Robson R L, Westwick J, Brown Z
Department of Pharmacology, University of Bath, Avon, England, United Kingdom.
Kidney Int. 1995 Dec;48(6):1767-77. doi: 10.1038/ki.1995.475.
We have previously proposed that activated mesangial cells (MC) have a direct role in the initiation and propagation of inflammatory events within the glomerulus via the generation of the mesangioproliferative cytokine IL-6 and the chemokines IL-8 and MCP-1. The objective of this study was to investigate the role of cAMP in the regulation of IL-6 and IL-8 gene expression and peptide production in IL-1 stimulated human MC. Agents known to elevate cAMP, including dibutyryl cAMP (db-cAMP), forskolin or isobutyl-methylxanthine (IBMX) were alone unable to induce IL-6 or IL-8 expression or production above media control levels, indicating activation of the cAMP pathway could not mimic IL-1 signaling events. In the presence of IL-1, all three agents produced a marked potentiation of IL-6 mRNA expression and dose-dependent increase in IL-6 peptide production (twofold), but had little or no effect on IL-8 mRNA expression or peptide generation. In marked contrast cholera toxin (CT) caused a dose-dependent potentiation of both IL-1-induced IL-6 (approximately fourfold) and IL-8 peptide (approximately twofold) generation. The control agent, the purified binding subunit of cholera toxin (CT-B) which is devoid of ADP-ribosylating activity also enhanced IL-6 and IL-8 (approximately twofold) peptide generation indicating cAMP-independent mechanisms may be involved in the CT up-regulation of these cytokines. Treatment of MC with the cycloxygenase inhibitor indomethacin resulted in partial inhibition (37%) of IL-6 production but had no effect on IL-8 generation. Thus our data show that cAMP can potentiate IL-1 induced IL-6 production, while having no effect on IL-8 induction, and PGE2 may operate via a positive feedback loop to up-regulate IL-1 induced IL-6. Taken together, our results demonstrate that cAMP differentially regulates IL-6 and IL-8 production in IL-1-stimulated human MC.
我们之前曾提出，活化的系膜细胞（MC）通过产生系膜增殖性细胞因子白细胞介素-6（IL-6）以及趋化因子白细胞介素-8（IL-8）和单核细胞趋化蛋白-1（MCP-1），在肾小球内炎症事件的起始和传播中起直接作用。本研究的目的是探讨环磷酸腺苷（cAMP）在白细胞介素-1刺激的人系膜细胞中对IL-6和IL-8基因表达及肽产生的调节作用。已知能升高cAMP的试剂，包括二丁酰环磷腺苷（db-cAMP）、福斯可林或异丁基甲基黄嘌呤（IBMX），单独使用时均无法诱导IL-6或IL-8的表达或产生超过培养基对照水平，这表明cAMP途径的激活无法模拟白细胞介素-1的信号传导事件。在存在白细胞介素-1的情况下，所有这三种试剂均显著增强了IL-6信使核糖核酸（mRNA）的表达，并使IL-6肽的产生呈剂量依赖性增加（两倍），但对IL-8 mRNA的表达或肽的产生几乎没有影响。与之形成鲜明对比的是，霍乱毒素（CT）导致白细胞介素-1诱导的IL-6（约四倍）和IL-8肽（约两倍）的产生呈剂量依赖性增强。对照试剂，即缺乏ADP-核糖基化活性的纯化霍乱毒素结合亚基（CT-B），也增强了IL-6和IL-8（约两倍）肽的产生，表明cAMP非依赖性机制可能参与了CT对这些细胞因子的上调作用。用环氧化酶抑制剂吲哚美辛处理系膜细胞导致IL-6产生部分受抑制（37%），但对IL-8的产生没有影响。因此，我们的数据表明，cAMP可增强白细胞介素-1诱导的IL-6产生，而对IL-8的诱导没有影响，并且前列腺素E2（PGE2）可能通过正反馈回路上调白细胞介素-1诱导的IL-6。综上所述，我们的结果表明，cAMP在白细胞介素-1刺激的人系膜细胞中对IL-6和IL-8的产生有不同的调节作用。
