Progression of atherosclerotic lesions induced by excess production of lysophosphatidic acid, a growth factor in serum

高胆固醇饲粮饲喂10 ~ 12周的家兔血清溶血磷脂酰胆碱（LPC）水平比正常家兔高5 ~ 6倍。高胆固醇血症大鼠血清（24h, 37℃）溶血磷脂酸（LPA）积累量随胆固醇负荷时间的延长而增加。有趣的是，在高胆固醇血症家兔的培养血清中，LPA的主要分子种是亚油酰(18:2)-LPA，尽管在动脉粥样硬化动物模型中，LPC的5个主要分子种的水平增加了18:2-LPA的产生，主要是由于18:2-LPC的增加，而不是溶血磷脂酶D本身。此外，LPA还能激活THP-1细胞（一种单核细胞系），刺激其附着在脐静脉内皮细胞上。这些结果表明，血循环中LPA的产生增加参与了动脉粥样硬化病变的进展。我们设计了一种简便的溶血磷脂酶D活性测定方法，并利用该方法从约950毫升的人血浆中纯化了溶血磷脂酶D。用胰蛋白酶对纯化的溶血磷脂酶D的多肽进行液相色谱/质谱/质谱分析，鉴定其为内核内酯磷酸二酯酶autotaxin。这一发现提示循环中的溶血磷脂酶可能通过水解溶血磷脂和核苷酸发挥多种功能。

The leves of lysophosphatidylcholine (LPC) in serum of rabbits fed a high-cholesterol diet for 10-12 weeks were 5-6 times higher than those of normal rabbits. The amounts of lysophosphatidic acids (LPA) accumulated in incubated serum (24h, 37℃) of the hypercholesterolemic rabbis increased with the increase in the period for cholesterol-loading. Interestingly, the major molecular species of LPA in the incubated serum of the hypercholesterolemic rabbits was linoleoyl (18:2) -LPA, althogh the levels of five major molecular spesies of LPC incceased production of 18:2-LPA was mainly due to the increase in 18:2-LPC, but not lysophospholipase D itself, in the animal model of atherosclerosis. In addition, LPA was found to activate THP-1 cells, a monocytic cell line, leading to their stimulated attachement to umbilical vein endothelial cells. These results indicate that increased production of LPA in blood circutation of the hypedipidemic rabbits is involved in the progression of atherosclerotic lesions. We deviced a convenient assay method for lysophospholipase D activity, and purifled lysophospholipase D from about 950 mi of human plasma using this method. LC/MS/MS of the peptides of the purified lysophospholipase D with trypsin resulted in its identification as autotaxin, a endo-nucleolide phosphodiesterase. This finding suggests that lysophospholipase Din the circulation may exert diverse functions by hydrolyzing both lysophospholipids and nucleotides.