Deramaudt T B, da Silva J L, Remy P, Kappas A, Abraham N G
Department of Pharmacology, New York Medical College, Valhalla 10595, USA.
Proc Soc Exp Biol Med. 1999 Nov;222(2):185-93. doi: 10.1046/j.1525-1373.1999.d01-130.x.
Heme oxygenase-1 (HO-1) is a stress protein, and its induction has been suggested to participate in defense mechanisms against agents that promote oxidative injury such as endotoxins and heme. We have shown that the inflammatory cytokines, interleukin-6 (IL-6) and heme-induced HO-1 gene expression, were suppressed by dexamethasone (Dex) in a sustained manner. We examined the mechanism by which the anti-inflammatory agent, Dex, inhibits IL-6 and heme-induced HO-1 expression in rabbit coronary endothelial cells. Endothelial cells treated with heme (10 microM) and IL-6 (25 ng/ml), increased HO-1 mRNA 15- and 60-fold, respectively. The activity of HO was increased 3-fold after such treatment. Although Dex failed to inhibit heme-mediated HO-1 mRNA and HO activity, it was able to reverse IL-6-stimulated HO activity. Several human HO-1 promoter-drive chloramphenicol acetyltransferase (CAT) constructs were examined to analyze IL-6 and Dex-mediated modulation of the HO-1 gene in endothelial cells. CAT assays revealed that the HO-1 promoter region between -180 and -1500 might contain a Dex-mediated negative regulator. Gel mobility shift assays using nuclear extracts from IL-6-treated endothelial cells showed a binding to the synthetic 21 base pairs of the HO-1 sequence that contains the putative STAT3 sequence. STAT3-specific probe inhibited nuclear binding protein to the putative HO-1-STAT3 sequence. This suggests that IL-6 induction of human HO-1 is mediated via the JAK-STAT pathway and that Dex inhibition of gene expression is carried out by activation of a transcriptional protein in competition with the STAT3 binding site.
血红素加氧酶-1（HO-1）是一种应激蛋白，有人认为其诱导表达参与了针对诸如内毒素和血红素等促进氧化损伤因子的防御机制。我们已经表明，炎症细胞因子白细胞介素-6（IL-6）和血红素诱导的HO-1基因表达受到地塞米松（Dex）的持续抑制。我们研究了抗炎药物Dex抑制兔冠状动脉内皮细胞中IL-6和血红素诱导的HO-1表达的机制。用血红素（10微摩尔）和IL-6（25纳克/毫升）处理的内皮细胞，HO-1 mRNA分别增加了15倍和60倍。经此类处理后，HO的活性增加了3倍。虽然Dex未能抑制血红素介导的HO-1 mRNA和HO活性，但它能够逆转IL-刺激的HO活性。研究了几种人HO-1启动子驱动的氯霉素乙酰转移酶（CAT）构建体，以分析IL-6和Dex介导的内皮细胞中HO-1基因的调节。CAT分析表明，-180至-1500之间的HO-1启动子区域可能含有一个Dex介导的负调节因子。使用来自IL-6处理的内皮细胞的核提取物进行凝胶迁移率变动分析，结果显示与包含假定STAT3序列的HO-1序列的21个碱基对的合成片段有结合。STAT3特异性探针抑制核结合蛋白与假定的HO-1-STAT3序列的结合。这表明人HO-1的IL-6诱导是通过JAK-STAT途径介导的，并且Dex对基因表达的抑制是通过激活一种与STAT3结合位点竞争的转录蛋白来实现的。
