REGULATION OF GENE EXPRESSION BY INTERLEUKIN10 IN ENDOTOXIN-STIMULATED HUMAN MONO

细菌内毒素、脂多糖（LPS）刺激人单核细胞可诱导多种细胞因子的表达，包括肿瘤坏死因子（TNF）、白细胞介素-1 （IL-1）、IL-6和IL-10。相对于TNF、IL-1和IL-6， IL-10的表达延迟。此外，IL-10反馈抑制TNF、IL-1和IL-6的表达，从而为控制单核细胞中促炎细胞因子的产生提供了有效的自分泌机制。在这个项目中，我们正在研究IL-10下调内毒素刺激单核细胞中TNF和IL-1等细胞因子产生的机制。我们还评估了IL-10对单核细胞中由ifn - γ (IFN-g)和IL-4等细胞因子激活的信号转导事件的影响。我们发现IL-10抑制IL-4和ifn - γ诱导的激活和基因表达（Dickensheets & Donnelly (1997) J. Immunol. 159:6226）。我们还确定，IL-10抑制il -4诱导基因表达的能力是酪氨酸磷酸化减少和il -4诱导转录因子STAT6核易位的结果（Dickensheets & Donnelly (1999) J. Leukoc）。生物65:307)。我们现在正在研究一个新的JAK/STAT抑制基因家族（SOCS基因）在介导这些il -10诱导的抑制效应中的作用。为了进一步确定IL-10对单核细胞功能活性的作用，我们还检查了这种细胞因子对某些可溶性细胞因子受体的合成和释放的影响，特别是i型和ii型IL-1受体（IL-1RI和IL-1RII）以及1型和2型TNF受体。TNF- r在LPS刺激后从单核细胞脱落，并可通过与膜相关的TNF- r竞争可用的TNF而发挥TNF拮抗剂的作用。我们发现IFN-g下调脂多糖刺激单核细胞的膜TNF-R2和可溶性TNF-R2 （sTNF-R2）的表达（Dickensheets et al. (1997) Blood 90:4162）。在ifn -g处理的单核细胞培养中，sTNF-R2产生的减少与TNF-R2 mRNA水平的下降直接相关，与TNF-a mRNA水平的下降成反比。相反，IL-10上调sTNF-R2的产生，并显著抑制TNF-a的产生。IL-10还能拮抗IFN-g抑制sTNF-R2的产生和增强TNF-a的产生的能力。这些发现表明，在单核细胞中，IL-10协同下调TNF-a（一种TNF-R激动剂）的产生，并上调sTNF-R2（一种TNF-R拮抗剂）的产生。重组人IL-10目前正在测试作为治疗某些炎症性疾病的潜在治疗剂，包括类风湿关节炎和克罗恩病。我们的研究结果将增加我们对IL-10生物作用的认识，从而提高该机构规范该生物制剂临床使用的能力。

Stimulation of human monocytes with bacterial endotoxin, lipopolysaccharide (LPS), induces expression of multiple cytokines, including tumor necrosis factor (TNF), interleukin-1 (IL-1), IL-6 and IL-10. IL-10 expression is delayed relative to that of TNF, IL-1 and IL-6. Furthermore, IL-10 feedback inhibits expression of TNF, IL-1 and IL-6, thus providing an efficient autocrine mechanism for controlling proinflammatory cytokine production in monocytes. In this project, we are examining the mechanism by which IL-10 down-regulates production of cytokines such as TNF and IL-1 in endotoxin-stimulated monocytes. We are also evaluating the effects of IL-10 on signal transduction events that are activated by cytokines such as IFN-gamma (IFN-g) and IL-4 in monocytes. We have found that IL-10 inhibits activation and gene expression induced by IL-4 and IFN-gamma (Dickensheets & Donnelly (1997) J. Immunol. 159:6226). We have also determined that the ability of IL-10 to inhibit IL-4-inducible gene expression is a consequence of decreased tyrosine phosphorylation and nuclear translocation of the IL-4-inducible transcription factor, STAT6 (Dickensheets & Donnelly (1999) J. Leukoc. Biol. 65:307). We are now examining the role of a novel family of JAK/STAT inhibitory genes (the SOCS genes) in mediating these IL-10-inducible inhibitory effects. To further define the actions of IL-10 on monocyte functional activities, we also examined the effects of this cytokine on synthesis and release of certain soluble cytokine receptors, particularly the type-I and type-II IL-1 receptors (IL-1RI and IL-1RII) and the type-1 and type-2 TNF receptors. TNF-Rs are shed from monocytes after stimulation by LPS, and can function as TNF antagonists by competing with membrane-associated TNF-R for available TNF. We have found that IFN-g down-regulates expression of both membrane TNF-R2 and soluble TNF-R2 (sTNF-R2) by LPS-stimulated monocytes (Dickensheets et al. (1997) Blood 90:4162). The decreased production of sTNF-R2 in cultures of IFN-g-treated monocytes correlated directly with decreased levels of TNF-R2 mRNA and inversely with the levels of TNF-a mRNA. In contrast, IL-10 up-regulated production of sTNF-R2 and markedly inhibited production of TNF-a. IL-10 also antagonized the ability of IFN-g to suppress production of sTNF-R2 and to potentiate production of TNF-a. These findings demonstrate that IL-10 coordinately down-regulates production of TNF-a (a TNF-R agonist), and up-regulates production of sTNF-R2 (a TNF-R antagonist) in monocytes. Recombinant human IL-10 is currently being tested as a potential therapeutic agent for the treatment of certain inflammatory diseases, including rheumatoid arthritis and Crohn's disease. The results of our studies will increase our knowledge of the biological actions of IL-10, and thereby improve the agency's ability to regulate the clinical use of this biologic agent.