Lysosomal Dysfunction and α-Synuclein Aggregation in Parkinson's Disease: Diagnostic Links

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.

RONIN/HCF1-TFEB Axis Protects Against D-Galactose-Induced Cochlear Hair Cell Senescence Through Autophagy Activation

Age-related hearing loss is characterized by senescent inner ear hair cells (HCs) and reduced autophagy. Despite the improved understanding of these processes, detailed molecular mechanisms underlying cochlear HC senescence remain unclear. Transcription Factor EB (TFEB), a key regulator of genes associated with autophagy and lysosomes, crucially affects aging-related illnesses. However, intricate regulatory networks that influence TFEB activity remain to be thoroughly elucidated. The findings revealed that RONIN (THAP11), through its interaction with host cell factor C1 (HCF1/HCFC1), modulated the transcriptional activity of Tfeb, thus contributing to the mitigation (D-galatactose [D-gal]) senescent HC loss. Specifically, RONIN overexpression improved autophagy levels and lysosomal activity and attenuated changes associated with the senescence of HCs triggered by D-gal. These findings highlight the possibility of using RONIN as a viable therapeutic target to ameliorate presbycusis by enhancing the TFEB function.

Manganese exposure induces parkinsonism-like symptoms by Serpina3n-TFEB-v/p-ATPase signaling mediated lysosomal dysfunction

Manganese (Mn) is a neurotoxin that has been etiologically linked to the development of neurodegenerative diseases in the case of overexposure. It is widely accepted that overexposure to Mn leads to manganism, which has clinical symptoms similar to Parkinson's disease (PD), and is referred to as parkinsonism. Astrocytes have been reported to scavenge and degrade extracellular α-synuclein (α-Syn) in the brain. However, the mechanisms of Mn-induced neurotoxicity associated with PD remain unclear. Serpina3n is highly expressed in astrocytes and has been implicated in several neuropathologies. The role Serpina3n plays in Mn neurotoxicity and PD pathogenesis is still unknown. Here, we used wild-type and Serpina3n knockout (KO) C57BL/6 J mice with i.p. injection of 32.5 mg/kg MnCl2 once a day for 6 weeks to elucidate the role of Serpina3n in Mn-caused neurotoxicity regarding parkinsonism pathogenesis. We performed behavioral tests (open field, suspension and pole-climbing tests) to observe Mn-induced motor changes, immunohistochemistry to detect Mn-induced midbrain changes, and Western blot to detect Mn-induced changes of protein expression. It was found that Serpina3n KO markedly alleviated Mn neurotoxicity in mice by attenuating midbrain dopaminergic neuron damage and ameliorating motor deficits. Furthermore, using immunofluorescence colocalization analysis, Western blot and quantitative real-time PCR on Mn-treated C8-D1A cells, we found that Serpina3n KO significantly improved astrocytic α-Syn clearance by suppressing Mn-induced lysosomal dysfunction. Reduced transcription factor EB (TFEB)-v/p-ATPase signaling is responsible for the impairment of the lysosomal acidic environment. These novel findings highlight Serpina3n as a detrimental factor in Mn neurotoxicity associated with parkinsonism, capture the novel role of Serpina3n in regulating lysosomal function, and provide a potential target for antagonizing Mn neurotoxicity and curing parkinsonism in humans.

A nanoparticle-based wireless deep brain stimulation system that reverses Parkinson's disease

Deep brain stimulation technology enables the neural modulation with precise spatial control but requires permanent implantation of conduits. Here, we describe a photothermal wireless deep brain stimulation nanosystem capable of eliminating α-synuclein aggregates and restoring degenerated dopamine neurons in the substantia nigra to treat Parkinson's disease. This nanosystem (ATB NPs) consists of gold nanoshell, an antibody against the heat-sensitive transient receptor potential vanilloid family member 1 (TRPV1), and β-synuclein (β-syn) peptides with a near infrared-responsive linker. ATB NPs by stereotactic injection target dopamine neurons expressing TRPV1 receptors in the substantia nigra. Upon pulsed near-infrared irradiation, ATB NPs, serving as nanoantennae, convert the light into heat, leading to calcium ion influx, depolarization, and action potentials in dopamine neurons through TRPV1 receptors. Simultaneously, β-synuclein peptides released from ATB NPs cooperate with chaperone-mediated autophagy initiated by heat shock protein, HSC70, to effectively eliminate α-synuclein fibrils in neurons. These orchestrated actions restored pathological dopamine neurons and locomotor behaviors of Parkinson's disease.

A systematic review of salivary biomarkers in Parkinson's disease

The search for reliable and easily accessible biomarkers in Parkinson's disease is receiving a growing emphasis, to detect neurodegeneration from the prodromal phase and to enforce disease-modifying therapies. Despite the need for non-invasively accessible biomarkers, the majority of the studies have pointed to cerebrospinal fluid or peripheral biopsies biomarkers, which require invasive collection procedures. Saliva represents an easily accessible biofluid and an incredibly wide source of molecular biomarkers. In the present study, after presenting the morphological and biological bases for looking at saliva in the search of biomarkers for Parkinson's disease, we systematically reviewed the results achieved so far in the saliva of different cohorts of Parkinson's disease patients. A comprehensive literature search on PubMed and SCOPUS led to the discovery of 289 articles. After screening and exclusion, 34 relevant articles were derived for systematic review. Alpha-synuclein, the histopathological hallmark of Parkinson's disease, has been the most investigated Parkinson's disease biomarker in saliva, with oligomeric alpha-synuclein consistently found increased in Parkinson's disease patients in comparison to healthy controls, while conflicting results have been reported regarding the levels of total alpha-synuclein and phosphorylated alpha-synuclein, and few studies described an increased oligomeric alpha-synuclein/total alpha-synuclein ratio in Parkinson's disease. Beyond alpha-synuclein, other biomarkers targeting different molecular pathways have been explored in the saliva of Parkinson's disease patients: total tau, phosphorylated tau, amyloid-β1-42 (pathological protein aggregation biomarkers); DJ-1, heme-oxygenase-1, metabolites (altered energy homeostasis biomarkers); MAPLC-3beta (aberrant proteostasis biomarker); cortisol, tumor necrosis factor-alpha (inflammation biomarkers); DNA methylation, miRNA (DNA/RNA defects biomarkers); acetylcholinesterase activity (synaptic and neuronal network dysfunction biomarkers); Raman spectra, proteome, and caffeine. Despite a few studies investigating biomarkers targeting molecular pathways different from alpha-synuclein in Parkinson's disease, these results should be replicated and observed in studies on larger cohorts, considering the potential role of these biomarkers in determining the molecular variance among Parkinson's disease subtypes. Although the need for standardization in sample collection and processing, salivary-based biomarkers studies have reported encouraging results, calling for large-scale longitudinal studies and multicentric assessments, given the great molecular potentials and the non-invasive accessibility of saliva.

LAMTOR1 regulates dendritic lysosomal positioning in hippocampal neurons through TRPML1 inhibition

Intracellular lysosomal trafficking and positioning are fundamental cellular processes critical for proper neuronal function. Among the diverse array of proteins involved in regulating lysosomal positioning, the Transient Receptor Potential Mucolipin 1 (TRPML1) and the Ragulator complex have emerged as central players. TRPML1, a lysosomal cation channel, has been implicated in lysosomal biogenesis, endosomal/lysosomal trafficking including in neuronal dendrites, and autophagy. LAMTOR1, a subunit of the Ragulator complex, also participates in the regulation of lysosomal trafficking. Here we report that LAMTOR1 regulates lysosomal positioning in dendrites of hippocampal neurons by interacting with TRPML1. LAMTOR1 knockdown (KD) increased lysosomal accumulation in proximal dendrites of cultured hippocampal neurons, an effect reversed by TRPML1 KD or inhibition. On the other hand, TRPML1 activation with ML-SA1 or prevention of TRPML1 interaction with LAMTOR1 using a TAT-decoy peptide induced dendritic lysosomal accumulation. LAMTOR1 KD-induced proximal dendritic lysosomal accumulation was blocked by the dynein inhibitor, ciliobrevin D, suggesting the involvement of a dynein-mediated transport. These results indicate that LAMTOR1-mediated inhibition of TRPML1 is critical for normal dendritic lysosomal distribution and that release of this inhibition or direct activation of TRPML1 results in abnormal dendritic lysosomal accumulation. The roles of LAMTOR1-TRPML1 interactions in lysosomal trafficking and positioning could have broad implications for understanding cognitive disorders associated with lysosomal pathology and calcium dysregulation.

Optineurin regulates motor and learning behaviors by affecting dopaminergic neuron survival in mice

Optineurin (OPTN) is an autophagy receptor that participates in the degradation of damaged mitochondria, protein aggregates, and invading pathogens. OPTN is closely related to various types of neurodegenerative diseases. However, the role of OPTN in the central nervous system is unclear. Here, we found that OPTN dysregulation in the compact part of substantia nigra (SNc) led to motor and learning deficits in animal models. Knockdown of OPTN increased total and phosphorylated α-synuclein levels which induced microglial activation and dopaminergic neuronal loss in the SNc. Overexpression of OPTN can't reverse the motor and learning phenotypes. Mechanistic analysis revealed that upregulation of OPTN increased α-synuclein phosphorylation independent of its autophagy receptor activity, which further resulted in microglial activation and dopaminergic neuronal loss similar to OPTN downregulation. Our study uncovers the crucial role of OPTN in maintaining dopaminergic neuron survival and motor and learning functions which are disrupted in PD patients.

Novel neuroprotective 5,6-dihydropyrido[2',1':2,3]imidazo[4,5-c]quinoline derivatives acting through cholinesterase inhibition and CB2 signaling modulation

A novel group of 5,6-dihydropyrido [2',1':2,3]imidazo [4,5-c]quinolines was prepared via a microwave assisted one-pot telescopic approach. The synthetic sequence involves the formation of an amine precursor of imidazo [1,2-a]pyridine via condensation and reduction under microwave irradiation. Subsequently, the Pictet-Spengler cyclisation reaction occurs with ketones (cyclic or acyclic) to obtain substituted 5,6-dihydropyrido [2',1':2,3]imidazo [4,5-c]quinolines in excellent yields. The compounds were tested as neuroprotective agents. Observed protection of neuron-like cells, SH-SY5Y differentiated with ATRA, in Parkinson's and Huntington's disease models inspired further mechanistic studies of protective activity against damage induced by 1-methyl-4-phenylpyridinium (MPP+), a compound causing Parkinson's disease. The novel compounds exhibit similar or higher potency than ebselen, an established drug with antioxidant activity, in the cells against MPP + -induced total cellular superoxide production and cell death. However, they exhibit a significantly higher capacity to reduce mitochondrial superoxide and preserve mitochondrial membrane potential. We also observed marked differences between a selected derivative and ebselen in terms of normalizing MPP + -induced phosphorylation of Akt and ERK1/2. The cytoprotective activity was abrogated when signaling through cannabinoid receptor CB2 was blocked. The compounds also inhibit both acetylcholine and butyrylcholine esterases. Overall the data show that novel 5,6-dihydropyrido [2',1':2,3]imidazo [4,5-c]quinoline have a broad cytoprotective activity which is mediated by several mechanisms including mitoprotection.

High frequency electrical stimulation reduces α-synuclein levels and α-synuclein-mediated autophagy dysfunction

Accumulation of α-synuclein (α-Syn) has been implicated in proteasome and autophagy dysfunction in Parkinson's disease (PD). High frequency electrical stimulation (HFS) mimicking clinical parameters used for deep brain stimulation (DBS) in vitro or DBS in vivo in preclinical models of PD have been found to reduce levels of α-Syn and, in certain cases, provide possible neuroprotection. However, the mechanisms by which this reduction in α-Syn improves cellular dysfunction associated with α-Syn accumulation remains elusive. Using HFS parameters that recapitulate DBS in vitro, we found that HFS led to a reduction of mutant α-Syn and thereby limited proteasome and autophagy impairments due to α-Syn. Additionally, we observed that HFS modulates via the ATP6V0C subunit of V-ATPase and mitigates α-Syn mediated autophagic dysfunction. This study highlights a role for autophagy in reduction of α-Syn due to HFS which may prove to be a viable approach to decrease pathological protein accumulation in neurodegeneration.

Black Phosphorus Nanosheets Protect Neurons by Degrading Aggregative α-syn and Clearing ROS in Parkinson's Disease

Although evidence indicates that the abnormal accumulation of α-synuclein (α-syn) in dopamine neurons of the substantia nigra is the main pathological feature of Parkinson's disease (PD), no compounds that have both α-syn antiaggregation and α-syn degradation functions have been successful in treating the disease in the clinic. Here, it is shown that black phosphorus nanosheets (BPNSs) interact directly with α-syn fibrils to trigger their disaggregation for PD treatment. Moreover, BPNSs have a specific affinity for α-syn through van der Waals forces. And BPNSs are found to activate autophagy to maintain α-syn homeostasis, improve mitochondrial dysfunction, reduce reactive oxygen species levels, and rescue neuronal death and synaptic loss in PC12 cells. It is also observed that BPNSs penetrate the blood-brain barrier and protect against dopamine neuron loss, alleviating behavioral disorders in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) induced mouse model and hA53T α-syn transgenic mice. Together, the study reveals that BPNSs have the potential as a novel integrated nanomedicine for clinical diagnosis and treatment of neurological diseases.

Novel and experimental therapeutics for the management of motor and non-motor Parkinsonian symptoms

BACKGROUND  : Both motor and non-motor symptoms of Parkinson's disease (PD) have a substantial detrimental influence on the patient's quality of life. The most effective treatment remains oral levodopa. All currently known treatments just address the symptoms; they do not completely reverse the condition.

METHODOLOGY

In order to find literature on the creation of novel treatment agents and their efficacy for PD patients, we searched PubMed, Google Scholar, and other online libraries.

RESULTS

According to the most recent study on Parkinson's disease (PD), a great deal of work has been done in both the clinical and laboratory domains, and some current scientists have even been successful in developing novel therapies for PD patients.

CONCLUSION

The quality of life for PD patients has increased as a result of recent research, and numerous innovative medications are being developed for PD therapy. In the near future, we will see positive outcomes regarding PD treatment.

Cathepsin-mediated regulation of alpha-synuclein in Parkinson's disease: a Mendelian randomization study

Objective

The observational association between cathepsin and Parkinson's disease (PD) has been partially explored in previous research. However, the causal relationship remains unclear. In this study, our objective is to investigate the causal link between cathepsin and PD using Mendelian randomization (MR) analysis and elucidate the underlying mechanisms governing their interaction.

Methods

Utilizing bidirectional two-sample MR and multivariable MR, we systematically investigates the causal relationship between nine cathepsins and PD. The data pertaining to cathepsins were obtained from the Integrative Epidemiology Unit (IEU) Open GWAS Project, while data related to PD were sourced from versions R9 and R10 of the FinnGen database. The primary analytical method utilized was the inverse variance weighted (IVW), with MR analysis initially conducted using PD data from R9, complemented by a series of sensitivity analyses. Subsequently, replication analysis was performed on the R10 dataset, and meta-analysis were employed to merge the findings from both datasets. To explore potential mechanisms by which Cathepsins may impact PD, MR analyses were performed on significant Cathepsins with alpha-synuclein. MR analysis and colocalization analysis were conducted on expression quantitative trait loci (eQTL) data of gene related to alpha-synuclein with PD data.

Result

Forward MR analyses revealed more cathepsin B (CTSB) associated with less PD risk (OR = 0.898, 95%CI: 0.834-0.966, p = 0.004), while more cathepsin H (CTSH) (OR = 1.076, 95%CI: 1.007-1.149, p = 0.029) and more cathepsin S (CTSS) (OR = 1.076, 95%CI: 1.007-1.150, p = 0.030) associated with increasing PD risk. Meta-analyses validated these associations. Multivariate MR Results were consistent with those before adjustment. No significant results were observed in bidirectional MR analysis. In the investigation of the underlying mechanism, our findings demonstrate that CTSB significantly reduces the levels of alpha-synuclein (OR = 0.909, 95%CI: 0.841-0.983, p = 0.017). Concurrently, a genetically determined positive correlation between alpha-synuclein and PD is illuminated by both eQTL MR and colocalization analysis.

Conclusion

In conclusion, this MR study yields robust evidence suggesting an association between elevated levels of CTSB and reduced PD risk, mediated by the downregulation of alpha-synuclein levels. Conversely, higher levels of CTSH and CTSS are associated with an increased risk of PD. These findings offer novel insights into the pathophysiological mechanisms of PD and identify potential drug targets for disease prevention and treatment warranting further clinical investigations.

Autophagy-associated non-coding RNAs: Unraveling their impact on Parkinson's disease pathogenesis

BACKGROUND

Parkinson's disease (PD) is a degenerative neurological condition marked by the gradual loss of dopaminergic neurons in the substantia nigra pars compacta. The precise etiology of PD remains unclear, but emerging evidence suggests a significant role for disrupted autophagy-a crucial cellular process for maintaining protein and organelle integrity.

METHODS

This review focuses on the role of non-coding RNAs (ncRNAs) in modulating autophagy in PD. We conducted a comprehensive review of recent studies to explore how ncRNAs influence autophagy and contribute to PD pathophysiology. Special attention was given to the examination of ncRNAs' regulatory impacts in various PD models and patient samples.

RESULTS

Findings reveal that ncRNAs are pivotal in regulating key processes associated with PD progression, including autophagy, α-synuclein aggregation, mitochondrial dysfunction, and neuroinflammation. Dysregulation of specific ncRNAs appears to be closely linked to these pathogenic processes.

CONCLUSION

ncRNAs hold significant therapeutic potential for addressing autophagy-related mechanisms in PD. The review highlights innovative therapeutic strategies targeting autophagy-related ncRNAs and discusses the challenges and prospective directions for developing ncRNA-based therapies in clinical practice. The insights from this study underline the importance of ncRNAs in the molecular landscape of PD and their potential in novel treatment approaches.

Meta-analysis of the association of prosaposin polymorphisms rs4747203 and rs885828 with risk of Parkinson's disease

BACKGROUND

Previous research has established a connection between polymorphisms rs4747203 and rs885828 in the prosaposin (PSAP) gene and an increased risk of Parkinson's disease (PD). However, other studies have found no significant difference in risk compared to the general population.

METHODS

To evaluate the current evidence linking rs4747203 and rs885828 to PD risk, we conducted a comprehensive search of PubMed, the Web of Science, Embase, and the Cochrane Library for relevant studies up until May 2023. In addition, we analyzed data from the publicly available "PD Variant Browser". We performed a meta-analysis using Stata 17.0 to synthesize the findings from the selected studies.

RESULTS

Our meta-analysis, which included data from six published studies and the public database, revealed no significant association between PD risk and either rs4747203 [OR (95% CI) = 0.99 (0.93-1.05), I2 = 90.3%, P = 0.635] or rs885828 [OR (95% CI) = 1.01 (0.95-1.07), I2 = 90.7%, P = 0.773]. These results remained consistent when examining subgroups of individuals within or outside of Asia.

CONCLUSION

The available evidence does not support an association between the genotype at rs4747203 or rs885828 and the risk of PD.

The Impact of 90 Parkinson's Disease-Risk Single Nucleotide Polymorphisms on Urinary Bis(monoacylglycerol)phosphate Levels in the Prodromal and PD Cohorts

Parkinson's disease (PD) is a common neurodegenerative disorder with a prolonged prodromal phase. Higher urinary bis(monoacylglycerol)phosphate (BMP) levels associate with LRRK2 (leucine-rich repeat kinase 2) and GBA1 (glucocerebrosidase) mutations, and are considered as potential noninvasive biomarkers for predicting those mutations and PD progression. However, their reliability has been questioned, with inadequately investigated genetics, cohorts, and population. In this study, multiple statistical hypothesis tests were employed on urinary BMP levels and sequences of 90 PD-risk single nucleotide polymorphisms (SNPs) from Parkinson's Progression Markers Institution (PPMI) participants. Those SNPs were categorized into four groups based on their impact on BMP levels in various cohorts. Variants rs34637584 G/A and rs34637584 A/A (LRRK2 G2019S) were identified as the most relevant on increasing urinary BMP levels in the PD cohort. Meanwhile, rs76763715 T/T (GBA1) was the primary factor elevating BMP levels in the prodromal cohort compared to its T/C and C/C variants (N370S) and the PD cohort. Proteomics analysis indicated the changed transport pathways may be the reasons for elevated BMP levels in prodromal patients. Our findings demonstrated that higher urinary BMP levels alone were not reliable biomarkers for PD progression or gene mutations but might serve as supplementary indicators for early diagnosis and treatment.

Investigating the TLR4/TAK1/IRF7 axis in NLRP3-Mediated Pyroptosis in Parkinson's Disease

In the realm of Parkinson's disease (PD) research, NLRP3 inflammasome-mediated pyroptosis has recently garnered significant attention as a potential novel form of dopaminergic neuronal death. Our previous research revealed the activation of innate immune-related genes, such as the TLR4 signaling pathway and interferon regulatory factor 7 (IRF7), although the specific mechanism remains unclear. Our current study shed light on whether the TLR4 signaling pathway and IRF7 can affect the pyroptosis of dopaminergic nerve cells and thus participate in the pathogenesis of PD. The PD model was constructed by MPP+ treatment of PC12 cells or stereotactic injection of the striatum of SD rats, and the expression of genes were detected by RT-qPCR and Western Blotting. Lentivirus, siRNA and (5Z)-7-Oxozeaenol were used to validate the regulation of this pathway on pyroptosis. The expression of TLR4, TAK1, IRF7 and pyroptosis molecular markers was upregulated after MPP+ treatment. IRF7 could affect dopaminergic neural cells pyroptosis by targeted regulation of NLRP3. Furthermore, inhibition of the TLR4/TAK1 signaling pathway led to a decrease in the expression of both IRF7 and NLRP3, while overexpression of IRF7 reversed the reduction in pyroptosis and increase in TH expression. TLR4/TAK1/IRF7 axis can promote PD by influencing pyroptosis through NLRP3.

Biofluid Markers and Tissue Biopsies Analyses for the Prodromal and Earliest Phase of Parkinson's Disease

The recent development of new methods to detect misfolded α-synuclein (αSyn) aggregates in biofluids and tissue biopsies in the earliest Parkinson's disease (PD) phases is dramatically challenging the biological definition of PD. The αSyn seed amplification methods in cerebrospinal fluid (CSF) showed high sensitivity and specificity for early diagnosis of PD and Lewy bodies disorders. Several studies in isolated REM sleep behavior disorders and other at-risk populations also demonstrated a high prevalence of CSF αSyn positivity and its potential value in predicting the phenoconversion to clinically manifested diseases. Growing evidence exists for αSyn aggregates in olfactory mucosa, skin, and other tissues in subjects with PD or at-risk subjects. DOPA decarboxylase and numerous other candidates have been additionally proposed for either diagnostic or prognostic purposes in earliest PD phases. The newly described αSyn detection in blood, through its quantification in neuronally-derived exosome vesicles, represents a technical challenge that could open a new scenario for the biological diagnosis of PD. Despite this growing evidence in the field, most of method of αSyn detection and markers still need to be validated in ongoing longitudinal studies through an accurate assessment of different prodromal disease subtypes and scenarios before being definitively implemented in clinical settings.

Clinical biomarkers for Lewy body diseases

Synucleinopathies are a group of neurodegenerative disorders characterized by pathologic aggregates of neural and glial α-synuclein (α-syn) in the form of Lewy bodies (LBs), Lewy neurites, and cytoplasmic inclusions in both neurons and glia. Two major classes of synucleinopathies are LB disease and multiple system atrophy. LB diseases include Parkinson's disease (PD), PD with dementia, and dementia with LBs. All are increasing in prevalence. Effective diagnostics, disease-modifying therapies, and therapeutic monitoring are urgently needed. Diagnostics capable of differentiating LB diseases are based on signs and symptoms which might overlap. To date, no specific diagnostic test exists despite disease-specific pathologies. Diagnostics are aided by brain imaging and cerebrospinal fluid evaluations, but more accessible biomarkers remain in need. Mechanisms of α-syn evolution to pathologic oligomers and insoluble fibrils can provide one of a spectrum of biomarkers to link complex neural pathways to effective therapies. With these in mind, we review promising biomarkers linked to effective disease-modifying interventions.

Autophagy in Parkinson's Disease

Parkinson's disease (PD) is a devastating disease associated with accumulation of α-synuclein (α-Syn) within dopaminergic neurons, leading to neuronal death. PD is characterized by both motor and non-motor clinical symptoms. Several studies indicate that autophagy, an important intracellular degradation pathway, may be involved in different neurodegenerative diseases including PD. The autophagic process mediates the degradation of protein aggregates, damaged and unneeded proteins, and organelles, allowing their clearance, and thereby maintaining cell homeostasis. Impaired autophagy may cause the accumulation of abnormal proteins. Incomplete or impaired autophagy may explain the neurotoxic accumulation of protein aggregates in several neurodegenerative diseases including PD. Indeed, studies have suggested the contribution of impaired autophagy to α-Syn accumulation, the death of dopaminergic neurons, and neuroinflammation. In this review, we summarize the recent literature on the involvement of autophagy in PD pathogenesis.

Curcumin, inflammation, and neurological disorders: How are they linked?

Background

Despite the extensive research in recent years, the current treatment modalities for neurological disorders are suboptimal. Curcumin, a polyphenol found in Curcuma genus, has been shown to mitigate the pathophysiology and clinical sequalae involved in neuroinflammation and neurodegenerative diseases.

Methods

We searched PubMed database for relevant publications on curcumin and its uses in treating neurological diseases. We also reviewed relevant clinical trials which appeared on searching PubMed database using 'Curcumin and clinical trials'.

Results

This review details the pleiotropic immunomodulatory functions and neuroprotective properties of curcumin, its derivatives and formulations in various preclinical and clinical investigations. The effects of curcumin on neurodegenerative diseases such as Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), brain tumors, epilepsy, Huntington's disorder (HD), ischemia, Parkinson's disease (PD), multiple sclerosis (MS), and traumatic brain injury (TBI) with a major focus on associated signalling pathways have been thoroughly discussed.

Conclusion

This review demonstrates curcumin can suppress spinal neuroinflammation by modulating diverse astroglia mediated cascades, ensuring the treatment of neurological disorders.

Alpha-synuclein-associated changes in PINK1-PRKN-mediated mitophagy are disease context dependent

Alpha-synuclein (αsyn) aggregates are pathological features of several neurodegenerative conditions including Parkinson disease (PD), dementia with Lewy bodies, and multiple system atrophy (MSA). Accumulating evidence suggests that mitochondrial dysfunction and impairments of the autophagic-lysosomal system can contribute to the deposition of αsyn, which in turn may interfere with health and function of these organelles in a potentially vicious cycle. Here we investigated a potential convergence of αsyn with the PINK1-PRKN-mediated mitochondrial autophagy pathway in cell models, αsyn transgenic mice, and human autopsy brain. PINK1 and PRKN identify and selectively label damaged mitochondria with phosphorylated ubiquitin (pS65-Ub) to mark them for degradation (mitophagy). We found that disease-causing multiplications of αsyn resulted in accumulation of the ubiquitin ligase PRKN in cells. This effect could be normalized by starvation-induced autophagy activation and by CRISPR/Cas9-mediated αsyn knockout. Upon acute mitochondrial damage, the increased levels of PRKN protein contributed to an enhanced pS65-Ub response. We further confirmed increased pS65-Ub-immunopositive signals in mouse brain with αsyn overexpression and in postmortem human disease brain. Of note, increased pS65-Ub was associated with neuronal Lewy body-type αsyn pathology, but not glial cytoplasmic inclusions of αsyn as seen in MSA. While our results add another layer of complexity to the crosstalk between αsyn and the PINK1-PRKN pathway, distinct mechanisms may underlie in cells and brain tissue despite similar outcomes. Notwithstanding, our finding suggests that pS65-Ub may be useful as a biomarker to discriminate different synucleinopathies and may serve as a potential therapeutic target for Lewy body disease.

Screening for Fabry disease in a series of Parkinson's disease patients and literature review

BACKGROUND

So far, mutations in genes encoding lysosomal enzymes have been associated with Parkinson's disease (PD). Fabry disease (FD) is an X-linked lysosomal storage disease caused by alpha-galactosidase A (α-GAL) deficiency, leading to deposition of globotriaosylceramide in the nervous system and other organs. We aimed to screen for FD a case series of PD patients from Southern Italy and to review the literature.

METHODS

One hundred and forty-four consecutive unrelated PD subjects were enrolled. The α-GAL activity was measured in all men and, in case of pathological values, subsequent determination of globotriaosylsphingosine (lyso-Gb3) and GLA gene sequencing were also performed. All the women underwent GLA gene sequencing.

RESULTS

α-GAL levels resulted low in fifteen men, whereas lyso-Gb3 testing showed values within the reference range in all of them. GLA gene variants were not detected in any tested subjects. One pathological study, six case series, and five case reports are currently reported in literature.

CONCLUSIONS

The few studies reviewed are heterogeneous, and the results are controversial. An unknown significance variant in GLA gene was detected in PD patients in one large study, whereas decreased α-GAL activity was observed in PD subjects in two other researches, but without confirmation by lyso-Gb3 assessment or genetic analysis. Vascular parkinsonism was associated to FD in five case reports. We found no association between PD and FD in our population. However, it is not possible to draw definitive conclusions due to limited sample size. Furthermore, controls would have been missing in case of a positive finding.

Fountain of youth—Targeting autophagy in aging

As our society ages inexorably, geroscience and research focusing on healthy aging is becoming increasingly urgent. Macroautophagy (referred to as autophagy), a highly conserved process of cellular clearance and rejuvenation has attracted much attention due to its universal role in organismal life and death. Growing evidence points to autophagy process as being one of the key players in the determination of lifespan and health. Autophagy inducing interventions show significant improvement in organismal lifespan demonstrated in several experimental models. In line with this, preclinical models of age-related neurodegenerative diseases demonstrate pathology modulating effect of autophagy induction, implicating its potential to treat such disorders. In humans this specific process seems to be more complex. Recent clinical trials of drugs targeting autophagy point out some beneficial effects for clinical use, although with limited effectiveness, while others fail to show any significant improvement. We propose that using more human-relevant preclinical models for testing drug efficacy would significantly improve clinical trial outcomes. Lastly, the review discusses the available cellular reprogramming techniques used to model neuronal autophagy and neurodegeneration while exploring the existing evidence of autophagy’s role in aging and pathogenesis in human-derived in vitro models such as embryonic stem cells (ESCs), induced pluripotent stem cell derived neurons (iPSC-neurons) or induced neurons (iNs).

Fabry Disease and Central Nervous System Involvement: From Big to Small, from Brain to Synapse

Fabry disease (FD) is an X-linked lysosomal storage disorder (LSD) secondary to mutations in the GLA gene that causes dysfunctional activity of lysosomal hydrolase α-galactosidase A and results in the accumulation of globotriaosylceramide (Gb3) and globotriaosylsphingosine (lyso-Gb3). The endothelial accumulation of these substrates results in injury to multiple organs, mainly the kidney, heart, brain and peripheral nervous system. The literature on FD and central nervous system involvement is scarce when focusing on alterations beyond cerebrovascular disease and is nearly absent in regard to synaptic dysfunction. In spite of that, reports have provided evidence for the CNS’ clinical implications in FD, including Parkinson’s disease, neuropsychiatric disorders and executive dysfunction. We aim to review these topics based on the current available scientific literature.

A Preclinical Model for Parkinson’s Disease Based on Transcriptional Gene Activation via KEAP1/NRF2 to Develop New Antioxidant Therapies

Investigations of the effect of antioxidants on idiopathic Parkinson’s disease have been unsuccessful because the preclinical models used to propose these clinical studies do not accurately represent the neurodegenerative process of the disease. Treatment with certain exogenous neurotoxins induces massive and extremely rapid degeneration; for example, MPTP causes severe Parkinsonism in just three days, while the degenerative process of idiopathic Parkinson´s disease proceeds over many years. The endogenous neurotoxin aminochrome seems to be a good alternative target since it is formed in the nigrostriatal system neurons where the degenerative process occurs. Aminochrome induces all the mechanisms reported to be involved in the degenerative processes of idiopathic Parkinson’s disease. The presence of neuromelanin-containing dopaminergic neurons in the postmortem brain of healthy elderly people suggests that neuromelanin synthesis is a normal and harmless process despite the fact that it requires oxidation of dopamine to three ortho-quinones that are potentially toxic, especially aminochrome. The apparent contradiction that neuromelanin synthesis is harmless, despite its formation via neurotoxic ortho-quinones, can be explained by the protective roles of DT-diaphorase and glutathione transferase GSTM2-2 as well as the neuroprotective role of astrocytes secreting exosomes loaded with GSTM2-2. Increasing the expression of DT-diaphorase and GSTM2-2 may be a therapeutic goal to prevent the degeneration of new neuromelanin-containing dopaminergic neurons. Several phytochemicals that induce DT-diaphorase have been discovered and, therefore, an interesting question is whether these phytochemical KEAP1/NRF2 activators can inhibit or decrease aminochrome-induced neurotoxicity.

A Combined Panel of Salivary Biomarkers in de novo Parkinson's Disease

OBJECTIVE

To investigate molecular biomarkers of a-synuclein and tau aggregation, autophagy, and inflammation in the saliva of de novo Parkinson's disease (PD) patients in comparison to healthy subjects (HS), and to correlate molecular data with clinical features of PD patients, in order to establish whether abnormalities of these parameters are associated with specific clusters of de novo PD patients, and their potential diagnostic power in differentiating PD patients from HS.

METHODS

We measured total and oligomeric a-synuclein, total-tau and phosphorylated-tau, microtubule-associated protein light chain 3 beta (MAP-LC3beta), and tumor necrosis factor alpha (TNFalpha) in the saliva of 80 de novo PD patients and 62 HS, using quantitative enzyme-linked immunosorbent Assay analysis.

RESULTS

Oligomeric a-synuclein, total-tau, MAP-LC3beta, and TNFalpha levels resulted significantly higher in patients with respect to HS, while no significant differences were detected for total a-synuclein or phosphorylated-tau. Phosphorylated-tau directly correlated with MAP-LC3beta, whereas it inversely correlated with TNFalpha in PD patients. An inverse correlation was detected between MAP-LC3beta and non-motor symptoms severity. Principal Component Analysis showed that molecular and clinical parameters were independent of each other in de novo PD patients. Receiver operating characteristic curve analysis reported an accurate diagnostic performance of oligomeric a-synuclein and MAP-LC3beta. The diagnostic accuracy of total a-synuclein increased when it was combined with other salivary biomarkers targeting different molecular pathways.

INTERPRETATION

Our study proposes a novel biomarker panel using saliva, a non-invasive biofluid, in de novo PD patients, with implications in understanding the molecular pathways involved in PD pathogenesis and the relevance of different molecular pathways in determining clinical PD subtypes. ANN NEUROL 2023;93:446-459.

Spautin-1 administration mitigates mild TBI-induced cognitive and memory dysfunction in mice via activation of caspase-3

BACKGROUND

Cognitive and memory dysfunction, a common sequela of traumatic brain injury (TBI), places a heavy social and economic burden on individuals, families, communities, and countries. Although the potent anti-tumor effects of spautin-1, a novel autophagy inhibitor, have been documented in malignant melanoma, little is known regarding its efficacy on alleviation of cognitive and memory dysfunction. Here, we describe the effect of spautin-1 administration on cognitive and memory impairment post-TBI, and reveal its underlying mechanism of action.

METHODS

We first induced mild TBI in mice through Feeney's weight-drop model, then immediately administered spautin-1 (10 mmol/μl, 2 μl) into the left lateral ventricle. Behavioral and pathological changes were assessed at 24 h, 7 and 30 days after TBI by analyzing neurological severity scores (NSS), novel objective recognition (NOR), Morris water maze (MWM) test, recording of local field potential (LFP), as well as western blot, and immunofluorescence assays.

RESULTS

Mild TBI not only reduced recognition index and times crossing platform, but also aggravated neuronal injury, including reduced MAP2, GAD2, VGlut2, and CHAT intensity. It also elevated activated microglia and CD86-occupied areas in TMEM119-positive cells, but suppressed θ, β, and γ oscillation power in the hippocampal CA1. However, spautin-1 administration significantly reversed these changes, whereas AC-DEVD-CHO an inhibitor of caspase-3 partially blocked the neuroprotective effects of spautin-1.

CONCLUSION

Spautin-1 administration mitigates mild TBI-induced cognitive and memory dysfunction in mice, potentially through activation of caspase-3.

Pathogenic Aspects and Therapeutic Avenues of Autophagy in Parkinson's Disease

The progressive aging of the population and the fact that Parkinson's disease currently does not have any curative treatment turn out to be essential issues in the following years, where research has to play a critical role in developing therapy. Understanding this neurodegenerative disorder keeps advancing, proving the discovery of new pathogenesis-related genes through genome-wide association analysis. Furthermore, the understanding of its close link with the disruption of autophagy mechanisms in the last few years permits the elaboration of new animal models mimicking, through multiple pathways, different aspects of autophagic dysregulation, with the presence of pathological hallmarks, in brain regions affected by Parkinson's disease. The synergic advances in these fields permit the elaboration of multiple therapeutic strategies for restoring autophagy activity. This review discusses the features of Parkinson's disease, the autophagy mechanisms and their involvement in pathogenesis, and the current methods to correct this cellular pathway, from the development of animal models to the potentially curative treatments in the preclinical and clinical phase studies, which are the hope for patients who do not currently have any curative treatment.

Motor and non-motor features in Parkinson's Disease patients carrying GBA gene mutations

BACKGROUND

Mutations of the Glucocerebrosidase (GBA) gene are the most common genetic risk factor yet discovered for Parkinson's Disease (PD), being found in about 5-14% of Caucasian patients.

OBJECTIVE

We aimed to assess motor and non-motor symptoms (NMS) in patients with GBA-related PD (GBA-PD) in comparison with idiopathic PD (iPD) subjects using standardized and validated scales.

METHODS

Eleven (4 M, 7 F) patients with GBA-PD and 22 iPD patients, selected from the same cohort and matched for gender, age, and disease duration, were enrolled. The disease severity was assessed by Unified Parkinson's Disease Rating Scale-section III, gait disorder and falls by Freezing of Gait Questionnaire, and motor fluctuations by Wearing off questionnaire. NMS were evaluated using the following scales: Mini-Mental State Examination and extended neuropsychological battery, if required, Non-Motor Symptoms Scale, SCOPA-AUT Questionnaire, Apathy Evaluation Scale, Beck Depression Inventory, Epworth Sleepiness Scale, Restless Legs Syndrome Rating Scale, REM Sleep Behavior Disorder Screening Questionnaire, and Questionnaire for Impulsive-Compulsive Disorders in Parkinson's disease.

RESULTS

GBA-PD patients showed a more severe and rapidly progressive disease, and more frequent positive family history for PD, akinetic-rigid phenotype, postural instability, dementia, and psychosis in comparison to iPD. Two of three subjects carrying L444P mutation presented with early dementia. We also found a higher occurrence of fatigue, diurnal sleepiness, and intolerance to heat/cold in the carriers group.

CONCLUSIONS

Our results confirm that NMS and a more severe and faster disease course more frequently occur among GBA-PD patients in comparison to iPD.

Systems level analysis of sex-dependent gene expression changes in Parkinson's disease

Parkinson's disease (PD) is a heterogeneous disorder, and among the factors which influence the symptom profile, biological sex has been reported to play a significant role. While males have a higher age-adjusted disease incidence and are more frequently affected by muscle rigidity, females present more often with disabling tremors. The molecular mechanisms involved in these differences are still largely unknown, and an improved understanding of the relevant factors may open new avenues for pharmacological disease modification. To help address this challenge, we conducted a meta-analysis of disease-associated molecular sex differences in brain transcriptomics data from case/control studies. Both sex-specific (alteration in only one sex) and sex-dimorphic changes (changes in both sexes, but with opposite direction) were identified. Using further systems level pathway and network analyses, coordinated sex-related alterations were studied. These analyses revealed significant disease-associated sex differences in mitochondrial pathways and highlight specific regulatory factors whose activity changes can explain downstream network alterations, propagated through gene regulatory cascades. Single-cell expression data analyses confirmed the main pathway-level changes observed in bulk transcriptomics data. Overall, our analyses revealed significant sex disparities in PD-associated transcriptomic changes, resulting in coordinated modulations of molecular processes. Among the regulatory factors involved, NR4A2 has already been reported to harbor rare mutations in familial PD and its pharmacological activation confers neuroprotective effects in toxin-induced models of Parkinsonism. Our observations suggest that NR4A2 may warrant further research as a potential adjuvant therapeutic target to address a subset of pathological molecular features of PD that display sex-associated profiles.

Role of TFEB in Diseases Associated with Lysosomal Dysfunction

Transcription factor EB (TFEB) plays a very important role in the maintenance of cellular homeostasis. TFEB is a transcription factor that regulates the expression of several genes in the Coordinated Lysosomal Expression and Regulation (CLEAR) network. The CLEAR network genes are known to regulate many processes associated with the autophagy pathway and lysosome biogenesis. Lysosomes, which are degradative organelles in the cell, are associated with several cellular mechanisms, such as autophagy and phagocytosis. Recent studies have shown that TFEB dysregulation and lysosomal dysfunction are associated with several degenerative diseases. Thus, enhancing TFEB activity and accompanied induction of lysosomal function and autophagy can have tremendous therapeutic potential for the treatment of several degenerative diseases including age-related macular degeneration (AMD). In this chapter, we briefly illustrate the expression and regulation of TFEB in response to several cellular stressors and discuss the effects of TFEB overexpression to induce cellular clearance functions.

Multiple checkpoints of protein clearance machinery are modulated by a common microRNA, miR-4813-3p, through its putative target genes: Studies employing transgenic C. elegans model

In order to maintain cellular homeostasis and a healthy state, aberrant and aggregated proteins are to be recognized and rapidly cleared from cells. Parkinson's disease, known to be associated with multiple factors; presents with impaired clearance of aggregated alpha synuclein as a key factor. We endeavored to study microRNA molecules with potential role on regulating multiple checkpoints of protein quality control within cells. Carrying out global miRNA profiling in a transgenic C. elegans model that expresses human alpha synuclein, we identified novel miRNA, miR-4813-3p, as a significantly downregulated molecule. Further studying its putative downstream target genes, we were able to mechanistically characterize six genes gbf-1, vha-5, cup-5, cpd-2, acs-1 and C27A12.7, which relate to endpoints associated with alpha synuclein expression, oxidative stress, locomotory behavior, autophagy and apoptotic pathways. Our study reveals the novel role of miR-4813-3p and provides potential functional characterization of its putative target genes, in regulating the various pathways associated with PQC network. miR-4813-3p modulates ER^UPR, MT^UPR, autophagosome-lysosomal-pathway and the ubiquitin-proteasomal-system, making this molecule an interesting target for further studies towards therapeutically addressing multifactorial aspect of Parkinson's disease.

Plasma-derived phosphoglycerate mutase 5 as a biomarker for Parkinson’s disease

Background

We aimed to examine whether plasma-derived phosphoglycerate mutase 5 (PGAM5) can be a biomarker for Parkinson’s disease (PD) diagnosis as well as its association with the severity of motor/non-motor manifestations of PD.

Methods

We enrolled 124 patients with PD (PD group) and 50 healthy controls (HC group). We measured plasma PGAM5 levels using a quantitative sandwich enzyme immunoassay. Patients with PD underwent baseline evaluations using the Unified Parkinson’s Disease Rating Scale (UPDRS), while participants in both groups were evaluated using scales for non-motor manifestations. Receiver operating characteristic curves were used to evaluate the predictive utility of plasma PAMG5 alone and combined with other factors.

Results

Plasma PAMG5 levels were significantly higher in the PD group; the area under the curve (AUC) of plasma PGAM5 levels alone was 0.76. The AUC values for elderly participants and patients without hypertension were 0.78 and that for was 0.79. Notably, plasma PGAM5 levels combined with plasma oligomeric α-synuclein (α-syn) and the score of the REM sleep behavior disorder questionnaire-Hong Kong (RBDQ-HK) showed AUC values of 0.80 and 0.82. Multivariable logistic analysis revealed that plasma PAMG5 levels were independently associated with PD (odds ratio,1.875 [95% confidence interval 1.206–2.916], p = 0.005) but not the severity of motor/non-motor manifestations of PD.

Conclusion

Plasma PGAM5 is an independent biomarker for PD, especially among elderly patients (age > 60 years) and patients without hypertension. The predictive utility of PGAM5 was improved when combined with plasma oligomeric α-syn or the RBDQ-HK score.

Saposin C, Key Regulator in the Alpha-Synuclein Degradation Mediated by Lysosome

Lysosomal dysfunction has been proposed as one of the most important pathogenic molecular mechanisms in Parkinson disease (PD). The most significant evidence lies in the GBA gene, which encodes for the lysosomal enzyme β-glucocerebrosidase (β-GCase), considered the main genetic risk factor for sporadic PD. The loss of β-GCase activity results in the formation of α-synuclein deposits. The present study was aimed to determine the activity of the main lysosomal enzymes and the cofactors Prosaposin (PSAP) and Saposin C in PD and healthy controls, and their contribution to α-synuclein (α-Syn) aggregation. 42 PD patients and 37 age-matched healthy controls were included in the study. We first analyzed the β-GCase, β-galactosidase (β-gal), β-hexosaminidase (Hex B) and Cathepsin D (CatD) activities in white blood cells. We also measured the GBA, β-GAL, β-HEX, CTSD, PSAP, Saposin C and α-Syn protein levels by Western-blot. We found a 20% reduced β-GCase and β-gal activities in PD patients compared to controls. PSAP and Saposin C protein levels were significantly lower in PD patients and correlated with increased levels of α-synuclein. CatD, in contrast, showed significantly increased activity and protein levels in PD patients compared to controls. Increased CTSD protein levels in PD patients correlated, intriguingly, with a higher concentration of α-Syn. Our findings suggest that lysosomal dysfunction in sporadic PD is due, at least in part, to an alteration in Saposin C derived from reduced PSAP levels. That would lead to a significant decrease in the β-GCase activity, resulting in the accumulation of α-syn. The accumulation of monohexosylceramides might act in favor of CTSD activation and, therefore, increase its enzymatic activity. The evaluation of lysosomal activity in the peripheral blood of patients is expected to be a promising approach to investigate pathological mechanisms and novel therapies aimed to restore the lysosomal function in sporadic PD.

Implications of intracellular protein degradation pathways in Parkinson's disease and therapeutics

Parkinson's disease (PD) pathology is the most common motor neurodegenerative disease that occurs due to the progressive degeneration of dopaminergic neurons of the nigrostriatal pathway of the brain. The histopathological hallmark of the disease is fibrillary aggregate called Lewy bodies which majorly contain α-synuclein, suggesting the critical implication of diminished protein degradation mechanisms in disease pathogenesis. This α-synuclein-containing Lewy bodies are evident in both experimental models as well as in postmortem PD brain and are speculated to be pathogenic but still, the lineal association between these aggregates and the complexity of disease pathology is not yet well established and needs further attention. However, it has been reported that α-synuclein aggregates have consorted with the declined proteasome and lysosome activities. Therefore, in this review, we reappraise intracellular protein degradation mechanisms during PD pathology. This article focused on the findings of the last two decades suggesting the implications of protein degradation mechanisms in disease pathogenesis and based on shreds of evidence, some of the approaches are also suggested which may be adopted to find out the novel therapeutic targets for the management of PD patients.

Clinical Manifestations and Molecular Backgrounds of Parkinson's Disease Regarding Genes Identified From Familial and Population Studies

Over the past 20 years, numerous robust analyses have identified over 20 genes related to familial Parkinson's disease (PD), thereby uncovering its molecular underpinnings and giving rise to more sophisticated approaches to investigate its pathogenesis. α-Synuclein is a major component of Lewy bodies (LBs) and behaves in a prion-like manner. The discovery of α-Synuclein enables an in-depth understanding of the pathology behind the generation of LBs and dopaminergic neuronal loss. Understanding the pathophysiological roles of genes identified from PD families is uncovering the molecular mechanisms, such as defects in dopamine biosynthesis and metabolism, excessive oxidative stress, dysfunction of mitochondrial maintenance, and abnormalities in the autophagy–lysosome pathway, involved in PD pathogenesis. This review summarizes the current knowledge on familial PD genes detected by both single-gene analyses obeying the Mendelian inheritance and meta-analyses of genome-wide association studies (GWAS) from genome libraries of PD. Studying the functional role of these genes might potentially elucidate the pathological mechanisms underlying familial PD and sporadic PD and stimulate future investigations to decipher the common pathways between the diseases.

Role of Lysosomal Gene Variants in Modulating GBA-Associated Parkinson's Disease Risk

BACKGROUND

To date, variants in the GBA gene represent the most frequent large-effect genetic factor associated with Parkinson's disease (PD). However, the reason why individuals with the same GBA variant may or may not develop neurodegeneration and PD is still unclear.

OBJECTIVES

Therefore, we evaluated the contribution of rare variants in genes responsible for lysosomal storage disorders (LSDs) to GBA-PD risk, comparing the burden of deleterious variants in LSD genes in PD patients versus asymptomatic subjects, all carriers of deleterious variants in GBA.

METHODS

We used a custom next-generation sequencing panel, including 50 LSD genes, to screen 305 patients and 207 controls (discovery cohort). Replication and meta-analysis were performed in two replication cohorts of GBA-variant carriers, of 250 patients and 287 controls, for whom exome or genome data were available.

RESULTS

Statistical analysis in the discovery cohort revealed a significantly increased burden of deleterious variants in LSD genes in patients (P = 0.0029). Moreover, our analyses evidenced that the two strongest modifiers of GBA penetrance are a second variation in GBA (5.6% vs. 1.4%, P = 0.023) and variants in genes causing mucopolysaccharidoses (6.9% vs. 1%, P = 0.0020). These results were confirmed in the meta-analysis, where we observed pooled odds ratios of 1.42 (95% confidence interval [CI] = 1.10-1.83, P = 0.0063), 4.36 (95% CI = 2.02-9.45, P = 0.00019), and 1.83 (95% CI = 1.04-3.22, P = 0.038) for variants in LSD genes, GBA, and mucopolysaccharidosis genes, respectively.

CONCLUSION

The identification of genetic lesions in lysosomal genes increasing PD risk may have important implications in terms of patient stratification for future therapeutic trials. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson Movement Disorder Society.

Recombinant pro-CTSD (cathepsin D) enhances SNCA/α-Synuclein degradation in α-Synucleinopathy models

Parkinson disease (PD) is a neurodegenerative disorder characterized by the abnormal intracellular accumulation of SNCA/α-synuclein. While the exact mechanisms underlying SNCA pathology are not fully understood, increasing evidence suggests the involvement of autophagy as well as lysosomal deficiencies. Because CTSD (cathepsin D) has been proposed to be the major lysosomal protease involved in SNCA degradation, its deficiency has been linked to the presence of insoluble SNCA conformers in the brain of mice and humans as well as to the transcellular transmission of SNCA aggregates. We here postulate that SNCA degradation can be enhanced by the application of the recombinant human proform of CTSD (rHsCTSD). Our results reveal that rHsCTSD is efficiently endocytosed by neuronal cells, correctly targeted to lysosomes and matured to an enzymatically active protease. In dopaminergic neurons derived from induced pluripotent stem cells (iPSC) of PD patients harboring the A53T mutation within the SNCA gene, we confirm the reduction of insoluble SNCA after treatment with rHsCTSD. Moreover, we demonstrate a decrease of pathological SNCA conformers in the brain and within primary neurons of a ctsd-deficient mouse model after dosing with rHsCTSD. Boosting lysosomal CTSD activity not only enhanced SNCA clearance in human and murine neurons as well as tissue, but also restored endo-lysosome and autophagy function. Our findings indicate that CTSD is critical for SNCA clearance and function. Thus, enzyme replacement strategies utilizing CTSD may also be of therapeutic interest for the treatment of PD and other synucleinopathies aiming to decrease the SNCA burden.Abbreviations: aa: amino acid; SNCA/α-synuclein: synuclein alpha; APP: amyloid beta precursor protein; BBB: blood brain barrier; BF: basal forebrain; CBB: Coomassie Brilliant Blue; CLN: neuronal ceroid lipofuscinosis; CNL10: neuronal ceroid lipofuscinosis type 10; Corr.: corrected; CTSD: cathepsin D; CTSB: cathepsin B; DA: dopaminergic; DA-iPSn: induced pluripotent stem cell-derived dopaminergic neurons; dox: doxycycline; ERT: enzyme replacement therapy; Fx: fornix, GBA/β-glucocerebrosidase: glucosylceramidase beta; h: hour; HC: hippocampus; HT: hypothalamus; i.c.: intracranially; IF: immunofluorescence; iPSC: induced pluripotent stem cell; KO: knockout; LAMP1: lysosomal associated membrane protein 1; LSDs: lysosomal storage disorders; MAPT: microtubule associated protein tau; M6P: mannose-6-phosphate; M6PR: mannose-6-phosphate receptor; MB: midbrain; mCTSD: mature form of CTSD; neurofil.: neurofilament; PD: Parkinson disease; proCTSD: proform of CTSD; PRNP: prion protein; RFU: relative fluorescence units; rHsCTSD: recombinant human proCTSD; SAPC: Saposin C; SIM: structured illumination microscopy; T-insol: Triton-insoluble; T-sol: Triton-soluble; TEM: transmission electron microscopy, TH: tyrosine hydroxylase; Thal: thalamus.

Over-Mutated Mitochondrial, Lysosomal and TFEB-Regulated Genes in Parkinson's Disease

The association between Parkinson's disease (PD) and mutations in genes involved in lysosomal and mitochondrial function has been previously reported. However, little is known about the involvement of other genes or cellular mechanisms. We aim to identify novel genetic associations to better understand the pathogenesis of PD. We performed WES in a cohort of 32 PD patients and 30 age-matched controls. We searched for rare variants in 1667 genes: PD-associated, related to lysosomal function and mitochondrial function and TFEB-regulated. When comparing the PD patient cohort with that of age matched controls, a statistically significant burden of rare variants in the previous group of genes were identified. In addition, the Z-score calculation, using the European population database (GnomAD), showed an over-representation of particular variants in 36 genes. Interestingly, 11 of these genes are implicated in mitochondrial function and 18 are TFEB-regulated genes. Our results suggest, for the first time, an involvement of TFEB-regulated genes in the genetic susceptibility to PD. This is remarkable as TFEB factor has been reported to be sequestered inside Lewy bodies, pointing to a role of TFEB in the pathogenesis of PD. Our data also reinforce the involvement of lysosomal and mitochondrial mechanisms in PD.

Update on CSF Biomarkers in Parkinson's Disease

Progress in developing disease-modifying therapies in Parkinson’s disease (PD) can only be achieved through reliable objective markers that help to identify subjects at risk. This includes an early and accurate diagnosis as well as continuous monitoring of disease progression and therapy response. Although PD diagnosis still relies mainly on clinical features, encouragingly, advances in biomarker discovery have been made. The cerebrospinal fluid (CSF) is a biofluid of particular interest to study biomarkers since it is closest to the brain structures and therefore could serve as an ideal source to reflect ongoing pathologic processes. According to the key pathophysiological mechanisms, the CSF status of α-synuclein species, markers of amyloid and tau pathology, neurofilament light chain, lysosomal enzymes and markers of neuroinflammation provide promising preliminary results as candidate biomarkers. Untargeted approaches in the field of metabolomics provide insights into novel and interconnected biological pathways. Markers based on genetic forms of PD can contribute to identifying subgroups suitable for gene-targeted treatment strategies that might also be transferable to sporadic PD. Further validation analyses in large PD cohort studies will identify the CSF biomarker or biomarker combinations with the best value for clinical and research purposes.

Astrocytes protect dopaminergic neurons against aminochrome neurotoxicity

Astrocytes protect neurons by modulating neuronal function and survival. Astrocytes support neurons in several ways. They provide energy through the astrocyte-neuron lactate shuttle, protect neurons from excitotoxicity, and internalize neuronal lipid droplets to degrade fatty acids for neuronal metabolic and synaptic support, as well as by their high capacity for glutamate uptake and the conversion of glutamate to glutamine. A recent reported astrocyte system for protection of dopamine neurons against the neurotoxic products of dopamine, such as aminochrome and other o-quinones, were generated under neuromelanin synthesis by oxidizing dopamine catechol structure. Astrocytes secrete glutathione transferase M2-2 through exosomes that transport this enzyme into dopaminergic neurons to protect these neurons against aminochrome neurotoxicity. The role of this new astrocyte protective mechanism in Parkinson´s disease is discussed.

Pitavastatin activates mitophagy to protect EPC proliferation through a calcium-dependent CAMK1-PINK1 pathway in atherosclerotic mice

Statins play a major role in reducing circulating cholesterol levels and are widely used to prevent coronary artery disease. Although they are recently confirmed to up-regulate mitophagy, little is known about the molecular mechanisms and its effect on endothelial progenitor cell (EPC). Here, we explore the role and mechanism underlying statin (pitavastatin, PTV)-activated mitophagy in EPC proliferation. ApoE^−/− mice are fed a high-fat diet for 8 weeks to induce atherosclerosis. In these mice, EPC proliferation decreases and is accompanied by mitochondrial dysfunction and mitophagy impairment via the PINK1-PARK2 pathway. PTV reverses mitophagy and reduction in proliferation. Pink1 knockout or silencing Atg7 blocks PTV-induced proliferation improvement, suggesting that mitophagy contributes to the EPC proliferation increase. PTV elicits mitochondrial calcium release into the cytoplasm and further phosphorylates CAMK1. Phosphorylated CAMK1 contributes to PINK1 phosphorylation as well as mitophagy and mitochondrial function recover in EPCs. Together, our findings describe a molecular mechanism of mitophagy activation, where mitochondrial calcium release promotes CAMK1 phosphorylation of threonine¹⁷⁷ before phosphorylation of PINK1 at serine²²⁸, which recruits PARK2 and phosphorylates its serine⁶⁵ to activate mitophagy. Our results further account for the pleiotropic effects of statins on the cardiovascular system and provide a promising and potential therapeutic target for atherosclerosis.

Endothelial progenitor cell (EPCs) proliferation decreased, accompanied by mitochondrial dysfunction and mitophagy impairment via the PINK1-PARK2 pathway in atherosclerosis. Statins induce mitophagy to protect EPCs by mitochondrial calcium release and CAMK1-mediated PINK1 phosphorylation.

Prevalence of Fabry Disease among Patients with Parkinson's Disease

BACKGROUND

An increased prevalence of Parkinson's disease (PD) disease has been previously reported in subjects with Fabry disease (FD) carrying alpha-galactosidase (GLA) mutations and their first-line relatives. Moreover, decreased alpha-galactosidase A (AGLA) enzymatic activity has been reported among cases with PD compared to controls.

OBJECTIVE

The aim of our study was to determine the prevalence of FD among patients with PD.

METHODS

We recruited 236 consecutive patients with PD from February 2018 to December 2020. Clinical and sociodemographic data, including the MDS-UPDRS-III scores and HY stage (the Hoehn and Yahr scale), were collected, and in-depth phenotyping was performed in subjects with identified GLA variants. A multistep approach, including standard determination of AGLA activity and LysoGb3 in males, and next-generation based GLA sequencing in all females and males with abnormal AGLA levels was performed in a routine diagnostic setting.

RESULTS

The mean age of our patients was 68.9 ± 8.9 years, 130 were men (55.1%), and the mean disease duration was 7.77 ± 5.35 years. Among 130 men, AGLA levels were low in 20 patients (15%), and subsequent Lyso-Gb3 testing showed values within the reference range for all tested subjects. In 126 subsequently genetically tested patients, four heterozygous p.(Asp313Tyr) GLA variants (3.2%, MAF 0.016) were identified; all were females. None of the 4 GLA variant carriers identified had any clinical manifestation suggestive of FD.

CONCLUSIONS

The results of this study suggest a possible relationship between FD and PD in a small proportion of cases. Nevertheless, the GLA variant found in our cohort is classified as a variant of unknown significance. Therefore, its pathogenic causative role in the context of PD needs further elucidation, and these findings should be interpreted with caution.

New Promising Therapeutic Avenues of Curcumin in Brain Diseases

Curcumin, the dietary polyphenol isolated from Curcuma longa (turmeric), is commonly used as an herb and spice worldwide. Because of its bio-pharmacological effects curcumin is also called "spice of life", in fact it is recognized that curcumin possesses important proprieties such as anti-oxidant, anti-inflammatory, anti-microbial, antiproliferative, anti-tumoral, and anti-aging. Neurodegenerative diseases such as Alzheimer's Diseases, Parkinson's Diseases, and Multiple Sclerosis are a group of diseases characterized by a progressive loss of brain structure and function due to neuronal death; at present there is no effective treatment to cure these diseases. The protective effect of curcumin against some neurodegenerative diseases has been proven by in vivo and in vitro studies. The current review highlights the latest findings on the neuroprotective effects of curcumin, its bioavailability, its mechanism of action and its possible application for the prevention or treatment of neurodegenerative disorders.

The Association Between Lysosomal Storage Disorder Genes and Parkinson's Disease: A Large Cohort Study in Chinese Mainland Population

Background: Recent years have witnessed an increasing number of studies indicating an essential role of the lysosomal dysfunction in Parkinson’s disease (PD) at the genetic, biochemical, and cellular pathway levels. In this study, we investigated the association between rare variants in lysosomal storage disorder (LSD) genes and Chinese mainland PD.

Methods: We explored the association between rare variants of 69 LSD genes and PD in 3,879 patients and 2,931 controls from Parkinson’s Disease & Movement Disorders Multicenter Database and Collaborative Network in China (PD-MDCNC) using next-generation sequencing, which were analyzed by using the optimized sequence kernel association test.

Results: We identified the significant burden of rare putative LSD gene variants in Chinese mainland patients with PD. This association was robust in familial or sporadic early-onset patients after excluding the GBA variants but not in sporadic late-onset patients. The burden analysis of variant sets in genes of LSD subgroups revealed a suggestive significant association between variant sets in genes of sphingolipidosis deficiency disorders and familial or sporadic early-onset patients. In contrast, variant sets in genes of sphingolipidoses, mucopolysaccharidoses, and post-translational modification defect disorders were suggestively associated with sporadic late-onset patients. Then, SMPD1 and other four novel genes (i.e., GUSB, CLN6, PPT1, and SCARB2) were suggestively associated with sporadic early-onset or familial patients, whereas GALNS and NAGA were suggestively associated with late-onset patients.

Conclusion: Our findings supported the association between LSD genes and PD and revealed several novel risk genes in Chinese mainland patients with PD, which confirmed the importance of lysosomal mechanisms in PD pathogenesis. Moreover, we identified the genetic heterogeneity in early-onset and late-onset of patients with PD, which may provide valuable suggestions for the treatment.

Downregulating expression of OPTN elevates neuroinflammation via AIM2 inflammasome- and RIPK1-activating mechanisms in APP/PS1 transgenic mice

BACKGROUND

Neuroinflammation is thought to be a cause of Alzheimer's disease (AD), which is partly caused by inadequate mitophagy. As a receptor of mitophagy, we aimed to reveal the regulatory roles of optineurin (OPTN) on neuroinflammation in the pathogenesis of AD.

METHODS

BV2 cells and APP/PS1 transgenic (Tg) mice were used as in vitro and in vivo experimental models to determine the regulatory roles of OPTN in neuroinflammation of AD. Sophisticated molecular technologies including quantitative (q) RT-PCR, western blot, enzyme linked immunosorbent assay (ELISA), co-immunoprecipitation (Co-IP) and immunofluorescence (IF) were employed to reveal the inherent mechanisms.

RESULTS

As a consequence, key roles of OPTN in regulating neuroinflammation were identified by depressing the activity of absent in melanoma 2 (AIM2) inflammasomes and receptor interacting serine/threonine kinase 1 (RIPK1)-mediated NF-κB inflammatory mechanisms. In detail, we found that expression of OPTN was downregulated, which resulted in activation of AIM2 inflammasomes due to a deficiency in mitophagy in APP/PS1 Tg mice. By ectopic expression, OPTN blocks the effects of Aβ oligomer (Aβo) on activating AIM2 inflammasomes by inhibiting mRNA expression of AIM2 and apoptosis-associated speck-like protein containing a C-terminal caspase recruitment domain (ASC), leading to a reduction in the active form of caspase-1 and interleukin (IL)-1β in microglial cells. Moreover, RIPK1 was also found to be negatively regulated by OPTN via ubiquitin protease hydrolysis, resulting in the synthesis of IL-1β by activating the transcriptional activity of NF-κB in BV2 cells. As an E3 ligase, the UBAN domain of OPTN binds to the death domain (DD) of RIPK1 to facilitate its ubiquitination. Based on these observations, ectopically expressed OPTN in APP/PS1 Tg mice deactivated microglial cells and astrocytes via the AIM2 inflammasome and RIPK-dependent NF-κB pathways, leading to reduce neuroinflammation.

CONCLUSIONS

These results suggest that OPTN can alleviate neuroinflammation through AIM2 and RIPK1 pathways, suggesting that OPTN deficiency may be a potential factor leading to the occurrence of AD.

Nanoparticles With Affinity for α-Synuclein Sequester α-Synuclein to Form Toxic Aggregates in Neurons With Endolysosomal Impairment

Parkinson's disease (PD) is one of the most common neurodegenerative diseases. It is characterized pathologically by the aggregation of α-synuclein (αS) in the form of Lewy bodies and Lewy neurites. A major challenge in PD therapy is poor efficiency of drug delivery to the brain due to the blood-brain barrier (BBB). For this reason, nanomaterials, with significant advantages in drug delivery, have gained attention. On the other hand, recent studies have shown that nanoparticles can promote αS aggregation in salt solution. Therefore, we tested if nanoparticles could have the same effect in cell models. We found that nanoparticle can induce cells to form αS inclusions as shown in immunocytochemistry, and detergent-resistant αS aggregates as shown in biochemical analysis; and nanoparticles of smaller size can induce more αS inclusions. Moreover, the induction of αS inclusions is in part dependent on endolysosomal impairment and the affinity of αS to nanoparticles. More importantly, we found that the abnormally high level of endogenous lysosomotropic biomolecules (e.g., sphingosine), due to impairing the integrity of endolysosomes could be a determinant factor for the susceptibility of cells to nanoparticle-induced αS aggregation; and deletion of GBA1 gene to increase the level of intracellular sphingosine can render cultured cells more susceptible to the formation of αS inclusions in response to nanoparticle treatment. Ultrastructural examination of nanoparticle-treated cells revealed that the induced inclusions contained αS-immunopositive membranous structures, which were also observed in inclusions seeded by αS fibrils. These results suggest caution in the use of nanoparticles in PD therapy. Moreover, this study further supports the role of endolysosomal impairment in PD pathogenesis and suggests a possible mechanism underlying the formation of membrane-associated αS pathology.

Selective Autophagy as a Potential Therapeutic Target in Age-Associated Pathologies

Progressive accumulation of damaged cellular constituents contributes to age-related diseases. Autophagy is the main catabolic process, which recycles cellular material in a multitude of tissues and organs. Autophagy is activated upon nutrient deprivation, and oncogenic, heat or oxidative stress-induced stimuli to selectively degrade cell constituents and compartments. Specificity and accuracy of the autophagic process is maintained via the precision of interaction of autophagy receptors or adaptors and substrates by the intricate, stepwise orchestration of specialized integrating stimuli. Polymorphisms in genes regulating selective autophagy have been linked to aging and age-associated disorders. The involvement of autophagy perturbations in aging and disease indicates that pharmacological agents balancing autophagic flux may be beneficial, in these contexts. Here, we introduce the modes and mechanisms of selective autophagy, and survey recent experimental evidence of dysfunctional autophagy triggering severe pathology. We further highlight identified pharmacological targets that hold potential for developing therapeutic interventions to alleviate cellular autophagic cargo burden and associated pathologies.