Triggers, Facilitators, and Aggravators: Redefining Parkinson's Disease Pathogenesis

Deep Brain Stimulation beyond the Clinic: Navigating the Future of Parkinson's and Alzheimer's Disease Therapy

Deep brain stimulation (DBS) is a surgical procedure that uses electrical neuromodulation to target specific regions of the brain, showing potential in the treatment of neurodegenerative disorders such as Parkinson's disease (PD) and Alzheimer's disease (AD). Despite similarities in disease pathology, DBS is currently only approved for use in PD patients, with limited literature on its effectiveness in AD. While DBS has shown promise in ameliorating brain circuits in PD, further research is needed to determine the optimal parameters for DBS and address any potential side effects. This review emphasizes the need for foundational and clinical research on DBS in different brain regions to treat AD and recommends the development of a classification system for adverse effects. Furthermore, this review suggests the use of either a low-frequency system (LFS) or high-frequency system (HFS) depending on the specific symptoms of the patient for both PD and AD.

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.

The Crucial Roles of Pitx3 in Midbrain Dopaminergic Neuron Development and Parkinson's Disease-Associated Neurodegeneration

The degeneration of midbrain dopaminergic (mDA) neurons, particularly in the substantia nigra pars compacta (SNc), is one of the most prominent pathological hallmarks of Parkinson's disease (PD). To uncover the pathogenic mechanisms of mDA neuronal death during PD may provide therapeutic targets to prevent mDA neuronal loss and slow down the disease's progression. Paired-like homeodomain transcription factor 3 (Pitx3) is selectively expressed in the mDA neurons as early as embryonic day 11.5 and plays a critical role in mDA neuron terminal differentiation and subset specification. Moreover, Pitx3-deficient mice exhibit some canonical PD-related features, including the profound loss of SNc mDA neurons, a dramatic decrease in striatal dopamine (DA) levels, and motor abnormalities. However, the precise role of Pitx3 in progressive PD and how this gene contributes to mDA neuronal specification during early stages remains unclear. In this review, we updated the latest findings on Pitx3 by summarizing the crosstalk between Pitx3 and its associated transcription factors in mDA neuron development. We further explored the potential benefits of Pitx3 as a therapeutic target for PD in the future. To better understand the transcriptional network of Pitx3 in mDA neuron development may provide insights into Pitx3-related clinical drug-targeting research and therapeutic approaches.

Urinary tract infections trigger synucleinopathy via the innate immune response

Symptoms in the urogenital organs are common in multiple system atrophy (MSA), also in the years preceding the MSA diagnosis. It is unknown how MSA is triggered and these observations in prodromal MSA led us to hypothesize that synucleinopathy could be triggered by infection of the genitourinary tract causing ɑ-synuclein (ɑSyn) to aggregate in peripheral nerves innervating these organs. As a first proof that peripheral infections could act as a trigger in MSA, this study focused on lower urinary tract infections (UTIs), given the relevance and high frequency of UTIs in prodromal MSA, although other types of infection might also be important triggers of MSA. We performed an epidemiological nested-case control study in the Danish population showing that UTIs are associated with future diagnosis of MSA several years after infection and that it impacts risk in both men and women. Bacterial infection of the urinary bladder triggers synucleinopathy in mice and we propose a novel role of ɑSyn in the innate immune system response to bacteria. Urinary tract infection with uropathogenic E. coli results in the de novo aggregation of ɑSyn during neutrophil infiltration. During the infection, ɑSyn is released extracellularly from neutrophils as part of their extracellular traps. Injection of MSA aggregates into the urinary bladder leads to motor deficits and propagation of ɑSyn pathology to the central nervous system in mice overexpressing oligodendroglial ɑSyn. Repeated UTIs lead to progressive development of synucleinopathy with oligodendroglial involvement in vivo. Our results link bacterial infections with synucleinopathy and show that a host response to environmental triggers can result in ɑSyn pathology that bears semblance to MSA.

LPS-induced mitochondrial dysfunction regulates innate immunity activation and α-synuclein oligomerization in Parkinson's disease

Sporadic Parkinson's disease (sPD) is a complex multifactorial disorder which etiology remains elusive. Several mechanisms have been described to contribute to PD development namely mitochondrial dysfunction, activation of inflammatory pathways and the deposition of unfolded proteins such as α-synuclein. Our work shows for the first time that lipopolysaccharide (LPS)-induced activation of innate immunity requires a functional mitochondria and mimics PD pathology in cells. We found in primary mesencephalic neurons that LPS targeted the mitochondria and activated neuronal innate immune responses, which culminated with α-synuclein oligomerization. Moreover, in cybrid cell lines repopulated with mtDNA from sPD subjects with inherent mitochondrial dysfunction and NT2-Rho0 obtained by long-term ethidium bromide exposure, and so without a functional mitochondrial, LPS was not able to further activate innate immunity or increase α-synuclein aggregation. Herein, we showed that mesencephalic neurons are able to activate innate immunity after LPS exposure and this pathway is dependent on mitochondria. Moreover, we disclose that α-synuclein over production is an innate immune response. Our data indicate that mitochondria provide the base for innate immunity activation in idiopathic PD.

Tumor necrosis factor α–induced protein 3 mediates inflammation and neuronal autophagy in Parkinson's disease via the NFκB and mTOR pathways

This study aimed to probe the function of tumor necrosis factor α-induced protein 3 (TNFAIP3) in the pathogenesis of Parkinson disease (PD) with its association with autophagy and inflammatory response. TNFAIP3 was reduced in the SN of PD patients (the GSE54282 dataset) and mice and in the MPP⁺-treated SK-N-SH cells. TNFAIP3 inhibited inflammatory response and enhanced autophagy, thereby alleviating PD in mice. NFκB and mTOR pathways were activated in the SN of PD mice and MPP⁺-treated cells. TNFAIP3 blocked the two pathways by preventing the p65 nuclear translocation and stabilizing DEPTOR, an endogenous inhibitor of mTOR. NFκB activator LPS and mTOR activator MHY1485 reversed the effects of TNFAIP3 on mitigation of injury in PD mice and in SK-N-SH cells induced with MPP⁺. Altogether, TNFAIP3 played a neuroprotective role in MPTP-induced mice by restricting NFκB and mTOR pathways.

Infectious Microorganisms Seen as Etiologic Agents in Parkinson’s Disease

Infections represent a possible risk factor for parkinsonism and Parkinson’s disease (PD) based on information from epidemiology and fundamental science. The risk is unclear for the majority of agents. Moreover, the latency between infection and PD seems to be very varied and often lengthy. In this review, the evidence supporting the potential involvement of infectious microorganisms in the development of Parkinson’s disease is examined. Consequently, it is crucial to determine the cause and give additional treatment accordingly. Infection is an intriguing suggestion regarding the cause of Parkinson’s disease. These findings demonstrate that persistent infection with viral and bacterial microorganisms might be a cause of Parkinson’s disease. As an initiating factor, infection may generate a spectrum of gut microbiota dysbiosis, engagement of glial tissues, neuroinflammation, and alpha-synuclein accumulation, all of which may trigger and worsen the onset in Parkinson’s disease also contribute to its progression. Still uncertain is the primary etiology of PD with infection. The possible pathophysiology of PD infection remains a matter of debate. Furthermore, additional study is required to determine if PD patients develop the disease due to infectious microorganisms or solely since they are more sensitive to infectious causes.

Modeling the enigma of complex disease etiology

BACKGROUND

Complex diseases often present as a diagnosis riddle, further complicated by the combination of multiple phenotypes and diseases as features of other diseases. With the aim of enhancing the determination of key etiological factors, we developed and tested a complex disease model that encompasses diverse factors that in combination result in complex diseases. This model was developed to address the challenges of classifying complex diseases given the evolving nature of understanding of disease and interaction and contributions of genetic, environmental, and social factors.

METHODS

Here we present a new approach for modeling complex diseases that integrates the multiple contributing genetic, epigenetic, environmental, host and social pathogenic effects causing disease. The model was developed to provide a guide for capturing diverse mechanisms of complex diseases. Assessment of disease drivers for asthma, diabetes and fetal alcohol syndrome tested the model.

RESULTS

We provide a detailed rationale for a model representing the classification of complex disease using three test conditions of asthma, diabetes and fetal alcohol syndrome. Model assessment resulted in the reassessment of the three complex disease classifications and identified driving factors, thus improving the model. The model is robust and flexible to capture new information as the understanding of complex disease improves.

CONCLUSIONS

The Human Disease Ontology's Complex Disease model offers a mechanism for defining more accurate disease classification as a tool for more precise clinical diagnosis. This broader representation of complex disease, therefore, has implications for clinicians and researchers who are tasked with creating evidence-based and consensus-based recommendations and for public health tracking of complex disease. The new model facilitates the comparison of etiological factors between complex, common and rare diseases and is available at the Human Disease Ontology website.

Disease mechanisms as subtypes: Immune dysfunction in Parkinson's disease

In recent years, the contraposition between inflammatory and neurodegenerative processes has been increasingly challenged. Inflammation has been emphasized as a key player in the onset and progression of Parkinson disease (PD) and other neurodegenerative disorders. The strongest indicators of the involvement of the immune system derived from evidence of microglial activation, profound imbalance in phenotype and composition of peripheral immune cells, and impaired humoral immune responses. Moreover, peripheral inflammatory mechanisms (e.g., involving the gut-brain axis) and immunogenetic factors are likely to be implicated. Even though several lines of preclinical and clinical studies are supporting and defining the complex relationship between the immune system and PD, the exact mechanisms are currently unknown. Similarly, the temporal and causal connections between innate and adaptive immune responses and neurodegeneration are unsettled, challenging our ambition to define an integrated and holistic model of the disease. Despite these difficulties, current evidence is providing the unique opportunity to develop immune-targeted approaches for PD, thus enriching our therapeutic armamentarium. This chapter aims to provide an extensive overview of past and present studies that explored the implication of the immune system in neurodegeneration, thus paving the road for the concept of disease modification in PD.

PET imaging in animal models of Parkinson's disease

Alpha-synucleinopathies, such as Parkinson's disease, dementia with Lewy bodies and multiple system atrophy, are characterized by aberrant accumulation of alpha-synuclein and synaptic dysfunction leading to motor and cognitive deficits. Animal models of alpha-synucleinopathy have greatly facilitated the mechanistic understanding of the disease and the development of therapeutics. Various transgenic, alpha-synuclein fibril-injected, and toxin-injected animal models of Parkinson's disease and multiple system atrophy that recapitulate the disease pathology have been developed and widely used. Recent advances in positron emission tomography have allowed the noninvasive visualization of molecular alterations, underpinning behavioral dysfunctions in the brains of animal models and the longitudinal monitoring of treatment effects. Imaging studies in these disease animal models have employed multi-tracer PET designs to reveal dopaminergic deficits together with other molecular alterations. This review focuses on the development of new positron emission tomography tracers and studies of alpha-synuclein, synaptic vesicle glycoprotein 2A neurotransmitter receptor deficits such as dopaminergic receptor, dopaminergic transporter, serotonergic receptor, vesicular monoamine transporter 2, hypometabolism, neuroinflammation, mitochondrial dysfunction and leucine rich repeat kinase 2 in animal models of Parkinson's disease. The outstanding challenges and emerging applications are outlined, such as investigating the gut-brain-axis by using positron emission tomography in animal models, and provide a future outlook.

Parallel Neurodegenerative Phenotypes in Sporadic Parkinson's Disease Fibroblasts and Midbrain Dopamine Neurons

Understanding the mechanisms causing Parkinson's disease (PD) is vital to the development of much needed early diagnostics and therapeutics for this debilitating condition. Here, we report cellular and molecular alterations in skin fibroblasts of late-onset sporadic PD subjects, that were recapitulated in matched induced pluripotent stem cell (iPSC)-derived midbrain dopamine (DA) neurons, reprogrammed from the same fibroblasts. Specific changes in growth, morphology, reactive oxygen species levels, mitochondrial function, and autophagy, were seen in both the PD fibroblasts and DA neurons, as compared to their respective controls. Additionally, significant alterations in alpha synuclein expression and electrical activity were also noted in the PD DA neurons. Interestingly, although the fibroblast and neuronal phenotypes were similar to each other, they also differed in their nature and scale. Furthermore, statistical analysis revealed novel associations between various clinical measures of the PD subjects and the different fibroblast and neuronal data. In essence, these findings encapsulate spontaneous, in-tandem, disease-related phenotypes in both sporadic PD fibroblasts and iPSC-based DA neurons, from the same patient, and generates an innovative model to investigate PD mechanisms with a view towards rational disease stratification and precision treatments.

Genome-wide association study using whole-genome sequencing identifies risk loci for Parkinson's disease in Chinese population

Genome-wide association studies (GWASs) have identified numerous susceptibility loci for Parkinson's disease (PD), but its genetic architecture remains underexplored in populations of non-European ancestry. To identify genetic variants associated with PD in the Chinese population, we performed a GWAS using whole-genome sequencing (WGS) in 1,972 cases and 2,478 controls, and a replication study in a total of 8209 cases and 9454 controls. We identified one new risk variant rs61204179 (Pcombined = 1.47 × 10-9) with low allele frequency, four previously reported risk variants (NUCKS1/RAB29-rs11557080, SNCA-rs356182, FYN-rs997368, and VPS13C-rs2251086), as well as three risk variants in LRRK2 coding region (A419V, R1628P, and G2385R) with genome-wide significance (P < 5 × 10-8) for PD in Chinese population. Moreover, of the reported genome-wide significant risk variants found mostly in European ancestry populations, the correlation coefficient (rb) of effect size accounting for sampling errors was 0.91 between datasets and 63.6% attained P < 0.05 in Chinese population. Accordingly, we estimated a heritability of 0.14-0.18 for PD, and a moderate genetic correlation between European ancestry and Chinese populations (rg = 0.47, se = 0.21). Polygenic risk score (PRS) analysis revealed that individuals with PRS values in the highest quartile had a 3.9-fold higher risk of developing PD than the lowest quartile. In conclusion, the present GWAS identified PD-associated variants in Chinese population, as well as genetic factors shared among distant populations. Our findings shed light on the genetic homogeneity and heterogeneity of PD in different ethnic groups and suggested WGS might continue to improve our understanding of the genetic architecture of PD.

Mitochondrial signalling and homeostasis: from cell biology to neurological disease

Efforts to understand how mitochondrial dysfunction contributes to neurodegeneration have primarily focussed on the role of mitochondria in neuronal energy metabolism. However, progress in understanding the etiological nature of emerging mitochondrial functions has yielded new ideas about the mitochondrial basis of neurological disease. Studies aimed at deciphering how mitochondria signal through interorganellar contacts, vesicular trafficking, and metabolic transmission have revealed that mitochondrial regulation of immunometabolism, cell death, organelle dynamics, and neuroimmune interplay are critical determinants of neural health. Moreover, the homeostatic mechanisms that exist to protect mitochondrial health through turnover via nanoscale proteostasis and lysosomal degradation have become integrated within mitochondrial signalling pathways to support metabolic plasticity and stress responses in the nervous system. This review highlights how these distinct mitochondrial pathways converge to influence neurological health and contribute to disease pathology.

Microbiome-gut-brain dysfunction in prodromal and symptomatic Lewy body diseases

Lewy body diseases, such as Parkinson's disease and dementia with Lewy bodies, vary in their clinical phenotype but exhibit the same defining pathological feature, α-synuclein aggregation. Microbiome-gut-brain dysfunction may play a role in the initiation or progression of disease processes, though there are multiple potential mechanisms. We discuss the need to evaluate gastrointestinal mechanisms of pathogenesis across Lewy body diseases, as disease mechanisms likely span across diagnostic categories and a 'body first' clinical syndrome may better account for the heterogeneity of clinical presentations across the disorders. We discuss two primary hypotheses that suggest that either α-synuclein aggregation occurs in the gut and spreads in a prion-like fashion to the brain or systemic inflammatory processes driven by gastrointestinal dysfunction contribute to the pathophysiology of Lewy body diseases. Both of these hypotheses posit that dysbiosis and intestinal permeability are key mechanisms and potential treatment targets. Ultimately, this work can identify early interventions targeting initial disease pathogenic processes before the development of overt motor and cognitive symptoms.

Host oligodendrogliopathy and α-synuclein strains dictate disease severity in multiple system atrophy

Multiple system atrophy is a progressive neurodegenerative disease with prominent autonomic and motor features. During early stages, different subtypes of the disease are distinguished by their predominant parkinsonian or cerebellar symptoms, reflecting its heterogeneous nature. The pathognomonic feature of multiple system atrophy is the presence of α-synuclein (αSyn) protein deposits in oligodendroglial cells. αSyn can assemble in specific cellular or disease environments and form αSyn strains with unique structural features, but the ability of αSyn strains to propagate in oligodendrocytes remains elusive. Recently, it was shown that αSyn strains with related conformations exist in the brains of patients. Here, we investigated whether different αSyn strains can influence multiple system atrophy progression in a strain-dependent manner. To this aim, we injected two recombinant αSyn strains (fibrils and ribbons) in multiple system atrophy transgenic mice and found that they determined disease severity in multiple system atrophy via host-restricted and cell-specific pathology in vivo. αSyn strains significantly impact disease progression in a strain-dependent way via oligodendroglial, neurotoxic and immune-related mechanisms. Neurodegeneration and brain atrophy were accompanied by unique microglial and astroglial responses and the recruitment of central and peripheral immune cells. The differential activation of microglial cells correlated with the structural features of αSyn strains both in vitro and in vivo. Spectral analysis showed that ribbons propagated oligodendroglial inclusions that were structurally distinct from those of fibrils, with resemblance to oligodendroglial inclusions, in the brains of patients with multiple system atrophy. This study, therefore, shows that the multiple system atrophy phenotype is governed by both the nature of the αSyn strain and the host environment and that by injecting αSyn strains into an animal model of the disease, a more comprehensive phenotype can be established.

⍺-Synuclein Structural Diversity and the Cellular Environment in ⍺-Synuclein Transmission Models and Humans

Parkinson's disease (PD), dementia with Lewy bodies (DLB), and multiple system atrophy (MSA) are termed synucleinopathies, disorders that are characterized by the intracellular aggregation of the protein ɑ-synuclein. The cellular tropism of synuclein pathology in these syndromes is notably distinct since in the Lewy disorders, PD and DLB, ɑSyn forms aggregates in neurons whereas in MSA ɑSyn forms aggregates in oligodendrocytes. Studies examining ɑSyn pathology in experimental models and in human brain have now identified fibrillar ɑSyn with unique but distinct molecular signatures, suggesting that the structure of these ɑSyn fibrils might be closely tied to their cellular ontogeny. In contrast to the native structural heterogeneity of ɑSyn in vitro, the conformational landscape of fibrillar ɑSyn in human brain and in vivo transmission models appears to be remarkably uniform. Here, we review the studies by which we propose a hypothesis that the cellular host environment might be in part responsible for how ɑSyn filaments assemble into phenotype-specific strains. We postulate that the maturation of ɑSyn strains develops as a function of their in vivo transmission routes and cell-specific risk factors. The impact of the cellular environment on the structural diversity of ɑSyn might have important implications for the design of preclinical studies and their use for the development of ɑSyn-based biomarkers and therapeutic strategies. By combining phenotype-specific fibrils and relevant synucleinopathy transmission models, preclinical models might more closely reflect unique disease phenotypes.

Parkinson's Disease: A Multisystem Disorder

The way sporadic Parkinson's disease (PD) is perceived has undergone drastic changes in recent decades. For a long time, PD was considered a brain disease characterized by motor disturbances; however, the identification of several risk factors and the hypothesis that PD has a gastrointestinal onset have shed additional light. Today, after recognition of prodromal non-motor symptoms and the pathological processes driving their evolution, there is a greater understanding of the involvement of other organ systems. For this reason, PD is increasingly seen as a multiorgan and multisystemic pathology that arises from the interaction of susceptible genetic factors with a challenging environment during aging-related decline.

Developmental pathways linked to the vulnerability of adult midbrain dopaminergic neurons to neurodegeneration

The degeneration of dopaminergic and other neurons in the aging brain is considered a process starting well beyond the infantile and juvenile period. In contrast to other dopamine-associated neuropsychiatric disorders, such as schizophrenia and drug addiction, typically diagnosed during adolescence or young adulthood and, thus, thought to be rooted in the developing brain, Parkinson's Disease (PD) is rarely viewed as such. However, evidences have accumulated suggesting that several factors might contribute to an increased vulnerability to death of the dopaminergic neurons at an already very early (developmental) phase in life. Despite the remarkable ability of the brain to compensate such dopamine deficits, the early loss or dysfunction of these neurons might predispose an individual to suffer from PD because the critical threshold of dopamine function will be reached much earlier in life, even if the time-course and strength of naturally occurring and age-dependent dopaminergic cell death is not markedly altered in this individual. Several signaling and transcriptional pathways required for the proper embryonic development of the midbrain dopaminergic neurons, which are the most affected in PD, either continue to be active in the adult mammalian midbrain or are reactivated at the transition to adulthood and under neurotoxic conditions. The persistent activity of these pathways often has neuroprotective functions in adult midbrain dopaminergic neurons, whereas the reactivation of silenced pathways under pathological conditions can promote the survival and even regeneration of these neurons in the lesioned or aging brain. This article summarizes our current knowledge about signaling and transcription factors involved in midbrain dopaminergic neuron development, whose reduced gene dosage or signaling activity are implicated in a lower survival rate of these neurons in the postnatal or aging brain. It also discusses the evidences supporting the neuroprotection of the midbrain dopaminergic system after the external supply or ectopic expression of some of these secreted and nuclear factors in the adult and aging brain. Altogether, the timely monitoring and/or correction of these signaling and transcriptional pathways might be a promising approach to a much earlier diagnosis and/or prevention of PD.

Hypoxic stress accelerates the propagation of pathological alpha-synuclein and degeneration of dopaminergic neurons

AIMS

The etiology of Parkinson's disease (PD) is complex and the mechanism is unclear. It has become a top priority to find common factors that induce and affect PD pathology. We explored the key role of hypoxia in promoting the pathological propagation of α-synuclein (α-syn) and the progression of PD.

METHODS

We performed PD modeling by conducting intracranial stereotaxic surgery in the unilateral striatum of mice. We then measured protein aggregation in vitro. The rotarod and pole tests were employed next to measure the damage of the phenotype. Pathological deposition and autophagy were also observed by immunofluorescence staining and protein levels measured by western blotting.

RESULTS

We demonstrated that short-term hypoxia activated phosphorylated (p)-α-syn in mice. We confirmed that p-α-syn was more readily formed aggregates than α-syn in vitro. Furthermore, we found that hypoxia promoted the activation and propagation of endogenous α-syn, contributing to the earlier degeneration of dopaminergic neurons in the substantia nigra and the deposition of p-α-syn in our animal model. Finally, autophagy inhibition contributed to the above pathologies.

CONCLUSION

Hypoxia was shown to accelerate the pathological progression and damage phenotype in PD model mice. The results provided a promising research target for determining common interventions for PD in the future.

Evaluation of Simvastatin as a Disease-Modifying Treatment for Patients With Parkinson Disease: A Randomized Clinical Trial

Importance

Current treatments manage symptoms of Parkinson disease (PD), but no known treatment slows disease progression. Preclinical and epidemiological studies support the potential use of statins as disease-modifying therapy.

Objective

To determine whether simvastatin has potential as a disease-modifying treatment for patients with moderate PD.

Design, Setting, and Participants

This randomized clinical trial, a double-blind, parallel-group, placebo-controlled futility trial, was conducted between March 2016 and May 2020 within 23 National Health Service Trusts in England. Participants aged 40 to 90 years with a diagnosis of idiopathic PD, with a modified Hoehn and Yahr stage of 3.0 or less while taking medication, and taking dopaminergic medication with wearing-off phenomenon were included. Data were analyzed from May 2020 to September 2020, with additional analysis in February 2021.

Interventions

Participants were allocated 1:1 to simvastatin or matched placebo via a computer-generated random sequence, stratified by site and Hoehn and Yahr stage. In the simvastatin arm, participants entered a 1-month phase of simvastatin, 40 mg daily, followed by 23 months of simvastatin, 80 mg daily, before a 2-month washout period.

Main Outcomes and Measures

The prespecified primary outcome was 24-month change in Movement Disorder Society Unified Parkinson Disease Rating Scale (MDS-UPDRS) part III score measured while not taking medication (high scores indicate worse outcome). The primary futility analysis included participants who commenced the 80-mg phase and had valid primary outcome data. The safety analysis included all participants who commenced trial treatment and is reported by dose at time of event.

Results

Of 332 patients assessed for eligibility, 32 declined and 65 were ineligible. Of 235 recruited participants, 97 (41%) were female, 233 (99%) were White, and the mean (SD) age was 65.4 (9.4) years. A total of 216 patients progressed to the 80-mg dose. Primary outcome analysis (n = 178) indicated the simvastatin group had an additional deterioration in MDS-UPDRS III score while not taking medication at 24 months compared with the placebo group (1.52 points; 2-sided 80% CI, -0.77 to 3.80; 1-sided futility test P = .006). A total of 37 serious adverse events (AEs), including 3 deaths, and 171 AEs were reported for participants receiving 0-mg simvastatin; 37 serious AEs and 150 AEs were reported for participants taking 40 mg or 80 mg of simvastatin. Four participants withdrew from the trial because of an AE.

Conclusions and Relevance

In this randomized clinical trial, simvastatin was futile as a disease-modifying therapy in patients with PD of moderate severity, providing no evidence to support proceeding to a phase 3 trial.

Trial Registration

ISRCTN Identifier: 16108482.

Blood-brain barrier (BBB)-on-a-chip: a promising breakthrough in brain disease research

The blood-brain barrier (BBB) represents a key challenge in developing brain-penetrating therapeutic molecules. BBB dysfunction is also associated with the onset and progression of various brain diseases. The BBB-on-a-chip (μBBB), an organ-on-chip technology, has emerged as a powerful in vitro platform that closely mimics the human BBB microenvironments. While the μBBB technology has seen wide application in the study of brain cancer, its utility in other brain disease models ("μBBB+") is less appreciated. Based on the advances of the μBBB technology and the evolution of in vitro models for brain diseases over the last decade, we propose the concept of a "μBBB+" system and summarize its major promising applications in pathological studies, personalized medical research, drug development, and multi-organ-on-chip approaches. We believe that such a sophisticated "μBBB+" system is a highly tunable and promising in vitro platform for further advancement of the understanding of brain diseases.

Inflammatory Animal Models of Parkinson’s Disease

Accumulating evidence suggests that microglia and peripheral immune cells may play determinant roles in the pathogenesis of Parkinson’s disease (PD). Consequently, there is a need to take advantage of immune-related models of PD to study the potential contribution of microglia and peripheral immune cells to the degeneration of the nigrostriatal system and help develop potential therapies for PD. In this review, we have summarised the main PD immune models. From a historical perspective, we highlight first the main features of intranigral injections of different pro-inflammogens, including lipopolysaccharide (LPS), thrombin, neuromelanin, etc. The use of adenoviral vectors to promote microglia-specific overexpression of different molecules in the ventral mesencephalon, including α-synuclein, IL-1β, and TNF, are also presented and briefly discussed. Finally, we summarise different models associated with peripheral inflammation whose contribution to the pathogenesis of neurodegenerative diseases is now an outstanding question. Illustrative examples included systemic LPS administration and dextran sulfate sodium-induced colitis in rodents.

Neuroprotective Function of Rasagiline and Selegiline, Inhibitors of Type B Monoamine Oxidase, and Role of Monoamine Oxidases in Synucleinopathies

Synucleinopathies are a group of neurodegenerative disorders caused by the accumulation of toxic species of α-synuclein. The common clinical features are chronic progressive decline of motor, cognitive, behavioral, and autonomic functions. They include Parkinson’s disease, dementia with Lewy body, and multiple system atrophy. Their etiology has not been clarified and multiple pathogenic factors include oxidative stress, mitochondrial dysfunction, impaired protein degradation systems, and neuroinflammation. Current available therapy cannot prevent progressive neurodegeneration and “disease-modifying or neuroprotective” therapy has been proposed. This paper presents the molecular mechanisms of neuroprotection by the inhibitors of type B monoamine oxidase, rasagiline and selegiline. They prevent mitochondrial apoptosis, induce anti-apoptotic Bcl-2 protein family, and pro-survival brain- and glial cell line-derived neurotrophic factors. They also prevent toxic oligomerization and aggregation of α-synuclein. Monoamine oxidase is involved in neurodegeneration and neuroprotection, independently of the catalytic activity. Type A monoamine oxidases mediates rasagiline-activated signaling pathways to induce neuroprotective genes in neuronal cells. Multi-targeting propargylamine derivatives have been developed for therapy in various neurodegenerative diseases. Preclinical studies have presented neuroprotection of rasagiline and selegiline, but beneficial effects have been scarcely presented. Strategy to improve clinical trials is discussed to achieve disease-modification in synucleinopathies.

Organ-On-A-Chip Models of the Blood-Brain Barrier: Recent Advances and Future Prospects

The human brain and central nervous system (CNS) present unique challenges in drug development for neurological diseases. One major obstacle is the blood-brain barrier (BBB), which hampers the effective delivery of therapeutic molecules into the brain while protecting it from blood-born neurotoxic substances and maintaining CNS homeostasis. For BBB research, traditional in vitro models rely upon Petri dishes or Transwell systems. However, these static models lack essential microenvironmental factors such as shear stress and proper cell-cell interactions. To this end, organ-on-a-chip (OoC) technology has emerged as a new in vitro modeling approach to better recapitulate the highly dynamic in vivo human brain microenvironment so-called the neural vascular unit (NVU). Such BBB-on-a-chip models have made substantial progress over the last decade, and concurrently there has been increasing interest in modeling various neurological diseases such as Alzheimer's disease and Parkinson's disease using OoC technology. In addition, with recent advances in other scientific technologies, several new opportunities to improve the BBB-on-a-chip platform via multidisciplinary approaches are available. In this review, an overview of the NVU and OoC technology is provided, recent progress and applications of BBB-on-a-chip for personalized medicine and drug discovery are discussed, and current challenges and future directions are delineated.

Gut-brain communication in COVID-19: molecular mechanisms, mediators, biomarkers, and therapeutics

INTRODUCTION

Infection with COVID-19 results in acute respiratory symptoms followed by long COVID multi-organ effects presenting with neurological, cardiovascular, musculoskeletal, and gastrointestinal (GI) manifestations. Temporal relationship between gastrointestinal and neurological symptoms is unclear but warranted for exploring better clinical care for COVID-19 patients.

AREAS COVERED

We critically reviewed the temporal relationship between gut-brain axis after SARS-CoV-2 infection and the molecular mechanisms involved in neuroinvasion following GI infection. Mediators are identified that could serve as biomarkers and therapeutic targets in SARS-CoV-2. We discussed the potential therapeutic approaches to mitigate the effects of GI infection with SARS-CoV-2.

EXPERT OPINION

Altered gut microbiota cause increased expression of various mediators, including zonulin causing disruption of tight junction. This stimulates enteric nervous system and signals to CNS precipitating neurological sequalae. Published reports suggest potential role of cytokines, immune cells, B(0)AT1 (SLC6A19), ACE2, TMRSS2, TMPRSS4, IFN-γ, IL-17A, zonulin, and altered gut microbiome in gut-brain axis and associated neurological sequalae. Targeting these mediators and gut microbiome to improve immunity will be of therapeutic significance. In-depth research and well-designed large-scale population-based clinical trials with multidisciplinary and collaborative approaches are warranted. Investigating the temporal relationship between organs involved in long-term sequalae is critical due to evolving variants of SARS-CoV-2.

A novel synthetic peptide SVHRSP attenuates dopaminergic neurodegeneration by inhibiting NADPH oxidase-mediated neuroinflammation in experimental models of Parkinson's disease

Current treatment of Parkinson's disease (PD) ameliorates symptoms but fails to block disease progression. This study was conducted to explore the protective effects of SVHRSP, a synthetic heat-resistant peptide derived from scorpion venom, against dopaminergic neurodegeneration in experimental models of PD. Results showed that SVHRSP dose-dependently reduced the loss of dopaminergic neuron in the nigrostriatal pathway and motor impairments in both rotenone and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine/probenecid (MPTP/p)-induced mouse PD models. Microglial activation and imbalance of M1/M2 polarization were also abrogated by SVHRSP in both models. In rotenone-treated primary midbrain neuron-glial cultures, loss of dopaminergic neuron and microglial activation were mitigated by SVHRSP. Furthermore, lipopolysaccharide (LPS)-elicited microglial activation, M1 polarization and related dopaminergic neurodegeneration in primary cultures were also abrogated by SVHRSP, suggesting that inhibition of microglial activation contributed to SVHRSP-afforded neuroprotection. Mechanistic studies revealed that SVHRSP blocked both LPS- and rotenone-induced microglial NADPH oxidase (NOX2) activation by preventing membrane translocation of cytosolic subunit p47phox. NOX2 knockdown by siRNA markedly attenuated the inhibitory effects of SVHRSP against LPS- and rotenone-induced gene expressions of proinflammatory factors and related neurotoxicity. Altogether, SVHRSP protects dopaminergic neurons by blocking NOX2-mediated microglial activation in experimental PD models, providing experimental basis for the screening of clinical therapeutic drugs for PD.

Establishing gene regulatory networks from Parkinson's disease risk loci

The latest meta-analysis of genome-wide association studies identified 90 independent variants across 78 genomic regions associated with Parkinson's disease, yet the mechanisms by which these variants influence the development of the disease remains largely elusive. To establish the functional gene regulatory networks associated with Parkinson's disease risk variants, we utilized an approach combining spatial (chromosomal conformation capture) and functional (expression quantitative trait loci) data. We identified 518 genes subject to regulation by 76 Parkinson's variants across 49 tissues, whicih encompass 36 peripheral and 13 CNS tissues. Notably, one-third of these genes were regulated via trans-acting mechanisms (distal; risk locus-gene separated by >1 Mb, or on different chromosomes). Of particular interest is the identification of a novel trans-expression quantitative trait loci-gene connection between rs10847864 and SYNJ1 in the adult brain cortex, highlighting a convergence between familial studies and Parkinson's disease genome-wide association studies loci for SYNJ1 (PARK20) for the first time. Furthermore, we identified 16 neurodevelopment-specific expression quantitative trait loci-gene regulatory connections within the foetal cortex, consistent with hypotheses suggesting a neurodevelopmental involvement in the pathogenesis of Parkinson's disease. Through utilizing Louvain clustering we extracted nine significant and highly intraconnected clusters within the entire gene regulatory network. The nine clusters are enriched for specific biological processes and pathways, some of which have not previously been associated with Parkinson's disease. Together, our results not only contribute to an overall understanding of the mechanisms and impact of specific combinations of Parkinson's disease variants, but also highlight the potential impact gene regulatory networks may have when elucidating aetiological subtypes of Parkinson's disease.

Neuronal ApoE Regulates the Cell-to-Cell Transmission of α-Synuclein

The presence of protein inclusions, called Lewy bodies (LBs) and Lewy neurites (LNs), in the brain is the main feature of Parkinson’s disease (PD). Recent evidence that the prion-like propagation of α-synuclein (α-syn), as a major component of LBs and LNs, plays an important role in the progression of PD has gained much attention, although the molecular mechanism remains unclear. In this study, we evaluated whether neuronal ApoE regulates the cell-to-cell transmission of α-syn and explored its molecular mechanism using in vitro and in vivo model systems. We demonstrate that neuronal ApoE deficiency attenuates both α-syn uptake and release by downregulating LRP-1 and LDLR expression and enhancing chaperone-mediated autophagy activity, respectively, thereby contributing to α-syn propagation. In addition, we observed that α-syn propagation was attenuated in ApoE knockout mice injected with pre-formed mouse α-syn fibrils. This study will help our understanding of the molecular mechanisms underlying α-syn propagation.

Convergence of signalling pathways in innate immune responses and genetic forms of Parkinson's disease

In recent years progress in molecular biology and genetics have advanced our understanding of neurological disorders and highlighted synergistic relationships with inflammatory and age-related processes. Parkinson's disease (PD) is a common neurodegenerative disorder that is characterized by loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc). Increasing extensive evidence supports the contribution of genetic risk variants and inflammation in the pathobiology of this disease. Functional and genetic studies demonstrate an overlap between genes linked to increased risk for PD and autoimmune diseases. Variants identified in loci adjacent to LRRK2, GBA, and HLA establish a crosstalk between the pathobiologies of the two disease spectra. Furthermore, common signalling pathways associated with the pathogenesis of genetic PD are also relevant to inflammatory signaling include MAPK, NF-κB, Wnt and inflammasome signaling. Importantly, post-mortem analyses of brain and cerebrospinal fluid from PD patients show the accumulation of proinflammatory cytokines. In this review we will focus on the principal mechanisms of genetic, inflammatory and age-related risk that intersect in the pathogenesis of PD.

LRRK2 and Proteostasis in Parkinson's Disease

Parkinson's disease is a neurodegenerative condition initially characterized by the presence of tremor, muscle stiffness and impaired balance, with the deposition of insoluble protein aggregates in Lewy's Bodies the histopathological hallmark of the disease. Although different gene variants are linked to Parkinson disease, mutations in the Leucine-Rich Repeat Kinase 2 (LRRK2) gene are one of the most frequent causes of Parkinson's disease related to genetic mutations. LRRK2 toxicity has been mainly explained by an increase in kinase activity, but alternative mechanisms have emerged as underlying causes for Parkinson's disease, such as the imbalance in LRRK2 homeostasis and the involvement of LRRK2 in aggregation and spreading of α-synuclein toxicity. In this review, we recapitulate the main LRRK2 pathological mutations that contribute to Parkinson's disease and the different cellular and therapeutic strategies devised to correct LRRK2 homeostasis. In this review, we describe the main cellular control mechanisms that regulate LRRK2 folding and aggregation, such as the chaperone network and the protein-clearing pathways such as the ubiquitin-proteasome system and the autophagic-lysosomal pathway. We will also address the more relevant strategies to modulate neurodegeneration in Parkinson's disease through the regulation of LRRK2, using small molecules or LRRK2 silencing.

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.

Redefining the hypotheses driving Parkinson's diseases research

Parkinson’s disease (PD) research has largely focused on the disease as a single entity centred on the development of neuronal pathology within the central nervous system. However, there is growing recognition that PD is not a single entity but instead reflects multiple diseases, in which different combinations of environmental, genetic and potential comorbid factors interact to direct individual disease trajectories. Moreover, an increasing body of recent research implicates peripheral tissues and non-neuronal cell types in the development of PD. These observations are consistent with the hypothesis that the initial causative changes for PD development need not occur in the central nervous system. Here, we discuss how the use of neuronal pathology as a shared, qualitative phenotype minimises insights into the possibility of multiple origins and aetiologies of PD. Furthermore, we discuss how considering PD as a single entity potentially impairs our understanding of the causative molecular mechanisms, approaches for patient stratification, identification of biomarkers, and the development of therapeutic approaches to PD. The clear consequence of there being distinct diseases that collectively form PD, is that there is no single biomarker or treatment for PD development or progression. We propose that diagnosis should shift away from the clinical definitions, towards biologically defined diseases that collectively form PD, to enable informative patient stratification. N-of-one type, clinical designs offer an unbiased, and agnostic approach to re-defining PD in terms of a group of many individual diseases.

Transcriptional analysis of peripheral memory T cells reveals Parkinson's disease-specific gene signatures

Parkinson's disease (PD) is a multi-stage neurodegenerative disorder with largely unknown etiology. Recent findings have identified PD-associated autoimmune features including roles for T cells. To further characterize the role of T cells in PD, we performed RNA sequencing on PBMC and peripheral CD4 and CD8 memory T cell subsets derived from PD patients and age-matched healthy controls. When the groups were stratified by their T cell responsiveness to alpha-synuclein (α-syn) as a proxy for an ongoing inflammatory autoimmune response, the study revealed a broad differential gene expression profile in memory T cell subsets and a specific PD associated gene signature. We identified significant enrichment of transcriptomic signatures previously associated with PD, including for oxidative stress, phosphorylation, autophagy of mitochondria, cholesterol metabolism and inflammation, and the chemokine signaling proteins CX3CR1, CCR5, and CCR1. In addition, we identified genes in these peripheral cells that have previously been shown to be involved in PD pathogenesis and expressed in neurons, such as LRRK2, LAMP3, and aquaporin. Together, these findings suggest that features of circulating T cells with α-syn-specific responses in PD patients provide insights into the interactive processes that occur during PD pathogenesis and suggest potential intervention targets.

Band S, Mosavi A. A Multi-Agent Formalism Based on Contextual Defeasible Logic for Healthcare Systems

In the last decade, smart computing has garnered much attention, particularly in ubiquitous environments, thus increasing the ease of everyday human life. Users can dynamically interact with the systems using different modalities in a smart computing environment. The literature discussed multiple mechanisms to enhance the modalities for communication using different knowledge sources. Among others, Multi-context System (MCS) has been proven quite significant to interlink various context domains dynamically to a distributed environment. MCS is a collection of different contexts (independent knowledge sources), and every context contains its own set of defined rules and facts and inference systems. These contexts are interlinked via bridge rules. However, the interaction among knowledge sources could have the consequences such as bringing out inconsistent results. These issues may report situations such as the system being unable to reach a conclusion or communication in different contexts becoming asynchronous. There is a need for a suitable framework to resolve inconsistencies. In this article, we provide a framework based on contextual defeasible reasoning and a formalism of multi-agent environment is to handle the issue of inconsistent information in MCS. Additionally, in this work, a prototypal simulation is designed using a simulation tool called NetLogo, and a formalism about a Parkinson's disease patient's case study is also developed. Both of these show the validity of the framework.

Research progress on the relationship between chronic periodontitis and Parkinson's disease

Chronic periodontitis is an infectious disease, which has a reciprocal relationship with a variety of systemic disorders. Parkinson's disease is a prevalent neurodegenerative disease in which inflammation plays an important role for its progression. A vast number of studies suggest that there is a potential connection between chronic periodontitis and neurodegenerative diseases such as Parkinson's disease. Individuals with Parkinson's disease usually have poor periodontal health, and their oral flora composition differs from that of healthy people; at the same time, patients with chronic periodontitis have a higher risk of Parkinson's disease, which can be reduced with regular periodontal treatment. In fact, the mechanism of interaction between chronic periodontitis and Parkinson's disease is not clear. According to several studies, the clinical symptoms of Parkinson's disease prevent patients to maintain oral hygiene effectively, increasing the risk of periodontitis. Neuroinflammation mediated by microglia may be the key to the influence of chronic periodontitis on Parkinson's disease. Periodontal pathogens and inflammatory mediators may enter the brain and activate microglia in various ways, and ultimately leading to occurrence and development of Parkinson's disease. This article reviews the recent research progress on the association between chronic periodontitis and Parkinson's disease, and its potential mechanism to provide information for further research.

Engineering of a protein probe with multiple inputs and multiple outputs for evaluation of alpha synuclein aggregation states

The aggregation of α-synuclein (αS) into oligomers and fibrils is implicated in the pathology of Parkinson's Disease (PD). While a molecular probe for rapid and comprehensive evaluation of αS aggregation states is critical for a better understanding of PD pathology, identification of therapeutic candidates, and the development of early diagnostic strategies, no such probe has yet to be developed. A structurally flexible αS variant, PG65, was previously developed as a target binding-driven, conformation-switching molecular probe for rapid αS oligomer detection. Though informative, detection using PG65 provides no comprehensive assessment of the αS aggregation states. In the present study, we report engineering of a molecular probe, PG65-MIMO (a PG65 variant with Multiple-Inputs and Multiple-Outputs), that rapidly (within 2 hr) produces comprehensive information on αS aggregation states. PG65-MIMO generates distinct fluorescence responses to the three major αS conformers (monomers, oligomers, and fibrils). PG65-MIMO also displays unique fluorescent signals for αS oligomers, depending on the tris(2-carboxyethyl)phosphine (TCEP) concentration. Our results suggest that the TCEP dependent signaling of PG65-MIMO may be associated with its conformational states. Overall, our study illustrates engineering of an αS variant to create a molecular probe for handling multiple inputs and multiple outputs, addressing the technological gap in αS detection.

Isoliquiritigenin attenuates neuroinflammation in mice model of Parkinson's disease by promoting Nrf2/NQO-1 pathway

Parkinson's disease (PD) is a common neurodegenerative disease that severely affects the quality of life of patients. There is no specific drug for PD up to now. Previous studies have shown that neuroinflammation plays an important role in the pathogenesis of PD. Isoliquiritigenin (ILG) is thought to have a variety of biological activities including anti-inflammatory. However, to date, no studies have reported the role of ILG on neuroinflammation in PD in vivo. This study aimed to investigate the effect of ILG on PD in vivo and its mechanism, and to provide an experimental basis for clinical treatment of PD. Our results showed that ILG at a concentration of 20 mg/kg was effective in reducing the number of rotations in PD mice. In addition, ILG increased the expression of tyrosine hydroxylase and decreased the expression of α-synuclein. The results also showed that ILG reduced the expression of Iba1, IL-1β, IL-6, and TNF-α. Not only that, ILG also upregulated the expression of Nrf2 and NQO-1 in vivo. Our results suggest that ILG significantly attenuates neurological deficits in PD, and the mechanism may be through the activation of the Nrf2/NQO-1 signaling pathway to reduce neuroinflammation. Moreover, our findings provide a new therapeutic strategy for PD.

Multi-omic landscaping of human midbrains identifies disease-relevant molecular targets and pathways in advanced-stage Parkinson's disease

BACKGROUND

Parkinson's disease (PD) is the second most common neurodegenerative disorder whose prevalence is rapidly increasing worldwide. The molecular mechanisms underpinning the pathophysiology of sporadic PD remain incompletely understood. Therefore, causative therapies are still elusive. To obtain a more integrative view of disease-mediated alterations, we investigated the molecular landscape of PD in human post-mortem midbrains, a region that is highly affected during the disease process.

METHODS

Tissue from 19 PD patients and 12 controls were obtained from the Parkinson's UK Brain Bank and subjected to multi-omic analyses: small and total RNA sequencing was performed on an Illumina's HiSeq4000, while proteomics experiments were performed in a hybrid triple quadrupole-time of flight mass spectrometer (TripleTOF5600+) following quantitative sequential window acquisition of all theoretical mass spectra. Differential expression analyses were performed with customized frameworks based on DESeq2 (for RNA sequencing) and with Perseus v.1.5.6.0 (for proteomics). Custom pipelines in R were used for integrative studies.

RESULTS

Our analyses revealed multiple deregulated molecular targets linked to known disease mechanisms in PD as well as to novel processes. We have identified and experimentally validated (quantitative real-time polymerase chain reaction/western blotting) several PD-deregulated molecular candidates, including miR-539-3p, miR-376a-5p, miR-218-5p and miR-369-3p, the valid miRNA-mRNA interacting pairs miR-218-5p/RAB6C and miR-369-3p/GTF2H3, as well as multiple proteins, such as CHI3L1, HSPA1B, FNIP2 and TH. Vertical integration of multi-omic analyses allowed validating disease-mediated alterations across different molecular layers. Next to the identification of individual molecular targets in all explored omics layers, functional annotation of differentially expressed molecules showed an enrichment of pathways related to neuroinflammation, mitochondrial dysfunction and defects in synaptic function.

CONCLUSIONS

This comprehensive assessment of PD-affected and control human midbrains revealed multiple molecular targets and networks that are relevant to the disease mechanism of advanced PD. The integrative analyses of multiple omics layers underscore the importance of neuroinflammation, immune response activation, mitochondrial and synaptic dysfunction as putative therapeutic targets for advanced PD.

c-Abl phosphorylation primes PARIS for neurodegeneration

This scientific commentary refers to ‘Parkin interacting substrate phosphorylation by c-Abl drives dopaminergic neurodegeneration’ by Kim et al. (doi:10.1093/brain/awab356).

Systematic Review on Parkinson's Disease Medications, Emphasizing on Three Recently Approved Drugs to Control Parkinson's Symptoms

Parkinson's Disease (PD) is a disease that involves neurodegeneration and is characterised by the motor symptoms which include muscle rigidity, tremor, and bradykinesia. Other non-motor symptoms include pain, depression, anxiety, and psychosis. This disease affects up to ten million people worldwide. The pathophysiology behind PD is due to the neurodegeneration of the nigrostriatal pathway. There are many conventional drugs used in the treatment of PD. However, there are limitations associated with conventional drugs. For instance, levodopa is associated with the on-off phenomenon, and it may induce wearing off as time progresses. Therefore, this review aimed to analyze the newly approved drugs by the United States-Food and Drug Administration (US-FDA) from 2016-2019 as the adjuvant therapy for the treatment of PD symptoms in terms of efficacy and safety. The new drugs include safinamide, istradefylline and pimavanserin. From this review, safinamide is considered to be more efficacious and safer as the adjunct therapy to levodopa as compared to istradefylline in controlling the motor symptoms. In Study 016, both safinamide 50 mg (p = 0.0138) and 100 mg (p = 0.0006) have improved the Unified Parkinson's Disease Rating Scale (UPDRS) part III score as compared to placebo. Improvement in Clinical Global Impression-Change (CGI-C), Clinical Global Impression-Severity of Illness (CGI-S) and off time were also seen in both groups of patients following the morning levodopa dose. Pimavanserin also showed favorable effects in ameliorating the symptoms of Parkinson's Disease Psychosis (PDP). A combination of conventional therapy and non-pharmacological treatment is warranted to enhance the well-being of PD patients.

Disease Duration Influences Gene Expression in Neuromelanin-Positive Cells From Parkinson's Disease Patients

Analyses of gene expression in cells affected by neurodegenerative disease can provide important insights into disease mechanisms and relevant stress response pathways. Major symptoms in Parkinson’s disease (PD) are caused by the degeneration of midbrain dopamine (mDA) neurons within the substantia nigra. Here we isolated neuromelanin-positive dopamine neurons by laser capture microdissection from post-mortem human substantia nigra samples recovered at both early and advanced stages of PD. Neuromelanin-positive cells were also isolated from individuals with incidental Lewy body disease (ILBD) and from aged-matched controls. Isolated mDA neurons were subjected to genome-wide gene expression analysis by mRNA sequencing. The analysis identified hundreds of dysregulated genes in PD. Results showed that mostly non-overlapping genes were differentially expressed in ILBD, subjects who were early after diagnosis (less than five years) and those autopsied at more advanced stages of disease (over five years since diagnosis). The identity of differentially expressed genes suggested that more resilient, stably surviving DA neurons were enriched in samples from advanced stages of disease, either as a consequence of positive selection of a less vulnerable long-term surviving mDA neuron subtype or due to up-regulation of neuroprotective gene products.

Emerging roles of ATG7 in human health and disease

The cardinal stages of macroautophagy are driven by core autophagy-related (ATG) proteins, whose ablation largely abolishes intracellular turnover. Disrupting ATG genes is paradigmatic of studying autophagy deficiency, yet emerging data suggest that ATG proteins have extensive biological importance beyond autophagic elimination. An important example is ATG7, an essential autophagy effector enzyme that in concert with other ATG proteins, also regulates immunity, cell death and protein secretion, and independently regulates the cell cycle and apoptosis. Recently, a direct association between ATG7 dysfunction and disease was established in patients with biallelic ATG7 variants and childhood-onset neuropathology. Moreover, a prodigious body of evidence supports a role for ATG7 in protecting against complex disease states in model organisms, although how dysfunctional ATG7 contributes to manifestation of these diseases, including cancer, neurodegeneration and infection, in humans remains unclear. Here, we systematically review the biological functions of ATG7, discussing the impact of its impairment on signalling pathways and human pathology. Future studies illuminating the molecular relationship between ATG7 dysfunction and disease will expedite therapies for disorders involving ATG7 deficiency and/or impaired autophagy.

Integrated multi-omics approach identified molecular mechanism and pathogenetic processes of COVID-19 that affect patient with Parkinson's disorder

The novel coronavirus named SARS-CoV-2 has emerged at the end of 2019, which causes coronavirus disease (COVID-2019). Recent case reports of COVID-19 patients have revealed the onset of Parkinson's disease (PD) symptoms in patients who do not have a family history of the PD. However, till recently, no genetic impact or mechanisms that may induce Parkinsonism in COVID-19 patients or after COVID-19 have been found.. This study aimed to detect the commonly dysregulated genes, transcriptional regulators, and pathways between PD and COVID-19. We integrated genome-wide transcriptomic datasets from peripheral blood mononuclear cells (PBMC) samples from COVID-19 and PD and associated pathways. Our study revealed 81 upregulated and 48 downregulated differentially expressed genes (DEGs) shared between PD and COVID-19. These dysregulated genes were involved in key pathways "mitochondrion structure organization", "cell activation in immune response", and "signalling by interleukins". Our analysis showed RELA, TP53 and SP1 TFs that may regulate the upregulated DEGs. We have discovered key dysregulated genes and characterized the biological processes of commonly dysregulated in COVID-19 and PD, which could be used for the design of personalized treatment of PD following COVID-19.

Common Inflammatory Mechanisms in COVID-19 and Parkinson's Diseases: The Role of Microbiome, Pharmabiotics and Postbiotics in Their Prevention

In the last decade, metagenomic studies have shown the key role of the gut microbiome in maintaining immune and neuroendocrine systems. Malfunction of the gut microbiome can induce inflammatory processes, oxidative stress, and cytokine storm. Dysfunction of the gut microbiome can be caused by short-term (virus infection and other infectious diseases) or long-term (environment, nutrition, and stress) factors. Here, we reviewed the inflammation and oxidative stress in neurodegenerative diseases and coronavirus infection (COVID-19). Here, we reviewed the renin-angiotensin-aldosterone system (RAAS) involved in the processes of formation of oxidative stress and inflammation in viral and neurodegenerative diseases. Moreover, the coronavirus uses ACE2 receptors of the RAAS to penetrate human cells. The coronavirus infection can be the trigger for neurodegenerative diseases by dysfunction of the RAAS. Pharmabiotics, postbiotics, and next-generation probiotics, are considered as a means to prevent oxidative stress, inflammatory processes, neurodegenerative and viral diseases through gut microbiome regulation.

Gastrointestinal mucosal biopsies in Parkinson's disease: beyond alpha-synuclein detection

Alpha-synuclein deposits, the pathological hallmarks of Parkinson's disease, are consistently found in the gastrointestinal tract of parkinsonian subjects. These observations have raised the potential that endoscopically obtainable mucosal biopsies can aid to a molecular diagnosis of the disease. The possible usefulness of mucosal biopsies is, however, not limited to the detection of alpha-synuclein, but also extends to other essential aspects underlying pathophysiological mechanisms of gastrointestinal manifestations in Parkinson's disease. The aim of the current review is to provide an appraisal of the existing studies showing that gastrointestinal biopsies can be used for the analysis of enteric neuronal and glial cell morphology, intestinal epithelial barrier function, and gastrointestinal inflammation in Parkinson's disease. A perspective on the generation of organoids with GI biopsies and the potential use of single-cell and spatial transcriptomic technologies will be also addressed.

TLR2 and TLR4 in Parkinson's disease pathogenesis: the environment takes a toll on the gut

Parkinson's disease (PD) is an incurable, devastating disorder that is characterized by pathological protein aggregation and neurodegeneration in the substantia nigra. In recent years, growing evidence has implicated the gut environment and the gut-brain axis in the pathogenesis and progression of PD, especially in a subset of people who exhibit prodromal gastrointestinal dysfunction. Specifically, perturbations of gut homeostasis are hypothesized to contribute to α-synuclein aggregation in enteric neurons, which may spread to the brain over decades and eventually result in the characteristic central nervous system manifestations of PD, including neurodegeneration and motor impairments. However, the mechanisms linking gut disturbances and α-synuclein aggregation are still unclear. A plethora of research indicates that toll-like receptors (TLRs), especially TLR2 and TLR4, are critical mediators of gut homeostasis. Alongside their established role in innate immunity throughout the body, studies are increasingly demonstrating that TLR2 and TLR4 signalling shapes the development and function of the gut and the enteric nervous system. Notably, TLR2 and TLR4 are dysregulated in patients with PD, and may thus be central to early gut dysfunction in PD. To better understand the putative contribution of intestinal TLR2 and TLR4 dysfunction to early α-synuclein aggregation and PD, we critically discuss the role of TLR2 and TLR4 in normal gut function as well as evidence for altered TLR2 and TLR4 signalling in PD, by reviewing clinical, animal model and in vitro research. Growing evidence on the immunological aetiology of α-synuclein aggregation is also discussed, with a focus on the interactions of α-synuclein with TLR2 and TLR4. We propose a conceptual model of PD pathogenesis in which microbial dysbiosis alters the permeability of the intestinal barrier as well as TLR2 and TLR4 signalling, ultimately leading to a positive feedback loop of chronic gut dysfunction promoting α-synuclein aggregation in enteric and vagal neurons. In turn, α-synuclein aggregates may then migrate to the brain via peripheral nerves, such as the vagal nerve, to contribute to neuroinflammation and neurodegeneration typically associated with PD.