CYTOKINES, ENDOTOXIN, AND GLUCOCORTICOIDS REGULATE THE EXPRESSION OF INDUCIBLE NITRIC-OXIDE SYNTHASE IN HEPATOCYTES
CYTOKINES, ENDOTOXIN, AND GLUCOCORTICOIDS REGULATE THE EXPRESSION OF INDUCIBLE NITRIC-OXIDE SYNTHASE IN HEPATOCYTES
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DOI：
10.1073/pnas.90.2.522
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发表时间：
1993-01-15
影响因子：
11.1
通讯作者：
BILLIAR, TR
中科院分区：
文献类型：
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作者：
GELLER, DA;NUSSLER, AK;BILLIAR, TR
一氧化氮（NO.）是一种短寿命介质，可以在多种细胞类型中被诱导，并在靶细胞中产生许多生理和代谢变化。诱导的或高输出的NO。合成酶（NOS）途径首次在脂多糖（LPS）和干扰素γ (ifn - γ)激活的巨噬细胞中被表征。肝细胞在暴露于内毒素（LPS）、肿瘤坏死因子（TNF）、白细胞介素1 （IL-1）和ifn - γ的联合作用下也表达可诱导的NOS。在本研究中，为了确定哪些细胞因子（如果有的话）会诱导肝细胞NOS的基因表达，我们在体外用各种内毒素和细胞因子组合刺激大鼠肝细胞NOS mRNA的水平，通过Northern blot分析。我们发现肝细胞NOS的mRNA是一个几乎等于4.5千碱基的单带，通过TNF， IL-1， ifn - γ和LPS的组合，最大限度地上调（几乎等于70倍）。NOS mRNA丰度在刺激后6-8小时达到峰值，24小时时下降25%。体外未受刺激的肝细胞在长时间放射自显像暴露后仅显示微量mRNA带。作为单一药物，TNF和IL-1是肝细胞NOS mRNA最有效的诱导剂。两种或三种刺激的组合显示TNF， IL-1和ifn - γ之间有很强的协同作用。mRNA水平升高与培养上清液中氮氧化物释放和cGMP水平升高相关。地塞米松和环己亚胺以剂量依赖性方式抑制肝细胞NOS mRNA的诱导。添加N(G)-单甲基- l-精氨酸对mRNA水平无影响，但能有效阻断no。形成。在体内小棒状杆菌引起的慢性肝脏炎症大鼠肝细胞中也检测到诱导型肝细胞NOS mRNA的表达。这些数据表明，诱导型NOS在体外和体内均能在大鼠肝细胞中发挥作用，并且该途径受到复杂的控制。内毒素和炎性细胞因子协同上调肝细胞NOS基因表达，而糖皮质激素则下调mRNA表达。
Nitric oxide (NO.) is a short-lived mediator which can be induced in a variety of cell types and produces many physiologic and metabolic changes in target cells. The inducible or high-output NO. synthase (NOS) pathway was first characterized in macrophages activated by lipopolysaccharide (LPS) and interferon gamma (IFN-gamma). Hepatocytes also express an inducible NOS following exposure to the combination of endotoxin (LPS) and tumor necrosis factor (TNF), interleukin 1 (IL-1), and IFN-gamma. In this study, to identify which of these cytokines, if any, was acting to induce the gene expression for hepatocyte NOS, we measured the levels of rat hepatocyte NOS mRNA by Northern blot analysis after stimulation by various combinations of endotoxin and cytokines in vitro. We found the mRNA for hepatocyte NOS to be a single band at almost-equal-to 4.5 kilobases which was maximally up-regulated (almost-equal-to 70-fold) by the combination of TNF, IL-1, IFN-gamma, and LPS. Abundance of NOS mRNA peaked 6-8 hr after stimulation and then declined by 25% at 24 hr. Unstimulated hepatocytes in vitro showed only a trace mRNA band after prolonged autoradiographic exposure. As single agents, TNF and IL-1 were the most effective inducers of hepatocyte NOS mRNA. Combinations of two or three stimuli revealed strong synergy between TNF, IL-1, and IFN-gamma. The increased mRNA levels correlated with elevated nitrogen oxide release and cGMP levels in the culture supernatants. Dexamethasone and cycloheximide inhibited induction of mRNA for hepatocyte NOS in a dose-dependent fashion. The addition of N(G)-monomethyl-L-arginine had no effect on mRNA levels but effectively blocked NO. formation. The inducible hepatocyte NOS mRNA was also detected in rat hepatocytes following chronic hepatic inflammation triggered by Corynebacterium parvum injection in vivo. These data demonstrate that the inducible NOS is functional in rat hepatocytes both in vitro and in vivo and that this pathway is under complex control. Endotoxin and inflammatory cytokines act synergistically to up-regulate gene expression for hepatocyte NOS, whereas glucocorticoids down-regulate the mRNA.