Wang Tongguang, Pei Zhong, Zhang Wei, Liu Bin, Langenbach Robert, Lee Christopher, Wilson Belinda, Reece Jeffrey M, Miller David S, Hong Jau-Shyong
Neuropharmacology Section, Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina, USA.
FASEB J. 2005 Jul;19(9):1134-6. doi: 10.1096/fj.04-2457fje. Epub 2005 Apr 21.
The importance of cyclooxygenase-2 (COX-2) in mediating Parkinson's disease (PD) was suggested in reports, indicating that COX-2 selective inhibitors or genetic knockout reduce 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced dopaminergic (DA) neurotoxicity in a mouse model of PD. However, cell types and mechanisms underlying the activation of COX-2 have not been clearly elucidated in these animal studies. Using primary neuron-glia cultures, we aimed to determine 1) whether microglia participate in 1-methyl-4-phenylpryridinium (MPP)-induced COX-2 activation and 2) whether the activation of COX-2 contributes to subsequent neurotoxicity. MPP, in a concentration-dependent manner, increased prostaglandin E2 (PGE2) production in mixed neuron-microglia cultures but not in enriched neuron, microglia, or astroglia cultures nor in mixed neuron-astroglia cultures. MPP-induced PGE2 increase was completely abolished by treatment with DuP697, a COX-2 selective inhibitor. DuP697 also significantly reduced MPP-induced DA neurotoxicity as determined by DA uptake assay. Immunocytochemistry and confocal microscopy studies showed enhanced COX-2 expression in both microglia and neurons after MPP treatment. However, neuronal increase in COX-2 expression was not totally dependent on the production of PGE2 from microglia, since microglia deficient in COX-2 only attenuated, but did not completely block, MPP-increased PGE2 production in mixed neuron-microglia cultures, suggesting that part of PGE2 production was originated from neurons. Together, these results indicate that MPP-induced COX-2 expression and subsequent PGE2 production depend on interactions between neurons and microglia. Microgliosis may also be responsible for the COX-2 activation in neurons, leading to the enhanced DA neurotoxicity, which, in turn, reinforces microgliosis. Thus inhibition of microgliosis and COX-2 activity may stop this vicious circle and be valuable strategies in PD therapy.
报告提示环氧化酶 -2（COX-2）在介导帕金森病（PD）中具有重要作用，这表明COX-2选择性抑制剂或基因敲除可减轻1-甲基-4-苯基-1,2,3,6-四氢吡啶（MPTP）诱导的PD小鼠模型中的多巴胺能（DA）神经毒性。然而，在这些动物研究中，COX-2激活的细胞类型和机制尚未明确阐明。利用原代神经元-胶质细胞培养物，我们旨在确定：1）小胶质细胞是否参与1-甲基-4-苯基吡啶鎓（MPP）诱导的COX-2激活；2）COX-2的激活是否导致随后的神经毒性。MPP以浓度依赖性方式增加混合神经元-小胶质细胞培养物中前列腺素E2（PGE2）的产生，但在富集的神经元、小胶质细胞或星形胶质细胞培养物以及混合神经元-星形胶质细胞培养物中未增加。用COX-2选择性抑制剂DuP697处理可完全消除MPP诱导的PGE2增加。如通过DA摄取试验所确定的，DuP697也显著降低了MPP诱导的DA神经毒性。免疫细胞化学和共聚焦显微镜研究显示，MPP处理后小胶质细胞和神经元中COX-2表达均增强。然而，神经元中COX-2表达的增加并不完全依赖于小胶质细胞产生的PGE2，因为缺乏COX-2的小胶质细胞仅减弱但未完全阻断混合神经元-小胶质细胞培养物中MPP增加的PGE2产生，这表明部分PGE2产生源自神经元。总之，这些结果表明MPP诱导的COX-2表达及随后的PGE2产生依赖于神经元与小胶质细胞之间的相互作用。小胶质细胞增生也可能是神经元中COX-2激活的原因，导致DA神经毒性增强，进而加强小胶质细胞增生。因此，抑制小胶质细胞增生和COX-2活性可能会终止这种恶性循环，是PD治疗中有价值的策略。
