PLATELET-ACTIVATING-FACTOR (PAF) STIMULATES THE PRODUCTION OF PAF ACETYLHYDROLASE BY THE HUMAN HEPATOMA-CELL LINE, HEPG2
PLATELET-ACTIVATING-FACTOR (PAF) STIMULATES THE PRODUCTION OF PAF ACETYLHYDROLASE BY THE HUMAN HEPATOMA-CELL LINE, HEPG2
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DOI：
10.1172/jci115020
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发表时间：
1991-02-01
影响因子：
15.9
通讯作者：
TAKAMATSU, M
中科院分区：
文献类型：
--
作者：
SATOH, K;IMAIZUMI, T;TAKAMATSU, M
人肝癌细胞系HepG 2通过水解sn-2乙酰基分泌降解血小板活化因子（PAF）的活性。这种活性是Ca++独立的，抑制二异丙基氟磷酸盐，但不是由p-溴苯甲酰甲基溴，和抗胰蛋白酶或链霉蛋白酶治疗。通过凝胶过滤分离HepG 2-条件培养基揭示了活性与脂蛋白相关。PAF乙酰水解酶的抗血清免疫沉淀这种活性。它不被抗卵磷脂：胆固醇酰基转移酶（LCAT）的抗体识别，LCAT也由HepG 2细胞分泌。因此，排除LCAT的磷脂酶A2活性作为观察到的活性来源。PAF能刺激HepG 2细胞分泌PAF降解活性，而lyso-PAF无活性。用5 ng/ml PAF观察到最大刺激，其诱导5倍增加。5 ng/ml PAF可促进[S-35]蛋氨酸标记的PAF乙酰水解酶的分泌，放线菌酮可抑制PAF刺激的和基础的PAF乙酰水解酶分泌，说明HepG 2细胞产生PAF乙酰水解酶。肝脏可能是血浆PAF乙酰水解酶的主要来源，PAF可诱导肝脏产生其失活酶。
The human hepatoma cell line, HepG2, secreted an activity that degrades platelet-activating factor (PAF) by the hydrolysis of the sn-2 acetyl group. This activity was Ca++ independent, inhibited by diisopropylfluorophosphate but not by p-bromophenacyl bromide, and resistant to treatment with trypsin or pronase. Separation of HepG2-conditioned medium by gel filtration disclosed that the activity was associated with lipoproteins. An antiserum against PAF acetylhydrolase immunoprecipitated this activity. It was not recognized by an antibody against lecithin:cholesterol acyltransferase (LCAT), which also is secreted by HepG2 cells. Therefore the phospholipase A2 activity of LCAT was excluded as a source of the observed activity. PAF added to the culture medium stimulated the secretion of the PAF-degrading activity by HepG2 cells, while lyso-PAF was inactive. Maximal stimulation was observed with 5 ng/ml PAF, which induced a fivefold increase. The presence of 5 ng/ml PAF enhanced the secretion of [S-35]methionine-labeled PAF acetylhydrolase and cycloheximide inhibited both the basal and PAF-stimulated secretion of the labeled enzyme.We conclude that HepG2 cells produce PAF acetylhydrolase. The liver may be a major source of plasma PAF acetylhydrolase, and PAF may induce the production of its inactivating enzyme by the liver.