The study aimed to investigate the effect of the CD200R1 gene deletion on microglia activation and nigrostriatal dopamine neuron loss in the Parkinson's disease (PD) process. The CRISPR-Cas9 technology was applied to construct the CD200R1^-/- mice. The primary microglia cells of wild-type and CD200R1^-/- mice were cultured and treated with bacterial lipopolysaccharide (LPS). Microglia phagocytosis level was assessed by a fluorescent microsphere phagocytosis assay. PD mouse model was prepared by nigral stereotaxic injection of recombinant adeno-associated virus vector carrying human α-synuclein (α-syn). The changes in the motor behavior of the mice with both genotypes were evaluated by cylinder test, open field test, and rotarod test. Immunohistochemical staining was used to assess the loss of dopamine neurons in substantia nigra. Immunofluorescence staining was used to detect the expression level of CD68 (a key molecule involved in phagocytosis) in microglia. The results showed that CD200R1 deletion markedly enhanced LPS-induced phagocytosis in vitro by the microglial cells. In the mouse model of PD, CD200R1 deletion exacerbated motor behavior impairment and dopamine neuron loss in substantia nigra. Fluorescence intensity analysis results revealed a significant increase in CD68 expression in microglia located in the substantia nigra of CD200R1^-/- mice. The above results suggest that CD200R1 deletion may further activates microglia by promoting microglial phagocytosis, leading to increased loss of the nigrostriatal dopamine neurons in the PD model mice. Therefore, targeting CD200R1 could potentially serve as a novel therapeutic target for the treatment of early-stage PD.
Animals ; Microglia/physiology* ; Mice ; Phagocytosis ; Parkinson Disease/genetics* ; Disease Models, Animal ; Receptors, Cell Surface/physiology* ; Dopaminergic Neurons/pathology* ; Antigens, CD/metabolism* ; Gene Deletion ; Substantia Nigra ; Mice, Inbred C57BL ; Mice, Knockout ; Cells, Cultured ; Male ; alpha-Synuclein ; CD68 Molecule ; Orexin Receptors

OBJECTIVES: To investigate the role of mitochondrial autophagy disorder caused by deletion of E3 ubiquitin ligase Parkin in neuroinflammation in a mouse model of MPTP-induced Parkinson's disease (PD). METHODS: Wild-type (WT) male C57BL/6 mice and Parkin^-/- mice were given intraperitoneal injections with MPTP or PBS for 5 consecutive days, and the changes in motor behaviors of the mice were observed using open field test. The effects of Parkin deletion on PD development and neuroinflammation were evaluated using immunofluorescence and Western blotting. The changes of the PINK 1/Parkin signaling pathway in the midbrain substantia nigra of the mice were examined to explore the molecular mechanism of Parkin-mediated regulation of mitochondrial autophagy and its effect on neuroinflammation in PD mice. RESULTS: Compared with their WT counterparts, the Parkin^-/- mice with MPTP injections exhibited significant impairment of motor function with decreased TH⁺ neurons, increased α-synuclein (α-syn) accumulation, and increased numbers of GFAP⁺ and I-ba1⁺ cells in the midbrain substantia nigra. Parkin deletion obviously affected PINK1/Parkin-mediated mitochondrial autophagy to result in significantly increased mtDNA and upregulated expressions of STING and NLRP3 inflammatosomes in the midbrain substantia nigra of MPTP-treated transgenic mice. CONCLUSIONS Parkin deletion causes mitochondrial autophagy disorder to accelerate PD progression and exacerbates neuroinflammation in mice by affecting the PINK1/Parkin signaling pathway, suggesting the important role of Parkin in early pathogenesis of PD.
Animals ; Ubiquitin-Protein Ligases/genetics* ; Mice ; Mice, Inbred C57BL ; Male ; Parkinson Disease/genetics* ; Protein Kinases/genetics* ; Mitochondria/metabolism* ; Disease Models, Animal ; Autophagy ; Signal Transduction ; Neuroinflammatory Diseases/metabolism* ; Mice, Knockout ; alpha-Synuclein/metabolism* ; Substantia Nigra/metabolism* ; Mitophagy ; Disease Progression

Humans ; alpha-Synuclein/genetics* ; Parkinson Disease/pathology*

Parkinson's disease (PD) is a multifaceted disease in which environmental variables combined with genetic predisposition cause dopaminergic (DAergic) neuron loss in the substantia nigra pars compacta. The mutation of leucine-rich repeat kinase 2 (Lrrk2) is the most common autosomal dominant mutation in PD, and it has also been reported in sporadic cases. A growing body of research suggests that circadian rhythm disruption, particularly sleep-wake abnormality, is common during the early phase of PD. Our present study aimed to evaluate the impact of sleep deprivation (SD) on motor ability, sleep performance, and PD pathologies in Lrrk2^G2019S transgenic mice. After two months of SD, Lrrk2^G2019S mice at 12 months of age showed an exacerbated PD-like phenotype with motor deficits, a reduced striatal DA level, degenerated DAergic neurons, and altered sleep structure and biological rhythm accompanied by the decreased protein expression level of circadian locomotor output cycles kaput Lrrk2 gene in the brain. All these changes persisted and were even more evident in 18-month-old mice after 6 months of follow-up. Moreover, a significant increase in α-synuclein aggregation was found in SD-treated transgenic mice at 18 months of age. Taken together, our findings indicate that sleep abnormalities, as a risk factor, may contribute to the pathogenesis and progression of PD. Early detection of sleep disorders and improvement of sleep quality may help to delay disease progression and provide long-term clinical benefits.
Animals ; Electroencephalography ; Leucine/genetics* ; Leucine-Rich Repeat Serine-Threonine Protein Kinase-2/genetics* ; Mice ; Mice, Transgenic ; Mutation ; Parkinson Disease/metabolism* ; Sleep Deprivation/complications* ; alpha-Synuclein/genetics*

Mammalian cells remove misfolded proteins using various proteolytic systems, including the ubiquitin (Ub)-proteasome system (UPS), chaperone mediated autophagy (CMA) and macroautophagy. The majority of misfolded proteins are degraded by the UPS, in which Ub-conjugated substrates are deubiquitinated, unfolded and cleaved into small peptides when passing through the narrow chamber of the proteasome. The substrates that expose a specific degradation signal, the KFERQ sequence motif, can be delivered to and degraded in lysosomes via the CMA. Aggregation-prone substrates resistant to both the UPS and the CMA can be degraded by macroautophagy, in which cargoes are segregated into autophagosomes before degradation by lysosomal hydrolases. Although most misfolded and aggregated proteins in the human proteome can be degraded by cellular protein quality control, some native and mutant proteins prone to aggregation into beta-sheet-enriched oligomers are resistant to all known proteolytic pathways and can thus grow into inclusion bodies or extracellular plaques. The accumulation of protease-resistant misfolded and aggregated proteins is a common mechanism underlying protein misfolding disorders, including neurodegenerative diseases such as Huntington's disease (HD), Alzheimer's disease (AD), Parkinson's disease (PD), prion diseases and Amyotrophic Lateral Sclerosis (ALS). In this review, we provide an overview of the proteolytic pathways in neurons, with an emphasis on the UPS, CMA and macroautophagy, and discuss the role of protein quality control in the degradation of pathogenic proteins in neurodegenerative diseases. Additionally, we examine existing putative therapeutic strategies to efficiently remove cytotoxic proteins from degenerating neurons.
Alzheimer Disease/drug therapy/metabolism ; Amyloid beta-Peptides/metabolism ; Amyotrophic Lateral Sclerosis/drug therapy/metabolism ; Animals ; Autophagy/drug effects ; DNA-Binding Proteins/metabolism ; Humans ; Huntington Disease/drug therapy/genetics/metabolism ; Lysosomes/metabolism ; Molecular Targeted Therapy ; Mutation ; Nerve Tissue Proteins/genetics/metabolism ; Neurodegenerative Diseases/drug therapy/*metabolism ; Parkinson Disease/drug therapy/metabolism ; PrPSc Proteins/metabolism ; Prion Diseases/drug therapy/metabolism ; Proteasome Endopeptidase Complex/metabolism ; Proteolysis ; Proteostasis Deficiencies/metabolism ; Superoxide Dismutase/metabolism ; Ubiquitin/metabolism ; alpha-Synuclein/metabolism ; tau Proteins/metabolism

Lysosomal dysfunction is a common pathological feature of neurodegenerative diseases. GTP-binding protein type A1 (GBA1) encodes beta-glucocerebrosidase 1 (GCase 1), a lysosomal hydrolase. Homozygous mutations in GBA1 cause Gaucher disease, the most common lysosomal storage disease, while heterozygous mutations are strong risk factors for Parkinson's disease. However, whether loss of GCase 1 activity is sufficient for lysosomal dysfunction has not been clearly determined. Here, we generated human neuroblastoma cell lines with nonsense mutations in the GBA1 gene using zinc-finger nucleases. Depending on the site of mutation, GCase 1 activity was lost or maintained. The cell line with GCase 1 deficiency showed indications of lysosomal dysfunction, such as accumulation of lysosomal substrates, reduced dextran degradation and accumulation of enlarged vacuolar structures. In contrast, the cell line with C-terminal truncation of GCase 1 but with intact GCase 1 activity showed normal lysosomal function. When alpha-synuclein was overexpressed, accumulation and secretion of insoluble aggregates increased in cells with GCase 1 deficiency but did not change in mutant cells with normal GCase 1 activity. These results demonstrate that loss of GCase 1 activity is sufficient to cause lysosomal dysfunction and accumulation of alpha-synuclein aggregates.
Cell Line ; Enzyme Activation/genetics ; Gene Knockout Techniques ; Gene Order ; Genetic Loci ; Glucosylceramidase/genetics/*metabolism ; Humans ; Lysosomes/*metabolism ; Mutation ; *Protein Aggregation, Pathological/genetics ; Protein Binding ; Zinc Fingers ; alpha-Synuclein/chemistry/*metabolism

OBJECTIVETo investigate the effect of curcumin on oligomer formation and mitochondrial ATP-sensitive potassium channels (mitoKATP) induced by overexpression or mutation of α-synuclein.

METHODSRecombinant plasmids α-synuclein-pEGFP-A53T and α-synuclein-pEGFP-WT were transfected into PC12 cells by lipofectamin method, and intervened by application of curcumin (20 μmol/L) and 5-hydroxydecanoate (5-HD). Oligomer formation in the cultured cells was identified by Western blotting and Dot blotting. Cytotoxicity and apoptosis of the PC12 cells were measured by lactate dehydrogenase (LDH) and JC-1 assays. mitoKATP were identified by Western blotting and whole cell patch clamp.

RESULTSCurcumin has significantly reduced the oligomer formation induced by overexpression or mutation of &alpha;-synuclein in the cultured cells. LDH has decreased by 36.3% and 23.5%, and red/green fluorescence ratio of JC-1 was increased respectively by 48.46% and 50.33% after application of curcumin (P<0.05). Protein expression of Kir6.2 has decreased and mitoKATP channel current has significantly increased (P<0.05).

CONCLUSIONCurcumin can inhibit &alpha;-synuclein gene overexpression or mutation induced &alpha;-synuclein oligomers formation. It may block apoptosis induced by wild-type overexpression or mutation of &alpha;-synuclein. By stabilizing mitochondrial membrane potential. Opening of mitoKATP channel may have been the initiating protective mechanism of apoptosis induced by wild-type overexpression or mutation of &alpha;-synuclein. Curcumin may antagonize above cytotoxicity through further opening the mitoKATP channel.

Animals ; Apoptosis ; drug effects ; Cell Line ; Curcumin ; pharmacology ; Humans ; KATP Channels ; chemistry ; genetics ; metabolism ; Mitochondria ; drug effects ; genetics ; metabolism ; Mutation ; drug effects ; PC12 Cells ; Parkinson Disease ; drug therapy ; genetics ; metabolism ; physiopathology ; Rats ; alpha-Synuclein ; genetics

Parkinson's disease (PD) is an age-related progressive neurodegenerative disease associated with selective loss of dopaminergic neurons. The characteristic hallmark of the disease is intracytoplasmic proteinacious inclusion bodies called Lewy bodies, primarily consisting of a presynaptic protein alpha-synuclein. Oxidative stress-mediated damage to macromolecules have been shown to occur frequently in PD. Oxidative damage to DNA in the form of oxidized guanine (8-oxodG) accumulates in both the mitochondrial and nuclear DNA of dopaminergic neurons of the substantia nigra in PD. 8-oxodG-mediated transcriptional mutagenesis has been shown to have the potential to alter phenotype of cells through production of mutant pool of proteins. This review comprehensively summarizes the role of oxidative stress-mediated damage incurred during neurodegeneration, and highlights the scope of transcriptional mutagenesis event in leading to alpha-synuclein aggregation as seen in PD.
Amino Acid Sequence ; Animals ; Deoxyguanosine/*analogs & derivatives/metabolism ; Humans ; Molecular Sequence Data ; Mutagenesis ; *Oxidative Stress ; Parkinson Disease/*genetics/metabolism/pathology ; Protein Aggregation, Pathological/*genetics/metabolism/pathology ; Substantia Nigra/metabolism/*pathology ; Transcription, Genetic ; alpha-Synuclein/chemistry/*genetics

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

Aged ; Cognition Disorders ; genetics ; F-Box Proteins ; genetics ; HSP40 Heat-Shock Proteins ; genetics ; Humans ; Male ; Monocytes ; metabolism ; Parkinson Disease ; genetics ; alpha-Synuclein ; genetics