Mitochondrial Dysfunction and Mitophagy in Parkinson's Disease: From Mechanism to Therapy

27-Hydroxycholesterol Drives the Spread of α-Synuclein Pathology in Parkinson's Disease

BACKGROUND

The accumulation and aggregation of α-synuclein (α-Syn) are characteristic of Parkinson's disease (PD). Epidemiological evidence indicates that hyperlipidemia is associated with an increased risk of PD. The levels of 27-hydroxycholesterol (27-OHC), a cholesterol oxidation derivative, are increased in the brain and cerebrospinal fluid of patients with PD. However, whether 27-OHC plays a role in α-Syn aggregation and propagation remains elusive.

OBJECTIVE

The aim of this study was to determine whether 27-OHC regulates α-Syn aggregation and propagation.

METHODS

Purified recombinant α-Syn, neuronal cultures, and α-Syn fibril-injected mouse model of PD were treated with 27-OHC. In addition, CYP27A1 knockout mice were used to investigate the effect of lowering 27-OHC on α-Syn pathology in vivo.

RESULTS

27-OHC accelerates the aggregation of α-Syn and enhances the seeding activity of α-Syn fibrils. Furthermore, the 27-OHC-modified α-Syn fibrils localize to the mitochondria and induce mitochondrial dysfunction and neurotoxicity. Injection of 27-OHC-modified α-Syn fibrils induces enhanced spread of α-Syn pathology and dopaminergic neurodegeneration compared with pure α-Syn fibrils. Similarly, subcutaneous administration of 27-OHC facilitates the seeding of α-Syn pathology. Genetic deletion of cytochrome P450 27A1 (CYP27A1), the enzyme that converts cholesterol to 27-OHC, ameliorates the spread of pathologic α-Syn, degeneration of the nigrostriatal dopaminergic pathway, and motor impairments. These results indicate that the cholesterol metabolite 27-OHC plays an important role in the pathogenesis of PD.

CONCLUSIONS

27-OHC promotes the aggregation and spread of α-Syn. Strategies aimed at inhibiting the CYP27A1-27-OHC axis may hold promise as a disease-modifying therapy to halt the progression of α-Syn pathology in PD. © 2023 International Parkinson and Movement Disorder Society.

Tethering ATG16L1 or LC3 induces targeted autophagic degradation of protein aggregates and mitochondria

Proteolysis-targeting chimeras (PROTACs) based on the ubiquitin-proteasome system have made great progress in the field of drug discovery. There is mounting evidence that the accumulation of aggregation-prone proteins or malfunctioning organelles is associated with the occurrence of various age-related neurodegenerative disorders and cancers. However, PROTACs are inefficient for the degradation of such large targets due to the narrow entrance channel of the proteasome. Macroautophagy (hereafter referred to as autophagy) is known as a self-degradative process involved in the degradation of bulk cytoplasmic components or specific cargoes that are sequestered into autophagosomes. In the present study, we report the development of a generalizable strategy for the targeted degradation of large targets. Our results suggested that tethering large target models to phagophore-associated ATG16L1 or LC3 induced targeted autophagic degradation of the large target models. Furthermore, we successfully applied this autophagy-targeting degradation strategy to the targeted degradation of HTT65Q aggregates and mitochondria. Specifically, chimeras consisting of polyQ-binding peptide 1 (QBP) and ATG16L1-binding peptide (ABP) or LC3-interacting region (LIR) induced targeted autophagic degradation of pathogenic HTT65Q aggregates; and the chimeras consisting of mitochondria-targeting sequence (MTS) and ABP or LIR promoted targeted autophagic degradation of dysfunctional mitochondria, hence ameliorating mitochondrial dysfunction in a Parkinson disease cell model and protecting cells from apoptosis induced by the mitochondrial stress agent FCCP. Therefore, this study provides a new strategy for the selective proteolysis of large targets and enrich the toolkit for autophagy-targeting degradation.Abbreviations: ABP: ATG16L1-binding peptide; ATG16L1: autophagy related 16 like 1; ATTEC: autophagy-tethering compound; AUTAC: autophagy-targeting chimera; AUTOTAC: autophagy-targeting chimera; Baf A1: bafilomycin A1; BCL2: BCL2 apoptosis regulator; CALCOCO2/NDP52: calcium binding and coiled-coil domain 2; CASP3: caspase 3; CPP: cell-penetrating peptide; CQ: chloroquine phosphate; DAPI: 4',6-diamidino-2-phenylindole; DCM: dichloromethane; DMF: N,N-dimethylformamide; DMSO: dimethyl sulfoxide; EBSS: Earle's balanced salt solution; FCCP: carbonyl cyanide 4-(trifluoromethoxy)phenylhydrazone; FITC: fluorescein-5-isothiocyanate; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; GFP: green fluorescent protein; HEK293: human embryonic kidney 293; HEK293T: human embryonic kidney 293T; HPLC: high-performance liquid chromatography; HRP: horseradish peroxidase; HTT: huntingtin; LIR: LC3-interacting region; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MFF: mitochondrial fission factor; MTS: mitochondria-targeting sequence; NBR1: NBR1 autophagy cargo receptor; NLRX1: NLR family member X1; OPTN: optineurin; P2A: self-cleaving 2A peptide; PB1: Phox and Bem1p; PBS: phosphate-buffered saline; PE: phosphatidylethanolamine; PINK1: PTEN induced kinase 1; PRKN: parkin RBR E3 ubiquitin protein ligase; PROTACs: proteolysis-targeting chimeras; QBP: polyQ-binding peptide 1; SBP: streptavidin-binding peptide; SDS-PAGE: sodium dodecyl sulfate-polyacrylamide gel electrophoresis; SPATA33: spermatogenesis associated 33; TIMM23: translocase of inner mitochondrial membrane 23; TMEM59: transmembrane protein 59; TOMM20: translocase of outer mitochondrial membrane 20; UBA: ubiquitin-associated; WT: wild type.

Poly (ADP-Ribose) polymerase 1 and parthanatos in neurological diseases: From pathogenesis to therapeutic opportunities

Poly (ADP-ribose) polymerase-1 (PARP-1) is the most extensively studied member of the PARP superfamily, with its primary function being the facilitation of DNA damage repair processes. Parthanatos is a type of regulated cell death cascade initiated by PARP-1 hyperactivation, which involves multiple subroutines, including the accumulation of ADP-ribose polymers (PAR), binding of PAR and apoptosis-inducing factor (AIF), release of AIF from the mitochondria, the translocation of the AIF/macrophage migration inhibitory factor (MIF) complex, and massive MIF-mediated DNA fragmentation. Over the past few decades, the role of PARP-1 in central nervous system health and disease has received increasing attention. In this review, we discuss the biological functions of PARP-1 in neural cell proliferation and differentiation, memory formation, brain ageing, and epigenetic regulation. We then elaborate on the involvement of PARP-1 and PARP-1-dependant parthanatos in various neuropathological processes, such as oxidative stress, neuroinflammation, mitochondrial dysfunction, excitotoxicity, autophagy damage, and endoplasmic reticulum (ER) stress. Additional highlight contains PARP-1's implications in the initiation, progression, and therapeutic opportunities for different neurological illnesses, including neurodegenerative diseases, stroke, autism spectrum disorder (ASD), multiple sclerosis (MS), epilepsy, and neuropathic pain (NP). Finally, emerging insights into the repurposing of PARP inhibitors for the management of neurological diseases are provided. This review aims to summarize the exciting advancements in the critical role of PARP-1 in neurological disorders, which may open new avenues for therapeutic options targeting PARP-1 or parthanatos.

Targeting mitophagy for depression amelioration: a novel therapeutic strategy

Major depressive disorder is a global psychiatric condition characterized by persistent low mood and anhedonia, which seriously jeopardizes the physical and mental well-being of affected individuals. While various hypotheses have been proposed to explicate the etiology of depression, the precise pathogenesis and effective treatment of this disorder remain elusive. Mitochondria, as the primary organelles responsible for cellular energy production, possess the ability to meet the essential energy demands of the brain. Research indicated that the accumulation of damaged mitochondria is associated with the onset of depression. Mitophagy, a type of cellular autophagy, specifically targets and removes excess or damaged mitochondria. Emerging evidence demonstrated that mitophagy dysfunction was involved in the progression of depression, and several pharmacological interventions that stimulating mitophagy exerted excellent antidepressant actions. We provided an overview of updated advancements on the regulatory mechanism of mitophagy and the mitophagy abnormality in depressed patients and animals, as well as in cell models of depression. Meanwhile, various therapeutic strategies to restore mitophagy for depression alleviation were also discussed in this review.

Phosphoproteome reveals long-term potentiation deficit following treatment of ultra-low dose soman exposure in mice

Soman, a warfare nerve agent, poses a significant threat by inducing severe brain damage that often results in death. Nonetheless, our understanding of the biological changes underlying persistent neurocognitive dysfunction caused by low dosage of soman remains limited. This study used mice to examine the effects of different doses of soman over time. Phosphoproteomic analysis of the mouse brain is the first time to be used to detect toxic effects of soman at such low or ultra-low doses, which were undetectable based on measuring the activity of acetylcholinesterase at the whole-animal level. We also found that phosphoproteome alterations could accurately track the soman dose, irrespective of the sampling time. Moreover, phosphoproteome revealed a rapid and adaptive cellular response to soman exposure, with the points of departure 8-38 times lower than that of acetylcholinesterase activity. Impaired long-term potentiation was identified in phosphoproteomic studies, which was further validated by targeted quantitative proteomics, immunohistochemistry, and immunofluorescence analyses, with significantly increased levels of phosphorylation of protein phosphatase 1 in the hippocampus following soman exposure. This increase in phosphorylation inhibits long-term potentiation, ultimately leading to long-term memory dysfunction in mice.

Loss of DJ-1 function contributes to Parkinson's disease pathogenesis in mice via RACK1-mediated PKC activation and MAO-B upregulation

Parkinson's disease (PD) is a common neurodegenerative motor disorder characterized by a dramatic reduction in pars compacta of substantia nigra dopaminergic neurons and striatal dopamine (DA) levels. Mutations or deletions in the PARK7/DJ-1 gene are associated with an early-onset familial form of PD. DJ-1 protein prevents neurodegeneration via its regulation of oxidative stress and mitochondrial function as well as its roles in transcription and signal transduction. In this study, we investigated how loss of DJ-1 function affected DA degradation, ROS generation and mitochondrial dysfunction in neuronal cells. We showed that loss of DJ-1 significantly increased the expression of monoamine oxidase (MAO)-B but not MAO-A in both neuronal cells and primary astrocytes. In DJ-1-knockout (KO) mice, MAO-B protein levels in the substantia nigra (SN) and striatal regions were significantly increased. We demonstrated that the induction of MAO-B expression by DJ-1 deficiency depended on early growth response 1 (EGR1) in N2a cells. By coimmunoprecipitation omics analysis, we found that DJ-1 interacted with receptor of activated protein C kinase 1 (RACK1), a scaffolding protein, and thus inhibited the activity of the PKC/JNK/AP-1/EGR1 cascade. The PKC inhibitor sotrastaurin or the JNK inhibitor SP600125 completely inhibited DJ-1 deficiency-induced EGR1 and MAO-B expression in N2a cells. Moreover, the MAO-B inhibitor rasagiline inhibited mitochondrial ROS generation and rescued neuronal cell death caused by DJ-1 deficiency, especially in response to MPTP stimulation in vitro and in vivo. These results suggest that DJ-1 exerts neuroprotective effects by inhibiting the expression of MAO-B distributed at the mitochondrial outer membrane, which mediates DA degradation, ROS generation and mitochondrial dysfunction. This study reveals a mechanistic link between DJ-1 and MAO-B expression and contributes to understanding the crosslinks among pathogenic factors, mitochondrial dysfunction and oxidative stress in PD pathogenesis.

Unveiling Nature's potential: Promising natural compounds in Parkinson's disease management

Parkinson's disease (PD) is a common neurodegenerative disorder characterized by the progressive degeneration of dopaminergic neurons in the substantia nigra pars compacta. Although the exact etiology of PD remains elusive, growing evidence suggests a complex interplay of genetic, environmental, and lifestyle factors in its development. Despite advances in pharmacological interventions, current treatments primarily focus on managing symptoms rather than altering the disease's underlying course. In recent years, natural phytocompounds have emerged as a promising avenue for PD management. Phytochemicals derived from plants, such as phenolic acids, flavones, phenols, flavonoids, polyphenols, saponins, terpenes, alkaloids, and amino acids, have been extensively studied for their potential neuroprotective effects. These bioactive compounds possess a wide range of therapeutic properties, including antioxidant, anti-inflammatory, anti-apoptotic, and anti-aggregation activities, which may counteract the neurodegenerative processes in PD. This comprehensive review delves into the pathophysiology of PD, with a specific focus on the roles of oxidative stress, mitochondrial dysfunction, and protein malfunction in disease pathogenesis. The review collates a wealth of evidence from preclinical studies and in vitro experiments, highlighting the potential of various phytochemicals in attenuating dopaminergic neuron degeneration, reducing α-synuclein aggregation, and modulating neuroinflammatory responses. Prominent among the natural compounds studied are curcumin, resveratrol, coenzyme Q10, and omega-3 fatty acids, which have demonstrated neuroprotective effects in experimental models of PD. Additionally, flavonoids like baicalein, luteolin, quercetin, and nobiletin, and alkaloids such as berberine and physostigmine, show promise in mitigating PD-associated pathologies. This review emphasizes the need for further research through controlled clinical trials to establish the safety and efficacy of these natural compounds in PD management. Although preclinical evidence is compelling, the translation of these findings into effective therapies for PD necessitates robust clinical investigation. Rigorous evaluation of pharmacokinetics, bioavailability, and potential drug interactions is imperative to pave the way for evidence-based treatment strategies. With the rising interest in natural alternatives and the potential for synergistic effects with conventional therapies, this review serves as a comprehensive resource for pharmaceutical industries, researchers, and clinicians seeking novel therapeutic approaches to combat PD. Harnessing the therapeutic potential of these natural phytocompounds may hold the key to improving the quality of life for PD patients and moving towards disease-modifying therapies in the future.

The Interplay between Mitochondrial Dysfunction and Ferroptosis during Ischemia-Associated Central Nervous System Diseases

Cerebral ischemia, a leading cause of disability and mortality worldwide, triggers a cascade of molecular and cellular pathologies linked to several central nervous system (CNS) disorders. These disorders primarily encompass ischemic stroke, Alzheimer's disease (AD), Parkinson's disease (PD), epilepsy, and other CNS conditions. Despite substantial progress in understanding and treating the underlying pathological processes in various neurological diseases, there is still a notable absence of effective therapeutic approaches aimed specifically at mitigating the damage caused by these illnesses. Remarkably, ischemia causes severe damage to cells in ischemia-associated CNS diseases. Cerebral ischemia initiates oxygen and glucose deprivation, which subsequently promotes mitochondrial dysfunction, including mitochondrial permeability transition pore (MPTP) opening, mitophagy dysfunction, and excessive mitochondrial fission, triggering various forms of cell death such as autophagy, apoptosis, as well as ferroptosis. Ferroptosis, a novel type of regulated cell death (RCD), is characterized by iron-dependent accumulation of lethal reactive oxygen species (ROS) and lipid peroxidation. Mitochondrial dysfunction and ferroptosis both play critical roles in the pathogenic progression of ischemia-associated CNS diseases. In recent years, growing evidence has indicated that mitochondrial dysfunction interplays with ferroptosis to aggravate cerebral ischemia injury. However, the potential connections between mitochondrial dysfunction and ferroptosis in cerebral ischemia have not yet been clarified. Thus, we analyzed the underlying mechanism between mitochondrial dysfunction and ferroptosis in ischemia-associated CNS diseases. We also discovered that GSH depletion and GPX4 inactivation cause lipoxygenase activation and calcium influx following cerebral ischemia injury, resulting in MPTP opening and mitochondrial dysfunction. Additionally, dysfunction in mitochondrial electron transport and an imbalanced fusion-to-fission ratio can lead to the accumulation of ROS and iron overload, which further contribute to the occurrence of ferroptosis. This creates a vicious cycle that continuously worsens cerebral ischemia injury. In this study, our focus is on exploring the interplay between mitochondrial dysfunction and ferroptosis, which may offer new insights into potential therapeutic approaches for the treatment of ischemia-associated CNS diseases.

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.

Nanowired delivery of antibodies to tau and neuronal nitric oxide synthase together with cerebrolysin attenuates traumatic brain injury induced exacerbation of brain pathology in Parkinson's disease

Concussive head injury (CHI) is one of the major risk factors for developing Parkinson's disease in later life of military personnel affecting lifetime functional and cognitive disturbances. Till date no suitable therapies are available to attenuate CHI or PD induced brain pathology. Thus, further exploration of novel therapeutic agents are highly warranted using nanomedicine in enhancing the quality of life of veterans or service members of US military. Since PD or CHI induces oxidative stress and perturbs neurotrophic factors regulation associated with phosphorylated tau (p-tau) deposition, a possibility exists that nanodelivery of agents that could enhance neurotrophic factors balance and attenuate oxidative stress could be neuroprotective in nature. In this review, nanowired delivery of cerebrolysin-a balanced composition of several neurotrophic factors and active peptide fragments together with monoclonal antibodies to neuronal nitric oxide synthase (nNOS) with p-tau antibodies was examined in PD following CHI in model experiments. Our results suggest that combined administration of nanowired antibodies to nNOS and p-tau together with cerebrolysin significantly attenuated CHI induced exacerbation of PD brain pathology. This combined treatment also has beneficial effects in CHI or PD alone, not reported earlier.

Liquid-liquid phase separation regulates alpha-synuclein aggregate and mitophagy in Parkinson's disease

Parkinson's disease (PD) is the second most common neurodegenerative disease in the world, and alpha-synuclein (α-syn) abnormal aggregate and mitochondrial dysfunction play a crucial role in its pathological development. Recent studies have revealed that proteins can form condensates through liquid-liquid phase separation (LLPS), and LLPS has been found to be widely present in α-syn aberrant aggregate and mitophagy-related protein physiological processes. This review summarizes the occurrence of α-syn LLPS and its influencing factors, introduces the production and transformation of the related protein LLPS during PINK1-Parkin-mediated mitophagy, hoping to provide new ideas and methods for the study of PD pathology.

Mitochondrial dysfunction and mitophagy defects in LRRK2-R1441C Parkinson's disease models

Mutations in the Leucine-Rich Repeat Kinase 2 (LRRK2) gene have been identified as one of the most common genetic causes of Parkinson's disease (PD). The LRRK2 PD-associated mutations LRRK2G2019S and LRRK2R1441C, located in the kinase domain and in the ROC-COR domain, respectively, have been demonstrated to impair mitochondrial function. Here, we sought to further our understanding of mitochondrial health and mitophagy by integrating data from LRRK2R1441C rat primary cortical and human induced pluripotent stem cell-derived dopamine (iPSC-DA) neuronal cultures as models of PD. We found that LRRK2R1441C neurons exhibit decreased mitochondrial membrane potential, impaired mitochondrial function and decreased basal mitophagy levels. Mitochondrial morphology was altered in LRRK2R1441C iPSC-DA but not in cortical neuronal cultures or aged striatal tissue, indicating a cell-type-specific phenotype. Additionally, LRRK2R1441C but not LRRK2G2019S neurons demonstrated decreased levels of the mitophagy marker pS65Ub in response to mitochondrial damage, which could disrupt degradation of damaged mitochondria. This impaired mitophagy activation and mitochondrial function were not corrected by the LRRK2 inhibitor MLi-2 in LRRK2R1441C iPSC-DA neuronal cultures. Furthermore, we demonstrate LRRK2 interaction with MIRO1, a protein necessary to stabilize and to anchor mitochondria for transport, occurs at mitochondria, in a genotype-independent manner. Despite this, we found that degradation of MIRO1 was impaired in LRRK2R1441C cultures upon induced mitochondrial damage, suggesting a divergent mechanism from the LRRK2G2019S mutation.

Peroxisom proliferator-activated receptor-γ coactivator-1α in neurodegenerative disorders: A promising therapeutic target

Neurodegenerative disorders (NDDs) are characterized by progressive loss of selectively vulnerable neuronal populations and myelin sheath, leading to behavioral and cognitive dysfunction that adversely affect the quality of life. Identifying novel therapies that attenuate the progression of NDDs would be of significance. Peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α), a widely expressed transcriptional regulator, modulates the expression of genes engaged in mitochondrial biosynthesis, metabolic regulation, and oxidative stress (OS). Emerging evidences point to the strong connection between PGC-1α and NDDs, suggesting its positive impaction on the progression of NDDs. Therefore, it is urgent to gain a deeper and broader understanding between PGC-1α and NDDs. To this end, this review presents a comprehensive overview of PGC-1α, including its basic characteristics, the post-translational modulations, as well as the interacting transcription factors. Secondly, the pathogenesis of PGC-1α in various NDDs, such as Alzheimer's (AD), Parkinson's (PD), and Huntington's disease (HD) is briefly discussed. Additionally, this study summarizes the underlying mechanisms that PGC-1α is neuroprotective in NDDs via regulating neuroinflammation, OS, and mitochondrial dysfunction. Finally, we briefly outline the shortcomings of current NDDs drug therapy, and summarize the functions and potential applications of currently available PGC-1α modulators (activator or inhibitors). Generally, this review updates our insight of the important role of PGC-1α on the development of NDDs, and provides a promising therapeutic target/ drug for the treatment of NDDs.

A blood-based marker of mitochondrial DNA damage in Parkinson's disease

Parkinson's disease (PD) is the most common neurodegenerative movement disorder, and neuroprotective or disease-modifying interventions remain elusive. High-throughput markers aimed at stratifying patients on the basis of shared etiology are required to ensure the success of disease-modifying therapies in clinical trials. Mitochondrial dysfunction plays a prominent role in the pathogenesis of PD. Previously, we found brain region-specific accumulation of mitochondrial DNA (mtDNA) damage in PD neuronal culture and animal models, as well as in human PD postmortem brain tissue. To investigate mtDNA damage as a potential blood-based marker for PD, we describe herein a PCR-based assay (Mito DNADX) that allows for the accurate real-time quantification of mtDNA damage in a scalable platform. We found that mtDNA damage was increased in peripheral blood mononuclear cells derived from patients with idiopathic PD and those harboring the PD-associated leucine-rich repeat kinase 2 (LRRK2) G2019S mutation in comparison with age-matched controls. In addition, mtDNA damage was elevated in non-disease-manifesting LRRK2 mutation carriers, demonstrating that mtDNA damage can occur irrespective of a PD diagnosis. We further established that Lrrk2 G2019S knock-in mice displayed increased mtDNA damage, whereas Lrrk2 knockout mice showed fewer mtDNA lesions in the ventral midbrain, compared with wild-type control mice. Furthermore, a small-molecule kinase inhibitor of LRRK2 mitigated mtDNA damage in a rotenone PD rat midbrain neuron model and in idiopathic PD patient-derived lymphoblastoid cell lines. Quantifying mtDNA damage using the Mito DNADX assay may have utility as a candidate marker of PD and for measuring the pharmacodynamic response to LRRK2 kinase inhibitors.

Shared Molecular Pathways in Glaucoma and Other Neurodegenerative Diseases: Insights from RNA-Seq Analysis and miRNA Regulation for Promising Therapeutic Avenues

Advances in RNA-sequencing technologies have led to the identification of molecular biomarkers for several diseases, including neurodegenerative diseases, such as Alzheimer's, Parkinson's, Huntington's diseases and Amyotrophic Lateral Sclerosis. Despite the nature of glaucoma as a neurodegenerative disorder with several similarities with the other above-mentioned diseases, transcriptional data about this disease are still scarce. microRNAs are small molecules (~17-25 nucleotides) that have been found to be specifically expressed in the CNS as major components of the system regulating the development signatures of neurodegenerative diseases and the homeostasis of the brain. In this review, we sought to identify similarities between the functional mechanisms and the activated pathways of the most common neurodegenerative diseases, as well as to discuss how those mechanisms are regulated by miRNAs, using RNA-Seq as an approach to compare them. We also discuss therapeutically suitable applications for these disease hallmarks in clinical future studies.

Mitochondrial heterogeneity in diseases

As key organelles involved in cellular metabolism, mitochondria frequently undergo adaptive changes in morphology, components and functions in response to various environmental stresses and cellular demands. Previous studies of mitochondria research have gradually evolved, from focusing on morphological change analysis to systematic multiomics, thereby revealing the mitochondrial variation between cells or within the mitochondrial population within a single cell. The phenomenon of mitochondrial variation features is defined as mitochondrial heterogeneity. Moreover, mitochondrial heterogeneity has been reported to influence a variety of physiological processes, including tissue homeostasis, tissue repair, immunoregulation, and tumor progression. Here, we comprehensively review the mitochondrial heterogeneity in different tissues under pathological states, involving variant features of mitochondrial DNA, RNA, protein and lipid components. Then, the mechanisms that contribute to mitochondrial heterogeneity are also summarized, such as the mutation of the mitochondrial genome and the import of mitochondrial proteins that result in the heterogeneity of mitochondrial DNA and protein components. Additionally, multiple perspectives are investigated to better comprehend the mysteries of mitochondrial heterogeneity between cells. Finally, we summarize the prospective mitochondrial heterogeneity-targeting therapies in terms of alleviating mitochondrial oxidative damage, reducing mitochondrial carbon stress and enhancing mitochondrial biogenesis to relieve various pathological conditions. The possibility of recent technological advances in targeted mitochondrial gene editing is also discussed.

HtrA1 prevents and reverses α-synuclein aggregation, rendering it non-toxic and seeding incompetent

Parkinson disease (PD) is closely linked to the misfolding and accumulation of α-synuclein (α-syn) into Lewy bodies. HtrA1 is a PDZ serine protease that degrades fibrillar tau, which is associated with Alzheimer disease (AD). Further, inactivating mutations to mitochondrial HtrA2 have been implicated in PD. Here, we establish that HtrA1 inhibits the aggregation of α-syn as well as FUS and TDP-43, which are implicated in amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). We demonstrate that the protease domain of HtrA1 is necessary and sufficient for inhibition of aggregation, yet this activity is independent of HtrA1 proteolytic activity. Further, we find that HtrA1 also disaggregates preformed α-syn fibrils, which may promote their clearance. Treatment of α-syn fibrils with HtrA1 renders α-syn incapable of seeding the aggregation of endogenous α-syn in mammalian biosensor cells. We find that HtrA1 remodels α-syn by specifically targeting the NAC domain, which is the key domain that catalyzes α-syn oligomerization and fibrillization. Finally, in a primary neuron model of α-syn aggregation, we show that HtrA1 and its proteolytically inactive form both detoxify α-syn and prevent the formation of hyperphosphorylated α-syn accumulations. Our findings suggest that HtrA1 prevents aggregation and promotes disaggregation of multiple disease-associated proteins, and may be a therapeutic target for treating a range of neurodegenerative disorders.

Phytochemical investigation of Asarum sieboldii var. seoulense and the phenotypic profiles of its constituents against a Parkinson's Disease olfactory cell line

Asarum sieboldii var. seoulense is a plant species under the family Aristolochiaceae and has been used for centuries as an ingredient in a well-known Traditional Chinese medicine (TCM), "Xixin", to treat symptoms of the neurodegenerative condition Parkinson's Disease (PD). Although there have been studies on the neuroprotective effect of this TCM, the phenotypic profiles of its chemical constituents against PD-implicated cellular organelles have not been reported. This research investigated the chemistry of A. sieboldii var. seoulense extract to identify the active small molecules that exhibited perturbation to the cellular compartments related to PD, potentially supporting its traditional application in treating this condition. 1H NMR-guided chemical investigation of this plant yielded twenty secondary metabolites which belong to isobutylamides, lignans and phenolics. The compounds were evaluated against an olfactory cell line derived from a PD patient using phenotypic assay. Several isolates, 2, 3, 7, 11, 13-16 and 18-20, were found to induce moderate perturbation to the staining of mitochondria, autophagosome and α-tubulin of the cells. Considering that PD pathogenesis is closely related to these cellular compartments, the results provided a rationale for the traditional application of Xixin in the treatment of PD.

Exploring Molecular Targets for Mitochondrial Therapies in Neurodegenerative Diseases

The progressive deterioration of function and structure of brain cells in neurodegenerative diseases is accompanied by mitochondrial dysfunction, affecting cellular metabolism, intracellular signaling, cell differentiation, morphogenesis, and the activation of programmed cell death. However, most of the efforts to develop therapies for Alzheimer's and Parkinson's disease have focused on restoring or maintaining the neurotransmitters in affected neurons, removing abnormal protein aggregates through immunotherapies, or simply treating symptomatology. However, none of these approaches to treating neurodegeneration can stop or reverse the disease other than by helping to maintain mental function and manage behavioral symptoms. Here, we discuss alternative molecular targets for neurodegeneration treatments that focus on mitochondrial functions, including regulation of calcium ion (Ca2+) transport, protein modification, regulation of glucose metabolism, antioxidants, metal chelators, vitamin supplementation, and mitochondrial transference to compromised neurons. After pre-clinical evaluation and studies in animal models, some of these therapeutic compounds have advanced to clinical trials and are expected to have positive outcomes in subjects with neurodegeneration. These mitochondria-targeted therapeutic agents are an alternative to established or conventional molecular targets that have shown limited effectiveness in treating neurodegenerative diseases.

Calcium dysregulation combined with mitochondrial failure and electrophysiological maturity converge in Parkinson's iPSC-dopamine neurons

Parkinson's disease (PD) is characterized by a progressive deterioration of motor and cognitive functions. Although death of dopamine neurons is the hallmark pathology of PD, this is a late-stage disease process preceded by neuronal dysfunction. Here we describe early physiological perturbations in patient-derived induced pluripotent stem cell (iPSC)-dopamine neurons carrying the GBA-N370S mutation, a strong genetic risk factor for PD. GBA-N370S iPSC-dopamine neurons show an early and persistent calcium dysregulation notably at the mitochondria, followed by reduced mitochondrial membrane potential and oxygen consumption rate, indicating mitochondrial failure. With increased neuronal maturity, we observed decreased synaptic function in PD iPSC-dopamine neurons, consistent with the requirement for ATP and calcium to support the increase in electrophysiological activity over time. Our work demonstrates that calcium dyshomeostasis and mitochondrial failure impair the higher electrophysiological activity of mature neurons and may underlie the vulnerability of dopamine neurons in PD.

Genomic Instability Evolutionary Footprints on Human Health: Driving Forces or Side Effects?

In this work, we propose a comprehensive perspective on genomic instability comprising not only the accumulation of mutations but also telomeric shortening, epigenetic alterations and other mechanisms that could contribute to genomic information conservation or corruption. First, we present mechanisms playing a role in genomic instability across the kingdoms of life. Then, we explore the impact of genomic instability on the human being across its evolutionary history and on present-day human health, with a particular focus on aging and complex disorders. Finally, we discuss the role of non-coding RNAs, highlighting future approaches for a better living and an expanded healthy lifespan.

Mitochondrial dysfunction in aging

Aging is a complex process that features a functional decline in many organelles. Although mitochondrial dysfunction is suggested as one of the determining factors of aging, the role of mitochondrial quality control (MQC) in aging is still poorly understood. A growing body of evidence points out that reactive oxygen species (ROS) stimulates mitochondrial dynamic changes and accelerates the accumulation of oxidized by-products through mitochondrial proteases and mitochondrial unfolded protein response (UPRmt). Mitochondrial-derived vesicles (MDVs) are the frontline of MQC to dispose of oxidized derivatives. Besides, mitophagy helps remove partially damaged mitochondria to ensure that mitochondria are healthy and functional. Although abundant interventions on MQC have been explored, over-activation or inhibition of any type of MQC may even accelerate abnormal energy metabolism and mitochondrial dysfunction-induced senescence. This review summarizes mechanisms essential for maintaining mitochondrial homeostasis and emphasizes that imbalanced MQC may accelerate cellular senescence and aging. Thus, appropriate interventions on MQC may delay the aging process and extend lifespan.

Novel therapeutic approaches to target neurodegeneration

Ageing is the main risk factor common to most primary neurodegenerative disorders. Indeed, age-related brain alterations have been long considered to predispose to neurodegeneration. Although protein misfolding and the accumulation of toxic protein aggregates have been considered as causative events in neurodegeneration, several other biological pathways affected by brain ageing also contribute to pathogenesis. Here, we discuss the evidence showing the involvement of the mechanisms controlling neuronal structure, gene expression, autophagy, cell metabolism and neuroinflammation in the onset and progression of neurodegenerative disorders. Furthermore, we review the therapeutic strategies currently under development or as future approaches designed to normalize these pathways, which may then increase brain resilience to cope with toxic protein species. In addition to therapies targeting the insoluble protein aggregates specifically associated with each neurodegenerative disorder, these novel pharmacological approaches may be part of combined therapies designed to rescue brain function.

Pooled analysis of frontal lobe transcriptomic data identifies key mitophagy gene changes in Alzheimer's disease brain

Background

The growing prevalence of Alzheimer's disease (AD) is becoming a global health challenge without effective treatments. Defective mitochondrial function and mitophagy have recently been suggested as etiological factors in AD, in association with abnormalities in components of the autophagic machinery like lysosomes and phagosomes. Several large transcriptomic studies have been performed on different brain regions from AD and healthy patients, and their data represent a vast source of important information that can be utilized to understand this condition. However, large integration analyses of these publicly available data, such as AD RNA-Seq data, are still missing. In addition, large-scale focused analysis on mitophagy, which seems to be relevant for the aetiology of the disease, has not yet been performed.

Methods

In this study, publicly available raw RNA-Seq data generated from healthy control and sporadic AD post-mortem human samples of the brain frontal lobe were collected and integrated. Sex-specific differential expression analysis was performed on the combined data set after batch effect correction. From the resulting set of differentially expressed genes, candidate mitophagy-related genes were identified based on their known functional roles in mitophagy, the lysosome, or the phagosome, followed by Protein-Protein Interaction (PPI) and microRNA-mRNA network analysis. The expression changes of candidate genes were further validated in human skin fibroblast and induced pluripotent stem cells (iPSCs)-derived cortical neurons from AD patients and matching healthy controls.

Results

From a large dataset (AD: 589; control: 246) based on three different datasets (i.e., ROSMAP, MSBB, & GSE110731), we identified 299 candidate mitophagy-related differentially expressed genes (DEG) in sporadic AD patients (male: 195, female: 188). Among these, the AAA ATPase VCP, the GTPase ARF1, the autophagic vesicle forming protein GABARAPL1 and the cytoskeleton protein actin beta ACTB were selected based on network degrees and existing literature. Changes in their expression were further validated in AD-relevant human in vitro models, which confirmed their down-regulation in AD conditions.

Conclusion

Through the joint analysis of multiple publicly available data sets, we identify four differentially expressed key mitophagy-related genes potentially relevant for the pathogenesis of sporadic AD. Changes in expression of these four genes were validated using two AD-relevant human in vitro models, primary human fibroblasts and iPSC-derived neurons. Our results provide foundation for further investigation of these genes as potential biomarkers or disease-modifying pharmacological targets.

Integrated insight into the molecular mechanisms of selenium-modulated, MPP+-induced cytotoxicity in a Parkinson's disease model

OBJECTIVE

Parkinson's disease (PD) is a neurodegenerative disease that is associated with oxidative stress. Due to the anti-inflammatory and antioxidant functions of Selenium (Se), this molecule may have neuroprotective functions in PD; however, the involvement of Se in such a protective function is unclear.

METHODS

1-methyl-4-phenylpyridinium (MPP⁺), which inhibits mitochondrial respiration, is generally used to produce a reliable cellular model of PD. In this study, a MPP⁺-induced PD model was used to test if Se could modulate cytotoxicity, and we further capture gene expression profiles following PC12 cell treatment with MPP⁺ with or without Se by genome wide high-throughput sequencing.

RESULTS

We identified 351 differentially expressed genes (DEGs) and 14 differentially expressed long non-coding RNAs (DELs) in MPP⁺-treated cells when compared to controls. We further document 244 DEGs and 27 DELs in cells treated with MPP⁺ and Se vs. cells treated with MPP⁺ only. Functional annotation analysis of DEGs and DELs revealed that these groups were enriched in genes that respond to reactive oxygen species (ROS), metabolic processes, and mitochondrial control of apoptosis. Thioredoxin reductase 1 (Txnrd1) was also identified as a biomarker of Se treatment.

CONCLUSIONS

Our data suggests that the DEGs Txnrd1, Siglec1 and Klf2, and the DEL AABR07044454.1 which we hypothesize to function in cis on the target gene Cdkn1a, may modulate the underlying neurodegenerative process, and act a protective function in the PC12 cell PD model. This study further systematically demonstrated that mRNAs and lncRNAs induced by Se are involved in neuroprotection in PD, and provides novel insight into how Se modulates cytotoxicity in the MPP⁺-induced PD model.

Morin exhibits a neuroprotective effect in MPTP-induced Parkinson's disease model via TFEB/AMPK-mediated mitophagy

BACKGROUND

Parkinson's disease (PD) is one of the most common neurodegenerative diseases in the world. Mitophagy has been implicated in PD etiology for decades and its pharmacological activation is recognized as a promising treatment strategy for PD. For mitophagy initiation, low mitochondrial membrane potential (ΔΨm) is essential. We identified a natural compound morin that could induce mitophagy without affecting ΔΨm. Morin is a flavonoid that can be isolated from fruits like mulberry.

PURPOSE

To reveal the effect of morin on the PD mice model and their potential underlying molecular mechanism.

METHODS

Mitophagy process induced by morin in N2a cells meditation were measured using flow cytometry and immunofluorescence. JC-1 fluorescence dye used to detect the mitochondrial membrane potential (ΔΨm). The TFEB nuclear translocation were examined by immunofluorescence staining and western blot assay. The PD mice model was induced by MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) intraperitoneal administration.

RESULTS

We found that morin also promoted nuclear translocation of the mitophagy regulator TFEB and activated the AMPK-ULK1 pathway. In MPTP-induced PD in vivo models, morin protected DA neurons from MPTP neurotoxicity and ameliorated behavioral deficit.

CONCLUSION

Although morin was previously reported to be neuroprotective in PD, the detailed molecular mechanisms remain to be elucidated. For the first time, we report morin served as a novel and safe mitophagy enhancer underlying AMPK-ULK1 pathway and exhibited anti-Parkinsonian effects indicating its potential as a clinical drug for PD treatment.

Deficiency of RAB39B Activates ER Stress-Induced Pro-apoptotic Pathway and Causes Mitochondrial Dysfunction and Oxidative Stress in Dopaminergic Neurons by Impairing Autophagy and Upregulating α-Synuclein

Deletion and missense or nonsense mutation of RAB39B gene cause familial Parkinson's disease (PD). We hypothesized that deletion and mutation of RAB39B gene induce degeneration of dopaminergic neurons by decreasing protein level of functional RAB39B and causing RAB39B deficiency. Cellular model of deletion or mutation of RAB39B gene-induced PD was prepared by knocking down endogenous RAB39B in human SH-SY5Y dopaminergic cells. Transfection of shRNA-induced 90% reduction in RAB39B level significantly decreased viability of SH-SY5Y dopaminergic neurons. Deficiency of RAB39B caused impairment of macroautophagy/autophagy, which led to increased protein levels of α-synuclein and phospho-α-synuclein^Ser129 within endoplasmic reticulum (ER) and mitochondria. RAB39B deficiency-induced increase of ER α-synuclein and phospho-α-synuclein^Ser129 caused activation of ER stress, unfolded protein response, and ER stress-induced pro-apoptotic cascade. Deficiency of RAB39B-induced increase of mitochondrial α-synuclein decreased mitochondrial membrane potential and increased mitochondrial superoxide. RAB39B deficiency-induced activation of ER stress pro-apoptotic pathway, mitochondrial dysfunction, and oxidative stress caused apoptotic death of SH-SY5Y dopaminergic cells by activating mitochondrial apoptotic cascade. In contrast to neuroprotective effect of wild-type RAB39B, PD mutant (T168K), (W186X), or (G192R) RAB39B did not prevent tunicamycin- or rotenone-induced increase of neurotoxic α-synuclein and activation of pro-apoptotic pathway. Our results suggest that RAB39B is required for survival and macroautophagy function of dopaminergic neurons and that deletion or PD mutation of RAB39B gene-induced RAB39B deficiency induces apoptotic death of dopaminergic neurons via impairing autophagy function and upregulating α-synuclein.

LC3B is a cofactor for LMX1B-mediated transcription of autophagy genes in dopaminergic neurons

It is becoming increasingly clear that the Atg8 family of autophagy proteins have roles not only in the cytoplasm, but also in the cell nucleus. In this issue, Jiménez-Moreno et al. (2023. J. Cell Biol.https://doi.org/10.1083/jcb.201910133) report that nuclear LC3B binds to the LIM homeodomain transcription factor LMX1B and acts as a cofactor for LMX1B-mediated transcription of autophagy genes, providing stress protection and ensuring survival of midbrain dopaminergic neurons.

Examining Sporadic Cancer Mutations Uncovers a Set of Genes Involved in Mitochondrial Maintenance

Mitochondria are key organelles for cellular health and metabolism and the activation of programmed cell death processes. Although pathways for regulating and re-establishing mitochondrial homeostasis have been identified over the past twenty years, the consequences of disrupting genes that regulate other cellular processes, such as division and proliferation, on affecting mitochondrial function remain unclear. In this study, we leveraged insights about increased sensitivity to mitochondrial damage in certain cancers, or genes that are frequently mutated in multiple cancer types, to compile a list of candidates for study. RNAi was used to disrupt orthologous genes in the model organism Caenorhabditis elegans, and a series of assays were used to evaluate these genes' importance for mitochondrial health. Iterative screening of ~1000 genes yielded a set of 139 genes predicted to play roles in mitochondrial maintenance or function. Bioinformatic analyses indicated that these genes are statistically interrelated. Functional validation of a sample of genes from this set indicated that disruption of each gene caused at least one phenotype consistent with mitochondrial dysfunction, including increased fragmentation of the mitochondrial network, abnormal steady-state levels of NADH or ROS, or altered oxygen consumption. Interestingly, RNAi-mediated knockdown of these genes often also exacerbated α-synuclein aggregation in a C. elegans model of Parkinson's disease. Additionally, human orthologs of the gene set showed enrichment for roles in human disorders. This gene set provides a foundation for identifying new mechanisms that support mitochondrial and cellular homeostasis.

The Role of Exercise in Maintaining Mitochondrial Proteostasis in Parkinson's Disease

Parkinson's disease (PD) is the second most common rapidly progressive neurodegenerative disease and has serious health and socio-economic consequences. Mitochondrial dysfunction is closely related to the onset and progression of PD, and the use of mitochondria as a target for PD therapy has been gaining traction in terms of both recognition and application. The disruption of mitochondrial proteostasis in the brain tissue of PD patients leads to mitochondrial dysfunction, which manifests as mitochondrial unfolded protein response, mitophagy, and mitochondrial oxidative phosphorylation. Physical exercise is important for the maintenance of human health, and has the great advantage of being a non-pharmacological therapy that is non-toxic, low-cost, and universally applicable. In this review, we investigate the relationships between exercise, mitochondrial proteostasis, and PD and explore the role and mechanisms of mitochondrial proteostasis in delaying PD through exercise.

Single-Atom Nanocatalytic Therapy for Suppression of Neuroinflammation by Inducing Autophagy of Abnormal Mitochondria

Catalysts have achieved efficacy in scavenging reactive oxygen species (ROS) to eliminate neuroinflammation, but it ignores the essential fact of blocking the source of ROS regeneration. Here, we report the single-atom catalysts (SACs) Pt/CeO₂, which can effectively catalyze the breakdown of existing ROS and induce mitochondrial membrane potential (Δψm) depolarization by interfering with the α-glycerophosphate shuttle pathway and malate-aspartate shuttle pathway, indirectly triggering the self-clearance of dysfunctional mitochondria and thus eradicating the source of ROS generation. In a therapeutic model of Parkinson's disease (PD), Pt/CeO₂ wrapped by neutrophil-like (HL-60) cell membranes and modified by rabies virus glycoprotein (RVG29) effectively crosses the blood-brain barrier (BBB), enters dopaminergic neurons entering the neuroinflammatory region breaking down existing ROS and inducing mitophagy by electrostatic adsorption targeting mitochondria to prevent ROS regeneration after catalyst discharge. This strategy of efficiently eliminating ROS at the lesion and fundamentally blocking the source of ROS production can address both symptoms and root causes and provides a mechanism of explanation and action target for the treatment of inflammation-related diseases.

Role of Sirtuin 3 in Degenerative Diseases of the Central Nervous System

An NAD⁺-dependent deacetylase called Sirtuin 3 (Sirt3) is involved in the metabolic processes of the mitochondria, including energy generation, the tricarboxylic acid cycle, and oxidative stress. Sirt3 activation can slow down or prevent mitochondrial dysfunction in response to neurodegenerative disorders, demonstrating a strong neuroprotective impact. The mechanism of Sirt3 in neurodegenerative illnesses has been elucidated over time; it is essential for neuron, astrocyte, and microglial function, and its primary regulatory factors include antiapoptosis, oxidative stress, and the maintenance of metabolic homeostasis. Neurodegenerative disorders, such as Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), amyotrophic lateral sclerosis (ALS), and multiple sclerosis (MS), may benefit from a thorough and in-depth investigation of Sirt3. In this review, we primarily cover Sirt3's role and its regulation in the nerve cells and the connection between Sirt3 and neurodegenerative disorders.

Redox Imbalance in Neurological Disorders in Adults and Children

Oxygen is a central molecule for numerous metabolic and cytophysiological processes, and, indeed, its imbalance can lead to numerous pathological consequences. In the human body, the brain is an aerobic organ and for this reason, it is very sensitive to oxygen equilibrium. The consequences of oxygen imbalance are especially devastating when occurring in this organ. Indeed, oxygen imbalance can lead to hypoxia, hyperoxia, protein misfolding, mitochondria dysfunction, alterations in heme metabolism and neuroinflammation. Consequently, these dysfunctions can cause numerous neurological alterations, both in the pediatric life and in the adult ages. These disorders share numerous common pathways, most of which are consequent to redox imbalance. In this review, we will focus on the dysfunctions present in neurodegenerative disorders (specifically Alzheimer's disease, Parkinson's disease and amyotrophic lateral sclerosis) and pediatric neurological disorders (X-adrenoleukodystrophies, spinal muscular atrophy, mucopolysaccharidoses and Pelizaeus-Merzbacher Disease), highlighting their underlining dysfunction in redox and identifying potential therapeutic strategies.

The Potential Regulation of A-to-I RNA Editing on Genes in Parkinson's Disease

Parkinson's disease (PD) is characterized by dopaminergic neurodegeneration and an abnormal accumulation of α-synuclein aggregates. A number of genetic factors have been shown to increase the risk of PD. Exploring the underlying molecular mechanisms that mediate PD's transcriptomic diversity can help us understand neurodegenerative pathogenesis. In this study, we identified 9897 A-to-I RNA editing events associated with 6286 genes across 372 PD patients. Of them, 72 RNA editing events altered miRNA binding sites and this may directly affect miRNA regulations of their host genes. However, RNA editing effects on the miRNA regulation of genes are more complex. They can (1) abolish existing miRNA binding sites, which allows miRNAs to regulate other genes; (2) create new miRNA binding sites that may sequester miRNAs from regulating other genes; or (3) occur in the miRNA seed regions and change their targets. The first two processes are also referred to as miRNA competitive binding. In our study, we found 8 RNA editing events that may alter the expression of 1146 other genes via miRNA competition. We also found one RNA editing event that modified a miRNA seed region, which was predicted to disturb the regulation of four genes. Considering the PD-related functions of the affected genes, 25 A-to-I RNA editing biomarkers for PD are proposed, including the 3 editing events in the EIF2AK2, APOL6, and miR-4477b seed regions. These biomarkers may alter the miRNA regulation of 133 PD-related genes. All these analyses reveal the potential mechanisms and regulations of RNA editing in PD pathogenesis.

An Efficient 2D Protocol for Differentiation of iPSCs into Mature Postmitotic Dopaminergic Neurons: Application for Modeling Parkinson's Disease

About 15% of patients with parkinsonism have a hereditary form of Parkinson's disease (PD). Studies on the early stages of PD pathogenesis are challenging due to the lack of relevant models. The most promising ones are models based on dopaminergic neurons (DAns) differentiated from induced pluripotent stem cells (iPSCs) of patients with hereditary forms of PD. This work describes a highly efficient 2D protocol for obtaining DAns from iPSCs. The protocol is rather simple, comparable in efficiency with previously published protocols, and does not require viral vectors. The resulting neurons have a similar transcriptome profile to previously published data for neurons, and have a high level of maturity marker expression. The proportion of sensitive (SOX6+) DAns in the population calculated from the level of gene expression is higher than resistant (CALB+) DAns. Electrophysiological studies of the DAns confirmed their voltage sensitivity and showed that a mutation in the PARK8 gene is associated with enhanced store-operated calcium entry. The study of high-purity DAns differentiated from the iPSCs of patients with hereditary PD using this differentiation protocol will allow for investigators to combine various research methods, from patch clamp to omics technologies, and maximize information about cell function in normal and pathological conditions.

Endoplasmic Reticulum Membrane Contact Sites, Lipid Transport, and Neurodegeneration

The Endoplasmic Reticulum (ER) is an endomembrane system that plays a multiplicity of roles in cell physiology and populates even the most distal cell compartments, including dendritic tips and axon terminals of neurons. Some of its functions are achieved by a cross talk with other intracellular membranous organelles and with the plasma membrane at membrane contacts sites (MCSs). As the ER synthesizes most membrane lipids, lipid exchanges mediated by lipid transfer proteins at MCSs are a particularly important aspect of this cross talk, which synergizes with the cross talk mediated by vesicular transport. Several mutations of genes that encode proteins localized at ER MCSs result in familial neurodegenerative diseases, emphasizing the importance of the normal lipid traffic within cells for a healthy brain. Here, we provide an overview of such diseases, with a specific focus on proteins that directly or indirectly impact lipid transport.

Mitophagy regulation in aging and neurodegenerative disease

Mitochondria are the primary cellular energy generators, supplying the majority of adenosine triphosphate through oxidative phosphorylation, which is necessary for neuron function and survival. Mitophagy is the metabolic process of eliminating dysfunctional or redundant mitochondria. It is a type of autophagy and it is crucial for maintaining mitochondrial and neuronal health. Impaired mitophagy leads to an accumulation of damaged mitochondria and proteins leading to the dysregulation of mitochondrial quality control processes. Recent research shows the vital role of mitophagy in neurons and the pathogenesis of major neurodegenerative diseases. Mitophagy also plays a major role in the process of aging. This review describes the alterations that are being caused in the mitophagy process at the molecular level in aging and in neurodegenerative diseases, particularly Alzheimer's, Parkinson's, and Huntington's diseases and amyotrophic lateral sclerosis, also looks at how mitophagy can be exploited as a therapeutic target for these diseases.

Mitochondrial Dysfunction and Parkinson's Disease: Pathogenesis and Therapeutic Strategies

Parkinson's disease (PD) is a common age-related neurodegenerative disorder whose pathogenesis is not completely understood. Mitochondrial dysfunction and increased oxidative stress have been considered as major causes and central events responsible for the progressive degeneration of dopaminergic (DA) neurons in PD. Therefore, investigating mitochondrial disorders plays a role in understanding the pathogenesis of PD and can be an important therapeutic target for this disease. This study discusses the effect of environmental, genetic and biological factors on mitochondrial dysfunction and also focuses on the mitochondrial molecular mechanisms underlying neurodegeneration, and its possible therapeutic targets in PD, including reactive oxygen species generation, calcium overload, inflammasome activation, apoptosis, mitophagy, mitochondrial biogenesis, and mitochondrial dynamics. Other potential therapeutic strategies such as mitochondrial transfer/transplantation, targeting microRNAs, using stem cells, photobiomodulation, diet, and exercise were also discussed in this review, which may provide valuable insights into clinical aspects. A better understanding of the roles of mitochondria in the pathophysiology of PD may provide a rationale for designing novel therapeutic interventions in our fight against PD.

Monoterpenoid Epoxidiol Ameliorates the Pathological Phenotypes of the Rotenone-Induced Parkinson’s Disease Model by Alleviating Mitochondrial Dysfunction

Parkinson’s disease is the second most common neurodegenerative disease. Unfortunately, there is still no definitive disease-modifying therapy. In our work, the antiparkinsonian potential of trans-epoxide (1S,2S,3R,4S,6R)-1-methyl-4-(prop-1-en-2-yl)-7-oxabicyclo [4.1.0]heptan-2,3-diol (E-diol) was analyzed in a rotenone-induced neurotoxicity model using in vitro, in vivo and ex vivo approaches. It was conducted as part of the study of the mitoprotective properties of the compound. E-diol has been shown to have cytoprotective properties in the SH-SY5Y cell line exposed to rotenone, which is associated with its ability to prevent the loss of mitochondrial membrane potential and restore the oxygen consumption rate after inhibition of the complex I function. Under the conditions of rotenone modeling of Parkinson’s disease in vivo, treatment with E-diol led to the leveling of both motor and non-motor disorders. The post-mortem analysis of brain samples from these animals demonstrated the ability of E-diol to prevent the loss of dopaminergic neurons. Moreover, that substance restored functioning of the mitochondrial respiratory chain complexes and significantly reduced the production of reactive oxygen species, preventing oxidative damage. Thus, E-diol can be considered as a new potential agent for the treatment of Parkinson’s disease.

Emerging mechanistic insights of selective autophagy in hepatic diseases

Macroautophagy (hereafter referred to as autophagy), a highly conserved metabolic process, regulates cellular homeostasis by degrading dysfunctional cytosolic constituents and invading pathogens via the lysosomal system. In addition, autophagy selectively recycles specific organelles such as damaged mitochondria (via mitophagy), and lipid droplets (LDs; via lipophagy) or eliminates specialized intracellular pathogenic microorganisms such as hepatitis B virus (HBV) and coronaviruses (via virophagy). Selective autophagy, particularly mitophagy, plays a key role in the preservation of healthy liver physiology, and its dysfunction is connected to the pathogenesis of a wide variety of liver diseases. For example, lipophagy has emerged as a defensive mechanism against chronic liver diseases. There is a prominent role for mitophagy and lipophagy in hepatic pathologies including non-alcoholic fatty liver disease (NAFLD), hepatocellular carcinoma (HCC), and drug-induced liver injury. Moreover, these selective autophagy pathways including virophagy are being investigated in the context of viral hepatitis and, more recently, the coronavirus disease 2019 (COVID-19)-associated hepatic pathologies. The interplay between diverse types of selective autophagy and its impact on liver diseases is briefly addressed. Thus, modulating selective autophagy (e.g., mitophagy) would seem to be effective in improving liver diseases. Considering the prominence of selective autophagy in liver physiology, this review summarizes the current understanding of the molecular mechanisms and functions of selective autophagy (mainly mitophagy and lipophagy) in liver physiology and pathophysiology. This may help in finding therapeutic interventions targeting hepatic diseases via manipulation of selective autophagy.

Differential Role of Active Compounds in Mitophagy and Related Neurodegenerative Diseases

Neurodegenerative diseases, such as Alzheimer's disease or Parkinson's disease, significantly reduce the quality of life of patients and eventually result in complete maladjustment. Disruption of the synapses leads to a deterioration in the communication of nerve cells and decreased plasticity, which is associated with a loss of cognitive functions and neurodegeneration. Maintaining proper synaptic activity depends on the qualitative composition of mitochondria, because synaptic processes require sufficient energy supply and fine calcium regulation. The maintenance of the qualitative composition of mitochondria occurs due to mitophagy. The regulation of mitophagy is usually based on several internal mechanisms, as well as on signals and substances coming from outside the cell. These substances may directly or indirectly enhance or weaken mitophagy. In this review, we have considered the role of some compounds in process of mitophagy and neurodegeneration. Some of them have a beneficial effect on the functions of mitochondria and enhance mitophagy, showing promise as novel drugs for the treatment of neurodegenerative pathologies, while others contribute to a decrease in mitophagy.

Astrocyte strategies in the energy-efficient brain

Astrocytes generate ATP through glycolysis and mitochondrion respiration, using glucose, lactate, fatty acids, amino acids, and ketone bodies as metabolic fuels. Astrocytic mitochondria also participate in neuronal redox homeostasis and neurotransmitter recycling. In this essay, we aim to integrate the multifaceted evidence about astrocyte bioenergetics at the cellular and systems levels, with a focus on mitochondrial oxidation. At the cellular level, the use of fatty acid β-oxidation and the existence of molecular switches for the selection of metabolic mode and fuels are examined. At the systems level, we discuss energy audits of astrocytes and how astrocytic Ca2+ signaling might contribute to the higher performance and lower energy consumption of the brain as compared to engineered circuits. We finish by examining the neural-circuit dysregulation and behavior impairment associated with alterations of astrocytic mitochondria. We conclude that astrocytes may contribute to brain energy efficiency by coupling energy, redox, and computational homeostasis in neural circuits.

2-Aminoethoxydiphenyl borate ameliorates mitochondrial dysfunctions in MPTP/MPP+ model of Parkinson's disease

Mitochondrial dysfunction is closely linked with the pathophysiology of several neurodegenerative disorders including Parkinson's disease (PD). Despite several therapeutic advancements related to symptomatic modification of PD pathology, strategies targeting mitochondrial dysfunctions remain largely elusive. Recently, transient receptor potential (TRP) channels have been shown to play a pivotal role in the control of mitochondrial and neuronal functioning in PD. In this study, the effect of 2-aminoethoxydiphenyl borate (2-APB), TRP channel blocker was investigated in the context of mitochondrial dysfunctions in 1-methyl-4-phenylpyridinium (MPP⁺)-treated SH-SY5Y cells and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-administered Sprague Dawley rats. MPP⁺-treated SH-SY5Y cells exhibited reductions in cell viability, generation of reactive oxygen species (ROS) and loss of mitochondrial membrane potential. Co-treatment with 2-APB led to an increase in cell viability, reduction in intracellular and mitochondrial ROS and improvement in mitochondrial membrane potential compared to MPP⁺-treated SH-SY5Y cells. In addition, intranigral administration of MPTP led to a significant reduction in motor function in the rats. Fourteen days of 2-APB (3 and 10 mg/kg, i.p.) treatment improved behavioural parameters. MPTP-induced decrease in complex I activity and mitochondrial potential were also blocked by 2-APB in the mitochondria isolated from the brain regions i.e. midbrain and striatum. MPTP-induced decrease in tyrosine hydroxylase levels were also restored by 2-APB. Moreover, MPTP-induced reduction in proteins involved in mitochondrial biogenesis, viz. peroxisome proliferator-activated-receptor-gamma coactivator and mitochondrial transcription factor-A were increased after 2-APB treatment in vivo. In summary, 2-APB has a promising neuroprotective role in the MPP⁺/MPTP models of PD via targeting mitochondrial dysfunctions and biogenesis.

Cell type- and region-specific translatomes in an MPTP mouse model of Parkinson's disease

Parkinson's disease (PD) is the most common neurodegenerative movement disorder, characterized by the progressive loss of nigrostriatal dopaminergic neurons (DANs), involving the dysregulation of both neurons and glial cells. Cell type- and region-specific gene expression profiles can provide an effective source for revealing the mechanisms of PD. In this study, we adopted the RiboTag approach to obtain cell type (DAN, microglia, astrocytes)- and brain region (substantia nigra, caudate-putamen)-specific translatomes at an early stage in an MPTP-induced mouse model of PD. Through DAN-specific translatome analysis, the glycosphingolipid biosynthetic process was identified as a significantly downregulated pathway in the MPTP-treated mice. ST8Sia6, a key downregulated gene related to glycosphingolipid biosynthesis, was confirmed to be downregulated in nigral DANs from postmortem brains of patients with PD. Specific expression of ST8Sia6 in DANs exerts anti-inflammatory and neuroprotective effects in MPTP-treated mice. Through cell type (microglia vs. astrocyte) and brain region (substantia nigra vs. caudate-putamen) comparisons, nigral microglia showed the most intense immune responses. Microglia and astrocytes in the substantia nigra showed similar levels of activation in interferon-related pathways and interferon gamma (IFNG) was identified as the top upstream regulator in both cell types. This work highlights that the glycosphingolipid metabolism pathway in the DAN is involved in neuroinflammation and neurodegeneration in an MPTP mouse model of PD and provides a new data source for elucidating the pathogenesis of PD.

HCH6-1, an antagonist of formyl peptide receptor-1, exerts anti-neuroinflammatory and neuroprotective effects in cellular and animal models of Parkinson’s disease

Microglial activation-induced neuroinflammation contributes to onset and progression of sporadic and hereditary Parkinson's disease (PD). Activated microglia secrete pro-inflammatory and neurotoxic IL-1β, IL-6 and TNF-α, which subsequently promote neurodegeneration. Formyl peptide receptor-1 (FPR1) of CNS microglia functions as pattern recognition receptor and is activated by N-formylated peptides, leading to microglial activation, induction of inflammatory responses and resulting neurotoxicity. In this study, it was hypothesized that FPR1 activation of microglia causes loss of dopaminergic neurons by activating inflammasome and upregulating IL-1β, IL-6 or TNF-α and that FPR1 antagonist HCH6-1 exerts neuroprotective effect on dopaminergic neurons. FPR1 agonist fMLF induced activation of microglia cells by causing activation of NLRP3 inflammasome and upregulation and secretion of IL-1β, IL-6 or TNF-α. Conditioned medium (CM) of fMLF-treated microglia cells, which contains neurotoxic IL-1β, IL-6 and TNF-α, caused apoptotic death of differentiated SH-SY5Y dopaminergic neurons by inducing mitochondrial oxidative stress and activating pro-apoptotic signaling. FPR1 antagonist HCH6-1 prevented fMLF-induced activation of inflammasome and upregulation of pro-inflammatory cytokines in microglia cells. HCH6-1 co-treatment reversed CM of fMLF-treated microglia-induced apoptotic death of dopaminergic neurons. FPR1 antagonist HCH6-1 inhibited rotenone-induced upregulation of microglial marker Iba-1 protein level, cell death of dopaminergic neurons and motor impairment in zebrafish. HCH6-1 ameliorated rotenone-induced microglial activation, upregulation of FPR1 mRNA, activation of NLRP3 inflammasome, cell death of SN dopaminergic neurons and PD motor deficit in mice. Our results suggest that FPR1 antagonist HCH6-1 possesses anti-neuroinflammatory and neuroprotective effects on dopaminergic neurons by inhibiting microglial activation and upregulation of inflammasome activity and pro-inflammatory cytokines.

Inter and intracellular mitochondrial transfer: Future of mitochondrial transplant therapy in Parkinson's disease

Parkinson's disease (PD) is marked by the gradual degeneration of dopaminergic neurons and the intracellular build-up of Lewy bodies rich in α-synuclein protein. This impairs various aspects of the mitochondria including the generation of ROS, biogenesis, dynamics, mitophagy etc. Mitochondrial dynamics are regulated through the inter and intracellular movement which impairs mitochondrial trafficking within and between cells. This inter and intracellular mitochondrial movement plays a significant role in maintaining neuronal dynamics in terms of energy and growth. Kinesin, dynein, myosin, Mitochondrial rho GTPase (Miro), and TRAK facilitate the retrograde and anterograde movement of mitochondria. Enzymes such as Kinases along with Calcium (Ca²⁺), Adenosine triphosphate (ATP) and the genes PINK1 and Parkin are also involved. Extracellular vesicles, gap junctions, and tunneling nanotubes control intercellular movement. The knowledge and understanding of these proteins, enzymes, molecules, and movements have led to the development of mitochondrial transplant as a therapeutic approach for various disorders involving mitochondrial dysfunction such as stroke, ischemia and PD. A better understanding of these pathways plays a crucial role in establishing extracellular mitochondrial transplant therapy for reverting the pathology of PD. Currently, techniques such as mitochondrial coculture, mitopunch and mitoception are being utilized in the pre-clinical stages and should be further explored for translational value. This review highlights how intercellular and intracellular mitochondrial dynamics are affected during mitochondrial dysfunction in PD. The field of mitochondrial transplant therapy in PD is underlined in particular due to recent developments and the potential that it holds in the near future.

Plasma and cerebrospinal fluid pharmacokinetics of vodobatinib, a neuroprotective c-Abl tyrosine kinase inhibitor for the treatment of Parkinson's disease

BACKGROUND

Preclinical evidence suggests that c-Abl is critical in the pathogenesis of Parkinson's Disease (PD). Vodobatinib (K0706) is a potent, specific Abl kinase inhibitor currently being developed for the treatment of PD. In previously reported studies, nilotinib, a multikinase c-Abl inhibitor, did not show clinical activity as evidenced by no improvement of symptoms or the rate of decline after one to six months of treatment at the maximum permissible dose, presumably because of insufficient CNS penetration. Here we report clinical PK and safety data for vodobatinib.

OBJECTIVES

To determine safety, plasma PK, and CSF penetration of vodobatinib in healthy volunteers and PD subjects following oral administration, and compare CSF levels to in vitro concentrations required for c-Abl inhibition relative to data reported for nilotinib.

METHODS

Inhibition of c-Abl kinase activity and c-Abl binding affinity were first assessed in vitro. Healthy human volunteers and PD patients received various oral doses of vodobatinib once-daily for seven and fourteen days respectively, to assess safety, and plasma and CSF PK.

RESULTS

In in vitro assays, vodobatinib was more potent (kinase IC₅₀ = 0.9 nM) than nilotinib (kinase IC₅₀ = 15-45 nM). Administration of vodobatinib 48, 192 and 384 mg to healthy subjects for 7 days yielded mean C_{max, CSF} values of 1.8, 11.6, and 12.2 nM respectively, with the two highest doses exceeding the IC₅₀ over the entire dosing interval. C_{avg, CSF} values were 6-8 times greater than the IC₅₀. Comparable CSF levels were observed in PD patients. All doses were well tolerated in both cohorts.

CONCLUSION

Based on achieved CSF concentrations, the potential for c-Abl inhibition in the brain is substantially higher with vodobatinib than with nilotinib. The CSF PK profile of vodobatinib is suitable for determining if c-Abl inhibition will be neuroprotective in PD patients.

Disease mechanisms as Subtypes: Mitochondrial and bioenergetic dysfunction

Parkinson disease (PD) is the second most common neurodegenerative disease in the world. Despite its enormous human and societal cost, there is no disease-modifying therapy for PD. This unmet medical need reflects our limited understanding of PD pathogenesis. One of the most important clues comes from the recognition that PD motor symptoms arises from the dysfunction and degeneration of a very select group of neurons in the brain. These neurons have a distinctive set of anatomic and physiologic traits that reflect their role in brain function. These traits elevate mitochondrial stress, potentially making them particularly vulnerable to age, as well as to genetic mutations and environmental toxins linked to PD incidence. In this chapter, the literature supporting this model is outlined, along with gaps in our knowledge base. The translational implications of this hypothesis are then discussed, with a focus on why disease-modification trials have failed to date and what this means for the development of new strategies for altering disease course.

Identification of Parkinson's disease-associated chromatin regulators

Parkinson's disease (PD) is a common neurological disorder that causes quiescent tremors, motor delays, depression, and sleep disturbances. Existing treatments can only improve symptoms, not stop progression or cure the disease, but effective treatments can significantly improve patients' quality of life. There is growing evidence that chromatin regulatory proteins (CRs) are involved in a variety of biological processes, including inflammation, apoptosis, autophagy, and proliferation. But the relationship of chromatin regulators in Parkinson's disease has not been studied. Therefore, we aim to investigate the role of CRs in the pathogenesis of Parkinson's disease. We collected 870 chromatin regulatory factors from previous studies and downloaded data on patients with PD from the GEO database. 64 differentially expressed genes were screened, the interaction network was constructed and the key genes with the top 20 scores were calculated. Then we discussed its correlation with the immune function of PD. Finally, we screened potential drugs and miRNAs. Five genes related to the immune function of PD, BANF1, PCGF5, WDR5, RYBP and BRD2, were obtained by using the absolute value of correlation greater than 0.4. And the disease prediction model showed good predictive efficiency. We also screened 10 related drugs and 12 related miRNAs, which provided a reference for the treatment of PD. BANF1, PCGF5, WDR5, RYBP and BRD2 are related to the immune process of Parkinson's disease and can predict the occurrence of Parkinson's disease, which is expected to become a new target for the diagnosis and treatment of Parkinson's disease.

ATP and NAD+ Deficiency in Parkinson's Disease

The goal of this study is to identify a signature of bioenergetic and functional markers in the muscles of individuals with Parkinson's disease (PD). Quantitative physiological properties of in vivo hand muscle (FDI, first dorsal interosseus) and leg muscle (TA, Tibialis Anterior) of older individuals with PD were compared to historical age/gender-matched controls (N = 30). Magnetic resonance spectroscopy and imaging (MRS) were used to assess in vivo mitochondrial and cell energetic dysfunction, including maximum mitochondrial ATP production (ATPmax), NAD concentrations linked to energy/stress pathways, and muscle size. Muscle function was measured via a single muscle fatigue test. TA ATPmax and NAD levels were significantly lower in the PD cohort compared to controls (ATPmax: 0.66 mM/s ± 0.03 vs. 0.76 ± 0.02; NAD: 0.75 mM ± 0.05 vs. 0.91 ± 0.04). Muscle endurance and specific force were also lower in both hand and leg muscles in the PD subjects. Exploratory analyses of mitochondrial markers and individual symptoms suggested that higher ATPmax was associated with a greater sense of motivation and engagement and less REM sleep behavior disorder (RBD). ATPmax was not associated with clinical severity or individual symptom(s), years since diagnosis, or quality of life. Results from this pilot study contribute to a growing body of evidence that PD is not a brain disease, but a systemic metabolic syndrome with disrupted cellular energetics and function in peripheral tissues. The significant impairment of both mitochondrial ATP production and resting metabolite levels in the TA muscles of the PD patients suggests that skeletal muscle mitochondrial function may be an important tool for mechanistic understanding and clinical application in PD patients. This study looked at individuals with mid-stage PD; future research should evaluate whether the observed metabolic perturbations in muscle dysfunction occur in the early stages of the disease and whether they have value as theragnostic biomarkers.