Non-Motor Symptoms of Parkinson's Disease: The Neurobiology of Early Psychiatric and Cognitive Dysfunction

The Prevalence of Depressive Symptoms in Patients with Idiopathic Parkinson's Disease: Cross-Sectional Study from Somalia

Introduction

Depression is one of the most common non-motor symptom of Parkinson's disease (PD), with an increasing prevalence in recent years. It causes significant psychological consequences that affect the disease course, overall quality of life, and functioning. The objective of this study was to determine the prevalence of depression in outpatients with Parkinson's disease evaluated in the neurology clinic at tertiary hospital in Mogadishu, Somalia.

Methods

A cross-sectional study was conducted among 50 PD patients without dementia to determine the prevalence of depression at the neurology clinic of the Mogadishu Somalia Türkiye Training and Research Hospital between February and November 2022. All eligible participants were interviewed by a team of doctors using a structured questionnaire that consisted of sociodemographics and clinical characteristics, the Beck Depression Inventory-II (BDI-II) for depression assessment, and the Modified Hoehn and Yahr Scale for PD staging.

Results

Of the 50 PD participants, 60% were male and 58% were older than 60 years. 20% of them had a family history of PD and HTN as comorbid conditions. The prevalence of depression among the participants was 46% (95% CI 31.8-60.7). Of the patients with depression, 22% and 24% had mild and moderate depressive symptoms, respectively. The Mann-Whitney U-test revealed a statistically significant association between depression symptoms and the presence of comorbidity (χ2 = 136.50, p<0.01). The Kruskal-Wallis test revealed a statistically significant association between depression symptoms and a longer duration of PD (χ2 (2) = 18.21, p<0.01) and advanced stages of PD (χ2 (2) = 13.74, p<0.01).

Conclusion

This is the first study conducted on patients with PD in Somalia and found that a significant proportion of these patients experienced depressive symptoms. We also highlighted that factors such the presence of medical comorbidities, high monthly income, advanced PD stage, longer duration of PD, and use of multiple medications for PD were significantly associated with the presence of depressive symptoms.

Microstructural correlates of olfactory dysfunction in Parkinson's Disease: a systematic review of diffusion MRI studies

Olfactory dysfunction (OD) is a non-motor symptom of Parkinson's Disease, affecting 75-95% of the patients. This symptom usually emerges before the clinical diagnosis, and patients with OD present with more severe forms of PD and need higher doses of therapy. It remains unknown whether OD is just a mere non-motor symptom or if it is a part of a series of pathological changes in different brain regions of the affected patients. We performed a systematic review to find the microstructural correlates of OD in people with PD. The systematic search in PubMed, Scopus, Embase, and Web of Science yielded ten eligible studies. Assessments in most included studies were inconclusive. However, we found variable brain regions and tracts associated with OD. The most repeated areas included the primary olfactory cortex, gyrus rectus, inferior fronto-occipital fasciculus, inferior longitudinal fasciculus, corticospinal tract, uncinate fasciculus, cingulum, and cerebellar peduncle. Despite some limitations, we pointed out the microstructural correlates of OD, which were also present in areas other than the olfactory system. These findings imply that OD might be a manifestation of an unknown, greater pathology in the brain of patients with PD.

Astrocytic LRRK2 Controls Synaptic Connectivity via Regulation of ERM Phosphorylation

Astrocytes, a major glial cell type of the brain, regulate synapse numbers and function. However, whether astrocyte dysfunction can cause synaptic pathologies in neurological disorders such as Parkinson's Disease (PD) is unknown. Here, we investigated the impact of the most common PD-linked mutation in the leucine-rich repeat kinase 2 (LRRK2) gene (G2019S) on the synaptic functions of astrocytes. We found that both in human and mouse cortex, the LRRK2 G2019S mutation causes astrocyte morphology deficits and enhances the phosphorylation of the ERM proteins (Ezrin, Radixin, and Moesin), which are important components of perisynaptic astrocyte processes. Reducing ERM phosphorylation in LRRK2 G2019S mouse astrocytes restored astrocyte morphology and corrected excitatory synaptic deficits. Using an in vivo BioID proteomic approach, we found Ezrin, the most abundant astrocytic ERM protein, interacts with the Autophagy-Related 7 (Atg7), a master regulator of catabolic processes. The Ezrin/Atg7 interaction is inhibited by Ezrin phosphorylation, thus diminished in the LRRK2 G2019S astrocytes. Importantly, Atg7 function is required to maintain proper astrocyte morphology. These studies reveal an astrocytic molecular mechanism that could serve as a therapeutic target in PD.

Palmatine Ameliorates Motor Deficits and Dopaminergic Neuron Loss by Regulating NLRP3 Inflammasome through Mitophagy in Parkinson's Disease Model Mice

NLRP3 inflammasomes-mediated proinflammatory response and mitochondrial dysfunction play a critical role in the etiology and pathogenesis of Parkinson's disease. Negative regulation of NLRP3 inflammasome activation through mitophagy may be an important strategy to control NLRP3 inflammasome-mediated proinflammatory responses. Palmatine (PAL), an isoquinoline alkaloid found in various of plants, has potent pharmacological effects such as anti-inflammatory and anti-oxidation. However, the specific role of PAL in the pathology of Parkinson's disease remains unclear. In this study, we found that treatment with PAL improved motor deficits and reduced the loss of dopaminergic neurons in MPTP mice. Further results showed that PAL promoted mitophagy and inhibited the proinflammatory response mediated by NLRP3 inflammasomes. In addition, chloroquine (CQ, mitophagy inhibitor) attenuated the ameliorative effects of PAL on the motor deficits and dopaminergic neuron damage, as well as the inhibitory effect of PAL on NLRP3 inflammasome. Collectively, these results provide strong evidence that PAL ameliorates motor deficits and dopaminergic neuron death in Parkinson's disease, and the mechanism may be related to its inhibition of NLRP3 inflammasome activation via promoting mitophagy.

Protopanaxadiols Eliminate Behavioral Impairments and Mitochondrial Dysfunction in Parkinson's Disease Mice Model

Currently, there are no effective therapies to cure Parkinson's disease (PD), which is the second most common neurodegenerative disease primarily characterized by motor dysfunction and degeneration of dopaminergic neurons in the substantia nigra pars compacta (SNc). Protopanaxadiols (PPDs), including 20 (R)- protopanaxadiol (R-PPD) and 20 (S)- protopanaxadiol (S-PPD), are main metabolites of ginsenosides. The role of ginsenosides in neurodegenerative diseases has been thoroughly studied, however, it is unknown whether PPDs can attenuate behavioral deficits and dopaminergic neuron injury in PD model mice to date. Here, we administered PPDs to MPTP-induced PD model mice and monitored the effects on behavior and dopaminergic neurons to investigate the effects of R-PPD and S-PPD against PD. Our results showed that R-PPD and S-PPD (at a dose of 20 mg/kg, i.g.) treatment alleviated MPTP (30 mg/kg, i.p.) induced behavioral deficits. Besides, R-PPD and S-PPD protected MPP+-induced neuron injury and mitochondrial dysfunction, and reduced the abnormal expression of Cyt C, Bax, caspase-3 and Bcl-2. These findings demonstrate that R-PPD and S-PPD were potentially useful to ameliorate PD.

The VEGFs/VEGFRs system in Alzheimer's and Parkinson's diseases: Pathophysiological roles and therapeutic implications

The vascular endothelial growth factors (VEGFs) and their cognate receptors (VEGFRs), besides their well-known involvement in physiological angiogenesis/lymphangiogenesis and in diseases associated to pathological vessel formation, play multifaceted functions in the central nervous system (CNS). In addition to shaping brain development, by controlling cerebral vasculogenesis and regulating neurogenesis as well as astrocyte differentiation, the VEGFs/VEGFRs axis exerts essential functions in the adult brain both in physiological and pathological contexts. In this article, after describing the physiological VEGFs/VEGFRs functions in the CNS, we focus on the VEGFs/VEGFRs involvement in neurodegenerative diseases by reviewing the current literature on the rather complex VEGFs/VEGFRs contribution to the pathogenic mechanisms of Alzheimer's (AD) and Parkinson's (PD) diseases. Thereafter, based on the outcome of VEGFs/VEGFRs targeting in animal models of AD and PD, we discuss the factual relevance of pharmacological VEGFs/VEGFRs modulation as a novel and potential disease-modifying approach for these neurodegenerative pathologies. Specific VEGFRs targeting, aimed at selective VEGFR-1 inhibition, while preserving VEGFR-2 signal transduction, appears as a promising strategy to hit the molecular mechanisms underlying AD pathology. Moreover, therapeutic VEGFs-based approaches can be proposed for PD treatment, with the aim of fine-tuning their brain levels to amplify neurotrophic/neuroprotective effects while limiting an excessive impact on vascular permeability.

Cerium oxide nanoparticles modulating the Parkinson's disease conditions: From the alpha synuclein structural point of view and antioxidant properties of cerium oxide nanoparticles

Parkinson's and Alzheimer's disease is the main cause of dementia, which is associated with the progressive deterioration of the intelligence and senses. Free radicals are created during oxidative stress in cells, which are considered one of the destructive factors in neurodegenerative diseases. In this study, the antifibrillar and antioxidant properties of cerium oxide nanoparticles (CeO2 NPs) were investigated experimentally and theoretically. The CeO2 NPs were synthesized and analyzed to reveal the physicochemical and biological properties. The results showed that the CeO2 NPs have unique properties with potent antioxidant activities. The experimental and computational studies showed that the CeO2 NPs interact with the active site of Alpha-synuclein. The existence of hydrogen bonding between O atoms of CeO2 NPs and N-H of adjacent acid amines and the equilibrium distances were confirmed by 1.751 (Leu100), 1.786 (Gln99) and 2.213 Å (Lys97). The minimum free energy binding of L-DOPA drug (as positive control) and CeO2 NPs were negative, resulting interaction between compounds and protein. As a result, these compounds inhibited Alpha-synuclein protein aggregation. In addition, that CeO2 NPs strongly binds with receptor by relative binding energy as compared with L-DOPA drug. These findings revealed that CeO2 NPs prevent Alpha-synuclein fibrillation and can be applied as nano-drug against the Parkinson's disease.

Decreased muscle strength in adjuvant-induced rheumatoid arthritis animal model: A relationship to behavioural assessments

Rheumatoid arthritis (RA) is an autoimmune disorder with unknown aetiology. Patients suffering from RA face persistent pain due to joint inflammation, and tissue destruction. Behavioural phenotyping is an approach to target the role of different behavioural traits associated with disease progression. The study aimed to assess behavioural patterns associated with decreased muscle strength in the adjuvant-induced rheumatoid arthritis animal model. The study was conducted on male Albino Wister rats (n = 30) [Control, Vehicle, and Disease groups]. After taking ethical approvals RA was induced by complete Freund's adjuvant (CFA) intradermally base of tail. The weight of animals, macroscopic analysis of inflammatory signs, and arthritic scores were measured weekly. Grip strength, ganglia-based movement, cataleptic activity, and motor-coordination-related behaviours were assessed among the groups. Radiographs and spleen index assay were performed followed by data analysis using one-way and two-way ANOVA (Analysis of Variance). A significant decrease in weight and an increase in arthritic scores among the diseased group was observed. Behavioural analyses confirmed that diseased animals had significantly decreased grip strength and increased cataleptic activity with less motor coordination. Radiographic images and spleen index assay confirmed the pattern of RA. Therefore, it can be suggested that the development of the disease animal model is an effective approach to identifying the disease progression and associated behavioural changes. Moreover, this prepared laboratory animal model may be utilised for pathway analyses to understand the key role of immune regulators and genetic insight into molecular pathways associated with acute and chronic phases of RA.

Association of psychological distress and DNA methylation: A 5-year longitudinal population-based twin study

AIM

To identify the psychological distress (PD)-associated 5'-cytosine-phosphate-guanine-3' sites (CpGs), and investigate the temporal relationship between dynamic changes in DNA methylation (DNAm) and PD.

METHODS

This study included 1084 twins from the Chinese National Twin Register (CNTR). The CNTR conducted epidemiological investigations and blood withdrawal twice in 2013 and 2018. These included twins were used to perform epigenome-wide association studies (EWASs) and to validate the previously reported PD-associated CpGs selected from previous EWASs in PubMed, Embase, and the EWAS catalog. Next, a cross-lagged study was performed to examine the temporality between changes in DNAm and PD in 308 twins who completed both 2013 and 2018 surveys.

RESULTS

The EWAS analysis of our study identified 25 CpGs. In the validation analysis, 741 CpGs from 29 previous EWASs on PD were selected for validation, and 101 CpGs were validated to be significant at a false discovery rate <0.05. The cross-lagged analysis found a unidirectional path from PD to DNAm at 14 CpGs, while no sites showed significance from DNAm to PD.

CONCLUSIONS

This study identified and validated PD-related CpGs in a Chinese twin population, and suggested that PD may be the cause of changes in DNAm over time. The findings provide new insights into the molecular mechanisms underlying PD pathophysiology.

Pathways from the Superior Colliculus to the Basal Ganglia

The present work aims to review the structural organization of the mammalian superior colliculus (SC), the putative pathways connecting the SC and the basal ganglia, and their role in organizing complex behavioral output. First, we review how the complex intrinsic connections between the SC's laminae projections allow for the construction of spatially aligned, visual-multisensory maps of the surrounding environment. Moreover, we present a summary of the sensory-motor inputs of the SC, including a description of the integration of multi-sensory inputs relevant to behavioral control. We further examine the major descending outputs toward the brainstem and spinal cord. As the central piece of this review, we provide a thorough analysis covering the putative interactions between the SC and the basal ganglia. To this end, we explore the diverse thalamic routes by which information from the SC may reach the striatum, including the pathways through the lateral posterior, parafascicular, and rostral intralaminar thalamic nuclei. We also examine the interactions between the SC and subthalamic nucleus, representing an additional pathway for the tectal modulation of the basal ganglia. Moreover, we discuss how information from the SC might also be relayed to the basal ganglia through midbrain tectonigral and tectotegmental projections directed at the substantia nigra compacta and ventrotegmental area, respectively, influencing the dopaminergic outflow to the dorsal and ventral striatum. We highlight the vast interplay between the SC and the basal ganglia and raise several missing points that warrant being addressed in future studies.

Pathobiology of Cognitive Impairment in Parkinson Disease: Challenges and Outlooks

Cognitive impairment (CI) is a characteristic non-motor feature of Parkinson disease (PD) that poses a severe burden on the patients and caregivers, yet relatively little is known about its pathobiology. Cognitive deficits are evident throughout the course of PD, with around 25% of subtle cognitive decline and mild CI (MCI) at the time of diagnosis and up to 83% of patients developing dementia after 20 years. The heterogeneity of cognitive phenotypes suggests that a common neuropathological process, characterized by progressive degeneration of the dopaminergic striatonigral system and of many other neuronal systems, results not only in structural deficits but also extensive changes of functional neuronal network activities and neurotransmitter dysfunctions. Modern neuroimaging studies revealed multilocular cortical and subcortical atrophies and alterations in intrinsic neuronal connectivities. The decreased functional connectivity (FC) of the default mode network (DMN) in the bilateral prefrontal cortex is affected already before the development of clinical CI and in the absence of structural changes. Longitudinal cognitive decline is associated with frontostriatal and limbic affections, white matter microlesions and changes between multiple functional neuronal networks, including thalamo-insular, frontoparietal and attention networks, the cholinergic forebrain and the noradrenergic system. Superimposed Alzheimer-related (and other concomitant) pathologies due to interactions between α-synuclein, tau-protein and β-amyloid contribute to dementia pathogenesis in both PD and dementia with Lewy bodies (DLB). To further elucidate the interaction of the pathomechanisms responsible for CI in PD, well-designed longitudinal clinico-pathological studies are warranted that are supported by fluid and sophisticated imaging biomarkers as a basis for better early diagnosis and future disease-modifying therapies.

The Effects of Serping1 siRNA in α-Synuclein Regulation in MPTP-Induced Parkinson's Disease

Our understanding of the gastrointestinal system in the pathophysiology of Parkinson's disease (PD) has grown considerably over the last two decades. Patients with PD experience notable gastrointestinal symptoms, including constipation. In this study, the effects of knocked-down serping1, associated with the contraction and relaxation of smooth muscle and inflammation responses, by applying the serping1 siRNA were investigated in 1-methyl 4-phenyl 1,2,3,6-tetrahydropyridine-induced PD mice in an α-syn change aspect. In the result, serping1 expression was knocked down by the treatment of serping1 siRNA, and decreased serping1 induced the decrease α-syn in the colon. Furthermore, the changes in α-syn aggregation were also examined in the brain, and alleviated α-syn aggregation was also observed in an serping1 siRNA treatment group. The results indicated that serping1 siRNA could ease synucleinopathy related to the gastrointestinal system in PD. This study also raises the possibility that serping1 siRNA could alleviate α-syn aggregation in striatum and substantia nigra regions of the brain.

Updates on the Physiopathology of Group I Metabotropic Glutamate Receptors (mGluRI)-Dependent Long-Term Depression

Group I metabotropic glutamate receptors (mGluRI), including mGluR1 and mGluR5 subtypes, modulate essential brain functions by affecting neuronal excitability, intracellular calcium dynamics, protein synthesis, dendritic spine formation, and synaptic transmission and plasticity. Nowadays, it is well appreciated that the mGluRI-dependent long-term depression (LTD) of glutamatergic synaptic transmission (mGluRI-LTD) is a key mechanism by which mGluRI shapes connectivity in various cerebral circuitries, directing complex brain functions and behaviors, and that it is deranged in several neurological and psychiatric illnesses, including neurodevelopmental disorders, neurodegenerative diseases, and psychopathologies. Here, we will provide an updated overview of the physiopathology of mGluRI-LTD, by describing mechanisms of induction and regulation by endogenous mGluRI interactors, as well as functional physiological implications and pathological deviations.

The dosage of curcumin to alleviate movement symptoms in a 6-hydroxydopamine-induced Parkinson's disease rat model

Background

Curcumin is a natural compound with extensive pharmacological effects. This research is to verify the optimal dose and administration duration efficacy of curcumin in alleviating the movement symptoms of Parkinson's disease (PD).

Methods

Wistar rats were divided into six groups including control, model, levodopa treatment and low/middle/high (40/80/160 mg/kg/d) curcumin treatment groups. After stereotactic brain injection of 6-hydroxydopamine (6-OHDA), curcumin was given by intragastric administration for 2 weeks. To evaluate the drug effect, the rats received behavioral tests including apomorphine (APO)-induced rotation test, rotarod test and open field test. Then the rats were sacrificed and the brain slices including substantia nigra pars compacta (SNc) were used for immunofluorescence staining.

Results

After 6-OHDA injection, the model group showed typical movement symptoms including the severe APO-induced rotation to the healthy side, decreased latency in the rotarod with constant or accelerative mode, and decreased total distance and average speed in the open field test. In the results of immunofluorescence staining, the 6-OHDA induced a severe damage of dopaminergic neurons in SNc. The 160 mg/kg/d treatment of curcumin to intervene for 2 weeks alleviated most of the behavioral disorders but the 40/80 mg/kg/d treatment showed limitations. Then, we compared the effect of 1 week intervention to the 2 weeks with 160 mg/kg/d treatment of curcumin to intervene and results indicated that the treatment of 2 weeks could better alleviate the symptoms.

Conclusions

Curcumin alleviated 6-OHDA-induced movement symptoms in a PD rat model. Additionally, the effect of curcumin against PD indicated dose and duration dependent and the intervention of 160 mg/kg/d for 2 weeks showed optimally therapeutic effect.

The Effects of Extrinsic and Intrinsic Factors on Neurogenesis

In the mammalian brain, neurogenesis is maintained throughout adulthood primarily in two typical niches, the subgranular zone (SGZ) of the dentate gyrus and the subventricular zone (SVZ) of the lateral ventricles and in other nonclassic neurogenic areas (e.g., the amygdala and striatum). During prenatal and early postnatal development, neural stem cells (NSCs) differentiate into neurons and migrate to appropriate areas such as the olfactory bulb where they integrate into existing neural networks; these phenomena constitute the multistep process of neurogenesis. Alterations in any of these processes impair neurogenesis and may even lead to brain dysfunction, including cognitive impairment and neurodegeneration. Here, we first summarize the main properties of mammalian neurogenic niches to describe the cellular and molecular mechanisms of neurogenesis. Accumulating evidence indicates that neurogenesis plays an integral role in neuronal plasticity in the brain and cognition in the postnatal period. Given that neurogenesis can be highly modulated by a number of extrinsic and intrinsic factors, we discuss the impact of extrinsic (e.g., alcohol) and intrinsic (e.g., hormones) modulators on neurogenesis. Additionally, we provide an overview of the contribution of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection to persistent neurological sequelae such as neurodegeneration, neurogenic defects and accelerated neuronal cell death. Together, our review provides a link between extrinsic/intrinsic factors and neurogenesis and explains the possible mechanisms of abnormal neurogenesis underlying neurological disorders.

Sexual Dysfunctions in Females with Parkinson's Disease: A Cross-Sectional Study with a Psycho-Endocrinological Perspective

Background and Objectives: Normal human sexual functioning is a complex integration of an intact neuroanatomic substrate, vascular supply, a balanced hormonal profile, and a predominance of excitatory over inhibitory psychological mechanisms. However, sexual functioning in Parkinson's disease (PD) is often overlooked in clinical practice, especially in female patients. Materials and Methods: In this cross-sectional study, we have investigated the frequency of sexual dysfunction and the possible correlation with psycho-endocrinological factors in a sample of women with idiopathic PD. Patients were assessed using a semi-structured sexual interview, in addition to psychometric tools, including the Hamilton Rating Scale for Anxiety and for Depression and the Coping Orientation to the Problems Experiences-New Italian Version. Specific blood tests, including testosterone, follicle-stimulating hormone (FSH), luteinizing hormone (LH), estrogen E2, prolactin (PRL), and vitamin D3 were also evaluated. Results: Our results reported a statistical difference in sexual intercourse frequency before and after the onset of PD (p < 0.001). The percentage of women who complained about reduced sexual desire increased after diagnosis (52.7%) compared to the period before the onset of the illness (36.8%). The endocrinological profile in females with PD revealed statistically significant differences regarding testosterone (p < 0.0006), estradiol (p < 0.00), vitamin D3 (p < 0.006), and calcium (0.002). Depression (44% characterized by perceived feelings of anger and frustration during sexual intercourse) and anxiety symptoms (29.5% reported feelings of fear and anxiety for not satisfying the partner) with abnormal coping strategies (48.14% experienced feelings of anger and intolerance) were also found to be statistically significant. This study showed a high frequency of sexual dysfunction in female patients with PD, which correlated with sexual hormone abnormalities, mood/anxiety, and coping strategies alterations. This supports the idea that there is a need to better investigate the sexual function of female patients with PD to provide them with an adequate therapeutic approach and potentially improve quality of life.

Neurobiology of depression in Parkinson's disease: Insights into epidemiology, molecular mechanisms and treatment strategies

Parkinson's disease (PD) is characterized mainly by motor dysfunctions due to the progressive loss of dopaminergic neurons. However, PD patients experience a multitude of debilitating non-motor symptoms, including depression, which may have deleteriously detrimental effects on life. Depression is multifactorial and exhibits a bimodal progression in PD, but its underlying molecular mechanisms are poorly understood. Studies demonstrating the pathophysiology of depression in PD and the specific treatment strategies for depression-like symptoms in PD patients are largely lacking, often underrated, under-recognized and, consequently, inadequately/under-treated. Nevertheless, reports suggest that the incidence of depression is approximately 20-30% of PD patients and may precede the onset of motor symptoms. Diagnosing depression in PD becomes difficult due to the clinical overlap in symptomatology between the two diseases, and the nigrostriatal dysfunction alone is insufficient to explain depressive symptoms in PD. Therefore, the current study provides an overview of the molecular mechanisms underlying the development of depression in PD and new insights into developing current antidepressant strategies to treat depression in PD. This review will identify and understand the molecular pathological mechanisms of depression in PD that will fundamentally help tailoring therapeutic interventions for depressive symptoms in PD.

Both Motor and Non-Motor Fluctuations Matter in the Clinical Management of Patients with Parkinson's Disease: An Exploratory Study

Non-motor symptoms (NMS) characterize the Parkinson's disease (PD) clinical picture, and as well as motor fluctuations, PD patients can also experience NMS fluctuations (NMF). The aim of this observational study was to investigate the presence of NMS and NMF in patients with PD using the recently validated Non-Motor Fluctuation Assessment questionnaire (NoMoFa) and to evaluate their associations with disease characteristics and motor impairment. Patients with PD were consecutively recruited, and NMS, NMF, motor impairment, motor fluctuations, levodopa-equivalent daily dose, and motor performance were evaluated. One-third of the 25 patients included in the study (10 females, 15 males, mean age: 69.9 ± 10.3) showed NMF, and patients with NMF presented a higher number of NMS (p < 0.01). Static NMS and NoMoFa total score were positively associated with motor performance assessed with the Global Mobility Task (p < 0.01 and p < 0.001), and the latter was also correlated with motor impairment (p < 0.05) but not with motor fluctuations. Overall, this study shows evidence that NMF are frequently reported by mild-to-moderate PD patients and associated with an increased number of NMS. The relationship between NoMoFa total score and motor functioning highlights the importance of understanding the clinical role of NMS and NMF in the management of PD patients.

Evaluating depression- and anxiety-like behaviors in non-human primates

Depression and anxiety are some of the most prevalent and debilitating mental health conditions in humans. They can present on their own or as co-morbidities with other disorders. Like humans, non-human primates (NHPs) can develop depression- and anxiety-like signs. Here, we first define human depression and anxiety, examine equivalent species-specific behaviors in NHPs, and consider models and current methods to identify and evaluate these behaviors. We also discuss knowledge gaps, as well as the importance of evaluating the co-occurrence of depression- and anxiety-like behaviors in animal models of human disease. Lastly, we consider ethical challenges in depression and anxiety research on NHPs in order to ultimately advance the understanding and the personalized treatment of these disorders.

The efficient generation of knockout microglia cells using a dual-sgRNA strategy by CRISPR/Cas9

Gene deletion in microglia has become an important and exciting approach for studying neuroinflammation, especially after the development of the CRISPR/Cas9 system for genome editing during the last decade. In this study, we described a protocol for the highly efficient generation of knockout microglia cells using a dual-short guide RNA (sgRNA) strategy by CRISPR/Cas9. Leucine-rich repeat kinase 2 (LRRK2), a pathogenic gene of Parkinson's disease (PD), has played versatile roles during the disease development. Despite many key insights into LRRK2 studies, the normal and disease-related functions of LRRK2 in microglia and neuroinflammation remain to be fully investigated. Given the importance of LRRK2 in PD pathogenesis, we designed and applied the protocol to target LRRK2. Specifically, we designed two sgRNAs targeting the N terminus of LRRK2, spanning the 5' untranslated region (UTR) and exon 1, and screened knockout cells by single-cell expansion. In practice, the dual-sgRNA system can facilitate in obtaining knockout cells in a more convenient, rapid, and accurate way. Candidate knockout cells can be easily distinguished by genomic PCR and running on agarose gels, based on the different band sizes. Successful knockouts were further verified by Sanger sequencing and Western blot. Using this protocol, we obtained an LRRK2-deficient microglia cell line, which was characterized by longer cellular processes, enhanced adhesion, and weakened migration capacity. The knockout microglia may further serve as an important cellular tool to reveal conserved and novel aspects of LRRK2 functions in the development and progression of PD. Our protocol using dual-sgRNA targeting guarantees > 60% targeting efficiency and could also be applied to targeting other genes/loci, especially non-coding RNAs and regulatory elements.

Inflammatory gut as a pathologic and therapeutic target in Parkinson’s disease

Parkinson’s disease (PD) remains a significant unmet clinical need. Gut dysbiosis stands as a PD pathologic source and therapeutic target. Here, we assessed the role of the gut-brain axis in PD pathology and treatment. Adult transgenic (Tg) α-synuclein-overexpressing mice served as subjects and were randomly assigned to either transplantation of vehicle or human umbilical cord blood-derived stem cells and plasma. Behavioral and immunohistochemical assays evaluated the functional outcomes following transplantation. Tg mice displayed typical motor and gut motility deficits, elevated α-synuclein levels, and dopaminergic depletion, accompanied by gut dysbiosis characterized by upregulation of microbiota and cytokines associated with inflammation in the gut and the brain. In contrast, transplanted Tg mice displayed amelioration of motor deficits, improved sparing of nigral dopaminergic neurons, and downregulation of α-synuclein and inflammatory-relevant microbiota and cytokines in both gut and brain. Parallel in vitro studies revealed that cultured dopaminergic SH-SY5Y cells exposed to homogenates of Tg mouse-derived dysbiotic gut exhibited significantly reduced cell viability and elevated inflammatory signals compared to wild-type mouse-derived gut homogenates. Moreover, treatment with human umbilical cord blood-derived stem cells and plasma improved cell viability and decreased inflammation in dysbiotic gut-exposed SH-SY5Y cells. Intravenous transplantation of human umbilical cord blood-derived stem/progenitor cells and plasma reduced inflammatory microbiota and cytokine, and dampened α-synuclein overload in the gut and the brain of adult α-synuclein-overexpressing Tg mice. Our findings advance the gut-brain axis as a key pathological origin, as well as a robust therapeutic target for PD.

Gut-Brain Axis as a PD Pathologic Source and Therapeutic Target. The PD murine model of α-synuclein overexpression at around 8 weeks of age manifests gut dysbiosis, characterized by inflammation-specific microbiota and cytokines, which can trigger brain neurodegeneration, especially dopaminergic depletion reminiscent of PD pathology. Targeting the dysbiotic gut via intravenous hUCB stem cell transplantation can render gut homeostasis and sequester peripheral as well as central inflammation, leading to brain repair and amelioration of PD behavioral and histological deficits.

Cognitive deficits and altered cholinergic innervation in young adult male mice carrying a Parkinson's disease Lrrk2G2019S knockin mutation

Impaired executive function is a common and debilitating non-motor symptom of idiopathic and hereditary Parkinson's disease (PD), but there is little understanding of the underlying pathophysiological mechanisms and circuits. The G2019S mutation in the kinase domain of leucine-rich repeat kinase 2 (LRRK2) greatly increases risk for late-onset PD, and non-manifesting LRRK2^G2019S carriers can also exhibit early and significant cognitive impairment. Here, we subjected young adult male mice carrying a Lrrk2^G2019S knockin mutation to touchscreen-based operant tasks that measure attention, goal-directed learning and cognitive flexibility, all of which rely on frontal-striatal connectivity and are strongly modulated by cholinergic innervation. In a visuospatial attention task, mutant mice exhibited significantly more omissions and longer response latencies than controls that could not be attributed to deficits in motivation, visual sensory perception per se or locomotion, thereby suggesting impairments in divided attention and/or action-selection as well as generally slower information processing speed. Pretreating mice with the acetylcholinesterase inhibitor donepezil normalized both higher omission rates and longer response latencies in the mutants, but did not affect any performance metric in controls. Strikingly, cholinergic fiber density in cortical areas PL/IL and DMS (dorsomedial striatum) was significantly sparser in mutants than in controls, while further behavioral interrogation of the mutants revealed significant impairments in action-outcome associations but preserved cognitive flexibility. These data suggest that the Lrrk2^G2019S mutation negatively impacts cholinergic innervation anatomically and functionally by young adulthood, impairing corticostriatal network function in ways that may contribute to early PD-associated executive function deficits.

DIFFERENTIAL CONTRIBUTION OF ESTROGEN RECEPTORS TO THE INTESTINAL THERAPEUTIC EFFECTS OF 17β-ESTRADIOL IN A MURINE MODEL OF PARKINSON'S DISEASE

Beneficial effects of estrogens have been reported in Parkinson's disease (PD) for many years. We previously reported their neuroprotective and anti-inflammatory potentials in the enteric nervous system of the intestine, a region possibly affected during the early stages of the disease according to Braak's hypothesis. Three different estrogen receptors have been characterized to date: the estrogen receptor alpha (ERα), the estrogen receptor beta (ERβ) and the G protein coupled estrogen receptor 1 (GPER1). The aim of the present study was to decipher the individual contribution of each estrogen receptor to the therapeutic properties of 17β-estradiol (E2) in the myenteric plexus of the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD. Different agonists, 4,4',4''-(4-propyl-[1H]-pyrazole-1,3,5-triyl)trisphenol (PPT; ERα), 2,3-bis(4-hydroxyphenyl)-propionitrile (DPN; ERβ), G1 (GPER1), and antagonists, ICI 182,780 (ERα and ERβ), G15 (GPER1), were used to analyze the involvement of each receptor. We confirmed that G1 protects dopamine (DA) neurons to a similar extent as E2. An anti-inflammatory effect on proinflammatory macrophages and cultured human monocytes was also demonstrated with E2 and G1. The effects of PPT and DPN were less potent than G1 with only a partial neuroprotection of DA neurons by PPT and a partial reduction of interleukin (IL)-1β production in monocytes by PPT and DPN. Overall, the present results indicate that the positive outcomes of estrogens are mainly through activation of GPER1. Therefore, this suggests that targeting GPER1 could be a promising approach for future estrogen-based hormone therapies during early PD.

The Pathological Mechanism Between the Intestine and Brain in the Early Stage of Parkinson's Disease

Parkinson's disease (PD) is the second most common chronic progressive neurodegenerative disease. The main pathological features are progressive degeneration of neurons and abnormal accumulation of α-synuclein. At present, the pathogenesis of PD is not completely clear, and many changes in the intestinal tract may be the early pathogenic factors of PD. These changes affect the central nervous system (CNS) through both nervous and humoral pathways. α-Synuclein deposited in the intestinal nerve migrates upward along the vagus nerve to the brain. Inflammation and immune regulation mediated by intestinal immune cells may be involved, affecting the CNS through local blood circulation. In addition, microorganisms and their metabolites may also affect the progression of PD. Therefore, paying attention to the multiple changes in the intestinal tract may provide new insight for the early diagnosis and treatment of PD.

The Double-Faceted Role of Leucine-Rich Repeat Kinase 2 in the Immunopathogenesis of Parkinson’s Disease

Leucine-rich repeat kinase 2 (LRRK2) is one of the most common causative genes in Parkinson’s disease (PD). The complex structure of this multiple domains’ protein determines its versatile functions in multiple physiological processes, including migration, autophagy, phagocytosis, and mitochondrial function, among others. Mounting studies have also demonstrated the role of LRRK2 in mediating neuroinflammation, the prominent hallmark of PD, and intricate functions in immune cells, such as microglia, macrophages, and astrocytes. Of those, microglia were extensively studied in PD, which serves as the resident immune cell of the central nervous system that is rapidly activated upon neuronal injury and pathogenic insult. Moreover, the activation and function of immune cells can be achieved by modulating their intracellular metabolic profiles, in which LRRK2 plays an emerging role. Here, we provide an updated review focusing on the double-faceted role of LRRK2 in regulating various cellular physiology and immune functions especially in microglia. Moreover, we will summarize the latest discovery of the three-dimensional structure of LRRK2, as well as the function and dysfunction of LRRK2 in immune cell-related pathways.

Cholinergic Receptor Modulation as a Target for Preventing Dementia in Parkinson's Disease

Parkinson’s disease (PD) is a neurodegenerative condition characterized by the loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc) in the midbrain resulting in progressive impairment in cognitive and motor abilities. The physiological and molecular mechanisms triggering dopaminergic neuronal loss are not entirely defined. PD occurrence is associated with various genetic and environmental factors causing inflammation and mitochondrial dysfunction in the brain, leading to oxidative stress, proteinopathy, and reduced viability of dopaminergic neurons. Oxidative stress affects the conformation and function of ions, proteins, and lipids, provoking mitochondrial DNA (mtDNA) mutation and dysfunction. The disruption of protein homeostasis induces the aggregation of alpha-synuclein (α-SYN) and parkin and a deficit in proteasome degradation. Also, oxidative stress affects dopamine release by activating ATP-sensitive potassium channels. The cholinergic system is essential in modulating the striatal cells regulating cognitive and motor functions. Several muscarinic acetylcholine receptors (mAChR) and nicotinic acetylcholine receptors (nAChRs) are expressed in the striatum. The nAChRs signaling reduces neuroinflammation and facilitates neuronal survival, neurotransmitter release, and synaptic plasticity. Since there is a deficit in the nAChRs in PD, inhibiting nAChRs loss in the striatum may help prevent dopaminergic neurons loss in the striatum and its pathological consequences. The nAChRs can also stimulate other brain cells supporting cognitive and motor functions. This review discusses the cholinergic system as a therapeutic target of cotinine to prevent cognitive symptoms and transition to dementia in PD.