Parkinson's disease (PD), a progressive neurodegenerative disorder, is pathologically characterized by the progressive loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc) and the presence of deposits of aggregated α-synuclein in intracellular inclusions known as Lewy bodies (LB). A highly localized inflammatory response mediated by reactive microglia is prominent in PD brains, but the mechanisms underlying the microglial activation are poorly understood. Recently some lines of evidences have shown that monomeric, or aggregated α-synuclein can activate microglia, the toxic factors released from activated microglia may lead to the cell death of dopaminergic neurons. This review is to summarize the recent progress on the role of α-synuclein induced microglia activation on the PD pathogenesis and progression, and to discuss the possible mechanisms involved.
Humans ; Microglia ; pathology ; Parkinson Disease ; etiology ; metabolism ; pathology ; alpha-Synuclein ; chemistry ; metabolism ; physiology

OBJECTIVETo construct specific and effective RNA interference(RNAi) plasmid for alpha-synuclein gene and investigate RNAi blockade of the aberrant aggregation of alpha-synuclein in HEK293 cells induced by overexpression of wild-type alpha-synuclein.

METHODSHairpin RNAs for four target sites were designed to construct four RNAi plasmids pSYNi-1, pSYNi-2, pSYNi-3 and pSYNi-4, using plasmid pBSHH1 vector under the control of the H1 promoter. Western blot and reverse transcription-PCR(RT-PCR) were performed to screen the most specific and effective RNAi plasmid. After confirming the sequences of the plasmids, they were co-transfected into HEK293 cells with the recombinant plasmids alpha-synuclein-pEGFP by using lipofectamin 2000. The aberrant aggregation of alpha-synuclein was measured by EGFP fluorescence and immunocytochemistry for alpha-synuclein. The inclusions in the cultured cells were identified with HE staining.

RESULTSBy Western blot and RT-PCR, pSYNi-1 showed the most effective RNAi gene silencing effect (69.6%). After transfecting the RNAi plasmid, the aberrant aggregation of alpha-synuclein in HEK293 cells induced by overexpression of wild-type alpha-synuclein was inhibited. The Lewy body-like inclusions were found in cytoplasm of cultured cells in control group, but disappeared in HEK293 cells cotransfected by pSYNi-1 and alpha-synuclein-pEGFP plasmid.

CONCLUSIONRNAi can block the aberrant aggregation and Lewy body-like inclusion formation in cytoplasm of HEK293 cell induced by overexpression of wild-type alpha-synuclein.

Blotting, Western ; Cell Line ; Genetic Vectors ; genetics ; Humans ; Immunohistochemistry ; Plasmids ; genetics ; RNA Interference ; physiology ; Reverse Transcriptase Polymerase Chain Reaction ; Transfection ; alpha-Synuclein ; genetics ; metabolism

Both genetic and environmental factors are involved in the pathogenesis of Parkinsonos disease (PD). Epidemiological studies showed that environmental factors shared with the common mechanisms of resulting in alpha-synuclein aggregation by inhibiting complex I of mitochondria and leading to oxidative stress. To investigate the relationship between alpha-synuclein and oxidative stress, we used human dopaminergic SH-SY5Y cells transfected with alpha-synuclein-enhanced green fluorescent protein (EGFP). alpha-synuclein gene expression was determined by immunocytochemistry and real-time quantitative PCR. Both SH-SY5Y and alpha-synuclein overexpressed SH-SY5Y (SH-SY5Y/Syn) cells were treated with various concentrations of rotenone for different time. Cell viability and oxidative stress were detected by MTT assay and DCF assay. Superoxide dismutase (SOD) activity was assessed with xanthine peroxidase method. Cell apoptosis was detected with flow cytometry. Results showed that alpha-synuclein gene was constantly overexpressed in SH-SY5Y/Syn cells. After treatment with rotenone, both cell viability and complex I activity in these cells were reduced in a concentration-dependent manner. Oxidative stress was also found in these cells. Compared with SH-SY5Y cells, SOD activity in SH-SY5Y/Syn cells was increased distinctly (P<0.05) and alpha-synuclein significantly attenuated rotenone-induced cell apoptosis. These results suggest that the alpha-synuclein overexpression in SH-SY5Y cells has a tendency to partially resist oxidative stress induced by rotenone and this response may assist cell survival.
Apoptosis ; drug effects ; Cell Line ; Cell Survival ; drug effects ; Cytoprotection ; Dose-Response Relationship, Drug ; Electron Transport Complex I ; metabolism ; Humans ; Oxidative Stress ; Rotenone ; toxicity ; Superoxide Dismutase ; metabolism ; Superoxides ; metabolism ; alpha-Synuclein ; genetics ; physiology

Inflammation, a self-defensive reaction against various pathogenic stimuli, may become harmful self-damaging process. Increasing evidence has linked chronic inflammation to a number of neurodegenerative disorders including Alzheimer's disease (AD), Parkinson's disease (PD), and multiple sclerosis. In the central nervous system, microglia, the resident innate immune cells play major role in the inflammatory process. Although they form the first line of defense for the neural parenchyma, uncontrolled activation of microglia may directly toxic to neurons by releasing various substances such as inflammatory cytokines (IL-1beta, TNF-alpha, IL-6), NO, PGE
alpha-Synuclein/physiology ; Signal Transduction ; Parkinson Disease/*etiology/immunology ; Multiple Sclerosis/etiology ; Models, Biological ; Microglia/immunology/metabolism/*physiology ; Metalloproteases/physiology ; Melanins/physiology ; Matrix Metalloproteinase 3 ; Inflammation Mediators/metabolism ; Humans ; Encephalitis/*etiology/immunology ; Cytokines/secretion ; Animals ; Alzheimer Disease/etiology ; AIDS Dementia Complex/etiology

Chronic neuroinflammation is an integral pathological feature of major neurodegenerative diseases. The recruitment of microglia to affected brain regions and the activation of these cells are the major events leading to disease-associated neuroinflammation. In a previous study, we showed that neuron-released alpha-synuclein can activate microglia through activating the Toll-like receptor 2 (TLR2) pathway, resulting in proinflammatory responses. However, it is not clear whether other signaling pathways are involved in the migration and activation of microglia in response to neuron-released alpha-synuclein. In the current study, we demonstrated that TLR2 activation is not sufficient for all of the changes manifested by microglia in response to neuron-released alpha-synuclein. Specifically, the migration of and morphological changes in microglia, triggered by neuron-released alpha-synuclein, did not require the activation of TLR2, whereas increased proliferation and production of cytokines were strictly under the control of TLR2. Construction of a hypothetical signaling network using computational tools and experimental validation with various peptide inhibitors showed that beta1-integrin was necessary for both the morphological changes and the migration. However, neither proliferation nor cytokine production by microglia was dependent on the activation of beta1-integrin. These results suggest that beta1-integrin signaling is specifically responsible for the recruitment of microglia to the disease-affected brain regions, where neurons most likely release relatively high levels of alpha-synuclein.
Animals ; Antigens, CD29/genetics/*metabolism ; Cell Line, Tumor ; *Cell Movement ; Cells, Cultured ; Culture Media, Conditioned/*pharmacology ; Gene Regulatory Networks ; Humans ; Mice ; Mice, Inbred C57BL ; Microglia/drug effects/metabolism/*physiology ; Neurons/*metabolism ; Rats ; Rats, Sprague-Dawley ; Signal Transduction ; Toll-Like Receptor 2/metabolism ; alpha-Synuclein/*pharmacology