Involvement of calcium-independent phospholipase A2 in hydrogen peroxide-induced accumulation of free fatty acids in human U937 cells
Involvement of calcium-independent phospholipase A2 in hydrogen peroxide-induced accumulation of free fatty acids in human U937 cells
复制标题
DOI：
10.1074/jbc.m206155200
复制
发表时间：
2002-10-25
影响因子：
4.8
通讯作者：
Balsinde, J
中科院分区：
文献类型：
--
作者：
Balboa, MA;Balsinde, J
先前的研究已经证明，U937细胞能够动员花生四烯酸（AA）和合成阿糖胞苷响应受体定向和可溶性刺激的机制，涉及激活IV型胞质磷脂酶A（2）α。在本文中，我们表明，这些细胞也动员AA响应氧化应激诱导的H2 O2通过一种机制，似乎不是由胞质磷脂酶A（2）α，但钙非依赖性VI族磷脂酶A（2）（iPLA，）介导的。这得到了以下证据的支持：（i）该反应基本上不依赖于钙，（ii）它被溴烯醇内酯抑制，（iii）它被iPLA（2）反义寡核苷酸抑制。在各种条件下进行的酶试验表明，iPLA（2）的比活性不会因H2 O2暴露而发生变化，这与终止于iPLA（2）的特定信号级联的激活相反。相反，氧化剂以酶对其底物的敏感性/可接近性增加的方式扰乱膜稳态，这导致脂肪酸释放改变。为了支持这一观点，不仅AA，而且其他脂肪酸，被发现在H2 O2处理的细胞中以iPLA（2）依赖的方式释放。总的来说，这些研究强调了iPLA（2）在调节稳态脂肪酸脱酰反应中的重要性，并记录了在氧化应激期间增加游离脂肪酸水平的病理生理条件下的潜在重要途径。
Previous studies have demonstrated that U937 cells are able to mobilize arachidonic acid (AA) and synthesize prostaglandins in response to receptor-directed and soluble stimuli by a mechanism that involves the activation of Group IV cytosolic phospholipase A(2)alpha. In this paper we show that these cells also mobilize AA in response to an oxidative stress induced by H2O2 through a mechanism that appears not to be mediated by cytosolic phospholipase A(2)alpha but by the calcium-independent Group VI phospholipase A(2) (iPLA,). This is supported by the following lines of evidence: (i) the response is essentially calcium-independent, (ii) it is inhibited by bromoenol lactone, and (iii) it is inhibited by an iPLA(2) antisense oligonucleotide. Enzyme assays conducted under a variety of conditions reveal that the specific activity of the iPLA(2) does not change as a result of H2O2 exposure, which argues against the activation of a specific signaling cascade ending in the iPLA(2). Rather, the oxidant acts to perturb membrane homeostasis in a way that the enzyme susceptibility/accessibility to its substrate increases, and this results in altered fatty acid release. In support of this view, not only AA, but also other fatty acids, were found to be liberated in an iPLA(2)-dependent manner in the H2O2-treated cells. Collectively, these studies underscore the importance of the iPLA(2) in modulating homeostatic fatty acid deacylation reactions and document a potentially important route under pathophysiological conditions for increasing free fatty acid levels during oxidative stress.