Lipoxin A4:: A new class of ligand for the Ah receptor
Lipoxin A4:: A new class of ligand for the Ah receptor
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DOI：
10.1021/bi982861e
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发表时间：
1999-06-08
期刊：
影响因子：
2.9
通讯作者：
Bjeldanes, LF
中科院分区：
文献类型：
--
作者：
Schaldach, CM;Riby, J;Bjeldanes, LF
Ah受体是一种配体激活的转录因子，介导了大量环境化合物的许多生物作用。支持Ah受体在正常生理中的作用也有报道，但内源性调节配体尚未确定。我们研究了候选的内源性亲脂物质，并报道了花生四烯酸代谢物脂素A(4)结合并激活Hepa-1细胞中的Ah受体的能力。脂素A(4)在一个由dred驱动的CAT报告结构中产生了浓度依赖性的反应，在0.3 μ m处，CAT活性增加了10倍以上。凝胶迁移量转移分析表明，脂素A(4)以浓度依赖性的方式将Ah受体转化为活性的dred结合形式。Ah受体竞争结合实验结果表明，在100 nM浓度下，脂素a(4)对[H-3]TCDD的结合产生了一半最大位移（EC50）。Northern blot分析结果显示，Ah受体应答基因CYP1A1的mRNA水平瞬间升高，并在4小时达到峰值，与脂素a(4)诱导CYP1A1酶活性的动力学观察结果一致。此外，脂素A(4)被发现是CYP1A1酶的竞争性抑制剂，计算出的K-i = 1.1 μ m。这些结果表明，脂素是一类新的Ah受体配体，与传统的Ah受体配体有很大不同。
The Ah receptor is a Ligand-activated transcription factor that mediates many of the biological actions of a large class of environmental compounds. Support for a role of the Ah receptor in normal physiology also has been reported, but an endogenous regulating ligand has not been identified. We have examined candidate endogenous lipophilic substances and report here the ability of the arachidonic acid metabolite, lipoxin A(4), to bind to and activate the Ah receptor in Hepa-1 cells. Lipoxin A(4) produced a concentration-dependent response in a DRE-driven CAT reporter construct, with a greater than 10-fold increase in CAT activity at 0.3 mu M. Lipoxin A(4) transformed the Ah receptor to an active DRE-binding form in a concentration-dependent manner as indicated by gel mobility shift analysis. Results of Ah receptor competitive binding experiments indicated that at a concentration of 100 nM, lipoxin A(4) produced a half-maximum displacement(EC50) of [H-3]TCDD binding. Results of Northern blot analyses indicated a transient increase in mRNA levels of the Ah receptor-responsive gene CYP1A1, which peaked at 4 h, consistent with the kinetics observed for lipoxin A(4)-induced CYP1A1 enzyme activity. Further, lipoxin A(4) was found to be a competitive inhibitor for the CYP1A1 enzyme, with a calculated K-i = 1.1 mu M. These results establish lipoxin as a new class of Ah receptor ligand, one that differs dramatically from classical Ah receptor ligands.