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Role and Mechanism of Microglial Activation in Iron-Induced Selective and Progressive Dopaminergic Neurodegeneration |
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| Authors: | Wei Zhang Zhao-fen Yan Jun-hua Gao Li Sun Xi-yan Huang Zhuo Liu Shu-yang Yu Chen-Jie Cao Li-jun Zuo Ze-Jie Chen Yang Hu Fang Wang Jau-shyong Hong Xiao-min Wang |
| Institution: | 1. Department of Neurology, Beijing Tiantan Hospital, Capital Medical University, Beijing, 100050, China 2. Parkinson’s Disease Center of Beijing Institute of Brain Disorders, Beijing, 100053, China 3. Beijing Key Laboratory on Parkinson’s Disease, Beijing, 100053, China 4. Neuropharmacology Section, Laboratory of Pharmacology and Chemistry, National Institute of Environmental Health Sciences/National Institutes of Health, Research Triangle Park, North Carolina, 27709, USA 5. Department of Physiology, Capital Medical University, Beijing, 100069, China 6. Department of Neurobiology, Capital Medical University, Beijing, 100069, China 7. Key Laboratory for Neurodegenerative Disorders of the Ministry of Education, Beijing, 100069, China 8. Beijing Institute for Brain Disorders, Beijing, 100069, China |
| Abstract: | Parkinson’s disease (PD) patients have excessive iron depositions in substantia nigra (SN). Neuroinflammation characterized by microglial activation is pivotal for dopaminergic neurodegeneration in PD. However, the role and mechanism of microglial activation in iron-induced dopaminergic neurodegeneration in SN remain unclear yet. This study aimed to investigate the role and mechanism of microglial β-nicotinamide adenine dinucleotide phosphate oxidase 2 (NOX2) activation in iron-induced selective and progressive dopaminergic neurodegeneration. Multiple primary midbrain cultures from rat, NOX2+/+ and NOX2?/? mice were used. Dopaminergic neurons, total neurons, and microglia were visualized by immunostainings. Cell viability was measured by MTT assay. Superoxide (O2 ·?) and intracellular reactive oxygen species (iROS) were determined by measuring SOD-inhibitable reduction of tetrazolium salt WST-1 and DCFH-DA assay. mRNA and protein were detected by real-time PCR and Western blot. Iron induces selective and progressive dopaminergic neurotoxicity in rat neuron–microglia–astroglia cultures and microglial activation potentiates the neurotoxicity. Activated microglia produce a magnitude of O2 ·? and iROS, and display morphological alteration. NOX2 inhibitor diphenylene iodonium protects against iron-elicited dopaminergic neurotoxicity through decreasing microglial O2 ·? generation, and NOX2?/? mice are resistant to the neurotoxicity by reducing microglial O2 ·? production, indicating that iron-elicited dopaminergic neurotoxicity is dependent of NOX2, a O2 ·?-generating enzyme. NOX2 activation is indicated by the increased mRNA and protein levels of subunits P47 and gp91. Molecules relevant to NOX2 activation include PKC-σ, P38, ERK1/2, JNK, and NF-КBP65 as their mRNA and protein levels are enhanced by NOX2 activation. Iron causes selective and progressive dopaminergic neurodegeneration, and microglial NOX2 activation potentiates the neurotoxicity. PKC-σ, P38, ERK1/2, JNK, and NF-КBP65 are the potential molecules relevant to microglial NOX2 activation. |
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