Kuwata H, Nakatani Y, Murakami M, Kudo I
Department of Health Chemistry, School of Pharmaceutical Sciences, Showa University, Tokyo, Japan.
J Biol Chem. 1998 Jan 16;273(3):1733-40. doi: 10.1074/jbc.273.3.1733.
Activation of rat fibroblastic 3Y1 cells with interleukin-1 beta (IL-1 beta) and tumor necrosis factor alpha (TNF alpha) induced delayed prostaglandin (PG) E2 generation over 6-48 h, which occurred in parallel with de novo induction of type IIA secretory phospholipase A2 (sPLA2) and cyclooxygenase (COX)-2, without accompanied by changes in the constitutive expression of type IV cytosolic PLA2 (cPLA2) and COX-1. Types V and IIC sPLA2s were barely detectable in these cells. Studies using an anti-type IIA sPLA2 antibody, sPLA2 inhibitors, and a type IIA sPLA2-specific antisense oligonucleotide revealed that IL-1 beta/TNF alpha-induced delayed PGE2 generation by these cells was largely dependent on inducible type IIA sPLA2, which was functionally linked to inducible COX-2. Delayed PGE2 generation was also suppressed markedly by the cPLA2 inhibitor arachidonoyl trifluoromethyl ketone (AACOCF3), which attenuated induction of type IIA sPLA2, but not COX-2, expression. AACOCF3 inhibited the initial phase of cytokine-stimulated arachidonic acid release, and supplementing AACOCF3-treated cells with exogenous arachidonic acid partially restored type IIA sPLA2 expression. These results suggest that certain metabolites produced by the cPLA2-dependent pathway are crucial for the subsequent induction of type IIA sPLA2 expression and attendant delayed PGE2 generation. Some lipoxygenase-derived products might be involved in this event, since IL-1 beta/TNF alpha-induced type IIA sPLA2 induction and PGE2 generation were reduced markedly by lipoxygenase, but not COX, inhibitors. In contrast, Ca2+ ionophore-stimulated immediate PGE2 generation was regulated predominantly by the constitutive enzymes cPLA2 and COX-1, even when type IIA sPLA2 and COX-2 were maximally induced after IL-1 beta/TNF alpha treatment, revealing functional segregation of the constitutive and inducible PG biosynthetic enzymes.
用白细胞介素-1β（IL-1β）和肿瘤坏死因子α（TNFα）激活大鼠成纤维细胞3Y1，会在6 - 48小时内诱导前列腺素（PG）E2延迟生成，这与IIA型分泌型磷脂酶A2（sPLA2）和环氧化酶（COX）-2的从头诱导同时发生，而IV型胞质磷脂酶A2（cPLA2）和COX-1的组成型表达没有变化。在这些细胞中几乎检测不到V型和IIC型sPLA2。使用抗IIA型sPLA2抗体、sPLA2抑制剂和IIA型sPLA2特异性反义寡核苷酸的研究表明，IL-1β/TNFα诱导这些细胞延迟生成PGE2在很大程度上依赖于可诱导的IIA型sPLA2，它在功能上与可诱导的COX-2相关联。延迟的PGE2生成也被cPLA2抑制剂花生四烯酰三氟甲基酮（AACOCF3）显著抑制，该抑制剂减弱了IIA型sPLA2的诱导，但不影响COX-2的表达。AACOCF3抑制了细胞因子刺激的花生四烯酸释放的初始阶段，用外源性花生四烯酸补充经AACOCF3处理的细胞可部分恢复IIA型sPLA2的表达。这些结果表明，cPLA2依赖性途径产生的某些代谢产物对于随后IIA型sPLA2表达的诱导和随之而来的PGE2延迟生成至关重要。一些脂氧合酶衍生的产物可能参与了这一事件，因为脂氧合酶抑制剂可显著降低IL-1β/TNFα诱导的IIA型sPLA2诱导和PGE2生成，而COX抑制剂则无此作用。相反，即使在IL-1β/TNFα处理后IIA型sPLA2和COX-2被最大程度诱导，钙离子载体刺激的即时PGE2生成仍主要由组成型酶cPLA2和COX-1调节，这揭示了组成型和可诱导的PG生物合成酶的功能分离。
