Department of Environmental and Radiological Health Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, 1680 Campus Delivery, Physiology Building, Room 101, Fort Collins, CO, 80523-1680, USA.
Department of Microbiology, Immunology and Pathology, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA.
J Neuroinflammation. 2018 Nov 21;15(1):324. doi: 10.1186/s12974-018-1349-4.
Exposure to increased manganese (Mn) causes inflammation and neuronal injury in the cortex and basal ganglia, resulting in neurological symptoms resembling Parkinson's disease. The mechanisms underlying neuronal death from exposure to Mn are not well understood but involve inflammatory activation of microglia and astrocytes. Expression of neurotoxic inflammatory genes in glia is highly regulated through the NF-κB pathway, but factors modulating neurotoxic glial-glial and glial-neuronal signaling by Mn are not well understood.
We examined the role of NF-κB in Mn-induced neurotoxicity by exposing purified microglia, astrocytes (from wild-type and astrocyte-specific IKK knockout mice), and mixed glial cultures to varying Mn concentrations and then treating neurons with the conditioned media (GCM) of each cell type. We hypothesized that mixed glial cultures exposed to Mn (0-100 μM) would enhance glial activation and neuronal death compared to microglia, wild-type astrocytes, or IKK-knockout astrocytes alone or in mixed cultures.
Mixed glial cultures treated with 0-100 μM Mn for 24 h showed the most pronounced effect of increased expression of inflammatory genes including inducible nitric oxide synthase (Nos2), Tnf, Ccl5, Il6, Ccr2, Il1b, and the astrocyte-specific genes, C3 and Ccl2. Gene deletion of IKK2 in astrocytes dramatically reduced cytokine release in Mn-treated mixed glial cultures. Measurement of neuronal viability and apoptosis following exposure to Mn-GCM demonstrated that mixed glial cultures induced greater neuronal death than either cell type alone. Loss of IKK in astrocytes also decreased neuronal death compared to microglia alone, wild-type astrocytes, or mixed glia.
This suggests that astrocytes are a critical mediator of Mn neurotoxicity through enhanced expression of inflammatory cytokines and chemokines, including those most associated with a reactive phenotype such as CCL2 but not C3.
暴露于增加的锰（Mn）会导致皮质和基底神经节的炎症和神经元损伤，从而导致类似于帕金森病的神经症状。暴露于 Mn 导致神经元死亡的机制尚不清楚，但涉及小胶质细胞和星形胶质细胞的炎症激活。神经毒性炎症基因在神经胶质细胞中的表达受到 NF-κB 途径的高度调控，但 Mn 调节神经毒性神经胶质-神经胶质和神经胶质-神经元信号的因素尚不清楚。
我们通过暴露于不同 Mn 浓度的纯化小胶质细胞、星形胶质细胞（来自野生型和星形胶质细胞特异性 IKK 敲除小鼠）和混合神经胶质细胞培养物来检查 NF-κB 在 Mn 诱导的神经毒性中的作用，然后用每种细胞类型的条件培养基（GCM）处理神经元。我们假设暴露于 Mn（0-100 μM）的混合神经胶质细胞与小胶质细胞、野生型星形胶质细胞或 IKK 敲除星形胶质细胞单独或混合培养物相比，会增强神经胶质细胞的激活和神经元的死亡。
用 0-100 μM Mn 处理 24 h 的混合神经胶质细胞显示出最明显的炎症基因表达增加的效果，包括诱导型一氧化氮合酶（Nos2）、Tnf、Ccl5、Il6、Ccr2、Il1b 和星形胶质细胞特异性基因 C3 和 Ccl2。星形胶质细胞中 IKK2 的基因缺失显著减少了 Mn 处理的混合神经胶质细胞中的细胞因子释放。暴露于 Mn-GCM 后测量神经元活力和凋亡表明，混合神经胶质细胞诱导的神经元死亡比任何一种细胞类型单独诱导的神经元死亡都多。与小胶质细胞单独、野生型星形胶质细胞或混合神经胶质细胞相比，星形胶质细胞中 IKK 的缺失也减少了神经元的死亡。
这表明星形胶质细胞通过增强炎症细胞因子和趋化因子的表达，特别是与反应性表型最相关的 CCL2 而不是 C3，是 Mn 神经毒性的关键介质。
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