Interactive role of the toll-like receptor 4 and reactive oxygen species in LPS-induced microglia activation
Interactive role of the toll-like receptor 4 and reactive oxygen species in LPS-induced microglia activation
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作者：
Qin, LY;Li, GR;Block, ML
小胶质细胞被脂多糖（LPS）激活以产生神经毒性促炎因子和活性氧（ROS）。虽然已经鉴定了大量的LPS受体和相应的通路，但介导小胶质细胞对LPS反应的详细机制尚不清楚。使用缺乏功能性Toll样受体4（TLR 4）的小鼠，我们证明TLR 4和ROS协同工作以介导小胶质细胞活化，其中来自每个途径的贡献取决于LPS的浓度。用针对F4/80的抗体对神经元细胞培养物中的小胶质细胞进行免疫细胞化学染色显示，当TLR 4（+/+）小胶质细胞被1 ng/ml的低浓度LPS激活时，TLR 4（-/-）小胶质细胞仅在较高浓度（100- 1，000 ng/ml）的LPS反应中表现出激活的形态。此外，肿瘤坏死因子-α（TNF-α）仅在富含TLR 4（-/-）的小胶质细胞培养物中由较高浓度（100- 1，000 ng/ml）的LPS产生。NADPH氧化酶抑制剂二苯基碘鎓（DPI）可减少TLR 4（-/-）小胶质细胞产生TNF-α。在大鼠富集的小胶质细胞培养物中测试TLR 4对LPS诱导的超氧化物产生的影响，其中血清的存在或不存在未能显示对超氧化物产生的任何影响。此外，TLR 4（-/-）和TLR 4（+/+）小胶质细胞在暴露于LPS（1- 1，000 ng/ml）时显示出细胞外超氧化物产生的类似增加。这些数据表明，LPS诱导的超氧化物产生的小胶质细胞是独立的TLR 4和ROS的细胞外超氧化物的产生小胶质细胞介导的LPS诱导的TNF-α反应的TLR 4依赖性和独立的途径。(c)2005 Wiley-Liss，Inc.
Microglia are activated by lipopolysaccharide (LPS) to produce neurotoxic pro-inflammatory factors and reactive oxygen species (ROS). While a multitude of LPS receptors and corresponding pathways have been identified, the detailed mechanisms mediating the microglial response to LPS are unclear. Using mice lacking a functional toll-like receptor 4 (TLR4), we demonstrate that TLR4 and ROS work in concert to mediate microglia activation, where the contribution from each pathway is dependent on the concentration of LPS. Immunocytochemical staining of microglia in neuronglia cultures with antibodies against F4/80 revealed that while TLR4(+/+) microglia were activated the low concentration of 1 ng/ml of LPS, TLR4(-/-) microglia exhibit activated morphology in response to LPS only at higher concentrations (100-1,000 ng/ml). Additionally, tumor necrosis factor-alpha (TNF-alpha) was only produced from higher concentrations (100-1,000 ng/ml) of LPS in TLR4(-/-) enriched microglia cultures. Diphenylene iodonium (DPI), an inhibitor of NADPH oxidase, reduced TNF-a production from TLR4(-/-) microglia. The influence of TLR4 on LPS-induced superoxide production was tested in rat enriched microglia cultures, where the presence or absence of serum failed to show any effect on the superoxide production. Further, both TLR4(-/-) and TLR4(+/+) microglia showed a similar increase in extracellular superoxide production when exposed to LPS (1-1,000 ng/ml). These data indicate that LPS-induced superoxide production in microglia is independent of TLR4 and that ROS derived from the production of extracellular superoxide in microglia mediates the LPS-induced TNF-a response of both the TLR4-dependent and independent pathway. (c) 2005 Wiley-Liss, Inc.