Genetic and Environmental Factors in Parkinson's Disease Converge on Immune Function and Inflammation

The role of peripheral inflammation-related biomarkers in distinguishing Parkinson's disease

BACKGROUND

Peripheral inflammation plays a significant role in Parkinson's disease (PD). Conflicting studies on whether inflammatory indicators in blood could serve as biomarkers to distinguish PD.

OBJECTIVE

Include a wider range of biomarkers and control confounding factors to comprehensively evaluate the value of peripheral inflammation-related indicators.

METHODS

A total of 80 PD patients were recruited and 80 one-to-one matched healthy controls (HCs). The levels of B-cell, T-cell, and natural killer (NK)-cell in blood were measured using flow cytometry. The levels of neurodegeneration-related proteins in serum were detected and clinical blood test results were collected. Multivariable logistic regression analysis was conducted to explore the role of significant variables in PD. Receiver operating characteristic curve analysis was performed to assess the potential value of these variables.

RESULTS

Compared to HCs, PD patients showed lower levels of lymphocyte, B-cell, T-cell, high-density lipoprotein cholesterol (HDL-C) and lymphocyte-to-monocyte ratio, while the levels of neutrophil, NK-cell, β-amyloid40, neurofilament light chain, neutrophil-to-lymphocyte ratio, and neutrophil-to-HDL-C ratio (NHR) were increased. A higher B-cell count was associated with a lower risk of PD, while higher levels of NK-cell and NHR were associated with a higher risk of PD. B-cell, NK-cell and NHR have potential value in distinguishing PD from non-PD. B-cell and NHR levels were significantly correlated with PD dyskinesia scores.

CONCLUSIONS

B-cell, NK-cell, and NHR may potentially contribute to distinguishing PD patients from HCs. There could be a correlation between the number of B-cell, the level of NHR, and the severity of PD dyskinesia.

Indoleamine 2,3-dioxygenase (IDO1) - Can dendritic cells and monocytes expressing this moonlight enzyme change the phase of Parkinson's Disease?

Parkinson's Disease (PD) is the second most common neurodegenerative disease where central and peripheral immune dysfunctions have been pointed out as a critical component of susceptibility and progression of this disease. Dendritic cells (DCs) and monocytes are key players in promoting immune response regulation and can induce the enzyme indoleamine 2,3-dioxygenase 1 (IDO1) under pro-inflammatory environments. This enzyme with catalytic and signaling activity supports the axis IDO1-KYN-aryl hydrocarbon receptor (AhR), promoting disease-specific immunomodulatory effects. IDO1 is a rate-limiting enzyme of the kynurenine pathway (KP) that begins tryptophan (Trp) catabolism across this pathway. The immune functions of the pathway, which are extensively described in cancer, have been forgotten so far in neurodegenerative diseases, where a chronic inflammatory environment underlines the progression of the disease. Despite dysfunctions of KP have been described in PD, these are mainly associated with neurotoxic functions. With this review, we aim to focus on the immune properties of IDO1+DCs and IDO1+monocytes as a possible strategy to balance the pro-inflammatory profile described in PD. We also highlight the importance of exploring the role of dopaminergic therapeutics in IDO1 modulation to possibly optimize current PD therapeutic strategies.

Occupational Pesticide Exposure in Parkinson's Disease Related to GBA and LRRK2 Variants

Background

The penetrance of common genetic risk variants for Parkinson's disease (PD) is low. Pesticide exposure increases PD risk, but how exposure affects penetrance is not well understood.

Objective

To determine the relationship between occupational pesticide exposure and PD in people with LRRK2 and GBA risk variants.

Methods

Participants of the Parkinson's Progression Markers Initiative (PPMI) with a LRRK2-G2019 S or GBA risk variant provided information about occupational pesticide exposure. We compared exposure in carriers with and without PD. Among carriers with PD, we used Cox proportional hazard models to compare time-to impairment in balance, cognition, and activities of daily living (ADLs) between participants with and without prior occupational pesticide exposure.

Results

378 participants with a risk variant provided exposure information; 176 with LRRK2-G2019 S (54 with and 122 without PD) and 202 with GBA variants (47 with and 155 without PD). Twenty-six participants reported pesticide exposure. People with a GBA variant and occupational pesticide exposure had much higher odds of PD (aOR: 5.4, 95% CI 1.7-18.5, p < 0.01). People with a LRRK2 variant and a history of occupational pesticide exposure had non-significantly elevated odds of PD (aOR 1.3, 95% CI 0.4-4.6, p = 0.7). Among those with PD, pesticide exposure was associated with a higher risk of balance problems and cognitive impairment in LRRK2-PD and functional impairment in GBA-PD, although associations were not statistically significant.

Conclusions

Occupational pesticide exposure may increase penetrance of GBA-PD and may be associated with faster symptom progression. Further studies in larger cohorts are necessary.

Global prevalence and incidence of Young Onset Parkinson's disease: A systematic review and meta-analysis

BACKGROUND

There is a lack of enough evidence regarding the epidemiology of Young-onset Parkinson's disease (YOPD) which is needed by clinicians and healthcare policymakers.

AIM

Herein, in this systematic review and meta-analysis, we aimed to estimate the global prevalence and incidence rates of YOPD.

METHODS

We searched the literature in PubMed, Scopus, and Web of Science in May 2022. We included retrospective, prospective, cross-sectional observational population-based studies that reported the prevalence or incidence of PD in individuals younger than 40 years with known diagnostic criteria.

RESULTS

After two-step screening, 50 studies were eligible to be included in our study. The age-standardized prevalence of YOPD was 10.2 per 100,000 persons globally while it was 14.7 per 100,000 population in European countries. Age-standardized prevalence estimates for 5-year age bands showed that the YOPD prevalence estimates varied from 6.1 per 100,000 population in the group aged 20-24 to 16.1 per 100,000 population in the group aged 35-39. Also, the age-standardized incidence of YOPD was 1.3 per 100,000 person-years population worldwide and 1.2 per 100,000 person-years in the European population.

CONCLUSION

Based on this systematic review and meta-analysis, the overall prevalence of YOPD is 10.2 per 100,000 population, although estimates of the prevalence and incidence in low-income countries remain scarce. To improve monitoring and certain diagnoses of YOPD, healthcare providers and policymakers should be aware that much more effective tools are required.

Bowel function and inflammation: Is motility the other side of the coin?

Digestion and intestinal absorption allow the body to sustain itself and are the emblematic functions of the bowel. On the flip side, functions also arise from its role as an interface with the environment. Indeed, the gut houses microorganisms, collectively known as the gut microbiota, which interact with the host, and is the site of complex immune activities. Its role in human pathology is complex and scientific evidence is progressively elucidating the functions of the gut, especially regarding the pathogenesis of chronic intestinal diseases and inflammatory conditions affecting various organs and systems. This editorial aims to highlight and relate the factors involved in the pathogenesis of intestinal and systemic inflammation.

Locus coeruleus injury modulates ventral midbrain neuroinflammation during DSS-induced colitis

Parkinson's disease (PD) is characterized by a decades-long prodrome, consisting of a collection of non-motor symptoms that emerges prior to the motor manifestation of the disease. Of these non-motor symptoms, gastrointestinal dysfunction and deficits attributed to central norepinephrine (NE) loss, including mood changes and sleep disturbances, are frequent in the PD population and emerge early in the disease. Evidence is mounting that injury and inflammation in the gut and locus coeruleus (LC), respectively, underlie these symptoms, and the injury of these systems is central to the progression of PD. In this study, we generate a novel two-hit mouse model that captures both features, using dextran sulfate sodium (DSS) to induce gut inflammation and N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4) to lesion the LC. We first confirmed the specificity of DSP-4 for central NE using neurochemical methods and fluorescence light-sheet microscopy of cleared tissue, and established that DSS-induced outcomes in the periphery, including weight loss, gross indices of gut injury and systemic inflammation, the loss of tight junction proteins in the colonic epithelium, and markers of colonic inflammation, were unaffected with DSP-4 pre-administration. We then measured alterations in neuroimmune gene expression in the ventral midbrain in response to DSS treatment alone as well as the extent to which prior LC injury modified this response. In this two-hit model we observed that DSS-induced colitis activates the expression of key cytokines and chemokines in the ventral midbrain only in the presence of LC injury and the typical DSS-associated neuroimmune is blunted by pre-LC lesioning with DSP-4. In all, this study supports the growing appreciation for the LC as neuroprotective against inflammation-induced brain injury and draws attention to the potential for NEergic interventions to exert disease-modifying effects under conditions where peripheral inflammation may compromise ventral midbrain dopaminergic neurons and increase the risk for development of PD.

A leaky gut dysregulates gene networks in the brain associated with immune activation, oxidative stress, and myelination in a mouse model of colitis

The gut and brain are increasingly linked in human disease, with neuropsychiatric conditions classically attributed to the brain showing an involvement of the intestine and inflammatory bowel diseases (IBDs) displaying an ever-expanding list of neurological comorbidities. To identify molecular systems that underpin this gut-brain connection and thus discover therapeutic targets, experimental models of gut dysfunction must be evaluated for brain effects. In the present study, we examine disturbances along the gut-brain axis in a widely used murine model of colitis, the dextran sodium sulfate (DSS) model, using high-throughput transcriptomics and an unbiased network analysis strategy coupled with standard biochemical outcome measures to achieve a comprehensive approach to identify key disease processes in both colon and brain. We examine the reproducibility of colitis induction with this model and its resulting genetic programs during different phases of disease, finding that DSS-induced colitis is largely reproducible with a few site-specific molecular features. We focus on the circulating immune system as the intermediary between the gut and brain, which exhibits an activation of pro-inflammatory innate immunity during colitis. Our unbiased transcriptomics analysis provides supporting evidence for immune activation in the brain during colitis, suggests that myelination may be a process vulnerable to increased intestinal permeability, and identifies a possible role for oxidative stress and brain oxygenation. Overall, we provide a comprehensive evaluation of multiple systems in a prevalent experimental model of intestinal permeability, which will inform future studies using this model and others, assist in the identification of druggable targets in the gut-brain axis, and contribute to our understanding of the concomitance of intestinal and neuropsychiatric dysfunction.

Targeted upregulation of dMyc restricts JNK-mediated degeneration of dopaminergic neurons in the paraquat-induced Parkinson's disease model of Drosophila

Parkinson's disease is the second most common neurodegenerative disease characterized by the loss of dopaminergic neurons in the brain. Parkinson's disease has both familial and sporadic cases of origin governed differentially by genetic and/or environmental factors. Different epidemiological studies have proposed an association between the pathogenesis of cancer and Parkinson's disease; however, a precise correlation between these two illnesses could not be established yet. In this study, we examined the disease-modifying property of dmyc (a Drosophila homolog of human cmyc proto-oncogene) in the paraquat-induced sporadic Parkinson's disease model of Drosophila. We report for the first time that targeted upregulation of dMyc significantly restricts paraquat-mediated neurotoxicity. We observed that paraquat feeding reduces the cellular level of dMyc. We further noted that targeted upregulation of dMyc in paraquat-exposed flies mitigates degeneration of dopaminergic neurons by reinstating the aberrantly activated JNK pathway, and this in turn improves the motor performance and survival rate of the flies. Our study provides the first evidence that improved cellular level of dMyc could efficiently minimize the neurotoxic effects of paraquat, which could be beneficial in designing novel therapeutic strategies against Parkinson's disease.

Morphometric similarity differences in drug-naive Parkinson's disease correlate with transcriptomic signatures

BACKGROUND

Differences in cortical morphology have been reported in individuals with Parkinson's disease (PD). However, the pathophysiological mechanism of transcriptomic vulnerability in local brain regions remains unclear.

OBJECTIVE

This study aimed to characterize the morphometric changes of brain regions in early drug-naive PD patients and uncover the brain-wide gene expression correlates.

METHODS

The morphometric similarity (MS) network analysis was used to quantify the interregional structural similarity from multiple magnetic resonance imaging anatomical indices measured in each brain region of 170 early drug-naive PD patients and 123 controls. Then, we applied partial least squares regression to determine the relationship between regional changes in MS and spatial transcriptional signatures from the Allen Human Brain Atlas dataset, and identified the specific genes related to MS differences in PD. We further investigated the biological processes by which the PD-related genes were enriched and the cellular characterization of these genes.

RESULTS

Our results showed that MS was mainly decreased in cingulate, frontal, and temporal cortical areas and increased in parietal and occipital cortical areas in early drug-naive PD patients. In addition, genes whose expression patterns were associated with regional MS changes in PD were involved in astrocytes, excitatory, and inhibitory neurons and were functionally enriched in neuron-specific biological processes related to trans-synaptic signaling and nervous system development.

CONCLUSIONS

These findings advance our understanding of the microscale genetic and cellular mechanisms driving macroscale morphological abnormalities in early drug-naive PD patients and provide potential targets for future therapeutic trials.

Sleep disorders cause Parkinson's disease or the reverse is true: Good GABA good night

BACKGROUND

Parkinson's disease (PD) is a progressive neurodegenerative brain disease due to degeneration of dopaminergic neurons (DNs) presented with motor and non-motor symptoms. PD symptoms are developed in response to the disturbance of diverse neurotransmitters including γ-aminobutyric acid (GABA). GABA has a neuroprotective effect against PD neuropathology by protecting DNs in the substantia nigra pars compacta (SNpc). It has been shown that the degeneration of GABAergic neurons is linked with the degeneration of DNs and the progression of motor and non-motor PD symptoms. GABA neurotransmission is a necessary pathway for normal sleep patterns, thus deregulation of GABAergic neurotransmission in PD could be the potential cause of sleep disorders in PD.

AIM

Sleep disorders affect GABA neurotransmission leading to memory and cognitive dysfunction in PD. For example, insomnia and short sleep duration are associated with a reduction of brain GABA levels. Moreover, PD-related disorders including rigidity and nocturia influence sleep patterns leading to fragmented sleep which may also affect PD neuropathology. However, the mechanistic role of GABA in PD neuropathology regarding motor and non-motor symptoms is not fully elucidated. Therefore, this narrative review aims to clarify the mechanistic role of GABA in PD neuropathology mainly in sleep disorders, and how good GABA improves PD. In addition, this review of published articles tries to elucidate how sleep disorders such as insomnia and REM sleep behavior disorder (RBD) affect PD neuropathology and severity. The present review has many limitations including the paucity of prospective studies and most findings are taken from observational and preclinical studies. GABA involvement in the pathogenesis of PD has been recently discussed by recent studies. Therefore, future prospective studies regarding the use of GABA agonists in the management of PD are suggested to observe their distinct effects on motor and non-motor symptoms.

CONCLUSION

There is a bidirectional relationship between the pathogenesis of PD and sleep disorders which might be due to GABA deregulation.

The Synergistic Effect Study of Lipopolysaccharide (LPS) and A53T-α-Synuclein: Intranasal LPS Exposure on the A53T-α-Synuclein Transgenic Mouse Model of Parkinson's Disease

Aging and interactions between genetic and environmental factors are believed to be involved the chronic development of Parkinson's disease (PD). Among PD patients, abnormally aggregated α-synuclein is a major component of the Lewy body. Generally, the intranasal route is believed to be a gate way to the brain, and it assists environmental neurotoxins in entering the brain and is related to anosmia during early PD. The current study applies the chronic intranasal application of lipopolysaccharides (LPS) in 4-, 8-, 12- and 16-month-old A53T-α-synuclein (A53T-α-Syn) transgenic C57BL/6 mice at 2-day intervals for a 2-month period, for evaluating the behavioral, pathological, and biochemical changes and microglial activation in these animals. According to our results, after intranasal administration of LPS, A53T-α-Syn mice showed severe progressive anosmia, hypokinesia, selective dopaminergic (DAergic) neuronal losses, decreased striatal dopamine (DA) level, and enhanced α-synuclein accumulation within the substantia nigra (SN) in an age-dependent way. In addition, we found obvious NF-кB activation, Nurr1 inhibition, IL-1β, and TNF-α generation within the microglia of the SN. Conversely, the wild-type (WT) mice showed mild, whereas A53T-α-Syn mice had moderate PD-like changes among the old mice. This study demonstrated the synergistic effect of intranasal LPS and α-synuclein burden on PD development. Its underlying mechanism may be associated with Nurr1 inhibition within microglia and the amplification of CNS neuroinflammation. The mice with multiple factors, including aging, neuroinflammation, and α-synuclein mutation, have played a significant role in enhancing our understanding of how inflammation and α-synuclein mutation contribute to the neurodegeneration observed in PD.

Locus coeruleus injury modulates ventral midbrain neuroinflammation during DSS-induced colitis

Parkinson's disease (PD) is characterized by a decades-long prodrome, consisting of a collection of non-motor symptoms that emerges prior to the motor manifestation of the disease. Of these non-motor symptoms, gastrointestinal dysfunction and deficits attributed to central norepinephrine (NE) loss, including mood changes and sleep disturbances, are frequent in the PD population and emerge early in the disease. Evidence is mounting that injury and inflammation in the gut and locus coeruleus (LC), respectively, underlie these symptoms, and the injury of these systems is central to the progression of PD. In this study, we generate a novel two-hit mouse model that captures both features, using dextran sulfate sodium (DSS) to induce gut inflammation and N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4) to lesion the LC. We first confirmed the specificity of DSP-4 for central NE using neurochemical methods and fluorescence light-sheet microscopy of cleared tissue, and established that DSS-induced outcomes in the periphery, including weight loss, gross indices of gut injury and systemic inflammation, the loss of tight junction proteins in the colonic epithelium, and markers of colonic inflammation, were unaffected with DSP-4 pre-administration. We then measured alterations in neuroimmune gene expression in the ventral midbrain in response to DSS treatment alone as well as the extent to which prior LC injury modified this response. In this two-hit model we observed that DSS-induced colitis activates the expression of key cytokines and chemokines in the ventral midbrain only in the presence of LC injury and the typical DSS-associated neuroimmune is blunted by pre-LC lesioning with DSP-4. In all, this study supports the growing appreciation for the LC as neuroprotective against inflammation-induced brain injury and draws attention to the potential for NEergic interventions to exert disease-modifying effects under conditions where peripheral inflammation may compromise ventral midbrain dopaminergic neurons and increase the risk for development of PD.

The role of exosomes in adult neurogenesis: implications for neurodegenerative diseases

Exosomes are cup-shaped extracellular vesicles with a lipid bilayer that is approximately 30 to 200 nm in thickness. Exosomes are widely distributed in a range of body fluids, including urine, blood, milk, and saliva. Exosomes exert biological function by transporting factors between different cells and by regulating biological pathways in recipient cells. As an important form of intercellular communication, exosomes are increasingly being investigated due to their ability to transfer bioactive molecules such as lipids, proteins, mRNAs, and microRNAs between cells, and because they can regulate physiological and pathological processes in the central nervous system. Adult neurogenesis is a multistage process by which new neurons are generated and migrate to be integrated into existing neuronal circuits. In the adult brain, neurogenesis is mainly localized in two specialized niches: the subventricular zone adjacent to the lateral ventricles and the subgranular zone of the dentate gyrus. An increasing body of evidence indicates that adult neurogenesis is tightly controlled by environmental conditions with the niches. In recent studies, exosomes released from different sources of cells were shown to play an active role in regulating neurogenesis both in vitro and in vivo, thereby participating in the progression of neurodegenerative disorders in patients and in various disease models. Here, we provide a state-of-the-art synopsis of existing research that aimed to identify the diverse components of exosome cargoes and elucidate the therapeutic potential of exosomal contents in the regulation of neurogenesis in several neurodegenerative diseases. We emphasize that exosomal cargoes could serve as a potential biomarker to monitor functional neurogenesis in adults. In addition, exosomes can also be considered as a novel therapeutic approach to treat various neurodegenerative disorders by improving endogenous neurogenesis to mitigate neuronal loss in the central nervous system.

Phosphorylation of AQP4 by LRRK2 R1441G impairs glymphatic clearance of IFNγ and aggravates dopaminergic neurodegeneration

Aquaporin-4 (AQP4) is essential for normal functioning of the brain's glymphatic system. Impaired glymphatic function is associated with neuroinflammation. Recent clinical evidence suggests the involvement of glymphatic dysfunction in LRRK2-associated Parkinson's disease (PD); however, the precise mechanism remains unclear. The pro-inflammatory cytokine interferon (IFN) γ interacts with LRRK2 to induce neuroinflammation. Therefore, we examined the AQP4-dependent glymphatic system's role in IFNγ-mediated neuroinflammation in LRRK2-associated PD. We found that LRRK2 interacts with and phosphorylates AQP4 in vitro and in vivo. AQP4 phosphorylation by LRRK2 R1441G induced AQP4 depolarization and disrupted glymphatic IFNγ clearance. Exogeneous IFNγ significantly increased astrocyte expression of IFNγ receptor, amplified AQP4 depolarization, and exacerbated neuroinflammation in R1441G transgenic mice. Conversely, inhibiting LRRK2 restored AQP4 polarity, improved glymphatic function, and reduced IFNγ-mediated neuroinflammation and dopaminergic neurodegeneration. Our findings establish a link between LRRK2-mediated AQP4 phosphorylation and IFNγ-mediated neuroinflammation in LRRK2-associated PD, guiding the development of LRRK2 targeting therapy.

Integrative analysis of gene expression profiles of substantia nigra identifies potential diagnosis biomarkers in Parkinson's disease

Parkinson's disease (PD) is a progressive neurodegenerative disease whose etiology is attributed to development of Lewy bodies and degeneration of dopaminergic neurons in the substantia nigra (SN). Currently, there are no definitive diagnostic indicators for PD. In this study, we aimed to identify potential diagnostic biomarkers for PD and analyzed the impact of immune cell infiltrations on disease pathogenesis. The PD expression profile data for human SN tissue, GSE7621, GSE20141, GSE20159, GSE20163 and GSE20164 were downloaded from the Gene Expression Omnibus (GEO) database for use in the training model. After normalization and merging, we identified differentially expressed genes (DEGs) using the Robust rank aggregation (RRA) analysis. Simultaneously, DEGs after batch correction were identified. Gene interactions were determined through venn Diagram analysis. Functional analyses and protein-protein interaction (PPI) networks were used to the identify hub genes, which were visualized through Cytoscape. A Lasso Cox regression model was employed to identify the potential diagnostic genes. The GSE20292 dataset was used for validation. The proportion of infiltrating immune cells in the samples were determined via the CIBERSORT method. Sixty-two DEGs were screened in this study. They were found to be enriched in nerve conduction, dopamine (DA) metabolism, and DA biosynthesis Gene Ontology (GO) terms. The PPI network and Lasso Cox regression analysis revealed seven potential diagnostic genes, namely SLC18A2, TAC1, PCDH8, KIAA0319, PDE6H, AXIN1, and AGTR1, were subsequently validated in peripheral blood samples obtained from healthy control (HC) and PD patients, as well as in the GSE20292 dataset. The results revealed the exceptional sensitivity and specificity of these genes in PD diagnosis and monitoring. Moreover, PD patients exhibited a higher number of plasma cells, compared to HC individuals. The SLC18A2, TAC1, PCDH8, KIAA0319, PDE6H, AXIN1, and AGTR1 are potential diagnostic biomarkers for PD. Our findings also reveal the essential roles of immune cell infiltration in both disease onset and trajectory.

Fighting Against the Clock: Circadian Disruption and Parkinson's Disease

Circadian disruption is being increasingly recognized as a critical factor in the development and progression of Parkinson's disease (PD). This review aims to provide an in-depth overview of the relationship between circadian disruption and PD by exploring the molecular, cellular, and behavioral aspects of this interaction. This review will include a comprehensive understanding of how the clock gene system and transcription-translation feedback loops function and how they are diminished in PD. The article also discusses the role of clock genes in the regulation of circadian rhythms, as well as the impact of clock gene dysregulation on mitochondrial function, oxidative stress, and neuroinflammation, including the microbiota-gut-brain axis, which have all been proposed as being crucial mechanisms in the pathophysiology of PD. Finally, this review highlights potential therapeutic strategies targeting the clock gene system and circadian rhythm for the treatment of PD.

Unravelling the Parkinson's puzzle, from medications and surgery to stem cells and genes: a comprehensive review of current and future management strategies

Parkinson's disease (PD) is a neurodegenerative disorder, prevalent in the elderly population. Neuropathological hallmarks of PD include loss of dopaminergic cells in the nigro-striatal pathway and deposition of alpha-synuclein protein in the neurons and synaptic terminals, which lead to a complex presentation of motor and non-motor symptoms. This review focuses on various aspects of PD, from clinical diagnosis to currently accepted treatment options, such as pharmacological management through dopamine replacement and surgical techniques such as deep brain stimulation (DBS). The review discusses in detail the potential of emerging stem cell-based therapies and gene therapies to be adopted as a cure, in contrast to the present symptomatic treatment in PD. The potential sources of stem cells for autologous and allogeneic stem cell therapy have been discussed, along with the progress evaluation of pre-clinical and clinical trials. Even though recent techniques hold great potential to improve the lives of PD patients, we present the importance of addressing the safety, efficacy, ethical, cost, and regulatory concerns before scaling them to clinical use.

Towards improved screening of toxins for Parkinson's risk

Parkinson's disease (PD) is a chronic, progressive and disabling neurodegenerative disorder. The prevalence of PD has risen considerably over the past decades. A growing body of evidence suggest that exposure to environmental toxins, including pesticides, solvents and heavy metals (collectively called toxins), is at least in part responsible for this rapid growth. It is worrying that the current screening procedures being applied internationally to test for possible neurotoxicity of specific compounds offer inadequate insights into the risk of developing PD in humans. Improved screening procedures are therefore urgently needed. Our review first substantiates current evidence on the relation between exposure to environmental toxins and the risk of developing PD. We subsequently propose to replace the current standard toxin screening by a well-controlled multi-tier toxin screening involving the following steps: in silico studies (tier 1) followed by in vitro tests (tier 2), aiming to prioritize agents with human relevant routes of exposure. More in depth studies can be undertaken in tier 3, with whole-organism (in)vertebrate models. Tier 4 has a dedicated focus on cell loss in the substantia nigra and on the presumed mechanisms of neurotoxicity in rodent models, which are required to confirm or refute the possible neurotoxicity of any individual compound. This improved screening procedure should not only evaluate new pesticides that seek access to the market, but also critically assess all pesticides that are being used today, acknowledging that none of these has ever been proven to be safe from a perspective of PD. Importantly, the improved screening procedures should not just assess the neurotoxic risk of isolated compounds, but should also specifically look at the cumulative risk conveyed by exposure to commonly used combinations of pesticides (cocktails). The worldwide implementation of such an improved screening procedure, would be an essential step for policy makers and governments to recognize PD-related environmental risk factors.

The application of weighted gene co-expression network analysis and support vector machine learning in the screening of Parkinson's disease biomarkers and construction of diagnostic models

Background

This study aims to utilize Weighted Gene Co-expression Network Analysis (WGCNA) and Support Vector Machine (SVM) algorithm for screening biomarkers and constructing a diagnostic model for Parkinson's disease.

Methods

Firstly, we conducted WGCNA analysis on gene expression data from Parkinson's disease patients and control group using three GEO datasets (GSE8397, GSE20163, and GSE20164) to identify gene modules associated with Parkinson's disease. Then, key genes with significantly differential expression from these gene modules were selected as candidate biomarkers and validated using the GSE7621 dataset. Further functional analysis revealed the important roles of these genes in processes such as immune regulation, inflammatory response, and cell apoptosis. Based on these findings, we constructed a diagnostic model by using the expression data of FLT1, ATP6V0E1, ATP6V0E2, and H2BC12 as inputs and training and validating the model using SVM algorithm.

Results

The prediction model demonstrated an AUC greater than 0.8 in the training, test, and validation sets, thereby validating its performance through SMOTE analysis. These findings provide strong support for early diagnosis of Parkinson's disease and offer new opportunities for personalized treatment and disease management.

Conclusion

In conclusion, the combination of WGCNA and SVM holds potential in biomarker screening and diagnostic model construction for Parkinson's disease.

The mechanism of LZ-8-mediated immune response in the mouse model of Parkinson's disease

Parkinson's disease (PD) is associated with microscopic changes in the brain, particularly substantia nigra (SN). Ganoderma lucidum immunoregulatory protein (rLZ-8) is might confer protective effects against PD. We developed a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced murine model of PD and determined the effects of rLZ-8 on molecular and cellular components of SN and whole brain tissue. The levels of SOD, GSH-Px, p-JAK2 and p-STAT3 in the brain tissue and SN were downregulated, while IL-6, IL-1β, and TNF-α and MDA were upregulated. These effects were significantly reversed upon treatment rLZ-8. In summary, oxidative stress and inflammatory response in PD can be alleviated using rLZ-8.

Sink or swim: Does a worm paralysis phenotype hold clues to neurodegenerative disease?

Receiving a neurodegenerative disease (NDD) diagnosis, such as Alzheimer's disease, Parkinson's disease, Huntington's disease, or amyotrophic lateral sclerosis, is devastating, particularly given the limited options for treatment. Advances in genetic technologies have allowed for efficient modeling of NDDs in animals and brought hope for new disease-modifying medications. The complexity of the mammalian brain and the costs and time needed to identify and develop therapeutic leads limits progress. Modeling NDDs in invertebrates, such as the fruit fly Drosophila melanogaster and the nematode Caenorhabditis elegans, offers orders of magnitude increases in speed of genetic analysis and manipulation, and can be pursued at substantially reduced cost, providing an important, platform complement and inform research with mammalian NDD models. In this review, we describe how our efforts to exploit C. elegans for the study of neural signaling and health led to the discovery of a paralytic phenotype (swimming-induced paralysis) associated with altered dopamine signaling and, surprisingly, to the discovery of a novel gene and pathway whose dysfunction in glial cells triggers neurodegeneration. Research to date on swip-10 and its putative mammalian ortholog MBLAC1, suggests that a tandem analysis will offer insights into NDD mechanisms and insights into novel, disease-modifying therapeutics.

Interaction of Mitochondrial Polygenic Score and Lifestyle Factors in LRRK2 p.Gly2019Ser Parkinsonism

BACKGROUND

A mitochondrial polygenic score (MGS) is composed of genes related to mitochondrial function and found to be associated with Parkinson's disease (PD) risk.

OBJECTIVE

To investigate the impact of the MGS and lifestyle/environment on age at onset (AAO) in LRRK2 p.Gly2019Ser parkinsonism (LRRK2-PD) and idiopathic PD (iPD).

METHODS

We included N = 486 patients with LRRK2-PD and N = 9259 with iPD from the Accelerating Medicines Partnership® Parkinson's Disease Knowledge Platform (AMP-PD), Fox Insight, and a Tunisian Arab-Berber founder population. Genotyping data were used to perform the MGS analysis. Additionally, lifestyle/environmental data were obtained from the PD Risk Factor Questionnaire (PD-RFQ). Linear regression models were used to assess the relationship between MGS, lifestyle/environment, and AAO.

RESULTS

Our derived MGS was significantly higher in PD cases compared with controls (P = 1.1 × 10-8 ). We observed that higher MGS was significantly associated with earlier AAO in LRRK2-PD (P = 0.047, β = -1.40) and there was the same trend with a smaller effect size in iPD (P = 0.231, β = 0.22). There was a correlation between MGS and AAO in LRRK2-PD patients of European descent (P = 0.049, r = -0.12) that was visibly less pronounced in Tunisians (P = 0.449, r = -0.05). We found that the MGS interacted with caffeinated soda consumption (P = 0.003, β = -5.65) in LRRK2-PD and with tobacco use (P = 0.010, β = 1.32) in iPD. Thus, patients with a high MGS had an earlier AAO only if they consumed caffeinated soda or were non-smokers.

CONCLUSIONS

The MGS was more strongly associated with earlier AAO in LRRK2-PD compared with iPD. Caffeinated soda consumption or tobacco use interacted with MGS to predict AAO. Our study suggests gene-environment interactions as modifiers of AAO in LRRK2-PD. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

A leaky gut dysregulates gene networks in the brain associated with immune activation, oxidative stress, and myelination in a mouse model of colitis

The gut and brain are increasingly linked in human disease, with neuropsychiatric conditions classically attributed to the brain showing an involvement of the intestine and inflammatory bowel diseases (IBDs) displaying an ever-expanding list of neurological comorbidities. To identify molecular systems that underpin this gut-brain connection and thus discover therapeutic targets, experimental models of gut dysfunction must be evaluated for brain effects. In the present study, we examine disturbances along the gut-brain axis in a widely used murine model of colitis, the dextran sodium sulfate (DSS) model, using high-throughput transcriptomics and an unbiased network analysis strategy coupled with standard biochemical outcome measures to achieve a comprehensive approach to identify key disease processes in both colon and brain. We examine the reproducibility of colitis induction with this model and its resulting genetic programs during different phases of disease, finding that DSS-induced colitis is largely reproducible with a few site-specific molecular features. We focus on the circulating immune system as the intermediary between the gut and brain, which exhibits an activation of pro-inflammatory innate immunity during colitis. Our unbiased transcriptomics analysis provides supporting evidence for immune activation in the brain during colitis, suggests that myelination may be a process vulnerable to increased intestinal permeability, and identifies a possible role for oxidative stress and brain oxygenation. Overall, we provide a comprehensive evaluation of multiple systems in a prevalent experimental model of intestinal permeability, which will inform future studies using this model and others, assist in the identification of druggable targets in the gut-brain axis, and contribute to our understanding of the concomitance of intestinal and neuropsychiatric dysfunction.

Parkinson's disease relevant pathological features are manifested in male Pink1/Parkin deficient rats

Animal disease models are important for neuroscience experimentation and in the study of neurodegenerative disorders. The major neurodegenerative disorder leading to motor impairments is Parkinson's disease (PD). The identification of hereditary forms of PD uncovered gene mutations and variants, such as loss-of-function mutations in PTEN-induced putative kinase 1 (Pink1) and the E3 ubiquitin ligase Parkin, two proteins involved in mitochondrial quality control, that could be harnessed to create animal models. However, to date, such models have not reproducibly recapitulated major aspects of the disease. Here, we describe the generation and phenotypic characterization of a combined Pink1/Parkin double knockout (dKO) rat, which reproducibly exhibits PD-relevant abnormalities, particularly in male animals. Motor dysfunction in Pink1/Parkin dKO rats was characterized by gait abnormalities and decreased rearing frequency, the latter of which was responsive to levodopa treatment. Pink1/Parkin dKO rats exhibited elevated plasma levels of neurofilament light chain and significant loss of tyrosine hydroxylase expression in the substantia nigra pars compacta (SNpc). Glial cell activation was also observed in the SNpc. Pink1/Parkin dKO rats showed elevated plasma and reduced cerebrospinal levels of alpha-synuclein as well as the presence of alpha-synuclein aggregates in the striatum. Further, the profile of circulating lymphocytes was altered, as elevated CD3⁺CD4⁺ T cells and reduced CD3⁺CD8⁺ T cells in Pink1/Parkin dKO rats were found. This coincided with mitochondrial dysfunction and infiltration of CD3⁺ T cells in the striatum. Altogether, the Pink1/Parkin dKO rats exhibited phenotypes similar to what is seen with PD patients, thus highlighting the suitability of this model for mechanistic studies of the role of Pink1 and Parkin in PD pathogenesis and as therapeutic targets.

The Endotoxin Hypothesis of Parkinson's Disease

The endotoxin hypothesis of Parkinson's disease (PD) is the idea that lipopolysaccharide (LPS) endotoxins contribute to the pathogenesis of this disorder. LPS endotoxins are found in, and released from, the outer membrane of Gram-negative bacteria, for example in the gut. It is proposed that gut dysfunction in early PD leads to elevated LPS levels in the gut wall and blood, which promotes both α-synuclein aggregation in the enteric neurons and a peripheral inflammatory response. Communication to the brain via circulating LPS and cytokines in the blood and/or the gut-brain axis leads to neuroinflammation and spreading of α-synuclein pathology, exacerbating neurodegeneration in brainstem nuclei and loss of dopaminergic neurons in the substantia nigra, and manifesting in the clinical symptoms of PD. The evidence supporting this hypothesis includes: (1) gut dysfunction, permeability, and bacterial changes occur early in PD, (2) serum levels of LPS are increased in a proportion of PD patients, (3) LPS induces α-synuclein expression, aggregation, and neurotoxicity, (4) LPS causes activation of peripheral monocytes leading to inflammatory cytokine production, and (5) blood LPS causes brain inflammation and specific loss of midbrain dopaminergic neurons, mediated by microglia. If the hypothesis is correct, then treatment options might include: (1) changing the gut microbiome, (2) reducing gut permeability, (3) reducing circulating LPS levels, or (4) blocking the response of immune cells and microglia to LPS. However, the hypothesis has a number of limitations and requires further testing, in particular whether reducing LPS levels can reduce PD incidence, progression, or severity. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Lifestyle factors and clinical severity of Parkinson's disease

Genetic factors, environmental factors, and gene-environment interactions have been found to modify PD risk, age at onset (AAO), and disease progression. The objective of this study was to explore the association of coffee drinking, aspirin intake, and smoking, with motor and non-motor symptoms in a cohort of 35,959 American patients with PD from the Fox Insight Study using generalized linear models. Coffee drinkers had fewer problems swallowing but dosage and duration of coffee intake were not associated with motor or non-motor symptoms. Aspirin intake correlated with more tremor (p = 0.0026), problems getting up (p = 0.0185), light-headedness (p = 0.0043), and problems remembering (p = 1 × 10^-5). Smoking was directly associated with symptoms: smokers had more problems with drooling (p = 0.0106), swallowing (p = 0.0002), and freezing (p < 1 × 10^-5). Additionally, smokers had more possibly mood-related symptoms: unexplained pains (p < 1 × 10^-5), problems remembering (p = 0.0001), and feeling sad (p < 1 × 10^-5). Confirmatory and longitudinal studies are warranted to investigate the clinical correlation over time.

Beyond the Microbiota: Understanding the Role of the Enteric Nervous System in Parkinson's Disease from Mice to Human

The enteric nervous system (ENS) is a nerve network composed of neurons and glial cells that regulates the motor and secretory functions of the gastrointestinal (GI) tract. There is abundant evidence of mutual communication between the brain and the GI tract. Dysfunction of these connections appears to be involved in the pathophysiology of Parkinson's disease (PD). Alterations in the ENS have been shown to occur very early in PD, even before central nervous system (CNS) involvement. Post-mortem studies of PD patients have shown aggregation of α-synuclein (αS) in specific subtypes of neurons in the ENS. Subsequently, αS spreads retrogradely in the CNS through preganglionic vagal fibers to this nerve's dorsal motor nucleus (DMV) and other central nervous structures. Here, we highlight the role of the ENS in PD pathogenesis based on evidence observed in animal models and using a translational perspective. While acknowledging the putative role of the microbiome in the gut-brain axis (GBA), this review provides a comprehensive view of the ENS not only as a "second brain", but also as a window into the "first brain", a potentially crucial element in the search for new therapeutic approaches that can delay and even cure the disease.

The cervical lymph node contributes to peripheral inflammation related to Parkinson's disease

BACKGROUND

Peripheral inflammation is an important feature of Parkinson's disease (PD). However, if and how CNS pathology is involved in the peripheral inflammation in PD remains to be fully investigated. Recently, the existence of meningeal lymphatics and its involvement in draining cerebral spinal fluid (CSF) to the cervical lymph node has been discovered. It is known that meningeal lymphatic dysfunction exists in idiopathic PD. The deep cervical lymph node (dCLN) substantially contributes to the drainage of the meningeal lymphatics. In addition, one of the lymphatics draining components, CSF, contains abundant α-synuclein (α-syn), a protein critically involved in PD pathogenesis and neuroinflammation. Thus, we began with exploring the possible structural and functional alterations of the dCLN in a PD mouse model (A53T mice) and investigated the role of pathological α-syn in peripheral inflammation and its potential underlying molecular mechanisms.

METHODS

In this study, the transgenic mice (prnp-SNCA*A53T) which specifically overexpressed A53T mutant α-syn in CNS were employed as the PD animal model. Immunofluorescent and Hematoxylin and eosin staining were used to evaluate structure of dCLN. Inflammation in dCLNs as well as in bone-marrow-derived macrophages (BMDMs) was assessed quantitatively by measuring the mRNA and protein levels of typical inflammatory cytokines (including IL-1β, IL-6 and TNF-α). Intra-cisterna magna injection, flow cytometric sorting and electrochemiluminescence immunoassays were applied to investigate the lymphatic drainage of α-syn from the CNS. RNA-seq and Western blot were used to explore how pathological α-syn mediated the inflammation in PD mice.

RESULTS

The results unequivocally revealed substantially enlarged dCLNs, along with slow lymphatic flow, and increased inflammation in the dCLNs of A53T mice. Oligomeric α-syn drained from CSF potently activated macrophages in the dCLN via endoplasmic reticulum (ER) stress. Notably, inhibition of ER stress effectively suppressed peripheral inflammation in PD mice.

CONCLUSIONS

Our findings indicate that lymph node enlargement is closely related to macrophage activation, induced by meningeal lymphatics draining oligomeric α-syn, and contributes to the peripheral inflammation in PD. In addition, ER stress is a potential therapeutic target to ameliorate PD pathogenesis.

A story of the potential effect of non-steroidal anti-inflammatory drugs (NSAIDs) in Parkinson's disease: beneficial or detrimental effects

Parkinson's disease (PD) is an advanced neurodegenerative disease (NDD) caused by the degeneration of dopaminergic neurons (DNs) in the substantia nigra (SN). As PD is an age-related disorder, the majority of PD patients are associated with musculoskeletal disorders with prolonged use of analgesic and anti-inflammatory agents, such as non-steroidal anti-inflammatory drugs (NSAIDs). Therefore, NSAIDs can affect PD neuropathology in different ways. Thus, the objective of the present narrative review was to clarify the potential role of NSAIDs in PD according to the assorted view of preponderance. Inhibition of neuroinflammation and modulation of immune response by NSAIDs could be an effective way in preventing the development of NDD. NSAIDs affect PD neuropathology in different manners could be beneficial or detrimental effects. Inhibition of cyclooxygenase 2 (COX2) by NSAIDs may prevent the development of PD. NSAIDs afforded a neuroprotective role against the development and progression of PD neuropathology through the  modulation of neuroinflammation. Though, NSAIDs may lead to neutral or harmful effects by inhibiting neuroprotective prostacyclin (PGI2) and accentuation of pro-inflammatory leukotrienes (LTs). In conclusion, there is still a potential conflict regarding the effect of NSAIDs on PD neuropathology.

Dopamine Transmission Imbalance in Neuroinflammation: Perspectives on Long-Term COVID-19

Dopamine (DA) is a key neurotransmitter in the basal ganglia, implicated in the control of movement and motivation. Alteration of DA levels is central in Parkinson’s disease (PD), a common neurodegenerative disorder characterized by motor and non-motor manifestations and deposition of alpha-synuclein (α-syn) aggregates. Previous studies have hypothesized a link between PD and viral infections. Indeed, different cases of parkinsonism have been reported following COVID-19. However, whether SARS-CoV-2 may trigger a neurodegenerative process is still a matter of debate. Interestingly, evidence of brain inflammation has been described in postmortem samples of patients infected by SARS-CoV-2, which suggests immune-mediated mechanisms triggering the neurological sequelae. In this review, we discuss the role of proinflammatory molecules such as cytokines, chemokines, and oxygen reactive species in modulating DA homeostasis. Moreover, we review the existing literature on the possible mechanistic interplay between SARS-CoV-2-mediated neuroinflammation and nigrostriatal DAergic impairment, and the cross-talk with aberrant α-syn metabolism.

A functional role for alpha-synuclein in neuroimmune responses

Alpha-synuclein is a neuronal protein with unclear function but is associated with the pathogenesis of Parkinson's disease and other synucleinopathies. In this review, we discuss the emerging functional role of alpha-synuclein in support of the unique immune responses in the nervous system. Recent data now show that alpha-synuclein functions to support interferon signaling within neurons and is released from neurons to support chemoattraction and activation of local glial cells and infiltrating immune cells. Inflammatory activation and interferon signaling also induce post-translational modifications of alpha-synuclein that are commonly associated with Parkinson's disease pathogenesis. Taken together, emerging data implicate complex interactions between alpha-synuclein and host immune responses that may contribute to the pathogenesis of Parkinson's disease. Additional study of the function of alpha-synuclein in the brain's immune response may provide disease-modifying therapeutic targets for Parkinson's disease in the future.

Peripheral inflammatory immune response differs among sporadic and familial Parkinson's disease

Peripheral inflammatory immune responses are thought to play a major role in the pathogenesis of Parkinson's disease (PD). The neutrophil-to-lymphocyte ratio (NLR), a biomarker of systemic inflammation, has been reported to be higher in patients with PD than in healthy controls (HCs). The present study was aimed at determining if the peripheral inflammatory immune response could be influenced by the genetic background of patients with PD. We included a discovery cohort with 222 patients with PD (132 sporadic PD, 44 LRRK2-associated PD (with p.G2019S and p.R1441G variants), and 46 GBA-associated PD), as well as 299 HCs. Demographic and clinical data were recorded. Leukocytes and their subpopulations, and the NLR were measured in peripheral blood. Multivariate lineal regression and post-hoc tests were applied to determine the differences among the groups. Subsequently, a replication study using the Parkinson's Progression Markers Initiative cohort was performed which included 401 patients with PD (281 sPD patients, 66 LRRK2-PD patients, 54 GBA-PD patients) and a group of 174 HCs. Patients with sporadic PD and GBA-associated PD showed a significantly lower lymphocyte count, a non-significantly higher neutrophil count and a significantly higher NLR than HCs. The peripheral inflammatory immune response of patients with LRRK2-associated PD did not differ from HCs. Our study supports the involvement of a peripheral inflammatory immune response in the pathophysiology of sPD and GBA-associated PD. However, this inflammatory response was not found in LRRK2-associated PD, probably reflecting different pathogenic inflammatory mechanisms.

Identification of immune signatures in Parkinson's disease based on co-expression networks

Parkinson's disease (PD) is a common neurodegenerative disease in middle-aged and elderly people, and there is less research on the relationship between immunity and PD. In this study, the protein-protein interaction networks (PPI) data, 2747 human immune-related genes (HIRGs), 2078 PD-related genes (PDRGs), and PD-related datasets (GSE49036 and GSE20292) were downloaded from the Human Protein Reference Database (HPRD), Amigo 2, DisGeNET, and Gene Expression Omnibus (GEO) databases, respectively. An immune- or PD-directed neighbor co-expressed network construction (IOPDNC) was drawn based on the GSE49036 dataset and HPRD database. Furthermore, a PD-directed neighbor co-expressed network was constructed. Modular clustering analysis was performed on the genes of the gene interaction network obtained in the first step to obtain the central core genes using the GraphWeb online website. The modules with the top 5 functional scores and the number of core genes greater than six were selected as PD-related gene modules. The Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses of different module genes were performed. The single sample Gene Set Enrichment Analysis (ssGSEA) algorithm was used to calculate the immune cell infiltration of the PD and the normal samples. The quantitative Reverse Transcription Polymerase Chain Reaction (qRT-PCR) was performed to investigate the expression of module genes. An IOPDNC and PD-directed neighbor co-expressed network (PDNC network) were constructed. Furthermore, a total of 5 immune-PD modules were identified which could distinguish between PD and normal samples, and these module genes were strongly related to PD in protein interaction level or gene expression level. In addition, functional analysis indicated that module genes were involved in various neurodegenerative diseases, such as Alzheimer disease, Huntington disease, Parkinson disease, and Long-term depression. In addition, the genes of the 6 modules were significantly associated with these 4 differential immune cells (aDC cells, eosinophils, neutrophils, and Th2 cells). Finally, the result of qRT-PCR manifested that the expression of 6 module genes was significantly higher in normal samples than in PD samples. In our study, the immune-related genes were found to be strongly related to PD and might play key roles in PD.

α-Synuclein Induces Neuroinflammation Injury through the IL6ST-AS/STAT3/HIF-1α Axis

The aggregation of α-synuclein (α-syn) promotes neuroinflammation and neuronal apoptosis, which eventually contribute to the pathogenesis of Parkinson's disease (PD). Our microarray analysis and experimental data indicated a significant expression difference of the long noncoding RNA IL6ST-AS and its anti-sense strand, IL6ST, in α-synuclein-induced microglia, compared with unstimulated microglia. IL6ST is a key component of the IL6R/IL6ST complex in the microglial membrane, which recognizes extracellular inflammatory factors, such as IL6. Studies have shown that the binding of IL6 to the IL6R/IL6ST complex could activate the JAK2-STAT3 pathway and promote an excessive immune response in glia cells. Meanwhile, the phosphorylation and activation of STAT3 could increase the transcription of HIF1A, encoding a hypoxia-inducible factor related to cytotoxic damage. Our results indicated that the overexpression of IL6ST-AS induced by exogenous α-synuclein could inhibit the expression of IL6ST and the activation of JAK2-STAT3 pathway in HMC3 cells. In addition, a reduction in STAT3 resulted in the transcription inhibition of HIF1A and the acceleration of oxidative stress injury in SH-SY5Y cells co-cultured with α-synuclein-induced HMC3 cells. Our findings indicate that IL6ST-AS is an important factor that regulates microglia activation and neuronal necrosis in the progression of PD. In the HMC3 and SH-SY5Y cell co-culture system, the overexpression of IL6ST-AS led to microglial dysfunction and neurotoxicology through the IL6ST-AS/STAT3/HIF-1α axis. Our research revealed the relationships among α-synuclein, IL6ST, STAT3, and HIF-1α in the pathological process of PD and provided a new inflammation hypothesis for the pathogenesis of PD.

Quantitative and causal analysis for inflammatory genes and the risk of Parkinson's disease

Background

The dysfunction of immune system and inflammation contribute to the Parkinson's disease (PD) pathogenesis. Cytokines, oxidative stress, neurotoxin and metabolism associated enzymes participate in neuroinflammation in PD and the genes involved in them have been reported to be associated with the risk of PD. In our study, we performed a quantitative and causal analysis of the relationship between inflammatory genes and PD risk.

Methods

Standard process was performed for quantitative analysis. Allele model (AM) was used as primary outcome analysis and dominant model (DM) and recessive model (RM) were applied to do the secondary analysis. Then, for those genes significantly associated with the risk of PD, we used the published GWAS summary statistics for Mendelian Randomization (MR) to test the causal analysis between them.

Results

We included 36 variants in 18 genes for final pooled analysis. As a result, IL-6 rs1800795, TNF-α rs1799964, PON1 rs854560, CYP2D6 rs3892097, HLA-DRB rs660895, BST1 rs11931532, CCDC62 rs12817488 polymorphisms were associated with the risk of PD statistically with the ORs ranged from 0.66 to 3.19 while variants in IL-1α, IL-1β, IL-10, MnSOD, NFE2L2, CYP2E1, NOS1, NAT2, ABCB1, HFE and MTHFR were not related to the risk of PD. Besides, we observed that increasing ADP-ribosyl cyclase (coded by BST1) had causal effect on higher PD risk (OR[95%CI] =1.16[1.10-1.22]) while PON1(coded by PON1) shown probably protective effect on PD risk (OR[95%CI] =0.81[0.66-0.99]).

Conclusion

Several polymorphisms from inflammatory genes of IL-6, TNF-α, PON1, CYP2D6, HLA-DRB, BST1, CCDC62 were statistically associated with the susceptibility of PD, and with evidence of causal relationships for ADP-ribosyl cyclase and PON1 on PD risk, which may help understand the mechanisms and pathways underlying PD pathogenesis.

Synucleins: New Data on Misfolding, Aggregation and Role in Diseases

The synucleins are a family of natively unfolded (or intrinsically unstructured) proteins consisting of α-, β-, and γ-synuclein involved in neurodegenerative diseases and cancer. The current number of publications on synucleins has exceeded 16.000. They remain the subject of constant interest for over 35 years. Two reasons explain this unchanging attention: synuclein's association with several severe human diseases and the lack of understanding of the functional roles under normal physiological conditions. We analyzed recent publications to look at the main trends and developments in synuclein research and discuss possible future directions. Traditional areas of peak research interest which still remain high among last year's publications are comparative studies of structural features as well as functional research on of three members of the synuclein family. Another popular research topic in the area is a mechanism of α-synuclein accumulation, aggregation, and fibrillation. Exciting fast-growing area of recent research is α-synuclein and epigenetics. We do not present here a broad and comprehensive review of all directions of studies but summarize only the most significant recent findings relevant to these topics and outline potential future directions.

Mushroom Natural Products in Neurodegenerative Disease Drug Discovery

The variety of drugs available to treat neurodegenerative diseases is limited. Most of these drug's efficacy is restricted by individual genetics and disease stages and usually do not prevent neurodegeneration acting long after irreversible damage has already occurred. Thus, drugs targeting the molecular mechanisms underlying subsequent neurodegeneration have the potential to negate symptom manifestation and subsequent neurodegeneration. Neuroinflammation is a common feature of neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, Huntington's disease, and multiple sclerosis, and is associated with the activation of the NLRP3 inflammasome, which in turn leads to neurodegeneration. Inflammasome activation and oligomerisation is suggested to be a major driver of disease progression occurring in microglia. With several natural products and natural product derivatives currently in clinical trials, mushrooms have been highlighted as a rich and largely untapped source of biologically active compounds in both in vitro and in vivo neurodegenerative disease models, partially supported by successful clinical trial evaluations. Additionally, novel high-throughput methods for the screening of natural product compound libraries are being developed to help accelerate the neurodegenerative disease drug discovery process, targeting neuroinflammation. However, the breadth of research relating to mushroom natural product high-throughput screening is limited, providing an exciting opportunity for further detailed investigations.

Inflammation and immune dysfunction in Parkinson disease

Parkinson disease (PD) is a progressive neurodegenerative disease that affects peripheral organs as well as the central nervous system and involves a fundamental role of neuroinflammation in its pathophysiology. Neurohistological and neuroimaging studies support the presence of ongoing and end-stage neuroinflammatory processes in PD. Moreover, numerous studies of peripheral blood and cerebrospinal fluid from patients with PD suggest alterations in markers of inflammation and immune cell populations that could initiate or exacerbate neuroinflammation and perpetuate the neurodegenerative process. A number of disease genes and risk factors have been identified as modulators of immune function in PD and evidence is mounting for a role of viral or bacterial exposure, pesticides and alterations in gut microbiota in disease pathogenesis. This has led to the hypothesis that complex gene-by-environment interactions combine with an ageing immune system to create the 'perfect storm' that enables the development and progression of PD. We discuss the evidence for this hypothesis and opportunities to harness the emerging immunological knowledge from patients with PD to create better preclinical models with the long-term goal of enabling earlier identification of at-risk individuals to prevent, delay and more effectively treat the disease.

Epigallocatechin-3-gallate: A phytochemical as a promising drug candidate for the treatment of Parkinson’s disease

Epigallocatechin 3-gallate (EGCG), an abundant polyphenolic component derived from green tea extract, possesses versatile bioactivities that can combat many diseases. During the last decade, EGCG was shown to be effective in experimental models of Parkinson’s disease (PD). Several experimental studies have suggested that it has pleiotropic neuroprotective effects, which has enhanced the appeal of EGCG as a therapeutic strategy in PD. In this review, we compiled recent updates and knowledge of the molecular mechanisms underlying the neuroprotective effects of EGCG in PD. We focused on the effects of EGCG on apoptosis, oxidative stress, inflammation, ferroptosis, modulation of dopamine production, and the aggregation of α-synuclein. The review highlights the pharmacological features of EGCG and its therapeutic implications in PD. Taken together, the accumulated data indicate that EGCG is a promising neuroprotective compound for the treatment of PD.

Reduced penetrance of Parkinson’s disease models

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

Hypoxia and Alpha-Synuclein: Inextricable Link Underlying the Pathologic Progression of Parkinson's Disease

Parkinson's disease (PD) is the second most common neurodegenerative disease after Alzheimer's disease, with typical motor symptoms as the main clinical manifestations. At present, there are about 10 million patients with PD in the world, and its comorbidities and complications are numerous and incurable. Therefore, it is particularly important to explore the pathogenesis of PD and find possible therapeutic targets. Because the etiology of PD is complex, involving genes, environment, and aging, finding common factors is the key to identifying intervention targets. Hypoxia is ubiquitous in the natural environment and disease states, and it is considered to be closely related to the etiology of PD. Despite research showing that hypoxia increases the expression and aggregation of alpha-synuclein (α-syn), the most important pathogenic protein, there is still a lack of systematic studies on the role of hypoxia in α-syn pathology and PD pathogenesis. Considering that hypoxia is inextricably linked with various causes of PD, hypoxia may be a co-participant in many aspects of the PD pathologic process. In this review, we describe the risk factors for PD, and we discuss the possible role of hypoxia in inducing PD pathology by these risk factors. Furthermore, we attribute the pathological changes caused by PD etiology to oxygen uptake disorder and oxygen utilization disorder, thus emphasizing the possibility of hypoxia as a critical link in initiating or promoting α-syn pathology and PD pathogenesis. Our study provides novel insight for exploring the pathogenesis and therapeutic targets of PD.

Nootkatone alleviates rotenone-induced Parkinson's disease symptoms through activation of the PI3K/Akt signaling pathway

Parkinson's disease (PD) is the second most common neurodegenerative disease worldwide. Nootkatone (NKT) has been shown to have neuroprotective, anti-inflammatory, and antioxidant effects and in this study, we systematically studied the efficacy and mechanism of action of NKT in rotenone (ROT)-induced PD rats. Firstly, through behavioral experiments and brain tissue staining, we found that NKT alleviated behavioral dysfunction and protected dopaminergic neurons associated with ROT-induced PD rats. Next, target prediction, protein-protein interaction (PPI), Gene Ontology (GO), and pathway enrichment analyses were used to obtain potential targets, specific biological processes, and molecular mechanisms of NKT for the potential treatment of PD. Furthermore, we also applied molecular docking to predict the binding capacity of NKT and related targets. Additionally, in vivo experiments confirmed that NKT could inhibit the expression of Mitogen-activated protein kinase 3 (MAPK3) by activating the PI3K/Akt signaling pathway, reducing neuroinflammation, and ultimately ameliorating ROT-induced PD symptoms. Taken together, the results of the study provide a clear explanation for the remission of PD symptoms by NKT, suggesting that it may be a promising candidate for the treatment of PD.

The microbiome-gut-brain axis in Parkinson disease - from basic research to the clinic

Evidence for a close bidirectional link between the brain and the gut has led to a paradigm shift in neurology, especially in the case of Parkinson disease (PD), in which gastrointestinal dysfunction is a prominent feature. Over the past decade, numerous high-quality preclinical and clinical publications have shed light on the highly complex relationship between the gut and the brain in PD, providing potential for the development of new biomarkers and therapeutics. With the advent of high-throughput sequencing, the role of the gut microbiome has been specifically highlighted. Here, we provide a critical review of the literature on the microbiome-gut-brain axis in PD and present perspectives that will be useful for clinical practice. We begin with an overview of the gut-brain axis in PD, including the potential roles and interrelationships of the vagus nerve, α-synuclein in the enteric nervous system, altered intestinal permeability and inflammation, and gut microbes and their metabolic activities. The sections that follow synthesize the proposed roles of gut-related factors in the development and progression of, in responses to PD treatment, and as therapeutic targets. Finally, we summarize current knowledge gaps and challenges and delineate future directions for the field.

Neuroprotective approaches to halt Parkinson's disease progression

One of the most significant threats in Parkinson's disease (PD) is neurodegeneration. Neurodegeneration at both nigral as well as non-nigral regions of the brain is considered responsible for disease progression in PD. The key factors that initiate neurodegeneration are oxidative stress, neuroinflammation, mitochondrial complex-1 inhibition, and abnormal α-synuclein (SNCA) protein aggregations. Nigral neurodegeneration results in motor symptoms (tremor, bradykinesia, rigidity, shuffling gait, and postural instability) whereas; non-nigral neurodegeneration is responsible for non-motor symptoms (depression, cognitive dysfunctions, sleep disorders, hallucination, and psychosis). The available therapies for PD aim at increasing dopamine levels. The medications such as Monoamine oxidase B (MAO-B) inhibitors, catechol o-methyltransferase (COMT) inhibitors, Dopamine precursor (Levodopa), dopamine agonists, and dopamine reuptake inhibitors drastically improve the motor symptoms and quality of life only in the early stages of the disease. However, dopa resistant motor symptoms (abnormality in posture, speech impediment, gait, and balance problems), dopa resistant non-motor signs (sleep problems, autonomic dysfunction, mood, and cognitive impairment, pain), and drug-related side effects (motor fluctuations, psychosis, and dyskinesias) are considered responsible for the failure of these therapies. Further, none of the treatments, alone or in combination, are capable of halting the disease progression in the long run. Therefore, there is a need to develop safe and efficient neuroprotective agents, which can slow or stop the disease progression for the better management of PD. In this review, an effort has been made to discuss the various mechanisms responsible for progressive neurodegeneration (disease progression) in PD and also multiple strategies available for halting disease progression.

DAT and TH expression marks human Parkinson's disease in peripheral immune cells

Parkinson's disease (PD) is marked by a loss of dopamine neurons, decreased dopamine transporter (DAT) and tyrosine hydroxylase (TH) expression. However, this validation approach cannot be used for diagnostic, drug effectiveness or investigational purposes in human patients because midbrain tissue is accessible postmortem. PD pathology affects both the central nervous and peripheral immune systems. Therefore, we immunophenotyped blood samples of PD patients for the presence of myeloid derived suppressor cells (MDSCs) and discovered that DAT+/TH+ monocytic MDSCs, but not granulocytic MDSCs are increased, suggesting a targeted immune response to PD. Because in peripheral immune cells DAT activity underlies an immune suppressive mechanism, we investigated whether expression levels of DAT and TH in the peripheral immune cells marks PD. We found drug naïve PD patients exhibit differential DAT+/TH+ expression in peripheral blood mononuclear cells (PBMCs) compared to aged/sex matched healthy subjects. While total PBMCs are not different between the groups, the percentage of DAT+/TH+ PBMCs was significantly higher in drug naïve PD patients compared to healthy controls irrespective of age, gender, disease duration, disease severity or treatment type. Importantly, treatment for PD negatively modulates DAT+/TH+ expressing PBMCs. Neither total nor the percentage of DAT+/TH+ PBMCs were altered in the Alzheimer's disease cohort. The mechanistic underpinning of this discovery in human PD was revealed when these findings were recapitulated in animal models of PD. The reverse translational experimental strategy revealed that alterations in dopaminergic markers in peripheral immune cells are due to the disease associated changes in the CNS. Our study demonstrates that the dopaminergic machinery on peripheral immune cells displays an association with human PD, with exciting implications in facilitating diagnosis and investigation of human PD pathophysiology.

A Mendelian randomization study investigating the causal role of inflammation on Parkinson’s disease

There is increasing evidence for inflammation as a determinant in the pathogenesis of Parkinson’s disease, but its role in parkinsonian neurodegeneration remains elusive. It is not clear whether inflammatory cascades are causes or consequences of dopamine neuron death. In the present study, we aim to perform an in-depth statistical investigation of the causal relationship between inflammation and Parkinson’s disease using a two-sample Mendelian randomization design.

Genetic instruments were selected using summary-level data from the largest genome-wide association studies to date (sample size ranging from 13 955 to 204 402 individuals) conducted on a European population for the following inflammation biomarkers: C-reactive protein, interleukin-6, interleukin 1 receptor antagonist and tumour necrosis factor α. Genetic association data on Parkinson’s disease (56 306 cases and 1 417 791 controls) and age at onset of Parkinson’s disease (28 568 cases) were obtained from the International Parkinson’s Disease Genomics Consortium. On primary analysis, causal associations were estimated on sets of strong (P-value < 5 × 10⁻⁸; F-statistic > 10) and independent (linkage disequilibrium r² < 0.001) genetic instruments using the inverse-variance weighted method. In sensitivity analysis, we estimated causal effects using robust Mendelian randomization methods and after removing pleiotropic genetic variants. Reverse causation was also explored. We repeated the analysis on different data sources for inflammatory biomarkers to check the consistency of the findings.

In all the three data sources selected for interleukin-6, we found statistical evidence for an earlier age at onset of Parkinson’s disease associated with increased interleukin-6 concentration [years difference per 1 log-unit increase = −2.364, 95% confidence interval (CI) = −4.789–0.060; years difference per 1 log-unit increase = −2.011, 95% CI = −3.706 to −0.317; years difference per 1 log-unit increase = −1.569, 95% CI = −2.891 to −0.247]. We did not observe any statistical evidence for causal effects of C-reactive protein, interleukin 1 receptor antagonist and tumour necrosis factor α on both Parkinson’s disease and its age at onset. Results after excluding possible pleiotropic genetic variants were consistent with findings from primary analyses. When investigating reverse causation, we did not find evidence for a causal effect of Parkinson’s disease or age at onset on any biomarkers of inflammation.

We found evidence for a causal association between the onset of Parkinson’s disease and interleukin-6. The findings of this study suggest that the pro-inflammatory activity of the interleukin-6 cytokine could be a determinant of prodromal Parkinson’s disease.

COVID-19 infection enhances susceptibility to oxidative-stress induced parkinsonism

Background

Viral induction of neurological syndromes has been a concern since parkinsonian‐like features were observed in patients diagnosed with encephalitis lethargica subsequent to the 1918 influenza pandemic. Given the similarities in the systemic responses after severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) infection with those observed after pandemic influenza, there is a question whether a similar syndrome of postencephalic parkinsonism could follow coronavirus disease 2019 infection.

Objective

The goal of this study was to determine whether prior infection with SARS‐CoV‐2 increased sensitivity to a mitochondrial toxin known to induce parkinsonism.

Methods

K18‐hACE2 mice were infected with SARS‐CoV‐2 to induce mild‐to‐moderate disease. After 38 days of recovery, mice were administered a non‐lesion‐inducing dose of the parkinsonian toxin 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine (MPTP) and euthanized 7 days later. Subsequent neuroinflammation and substantia nigra pars compacta (SNpc) dopaminergic (DA) neuron loss were determined and compared with SARS‐CoV‐2 or MPTP alone.

Results

K18‐hACE2 mice infected with SARS‐CoV‐2 or MPTP showed no SNpc DA neuron loss after MPTP. In mice infected and recovered from SARS‐CoV‐2 infection, MPTP induced a 23% or 19% greater loss of SNpc DA neurons than SARS‐CoV‐2 or MPTP, respectively (P < 0.05). Examination of microglial activation showed a significant increase in the number of activated microglia in both the SNpc and striatum of the SARS‐CoV‐2 + MPTP group compared with SARS‐CoV‐2 or MPTP alone.

Conclusions

Our observations have important implications for long‐term public health, given the number of people who have survived SARS‐CoV‐2 infection, as well as for future public policy regarding infection mitigation. However, it will be critical to determine whether other agents known to increase risk for PD also have synergistic effects with SARS‐CoV‐2 and are abrogated by vaccination. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society

Long noncoding RNA BACE1-antisense transcript plays a critical role in Parkinson's disease via microRNA-214-3p/Cell death-inducing p53-target protein 1 axis

This study aimed to analyze the function and latent mechanism of long noncoding RNA BACE1-antisense transcript (lncRNA BACE1-AS) in MPP⁺-induced SH-SY5Y cells. SH-SY5Y cells were cultivated in 1 mM MPP⁺ for 24 h to establish Parkinson’s disease (PD) model in vitro. TargetScan and luciferase reporter assay were conducted to predict and verify the interaction between microRNA (miR)-214-3p and CDIP1 (Cell death-inducing p53-target protein 1). Cell viability, lactate dehydrogenase (LDH) release, and cell apoptosis were evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2 H-tetrazolium bromide (MTT), LDH, and flow cytometer. The secretion of inflammatory factors and representative biomarkers of oxidative stress, including reactive oxygen species (ROS) and superoxide dismutase (SOD) were assessed using enzyme-linked immunosorbent assay (ELISA) and specific assay kits. Results suggested that lncRNA BACE1-AS was over-expressed and miR-214-3p was under-expressed in MPP⁺-stimulated SH-SY5Y cells. Further analyses revealed that MPP⁺ inhibited cell viability; enhanced cell apoptosis, Cleaved Caspase-3 expression and Cleaved Caspase-3/GAPDH ratio; induced oxidative stress and inflammation in SH-SY5Y cells were inhibited by lncRNA BACE1-AS-siRNA transfection; and all these inhibitions were reversed by miR-214-3p inhibitor. In addition, we found that CDIP1 was directly targeted by miR-214-3p and up-regulated in MPP⁺-stimulated SH-SY5Y cells. Further functional assays suggested that CDIP1-plasmid reversed the effects of miR-214-3p mimic on MPP⁺-stimulated SH-SY5Y cells. In conclusion, lncRNA BACE1-AS regulates SH-SY5Y cell proliferation, apoptosis, inflammatory response, and oxidative stress through direct regulation of miR-214-3p/CDIP1 signaling axis, and could be a potential candidate associated with the diagnosis and treatment of PD.