Prabhakaran K, Ghosh D, Chapman G D, Gunasekar P G
Naval Health Research Center Detachment, Environmental Health Effects Laboratory, Wright-Patterson Air Force Base, 2729 R Street, Area B, Building 837, Dayton, OH 45433, USA.
Brain Res Bull. 2008 Jul 1;76(4):361-7. doi: 10.1016/j.brainresbull.2008.03.004. Epub 2008 Apr 1.
Manganese (Mn) is an essential mineral that is found in varying amounts in aerosols or dust. Exposure to atmospheric Mn at high concentration is a risk factor in humans that can manifest as neuronal degeneration resembling Parkinson's disease (PD). Since the underlying mechanism of Mn and dopamine (DA) interaction-induced cell death remains unclear, here, we showed that Mn exposure alone to mesencephalic cells for 24h induced minimal apoptotic cell death. However, cells pre-exposed to DA for 2h accelerated Mn-induced apoptosis. The vulnerability of Mn-induced apoptotic cell death to DA was determined by measuring lactate dehydrogenase (LDH) and Apoptag TUNEL staining (terminaldeoxynucleotidyl transferase DNA labeling). This was further confirmed by the cell viability assay to support our hypothesis that DA at the cellular level interacts with Mn and causes cells to be more susceptible. Pretreatment with nitric oxide blocker (7-nitroindazole, 7-NI), vitamin E or NF-kappaB inhibitor (SN50) significantly protected the cells from Mn and DA interaction-induced reactive oxygen species (ROS) and apoptosis. Western blot analysis showed that Mn in the presence of DA markedly induced induction of NOS (iNOS) expression. Pretreatment with 7-NI, SN50 or vitamin E significantly attenuated increased iNOS expression indicating that iNOS expression is regulated by ROS and the transcription factor NF-kappaB. Further, the generation of ROS as an early event in Mn and DA interaction is not controlled by NF-kappaB as SN50 pretreatment did not prevent ROS. These findings suggest that NF-kappaB induction and the activation of nitric oxide synthase through ROS represent a proximate mechanism for Mn-induced neurotoxicity.
锰（Mn）是一种必需矿物质，在气溶胶或灰尘中的含量各不相同。高浓度暴露于大气中的锰是人类的一个风险因素，可能表现为类似帕金森病（PD）的神经元退化。由于锰与多巴胺（DA）相互作用诱导细胞死亡的潜在机制尚不清楚，在此，我们发现单独将中脑神经元细胞暴露于锰24小时只会诱导极少的凋亡性细胞死亡。然而，预先暴露于多巴胺2小时的细胞会加速锰诱导的凋亡。通过测量乳酸脱氢酶（LDH）和Apoptag TUNEL染色（末端脱氧核苷酸转移酶DNA标记）来确定锰诱导的凋亡性细胞死亡对多巴胺的易感性。细胞活力测定进一步证实了这一点，以支持我们的假设，即在细胞水平上多巴胺与锰相互作用并使细胞更易受影响。用一氧化氮阻滞剂（7-硝基吲唑，7-NI）、维生素E或核因子κB抑制剂（SN50）预处理可显著保护细胞免受锰和多巴胺相互作用诱导的活性氧（ROS）和凋亡的影响。蛋白质免疫印迹分析表明，在多巴胺存在的情况下，锰显著诱导一氧化氮合酶（iNOS）表达。用7-NI、SN50或维生素E预处理可显著减弱iNOS表达的增加，表明iNOS表达受ROS和转录因子核因子κB调控。此外，作为锰和多巴胺相互作用早期事件的ROS生成不受核因子κB控制，因为SN50预处理不能阻止ROS生成。这些发现表明，核因子κB的诱导以及通过ROS激活一氧化氮合酶是锰诱导神经毒性的一种直接机制。
