Osada-Oka Mayuko, Takahashi Minoru, Akiba Satoshi, Sato Takashi
Department of Pathological Biochemistry, Kyoto Pharmaceutical University, Kyoto, Japan.
Eur J Pharmacol. 2006 Nov 7;549(1-3):58-62. doi: 10.1016/j.ejphar.2006.08.026. Epub 2006 Aug 30.
We investigated the role of Ca2+-independent phospholipase A2 (iPLA2) as well as cytosolic phospholipase A2 (cPLA2) in hypoxia-inducible factor-1 (HIF-1)-dependent gene expression. An inhibitor of both iPLA2 and cPLA2, methyl arachidonyl fluorophosphonate (MAFP), prevented hypoxia-induced erythropoietin mRNA expression without affecting HIF-1alpha accumulation in Hep3B cells. The DNA-binding of HIF-1alpha was suppressed by MAFP as confirmed by luciferase reporter gene assays with the hypoxia response element. Translocation of HIF-1alpha to the nucleus assessed by its presence in the nuclear extracts of cells exposed to hypoxia, was diminished by MAFP. However, hypoxia-dependent gene expression was not affected in mesangial cells obtained from cPLA2alpha null mice. Furthermore, a specific iPLA2 inhibitor, bromoenol lactone, suppressed erythropoietin mRNA expression and HIF-1alpha translocation to the nucleus under hypoxic conditions. Thus, iPLA2, but not cPLA2alpha, may play an important role in regulating the transport of HIF-1alpha to the nucleus.
我们研究了钙离子非依赖性磷脂酶A2（iPLA2）以及胞质磷脂酶A2（cPLA2）在缺氧诱导因子-1（HIF-1）依赖性基因表达中的作用。iPLA2和cPLA2的抑制剂甲基花生四烯酰氟磷酸酯（MAFP）可阻止缺氧诱导的促红细胞生成素mRNA表达，而不影响Hep3B细胞中HIF-1α的积累。荧光素酶报告基因检测结合缺氧反应元件证实，MAFP可抑制HIF-1α的DNA结合。通过检测暴露于缺氧环境的细胞的核提取物中HIF-1α的存在来评估其向细胞核的转位，结果显示MAFP可使其减少。然而，cPLA2α基因敲除小鼠的系膜细胞中缺氧依赖性基因表达并未受到影响。此外，一种特异性iPLA2抑制剂溴代烯醇内酯可抑制缺氧条件下促红细胞生成素mRNA表达以及HIF-1α向细胞核的转位。因此，iPLA2而非cPLA2α可能在调节HIF-1α向细胞核的转运中起重要作用。
