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

Proof of concept study for developing 1-thienyl-β-carboline derivatives as IDO1 and TDO dual inhibitors to treat Parkinson's disease complicating depression

Depressive symptoms are the most common neuropsychiatric disorders at all stages of Parkinson's disease (PD). Imbalances of the kynurenine pathway of tryptophan metabolism have been closely linked to the pathogenesis of PD and depression. Herein, we designed and synthesized a series of 1-thienyl-β-carboline derivatives as IDO1 and TDO dual inhibitors; among them, compound CZ-17 manifested moderate inhibitory activities to IDO1 and TDO with IC50 values of 0.33 and 1.78 μM, respectively. CZ-17 inhibited the kynurenine pathway of tryptophan degradation at the cellular level, and remarkably reduced the kynurenine/tryptophan ratio. CZ-17 displayed directly neuroprotective effect in corticosterone-induced PC12 neural cell injury model. In vivo experiments demonstrated that CZ-17 significantly increased dopamine and serotonin levels, improved MPTP-induced motor disability and rescued LPS-induced depressive behavior in zebrafish model. Acute toxicity tests of CZ-17 in zebrafish embryos showed no toxicity within the effective dose range. Additionally, CZ-17 displayed the potential to cross the BBB via passive diffusion according to ADMET prediction and Caco-2 permeability assay. Thus, CZ-17 may be a promising drug candidate for PD complicating depression.

Associations between major depressive disorders and Parkinson's Disease and impact of their comorbidity sequence

BACKGROUND

The comorbidity of major depressive disorder (MDD) and Parkinson's disease (PD) were prevalent and has a profound impact on patients. However, whether this comorbidity results from specific pathological processes or a mutual cause-and-effect relationship was largely controversial. Additionally, although MDD can appear before or after PD, the health impact of the comorbidity sequence is poorly understood.

METHODS

We used mendelian randomization (MR) and UK biobank (UKB) cohort to explore the associations between MDD and PD. MR was also utilized to investigate potential confounders. By classifying UKB patients into MDD first and PD first groups, we evaluated the health impact of the comorbidity sequence using Cox regression.

RESULTS

Bidirectional MR and cohort study showed conflicting results. MR did not find associations between MDD followed by PD (odds ratio [OR] = 1.28, 95 % confidence interval [CI] = 0.85-1.94) or PD followed by MDD (OR = 0.99, 95 % CI = 0.97-1.01). However, the cohort study found a significant effect of MDD on PD (hazard ratio [HR] = 1.75, 95 % CI = 1.55-1.97) and PD on MDD (HR = 4.35, 95 % CI = 3.65-5.19). By performing MR on 4709 proteins, we identified ESD, LEAP2, NDRG3, NRXN3, and PLXNB2 as potential common causes of MDD and PD. Additionally, PD first group had higher risks of all-cause mortality (HR = 1.65, 95 % CI = 1.03-1.90), dementia (HR = 1.88, 95 % CI = 1.16-3.04), and aspiration pneumonia (HR = 1.89, 95 % CI = 1.09-3.27).

CONCLUSIONS

Our study suggested the comorbidity of MDD and PD is likely the result of certain pathological processes. Additionally, patients with PD first had higher risks of several adverse outcomes.

α -Lipoic acid alleviates Parkinson's disease by suppressing S100A9-mediated pyroptosis

Parkinson's disease (PD) is a neurodegenerative disease, and inflammation is a key factor in the progression of PD. S100A9 mediates pyroptosis and implicates in various diseases including PD. Pyroptosis, an emerging form of programmed cell death, usually causes cell rupture and death via an inflammatory response. α-Lipoic acid (α-ALA), a cellular coenzyme, participates in anti-inflammatory and antioxidant processes. Although its role in PD has been confirmed, but the exact mechanism of its anti-inflammatory effect remains unclear. In our research, we examined the potential mechanisms of pyroptosis mediated by S100A9 in PD and the neuroprotective effects of α-ALA. We used 6-hydroxydopamine (6-OHDA) to induce SH-SY5Y cells in vitro and in C57BL/6 mice in vivo. The cell viability of SH-SY5Y cells confirmed the neuroprotective effect of α-ALA. Proteomics analysis indicated that S100A9 was involved in 6-OHDA-mediated neuronal injury, while α-ALA could inhibit. We found that α-ALA ameliorated PD symptoms induced by 6-OHDA and decreased the levels of NLRP3 inflammasome, Gasdermin D, and IL-1β, which are major hallmarks of pyroptosis. Furthermore, our research demonstrated that α-ALA mitigated cell injury by suppressing NLRP3-dependent pyroptosis mediated by S100A9. In brief, pyroptosis is pivotal in PD, while α-ALA protects dopaminergic neurons by suppressing pyroptosis mediated through the NLRP3 inflammasome, directly reducing S100A9, and subsequently inhibiting the NLRP3/Gasdermin D signaling pathways. Our results collectively suggest that suppressing S100A9-mediated pyroptosis and administering α-ALA may represent a novel approach in treating of PD.

Clinical characteristics of pathological confirmed DLB without parkinsonism

INTRODUCTION

The misdiagnosis rate of Dementia with Lewy Bodies (DLB) remains high. Accurate diagnosis is paramount in the era of anti-amyloid therapy. The main objective of the current study is to elucidate early clinical features of pathologically confirmed DLB without parkinsonism (DLB-nP) that potentially resemble Alzheimer's disease (AD).

METHODS

We accessed the National Alzheimer's Coordinating Center database from 2005 to December 2022 data freeze and included 3159 Alzheimer's disease, 91 DLB-nP, and 307 DLB with parkinsonism (DLBP) cases. Diagnosis of AD and DLB were based on existing pathological criteria. First visit data was analyzed.

RESULTS

Clinician-determined memory impairment is common in DLB-nP (87.9 % vs. AD 97.4 %) but is associated with a higher risk of AD diagnosis. Misdiagnosis as AD in DLB-nP stands at 75.8 %. Visual hallucinations (VH) or hallucinations are the only variables favoring DLB-nP diagnosis, but they only account for 22 % and 14 % of the cohort, respectively. After patients with VH were removed from the model, the misdiagnosis rate as AD increased to 85.2 %, and nighttime behavior was the only variable found to favor DLB-nP diagnosis. Visuospatial dysfunction is more common in DLB-P than DLB-nP but does not distinguish DLB-nP from AD.

CONCLUSION

Amnestic presentation, while favoring AD diagnosis, is common in DLB without parkinsonism, and misdiagnosis is common. While VH remains the most prominent clinical feature for prompting DLB diagnosis, misdiagnosis becomes more profound in its absence during the early phase. In this study, exercising great caution during clinical assessment appears to be the fundamental way to minimize misdiagnosis for patients with amnestic presentation yet without parkinsonism and VH.

Multidimensional mechanisms of anxiety and depression in Parkinson's disease: Integrating neuroimaging, neurocircuits, and molecular pathways

Anxiety and depression are common non-motor symptoms of Parkinson's disease (PD) that significantly affect patients' quality of life. In recent years, our understanding of PD has advanced through multifaceted studies on the pathological mechanisms associated with anxiety and depression in PD. These classic psychiatric symptoms involve complex pathophysiology, with both distinct features and connections to the mechanisms underlying the aetiology of PD. Furthermore, the co-occurrence of anxiety and depression in PD blurs the boundaries between them. Therefore, a comprehensive summary of the pathogenic mechanisms associated with anxiety and depression will aid in better addressing the emergence of these classic psychiatric symptoms in PD. This article integrates neuroanatomical, neural projection, neurotransmitter, neuroinflammatory, brain-gut axis, neurotrophic, hypothalamic-pituitary-adrenal axis, and genetic perspectives to provide a comprehensive description of the core pathological alterations underlying anxiety and depression in PD, aiming to provide an up-to-date perspective and broader therapeutic prospects for PD patients suffering from anxiety or depression.

Global, regional and national burden of Parkinson's disease in people over 55 years of age: a systematic analysis of the global burden of disease study, 1991-2021

BACKGROUND

Parkinson's disease (PD) has emerged as a major global public health challenge. However, there is currently a lack of systematic analysis regarding the burden of PD and its long-term trends among people over 55 years of age.

METHODS

This study utilizes data from the Global Burden of Disease 2021 database to analyze the prevalence, incidence, disability-adjusted life years (DALYs), and mortality rates of PD in individuals aged 55 and older from 1990 to 2021. The annual percentage change was calculated to assess the temporal trends of the disease burden. Point estimates and their corresponding ranges were reported with 95% uncertainty intervals.

RESULTS

Globally, the prevalence, incidence, DALYs, and mortality rates of PD in individuals aged 55 and above significantly increased from 1990 to 2021, with all indicators being higher in males than in females. This trend was evident across all five Socio-Demographic Index (SDI) groups and in 21 regions worldwide. The number of prevalent cases, incident cases, DALYs, and deaths all showed significant increases and were positively correlated with SDI (R = 0.645, P < 0.001). Among 185 countries, the incidence rate increased, with DALY rates rising in 74 countries and mortality rates rising in 65 countries. Notably, in the population aged 95 years and older, the prevalence and incidence of PD showed particularly remarkable increases, at 735% and 505%, respectively. Furthermore, the greatest increase in prevalence was observed in the 55-59 age group, especially in countries with Middle SDI and High-middle SDI regions.

CONCLUSIONS

This study indicates that the burden of PD in individuals aged 55 and above has significantly increased over the past three decades. This trend reflects the profound impact of global aging and socioeconomic development levels on the burden of PD, underscoring the urgency of addressing PD as a major global public health challenge.

Serum sirtuin 3 levels and multimodal abnormalities in brain structure and function in parkinson's disease patients with depression

BACKGROUND

Depression is a common nonmotor symptom in patients with Parkinson's disease (PD). Currently, few studies have investigated the relationships between serum markers and neuroimaging changes associated with depression in PD patients.

OBJECTIVE

To explore the correlations among depression, serum SIRT3 levels, and brain structural and functional alterations in PD patients.

METHODS

The Hamilton Depression Scale-17 (HAMD-17) was used to assess depression. Serum SIRT3 levels were measured using an enzyme-linked immunosorbent assay (ELISA). Voxel-based morphometry (VBM) and resting-state functional magnetic resonance imaging (rs-fMRI) were used to examine structural and functional alterations.

RESULTS

Compared to healthy individuals, serum SIRT3 levels were lower in PD patients, especially in those with depression. PD patients with depression had lower total gray matter volume/total intracranial volume (GMV/TIV) ratio, and GMVs of the right amygdala, lower fractional amplitude of low-frequency fluctuations (fALFF) values of the left middle frontal gyrus (MidFG.L) and left superior parietal lobule (SPL.L), and altered functional connectivity(FC) primarily involving the Salience Network (SN) and the default Mode Network (DMN) compared to those without depression. Serum SIRT3 levels, total GMV/TIV ratios, and fALFF values of the MidFG.L and SPL.L have diagnostic value for PD patients with depression, and their combination can improve predictive accuracy.

CONCLUSIONS

Depression in PD patients is associated with lower serum SIRT3 levels, right amygdala atrophy, decreased spontaneous activity in MidFG.L and SPL.L, and altered FC in the DMN and SN.

Oral health implications in Parkinson's disease

To assist patients in maintaining oral health in patients with Parkinson's disease (PD), this review aims to search the literature on aspects related to oral health in PD patients. In contrast to other research, we included the involvement of microbes in PD patients' poor oral health. Finally, we conclude that, in comparison to healthy individuals, PD patients have poorer oral health and a higher incidence of oral ailments.

The Role and Mechanisms of Ubiquitin-Proteasome System-Mediated Ferroptosis in Neurological Disorders

Ferroptosis is a form of cell death elicited by an imbalance in intracellular iron concentrations, leading to enhanced lipid peroxidation. In neurological disorders, both oxidative stress and mitochondrial damage can contribute to ferroptosis, resulting in nerve cell dysfunction and death. The ubiquitin-proteasome system (UPS) refers to a cellular pathway in which specific proteins are tagged with ubiquitin for recognition and degradation by the proteasome. In neurological conditions, the UPS plays a significant role in regulating ferroptosis. In this review, we outline how the UPS regulates iron metabolism, ferroptosis, and their interplay in neurological diseases. In addition, we discuss the future application of small-molecule inhibitors and identify potential drug targets. Further investigation into the mechanisms of UPS-mediated ferroptosis will provide novel insights and strategies for therapeutic interventions and clinical applications in neurological diseases.

Cannabidiol induces autophagy via CB1 receptor and reduces α-synuclein cytosolic levels

Numerous studies have explored the role of cannabinoids in neurological conditions, chronic pain and neurodegenerative diseases. Restoring autophagy has been proposed as a potential target for the treatment of neurodegenerative diseases. In our study, we used a neuroblastoma cell line that overexpresses wild-type α-synuclein to investigate the effects of cannabidiol on autophagy modulation and reduction in the level of cytosolic α-synuclein. Our results demonstrated that cannabidiol enhances the accumulation of LC3-II- and GFP-LC3-positive vesicles, which indicates an increase in autophagic flux. In addition, cannabidiol-treated cells showed a reduction in cytosolic α-synuclein levels. These effects were inhibited when the cells were treated with a CB1 receptor-selective antagonist, which indicates that the biological effects of cannabidiol are mediated via its interaction with CB1 receptor. Additionally, we also observed that cannabinoid compounds induce autophagy and α-synuclein degradation after they interact with the CB1 receptor. In summary, our data suggest that cannabidiol induces autophagy and reduces cytosolic α-synuclein levels. These biological effects are mediated preferentially through the interaction of cannabidiol with CB1 receptors, and therefore, cannabinoid compounds that act selectively on this receptor could represent a new approach for autophagy modulation and degradation of protein aggregates.

The Relationship between Emotional Expression, Difficulty in Emotion Regulation and Anhedonia in Parkinson's Disease

Parkinson's disease (PD), a range of neuropsychiatric symptoms, including anhedonia, depression, emotional control, and cognitive deficits, may manifest. This study aims to investigate the impact of anhedonia, emotional regulation, and emotional expression on PD. The research included 68 PD patients and 60 healthy controls. Both groups were assessed using the Hospital Anxiety and Depression Scale (HADS), Emotional Expression Scale (EES), the Short Form of the Difficulties in Emotion Regulation Scale (DERS), and the Clinician-Administered Snaith-Hamilton Pleasure Scale (SHAPS), all administered by a psychiatrist. The PD group was evaluated by a neurology specialist using the Unified Parkinson's Disease Rating Scale (UPDRS). Results showed that the PD group scored significantly higher on the HADS (p < 0.01), DERS (p < 0.01), and SHAPS (p < 0.01), while their EES scores were significantly lower (p < 0.01) compared to the control group. Further analysis indicated that a one-unit increase in anhedonia scores corresponded to a 3.125 unit rise in non-motor symptom scores and a 5.034 unit rise in motor symptom scores. The findings suggest that anhedonia is a strong predictor of both motor and non-motor symptoms in PD. The data indicate that the link between anhedonia and PD exists independently of depression and anxiety, highlighting the necessity of addressing anhedonia as a distinct symptom in PD.

Progress and prospects of Parkinson's disease with depression research: A global bibliometric analysis based on CiteSpace

BACKGROUND

Parkinson's disease (PD) is a common neurodegenerative disorder marked by motor impairments such as stiffness, involuntary shaking, and slowed movement. In addition, PD patients frequently experience nonmotor symptoms, especially depression. This study uses a mixed-methods scientometric analysis to review global research trends and advancements in PD and depression. This analysis is vital for clinicians, researchers, and policymakers, identifying knowledge gaps and directing future research efforts.

METHODS

We conducted a comprehensive literature review on PD and depression using the Web of Science database from 2004 to 2023, facilitated by CiteSpace 6.1.R6. Our analysis examined collaborations among authors, institutions, countries, and keywords, incorporating insights from RCTs and qualitative studies. We calculated effect sizes and confidence intervals with precision. Ethical approval was not required as the study used publicly available data without personal information.

RESULTS

Our analysis included 3048 research papers and 915 reviews, involving 17,927 authors and 12,466 institutions. The United States and the University of Toronto led in publications. Studies revealed significant effect sizes with narrow confidence intervals, particularly on the prevalence and impact of depression in PD patients. High-frequency keywords included "Parkinson's disease," "depression," "quality of life," "non-motor symptom," and "dementia." Visual mapping identified critical research nodes and future directions.

CONCLUSION

Over the past 2 decades, research on the PD-depression link has accelerated. Our analysis highlights prevailing trends and critical areas, providing evidence-based recommendations for therapeutic strategies. This study offers valuable insights for clinicians and researchers, emphasizing future research priorities to improve patient outcomes.

The effects of ursodeoxycholic acid on Parkinson's disease, a mechanistic review of the recent evidence

INTRODUCTION

Parkinson`s disease stands as the second-most widespread neurodegenerative disorder. Parkinson`s disease is relentless in progression and irreversible in nature, for which there is no cure. Therapies are only used to attenuate motor symptoms. As Parkinson`s disease is primarily defined by degeneration of dopaminergic neurons in the substantia nigra, and considering that neuroinflammation and mitochondrial dysfunction in these neurons are key factors contributing to disease progression, alternative therapies should aim to preserve healthy mitochondria. Method. Eligible studies on the effect of Ursodeoxycholic acid (UDCA) on Parkinson`s disease were collected from PubMed, Google Scholar, Scopus, Web of Science and Cochrane library for clinical, in-vivo, and in-vitro studies. Result. UDCA and its taurine conjugate (TUDCA), which are endogenous bile acids, have exhibited neuroprotective potential in various neurological conditions, such as Alzheimer's disease, Parkinson's disease and Huntington's disease, in both animal experimental models and clinical investigations. This is attributed to three significant properties, in addition to their capability to cross the blood-brain barrier. First, their anti-inflammatory properties are manifested through the reduction of significant inflammatory factors such as tumor necrosis factor-α, interleukin 1β and other related elements. Second, their antioxidant property is marked by an increase in the expression of superoxide dismuthase, glutathione peroxidase and other antioxidant enzymes. The third property is the antiapoptotic activity, characterized by decreased caspase-3 activity and lower expression of pro-apoptotic Bax in the striatum. Conclusion. Based on this comprehensive review, UDCA and TUDCA have the potential to be considered as a therapeutic agent in the management of the Parkinson's disease.

Identification of Depression Subtypes in Parkinson's Disease Patients via Structural MRI Whole-Brain Radiomics: An Unsupervised Machine Learning Study

OBJECTIVE

Current clinical evaluation may tend to lack precision in detecting depression in Parkinson's disease (DPD). Radiomics features have gradually shown potential as auxiliary diagnostic tools in identifying and distinguishing different subtypes of Parkinson's disease (PD), and a radiomic approach that combines unsupervised machine learning has the potential to identify DPD.

METHODS

Analyze the clinical and imaging data of 272 Parkinson's disease (PD) patients from the PPMI dataset, along with 45 PD patients from the NACC dataset. Extract radiomic features from T1-weighted MRI images and employ principal component analysis (PCA) for dimensionality reduction. Subsequently, apply four unsupervised clustering methods including Gaussian mixture model (GMM), hierarchical clustering, K-means, and partitioning around medoids (PAM) to classify cases in the PPMI dataset into distinct subtypes. Identify high-risk subtypes of DPD on the basis of the time and number of depression progression, and validate these findings using the NACC dataset. The data from the high-risk subtype were divided into a training subtype and a testing subtype in a 7:3 ratio. Multiple logistic regression analysis was conducted on the training subtype data to develop a traditional logistic regression model for the high-risk subtype, which was subsequently compared with a supervised logistic regression model constructed for the entire PPMI cohort. Finally, the performance of both models was evaluated using receiver operating characteristic (ROC) curves. In addition, a decision tree (DT) model was constructed based on independent risk factors of high-risk subtypes and validated using low-risk subtype data. ROC curves were employed to validate this model across training subtype, testing subtype, and low-risk subtype datasets.

RESULTS

The PAM clustering method demonstrates superior performance compared to the other three clustering methods when the number of clusters is 2. High-risk subtypes of DPD can be effectively distinguished in both the PPMI and NACC datasets. A traditional logistic regression model was developed based on rapid-eye-movement behavior disorder, UPDRS I score, UPDRS II score, and ptau in high-risk subgroups. This model exhibits a diagnostic efficacy (AUC = 0.731) that surpasses that of the traditional regression model constructed using the entire PPMI cohort (AUC = 0.674). The prediction model based on high-risk subtypes had AUC values of 0.853 and 0.81 in the training and testing subtypes, sensitivities of 0.765 and 0.786, and specificities of 0.771 and 0.815, respectively. The AUC, sensitivity, and specificity in the nonhigh-risk subtype were 0.859, 0.654, and 0.852, respectively.

CONCLUSION

By identifying MRI structural radiomics and clinical features as potential biomarkers, the radiomic approach and UCA provide new insights into the pathophysiology of DPD to support the clinical diagnosis with high prediction accuracy.

Optimal dose and type of exercise improve walking velocity in adults with Parkinson's disease: a systematic review and Bayesian network meta-analysis

To examine the dose-response relationship between specific types of exercise for improving walking velocity in Parkinson's disease (PD). This systematic review and network meta-analysis included searches of PubMed, Medline, Embase, PsycINFO, Cochrane Library, and Web of Science were searched from inception until February 18th, 2024. Data analysis was performed using R software with the MBNMA and RJAGS packages. Outcome indicators were measured as mean standard deviation (SMD) along with 95% confidence intervals (95% CrI). The network's risk of bias was independently evaluated by two reviewers employing the ROB2 tool. Our review encompassed 54 studies with 2,828 PD patients, examining the dose-response effects of different exercises on walking velocity. Aerobic Exercise (AE) demonstrated the greatest improvement at an optimal dose of 1,400 METs-min/week (SMD:1.215, 95% Crl: 0.113 to 2.306). Both Multicomponent Exercise (Mul) (SMD: 1.202, 95% Crl: 0.193 to 2.231) and Sensory Exercise (SE) (SMD: 0.649, 95% Crl: 0.139 to 1.183) showed optimal outcomes at a dose of 1,000 METs-min/week. Resistance Training (RT) was most effective at 750 METs-min/week (SMD:0.778, 95% Crl: 0.062 to 1.549), while Mind-Body Exercise (MBE) yielded significant improvements at a lower optimal dose of 500 METs-min/week (SMD: 0.580, 95% Crl: 0.218 to 1.137), offering valuable insights for exercise prescription in PD management. Various types of exercise showed specific optimal benefits at corresponding doses, among which AE was the most effective in improving the walking speed of PD patients at 1,400 Mets*min/week.Trial registration: PROSPERO (CRD42024506919).

Longitudinal associations between cerebrospinal fluid glial activation markers, depression, and dopamine transporter availability in patients with Parkinson's disease

BACKGROUND

Depression and decreased dopamine transporter (DAT) availability are prevalent in Parkinson's disease (PD), yet early predictive biomarkers are lacking. This study investigates the longitudinal associations between cerebrospinal fluid (CSF) neuroglial activation markers, sTREM2 and YKL-40, and depression, as well as DAT availability, in PD patients.

METHODS

We analyzed data from 172 PD subjects and 80 matched healthy controls from a large longitudinal study. A generalized linear mixed-effects model assessed the longitudinal associations of CSF sTREM2 and YKL-40 with depression and DAT availability. Causal mediation analysis determined if DAT decline mediated the effects of sTREM2 and YKL-40 on depression.

RESULTS

Cross-sectional analysis revealed a negative correlation between CSF sTREM2 and baseline depression scores in PD patients. CSF YKL-40 negatively correlated with baseline left caudate nucleus, left anterior putamen, and right anterior putamen specific binding ratios (SBR). Longitudinally, higher baseline CSF sTREM2 predicted faster depression progression (β = 0.828, p < 0.001) and a rapid decline in right putamen SBR (β = 0.072, p = 0.016). Similarly, higher baseline CSF YKL-40 predicted faster depression progression (β = 0.586, p = 0.004) and a decline in left anterior putamen SBR (β = 0.058, p = 0.035). Causal mediation analysis indicated that baseline CSF sTREM2 accelerated depression progression via its effect on right putamen and right anterior putamen SBR (Indirect effect = 0.103, p = 0.020; Indirect effect = 0.129, p = 0.016).

CONCLUSION

CSF sTREM2 and YKL-40 are effective predictors for depression and DAT decline in PD, suggesting that neuroglial activation-induced dopaminergic neuron apoptosis significantly contributes to depression onset in PD.

Melatonin alleviates LPS-induced depression-like behavior in mice by inhibiting ferroptosis by regulating RNA methylation-mediated SIRT6/Nrf2/HO-1 pathway

PURPOSE

The objective of this study is to investigate the impact of ferroptosis on depression and elucidate the molecular mechanism underlying melatonin's inhibitory effect on ferroptosis in the treatment of depression.

METHODS

In this study, a depression-like behavior model was induced in mice using LPS, and the effect of melatonin on depression-like behavior was evaluated through behavioral experiments (such as forced swimming test (FST) and sucrose preference test (SPT)). Additionally, molecular biological techniques (including real-time fluorescence quantitative PCR, Western blotting, immunoprecipitation) were employed to detect the expression levels and interactions of METTL3, SIRT6 and ferroptosis-related genes in mouse brain tissue. Furthermore, both in vitro and in vivo experiments were conducted to verify the regulatory effect of melatonin on Nrf2/HO-1 pathway and explore its potential molecular mechanism for regulating ferroptosis.

RESULTS

Melatonin was found to significantly ameliorate depression-like behavior in mice, as evidenced by reduced immobility time in the forced swimming test and increased sucrose intake in the sucrose preference test. Subsequent investigations revealed that melatonin modulated SIRT6 stability through METTL3-mediated ubiquitination of SIRT6, leading to its degradation. As a deacetylase, SIRT6 plays a pivotal role in cellular metabolism regulation and antioxidative stress response. This study elucidated potential signaling pathways involving Nrf2/HO-1 through which SIRT6 may exert its effects.

CONCLUSION

The findings suggest that melatonin can improve depressive behavior by suppressing ferroptosis and protecting neurons through its antioxidant properties. Additionally, targeting the Nrf2/HO-1 pathway via METTL3 and NEDD4 regulation may be a potential therapeutic approach for depression.

Serum neurotransmitter analysis of motor and non-motor symptoms in Parkinson's patients

Clinical symptoms of Parkinson's disease (PD) are classified into motor and non-motor symptoms. Mental disorders, especially depression, are one of the major non-motor manifestations of PD. However, the underlying mechanisms remain poorly understood. In the present study, 21 neurotransmitters associated with mental disorders were measured in serum samples from patients and controls using the ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) assay. Additionally, five clinical scales-the MDS Unified Parkinson's Disease Rating Scale (UPDRS), the Non-Motor Symptoms Scale (NMSS), the Mini-Mental State Examination (MMSE), the Hamilton Anxiety Scale (HAMA), and the Hamilton Depression Scale (HAMD)-were used to evaluate the severity of both motor and non-motor symptoms in PD patients. Analysis of neurotransmitter metabolism revealed significant changes in the tryptophan (Trp) metabolic pathway in PD patients. Specifically, levels of Trp, kynurenine (KYN), kynurenic acid (KA), nicotinamide (NAM), and 5-methoxyltryptamine (MeOTA) were substantially decreased. Additionally, three other excitation/inhibiting amino acids-glutamic acid (Glu), 4-aminobutyric acid (GABA), and aspartic acid (Asp)-also declined. Moreover, neurotransmitter conversion ratios, such as KA/KYN, nicotinamide/niacin (NAM/NA), 5-hydroxytryptophan/tryptophan (5-HTP/Trp), and quinolinic acid/kynurenic acid (QA/KA), provided more dynamic insights into disrupted neurotransmitter metabolism. Correlation analyses between scale scores and neurotransmitter levels showed that concentrations of xanthurenic acid (XA) and the turnover rate of 3-hydroxykynurenine (3-HK) were negatively correlated with UPDRS scores, while 5-hydroxytryptamine (5-HT) and GABA levels were negatively correlated with non-motor symptoms in PD patients. In summary, this study elucidates, for the first time, the potential association and dynamics between altered neurotransmitter metabolism and the etiology of PD in terms of motor and non-motor functions. These findings offer novel biomarkers and therapeutic targets for the treatment of PD.

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.

P1 evoked by facial expression images is enhanced in Parkinson's disease patients with depressive symptoms

Introduction

Depressive symptoms are most common non-motor symptoms in Parkinson's disease (PD), which is often overlooked due to absence of rapid and objective diagnostic biomarkers. Electroencephalography (EEG)-based event-related potentials (ERPs) is commonly used to assess emotional processes. The aim of this study was to investigate changes in ERPs in PD patients exhibiting depressive symptoms and to provide a reliable biomarker for assisting in the diagnosis of PD with depressive symptoms.

Methods

We conducted a case-control study involving 30 PD patients with (dPD group) or without depressive symptoms (nPD group) and 13 age matched healthy controls (HC). We recorded EEG of the patients during the emotional picture stimulation task and analyzed the difference in the early ERPs potentials (P1, N170, early posterior negativity) and their correlation with the severity of symptoms in PD patients.

Results

Our results found that P1 amplitude in the occipital region of the dPD group in response to emotional faces was significantly higher than that of nPD and HC group, and it was positively correlated with severity of depressive symptoms in PD patients.

Conclusion

Our study shows that facial expression-induced enhancement of P1 amplitude can be utilized as a rapid and objective indicator to screen for depressive symptoms in PD.

Serum neurofilament light chain, markers of systemic inflammation and clinically relevant depressive symptoms in US adults

BACKGROUND

Neurofilament light chain (NFL), a biomarker of neuroaxonal damage, has been linked to inflammation and depressive disorders, albeit with inconsistent results. We aimed to evaluate the association between serum NFL concentration and clinically relevant depressive symptoms in the general population and to examine the potential involvement of systemic inflammation in this association.

METHODS

The data of 1881 adults aged 20-75 years were extracted from the National Health and Nutrition Examination Survey (NHANES) 2013-2014 cycle. Serum NFL levels were quantified using a highly sensitive immunoassay. Further, markers of systemic inflammation, including systemic immune inflammation index (SII), system inflammation response index (SIRI), and white blood cell (WBC) counts were calculated based on whole blood cell counts. Clinically relevant depressive symptoms were evaluated using the 9-item Patient Health Questionnaire (PHQ-9) with a cut-off score of 10.

RESULTS

After adjusting for potential confounders, we found that each one-unit increase in ln-transformed serum NFL concentration was significantly associated with a 1.37-fold increase in the risk of clinically relevant depressive symptoms (95 % confidence interval [CI]: 1.06, 1.77; p = 0.017). Serum NFL level was significantly related to increased SII (regression coefficient [β] = 0.04, 95%CI: 0.01, 0.08; p = 0.027), SIRI (β = 0.09, 95%CI: 0.05, 0.14; p < 0.001), and WBC (β = 0.05, 95%CI: 0.03, 0.07; p < 0.001), respectively. These significant associations were observed only in elderly participants.

LIMITATIONS

The cross-sectional study design is limited in causal inference.

CONCLUSIONS

Our findings indicate that serum NFL levels are related to an increased risk of clinically relevant depressive symptoms and higher levels of markers of systemic inflammation.

Progress of non‐motor symptoms in early‐onset Parkinson's disease

Parkinson's disease (PD) is a common degenerative disease of the central nervous system that is characterized by movement disorders and non‐motor symptoms (NMSs). The associated NMSs primarily include neuropsychiatric symptoms, autonomic dysfunction, sleep‐wake disorders, pain, fatigue, and hyposmia. These NMSs can occur at any stage of PD, especially before the onset of motor symptoms, and may affect a patient's quality of life more than motor symptoms. Although PD is most commonly diagnosed in people over 65 years, some patients exhibit symptom onset before the age of 50, which is clinically known as early‐onset Parkinson's disease (EOPD). The high heterogeneity and incidence of EOPD‐associated NMSs can lead to the misdiagnosis of EOPD as other neurodegenerative diseases. In this review, we discuss the research progress related to NMSs in patients with EOPD, focusing on neuropsychiatric disorders, autonomic dysfunction, sleep disorders, and sensory impairment, and outline the association of NMSs with different genotypic alterations, with the aim of providing assistance in the clinical management of patients.

Disentangling gray matter atrophy and its neurotransmitter architecture in drug-naïve Parkinson's disease: an atlas-based correlation analysis

Parkinson's disease is characterized by multiple neurotransmitter systems beyond the traditional dopaminergic pathway, yet their influence on volumetric alterations is not well comprehended. We included 72 de novo, drug-naïve Parkinson's disease patients and 61 healthy controls. Voxel-wise gray matter volume was evaluated between Parkinson's disease and healthy controls, as well as among Parkinson's disease subgroups categorized by clinical manifestations. The Juspace toolbox was utilized to explore the spatial relationship between gray matter atrophy and neurotransmitter distribution. Parkinson's disease patients exhibited widespread GM atrophy in the cerebral and cerebellar regions, with spatial correlations with various neurotransmitter receptors (FDR-P < 0.05). Cognitively impaired Parkinson's disease patients showed gray matter atrophy in the left middle temporal atrophy, which is associated with serotoninergic, dopaminergic, cholinergic, and glutamatergic receptors (FDR-P < 0.05). Postural and gait disorder patients showed atrophy in the right precuneus, which is correlated with serotoninergic, dopaminergic, gamma-aminobutyric acid, and opioid receptors (FDR-P < 0.05). Patients with anxiety showed atrophy in the right superior orbital frontal region; those with depression showed atrophy in the left lingual and right inferior occipital regions. Both conditions were linked to serotoninergic and dopaminergic receptors (FDR-P < 0.05). Parkinson's disease patients exhibited regional gray matter atrophy with a significant distribution of specific neurotransmitters, which might provide insights into the underlying pathophysiology of clinical manifestations and develop targeted intervention strategies.

Research progress on the protection and mechanism of active peptides in Alzheimer's disease and Parkinson's disease

Neurodegenerative diseases are the main causes of death and morbidity among elderly people worldwide. From the pathological point of view, oxidative stress, neuroinflammation, mitochondrial damage and apoptosis are the causes of neuronal diseases, and play a harmful role in the process of neuronal cell death and neurodegeneration. The most common neurodegenerative diseases are Alzheimer's disease(AD) and Parkinson's disease(PD), and there is no effective treatment. The physiological role of active peptides in the human body is significant. Modern medical research has found that animal and plant peptides, natural peptides in human body, can act on the central nervous system, and their active components can improve learning and memory ability, and play the roles of antioxidation, anti-inflammation, anti-apoptosis and maintaining the structure and function of mitochondria. This review reviews the reports on neurodegenerative diseases such as AD and PD by active peptides from animals and plants and natural peptides from the human body, and summarizes the neuroprotective mechanism of peptides. A theoretical basis for further research and development of active peptides was provided by examining the research and application of peptides, which provided a theoretical basis for further research and development.

Parkin, a Parkinson's disease-associated protein, mediates the mitophagy that plays a vital role in the pathophysiology of major depressive disorder

Depression is a complex mood disorder with multifactorial etiology and is also the most frequent non-motor symptom of Parkinson's disease. Emerging research suggests a potential link between mitochondrial dysfunction and the pathophysiology of major depressive disorder. By synthesizing current knowledge and research findings, this review sheds light on the intricate relationship between Parkin, a protein classically associated with Parkinson's disease, and mitochondrial quality control mechanisms (e.g., mitophagy, mitochondrial biogenesis, and mitochondrial dynamic), specifically focusing on their relevance in the context of depression. Additionally, the present review discusses therapeutic strategies targeting Parkin-medicated mitophagy and calls for further research in this field. These findings suggest promise for the development of novel depression treatments through modulating Parkin-mediated mitophagy.

Z-ligustilide provides a neuroprotective effect by regulating the phenotypic polarization of microglia via activating Nrf2-TrxR axis in the Parkinson's disease mouse model

The polarization phenotype of microglia is critical in the progression of Parkinson's disease (PD). Molecules that can polarize microglia toward the M2 phenotype represent a promising class of compounds for anti-PD medications. Z-ligustilide (ZLG) is a naturally occurring enol ester with diverse pharmacological properties, especially in neuroprotection. For the first time, we investigated the effect of ZLG on anti-PD and elucidated its underlying mechanism. The results primarily showed that ZLG attenuated motor deficits in mice and prevented the loss of dopaminergic neurons in the substantia nigra. Mechanistically, ZLG alleviates oxidative stress-induced apoptosis of microglia by triggering the endogenous antioxidant system. Besides, ZLG modulated phenotypic polarization of the microglia through the activation of the Nrf2-TrxR axis, leading to microglia polarization towards the M2 phenotype. Taken together, our research showed that ZLG is a prospective therapy candidate for PD by altering microglia polarization and restoring redox equilibrium through the Nrf2-TrxR axis.

The Brain-Gut-Bone Axis in Neurodegenerative Diseases: Insights, Challenges, and Future Prospects

Neurodegenerative diseases are global health challenges characterized by the progressive degeneration of nerve cells, leading to cognitive and motor impairments. The brain-gut-bone axis, a complex network that modulates multiple physiological systems, has gained increasing attention owing to its profound effects on the occurrence and development of neurodegenerative diseases. No comprehensive review has been conducted to clarify the triangular relationship involving the brain-gut-bone axis and its potential for innovative therapies for neurodegenerative disorders. In light of this, a new perspective is aimed to propose on the interplay between the brain, gut, and bone systems, highlighting the potential of their dynamic communication in neurodegenerative diseases, as they modulate multiple physiological systems, including the nervous, immune, endocrine, and metabolic systems. Therapeutic strategies for maintaining the balance of the axis, including brain health regulation, intestinal microbiota regulation, and improving skeletal health, are also explored. The intricate physiological interactions within the brain-gut-bone axis pose a challenge in the development of effective treatments that can comprehensively target this system. Furthermore, the safety of these treatments requires further evaluation. This review offers a novel insights and strategies for the prevention and treatment of neurodegenerative diseases, which have important implications for clinical practice and patient well-being.

Risk of Parkinson's disease and depression severity in different populations: A two-sample Mendelian randomization analysis

BACKGROUND

Depression is widely recognized as a common non-motor symptom of Parkinson's disease (PD). Across different studies, the reported prevalence of depression in PD varies widely, ranging from 2.7% to 90%, but it is unclear whether this association is due to genetic or acquired factors. Whether there is a causal relationship remains unknown. The aim of this study was to use a two-sample Mendelian randomization (MR) approach to investigate the causal effect of PD on depression.

METHODS

Analyses were conducted separately for individuals of European and East Asian ancestry using publicly available summary data from genome-wide association studies. Depression was divided into two categories: ever depressed for a whole week and major depressive disorder (MDD). PD data were used as the exposure and were obtained from the International Parkinson's Disease Genomics Consortium and the BioBank Japan PheWeb, while depression data were used as the outcome and were obtained from the ntegrative Epidemiology Unit (IEU) Open GWAS Project(A public GWAS database） and the Psychiatric Genomics Consortium. The influence of PD on depression was assessed using inverse variance weighted (IVW), weighted median, MR-Egger, and weighted mode methods. Heterogeneity and pleiotropy were tested, and the results were validated using FinnGen GWAS data from version R9.

RESULTS

In individuals of European ancestry, there was a causal relationship between PD and ever depressed for a whole week (IVW method, odds ratio [OR] = 0.990; 95% CI, 0.984-0.996; p = .002), but no causal relationship was observed between PD and MDD (IVW method, OR = 0.974; 95% CI, 0.942-1.009; p = .141). In individuals of East Asian ancestry, no causal relationship was observed between PD and ever depressed for a whole week (IVW method, OR = 1.001; 95% CI, 0.829-1.209; p = .990) and between PD and MDD (IVW method, OR = 1.017; 95% CI, 0.982-1.052; p = .342). The results of the three additional analysis methods were similar to those of the IVW method, and there was no heterogeneity according to Cochran's Q-test. There was no evidence of pleiotropy based on MR-Egger intercept test and MR-PRESSO. The FinnGen validation dataset supported these findings. The results are stable and reliable.

CONCLUSION

The observed increase in depression among PD patients could potentially be attributed to modifiable acquired factors. Consequently, there is an urgent need to strengthen the management of PD patients in order to prevent the development of depression in the future.

Unraveling the complexity of human brain: Structure, function in healthy and disease states

The human brain stands as an intricate organ, embodying a nexus of structure, function, development, and diversity. This review delves into the multifaceted landscape of the brain, spanning its anatomical intricacies, diverse functional capacities, dynamic developmental trajectories, and inherent variability across individuals. The dynamic process of brain development, from early embryonic stages to adulthood, highlights the nuanced changes that occur throughout the lifespan. The brain, a remarkably complex organ, is composed of various anatomical regions, each contributing uniquely to its overall functionality. Through an exploration of neuroanatomy, neurophysiology, and electrophysiology, this review elucidates how different brain structures interact to support a wide array of cognitive processes, sensory perception, motor control, and emotional regulation. Moreover, it addresses the impact of age, sex, and ethnic background on brain structure and function, and gender differences profoundly influence the onset, progression, and manifestation of brain disorders shaped by genetic, hormonal, environmental, and social factors. Delving into the complexities of the human brain, it investigates how variations in anatomical configuration correspond to diverse functional capacities across individuals. Furthermore, it examines the impact of neurodegenerative diseases on the structural and functional integrity of the brain. Specifically, our article explores the pathological processes underlying neurodegenerative diseases, such as Alzheimer's, Parkinson's, and Huntington's diseases, shedding light on the structural alterations and functional impairments that accompany these conditions. We will also explore the current research trends in neurodegenerative diseases and identify the existing gaps in the literature. Overall, this article deepens our understanding of the fundamental principles governing brain structure and function and paves the way for a deeper understanding of individual differences and tailored approaches in neuroscience and clinical practice-additionally, a comprehensive understanding of structural and functional changes that manifest in neurodegenerative diseases.

Non-coding RNAs in Parkinson's disease: Regulating SNCA and alpha-synuclein aggregation

Parkinson's disease is one of the vital neurodegenerative ailments attributed to a rise in Alpha-synuclein proteins leading to the advancement of motor and cognitive deterioration. Interestingly, in PD lncRNAs, miRNAs and siRNAs are also key regulators of SNCA and alpha-synuclein aggregation. This review will focus on the roles of these three types of small RNAs in trebling the development of PD through regulating SNCA expression or alpha-synuclein protein mediating the RNA from acting. Parkinson's disease is defined by the build-up of alpha-synuclein protein resulting predominantly from the elevated expression level of the SNCA gene. Non-coding RNAs have gained broad appeal as fundamental modulators of gene expression and protein aggregation dynamics, with significant implications on the aetiology of PD. LncRNAs modulate SNCA transcription and edit epigenetic modifications, while miRNA target mRNA is involved in the stability and translation of count alpha-synuclein. Considering all these data, siRNAs can achieve the precise gene silencing effect that directly induces the downregulation of SNCA mRNA. This review also summarizes some recent reports about the interaction between these ncRNAs with the SNCA gene and alpha-synuclein protein, each through its independent in addition to synergistic mechanisms. This review highlights the possibility of therapeutic interventions to perturb SNCA expression to prevent alpha-synuclein aggregation via targeting ncRNAs that might be spun off novel drug development for PD.

The effect of crocin on movement disorders and oxidative DNA damage in Parkinson's disease: Insights from a randomized controlled trial

BACKGROUND

Parkinson's disease (PD), the second most prevalent neurological disorder in the elderly, manifests with distinctive movement disorders, including bradykinesia, resting tremor, and stiffness. With a progressive course, current treatment strategies primarily target symptomatic relief. Crocin is a chemical compound isolated from the dry stigma of Crocus sativus, and has demonstrated neuroprotective properties.

OBJECTIVES

This study explores the impact of crocin on movement disorders and neuronal oxidative DNA damage in PD patients.

METHOD

Conducted as a randomized, blinded, and controlled trial, this research focused on patients aged 30 to 80 with idiopathic PD. Using the second and third parts of the movement disorder society-unified PD rating scale (MDS-UPDRS), aspects of daily life activity and movement disorders were assessed before and after an 8-week intervention. Patients in the crocin groups received capsules containing 30 mg of crocin twice daily. Additionally, the 8-hydroxy-2-deoxydiguanosine (8-OHdG) to urinary creatinine ratio (8-OHdG/uCr) was measured to evaluate neuronal oxidative DNA damage.

RESULTS

Out of the initially evaluated 164 patients, 30 were randomly assigned to each group, with 53 subjects completing the study. Within-group analysis revealed a significant improvement in the second and third parts of MDS-UPDRS after 8 weeks of crocin intervention (P < 0.05). However, the 8-OHdG/uCr did not show significant changes. The well-tolerated daily dose of 60 mg of crocin demonstrated minimal side effects.

CONCLUSION

This study establishes the efficacy of crocin in enhancing daily life activities and mitigating movement disorders, suggesting its potential as a supplementary intervention alongside conventional PD medications.

Study on the mechanism of gut microbiota in the pathogenetic interaction between depression and Parkinson 's disease

Depression and Parkinson's disease share pathogenetic characteristics, meaning that they can impact each other and exacerbate their respective progression. From a pathogenetic perspective, depression can develop into Parkinson's disease and is a precursor symptom of Parkinson's disease; Parkinson's disease is also often accompanied by depression. From a pharmacological perspective, the use of antidepressants increases the risk of developing Parkinson's disease, and therapeutic medications for Parkinson's disease can exacerbate symptoms of depression. Therefore, identifying how Parkinson's disease and depression impact each other in their development is key to formulating preventive measures and targeted treatment. One commonality in the pathogenesis of depression and Parkinson's disease are alterations in the gut microbiota, with mechanisms interacting in neural, immune inflammatory, and neuroendocrine pathways. This paper reviews the role of gut microbiota in the pathogenesis of depression and Parkinson's disease; conducts a study of the relationship between both conditions and medication; and suggests that dysregulated gut microbiota may be a key factor in explaining the relationship between Parkinson's disease and depression. Finally, on the basis of these findings, this article hopes to provide suggestions that new ideas for the prevention and treatment of depression and Parkinson's disease.

Can exercise benefits be harnessed with drugs? A new way to combat neurodegenerative diseases by boosting neurogenesis

Adult hippocampal neurogenesis (AHN) is affected by multiple factors, such as enriched environment, exercise, ageing, and neurodegenerative disorders. Neurodegenerative disorders can impair AHN, leading to progressive neuronal loss and cognitive decline. Compelling evidence suggests that individuals engaged in regular exercise exhibit higher production of proteins that are essential for AHN and memory. Interestingly, specific molecules that mediate the effects of exercise have shown effectiveness in promoting AHN and cognition in different transgenic animal models. Despite these advancements, the precise mechanisms by which exercise mimetics induce AHN remain partially understood. Recently, some novel exercise molecules have been tested and the underlying mechanisms have been proposed, involving intercommunications between multiple organs such as muscle-brain crosstalk, liver-brain crosstalk, and gut-brain crosstalk. In this review, we will discuss the current evidence regarding the effects and potential mechanisms of exercise mimetics on AHN and cognition in various neurological disorders. Opportunities, challenges, and future directions in this research field are also discussed.

The Aggregation of α-Synuclein in the Dorsomedial Striatum Significantly Impairs Cognitive Flexibility in Parkinson's Disease Mice

This study focused on α-synuclein (α-syn) aggregation in the dorsomedial striatum (DMS) so as to investigate its role in the cognitive flexibility of Parkinson's disease (PD). Here, we investigated the cognitive flexibility by assessing reversal learning abilities in MPTP-induced subacute PD model mice and in C57BL/6J mice with α-syn aggregation in the DMS induced by adenovirus (AAV-SNCA) injection, followed by an analysis of the target protein's expression and distribution. PD mice exhibited impairments in reversal learning, positively correlated with the expression of phosphorylated α-syn in the DMS. Furthermore, the mice in the AAV-SNCA group exhibited reversal learning deficits and a reduction in acetylcholine levels, accompanied by protein alterations within the DMS. Notably, the administration of a muscarinic receptor 1 (M1R) agonist was able to alleviate the aforementioned phenomenon. These findings suggest that the impaired cognitive flexibility in PD may be attributed to the diminished activation of acetylcholine to M1R caused by α-syn aggregation.

Escitalopram moderately outperforms citalopram towards anti-neuroinflammation and neuroprotection in 6-hydroxydopamine-induced mouse model of Parkinson's disease

Citalopram and escitalopram are structurally close-related antidepressants and both forms are widely used in the world. We aimed to comparatively evaluate the anti-neuroinflammatory and neuroprotective effects of escitalopram and citalopram in Parkinson's disease (PD) mouse model. Mice were randomly divided into six groups and received 6-hydroxydopamine (6-OHDA) or vehicle administration. The mice were then treated with escitalopram, citalopram or saline for consecutive 7 days. Behaviors, neuroinflammation, neurotransmitters, and neurotoxicity were assessed. Results showed that citalopram but not escitalopram worsened body weight loss and increased freezing time in the PD mice. Both drugs had no impact on the anxiety-like behaviors but ameliorated the depressive-like behaviors as in elevated plus maze and sucrose splash tests. Escitalopram but not citalopram ameliorated motor discoordination in the PD mice as in rotarod test. In accordance, escitalopram but not citalopram attenuated the 6-OHDA-induced nigrostriatal dopaminergic loss. Further mechanistic investigations showed that both drugs mitigated activations of microglia and astrocytes and/or levels of pro-inflammatory cytokines in the PD mice, but escitalopram showed appreciably better effects in the substantia nigra. Neurotransmitter examination in the prefrontal cortex suggested that the two drugs had comparable effects on the disturbed neurotransmitters in the PD mice, but citalopram was prone to disrupt certain normal homeostasis. In conclusion, escitalopram is moderately superior than citalopram to suppress neuroinflammation and to protect against dopaminergic neuronal death and motor discoordination in the 6-OHDA-induced PD mice. Our findings imply that escitalopram shall be prescribed with priority over citalopram to treat PD patients with depression as escitalopram may meanwhile provide greater additional benefits to the patients.

New insights into the effects of serotonin on Parkinson's disease and depression through its role in the gastrointestinal tract

Neuropsychiatric and neurodegenerative disorders are frequently associated with gastrointestinal (GI) co-pathologies. Although the central and enteric nervous systems (CNS and ENS, respectively) have been studied separately, there is increasing interest in factors that may contribute to conditions affecting both systems. There is compelling evidence that serotonin (5-HT) may play an important role in several gut-brain disorders. It is well known that 5-HT is essential for the development and functioning of the CNS. However, most of the body's 5-HT is produced in the GI tract. A deeper understanding of the specific effects of enteric 5-HT on gut-brain disorders may provide the basis for the development of new therapeutic targets. This review summarizes current data focusing on the important role of 5-HT in ENS development and motility, with particular emphasis on novel aspects of 5-HT signaling in conditions where CNS and ENS comorbidities are common, such as Parkinson's disease and depressive disorders.

Bidirectional communication of the gut-brain axis: new findings in Parkinson's disease and inflammatory bowel disease

Parkinson's disease (PD) and inflammatory bowel disease (IBD) are the two chronic inflammatory diseases that are increasingly affecting millions of people worldwide, posing a major challenge to public health. PD and IBD show similarities in epidemiology, genetics, immune response, and gut microbiota. Here, we review the pathophysiology of these two diseases, including genetic factors, immune system imbalance, changes in gut microbial composition, and the effects of microbial metabolites (especially short-chain fatty acids). We elaborate on the gut-brain axis, focusing on role of gut microbiota in the pathogenesis of PD and IBD. In addition, we discuss several therapeutic strategies, including drug therapy, fecal microbiota transplantation, and probiotic supplementation, and their potential benefits in regulating intestinal microecology and relieving disease symptoms. Our analysis will provide a new understanding and scientific basis for the development of more effective therapeutic strategies for these diseases.

Decreased resting-state functional connectivity and brain network abnormalities in the prefrontal cortex of elderly patients with Parkinson's disease accompanied by depressive symptoms

This study aimed to explore the brain network characteristics in elderly patients with Parkinson's disease (PD) with depressive symptoms. Thirty elderly PD patients with depressive symptoms (PD-D) and 26 matched PD patients without depressive symptoms (PD-NOD) were recruited based on HAMD-24 with a cut-off of 7. The resting-state functional connectivity (RSFC) was conducted by 53-channel functional near-infrared spectroscopy (fNIRS). There were no statistically significant differences in MMSE scores, disease duration, Hoehn-Yahr stage, daily levodopa equivalent dose, and MDS-UPDRS III between the two groups. However, compared to the PD-NOD group, the PD-D group showed significantly higher MDS-UPDRS II, HAMA-14, and HAMD-24. The interhemispheric FC strength and the FC strength between the left dorsolateral prefrontal cortex (DLPFC-L) and the left frontal polar area (FPA-L) was significantly lower in the PD-D group (FDR p < 0.05). As for graph theoretic metrics, the PD-D group had significantly lower degree centrality (aDc) and node efficiency (aNe) in the DLPFC-L and the FPA-L (FDR, p < 0.05), as well as decreased global efficiency (aEg). Pearson correlation analysis indicated moderate negative correlations between HAMD-24 scores and the interhemispheric FC strength, FC between DLPFC-L and FPA-L, aEg, aDc in FPA-L, aNe in DLPFC-L and FPA-L. In conclusion, PD-D patients show decreased integration and efficiency in their brain networks. Furthermore, RSFC between DLPFC-L and FPA-L regions is negatively correlated with depressive symptoms. These findings propose that targeting DLPFC-L and FPA-L regions via non-invasive brain stimulation may be a potential intervention for alleviating depressive symptoms in elderly PD patients.

The enigma of depression in corticobasal degeneration, a frequent but poorly understood co-morbidity

Depression is one of the most frequent neuropsychiatric symptoms in corticobasal degeneration (CBD), a rare, sporadic, and late-onset progressive neurodegenerative disorder of unknown etiology. It is clinically characterized by a levodopa-poorly responsible akinetic-rigid syndrome, apraxia, limb dystonia, cognitive, mood, behavioral, and language disorders. This 4-repeat (4R) tauopathy is morphologically featured by asymmetric frontoparietal atrophy, neuronal loss, and gliosis in cortex and subcortex including substantia nigra, ballooned/achromatic neurons with filamentous 4R tau aggregates in cortex and striatum, widespread thread-like structures, pathognomonic "astroglial plaques", "tufted astrocytes", and numerous "coiled bodies" (in astrocytes and oligodendroglia) in cerebral white matter. CBD is non-specific, as pathologically proven cases include several clinical phenotypes. Pubmed and Google Scholar were systematically analyzed until October 2023, with focus on the prevalence, clinical manifestation, neuroimaging data, and treatment options of depression in CBD. Its prevalence is about 30-40% which is more frequent than in most other atypical parkinsonian syndromes. Depression usually does not correlate with motor and other clinical parameters, suggesting different pathophysiological mechanisms. Asymmetric atrophy and hypometabolism of frontoparietal cortical areas are associated with disruption of fronto-subcortical circuits, nigrostriatal dopaminergic, and cholinergic deficiency. Since no specific neuroimaging, neuropathological, or biomarker studies of depression in CBD are available, its pathobiological mechanisms and pathogenesis are poorly understood. Antidepressive therapy may be useful, but is often poorly tolerated. Depression in CBD, like in other parkinsonian syndromes, may be related to multi-regional patterns of cerebral disturbances and complex pathogenic mechanisms that deserve further elucidation as a basis for early diagnosis and adequate treatment to improve the quality of life in this fatal disease.

The simultaneous presence of demoralization, apathy, and depression has a detrimental impact on both cognitive function and motor symptoms in Parkinson's disease patients

Objective

Parkinson's disease (PD) is marked not only by motor symptoms but also by neuropsychiatric manifestations, including demoralization, apathy, and depression. Understanding the clinical distribution and characteristics of these co-occurring symptoms is crucial for improving quality of life of PD patients.

Methods

This study enrolled 195 Chinese PD patients from Xinhua Hospital affiliated to Shanghai Jiao Tong University School of Medicine. The study involved analyzing the clinical characteristics related to the simultaneous presence of demoralization, apathy, and depression in PD patients. Linear regression was employed to elucidate the linear trend between the quantity of negative neuropsychiatric symptoms and cognitive function, as well as motor symptoms and motor complications. SPSS mediation models were utilized to investigate whether the severity of cognitive function mediated the connection between multiple negative neuropsychiatric symptoms and motor symptoms.

Results

Among PD patients, a notable 57.5% experience the presence of multiple concurrent negative neuropsychiatric symptoms. Our investigation unveiled a correlation where patients with more negative neuropsychiatric symptoms displayed heightened cognitive impairment (P=0.048) and more severe motor symptoms (P=0.024), following a linear trend with increasing symptom numbers. Additionally, cognitive impairment played a partial mediating role in the impact of multiple negative neuropsychiatric symptoms on motor symptoms (β=0.747; 95% bootstrap confidence interval: 0.195 to 1.532).

Conclusions

The co-occurrence of these negative neuropsychiatric symptoms has the potential to worsen cognitive function and motor symptoms in PD patients. Moreover, cognitive impairment was identified as playing a partial mediating role in the relationship between multiple negative neuropsychiatric symptoms and motor symptoms.

Effect of Transcranial Direct Current Stimulation (tDCS) on Depression in Parkinson's Disease-A Narrative Review

INTRODUCTION

Depression is the most prevalent comorbid neuropsychiatric condition in individuals with Parkinson's disease (PD), and its underlying mechanisms are not yet fully understood. Current treatment methods are characterised by moderate effectiveness and possible side effects, prompting the search for new non-invasive and safe treatment methods.

METHODS

This narrative review explores the use of transcranial direct current stimulation (tDCS) in the treatment of depression in PD, based on neuropsychological measures. Searches were conducted in the PubMed/Medline, Research Gate, and Cochrane databases.

RESULTS

Nine relevant studies were identified, where depression scores served as either primary or secondary outcomes. Stimulation protocols displayed heterogeneity, especially concerning choice of stimulation site. Patient samples were also heterogeneous. The majority of the studies incorporated anodal stimulation targeting the left dorsolateral prefrontal cortex (DLPFC). The results revealed a reduction in depression scores among PD patients following tDCS. Potential mechanisms through which tDCS may alleviate depression in PD were discussed and recommendations for future research were made.

CONCLUSIONS

Preliminary evidence suggests that tDCS applied anodally to the left DLPFC reduces depression scores in people with PD; however, due to the heterogeneity of the studies analysed, the use of tDCS in this field should be approached with caution and warrants further validation and confirmation.

Exploring Parkinson's Disease-Associated Depression: Role of Inflammation on the Noradrenergic and Serotonergic Pathways

Parkinson's disease (PD) is a multifactorial disease, with genetic and environmental factors contributing to the disease onset. Classically, PD is a movement disorder characterized by the loss of dopaminergic neurons in the nigrostriatal pathway and intraneuronal aggregates mainly constituted of the protein α-synuclein. However, PD patients also display non-motor symptoms, including depression, which have been linked to functional abnormalities of non-dopaminergic neurons, including serotonergic and noradrenergic ones. Thus, through this comprehensive literature review, we shed light on the noradrenergic and serotonergic impairment linked to depression in PD, focusing on the putative involvement of inflammatory mechanisms.

Trends and hotspots in non-motor symptoms of Parkinson's disease: a 10-year bibliometric analysis

Non-motor symptoms are prevalent among individuals with Parkinson's disease (PD) and seriously affect patient quality of life, even more so than motor symptoms. In the past decade, an increasing number of studies have investigated non-motor symptoms in PD. The present study aimed to comprehensively analyze the global literature, trends, and hotspots of research investigating non-motor symptoms in PD through bibliometric methods. Studies addressing non-motor symptoms in the Web of Science Core Collection (WoSCC), published between January 2013 and December 2022, were retrieved. Bibliometric methods, including the R package "Bibliometrix," VOS viewer, and CiteSpace software, were used to investigate and visualize parameters, including yearly publications, country/region, institution, and authors, to collate and quantify information. Analysis of keywords and co-cited references explored trends and hotspots. There was a significant increase in the number of publications addressing the non-motor symptoms of PD, with a total of 3,521 articles retrieved. The United States was ranked first in terms of publications (n = 763) and citations (n = 11,269), maintaining its leadership position among all countries. King's College London (United Kingdom) was the most active institution among all publications (n = 133) and K Ray Chaudhuri was the author with the most publications (n = 131). Parkinsonism & Related Disorders published the most articles, while Movement Disorders was the most cited journal. Reference explosions have shown that early diagnosis, biomarkers, novel magnetic resonance imaging techniques, and deep brain stimulation have become research "hotspots" in recent years. Keyword clustering revealed that alpha-synuclein is the largest cluster for PD. The keyword heatmap revealed that non-motor symptoms appeared most frequently (n = 1,104), followed by quality of life (n = 502), dementia (n = 403), and depression (n = 397). Results of the present study provide an objective, comprehensive, and systematic analysis of these publications, and identifies trends and "hot" developments in this field of research. This work will inform investigators worldwide to help them conduct further research and develop new therapies.

Manganese activates autophagy and microglia M2 polarization against endoplasmic reticulum stress-induced neuroinflammation: Involvement of GSK-3β signaling

BACKGROUND

Endoplasmic reticulum (ER) stress-induced nerve cell damage has been known to be a hallmark feature of Mn-induced parkinsonism pathogenesis. However, several compensatory machineries, such as unfolded protein response (UPR), autophagy, and immune response, play an essential role in this damage, and the underlying molecular mechanisms are poorly understood.

METHODS

Neurobehavioral impairment was assessed using catwalk gait analysis and open field test. RNA-seq analyzed the differentially expressed genes (DEGs). TUNEL staining and immunohistochemical analysis evaluated the nerve cells apoptosis and microglial cell activation. Flow cytometry assay measured microglia M1/M2 polarization. Western blotting measured protein expression. Immunofluorescence staining was used to observe the target molecules' subcellular localization.

RESULTS

The study revealed that Mn caused a reduction in motor capacity, nerve cell apoptosis, and microglia activation with an imbalance in M1/M2 polarization, coupled with NF-κB signaling and PERK signaling activation. 4-PBA pretreatment could counteract these effects, while 3-MA administration exacerbated them. Additionally, autophagy could be activated by Mn. This activation could be further upregulated by 4-PBA pretreatment, whereas it was suppressed under 3-MA administration. Mn also decreased inactive GSK-3β, increased STAT3 signaling activation, and increased colocalization of GSK-3β and STAT3. These effects were strengthened by 4-PBA pretreatment, while 3-MA administration reversed them.

DISCUSSION

This study suggests that autophagy and M2 microglia polarization might be protective in Mn-induced ER stress damage, possibly through GSK-3β-ULK1 autophagy signaling and STAT3 signaling activation.

Effect of Zishen pingchan granules combined with pramipexole on serum BDNF, IL-1β, IL-6, CRP, TNF-α levels in depressed patients with Parkinson's disease: Results of a randomized, double-blind, controlled study

INTRODUCTION

Depression is a common comorbidity in Parkinson's Disease (PD) and treatment of depression can significantly support PD management. Zishen pingchan granules (ZPG), a traditional Chinese herbal formula, may help ameliorate depressive symptoms in PD patients. However, the molecular mechanisms underlying the effects of ZPG remain unclear. This study aimed to investigate the impact of ZPG on serum levels of brain-derived neurotrophic factor (BDNF), interleukin-1β (IL-1β), interleukin-6 (IL-6), C-reactive protein (CRP), and tumor necrosis factor-α (TNF-α) in PD patients with depression.

METHODS

Eighty PD patients treated with pramipexole but still experiencing mild to moderate depression symptoms were randomly allocated to a group receiving 12-week ZPG treatment (n = 40) or placebo (n = 40). The Hamilton Depression Scale 17 items (HAM-D-17) was utilized to evaluate changes in depressive symptoms from baseline over 12 weeks, while the Unified Parkinson's Disease Rating Scales (UPDRS) part 3 was employed to assess changes in motor symptoms over the same duration. Serum levels of BDNF, IL-1β, IL-6, CRP, and TNF-α were measured at baseline and post-treatment.

RESULTS

Seventy-one participants completed the study. Following treatment, both groups showed significantly reduced HAMD scores. The placebo group demonstrated a decrease in BDNF levels, while the ZPG group showed an increase in IL-6 levels post-treatment. In the examination of the group-time interaction, the ZPG group exhibited a greater decrease in HAMD scores and increase in IL-6 levels compared to the placebo group. Conversely, the placebo group showed a greater decrease in BDNF levels compared to the ZPG group. However, no significant group differences were observed in UPDRS part 3 change scores or serum levels of IL-1β, CRP, or TNF-α change from baseline.

CONCLUSION

ZPG may potentially ameliorate depressive symptoms in PD patients, with the potential mechanism involving mitigation of reductions in serum BDNF level and an increase in IL-6 level.

Downregulation of PACAP and the PAC1 Receptor in the Basal Ganglia, Substantia Nigra and Centrally Projecting Edinger-Westphal Nucleus in the Rotenone model of Parkinson's Disease

Numerous in vitro and in vivo models of Parkinson's disease (PD) demonstrate that pituitary adenylate cyclase-activating polypeptide (PACAP) conveys its strong neuroprotective actions mainly via its specific PAC1 receptor (PAC1R) in models of PD. We recently described the decrease in PAC1R protein content in the basal ganglia of macaques in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) model of PD that was partially reversed by levodopa therapy. In this work, we tested whether these observations occur also in the rotenone model of PD in the rat. The rotarod test revealed motor skill deterioration upon rotenone administration, which was reversed by benserazide/levodopa (B/L) treatment. The sucrose preference test suggested increased depression level while the open field test showed increased anxiety in rats rendered parkinsonian, regardless of the received B/L therapy. Reduced dopaminergic cell count in the substantia nigra pars compacta (SNpc) diminished the dopaminergic fiber density in the caudate-putamen (CPu) and decreased the peptidergic cell count in the centrally projecting Edinger-Westphal nucleus (EWcp), supporting the efficacy of rotenone treatment. RNAscope in situ hybridization revealed decreased PACAP mRNA (Adcyap1) and PAC1R mRNA (Adcyap1r1) expression in the CPu, globus pallidus, dopaminergic SNpc and peptidergic EWcp of rotenone-treated rats, but no remarkable downregulation occurred in the insular cortex. In the entopeduncular nucleus, only the Adcyap1r1 mRNA was downregulated in parkinsonian animals. B/L therapy attenuated the downregulation of Adcyap1 in the CPu only. Our current results further support the evolutionarily conserved role of the PACAP/PAC1R system in neuroprotection and its recruitment in the development/progression of neurodegenerative states such as PD.

HDAC6 Deficiency Has Moderate Effects on Behaviors and Parkinson's Disease Pathology in Mice

Histone deacetylase 6 (HDAC6) is involved in the regulation of protein aggregation and neuroinflammation, but its role in Parkinson's disease (PD) remains controversial. In this study, Hdac6^-/- mice were generated by CRISPR-Cas9 technology for exploring the effect of HDAC6 on the pathological progression of PD. We found that male Hdac6^-/- mice exhibit hyperactivity and certain anxiety. In the acute 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD mice, though motor injury was slightly alleviated by HDAC6 deficiency, dopamine (DA) depletion in the striatum, the decrease in the number of DA neurons in the substantia nigra (SN) and the reduction in DA neuronal terminals were not affected. In addition, activation of glial cells and the expression of α-synuclein, as well as the levels of apoptosis-related proteins in the nigrostriatal pathway, were not changed in MPTP-injected wild-type and Hdac6^-/- mice. Therefore, HDAC6 deficiency leads to moderate alterations of behaviors and Parkinson's disease pathology in mice.

Possible Signaling Pathways in the Gut Microbiota-Brain Axis for the Development of Parkinson's Disease Caused by Chronic Consumption of Food Additives

It is well-known that consumption of synthetic and natural food additives has both positive and negative effects in the human body. However, it is not clear yet how food additives are related to the development of Parkinson's disease. Therefore, in this review work, the food additive effects related to the gut microbiota-brain axis and the processes that are carried out to develop Parkinson's disease are studied. To this end, a systematic literature analysis is performed with the selected keywords and the food additive effects are studied to draw possible routes of action. This analysis leads to the proposition of a model that explains the pathways that relate the ingestion of food additives to the development of Parkinson's disease. This work motivates further research that ponders the safety of food additives by measuring their impacts over the gut microbiota-brain axis.