡旋聚集低密度脂蛋白预先孵育21h时，只有氧化低密度脂蛋白抑制上述脂蛋白的I-125标记形式的随后降解。预先孵育的氧化低密度脂蛋白对标记脂蛋白的摄取没有明显影响，表明这种抑制作用是在溶酶体降解的水平上进行的。在pH值为4.0的MPM中，与氧化低密度脂蛋白预先孵育的细胞相比，氧化低密度脂蛋白预先孵育的细胞提取液的硫醇蛋白水解酶活性比单独用低密度脂蛋白预育的细胞低。未经处理的MPM或组织蛋白酶B和D的混合物的提取物在pH值为4.5时，与氧化型低密度脂蛋白孵育后，与与低密度脂蛋白孵育相比，其降解I-125-低密度脂蛋白的能力降低，组织蛋白酶B活性降低。因此，氧化低密度脂蛋白处理的MPM中脂蛋白降解的减少可能是由于溶酶体蛋白水解酶组织蛋白酶B的直接失活。
Deficient processing of apo B in oxidized LDL (ox-LDL) by macrophage lysosomal proteases has been documented and attributed to modifications in apo B. We have investigated whether direct inactivation of lysosomal proteases by ox-LDL could also be responsible for this deficient degradation. When mouse peritoneal macrophages (MPM) were preincubated for 21 h at 37 degrees C with ox-LDL, LDL, or vortex-aggregated LDL, only ox-LDL inhibited the subsequent degradation of I-125-labeled forms of the above lipoproteins. Uptake of labeled lipoproteins was not appreciably affected by preincubation ,vith ox-LDL, suggesting that the inhibition was at the level of lysosomal degradation. Thiol protease activity of cell extracts at pH 4.0, was reduced in MPM preincubated with ox-LDL relative to cells preincubated with LDL or medium alone. Extracts from untreated MPM, or mixtures of cathepsin B and D, showed a reduced ability to degrade I-125-LDL at pH 4.5 and reduced cathepsin B activity, after incubation with ox-LDL relative to incubation with LDL. Thus, the reduced degradation of lipoproteins in MPM pretreated with ox-LDL could be due to direct inactivation of the lysosomal protease, cathepsin B.