Animal Models Of Parkinson's Disease Research Articles

The kainate receptor antagonist UBP310 but not single deletion of GluK1, GluK2, or GluK3 subunits, inhibits MPTP-induced degeneration in the mouse midbrain

The excitatory neurotransmitter glutamate is essential in basal ganglia motor circuits and has long been thought to contribute to cell death and degeneration in Parkinson's disease (PD). While previous research has shown a significant role of NMDA and AMPA receptors in both excitotoxicity and PD, the third class of ionotropic glutamate receptors, kainate receptors, have been less well studied. Given the expression of kainate receptor subunits GluK1-GluK3 in key PD-related brain regions, it has been suggested that GluK1-GluK3 may contribute to excitotoxic cell loss. Therefore the neuroprotective potential of the kainate receptor antagonist UBP310 in animal models of PD was investigated in this study. Stereological quantification revealed administration of UBP310 significantly increased survival of dopaminergic and total neuron populations in the substantia nigra pars compacta in the acute MPTP mouse model of PD. In contrast, UBP310 was unable to rescue MPTP-induced loss of dopamine levels or dopamine transporter expression in the striatum. Furthermore, deletion of GluK1, GluK2 or GluK3 had no effect on MPTP or UBP310-mediated effects across all measures. Interestingly, UBP310 did not attenuate cell loss in the midbrain induced by intrastriatal 6-OHDA toxicity. These results indicate UBP310 provides neuroprotection in the midbrain against MPTP neurotoxicity that is not dependent on specific kainate receptor subunits.

Downregulated lncRNA-SNHG1 enhances autophagy and prevents cell death through the miR-221/222 /p27/mTOR pathway in Parkinson's disease

Autophagy has been shown to be critically associated with the central mechanisms underlying Parkinson's disease (PD), while the mechanisms contributing to the imbalance of autophagy remain unclear. Small nucleolar RNA host gene 1 (SNHG1), a well-studied long noncoding RNA, has been reported to be significantly increased in PD. The potential biological functions of SNHG1 in the regulation of neuronal autophagy and cell death in PD, however, have not yet been completely elucidated. In this study, we examined the existence of regulatory networks involving SNHG1, the miR-221/222 cluster and the cyclin-dependent kinase inhibitor 1B (CDKN1B/p27)/mammalian target of rapamycin (mTOR) signaling pathway in PD. We observed that SNHG1 expression was gradually upregulated in PD cellular and animal models. Furthermore, silencing SNHG1 promoted autophagy and prevented MPP+-induced cell death, similar to the overexpression of the miR-221/222 cluster. Mechanistically, SNHG1 competitively binds to the miR-221/222 cluster and indirectly regulates the expression of p27/mTOR. In conclusion, these results demonstrated that downregulation of SNHG1 attenuated MPP+-induced decreases in LC3-II (an autophagic marker) levels and cytotoxicity through the miR-221/222/p27/mTOR pathway, suggesting that SNHG1 may be a therapeutic target for neuroprotection and disease treatment in PD.

Evaluation of Betaine Neuroprotective Effects on 6-Hydroxydopamine-Induced hemi-Parkinsonism in Male Wistar Rats

BACKGROUND: Parkinson's disease (PD) is one of the prevalent debilitating neurodegenerative disor- ders. Accordingly, researchers are working on methods to modify PD progression. Previously, the neuro- protective effects of betaine, as a methyl donor agent in homocysteine metabolism, have been demonstrated in animal models of chronic cerebral hypoperfusion and memory deficits. OBJECTIVES: It was aimed to investigate the neuroprotective effects of betaine in an animal model of PD. METHODS: In male Wistar rats under two-week course of oral betaine administration (50, 100, and 200 mg/kg per day), the behavioral, biochemical, and histological evaluations were conducted one week follow- ing unilateral nigral 6-OHDA injection. RESUTLS: Betaine administration with dose of 200 mg/kg, one week before and after 6-OHDA lesioning, was associated with a meaningful reduction in the plasma levels of homocysteine (Hcy) in comparison with the control and sham groups (P < 0.05). Our evaluations revealed a remarkable improvement in motor asymmetry induced by apomorphine in the rats under treatment of betaine 200 mg/kg. Moreover, in this group, a significant decrease of malondyaldehyde (MDA) concentrations was detected in the brain tissues, as well as a significantly diminished neuronal cell loss (percent) in substantia nigra pars compacta (P < 0.05). The results of 50 and 100 mg/kg betaine groups were not significant. CONCLUSIONS: Altogether, our findings indicate the antioxidant neuroprotective effects of betaine in this animal model of PD and it is in concordance with betaine properties in decreasing the plasma levels and possible neurotoxic effects of Hcy.

Anti-inflammatory and neuroprotective effects of PDE-10 inhibitor in neuroinflammation and Parkinson's disease animal models

Anti-inflammatory and neuroprotective effects of PDE-10 inhibitor in neuroinflammation and Parkinson's disease animal models

Gami-Chunggan Formula Prevents Motor Dysfunction in MPTP/p-Induced and A53T α-Synuclein Overexpressed Parkinson's Disease Mouse Model Though DJ-1 and BDNF Expression.

The Gami–Chunggan formula (GCF) is a modification of the Chunggan (CG) decoction, which has been used to treat movement disorders such as Parkinson’s disease (PD) in Traditional East Asian Medicine. To evaluate the neuroprotective effects of GCF in chronic PD animal models, we used either a 5-week treatment of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine with probenecid (MPTP/p) or the α-synuclein A53T overexpressed PD mouse model. C57BL/6 mice were treated with MPTP, in combination with probenecid, for 5 weeks. GCF was administered simultaneously with MPTP injection for 38 days. The A53T α-synuclein overexpressed mice were also fed with GCF for 60 days. Using behavioral readouts and western blot analyses, it was observed that GCF prevents motor dysfunction in the MPTP/p-induced and A53T α-synuclein overexpressed mice. Moreover, GCF inhibited the reduction of dopaminergic neurons in the substantia nigra (SN) and fibers in the striatum (ST) against MPTP/p challenge. The expression of DJ-1 was increased but that of α-synuclein was decreased in the SN of PD-like brains by GCF administration. In vitro experiments also showed that GCF inhibited 6-OHDA-induced neurotoxicity in SH-SY5Y neuroblastoma cell lines and that it did so to a greater degree than CG. Furthermore, GCF induced BDNF expression through phosphorylation of Akt, ERK, CREB, and AMPK in the SN of PD-like brains. Therefore, use of the herbal medicine GCF offers a potential remedy for neurodegenerative disorders, including Parkinson’s disease.

SINEUP Non-coding RNA Targeting GDNF Rescues Motor Deficits and Neurodegeneration in a Mouse Model of Parkinson's Disease.

Glial cell-derived neurotrophic factor (GDNF) has a potent action in promoting the survival of dopamine (DA) neurons. Several studies indicate that increasing GDNF levels may be beneficial for the treatment of Parkinson’s disease (PD) by reducing neurodegeneration of DA neurons. Despite a plethora of preclinical studies showing GDNF efficacy in PD animal models, its application in humans remains questionable for its poor efficacy and side effects due to its uncontrolled, ectopic expression. Here we took advantage of SINEUPs, a new class of antisense long non-coding RNA, that promote translation of partially overlapping sense protein-coding mRNAs with no effects on their mRNA levels. By synthesizing a SINEUP targeting Gdnf mRNA, we were able to increase endogenous GDNF protein levels by about 2-fold. Adeno-associated virus (AAV)9-mediated delivery in the striatum of wild-type (WT) mice led to an increase of endogenous GDNF protein for at least 6 months and the potentiation of the DA system’s functions while showing no side effects. Furthermore, SINEUP-GDNF was able to ameliorate motor deficits and neurodegeneration of DA neurons in a PD neurochemical mouse model. Our data indicate that SINEUP-GDNF could represent a new strategy to increase endogenous GDNF protein levels in a more physiological manner for therapeutic treatments of PD.

MPTP-induced dopaminergic neurotoxicity in mouse brain is attenuated after subsequent intranasal administration of (R)-ketamine: a role of TrkB signaling.

Parkinson's disease (PD) is characterized as a chronic and progressive neurodegenerative disorder, and PD patients have non-motor features such as depressive symptoms. Although there are several available medications to treat PD symptoms, these medications do not prevent the progression of the disease. (R)-ketamine has greater and longer-lasting antidepressant effects than (S)-ketamine in animal models of depression. This study was undertaken to investigate whether two enantiomers of ketamine and its metabolite norketamine shows neuroprotective effects in an animal model of PD. Effects of (R)-ketamine, (S)-ketamine, and their metabolites on MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine)-induced reduction of dopamine transporter (DAT) and tyrosine hydroxylase (TH) in the mouse striatum and substantia nigra (SNr) were examined. MPTP-induced reduction of DAT in the striatum was attenuated by subsequent repeated intranasal administration of both enantiomers of ketamine although (R)-ketamine was more potent than (S)-ketamine. MPTP-induced reduction of TH in the striatum and SNr was attenuated by administration of (R)-ketamine, but not (S)-ketamine. Interestingly, MPTP-induced reduction of DAT in the striatum was also attenuated by a single intranasal administration of (R)-ketamine. In contrast, MPTP-induced reduction of DAT in the striatum was not attenuated by repeated intranasal administration of two enantiomers of norketamine. Furthermore, the pretreatment with TrkB antagonist ANA-12 significantly blocked the neuroprotective effects of (R)-ketamine in the MPTP-induced reduction of DAT in the striatum. These findings suggest that (R)-ketamine can protect against MPTP-induced neurotoxicity in the mouse brain via TrkB activation. Therefore, (R)-ketamine could represent a therapeutic drug for neurodegenerative disorders such as PD.

Sex-specific neuroprotection by inhibition of the Y-chromosome gene, SRY, in experimental Parkinson’s disease

Parkinson's disease (PD) is a debilitating neurodegenerative disorder caused by the loss of midbrain dopamine (DA) neurons. While the cause of DA cell loss in PD is unknown, male sex is a strong risk factor. Aside from the protective actions of sex hormones in females, emerging evidence suggests that sex-chromosome genes contribute to the male bias in PD. We previously showed that the Y-chromosome gene, SRY, directly regulates adult brain function in males independent of gonadal hormone influence. SRY protein colocalizes with DA neurons in the male substantia nigra, where it regulates DA biosynthesis and voluntary movement. Here we demonstrate that nigral SRY expression is highly and persistently up-regulated in animal and human cell culture models of PD. Remarkably, lowering nigral SRY expression with antisense oligonucleotides in male rats diminished motor deficits and nigral DA cell loss in 6-hydroxydopamine (6-OHDA)-induced and rotenone-induced rat models of PD. The protective effect of the SRY antisense oligonucleotides was associated with male-specific attenuation of DNA damage, mitochondrial degradation, and neuroinflammation in the toxin-induced rat models of PD. Moreover, reducing nigral SRY expression diminished or removed the male bias in nigrostriatal degeneration, mitochondrial degradation, DNA damage, and neuroinflammation in the 6-OHDA rat model of PD, suggesting that SRY directly contributes to the sex differences in PD. These findings demonstrate that SRY directs a previously unrecognized male-specific mechanism of DA cell death and suggests that suppressing nigral Sry synthesis represents a sex-specific strategy to slow or prevent DA cell loss in PD.

Potential Benefits of Nobiletin, A Citrus Flavonoid, against Alzheimer's Disease and Parkinson's Disease.

Alzheimer’s disease (AD), which is characterized by the presence of amyloid-β (Aβ) plaques and neurofibrillary tangles, accompanied by neurodegeneration, is the most common form of age-related neurodegenerative disease. Parkinson’s disease (PD) is the second most common neurodegenerative disease after AD, and is characterized by early prominent loss of dopaminergic neurons in the substantia nigra pars compacta. As currently available treatments are not able to significantly alter the progression of these diseases, successful therapeutic and preventive interventions are strongly needed. In the course of our survey of substances from natural resources having anti-dementia and neuroprotective activity, we found nobiletin, a polymethoxylated flavone from the peel of Citrus depressa. Nobiletin improved cognitive deficits and the pathological features of AD, such as Aβ pathology, hyperphosphorylation of tau, and oxidative stress, in animal models of AD. In addition, nobiletin improved motor and cognitive deficits in PD animal models. These observations suggest that nobiletin has the potential to become a novel drug for the treatment and prevention of neurodegenerative diseases such as AD and PD.

Longitudinal PET Imaging of α7 Nicotinic Acetylcholine Receptors with [18F]ASEM in a Rat Model of Parkinson's Disease.

The nicotinic acetylcholine alpha-7 receptors (α7R) are involved in a number of neuropsychiatric and neurodegenerative brain disorders such as Parkinson's disease (PD). However, their specific pathophysiologic roles are still unclear. In this context, we studied the evolution of these receptors in vivo by positron emission tomography (PET) imaging using the recently developed tracer 3-(1,4-diazabicyclo[3.2.2]nonan-4-yl)-6-[18F]fluorodibenzo[b,d]thiophene-5,5-dioxide) in a rat model mimicking early stages of PD. PET imaging of α7R was performed at 3, 7, and 14days following a partial striatal unilateral lesion with 6-hydroxydopamine in adult rats. After the last imaging experiments, the status of nigro-striatal dopamine neurons as well as different markers of neuroinflammation was evaluated on brain sections by autoradiographic and immunofluorescent experiments. We showed an early and transitory rise in α7R expression in the lesioned striatum and substantia nigra, followed by over-expression of several gliosis activation markers in these regions of interest. These findings support a longitudinally follow-up of α7R in animal models of PD and highlight the requirement to use a potential neuroprotective approach through α7R ligands at the early stages of PD.

Trabecular meshwork mesenchymal stem cell transplantation improve motor symptoms of parkinsonian rat model

Stem cell transplantation is a new therapeutic strategy in the treatment of neurodegenerative disorders such as Parkinson's disease (PD). Therefore, in this study, the therapeutic effects of Trabecular Meshwork Mesenchymal Stem Cells (TM-MSCs) transplantation, as a new source of mesenchymal stem cells, were evaluated in the animal model of PD.After the development and confirmation of hemi-parkinsonian rats by administration of 6-hydroxy dopamine (6-OHDA) and apomorphine-induced rotation test, green fluorescent protein (GFP) labeled TM-MSCs (normal and induced cells) were transplanted in the striatum of rats. Next, the rotation test, rotarod test, open field, passive avoidance memory tests and immunohistochemistry for tyrosine hydroxylase (TH) were done.The results showed that the number of turns significantly decreased and the improvement of motor performance was achieved after cell transplantation. However, there was no significant difference in passive avoidance memory of animals documented by shuttle box test. The number of GFP- labeled cells expressing TH significantly is increased compared to the vehicle group.Collectively, it seems that TM-MSCs and induced TM-MSCs cell transplantation have positive effects on some aspects of the animal model of PD. Other studies may reveal the potentially positive aspects of these cells in the laboratory and clinical studies.

Potential of Prebiotic Butyrogenic Fibers in Parkinson's Disease.

Parkinson's Disease (PD) is a neurodegenerative disorder characterized by loss of dopaminergic neurons in the substantia nigra. Recent evidence supports the involvement of the gastrointestinal tract in PD pathogenesis, including alterations in microbiota and intestinal permeability. Apart from being the preferred energy source for colonic epithelial cells, butyrate is involved in anti-inflammatory, enteroendocrine and epigenetic mechanisms that influence colonic and systemic health, including brain function. A few studies using oral administration of sodium butyrate indicate beneficial effects in PD animal models; however, prebiotic fibers that generate butyrate locally in the gut may be more effective. The design and selection of butyrogenic prebiotic fibers would allow preclinical studies to evaluate how gut-derived butyrate could affect PD pathophysiology. This review describes potential benefits of increasing gut butyrate production in PD through a prebiotic approach. Moreover, physico-chemical features of prebiotic fibers that target butyrogenic colonic bacteria are discussed.

Differential impairment of short working and spatial memories in a rat model of progressive Parkinson’s disease onset: A focus on the prodromal stage

Studying the non-motor disorders of the prodromal phase of Parkinson's disease (PD) is of great importance because of their negative impact on patient's quality of life. Classical neurotoxic animal models of PD generally unable the exploration of the progression of the non-motor phase of the prodromal stage of the disease. The aim of this study is to assess the evolution of two types of memory alteration namely; short working and spatial memories at different stages of the prodromal phase of a rat model of PD, using repetitive reserpine administration at low dose. The study was carried out in rat with repeated i.p reserpine administration (0.2 mg/kg/day) during 13 days. Working memory was assessed by the Novel Object Recognition test (NOR) and the T-maze, while spatial memory was assessed by Morris Water maze (MWM) at to stages (7days and 13days) of prodromal phase of the disease. By means of immunohistochemistry, the serotonergic innervation of the Baso-Lateral Amygdala nucleus (BLA) as well as the morphological changes of astroglia within hippocampus (using anti-GFAP marker) were examined at the latest stage (13days) of the disease. Our data show a differential deterioration of short-term working memory without the long-term spatial memory being changed which was accompanied by a significant decrease in serotonin innervation of the BLA and a striking change in both density and morphology of the astrocyte at the level of the hippocampus. The present study has brought evidence of an early deficit of short working memory rather than spatial memory deficit which seems to be intact even at the latest stage of the prodromal phase of PD. Such deficit could arise from the loss of 5-HT innervation in BLA and/or the astroglial morpho-functional changes within the hippocampus leading to possible neurophysiological disturbances of the different neighboring neuronal populations involved in short working memory.

Acrolein-mediated alpha-synuclein pathology involvement in the early post-injury pathogenesis of mild blast-induced Parkinsonian neurodegeneration

Survivors of blast-induced traumatic brain injury (bTBI) have increased susceptibility to Parkinson's disease (PD), characterized by α-synuclein aggregation and the progressive degeneration of nigrostriatal dopaminergic neurons. Using an established bTBI rat model, we evaluated the changes of α-synuclein and tyrosine hydroxylase (TH), known hallmarks of PD, and acrolein, a reactive aldehyde and marker of oxidative stress, with the aim of revealing key pathways leading to PD post-bTBI. Indicated in both animal models of PD and TBI, acrolein is likely a point of pathogenic convergence. Here we show that after a single mild bTBI, acrolein is elevated up to a week, systemically in urine, and in whole brain tissue, specifically the substantia nigra and striatum. Acrolein elevation is accompanied by heightened α-synuclein oligomerization, dopaminergic dysregulation, and acrolein/α-synuclein interaction in the same brain regions. We further show that acrolein can directly modify and oligomerize α-synuclein in vitro. Taken together, our data suggests acrolein likely plays an important role in inducing PD pathology following bTBI by encouraging α-synuclein aggregation. These results are expected to advance our understanding of the long-term post-bTBI pathological changes leading to the development of PD, and suggest intervention targets to curtail such pathology.

Macrophage Migration Inhibitory Factor Mediates Neuroprotective Effects by Regulating Inflammation, Apoptosis and Autophagy in Parkinson's Disease

The influence of neuroinflammation in the development and progression of Parkinson's disease (PD) remains unknown. Macrophage migration inhibitory factor (MIF) is a multipotent and key cytokine involved in the pathogenesis of acute and chronic inflammatory and immune disorders. The aim of this study was to investigate the neuroprotective effects mediated by MIF in PD. Cellular apoptosis was measured by RT-qPCR analysis, fluorescence-activated cell sorting (FACS) analysis and western blotting. JC-1 staining was used to analyze the mitochondrial membrane potential (MMP). The formation of autophagosomes was detected by western blot analysis. Autophagic flux was assessed by tandem mRFP-GFP-LC3 fluorescence microscopy. Expression of MIF, cleaved-PARP and LC3B-II was increased significantly in both acute and chronic PD animal models. MIF was positively associated with IL-10 (P < 0.001), but inversely with TNF-α (P < 0.05). The PD cells (1 mM MPP+ treated group) showed an increase in early-apoptotic cells by FACS. Upregulating MIF expression resulted in a lower concentration of cleaved-PARP than the control group (P < 0.001). The MMP was higher in the MIF upregulated group than in the MIF knockdown group (P < 0.001). Upregulating MIF expression resulted in a higher concentration of LC3B-II than the control group (P < 0.001). Finally, LC3 puncta were markedly increased in the MIF upregulated group and in the MIF + MPP+ group. This study indicates that MIF mediates a neuroprotective effect via suppressing inflammatory responses, inhibiting apoptosis and inducing autophagy in PD.

An Infection Hypothesis of Parkinson’s Disease

Parkinson’s disease (PD) is a multifactorial progressive neurodegenerative disease characterized by predominant degeneration of dopaminergic neurons in the substantia nigra. Neuroinflammation is one of the key components of the pathogenesis of PD, though the mechanisms initiating the inflammatory process and the triggers launching the irreversible neuroinflammatory process in patients with PD thus far remain unstudied. The present review addresses the role of infection-related factors in the etiology of PD. We evaluate the question of whether PD is the result of prior viral or bacterial infections due to the action of endotoxins on brain cells initiating the development of the inflammatory process in the CNS. Some cellular and animal models of PD of the infection type are presented and the molecular mechanisms of the development of neuroinflammation and neurodegeneration in these models are laid out. The final part of the review contains an analysis of reports, including those from the authors of this review, on the creation of valid models of the clinical and preclinical stages of PD in animals based on the proteasome inhibitor lactacystin, a metabolite of the soil bacterium Streptomyces sp.

Classic animal models of Parkinson's disease: a historical perspective.

The quest to better understand the pathophysiology of Parkinson's disease (PD) and to find new therapies to provide greater relief to affected patients continues. The use of animal models of PD has been invaluable in the process. Here, we review, through a historical lens, some of the contribution of the 6-hydroxydopamine-lesioned rat and of the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-lesioned nonhuman primate, in refining our understanding of PD and its treatment-related complications. We examine the mechanisms underlying the toxicity of 6-hydroxydopamine and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, and then explore some of the advances at the molecular, pharmacological, electrophysiological and surgical levels made while experimenting on these animal models. We also discuss behavioural testing that can be performed with these animal models and highlight some of their limitations.

Co-Administration of Aspirin and L-DOPA Against 6-OHDA-Induced Dopamine Neurotoxicity

Background: At present, L-DOPA remained the gold standard therapy for motor symptoms of Parkinson's disease (PD) patients. However, prolonged administration of L-DOPA led to the development of dyskinesia. Aspirin, a non-steroidal anti-inflammatory drug (NSAID), has been widely used to relieve pain and inflammation. Recent studies indicated that aspirin produced neuroprotection against DA neuronal loss in PD animal model. Methods: Rats lesioned with 6-hydroxydopamine (6-OHDA) in substantia nigra were employed and treated with L-DOPA and aspirin for 21 days. The movement disorders elicited by L-DOPA were determined by the abnormal involuntary movements (AIM) scores analysis. Finding: In 6-OHDA lesioned rat PD model, aspirin or L-DOPA evoked DA neuroprotection 7 days after treatment. Co-administration of aspirin and L-DOPA still conferred neuroprotection. In addition, aspirin attenuated the development of LID, as evidenced by the decreased AIM scores without interfering with L-DOPA efficacy 21 days after treatment. Furthermore, aspirin combined with L-DOPA inhibited microglia and astroglia activation and the subsequent neuroinflammatory responses. Importantly, aspirin didn't produce side effects during this neuroprotection. Interpretation: These results suggest that aspirin might have beneficial potential to attenuate L-DOPA efficacy and alleviate LID in PD. Funding Statement: National Natural Science Foundation of China (No. 81760658), foundation for High-level Innovative Talents of Guizhou Province (No. 20164027), Shijingshan's Tutor Studio of Pharmacology (No. GZS-201607), Innovation Research Group project of Education Department of Guizhou Province (No. 2016038), foundation for Excellent Young Talents of Zunyi Medical University (No.201603). Declaration of Interests: The authors have declared no any conflict of interests. Ethics Approval Statement: All animal experiments were performed in accordance with Chinese Guidelines of Animal Care and Welfare, and the present study was approved by the Animal Care and Use Committee of Zunyi Medical University (Zunyi, China).

Anxiety-like behavior induced by 6-OHDA animal model of Parkinson’s disease may be related to a dysregulation of neurotransmitter systems in brain areas related to anxiety

Anxiety in Parkinson’s disease may represent a physiological reaction to the development of other symptoms during disease progression. However, evidence suggests that the incidence of anxiety disorders in Parkinson’s disease may be related to neurochemical changes. The present study addresses the question whether dopamine, noradrenaline and serotonin levels in brain structures related to Parkinson’s disease and anxiety are responsible for anxiety-like behavior by using an animal model of parkinsonism based in the bilateral injection of the neurotoxin 6-hydroxydopamine (6-OHDA) in the substantia nigra pars compacta. For this, one day after the injection of 6-OHDA, the animals exhibited hypolocomotion and a lower frequency of rearings in the open field test, which was spontaneously reversed on the last day of motor assessment (day 21). The 6-OHDA injection also induced anxiety-like behavior in the elevated plus maze and contextual fear conditioning test (day 21 and 24, respectively). Neurochemical analysis showed a reduction of dopamine and norepinephrine levels in the striatum, prefrontal cortex, and amygdala. In addition, while the serotonin levels were reduced in the striatum and prefrontal cortex, it was increased in the amygdala. The present study indicates that the model of 6-OHDA-induced parkinsonism in rats induced an anxiety-like behavior that may be related to a dysregulation of neurotransmitter systems in brain areas involved with anxiety such as the amygdala, prefrontal cortex and striatum.

FTY720 Inhibits MPP+-Induced Microglial Activation by Affecting NLRP3 Inflammasome Activation.

Parkinson's disease (PD) is characterized by the degeneration of dopaminergic neurons and excessive microglial activation in the substantia nigra pars compacta (SNpc). In the present study, we aimed to demonstrate the therapeutic effectiveness of the potent sphingosine-1-phosphate receptor antagonist fingolimod (FTY720) in an animal model of PD induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), and to identify the potential mechanisms underlying these therapeutic effects. C57BL/6J mice were orally administered FTY720 before subcutaneous injection of MPTP. Open-field and rotarod tests were performed to determine the therapeutic effect of FTY720. The damage to dopaminergic neurons and the production of monoamine neurotransmitters were assessed using immunohistochemistry, high-performance liquid chromatography, and flow cytometry. Immunofluorescence (CD68- positive) and enzyme-linked immunosorbent assay were used to analyze the activation of microglia, and the levels of activated signaling molecules were measured using Western blotting. Our findings indicated that FTY720 significantly attenuated MPTP-induced behavioral deficits, reduced the loss of dopaminergic neurons, and increased dopamine release. FTY720 directly inhibited MPTP-induced microglial activation in the SNpc, suppressed the production of interleukin (IL)-6, IL-1β, and tumor necrosis factor-α in BV-2 microglial cells treated with 1-methyl-4-phenylpyridinium (MPP+), and subsequently decreased apoptosis in SH-SY5Y neuroblastoma cells. Moreover, in MPP+-treated BV-2 cells and primary microglia, FTY720 treatment significantly attenuated the increases in the phosphorylation of PI3K/AKT/GSK-3β, reduced ROS generation and p65 activation, and also inhibited the activation of NLRP3 inflammasome and caspase-1. In conclusion, FTY720 may reduce PD progression by inhibiting NLRP3 inflammasome activation via its effects on ROS generation and p65 activation in microglia. These findings provide novel insights into the mechanisms underlying the therapeutic effects of FTY720, suggesting its potential as a novel therapeutic strategy against PD. Graphical Abstract FTY720 may reduce ROS production by inhibiting the PI3K/AKT/GSK-3β signaling pathway, while at the same time reducing p65 phosphorylation, thus decreasing NLRP3 inflammasome activation through these two pathways, ultimately reducing microglia activation-induced neuronal damage.