Behavioral phenotyping of the MPTP mouse model of Parkinson's disease

Nervonic acid protects against oligodendrocytes injury following chronic cerebral hypoperfusion in mice

Chronic cerebral hypoperfusion (CCH) has been acknowledged as a potential contributor to cognitive dysfunction and brain injury, causing progressive demyelination of white matter, oligodendrocytes apoptosis and microglia activation. Nervonic acid (NA), a naturally occurring fatty acid with various pharmacological effects, has been found to alleviate neurodegeneration. Nonetheless, evidence is still lacking on whether NA can protect against neurological dysfunction resulting from CCH. To induce CCH in mice, we employed the right unilateral common carotid artery occlusion (rUCCAO) method, followed by oral administration of NA daily for 28 days after the onset of hypoperfusion. We found that NA ameliorated cognitive function, as evidenced by improved performance of NA-treated mice in both novel object recognition test and Morris water maze test. Moreover, NA mitigated demyelination and loss of oligodendrocytes in the corpus callosum and hippocampus of rUCCAO-treated mice, and prevented oligodendrocyte apoptosis. Furthermore, NA protected primary cultured murine oligodendrocytes against oxygen-glucose deprivation (OGD)-induced cell death in a concentration-dependent manner. These findings indicated that NA promotes oligodendrocyte maturation both in vivo and in vitro. Our findings suggest that NA offers protective effects against cerebral hypoperfusion, highlighting its potential as a promising treatment for CCH and related neurological disorders.

Lactoferrin/lactoferrin receptor: Neurodegenerative or neuroprotective in Parkinson's disease?

Lactoferrin (Lf) is a multifunctional protein in the transferrin family. It is involved in many physiological functions, including the regulation of iron absorption and immune response. It also has antibacterial, antiviral, anti-inflammatory, anticancer and antioxidant capabilities under pathophysiological conditions. The mammalian lactoferrin receptor (LfR) plays a key role in mediating multiple functions of Lf. Studies have shown that Lf/LfR is abnormally expressed in the brain of Parkinson's disease, and the excessive accumulation of iron in the brain caused by the overexpression of Lf and LfR is considered to be one of the initial causes of the degeneration of dopaminergic neurons in Parkinson's disease. On the other hand, a number of recent studies have reported that Lf/LfR has a significant neuroprotective effect on Parkinson's disease. In other words, it seems paradoxical that Lf/LfR has both neurodegenerative and neuroprotective effects in Parkinson's disease. This article focuses on recent advances in the possible mechanisms of the neurodegenerative and neuroprotective effects of Lf/LfR in Parkinson's disease and discusses why Lf/LfR has a seemingly contradictory role in the development of Parkinson's disease. Based on the evidence obtained so far, we believed that Lf/LfR has a neuroprotective effect on Parkinson's disease, while as to whether the overexpressed Lf/LfR is the cause of the development of Parkinson's disease, the current evidence is insufficient and further investigation needed.

TAT-PPA1 protects against oxidative stress-induced loss of dopaminergic neurons

Parkinson's disease (PD) is a neurodegenerative disorder characterized by the progressive loss of dopaminergic neurons in the substantia nigra (SN) of the midbrain, resulting in severe motor impairments. Inorganic pyrophosphatase 1 (PPA1) plays a key role in various biological processes, and this study introduces a cell-penetrating PPA1 fusion protein (TAT-PPA1) to explore its transduction into cells and brain tissues. TAT-PPA1 effectively penetrates SH-SY5Y cells and the SN region of PD animal models without toxicity, exhibiting protective effects against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP-)-induced cell death. TAT-PPA1 revealed an inhibitory influence on the MAPK signaling pathway and MPTP-induced reactive oxygen species (ROS) production. TAT-PPA1 suppresses JNK, AKT, p53, ERK, and p38 phosphorylation, showcasing its multifaceted role in cell survival pathways. In the MPTP-induced PD animal model, TAT-PPA1 prevents dopaminergic cell death and enhances motor function. This study shows that TAT-PPA1 protects against oxidative stress and cell death in neurodegenerative diseases, suggesting potential as a PD treatment.

Different neurotoxicity and seeding activity between α-synuclein oligomers formed in plasma of patients with Parkinson's disease and multiple system atrophy

Previous studies have shown that α-synuclein (α-Syn) aggregates derived from the brains of patients with Parkinson's disease (PD) and multiple system atrophy (MSA) exhibit different phosphorylation, cytotoxicity, and seeding activity. However, the mechanism underlying the differences remains poorly understood. Here, recombinant human α-Syn was incubated in the plasma of patients with PD and MSA, and the oligomers formed in the plasma (PD-O-α-Syn and MSA-O-α-Syn) were purified and analyzed for their phosphorylation, cytotoxicity and seeding activity. In vitro assays revealed that both PD-O-α-Syn and MSA-O-α-Syn were phosphorylated at serine 129. However, the phosphorylation degree of MSA-O-α-Syn was significantly higher than that of PD-O-α-Syn. In addition, MSA-O-α-Syn exhibited stronger cytotoxicity and seeding activity compared with PD-O-α-Syn. In vivo experiments showed that mice receiving intrastriatal inoculation of MSA-O-α-Syn developed more severe motor dysfunction and dopaminergic degeneration than mice receiving intrastriatal inoculation of PD-O-α-Syn. Compared with the mice inoculated with PD-O-α-Syn, the mice inoculated with MSA-O-α-Syn accumulated more phosphorylated and oligomerized α-Syn in the striatum and brain regions (substantia nigra, hippocampus and prefrontal cortex) away from the inoculated site. The results obtained suggest that α-Syn oligomers formed in PD and MSA plasma are different in phosphorylation, cytotoxicity, and seeding activity.

Explore the Role of the Sphingosine-1-Phosphate Signalling as a Novel Promising Therapeutic Target for the Management of Parkinson's Disease

Sphingosine-1-phosphate (S1P) is a cellular signalling molecule derived from sphingosine, which is a pro-apoptotic sphingolipid. Sphingolipids control various cellular actions like growth, homeostasis, and stress-related responses. The main sources of S1P in our body are erythrocytes. S1P controls both cellular mediators and other second messengers intracellularly. The S1P receptor also helps in inflammatory and neuroprotective effects (required to manage of Parkinson's). A large number of anti-Parkinson drugs are available, but still, there is a need for more effective and safer drugs. S1P and its receptors could be targeted as novel drugs due to their involvement in neuro-inflammation and Parkinson's. The present review effort to explore the biological role of S1P and related receptors, for their possible involvement in PD; furthermore. Overall, S1P and other related metabolizing enzymes have significant therapeutic opportunities for Parkinson's disease along with other neurological disorders.

The Tree Shrew Model of Parkinson Disease: A Cost-Effective Alternative to Nonhuman Primate Models

The surge in demand for experimental monkeys has led to a rapid increase in their costs. Consequently, there is a growing need for a cost-effective model of Parkinson disease (PD) that exhibits all core clinical and pathologic phenotypes. Evolutionarily, tree shrews (Tupaia belangeri) are closer to primates in comparison with rodents and could be an ideal species for modeling PD. To develop a tree shrew PD model, we used the 1-methyl-4-phenylpyridinium (MPP+), a metabolite derived from 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, to induce lesions in dopaminergic neurons of the unilateral substantia nigra. The induced tree shrew model consistently exhibited and maintained all classic clinical manifestations of PD for a 5-month period. The symptoms included bradykinesia, rest tremor, and postural instability, and ∼50% individuals showed apomorphine-induced rotations, a classic phenotype of unilateral PD models. All these are closely resembled the ones observed in PD monkeys. Meanwhile, this model was also sensitive to L-dopa treatment in a dose-dependent manner, which suggested that the motor deficits are dopamine dependent. Immunostaining showed a significant loss of dopaminergic neurons (∼95%) in the lesioned substantia nigra, which is a crucial PD pathological marker. Moreover, a control group of nigral saline injection did not show any motor deficits and pathological changes. Cytomorphologic analysis revealed that the size of nigral dopaminergic neurons in tree shrews is much bigger than that of rodents and is close to that of macaques. The morphologic similarity may be an important structural basis for the manifestation of the highly similar phenotypes between monkey and tree shrew PD models. Collectively, in this study, we have successfully developed a PD model in a small animal species that faithfully recapitulated the classic clinical symptoms and key pathological indicators of PD monkeys, providing a novel and low-cost avenue for evaluation of PD treatments and underlying mechanisms.

The regulation of NFKB1 on CD200R1 expression and their potential roles in Parkinson's disease

BACKGROUND

Overactivated microglia are a key contributor to Parkinson's disease (PD) by inducing neuroinflammation. CD200R1, a membrane glycoprotein mainly found on microglia, is crucial for maintaining quiescence with its dysregulation linked to microglia's abnormal activation. We and other groups have reported a decline in CD200R1 levels in several neurological disorders including PD. However, the mechanism regulating CD200R1 expression and the specific reasons for its reduction in PD remain largely unexplored. Given the pivotal role of transcription factors in gene expression, this study aimed to elucidate the transcriptional regulation of CD200R1 and its implications in PD.

METHODS

The CD200R1 promoter core region was identified via luciferase assays. Potential transcription factors were predicted using the UCSC ChIP-seq database and JASPAR. NFKB1 binding to the CD200R1 core promoter was substantiated through electrophoretic mobility shift and chromatin immunoprecipitation assays. Knocking-down or overexpressing NFKB1 validated its regulatory effect on CD200R1. Correlation between decreased CD200R1 and deficient NFKB1 was studied using Genotype-Tissue Expression database. The clinical samples of the peripheral blood mononuclear cells were acquired from 44 PD patients (mean age 64.13 ± 9.78, 43.2% male, median Hoehn-Yahr stage 1.77) and 45 controls (mean age 64.70 ± 9.41, 52.1% male). NFKB1 knockout mice were utilized to study the impact of NFKB1 on CD200R1 expression and to assess their roles in PD pathophysiology.

RESULTS

The study identified the CD200R1 core promoter region, located 482 to 146 bp upstream of its translation initiation site, was directly regulated by NFKB1. Significant correlation between NFKB1 and CD200R1 expression was observed in human PMBCs. Both NFKB1 and CD200R1 were significantly decreased in PD patient samples. Furthermore, NFKB1-/- mice exhibited exacerbated microglia activation and dopaminergic neuron loss after 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) treatment.

CONCLUSION

Our study identified that NFKB1 served as a direct regulator of CD200R1. Reduced NFKB1 played a critical role in CD200R1 dysregulation and subsequent microglia overactivation in PD. These findings provide evidence that targeting the NFKB1-CD200R1 axis would be a novel therapeutic strategy for PD.

Nrf2 Deficiency Exacerbates Parkinson's Disease by Aggravating NLRP3 Inflammasome Activation in MPTP-Induced Mouse Models and LPS-Induced BV2 Cells

Background

Parkinson's disease (PD) is a movement disorder characterized by the progressive loss of dopamine neurons. Microglia-mediated neuroinflammation drives disease progression and becomes a critical factor in neuronal degeneration. Recent studies have found that nuclear factor-erythroid 2-related-2 (Nrf2) expression levels are reduced during aging and neurodegenerative diseases, but its regulatory mechanism on microglia-induced neuroinflammation has not been fully elucidated.

Methods

In vivo, we used the intraperitoneal injection of the neurotoxic drug neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) to establish an animal model of PD and, at the same time, administered Nrf2 inhibitors ML385 and dimethyl fumarate to regulate Nrf2 protein levels. In vitro, we used si-RNA to knock out the Nrf2 gene to intervene in BV2 cells and used lipopolysaccharide (LPS) to stimulate and induce the cell model.

Results

The study found that inhibition of Nrf2 expression aggravated the motor defects of PD mice, accompanied by a significant loss of dopaminergic neurons in the substantia nigra and striatum of the brain. In addition, after inhibition of Nrf2, the malondialdehyde (MDA) level in the substantia nigra of the midbrain of mice increased, and the levels of superoxide dismutase (SOD) and heme oxygenase-1 (HO-1) decreased, accompanied by the proliferation of microglia and astrocytes. In addition, the activation of the NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) inflammasome, the assembly of apoptosis-associated speck-like protein containing a CARD (ASC) protein in microglia, and the release of downstream inflammatory factors caspase-1 and interleukin (IL)-1β, were aggravated. At the cellular level, it was found that knocking out the expression of Nrf2 would aggravate the activation of NLRP3 inflammasomes and the assembly of ASC in LPS-induced BV2 cells.

Conclusion

Inhibited Nrf2 activity can reduce the downstream antioxidant enzyme HO-1 and antioxidant levels, induce NLRP3 inflammasome activation and ASC protein assembly in microglia, and ultimately aggravate PD inflammatory response and dopamine neuron degeneration.

Experimental Parkinson models and green chemistry approach

Parkinson's is the most common neurodegenerative disease after Alzheimer's. Motor findings in Parkinson's occur as a result of the degeneration of dopaminergic neurons starting in the substantia nigra pars compacta and ending in the putamen and caudate nucleus. Loss of neurons and the formation of inclusions called Lewy bodies in existing neurons are characteristic histopathological findings of Parkinson's. The disease primarily impairs the functional capacity of the person with cardinal findings such as tremor, bradykinesia, etc., as a result of the loss of dopaminergic neurons in the substantia nigra. Experimental animal models of Parkinson's have been used extensively in recent years to investigate the pathology of this disease. These models are generally based on systemic or local(intracerebral) administration of neurotoxins, which can replicate many features of Parkinson's mammals. The development of transgenic models in recent years has allowed us to learn more about the modeling of Parkinson's. Applying animal modeling, which shows the most human-like effects in studies, is extremely important. It has been demonstrated that oxidative stress increases in many neurodegenerative diseases such as Parkinson's and various age-related degenerative diseases in humans and that neurons are sensitive to it. In cases where oxidative stress increases and antioxidant systems are inadequate, natural molecules such as flavonoids and polyphenols can be used as a new antioxidant treatment to reduce neuronal reactive oxygen species and improve the neurodegenerative process. Therefore, in this article, we examined experimental animal modeling in Parkinson's disease and the effect of green chemistry approaches on Parkinson's disease.

Benfotiamine protects MPTP-induced Parkinson's disease mouse model via activating Nrf2 signaling pathway

The pursuit of drugs and methods to safeguard dopaminergic neurons holds paramount importance in Parkinson's disease (PD) research. Benfotiamine (BFT) has demonstrated neuroprotective properties, yet its precise mechanisms in PD remain elusive. This study investigated BFT's potential protective effects against dopamine neuron damage in a PD animal model and the underlying mechanisms. The PD mouse model was induced by 5 consecutive MPTP injections, followed by BFT intervention for 28 days. Motor deficits were assessed via pole test, hang test, gait analysis, and open field test, while dopaminergic neuron damage was evaluated through Immunofluorescence, Nissl staining, and Western blot analysis of Tyrosine Hydroxylase (TH) in the substantia nigra and striatum. High Performance Liquid Chromatography quantified dopamine (DA) levels and its metabolites. Genetic pathways were explored using RNA-seq and bioinformatics analysis on substantia nigra tissues, confirmed by qPCR. Activation of the Nrf2 pathway was examined through nuclear translocation and expression of downstream antioxidant enzymes HO-1, GCLM, and NQO1 at mRNA and protein levels. Additionally, measurements of MDA content, GSH activity, and SOD activity were taken in the substantia nigra and striatum. BFT administration improved motor function and protected against dopaminergic neuron degeneration in MPTP mice, with partial recovery in TH expression and DA levels. RNA-seq analysis revealed distinct effects of BFT and the NLRP3 inhibitor MCC950 on Parkinson-related pathways and genes. Control of Nrf2 proved crucial for BFT, as it facilitated Nrf2 movement to the nucleus, upregulating antioxidant genes and enzymes while mitigating oxidative damage. This study elucidates BFT's neuroprotective effects in a PD mouse model via Nrf2-mediated antioxidant mechanisms and gene expression modulation, underscoring its potential as a therapeutic agent for PD.

Physical exercise regulates microglia in health and disease

There is a well-established link between physical activity and brain health. As such, the effectiveness of physical exercise as a therapeutic strategy has been explored in a variety of neurological contexts. To determine the extent to which physical exercise could be most beneficial under different circumstances, studies are needed to uncover the underlying mechanisms behind the benefits of physical activity. Interest has grown in understanding how physical activity can regulate microglia, the resident immune cells of the central nervous system. Microglia are key mediators of neuroinflammatory processes and play a role in maintaining brain homeostasis in healthy and pathological settings. Here, we explore the evidence suggesting that physical activity has the potential to regulate microglia activity in various animal models. We emphasize key areas where future research could contribute to uncovering the therapeutic benefits of engaging in physical exercise.

Citrobacter rodentium infection impairs dopamine metabolism and exacerbates the pathology of Parkinson's disease in mice

Parkinson's disease (PD) is a prevalent neurodegenerative disorder with indistinct etiology and ill-defined pathophysiology. Intestinal inflammation involved in the pathogenesis of PD, but the underlying mechanism is not fully understood. Citrobacter rodentium (C.R) is a gram-negative bacterium that can be used to induce human inflammatory bowel disease in mice. Here, we investigated whether the proinflammatory effects caused by C.R infection initiate PD-like injury and/or exacerbate PD pathology and extensively studied the underlying mechanism. Mice were gavaged once with C.R and monitored for several pathological features at 9 days post infection. The results showed that C.R delivery in mice induced IBD-like symptoms, including significant weight loss, increased fecal water content, an impaired intestinal barrier, intestinal hyperpermeability and inflammation, and intestinal microbiota disturbances. Notably, C.R infection modified dopamine (DA) metabolism in the brains of both male and female mice. Subsequently, a single high dose of MPTP or normal saline was administered at 6 days post infection. At 3 days after MPTP administration, the feces were collected for 16 S rRNA analysis, and PD-like phenotypes and mechanisms were systemically analyzed. Compared with C.R or MPTP injection alone, the injection of C.R and MPTP combined worsened behavioral performance. Moreover, such combination triggered more severe dopaminergic degeneration and glial cell overactivation in the nigrostriatal pathway of mice. Mechanistically, the combination of C.R and MPTP increased the expression of TLR4 and NF-κB p65 in the colon and striatum and upregulated proinflammatory cytokine expression. Therefore, C.R infection-induced intestinal inflammation can impair dopamine metabolism and exacerbate PD pathological processes.

Rodent Models of Alzheimer's Disease: Past Misconceptions and Future Prospects

Alzheimer's disease (AD) is a progressive neurodegenerative disease with no effective treatments, not least due to the lack of authentic animal models. Typically, rodent models recapitulate the effects but not causes of AD, such as cholinergic neuron loss: lesioning of cholinergic neurons mimics the cognitive decline reminiscent of AD but not its neuropathology. Alternative models rely on the overexpression of genes associated with familial AD, such as amyloid precursor protein, or have genetically amplified expression of mutant tau. Yet transgenic rodent models poorly replicate the neuropathogenesis and protein overexpression patterns of sporadic AD. Seeding rodents with amyloid or tau facilitates the formation of these pathologies but cannot account for their initial accumulation. Intracerebral infusion of proinflammatory agents offer an alternative model, but these fail to replicate the cause of AD. A novel model is therefore needed, perhaps similar to those used for Parkinson's disease, namely adult wildtype rodents with neuron-specific (dopaminergic) lesions within the same vulnerable brainstem nuclei, 'the isodendritic core', which are the first to degenerate in AD. Site-selective targeting of these nuclei in adult rodents may recapitulate the initial neurodegenerative processes in AD to faithfully mimic its pathogenesis and progression, ultimately leading to presymptomatic biomarkers and preventative therapies.

Experimental Models to Study Immune Dysfunction in the Pathogenesis of Parkinson's Disease

Parkinson's disease (PD) is a chronic, age-related, progressive multisystem disease associated with neuroinflammation and immune dysfunction. This review discusses the methodological approaches used to study the changes in central and peripheral immunity in PD, the advantages and limitations of the techniques, and their applicability to humans. Although a single animal model cannot replicate all pathological features of the human disease, neuroinflammation is present in most animal models of PD and plays a critical role in understanding the involvement of the immune system (IS) in the pathogenesis of PD. The IS and its interactions with different cell types in the central nervous system (CNS) play an important role in the pathogenesis of PD. Even though culture models do not fully reflect the complexity of disease progression, they are limited in their ability to mimic long-term effects and need validation through in vivo studies. They are an indispensable tool for understanding the interplay between the IS and the pathogenesis of this disease. Understanding the immune-mediated mechanisms may lead to potential therapeutic targets for the treatment of PD. We believe that the development of methodological guidelines for experiments with animal models and PD patients is crucial to ensure the validity and consistency of the results.

Effects of Cardiac Glycoside Digoxin on Dendritic Spines and Motor Learning Performance in Mice

Synapse formation following the generation of postsynaptic dendritic spines is essential for motor learning and functional recovery after brain injury. The C-terminal fragment of agrin cleaved by neurotrypsin induces dendritic spine formation in the adult hippocampus. Since the α3 subunit of sodium-potassium ATPase (Na/K ATPase) is a neuronal receptor for agrin in the central nervous system, cardiac glycosides might facilitate dendritic spine formation and subsequent improvements in learning. This study investigated the effects of cardiac glycoside digoxin on dendritic spine turnover and learning performance in mice. Golgi-Cox staining revealed that intraperitoneal injection of digoxin less than its IC50 in the brain significantly increased the density of long spines (≥2 µm) in the cerebral cortex in wild-type mice and neurotrypsin-knockout (NT-KO) mice showing impairment of activity-dependent spine formation. Although the motor learning performance of NT-KO mice was significantly lower than control wild-type mice under the control condition, low doses of digoxin enhanced performance to a similar degree in both strains. In NT-KO mice, lower digoxin doses equivalent to clinical doses also significantly improved motor learning performance. These data suggest that lower doses of digoxin could modify dendritic spine formation or recycling and facilitate motor learning in compensation for the disruption of neurotrypsin-agrin pathway.

Dimethyl Fumarate Exerts a Neuroprotective Effect by Enhancing Mitophagy via the NRF2/BNIP3/PINK1 Axis in the MPP+ Iodide-Induced Parkinson's Disease Mice Model

Background

Parkinson's disease (PD) is a progressive neurodegenerative disorder linked to the loss of dopaminergic neurons in the substantia nigra. Mitophagy, mitochondrial selective autophagy, is critical in maintaining mitochondrial and subsequently neuronal homeostasis. Its impairment is strongly implicated in PD and is associated with accelerated neurodegeneration.

Objective

To study the positive effect of dimethyl fumarate (DMF) on mitophagy via the NRF2/BNIP3/PINK1 axis activation in PD disease models.

Methods

The neuroprotective effect of DMF was explored in in vitro and in vivo PD models. MTT assay was performed to determine the DMF dose followed by JC-1 assay to study its mitoprotective effect in MPP+ exposed SHSY5Y cells. For the in vivo study, C57BL/6 mice were divided into six groups: Normal Control (NC), Disease Control (DC), Sham (Saline i.c.v.), Low Dose (MPP+ iodide+DMF 15 mg/kg), Mid Dose (MPP+ iodide+DMF 30 mg/kg), and High Dose (MPP+ iodide+DMF 60 mg/kg). The neuroprotective effect of DMF was assessed by performing rotarod, open field test, and pole test, and biochemical parameter analysis using immunofluorescence, western blot, and RT-PCR.

Results

DMF treatment significantly alleviated the loss of TH positive dopaminergic neurons and enhanced mitophagy by increasing PINK1, Parkin, BNIP3, and LC3 levels in the MPP+ iodide-induced PD mice model. DMF treatment groups showed good locomotor activity and rearing time when compared to the DC group.

Conclusions

DMF confers neuroprotection by activating the BNIP3/PINK1/Parkin pathway, enhancing the autophagosome formation via LC3, and improving mitophagy in PD models, and could be a potential therapeutic option in PD.

Artemisinin protects dopaminergic neurons against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced neurotoxicity in a mouse model of Parkinson's disease

Artemisinin is an antimalarial drug that has been used for almost half a century. However, the anti-Parkinson's disease (PD) effects of artemisinin with respect to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced oxidative stress have not yet been investigated while focusing on NF-E2-related factor 2 (Nrf2) signaling. Thus, we sought to assess the behavioral and oxidative mechanistic effects of artemisinin on MPTP-induced toxicity via the Nrf2 signaling pathway. We explored this through immunohistochemical assays, ELISA, in differentiated PC12 cells treated with siRNA, and with a PD mouse model. Artemisinin increased Nrf2 DNA-binding activity and HO-1 and NQO1 expression. Artemisinin treatment protected cells against MPP+ -induced neuronal death signaling, including NADH dehydrogenase activity, reactive oxygen species, mitochondrial membrane potential, and cleaved caspase-3. Moreover, it protected cells against MPTP-induced behavioral impairments and significantly reduced dopaminergic neuronal loss. Additionally, Nrf2 pre-inhibition using ML385 neutralized the inhibitory effects of artemisinin on dopaminergic neuronal damage and behavioral impairments induced by MPTP. Our results suggest that artemisinin inhibits MPTP-induced behavioral and neurotoxic effects in mice. This provides a foundation for further research to evaluate artemisinin as a potential therapeutic agent for PD.

Dopamine-Depleted Dopamine Transporter Knockout (DDD) Mice: Dyskinesia with L-DOPA and Dopamine D1 Agonists

L-DOPA is the mainstay of treatment for Parkinson's disease (PD). However, over time this drug can produce dyskinesia. A useful acute PD model for screening novel compounds for anti-parkinsonian and L-DOPA-induced dyskinesia (LID) are dopamine-depleted dopamine-transporter KO (DDD) mice. Treatment with α-methyl-para-tyrosine rapidly depletes their brain stores of DA and renders them akinetic. During sensitization in the open field (OF), their locomotion declines as vertical activities increase and upon encountering a wall they stand on one leg or tail and engage in climbing behavior termed "three-paw dyskinesia". We have hypothesized that L-DOPA induces a stereotypic activation of locomotion in DDD mice, where they are unable to alter the course of their locomotion, and upon encountering walls engage in "three-paw dyskinesia" as reflected in vertical counts or beam-breaks. The purpose of our studies was to identify a valid index of LID in DDD mice that met three criteria: (a) sensitization with repeated L-DOPA administration, (b) insensitivity to a change in the test context, and (c) stimulatory or inhibitory responses to dopamine D1 receptor agonists (5 mg/kg SKF81297; 5 and 10 mg/kg MLM55-38, a novel compound) and amantadine (45 mg/kg), respectively. Responses were compared between the OF and a circular maze (CM) that did not hinder locomotion. We found vertical counts and climbing were specific for testing in the OF, while oral stereotypies were sensitized to L-DOPA in both the OF and CM and responded to D1R agonists and amantadine. Hence, in DDD mice oral stereotypies should be used as an index of LID in screening compounds for PD.

Alpha-Synuclein-Specific Regulatory T Cells Ameliorate Parkinson's Disease Progression in Mice

Parkinson's disease (PD) is a long-term neurodegenerative disease characterized by dopaminergic neuronal loss and the aggregation of alpha-synuclein (α-syn) in the brain. Cell therapy using regulatory T cells (Tregs) has therapeutic potential on PD progression in a mouse model; however, several challenges were associated with its applications. Here, we propose a strategy for α-syn specific Treg expansion (α-syn Treg). We presented α-syn to T cells via dendritic cells. This method increased the mobility of Tregs towards the site of abundant α-syn in vitro (p < 0.01; α-syn Tregs versus polyclonal Tregs (poly Tregs)) and in vivo. Consequently, α-syn Tregs showed noteworthy neuroprotective effects against motor function deficits (p < 0.05, p < 0.01; α-syn Tregs versus poly Tregs), dopaminergic neuronal loss (p < 0.001; α-syn Tregs versus poly Tregs), and α-syn accumulation (p < 0.05; α-syn Tregs versus poly Tregs) in MPTP-induced PD mice. Furthermore, the adoptive transfer of α-syn Tregs exerted immunosuppressive effects on activated microglia, especially pro-inflammatory microglia, in PD mice. Our findings suggest that α-syn presentation may provide a significant improvement in neuroprotective activities of Tregs and suggest the effective clinical application of Treg therapy in PD.

Effects of Tiliroside and Lisuride Co-Treatment on the PI3K/Akt Signal Pathway: Modulating Neuroinflammation and Apoptosis in Parkinson's Disease

Researchers are actively exploring potential bioactive compounds to enhance the effectiveness of Lisuride (Lis) in treating Parkinson's disease (PD) over the long term, aiming to mitigate the serious side effects associated with its extended use. A recent study found that combining the dietary flavonoid Tiliroside (Til) with Lis has potential anti-Parkinson's benefits. The study showed significant improvements in PD symptoms induced by 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) when Til and Lis were given together, based on various behavioral tests. This combined treatment significantly improved motor function and protected dopaminergic neurons in rats with PD induced by MPTP. It also activated important molecular pathways related to cell survival and apoptosis control, as indicated by the increased pAkt/Akt ratio. Til and Lis together increased B-cell lymphoma 2 (Bcl-2), decreased caspase 3 activity, and prevented brain cell decay. Co-administration also reduced tumor necrosis factor alpha (TNF-α) and Interleukin-1 (IL-1). Antioxidant markers such as superoxide dismutase (SOD), catalase, and reduced glutathione significantly improved compared to the MPTP-induced control group. This study shows that using Til and Lis together effectively treats MPTP-induced PD in rats, yielding results comparable to an 8 mg/kg dose of levodopa, highlighting their potential as promising Parkinson's treatments.

Aging, Parkinson's Disease, and Models: What Are the Challenges?

Parkinson's disease (PD) is a chronic, neurodegenerative condition characterized by motor symptoms such as bradykinesia, rigidity, and tremor, alongside multiple nonmotor symptoms. The appearance of motor symptoms is linked to progressive dopaminergic neuron loss within the substantia nigra. PD incidence increases sharply with age, suggesting a strong association between mechanisms driving biological aging and the development and progression of PD. However, the role of aging in the pathogenesis of PD remains understudied. Numerous models of PD, including cell models, toxin-induced models, and genetic models in rodents and nonhuman primates (NHPs), reproduce different aspects of PD, but preclinical studies of PD rarely incorporate age as a factor. Studies using patient neurons derived from stem cells via reprogramming methods retain some aging features, but their characterization, particularly of aging markers and reproducibility of neuron type, is suboptimal. Investigation of age-related changes in PD using animal models indicates an association, but this is likely in conjunction with other disease drivers. The biggest barrier to drawing firm conclusions is that each model lacks full characterization and appropriate time-course assessments. There is a need to systematically investigate whether aging increases the susceptibility of mouse, rat, and NHP models to develop PD and understand the role of cell models. We propose that a significant investment in time and resources, together with the coordination and sharing of resources, knowledge, and data, is required to accelerate progress in understanding the role of biological aging in PD development and improve the reliability of models to test interventions.

Alteration of Postural Reactions in Rats with Different Levels of Dopamine Depletion

Dopamine (DA) is the critical neurotransmitter involved in the unconscious control of muscle tone and body posture. We evaluated the general motor capacities and muscle responses to postural disturbance in three conditions: normal DA level (wild-type rats, WT), mild DA deficiency (WT after administration of α-methyl-p-tyrosine-AMPT, that blocks DA synthesis), and severe DA depletion (DAT-KO rats after AMPT). The horizontal displacements in WT rats elicited a multi-component EMG corrective response in the flexor and extensor muscles. Similar to the gradual progression of DA-related diseases, we observed different degrees of bradykinesia, rigidity, and postural instability after AMPT. The mild DA deficiency impaired the initiation pattern of corrective responses, specifically delaying the extensor muscles' activity ipsilaterally to displacement direction and earlier extensor activity from the opposite side. DA depletion in DAT-KO rats after AMPT elicited tremors, general stiffness, and akinesia, and caused earlier response to horizontal displacements in the coactivated flexor and extensor muscles bilaterally. The data obtained show the specific role of DA in postural reactions and suggest that this experimental approach can be used to investigate sensorimotor control in different dopamine-deficient states and to model DA-related diseases.

Neuroprotective Efficacy of a Nanomicellar Complex of Carnosine and Lipoic Acid in a Rat Model of Rotenone-Induced Parkinson's Disease

Oxidative stress, accompanied by mitochondrial dysfunction, is a key mechanism involved in the pathogenesis of Parkinson's disease (PD). Both carnosine and lipoic acid are potent antioxidants, the applicability of which in therapy is hindered by their limited bioavailability. This study aimed to evaluate the neuroprotective properties of a nanomicellar complex of carnosine and lipoic acid (CLA) in a rotenone-induced rat model of PD. Parkinsonism was induced via the administration of 2 mg/kg rotenone over the course of 18 days. Two doses of intraperitoneal CLA (25 mg/kg and 50 mg/kg) were administered alongside rotenone to assess its neuroprotective effect. At 25 mg/kg CLA decreased muscle rigidity and partially restored locomotor activity in animals that received rotenone. Furthermore, it caused an overall increase in brain tissue antioxidant activity, accompanied by a 19% increase in neuron density in the substantia nigra and increased dopamine levels in the striatum relative to animals that only received rotenone. Based on the acquired results, it may be concluded that CLA have neuroprotective properties and could potentially be beneficial in PD treatment when used in conjunction with the base therapy.

Parkinson's Disease: Exploring Different Animal Model Systems

Disease modeling in non-human subjects is an essential part of any clinical research. To gain proper understanding of the etiology and pathophysiology of any disease, experimental models are required to replicate the disease process. Due to the huge diversity in pathophysiology and prognosis in different diseases, animal modeling is customized and specific accordingly. As in other neurodegenerative diseases, Parkinson's disease is a progressive disorder coupled with varying forms of physical and mental disabilities. The pathological hallmarks of Parkinson's disease are associated with the accumulation of misfolded protein called α-synuclein as Lewy body, and degeneration of dopaminergic neurons in the substantia nigra pars compacta (SNc) area affecting the patient's motor activity. Extensive research has already been conducted regarding animal modeling of Parkinson's diseases. These include animal systems with induction of Parkinson's, either pharmacologically or via genetic manipulation. In this review, we will be summarizing and discussing some of the commonly employed Parkinson's disease animal model systems and their applications and limitations.

Neurochemical, histological, and behavioral profiling of the acute, sub-acute, and chronic MPTP mouse model of Parkinson's disease

Parkinson's disease (PD) is a heterogeneous multi-systemic disorder unique to humans characterized by motor and non-motor symptoms. Preclinical experimental models of PD present limitations and inconsistent neurochemical, histological, and behavioral readouts. The 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD is the most common in vivo screening platform for novel drug therapies; nonetheless, behavioral endpoints yielded amongst laboratories are often discordant and inconclusive. In this study, we characterized neurochemically, histologically, and behaviorally three different MPTP mouse models of PD to identify translational traits reminiscent of PD symptomatology. MPTP was intraperitoneally (i.p.) administered in three different regimens: (i) acute-four injections of 20 mg/kg of MPTP every 2 h; (ii) sub-acute-one daily injection of 30 mg/kg of MPTP for 5 consecutive days; and (iii) chronic-one daily injection of 4 mg/kg of MPTP for 28 consecutive days. A series of behavioral tests were conducted to assess motor and non-motor behavioral changes including anxiety, endurance, gait, motor deficits, cognitive impairment, circadian rhythm and food consumption. Impairments in balance and gait were confirmed in the chronic and acute models, respectively, with the latter showing significant correlation with lesion size. The sub-acute model, by contrast, presented with generalized hyperactivity. Both, motor and non-motor changes were identified in the acute and sub-acute regime where habituation to a novel environment was significantly reduced. Moreover, we report increased water and food intake across all three models. Overall, the acute model displayed the most severe lesion size, while across the three models striatal dopamine content (DA) did not correlate with the behavioral performance. The present study demonstrates that detection of behavioral changes following MPTP exposure is challenging and does not correlate with the dopaminergic lesion extent.

Actaea racemosa L. Rhizome Protect against MPTP-Induced Neurotoxicity in Mice by Modulating Oxidative Stress and Neuroinflammation

Parkinson's disease (PD) is a dopaminergic neuron-related neurodegenerative illness. Treatments exist that alleviate symptoms but have a variety of negative effects. Recent research has revealed that oxidative stress, along with neuroinflammation, is a major factor in the course of this disease. Therefore, the aim of our study was to observe for the first time the effects of a natural compound such as Actaea racemosa L. rhizome in an in vivo model of PD induced by neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). For the study, mice received four injections of MPTP (20 mg/kg) for the induction of PD. Starting 24 h after the first administration of MPTP we treated mice with Actaea racemosa L. rhizome (100 mg/kg) daily for seven days. Our findings clearly demonstrated that Actaea racemosa L. rhizome treatment decreases oxidative stress by activating redox balance enzymes such as Nrf2/HO-1. We also demonstrated that Actaea racemosa L. rhizome is capable of modulating inflammatory indicators involved in PD, such as IκB-α, NF-κB, GFAP and Iba1, thus reducing the degeneration of dopaminergic neurons and motor and non-motor alterations. To summarize, Actaea racemosa L. rhizome, which is subject to fewer regulations than traditional medications, could be used as a dietary supplement to improve patients' brain health and could be a promising nutraceutical choice to slow the course and symptoms of PD.

Multiscale imaging informs translational mouse modeling of neurological disease

Multiscale neurophysiology reveals that simple motor actions are associated with changes in neuronal firing in virtually every brain region studied. Accordingly, the assessment of focal pathology such as stroke or progressive neurodegenerative diseases must also extend widely across brain areas. To derive mechanistic information through imaging, multiple resolution scales and multimodal factors must be included, such as the structure and function of specific neurons and glial cells and the dynamics of specific neurotransmitters. Emerging multiscale methods in preclinical animal studies that span micro- to macroscale examinations fill this gap, allowing a circuit-based understanding of pathophysiological mechanisms. Combined with high-performance computation and open-source data repositories, these emerging multiscale and large field-of-view techniques include live functional ultrasound, multi- and single-photon wide-scale light microscopy, video-based miniscopes, and tissue-penetrating fiber photometry, as well as variants of post-mortem expansion microscopy. We present these technologies and outline use cases and data pipelines to uncover new knowledge within animal models of stroke, Alzheimer's disease, and movement disorders.

Neuroprotective repositioning and anti-tau effect of carvedilol on rotenone induced neurotoxicity in rats: Insights from an insilico& in vivo anti-Parkinson's disease study

Current treatments for Parkinson's Disease (PD) only provide symptomatic relief; however, they don't delay the disease progression, hence new treatment options should be considered. Carvedilol is a nonselective β & α1 blocker with additional effects as an antioxidant, anti-inflammatory and neuro protective properties. In this research, an insilico study was conducted to primarily evaluate carvedilol as an anti-parkinsonian and anti-tau protein target. PASS prediction was performed followed by a docking study of carvedilol. Carvedilol yielded promising results and forward guided this study onto its in vivo evaluation. The in vivo study aimed to assess the neuro-protective effects of carvedilol in rotenone-induced rat model of PD and investigate the potential underlying mechanisms. The effects of carvedilol (2.5, 5, and 10 mg/kg) on the measured parameters of open field, catalepsy, Y-maze tests as well as brain histology, and tyrosine hydroxylase (TH) were evaluated. The effective doses (5 and 10 mg/kg) were further tested for their potential anti-tau protein effects. Carvedilol (5 and 10 mg/kg) prevented rotenone-induced motor deficits, spatial memory dysfunction, and histological damage. Additionally, carvedilol significantly inhibited rotenone-induced decrease in TH expression in the striata of the rats. These effects were associated with reduction of rotenone-induced neuro-inflammation, microglial activation and release of glial fibrillary acidic protein (GFAP), along with reduction in N-methyl-D-aspartate receptors activation, alpha-synculein and phospho-Tau (P-Tau) protein expression. Carvedilol also reduced tau protein hyper-phosphosrylation by Glycogen synthase 3β (GSK 3β) inhibition and Phosphoinositide 3-kinase (PI3K) stimulation. Collectively, these results suggest that carvedilol might be a possible candidate for management of PD.

Açai Berry Mitigates Parkinson's Disease Progression Showing Dopaminergic Neuroprotection via Nrf2-HO1 Pathways

The current pharmacological treatment for Parkinson's disease (PD) is focused on symptom alleviation rather than disease prevention. In this study, we look at a new strategy to neuroprotection that focuses on nutrition, by a supplementation with Açai berry in an experimental models of PD. Daily orally supplementation with Açai berry dissolved in saline at the dose of 500 mg/kg considerably reduced motor and non-motor symptom and neuronal cell death of the dopaminergic tract induced by 4 injections of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Furthermore, Açai berry administration reduced α-synuclein aggregation in neurons, enhanced tyrosine hydroxylase and dopamine transporter activities, and avoided dopamine depletion. Moreover, Açai berry administration was able to reduce astrogliosis and microgliosis as well as neuronal death. Its beneficial effects could be due to its bioactive phytochemical components that are able to stimulate nuclear factor erythroid 2-related factor 2 (Nrf2) by counteracting the oxidative stress and neuroinflammation that are the basis of this neurodegenerative disease.

Modeling Parkinson's disease-related symptoms in alpha-synuclein overexpressing mice

BACKGROUND

Intracellular deposition of alpha-synuclein (α-syn) as Lewy bodies and Lewy neurites is a central event in the pathogenesis of Parkinson's disease (PD) and other α-synucleinopathies. Transgenic mouse models overexpressing human α-syn, are useful research tools in preclinical studies of pathogenetic mechanisms. Such mice develop α-syn inclusions as well as neurodegeneration with a topographical distribution that varies depending on the choice of promoter and which form of α-syn that is overexpressed. Moreover, they display motor symptoms and cognitive disturbances that to some extent resemble the human conditions.

PURPOSE

One of the main motives for assessing behavior in these mouse models is to evaluate the potential of new treatment strategies, including their impact on motor and cognitive symptoms. However, due to a high within-group variability with respect to such features, the behavioral studies need to be applied with caution. In this review, we discuss how to make appropriate choices in the experimental design and which tests that are most suitable for the evaluation of PD-related symptoms in such studies.

METHODS

We have evaluated published results on two selected transgenic mouse models overexpressing wild type (L61) and mutated (A30P) α-syn in the context of their validity and utility for different types of behavioral studies.

CONCLUSIONS

By applying appropriate behavioral tests, α-syn transgenic mouse models provide an appropriate experimental platform for studies of symptoms related to PD and other α-synucleinopathies.

Characterization of Affective Behaviors and Motor Functions in Mice With a Striatal-Specific Deletion of Bmal1 and Per2

The expression of circadian clock genes, either centrally or in the periphery, has been shown to play an integral role in the control of behavior. Brain region-specific downregulation of clock genes revealed behavioral phenotypes associated with neuropsychiatric disorders and neurodegenerative disease. The specific function of the clock genes as well as the underlying mechanisms that contribute to the observed phenotypes, however, are not yet fully understood. We assessed anxiety- and depressive-like behavior and motor functions in male and female mice with a conditional ablation of Bmal1 or Per2 from medium spiny neurons (MSNs) of the striatum as well as mice lacking one copy of Gpr88. Whereas the conditional knockout of Bmal1 and Per2 had mild effects on affective behaviors, a pronounced effect on motor functions was found in Bmal1 knockout mice. Subsequent investigation revealed an attenuated response of Bmal1 knockout mice to dopamine receptor type 1 agonist treatment, independently of the expression of targets of the dopamine signaling pathway or mitochondrial respiration in MSNs. The study thus suggests a potential interaction of Bmal1 within the direct dopamine signaling pathway, which may provide the link to a shared, MSN-dependent mechanism regulating affective behavior and motor function in mice.

Reduced penetrance of Parkinson's disease models

The etiology and progression of Parkinson's Disease (PD), the second most prevalent neurological disorder, have been widely investigated for several decades; however, a cure is still lacking. Despite the development of several neurotoxins and animal models to study this rather heterogeneous disease, a complete recapitulation of the neurophysiology and neuropathology of PD has not been fully achieved. One underlying cause for this could be that mutations in PD-associated genes have reduced penetrance. Therefore, the quest for novel PD models is required where a double hit approach needs to be evoked - a combination of genetic alterations and environmental factors need to be accounted for in one unique model simultaneously.

Soluble Epoxide Hydrolase as a Therapeutic Target for Neuropsychiatric Disorders

It has been found that soluble epoxide hydrolase (sEH; encoded by the EPHX2 gene) in the metabolism of polyunsaturated fatty acids (PUFAs) plays a key role in inflammation, which, in turn, plays a part in the pathogenesis of neuropsychiatric disorders. Meanwhile, epoxy fatty acids such as epoxyeicosatrienoic acids (EETs), epoxyeicosatetraenoic acids (EEQs), and epoxyeicosapentaenoic acids (EDPs) have been found to exert neuroprotective effects in animal models of neuropsychiatric disorders through potent anti-inflammatory actions. Soluble expoxide hydrolase, an enzyme present in all living organisms, metabolizes epoxy fatty acids into the corresponding dihydroxy fatty acids, which are less active than the precursors. In this regard, preclinical findings using sEH inhibitors or Ephx2 knock-out (KO) mice have indicated that the inhibition or deficiency of sEH can have beneficial effects in several models of neuropsychiatric disorders. Thus, this review discusses the current findings of the role of sEH in neuropsychiatric disorders, including depression, autism spectrum disorder (ASD), schizophrenia, Parkinson’s disease (PD), and stroke, as well as the potential mechanisms underlying the therapeutic effects of sEH inhibitors.

Paeoniflorin ameliorates cognitive impairment in Parkinson's disease via JNK/p53 signaling

Paeoniflorin (PF) has numerous benefits, including anti-inflammatory and anti-apoptosis effects. However, it is not clear if it has neuroprotective effects against cognitive impairment (CI) in Parkinson's disease (PD). Through network pharmacology, we identified probable targets as well as signal pathways through which PF might affect CI in PD. Then, we experimentally validated our findings. The core genes of the protein-protein interactions (PPI) network include MAPK8 (JNK), TP53, CASP3 (caspase-3), postsynaptic density protein-95 (PSD-95) and synaptophysin (SYN). Pathway enrichment analysis revealed that genes involved in apoptosis and mitogen-activated protein kinase (MAPK) signaling were significantly enriched. Because JNK is a key mediator of p53-induced apoptosis, we wondered if JNK/p53 pathway influences the effects of PF against apoptosis in mouse model of PD. Molecular docking analysis showed that PF had good affinity for JNK/p53. The results of the experiments indicated that PF ameliorated behavioral impairments and upregulated the expression of the dopamine (DA) neurons, suppressed cell apoptosis in substantia nigra pars compacta (SNpc) of PD. Additionally, PF improved 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced neuronal injury by inhibiting apoptosis in hippocampal neurons of the CA1 and CA3, and upregulating PSD-95 as well as SYN protein levels. Similar protective effects were observed upon JNK/p53 pathway inhibition using SP600125. Overall, PF improved CI in PD by inhibiting JNK/p53 pathway.

Age-Dependent Neuropsychiatric Symptoms in the NF-κB/c-Rel Knockout Mouse Model of Parkinson’s Disease

Non-motor symptoms are frequently observed in Parkinson’s disease (PD) and precede the onset of motor deficits by years. Among them, neuropsychiatric symptoms, including anxiety, depression, and apathy, are increasingly considered as a major challenge for patients with PD and their caregivers. We recently reported that mice lacking the nuclear factor-κB (NF-κB)/c-Rel protein (c-rel^–/– mice) develop an age-dependent PD-like pathology and phenotype characterized by the onset of non-motor symptoms, including constipation and hyposmia, starting at 2 months of age, and motor deficits at 18 months. To assess whether c-rel^–/– mice also suffer from neuropsychiatric symptoms, in this study we tested different cohorts of wild-type (wt) and c-rel^–/– mice at 3, 6, 12, and 18–20 months with different behavioral tests. Mice lacking c-Rel displayed anxiety and depressive-like behavior starting in the premotor phase at 12 months, as indicated by the analysis with the open field (OF) test and the forced swim test with water wheel (FST), respectively. A deficit in the goal-oriented nesting building test was detected at 18–20 months, suggesting apathetic behavior. Taken together, these results indicate that c-rel^–/– mice recapitulate the onset and the progression of PD-related neuropsychiatric symptoms. Therefore, this animal model may represent a valuable tool to study the prodromal stage of PD and for testing new therapeutic strategies to alleviate neuropsychiatric symptoms.

Dexmedetomidine attenuates motor deficits via restoring the function of neurons in the nigrostriatal circuit in Parkinson's disease model mice

Parkinson's disease (PD) is a neurodegenerative disorder characterized by a progressive degeneration in nigrostriatal dopamine pathway that is essential to control motor functions. Dexmedetomidine (DEX), a sedative and analgesic drug, is often used in patients with PD undergoing surgery. Although DEX seems to have promising future applications in neuroprotection, whether and how DEX alter the function of nigrostriatal circuit and its roles on motor deficits in PD remain unclear. Here we report that DEX attenuated motor deficits in a dose-dependent manner and protected the degeneration of dopaminergic neurons in MPTP-induced PD model mice. The DEX acted on the neurons in the nigrostriatal circuits, including activation of dopaminergic neurons and the reduction of the excitabilities of striatal neurons via dopamine D2 receptors. We further found that DEX prevented the increase in glutamatergic transmission of cholinergic interneurons (CINs) to alleviate motor dysfunction. It also decreased the intrinsic excitability and glutamatergic transmission of striatal D2 medium spiny neurons (D2-MSNs). Finally, D2 receptor antagonists prevented the restoration of DEX on motor deficits. These results demonstrate that DEX, a neuroprotective drug, restores the function of nigrostriatal neurons and improves the motor deficits, providing a potential neural mechanism of the effects of anesthetic drugs on PD progression.

Animal models in the study of Alzheimer's disease and Parkinson's disease: A historical perspective

Alzheimer's disease and Parkinson's disease are two of the most prevalent and disabling neurodegenerative diseases globally. Both are proteinopathic conditions and while occasionally inherited, are largely sporadic in nature. Although the advances in our understanding of the two have been significant, they are far from complete and neither diagnosis nor the current practices in treatment and rehabilitation is adequately helpful. Animal models have historically found application as testing beds for novel therapeutics and continue to be valuable aids in pharmacological research. This review chronicles the development of those models in the context of Alzheimer's and Parkinson's disease, and highlights the shifting paradigms in studying two human-specific conditions in non-human organisms.

Idebenone improves motor dysfunction, learning and memory by regulating mitophagy in MPTP-treated mice

The progression of Parkinson’s disease (PD) is often accompanied by the loss of substantia nigra dopaminergic neurons, mitophagy damage, learning, and memory impairment. Idebenone is a therapeutic drug that targets the mitochondria of neurodegenerative diseases, but its role in Parkinson’s disease and its pathological mechanism are still unclear. The purpose of this study was to investigate whether idebenone could improve behavioral disorders, especially motor, learning, and memory disorders, in mouse PD models and to explore its molecular mechanism. In the present study, C57BL-6 mice underwent intraperitoneal injection of MPTP (30 mg/kg) once a day for five consecutive days. Then, a 200 mg/kg dose was given as a single daily gavage of idebenone dissolved in water for 21 days after the successful establishment of the subacute MPTP model. Motor, learning, and memory were measured by a water maze and a rotarod test. Our results showed that idebenone could reduce MPTP-induced dopaminergic neuron damage and improve movement disorders, memory, and learning ability, which may be associated with upregulating mitochondrial autophagy-related outer membrane proteins VDAC1 and BNIP3 and activating the Parkin/PINK1 mitochondrial autophagy pathway. To confirm whether idebenone promotes the smooth progression of autophagy, we used eGFP-mCherry-LC3 mice to construct a subacute model of Parkinson’s disease and found that idebenone can increase autophagy in dopaminergic neurons in Parkinson’s disease. In summary, our results confirm that idebenone can regulate the expression of the mitochondrial outer membrane proteins VDAC1 and BNIP3, activate Parkin/PINK1 mitophagy, promote the degradation of damaged mitochondria, reduce dopaminergic neuron damage, and improve behavioral disorders in Parkinson’s disease mice.

Self-Catalytic Small Interfering RNA Nanocarriers for Synergistic Treatment of Neurodegenerative Diseases

Gene therapy has shown great potential for neurodegenerative diseases with complex pathology. However, its therapeutic effect is limited due to the delivery barriers and its own single function. Herein, self-catalytic small interfering RNA (siRNA) nanocarriers (S/Ce-PABMS) are developed to catalyze delivery process and treatment process for synergistic treatment of neurodegenerative diseases. On the one hand, the rough surface of the S/Ce-PABMS mediated by ceria (CeO₂ ) nanozymes can catalyze cellular uptake in the delivery process, so that S/Ce-PABMS with acetylcholine analogs penetrate the blood-brain barrier and enter neurons more effectively. On the other hand, the CeO₂ nanozymes can catalyze the treatment process by scavenging excess reactive oxygen species, and cooperate with siRNA-targeting SNCA to decrease the α-synuclein (α-syn) aggregation and alleviate the Parkinsonian pathology. Moreover, the S/Ce-PABMS treatment reduces the number of activated microglia and regulates the release of inflammatory cytokine, thereby relieving neuroinflammation. After treatment with S/Ce-PABMS, dyskinesia in Parkinson's disease model mice is significantly alleviated. The finding shows that the self-catalytic nanocarriers, S/Ce-PABMS, have great potential in the treatment of neurodegenerative diseases.

Atrazine Inhalation Causes Neuroinflammation, Apoptosis and Accelerating Brain Aging

BACKGROUND

exposure to environmental contaminants has been linked to an increased risk of neurological diseases and poor outcomes. Chemical name of Atrazine (ATR) is 6-chloro-N-ethyl-N'-(1-methylethyl)-1,3,5-triazine-2,4-diamine, and it is the most commonly used broad-spectrum herbicide in agricultural crops. Several studies have demonstrated that ATR has the potential to be harmful to the brain's neuronal circuits. Until today nobody has explored the effect of ATR inhalation on young and aged mice.

METHODS

young and aged mice were subject to 25 mg of ATR in a vehicle made with saline and 10% of Dimethyl sulfoxide (DMSO) every day for 28 days. At the end of experiment different behavioral test were made and brain was collected.

RESULTS

exposure to ATR induced the same response in terms of behavioral alterations and motor and memory impairment in mice but in aged group was more marked. Additionally, in both young and aged mice ATR inhalations induced oxidative stress with impairment in physiological antioxidant response, lipid peroxidation, nuclear factor kappa-light-chain-enhancer of activated B cells (nf-κb) pathways activation with consequences of pro-inflammatory cytokines release and apoptosis. However, the older group was shown to be more sensitive to ATR inhalation.

CONCLUSIONS

our results showed that aged mice were more susceptible compared to young mice to air pollutants exposure, put in place a minor physiologically response was seen when exposed to it.

Glucagon-Like Peptide-1 Receptor Agonist Ameliorates 1-Methyl-4-Phenyl-1,2,3,6-Tetrahydropyridine (MPTP) Neurotoxicity Through Enhancing Mitophagy Flux and Reducing α-Synuclein and Oxidative Stress

Parkinson disease (PD) is the second most common neurodegenerative disease without known disease modification therapy to slow down disease progression. This disease has pathological features of Lewy bodies with α-synuclein aggregation being the major component and selective dopaminergic neuronal loss over the substantia nigra. Although the exact etiology is still unknown, mitochondrial dysfunction has been shown to be central in PD pathophysiology. Type 2 diabetes mellitus has recently been connected to PD, and anti-diabetic drugs, such as glucagon-like peptide-1 receptor agonists (GLP-1RAs), have been shown to possess neuroprotective effects in PD animal models. The GLP-1RA liraglutide is currently under a phase 2 clinical trial to measure its effect on motor and non-motor symptoms in PD patients. In this study, we used an acute 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD to test the possible mechanism of the GLP-1RA liraglutide in the pathogenesis of PD. We show that the neurobehavioral and motor dysfunction caused by the mitochondrial complex I inhibitor, MPTP, can be partially reversed by liraglutide. The GLP-1RA can protect mice from apoptosis of substantia nigra neurons induced by MPTP. MPTP treatment led to imbalanced mitochondrial fusion and fission dynamics, altered mitochondrial morphology, impeded autophagy flux, increased α-synuclein accumulation, and elevated oxidative stress. Specifically, the normalizing of mitochondrial fusion-fission dynamic-related proteins and enhancement of autophagy flux after administration of liraglutide is associated with improving neuronal survival. This suggests that GLP-1RAs may provide potential beneficial effects for PD caused by mitochondrial dysfunction through improvement of mitochondrial morphology balance and enhancing damaged organelle degradation.

Multi-View Mouse Social Behaviour Recognition With Deep Graphic Model

Home-cage social behaviour analysis of mice is an invaluable tool to assess therapeutic efficacy of neurodegenerative diseases. Despite tremendous efforts made within the research community, single-camera video recordings are mainly used for such analysis. Because of the potential to create rich descriptions for mouse social behaviors, the use of multi-view video recordings for rodent observations is increasingly receiving much attention. However, identifying social behaviours from various views is still challenging due to the lack of correspondence across data sources. To address this problem, we here propose a novel multi-view latent-attention and dynamic discriminative model that jointly learns view-specific and view-shared sub-structures, where the former captures unique dynamics of each view whilst the latter encodes the interaction between the views. Furthermore, a novel multi-view latent-attention variational autoencoder model is introduced in learning the acquired features, enabling us to learn discriminative features in each view. Experimental results on the standard CRMI13 and our multi-view Parkinson's Disease Mouse Behaviour (PDMB) datasets demonstrate that our proposed model outperforms the other state of the arts technologies, has lower computational cost than the other graphical models and effectively deals with the imbalanced data problem.

Schisandra chinensis protects against dopaminergic neuronal oxidative stress, neuroinflammation and apoptosis via the BDNF/Nrf2/NF-κB pathway in 6-OHDA-induced Parkinson's disease mice

Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized by a disorder of both the motor and nonmotor systems due to a loss of dopaminergic (DA) neurons. Herein, we aimed to investigate the potential neuroprotective role of Schisandra chinensis (Sch) and to determine the mechanism by which Sch functions to ameliorate PD in a 6-hydroxydopamin (6-OHDA)-induced PD model. The open field test, sucrose preference test, and Y-maze test were utilized to evaluate the motor and nonmotor symptoms. We found that administration of Sch improved both disorders and DA neurodegeneration in 6-OHDA-induced mice. Additional data confirmed that Sch treatment significantly increased BDNF expression and decreased the activity of GSK-3β in the striatum and hippocampus. Moreover, Sch was able to alleviate the abnormal levels of ROS and increase SOD by boosting Nrf2 expression. The nuclear translocation of NF-κB was inhibited by Sch, which subsequently led to a downregulation of proinflammatory cytokines. Sch effectively suppressed apoptosis by decreasing expressions of caspase 3, caspase 9, and p53 in the PD mouse model. Our findings demonstrate that Sch protects against DA neurodegeneration in 6-OHDA-induced PD mice by suppressing oxidative stress, neuroinflammation and apoptosis through the involvement of the BDNF/Nrf2/NF-κB signaling pathway.

Caffeine, a natural methylxanthine nutraceutical, exerts dopaminergic neuroprotection

Parkinson's disease (PD) is a progressive neurodegenerative disorder that affects more than 10 million people worldwide. Oxidative stress and mitochondrial dysfunction play a significant role in altering the homeostasis of energy production and free radical generation. Current PD therapies are focused on reducing the cardinal symptoms rather than preventing disease progression in the patients. Adenosine A_2A receptor (A_2A R) antagonist (Istradephylline) combined with levodopa shows a promising therapy for PD. In animal studies, caffeine administration showed to improve motor functions and neuroprotective effect in the neurons. Caffeine is probably the most extensively used psychoactive substance. In this current study, we investigated the neuroprotective effect of caffeine against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced neurodegeneration. Here, we demonstrate that caffeine improves behavioral and neurotransmitter recovery against MPTP-induced toxicity. Caffeine restores endogenous antioxidant levels and suppresses neuroinflammation. Our finding suggests that the blockage of A_2AR is a promising disease-modifying therapy for PD. Target engagement strategies could be more beneficial in preventing disease progression rather than symptomatic reliefs in PD patients.

Targeted graphene oxide for drug delivery as a therapeutic nanoplatform against Parkinson's disease

There has been an exponential increase in the rate of incidence of Parkinson's disease (PD) with aging in the global population. PD, the second most common neurodegenerative disorder, results from damaged dopamine neurons in the substantia nigra pars compacta (SNpc), along with the deposition of abnormal α-synuclein (α-Syn), and the progressive degeneration of neurons in striatal regions. Despite extensive investigations to understand the pathophysiology of PD to develop effective therapies to restrict its progression, there is currently no cure for PD. Puerarin (Pue) is a natural compound with remarkable anti-PD properties. However, its poor pharmacological properties, including poor water solubility, inadequate bioavailability, and incomplete penetration of the blood-brain barrier (BBB) have restricted its use for the treatment of PD. Nevertheless, advancements in nanotechnology have revealed the potential advantages of targeted drug delivery into the brain to treat PD. Here, we used Pue-loaded graphene oxide (GO) nanosheets, which have an excellent drug-loading ability, modifiable surface functional groups, and good biocompatibility. Then, Pue was transported across the BBB into the brain using lactoferrin (Lf) as the targeting ligand, which could bind to the vascular endothelial receptor on the BBB. In vivo and in vitro results indicated that this multifunctional brain targeted drug delivery system (Lf-GO-Pue) was an effective and safe therapy for PD.

Recuperative effect of estrogen on rotenone-induced experimental model of Parkinson's disease in rats

Parkinson's disease (PD) is described as the loss of dopaminergic neurons located in the substantia nigra (SN) region of the brain and a progressive motor failure. Increased frequency of PD in women, especially after menopause, suggests the effect of estrogen. This view has been supported with empirical studies. Therefore, the effect of estrogen in an experimental model of Parkinson's disease induced by rotenone was investigated. A total of 32 female Wistar Albino rats were randomly assigned to four groups (control group, ovariectomy group, Parkinson's group, Parkinson's + estrogen group). The Parkinson's group received rotenone subcutanously at the dose of 2.5 mg/kg bw, on the 1st, 2nd, 3rd 4th, 6th, 9th, 12th, 15th, 18th, and 21st days animals in the Parkinson's + estrogen group received retonon as in the Parkinson's group and was additionally subcutaneously given estrogen (implant containing 0.5 mg 17 β-estradiol lasting for 21 days). The rats were subjected to rotarod, pole, and swimming tests at the end of the experiment for comparison of their motor activities, and then, histopathological and biochemical analyses were performed on the tissues that were extracted. The rotarod results revealed that Parkinson's group had the shortest time (32.33 ± 3.98 sn) than the groups of control (92.50 ± 12.60 s) ovariectomy (71.42 ± 10.58 s), and Parkinson's + estrogen (71.37 ± 9.26 s). The results of pole disclosed that return and landing time prolonged for Parkinson's group when compared with other groups (return time for control 2.98 ± 0.38 s, ovariectomy 3.02 ± 0.75 s, Parkinson 5.91 ± 0.33 s, Parkinson's + estrogen 3.48 ± 0.42 s and landing time for control 5.30 ± 0.59 s, ovariectomy 5.45 ± 0.73 s, Parkinson 9.80 ± 0.90 s, Parkinson's + estrogen 5.37 ± 1.02 s). Parkinson's group had longest (90.71 ± 12.56 s) swimming time to reach the target when compared with control (33.16 ± 8.68 s), ovariectomy (47.37 ± 12.19 s), and Parkinson's + estrogen (49.82 ± 5.78 s). Histopathological examination indicated a significant difference in tyrosine hydroxylase-stained cells (dopaminergic neurons and dopamine) between the Parkinson's + estrogen group and the Parkinson's group. The biochemical analyses of Caspas-3 activation in SN and striatum (STR) was significantly different between the Parkinson's + estrogen group and the Parkinson's group, but this difference was not observed in STR while evaluating Bcl-2. The results of this study suggested that estrogen may have a recuperative effect on PD.

MicroPET imaging of vesicular monoamine transporter 2 revealed the potentiation of (+)-dihydrotetrabenazine on MPTP-induced degeneration of dopaminergic neurons

INTRODUCTION

Vesicular monoamine transporter 2 (VMAT2) has been associated with the risk of PD. Genetic reduction of VMAT2 level is reported to increase the vulnerability for dopaminergic neurodegeneration. In this study, by using in vivo microPET imaging with a VMAT2 radioligand [18F]fluoropropyl-(+)-dihydrotetrabenazine ([18F]FP-(+)-DTBZ), we investigated the enhanced role of inhibiting VMAT2 in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced loss of dopaminergic neurons.

METHODS

The (+)-α-dihydrotetrabenazine ((+)-DTBZ, an inhibitor of VMAT2, 5 mg/kg), or MPTP (low dose (ld): 10 mg/kg, high dose (hd): 30 mg/kg) or both of them were intraperitoneally injected into C57BL/6 mice for 5 or 10 consecutive days. MicroPET imaging with [18F]FP-(+)-DTBZ was performed to test the dopaminergic neuronal integrity. [18F]FP-(+)-DTBZ uptake in striatum was quantified as standardized uptake value (SUV). The pathological changes in the striata and substantia nigra were confirmed by measuring the DA contents and immunohistochemical staining of tyrosine hydroxylase (TH).

RESULTS

In vivo imaging results showed that the striatal SUVs of both DTBZ&MPTPld and MPTPhd groups were substantially declined compared to the baseline. Moreover, the striatal uptakes of [18F]FP-(+)-DTBZ in DTBZ&MPTPld and MPTPhd groups were obviously lower than the control, DTBZ group and MPTPld group. Notably, the decrease of the striatal uptake in the DTBZ&MPTPld/10d group was more serious than the DTBZ&MPTPld/5d group and comparable to the MPTPhd group. Consistently, the ratios of DA metabolites to DA in DTBZ&MPTPld/10d and MPTPhd mice were significantly increased. The correlation analysis showed that SUVs were highly correlated to the striatal dopaminergic fiber density and TH-positive dopaminergic neuron number in the substantia nigra.

CONCLUSIONS

MicroPET brain imaging with [18F]FP-(+)-DTBZ noninvasively revealed that (+)-DTBZ co-administration significantly aggravated the neurotoxicity of MPTP to dopaminergic neurons, suggesting that inhibition of VMAT2 may be related to the pathogenesis of PD and tracing VMAT2 activity with PET imaging is of potential value in monitoring PD progression.

Neural Basis of Dental Pulp Stem Cells and its Potential Application in Parkinson's disease

Parkinson's disease (PD) is the second most common neurodegenerative disease after Alzheimer's disease. Though significant insights into the molecular-biochemical-cellular-behavioral basis of PD have been understood, there is no appreciable treatment available till date. Current therapies provide symptomatic relief without any influence on the progression of the disease. Stem cell therapy has been vigorously explored to treat PD. In this comprehensive review, we analyze various stem cell candidates for treating PD and discuss the possible mechanisms. We advocate the advantage of using neural crest originated dental pulp stem cells (DPSC) due to their predisposition towards neural differentiation and their potential to regenerate neurons far better than commonly used bone marrow derived mesenchymal stem cells (BM-MSCs). Eventually, we highlight the current challenges in the field and the strategies which may be used for overcoming the impediments.

A Comprehensive Phenotype of Non-motor Impairments and Distribution of Alpha-Synuclein Deposition in Parkinsonism-Induced Mice by a Combination Injection of MPTP and Probenecid

Parkinson's disease (PD) is characterized by non-motor symptoms as well as motor deficits. The non-motor symptoms rarely appear individually and occur simultaneously with motor deficits or independently. However, a comprehensive research on the non-motor symptoms using an experimental model of PD remains poorly understood. The aim of the current study is to establish a chronic mouse model of PD mimicking the comprehensive non-motor symptoms of human PD by injection of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and probenecid (MPTP/p). The non-motor and motor symptoms were evaluated by performing buried food, short-term olfactory memory, hot plate, open field, tail suspension, Y maze, novel object recognition, bead expulsion, one-h stool collection, rotarod, rearing, catalepsy, and akinesia tests after 10 injections of MPTP/p into mice. The expression levels of α-synuclein, glial fibrillary acidic protein (GFAP), tyrosine hydroxylase (TH) or DJ-1 were analyzed by Western blotting or immunostaining. MPTP/p-treated mice achieved to reproduce the key features of non-motor symptoms including olfactory deficit, thermal hyperalgesia, anxiety, depression, cognitive decline, and gastrointestinal dysfunction in addition to motor deficits. The MPTP/p-treated mice also showed the high levels of α-synuclein and low levels of TH and DJ-1 in striatum, substantia nigra, olfactory bulb, hippocampus, amygdala, prefrontal cortex, locus coeruleus, or colon. In addition, the expression levels of phosphorylated-α-synuclein and GFAP were elevated in the striatum and substantia nigra in the MPTP/p-treated mice. Taken together, our study clarifies that the chronic MPTP/p-treated mice have a variety of non-motor dysfunctions as well as motor abnormalities by α-synuclein overexpression and dopaminergic depletion. Therefore, the study of comprehensive phenotypes of non-motor symptoms in one PD model would advance in-depth understandings of neuropathological alternations and contribute to future strategies for PD treatment.