Regional nigral neuromelanin degeneration in asymptomatic leucine-rich repeat kinase 2 gene carrier using MRI.

Asymptomatic Leucine-Rich Repeat Kinase 2 Gene (LRRK2) carriers are at risk for developing Parkinson's disease (PD). We studied presymptomatic substantia nigra pars compacta (SNc) regional neurodegeneration in asymptomatic LRRK2 carriers compared to idiopathic PD patients using neuromelanin-sensitive MRI technique (NM-MRI). Fifteen asymptomatic LRRK2 carriers, 22 idiopathic PD patients, and 30 healthy controls (HCs) were scanned using NM-MRI. We computed volume and contrast-to-noise ratio (CNR) derived from the whole SNc and the sensorimotor, associative, and limbic SNc regions. An analysis of covariance was performed to explore the differences of whole and regional NM-MRI values among the groups while controlling the effect of age and sex. In whole SNc, LRRK2 had significantly lower CNR than HCs but non-significantly higher volume and CNR than PD patients, and PD patients significantly lower volume and CNR compared to HCs. Inside SNc regions, there were significant group effects for CNR in all regions and for volumes in the associative region, with a trend in the sensorimotor region but no significant changes in the limbic region. PD had reduced volume and CNR in all regions compared to HCs. Asymptomatic LRRK2 carriers showed globally decreased SNc volume and CNR suggesting early nigral neurodegeneration in these subjects at risk of developing PD.

Adenosine A2A Receptor Blockade Provides More Effective Benefits at the Onset Rather than after Overt Neurodegeneration in a Rat Model of Parkinson's Disease.

Adenosine A2A receptor (A2AR) antagonists are the leading nondopaminergic therapy to manage Parkinson's disease (PD) since they afford both motor benefits and neuroprotection. PD begins with a synaptic dysfunction and damage in the striatum evolving to an overt neuronal damage of dopaminergic neurons in the substantia nigra. We tested if A2AR antagonists are equally effective in controlling these two degenerative processes. We used a slow intracerebroventricular infusion of the toxin MPP+ in male rats for 15 days, which caused an initial loss of synaptic markers in the striatum within 10 days, followed by a neuronal loss in the substantia nigra within 30 days. Interestingly, the initial loss of striatal nerve terminals involved a loss of both dopaminergic and glutamatergic synaptic markers, while GABAergic markers were preserved. The daily administration of the A2AR antagonist SCH58261 (0.1 mg/kg, i.p.) in the first 10 days after MPP+ infusion markedly attenuated both the initial loss of striatal synaptic markers and the subsequent loss of nigra dopaminergic neurons. Strikingly, the administration of SCH58261 (0.1 mg/kg, i.p. for 10 days) starting 20 days after MPP+ infusion was less efficacious to attenuate the loss of nigra dopaminergic neurons. This prominent A2AR-mediated control of synaptotoxicity was directly confirmed by showing that the MPTP-induced dysfunction (MTT assay) and damage (lactate dehydrogenase release assay) of striatal synaptosomes were prevented by 50 nM SCH58261. This suggests that A2AR antagonists may be more effective to counteract the onset rather than the evolution of PD pathology.

GLP-1 modulated the firing activity of nigral dopaminergic neurons in both normal and parkinsonian mice.

The spontaneous firing activity of nigral dopaminergic neurons is associated with some important roles including modulation of dopamine release, expression of tyrosine hydroxylase (TH), as well as neuronal survival. The decreased neuroactivity of nigral dopaminergic neurons has been revealed in Parkinson's disease. Central glucagon-like peptide-1 (GLP-1) functions as a neurotransmitter or neuromodulator to exert multiple brain functions. Although morphological studies revealed the expression of GLP-1 receptors (GLP-1Rs) in the substantia nigra pars compacta, the possible modulation of GLP-1 on spontaneous firing activity of nigral dopaminergic neurons is unknown. The present extracellular in vivo single unit recordings revealed that GLP-1R agonist exendin-4 significantly increased the spontaneous firing rate and decreased the firing regularity of partial nigral dopaminergic neurons of adult male C57BL/6 mice. Blockade of GLP-1Rs by exendin (9-39) decreased the firing rate of nigral dopaminergic neurons suggesting the involvement of endogenous GLP-1 in the modulation of firing activity. Furthermore, the PKA and the transient receptor potential canonical (TRPC) 4/5 channels are involved in activation of GLP-1Rs-induced excitatory effects of nigral dopaminergic neurons. Under parkinsonian state, both the exogenous and endogenous GLP-1 could still induce excitatory effects on the surviving nigral dopaminergic neurons. As the mild excitatory stimuli exert neuroprotective effects on nigral dopaminergic neurons, the present GLP-1-induced excitatory effects may partially contribute to its antiparkinsonian effects.

Effects of electroacupuncture on Sirt3/NLRP3/GSDMD signaling pathway in the substantia nigra of midbrain of rats with Parkinson's disease. / ç”µé’ˆå¯¹å¸•é‡‘æ£®ç— å¤§é¼ ä¸­è„‘é»‘è´¨Sirt3/NLRP3/GSDMD信号通路的影响.

OBJECTIVES: To observe the effects on tyrosine hydroxylase (TH), α-synaptic nucleoprotein (α-syn), sirtuin 3 (Sirt3), NOD-like receptor 3 (NLRP3) and gasdermin-D (GSDMD) in the substantia nigra of midbrain after electroacupuncture (EA) at "Fengfu"(GV16), "Taichong" (LR3) and "Zusanli" (ST36) in rats of Parkinson's disease (PD), so as to explore the mechanism of EA in treatment of PD. METHODS: SD rats were randomly divided into control, model and EA groups, with 10 rats in each group. The PD model was established by injecting rotenone into the neck and back, lasting 28 days. In the EA group, EA was applied to GV16, LR3 and ST36, 30 min each time, once daily, consecutively for 28 days. The open-field test was adopted to detect the total distance of autonomic movement of rats, and the pole climbing test was used to detect the body coordination ability of rats. In the substania nigra of midbrain, the positive expression of TH was determined using immunohistochemistry, the mRNA expression levels of α - syn, Sirt3, NLRP3 and GSDMD were detected by quantitative real-time fluorescence PCR, and the protein expression levels of NLRP3, apoptosis-associated speck-like protein containing a caspase-recruitment domain (ASC) and cysteinyl aspartate specific proteinase (Caspase)-1 were detected by Western blot. RESULTS: Compared with the control group, the total distance of autonomous movement was decreased (P<0.01) in the model group, and the score of pole climbing experiment was increased (P<0.01)；in the midbrain substantia nigra the positive expression of TH was decreased (P<0.01)；the mRNA expression level of Sirt3 was decreased (P<0.01), and those of α-syn, NLRP3 and GSDMD were increased (P<0.01)；while the protein expression levels of NLRP3, ASC and Caspase-1 were increased (P<0.01). When compared with the model group, the total distance of autonomous movement in open field experiment was increased (P<0.01) in the EA group and the score of pole climbing experiment was lower (P<0.05)；in the midbrain substantia nigra the positive expression of TH was increased (P<0.01)；the mRNA expression level of Sirt3 in the midbrain substantia nigra was increased (P<0.01), and those of α-syn, NLRP3 and GSDMD were reduced (P<0.01)；while the protein expression levels of NLRP3, ASC and Caspase-1 decreased (P<0.01, P<0.05). CONCLUSIONS: EA at "GV16" "LR3" and "ST36" can repair the neuronal injury, clear the abnormal accumulation of α-syn in the substania nigra of midbrain, and ameliorate mitochondrial damage in PD rats, which may be obtained by regulating Sirt3/NLRP3/GSDMD signaling pathway, so as to delay the occurrence and development of Parkinson's disease.

Alpha-synuclein inclusion responsive microglia are resistant to CSF1R inhibition.

BACKGROUND: Parkinson's disease (PD) is a neurodegenerative disorder that is characterized by the presence of proteinaceous alpha-synuclein (α-syn) inclusions (Lewy bodies), markers of neuroinflammation and the progressive loss of nigrostriatal dopamine (DA) neurons. These pathological features can be recapitulated in vivo using the α-syn preformed fibril (PFF) model of synucleinopathy. We have previously determined that microglia proximal to PFF-induced nigral α-syn inclusions increase in soma size, upregulate major-histocompatibility complex-II (MHC-II) expression, and increase expression of a suite of inflammation-associated transcripts. This microglial response is observed months prior to degeneration, suggesting that microglia reacting to α-syn inclusion may contribute to neurodegeneration and could represent a potential target for novel therapeutics. The goal of this study was to determine whether colony stimulating factor-1 receptor (CSF1R)-mediated microglial depletion impacts the magnitude of α-syn aggregation, nigrostriatal degeneration, or the response of microglial in the context of the α-syn PFF model. METHODS: Male Fischer 344 rats were injected intrastriatally with either α-syn PFFs or saline. Rats were continuously administered Pexidartinib (PLX3397B, 600 mg/kg), a CSF1R inhibitor, to deplete microglia for a period of either 2 or 6 months. RESULTS: CSF1R inhibition resulted in significant depletion (~ 43%) of ionized calcium-binding adapter molecule 1 immunoreactive (Iba-1ir) microglia within the SNpc. However, CSF1R inhibition did not impact the increase in microglial number, soma size, number of MHC-II immunoreactive microglia or microglial expression of Cd74, Cxcl10, Rt-1a2, Grn, Csf1r, Tyrobp, and Fcer1g associated with phosphorylated α-syn (pSyn) nigral inclusions. Further, accumulation of pSyn and degeneration of nigral neurons was not impacted by CSF1R inhibition. Paradoxically, long term CSF1R inhibition resulted in increased soma size of remaining Iba-1ir microglia in both control and PFF rats, as well as expression of MHC-II in extranigral regions. CONCLUSIONS: Collectively, our results suggest that CSF1R inhibition does not impact the microglial response to nigral pSyn inclusions and that CSF1R inhibition is not a viable disease-modifying strategy for PD.

Aging accelerates locomotor decline in PINK1 knockout rats in association with decreased nigral, but not striatal, dopamine and tyrosine hydroxylase expression.

Parkinson's disease (PD) rodent models provide insight into the relationship between nigrostriatal dopamine (DA) signaling and locomotor function. Although toxin-based rat models produce frank nigrostriatal neuron loss and eventual motor decline characteristic of PD, the rapid nature of neuronal loss may not adequately translate premotor traits, such as cognitive decline. Unfortunately, rodent genetic PD models, like the Pink1 knockout (KO) rat, often fail to replicate the differential severity of striatal DA and tyrosine hydroxylase (TH) loss, and a bradykinetic phenotype, reminiscent of human PD. To elucidate this inconsistency, we evaluated aging as a progression factor in the timing of motor and non-motor cognitive impairments. Male PINK1 KO and age-matched wild type (WT) rats were evaluated in a longitudinal study from 3 to 16 months old in one cohort, and in a cross-sectional study of young adult (6-7 months) and aged (18-19 months) in another cohort. Young adult PINK1 KO rats exhibited hyperkinetic behavior associated with elevated DA and TH in the substantia nigra (SN), which decreased therein, but not striatum, in the aged KO rats. Additionally, norepinephrine levels decreased in aged KO rats in the prefrontal cortex (PFC), paired with a higher DA levels in young and aged KO. Although a younger age of onset characterizes familial forms of PD, our results underscore the critical need to consider age-related factors. Moreover, the results indicate that compensatory mechanisms may exist to preserve locomotor function, evidenced by increased DA in the SN early in the lifespan, in response to deficient PINK1 function, which declines with aging and the onset of motor decline.

[Improvement effect of cinnamaldehyde on reserpine-induced Parkinson's disease rat model].

In order to study the neuroprotective mechanism of cinnamaldehyde on reserpine-induced Parkinson's disease(PD) rat models, 72 male Wistar rats were randomly divided into blank group, model group, Madopar group, and cinnamaldehyde high-, medium-, and low-dose groups. Except for the blank group, the other groups were intraperitoneally injected with reserpine of 0.1 mg·kg~(-1) once every other morning, and cinnamaldehyde and Madopar solutions were gavaged every afternoon. Open field test, rotarod test, and oral chewing movement evaluation were carried out in the experiment. The brain was taken and fixed. The positive expression of dopamine receptor D1(DRD1) was detected by TSA, and the changes in neurotransmitters such as dopamine(DA) and 3,4-dihydroxyphenylacetic acid(DOPAC) in the brain were detected by enzyme-linked immunosorbent assay(ELISA). The protein and mRNA expression levels of tyrosine hydroxylase(TH) and α-synuclein(α-Syn) in substantia nigra(SN) were detected by RT-PCR and Western blot. The results showed that after the injection of reserpine, the hair color of the model group became yellow and dirty; the arrest behavior was weakened, and the body weight was reduced. The spontaneous movement and exploration behavior were reduced, and the coordination exercise ability was decreased. The number of oral chewing was increased, but the cognitive ability was decreased, and the proportion of DRD1 positive expression area in SN was decreased. The expression of TH protein and mRNA was down-regulated, and that of α-Syn protein and mRNA was up-regulated. After cinnamaldehyde intervention, it had an obvious curative effect on PD model animals. The spontaneous movement behavior, the time of staying in the rod, the time of movement, the distance of movement, and the number of standing times increased, and the number of oral chewing decreased. The proportion of DRD1 positive expression area in SN increased, and the protein and mRNA expression levels of α-Syn were down-regulated. The protein and mRNA expression levels of TH were up-regulated. In addition, the levels of DA, DOPAC, and homovanillic acid(HVA) neurotransmitters in the brain were up-regulated. This study can provide a new experimental basis for clinical treatment and prevention of PD.

High-fat diet exacerbates 1-Bromopropane-induced loss of dopaminergic neurons in the substantia nigra of mice through mitochondrial damage associated necroptotic pathway.

In recent years, accumulating evidence supports that occupational exposure to solvents is associated with an increased incidence of Parkinson's disease (PD) among workers. The neurotoxic effects of 1-bromopropane (1-BP), a widely used new-type solvent, are well-established, yet data on its relationship with the etiology of PD remain limited. Simultaneously, high-fat consumption in modern society is recognized as a significant risk factor for PD. However, whether there is a synergistic effect between a high-fat diet and 1-BP exposure remains unclear. In this study, adult C57BL/6 mice were fed either a chow or a high-fat diet for 18 weeks prior to 12-week 1-BP treatment. Subsequent neurobehavioral and neuropathological examinations were conducted to assess the effects of 1-BP exposure on parkinsonian pathology. The results demonstrated that 1-BP exposure produced obvious neurobehavioral abnormalities and dopaminergic degeneration in the nigral region of mice. Importantly, a high-fat diet further exacerbated the impact of 1-BP on motor and cognitive abnormalities in mice. Mechanistic investigation revealed that mitochondrial damage and mtDNA release induced by 1-BP and high-fat diet activate NLRP3 and cGAS-STING pathway- mediated neuroinflammatory response, and ultimately lead to necroptosis of dopaminergic neurons. In summary, our study unveils a potential link between chronic 1-BP exposure and PD-like pathology with motor and no-motor defects in experimental animals, and long-term high-fat diet can further promote 1-BP neurotoxicity, which underscores the pivotal role of environmental factors in the etiology of PD.

Neuromelanin levels in individuals with substance use disorders: A systematic review and meta-analysis.

Dopamine's role in addiction has been extensively studied, revealing disruptions in its functioning throughout all addiction stages. Neuromelanin in the substantia nigra (SN) may reflect dopamine auto-oxidation, and can be quantified using neuromelaninsensitive magnetic resonance imaging (neuromelanin-MRI) in a non-invasive manner.In this pre-registered systematic review, we assess the current body of evidence related to neuromelanin levels in substance use disorders, using both post-mortem and MRI examinations. The systematic search identified 10 relevant articles, primarily focusing on the substantia nigra. An early-stage meta-analysis (n = 6) revealed varied observations ranging from standardized mean differences of -3.55 to +0.62, with a pooled estimate of -0.44 (95 % CI = -1.52, 0.65), but there was insufficient power to detect differences in neuromelanin content among individuals with substance use disorders. Our gap analysis highlights the lack of sufficient replication studies, with existing studies lacking the power to detect a true difference, and a complete lack of neuromelanin studies on certain substances of clinical interest. We provide recommendations for future studies of dopaminergic neurobiology in addictions and related psychiatric comorbidities.

Mitochondrial complex I deficiency stratifies idiopathic Parkinson's disease.

Idiopathic Parkinson's disease (iPD) is believed to have a heterogeneous pathophysiology, but molecular disease subtypes have not been identified. Here, we show that iPD can be stratified according to the severity of neuronal respiratory complex I (CI) deficiency, and identify two emerging disease subtypes with distinct molecular and clinical profiles. The CI deficient (CI-PD) subtype accounts for approximately a fourth of all cases, and is characterized by anatomically widespread neuronal CI deficiency, a distinct cell type-specific gene expression profile, increased load of neuronal mtDNA deletions, and a predilection for non-tremor dominant motor phenotypes. In contrast, the non-CI deficient (nCI-PD) subtype exhibits no evidence of mitochondrial impairment outside the dopaminergic substantia nigra and has a predilection for a tremor dominant phenotype. These findings constitute a step towards resolving the biological heterogeneity of iPD with implications for both mechanistic understanding and treatment strategies.

Long-term benefits of hematopoietic stem cell-based macrophage/microglia delivery of GDNF to the CNS in a mouse model of Parkinson's disease.

Glial cell line-derived neurotrophic factor (GDNF) protects dopaminergic neurons in various models of Parkinson's disease (PD). Cell-based GDNF gene delivery mitigates neurodegeneration and improves both motor and non-motor functions in PD mice. As PD is a chronic condition, this study aims to investigate the long-lasting benefits of hematopoietic stem cell (HSC)-based macrophage/microglia-mediated CNS GDNF (MMC-GDNF) delivery in an MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) mouse model. The results indicate that GDNF treatment effectively ameliorated MPTP-induced motor deficits for up to 12 months, which coincided with the protection of nigral dopaminergic neurons and their striatal terminals. Also, the HSC-derived macrophages/microglia were recruited selectively to the neurodegenerative areas of the substantia nigra. The therapeutic benefits appear to involve two mechanisms: (1) macrophage/microglia release of GDNF-containing exosomes, which are transferred to target neurons, and (2) direct release of GDNF by macrophage/microglia, which diffuses to target neurons. Furthermore, the study found that plasma GDNF levels were significantly increased from baseline and remained stable over time, potentially serving as a convenient biomarker for future clinical trials. Notably, no weight loss, altered food intake, cerebellar pathology, or other adverse effects were observed. Overall, this study provides compelling evidence for the long-term therapeutic efficacy and safety of HSC-based MMC-GDNF delivery in the treatment of PD.

Effect of electroacupuncture on brain-gut oxidative stress in Parkinson's disease mice. / ç”µé’ˆå¯¹å¸•é‡‘æ£®ç— å°é¼ è„‘è‚ æ°§åŒ–åº”æ¿€çš„å½±å“.

OBJECTIVES: To observe the effect of electroacupuncture (EA) on behavior, oxidative stress factors in colon and substantia nigra of Parkinson's disease (PD) mice, so as to explore the mechanism of EA in treating PD. METHODS: C57BL/6 mice were randomly divided into blank, model and EA groups, with 12 mice in each group. The PD mouse model was established by continuous gavage of rotenone for 4 weeks. Mice in the EA group received EA (2 Hz/15 Hz) at "Baihui" (GV20), "Quchi" (LI11) and "Zusanli" (ST36) for 20 min, 5 days a week for 2 weeks. After intervention, gait analysis was used to evaluate the motor ability and motor coordination. Ink propulsion rate was used to evaluate the intestinal transport function. The level of reactive oxygen species (ROS) in the colon was detected by flow cytometry. The contents of total protein (TP), malondialdehyde (MDA) and activities of glutathione peroxidase (GSH-Px), superoxide dismutase (SOD) in colon and substantia nigra were detected by ELISA. The expression of nuclear factor E2-related factor 2 (Nrf2) in substantia nigra was detected by immunofluorescence staining. RESULTS: Compared with the blank group, the average speed, step rate, normal step ratio, distance between the front and hind feet, stride length, swing speed and maximum intensity of the maximum contact area of mice in the model group were decreased (P<0.000 1, P<0.01, P<0.001), the maximum change rate of gait was increased (P<0.001) in the model group. The intestinal propulsion rate, the activities of GSH-Px and SOD in the colon and substantia nigra, and the positive expression of Nrf2 in substantia nigra were decreased (P<0.000 1, P<0.01, P<0.05), while the fluorescence intensity of ROS in the colon, the contents of MDA in colon and substantia nigra were increased (P<0.01). Compared with the model group, the average speed, step rate, normal step ratio, distance between the front and hind feet, stride length, swing speed, and maximum intensity of the maximum contact area of the mice in the EA group were increased (P<0.01, P<0.05, P<0.001, P<0.000 1), the maximum change rate of gait was decreased (P<0.01). The intestinal propulsion rate, the activities of GSH-Px and SOD in the colon and substantia nigra, the positive expression of Nrf2 in substantia nigra were increased (P<0.001, P<0.05, P<0.000 1), while the ROS fluorescence intensity in the colon, the MDA contents in the colon and substantia nigra were decreased (P<0.01). CONCLUSIONS: EA can improve the movement disorder, gait disorder and intestinal motor function of PD mice, and protect dopaminergic neurons from damage, which may be related to its effect in antagonistic brain-gut oxidative stress.

Establishment of a 6-OHDA Induced Unilaterally Lesioned Male Wistar Rat Model of Parkinson's Disease.

Robust preclinical models of Parkinson's disease (PD) are valuable tools for understanding the biology and treatment of this complex disease. 6-Hydroxydopamine (6-OHDA) is a selective catecholaminergic drug injected into the substantia nigra pars compacta (SNc), medial forebrain bundle (MFB), or striatum, which is then metabolized to induce parkinsonism. Unilateral injection of 6-OHDA produces loss of dopaminergic (DAergic) neurons on the injected side with a marked motor asymmetry known as hemiparkinsonism, typically characterized by a rotational behavior to the impaired side. The present work describes a stable unilateral 6-OHDA-lesioned rat model of PD. 6-OHDA was administered into the MFB, leading to the consistent loss of striatal dopamine (DA) and behavioral imbalance in unilateral 6-OHDA-lesioned rats to establish the model of PD. This model of PD is a valuable tool for understanding the mechanisms underlying the generation of parkinsonian symptoms.

Chrysin for Neurotrophic and Neurotransmitter Balance in Parkinson's Disease.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) has a direct impact on the dopaminergic neurons in the substantia nigra pars compacta (SNpc), dopamine in the striatum (ST), homovanillic acid (HVA), neurotrophic factors of the SNpc, and ST regions leading to Parkinson's disease (PD). Dopaminergic neuron atrophy in the SNpc and dopamine degradation in the ST have an explicit link to disrupted homeostasis of the neurotrophic factor brain-derived neurotrophic factor (BDNF) of the SNpc and ST regions. Chrysin is a flavonoid with a pharmacological potential that directly influences neurotrophic levels as well as neurotransmitters. As a result, analysis of the altering levels of neurotransmitters such as dopamine and its metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), are observed via high-performance liquid chromatography (HPLC) and the confirmation of the influential role of BDNF and glial-derived neurotrophic factor (GDNF) in the homeostasis of dopamine, DOPAC, and HAV via examination of gene expression. The observation confirmed that chrysin balances the altering levels of neurotransmitters as well as neurotrophic factors. The protocols for reverse transcription-polymerase chain reaction (RT-PCR) and HPLC analysis for neurotransmitter levels from the SNpc and ST regions of acute PD mice brain-induced MPTP are described in this chapter.

Engrailed 1 deficiency induces changes in ciliogenesis during human neuronal differentiation.

A key pathological feature of Parkinson's Disease (PD) is the progressive degeneration of dopaminergic neurons (DAns) in the substantia nigra pars compacta. Considering the major role of EN1 in the development and maintenance of these DAns and the implications from En1 mouse models, it is highly interesting to study the molecular and protective effect of EN1 also in a human cellular model. Therefore, we generated EN1 knock-out (ko) human induced pluripotent stem cell (hiPSCs) lines and analyzed these during neuronal differentiation. Although the EN1 ko didn't interfere with neuronal differentiation and generation of tyrosine hydroxylase positive (TH+) neurons per se, the neurons exhibited shorter neurites. Furthermore, mitochondrial respiration, as well as mitochondrial complex I abundance was significantly reduced in fully differentiated neurons. To understand the implications of an EN1 ko during differentiation, we performed a transcriptome analysis of human neuronal precursor cells (hNPCs) which unveiled alterations in cilia-associated pathways. Further analysis of ciliary morphology revealed an elongation of primary cilia in EN1-deficient hNPCs. Besides, also Wnt signaling pathways were severely affected. Upon stimulating hNPCs with Wnt which drastically increased EN1 expression in WT lines, the phenotypes concerning mitochondrial function and cilia were exacerbated in EN1 ko hNPCs. They failed to enhance the expression of the complex I subunits NDUFS1 and 3, and now displayed a reduced mitochondrial respiration. Furthermore, Wnt stimulation decreased ciliogenesis in EN1 ko hNPCs but increased ciliary length even further. This further highlights the relevance of primary cilia next to mitochondria for the functionality and correct maintenance of human DAns and provides new possibilities to establish neuroprotective therapies for PD.

Unveiling the therapeutic prospects of EGFR inhibition in rotenone-mediated parkinsonism in rats: Modulation of dopamine D3 receptor.

Parkinson's disease (PD) is characterized by the progressive loss of dopaminergic neurons in the substantia nigra. The dopamine D3 receptor (D3R) plays a significant role in the pathogenesis and treatment of PD. Activation of receptor tyrosine kinases (RTKs) inhibits signaling mediated by G protein-coupled receptor (GPCR). Epidermal growth factor receptors (EGFRs) and dopamine D3 receptors in the brain are directly associated with PD, both in terms of its development and potential treatment. Therefore, we investigated the impact of modulating the EGFR, a member of the RTKs family, and the dopamine D3R, a member of the GPCR family. In the present study, 100 mg/kg of lapatinib (LAP) was administered to rotenone-intoxicated rats for three weeks. Our findings indicate that LAP effectively alleviated motor impairment, improved histopathological abnormalities, and restored dopaminergic neurons in the substantia nigra. This restoration was achieved through the upregulation of dopamine D3R and increase of tyrosine hydroxylase (TH) expression, as well as boosting dopamine levels. Furthermore, LAP inhibited the activity of p-EGFR, GRK2, and SCR. Additionally, LAP exhibited antioxidant properties by inhibiting the 4-hydroxynonenal (4-HNE) and PLCγ/PKCßII pathway, while enhancing the antioxidant defense mechanism by increasing GSH-GPX4 pathway. The current study offers insights into the potential repositioning of LAP as a disease-modifying drug for PD. This could be achieved by modulating the dopaminergic system and curbing oxidative stress.

Reduction of alpha-synuclein oligomers in preclinical models of Parkinson's disease by electrical stimulation in vitro and deep brain stimulation in vivo.

BACKGROUND: Deep brain stimulation (DBS) has been widely used to manage debilitating neurological symptoms in movement disorders such as Parkinson's disease (PD). Despite its well-established symptomatic benefits, our understanding of the mechanisms underlying DBS and its possible effect on the accumulation of pathological proteins in neurodegeneration remains limited. Accumulation and oligomerization of the protein alpha-synuclein (α-Syn) are implicated in the loss of dopaminergic neurons in the substantia nigra in PD, making α-Syn a potential therapeutic target for disease modification. OBJECTIVE: We examined the effects of high frequency electrical stimulation on α-Syn levels and oligomerization in cell and rodent models. METHODS: High frequency stimulation, mimicking DBS parameters used for PD, was combined with viral-mediated overexpression of α-Syn in cultured rat primary cortical neurons or in substantia nigra of rats. Bimolecular protein complementation with split fluorescent protein reporters was used to detect and quantify α-Syn oligomers. RESULTS: High frequency electrical stimulation reduced the expression of PD-associated mutant α-Syn and mitigated α-Syn oligomerization in cultured neurons. Furthermore, DBS in the substantia nigra, but not the subthalamic nucleus, decreased overall levels of α-Syn, including oligomer levels, in the substantia nigra. CONCLUSIONS: Taken together, our results demonstrate that direct high frequency stimulation can reduce accumulation and pathological forms of α-Syn in cultured neurons in vitro and in substantia nigra in vivo. Thus, DBS therapy could have a role beyond symptomatic treatment, with potential disease-modifying properties that can be exploited to target pathological proteins in neurodegenerative diseases.

Dopamine and serotonin in human substantia nigra track social context and value signals during economic exchange.

Dopamine and serotonin are hypothesized to guide social behaviours. In humans, however, we have not yet been able to study neuromodulator dynamics as social interaction unfolds. Here, we obtained subsecond estimates of dopamine and serotonin from human substantia nigra pars reticulata during the ultimatum game. Participants, who were patients with Parkinson's disease undergoing awake brain surgery, had to accept or reject monetary offers of varying fairness from human and computer players. They rejected more offers in the human than the computer condition, an effect of social context associated with higher overall levels of dopamine but not serotonin. Regardless of the social context, relative changes in dopamine tracked trial-by-trial changes in offer value-akin to reward prediction errors-whereas serotonin tracked the current offer value. These results show that dopamine and serotonin fluctuations in one of the basal ganglia's main output structures reflect distinct social context and value signals.

Single-cell spatial transcriptomic and translatomic profiling of dopaminergic neurons in health, aging, and disease.

The brain is spatially organized and contains unique cell types, each performing diverse functions and exhibiting differential susceptibility to neurodegeneration. This is exemplified in Parkinson's disease with the preferential loss of dopaminergic neurons of the substantia nigra pars compacta. Using a Parkinson's transgenic model, we conducted a single-cell spatial transcriptomic and dopaminergic neuron translatomic analysis of young and old mouse brains. Through the high resolving capacity of single-cell spatial transcriptomics, we provide a deep characterization of the expression features of dopaminergic neurons and 27 other cell types within their spatial context, identifying markers of healthy and aging cells, spanning Parkinson's relevant pathways. We integrate gene enrichment and genome-wide association study data to prioritize putative causative genes for disease investigation, identifying CASR as a regulator of dopaminergic calcium handling. These datasets represent the largest public resource for the investigation of spatial gene expression in brain cells in health, aging, and disease.

Alpha-synuclein pathology is associated with astrocyte senescence in a midbrain organoid model of familial Parkinson's disease.

Parkinson's disease (PD) is a complex, progressive neurodegenerative disease characterized by the loss of dopaminergic neurons in the substantia nigra pars compacta in the midbrain. Despite extensive research efforts, the molecular and cellular changes that precede neurodegeneration in PD are poorly understood. To address this, here we describe the use of patient specific human midbrain organoids harboring the SNCA triplication to investigate mechanisms underlying dopaminergic degeneration. Our midbrain organoid model recapitulates key pathological hallmarks of PD, including the aggregation of α-synuclein and the progressive loss of dopaminergic neurons. We found that these pathological hallmarks are associated with an increase in senescence associated cellular phenotypes in astrocytes including nuclear lamina defects, the presence of senescence associated heterochromatin foci, and the upregulation of cell cycle arrest genes. These results suggest a role of pathological α-synuclein in inducing astrosenescence which may, in turn, increase the vulnerability of dopaminergic neurons to degeneration.