Analysys of upregulated gene expression of interleukin-15 by synoviocytes in patients with rheumatoid arthritis

已知TNFα-TNF受体信号在类风湿关节炎（RA）中促进关节破坏中起关键作用。最近有报道称，一种主要由巨噬细胞产生的新发现的细胞因子IL-15 （Interleukin-15, IL-15）在RA的滑液中升高，并可介导TNFα的分泌。本研究利用新鲜分离和培养的风湿性关节炎（RA）或骨关节炎（OA）患者的滑膜细胞，研究了类风湿滑膜细胞中IL-15 mRNA表达的上调。RT-PCR分析IL-15在RA患者和部分OA患者滑膜细胞中的表达均上调。通过细胞内FACS染色还观察到IL-15在RA和OA滑膜细胞中蛋白水平的表达，表明IL-15本身的表达不是RA特异性的。当TNFα或LPS刺激时，RA和OA滑膜细胞IL-15 mRNA均表现出刺激依赖性上调。由于NF-κB和IRF-1已被证明是IL-15 mRNA调控的关键转录因子，因此我们也使用这些来自IL-15启动子的顺式作用元件进行了EMSA分析。在TNFα或LPS刺激下，诱导NF-κB dna结合活性增强，而IRF-1 dna结合活性不增强。这些结果表明，IL15不是ra特异性的tnf - α表达诱导性因子，而是通过诱导NF-κB活性相互作用的tnf - α基因表达增强剂。

TNFα-TNF receptor signaling is known to play a pivotal role in the promotion of joint destruction in Rheumatoid arthritis (RA). It has been recently reported that Interleukin-15 (IL-15) a newly discovered cytokine largely produced by macrophages, is increased in synovial fluid in RA, and can mediate secretion of TNFα. In current study, upregulated mRNA expression of IL-15 in rheumatoid synoviocytes was investigated by using freshly isolated and cultured synoviocytes from RA or osteoarthritis (OA) patients. mRNA expression analyzes using RT-PCR showed upregulated expression of IL-15 by synoviocytes, not only from RA patients but also from some OA patients. Expression of IL-15 was also observed in both RA and OA synoviocytes at protein levels by using intracellular FACS staining, indicating that IL-15 expression by itself is not specific to RA. When stimulated by TNFα or LPS, both RA and OA synoviocytes showed stimulation dependent upregulation of IL-15 mRNA. Since NF-κB and IRF-1 have been shown to be critical transcription factors in IL-15 mRNA regulation, EMSA analysis using these cis-acting elements from IL-15 promoters was also performed. Upon stimulation by either of TNFα or LPS, increased NF-κB DNA-binding activity was induced while not in IRF-1 DNA-binding. These results suggest that IL15 is not RA-specific inducer of TNFα expression, but enhancer of TNFα gene expression that mutually act through induction of NF-κB activities.