Amplification mechanisms of inflammation:: Paracrine stimulation of arachidonic acid mobilization by secreted phospholipase A2 is regulated by cytosolic phospholipase A2-derived hydroperoxyeicosatetraenoic acid
Amplification mechanisms of inflammation:: Paracrine stimulation of arachidonic acid mobilization by secreted phospholipase A2 is regulated by cytosolic phospholipase A2-derived hydroperoxyeicosatetraenoic acid
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DOI：
10.4049/jimmunol.171.2.989
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发表时间：
2003-07-15
影响因子：
4.4
通讯作者：
Balsinde, J
中科院分区：
文献类型：
--
作者：
Balboa, MA;Pérez, R;Balsinde, J
在巨噬细胞和其他主要免疫炎症细胞中，两种磷脂酶A（2）（PLA（2））协同作用以动员花生四烯酸（AA）用于立即PG合成，即IV型胞质磷脂酶A（2）（cPLA（2））和分泌型磷脂酶A（2）（sPLA（2））。在这项研究中，两个PLA（2）之间的串扰在旁分泌信号的分子机制进行了研究。U937巨噬细胞样细胞对ConA的反应是以cPLA（2）依赖的方式释放AA，向活化的细胞中加入外源性V族sPLA增加了AA的释放。如果用cPLA（2）抑制剂预处理细胞，这种sPLA（2）效应被消除，但通过加入外源性游离AA恢复。环氧合酶和5-脂氧合酶抑制剂对sPLA的反应没有影响（2）。在吡咯苯酮处理的细胞中进行的消除cPLA（2）活性的重建实验表明，12-和15-氢过氧二十碳四烯酸（HPETE）能够将sPLA（2）反应恢复到显示正常cPLA（2）活性的细胞中的水平。此外，12-和15-HPETE能够增强sPLA（2）的活性在体外，使用自然膜测定。12-或15-羟基二十碳四烯酸都无法模拟这两种作用，这表明HPETE的过氧化氢基团对其生物活性负责。总的来说，这些结果确立了12/15-HPETE在巨噬细胞旁分泌刺激期间作为sPLA（2）介导的磷脂分解的内源性激活剂的作用，并确定了将sPLA（2）与cPLA（2）连接起来以实现完全AA动员反应的机制。
In macrophages and other major immunoinflammatory cells, two phospholipase A(2) (PLA(2)) enzymes act in concert to mobilize arachidonic acid (AA) for immediate PG synthesis, namely group IV cytosolic phospholipase A(2) (cPLA(2)) and a secreted phospholipase A(2) (sPLA(2)). In this study, the molecular mechanism underlying cross-talk between the two PLA(2)s during paracrine signaling has been investigated. U937 macrophage-like cells respond to Con A by releasing AA in a cPLA(2)-dependent manner, and addition of exogenous group V sPLA, to the activated cells increases the release. This sPLA(2) effect is abolished if the cells are pretreated with cPLA(2) inhibitors, but is restored by adding exogenous free AA. Inhibitors of cyclooxygenase and 5-lipoxygenase have no effect on the response to sPLA(2). In contrast, ebselen strongly blocks it. Reconstitution experiments conducted in pyrrophenone-treated cells to abolish cPLA(2) activity reveal that 12- and 15-hydroperoxyeicosatetraenoic acid (HPETE) are able to restore the sPLA(2) response to levels found in cells displaying normal cPLA(2) activity. Moreover, 12- and 15-HPETE are able to enhance sPLA(2) activity in vitro, using a natural membrane assay. Neither of these effects is mimicked by 12- or 15-hydroxyeicosatetraenoic acid, indicating that the hydroperoxy group of HPETE is responsible for its biological activity. Collectively, these results establish a role for 12/15-HPETE as an endogenous activator of sPLA(2)-mediated phospholipolysis during paracrine stimulation of macrophages and identify the mechanism that connects sPLA(2) with cPLA(2) for a full AA mobilization response.