Parkinson's disease (PD) is characterized by selective and progressive degeneration of dopamine (DA)-producing neurons in the substantia nigra pars compacta (SNpc) and by abnormal aggregation of alpha-synuclein. Previous studies have suggested that DA can interact with alpha-synuclein, thus modulating the aggregation process of this protein; this interaction may account for the selective vulnerability of DA neurons in patients with PD. However, the relationship between DA and alpha-synuclein, and the role in progressive degeneration of DA neurons remains elusive. We have shown that in the presence of DA, recombinant human alpha-synuclein produces non-fibrillar, SDS-resistant oligomers, while beta-sheet-rich fibril formation is inhibited. Pharmacologic elevation of the cytoplasmic DA level increased the formation of SDS-resistant oligomers in DA-producing neuronal cells. DA promoted alpha-synuclein oligomerization in intracellular vesicles, but not in the cytosol. Furthermore, elevation of DA levels increased secretion of alpha-synuclein oligomers to the extracellular space, but the secretion of monomers was not changed. DA-induced secretion of alpha-synuclein oligomers may contribute to the progressive loss of the dopaminergic neuronal population and the pronounced neuroinflammation observed in the SNpc in patients with PD.
Blotting, Western ; Cell Line, Tumor ; Dopamine/*metabolism ; Humans ; Levodopa/pharmacology ; Neurons/*metabolism/pathology/*secretion ; Parkinson Disease/metabolism/pathology ; Substantia Nigra/metabolism/pathology ; alpha-Synuclein/*biosynthesis/*secretion

OBJECTIVE: To determine, using proton magnetic resonance spectroscopy (1H MRS) whether thalamotomy in patients with Parkinson's disease gives rise to significant changes in regional brain metabolism. MATERIALS AND METHODS: Fifteen patients each underwent stereotactic thalamotomy for the control of medically refractory parkinsonian tremor. Single-voxel 1H MRS was performed on a 1.5T unit using a STEAM sequence (TR/TM/TE, 2000/14/20 msec), and spectra were obtained from substantia nigra, thalamus and putamen areas, with volumes of interest of 7-8ml, before and after thalamotomy. NAA/Cho, NAA/Cr and Cho/Cr metabolite ratios were calculated from relative peak area measurements, and any changes were recorded and assessed. RESULTS: In the substantia nigra and thalamus, NAA/Cho ratios were generally low. In the substantia nigra of 80% of patients (12/15) who showed clinical improvement, decreased NAA/Cho ratios were observed in selected voxels after thalamic surgery (p < 0.05). In the thalamus of 67% of such patients (10/15), significant decreases were also noted (p < 0.05). CONCLUSION: Our results suggest that the NAA/Cho ratio may be a valuable criterion for the evaluation of Parkinson's disease patients who show clinical improvement following surgery. By highlighting variations in this ratio, 1H MRS may help lead to a better understanding of the pathophysiologic processes occurring in those with Parkinson's disease.
Adult ; Aged ; Aspartic Acid/*analogs & derivatives/metabolism ; Brain/*metabolism/pathology ; Choline/metabolism ; Female ; Human ; Magnetic Resonance Imaging ; Magnetic Resonance Spectroscopy ; Male ; Middle Age ; Parkinson Disease/*metabolism/pathology/*surgery ; Protons ; Putamen/metabolism/pathology ; Substantia Nigra/metabolism/pathology ; Thalamus/*metabolism/pathology/*surgery

To study the effects of 6-hydroxydopamine (6-OHDA) and reduced glutathione (GSH) on the nigral dopaminergic neurons in brain slices in vitro, immolunohistochemical technique was used to observe the changes of TH-stained neurons, including cell bodies and the dendrites, in the substantia nigra (SN) of midbrain slices of rats after incubation for 1 h in the presence of GSH 15 min before and during the period of incubation with 6-OHDA. The results showed that cell bodies remained intact but dendrites were fragmented and truncated after treatment with 6-OHDA. The antioxidant GSH alone did not significantly affect the dendrites of SN neurons but prevented 6-O-HDA-induced damage of dendrites. It was concluded that glutathione may prevent 6-OHDA-induced dopaminergic neurodegeneration and play a protective role in dopaminergic neurons.
Glutathione/*therapeutic use ; Neurons/pathology ; Oxidopamine ; Parkinson Disease, Secondary/chemically induced ; Parkinson Disease, Secondary/*drug therapy ; Random Allocation ; Rats, Sprague-Dawley ; Substantia Nigra/pathology ; Tyrosine 3-Monooxygenase/metabolism

In order to investigate the neurotoxicity of lipopolysaccharide (LPS) on the dopaminergic neurons of substantia nigra and the pathogenesis of Parkinson disease, LPS was stereotaxically infused into substantia nigra (SN). At different dosages and different time points with 5 microg LPS, the damage of the dopaminergic neurons in SN was observed by using tyrosine-hydroxylase (TH) immunohistochemical staining. The results showed that 14 days after injection of 0.1 microg to 10 microg LPS into the rat SN, TH-positive (TH+) neurons in the SN were decreased by 5%, 15%, 20%, 45 %, 96% and 99% respectively. After injection of 5 microg LPS, as compared with the control groups, TH+ neurons began to decrease at 3rd day and obviously decrease at 14th day, only 5% of total cells, and almost disappeared 30 days later. The results suggested that LPS could induce the degeneration of dopaminergic neurons in the SN in a dose- and time-dependent manner.
Dopamine/metabolism ; Dose-Response Relationship, Drug ; Lipopolysaccharides/*toxicity ; *Nerve Degeneration ; Neurons/pathology ; Parkinson Disease, Secondary/*chemically induced ; Random Allocation ; Rats, Sprague-Dawley ; Substantia Nigra/*pathology

OBJECTIVETo explore the mechanism of acupuncture in treatment of Parkinson's disease.

METHODSFifty Wistar rats were randomly divided into a normal control group, a sham-operation control group, a model group, a Fengfu-Taichong group and a Shuanggu Yitong group. The hemilateral rotation Parkinson's disease model was prepared by micro-injection of 6-hydroxyl-dopamine into the right striatum. Effects of acupuncture at "Fengfu" (GV 16), "Taichong" (LR 3) hy Shoanggu Yitong needling method on proliferation and differentiation of nerve stem cells in the Parkinson's disease model rat were compared. Proliferation and numher changes of the nerve stem cells in the suhstantia nigra and the striatum were investigated with immunohistochemical method, and the number of nerve stem cells transforming neurons were observed with immunohistochemical double-labeling method.

RESULTSIn the two acupuncture groups, the proliferative cells in the substantia nigra and thestriatum of the destroyed side increased significantly (P < 0.01), and the number of nerve stem cells and the number of transformed neurons in the destroyed side of the substantia nigra and the striatum increased significantly only in the Shuanggu Yitong group (P < 0.01).

CONCLUSIONShuanggu Yitong needling method can induce proliferation and differentiation of nerve stem cells in the substantia nigra and the striatum regions in the Parkinson's disease model rat.

Acupuncture Therapy ; methods ; Animals ; Bromodeoxyuridine ; metabolism ; Cell Differentiation ; Cell Proliferation ; Corpus Striatum ; pathology ; Male ; Neurons ; cytology ; Parkinson Disease ; therapy ; Rats ; Rats, Wistar ; Stem Cells ; cytology ; Substantia Nigra ; pathology

In order to investigate the neurotoxicity of lipopolysaccharide (LPS) on the dopaminergic neurons of substantia nigra and the pathogenesis of Parkinson disease, LPS was stereotaxically infused into substantia nigra (SN). At different dosages and different time points with 5 microg LPS, the damage of the dopaminergic neurons in SN was observed by using tyrosine-hydroxylase (TH) immunohistochemical staining. The results showed that 14 days after injection of 0.1 microg to 10 microg LPS into the rat SN, TH-positive (TH+) neurons in the SN were decreased by 5%, 15%, 20%, 45 %, 96% and 99% respectively. After injection of 5 microg LPS, as compared with the control groups, TH+ neurons began to decrease at 3rd day and obviously decrease at 14th day, only 5% of total cells, and almost disappeared 30 days later. The results suggested that LPS could induce the degeneration of dopaminergic neurons in the SN in a dose- and time-dependent manner.
Animals ; Dopamine ; metabolism ; Dose-Response Relationship, Drug ; Female ; Lipopolysaccharides ; toxicity ; Nerve Degeneration ; Neurons ; pathology ; Parkinson Disease, Secondary ; chemically induced ; Random Allocation ; Rats ; Rats, Sprague-Dawley ; Substantia Nigra ; pathology

To study the effects of 6-hydroxydopamine (6-OHDA) and reduced glutathione (GSH) on the nigral dopaminergic neurons in brain slices in vitro, immolunohistochemical technique was used to observe the changes of TH-stained neurons, including cell bodies and the dendrites, in the substantia nigra (SN) of midbrain slices of rats after incubation for 1 h in the presence of GSH 15 min before and during the period of incubation with 6-OHDA. The results showed that cell bodies remained intact but dendrites were fragmented and truncated after treatment with 6-OHDA. The antioxidant GSH alone did not significantly affect the dendrites of SN neurons but prevented 6-O-HDA-induced damage of dendrites. It was concluded that glutathione may prevent 6-OHDA-induced dopaminergic neurodegeneration and play a protective role in dopaminergic neurons.
Animals ; Glutathione ; therapeutic use ; Male ; Neurons ; pathology ; Oxidopamine ; Parkinson Disease, Secondary ; chemically induced ; drug therapy ; Random Allocation ; Rats ; Rats, Sprague-Dawley ; Substantia Nigra ; pathology ; Tyrosine 3-Monooxygenase ; metabolism

Objective: To observe the dynamic changes of brainstem locus coeruleus (LC) damage in Parkinson' s disease (PD) -like mice by paraquat (PQ) . Methods: In October 2019, 36 male C57BL/6 mice were randomly divided into the exposure group and the control group, with 18 mice in each group. The mice in the exposure group were given intraperitoneal injection of 15 mg/kg PQ, and the mice in the control group were given intraperitoneal injection of 0.9% saline, twice a week for 8 weeks. Neurobehavioral changes (pole climbing test, swimming test, open field test, tail hanging test, high plus maze test and water maze test) were observed at 4 weeks, 6 weeks and 8 weeks, respectively, and the changes of motor ability, emotion and cognitive function were evaluated. The brain tissue of mice were taken and stained with Hematoxylin-Eosin (HE) to observe the pathological changes of LC. Nissl staining was used to detect the changes of neuronal Nissl bodies in LC. Immunohistochemistry (IHC) staining was used to detect the expression of neuron nuclear antigen (NeuN) , dopamine (DA) neurons and norepinephrine (NE) neuron markers tyrosine hydroxylase (TH) , α-synuclein (α-syn) in substantia nigra (SN) and LC. The expression levels of NeuN, TH and α-syn in the midbrain and brainstem were detected by Western blotting. TUNEL staining was used to detect neuronal apoptosis in LC. Results: Compared with the 4th week of PQ exposure group, the time of pole climbing and swimming immobility were gradually increased, the ratio of open arm residence time of high plus maze test and the number of times of the platform and the residence time of platform quadrant in water maze test were gradually decreased (P<0.05) in the exposure group with the progress of exposure time. The results of HE and Nissl staining showed that the neurons in LC gradually arranged loosely, the nucleus were deeply stained, the cytoplasm was pyknosis, and the number of Nissl bodies gradually decreased (P<0.05) in the exposure group with the progress of exposure time. IHC results showed that the number of NeuN and TH positive cells in SN and LC of mice were gradually decreased, and the positive expression of α-syn was gradually increased (P<0.05) in the exposure group with the progress of exposure time. Western blotting results showed that the expression levels of NeuN and TH in the midbrain and brainstem were gradually decreased, and the expression level of α-syn was gradually increased (P<0.05) in the exposure group with the progress of exposure time. TUNEL staining showed that the apoptosis rates of neurons in LC were gradually increased (P<0.05) in the exposure group with the progress of exposure time. Conclusion: PQ induces progressive damage in the LC area of PD-like mice, which may be caused by the abnormal accumulation of pathological α-syn in the LC area.
Animals ; Dopaminergic Neurons ; Locus Coeruleus/pathology* ; Male ; Mice ; Mice, Inbred C57BL ; Paraquat/toxicity* ; Parkinson Disease/metabolism* ; Substantia Nigra ; Tyrosine 3-Monooxygenase/metabolism*

BACKGROUNDParkinson's disease (PD) is a common neurodegenerative disease, which occurs mainly in the elderly. Recent studies have demonstrated that apoptosis plays an important role in the occurrence and development of PD. Subthalamic nucleus deep brain stimulation (STN-DBS) has been recognized as an effective treatment for PD. Recent clinical observations have shown that STN-DBS was able to delay early PD progression, and experiments in animal models have also demonstrated a protective effect of STN-DBS on neurons. However, the correlation between the neuron-protective effect of STN-DBS and the progression of substantia nigra pars compacta (SNc) neuronal apoptosis is still unknown. The aim of this study was to investigate the protective effect and potential mechanism of STN-DBS on SNc neurons in PD rats.

METHODSAfter the establishment of a PD rat model by unilateral/2-point injection of 6-hydroxydopamine in the medial forebrain bundle of the brain, DBS by implanting electrodes in the STN was administered. Behavioral changes were observed, and morphological changes of SNc neurons were analyzed by Nissl staining and DNA in situ end-labeling. Through extracellular recording of single neuron discharges and microelectrophoresis, the causes of and changes in SNc excitability during STN-DBS were analyzed, and the protective effect and potential mechanism of action of STN-DBS on SNc neurons in PD rats was investigated.

RESULTSSNc neuron apoptosis was significantly decreased (P < 0.05) in the stimulation group, compared with the sham stimulation PD group. Spontaneous discharges of SNc neurons were observed in normal rats and PD model rats, and the mean frequency of spontaneous discharges of SNc neurons in normal rats ((40.65 ± 11.08) Hz) was higher than that of residual SNc neurons in PD rats ((36.71 ± 9.23) Hz). Electrical stimulation of the STN in rats was associated with elevated excitation in unilateral SNc neurons. However, administering the gamma-aminobutyric acid receptor blocker, bicuculline significantly reduced SNc neuron excitation, but the change in SNc neuron excitation was not present when MK801, a glutamate receptor blocker, was administered.

CONCLUSIONSHigh-frequency stimulation of the STN has a protective effect on SNc neurons in PD rats. The possible molecular mechanism may be related to changes in the distribution and metabolism of neurotransmitters in the SNc region.

Animals ; Deep Brain Stimulation ; methods ; Disease Models, Animal ; Male ; Neurons ; cytology ; metabolism ; Parkinson Disease ; pathology ; therapy ; Rats ; Rats, Sprague-Dawley ; Substantia Nigra ; cytology

Parkinson's disease (PD) is characterized pathologically by the relatively preferential loss of dopaminergic neurons with resultant depletion of striatal dopamine and presence of Lewy bodies mainly composed by alpha-synuclein (alpha-SYN) in the remaining neurons in the substantia nigra. A lot of evidence suggests that the aggregation of alpha-SYN play an essential role in the pathogenesis of PD and formation of Lewy body. Increasing findings have implicated that some proteins, including parkin, synphilin-1,14-3-3, agrin and tau, interact with alpha-SYN and are involved in the abnormal aggregation of alpha-SYN.
Animals ; Carrier Proteins ; metabolism ; HSP70 Heat-Shock Proteins ; metabolism ; Humans ; Lewy Bodies ; metabolism ; pathology ; Nerve Tissue Proteins ; metabolism ; Parkinson Disease ; etiology ; metabolism ; Protein Interaction Domains and Motifs ; Substantia Nigra ; pathology ; alpha-Synuclein ; metabolism