Interleukin 1 receptor antagonist (IL-1Ra) is an acute-phase protein
Interleukin 1 receptor antagonist (IL-1Ra) is an acute-phase protein
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DOI：
10.1172/jci119488
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发表时间：
1997-06-15
影响因子：
15.9
通讯作者：
Arend, WP
中科院分区：
文献类型：
--
作者：
Gabay, C;Smith, MF;Arend, WP
白介素1受体拮抗剂(IL-1ra)在各种感染性、免疫性或创伤性疾病患者的血液中水平升高。为了验证IL-1ra是否是由具有类似急性时相蛋白的特征的肝细胞产生的，从肝活检组织中分离的人原代肝细胞和HepG2肝癌细胞被IL-1β、IL-6和肿瘤坏死因子α刺激。IL-1ra存在于两种细胞的培养上清液中，IL-1β和IL-1β与IL-6的结合显著促进了IL-1ra的产生。术语IL-1ra指的是由同一基因编码的两种不同的蛋白质，但由两个不同的第一外显子交替剪接而产生。一个亚型分泌(17-kD sIL-1Ra)，另一个亚型保留在细胞质中(18-kD icIL-1ra)。经Western印迹分析，人肝癌细胞(HepG2)上清液中仅含有sIL-1Ra，而裂解物中含有一种新的较小分子质量的16kD亚型。逆转录聚合酶链式反应和核糖核酸酶保护实验表明，仅有sIL-1Ra的mRNA表达，证实了IL-1β和IL-6的诱导作用。使用包含sIL-1ra或icIL-1ra的启动子与荧光素酶报告基因偶联的构建体进行转染研究。在IL-1β和/或IL-6刺激的HepG2细胞中，sIL-1ra启动子是活性的，而icIL-1ra启动子是无效的。与野生型启动子相比，sIL-1Ra启动子近端转录因子NF-kappa B和/或C/EBP结合位点的突变导致对IL-1β和IL-6的反应显著降低。电迁移凝胶位移分析证实在sIL-1Ra启动子内存在核因子-KB和C/EBP结合位点，并表明经IL-1β和IL-6处理的HepG2细胞核蛋白的结合活性显著增加。综上所述，sIL-1ra，而不是icIL-1ra，是由肝细胞产生的，并且作为急性期蛋白受到促炎细胞因子的调节。此外，在炎症状态下肝细胞充分表达IL-1ra的过程中，核因子-kappaB和C/EBP家族成员可能发挥重要作用。
Interleukin 1 receptor antagonist (IL-1Ra) levels are elevated in the blood of patients with a variety of infectious, immune, or traumatic conditions. To examine whether IL-1Ra is produced by liver cells with characteristics resembling an acute-phase protein, human primary hepatocytes isolated from liver biopsies and HepG2 hepatoma cells were stimulated with IL-1 beta, IL-6, and TNF alpha. IL-1Ra was present in the supernatants of both cells, with production significantly enhanced by IL-1 beta, and by the combination of IL-1 beta and IL-6. The term IL-1Ra refers to two different proteins encoded by the same gene, but generated by alternative splicing of two different first exons. One isoform is secreted (17-kD sIL-1Ra), and the other isoform remains in the cytoplasm (18-kD icIL-1Ra). By Western blot analysis, the supernatants of human hepatoma (HepG2) cells contained only sIL-1Ra, whereas the lysates contained a novel smaller molecular mass isoform of 16 kD. RT-PCR and ribonuclease protection assay with RNA from HepG2 cells showed that only sIL-1Ra mRNA was expressed, and confirmed the inducing effect of IL-1 beta and IL-6. Transfection studies were performed using constructs containing the promoters of either sIL-1Ra or icIL-1Ra coupled to the luciferase reporter gene. The sIL-1Ra promoter was active in HepG2 cells stimulated by IL-1 beta and/or IL-6, whereas the icIL-1Ra promoter was inactive. Mutation of binding sites for transcription factors NF-kappa B and/or C/EBP within the proximal sIL-1Ra promoter led to significant decreases in response to IL-1 beta and IL-6 in comparison to the wild-type promoter. Electromobility gel shift assays confirmed the presence of NF-KB and C/EBP binding sites within the sIL-1Ra promoter, and indicated a significant increase in the binding activities of nuclear proteins from HepG2 cells treated with IL-1 beta and IL-6. In summary, sIL-1Ra, but not icIL-1Ra, is produced by hepatocytes, and is regulated by proinflammatory cytokines as an acute-phase protein. In addition, NF-kappa B and C/EBP family members are likely to play important roles in the full expression of IL-1Ra by hepatocytes during inflammatory conditions.