Neurodegeneration In PD Research Articles

Usp14 down-regulation corrects sleep and circadian dysfunction of a Drosophila model of Parkinson's disease.

PD is a complex, multifactorial neurodegenerative disease, which occurs sporadically in aged population, with some genetically linked cases. Patients develop a very obvious locomotor phenotype, with symptoms such as bradykinesia, resting tremor, muscular rigidity, and postural instability. At the cellular level, PD pathology is characterized by the presence of intracytoplasmic neurotoxic aggregates of misfolded proteins and dysfunctional organelles, resulting from failure in mechanisms of proteostasis. Nonmotor symptoms, such as constipation and olfactory deficits, are also very common in PD. They include alteration in the circadian clock, and defects in the sleep-wake cycle, which is controlled by the clock. These non-motor symptoms precede the onset of the motor symptoms by many years, offering a window of therapeutic intervention that could delay-or even prevent-the progression of the disease. The mechanistic link between aberrant circadian rhythms and neurodegeneration in PD is not fully understood, although proposed underlying mechanisms include alterations in protein homeostasis (proteostasis), which can impact protein levels of core components of the clock. Loss of proteostasis depends on the progressive pathological decline in the proteolytic activity of two major degradative systems, the ubiquitin-proteasome and the lysosome-autophagy systems, which is exacerbated in age-dependent neurodegenerative conditions like PD. Accordingly, it is known that promoting proteasome or autophagy activity increases lifespan, and rescues the pathological phenotype of animal models of neurodegeneration, presumably by enhancing the degradation of misfolded proteins and dysfunctional organelles, which are known to accumulate in these models, and to induce intracellular damage. We can enhance proteostasis by pharmacologically inhibiting or down-regulating Usp14, a proteasome-associated deubiquitinating enzyme (DUB). In a previous work, we showed that inhibition of Usp14 enhances the activity of the ubiquitin-proteasome system (UPS), autophagy and mitophagy, and abolishes motor symptoms of two well-established fly models of PD that accumulate dysfunctional mitochondria. In this work we extended the evidence on the protective effect of Usp14 down-regulation, and investigated the beneficial effect of down-regulating Usp14 in a Pink1 Drosophila model of PD that develop circadian and sleep dysfunction. We show that down-regulation of Usp14 ameliorates sleep disturbances and circadian defects that are associated to Pink1 KO flies.

Magnolol extends lifespan and improves age-related neurodegeneration in Caenorhabditis elegans via increase of stress resistance

Magnolol is a naturally occurring polyphenolic compound in many edible plants, which has various biological effects including anti-aging and alleviating neurodegenerative diseases. However, the underlying mechanism on longevity is uncertain. In this study, we investigated the effect of magnolol on the lifespan of Caenorhabditis elegans and explored the mechanism. The results showed that magnolol treatment significantly extended the lifespan of nematode and alleviated senescence-related decline in the nematode model. Meanwhile, magnolol enhanced stress resistance to heat shock, hydrogen peroxide (H2O2), mercuric potassium chloride (MeHgCl) and paraquat (PQ) in nematode. In addition, magnolol reduced reactive oxygen species and malondialdehyde (MDA) levels, and increased superoxide dismutase and catalase (CAT) activities in nematodes. Magnolol also up-regulated gene expression of sod-3, hsp16.2, ctl-3, daf-16, skn-1, hsf-1, sir2.1, etc., down-regulated gene expression of daf-2, and promoted intranuclear translocation of daf-16 in nematodes. The lifespan-extending effect of magnolol were reversed in insulin/IGF signaling (IIS) pathway-related mutant lines, including daf-2, age-1, daf-16, skn-1, hsf-1 and sir-2.1, suggesting that IIS signaling is involved in the modulation of longevity by magnolol. Furthermore, magnolol improved the age-related neurodegeneration in PD and AD C. elegans models. These results indicate that magnolol may enhance lifespan and health span through IIS and sir-2.1 pathways. Thus, the current findings implicate magnolol as a potential candidate to ameliorate the symptoms of aging.

Toxic interactions between dopamine, α-synuclein, monoamine oxidase, and genes in mitochondria of Parkinson's disease.

Parkinson's disease is characterized by its distinct pathological features; loss of dopamine neurons in the substantia nigra pars compacta and accumulation of Lewy bodies and Lewy neurites containing modified α-synuclein. Beneficial effects of L-DOPA and dopamine replacement therapy indicate dopamine deficit as one of the main pathogenic factors. Dopamine and its oxidation products are proposed to induce selective vulnerability in dopamine neurons. However, Parkinson's disease is now considered as a generalized disease with dysfunction of several neurotransmitter systems caused by multiple genetic and environmental factors. The pathogenic factors include oxidative stress, mitochondrial dysfunction, α-synuclein accumulation, programmed cell death, impaired proteolytic systems, neuroinflammation, and decline of neurotrophic factors. This paper presents interactions among dopamine, α-synuclein, monoamine oxidase, its inhibitors, and related genes in mitochondria. α-Synuclein inhibits dopamine synthesis and function. Vice versa, dopamine oxidation by monoamine oxidase produces toxic aldehydes, reactive oxygen species, and quinones, which modify α-synuclein, and promote its fibril production and accumulation in mitochondria. Excessive dopamine in experimental models modifies proteins in the mitochondrial electron transport chain and inhibits the function. α-Synuclein and familiar Parkinson's disease-related gene products modify the expression and activity of monoamine oxidase. Type A monoamine oxidase is associated with neuroprotection by an unspecific dose of inhibitors of type B monoamine oxidase, rasagiline and selegiline. Rasagiline and selegiline prevent α-synuclein fibrillization, modulate this toxic collaboration, and exert neuroprotection in experimental studies. Complex interactions between these pathogenic factors play a decisive role in neurodegeneration in PD and should be further defined to develop new therapies for Parkinson's disease.

Transcriptomic similarities in vulnerable and resilient brain regions of Parkinson’s disease and Alzheimer’s disease

AbstractBackgroundParkinson’s disease (PD) and Alzheimer’s disease (AD) share multiple pathophysiological features but affect different brain regions. While the hippocampus is highly vulnerable in AD, the loss of dopaminergic neurons in the substantia nigra (SN) is a hallmark of PD. By contrast, other brain regions, such as the cerebellum, seem resilient to neurodegenerative processes in both diseases. However, the biological mechanisms driving brain regional vulnerability and resilience to neurodegeneration in PD and AD remain elusive. Here, we aimed to analyze the transcriptomic profiles of PD and AD in vulnerable (VR) and resilient (RR) brain regions.MethodPD and AD datasets were obtained from the Gene Expression Omnibus public data repository (PD: GSE28894, GSE20186, GSE20314, GSE42966, GSE49036, GSE54282, GSE20164, GSE20163, and GSE8397; AD: GSE118553, GSE44768, GSE036980, GSE084422, GSE1297, GSE29378, and GSE48350). Hippocampal, SN, and cerebellar differential expression analysis was performed to identify differentially expressed genes (DEGs) for each disease versus age‐matched controls. Functional enrichment analysis (FEA) was accomplished to identify similar signatures in VR and RR in PD and AD. Analyses were performed using the R (adj p‐value <0.05).Result607 DEGs overlapped in the VR of PD and AD, while 1780 DEGs in the RR. FEA revealed 114 gene ontology (GO) terms shared between the VR and 276 GO terms overlapping between PD and AD RR. The GO terms were assembled in clusters of biological processes (Table 1). Cluster observation suggests that both VR and RR share similar enriched processes, such as “cellular respiration”, “regulation of neuron death”, “catabolic pathways”, “response to injury and DNA damage”, and “exocytosis and neurotransmitter secretion”. By contrast, “regulation of cell growth”, “response to steroid hormones”, and “regulation of nervous system development” were unique for the RR, while “membrane lipid metabolic process” and “regulation of cell communication” clusters were found only in the VR.ConclusionOur results highlight a transcriptomic landscape shared by PD and AD in both VR and RR. Looking at the similarities between brain regions vulnerable and resilient in different neurodegenerative diseases may contribute to the understanding of their pathogenesis and clinical course, as well as guide the development of therapeutic strategies.

Buddlejasaponin IVb ameliorates ferroptosis of dopaminergic neuron by suppressing IRP2-mediated iron overload in Parkinson's disease

Ethnopharmacological relevanceParkinson's disease (PD) is the second neurodegenerative disease that lacks effective treatments. Buddlejasaponin IVb (BJP-IVb) is the main bioactive component of herbs in genus Clinopodium which display antioxidative, anti-inflammatory and neuroprotective activities. However, the role of BJP-IVb in PD still remains unknown. Aim of the studyThis study aimed to evaluate the effect of BJP-IVb on dopaminergic neurodegeneration in PD and clarified the underlying mechanisms from the aspect of iron overload-mediated ferroptosis. Materials and methodsOne-methyl-4-phenylpyridinium (MPP+) and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD models were established in this study. Behavioral tests, cell cytotoxicity assay, tyrosine hydroxylase (TH) and Nissl staining were performed to evaluate the antiparkinsonian effect of BJP-IVb. Cellular ultrastructure, iron content and lipid peroxidation were detected to evaluate iron overload-mediated dopaminergic neuron ferroptosis. Iron regulatory protein 2 (IRP2) and iron transport-related proteins were detected by immunofluorescence and Western blot to evaluated iron transport. Finally, plasmid vector-mediated IRP2 overexpression were performed to further clarify the molecular mechanism. ResultsBJP-IVb alleviated MPP+-induced neurotoxicity in vitro and improved MPTP-induced dopaminergic neuron loss and motor dysfunctions of PD mice, confirming an effect of BJP-IVb against dopaminergic neurodegeneration of PD. Further results revealed that BJP-IVb protected against PD by suppressing iron overload-mediated dopaminergic neuron ferroptosis, as evidenced by the attenuated lipid peroxidation, decreased iron content and changes in cellular ultrastructure. Finally, the decreased iron regulatory protein (IRP2) was confirmed to be responsible for BJP-IVb-mediated ferroptosis suppression by modulating iron transport-related proteins and alleviating iron overload. ConclusionBJP-IVb suppressed iron overload-mediated dopaminergic neuron ferroptosis and improved motor dysfunctions in PD, which was achieved by inhibiting IRP2-mediated iron overload. This study provided a potential drug candidate for the treatment of PD.

Search for Molecular Biomarkers of Parkinson’s Disease. New Tissues and Methods

Abstract Parkinson’s disease (PD) is a chronic neurodegenerative disorder that is clinically manifested by motor and non-motor symptoms. At the early stage of the disease, it can be misdiagnosed with some neurologic disorders due to overlapping or similar clinical features. In addition, the pathogenesis of this disease is initiated several years prior to the appearance of classical motor symptoms. This latent phase of neurodegeneration in PD characterised at cellular level by preservation of significant fraction of dopaminergic neurones is of particular interest with respect to the development of disease-modifying or neuroprotective therapies which would require intervention at the earliest stages of disease with an aim to slow down or reverse the disease progression. Therefore, huge effort was performed in order to find and validate a biomarker that would reliably differentiate PD from other neurologic diseases as well as a biomarker that would reveal preclinical/prodromal stage of PD. This short review summarises a recent progress in validation of molecular biomarkers of PD, distinct from genetic markers of PD, with some focus on new analysed tissues and new methods.

The Relationship between Rem Sleep Behaviour Disorder and Parkinson’s Disease Revisited – Are They One and the Same?

This paper reviews the relationship between RBD and PD and the pathophysiology. Most RBD patients develop PD within 14 years. PD pathophysiology is α-synucleinopathy with dopamine degeneration in nigrostriatal pathways. RBD pathology is poorly understood. Anomalies suggest RBD and PD are different, evidenced by smoking. RBD and PD are associated with glucocerebrosidase gene mutations (GBA gene), suggesting RDB with GBA gene mutation predicts PD. PET imaging, assessing vesicular monoamine transporter 2 (VMAT2), indexing nigrostriatal dopamine innervation, is lower in PD and RBD, in the putamen, ventral striatum and globus pallidus but not substantia nigra or subthalamus, compared with controls. VMAT2 may not contribute to pathophysiology of RBD in PD. Treatments for RBD and PD differ. PD with RBD had more depression, compared to PD without RBD. Only PD with RBD had statistically significant increased depression, compared with controls, and non-significant lowered cognition. PD patients, with and without RBD, had decreased ligand binding, compared to healthy controls, indicating no difference in VMAT2 within the caudate and putamen. Research showed differences in cholinergic levels, noradrenaline and glucose metabolism for PD with and without RBD. RBD with PD, is multi-systematic, affecting regions beyond dopaminergic pathways. Treatment of RBD does not affects PD neurodegeneration. Researchers continue to search for neuro-protective intervention. There is a relationship between PD and RBD but it is not absolute. PD nigrostriatal degeneration is independent of RBD. Pathophysiological differences may explain why treatment of RBD does not alter its natural history.

Brain microglia activation and peripheral adaptive immunity in Parkinson’s disease: a multimodal PET study

BackgroundAbnormal activation of immune system is an important pathogenesis of Parkinson’s disease, but the relationship between peripheral inflammation, central microglia activation and dopaminergic degeneration remains unclear.ObjectivesTo evaluate the brain regional microglia activation and its relationship with clinical severity, dopaminergic presynaptic function, and peripheral inflammatory biomarkers related to adaptive immunity.MethodsIn this case–control study, we recruited 23 healthy participants and 24 participants with early-stage Parkinson’s disease. 18F-PBR06 PET/MR for microglia activation, 18F-FP-DTBZ for dopaminergic denervation, total account of T cells and subpopulations of T helper (Th1/Th2/Th17) cells, and the levels of serum inflammatory cytokines were assessed. Sanger sequencing was used to exclude the mix-affinity binders of 18F-PBR06-PET.ResultsCompared to healthy controls, patients with Parkinson’s disease had an increased 18F-PBR06-PET standardized uptake value ratio (SUVR) in the putamen, particularly in the ipsilateral side of the motor onset. 18F-PBR06-PET SUVR was positively associated with 18F-FP-DTBZ-PET SUVR in the brainstem and not associated with disease severity measured by Hoehn and Yahr stage, MDS-UPDRS III scores. Patients with Parkinson’s disease had elevated frequencies of Th1 cells and serum levels of IL10 and IL17A as compared to healthy controls. No significant association between peripheral inflammation markers and microglia activation in the brain of PD was observed.ConclusionParkinson’s disease is associated with early putaminal microglial activation and peripheral phenotypic Th1 bias. Peripheral adaptive immunity might be involved in microglia activation in the process of neurodegeneration in PD indirectly, which may be a potential biomarker for the early detection and the target for immunomodulating therapy.

Rationalizing the Use of Polyphenol Nano-formulations in the Therapy of Neurodegenerative Diseases.

Neurodegenerative diseases are a heterogeneous group of disorders among aging populations worldwide characterized by the progressive degeneration of the structure and function of brain cells and the nervous system. Alzheimer's disease and Parkinson's disease are common neurodegenerative diseases (NDs). Classic pathological features of AD are the accumulation of the amyloid betaprotein and aggregates of hyperphosphorylated tau protein around the brain cells. Dopaminergic neuronal death in the midbrain and accumulation of α- synuclein in the neurons are the hallmark of Parkinson's disease. The pathogenesis is multifactorial, and both neurodegenerative disorders have complex etiology. Oxidative stress closely linked with mitochondrial dysfunction, excitotoxicity, nitric oxide toxicity, and neuro-inflammation, is anticipated to trigger neuronal death. Ample evidence has implicated that oxidative stress and inflammation contribute to the pathology of neurodegeneration in AD and PD. Currently, acetylcholinesterase inhibitors are the main treatment option for AD, while L-DOPA is the gold standard therapy for PD. Along with the main therapy, many endogenous antioxidants, like vitamin E, selenium, etc., are also given to the patients to combat oxidative stress. Current treatment for these NDs is limited due to the blood-brain barrier (BBB) that hinders drug targeting towards neurons. In this review, we emphasize adjunct treatment with anti-inflammatory agents that act at the site of the disease and can halt the disease progression by attenuating the effect of ROS triggering neuro-inflammatory response. Polyphenols, either as purified compounds or extracts from various natural plant sources, have been well studied and documented for anti-inflammatory effects, but their use for ND is limited due to their physicochemical attributes. Nanoparticle-mediated drug delivery system exhibits immense potential to overcome these hurdles in drug delivery to the CNS, enabling nanoparticle-based therapies to directly target the inflammation and release bioactive compounds with anti-inflammatory properties to the site of action.

Intestinal Barrier Dysfunction in the Absence of Systemic Inflammation Fails to Exacerbate Motor Dysfunction and Brain Pathology in a Mouse Model of Parkinson's Disease.

IntroductionParkinson's disease (PD) is the second most common neurodegenerative disease associated with aging. PD patients have systemic and neuroinflammation which is hypothesized to contribute to neurodegeneration. Recent studies highlight the importance of the gut-brain axis in PD pathogenesis and suggest that gut-derived inflammation can trigger and/or promote neuroinflammation and neurodegeneration in PD. However, it is not clear whether microbiota dysbiosis, intestinal barrier dysfunction, or intestinal inflammation (common features in PD patients) are primary drivers of disrupted gut-brain axis in PD that promote neuroinflammation and neurodegeneration.ObjectiveTo determine the role of microbiota dysbiosis, intestinal barrier dysfunction, and colonic inflammation in neuroinflammation and neurodegeneration in a genetic rodent model of PD [α-synuclein overexpressing (ASO) mice].MethodsTo distinguish the role of intestinal barrier dysfunction separate from inflammation, low dose (1%) dextran sodium sulfate (DSS) was administered in cycles for 52 days to ASO and control mice. The outcomes assessed included intestinal barrier integrity, intestinal inflammation, stool microbiome community, systemic inflammation, motor function, microglial activation, and dopaminergic neurons.ResultsLow dose DSS treatment caused intestinal barrier dysfunction (sugar test, histological analysis), intestinal microbiota dysbiosis, mild intestinal inflammation (colon shortening, elevated MPO), but it did not increase systemic inflammation (serum cytokines). However, DSS did not exacerbate motor dysfunction, neuroinflammation (microglial activation), or dopaminergic neuron loss in ASO mice.ConclusionDisruption of the intestinal barrier without overt intestinal inflammation is not associated with worsening of PD-like behavior and pathology in ASO mice.

GAIT-GM integrative cross-omics analyses reveal cholinergic defects in a C. elegans model of Parkinson\u2019s disease

Parkinson’s disease (PD) is a disabling neurodegenerative disorder in which multiple cell types, including dopaminergic and cholinergic neurons, are affected. The mechanisms of neurodegeneration in PD are not fully understood, limiting the development of therapies directed at disease-relevant molecular targets. C. elegans is a genetically tractable model system that can be used to disentangle disease mechanisms in complex diseases such as PD. Such mechanisms can be studied combining high-throughput molecular profiling technologies such as transcriptomics and metabolomics. However, the integrative analysis of multi-omics data in order to unravel disease mechanisms is a challenging task without advanced bioinformatics training. Galaxy, a widely-used resource for enabling bioinformatics analysis by the broad scientific community, has poor representation of multi-omics integration pipelines. We present the integrative analysis of gene expression and metabolite levels of a C. elegans PD model using GAIT-GM, a new Galaxy tool for multi-omics data analysis. Using GAIT-GM, we discovered an association between branched-chain amino acid metabolism and cholinergic neurons in the C. elegans PD model. An independent follow-up experiment uncovered cholinergic neurodegeneration in the C. elegans model that is consistent with cholinergic cell loss observed in PD. GAIT-GM is an easy to use Galaxy-based tool for generating novel testable hypotheses of disease mechanisms involving gene-metabolite relationships.

Dopamine signaling modulates microglial NLRP3 inflammasome activation: implications for Parkinson\u2019s disease

BackgroundParkinson’s disease (PD) is characterized by the loss of nigral dopaminergic neurons leading to impaired striatal dopamine signaling, α-synuclein- (α-syn-) rich inclusions, and neuroinflammation. Degenerating neurons are surrounded by activated microglia with increased secretion of interleukin-1β (IL-1β), driven largely by the NLRP3 inflammasome. A critical role for microglial NLRP3 inflammasome activation in the progression of both dopaminergic neurodegeneration and α-syn pathology has been demonstrated in parkinsonism mouse models. Fibrillar α-syn activates this inflammasome in mouse and human macrophages, and we have shown previously that the same holds true for primary human microglia. Dopamine blocks microglial NLRP3 inflammasome activation in the MPTP model, but its effects in this framework, highly relevant to PD, remain unexplored in primary human microglia and in other in vivo parkinsonism models.MethodsBiochemical techniques including quantification of IL-1β secretion and confocal microscopy were employed to gain insight into dopamine signaling-mediated inhibition of the NLRP3 inflammasome mechanism in primary human microglia and the SYN120 transgenic mouse model. Dopamine and related metabolites were applied to human microglia together with various inflammasome activating stimuli. The involvement of the receptors through which these catecholamines were predicted to act were assessed with agonists in both species.ResultsWe show in primary human microglia that dopamine, l-DOPA, and high extracellular K+, but not norepinephrine and epinephrine, block canonical, non-canonical, and α-syn-mediated NLRP3 inflammasome-driven IL-1β secretion. This suggests that dopamine acts as an inflammasome inhibitor in human microglia. Accordingly, we provide evidence that dopamine exerts its inhibitory effect through dopamine receptor D1 and D2 (DRD1 and DRD2) signaling. We also show that aged mice transgenic for human C-terminally truncated (1–120) α-syn (SYN120 tg mice) display increased NLRP3 inflammasome activation in comparison to WT mice that is diminished upon DRD1 agonism.ConclusionsDopamine inhibits canonical, non-canonical, and α-syn-mediated activation of the NLRP3 inflammasome in primary human microglia, as does high extracellular K+. We suggest that dopamine serves as an endogenous repressor of the K+ efflux-dependent microglial NLRP3 inflammasome activation that contributes to dopaminergic neurodegeneration in PD, and that this reciprocation may account for the specific vulnerability of these neurons to disease pathology.

Mouse midbrain dopaminergic neurons survive loss of the PD-associated mitochondrial protein CHCHD2.

Mutations in the mitochondrial protein CHCHD2 cause autosomal dominant Parkinson's disease characterized by the preferential loss of substantia nigra dopamine (DA) neurons. Therefore, understanding the function of CHCHD2 in neurons may provide vital insights into how mitochondrial dysfunction contributes to neurodegeneration in PD. To investigate the normal requirement and function of CHCHD2 in neurons, we first examined CHCHD2 levels and showed that DA neurons have higher CHCHD2 levels than other neuron types, both in vivo and in co-culture. We then generated mice with either a targeted deletion of CHCHD2 in DA neurons or a deletion in the brain or total body. All three models were viable, and loss of CHCHD2 in the brain did not cause degeneration of DA neurons. Mice lacking CHCHD2 in DA neurons did display sex-specific changes to locomotor activity, but we did not observe differences in assays of muscle strength, exercise endurance or motor coordination. Furthermore, mitochondria derived from mice lacking CHCHD2 did not display abnormalities in OXPHOS function. Lastly, resilience to CHCHD2 deletion could not be explained by functional complementation by its paralog CHCHD10, as deletion of both CHCHD10 and CHCHD2 did not cause degeneration of DA neurons in the midbrain. These findings support the hypothesis that pathogenic CHCHD2 mutations cause PD through a toxic gain-of-function, rather than loss-of-function mechanism.

Integrative genome-wide analysis of dopaminergic neuron-specific PARIS expression in Drosophila dissects recognition of multiple PPAR-\u03b3 associated gene regulation

The transcriptional repressor called parkin interacting substrate (PARIS; ZNF746) was initially identified as a novel co-substrate of parkin and PINK1 that leads to Parkinson’s disease (PD) by disrupting mitochondrial biogenesis through peroxisome proliferator-activated receptor gamma (PPARγ) coactivator -1α (PGC-1α) suppression. Since its initial discovery, growing evidence has linked PARIS to defective mitochondrial biogenesis observed in PD pathogenesis. Yet, dopaminergic (DA) neuron-specific mechanistic underpinnings and genome-wide PARIS binding landscape has not been explored. We employed conditional translating ribosome affinity purification (TRAP) followed by RNA sequencing (TRAP-seq) for transcriptome profiling of DA neurons in transgenic Drosophila lines expressing human PARIS wild type (WT) or mutant (C571A). We also generated genome-wide maps of PARIS occupancy using ChIP-seq in human SH-SY5Y cells. The results demonstrated that PPARγ functions as a master regulator of PARIS-induced molecular changes at the transcriptome level, confirming that PARIS acts primarily on PGC-1α to lead to neurodegeneration in PD. Moreover, we identified that PARIS actively modulates expression of PPARγ target genes by physically binding to the promoter regions. Together, our work revealed how PARIS drives adverse effects on modulation of PPAR-γ associated gene clusters in DA neurons.

Corneal nerve fiber loss relates to cognitive impairment in patients with Parkinson\u2019s disease

Cognitive impairment in Parkinson’s disease (PD) adversely influences quality of life. There is currently no available biomarker to predict cognitive decline in PD. Corneal confocal microscopy (CCM) has been used as a non-invasive tool for quantifying small nerve damage in PD. The present study investigated whether corneal nerve measures were associated with cognitive function in PD. Patients with PD were classified into those with normal cognitive function (PD-CN), mild cognitive impairment (PD-MCI), and dementia (PDD). Corneal nerve fiber density (CNFD), corneal nerve branch density (CNBD), and corneal nerve fiber length (CNFL) were quantified with CCM and compared with a control group. Sixty-five PD patients and thirty controls were studied. CNFD was decreased and CNBD was increased in PD patients compared to controls (P < 0.05). CNBD and CNBD/CNFD ratio was higher in PD-CN compared to controls. CNFD was positively correlated with the Montreal cognitive assessment (MoCA) score (r = 0.683, P < 0.001), but negatively associated with unified Parkinson disease rating scale (UPDRS)-part III (r = −0.481, P < 0.001) and total UPDRS scores (r = −0.401, P = 0.001) in PD patients. There was no correlation between CNFD and Levodopa equivalent daily dose (LEDD) (r = 0.176, P = 0.161). CNFD, CNBD, CNFL, and CNBD/CNFD ratio was lower with increasing Hoehn and Yahr stage. PD patients show evidence of corneal nerve loss compared with controls and corneal nerve parameters are associated with the severity of cognitive and motor dysfunction in PD. CCM could serve as an objective in vivo ophthalmic imaging technique to assess neurodegeneration in PD.

Novel Approaches Used to Examine and Control Neurogenesis in Parkinson's Disease.

Neurogenesis is a key mechanism of brain development and plasticity, which is impaired in chronic neurodegeneration, including Parkinson’s disease. The accumulation of aberrant α-synuclein is one of the features of PD. Being secreted, this protein produces a prominent neurotoxic effect, alters synaptic plasticity, deregulates intercellular communication, and supports the development of neuroinflammation, thereby providing propagation of pathological events leading to the establishment of a PD-specific phenotype. Multidirectional and ambiguous effects of α-synuclein on adult neurogenesis suggest that impaired neurogenesis should be considered as a target for the prevention of cell loss and restoration of neurological functions. Thus, stimulation of endogenous neurogenesis or cell-replacement therapy with stem cell-derived differentiated neurons raises new hopes for the development of effective and safe technologies for treating PD neurodegeneration. Given the rapid development of optogenetics, it is not surprising that this method has already been repeatedly tested in manipulating neurogenesis in vivo and in vitro via targeting stem or progenitor cells. However, niche astrocytes could also serve as promising candidates for controlling neuronal differentiation and improving the functional integration of newly formed neurons within the brain tissue. In this review, we mainly focus on current approaches to assess neurogenesis and prospects in the application of optogenetic protocols to restore the neurogenesis in Parkinson’s disease.

Soluble CD163 Changes Indicate Monocyte Association With Cognitive Deficits in Parkinson's Disease.

BackgroundParkinson's disease (PD) is a neurodegenerative disorder with a significant immune component, as demonstrated by changes in immune biomarkers in patients' biofluids. However, which specific cells are responsible for those changes is unclear because most immune biomarkers can be produced by various cell types.ObjectivesThe aim of this study was to explore monocyte involvement in PD.MethodsWe investigated the monocyte‐specific biomarker sCD163, the soluble form of the receptor CD163, in cerebrospinal fluid (CSF) and serum in two experiments, and compared it with other biomarkers and clinical data. Potential connections between CD163 and alpha‐synuclein were studied in vitro.ResultsCSF‐sCD163 increased in late‐stage PD and correlated with the PD biomarkers alpha‐synuclein, Tau, and phosphorylated Tau, whereas it inversely correlated with the patients' cognitive scores, supporting monocyte involvement in neurodegeneration and cognition in PD. Serum‐sCD163 increased only in female patients, suggesting a sex‐distinctive monocyte response. CSF‐sCD163 also correlated with molecules associated with adaptive and innate immune system activation and with immune cell recruitment to the brain. Serum‐sCD163 correlated with proinflammatory cytokines and acute‐phase proteins, suggesting a relation to chronic systemic inflammation. Our in vitro study showed that alpha‐synuclein activates macrophages and induces shedding of sCD163, which in turn enhances alpha‐synuclein uptake by myeloid cells, potentially participating in its clearance.ConclusionsOur data present sCD163 as a potential cognition‐related biomarker in PD and suggest a role for monocytes in both peripheral and brain immune responses. This may be directly related to alpha‐synuclein's proinflammatory capacity but could also have consequences for alpha‐synuclein processing. © 2020 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society

Corneal confocal microscopy detects small fibre neurodegeneration in Parkinson's disease using automated analysis

We studied the utility of corneal confocal microscopy (CCM) in detecting a reduction in corneal nerve parameters in a large cohort of patients with Parkinson’s disease (PD) compared to controls using a fully automated potentially scalable method of analysis. We also assessed if CCM parameters are related to the severity and sub-type of PD. 98 participants with PD and 26 healthy controls underwent CCM with automated corneal nerve quantification, MDS-UPDRS III, Hoehn and Yahr scale, Montreal Cognitive Assessment, Parkinson’s Disease Questionnaire-39 and PD subtype assessment. Corneal nerve fibre density (mean difference: − 5.00 no/mm2, 95% confidence interval (CI) [− 7.89, − 2.12], p = 0.001), corneal nerve branch density (mean difference: − 10.71 no/mm2, 95% CI [− 16.93, − 4.48], p = 0.003), corneal total branch density (mean difference: − 14.75 no/mm2, 95% CI [− 23.58, − 5.92], p = 0.002), and corneal nerve fibre length (mean difference: − 2.57 mm/mm2, 95% CI [− 4.02, − 1.12], p = 0.001) were significantly lower in PD participants compared to controls. There was no correlation between corneal nerve parameters and duration, severity or subtype of PD, cognitive function or quality of life. CCM with automated corneal nerve analysis identifies nerve fibre damage and may act as a biomarker for neurodegeneration in PD.

Substantia nigra Smad3 signaling deficiency: relevance to aging and Parkinson\u2019s disease and roles of microglia, proinflammatory factors, and MAPK

BackgroundSmad3 signaling is indicated to regulate microglia activity. Parkinson’s disease (PD) neurodegeneration is shown to be associated with aging and neuroinflammation. However, it remains unclear about the relationship among Smad3 signaling, aging, neuroinflammation, and PD.MethodsRats were treated with SIS3 (a specific inhibitor of Smad3, intranigal injection) and/or lipopolysaccharide (intraperitoneal injection). We investigated the effect of SIS3 and lipopolysaccharide and their mechanism of action on motor behavior and nigrostriatal dopaminergic system in the rats. Furthermore, we explored the effect of SIS3 and LPS and their potential signaling mechanism of action on inflammatory response by using primary microglial cultures. Finally, we investigated the relationship among aging, Smad3 signaling, and neuroinflammation using animals of different ages.ResultsBoth SIS3 and lipopolysaccharide induced significant behavior deficits and nigrostriatal dopaminergic neurodegeneration in the rats compared with the vehicle-treated (control) rats. Significantly increased behavior deficits and nigrostriatal dopaminergic neurodegeneration were observed in the rats co-treated with SIS3 and lipopolysaccharide compared with the rats treated with vehicle, SIS3, or lipopolysaccharide. Furthermore, both SIS3 and lipopolysaccharide induced significant microglia activation and proinflammatory factor (IL-1β, IL-6, iNOS, and ROS) level increase in the SN of rats compared with the control rats. Significantly enhanced microglial inflammatory response was observed in the rats co-treated with SIS3 and lipopolysaccharide compared with the other three groups. For our in vitro study, both SIS3 and lipopolysaccharide induced significant proinflammatory factor level increase in primary microglia cultures compared with the control cultures. Significantly increased inflammatory response was observed in the cultures co-treated with SIS3 and lipopolysaccharide compared with the other three groups. MAPK (ERK/p38) contributed to microglial inflammatory response induced by co-treatment with SIS3 and lipopolysaccharide. Interestingly, there was decrease in Smad3 and pSmad3 expression (protein) and enhancement of neuroinflammation in the mouse SN with aging. Proinflammatory factor levels were significantly inversely correlated with Smad3 and pSmad3 expression.ConclusionOur study strongly indicates the involvement of SN Smad3 signaling deficiency in aging and PD neurodegeneration and provides a novel molecular mechanism underlying the participation of aging in PD and helps to elucidate the mechanisms for the combined effect of multiple factors in PD.

Association of potential premotor clinical features with subtypes of motor symptoms in Parkinson's disease

Background: As it has been recognized that neurodegeneration in PD starts before the manifestation of the motor symptoms, detecting PD earlier in premotor stage which includes some nonmotor manifestations will help the patients benefit from potential neuroprotective therapies.