Kirsch Jeffrey D, Yi Ae-Kyung, Spitz Douglas R, Krieg Arthur M
Department of Internal Medicine, University of Iowa, Iowa City 52242, USA.
Antisense Nucleic Acid Drug Dev. 2002 Oct;12(5):327-40. doi: 10.1089/108729002761381302.
Innate immune cells recognize pathogens by detecting molecular patterns that are distinct from those of the host. One such pattern is unmethylated CpG dinucleotides, which are common in bacterial DNA but not in vertebrate genomes. Macrophages respond to such CpG motifs in bacterial DNA or synthetic oligodeoxynucleotides (ODN) by inducing NF-kappaB and secreting proinflammatory cytokines, such as interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha), but the mechanisms regulating this have been unclear. CpG ODN-stimulated cells produce reactive oxygen species (ROS) and have a decreased ratio of intracellular glutathione/glutathione disulfide (GSH/GSSG), indicating a shift to a more oxidized intracellular redox state. To determine whether this may play a role in mediating the CpG-induced macrophage activation, the GSH/GSSG redox state was manipulated in the murine macrophagelike cell line RAW264.7. Treatment of cells with BCNU to inhibit glutathione reductase (GR) enhanced the CpG-induced intracellular oxidation and decreased the GSH/GSSG, with increased activation of NF-kappaB and a doubling in the CpG-induced production of IL-6 and TNF-alpha. Experimental manipulation of the intracellular GSSG concentration during inhibition of cellular prooxidant production demonstrated that increased intracellular GSSG is a primary signal that is directly or indirectly required for CpG-induced NF-kappaB activation but is not in itself sufficient to trigger this in the absence of CpG ODN. These data suggest the existence of a second CpG-induced intracellular signal, independent of GSSG, mediating the activation of innate immunity by bacterial DNA.
天然免疫细胞通过检测与宿主不同的分子模式来识别病原体。其中一种模式是未甲基化的CpG二核苷酸，其在细菌DNA中常见，但在脊椎动物基因组中不存在。巨噬细胞通过诱导核因子κB（NF-κB）并分泌促炎细胞因子，如白细胞介素-6（IL-6）和肿瘤坏死因子-α（TNF-α），对细菌DNA或合成寡脱氧核苷酸（ODN）中的此类CpG基序作出反应，但调节这一过程的机制尚不清楚。CpG ODN刺激的细胞产生活性氧（ROS），细胞内谷胱甘肽/谷胱甘肽二硫化物（GSH/GSSG）的比例降低，表明细胞内氧化还原状态向更氧化的方向转变。为了确定这是否可能在介导CpG诱导的巨噬细胞活化中发挥作用，在小鼠巨噬细胞样细胞系RAW264.7中对GSH/GSSG氧化还原状态进行了调控。用卡莫司汀（BCNU）处理细胞以抑制谷胱甘肽还原酶（GR），增强了CpG诱导的细胞内氧化并降低了GSH/GSSG，同时NF-κB的活化增加，且CpG诱导的IL-6和TNF-α的产生增加了一倍。在抑制细胞促氧化剂产生期间对细胞内GSSG浓度进行实验性调控表明，细胞内GSSG增加是CpG诱导的NF-κB活化直接或间接需要的主要信号，但在没有CpG ODN的情况下，其本身不足以触发这一过程。这些数据表明存在第二种CpG诱导的细胞内信号，独立于GSSG，介导细菌DNA对天然免疫的激活。
