Couturier C, Brouillet A, Couriaud C, Koumanov K, Béréziat G, Andréani M
Unité Propre de Recherche de l'Université Pierre et Marie Curie, Associée au CNRS, ESA7079, 7 quai St. Bernard, 75252 Paris, Cedex 5, France.
J Biol Chem. 1999 Aug 13;274(33):23085-93. doi: 10.1074/jbc.274.33.23085.
Type II-secreted phospholipase A(2) (type II-sPLA(2)) is expressed in smooth muscle cells during atherosclerosis or in response to interleukin-1beta. The present study shows that the induction of type II-sPLA(2) gene by interleukin-1beta requires activation of the NFkappaB pathway and cytosolic PLA(2)/PPARgamma pathway, which are both necessary to achieve the transcriptional process. Interleukin-1beta induced type II-sPLA(2) gene dose- and time-dependently and increased the binding of NFkappaB to a specific site of type II-sPLA(2) promoter. This effect was abolished by proteinase inhibitors that block the proteasome machinery and NFkappaB nuclear translocation. Type II-sPLA(2) induction was also obtained by free arachidonic acid and was blocked by either AACOCF(3), a specific cytosolic-PLA(2) inhibitor, PD98059, a mitogen-activated protein kinase kinase inhibitor which prevents cytosolic PLA(2) activation, or nordihydroguaiaretic acid, a lipoxygenase inhibitor, but not by the cyclooxygenase inhibitor indomethacin, suggesting a role for a lipoxygenase product. Type II-sPLA(2) induction was obtained after treatment of the cells by 15-deoxy-Delta(12,14)-dehydroprostaglandin J(2), carbaprostacyclin, and 9-hydroxyoctadecadienoic acid, which are ligands of peroxisome proliferator-activated receptor (PPAR) gamma, whereas PPARalpha ligands were ineffective. Interleukin-1beta as well as PPARgamma-ligands stimulated the activity of a reporter gene containing PPARgamma-binding sites in its promoter. Binding of both NFkappaB and PPARgamma to their promoter is required to stimulate the transcriptional process since inhibitors of each class block interleukin-1beta-induced type II-sPLA(2) gene activation. We therefore suggest that NFkappaB and PPARgamma cooperate at the enhanceosome-coactivator level to turn on transcription of the proinflammatory type II-sPLA(2) gene.
II型分泌型磷脂酶A2（II型-sPLA2）在动脉粥样硬化过程中的平滑肌细胞中表达，或在白细胞介素-1β刺激下表达。本研究表明，白细胞介素-1β诱导II型-sPLA2基因表达需要激活NFκB途径和胞质型磷脂酶A2/过氧化物酶体增殖物激活受体γ（PPARγ）途径，这两条途径对于实现转录过程都是必需的。白细胞介素-1β以剂量和时间依赖的方式诱导II型-sPLA2基因表达，并增加NFκB与II型-sPLA2启动子特定位点的结合。这种效应被阻断蛋白酶体机制和NFκB核转位的蛋白酶抑制剂所消除。游离花生四烯酸也可诱导II型-sPLA2表达，而特异性胞质型磷脂酶A2抑制剂AACOCF3、阻止胞质型磷脂酶A2激活的丝裂原活化蛋白激酶激酶抑制剂PD98059或脂氧合酶抑制剂去甲二氢愈创木酸均可阻断其表达，但环氧化酶抑制剂吲哚美辛则无此作用，提示脂氧合酶产物发挥了作用。用15-脱氧-Δ12,14-前列腺素J2、卡前列环素和9-羟基十八碳二烯酸（均为过氧化物酶体增殖物激活受体γ（PPARγ）的配体）处理细胞后可诱导II型-sPLA2表达，而过氧化物酶体增殖物激活受体α（PPARα）的配体则无此作用。白细胞介素-1β以及PPARγ配体均可刺激其启动子中含有PPARγ结合位点的报告基因的活性。由于每一类抑制剂均可阻断白细胞介素-1β诱导的II型-sPLA2基因激活，因此NFκB和PPARγ与它们的启动子结合对于刺激转录过程是必需的。因此，我们认为NFκB和PPARγ在增强体-共激活因子水平协同作用，开启促炎II型-sPLA2基因的转录。
