Genetic predispositions of Parkinson's disease revealed in patient-derived brain cells

Short-term lipopolysaccharide treatment leads to astrocyte activation in LRRK2 G2019S knock-in mice without loss of dopaminergic neurons

BACKGROUND

The G2019S mutation of LRRK2, which enhances kinase activity of the protein, confers a substantial risk of developing Parkinson's disease (PD). However, the mutation demonstrates incomplete penetrance, suggesting the involvement of other genetic or environmental modulating factors. Here, we investigated whether LRRK2 G2019S knock-in (KI) mice treated with the inflammogen lipopolysaccharide (LPS) could model LRRK2 PD.

RESULTS

We found that short-term (2 weeks) treatment with LPS did not result in the loss of dopaminergic neurons in either LRRK2 G2019S KI or wild-type (WT) mice. Compared with WT mice, LRRK2 G2019S-KI mice showed incomplete recovery from LPS-induced weight loss. In LRRK2 G2019S KI mice, LPS treatment led to upregulated phosphorylation of LRRK2 at the autophosphorylation site Serine 1292, which is known as a direct readout of LRRK2 kinase activity. LPS treatment caused a greater increase in the activated astrocyte marker glial fibrillary acidic protein (GFAP) in the striatum and substantia nigra of LRRK2 G2019S mice than in those of WT mice. The administration of caffeine, which was recently identified as a biomarker of resistance to developing PD in individuals with LRRK2 mutations, attenuated LPS-induced astrocyte activation specifically in LRRK2 G2019S KI mice.

CONCLUSIONS

Our findings suggest that 2 weeks of exposure to LPS is not sufficient to cause dopaminergic neuronal loss in LRRK2 G2019S KI mice but rather results in increased astrocyte activation, which can be ameliorated by caffeine.

Aging, cellular senescence and Parkinson's disease

Parkinson's disease (PD) is the most common neurodegenerative movement disorder, affecting 1-2% of people over age 65. The risk of developing PD dramatically increases with advanced age, indicating that aging is likely a driving factor in PD neuropathogenesis. Several age-associated biological changes are also hallmarks of PD neuropathology, including mitochondrial dysfunction, oxidative stress, and neuroinflammation. Accumulation of senescent cells is an important feature of aging that contributes to age-related diseases. How age-related cellular senescence affects brain health and whether this phenomenon contributes to neuropathogenesis in PD is not yet fully understood. In this review, we highlight hallmarks of aging, including mitochondrial dysfunction, loss of proteostasis, genomic instability and telomere attrition in relation to well established PD neuropathological pathways. We then discuss the hallmarks of cellular senescence in the context of neuroscience and review studies that directly examine cellular senescence in PD. Studying senescence in PD presents challenges and holds promise for advancing our understanding of disease mechanisms, which could contribute to the development of effective disease-modifying therapeutics. Targeting senescent cells or modulating the senescence-associated secretory phenotype (SASP) in PD requires a comprehensive understanding of the complex relationship between PD pathogenesis and cellular senescence.

Limitations and Applications of Rodent Models in Tauopathy and Synucleinopathy Research

Rodent models that accurately recapitulate key aspects of human disease have long been fundamental to the successful development of clinical interventions. This is greatly underscored in the neurodegenerative disease field, where preclinical testing of anti-prion therapeutics against rodent-adapted prions resulted in the development of small molecules effective against rodent-adapted prions but not against human prions. These findings provided critical lessons for ongoing efforts to develop treatments for patients with neurodegenerative diseases caused by misfolding and accumulation of the proteins tau and α-synuclein, or tauopathies and synucleinopathies, respectively. To avoid the potential pitfalls previously identified in the prion field, this review focuses on rodent models currently available to study tau and α-synuclein disease pathogenesis, emphasizing the strengths and limitations of each with the particular goal of better supporting preclinical research.

Wild-Type Drosophila melanogaster Strains Respond Differentially to Rotenone Exposure

Drosophila melanogaster has been established as a reliable in vivo model for studying human diseases. However, the varied designs of such studies and the different origins of the strains have significantly contributed to metabolic and molecular differences between strains. Parkinson's disease (PD) is a neurodegenerative disorder involving the loss of dopaminergic neurons, leading to various motor and non-motor symptoms including but not limited to bradykinesia, postural instability, cognitive decline, and gut dysbiosis. Chronic exposure to toxins such as rotenone can induce neuronal cell death. We have developed a sporadic PD model by direct feeding of rotenone-supplemented food to Drosophila melanogaster wild-type strains, which has previously been shown to cause neuronal cell death and used to mimic PD in Drosophila. Upon exposure to rotenone in two wild-type strains ( Oregon-R and Canton-S) , differences in their climbing ability and lifespan were monitored. We found that the degree of motor defects upon rotenone exposure is higher in Oregon-R compared to age-matched Canton-S flies. We also observed that the Canton-S flies (rotenone-fed and non-rotenone-fed) exhibited a lower survival percentage than Oregon-R flies. However, the climbing defects in Canton-S flies are not as pronounced as in Oregon-R flies. The mechanism(s) involved in such differential effects in different wild-type Drosophila strains are yet to be explored and may provide a perspective on differential symptoms of PD patients belonging to different demographics.

Genomic and Transcriptomic Approaches Advance the Diagnosis and Prognosis of Neurodegenerative Diseases

Neurodegenerative diseases, such as Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), and amyotrophic lateral sclerosis (ALS), represent a growing societal challenge due to their irreversible progression and significant impact on patients, caregivers, and healthcare systems. Despite advances in clinical and imaging-based diagnostics, these diseases are often detected at advanced stages, limiting the effectiveness of therapeutic interventions. Recent breakthroughs in genomic and transcriptomic technologies, including whole-genome sequencing, single-cell RNA sequencing (scRNA-seq), and CRISPR-based screens, have revolutionized the field, offering new avenues for early diagnosis and personalized prognosis. Genomic approaches have elucidated disease-specific genetic risk factors and molecular pathways, while transcriptomic studies have identified stage-specific biomarkers that correlate with disease progression and severity. Furthermore, genome-wide association studies (GWAS), polygenic risk scores (PRS), and spatial transcriptomics are enabling the stratification of patients based on their risk profiles and prognostic trajectories. Advances in functional genomics have uncovered actionable targets, such as ATXN2 in ALS and TREM2 in AD, paving the way for tailored therapeutic strategies. Despite these achievements, challenges remain in translating genomic discoveries into clinical practice due to disease heterogeneity and the complexity of neurodegenerative pathophysiology. Future integration of genetic technologies holds promise for transforming diagnostic and prognostic paradigms, offering hope for improved patient outcomes and precision medicine approaches.

Genetic-based diagnostics of Parkinson's disease and other Parkinsonian syndromes

INTRODUCTION

Parkinson's disease (PD) is a complex disorder with vast clinical heterogeneity. Recent genetic, imaging and clinical evidence suggest that there are multiple subtypes of PD, and perhaps even distinct clinical entities, which are being diagnosed under the umbrella of PD. These might have similar clinical presentation, but potentially different underlying mechanisms, which, in future, will require different treatments. Despite extensive genetic research progress, genetic testing is still not a common practice in clinical patient care.

AREAS COVERED

This review examines the numerous genes that have been discovered to affect the risk of, or cause, PD. We also outline genetic variants that affect PD age at onset, its progression, and the presence or severity of motor and non-motor symptoms. We differentiate between PD, other synucleinopathies, and atypical parkinsonism syndromes, and describe genes responsible for familial forms of typical PD and atypical parkinsonism. Lastly, we present current clinical trails that are underway for targeted therapies, particularly for GBA1-PD and LRRK2-PD which are the most significant subtypes.

EXPERT OPINION

While genetic studies alone cannot be diagnostic for PD, proper utilization of genetic screening for PD could improve diagnostic accuracy and predictions for prognosis, guide treatment, and identify individuals that qualify for clinical trials.

Targeting serum response factor (SRF) deactivates ΔFosB and mitigates Levodopa-induced dyskinesia in a mouse model of Parkinson's disease

L-3,4-dihydroxyphenylalanine (L-DOPA) is currently the preferred treatment for Parkinson's Disease (PD) and is considered the gold standard. However, prolonged use of L-DOPA in patients can result in involuntary movements known as Levodopa-induced dyskinesia (LID), which includes uncontrollable dystonia affecting the trunk, limbs, and face. The role of ΔFosB protein, a truncated splice variant of the FosB gene, in LID has been acknowledged, but its underlying mechanism has remained elusive. Here, using a mouse model of Parkinson's disease treated with chronic levodopa we demonstrate that serum response factor (SRF) binds to the FosB promoter, thereby activating FosB expression and levodopa induced-dyskinetic movements. Western blot analysis demonstrates a significant increase in SRF expression in the dyskinetic group compared to the control group. Knocking down SRF significantly reduced abnormal involuntary movements (AIMS) and ΔFosB expression compared to the control. Conversely, overexpression of SRF led to an increase in ΔFosB expression and worsened levodopa-induced dyskinesia. To shed light on the regulatory role of the Akt signaling pathway in this phenomenon, we administered the Akt agonist SC79 to PD mouse models via intraperitoneal injection, followed by L-DOPA administration. The expression of SRF, ΔFosB, and phosphorylated Akt (p-Akt) significantly increased in this group compared to the group receiving normal saline to signify that these happen through Akt signaling pathway. Collectively, our findings identify a promising therapeutic target for addressing levodopa-induced dyskinesia.

Current progress in understanding schizophrenia using genomics and pluripotent stem cells: A meta-analytical overview

Schizophrenia (SCZ) is a complex, heritable and polygenic neuropsychiatric disease, which disables the patients as well as decreases their life expectancy and quality of life. Common and rare variants studies on SCZ subjects have provided >100 genomic loci that hold importance in the context of SCZ pathophysiology. Transcriptomic studies from clinical samples have informed about the differentially expressed genes (DEGs) and non-coding RNAs in SCZ patients. Despite these advancements, no causative genes for SCZ were found and hence SCZ is difficult to recapitulate in animal models. In the last decade, induced Pluripotent Stem Cells (iPSCs)-based models have helped in understanding the neural phenotypes of SCZ by studying patient iPSC-derived 2D neuronal cultures and 3D brain organoids. Here, we have aimed to provide a simplistic overview of the current progress and advancements after synthesizing the enormous literature on SCZ genetics and SCZ iPSC-based models. Although further understanding of SCZ genetics and pathophysiological mechanisms using these technological advancements is required, the recent approaches have allowed to delineate important cellular mechanisms and biological pathways affected in SCZ.

Substantia nigra alterations in mice modeling Parkinson's disease

Parkinson's disease (PD) is an age-related neurodegenerative pathology of the central nervous system. The well-known abnormalities characteristic of PD are dysfunctions in the nigrostriatal system including the substantia nigra of the midbrain and the striatum. Moreover, in PD persons, alpha-synucleinopathy is associated with abnormalities in the dopaminergic brain system. To study the mechanisms of this pathology, genetic models in mice have been designed. Transgenic mice of the B6.Cg-Tg(Prnp-SNCA*A53T)23Mkle/J strain (referred to as B6.Cg-Tg further in the text) possess the A53T mutation in the human alpha-synuclein SNCA gene. The density of neurons in the prefrontal cortex, hippocampus, substantia nigra and striatum in B6.Cg-Tg mice was assessed in our previous work, but the dopaminergic system was not studied there, although it plays a key role in the development of PD. The aim of the current study was to investigate motor coordination and body balance, as well as dopaminergic neuronal density and alpha-synuclein accumulation in the substantia nigra in male B6.Cg-Tg mice at the age of six months. Wild-type mice of the same sex and age, siblings of the B6.Cg-Tg mice from the same litters, lacking the SNCA gene with the A53T mutation, but expressing murine alpha-synuclein, were used as controls (referred to as the wild type further in the text). Motor coordination and body balance were assessed with the rota-rod test; the density of dopaminergic neurons and accumulation of alpha-synuclein in the substantia nigra were evaluated by the immunohistochemical method. There was no difference between B6.Cg-Tg mice and WT siblings in motor coordination and body balance. However, accumulation of alpha-synuclein and a decrease in the number of dopaminergic neurons in the substantia nigra were found in the B6.Cg-Tg mouse strain. Thus, the mice of the B6.Cg-Tg strain at the age of six months have some symptoms of the onset of PD, such as the accumulation of mutant alpha-synuclein and a decrease in the number of dopaminergic neurons in the substantia nigra. Taken together, the results obtained in our work qualify the B6.Cg-Tg strain as a pertinent model for studying the early stage of human PD already at the age of six months.

Microbiota Orchestra in Parkinson's Disease: The Nasal and Oral Maestros

Parkinson's disease (PD) is characterized by the progressive degeneration of dopaminergic neurons, leading to a range of motor and non-motor symptoms.

BACKGROUND/OBJECTIVES

Over the past decade, studies have identified a potential link between the microbiome and PD pathophysiology. The literature suggests that specific bacterial communities from the gut, oral, and nasal microbiota may be involved in neuroinflammatory processes, which are hallmarks of PD. This review aims to comprehensively analyze the current research on the composition, diversity, and dysbiosis characteristics of the nasal and oral microbiota in PD.

METHODS

Through a comprehensive search across scientific databases, we identify twenty original studies investigating the nasal and oral microbiota in PD.

RESULTS

Most of these studies demonstrate the substantial roles of bacterial communities in neuroinflammatory pathways associated with PD progression. They also underscore the influences of microbiota-derived factors on key aspects of PD pathology, including alpha-synuclein aggregation and immune dysregulation.

CONCLUSIONS

Finally, we discuss the potential diagnostic and therapeutic implications of modulating the nasal and oral microbiota in PD management. This analysis seeks to identify potential avenues for future research in order to clarify the complex relationships between these microorganisms and PD.

Associations between Thyroid Hormones and Cognitive Impairment in Patients with Parkinson's Disease

This study aims to explore the correlation of serum thyroid hormone levels to cognitive impairments in Parkinson's disease (PD) patients. In this retrospective study, 106 Chinese patients without cognitive impairments and 94 patients with cognitive impairments, including 55 with mild cognitive impairment (PD-MCI) and 39 with PD dementia (PDD), were analyzed. Clinical data regarding the PD assessments, including disease duration, Unified Parkinson's Disease Rating Scale (UPDRS) Part 3 scores, and Hoehn and Yahr (H-Y) staging, were analyzed. Cognitive functions were evaluated using the Montreal Cognitive Assessment score. Serum levels of thyroid-stimulating hormone (TSH), free thyroxine (FT4), and free triiodothyronine (FT3), were measured using ELISA. Significantly altered H-Y staging, disease duration, and UPDRS Part 3 scores were observed in PD patients with cognitive impairment compared with those without. Serum levels of FT3 were significantly decreased, while FT4 and TSH levels were significantly elevated in PD patients with cognitive impairment compared with those without. Combined detection of TSH, FT3, and FT4 showed value in distinguishing PD patients with and without cognitive impairment. Furthermore, a comparison of serum levels between PD-MCI and PDD patients revealed significant association between thyroid hormone levels and the degree of cognitive impairment in PD patients. Our findings suggest a relationship between changes in serum thyroid hormone levels and cognitive impairments in PD patients. Thyroid hormone levels, particularly FT3, may serve as potential markers for cognitive dysfunction in PD.

Unveiling defects of secretion mechanisms in Parkinson's disease

Neurodegenerative diseases are characterized by progressive dysfunction and loss of specific sets of neurons. While extensive research has focused on elucidating the genetic and epigenetic factors and molecular mechanisms underlying these disorders, emerging evidence highlights the critical role of secretion in the pathogenesis, possibly even onset, and progression of neurodegenerative diseases, suggesting the occurrence of non-cell-autonomous mechanisms. Secretion is a fundamental process that regulates intercellular communication, supports cellular homeostasis, and orchestrates various physiological functions in the body. Defective secretion can impair the release of neurotransmitters and other signaling molecules, disrupting synaptic transmission and compromising neuronal survival. It can also contribute to the accumulation, misfolding, and aggregation of disease-associated proteins, leading to neurotoxicity and neuronal dysfunction. In this review, we discuss the implications of defective secretion in the context of Parkinson's disease, emphasizing its role in protein aggregation, synaptic dysfunction, extracellular vesicle secretion, and neuroinflammation. We propose a multiple-hit model whereby protein accumulation and secretory defects must be combined for the onset and progression of the disease.

Wood dust and risk of leukemia: Systematic review and meta-analysis

OBJECTIVES

This study aimed to perform a systematic review and meta-analysis to investigate the relationship between wood dust exposure and leukemia. The objectives included synthesizing available evidence, assessing its quality, identifying potential sources of heterogeneity, and drawing conclusions regarding the association between wood dust and leukemia.

METHODS

A systematic literature search was conducted to identify studies meeting that report on the association between wood dust and leukemia. The Joanna Briggs Institute Critical Appraisal tools were employed to ensure robust quality assessment. Meta-analysis, using random-effects models, synthesized evidence from studies with low risk of bias. Overall odds ratios (ORs) and 95% confidence intervals (CIs) were calculated. Subgroup analyses explored potential sources of heterogeneity.

RESULTS

The meta-analysis included a comprehensive review of various study types, encompassing 7 studies that examined the association between wood dust exposure and leukemia risk. The analysis revealed a statistically significant positive association, with an overall odds ratio (OR) of 1.56 (95% CI: 1.15-2.12). This indicates that individuals exposed to wood dust are 1.56 times more likely to develop leukemia compared to those not exposed, with the 95% confidence interval ranging from 1.15 to 2.12, highlighting a substantial risk elevation across different study designs. Quality assessment using The Joanna Briggs Institute Critical Appraisal tools demonstrated a low risk of bias across all included studies, enhancing the credibility of the observed association. Subgroup analyses were conducted to explore potential sources of heterogeneity within the studies. Notably, subgroup analysis based on the year of the study revealed significant differences, as indicated by an I^2 value of 87%. The robustness of these results underscores the importance of addressing wood dust exposure as an occupational hazard, particularly in industries related to woodworking and forestry.

CONCLUSION

This meta-analysis provides robust evidence supporting an increased risk of leukemia associated with wood dust exposure implying proactive measures in people exposed to dust.

Residues 2 to 7 of α-synuclein regulate amyloid formation via lipid-dependent and lipid-independent pathways

Amyloid formation by α-synuclein (αSyn) occurs in Parkinson's disease, multiple system atrophy, and dementia with Lewy bodies. Deciphering the residues that regulate αSyn amyloid fibril formation will not only provide mechanistic insight but may also reveal targets to prevent and treat disease. Previous investigations have identified several regions of αSyn to be important in the regulation of amyloid formation, including the non-amyloid-β component (NAC), P1 region (residues 36 to 42), and residues in the C-terminal domain. Recent studies have also indicated the importance of the N-terminal region of αSyn for both its physiological and pathological roles. Here, the role of residues 2 to 7 in the N-terminal region of αSyn is investigated in terms of their ability to regulate amyloid fibril formation in vitro and in vivo. Deletion of these residues (αSynΔN7) slows the rate of fibril formation in vitro and reduces the capacity of the protein to be recruited by wild-type (αSynWT) fibril seeds, despite cryo-EM showing a fibril structure consistent with those of full-length αSyn. Strikingly, fibril formation of αSynΔN7 is not induced by liposomes, despite the protein binding to liposomes with similar affinity to αSynWT. A Caenorhabditis elegans model also showed that αSynΔN7::YFP forms few puncta and lacks motility and lifespan defects typified by expression of αSynWT::YFP. Together, the results demonstrate the involvement of residues 2 to 7 of αSyn in amyloid formation, revealing a target for the design of amyloid inhibitors that may leave the functional role of the protein in membrane binding unperturbed.

Gene network analysis combined with preclinical studies to identify and elucidate the mechanism of action of novel irreversible Keap1 inhibitor for Parkinson's disease

The cysteine residues of Keap1 such as C151, C273, and C288 are critical for its repressor activity on Nrf2. However, to date, no molecules have been identified to covalently modify all three cysteine residues for Nrf2 activation. Hence, in this study, our goal is to discover new Keap1 covalent inhibitors that can undergo a Michael addition with all three cysteine residues. The Keap1's intervening region was modeled using Modeller v10.4. Covalent docking and binding free energy were calculated using CovDock. Molecular dynamics (MD) was performed using Desmond. Various in-vitro assays were carried out to confirm the neuroprotective effects of the hit molecule in 6-OHDA-treated SH-SY5Y cells. Further, the best hit was evaluated in vivo for its ability to improve rotenone-induced postural instability and cognitive impairment in male rats. Finally, network pharmacology was used to summarize the complete molecular mechanism of the hit molecule. Chalcone and plumbagin were found to form the necessary covalent bonds with all three cysteine residues. However, MD analysis indicated that the binding of plumbagin is more stable than chalcone. Plumbagin displayed neuroprotective effects in 6-OHDA-treated SH-SY5Y cells at concentrations 0.01 and 0.1 μM. Plumbagin at 0.1 µM had positive effects on reactive oxygen species formation and glutathione levels. Plumbagin also improved postural instability and cognitive impairment in rotenone-treated male rats. Our network analysis indicated that plumbagin could also improve dopamine signaling. Additionally, plumbagin could exhibit anti-oxidant and anti-inflammatory activity through the activation of Nrf2. Cumulatively, our study suggests that plumbagin is a novel Keap1 covalent inhibitor for Nrf2-mediated neuroprotection in PD.

Generation of integration-free human induced pluripotent stem cells from a patient with sporadic Parkinson's disease

A human induced pluripotent stem cell (iPSC) line (KKUi002-A) was generated from a skin fibroblast of a 57-years-old (at sampling) male patient diagnosed with a sporadic Parkinson's disease (PD). A non-integration system was used to reprogram fibroblasts into iPSCs by an episomal vector (OCT4/p53, SOX2/KLF4, L-MYC/LIN28). The KKUi002-A iPSCs displayed typical iPSC morphology, expressed pluripotency markers, differentiated into derivatives of three germ layers, and had a normal karyotype. These PD-derived iPSCs can be used to understand the mechanism underlying PD pathogenesis.

A Plant Model of α-Synucleinopathy: Expression of α-Synuclein A53T Variant in Hairy Root Cultures Leads to Proteostatic Stress and Dysregulation of Iron Metabolism

Synucleinopathies, typified by Parkinson's disease (PD), entail the accumulation of α-synuclein (αSyn) aggregates in nerve cells. Various αSyn mutants, including the αSyn A53T variant linked to early-onset PD, increase the propensity for αSyn aggregate formation. In addition to disrupting protein homeostasis and inducing proteostatic stress, the aggregation of αSyn in PD is associated with an imbalance in iron metabolism, which increases the generation of reactive oxygen species and causes oxidative stress. This study explored the impact of αSyn A53T expression in transgenic hairy roots of four medicinal plants (Lobelia cardinalis, Artemisia annua, Salvia miltiorrhiza, and Polygonum multiflorum). In all tested plants, αSyn A53T expression triggered proteotoxic stress and perturbed iron homeostasis, mirroring the molecular profile observed in human and animal nerve cells. In addition to the common eukaryotic defense mechanisms against proteostatic and oxidative stresses, a plant stress response generally includes the biosynthesis of a diverse set of protective secondary metabolites. Therefore, the hairy root cultures expressing αSyn A53T offer a platform for identifying secondary metabolites that can ameliorate the effects of αSyn, thereby aiding in the development of possible PD treatments and/or treatments of synucleinopathies.

Alterations in Blood Methylome as Potential Epigenetic Biomarker in Sporadic Parkinson's Disease

OBJECTIVE

To characterize DNA methylation (DNAm) differences between sporadic Parkinson's disease (PD) and healthy control (HC) individuals enrolled in the Parkinson's Progression Markers Initiative (PPMI).

METHODS

Using whole blood, we characterized longitudinal differences in DNAm between sporadic PD patients (n = 196) and HCs (n = 86) enrolled in PPMI. RNA sequencing (RNAseq) was used to conduct gene expression analyses for genes mapped to differentially methylated cytosine-guanine sites (CpGs).

RESULTS

At the time of patient enrollment, 5,178 CpGs were differentially methylated (2,683 hypermethylated and 2,495 hypomethylated) in PD compared to HC. Of these, 579 CpGs underwent significant methylation changes over 3 years. Several differentially methylated CpGs were found near the cytochrome P450 family 2 subfamily E member 1 (CYP2E1) gene. Additionally, multiple hypermethylated CpGs were associated with the N-myc downregulated gene family member 4 (NDRG4) gene. RNA-Seq analyses showed 75 differentially expressed genes in PD patients compared to controls. An integrative analysis of both differentially methylated sites and differentially expressed genes revealed 20 genes that exhibited hypomethylation concomitant with overexpression. Additionally, 1 gene, cathepsin H (CTSH), displayed hypermethylation that was associated with its decreased expression.

INTERPRETATION

We provide initial evidence of alterations in DNAm in blood of PD patients that may serve as potential epigenetic biomarker of disease. To evaluate the significance of these changes throughout the progression of PD, additional profiling at longer intervals and during the prodromal stages of disease will be necessary. ANN NEUROL 2024;95:1162-1172.

Upregulated ECM genes and increased synaptic activity in Parkinson's human DA neurons with PINK1/ PRKN mutations

Parkinson's disease (PD) is the second most prevalent neurodegenerative disease. Primary symptoms of PD arise with the loss of dopaminergic (DA) neurons in the Substantia Nigra Pars Compacta, but PD also affects the hippocampus and cortex, usually in its later stage. Approximately 15% of PD cases are familial with a genetic mutation. Two of the most associated genes with autosomal recessive (AR) early-onset familial PD are PINK1 and PRKN. In vitro studies of these genetic mutations are needed to understand the neurophysiological changes in patients' neurons that may contribute to neurodegeneration. In this work, we generated and differentiated DA and hippocampal neurons from human induced pluripotent stem cells (hiPSCs) derived from two patients with a double mutation in their PINK1 and PRKN (one homozygous and one heterozygous) genes and assessed their neurophysiology compared to two healthy controls. We showed that the synaptic activity of PD neurons generated from patients with the PINK1 and PRKN mutations is impaired in the hippocampus and dopaminergic neurons. Mutant dopaminergic neurons had enhanced excitatory post-synaptic activity. In addition, DA neurons with the homozygous mutation of PINK1 exhibited more pronounced electrophysiological differences compared to the control neurons. Signaling network analysis of RNA sequencing results revealed that Focal adhesion and ECM receptor pathway were the top two upregulated pathways in the mutant PD neurons. Our findings reveal that the phenotypes linked to PINK1 and PRKN mutations differ from those from other PD mutations, suggesting a unique interplay between these two mutations that drives different PD mechanisms.

Disruption of Dopamine Homeostasis Associated with Alteration of Proteins in Synaptic Vesicles: A Putative Central Mechanism of Parkinson's Disease Pathogenesis

Vestigial dopaminergic cells in PD have selectivity for a sub-class of hypersensitive neurons with the nigrostriatal dopamine (DA) tract. DA is modulated in pre-synaptic nerve terminals to remain stable. To be specific, proteins at DA release sites that have a function of synthesizing and packing DA in cytoplasm, modulating release and reingestion, and changing excitability of neurons, display regional discrepancies that uncover relevancy of the observed sensitivity to neurodegenerative changes. Although the reasons of a majority of PD cases are still indistinct, heredity and environment are known to us to make significant influences. For decades, genetic analysis of PD patients with heredity in family have promoted our comprehension of pathogenesis to a great extent, which reveals correlative mechanisms including oxidative stress, abnormal protein homeostasis and mitochondrial dysfunction. In this review, we review the constitution of presynaptic vesicle related to DA homeostasis and describe the genetic and environmental evidence of presynaptic dysfunction that increase risky possibility of PD concerning intracellular vesicle transmission and their functional outcomes. We summarize alterations in synaptic vesicular proteins with great involvement in the reasons of some DA neurons highly vulnerable to neurodegenerative changes. We generalize different potential targets and therapeutic strategies for different pathogenic mechanisms, providing a reference for further studies of PD treatment in the future. But it remains to be further researched on this recently discovered and converging mechanism of vesicular dynamics and PD, which will provide a more profound comprehension and put up with new therapeutic tactics for PD patients.

Impact of genetic predisposition to late-onset neurodegenerative diseases on early life outcomes and brain structure

Most patients with late-onset neurodegenerative diseases such as Alzheimer's and Parkinson's have a complex aetiology resulting from numerous genetic risk variants of small effects located across the genome, environmental factors, and the interaction between genes and environment. Over the last decade, genome-wide association studies (GWAS) and post-GWAS analyses have shed light on the polygenic architecture of these diseases, enabling polygenic risk scores (PRS) to estimate an individual's relative genetic liability for presenting with the disease. PRS can screen and stratify individuals based on their genetic risk, potentially years or even decades before the onset of clinical symptoms. An emerging body of evidence from various research studies suggests that genetic susceptibility to late-onset neurodegenerative diseases might impact early life outcomes, including cognitive function, brain structure and function, and behaviour. This article summarises recent findings exploring the potential impact of genetic susceptibility to neurodegenerative diseases on early life outcomes. A better understanding of the impact of genetic susceptibility to neurodegenerative diseases early in life could be valuable in disease screening, detection, and prevention and in informing treatment strategies before significant neural damage has occurred. However, ongoing studies have limitations. Overall, our review found several studies focused on APOE haplotypes and Alzheimer's risk, but a limited number of studies leveraging polygenic risk scores or focused on genetic susceptibility to other late-onset conditions.

Stochastic models for the onset and disease course of multiple sclerosis

OBJECTIVE

Exact causes and mechanisms regulating the onset and progression in many chronic diseases, including multiple sclerosis (MS), remain uncertain. Until now, the potential role of random process based on stochastic models in the temporal course of chronic diseases remains largely unevaluated. Therefore, the present study investigated the applicability of stochastic models for the onset and disease course of MS.

METHODS

Stochastic models with random temporal process in disease activity, underlying clinical relapse and/or subclinical brain atrophy, were developed. The models incorporated parameters regarding the distribution of temporal changes in disease activity and the drift constant.

RESULTS

By adjusting the parameters (temporal change dispersion and drift constant) and the threshold for the onset of disease, the stochastic disease progression models could reproduce various types of subsequent disease course, such as clinically isolated syndrome (monophasic), relapsing-remitting MS, primary-progressive MS, and secondary-progressive MS. Furthermore, the disease prevalence and distribution of onset age could be also reproduced with stochastic models by adjusting the parameters. The models could further explain why approximately half of the patients with relapsing-remitting MS will eventually experience a transition to secondary-progressive MS.

CONCLUSION

Stochastic models with random temporal changes in disease activity could reproduce the characteristic onset age distribution and disease course forms in MS. Further studies by using real-world data to underscore the significance of random process in the occurrence and progression of MS are warranted.

Short-term lipopolysaccharide treatment leads to astrocyte activation in LRRK2 G2019S knock-in mice without loss of dopaminergic neurons

Background

The G2019S mutation of LRRK2, which enhances kinase activity of the protein, confers a substantial risk of developing Parkinson's disease (PD). However, the mutation demonstrates incomplete penetrance, suggesting the involvement of other genetic or environmental modulating factors. Here, we investigated whether LRRK2 G2019S knock-in (KI) mice treated with the inflammogen lipopolysaccharide (LPS) could model LRRK2 PD.

Results

We found that short-term (2 weeks) treatment with LPS did not result in the loss of dopaminergic neurons in either LRRK2 G2019S KI or wild-type (WT) mice. Compared with WT mice, LRRK2 G2019S-KI mice showed incomplete recovery from LPS-induced weight loss. In LRRK2 G2019S KI mice, LPS treatment led to upregulated phosphorylation of LRRK2 at the autophosphorylation site Serine 1292, which is known as a direct readout of LRRK2 kinase activity. LPS treatment caused a greater increase in the activated astrocyte marker glial fibrillary acidic protein (GFAP) in the striatum and substantia nigra of LRRK2 G2019S mice than in those of WT mice. The administration of caffeine, which was recently identified as a biomarker of resistance to developing PD in individuals with LRRK2 mutations, attenuated LPS-induced astrocyte activation specifically in LRRK2 G2019S KI mice.

Conclusions

Our findings suggest that 2 weeks of exposure to LPS is not sufficient to cause dopaminergic neuronal loss in LRRK2 G2019S KI mice but rather results in increased astrocyte activation, which can be ameliorated by caffeine.

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.

NMDA glutamate receptor antagonist MK-801 induces proteome changes in adult human brain slices which are partially counteracted by haloperidol and clozapine

Deciphering the molecular pathways associated with N-methyl-D-aspartate receptor (NMDAr) hypofunction and its interaction with antipsychotics is necessary to advance our understanding of the basis of schizophrenia, as well as our capacity to treat this disease. In this regard, the development of human brain-derived models that are amenable to studying the neurobiology of schizophrenia may contribute to filling the gaps left by the widely employed animal models. Here, we assessed the proteomic changes induced by the NMDA glutamate receptor antagonist MK-801 on human brain slice cultures obtained from adult donors submitted to respective neurosurgery. Initially, we demonstrated that MK-801 diminishes NMDA glutamate receptor signaling in human brain slices in culture. Next, using mass-spectrometry-based proteomics and systems biology in silico analyses, we found that MK-801 led to alterations in proteins related to several pathways previously associated with schizophrenia pathophysiology, including ephrin, opioid, melatonin, sirtuin signaling, interleukin 8, endocannabinoid, and synaptic vesicle cycle. We also evaluated the impact of both typical and atypical antipsychotics on MK-801-induced proteome changes. Interestingly, the atypical antipsychotic clozapine showed a more significant capacity to counteract the protein alterations induced by NMDAr hypofunction than haloperidol. Finally, using our dataset, we identified potential modulators of the MK-801-induced proteome changes, which may be considered promising targets to treat NMDAr hypofunction in schizophrenia. This dataset is publicly available and may be helpful in further studies aimed at evaluating the effects of MK-801 and antipsychotics in the human brain.

Synaptic dysfunction and extracellular matrix dysregulation in dopaminergic neurons from sporadic and E326K-GBA1 Parkinson's disease patients

Parkinson's disease (PD) is a neurodegenerative disease with both genetic and sporadic origins. In this study, we investigated the electrophysiological properties, synaptic activity, and gene expression differences in dopaminergic (DA) neurons derived from induced pluripotent stem cells (iPSCs) of healthy controls, sporadic PD (sPD) patients, and PD patients with E326K-GBA1 mutations. Our results demonstrate reduced sodium currents and synaptic activity in DA neurons derived from PD patients with E326K-GBA1 mutations, suggesting a potential contribution to PD pathophysiology. We also observed distinct electrophysiological alterations in sPD DA neurons, which included a decrease in synaptic currents. RNA sequencing analysis revealed unique dysregulated pathways in sPD neurons and E326K-GBA1 neurons, further supporting the notion that molecular mechanisms driving PD may differ between PD patients. In agreement with our previous reports, Extracellular matrix and Focal adhesion pathways were among the top dysregulated pathways in DA neurons from sPD patients and from patients with E326K-GBA1 mutations. Overall, our study further confirms that impaired synaptic activity is a convergent functional phenotype in DA neurons derived from PD patients across multiple genetic mutations as well as sPD. At the transcriptome level, we find that the brain extracellular matrix is highly involved in PD pathology across multiple PD-associated mutations as well as sPD.

Changes in Bacterial Gut Composition in Parkinson's Disease and Their Metabolic Contribution to Disease Development: A Gut Community Reconstruction Approach

Parkinson's disease (PD) is a chronic and progressive neurodegenerative disease with the major symptoms comprising loss of movement coordination (motor dysfunction) and non-motor dysfunction, including gastrointestinal symptoms. Alterations in the gut microbiota composition have been reported in PD patients vs. controls. However, it is still unclear how these compositional changes contribute to disease etiology and progression. Furthermore, most of the available studies have focused on European, Asian, and North American cohorts, but the microbiomes of PD patients in Latin America have not been characterized. To address this problem, we obtained fecal samples from Colombian participants (n = 25 controls, n = 25 PD idiopathic cases) to characterize the taxonomical community changes during disease via 16S rRNA gene sequencing. An analysis of differential composition, diversity, and personalized computational modeling was carried out, given the fecal bacterial composition and diet of each participant. We found three metabolites that differed in dietary habits between PD patients and controls: carbohydrates, trans fatty acids, and potassium. We identified six genera that changed significantly in their relative abundance between PD patients and controls, belonging to the families Lachnospiraceae, Lactobacillaceae, Verrucomicrobioaceae, Peptostreptococcaceae, and Streptococcaceae. Furthermore, personalized metabolic modeling of the gut microbiome revealed changes in the predicted production of seven metabolites (Indole, tryptophan, fructose, phenylacetic acid, myristic acid, 3-Methyl-2-oxovaleric acid, and N-Acetylneuraminic acid). These metabolites are associated with the metabolism of aromatic amino acids and their consumption in the diet. Therefore, this research suggests that each individual's diet and intestinal composition could affect host metabolism. Furthermore, these findings open the door to the study of microbiome-host interactions and allow us to contribute to personalized medicine.

Sortilin Expression Levels and Peripheral Immunity: A Potential Biomarker for Segregation between Parkinson's Disease Patients and Healthy Controls

Parkinson's disease (PD) is characterized by substantial phenotypic heterogeneity that limits the disease prognosis and patient's counseling, and complicates the design of further clinical trials. There is an unmet need for the development and validation of biomarkers for the prediction of the disease course. In this study, we utilized flow cytometry and in vitro approaches on peripheral blood cells and isolated peripheral blood mononuclear cell (PBMC)-derived macrophages to characterize specific innate immune populations in PD patients versus healthy donors. We found a significantly lower percentage of B lymphocytes and monocyte populations in PD patients. Monocytes in PD patients were characterized by a higher CD40 expression and on-surface expression of the type I membrane glycoprotein sortilin, which showed a trend of negative correlation with the age of the patients. These results were further investigated in vitro on PBMC-derived macrophages, which, in PD patients, showed higher sortilin expression levels compared to cells from healthy donors. The treatment of PD-derived macrophages with oxLDL led to higher foam cell formation compared to healthy donors. In conclusion, our results support the hypothesis that surface sortilin expression levels on human peripheral monocytes may potentially be utilized as a marker of Parkinson's disease and may segregate the sporadic versus the genetically induced forms of the disease.

Aquaporin-4 and Parkinson's Disease

The water-selective channel aquaporin-4 (AQP4) is implicated in water homeostasis and the functioning of the glymphatic system, which eliminates various metabolites from the brain tissue, including amyloidogenic proteins. Misfolding of the α-synuclein protein and its post-translational modifications play a crucial role in the development of Parkinson's disease (PD) and other synucleopathies, leading to the formation of cytotoxic oligomers and aggregates that cause neurodegeneration. Human and animal studies have shown an interconnection between AQP4 dysfunction and α-synuclein accumulation; however, the specific role of AQP4 in these mechanisms remains unclear. This review summarizes the current knowledge on the role of AQP4 dysfunction in the progression of α-synuclein pathology, considering the possible effects of AQP4 dysregulation on brain molecular mechanisms that can impact α-synuclein modification, accumulation and aggregation. It also highlights future directions that can help study the role of AQP4 in the functioning of the protective mechanisms of the brain during the development of PD and other neurodegenerative diseases.

Leucine-rich repeat kinase 2 (LRRK2) inhibition upregulates microtubule-associated protein 1B to ameliorate lysosomal dysfunction and parkinsonism

Mutations in LRRK2 (encoding leucine-rich repeat kinase 2 protein, LRRK2) are the most common genetic risk factors for Parkinson's disease (PD), and increased LRRK2 kinase activity was observed in sporadic PD. Therefore, inhibition of LRRK2 has been tested as a disease-modifying therapeutic strategy using the LRRK2 mutant mice and sporadic PD. Here, we report a newly designed molecule, FL090, as a LRRK2 kinase inhibitor, verified in cell culture and animal models of PD. Using the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine mice and SNCA A53T transgenic mice, FL090 ameliorated motor dysfunctions, reduced LRRK2 kinase activity, and rescued loss in the dopaminergic neurons in the substantia nigra. Notably, by RNA-Seq analysis, we identified microtubule-associated protein 1 (MAP1B) as a crucial mediator of FL090's neuroprotective effects and found that MAP1B and LRRK2 co-localize. Overexpression of MAP1B rescued 1-methyl-4-phenylpyridinium induced cytotoxicity through rescuing the lysosomal function, and the protective effect of FL090 was lost in MAP1B knockout cells. Further studies may be focused on the in vivo mechanisms of MAP1B and microtubule function in PD. Collectively, these findings highlight the potential of FL090 as a therapeutic agent for sporadic PD and familial PD without LRRK2 mutations.

Impaired skeletal muscle health in Parkinsonian syndromes: clinical implications, mechanisms and potential treatments

There is increasing evidence that neurodegenerative disorders including the Parkinsonian syndromes are associated with impaired skeletal muscle health, manifesting as wasting and weakness. Many of the movement problems, lack of muscle strength and reduction in quality of life that are characteristic of these syndromes can be attributed to impairments in skeletal muscle health, but this concept has been grossly understudied and represents an important area of unmet clinical need. This review describes the changes in skeletal muscle health in idiopathic Parkinson's disease and in two atypical Parkinsonian syndromes, the most aggressive synucleinopathy multiple system atrophy, and the tauopathy progressive supranuclear palsy. The pathogenesis of the skeletal muscle changes is described, including the contribution of impairments to the central and peripheral nervous system and intrinsic alterations. Pharmacological interventions targeting the underlying molecular mechanisms with therapeutic potential to improve skeletal muscle health in affected patients are also discussed. Although little is known about the mechanisms underlying these conditions, current evidence implicates multiple pathways and processes, highlighting the likely need for combination therapies to protect muscle health and emphasizing the merit of personalized interventions for patients with different physical capacities at different stages of their disease. As muscle fatigue is often experienced by patients prior to diagnosis, the identification and measurement of this symptom and related biomarkers to identify early signs of disease require careful interrogation, especially for multiple system atrophy and progressive supranuclear palsy where diagnosis is often made several years after onset of symptoms and only confirmed post-mortem. We propose a multidisciplinary approach for early diagnosis and implementation of personalized interventions to preserve muscle health and improve quality of life for patients with typical and atypical Parkinsonian syndromes.

Protein network analysis links the NSL complex to Parkinson's disease via mitochondrial and nuclear biology

Whilst the majority of Parkinson's Disease (PD) cases are sporadic, much of our understanding of the pathophysiological basis of the disease can be traced back to the study of rare, monogenic forms of PD. In the past decade, the availability of genome-wide association studies (GWAS) has facilitated a shift in focus, toward identifying common risk variants conferring increased risk of developing PD across the population. A recent mitophagy screening assay of GWAS candidates has functionally implicated the non-specific lethal (NSL) complex in the regulation of PINK1-mitophagy. Here, a bioinformatics approach has been taken to investigate the proteome of the NSL complex, to unpick its relevance to PD pathogenesis. The NSL interactome has been built, using 3 online tools: PINOT, HIPPIE and MIST, to mine curated, literature-derived protein-protein interaction (PPI) data. We built (i) the 'mitochondrial' NSL interactome exploring its relevance to PD genetics and (ii) the PD-oriented NSL interactome to uncover biological pathways underpinning the NSL/PD association. In this study, we find the mitochondrial NSL interactome to be significantly enriched for the protein products of PD-associated genes, including the Mendelian PD genes LRRK2 and VPS35. In addition, we find nuclear processes to be amongst those most significantly enriched within the PD-associated NSL interactome. These findings strengthen the role of the NSL complex in sporadic and familial PD, mediated by both its mitochondrial and nuclear functions.

PRKN/parkin-mediated mitophagy is induced by the probiotics Saccharomyces boulardii and Lactococcus lactis

Mitochondrial impairment is a hallmark feature of neurodegenerative disorders, such as Parkinson disease, and PRKN/parkin-mediated mitophagy serves to remove unhealthy mitochondria from cells. Notably, probiotics are used to alleviate several symptoms of Parkinson disease including impaired locomotion and neurodegeneration in preclinical studies and constipation in clinical trials. There is some evidence to suggest that probiotics can modulate mitochondrial quality control pathways. In this study, we screened 49 probiotic strains and tested distinct stages of mitophagy to determine whether probiotic treatment could upregulate mitophagy in cells undergoing mitochondrial stress. We found two probiotics, Saccharomyces boulardii and Lactococcus lactis, that upregulated mitochondrial PRKN recruitment, phospho-ubiquitination, and MFN degradation in our cellular assays. Administration of these strains to Drosophila that were exposed to paraquat, a mitochondrial toxin, resulted in improved longevity and motor function. Further, we directly observed increased lysosomal degradation of dysfunctional mitochondria in the treated Drosophila brains. These effects were replicated in vitro and in vivo with supra-physiological concentrations of exogenous soluble factors that are released by probiotics in cultures grown under laboratory conditions. We identified methyl-isoquinoline-6-carboxylate as one candidate molecule, which upregulates mitochondrial PRKN recruitment, phospho-ubiquitination, MFN degradation, and lysosomal degradation of damaged mitochondria. Addition of methyl-isoquinoline-6-carboxylate to the fly food restored motor function to paraquat-treated Drosophila. These data suggest a novel mechanism that is facilitated by probiotics to stimulate mitophagy through a PRKN-dependent pathway, which could explain the potential therapeutic benefit of probiotic administration to patients with Parkinson disease.

Eleven Crucial Pesticides Appear to Regulate Key Genes That Link MPTP Mechanism to Cause Parkinson's Disease through the Selective Degeneration of Dopamine Neurons

Pesticides kill neurons, but the mechanism leading to selective dopaminergic loss in Parkinson's disease (PD) is unknown. Understanding the pesticide's effect on dopaminergic neurons (DA) can help to screen and treat PD. The critical uptake of pesticides by the membrane receptors at DA is hypothesized to activate a signaling cascade and accelerate degeneration. Using MPTP as a reference, we demonstrate the mechanisms of eleven crucial pesticides through molecular docking, protein networks, regulatory pathways, and prioritization of key pesticide-regulating proteins. Participants were recruited and grouped into control and PD based on clinical characteristics as well as pesticide traces in their blood plasma. Then, qPCR was used to measure pesticide-associated gene expression in peripheral blood mononuclear cells between groups. As a result of molecular docking, all eleven pesticides and the MPTP showed high binding efficiency against 274 membrane receptor proteins of DA. Further, the protein interaction networks showed activation of multiple signaling cascades through these receptors. Subsequent analysis revealed 31 biological pathways shared by all 11pesticides and MPTP that were overrepresented by 46 crucial proteins. Among these, CTNNB1, NDUFS6, and CAV1 were prioritized to show a significant change in gene expression in pesticide-exposed PD which guides toward therapy.

Sex and Brain: The Role of Sex Chromosomes and Hormones in Brain Development and Parkinson's Disease

Sex hormones and genes on the sex chromosomes are not only key factors in the regulation of sexual differentiation and reproduction but they are also deeply involved in brain homeostasis. Their action is crucial for the development of the brain, which presents different characteristics depending on the sex of individuals. The role of these players in the brain is fundamental in the maintenance of brain function during adulthood as well, thus being important also with respect to age-related neurodegenerative diseases. In this review, we explore the role of biological sex in the development of the brain and analyze its impact on the predisposition toward and the progression of neurodegenerative diseases. In particular, we focus on Parkinson's disease, a neurodegenerative disorder that has a higher incidence in the male population. We report how sex hormones and genes encoded by the sex chromosomes could protect from the disease or alternatively predispose toward its development. We finally underline the importance of considering sex when studying brain physiology and pathology in cellular and animal models in order to better understand disease etiology and develop novel tailored therapeutic strategies.

The role of the microbiota-gut-brain axis and intestinal microbiome dysregulation in Parkinson's disease

Parkinson's disease (PD) is a complex progressive neurodegenerative disease associated with aging. Its main pathological feature is the degeneration and loss of dopaminergic neurons related to the misfolding and aggregation of α-synuclein. The pathogenesis of PD has not yet been fully elucidated, and its occurrence and development process are closely related to the microbiota-gut-brain axis. Dysregulation of intestinal microbiota may promote the damage of the intestinal epithelial barrier, intestinal inflammation, and the upward diffusion of phosphorylated α-synuclein from the enteric nervous system (ENS) to the brain in susceptible individuals and further lead to gastrointestinal dysfunction, neuroinflammation, and neurodegeneration of the central nervous system (CNS) through the disordered microbiota-gut-brain axis. The present review aimed to summarize recent advancements in studies focusing on the role of the microbiota-gut-brain axis in the pathogenesis of PD, especially the mechanism of intestinal microbiome dysregulation, intestinal inflammation, and gastrointestinal dysfunction in PD. Maintaining or restoring homeostasis in the gut microenvironment by targeting the gut microbiome may provide future direction for the development of new biomarkers for early diagnosis of PD and therapeutic strategies to slow disease progression.

An update on pathogenesis and clinical scenario for Parkinson's disease: diagnosis and treatment

In severe cases, Parkinson's disease causes uncontrolled movements known as motor symptoms such as dystonia, rigidity, bradykinesia, and tremors. Parkinson's disease also causes non-motor symptoms such as insomnia, constipation, depression and hysteria. Disruption of dopaminergic and non-dopaminergic neural networks in the substantia nigra pars compacta is a major cause of motor symptoms in Parkinson's disease. Furthermore, due to the difficulty of clinical diagnosis of Parkinson's disease, it is often misdiagnosed, highlighting the need for better methods of detection. Treatment of Parkinson's disease is also complicated due to the difficulties of medications passing across the blood-brain barrier. Moreover, the conventional methods fail to solve the aforementioned issues. As a result, new methods are needed to detect and treat Parkinson's disease. Improved diagnosis and treatment of Parkinson's disease can help avoid some of its devastating symptoms. This review explores how nanotechnology platforms, such as nanobiosensors and nanomedicine, have improved Parkinson's disease detection and treatment. Nanobiosensors integrate science and engineering principles to detect Parkinson's disease. The main advantages are their low cost, portability, and quick and precise analysis. Moreover, nanotechnology can transport medications in the form of nanoparticles across the blood-brain barrier. However, because nanobiosensors are a novel technology, their use in biological systems is limited. Nanobiosensors have the potential to disrupt cell metabolism and homeostasis, changing cellular molecular profiles and making it difficult to distinguish sensor-induced artifacts from fundamental biological phenomena. In the treatment of Parkinson's disease, nanoparticles, on the other hand, produce neurotoxicity, which is a challenge in the treatment of Parkinson's disease. Techniques must be developed to distinguish sensor-induced artifacts from fundamental biological phenomena and to reduce the neurotoxicity caused by nanoparticles.

A novel splicing variant of DJ-1 in Parkinson's disease induces mitochondrial dysfunction

Several studies have identified mutations in neuroprotective genes in a few cases of Parkinson's disease (PD); however, the role of alternative splicing changes in PD remains unelucidated. Based on the transcriptome analysis of substantia nigra (SN) tissues obtained from PD cases and age-matched healthy controls, we identified a novel alternative splicing variant of DJ-1, lacking exon 6 (DJ-1 ^ΔE6), frequently detected in the SN of patients with PD. We found that the exon 6 skipping of DJ-1 induces mitochondrial dysfunction and impaired antioxidant capability. According to an in silico modeling study, the exon 6 skipping of DJ-1 disrupts the structural state suitable for the oxidation of the cysteine 106 residue that is a prerequisite for activating its neuroprotective roles. Our results suggest that change in DJ-1 alternative splicing may contribute to PD progression and provide an insight for studying PD etiology and its potential therapeutic targets.

Role of α-synuclein in microglia: autophagy and phagocytosis balance neuroinflammation in Parkinson's disease

BACKGROUND

Parkinson's disease (PD) is the second most common neurodegenerative disease, and is characterized by accumulation of α-synuclein (α-syn). Neuroinflammation driven by microglia is an important pathological manifestation of PD. α-Syn is a crucial marker of PD, and its accumulation leads to microglia M1-like phenotype polarization, activation of NLRP3 inflammasomes, and impaired autophagy and phagocytosis in microglia. Autophagy of microglia is related to degradation of α-syn and NLRP3 inflammasome blockage to relieve neuroinflammation. Microglial autophagy and phagocytosis of released α-syn or fragments from apoptotic neurons maintain homeostasis in the brain. A variety of PD-related genes such as LRRK2, GBA and DJ-1 also contribute to this stability process.

OBJECTIVES

Further studies are needed to determine how α-syn works in microglia.

METHODS

A keyword-based search was performed using the PubMed database for published articles.

CONCLUSION

In this review, we discuss the interaction between microglia and α-syn in PD pathogenesis and the possible mechanism of microglial autophagy and phagocytosis in α-syn clearance and inhibition of neuroinflammation. This may provide a novel insight into treatment of PD.

Aggregation of Disordered Proteins Associated with Neurodegeneration

Cellular deposition of protein aggregates, one of the hallmarks of neurodegeneration, disrupts cellular functions and leads to neuronal death. Mutations, posttranslational modifications, and truncations are common molecular underpinnings in the formation of aberrant protein conformations that seed aggregation. The major proteins involved in neurodegeneration include amyloid beta (Aβ) and tau in Alzheimer's disease, α-synuclein in Parkinson's disease, and TAR DNA-binding protein (TDP-43) in amyotrophic lateral sclerosis (ALS). These proteins are described as intrinsically disordered and possess enhanced ability to partition into biomolecular condensates. In this review, we discuss the role of protein misfolding and aggregation in neurodegenerative diseases, specifically highlighting implications of changes to the primary/secondary (mutations, posttranslational modifications, and truncations) and the quaternary/supramolecular (oligomerization and condensation) structural landscapes for the four aforementioned proteins. Understanding these aggregation mechanisms provides insights into neurodegenerative diseases and their common underlying molecular pathology.

Dendrimers in Neurodegenerative Diseases

Neurodegenerative diseases (NDs), such as Parkinson’s Disease (PD), Alzheimer’s Disease (AD), Multiple Sclerosis (MS) and amyotrophic lateral sclerosis (ALS), are characterized by progressive loss of structure or function of neurons. Current therapies for NDs are only symptomatic and long-term ineffective. This challenge has promoted the development of new therapies against relevant targets in these pathologies. In this review, we will focus on the most promising therapeutic approaches based on dendrimers (DDs) specially designed for the treatment and diagnosis of NDs. DDs are well-defined polymeric structures that provide a multifunctional platform for developing different nanosystems for a myriad of applications. DDs have been proposed as interesting drug delivery systems with the ability to cross the blood–brain barrier (BBB) and increase the bioavailability of classical drugs in the brain, as well as genetic material, by reducing the synthesis of specific targets, as β-amyloid peptide. Moreover, DDs have been shown to be promising anti-amyloidogenic systems against amyloid-β peptide (Aβ) and Tau aggregation, powerful agents for blocking α-synuclein (α-syn) fibrillation, exhibit anti-inflammatory properties, promote cellular uptake to certain cell types, and are potential tools for ND diagnosis. In summary, DDs have emerged as promising alternatives to current ND therapies since they may limit the extent of damage and provide neuroprotection to the affected tissues.

Chaperone-Dependent Mechanisms as a Pharmacological Target for Neuroprotection

Modern pharmacotherapy of neurodegenerative diseases is predominantly symptomatic and does not allow vicious circles causing disease development to break. Protein misfolding is considered the most important pathogenetic factor of neurodegenerative diseases. Physiological mechanisms related to the function of chaperones, which contribute to the restoration of native conformation of functionally important proteins, evolved evolutionarily. These mechanisms can be considered promising for pharmacological regulation. Therefore, the aim of this review was to analyze the mechanisms of endoplasmic reticulum stress (ER stress) and unfolded protein response (UPR) in the pathogenesis of neurodegenerative diseases. Data on BiP and Sigma1R chaperones in clinical and experimental studies of Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and Huntington's disease are presented. The possibility of neuroprotective effect dependent on Sigma1R ligand activation in these diseases is also demonstrated. The interaction between Sigma1R and BiP-associated signaling in the neuroprotection is discussed. The performed analysis suggests the feasibility of pharmacological regulation of chaperone function, possibility of ligand activation of Sigma1R in order to achieve a neuroprotective effect, and the need for further studies of the conjugation of cellular mechanisms controlled by Sigma1R and BiP chaperones.

Cell Biology of Parkin: Clues to the Development of New Therapeutics for Parkinson's Disease

Parkinson's disease is the second most prevalent neurodegenerative disease and contributes significantly to morbidity globally. Currently, no disease-modifying therapies exist to combat this disorder. Insights from the molecular and cellular pathobiology of the disease seems to indicate promising therapeutic targets. The parkin protein has been extensively studied for its role in autosomal recessive Parkinson's disease and, more recently, its role in sporadic Parkinson's disease. Parkin is an E3 ubiquitin ligase that plays a prominent role in mitochondrial quality control, mitochondrial-dependent cell death pathways, and other diverse functions. Understanding the numerous roles of parkin has introduced many new possibilities for therapeutic modalities in treating both autosomal recessive Parkinson's disease and sporadic Parkinson's disease. In this article, we review parkin biology with an emphasis on mitochondrial-related functions and propose novel, potentially disease-modifying therapeutic approaches for treating this debilitating condition.

Human pericytes degrade diverse α-synuclein aggregates

Parkinson's disease (PD) is a progressive, neurodegenerative disorder characterised by the abnormal accumulation of α-synuclein (α-syn) aggregates. Central to disease progression is the gradual spread of pathological α-syn. α-syn aggregation is closely linked to progressive neuron loss. As such, clearance of α-syn aggregates may slow the progression of PD and lead to less severe symptoms. Evidence is increasing that non-neuronal cells play a role in PD and other synucleinopathies such as Lewy body dementia and multiple system atrophy. Our previous work has shown that pericytes-vascular mural cells that regulate the blood-brain barrier-contain α-syn aggregates in human PD brains. Here, we demonstrate that pericytes efficiently internalise fibrillar α-syn irrespective of being in a monoculture or mixed neuronal cell culture. Pericytes cleave fibrillar α-syn aggregates (Fibrils, Ribbons, fibrils65, fibrils91 and fibrils110), with cleaved α-syn remaining present for up to 21 days. The number of α-syn aggregates/cell and average aggregate size depends on the type of strain, but differences disappear within 5 five hours of treatment. Our results highlight the role brain vasculature may play in reducing α-syn aggregate burden in PD.

Druggable transcriptomic pathways revealed in Parkinson's patient-derived midbrain neurons

Complex genetic predispositions accelerate the chronic degeneration of midbrain substantia nigra neurons in Parkinson’s disease (PD). Deciphering the human molecular makeup of PD pathophysiology can guide the discovery of therapeutics to slow the disease progression. However, insights from human postmortem brain studies only portray the latter stages of PD, and there is a lack of data surrounding molecular events preceding the neuronal loss in patients. We address this gap by identifying the gene dysregulation of live midbrain neurons reprogrammed in vitro from the skin cells of 42 individuals, including sporadic and familial PD patients and matched healthy controls. To minimize bias resulting from neuronal reprogramming and RNA-seq methods, we developed an analysis pipeline integrating PD transcriptomes from different RNA-seq datasets (unsorted and sorted bulk vs. single-cell and Patch-seq) and reprogramming strategies (induced pluripotency vs. direct conversion). This PD cohort’s transcriptome is enriched for human genes associated with known clinical phenotypes of PD, regulation of locomotion, bradykinesia and rigidity. Dysregulated gene expression emerges strongest in pathways underlying synaptic transmission, metabolism, intracellular trafficking, neural morphogenesis and cellular stress/immune responses. We confirmed a synaptic impairment with patch-clamping and identified pesticides and endoplasmic reticulum stressors as the most significant gene-chemical interactions in PD. Subsequently, we associated the PD transcriptomic profile with candidate pharmaceuticals in a large database and a registry of current clinical trials. This study highlights human transcriptomic pathways that can be targeted therapeutically before the irreversible neuronal loss. Furthermore, it demonstrates the preclinical relevance of unbiased large transcriptomic assays of reprogrammed patient neurons.

Genetics in parkinson's disease: From better disease understanding to machine learning based precision medicine

Parkinson's Disease (PD) is a neurodegenerative disorder with highly heterogeneous phenotypes. Accordingly, it has been challenging to robustly identify genetic factors associated with disease risk, prognosis and therapy response via genome-wide association studies (GWAS). In this review we first provide an overview of existing statistical methods to detect associations between genetic variants and the disease phenotypes in existing PD GWAS. Secondly, we discuss the potential of machine learning approaches to better quantify disease phenotypes and to move beyond disease understanding towards a better-personalized treatment of the disease.

Molecular Pathways Involved in LRRK2-Linked Parkinson’s Disease: A Systematic Review

Parkinson’s disease is one of the most common neurodegenerative diseases affecting the ageing population, with a prevalence that has doubled over the last 30 years. As the mechanism of the disease is not fully elucidated, the current treatments are unable to effectively prevent neurodegeneration. Studies have found that mutations in Leucine-rich-repeat-kinase 2 (LRRK2) are the most common cause of familial Parkinson’s disease (PD). Moreover, aberrant (higher) LRRK2 kinase activity has an influence in idiopathic PD as well. Hence, the aim of this review is to categorize and synthesize current information related to LRRK2-linked PD and present the factors associated with LRRK2 that can be targeted therapeutically. A systematic review was conducted using the databases PubMed, Medline, SCOPUS, SAGE, and Cochrane (January 2016 to July 2021). Search terms included “Parkinson’s disease”, “mechanism”, “LRRK2”, and synonyms in various combinations. The search yielded a total of 988 abstracts for initial review, 80 of which met the inclusion criteria. Here, we emphasize molecular mechanisms revealed in recent in vivo and in vitro studies. By consolidating the recent updates in the field of LRRK2-linked PD, researchers can further evaluate targets for therapeutic application.

CRISPR and iPSCs: Recent Developments and Future Perspectives in Neurodegenerative Disease Modelling, Research, and Therapeutics

Neurodegenerative diseases are prominent causes of pain, suffering, and death worldwide. Traditional approaches modelling neurodegenerative diseases are deficient, and therefore, improved strategies that effectively recapitulate the pathophysiological conditions of neurodegenerative diseases are the need of the hour. The generation of human-induced pluripotent stem cells (iPSCs) has transformed our ability to model neurodegenerative diseases in vitro and provide an unlimited source of cells (including desired neuronal cell types) for cell replacement therapy. Recently, CRISPR/Cas9-based genome editing has also been gaining popularity because of the flexibility they provide to generate and ablate disease phenotypes. In addition, the recent advancements in CRISPR/Cas9 technology enables researchers to seamlessly target and introduce precise modifications in the genomic DNA of different human cell lines, including iPSCs. CRISPR-iPSC-based disease modelling, therefore, allows scientists to recapitulate the pathological aspects of most neurodegenerative processes and investigate the role of pathological gene variants in healthy non-patient cell lines. This review outlines how iPSCs, CRISPR/Cas9, and CRISPR-iPSC-based approaches accelerate research on neurodegenerative diseases and take us closer to a cure for neurodegenerative diseases such as Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, Amyotrophic Lateral Sclerosis, and so forth.

Chronic di(2-ethylhexyl) phthalate exposure leads to dopaminergic neuron degeneration through mitochondrial dysfunction in C. elegans

The plasticizer di(2-ethylhexyl) phthalate (DEHP) is frequently detected in the environment due to the abundance of its use. These levels might be hazardous to human health and ecosystems. Phthalates have been associated with neurological disorders, yet whether chronic DEHP exposure plays a role in Parkinson's disease (PD) or its underlying mechanisms is unknown. We investigated the effects of chronic DEHP exposure less than an environmentally-relevant dose on PD hallmarks, using Caenorhabditis elegans as a model. We show that developmental stage and exposure timing influence DEHP-induced dopaminergic neuron degeneration. In addition, in response to chronic DEHP exposure at 5 mg/L, mitochondrial fragmentation became significantly elevated, reactive oxygen species (ROS) levels increased, and ATP levels decreased, suggesting that mitochondrial dysfunction occurs. Furthermore, the data show that mitochondrial complex I (nuo-1 and gas-1) and complex II (mev-1) are involved in DEHP-induced dopaminergic neuron toxicity. These results suggest that chronic exposure to DEHP at levels less than an environmentally-relevant dose causes dopaminergic neuron degeneration through mitochondrial dysfunction involving mitochondrial complex I and II. Considering the high level of genetic conservation between C. elegans and mammals, chronic DEHP exposure might elevate the risk of developing PD in humans.

Reduced synaptic activity and dysregulated extracellular matrix pathways in midbrain neurons from Parkinson's disease patients

Several mutations that cause Parkinson's disease (PD) have been identified over the past decade. These account for 15-25% of PD cases; the rest of the cases are considered sporadic. Currently, it is accepted that PD is not a single monolithic disease but rather a constellation of diseases with some common phenotypes. While rodent models exist for some of the PD-causing mutations, research on the sporadic forms of PD is lagging due to a lack of cellular models. In our study, we differentiated PD patient-derived dopaminergic (DA) neurons from the induced pluripotent stem cells (iPSCs) of several PD-causing mutations as well as from sporadic PD patients. Strikingly, we observed a common neurophysiological phenotype: neurons derived from PD patients had a severe reduction in the rate of synaptic currents compared to those derived from healthy controls. While the relationship between mutations in genes such as the SNCA and LRRK2 and a reduction in synaptic transmission has been investigated before, here we show evidence that the pathogenesis of the synapses in neurons is a general phenotype in PD. Analysis of RNA sequencing results displayed changes in gene expression in different synaptic mechanisms as well as other affected pathways such as extracellular matrix-related pathways. Some of these dysregulated pathways are common to all PD patients (monogenic or idiopathic). Our data, therefore, show changes that are central and convergent to PD and suggest a strong involvement of the tetra-partite synapse in PD pathophysiology.