Statins reduce neuronal alpha-synuclein aggregation in in vitro models of Parkinson's disease

Interactions of alpha-synuclein with membranes in Parkinson's disease: Mechanisms and therapeutic strategies

Parkinson's disease (PD), the second most common neurodegenerative disease worldwide, is marked by the presence of Lewy bodies and Lewy neurites, neuronal lesions containing large amounts of the synaptic protein alpha-synuclein (αS). While the underlying mechanisms of disease progression in PD remain unclear, increasing evidence supports the importance of interactions between αS and cellular membranes in PD pathology. Therefore, understanding the αS-membrane interplay in health and disease is crucial for the development of therapeutic strategies. In this review, we (1) discuss key scenarios of pathological αS-membrane interactions; (2) present in detail therapeutic strategies explicitly reported to modify αS-membrane interactions; and (3) introduce additional therapeutic strategies that may involve aspects of interfering with αS-membrane interaction. This way, we aim to provide a holistic perspective on this important aspect of disease-modifying strategies for PD and other α-synucleinopathies.

Cholesterol Metabolism in Neurodegenerative Diseases

Significance: Cholesterol plays a crucial role in the brain, where it is highly concentrated and tightly regulated to support normal brain functions. It serves as a vital component of cell membranes, ensuring their integrity, and acts as a key regulator of various brain processes. Dysregulation of cholesterol metabolism in the brain has been linked to impaired brain function and the onset of neurodegenerative diseases such as Alzheimer's disease (AD), Parkinson's disease, and Huntington's disease. Recent Advances: A significant advancement has been the identification of astrocyte-derived apoliprotein E as a key regulator of de novo cholesterol biosynthesis in neurons, providing insights into how extracellular signals influence neuronal cholesterol levels. In addition, the development of antibody-based therapies, particularly for AD, presents promising opportunities for therapeutic interventions. Critical Issues: Despite significant research, the association between cholesterol and neurodegenerative diseases remains inconclusive. It is crucial to distinguish between plasma cholesterol and brain cholesterol, as these pools are relatively independent. This differentiation should be considered when evaluating statin-based treatment approaches. Furthermore, assessing not only the total cholesterol content in the brain but also its distribution among different types of brain cells is essential. Future Direction: Establishing a causal link between changes in brain/plasma cholesterol levels and the onset of brain dysfunction/neurodegenerative diseases remains a key objective. In addition, conducting cell-specific analyses of cholesterol homeostasis in various types of brain cells under pathological conditions will enhance our understanding of cholesterol metabolism in neurodegenerative diseases. Manipulating cholesterol levels to restore homeostasis may represent a novel approach for alleviating neurological symptoms.

Association of lipid levels with motor and cognitive function and decline in Parkinson's disease

BACKGROUND

Most studies have focused on comparing blood lipid biomarkers between Parkinson's disease (PD) and normal controls (NC). However, further research is necessary to explore the impact of blood lipid levels on motor and cognitive function, as well as the progression of motor dysfunction and cognitive decline over time. Thus, the aim of this study is to investigate the relationship between blood lipid biomarkers and these indicators in individuals with PD.

METHODS

The cohort study enrolled 157 PD patients and 146 NC from the Tianjin Huanhu Hospital from September 2017 to September 2019. Serum lipid fractions were detected in fasting serum samples. PD patients were followed up at 2 ± 0.6 years for clinical assessment.

RESULTS

PD patients exhibited lower serum triglyceride (TG) levels as compared to NC (P = 0.008). PD male patients exhibited lower serum lipoprotein cholesterol(LDL-C) and total cholesterol (TC) levels than female patients (LDL-C: P = 0.034; TC: P = 0.019). Serum TG levels correlated significantly with Unified PD Rating Scale III, Hoehn and Yahr stage and Montreal Cognitive Assessment scores in PD patients. Additionally, serum TG levels were associated with follow-up motor function decline and cognitive decline in adjusted regression models in PD patients.

CONCLUSIONS

To summarise, the study findings suggest that decreased serum TG levels are significantly associated with greater motor dysfunction, cognitive dysfunction and the greater deterioration of the two indicators.

Targeting dysregulated lipid metabolism for the treatment of Alzheimer's disease and Parkinson's disease: Current advancements and future prospects

Alzheimer's and Parkinson's diseases are two of the most frequent neurological diseases. The clinical features of AD are memory decline and cognitive dysfunction, while PD mainly manifests as motor dysfunction such as limb tremors, muscle rigidity abnormalities, and slow gait. Abnormalities in cholesterol, sphingolipid, and glycerophospholipid metabolism have been demonstrated to directly exacerbate the progression of AD by stimulating Aβ deposition and tau protein tangles. Indirectly, abnormal lipids can increase the burden on brain vasculature, induce insulin resistance, and affect the structure of neuronal cell membranes. Abnormal lipid metabolism leads to PD through inducing accumulation of α-syn, dysfunction of mitochondria and endoplasmic reticulum, and ferroptosis. Great progress has been made in targeting lipid metabolism abnormalities for the treatment of AD and PD in recent years, like metformin, insulin, peroxisome proliferator-activated receptors (PPARs) agonists, and monoclonal antibodies targeting apolipoprotein E (ApoE). This review comprehensively summarizes the involvement of dysregulated lipid metabolism in the pathogenesis of AD and PD, the application of Lipid Monitoring, and emerging lipid regulatory drug targets. A better understanding of the lipidological bases of AD and PD may pave the way for developing effective prevention and treatment methods for neurodegenerative disorders.

Brain cholesterol homeostasis and its association with neurodegenerative diseases

The brain is the most cholesterol-rich organ in mammals. However, cholesterol metabolism in the brain is completely independent of other tissues due to the presence of the blood-brain barrier (BBB). Neurons, astrocytes and oligodendrocytes are the main cells responsible for cholesterol synthesis in the brain. The cholesterol content in the brain is maintained at a relatively constant level under strict regulation of synthesis, transport, and turnover, that is, brain cholesterol homeostasis. Once this balance is disrupted, neurodegenerative diseases including Alzheimer's disease (AD), Parkinson's disease (PD) and Huntington's disease (HD) ensue. This review summarizes the processes controlling cholesterol homeostasis with respect to the synthesis, transport and turnover of cholesterol in the brain. We further focus on how cholesterol imbalance contributes to neurodegenerative diseases to explore the possibilities to modulate the key steps involved, which will provide clues for the development of therapies for the treatment of central nervous system (CNS) diseases.

The Bidirectional Interplay of α-Synuclein with Lipids in the Central Nervous System and Its Implications for the Pathogenesis of Parkinson's Disease

The alteration and aggregation of alpha-synuclein (α-syn) play a crucial role in neurodegenerative diseases collectively termed as synucleinopathies, including Parkinson's disease (PD). The bidirectional interaction of α-syn with lipids and biomembranes impacts not only α-syn aggregation but also lipid homeostasis. Indeed, lipid composition and metabolism are severely perturbed in PD. One explanation for lipid-associated alterations may involve structural changes in α-syn, caused, for example, by missense mutations in the lipid-binding region of α-syn as well as post-translational modifications such as phosphorylation, acetylation, nitration, ubiquitination, truncation, glycosylation, and glycation. Notably, different strategies targeting the α-syn-lipid interaction have been identified and are able to reduce α-syn pathology. These approaches include the modulation of post-translational modifications aiming to reduce the aggregation of α-syn and modify its binding properties to lipid membranes. Furthermore, targeting enzymes involved in various steps of lipid metabolism and exploring the neuroprotective potential of lipids themselves have emerged as novel therapeutic approaches. Taken together, this review focuses on the bidirectional crosstalk of α-syn and lipids and how alterations of this interaction affect PD and thereby open a window for therapeutic interventions.

Statins suppress cell-to-cell propagation of α-synuclein by lowering cholesterol

Cell-to-cell propagation of protein aggregates has been implicated in the progression of neurodegenerative diseases. However, the underlying mechanism and modulators of this process are not fully understood. Here, we screened a small-molecule library in a search for agents that suppress the propagation of α-synuclein and mutant huntingtin (mHtt). These screens yielded several molecules, some of which were effective against both α-synuclein and mHtt. Among these molecules, we focused on simvastatin and pravastatin. Simvastatin administration in a transgenic model of synucleinopathy effectively ameliorated behavioral deficits and α-synuclein accumulation, whereas pravastatin had no effect. Because only simvastatin enters the brain effectively, these results suggest that inhibition of brain cholesterol synthesis is important in simvastatin effects. In cultured cells, accumulation of intracellular cholesterol, induced by genetic ablation of the NPC1 gene or by pharmacological treatment with U18666A, increased α-synuclein aggregation and secretion. In contrast, lowering cholesterol using methyl-β-cyclodextrin or statins reversed α-synuclein aggregation and secretion in NPC1-knockout cells. Consistent with these observations, feeding a high-fat diet aggravated α-synuclein pathology and behavioral deficits in the preformed fibril-injected mouse model, an effect that was also reversed by simvastatin administration. These results suggest that statins suppress propagation of protein aggregates by lowering cholesterol in the brain.

UBL3 Interacts with Alpha-Synuclein in Cells and the Interaction Is Downregulated by the EGFR Pathway Inhibitor Osimertinib

Ubiquitin-like 3 (UBL3) acts as a post-translational modification (PTM) factor and regulates protein sorting into small extracellular vesicles (sEVs). sEVs have been reported as vectors for the pathology propagation of neurodegenerative diseases, such as α-synucleinopathies. Alpha-synuclein (α-syn) has been widely studied for its involvement in α-synucleinopathies. However, it is still unknown whether UBL3 interacts with α-syn, and is influenced by drugs or compounds. In this study, we investigated the interaction between UBL3 and α-syn, and any ensuing possible functional and pathological implications. We found that UBL3 can interact with α-syn by the Gaussia princeps based split luciferase complementation assay in cells and immunoprecipitation, while cysteine residues at its C-terminal, which are considered important as PTM factors for UBL3, were not essential for the interaction. The interaction was upregulated by 1-methyl-4-phenylpyridinium exposure. In drug screen results, the interaction was significantly downregulated by the treatment of osimertinib. These results suggest that UBL3 interacts with α-syn in cells and is significantly downregulated by epidermal growth factor receptor (EGFR) pathway inhibitor osimertinib. Therefore, the UBL3 pathway may be a new therapeutic target for α-synucleinopathies in the future.

Metabolic dysfunctions in the intranigral rotenone model of Parkinson's disease

Parkinson disease (PD) is a chronic neurodegenerative disorder characterized by a progressive loss of dopamine neurons in the substantia nigra pars compacta (SNpc). In the last years, a growing interest to study the relationship between metabolic dysfunction and neurodegenerative disease like PD has emerged. This study aimed to evaluate the occurrence of possible changes in metabolic homeostasis due to intranigral rotenone administration, a neurotoxin that damages dopaminergic neurons leading to motor impairments mimicking those that happen in PD. Male Wistar rats were distributed into two groups: sham (n = 10) or rotenone (n = 10). Sham group received, bilaterally, within the SNpc, 1 µL of vehicle dimethyl-sulfoxide (DMSO) and the experimental group was bilaterally injected with 1 µL of rotenone (12 µg/µL). Twenty-four hours after the stereotaxic surgeries, the animals underwent the open field test followed by subsequent peripheral blood and cerebrospinal fluid (CSF) samples collection for biochemical testing. The results showed that rotenone was able to replicate the typical motor behavior impairment seen in the disease, i.e., decrease in locomotion (P = 0.05) and increase in immobility (P = 0.01) with a strong correlation (r = - 0.85; P < 0.0001) between them. In addition, it was demonstrated that this model is able to decrease plasmatic total-cholesterol (P = 0.04) and HDL-cholesterol (P = 0.007) potentially impacting peripheral metabolism. Hence, it was revealed a potential ability to reproduce relevant metabolic dysfunctions like hyperglycemia which could be explained by acute and systemic mitochondrial rotenone toxicity and SNpc nigral toxicity. Such mechanisms may still be responsible for the potential occurrence of CSF-hyperglycemia (d = 0.7). Since intranigral rotenone is an early phase model of PD, the present results open a new road for studies aiming to investigate metabolic changes in PD.

Promising biomarkers and therapeutic targets for the management of Parkinson's disease: recent advancements and contemporary research

Parkinson's disease (PD) is one of the progressive neurological diseases which affect around 10 million population worldwide. The clinical manifestation of motor symptoms in PD patients appears later when most dopaminergic neurons have degenerated. Thus, for better management of PD, the development of accurate biomarkers for the early prognosis of PD is imperative. The present work will discuss the potential biomarkers from various attributes covering biochemical, microRNA, and neuroimaging aspects (α-synuclein, DJ-1, UCH-L1, β-glucocerebrosidase, BDNF, etc.) for diagnosis, recent development in PD management, and major limitations with current and conventional anti-Parkinson therapy. This manuscript summarizes potential biomarkers and therapeutic targets, based on available preclinical and clinical evidence, for better management of PD.

Recent Advances in Drug Therapy for Parkinson's Disease

Parkinson's disease (PD) is a neurodegenerative disease manifesting with motor and non-motor symptoms. Current treatment mainly relies on medication as a symptomatic therapy modulating neurotransmitters. Dopamine replacement therapy has been established, and levodopa is the gold standard for treatment of PD. However, the emergence of motor complications, such as a wearing-off phenomenon, is a clinical problem. Both primary symptoms and motor complications have been targets for the development of treatments for PD. Recent progression in the management of motor complications is supported by newly developed agents and advances in device and formulation technology to deliver drugs continuously. Elucidation of the pathophysiology of PD and the development of disease-modifying therapy that affects the underlying fundamental pathophysiology of the disease are also progressing. In this review, we introduce current knowledge on developments concerning medications for patients with PD.

LRRK2 and Lipid Pathways: Implications for Parkinson's Disease

Genetic alterations in the LRRK2 gene, encoding leucine-rich repeat kinase 2, are a common risk factor for Parkinson's disease. How LRRK2 alterations lead to cell pathology is an area of ongoing investigation, however, multiple lines of evidence suggest a role for LRRK2 in lipid pathways. It is increasingly recognized that in addition to being energy reservoirs and structural entities, some lipids, including neural lipids, participate in signaling cascades. Early investigations revealed that LRRK2 localized to membranous and vesicular structures, suggesting an interaction of LRRK2 and lipids or lipid-associated proteins. LRRK2 substrates from the Rab GTPase family play a critical role in vesicle trafficking, lipid metabolism and lipid storage, all processes which rely on lipid dynamics. In addition, LRRK2 is associated with the phosphorylation and activity of enzymes that catabolize plasma membrane and lysosomal lipids. Furthermore, LRRK2 knockout studies have revealed that blood, brain and urine exhibit lipid level changes, including alterations to sterols, sphingolipids and phospholipids, respectively. In human LRRK2 mutation carriers, changes to sterols, sphingolipids, phospholipids, fatty acyls and glycerolipids are reported in multiple tissues. This review summarizes the evidence regarding associations between LRRK2 and lipids, and the functional consequences of LRRK2-associated lipid changes are discussed.

Regulation of cholesterol homeostasis in health and diseases: from mechanisms to targeted therapeutics

Disturbed cholesterol homeostasis plays critical roles in the development of multiple diseases, such as cardiovascular diseases (CVD), neurodegenerative diseases and cancers, particularly the CVD in which the accumulation of lipids (mainly the cholesteryl esters) within macrophage/foam cells underneath the endothelial layer drives the formation of atherosclerotic lesions eventually. More and more studies have shown that lowering cholesterol level, especially low-density lipoprotein cholesterol level, protects cardiovascular system and prevents cardiovascular events effectively. Maintaining cholesterol homeostasis is determined by cholesterol biosynthesis, uptake, efflux, transport, storage, utilization, and/or excretion. All the processes should be precisely controlled by the multiple regulatory pathways. Based on the regulation of cholesterol homeostasis, many interventions have been developed to lower cholesterol by inhibiting cholesterol biosynthesis and uptake or enhancing cholesterol utilization and excretion. Herein, we summarize the historical review and research events, the current understandings of the molecular pathways playing key roles in regulating cholesterol homeostasis, and the cholesterol-lowering interventions in clinics or in preclinical studies as well as new cholesterol-lowering targets and their clinical advances. More importantly, we review and discuss the benefits of those interventions for the treatment of multiple diseases including atherosclerotic cardiovascular diseases, obesity, diabetes, nonalcoholic fatty liver disease, cancer, neurodegenerative diseases, osteoporosis and virus infection.

Two statins and cromolyn as possible drugs against the cytotoxicity of Aβ(31-35) and Aβ(25-35) peptides: a comparative study by advanced computer simulation methods

In this work, possible effective mechanisms of cromolyn, atorvastatin and lovastatin on the cytotoxicity of Aβ(31-35) and Aβ(25-35) peptides were investigated by classical molecular dynamics and well-tempered metadynamics simulations. The results demonstrate that all the drugs affect the behavior of the peptides, such as their ability to aggregate, and alter their secondary structures and their affinity to a particular drug. Our findings from the computed properties suggest that the best drug candidate is lovastatin. This medicine inhibits peptide aggregation, adsorbs the peptides on the surface of the drug clusters, changes the secondary structure and binds to MET₃₅, which has been seen as the reason for the toxicity of the studied peptide sequences. Moreover, lovastatin is the drug which previously has demonstrated the strongest ability to penetrate the blood-brain barrier and makes lovastatin the most promising medicine among the three investigated drugs. Atorvastatin is also seen as a potential candidate if its penetration through the blood-brain barrier could be improved. Otherwise, its properties are even better than the ones demonstrated by lovastatin. Cromolyn appears to be less interesting as an anti-aggregant from the computational data, in comparison to the two statins.

Parkinson’s Disease Progression and Statins: Hydrophobicity Matters

Background: Recent randomized clinical trials using hydrophobic statins reported no influence on Parkinson’s disease (PD) clinical progression. Hydrophobicity is a key determinant for blood-brain barrier penetrance. Objective: Investigate a potential effect of statins on PD progression. Methods: Statin use was determined at baseline and subtyped according to hydrophobicity in 125 PD patients participating in the PD Biomarker Program (PDBP, 2012–2015) at our site. Clinical (N = 125) and susceptibility MRI (N = 86) data were obtained at baseline and 18-months. Movement Disorders Society-Unified PD Rating Scales were used to track progression of non-motor (MDS-UPDRS-I) and motor (MDS-UPDRS-II) symptoms, and rater-based scores (MDS-UPDRS-III) of patients in the “on” drug state. R2* values were used to capture pathological progression in the substantia nigra. Associations between statin use, its subtypes, and PD progression were evaluated with linear mixed effect regressions. Results: Compared to statin non-users, overall statin or lipophilic statin use did not significantly influence PD clinical or imaging progression. Hydrophilic statin users, however, demonstrated faster clinical progression of non-motor symptoms [MDS-UPDRS-I (β= 4.8, p = 0.010)] and nigral R2* (β= 3.7, p = 0.043). A similar trend was found for MDS-UPDRS-II (β= 3.9, p = 0.10), but an opposite trend was observed for rater-based MDS-UPDRS-III (β= –7.3, p = 0.10). Compared to lipophilic statin users, hydrophilic statin users also showed significantly faster clinical progression of non-motor symptoms [MDS-UPDRS-I (β= 5.0, p = 0.020)], but R2* did not reach statistical significance (β= 2.5, p = 0.24). Conclusion: This study suggests that hydrophilic, but not lipophilic, statins may be associated with faster PD progression. Future studies may have clinical and scientific implications.

Association between statin use and Parkinson's disease in Korean patients with hyperlipidemia

INTRODUCTION

Findings on the association between statin therapy and Parkinson's disease (PD) occurrence have been inconsistent. This study aimed to identify the association between statin use and PD in participants with a history of hyperlipidemia or blood cholesterol >200 in a Korean population to exclude nonstatin users owing to normal lipid values.

METHODS

We conducted a nested case-control analysis using the Korean National Health Insurance Service-National Sample Cohort assessed between 2002 and 2015. We identified 3026 PD cases. A total of 12,104 controls were then individually matched by age, sex, income, and region of residence at a ratio of 1:4. Potential confounders comprised basic demographic factors, lifestyle factors, various medical conditions and comorbidities. A conditional/unconditional logistic regression method was applied.

RESULTS

Compared with statin use for <6 months, adjusted odds ratios (aORs) with 95% confidence intervals (CIs) for 6-12 months of statin use and ≥12 months of statin use were 1.03 (0.92-1.15) and 1.61 (1.35-1.93) after adjustment for confounders, respectively (P = 0.664 and P < 0.001). In analyses according to statin solubility, only the association between lipophilic statin use for ≥12 months and PD maintained statistical significance, with an aOR of 1.64 (95% CI = 1.34-2.01, P < 0.001). These relations were consistent in subgroup analyses by covariates.

CONCLUSIONS

Statin use for more than 12 months was associated with a higher probability of PD in the Korean population with hyperlipidemia. This probability was significant for lipophilic statins but not hydrophilic statins.

Emerging Therapeutic Strategies for Parkinson’s Disease and Future Prospects: A 2021 Update

Parkinson’s disease (PD) is a neurodegenerative disorder pathologically distinguished by degeneration of dopaminergic neurons in the substantia nigra pars compacta. Muscle rigidity, tremor, and bradykinesia are all clinical motor hallmarks of PD. Several pathways have been implicated in PD etiology, including mitochondrial dysfunction, impaired protein clearance, and neuroinflammation, but how these factors interact remains incompletely understood. Although many breakthroughs in PD therapy have been accomplished, there is currently no cure for PD, only trials to alleviate the related motor symptoms. To reduce or stop the clinical progression and mobility impairment, a disease-modifying approach that can directly target the etiology rather than offering symptomatic alleviation remains a major unmet clinical need in the management of PD. In this review, we briefly introduce current treatments and pathophysiology of PD. In addition, we address the novel innovative therapeutic targets for PD therapy, including α-synuclein, autophagy, neurodegeneration, neuroinflammation, and others. Several immunomodulatory approaches and stem cell research currently in clinical trials with PD patients are also discussed. Moreover, preclinical studies and clinical trials evaluating the efficacy of novel and repurposed therapeutic agents and their pragmatic applications with encouraging outcomes are summarized. Finally, molecular biomarkers under active investigation are presented as potentially valuable tools for early PD diagnosis.

Lipid-lowering drug targets and Parkinson's disease: A sex-specific Mendelian randomization study

Parkinson's disease (PD) affects millions of individuals worldwide, and it is the second most common late-onset neurodegenerative disorder. There is no cure and current treatments only alleviate symptoms. Modifiable risk factors have been explored as possible options for decreasing risk or developing drug targets to treat PD, including low-density lipoprotein cholesterol (LDL-C). There is evidence of sex differences for cholesterol levels as well as for PD risk. Genetic datasets of increasing size are permitting association analyses with increased power, including sex-stratified analyses. These association results empower Mendelian randomization (MR) studies, which, given certain assumptions, test whether there is a causal relationship between the risk factor and the outcome using genetic instruments. Sex-specific causal inference approaches could highlight sex-specific effects that may otherwise be masked by sex-agnostic approaches. We conducted a sex-specific two-sample cis-MR analysis based on genetic variants in LDL-C target encoding genes to assess the impact of lipid-lowering drug targets on PD risk. To complement the cis-MR analysis, we also conducted a sex-specific standard MR analysis (using genome-wide independent variants). We did not find evidence of a causal relationship between LDL-C levels and PD risk in females [OR (95% CI) = 1.01 (0.60, 1.69), IVW random-effects] or males [OR (95% CI) = 0.93 (0.55, 1.56)]. The sex-specific standard MR analysis also supported this conclusion. We encourage future work assessing sex-specific effects using causal inference techniques to better understand factors that may contribute to complex disease risk differently between the sexes.

Perspective insights of repurposing the pleiotropic efficacy of statins in neurodegenerative disorders: An expository appraisal

Neurodegenerative disorders which affects a larger population pose a great clinical challenge. These disorders impact the quality of life of an individual by damaging the neurons, which are the unit cells of the brain. Clinicians are faced with the grave challenge of inhibiting the progression of these diseases as available treatment options fail to meet the clinical demand. Thus, treating the disease/disorder symptomatically is the Hobson's choice. The goal of the researchers is to introduce newer therapies in this segment and introducing a new molecule will take long years of development. Hence, drug repurposing/repositioning can be a better substitute in comparison to time consuming and expensive drug discovery and development cycle. Presently, a paradigm shift towards the re-purposing of drugs can be witnessed. Statins which have been previously approved as anti-hyperlipidemic agents are in the limelight of research for re-purposed drugs. Owing to their anti-inflammatory and antioxidant nature, statins act as neuroprotective in several brain disorders. Further they attenuate the amyloid plaques and protein aggregation which are the triggering factors in the Alzheimer's and Parkinson's respectively. In case of Huntington disease and Multiple sclerosis they help in improving the psychomotor symptoms and stimulate remyelination thus acting as neuroprotective. This article reviews the potential of statins in treating neurodegenerative disorders along with a brief discussion on the safety concerns associated with use of statins and human clinical trial data linked with re-tasking statins for neurodegenerative disorders along with the regulatory perspectives involved with the drug repositioning.

A Possible Role for HMG-CoA Reductase Inhibitors and Its Association with HMGCR Genetic Variation in Parkinson's Disease

Parkinson's disease (PD) is the second most common neurodegenerative disease characterised by both motor- and non-motor symptoms, including cognitive impairment. The aetiopathogenesis of PD, as well as its protective and susceptibility factors, are still elusive. Neuroprotective effects of 3-hydroxy-3-methyl-glutaryl-coenzyme A (HMG-CoA) reductase inhibitors-statins-via both cholesterol-dependent and independent mechanisms have been shown in animal and cell culture models. However, the available data provide conflicting results on the role of statin treatment in PD patients. Moreover, cholesterol is a vital component for brain functions and may be considered as protective against PD. We present possible statin effects on PD under the hypothesis that they may depend on the HMG-CoA reductase gene (HMGCR) variability, such as haplotype 7, which was shown to affect cholesterol synthesis and statin treatment outcome, diminishing possible neuroprotection associated with HMG-CoA reductase inhibitors administration. Statins are among the most prescribed groups of drugs. Thus, it seems important to review the available data in the context of their possible neuroprotective effects in PD, and the HMG-CoA reductase gene's genetic variability.

Glycoconjugate journal special issue on: the glycobiology of Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder that affects over 10 million aging people worldwide. This condition is characterized by the degeneration of dopaminergic neurons in the pars compacta region of the substantia nigra (SNpc) and by aggregation of proteins, commonly α-synuclein (SNCA). The formation of Lewy bodies that encapsulate aggregated proteins in lipid vesicles is a hallmark of PD. Glycosylation of proteins and neuroinflammation are involved in the pathogenesis. SNCA has many posttranslational modifications and interacts with components of membranes that affect aggregation. The large membrane lipid dolichol accumulates in the brain upon age and has a significant effect on membrane structure. The replacement of dopamine and dopaminergic neurons are at the forefront of therapeutic development. This review examines the role of membrane lipids, glycolipids, glycoproteins and dopamine in the aggregation of SNCA and development of PD. We discuss the SNCA-dopamine-neuromelanin-dolichol axis and the role of membranes in neuronal stem cells that could be a regenerative therapy for PD patients.

Cholesterol in Synaptic Vesicle Membranes Regulates the Vesicle-Binding, Function, and Aggregation of α-Synuclein

Loss of function and aggregation of the neuronal protein α-Synuclein (A-Syn) underlies the pathogenesis of Parkinson's disease (PD), and both the function and aggregation of this protein happen to be mediated via its binding to the synaptic vesicles (SVs) at the presynaptic termini. An essential constituent of SV membranes is cholesterol, with which A-Syn directly interacts while binding to membranes. Thus, cholesterol content in SV membranes is likely to affect the binding of A-Syn to these vesicles and consequently its functional and pathogenic behaviors. Interestingly, the dyshomeostasis of cholesterol has often been associated with PD, with reports linking both high and low cholesterol levels to an increased risk of neurodegeneration. Herein, using SV-mimicking liposomes containing increasing percentages of membrane cholesterol, we show (with mathematical interpretation) that the binding of A-Syn to synaptic-like vesicles is strongest in the presence of an optimum cholesterol content, which correlates to its maximum function and minimum aggregation. This implicates a minimum risk of neurodegeneration at optimum cholesterol levels and rationalizes the existing controversial relationship between cholesterol levels and PD. Increased membrane cholesterol was, however, found to protect against damage caused by aggregated A-Syn, complementing previous reports and portraying one advantage of high cholesterol over low.

Effects of statins on dopamine loss and prognosis in Parkinson's disease

Statins are more widely used not only for the primary and secondary prevention of cardiovascular disease by blocking cholesterol biosynthesis but also for the potential neuroprotective agents during neurological disorders due to their pleiotropic effects. In this study, we investigate whether the prior use of statins affect baseline nigrostriatal dopamine loss at the time of diagnosis and longitudinal motor and cognitive outcomes in patients with Parkinson's disease. Five hundred drug-naïve patients with Parkinson's disease who underwent dopamine transporter imaging were classified into two groups according to the prior use of statins: patients with and without statin use. Multivariate linear regression was used to determine inter-group differences in dopamine transporter availability. We evaluated the longitudinal changes in levodopa-equivalent dose and dementia conversion between the groups using a linear mixed model and survival analysis, respectively. In addition, mediation analysis was applied to examine the effect of total cholesterol. Patients with Parkinson's disease treated with statin had a lower baseline dopamine transporter availability in the anterior (2.13 ± 0.55 vs. 2.37 ± 0.67; p = 0.002), posterior (1.31 ± 0.43 vs. 1.49 ± 0.54; p = 0.003), and ventral putamina (1.40 ± 0.39 vs. 1.56 ± 0.47; p = 0.002) than that in matched patients with Parkinson's disease without statin. After adjusting for age at symptom onset, sex, disease duration and vascular risk factors, linear regression models showed that a prior treatment of statin remained significantly and independently associated with more severely decreased dopamine transporter availability in the anterior putamen (Beta = -0.140, p = 0.004), posterior putamen (Beta = -0.162, p = 0.001), and ventral putamen (Beta = -0.140, p = 0.004). A linear mixed model revealed that patients with Parkinson's disease being treated with statin had a faster longitudinal increase in levodopa-equivalent dose than those without statin. A survival analysis showed that the rate of dementia conversion was significantly higher in patients with Parkinson's disease with statin (hazard ratio, 2.019; 95% CI, 1.108 - 3.678; P = 0.022) than those without statin. Mediation analyses revealed that the effect of statin treatment on baseline dopamine transporter availability and longitudinal outcome was not mediated by total cholesterol levels. This study suggests that statin use may have a detrimental effect on baseline nigrostriatal dopamine degeneration and long-term outcomes in patients with Parkinson's disease.

Blood Cholesterol Decreases as Parkinson's Disease Develops and Progresses

BACKGROUND

Literature shows an inverse association of circulating cholesterol level with the risk of Parkinson's disease (PD); this finding has important ramifications, but its interpretation has been debated.

OBJECTIVE

To longitudinally examine how blood total cholesterol changes during the development of PD.

METHODS

In the Health, Aging and Body Composition study (n = 3,053, 73.6±2.9 years), blood total cholesterol was measured at clinic visit years 1, 2, 4, 6, 8, 10, and 11. We first examined baseline cholesterol in relation to PD risk, adjusting for potential confounders and competing risk of death. Then, by contrasting the observed with expected cholesterol levels, we examined the trajectory of changes in total cholesterol before and after disease diagnosis.

RESULTS

Compared to the lowest tertile of baseline total cholesterol, the cumulative incidence ratio of PD and 95% confidence interval was 0.41 (0.20, 0.86) for the second tertile, and 0.69 (0.35, 1.35) for the third tertile. In the analysis that examined change of total cholesterol level before and after PD diagnosis, we found that its level began to decrease in the prodromal stage of PD and became statistically lower than the expected values ∼4 years before disease diagnosis (observed-expected difference, -6.68 mg/dL (95% confidence interval: -13.14, -0.22)). The decreasing trend persisted thereafter; by year-6 post-diagnosis, the difference increased to -13.59 mg/dL (95% confidence interval: -22.12, -5.06), although the linear trend did not reach statistical significance (p = 0.10).

CONCLUSION

Circulating total cholesterol began to decrease in the prodromal stage of PD, which may in part explain its reported inverse association with PD.

Lovastatin Alleviates α-Synuclein Aggregation and Phosphorylation in Cellular Models of Synucleinopathy

Parkinson’s disease (PD) is one of the most common neurodegenerative diseases. Pathologically, it is characterized by the aberrant aggregation of α-synuclein (α-syn) in neurons. Clinical evidence shows that patients with hypercholesterolemia are more likely to get PD, while lovastatin users have a lower risk of suffering from it. In this study, we investigated the effects of lovastatin on the aggregation and phosphorylation of α-syn in vitro. Our results demonstrate that α-syn preformed fibrils induce the phosphorylation and aggregation of α-syn in HEK293 cells stably transfected with α-syn-GFP and SH-SY5Y cells as well, which could be attenuated by in a concentration-dependent manner. Besides, lovastatin inhibited oxidative stress, histone acetylation, and the activation of casein kinase 2 (CK2). Collectively, lovastatin alleviates α-syn aggregation and phosphorylation in cellular models of synucleinopathy, indicating its potential value of being adopted in the management of PD.

Statins in Parkinson's Disease: Influence on Motor Progression

BACKGROUND

It has been speculated that stains are neuroprotective and are associated with a reduced risk of Parkinson's disease (PD), but only a few studies have investigated the influence of statins on the progression of PD.

OBJECTIVE

To evaluate whether long-term statin use may affect motor progression in a large cohort of de novo patients with PD.

METHODS

We conducted a 4-year retrospective observational cohort study to assess patients with PD. The patients were consecutively recruited from a single tertiary center between January 2015 and January 2017. Information on motor function was obtained using the MDS-Unified Parkinson Disease Rating Scale (UPDRS)-III and all subjects were extensively characterized, including information about lifestyle habits, cardiovascular risk factors and cholesterol blood levels.

RESULTS

Of the 181 participants included in the study, 104 patients were evaluated for eligibility (42 patients were exposed to statin therapies and 62 were not treated with statins). They presented similar scores in UPDRS III at baseline but the statin users had a lower motor impairment at 4 years compared to non-user PD patients. Additionally, statin treatment resulted in slower progression of the rigidity score of UPDRS over 4 years. No other significant differences were observed between PD patients with and without statins.

CONCLUSION

Early PD patients with long-term statin usage showed lower motor deterioration after 4 years of disease duration compared with patients not taking statins at diagnosis, suggesting a possible influence of statins on disease progression in PD. Further investigation is warranted to understand the potential beneficial effects of statin treatment on clinical symptoms in PD.

Cholesterol-containing lipid nanodiscs promote an α-synuclein binding mode that accelerates oligomerization

Dysregulation of the biosynthesis of cholesterol and other lipids has been implicated in many neurological diseases, including Parkinson's disease. Misfolding of α-synuclein (α-Syn), the main actor in Parkinson's disease, is associated with changes in a lipid environment. However, the exact molecular mechanisms underlying cholesterol effect on α-Syn binding to lipids as well as α-Syn oligomerization and fibrillation remain elusive, as does the relative importance of cholesterol compared to other factors. We probed the interactions and fibrillation behaviour of α-Syn using styrene-maleic acid nanodiscs, containing zwitterionic and anionic lipid model systems with and without cholesterol. Surface plasmon resonance and thioflavin T fluorescence assays were employed to monitor α-Syn binding, as well as fibrillation in the absence and presence of membrane models. 1 H-15 N-correlated NMR was used to monitor the fold of α-Syn in response to nanodisc binding, determining individual residue apparent affinities for the nanodisc-contained bilayers. The addition of cholesterol inhibited α-Syn interaction with lipid bilayers and, however, significantly promoted α-Syn fibrillation, with a more than a 20-fold reduction of lag times before fibrillation onset. When α-Syn bilayer interactions were analysed at an individual residue level by solution-state NMR, we observed two different effects of cholesterol. In nanodiscs made of DOPC, the addition of cholesterol modulated the NAC part of α-Syn, leading to stronger interaction of this region with the lipid bilayer. In contrast, in the nanodiscs comprising DOPC, DOPE and DOPG, the NAC part was mostly unaffected by the presence of cholesterol, while the binding of the N and the C termini was both inhibited.

A Double-Blind, Randomized, Controlled Trial of Lovastatin in Early-Stage Parkinson's Disease

BACKGROUND

Recent evidence indicates that lipophilic statins have a neuroprotective benefit in animal models of Parkinson's disease (PD). The objective of this study was to evaluate whether lovastatin has the potential to slow motor symptom progression in patients with early-stage PD.

METHODS

This double-blind, randomized, placebo-controlled trial enrolled 77 patients with early-stage PD between May 23, 2017, and July 12, 2018, with follow-up ending September 1, 2019. Lovastatin 80 mg/day or placebo with 1:1 randomization was administered for 48 weeks. Mean change in the parts I-III scores of the Movement Disorder Society-Unified Parkinson's Disease Rating Scale (MDS-UPDRS), changes in the striatal dopamine uptake ratio measured by ¹⁸ F-dopa PET scan, and changes in PD medications between baseline and the week 48 visit were measured.

RESULTS

Of the 77 randomized patients, 70 (90.9%) completed the study. There was a slightly beneficial trend of the MDS-UPDRS motor score in the lovastatin group (-3.18 ± 5.50) compared with the placebo group (-0.50 ± 6.11); P = 0.14 adjusted for age, sex, disease duration, and baseline LEDD. Mean percentage change in the striatal ¹⁸ F-dopa uptake ratio deteriorated less in the lovastatin group than in the placebo group on the dominant side of caudate (1.2% ± 7.3% vs -7.1% ± 8.2%, P < 0.01) and putamen (2.3% ± 7.1% vs -6.4% ± 8.1%, P < 0.01). We found no between-group differences in the change in part I or part II MDS-UPDRS scores. Lovastatin was generally well tolerated.

CONCLUSIONS

Lovastatin treatment in patients with early-stage PD was associated with a trend of less motor symptom worsening and was well tolerated. A future larger long-term follow-up study is needed to confirm our findings. © 2021 International Parkinson and Movement Disorder Society.

Cholesterol Metabolism in Neurodegenerative Diseases: Molecular Mechanisms and Therapeutic Targets

Cholesterol is an indispensable component of the cell membrane and plays vital roles in critical physiological processes. Brain cholesterol accounts for a large portion of total cholesterol in the human body, and its content must be tightly regulated to ensure normal brain function. Disorders of cholesterol metabolism in the brain are linked to neurodegenerative diseases, including Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), and other atypical cognitive deficits that arise at old age. However, the specific role of cholesterol metabolism disorder in the pathogenesis of neurodegenerative diseases has not been fully elucidated. Statins that are a class of lipid-lowering drugs have been reported to have a positive effect on neurodegenerative diseases. Herein, we reviewed the physiological and pathological conditions of cholesterol metabolism and discussed the possible mechanisms of cholesterol metabolism and statin therapy in neurodegenerative diseases.

Hsp70 chaperone blocks α-synuclein oligomer formation via a novel engagement mechanism

Overexpression and aggregation of α-synuclein (ASyn) are linked to the onset and pathology of Parkinson's disease and related synucleinopathies. Elevated levels of the stress-induced chaperone Hsp70 protect against ASyn misfolding and ASyn-driven neurodegeneration in cell and animal models, yet there is minimal mechanistic understanding of this important protective pathway. It is generally assumed that Hsp70 binds to ASyn using its canonical and promiscuous substrate-binding cleft to limit aggregation. Here we report that this activity is due to a novel and unexpected mode of Hsp70 action, involving neither ATP nor the typical substrate-binding cleft. We use novel ASyn oligomerization assays to show that Hsp70 directly blocks ASyn oligomerization, an early event in ASyn misfolding. Using truncations, mutations, and inhibitors, we confirm that Hsp70 interacts with ASyn via an as yet unidentified, noncanonical interaction site in the C-terminal domain. Finally, we report a biological role for a similar mode of action in H4 neuroglioma cells. Together, these findings suggest that new chemical approaches will be required to target the Hsp70-ASyn interaction in synucleinopathies. Such approaches are likely to be more specific than targeting Hsp70's canonical action. Additionally, these results raise the question of whether other misfolded proteins might also engage Hsp70 via the same noncanonical mechanism.

Research on developing drugs for Parkinson's disease

Current treatments for Parkinson's disease (PD) are mainly dopaminergic drugs. However, dopaminergic drugs are only symptomatic treatments and limited by several side effects. Recent studies into drug development focused on emerging new molecular mechanisms, including nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, nuclear receptor-related 1 (Nurr1), adenosine receptor A2, nicotine receptor, metabotropic glutamate receptors (mGluRs), and glucocerebrosidase (GCase). Also, immunotherapy and common pathological mechanisms shared with Alzheimer's Disease (AD) and diabetes have attracted much attention. In this review, we summarized the development of preclinical and clinical studies of novel drugs and the improvement of dopaminergic drugs to provide a prospect for PD treatment.

Role of RhoA-ROCK signaling in Parkinson's disease

Parkinson's disease (PD) is a complex and widespread neurodegenerative disease characterized by depletion of midbrain dopaminergic (DA) neurons. Key issues are the development of therapies that can stop or reverse the disease progression, identification of dependable biomarkers, and better understanding of the pathophysiological mechanisms of PD. RhoA-ROCK signals appear to have an important role in PD symptoms, making it a possible approach for PD treatment strategies. Activation of RhoA-ROCK (Rho-associated coiled-coil containing protein kinase) appears to stimulate various PD risk factors including aggregation of alpha-synuclein (αSyn), dysregulation of autophagy, and activation of apoptosis. This manuscript reviews current updates about the biology and function of the RhoA-ROCK pathway and discusses the possible role of this signaling pathway in causing the pathogenesis of PD. We conclude that inhibition of the RhoA-ROCK signaling pathway may have high translational potential and could be a promising therapeutic target in PD.

Beneficial Effects of Melatonin and Atorvastatin on Retinopathy in Streptozocin-induced Diabetic Rats

Objective:

The present study was designed to evaluate the effects of Atorvastatin (ATO) plus Melatonin (MEL) on streptozocin-induced Diabetic Retinopathy (DR) in rats.

Methods:

Diabetes was induced in Wistar rats with an intraperitoneal injection of streptozocin (50 mg/kg). Animals were randomly assigned to one of the following groups (8 rats/group): Control group, Diabetic group, Diabetic + MEL group (20 mg/kg/day), Diabetic + ATO group (10 mg/kg/day), Diabetic + MEL + ATO group (as above). Treatments were started one week after induction of diabetes and continued for 7 weeks. At the end of the experiment, angiography was performed and the rats were killed and retinas were harvested for pathological and molecular examinations.

Results:

Administration of MEL reduced the fluorescein leakage, MDA and ROS levels compared to diabetic group. Treatment with ATO only reduced ROS levels compared to diabetic group. In addition, administration of ATO plus MEL decreased these indices compared to the diabetic and ATO groups. Histologically, retinal vascular congestion was not observed in the combined ATO and MEL group as compared to the diabetic, ATO, and MEL groups.

Conclusion:

These data provide evidence for the therapeutic value of MEL in combination with ATO in clinical practice for prevention of DR.

A dual inhibitor targeting HMG-CoA reductase and histone deacetylase mitigates neurite degeneration in LRRK2-G2019S parkinsonism

Parkinson's disease (PD) is among the most common neurodegenerative disorders, and its etiology involves both genetic and environmental factors. The leucine-rich repeat kinase (LRRK2) G2019S mutation is the most common genetic cause of familial and sporadic PD. Current treatment is limited to dopaminergic supplementation, as no disease-modifying therapy is available yet. Recent evidence reveals that HMG-CoA reductase (HMGR) inhibitors (statins) exert neuroprotection through anti-neuroinflammatory effects, and histone deacetylase (HDAC) inhibitors mitigate neurodegeneration by promoting the transcription of neuronal survival factors. We designed and synthesized a dual inhibitor, statin hydroxamate JMF3086, that simultaneously inhibits HMGR and HDAC, and examined its neuroprotective effects on LRRK2-G2019S parkinsonism. JMF3086 restored dopaminergic neuron loss in aged LRRK2-G2019S flies and rescued neurite degeneration in primary hippocampal and dopaminergic neurons isolated from transgenic LRRK2-G2019S mice. The molecular mechanisms included downregulation of ERK1/2 phosphorylation, increased anti-apoptotic Akt phosphorylation, and inhibition of GSK3β activity to maintain cytoskeletal stability in stably transfected LRRK2-G2019S SH-SY5Y human dopaminergic cells. JMF3086 also promoted a-tubulin acetylation and kinesin-1 expression, facilitating antegrade mitochondrial transport in axons. Our findings demonstrate that JMF3086 exerted beneficial effects on restoring LRRK2-G2019S neurite degeneration by maintaining microtubule stability. This dual-target compound may be a promising mechanism-based therapy for PD.

Effects of Higher Serum Lipid Levels on the Risk of Parkinson's Disease: A Systematic Review and Meta-Analysis

Background: The causal relationship between serum lipid levels and the risk of Parkinson's disease (PD) remains largely uncertain. We summarized the existing controversial evidence on this topic.

Methods: We searched the electronic databases for observational studies from January 1988 to March 2020. We applied random-effects models to calculate pooled relative risk (RR) with their 95% confidence intervals (CI). Random-effects dose-response meta-analyses were further conducted to explore the dose-risk relationship.

Results: Twelve cohort studies and three case-control studies were included in this meta-analysis. Higher levels of serum low-density lipoprotein cholesterol (LDL-C) were inversely associated with the subsequent risk of PD (RR 0.73, 95% CI 0.57–0.93), whereas, there were no associations between serum levels of total cholesterol (TC) (RR 0.91, 95% CI 0.73–1.13), high-density lipoprotein cholesterol (HDL-C) (RR 0.97, 95% CI 0.73–1.27), or triglycerides (TG) (RR 0.85, 95% CI 0.55–1.29) and the risk of PD. Further dose-response meta-analysis revealed that every 38.6 mg/dL (1mmol/L) increase in serum LDL-C correlates with a 7% decreased risk of PD.

Conclusions: Our paper supports the protective effect of higher serum LDL-C on the subsequent risk of PD. More prospective cohort studies are warranted to confirm the conclusion, and further fundamental researches are needed to elucidate the underlying biological mechanisms.

A systematic review and meta-analysis of serum cholesterol and triglyceride levels in patients with Parkinson's disease

Objectives

Numerous studies have reported that lipid metabolic abnormalities may play an important role in the development of Parkinson’s disease (PD), with mixed results. This meta-analysis aims to systematically assess the relationship between serum cholesterol or triglyceride and the PD risk and to further determine the role of dyslipidemia in potential predictive value.

Methods

This research systematically consulted and screened observational studies to evaluate the association of serum lipids with the risk of PD as of April 01, 2020 based on the inclusion and exclusion criteria. Two researchers screened and extracted the data independently. Then this article summarized the characteristics of all clinical studies and collected the corresponding data to perform pooled and sensitivity analyses. The meta-analysis was performed by using the RevMan 5.3 software after data extraction, quality assessment and analysis of publication bias.

Results

Twenty-one related studies (13 case-control and 8 cohort studies) were selected with a total of 980,180 subjects, including 11,188 PD patients. Meta-analysis showed that higher levels of serum triglyceride (S-TG) [standard mean different (SMD) = − 0.26 (95% confidence interval (CI): − 0.39 to − 0.13, p<0.00001), relative risk (RR) = 0.67 (95% CI: 0.60 to 0.75, p<0.00001)] could be considered as protective factors for the pathogenesis of PD. However, there was no significant association between serum high density lipoprotein cholesterol (S-HDL) and the risk of PD. Meanwhile, serum low density lipoprotein cholesterol (S-LDL) [SMD = -0.26 (95% CI: − 0.43 to − 0.07, p = 0.006), RR = 0.76 (95% CI: 0.59 to 0.97, p = 0.03)] and serum total cholesterol (S-TC) levels [SMD = -0.21 (95% CI: − 0.33 to − 0.10, p = 0.0002), RR = 0.86 (95% CI: 0.77 to 0.97, p = 0.01)] were negatively associated with PD risk.

Conclusions

This systematic review suggests that elevated serum levels of TG, LDL and TC may be protective factors for the pathogenesis of PD. Further longitudinal and well-designed prospective studies with a large sample size are needed to confirm the findings in this meta-analysis.

Prevention of multiple system atrophy using human bone marrow-derived mesenchymal stem cells by reducing polyamine and cholesterol-induced neural damages

Background

Multiple system atrophy (MSA) is a sporadic neurodegenerative disorder of unknown etiology, but is closely associated with damage to dopaminergic neurons. MSA progression is rapid. Hence, long-term drug treatments do not have any therapeutic benefits. We assessed the inhibitory effect of mesenchymal stem cells (MSCs) on double-toxin-induced dopaminergic neurodegenerative MSA.

Results

Behavioral disorder was significantly improved and neurodegeneration was prevented following MSC transplantation. Proteomics revealed lower expression of polyamine modulating factor-binding protein 1 (PMFBP1) and higher expression of 3-hydroxymethyl-3-methylglutaryl-CoA lyase (HMGCL), but these changes were reversed after MSC transplantation. In the in vitro study, the 6-OHDA-induced effects were reversed following co-culture with MSC. However, PMFBP1 knockdown inhibited the recovery effect due to the MSCs. Furthermore, HMGCL expression was decreased following co-culture with MSCs, but treatment with recombinant HMGCL protein inhibited the recovery effects due to MSCs.

Conclusions

These data indicate that MSCs protected against neuronal loss in MSA by reducing polyamine- and cholesterol-induced neural damage.

Novel Small Molecules Targeting the Intrinsically Disordered Structural Ensemble of α-Synuclein Protect Against Diverse α-Synuclein Mediated Dysfunctions

The over-expression and aggregation of α-synuclein (αSyn) are linked to the onset and pathology of Parkinson’s disease. Native monomeric αSyn exists in an intrinsically disordered ensemble of interconverting conformations, which has made its therapeutic targeting by small molecules highly challenging. Nonetheless, here we successfully target the monomeric structural ensemble of αSyn and thereby identify novel drug-like small molecules that impact multiple pathogenic processes. Using a surface plasmon resonance high-throughput screen, in which monomeric αSyn is incubated with microchips arrayed with tethered compounds, we identified novel αSyn interacting drug-like compounds. Because these small molecules could impact a variety of αSyn forms present in the ensemble, we tested representative hits for impact on multiple αSyn malfunctions in vitro and in cells including aggregation and perturbation of vesicular dynamics. We thereby identified a compound that inhibits αSyn misfolding and is neuroprotective, multiple compounds that restore phagocytosis impaired by αSyn overexpression, and a compound blocking cellular transmission of αSyn. Our studies demonstrate that drug-like small molecules that interact with native αSyn can impact a variety of its pathological processes. Thus, targeting the intrinsically disordered ensemble of αSyn offers a unique approach to the development of small molecule research tools and therapeutics for Parkinson’s disease.

The role of NOX inhibitors in neurodegenerative diseases

Oxidative stress is a key player in both chronic and acute brain disease due to the higher metabolic demand of the brain. Among the producers of free radicals, NADPH-oxidase (NOX) is a major contributor to oxidative stress in neurological disorders. In the brain, the superoxide produced by NOX is mainly found in leukocytes. However, recent studies have reported that it can be found in several other cell types. NOX has been reported to regulate neuronal signaling, memory processing, and central cardiovascular homeostasis. However, overproduction of NOX can contribute to neurotoxicity, CNS degeneration, and cardiovascular disorders. Regarding the above functions, NOX has been shown to play a crucial role in chronic CNS diseases like Parkinson's disease (PD), Alzheimer's disease (AD), Huntington's disease (HD), multiple sclerosis (MS), and amyotrophic lateral sclerosis (ALS), and in acute CNS disorders such as stroke, spinal cord injury, traumatic brain injury (TBI), and related cerebrovascular diseases. NOX is a multi-subunit complex consisting of two membrane-associated and four cytosolic subunits. Thus, in recent years, inhibition of NOX activity has drawn a great deal of attention from researchers in the field of treating chronic and acute CNS disorders and preventing secondary complications. Mounting evidence has shown that NOX inhibition is neuroprotective and that inhibiting NOX in circulating immune cells can improve neurological disease conditions. This review summarizes recent studies on the therapeutic effects and pharmacological strategies regarding NOX inhibitors in chronic and acute brain diseases and focuses on the hurdles that should be overcome before their clinical implementation.

Evaluation of α-synuclein and apolipoprotein E as potential biomarkers in cerebrospinal fluid to monitor pharmacotherapeutic efficacy in dopamine dictated disease states of Parkinson's disease and schizophrenia

BACKGROUND AND OBJECTIVE

Dopamine plays an important role in the disease pathology of Parkinson's disease and schizophrenia. These two neuropsychiatric disorders represent disease end points of the dopaminergic spectrum where Parkinson's disease represents dopamine deficit and schizophrenia represents dopamine hyperactivity in the mid-brain. Therefore, current treatment strategies aim to restore normal dopamine levels. However, during treatment patients develop adverse effects due to overshooting of physiological levels of dopamine leading to psychosis in Parkinson's disease, and extrapyramidal symptoms in schizophrenia. Absence of any laboratory tests hampers modulation of pharmacotherapy. Apolipoprotein E and α-synuclein have an important role in the neuropathology of these two diseases. The objective of this study was to evaluate cerebrospinal fluid (CSF) concentrations of apolipoprotein E and α-synuclein in patients with these two diseases so that they may serve as biomarkers to monitor therapy in Parkinson's disease and schizophrenia.

METHODS

Drug-naïve Parkinson's disease patients and Parkinson's disease patients treated with dopaminergic therapy, neurological controls, schizophrenic patients treated with antidopaminergic therapy, and drug-naïve schizophrenic patients were recruited for the study and CSF was collected. Enzyme-linked immunosorbent assays were carried out to estimate the concentrations of apolipoprotein E and α-synuclein. Pathway analysis was done to establish a possible role of these two proteins in various pathways in these two dopamine dictated diseases.

RESULTS

Apolipoprotein E and α-synuclein CSF concentrations have an inverse correlation along the entire dopaminergic clinical spectrum. Pathway analysis convincingly establishes a plausible hypothesis for their co-regulation in the pathogenesis of Parkinson's disease and schizophrenia. Each protein by itself or as a combination has encouraging sensitivity and specificity values of more than 55%.

CONCLUSION

The dynamic variation of these two proteins along the spectrum is ideal for them to be pursued as pharmacotherapeutic biomarkers in CSF to monitor pharmacological efficacy in Parkinson's disease and schizophrenia.

Lipids at the Crossroad of α-Synuclein Function and Dysfunction: Biological and Pathological Implications

Since its discovery, the study of the biological role of α-synuclein and its pathological implications has been the subject of increasing interest. The propensity to adopt different conformational states governing its aggregation and fibrillation makes this small 14-kDa cytosolic protein one of the main etiologic factors associated with degenerative disorders known as synucleinopathies. The structure, function, and toxicity of α-synuclein and the possibility of different therapeutic approaches to target the protein have been extensively investigated and reviewed. One intriguing characteristic of α-synuclein is the different ways in which it interacts with lipids. Though in-depth studies have been carried out in this field, the information they have produced is puzzling and the precise role of lipids in α-synuclein biology and pathology and vice versa is still largely unknown. Here we provide an overview and discussion of the main findings relating to α-synuclein/lipid interaction and its involvement in the modulation of lipid metabolism and signaling.

Rho-inhibition and neuroprotective effect on rotenone-treated dopaminergic neurons in vitro

Mesencephalic cell cultures are a good model to study the vulnerability of dopaminergic neurons and reproduce, in vitro, experimental models of Parkinson's disease. Rotenone associated as an environmental neurotoxin related to PD, is able to provoke dopaminergic neuron degeneration by inhibiting complex I of the mitochondrial respiratory chain and by inducing accumulation of α-synuclein. Recently, rotenone has been described to activate RhoA, a GTPase protein. In the present study we evaluated a possible neuroprotective effect of Rho-inhibitor molecules on rotenone-damaged dopaminergic (DA) neurons obtained from mouse primary mesencephalic cell culture. Our results showed that Clostridium Botulinum C3 toxin (C3) and simvastatin, as RhoA inhibitors, were able to protect DA neurons from rotenone damages. In fact, pretreatment with C3 or simvastatin significantly prevented the reduction of [³H]dopamine uptake, neurites injury and the expression patterns of proteins like α-syn, actin and connexin 43.

Peroxisomal dysfunction in neurodegenerative diseases

Peroxisomes and their (patho-)physiological importance in heath and disease have attracted increasing interest during last few decades. Together with mitochondria, peroxisomes comprise key metabolic platforms for oxidation of various fatty acids and redox regulation. In addition, peroxisomes contribute to bile acid, cholesterol, and plasmalogen biosynthesis. The importance of functional peroxisomes for cellular metabolism is demonstrated by the marked brain and systemic organ abnormalities occuring in peroxisome biogenesis disorders and peroxisomal enzyme deficiencies. Current evidences indicate that peroxisomal function is declined with aging, with peroxisomal dysfunction being linked to early onset of multiple age-related diseases including neurodegenerative diseases. Herein, we review recent progress toward understanding the physiological roles and pathological implications of peroxisomal dysfunctions, focusing on neurodegenerative disease.

The Role of Lipids in Parkinson's Disease

Parkinson’s disease (PD) is a neurodegenerative disease characterized by a progressive loss of dopaminergic neurons from the nigrostriatal pathway, formation of Lewy bodies, and microgliosis. During the past decades multiple cellular pathways have been associated with PD pathology (i.e., oxidative stress, endosomal-lysosomal dysfunction, endoplasmic reticulum stress, and immune response), yet disease-modifying treatments are not available. We have recently used genetic data from familial and sporadic cases in an unbiased approach to build a molecular landscape for PD, revealing lipids as central players in this disease. Here we extensively review the current knowledge concerning the involvement of various subclasses of fatty acyls, glycerolipids, glycerophospholipids, sphingolipids, sterols, and lipoproteins in PD pathogenesis. Our review corroborates a central role for most lipid classes, but the available information is fragmented, not always reproducible, and sometimes differs by sex, age or PD etiology of the patients. This hinders drawing firm conclusions about causal or associative effects of dietary lipids or defects in specific steps of lipid metabolism in PD. Future technological advances in lipidomics and additional systematic studies on lipid species from PD patient material may improve this situation and lead to a better appreciation of the significance of lipids for this devastating disease.

Relationship between high dietary fat intake and Parkinson's disease risk: a meta-analysis

OBJECTIVE:

To assess whether dietary fat intake influences Parkinson’s disease risk.

DATA SOURCES:

We systematically surveyed the Embase and PubMed databases, reviewing manuscripts published prior to October 2018. The following terms were used: (“Paralysis agitans” OR “Parkinson disease” OR “Parkinson” OR “Parkinson’s” OR “Parkinson’s disease”) AND (“fat” OR “dietary fat” OR “dietary fat intake”).

DATA SELECTION:

Included studies were those with both dietary fat intake and Parkinson’s disease risk as exposure factors. The Newcastle-Ottawa Scale was adapted to investigate the quality of included studies. Stata V12.0 software was used for statistical analysis.

OUTCOME MEASURES:

The primary outcomes included the relationship between high total energy intake, high total fat intake, and Parkinson’s disease risk. The secondary outcomes included the relationship between different kinds of fatty acids and Parkinson’s disease risk.

RESULTS:

Nine articles met the inclusion criteria and were incorporated into this meta-analysis. Four studies scored 7 and the other five studies scored 9 on the Newcastle-Ottawa Scale, meaning that all studies were of high quality. Meta-analysis results showed that high total energy intake was associated with an increased risk of Parkinson’s disease (P = 0.000, odds ratio (OR) = 1.49, 95% confidence interval (CI): 1.26–1.75); in contrast, high total fat intake was not associated with Parkinson’s disease risk (P = 0.123, OR = 1.07, 95% CI: 0.91–1.25). Subgroup analysis revealed that polyunsaturated fatty acid intake (P = 0.010, OR = 1.03, 95% CI: 0.88–1.20) reduced the risk of Parkinson’s disease, while arachidonic acid (P = 0.026, OR = 1.15, 95% CI: 0.97–1.37) and cholesterol (P = 0.002, OR = 1.09, 95% CI: 0.92–1.29) both increased the risk of Parkinson’s disease. Subgroup analysis also demonstrated that, although the results were not significant, consumption of n-3 polyunsaturated fatty acids (P = 0.071, OR = 0.88, 95% CI: 0.73–1.05), α-linolenic acid (P = 0.06, OR = 0.86, 95% CI: 0.72–1.02), and the n-3 to n-6 ratio (P = 0.458, OR = 0.89, 95% CI: 0.75–1.06) were all linked with a trend toward reduced Parkinson’s disease risk. Monounsaturated fatty acid (P = 0.450, OR = 1.06, 95% CI: 0.91–1.23), n-6 polyunsaturated fatty acids (P = 0.100, OR = 1.15, 95% CI: 0.96–1.36) and linoleic acid (P = 0.053, OR = 1.11, 95% CI: 0.94–1.32) intakes were associated with a non-significant trend toward higher PD risk. Saturated fatty acid (P = 0.619, OR = 1.01, 95% CI: 0.87–1.18) intake was not associated with Parkinson’s disease.

CONCLUSION:

Dietary fat intake affects Parkinson’s disease risk, although this depends on the fatty acid subtype. Higher intake of polyunsaturated fatty acids may reduce the risk of Parkinson’s disease, while higher cholesterol and arachidonic acid intakes may elevate Parkinson’s disease risk. However, further studies and evidence are needed to validate any link between dietary fat intake and Parkinson’s disease.

Parkinsonism in Inherited Metabolic Disorders: Key Considerations and Major Features

Parkinson's Disease (PD) is a common neurodegenerative disorder manifesting as reduced facilitation of voluntary movements. Extensive research over recent decades has expanded our insights into the pathogenesis of the disease, where PD is indicated to result from multifactorial etiological factors involving environmental contributions in genetically predisposed individuals. There has been considerable interest in the association between neurological manifestations in PD and in inherited metabolic disorders (IMDs), which are genetic disorders characterized by a deficient activity in the pathways of intermediary metabolism leading to multiple-system manifestations. In addition to the parallel in various clinical features, there is increasing evidence for the notion that genetic mutations underlying IMDs may increase the risk of PD development. This review highlights the recent advances in parkinsonism in patients with IMDs, with the primary objective to improve the understanding of the overlapping pathogenic pathways and clinical presentations in both disorders. We discuss the genetic convergence and disruptions in biochemical mechanisms which may point to clues surrounding pathogenesis-targeted treatment and other promising therapeutic strategies in the future.

Evaluation of Serum Apolipoprotein E as a Potential Biomarker for Pharmacological Therapeutic Efficacy Monitoring in Dopamine Dictated Disease Spectrum of Schizophrenia and Parkinson's disease: A Preliminary Study

AIM OF THE STUDY

Parkinson's disease and schizophrenia are disease end points of dopaminergic deficit and hyperactivity, respectively, in the mid brain. Accordingly, current medications aim to restore normal dopamine levels, overshooting of which results in adverse effects of psychosis and extra-pyramidal symptoms, respectively. There are currently no available laboratory tests to guide treatment decisions or help predict adverse side effects of the drugs. The aim was to therefore explore the possibility of using apolipoprotein E as a biomarker to monitor pharmacological intervention in dopamine dictated states of Parkinson's disease and schizophrenia for optimum therapy.

METHODS

Naïve and treated, Parkinson's disease and schizophrenic patients were recruited from neurology and psychiatry clinics. Serum of healthy volunteers was collected as controls. Serum concentrations of apolipoprotein E was estimated by enzyme-linked immunosorbent assay (ELISA). Pathway analysis was carried out to delineate the interactions of apolipoprotein E in Parkinson's disease and schizophrenia.

RESULTS

Apolipoprotein E levels are higher in Parkinson's disease patients as compared with schizophrenic samples (P < .05). Also, post-treatment apolipoprotein E levels in both disease states were at par with levels seen in healthy controls. The interactions of apolipoprotein E validate the results and place the differential expression of the protein in Parkinson's disease and schizophrenia in the right perspective.

CONCLUSION

Apolipoprotein E concentration across the dopaminergic spectrum suggests that it can be pursued not only as a potential biomarker in schizophrenia and Parkinson's disease, but can also be an effective tool for clinicians to determine efficacy of drug-based therapy.

Simvastatin as a Potential Disease-Modifying Therapy for Patients with Parkinson's Disease: Rationale for Clinical Trial, and Current Progress

Many now believe the holy grail for the next stage of therapeutic advance surrounds the development of disease-modifying approaches aimed at intercepting the year-on-year neurodegenerative decline experienced by most patients with Parkinson’s disease (PD). Based on recommendations of an international committee of experts who are currently bringing multiple, potentially disease-modifying, PD therapeutics into long-term neuroprotective PD trials, a clinical trial involving 198 patients is underway to determine whether Simvastatin provides protection against chronic neurodegeneration. Statins are widely used to reduce cardiovascular risk, and act as competitive inhibitors of HMG-CoA reductase. It is also known that statins serve as ligands for PPARα, a known arbiter for mitochondrial size and number. Statins possess multiple cholesterol-independent biochemical mechanisms of action, many of which offer neuroprotective potential (suppression of proinflammatory molecules & microglial activation, stimulation of endothelial nitric oxide synthase, inhibition of oxidative stress, attenuation of α-synuclein aggregation, modulation of adaptive immunity, and increased expression of neurotrophic factors). We describe the biochemical, physiological and pharmaceutical credentials that continue to underpin the rationale for taking Simvastatin into a disease-modifying trial in PD patients. While unrelated to the Simvastatin trial (because this conducted in patients who already have PD), we discuss conflicting epidemiological studies which variously suggest that statin use for cardiovascular prophylaxis may increase or decrease risk of developing PD. Finally, since so few disease-modifying PD trials have ever been launched (compared to those of symptomatic therapies), we discuss the rationale of the trial structure we have adopted, decisions made, and lessons learnt so far.

Interaction between amyloidogenic proteins and biomembranes in protein misfolding diseases: Mechanisms, contributors, and therapy

The toxic deposition of misfolded amyloidogenic proteins is associated with more than fifty protein misfolding diseases (PMDs), including Alzheimer's disease, Parkinson's disease and type 2 diabetes mellitus. Protein deposition is a multi-step process modulated by a variety of factors, in particular by membrane-protein interaction. The interaction results in permeabilization of biomembranes contributing to the cytotoxicity that leads to PMDs. Different biological and physiochemical factors, such as protein sequence, lipid composition, and chaperones, are known to affect the membrane-protein interaction. Here, we provide a comprehensive review of the mechanisms and contributing factors of the interaction between biomembranes and amyloidogenic proteins, and a summary of the therapeutic approaches to PMDs that target this interaction. This article is part of a Special Issue entitled: Protein Aggregation and Misfolding at the Cell Membrane Interface edited by Ayyalusamy Ramamoorthy.