Parkinson's disease (PD) is the second most common neurodegenerative disease, characterized by loss of dopaminergic (DA) neurons in the dense part of the substantia nigra (SNpc). Postmortem analysis of PD patients and experimental animal studies found that microglial cell activation and increased levels of pro-inflammatory factors were common features of PD brain tissue. At the same time, the invasion and accumulation of peripheric immune cells were detected in the brain of PD patients. In this paper, peripheral inflammation across the blood-brain barrier (BBB), the misfolded α-synuclein (α-syn)-induced microglial cell activation and intracerebral inflammation in PD are summarized, providing potential therapeutic measures for delaying the onset of PD.
Animals ; Blood-Brain Barrier ; Dopaminergic Neurons ; pathology ; Humans ; Inflammation ; pathology ; Microglia ; Parkinson Disease ; pathology ; Substantia Nigra ; pathology ; alpha-Synuclein

AIM AND METHODSUsing Strain C57/BL of COX-2 deficient mice, the effect of Cyclooxygenase-2 (COX-2) on dopaminergic neurons in substantia nigra of Parkinson's disease (PD) mice induced by intraperitoneal injections of MPTP-HCl were investigated by immunocytochemistry(ICC) .

RESULTSWe found that the mortality in COX-2 heterozygous mice is much lower than that in wild type mice (P < 0.01) after injection of MPTP (30 mg/kg/day). The result of semiquantitative immunocytochemical staining showed that the number of tyrosine hydroxylase (TH) immunoreactive neurons in the substantia nigra pars compacta (SNc) declined more significantly in MPTP-treated wild type mice than that in COX-2 heterozygotes mice (P < 0.01).

CONCLUSIONCOX-2 may be related with lesion of dopaminergic neurons in the SNc of PD.

Animals ; Cyclooxygenase 2 ; deficiency ; Male ; Mice ; Mice, Inbred C57BL ; Neurons ; pathology ; Parkinson Disease ; pathology ; Substantia Nigra ; pathology

OBJECTIVETo explore the possibility of electroacupuncture (EA) for prevention of the injury of dopaminergic neurons in the substantia nigra of the rat with Parkinson's disease.

METHODSWistar rats were randomly divided into a normal group, a model group, a sham-operation group and an EA group. 6-OH-DA was injected into right substantia nigra of the midbrain to made Parkinson's disease rat model with single side substantia nigra injury, and TH/TUNEL method and rotation behavior observation method were used to observe changes of rotation behavior and apoptosis of dopaminergic neurons in the substantia nigra after EA at "Taichong" (LR 3) and "Fengfu" (GV 16) for 3 d, 7 d and 14 d.

RESULTSThe rotation times/min were same at 3 d, 7 d and 14 d were the basically same in the model group, and at 14 d significantly decreased in the EA group (P<0.05); the rotation starting time at 7 d and 14 d in the model group were significantly longer than those in the EA group (P<0.05); the rotation lasting time at 3 d, 7 d and 14 d in the model group and the EA group were gradually shortened (P<0.01, or P<0.05), but at 7 d, 14 d in the model group were significantly longer than those in the EA group (P<0.05); the DA neuron apoptosis number in the model group were significantly higher than those in the normal group, with a very significant difference (P<0.01); the apoptosis number in the EA group tended to decrease, at 7 d and 14 d were significantly lower than that in the model group (P<0.05).

CONCLUSIONElectroacupuncture can effectively prevent from injury of dopaminergic neurons in the substantia nigra of the rat with Parkinson's disease.

Animals ; Apoptosis ; Behavior, Animal ; Electroacupuncture ; Female ; Male ; Parkinson Disease ; pathology ; psychology ; therapy ; Rats ; Rats, Wistar ; Rotation ; Substantia Nigra ; pathology

Parkinson's disease (PD) is a multifactorial disorder of the nervous system where a progressive loss of dopaminergic neurons exist. However, the pathogenesis of PD remains undefined, which becomes the main limitation for the development of clinical PD treatment. Demethylenetetrahydroberberine (DMTHB) is a novel derivative of natural product berberine. This study was aimed to explore the neuroprotective effects and pharmacological mechanism of DMTHB on Parkinson's disease using C57BL/6 mice. A PD model of mice was induced by administration of MPTP (20 mg·kg^-1) and probenecid (200 mg·kg^-1) twice per week for five weeks. The mice were administered with DMTHB daily by gavage at the dose of 5 and 50 mg·kg^-1 for one- week prophylactic treatment and five-week theraputic treatment. The therapeutic effects of DMTHB were evaluated by behavior tests (the open field, rotarod and pole tests), immunohistochemical staining of tyrosine hydroxylase (TH), Nissl staining and biochemical assays. The molecular mechanisms of DMTHB on the key biomarkers of PD pathological states were analyzed by Western blot (WB) and qRT-PCR. DMTHB treatment alleviated the behavioral disorder induced by MPTP-probenecid. Nissl staining and TH staining showed that the damage of dopaminergic neurons in the substantia nigra was remarkably suppressed by DMTHB treatment. Western blot results showed that the ratio of Bcl-2/Bax and TH increased, but the level of α-synuclein (α-syn) was remarkably reduced, which indicated that the apoptosis of dopaminergic neurons in mice was significantly reduced. The protein phosphorylation of p-PI3K, p-AKT and p-mTOR also increased about 2-fold, compared with the model group. Furthermore, qRT-PCR results demonstrated that the mRNA levels of pro-inflammatory cytokines, IL-1β and TNF-α, were reduced, but the level of anti-inflammatory cytokine IL-10 increased after DMTHB treatment. Finally, the cellular assay displayed that DMTHB was also a strong antioxidant to protect neuron cell line PC12 by scavenging ROS. In this study, we demonstrated DMTHB alleviates the behavioral disorder and protects dopaminergic neurons through multiple-target effects includubg anti-apoptotic, anti-inflammatory and antioxidant effects.
Animals ; Dopaminergic Neurons/pathology* ; Mice ; Mice, Inbred C57BL ; Parkinson Disease/pathology* ; Parkinsonian Disorders/chemically induced* ; Substantia Nigra

Changes in morphology, immunophenotypes and proliferative activity of neuroglia are key features in most forms of CNS pathology. We compared proliferative activity of neuroglial cells in response to two different types of brain injury induced by medial forebrain bundle (MFB) axotomy. In the cannula track where acute necrosis occurs due to mechanical lesion caused by cannula inserted to incise the MFB, many BrdU-immunoreactive (ir) cells appeared around the cannula track already at 1 day post-lesion (1 dpl). Their number significantly increased by 7 dpl and then decreased, but considerable number of BrdU-ir cells was still found at 14 dpl. Some of the BrdU-ir cells were double-labeled with either OX-42 or GFAP. This finding suggests that both microglia and astrocytes are activated and proliferate immediately after the mechanical damage, and the proliferative activity is maintained in a considerable number of these cells by 14 dpl. In general, the main cell type showing BrdU immunoreactivity was amoeboid microglia within the necrotic zone immediately surrounding the cannula track, and was astrocytes in the periphery of the necrotic zone more or less apart from the cannula track. Previously, we reported that MFB axotomy induces apoptosis of dopaminergic (DA) neurons in the substantia nigra (SN). In the SN where axotomized DA neurons undergo apoptosis, only a few BrdU-ir cells were found at 1 dpl. Their number increased gradually from 3 dpl and peaked at 7 dpl, then significantly reduced at 14 dpl. Most of them were double-labeled with OX -42-positive ramified microglia but not with GFAP. This data indicates that microglia but not astrocyte are the cell type that proliferate in response to apoptotic neuronal cell death, and their morphology and proliferative activity are different from those observed in the cannula track. Meanwhile, in the both cannula track and SN, some BrdU-ir cells were thought to be neither GFAP-positive nor OX-42-positive, and thus they were presumed to be infiltrated peripheral immune cells. These results demonstrate that different types of neuronal cell death are accompanied with different neurogilal proliferative activities.
Apoptosis ; Astrocytes ; Axotomy* ; Brain Injuries ; Bromodeoxyuridine ; Catheters ; Cell Death ; Medial Forebrain Bundle* ; Microglia ; Necrosis ; Neuroglia ; Neurons ; Pathology ; Substantia Nigra

It has been suggested that brain inflammation is important in aggravation of brain damage and/or that inflammation causes neurodegenerative diseases including Parkinson's disease (PD). Recently, systemic inflammation has also emerged as a risk factor for PD. In the present study, we evaluated how systemic inflammation induced by intravenous (iv) lipopolysaccharides (LPS) injection affected brain inflammation and neuronal damage in the rat. Interestingly, almost all brain inflammatory responses, including morphological activation of microglia, neutrophil infiltration, and mRNA/protein expression of inflammatory mediators, appeared within 4-8 h, and subsided within 1-3 days, in the substantia nigra (SN), where dopaminergic neurons are located. More importantly, however, dopaminergic neuronal loss was not detectable for up to 8 d after iv LPS injection. Together, these results indicate that acute induction of systemic inflammation causes brain inflammation, but this is not sufficiently toxic to induce neuronal injury.
Animals ; Astrocytes/pathology ; Cell Death ; Encephalitis/chemically induced/immunology/*pathology ; Injections, Intravenous ; Lipopolysaccharides/*pharmacology ; Male ; Microglia/pathology ; Neutrophil Infiltration ; Rats ; Rats, Sprague-Dawley ; Substantia Nigra/immunology/*pathology

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

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

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