Parkinson's Disease Pathology Research Articles

Functional screening of lysosomal storage disorder genes identifies modifiers of alpha-synuclein neurotoxicity.

Heterozygous variants in the glucocerebrosidase (GBA) gene are common and potent risk factors for Parkinson's disease (PD). GBA also causes the autosomal recessive lysosomal storage disorder (LSD), Gaucher disease, and emerging evidence from human genetics implicates many other LSD genes in PD susceptibility. We have systemically tested 86 conserved fly homologs of 37 human LSD genes for requirements in the aging adult Drosophila brain and for potential genetic interactions with neurodegeneration caused by α-synuclein (αSyn), which forms Lewy body pathology in PD. Our screen identifies 15 genetic enhancers of αSyn-induced progressive locomotor dysfunction, including knockdown of fly homologs of GBA and other LSD genes with independent support as PD susceptibility factors from human genetics (SCARB2, SMPD1, CTSD, GNPTAB, SLC17A5). For several genes, results from multiple alleles suggest dose-sensitivity and context-dependent pleiotropy in the presence or absence of αSyn. Homologs of two genes causing cholesterol storage disorders, Npc1a / NPC1 and Lip4 / LIPA, were independently confirmed as loss-of-function enhancers of αSyn-induced retinal degeneration. The enzymes encoded by several modifier genes are upregulated in αSyn transgenic flies, based on unbiased proteomics, revealing a possible, albeit ineffective, compensatory response. Overall, our results reinforce the important role of lysosomal genes in brain health and PD pathogenesis, and implicate several metabolic pathways, including cholesterol homeostasis, in αSyn-mediated neurotoxicity.

Oscillatory beta dynamics inform biomarker-driven treatment optimization for Parkinson's disease.

Parkinson's disease (PD) is a neurodegenerative disorder characterized by loss of dopaminergic neurons and dysregulation of the basal ganglia. Cardinal motor symptoms include bradykinesia, rigidity, and tremor. Deep brain stimulation (DBS) of select subcortical nuclei is standard of care for medication-refractory PD. Conventional open-loop DBS delivers continuous stimulation with fixed parameters that do not account for a patient's dynamic activity state or medication cycle. In comparison, closed-loop DBS, or adaptive DBS (aDBS), adjusts stimulation based on biomarker feedback that correlates with clinical state. Recent work has identified several neurophysiological biomarkers in local field potential recordings from PD patients, the most promising of which are 1) elevated beta (∼13-30 Hz) power in the subthalamic nucleus (STN), 2) increased beta synchrony throughout basal ganglia-thalamocortical circuits, notably observed as coupling between the STN beta phase and cortical broadband gamma (∼50-200 Hz) amplitude, and 3) prolonged beta bursts in the STN and cortex. In this review, we highlight relevant frequency and time domain features of STN beta measured in PD patients and summarize how spectral beta power, oscillatory beta synchrony, phase-amplitude coupling, and temporal beta bursting inform PD pathology, neurosurgical targeting, and DBS therapy. We then review how STN beta dynamics inform predictive, biomarker-driven aDBS approaches for optimizing PD treatment. We therefore provide clinically useful and actionable insight that can be applied toward aDBS implementation for PD.

Overview of the Impact of Pathogenic LRRK2 Mutations in Parkinson's Disease.

Leucine-rich repeat kinase 2 (LRRK2) is a large protein kinase that physiologically phosphorylates and regulates the function of several Rab proteins. LRRK2 is genetically implicated in the pathogenesis of both familial and sporadic Parkinson's disease (PD), although the underlying mechanism is not well understood. Several pathogenic mutations in the LRRK2 gene have been identified, and in most cases the clinical symptoms that PD patients with LRRK2 mutations develop are indistinguishable from those of typical PD. However, it has been shown that the pathological manifestations in the brains of PD patients with LRRK2 mutations are remarkably variable when compared to sporadic PD, ranging from typical PD pathology with Lewy bodies to nigral degeneration with deposition of other amyloidogenic proteins. The pathogenic mutations in LRRK2 are also known to affect the functions and structure of LRRK2, the differences in which may be partly attributable to the variations observed in patient pathology. In this review, in order to help researchers unfamiliar with the field to understand the mechanism of pathogenesis of LRRK2-associated PD, we summarize the clinical and pathological manifestations caused by pathogenic mutations in LRRK2, their impact on the molecular function and structure of LRRK2, and their historical background.

Pathological convergence of APP and SNCA deficiency in hippocampal degeneration of young rats

The common pathogenesis of Alzheimer’s disease (AD) and Parkinson’s disease (PD) has been supported by biochemical, genetic and molecular evidence. Mitochondrial dysfunction is considered to be the common pathology in early AD and PD. The physiological regulation of APP and α-synuclein on mitochondria remains unclear, let alone whether they share common regulatory mechanisms affecting the development of neurodegenerative diseases. By studying gene knockout rats, the commonality of physiological APP and α-synuclein in maintaining mitochondrial function through calcium homeostasis regulation was revealed, which was critical in inhibiting hippocampal degeneration in young rats. APP and α-synuclein both control hippocampal mitochondrial calcium intake and outflow. In the mitochondrial calcium influx regulation, APP and α-synuclein are located on the mitochondrial-associated endoplasmic reticulum membrane (MAM) and converge to regulate the IP3R1-Grp75-VDAC2 axis. Mitochondrial calcium outflow is redundantly promoted by both α-synuclein and APP. Loss of APP or SNCA leads to mitochondrial calcium overload, thus enhancing aerobic respiration and ER stress, and ultimately causing excessive apoptosis in the hippocampus and spatial memory impairment in young rats. Based on this study, we believe that the physiological function impairment of APP and SNCA is the early core pathology to induce mitochondrial dysfunction at the early stage of AD and PD, while the IP3R1-Grp75-VDAC2 axis might be the common drug target of these two diseases.

Evaluation of Potential Neuroprotective Effects of Vanillin Against MPP+/MPTP-Induced Dysregulation of Dopaminergic Regulatory Mechanisms in SH-SY5Y Cells and a Mouse Model of Parkinson's Disease.

Parkinson's disease (PD) is a progressive neurodegenerative condition. The pathogenesis of PD is still unknown, and drugs available for PD treatment either have side effects or have suboptimal efficacy. Flavonoids are potent antioxidants having little toxicity with extended use, suggesting they might hold promising therapeutic potential against PD. Vanillin (Van) is a phenolic compound that has exhibited neuroprotective properties in various neurological disorders, including PD. However, the neuroprotective role of Van in PD and its underlying mechanisms are scarce and therefore need more exploration. Here, we evaluated the neuroprotective potential of Van and its associated mechanisms against MPP+/MPTP-induced neuronal loss in differentiated human neuroblastoma (SH-SY5Y) cells and the mouse model of PD. In the present study, Van treatment significantly enhanced the cell viability and alleviated oxidative stress, mitochondrial membrane potential, and apoptosis in MPP+-intoxicated SH-SY5Y cells. Moreover, Van significantly ameliorated the MPP+-induced dysregulations in protein expression of tyrosine hydroxylase (TH) and mRNA expressions of GSK-3β, PARP1, p53, Bcl-2, Bax, and Caspase-3 genes in SH-SY5Y cells. Similar to our in vitro results, Van significantly alleviated MPTP-induced neurobehavioral dysregulations, oxidative stress, aberrant TH protein expressions, and immunoreactivity in SNpc of mice brains. Treatment of Van also prevented MPTP-mediated loss of TH-positive intrinsic dopaminergic neurons to SNpc and TH-fibers projecting to the striatum of mice. Thus, Van exhibited promising neuroprotective properties in the current study against MPP+/MPTP-intoxicated SH-SY5Y cells and mice, indicating its potential therapeutic properties against PD pathology.

Intestinal origins of Parkinson's Disease pathologies

Accumulating evidence suggests that Parkinson’s disease (PD) pathology may arise in the gut. This likely occurs through the enteric nervous system (ENS), which facilitates bidirectional communication between the brain and intestines. A hallmark of PD is neuronal accumulation of misfolded α-synuclein (aSyn) proteins which have been shown to travel from the ENS to the brain via the vagus nerve. The goal of this study was to connect related neural and immune phenotypes in ex vivo and in vivo mouse models of PD.Recent data suggests that enteric neuronal fibers containing calcitonin gene related peptide (CGRP) act as chemo-sensors that can be stimulated to release CGRP in response to bacterial and chemical signals. CGRP can activate receptors that influence goblet cells (GCs) and immune cells. GCs are responsible for secreting mucus to maintain mucosal barrier integrity. Deterioration of gut barrier integrity is hallmark of PD patients. We hypothesize that alterations in luminal contents modifies and disturbs GCs disrupting the gut barrier in PD. This may result in increased release of CGRP leading to alterations in mucus production, immune responses, and aSyn aggregation in enteric neurons. In this study, the pesticide rotenone was given to C57BL/6 mice to facilitate aggregation of misfolded aSyn. Lectin and immuno-histochemistry were performed on sections of ileum and colon. GC mucopolysaccharides were fluorescently labeled with the lectin Ulex Europaeus Agglutinin I (UEA) conjugated to rhodamine. UEA-1+ cells in crypts were 25% more prevalent (68.5 +/- 0.5 vs. 52.5 +/-2.5) with rotenone treatment but 53% less prevalent in the luminal portion of crypts (22.5 +/- 2.5 vs. 47.5 +/-2.5). Fewer GCs in luminal positions is consistent with decreased mucus seen in PD patients. T cells were identified by immunoreactive (ir) CD3. Approximately 50% fewer CD3+ cells were in rotenone treated lamina propria (17 +/- 1.4) compared to control (36.2 +/- 3.5) consistent with previous reports. The area of CGRP-ir fibers in the lamina propria was 114% higher in control (6.4%+/-1.3) compared to rotenone treated tissue (5.6%+/-0.6). Rotenone treatment resulted in a 217% increase in the area average of CGRP-ir fibers in the region just below the epithelial monolayer (12.8%+/-1.3) compared to control (5.8%+/-0.7). While we did not observe CGRP fibers beyond the epithelial cell layer, GC cell disruption that could allow luminal contents to access CGRP fibers was suggested by the potential failure of GCs to migrate toward luminal surfaces from crypts. Future studies are needed to test the hypothesis that rotenone disturbance of mitochondrial function in GCs causes intestinal wall failure that leads to altered neuroimmune function. Aggregation of aSyn in enteric neurons may thereby be mediated by altered immune to neural actions as exacerbated by alterations in CGRP containing fibers and T cell populations in the gut. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

The alleviative effect of Calendula officinalis L. extract against Parkinson's disease-like pathology in zebrafish via the involvement of autophagy activation.

Parkinson's disease (PD) is the second most prevalent neurodegenerative disorder. However, effective preventative or therapeutic agents for PD remain largely limited. Marigold Calendula officinalis L. (CoL) has been reported to possess a wide range of biological activities, but its neuroprotective activity including anti-neurodegenerative diseases is unclear. Here, we aim to investigate whether the extract of CoL (ECoL) has therapeutic activity on PD. We identified the chemical composition of flavonoid, an important active ingredient in ECoL, by a targeted HPLC-Q-TOF-MS analysis. Subsequently, we evaluated the anti-PD effect of ECoL by using zebrafish PD model induced by 1-methyl-4-phenyl-1-1,2,3,6-tetrahydropyridine (MPTP). After ECoL+MPTP co-treatments, the changes of dopaminergic neurons, neural vasculature, nervous system, and locomotor activity were examined, respectively. The expressions of genes related to neurodevelopment and autophagy were detected by RT-qPCR. Further, the interaction between autophagy regulators and ECoL flavonoids was predicted using molecular docking method. As a result, 5 kinds of flavonoid were identified in ECoL, consisting of 121 flavones and flavonols, 32 flavanones, 22 isoflavonoids, 11 chalcones and dihydrochalcones, and 17 anthocyanins. ECoL significantly ameliorated the loss of dopaminergic neurons and neural vasculature, restored the injury of nervous system, and remarkably reversed the abnormal expressions of neurodevelopment-related genes. Besides, ECoL notably inhibited the locomotor impairment in MPTP-induced PD-like zebrafish. The underlying anti-PD effect of ECoL may be implicated in activating autophagy, as ECoL significantly upregulated the expressions of genes related to autophagy, which contributes to the degradation of α-synuclein aggregation and dysfunctional mitochondria. Molecular docking simulation showed the stable interaction between autophagy regulators (Pink, Ulk2, Atg7, and Lc3b) and 10 main compounds of flavonoid in ECoL, further affirming the involvement of autophagy activation by ECoL in anti-PD action. Our results suggested that ECoL has the anti-PD effect, and ECoL might be a promising therapeutic candidate for PD treatment.

A seed amplification assay to detect Parkinson disease pathology.

A seed amplification assay to detect Parkinson disease pathology.

Oxidative Stress and Neuroinflammation in Parkinson's Disease: The Role of Dopamine Oxidation Products.

Parkinson's disease (PD) is a chronic neurodegenerative condition affecting more than 1% of people over 65 years old. It is characterized by the preferential degeneration of nigrostriatal dopaminergic neurons, which is responsible for the motor symptoms of PD patients. The pathogenesis of this multifactorial disorder is still elusive, hampering the discovery of therapeutic strategies able to suppress the disease's progression. While redox alterations, mitochondrial dysfunctions, and neuroinflammation are clearly involved in PD pathology, how these processes lead to the preferential degeneration of dopaminergic neurons is still an unanswered question. In this context, the presence of dopamine itself within this neuronal population could represent a crucial determinant. In the present review, an attempt is made to link the aforementioned pathways to the oxidation chemistry of dopamine, leading to the formation of free radical species, reactive quinones and toxic metabolites, and sustaining a pathological vicious cycle.

Characterization of Pairs of Toxic and Nontoxic Misfolded Protein Oligomers Elucidates the Structural Determinants of Oligomer Toxicity in Protein Misfolding Diseases.

The aberrant misfolding and aggregation of peptides and proteins into amyloid aggregates occurs in over 50 largely incurable protein misfolding diseases. These pathologies include Alzheimer's and Parkinson's diseases, which are global medical emergencies owing to their prevalence in increasingly aging populations worldwide. Although the presence of mature amyloid aggregates is a hallmark of such neurodegenerative diseases, misfolded protein oligomers are increasingly recognized as of central importance in the pathogenesis of many of these maladies. These oligomers are small, diffusible species that can form as intermediates in the amyloid fibril formation process or be released by mature fibrils after they are formed. They have been closely associated with the induction of neuronal dysfunction and cell death. It has proven rather challenging to study these oligomeric species because of their short lifetimes, low concentrations, extensive structural heterogeneity, and challenges associated with producing stable, homogeneous, and reproducible populations. Despite these difficulties, investigators have developed protocols to produce kinetically, chemically, or structurally stabilized homogeneous populations of protein misfolded oligomers from several amyloidogenic peptides and proteins at experimentally ameneable concentrations. Furthermore, procedures have been established to produce morphologically similar but structurally distinct oligomers from the same protein sequence that are either toxic or nontoxic to cells. These tools offer unique opportunities to identify and investigate the structural determinants of oligomer toxicity by a close comparative inspection of their structures and the mechanisms of action through which they cause cell dysfunction.This Account reviews multidisciplinary results, including from our own groups, obtained by combining chemistry, physics, biochemistry, cell biology, and animal models for pairs of toxic and nontoxic oligomers. We describe oligomers comprised of the amyloid-β peptide, which underlie Alzheimer's disease, and α-synuclein, which are associated with Parkinson's disease and other related neurodegenerative pathologies, collectively known as synucleinopathies. Furthermore, we also discuss oligomers formed by the 91-residue N-terminal domain of [NiFe]-hydrogenase maturation factor from E. coli, which we use as a model non-disease-related protein, and by an amyloid stretch of Sup35 prion protein from yeast. These oligomeric pairs have become highly useful experimental tools for studying the molecular determinants of toxicity characteristic of protein misfolding diseases. Key properties have been identified that differentiate toxic from nontoxic oligomers in their ability to induce cellular dysfunction. These characteristics include solvent-exposed hydrophobic regions, interactions with membranes, insertion into lipid bilayers, and disruption of plasma membrane integrity. By using these properties, it has been possible to rationalize in model systems the responses to pairs of toxic and nontoxic oligomers. Collectively, these studies provide guidance for the development of efficacious therapeutic strategies to target rationally the cytotoxicity of misfolded protein oligomers in neurodegenerative conditions.

Targeted Extracellular Vesicle Gene Therapy for Modulating Alpha-Synuclein Expression in Gut and Spinal Cord.

The development of effective disease-modifying therapies to halt Parkinson's disease (PD) progression is required. In a subtype of PD patients, alpha-synuclein pathology may start in the enteric nervous system (ENS) or autonomic peripheral nervous system. Consequently, strategies to decrease the expression of alpha-synuclein in the ENS will be an approach to prevent PD progression at pre-clinical stages in these patients. In the present study, we aimed to assess if anti-alpha-synuclein shRNA-minicircles (MC) delivered by RVG-extracellular vesicles (RVG-EV) could downregulate alpha-synuclein expression in the intestine and spinal cord. RVG-EV containing shRNA-MC were injected intravenously in a PD mouse model, and alpha-synuclein downregulation was evaluated by qPCR and Western blot in the cord and distal intestine. Our results confirmed the downregulation of alpha-synuclein in the intestine and spinal cord of mice treated with the therapy. We demonstrated that the treatment with anti-alpha-synuclein shRNA-MC RVG-EV after the development of pathology is effective to downregulate alpha-synuclein expression in the brain as well as in the intestine and spinal cord. Moreover, we confirmed that a multidose treatment is necessary to maintain downregulation for long-term treatments. Our results support the potential use of anti-alpha-synuclein shRNA-MC RVG-EV as a therapy to delay or halt PD pathology progression.

Non-invasive auditory and visual stimulation attenuates α-Synuclein deposition and improves motor and non-motor symptoms in PD mice

Parkinson's disease (PD) is characterized by dopaminergic neuron loss and α-synuclein (α-Syn) aggregates, but lacks effective treatments for the disease progression and non-motor symptoms. Recently, combined 40 Hz auditory and visual stimulation is emerging as a promising non-invasive method to decrease amyloid and improve cognition in Alzheimer's disease (AD), but whether this treatment can modify α-Syn-induced PD pathology remains unclear. Here we evaluated the effects of chronic exposure to 40 Hz and 80 Hz auditory and visual stimulation on α-Syn accumulation and the functional effects of 40 Hz stimulation on motor, cognitive and mood dysfunctions in PD mice. We found that 40 Hz and 80 Hz auditory and visual stimulation activated multiple cortical regions, entrained gamma oscillations and markedly attenuated p-α-Syn deposition in neurons, but not astrocytes, microglial cells in the primary and secondary motor cortex (M1, M2), medial prefrontal cortex (mPFC) and the striatum. Moreover, 40 Hz stimulation significantly reduced cell apoptosis in M1, increased the neuromuscular strength selectively in PD mice, which correlated with p-α-Syn reduction in the motor cortex. In addition, 40 Hz stimulation improved spatial working memory and decreased depressive-like behaviors specifically in PD mice, which correlated with p-α-Syn reduction in mPFC, but promoted anxiety-like behaviors and increased stress-related adreno-cortico-tropic-hormone (ACTH), corticosterone levels in the plasma of normal mice. Collectively, we demonstrated that chronic multisensory gamma stimulation (40 Hz and 80 Hz) significantly attenuates α-Syn deposition in neurons of the interconnected cortex and 40 Hz stimulation improved neuromuscular strength, spatial working memory, and reduced depressive behaviors, which support its non-invasive therapeutic potential for modifying PD progression and treating non-motor symptoms.

DOPAL initiates αSynuclein-dependent impaired proteostasis and degeneration of neuronal projections in Parkinson’s disease

Dopamine dyshomeostasis has been acknowledged among the determinants of nigrostriatal neuron degeneration in Parkinson’s disease (PD). Several studies in experimental models and postmortem PD patients underlined increasing levels of the dopamine metabolite 3,4-dihydroxyphenylacetaldehyde (DOPAL), which is highly reactive towards proteins. DOPAL has been shown to covalently modify the presynaptic protein αSynuclein (αSyn), whose misfolding and aggregation represent a major trait of PD pathology, triggering αSyn oligomerization in dopaminergic neurons. Here, we demonstrated that DOPAL elicits αSyn accumulation and hampers αSyn clearance in primary neurons. DOPAL-induced αSyn buildup lessens neuronal resilience, compromises synaptic integrity, and overwhelms protein quality control pathways in neurites. The progressive decline of neuronal homeostasis further leads to dopaminergic neuron loss and motor impairment, as showed in in vivo models. Finally, we developed a specific antibody which detected increased DOPAL-modified αSyn in human striatal tissues from idiopathic PD patients, corroborating the translational relevance of αSyn-DOPAL interplay in PD neurodegeneration.

The role of exosomes in pathogenesis and the therapeutic efficacy of mesenchymal stem cell-derived exosomes against Parkinson's disease.

Parkinson's disease (PD) is a chronic, progressive, neurodegenerative disease. The predominant pathology of PD is the loss of dopaminergic cells in the substantia nigra. Cell transplantation is a strategy with significant potential for treating PD; mesenchymal stem cells (MSCs) are a tremendous therapeutic cell source because they are easily accessible. MSC-derived exosomes with potential protective action in lesioned sites serve as an essential promoter of neuroprotection, and neurodifferentiation, by modulating neural stem cells, neurons, glial cells, and axonal growth in vitro and in vivo environments. The biological properties of MSC-derived exosomes have been proposed as a beneficial tool in different pathological conditions, including PD. Therefore, in this review, we assort the current understanding of MSC-derived exosomes as a new possible therapeutic strategy for PD by providing an overview of the potential role of miRNAs as a component of exosomes in the cellular and molecular basis of PD.

Matrix metalloproteinase-9 inhibition prevents aquaporin-4 depolarization-mediated glymphatic dysfunction in Parkinson’s disease

IntroductionThe glymphatic system offers a perivascular pathway for the clearance of pathological proteins and metabolites to optimize neurological functions. Glymphatic dysfunction plays a pathogenic role in Parkinson's disease (PD); however, the molecular mechanism of glymphatic dysfunction in PD remains elusive. ObjectiveTo explore whether matrix metalloproteinase-9 (MMP-9)-mediated β-dystroglycan (β-DG) cleavage is involved in the regulation of aquaporin-4 (AQP4) polarity-mediated glymphatic system in PD. Methods1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD and A53T mice were used in this study. The glymphatic function was evaluated using ex vivo imaging. TGN-020, an AQP4 antagonist, was administered to investigate the role of AQP4 in glymphatic dysfunction in PD. GM6001, an MMP-9 antagonist, was administered to investigate the role of the MMP-9/β-DG pathway in regulating AQP4. The expression and distribution of AQP4, MMP-9, and β-DG were assessed using western blotting, immunofluorescence, and co-immunoprecipitation. The ultrastructure of basement membrane (BM)-astrocyte endfeet was detected using transmission electron microscopy. Rotarod and open-field tests were performed to evaluate motor behavior. ResultsPerivascular influx and efflux of cerebral spinal fluid tracers were reduced in MPTP-induced PD mice with impaired AQP4 polarization. AQP4 inhibition aggravated reactive astrogliosis, glymphatic drainage restriction, and dopaminergic neuronal loss in MPTP-induced PD mice. MMP-9 and cleaved β-DG were upregulated in both MPTP-induced PD and A53T mice, with reduced polarized localization of β-DG and AQP4 to astrocyte endfeet. MMP-9 inhibition restored BM-astrocyte endfeet-AQP4 integrity and attenuated MPTP-induced metabolic perturbations and dopaminergic neuronal loss. ConclusionAQP4 depolarization contributes to glymphatic dysfunction and aggravates PD pathologies, and MMP-9-mediated β-DG cleavage regulates glymphatic function through AQP4 polarization in PD, which may provide novel insights into the pathogenesis of PD.

Suppression of neuroinflammation and α-synuclein oligomerization by rotarod walking exercise in subacute MPTP model of Parkinson's disease

Parkinson's disease (PD) belongs to an α-synucleinopathy and manifests motor dysfunction attributed to nigrostriatal dopaminergic degeneration. In clinical practice, the beneficial role of physical therapy such as motor skill learning training has been recognized in PD-linked motor defects. Nevertheless, the disease-modifying effects of motor skill learning training on PD-related pathology remain unclear. Here, we investigated the disease-modifying effects of rotarod walking exercise (RWE), a modality of motor skill learning training, in a subacute 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD. In motor function and dopaminergic degeneration, RWE improved MPTP-induced deficits. In addition, RWE enhanced the expression of neurotrophic factors BDNF/GDNF, PGC1-α, Nurr1, and p-AMPK, thereby recovering dopaminergic neuronal cell death. Moreover, RWE inhibited microglial activation and the expression of pro-inflammatory markers, such as p-IκBα, iNOS, IL-1β, TNF-α, and cathepsin D, while elevating anti-inflammatory IL-10 and TGF-β. RWE also decreased oxidative stress markers in the substantia nigra, such as 4-HNE and 8-OHdG-positive cells, while increasing Nrf2-controlled antioxidant enzymes. Regarding the effect of RWE on α-synuclein, it reduced the monomer/oligomer forms of α-synuclein and phosphorylation at serine 129. Further mechanistic studies revealed that RWE suppressed the expression of matrix metalloproteinase-3 and p-GSK3β (Y216), which play key roles in α-synuclein aggregation. These data collectively suggest that inhibition of neuroinflammation and α-synuclein oligomerization by RWE may contribute to the improvement of PD pathology.

Potassium Channels in Parkinson's Disease: Potential Roles in Its Pathogenesis and Innovative Molecular Targets for Treatment.

Parkinson's disease (PD) is a neurodegenerative disorder characterized by selective loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc) region of the midbrain. The loss of neurons results in a subsequent reduction of dopamine in the striatum, which underlies the core motor symptoms of PD. To date, there are no effective treatments to stop, slow, or reverse the pathologic progression of dopaminergic neurodegeneration. This unfortunate predicament is because of the current early stages in understanding the biologic targets and pathways involved in PD pathogenesis. Ion channels have become emerging targets for new therapeutic development for PD due to their essential roles in neuronal function and neuroinflammation. Potassium channels are the most prominent ion channel family and have been shown to be critically important in PD pathology because of their roles in modulating neuronal excitability, neurotransmitter release, synaptic transmission, and neuroinflammation. In this review, members of the subfamilies of voltage-gated K+ channels, inward rectifying K+ channels, and Ca2+-activated K+ channels are described. Evidence of the role of these channels in PD etiology is discussed together with the latest views on related pathologic mechanisms and their potential as biologic targets for developing neuroprotective drugs for PD. SIGNIFICANCE STATEMENT: Parkinson's disease (PD) is the second most common neurodegenerative disorder, featuring progressive degeneration of dopaminergic neurons in the midbrain. It is a multifactorial disease involving multiple risk factors and complex pathobiological mechanisms. Mounting evidence suggests that ion channels play vital roles in the pathogenesis and progression of PD by regulating neuronal excitability and immune cell function. Therefore, they have become "hot" biological targets for PD, as demonstrated by multiple clinical trials of drug candidates targeting ion channels for PD therapy.

Progesterone exerts a neuroprotective action in a Parkinson's disease human cell model through membrane progesterone receptor α (mPRα/PAQR7).

Parkinson's disease (PD) is the second most common neurodegenerative disease worldwide, and current treatment options are unsatisfactory on the long term. Several studies suggest a potential neuroprotective action by female hormones, especially estrogens. The potential role of progestogens, however, is less defined, and no studies have investigated the potential involvement of membrane progesterone receptors (mPRs). In the present study, the putative neuroprotective role for mPRs was investigated in SH-SY5Y cells, using two established pharmacological treatments for cellular PD models, 6-hydroxydopamine (6-OHDA) and 1-methyl-4-phenylpyridinium (MPP+). Our results show that both the physiologic agonist progesterone and the specific mPR agonist Org OD 02-0 were effective in reducing SH-SY5Y cell death induced by 6-OHDA and MPP+, whereas the nuclear PR agonist promegestone (R5020) and the GABAA receptor agonist muscimol were ineffective. Experiments performed with gene silencing technology and selective pharmacological agonists showed that mPRα is the isoform responsible for the neuroprotective effects we observed. Further experiments showed that the PI3K-AKT and MAP kinase signaling pathways are involved in the mPRα-mediated progestogen neuroprotective action in SH-SY5Y cells. These findings suggest that mPRα could play a neuroprotective role in PD pathology and may be a promising target for the development of therapeutic strategies for PD prevention or management.

NF-κB/c-Rel DNA-binding is reduced in substantia nigra and peripheral blood mononuclear cells of Parkinson's disease patients

Although Parkinson's disease (PD) key neuropathological hallmarks are well known, the underlying pathogenic mechanisms of the disease still need to be elucidated to identify innovative disease-modifying drugs and specific biomarkers. NF-κB transcription factors are involved in regulating several processes associated with neurodegeneration, such as neuroinflammation and cell death, that could be related to PD pathology. NF-κB/c-Rel deficient (c-rel−/−) mice develop a progressive PD-like phenotype. The c-rel−/− mice present both prodromal and motor symptoms as well as key neuropathological features, including nigrostriatal dopaminergic neurons degeneration, accumulation of pro-apoptotic NF-κB/RelA acetylated at the lysine 310 residue (Ac-RelA(lys310)) and progressive caudo-rostral brain deposition of alpha-synuclein. c-Rel inhibition can exacerbate MPTP-induced neurotoxicity in mice. These findings support the claim that misregulation of c-Rel protein may be implicated in PD pathophysiology. In this study, we aimed at evaluating c-Rel levels and DNA-binding activity in human brains and peripheral blood mononuclear cells (PBMCs) of sporadic PD patients. We analyzed c-Rel protein content and activity in frozen substantia nigra (SN) samples from post-mortem brains of 10 PD patients and 9 age-matched controls as well as in PBMCs from 72 PD patients and 40 age-matched controls. c-Rel DNA-binding was significantly lower and inversely correlated with Ac-RelA(lys310) content in post-mortem SN of sporadic PD cases, when compared to healthy controls. c-Rel DNA-binding activity was also reduced in PBMCs of followed-up PD subjects. The decrease of c-Rel activity in PBMCs from PD patients appeared to be independent from dopaminergic medication or disease progression, as it was evident even in early stage, drug-naïve patients. Remarkably, the levels of c-Rel protein were comparable in PD and control subjects, pointing out a putative role for post-translational modifications of the protein in c-Rel dysfunctions.These findings support that PD is characterized by the loss of NF-κB/c-Rel activity that potentially has a role in PD pathophysiology. Future studies will be aimed at addressing whether the reduction of c-Rel DNA-binding could constitute a novel biomarker for PD.

Opposing effects of β-2 and β-1 adrenergic receptor signaling on neuroinflammation and dopaminergic neuron survival in α-synuclein-mediated neurotoxicity

BackgroundNoradrenergic neurons in the locus coeruleus (LC) are the primary source of norepinephrine (NE) in the brain and degeneration of these neurons is reported in the early stages of Parkinson’s disease (PD), even prior to dopaminergic neuron degeneration in the substantia nigra (SN), which is a hallmark of PD pathology. NE depletion is generally associated with increased PD pathology in neurotoxin-based PD models. The effect of NE depletion in other models of PD-like α-synuclein-based models is largely unexplored. In PD models and in human patients, β-adrenergic receptors’ (AR) signaling is associated with a reduction of neuroinflammation and PD pathology. However, the effect of NE depletion in the brain and the extent of NE and β-ARs signaling involvement in neuroinflammation, and dopaminergic neuron survival is poorly understood.MethodsTwo mouse models of PD, a 6OHDA neurotoxin-based model and a human α-synuclein (hα-SYN) virus-based model of PD, were used. DSP-4 was used to deplete NE levels in the brain and its effect was confirmed by HPLC with electrochemical detection. A pharmacological approach was used to mechanistically understand the impact of DSP-4 in the hα-SYN model of PD using a norepinephrine transporter (NET) and a β-AR blocker. Epifluorescence and confocal imaging were used to study changes in microglia activation and T-cell infiltration after β1-AR and β2-AR agonist treatment in the hα-SYN virus-based model of PD.ResultsConsistent with previous studies, we found that DSP-4 pretreatment increased dopaminergic neuron loss after 6OHDA injection. In contrast, DSP-4 pretreatment protected dopaminergic neurons after hα-SYN overexpression. DSP-4-mediated protection of dopaminergic neurons after hα-SYN overexpression was dependent on β-AR signaling since using a β-AR blocker prevented DSP-4-mediated dopaminergic neuron protection in this model of PD. Finally, we found that the β-2AR agonist, clenbuterol, reduced microglia activation, T-cell infiltration, and dopaminergic neuron degeneration, whereas xamoterol a β-1AR agonist showed increased neuroinflammation, blood brain barrier permeability (BBB), and dopaminergic neuron degeneration in the context of hα-SYN-mediated neurotoxicity.ConclusionsOur data demonstrate that the effects of DSP-4 on dopaminergic neuron degeneration are model specific, and suggest that in the context of α-SYN-driven neuropathology, β2-AR specific agonists may have therapeutic benefit in PD.