Hao A-J, Dheen S T, Ling E-A
Molecular Neurobiology Laboratory, Department of Anatomy, Faculty of Medicine, National University of Singapore, Singapore.
Neuroscience. 2002;112(4):889-900. doi: 10.1016/s0306-4522(02)00144-6.
Prenatal exposure to teratogen agents is linked to the pathogenesis of neurodevelopment disorders, but the mechanisms leading to the neurodevelopmental disturbance are poorly understood. To elucidate this, an in vitro model of microglial activation induced by neuronal injury has been characterized. In this connection, exposure of primary microglial cells to the conditioned medium from the neuronal damage induced by teratogen, cyclophosphamide, is accompanied by a reactive microgliosis as assessed by reverse transcription-polymerase chain reaction, enzyme-linked immunosorbent assay, lectin histochemistry, double labeling immunohistochemistry and in situ hybridization. Our results showed that reactive microglia were capable of releasing various cytokines such as tumor necrosis factor-alpha, interleukin-1, interleukin-6, transforming growth factor-beta and nitric oxide. Also, we have shown that macrophage colony-stimulating factor (M-CSF) was in fact produced by the reactive microglia. Concomitant to this was the increased expression of M-CSF receptor in these cells following the teratogen-induced neuronal injury. The up-regulation of M-CSF receptor suggests that the cells are capable of responding to self-derived M-CSF in an autocrine fashion. Results with antibody neutralization further suggest that microglial proinflammatory response, as manifested by cytokine expression in culture, is mediated by M-CSF, which acts as a molecular signal that initiates a microglial reaction. We therefore suggest that microglial activation following cyclophosphamide treatment is not only a response to the neuronal damage, but is also a cause of the damage during pathogenesis of neurodevelopment disorders. To this end, the increased expression of M-CSF and its receptor on microglia would be directly linked to the active cell proliferation and proinflammatory response in the teratogen-induced injury.
产前暴露于致畸剂与神经发育障碍的发病机制有关，但导致神经发育紊乱的机制尚不清楚。为了阐明这一点，已经建立了一种由神经元损伤诱导的小胶质细胞激活的体外模型。在此方面，将原代小胶质细胞暴露于由致畸剂环磷酰胺诱导的神经元损伤的条件培养基中，通过逆转录-聚合酶链反应、酶联免疫吸附测定、凝集素组织化学、双重标记免疫组织化学和原位杂交评估，会出现反应性小胶质细胞增生。我们的结果表明，反应性小胶质细胞能够释放各种细胞因子，如肿瘤坏死因子-α、白细胞介素-1、白细胞介素-6、转化生长因子-β和一氧化氮。此外，我们还表明，巨噬细胞集落刺激因子（M-CSF）实际上是由反应性小胶质细胞产生的。与此相伴的是，在致畸剂诱导的神经元损伤后，这些细胞中M-CSF受体的表达增加。M-CSF受体的上调表明这些细胞能够以自分泌方式对自身产生的M-CSF作出反应。抗体中和实验结果进一步表明，培养中细胞因子表达所表现出的小胶质细胞促炎反应是由M-CSF介导的，M-CSF作为一种分子信号启动小胶质细胞反应。因此，我们认为环磷酰胺处理后小胶质细胞的激活不仅是对神经元损伤的反应，也是神经发育障碍发病过程中损伤的一个原因。为此，小胶质细胞上M-CSF及其受体表达的增加将直接与致畸剂诱导损伤中的活跃细胞增殖和促炎反应相关联。
