Novel approaches to counter protein aggregation pathology in Parkinson's disease

Rethinking neurodegenerative diseases: neurometabolic concept linking lipid oxidation to diseases in the central nervous system

ABSTRACT

Currently, there is a lack of effective medicines capable of halting or reversing the progression of neurodegenerative disorders, including amyotrophic lateral sclerosis, Parkinson's disease, multiple sclerosis, or Alzheimer's disease. Given the unmet medical need, it is necessary to reevaluate the existing paradigms of how to target these diseases. When considering neurodegenerative diseases from a systemic neurometabolic perspective, it becomes possible to explain the shared pathological features. This innovative approach presented in this paper draws upon extensive research conducted by the authors and researchers worldwide. In this review, we highlight the importance of metabolic mitochondrial dysfunction in the context of neurodegenerative diseases. We provide an overview of the risk factors associated with developing neurodegenerative disorders, including genetic, epigenetic, and environmental factors. Additionally, we examine pathological mechanisms implicated in these diseases such as oxidative stress, accumulation of misfolded proteins, inflammation, demyelination, death of neurons, insulin resistance, dysbiosis, and neurotransmitter disturbances. Finally, we outline a proposal for the restoration of mitochondrial metabolism, a crucial aspect that may hold the key to facilitating curative therapeutic interventions for neurodegenerative disorders in forthcoming advancements.

Perspective Strategies for Interventions in Parkinsonism: Remedying the Neglected Role of TPPP

Neurological disorders such as Parkinsonism cause serious socio-economic problems as there are, at present, only therapies that treat their symptoms. The well-established hallmark alpha-synuclein (SYN) is enriched in the inclusion bodies characteristic of Parkinsonism. We discovered a prominent partner of SYN, termed Tubulin Polymerization Promoting Protein (TPPP), which has important physiological and pathological activities such as the regulation of the microtubule network and the promotion of SYN aggregation. The role of TPPP in Parkinsonism is often neglected in research, which we here attempt to remedy. In the normal brain, SYN and TPPP are expressed endogenously in neurons and oligodendrocytes, respectively, whilst, at an early stage of Parkinsonism, soluble hetero-associations of these proteins are found in both cell types. The cell-to-cell transmission of these proteins, which is central to disease progression, provides a unique situation for specific drug targeting. Different strategies for intervention and for the discovery of biomarkers include (i) interface targeting of the SYN-TPPP hetero-complex; (ii) proteolytic degradation of SYN and/or TPPP using the PROTAC technology; and (iii) depletion of the proteins by miRNA technology. We also discuss the potential roles of SYN and TPPP in the phenotype stabilization of neurons and oligodendrocytes.

Parkinson's Neuropathology Puzzle: A Systematic Review Uncovering the Pathological Culprits Behind the Neurological Disease

Being one of the most prevalent progressive neurodegenerative disorders (falling second only to Alzheimer's disease) with a clinical pattern affecting millions of lives all over the world, Parkinson's disease (PD) has never failed to attract a formidable interest from the vast majority of neurologists and researchers worldwide. This review article will analyze the pathophysiology, etiology, genetics, and pathological stages of Parkinson's disease with their corresponding clinical sequels. A review article was conducted using research databases including PubMed, PubMed Central, Springer, and Elsevier. The research articles reviewed using databases were written in English, German, Japanese, and Chinese and published within the preceding 50 years. Based on the article's findings, we concluded that Parkinson's disease is a progressive disorder with a variety of motor and non-motor symptoms that are influenced by a cascade of pathological neuronal abnormalities such as Lewy neurites and Lewy bodies that gradually build up with an eventual consequence of neurodegeneration of dopamine-secreting neurons. Multiple genetic mutations, pathophysiological events, and environmental factors act as the foundation to initiate that cascade.

Reverses Motor Deficits and Reduces Accumulation of Human α-Synuclein Protein in Two Different Parkinson's Disease Animal Models

Aggregation of misfolded α-synuclein (α-syn) protein in the periphery and central nervous system (CNS) gives rise to a group of disorders, which are labeled collectively as synucleinopathies. These clinically distinct disorders are known as pure autonomic failure, Parkinson's disease (PD), Parkinson's disease dementia (PDD), dementia with Lewy bodies (DLB), and multiple system atrophy (MSA). In the case of PD, it has been demonstrated that toxic aggregates of α-syn protein not only cause apoptosis of dopamine neurons but its accumulation in the neocortex and limbic area principally contributes to dementia. In our multifunctional drug discovery research for PD, we converted one of our catechol-containing lead dopamine agonist molecules D-520 into its prodrug D-685. The prodrug exhibited higher in vivo anti-Parkinsonian efficacy in a reserpinized PD animal model than the parent D-520 and exhibited facile brain penetration. In our study with an α-syn transgenic animal model (D line) for PD and dementia with Lewy bodies (DLB), we have shown that 1 month of chronic treatment with the compound D-685 was sufficient to reduce the accumulation of α-syn and phospho-α-syn in the cortex, hippocampus, and striatum areas significantly compared to the control tg mice. Furthermore, D-685 did not exhibit any deleterious effect in the CNS as was evident from the neuron and microglia studies. Future studies will further explore in depth the potential of D-685 to modify disease progression while addressing symptomatic deficits.

Bivalent dopamine agonists with co-operative binding and functional activities at dopamine D2 receptors, modulate aggregation and toxicity of alpha synuclein protein

To follow up on our previous report on bivalent compounds exhibiting potent co-operative binding at dopamine D2 receptors, we modified the structure of the linker in our earlier bivalent molecules (S)-6-((9-(((R)-5-hydroxy-1,2,3,4-tetrahydronaphthalen-2-yl)(propyl)amino)nonyl)-(propyl)amino)-5,6,7,8-tetrahydronaphthalen-1-ol (Ia) and (S)-6-((10-(((R)-5-hydroxy-1,2,3,4-tetrahydronaphthalen-2-yl)(propyl)amino)decyl)(propyl)amino)-5,6,7,8-tetrahydronaphthalen-1-ol (Ib) (Fig. 1) connecting the two pharmaophoric moieties to observe any tolerance in maintaining similar affinities and potencies. Specifically, we introduced aromatic and piperazine moieties in the linker to explore their effect. Overall, similar activities at D2 receptors as observed in our earlier study was maintained in the new molecules e.g. (6S,6'S)-6,6'-((1,4-phenylenebis(ethane-2,1-diyl))bis(propylazanediyl))bis(5,6,7,8-tetrahydronaphthalen-1-ol) (D-382) (Ki, D2 = 3.88 nM). The aromatic moiety in D-382 was next functionalized by introducing hydroxyl groups to mimic polyhydroxy natural products which are known to interact with amyloidogenic proteins. Such a transformation resulted in development of compounds like 2,5-bis(2-(((S)-5-hydroxy-1,2,3,4-tetrahydronaphthalen-2-yl)(propyl)amino)ethyl)benzene-1,4-diol (D-666) (Ki, D2 = 7.62 nM) which retained similar affinity and potency at D2 receptors. Such dihydroxyl compounds turned out to be potent inhibitors against aggregation and toxicity of recombinant alpha synuclein protein. The work reported here is in line with our overall goal to develop multifunctional dopamine agonist for symptomatic and disease modifying treatment of Parkinson's disease.

Alzheimer's and Parkinson's disease therapies in the clinic

Alzheimer's disease (AD) and Parkinson's disease (PD) are the most prevalent neurodegenerative diseases, affecting millions and costing billions each year in the United States alone. Despite tremendous progress in developing therapeutics that manage the symptoms of these two diseases, the scientific community has yet to develop a treatment that effectively slows down, inhibits, or cures neurodegeneration. To gain a better understanding of the current therapeutic frontier for the treatment of AD and PD, we provide a review on past and present therapeutic strategies for these two major neurodegenerative disorders in the clinical trial process. We briefly recap currently US Food and Drug Administration-approved therapies, and then explore trends in clinical trials across the variables of therapy mechanism of disease intervention, administration route, use of delivery vehicle, and outcome measures, across the clinical phases over time for "Drug" and "Biologic" therapeutics. We then present the success rate of past clinical trials and analyze the intersections in therapeutic approaches for AD and PD, revealing the shift in clinical trials away from therapies targeting neurotransmitter systems that provide symptomatic relief, and towards anti-aggregation, anti-inflammatory, anti-oxidant, and regeneration strategies that aim to inhibit the root causes of disease progression. We also highlight the evolving distribution of the types of "Biologic" therapies investigated, and the slowly increasing yet still severe under-utilization of delivery vehicles for AD and PD therapeutics. We then briefly discuss novel preclinical strategies for treating AD and PD. Overall, this review aims to provide a succinct overview of the clinical landscape of AD and PD therapies to better understand the field's therapeutic strategy in the past and the field's evolution in approach to the present, to better inform how to effectively treat AD and PD in the future.

Atremorine in Parkinson's disease: From dopaminergic neuroprotection to pharmacogenomics

Atremorine is a novel bioproduct obtained by nondenaturing biotechnological processes from a genetic species of Vicia faba. Atremorine is a potent dopamine (DA) enhancer with powerful effects on the neuronal dopaminergic system, acting as a neuroprotective agent in Parkinson's disease (PD). Over 97% of PD patients respond to a single dose of Atremorine (5 g, p.o.) 1 h after administration. This response is gender-, time-, dose-, and genotype-dependent, with optimal doses ranging from 5 to 20 g/day, depending upon disease severity and concomitant medication. Drug-free patients show an increase in DA levels from 12.14 ± 0.34 pg/ml to 6463.21 ± 1306.90 pg/ml; and patients chronically treated with anti-PD drugs show an increase in DA levels from 1321.53 ± 389.94 pg/ml to 16,028.54 ± 4783.98 pg/ml, indicating that Atremorine potentiates the dopaminergic effects of conventional anti-PD drugs. Atremorine also influences the levels of other neurotransmitters (adrenaline, noradrenaline) and hormones which are regulated by DA (e.g., prolactin, PRL), with no effect on serotonin or histamine. The variability in Atremorine-induced DA response is highly attributable to pharmacogenetic factors. Polymorphic variants in pathogenic (SNCA, NUCKS1, ITGA8, GPNMB, GCH1, BCKDK, APOE, LRRK2, ACMSD), mechanistic (DRD2), metabolic (CYP2D6, CYP2C9, CYP2C19, CYP3A4/5, NAT2), transporter (ABCB1, SLC6A2, SLC6A3, SLC6A4) and pleiotropic genes (APOE) influence the DA response to Atremorine and its psychomotor and brain effects. Atremorine enhances DNA methylation and displays epigenetic activity via modulation of the pharmacoepigenetic network. Atremorine is a novel neuroprotective agent for dopaminergic neurons with potential prophylactic and therapeutic activity in PD.

Cofilin 1 promotes the aggregation and cell-to-cell transmission of α-synuclein in Parkinson's disease

The histopathological hallmark of Parkinson's disease (PD) is the presence of fibrillar aggregates referred to as Lewy bodies (LBs), in which α-synuclein is the major component. Converging evidence supports the prion-like transmission of α-synuclein aggregates in the onset and progression of PD. Intracellular α-synuclein aggregates into pathological fibrils, which can be transferred from aggregate-producing cells to aggregate-free cells, triggering neuronal injury and the progression of pathology. However, the specific mechanisms mediating the aggregation and transmission of pathological α-synuclein remain unknown. Here we show that cofilin 1 binds to α-synuclein and promotes its aggregation. The mixed fibrils consist of cofilin 1 and α-synuclein are more compact and more potent than pure α-synuclein fibrils in seeding α-synuclein aggregation. Cofilin 1 also facilitates the uptake of α-synuclein fibrils and finally induces neuronal dysfunction. Together, these observations indicate that cofilin 1 acts as a crucial mediator in the aggregation and propagation of pathological α-synuclein, contributing to the pathogenesis of PD.