New therapeutic approaches to Parkinson's disease targeting GBA, LRRK2 and Parkin

Fostering Inclusivity in Research Engagement for Underrepresented Populations in Parkinson's Disease: The FIRE-UP PD study

BACKGROUND

Members of vulnerable populations are underrepresented in Parkinson's disease (PD) research. A complex web of research barriers perpetuates this gap. Community-based research methods are one approach to addressing this issue. The present PD study was designed to examine the effectiveness of community-based interventions to overcome barriers and increase research participation among underrepresented groups (URGs).

METHODS

Eight study sites across the US were selected and paired based on proposed interventions with specific URGs. Surveys assessed knowledge and attitudes toward PD research. Finally, researchers examined whether the present study affected recruitment to Fox Insight, an online PD research study also recruiting at each site.

RESULTS

In total, 474 participants were recruited. At post-intervention for the FIRE-UP PD Study, recruitment increased significantly in intervention compared to control sites among Black and African American non-Hispanic/Latino populations (p = 0.003), White Hispanic/Latino (p = 0.003) populations, and Not Listed Hispanic/Latino populations (p < 0.001) as well as those with an educational attainment of a high school diploma/General Education Diploma (GED) (p = 0.009), and an income <$20,000 (p = 0.005) or between $20,000-$34,999 (p < 0.001). Study surveys measuring changes in awareness and attitudes toward PD research had mixed results. In Fox Insight, 181 participants were passively recruited with a shift toward more diverse participant demographics.

CONCLUSION

Research participation demographics reflective of the general population are critical to PD investigation and treatment. The FIRE-UP PD Study showed the effectiveness of localized community engagement strategies in increasing URG recruitment to PD research. Therefore, further PD research employing community-based methods to improve diverse participant recruitment is needed.

Ethical Considerations for Identifying Individuals in the Prodromal/Early Phase of Parkinson's Disease: A Narrative Review

The ability to identify individuals in the prodromal phase of Parkinson's disease has improved in recent years, raising the question of whether and how those affected should be informed about the risk of future disease. Several studies investigated prognostic counselling for individuals with isolated REM sleep behavior disorder and have shown that most patients want to receive information about prognosis, but autonomy and individual preferences must be respected. However, there are still many unanswered questions about risk disclosure or early diagnosis of PD, including the impact on personal circumstances, cultural preferences and specific challenges associated with different profiles of prodromal symptoms, genetic testing or biomarker assessments. This narrative review aims to summarize the current literature on prognostic counselling and risk disclosure in PD, as well as highlight future perspectives that may emerge with the development of new biomarkers and their anticipated impact on the definition of PD.

Neurological symptoms in adults with Gaucher disease: a systematic review

INTRODUCTION

Gaucher disease (GD) is classically divided into three types, based on the presence or absence of neurological signs and symptoms. However, presentation can be highly variable in adulthood, and this aspect has not been adequately addressed in the literature so far. We performed a systematic literature review to analyze the entire spectrum of neurological manifestations in adult patients previously classified as GD type I, II, or III, evaluating the role of variants in different neurological manifestations.

METHODS

We searched databases for studies reporting clinical data of adult GD patients (age ≥ 18). Data extraction included GD types, GBA1 variants, age at disease onset and diagnosis, duration of GD, and age at onset and type of neurological symptoms reported.

RESULTS

Among 4190 GD patients from 85 studies, 555 exhibited neurological symptoms in adulthood. The median age at evaluation was 46.8 years (IQR 26.5), age at neurological symptoms onset was 44 years (IQR 35.1), and age at GD clinical onset was 23 years (IQR 23.4). Parkinsonism, including Parkinson's disease and Lewy Body dementia, was the most reported neurological manifestation. Other symptoms and signs encompassed oculomotor abnormalities, peripheral neuropathy, seizures, myoclonus, and cerebellar, cognitive and psychiatric symptoms. The genotype N370S/N370S mostly presented with Parkinsonism and the L444P variant with severe and earlier neurological symptoms.

CONCLUSION

The findings of this systematic review highlight: (1) the relevance of a comprehensive neurological assessment in GD patients, and (2) the importance of considering possible undiagnosed GD in adult patients with mild systemic symptoms presenting unexplained neurological symptoms.

Genome-wide association study of glucocerebrosidase activity modifiers

One of the most common genetic risk factors for Parkinson's disease (PD) are variants in GBA1, which encodes the lysosomal enzyme glucocerebrosidase (GCase). GCase deficiency has been associated with an increased PD risk, but not all individuals with low GCase activity are carriers of GBA1 mutations, suggesting other factors may be acting as modifiers. We aimed to discover common variants associated with GCase activity, as well as replicate previously reported associations, by performing a genome-wide association study using two independent cohorts: a Columbia University cohort consisting of 697 PD cases and 347 controls and the Parkinson's Progression Markers Initiative (PPMI) cohort consisting of 357 PD cases and 163 controls. As expected, GBA1 variants have the strongest association with decreased activity, led by p.N370S (beta = -4.36, se = 0.32, p = 5.05e-43). We also identify a novel association in the GAA locus (encoding for acid alpha-glucosidase, beta = -0.96, se = 0.17, p = 5.23e-09) that may be the result of an interaction between GCase and acid alpha-glucosidase based on various interaction analyses. Lastly, we show that several PD-risk loci are potentially associated with GCase activity. Further research will be needed to replicate and validate our findings and to uncover the functional connection between acid alpha-glucosidase and GCase.

Repurposing the inhibitors of MMP-9 and SGLT-2 against ubiquitin specific protease 30 in Parkinson's disease: computational modelling studies

Ubiquitin specific protease 30 (USP30) has been attributed to mitochondrial dysfunction and impediment of mitophagy in Parkinson's disease (PD). This happens once ubiquitin that supposed to bind with deformed mitochondria at the insistence of Parkin, it's been recruited by USP30 via the distal ubiquitin binding domain. This is a challenge when PINK1 and Parkin loss their functions due to mutation. Although, there are reports on USP30s' inhibitors but no study on the repurposing of inhibitors approved against MMP-9 and SGLT-2 as potential inhibitors of USP30 in PD. Thus, the highlight therein, is to repurpose approved inhibitors of MMP-9 and SGLT-2 against USP30 in PD using extensive computational modelling framework. 3D structures of Ligands and USP30 were obtained from PubChem and protein database (PDB) servers respectively, and were subjected to molecular docking, ADMET evaluation, DFT calculation, molecular dynamics simulation (MDS) and free energy calculations. Out of the 18 drugs, 2 drugs showed good binding affinity to the distal ubiquitin binding domain, moderate pharmacokinetic properties and good stability. The findings showed canagliflozin and empagliflozin as potential inhibitors of USP30. Thus, we present these drugs as repurposing candidates for the treatment of PD. However, the findings in this current study needs to be validated experimentally.Communicated by Ramaswamy H. Sarma.

Frequency of Hereditary and GBA1-Related Parkinsonism in Latin America: A Systematic Review and Meta-Analysis

BACKGROUND

Identifying hereditary parkinsonism is valuable for diagnosis, genetic counseling, patient prioritization in trials, and studying the disease for personalized therapies. However, most studies were conducted in Europeans, and limited data exist on admixed populations like those from Latin America.

OBJECTIVES

This study aims to assess the frequency and distribution of genetic parkinsonism in Latin America.

METHODS

We conducted a systematic review and meta-analysis of the frequency of parkinsonian syndromes associated with genetic pathogenic variants in Latin America. We defined hereditary parkinsonism as those caused by the genes outlined by the MDS Nomenclature of Genetic Movement Disorders and heterozygous carriers of GBA1 pathogenic variants. A systematic search was conducted in PubMed, Web of Science, Embase, and LILACS in August 2022. Researchers reviewed titles and abstracts, and disagreements were resolved by a third researcher. After this screening, five researchers reanalyzed the selection criteria and extracted information based on the full paper. The frequency for each parkinsonism-related gene was determined by the presence of pathogenic/likely pathogenic variants among screened patients. Cochran's Q and I2 tests were used to quantify heterogeneity. Meta-regression, publication bias tests, and sensitivity analysis regarding study quality were also used for LRRK2-, PRKN-, and GBA1-related papers.

RESULTS

We included 73 studies involving 3014 screened studies from 16 countries. Among 7668 Latin American patients, pathogenic variants were found in 19 different genes. The frequency of the pathogenic variants in LRRK2 was 1.38% (95% confidence interval [CI]: 0.52-2.57), PRKN was 1.16% (95% CI: 0.08-3.05), and GBA1 was 4.17% (95% CI: 2.57-6.08). For all meta-analysis, heterogeneity was high and publication bias tests were negative, except for PRKN, which was contradictory. Information on the number of pathogenic variants in the other genes is further presented in the text.

CONCLUSIONS

This study provides insights into hereditary and GBA1-related parkinsonism in Latin America. Lower GBA1 frequencies compared to European/North American cohorts may result from limited access to gene sequencing. Further research is vital for regional prevalence understanding, enabling personalized care and therapies. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Parkinson's Disease is Predominantly a Genetic Disease

The discovery of a pathogenic variant in the alpha-synuclein (SNCA) gene in the Contursi kindred in 1997 indisputably confirmed a genetic cause in a subset of Parkinson's disease (PD) patients. Currently, pathogenic variants in one of the seven established PD genes or the strongest known risk factor gene, GBA1, are identified in ∼15% of PD patients unselected for age at onset and family history. In this Debate article, we highlight multiple avenues of research that suggest an important - and in some cases even predominant - role for genetics in PD aetiology, including familial clustering, high rates of monogenic PD in selected populations, and complete penetrance with certain forms. At first sight, the steep increase in PD prevalence exceeding that of other neurodegenerative diseases may argue against a predominant genetic etiology. Notably, the principal genetic contribution in PD is conferred by pathogenic variants in LRRK2 and GBA1 and, in both cases, characterized by an overall late age of onset and age-related penetrance. In addition, polygenic risk plays a considerable role in PD. However, it is likely that, in the majority of PD patients, a complex interplay of aging, genetic, environmental, and epigenetic factors leads to disease development.

MAPT Locus in Parkinson's Disease Patients of Ashkenazi Origin: A Stratified Analysis

Introduction: MAPT locus is associated with Parkinson's disease (PD), which is located within a large inversion region of high linkage disequilibrium (LD). We aimed to determine whether the H2-haplotype protective effect and its effect size depends on the GBA1 or LRRK2 risk allele carrier status, and to further characterize genetic alterations that might contribute to its effect. Methods: LD analysis was performed using whole-genome sequencing data of 202 unrelated Ashkenazi Jewish (AJ) PDs. A haplotype-divergent variant was genotyped in a cohort of 1200 consecutively recruited AJ-PDs. The odd ratios were calculated using AJ-non-neuro cases from the gnomAD database as the controls in an un-stratified and a stratified manner according to the mutation carrier status, and the effect on the Age at Motor Symptom Onset (AMSO) was examined. Expression and splicing quantitative trait locus (eQTL and sQTL) analyses were carried out using brain tissues from a database. Results: The H2 haplotype exhibited significant association with PD protection, with a similar effect size in GBA1 carriers, LRRK2-G2019S carriers, and non-carriers (OR = 0.77, 0.69, and 0.82, respectively), and there was no effect on AMSO. The LD interval was narrowed to approximately 1.2 Mb. The H2 haplotype carried potential variants in candidate genes (MAPT and SPPL2C); structural deletions and segmental duplication (KANSL1); and variants affecting gene expression and intron excision ratio in brain tissues (LRRC37A/2). Conclusions: Our results demonstrate that H2 is associated with PD and its protective effect is not influenced by the GBA1/LRRK2 risk allele carrier status. This effect may be genetically complex, resulting from different levels of variations such as missense mutations in relevant genes, structural variations, epigenetic modifications, and RNA expression changes, which may operate independently or in synergy.

Exploring natural compound, Panicutine as leucine-rich repeat kinase 2 inhibitor against Parkinson's disease: a structure-guided approach

Leucine-rich repeat kinase 2 (LRRK2) is a promising drug target for the therapeutic management of Parkinson's disease (PD) and other neurodegenerative disorders. LRRK2 inhibitors have the potential to modulate neuroinflammation, reduce alpha-synuclein aggregation and improve motor symptoms in PD patients. Although LRRK2 inhibitors are still in the early stages of clinical development, the identification of potent and selective inhibitors through structure-guided approaches provides a promising avenue for the development of effective therapies for PD and other neurodegenerative disorders. In this study, natural compounds from the IMPPAT database were screened using a state-of-the-art computational virtual screening approach to identify potential inhibitors of LRRK2. We carried out a docking screening on a library of natural compounds and identified a few compounds with strong binding affinity, docking score and specificity towards LRRK2 as the top hits. These hits were then subjected to further analysis based on multiple parameters for the Pan-assay interference compounds and their physicochemical and pharmacokinetics evaluation followed by a detailed interaction analysis. After careful evaluation, one natural compound, Panicutine, was identified as a promising candidate for LRRK2 due to its significant affinity and specificity towards the LRRK2 binding pocket. Additionally, it exhibited drug-like properties with blood-brain barrier permeability as determined by ADMET properties. To gain a deeper understanding of the stability and conformational changes of the LRRK2-ligand complex, MD simulations were conducted for 100 nanoseconds under explicit solvent conditions followed by principal component analysis and free energy dynamics. The simulation results demonstrated that the LRRK2-Panicutine complex remained stable throughout the simulation trajectories. Based on these findings, it is concluded that Panicutine has the potential to act as a LRRK2 inhibitor against PD and other neurodegenerative disorders.Communicated by Ramaswamy H. Sarma.

Unraveling neurotransmitter changes in de novo GBA-related and idiopathic Parkinson's disease

BACKGROUND

Presently, neurotransmitter deficits in GBA-related Parkinson's disease (GBA-PD) and relationships with cognitive impairment are poorly understood. A better understanding of neurotransmitter impairments in GBA-PD - particularly in the newly diagnosed drug-naïve phase - may support developing targeted intervention strategies. We aimed to investigate patterns of neurotransmitter deficits in GBA-PD and idiopathic PD (iPD) and cognitive performance correlations.

METHODS

We recruited 189 newly diagnosed PD patients for GBA sequencing. Voxel-wise gray matter volume (GMV) was evaluated in a subgroup of 17 GBA-PD, 100 iPD, and 32 age- and sex-matched healthy controls (HCs). The JuSpace toolbox covering various neurotransmitter maps helped assess whether the spatial patterns of GMV alterations in GBA-PD or iPD patients (relative to HCs) were associated with specific neurotransmitter systems.

RESULTS

GBA-PD patients indicated widespread GM atrophy in the fronto-temporal-occipital region compared with HCs. GMV atrophy was spatially correlated in GBA-PD and iPD with serotonergic, dopaminergic, and acetylcholinergic pathway distributions (p < 0.05, false discovery rate corrected). Executive function and language in cognitive domains were also associated with the strength of GMV colocalization of serotonergic, dopaminergic, and acetylcholinergic circuits.

CONCLUSIONS

Regional GM atrophy related to specific neurotransmitter deficits in de novo GBA-PD and iPD patients could provide new insights into pathophysiological processes, facilitating potential therapeutic targets to support PD management.

GBA1 Variants and Parkinson's Disease: Paving the Way for Targeted Therapy

Glucosylceramidase beta 1 (GBA1) variants have attracted enormous attention as the most promising and important genetic candidates for precision medicine in Parkinson's disease (PD). A substantial correlation between GBA1 genotypes and PD phenotypes could inform the prediction of disease progression and promote the development of a preventive intervention for individuals at a higher risk of a worse disease prognosis. Moreover, the GBA1-regulated pathway provides new perspectives on the pathogenesis of PD, such as dysregulated sphingolipid metabolism, impaired protein quality control, and disrupted endoplasmic reticulum-Golgi trafficking. These perspectives have led to the development of novel disease-modifying therapies for PD targeting the GBA1-regulated pathway by repositioning treatment strategies for Gaucher's disease. This review summarizes the current hypotheses on a mechanistic link between GBA1 variants and PD and possible therapeutic options for modulating GBA1-regulated pathways in PD patients.

International Genetic Testing and Counseling Practices for Parkinson's Disease

BACKGROUND

There is growing clinical and research utilization of genetic testing in Parkinson's disease (PD), including direct-to-consumer testing.

OBJECTIVES

The aim is to determine the international landscape of genetic testing in PD to inform future worldwide recommendations.

METHODS

A web-based survey assessing current practices, concerns, and barriers to genetic testing and counseling was administered to the International Parkinson and Movement Disorders Society membership.

RESULTS

Common hurdles across sites included cost and access to genetic testing, and counseling, as well as education on genetic counseling. Region-dependent differences in access to and availability of testing and counseling were most notable in Africa. High-income countries also demonstrated heterogeneity, with European nations more likely to have genetic testing covered through insurance than Pan-American and Asian countries.

CONCLUSIONS

This survey highlights not only diversity of barriers in different regions but also the shared and highly actionable needs for improved education and access to genetic counseling and testing for PD worldwide. © 2023 International Parkinson and Movement Disorder Society.

GBA1 in Parkinson's disease: variant detection and pathogenicity scoring matters

BACKGROUND

GBA1 variants are the strongest genetic risk factor for Parkinson's disease (PD). However, the pathogenicity of GBA1 variants concerning PD is still not fully understood. Additionally, the frequency of GBA1 variants varies widely across populations.

OBJECTIVES

To evaluate Oxford Nanopore sequencing as a strategy, to determine the frequency of GBA1 variants in Norwegian PD patients and controls, and to review the current literature on newly identified variants that add to pathogenicity determination.

METHODS

We included 462 Norwegian PD patients and 367 healthy controls. We sequenced the full-length GBA1 gene on the Oxford Nanopore GridION as an 8.9 kb amplicon. Six analysis pipelines were compared using two aligners (NGMLR, Minimap2) and three variant callers (BCFtools, Clair3, Pepper-Margin-Deepvariant). Confirmation of GBA1 variants was performed by Sanger sequencing and the pathogenicity of variants was evaluated.

RESULTS

We found 95.8% (115/120) true-positive GBA1 variant calls, while 4.2% (5/120) variant calls were false-positive, with the NGMLR/Minimap2-BCFtools pipeline performing best. In total, 13 rare GBA1 variants were detected: two were predicted to be (likely) pathogenic and eleven were of uncertain significance. The odds of carrying one of the two common GBA1 variants, p.L483P or p.N409S, in PD patients were estimated to be 4.11 times the odds of carrying one of these variants in controls (OR = 4.11 [1.39, 12.12]).

CONCLUSIONS

In conclusion, we have demonstrated that Oxford long-read Nanopore sequencing, along with the NGMLR/Minimap2-BCFtools pipeline is an effective tool to investigate GBA1 variants. Further studies on the pathogenicity of GBA1 variants are needed to assess their effect on PD.

Novel C-Linked Isoquinoline Amides as LRRK2 Inhibitors for Treating Parkinson's Disease

Provided herein are novel C-linked isoquinoline amides as LRRK2 inhibitors, their pharmaceutical compositions, the use of such compounds in treating Parkinson's disease, and processes for preparing such compounds.

LRRK2 and Parkinson's disease: from genetics to targeted therapy

LRRK2 variants are implicated in both familial and sporadic PD. LRRK2-PD has a generally benign clinical presentation and variable pathology, with inconsistent presence of Lewy bodies and marked Alzheimer's disease pathology. The mechanisms underlying LRRK2-PD are still unclear, but inflammation, vesicle trafficking, lysosomal homeostasis, and ciliogenesis have been suggested, among others. As novel therapies targeting LRRK2 are under development, understanding the role and function of LRRK2 in PD is becoming increasingly important. Here, we outline the epidemiological, pathophysiological, and clinical features of LRRK2-PD, and discuss the arising therapeutic approaches targeting LRRK2 and possible future directions for research.

Potential Binding Sites of Pharmacological Chaperone NCGC00241607 on Mutant β-Glucocerebrosidase and Its Efficacy on Patient-Derived Cell Cultures in Gaucher and Parkinson's Disease

Mutations in the GBA1 gene, encoding the lysosomal enzyme glucocerebrosidase (GCase), cause Gaucher disease (GD) and are the most common genetic risk factor for Parkinson's disease (PD). Pharmacological chaperones (PCs) are being developed as an alternative treatment approach for GD and PD. To date, NCGC00241607 (NCGC607) is one of the most promising PCs. Using molecular docking and molecular dynamics simulation we identified and characterized six allosteric binding sites on the GCase surface suitable for PCs. Two sites were energetically more preferable for NCGC607 and located nearby to the active site of the enzyme. We evaluated the effects of NCGC607 treatment on GCase activity and protein levels, glycolipids concentration in cultured macrophages from GD (n = 9) and GBA-PD (n = 5) patients as well as in induced human pluripotent stem cells (iPSC)-derived dopaminergic (DA) neurons from GBA-PD patient. The results showed that NCGC607 treatment increased GCase activity (by 1.3-fold) and protein levels (by 1.5-fold), decreased glycolipids concentration (by 4.0-fold) in cultured macrophages derived from GD patients and also enhanced GCase activity (by 1.5-fold) in cultured macrophages derived from GBA-PD patients with N370S mutation (p < 0.05). In iPSC-derived DA neurons from GBA-PD patients with N370S mutation NCGC607 treatment increased GCase activity and protein levels by 1.1-fold and 1.7-fold (p < 0.05). Thus, our results showed that NCGC607 could bind to allosteric sites on the GCase surface and confirmed its efficacy on cultured macrophages from GD and GBA-PD patients as well as on iPSC-derived DA neurons from GBA-PD patients.

Variants in PSMB9 and FGR differentially affect Parkinson's disease risk in GBA and LRRK2 mutation carriers

INTRODUCTION

Recent studies found an association between Parkinson's disease (PD) and alterations in the innate immune system. However, whether the involvement of this system in two of the known genetic forms of PD, GBA-PD and LRRK2-PD, and in patients who do not carry these mutations is different, is yet to be determined. We aimed to test if genetic variations in the innate immune genes are differentially associated with PD in these subgroups.

METHODS

Innate immune genes were identified and classified into sub-lists according to Reactome pathways. Whole-genome-sequencing (WGS) was performed on 201 unrelated Ashkenazi-Jewish (AJ) PD patients including 104 GBA-PD, 32 LRRK2-PD, and 65 non-carriers-PD (NC-PD). To identify genes with different burden between these subgroups of PD, gene-based Sequence kernel association optimal unified test (SKAT-O) analysis was performed on innate immune pathways. Candidate variants within the significant genes were further genotyped in a cohort of 1200 unrelated, consecutively recruited, AJ-PD patients, and to evaluate their association with PD-risk their allele frequencies were compared to AJ-non-neuro cases in gnomAD database, in a stratified and un-stratified manner.

RESULTS

SKAT-O analysis showed significantly different burden for PSMB9 (GBA-PD versus NC-PD) and FGR (GBA-PD versus LRRK2-PD). Two candidate variants in PSMB9 showed an association with GBA-PD-risk and NC-PD-risk while one FGR variant showed an association with LRRK2-PD-risk.

CONCLUSION

Our data supports differential involvement of innate immunity risk alleles in PD and emphasizes the differences between the GBA- and LRRK2-PD subgroups.

How should future clinical trials be designed in the search for disease-modifying therapies for Parkinson's disease?

INTRODUCTION

Although there has been substantial progress in research and innovations in symptomatic treatments, similar success has not been achieved in disease-modifying therapy (DMT) for Parkinson's disease (PD). Considering the enormous motor, psychosocial and financial burden associated with PD, safe and effective DMT is of paramount importance.

AREAS COVERED

One of the reasons for the lack of progress in DMT for PD is poor or inappropriate design of clinical trials. In the first part of the article, the authors focus on the plausible reasons why the previous trials have failed and in the latter part, they provide their perspectives on future DMT trials.

EXPERT OPINION

There are several potential reasons why previous trials have failed, including broad clinical and etiopathogenic heterogeneity of PD, poor definition and documentation of target engagement, lack of appropriate biomarkers and outcome measures, and short duration of follow-up. To address these deficiencies, future trials may consider- (i) a more customized approach to select the most suitable participants and therapeutic approaches, (ii) explore combination therapies that would target multiple pathogenetic mechanisms, and (iii) moving beyond targeting only motor symptoms to also assessing non-motor features of PD in well-designed longitudinal studies.

Neuroprotective Effects of Licochalcone D in Oxidative-Stress-Induced Primitive Neural Stem Cells from Parkinson's Disease Patient-Derived iPSCs

Parkinson's disease (PD) is one of the most common neurodegenerative diseases caused by the loss of dopaminergic neurons in the substantia nigra pars compacta. Although the etiology of PD is still unclear, the death of dopaminergic neurons during PD progression was revealed to be associated with abnormal aggregation of α-synuclein, elevation of oxidative stress, dysfunction of mitochondrial functions, and increased neuroinflammation. In this study, the effects of Licochalcone D (LCD) on MG132-induced neurotoxicity in primitive neural stem cells (pNSCs) derived from reprogrammed iPSCs were investigated. A cell viability assay showed that LCD had anti-apoptotic properties in MG132-induced oxidative-stressed pNSCs. It was confirmed that apoptosis was reduced in pNSCs treated with LCD through 7-AAD/Annexin Ⅴ staining and cleaved caspase3. These effects of LCD were mediated through an interaction with JunD and through the EGFR/AKT and JNK signaling pathways. These findings suggest that LCD could be a potential antioxidant reagent for preventing disease-related pathological phenotypes of PD.

The genetic background of Parkinson's disease and novel therapeutic targets

INTRODUCTION

Parkinson's disease (PD) is the second most common neurodegenerative disease worldwide. The median age of disease onset is around 60 years. From a genetic point of view, PD is basically considered a sporadic, idiopathic disease, however, hereditary components can be detected in 5-10% of patients. Expanding data are available regarding the targeted molecular therapy of the disease.

AREAS COVERED

The aim of this current review article is to provide brief clinical and molecular insight into three important genetic forms (LRRK2, SNCA, GBA) of hereditary PD subtypes and to present the human clinical trials in relation to these forms of the disease.

EXPERT OPINION

These small hereditary subgroups are crucially important in drug development, because the general trend is that clinical trials that treat PD patients as a large group, without any separation, do not meet expectations. As a result, no long term conclusions can currently be drawn regarding the effectiveness of the molecules tested in these phase 1 and 2 studies. Further precise studies are needed in the near future.

Genome Sequencing in the Parkinson Disease Clinic

Background and Objectives

Genetic variants affect both Parkinson disease (PD) risk and manifestations. Although genetic information is of potential interest to patients and clinicians, genetic testing is rarely performed during routine PD clinical care. The goal of this study was to examine interest in comprehensive genetic testing among patients with PD and document reactions to possible findings from genome sequencing in 2 academic movement disorder clinics.

Methods

In 203 subjects with PD (age = 63 years, 67% male), genome sequencing was performed and filtered using a custom panel, including 49 genes associated with PD, parkinsonism, or related disorders, as well as a 90-variant PD genetic risk score. Based on the results, 231 patients (age = 67 years, 63% male) were surveyed on interest in genetic testing and responses to vignettes covering (1) familial risk of PD (LRRK2); (2) risk of PD dementia (GBA); (3) PD genetic risk score; and (4) secondary, medically actionable variants (BRCA1).

Results

Genome sequencing revealed a LRRK2 variant in 3% and a GBA risk variant in 10% of our clinical sample. The genetic risk score was normally distributed, identifying 41 subjects with a high risk of PD. Medically actionable findings were discovered in 2 subjects (1%). In our survey, the majority (82%) responded that they would share a LRRK2 variant with relatives. Most registered unchanged or increased interest in testing when confronted with a potential risk for dementia or medically actionable findings, and most (75%) expressed interest in learning their PD genetic risk score.

Discussion

Our results highlight broad interest in comprehensive genetic testing among patients with PD and may facilitate integration of genome sequencing in clinical practice.

LRRK2 and Proteostasis in Parkinson's Disease

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

Clinical outcome measures in dementia with Lewy bodies trials: critique and recommendations

The selection of appropriate outcome measures is fundamental to the design of any successful clinical trial. Although dementia with Lewy bodies (DLB) is one of the most common neurodegenerative conditions, assessment of therapeutic benefit in clinical trials often relies on tools developed for other conditions, such as Alzheimer's or Parkinson's disease. These may not be sufficiently valid or sensitive to treatment changes in DLB, decreasing their utility. In this review, we discuss the limitations and strengths of selected available tools used to measure DLB-associated outcomes in clinical trials and highlight the potential roles for more specific objective measures. We emphasize that the existing outcome measures require validation in the DLB population and that DLB-specific outcomes need to be developed. Finally, we highlight how the selection of outcome measures may vary between symptomatic and disease-modifying therapy trials.

Monogenic Parkinson’s Disease: Genotype, Phenotype, Pathophysiology, and Genetic Testing

Parkinson’s disease may be caused by a single pathogenic variant (monogenic) in 5–10% of cases, but investigation of these disorders provides valuable pathophysiological insights. In this review, we discuss each genetic form with a focus on genotype, phenotype, pathophysiology, and the geographic and ethnic distribution. Well-established Parkinson’s disease genes include autosomal dominant forms (SNCA, LRRK2, and VPS35) and autosomal recessive forms (PRKN, PINK1 and DJ1). Furthermore, mutations in the GBA gene are a key risk factor for Parkinson’s disease, and there have been major developments for X-linked dystonia parkinsonism. Moreover, atypical or complex parkinsonism may be due to mutations in genes such as ATP13A2, DCTN1, DNAJC6, FBXO7, PLA2G6, and SYNJ1. Furthermore, numerous genes have recently been implicated in Parkinson’s disease, such as CHCHD2, LRP10, TMEM230, UQCRC1, and VPS13C. Additionally, we discuss the role of heterozygous mutations in autosomal recessive genes, the effect of having mutations in two Parkinson’s disease genes, the outcome of deep brain stimulation, and the role of genetic testing. We highlight that monogenic Parkinson’s disease is influenced by ethnicity and geographical differences, reinforcing the need for global efforts to pool large numbers of patients and identify novel candidate genes.

Modeling Parkinson's disease in LRRK2 mice: focus on synaptic dysfunction and the autophagy-lysosomal pathway

Mutations in the leucine-rich repeat kinase 2 (LRRK2) gene are associated with familial and sporadic forms of Parkinson's disease (PD), for which the LRRK2 locus itself represents a risk factor. Idiopathic and LRRK2-related PD share the main clinical and neuropathological features, thus animals harboring the most common LRRK2 mutations, i.e. G2019S and R1441C/G, have been generated to replicate the parkinsonian phenotype and investigate the underlying pathological mechanisms. Most LRRK2 rodent models, however, fail to show the main neuropathological hallmarks of the disease i.e. the degeneration of dopaminergic neurons in the substantia nigra pars compacta and presence of Lewy bodies or Lewy body-like aggregates of α-synuclein, lacking face validity. Rather, they manifest dysregulation in cellular pathways and functions that confer susceptibility to a variety of parkinsonian toxins/triggers and model the presymptomatic/premotor stages of the disease. Among such susceptibility factors, dysregulation of synaptic activity and proteostasis are evident in LRRK2 mutants. These abnormalities are also manifest in the PD brain and represent key events in the development and progression of the pathology. The present minireview covers recent articles (2018-2021) investigating the role of LRRK2 and LRRK2 mutants in the regulation of synaptic activity and autophagy-lysosomal pathway. These articles confirm a perturbation of synaptic vesicle endocytosis and glutamate release in LRRK2 mutants. Likewise, LRRK2 mutants show a marked impairment of selective forms of autophagy (i.e. mitophagy and chaperone-mediated autophagy) and lysosomal function, with minimal perturbations of nonselective autophagy. Thus, LRRK2 rodents might help understand the contribution of these pathways to PD.

Special Issue on New therapeutic approaches to Parkinson disease

Parkinson's disease (PD) is a common neurodegenerative disorder. Age is the biggest risk factor, with the prevalence rising from 1% in 45-54 year age group to 2-4 % in 85 year or older. Population increases have led some to predict that we are facing a 'PD Pandemic' with the prevalence doubling in the next two decades. There is thus an urgent need for effective therapies to reduce disease burden. In this Special Issue of Neuropharmacology invited authors have reviewed current and emerging targets for pharmacological therapy for PD covering the areas of disease modification, i.e. addressing the underlying disease processes, through to symptomatic therapies, whether for motor or non-motor symptoms of the disease. The articles are from leaders in the field and represent preclinical and clinical stages of therapeutic development. The Special Issue highlights that there is ongoing significant activity across all these potential indications and a vast array of targets have been identified and validated to different extents. PD is, and will remain for the foreseeable future, for the neuropharmacologist a significant area of research, in both the preclinical and clinical space.