Parkinson's disease and related synucleinopathies, including dementia with Lewy bodies and multiple system atrophy, are characterised by the pathological aggregation of the α-synuclein (aSyn) protein in neuronal and glial cells, leading to cellular dysfunction and neurodegeneration. This review synthesizes knowledge of aSyn biology, including its structure, aggregation mechanisms, cellular interactions, and systemic influences. We highlight the structural diversity of aSyn aggregates, ranging from oligomers to fibrils, their strain-like properties, and their prion-like propagation. While the role of prion-like mechanisms in disease progression remains a topic of ongoing debate, these processes may contribute to the clinical heterogeneity of synucleinopathies. Dysregulation of protein clearance pathways, including chaperone-mediated autophagy and the ubiquitin-proteasome system, exacerbates aSyn accumulation, while post-translational modifications influence its toxicity and aggregation propensity. Emerging evidence suggests that immune responses and alterations in the gut microbiome are key modulators of aSyn pathology, linking peripheral processes-particularly those of intestinal origin-to central neurodegeneration. Advances in biomarker development, such as cerebrospinal fluid assays, post-translationally modified aSyn, and real-time quaking-induced conversion technology, hold promise for early diagnosis and disease monitoring. Furthermore, positron emission tomography imaging and conformation-specific antibodies offer innovative tools for visualising and targeting aSyn pathology in vivo. Despite significant progress, challenges remain in accurately modelling human synucleinopathies, as existing animal and cellular models capture only specific aspects of the disease. This review underscores the need for more reliable aSyn biomarkers to facilitate the development of effective treatments. Achieving this goal requires an interdisciplinary approach integrating genetic, epigenetic, and environmental insights.

Two major neuropathological features of Parkinson's disease (PD) are α-synuclein Lewy pathology and mitochondrial dysfunction. Although both α-synuclein pathology and mitochondrial dysfunction may independently contribute to PD pathogenesis, the interaction between these two factors is not yet fully understood. In this review, we discuss the physiological functions of α-synuclein and mitochondrial homeostasis in neurons as well as the pathological defects that ensue when these functions are disturbed in PD. Recent studies have highlighted that dysfunctional mitochondria can become sequestered within Lewy bodies, and cell biology studies have suggested that α-synuclein can directly impair mitochondrial function. There are also PD cases caused by genetic or environmental perturbation of mitochondrial homeostasis. Together, these studies suggest that mitochondrial dysfunction may be a common pathway to neurodegeneration in PD, triggered by multiple insults. We review the literature surrounding the interaction between α-synuclein and mitochondria and highlight open questions in the field that may be explored to advance our understanding of PD and develop novel, disease-modifying therapies.

Parkinson's disease (PD), a progressive neurodegenerative disorder, is characterized by the loss of dopaminergic neurons and pathological aggregation of α-synuclein (α-Syn). Emerging evidence highlights the interplay between genetic susceptibility, neuroinflammation, and transcriptional dysregulation in driving PD pathogenesis. This review brings together the latest information on three important players: α-Syn, the transcription factor Orphan nuclear receptor (NURR1), and the NOD-like receptor 3 (NLRP3) inflammasome. Pathogenic α-syn aggregates cause damage to neurons by disrupting mitochondria and lysosomes and spreading in a way similar to prion proteins. They also turn on the NLRP3 inflammasome, which is a key player in neuroinflammation. NLRP3-driven release of pro-inflammatory cytokines exacerbates neurodegeneration and creates a self-sustaining inflammatory milieu. Meanwhile, reduced NURR1 activity, a pivotal modulator of dopaminergic neuron survival and development, exposes neurons to oxidative stress, neuroinflammation, and α-Syn toxicity, hence exacerbating disease progression. So, targeting this trio exhibits transformative potential against PD pathogenesis.

Blood-brain barrier(BBB) disruption promotes the influx of the fibrinogen(FG); however, it remains unknown whether FG deposit contributes to neurodegeneration in Parkinson's disease(PD).

We aimed to examine the pathophysiologic link among FG, mitochondrial dysfunction and α-synuclein(α-syn) abnormality in PD.

First, plasma FG levels were measured in 60 healthy controls and 60 PD patients. Second, to determine whether FG contributes to PD pathogenesis, FG was injected into the substantia nigra pars compacta(SNpc) of healthy and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine(MPTP)-treated PD mice. Meanwhile, intraperitoneal injections of batroxobin were used to deplete FG in the brain of PD mice. Mitochondrial ultrastructure in mouse models was observed by transmission electron microscopy(TEM), and mitochondrial functions in SH-SY5Y cells were examined by different assay kits and flow cytometry. The mechanisms underlying FG-induced α-syn abnormality and mitochondrial dysfunction were observed by RNA sequencing and validated in various experiments including western blot and immunostaining. Last, the endocytosis of FG in primary neurons were detected by confocal microscopy, and α-syn aggregation after FG co-incubation were evaluated by western blot, ThT-binding assay and TEM.

PD patients exhibited elevated levels of FG in peripheral blood compared to HCs, and there was a positive correlation between the plasma FG and PD clinical severity. Excessive FG in the SNpc of MPTP-treated mice promoted poly (ADP-ribose) (PAR) polymerase-1(PARP1) elevation, mediated by the αvβ3 integrin receptor. FG exacerbated α-syn abnormalities and mitochondrial dysfunctions via PARP1 activation. Moreover, FG entered neurons by αvβ3 integrin mediation, potentially enhancing α-syn fibrillation and toxicity. FG facilitated α-syn aggregation subsequently reduced ATP-dependent Clp protease(ClpP) level, impairing neuronal mitochondrial unfolded response and increasing mitochondrial ROS. Pharmacological depletion of FG by batroxobin ameliorated neurodegeneration in MPTP-treated mice.

Our study indicate that FG plays an essential pathological role in α-syn abnormality. FG-targeting therapy can be a promising strategy against neurodegeneration in PD.

α-Synuclein (αSyn) is a key culprit in the pathogenesis of synucleinopathies such as Parkinson's Disease (PD), in which it forms not only insoluble aggregates called amyloid fibrils but also smaller, likely more detrimental species termed oligomers. This property is shared with other amyloidogenic proteins such as the Alzheimer's Disease-associated amyloid-β (Aβ). We previously found an intriguing interplay between off-pathway Aβ oligomers and Aβ fibrils, in which the oligomers interfere with fibril formation via inhibition of secondary nucleation by blocking secondary nucleation sites on the fibril surface. Here, using ThT aggregation kinetics and atomic force microscopy (AFM), we tested if the same interplay applies to αSyn fibrils. Both homotypic (i.e. αSyn) and heterotypic (i.e. Aβ) off-pathway oligomers inhibited αSyn aggregation in kinetic assays of secondary nucleation. Initially soluble, kinetically trapped Aβ oligomers co-precipitated with αSyn(1-108) fibrils. The resulting co-assemblies were imaged as clusters of curvilinear oligomers by AFM. The results indicate that off-pathway oligomers have a general tendency to bind amyloid fibril surfaces, also in the absence of sequence homology between fibril and oligomer. The interplay between off-pathway oligomers and amyloid fibrils adds another level of complexity to the homo- and hetero-assembly processes of amyloidogenic proteins.

Chimeric antigen receptor (CAR)-T-cell therapy achieves considerable success in the treatment of malignant tumors, but clinical relapse due to the tumor microenvironment (TME) is very common. The TME of solid tumors is characterized by weak acidity, hypoxia, and elevated reactive oxygen species (ROS) levels, which collectively impair the function and persistence of infiltrating CAR-T cells. In this study, acid-sensitive responsive CaMnCO3 nanoparticles (CMC NPs), are developed that simultaneously mitigate TME acidosis and hypoxia. IL-21 is encapsulated within CMC NPs (denoted as CMC-21), which are then surface-conjugated to CAR-T cells as functional 'vitality backpacks' to enhance cellular activity. The CMC-21 backpack enables sustained release of IL-21, persistently enhancing CAR-T cell antitumor immunity across both low- and high-dose infusion regimens. Furthermore, CMC NPs exert dual modulatory effects on the TME by: 1) consuming protons to neutralize acidic conditions, and 2) catalytically converting endogenous H2O2 to O2 to relieve hypoxia. This multimodal remodeling of the immunosuppressive TME significantly enhances the infiltration and activity of adoptively transferred CAR-T cells while simultaneously boosting endogenous T cell and NK cell recruitment in vivo. These findings establish a novel CAR-T cell enhancement strategy through sustained IL-21 release from CMC-21 backpacks, offering new possibilities for solid tumor immunotherapy.

Fatty acid-binding proteins (FABPs) act as lipid chaperones and play a role in the pathological processes of various lipid signaling pathways. Mitochondria are crucial for the regulation of lipid metabolism. As an aging marker, lipid-mediated mitochondrial dysfunction has been observed in the etiology of numerous diseases, including neurodegenerative diseases, metabolic syndromes, cardiovascular diseases, and tumorigenesis. Members of the FABP family have been identified to regulate mitochondrial function. Targeting FABPs specifically may provide a promising approach to improve mitochondrial function and treat age-related diseases. This review summarizes the connection between FABPs and mitochondrial function and highlights certain FABPs involved in age-related diseases that hold significant therapeutic promise.

Olfactory dysfunction (OD) is considered one of the early signs of Parkinson's disease (PD), affecting over 90% of PD patients. OD often appears several years before the onset of motor symptoms and is therefore considered an early biomarker of PD. Recent studies have shown that COVID-19 infection might lead to worsening of symptoms and acceleration of disease progression in neurodegenerative disorders, where OD is a common symptom to both. Hence, it is essential to accurately monitor olfactory fitness in clinical settings using any of the currently available olfactory function tests. Even after a quarter of a century of the discovery of α-synuclein (α-syn) pathogenesis in PD, many aspects related to the α-syn pathogenesis in OD remain unknown. Currently, there is no definitive cure for PD; the disease management options include dopaminergic medications, deep brain stimulations, stem cells, and immunotherapy. Generating reliable PD animal models is critical for understanding the molecular pathways and neural circuits affected by disease conditions. This might contribute to the development and validation of new therapeutic approaches. This review discusses the known mechanisms of α-syn aggregated forms causing neuronal death, the recent developments in the PD preclinical models with ODs, and the treatment strategies employed.

Parkinson's disease (PD) is a multifactorial disease that involves genetic and environmental factors, which play an essential role in the pathogenesis of PD. Mesenchymal stem cells release a set of bioactive molecules called "secretome" that regulates intercellular communication and cargo transfer in signaling pathways for PD treatment. Thus, this study aimed to evaluate the neuroprotective effects of neural-induced human adipose tissue-derived stem cell (NI-hADSC)-conditioned medium (NI-hADSC-CM) and its exosomes (NI-hADSC-Exo) in a rotenone (ROT)-induced model of PD in rats.

The NI-hADSC-CM was collected from NI-hADSC after 14 days of neural differentiation, and its NI-hADSC-Exo were isolated using a tangential flow filtration system. ROT (1 mg/kg) was subcutaneously administered for 28 days to establish a model of PD in rats. The treatment of NI-hADSC-CM or NI-hADSC-Exo was intravenously injected on days 15, 18, 21, 24, and 27. Animal behavioral effects were explored via a rotarod test. After 28 days, histological and western blot analyses were performed to investigate the tyrosine hydroxylase (TH), α-synuclein (α-syn) aggregation, and downstream signaling pathways for experimental validation.

NI-hADSC-Exo improved the motor balance and coordination skills against ROT toxicity. ROT reproduced the pathological features of PD, such as a decrease in TH-positive dopaminergic neurons and an increase in α-syn aggregation and glial fibrillary acidic protein (GFAP)-positive cells. NI-hADSC-CM and NI-hADSC-Exo improved the TH expression, decreased the Triton X-100 soluble and insoluble oligomeric p-S129 α-syn, and influenced the differential reactivity to astrocytes and microglia. Secretome treatment could reverse the ROT-induced damages in the neuronal structural and functional proteins, mitochondrial apoptosis, and caspase cascade. The treatment of NI-hADSC-CM and NI-hADSC-Exo ameliorated the ROT toxicity-induced serine-threonine protein kinase dysregulation and autophagy impairment to clear the aggregated α-syn.

NI-hADSC-CM and NI-hADSC-Exo significantly exerted neuroprotection by decreasing α-syn toxicity, inhibiting neuroinflammation and apoptosis, restoring autophagic flux properties, and promoting the neuronal function in ROT-injected rats; however, the influence of these treatments on signaling pathways differed slightly between the midbrain and striatum regions. Targeting α-syn degradation pathways provides a novel strategy to elucidate the beneficial effects of MSC secretome and future safe cell-free treatments for PD.

Parkinson's disease (PD), a globally prevalent neurodegenerative disorder, has been implicated with oxidative stress (OS) as a central pathomechanism. Excessive reactive oxygen species (ROS) trigger neuronal damage and may induce disulfidptosis-a novel cell death modality not yet characterized in PD pathogenesis.

Integrated bioinformatics analyses were conducted using GEO datasets to identify PD-associated differentially expressed genes (DEGs). These datasets were subjected to: immune infiltration analysis, gene set enrichment analysis (GSEA), weighted gene co-expression network analysis (WGCNA), intersection analysis of oxidative stress-related genes (ORGs) and disulfidptosis-related genes (DRGs) for functional enrichment annotation. Following hub gene identification, diagnostic performance was validated using independent cohorts. LASSO regression was applied for feature selection, with subsequent experimental validation in MPTP-induced PD mouse models. Single-cell transcriptomic profiling and molecular docking studies were performed to map target gene expression and assess drug-target interactions.

A total of 1615 PD DEGs and 200 WGCNA DEGs were obtained, and the intersection with ORGs and DRGs resulted in 202 DEORGs, 11 DEDRGs, and 5 DED-ORGs (NDUFS2, LRPPRC, NDUFS1, GLUD1, and MYH6). These genes are mainly associated with oxidative stress, the respiratory electron transport chain, the ATP metabolic process, oxidative phosphorylation, mitochondrial respiration, and the TCA cycle. 10 hub genes have good diagnostic value, including in the validation dataset (AUC ≥ 0.507). LASSO analysis of hub genes yielded a total of 6 target genes, ACO2, CYCS, HSPA9, SNCA, SDHA, and VDAC1. In the MPTP-induced PD mice model, the expression of ACO2, HSPA9, and SDHA was decreased while the expression of CYCS, SNCA, and VDAC1 was increased, and the expression of the 5 DED-ORGs was decreased. Additionally, it was discovered that N-Acetylcysteine (NAC) could inhibit the occurrence of disulfidptosis in the MPTP-induced PD model. Subsequently, the distribution of target genes with AUC > 0.7 in different cell types of the brain was analyzed. Finally, molecular docking was performed between the anti-PD drugs entering clinical phase IV and the target genes. LRPPRC has low binding energy and strong affinity with duloxetine and donepezil, with binding energies of -7.6 kcal/mol and - 8.7 kcal/mol, respectively.

This study elucidates the pathogenic role of OS-induced disulfidptosis in PD progression. By identifying novel diagnostic biomarkers (e.g., DED-ORGs) and therapeutic targets (e.g., LRPPRC), our findings provide a mechanistic framework for PD management and lay the groundwork for future therapeutic development.

Parkinson's disease (PD) is a progressive neurodegenerative disorder associated with mechanisms that results in loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc) region of the brain. Being a complex heterogeneous disorder, there is a requisite in discovering the underlying molecular signatures that could potentially help in resolving challenges associated with diagnosis as well as therapeutic management. SNCA gene that encodes for the protein α-synuclein is widely known for its indispensable role in aggravating the progression of sporadic and familial PD, upon mutations. Likewise, mitochondrial dysfunction is inferred to be playing a central role in both forms of PD. Observations from experimental models and human PD cases displayed strong evidence for disruption of mitochondrial dynamics, inhibition of mitochondrial complex I protein's function and elevation in reactive oxygen species (ROS) by the toxic aggregation of α-synuclein. Further, recent studies have raised the possibility of an underlying relationship, where the α-synuclein toxicity is exacerbated by the mutant mitochondrial complex proteins and vice-versa. In this review, we provide an overview of mechanisms influencing α-synuclein-related neurodegeneration, particularly, emphasizing the role of SNCA (α-synuclein) gene in leading to altered mitochondrial biogenesis during PD. We have described how transgenic Drosophila models were reliable at recapitulating some of the essential characteristics of PD. In addition, we highlight the capability of utilizing transgenic fly models in deciphering the altered α-synuclein toxicity and mitochondrial dysfunction, as induced by defects in the mitochondrial DNA.

Recent studies indicated that the dysregulation of mitochondria-associated endoplasmic reticulum membrane (MAM) could be a significant hub in the pathogenesis of Parkinson's disease (PD). However, little has been known about how MAM altered in PD. This study was aimed to observe morphological changes and analyze proteomic profiles of MAM in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD mouse models. In MPTP-treated mice, transmission electron microscopy was applied for MAM ultrastructural visualization. Nano ultra-high performance liquid chromatography-tandem mass spectrum and bioinformatic analysis were adopted to obtain underlying molecular data of MAM fractions. The loosened, shortened and reduced MAM tethering was found in substantia nigral neurons from MPTP-treated mice. In midbrain MAM proteomics, 158 differentially expressed proteins (DEPs) were identified between two groups. Specific DEPs were validated by western blot and exhibited significantly statistical changes, aligning with proteomic results. Bioinformatic analysis indicated that membrane, cytoplasm and cell projection were three major localizations for DEPs. Biological processes including metabolism, lipid transport, and immunological and apoptotic signaling pathways were greatly affected. For consensus MAM proteins, the enriched pathway analysis revealed the potential relationship between neurodegenerative diseases and MAM. Several biological processes such as peroxisome function and clathrin-mediated endocytosis, were clustered, which provided additional insights into the fundamental molecular pathways associated with MAM. In our study, we demonstrated disrupted ER-mitochondria contacts in an MPTP-induced PD mouse model. The underlying signatures of MAM were revealed by proteomics and bioinformatic analysis, providing valuable insights into its potential role in PD pathogenesis.

Gastrointestinal (GI) dysfunction emerges years before motor symptoms in Parkinson's disease (PD), implicating the enteric nervous system (ENS) in early disease progression. However, the mechanisms linking the PD hallmark protein, α-synuclein (α-syn), to ENS dysfunction - and whether these mechanisms are influenced by inflammation - remains elusive. Using iPSC-derived enteric neural lineages from patients with α-syn triplications, we reveal that TNF-α increases mitochondrial-α-syn interactions, disrupts the malate-aspartate shuttle, and forces a metabolic shift toward glutamine oxidation. These alterations drive mitochondrial dysfunction, characterizing metabolic impairment under cytokine stress. Interestingly, targeting glutamate metabolism with Chicago Sky Blue 6B restores mitochondrial function, reversing TNF-α-driven metabolic disruption. Our findings position the ENS as a central player in PD pathogenesis, establishing a direct link between cytokines, α-syn accumulation, metabolic stress and mitochondrial dysfunction. By uncovering a previously unrecognized metabolic vulnerability in the ENS, we highlight its potential as a therapeutic target for early PD intervention.

Protein aggregation is remarkably associated with several neuropathologies, including Alzheimer´s (AD) and Parkinson´s disease (PD). The first is characterized by hyperphosphorylated tau protein and Aβ peptide deposition, thus forming intracellular neurofibrillary tangles and extracellular senile plaques, respectively; while, in PD, α-synuclein aggregates and deposits as Lewy bodies. Considerable research has focused on developing protein aggregation models to be explored as research tools. In the present work, four in vitro models for studying protein aggregation were studied and compared, namely treatment with: the toxic Aβ1-42 peptide, the isoflavone rotenone, the ATP synthase inhibitor oligomycin, and the proteosome inhibitor MG-132. All treatments result in aggregation-relevant events in the human neural SH-SY5Y cell line, but significant model-dependent differences were observed. In terms of promoting aggregate formation, Aβ and MG-132 provoked the greatest effect, but only MG-132 was associated with an increase in HSP-70 chaperone expression. In fact, the type of aggregates formed appear to be dependent on the treatment employed, and supports the hypothesis that Aβ exposure is a relevant AD model, and rotenone is a valid model for PD. Furthermore, the results revealed that protein phosphorylation is relevant to aggregate formation and as expected, tau co-localized to the deposits formed in the Aβ peptide aggregate induction cell model. In summary, different molecular processes, from overall and specific protein aggregation to proteostatic modulation, can be induced by using distinct aggregation modelling strategies, and these can be used to study different protein-aggregation-related processes associated with distinct neuropathologies.

While the etiopathology of Parkinson's disease (PD) is complex, mitochondrial dysfunction is established to have a central role. Thus, mitochondria have emerged as targets of therapeutic interventions aiming to slow or modify PD progression. We have previously identified serotonergic 5-HT1F receptors as novel mediators of mitochondrial biogenesis (MB) - the process of producing new mitochondria. Given this, here, we assessed the therapeutic potential of the FDA-approved 5-HT1F receptor agonist, lasmiditan, in a chronic progressive PD model (Thy1-aSyn 'line 61' mice). It was observed that systemic lasmiditan exhibited robust brain penetration and reversed cognitive deficits in young (4-5.5 months old) Thy1-aSyn mice (1mg/kg, every other day). Anxiety-like behavior was also improved while motor function remained unaffected. These behavioral changes were associated with enhanced MB and mitochondrial function, paired with reduced alpha-synuclein aggregation particularly in cortico-hippocampal regions. Furthermore, in older (10-11.5 months old) mice, although the effects were milder, daily lasmiditan administration increased MB and bettered cognitive abilities. In essence, these findings indicate that repurposing lasmiditan could be a potent strategy to address PD-related cognitive decline.

Mitochondria have to import a large number of precursor proteins from the cytosol. Chaperones keep these proteins in a largely unfolded state and guide them to the mitochondrial import sites. Premature folding, mitochondrial stress and import defects can cause clogging of import sites and accumulation of non-imported precursors, representing a critical burden for cellular proteostasis. Here we discuss how cells respond to mitochondrial protein import stress by regenerating clogged import sites and inducing stress responses. The mitochondrial protein import machinery has a dual role by serving as sensor for detecting mitochondrial dysfunction and inducing stress-response pathways. The production of chaperones that fold or sequester precursor proteins in deposits is induced and the proteasomal activity is increased to remove the excess precursor proteins. Together, these pathways reveal how mitochondria are tightly integrated into a cellular proteostasis and stress response network to maintain cell viability.

Mitochondrial dysfunction is a major pathogenic mechanism in Parkinson's disease (PD). Emerging studies have shown that dysregulation in mitochondrial dynamics (fission/fusion/movement) has a major negative impact on mitochondria - both morphologically and functionally. Partial genetic deletion and pharmacological inhibition of the mitochondrial fission dynamin-related protein 1 (Drp1) have been demonstrated to be beneficial in experimental models of PD. However, the expression of DRP1 (and other fission and fusion genes/proteins) has not been investigated in the brains of Parkinson's patients. Without these data, the question remains whether targeting DRP1 is a valid therapeutic target for PD. To address this gap of knowledge, first, we used post-mortem substantia nigra specimens of Parkinson's patients and controls. Significant increases in the levels of both DNM1L , which encodes DRP1, as well as the DRP1 protein were detected in Parkinson's patients. Immunostaining revealed increased DRP1 expression in dopamine (DA) neurons, astrocytes, and microglia. In addition to DRP1, the levels of other fission and fusion genes/proteins were also altered in Parkinson's patients. To complement these human studies and given the significant role of α-synuclein in PD pathogenesis, we performed time-course studies (3-, 6- and 12-month) using transgenic mice overexpressing human wild-type SNCA under the mouse Thy-1 promoter. As early as 6 months old, we detected an upregulation of Dnm1l and Drp1 in the nigral DA neurons of the SNCA mice as compared to their WT littermates. Furthermore, these mutant animals exhibited more Drp1 phosphorylation at serine 616, which promotes its translocation to mitochondria to induce fragmentation. Together, this study shows an upregulation of DRP1/Drp1 and alterations in other fission/fusion proteins in both human and mouse PD brains, leading to a pro-fission phenotype, providing additional evidence that blocking mitochondrial fission or promoting fusion is a potential therapeutic strategy for PD.

Parkinson's disease (PD) is a neurodegenerative disorder characterized by protein aggregates mostly consisting of misfolded alpha-synuclein (αSyn). Progressive degeneration of midbrain dopaminergic neurons (mDANs) and nigrostriatal projections results in severe motor symptoms. While the preferential loss of mDANs has not been fully understood yet, the cell type-specific vulnerability has been linked to a unique intracellular milieu, influenced by dopamine metabolism, high demand for mitochondrial activity, and increased level of oxidative stress (OS). These factors have been shown to adversely impact αSyn aggregation. Reciprocally, αSyn aggregates, in particular oligomers, can impair mitochondrial functions and exacerbate OS. Recent drug-discovery studies have identified a series of small molecules, including NPT100-18A, which reduce αSyn oligomerization by preventing misfolding and dimerization. NPT100-18A and structurally similar compounds (such as NPT200-11/UCB0599, currently being assessed in clinical studies) point towards a promising new approach for disease-modification.

Induced pluripotent stem cell (iPSC)-derived mDANs from PD patients with a monoallelic SNCA locus duplication and unaffected controls were treated with NPT100-18A. αSyn aggregation was evaluated biochemically and reactive oxygen species (ROS) levels were assessed in living mDANs using fluorescent dyes. Adenosine triphosphate (ATP) levels were measured using a luminescence-based assay, and neuronal cell death was evaluated by immunocytochemistry.

Compared to controls, patient-derived mDANs exhibited higher cytoplasmic and mitochondrial ROS probe levels, reduced ATP-related signals, and increased activation of caspase-3, reflecting early neuronal cell death. NPT100-18A-treatment rescued cleaved caspase-3 levels to control levels and, importantly, attenuated mitochondrial oxidative stress probe levels in a compartment-specific manner and, at higher concentrations, increased ATP signals.

Our findings demonstrate that NPT100-18A limits neuronal degeneration in a human in vitro model of PD. In addition, we provide first mechanistic insights into how a compartment-specific antioxidant effect in mitochondria might contribute to the neuroprotective effects of NPT100-18A.

Parkinson's disease is a prevalent neurological condition that affects around 1% of adults over 60 worldwide. Deep brain stimulation and dopamine replacement therapy are common therapies for Parkinson's disease, yet they are unable to reverse the disease it simply because of the blood brain barrier. The use of bioengineered exosomes to treat Parkinson's disease is being studied because they have the ability to cross the blood-brain barrier. Their natural ability to cross the blood-brain barrier (BBB) and their biocompatibility make them highly suitable for delivering therapeutic agents to manage PD, specifically the role of astrocytes, microglial cells, and alpha-synuclein. It also explores the biogenesis and preparation of these bioengineered exosomes. In comparison to conventional nanocarriers, the modified exosomal-membrane-camouflaged abiotic nanocarriers show improved resilience and compatibility. Improved cellular absorption and targeted delivery of therapeutic payloads, such as medications and enzymes, are being shown in laboratory trials. A viable strategy for treating PD involves combining abiotic nanocarriers with bioengineered exosomal membranes. Despite their promising potential, successful clinical application requires overcoming hurdles related to scalable production, regulatory approval, and long-term safety evaluation. Nevertheless, the innovative use of bioengineered exosomes holds significant promise for advancing PD management and improving patient outcomes through more targeted and effective therapeutic strategies.

Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) is a key regulator of mitochondrial biogenesis and antioxidative defenses, and it may play a critical role in Parkinson's disease (PD). F-box/WD repeat domain-containing protein (FBXW7), an E3 protein ligase, promotes the degradation of substrate proteins through the ubiquitin-proteasome system (UPS) and leads to the clearance of PGC-1α. Here, we elucidate a novel post-translational mechanism for regulating PGC-1α levels in neurons. We show that enhancing chaperone-mediated autophagy (CMA) activity promotes the CMA-mediated degradation of FBXW7 and consequently increases PGC-1α. We confirm the relevance of this pathway in vivo by showing decreased FBXW7 and increased PGC-1α as a result of boosting CMA selectively in dopaminergic (DA) neurons by overexpressing lysosomal-associated membrane protein 2A (LAMP2A) in TH-Cre-LAMP2-loxp conditional mice. We further demonstrate that these mice are protected against MPTP-induced oxidative stress and neurodegeneration. These results highlight a novel regulatory pathway for PGC-1α in DA neurons and suggest targeted increasing of CMA or decreasing FBXW7 in DA neurons as potential neuroprotective strategies in PD.

Neurodegenerative diseases such as Alzheimer's, Parkinson's, and amyotrophic lateral sclerosis cause damage and gradual loss of neurons affecting the central nervous system. Neurodegenerative diseases are most commonly seen in the ageing process. Ageing causes increased reactive oxygen species and decreased mitochondrial ATP generation, resulting in redox imbalance and oxidative stress. Oxidative stress-generated free radicals cause damage to membrane lipids containing polyunsaturated fatty acids, leading to the formation of toxic lipid aldehyde products such as 4- hydroxynonenal and malondialdehyde. Several studies have shown that lipid peroxidation-derived aldehyde products form adducts with cellular proteins, altering their structure and function. Thus, these lipid aldehydes could act as secondary signaling intermediates, modifying important metabolic pathways, and contributing to the pathophysiology of several human diseases, including neurodegenerative disorders. Additionally, they could serve as biomarkers for disease progression. This narrative review article discusses the biological and clinical significance of oxidative stress-mediated lipid peroxidation-derived lipid aldehydes in the pathophysiology of various neurodegenerative diseases.

Parkinson's disease (PD) is an aging-associated neurodegenerative disorder, characterized by the progressive loss of dopaminergic neurons in the pars compacta of the substantia nigra and the presence of Lewy bodies containing α-synuclein within these neurons. Oligomeric α-synuclein exerts neurotoxic effects through mitochondrial dysfunction, glial cell inflammatory response, lysosomal dysfunction and so on. α-synuclein aggregation, often accompanied by oxidative stress, is generally considered to be a key factor in PD pathology. At present, emerging evidences suggest that metabolism alteration is closely associated with α-synuclein aggregation and PD progression, and improvement of key molecules in metabolism might be potentially beneficial in PD treatment. In this review, we highlight the tripartite relationship among metabolic changes, α-synuclein aggregation, and oxidative stress in PD, and offer updated insights into the treatments of PD, aiming to deepen our understanding of PD pathogenesis and explore new therapeutic strategies for the disease.

The maintenance of healthy mitochondria is essential for neuronal survival and relies upon mitochondrial quality control pathways involved in mitochondrial biogenesis, mitochondrial dynamics, and mitochondrial autophagy (mitophagy). Mitochondrial dysfunction is critically implicated in Parkinson's disease (PD), a brain disorder characterized by the progressive loss of dopaminergic neurons in the substantia nigra. Consequently, impaired mitochondrial quality control may play a key role in PD pathology. This is affirmed by work indicating that genes such as PRKN and PINK1, which participate in multiple mitochondrial processes, harbor PD-associated mutations. Furthermore, mitochondrial complex-I-inhibiting toxins like MPTP and rotenone are known to cause Parkinson-like symptoms. At the heart of PD is alpha-synuclein (αS), a small synaptic protein that misfolds and aggregates to form the disease's hallmark Lewy bodies. The specific mechanisms through which aggregated αS exerts its neurotoxicity are still unknown; however, given the vital role of both αS and mitochondria to PD, an understanding of how αS influences mitochondrial maintenance may be essential to elucidating PD pathogenesis and discovering future therapeutic targets. Here, the current knowledge of the relationship between αS and mitochondrial quality control pathways in PD is reviewed, highlighting recent findings regarding αS effects on mitochondrial biogenesis, dynamics, and autophagy.

Mitochondrial dysfunction and α-synuclein (αSyn) aggregation are key contributors to Parkinson's Disease (PD). While genetic and environmental risk factors, including mutations in mitochondrial-associated genes, are implicated in PD, the precise mechanisms linking mitochondrial defects to αSyn pathology remain incompletely understood, hindering the development of effective therapeutic interventions. Here, we identify the loss of branched chain ketoacid dehydrogenase kinase (BCKDK) as a mitochondrial risk factor that exacerbates αSyn pathology by disrupting Complex I function. Our findings reveal a consistent downregulation of BCKDK in dopaminergic (DA) neurons from A53T-αSyn mouse models, PD patient-derived induced pluripotent stem (iPS) cells, and postmortem brain tissues. BCKDK deficiency leads to mitochondrial dysfunction, including reduced membrane potential and increased reactive oxygen species (ROS) production upon administration of a stressor, which in turn promotes αSyn oligomerization. Mechanistically, BCKDK interacts with the NDUFS1 subunit of Complex I to stabilize its function. Loss of BCKDK disrupts this interaction, leading to Complex I destabilization and enhanced αSyn aggregation. Notably, restoring BCKDK expression in neuron-like cells rescues mitochondrial integrity and restores Complex I activity. Similarly, in patient-derived iPS cells differentiated to form dopaminergic neurons, NDUFS1 and phosphorylated aSyn levels are partially restored upon BCKDK expression. These findings establish a mechanistic link between BCKDK deficiency, mitochondrial dysfunction, and αSyn pathology in PD, positioning BCKDK as a potential therapeutic target to mitigate mitochondrial impairment and neurodegeneration in PD.

Mitochondrial dysfunction is a central aspect of Parkinson's disease (PD) pathology, yet the underlying mechanisms are not fully understood. This study investigates the link between α-Synuclein (α-Syn) pathology and the loss of translocase of the outer mitochondrial membrane 40 (TOM40), unraveling its implications for mitochondrial dysfunctions in neurons. We discovered that TOM40 protein depletion occurs in the brains of patients with Guam Parkinsonism-Dementia (Guam PD) and cultured neurons expressing α-Syn proteinopathy, notably, without corresponding changes in TOM40 mRNA levels. Cultured neurons expressing α-Syn mutants, with or without a mitochondria-targeting signal (MTS) underscores the role of α-Syn's mitochondrial localization in inducing TOM40 degradation. PDe-related etiological factors, such as 6-hydroxydopamine or ROS/metal ions stress, which promotes α-Syn oligomerization, exacerbate TOM40 depletion in PD patient-derived cells with SNCA gene triplication. Although α-Syn interacts with both TOM40 and TOM20 in the outer mitochondrial membrane, degradation is selective for TOM40, which occurs via the ubiquitin-proteasome system (UPS) pathway. Our comprehensive analyses using Seahorse technology, mitochondrial DNA sequencing, and damage assessments, demonstrate that mutant α-Syn-induced TOM40 loss results in mitochondrial dysfunction, characterized by reduced membrane potential, accumulation of mtDNA damage, deletion/insertion mutations, and altered oxygen consumption rates. Notably, ectopic supplementation of TOM40 or reducing pathological forms of α-Syn using ADP-ribosylation inhibitors ameliorate these mitochondrial defects, suggesting potential therapeutic avenues. In conclusion, our findings provide crucial mechanistic insights into how α-Syn accumulation leads to TOM40 degradation and mitochondrial dysfunction, offering insights for targeted interventions to alleviate mitochondrial defects in PD.

While reactive oxygen species (ROS) have long been known to drive aging and neurodegeneration, their persistent depletion below basal levels also disrupts organismal function. Cells counteract loss of basal ROS via the reductive stress response, but the identity and biochemical activity of ROS sensed by this pathway remain unknown. Here, we show that the central enzyme of the reductive stress response, the E3 ligase Cullin 2-FEM1 homolog B (CUL2FEM1B), specifically acts at mitochondrial TOM complexes, where it senses ROS produced by complex III of the electron transport chain (ETC). ROS depletion during times of low ETC activity triggers the localized degradation of CUL2FEM1B substrates, which sustains mitochondrial import and ensures the biogenesis of the rate-limiting ETC complex IV. As complex III yields most ROS when the ETC outpaces metabolic demands or oxygen availability, basal ROS are sentinels of mitochondrial activity that help cells adjust their ETC to changing environments, as required for cell differentiation and survival.

The accumulation of α-synuclein (α-syn), a key protein in Parkinson's disease (PD), contributes to progressive neuronal damage associated with mitochondrial dysfunction and interactions with various proteins. However, the precise mechanism by which α-syn affects energy metabolism remains unclear. In our study, we used human α-syn (hα-syn) transgenic mice, which exhibit progressive neuronal decline. Through an immunoprecipitation assay specific to hα-syn, we identified an enzyme in the mitochondrial tricarboxylic acid (TCA) cycle as a binding partner-mitochondrial aconitase 2 (ACO2), which converts citrate to isocitrate. Hα-syn increasingly interacted with ACO2 in mitochondria as mice aged, correlating with a progressive decrease in ACO2 activity. The overexpression of ACO2 and the addition of isocitrate, a downstream metabolite of ACO2, were observed to alleviate hα-syn-induced mitochondrial dysfunction and cytotoxicity. Furthermore, we designed an interfering peptide to block the interaction between ACO2 and hα-syn, which showed therapeutic effects in reducing hα-syn toxicity in vitro and in vivo. Our research establishes a direct link between α-syn and the TCA cycle and identifies ACO2 as a promising therapeutic target for improving mitochondrial function and reducing α-syn neurotoxicity in PD.

α-Synuclein (AS) is a small presynaptic protein that is genetically, biochemically, and neuropathologically linked to Parkinson's disease (PD) and related synucleinopathies. We present here a review of the topic of this relationship, focusing on more recent knowledge. In particular, we review the genetic evidence linking AS to familial and sporadic PD, including a number of recently identified point mutations in the SNCA gene. We briefly go over the relevant neuropathological findings, stressing the evidence indicating a correlation between aberrant AS deposition and nervous system dysfunction. We analyze the structural characteristics of the protein, in relation to both its physiologic and pathological conformations, with particular emphasis on posttranslational modifications, aggregation properties, and secreted forms. We review the interrelationship of AS with various cellular compartments and functions, with particular focus on the synapse and protein degradation systems. We finally go over the recent exciting data indicating that AS can provide the basis for novel robust biomarkers in the field of synucleinopathies, while at the same time results from the first clinical trials specifically targeting AS are being reported.

Under stress, protein synthesis is attenuated to preserve energy and mitigate challenges to protein homeostasis. Here, we describe, with high temporal resolution, the dynamic landscape of changes in the abundance of proteins synthesized upon stress from transient mitochondrial inner membrane depolarization. This nascent proteome was altered when global translation was attenuated by stress and began to normalize as translation was recovering. This transition was associated with a transient desynchronization of cytosolic and mitochondrial translation and recovery of cytosolic and mitochondrial ribosomal proteins. Further, the elongation factor EEF1A1 was downregulated upon mitochondrial stress, and its silencing mimicked the stress-induced nascent proteome remodeling, including alterations in the nascent respiratory chain proteins. Unexpectedly, the stress-induced alterations in the nascent proteome were independent of physiological protein abundance and turnover. In summary, we provide insights into the physiological and pathological consequences of mitochondrial function and dysfunction.

The etiology of Parkinson's disease (PD) remains elusive, and the limited availability of suitable animal models hampers research on pathogenesis and drug development. We report the development of a cynomolgus monkey model of PD that combines adeno-associated virus (AAV)-mediated overexpression of α-synuclein into the substantia nigra with an injection of poly(ADP-ribose) (PAR) into the striatum. Our results show that pathological processes were accelerated, including dopaminergic neuron degeneration, Lewy body aggregation, and hallmarks of inflammation in microglia and astrocytes. Behavioral phenotypes, dopamine transporter imaging, and transcriptomic profiling further demonstrate consistencies between the model and patients with PD. This model can help to determine the mechanisms underlying PD impacted by α-synuclein and PAR and aid in the accelerated development of therapeutic strategies for PD.

Chemotherapy for colorectal cancer (CRC) urgently needs low-toxicity and highly effective phytomedicine. Cepharanthine (Cep) shown to have multiple anti-tumor effects, including colorectal cancer, whose pivotal mechanisms are not fully understood. Herein, the present work aims to reveal the impact of Cep on the mitochondrial and anti-injury functions of CRC cells.

The TOM70/20 expression was screened by bioinformatic databases. SW480 cells were utilized as the colorectal cancer cell model. The expression of TOM70/20 and the downstream molecules were measured by western blots (WB). The ferroptosis was analyzed using Transmission electron microscopy (TEM), C11-BODIPY, PGSK, and DCFH-DA probes, wherein the detection was performed by flow cytometry and laser confocal microscopy. The anti-cancer efficacy was conducted by CCK-8 and Annexin-V/PI assay. The rescue experiments were carried out using Fer-1 and TOM70 plasmid transfection.

Bioinformatic data identified TOM20 and TOM70 were highly expressed in colorectal cancer, which could be down-regulated by Cep. Further findings disclosed that Cep treatment destroyed the mitochondria and inactivated the NRF2 signaling pathway, an essential pathway for resistance to ferroptosis, thereby promoting reactive oxygen species (ROS) generation in CRC cells. As a result, prominent ferroptosis could be observed in CRC cells in response to Cep, which thereby led to the reduced cell viability of cancer cells. On the contrary, recovery of TOM70 dampened the Cep-elicited mitochondria damage, ferroptosis, and anti-cancer efficacy.

In summary, Cep-mediated TOM inhibition inactivates the NRF2 signaling pathway, thereby triggering ferroptosis and achieving an anti-colorectal cancer effect. The current study provides an innovative chemotherapeutic approach for colorectal cancer with phytomedicine.

Pathological accumulation of aggregated α-synuclein (aSYN) is a common feature of Parkinson's disease (PD). However, the mechanisms by which intracellular aSYN pathology contributes to dysfunction and degeneration of neurons in the brain are still unclear. A potentially relevant target of aSYN is the mitochondrion. To test this hypothesis, genetic and physiological methods were used to monitor mitochondrial function in substantia nigra pars compacta (SNc) dopaminergic and pedunculopontine nucleus (PPN) cholinergic neurons after stereotaxic injection of aSYN pre-formed fibrils (PFFs) into the mouse brain.

aSYN PFFs were stereotaxically injected into the SNc or PPN of mice. Twelve weeks later, mice were studied using a combination of approaches, including immunocytochemical analysis, cell-type specific transcriptomic profiling, electron microscopy, electrophysiology and two-photon-laser-scanning microscopy of genetically encoded sensors for bioenergetic and redox status.

In addition to inducing a significant neuronal loss, SNc injection of PFFs induced the formation of intracellular, phosphorylated aSYN aggregates selectively in dopaminergic neurons. In these neurons, PFF-exposure decreased mitochondrial gene expression, reduced the number of mitochondria, increased oxidant stress, and profoundly disrupted mitochondrial adenosine triphosphate production. Consistent with an aSYN-induced bioenergetic deficit, the autonomous spiking of dopaminergic neurons slowed or stopped. PFFs also up-regulated lysosomal gene expression and increased lysosomal abundance, leading to the formation of Lewy-like inclusions. Similar changes were observed in PPN cholinergic neurons following aSYN PFF exposure.

Taken together, our findings suggest that disruption of mitochondrial function, and the subsequent bioenergetic deficit, is a proximal step in the cascade of events induced by aSYN pathology leading to dysfunction and degeneration of neurons at-risk in PD.

Oxidative stress has long been implicated in Parkinson's disease (PD) pathogenesis, although the sources and regulation of reactive oxygen species (ROS) production are poorly defined. Pathogenic mutations in the gene encoding leucine-rich repeat kinase 2 (LRRK2) are associated with increased kinase activity and a greater risk of PD. The substrates and downstream consequences of elevated LRRK2 kinase activity are still being elucidated, but overexpression of mutant LRRK2 has been associated with oxidative stress, and antioxidants reportedly mitigate LRRK2 toxicity. Here, using CRISPR-Cas9 gene-edited HEK293 cells, RAW264.7 macrophages, rat primary ventral midbrain cultures, and PD patient-derived lymphoblastoid cells, we found that elevated LRRK2 kinase activity was associated with increased ROS production and lipid peroxidation and that this was blocked by inhibitors of either LRRK2 kinase or NADPH oxidase 2 (NOX2). Oxidative stress induced by the pesticide rotenone was ameliorated by LRRK2 kinase inhibition and was absent in cells devoid of LRRK2. In a rat model of PD induced by rotenone, a LRRK2 kinase inhibitor prevented the lipid peroxidation and NOX2 activation normally seen in nigral dopaminergic neurons in this model. Mechanistically, LRRK2 kinase activity was shown to regulate phosphorylation of serine-345 in the p47phox subunit of NOX2. This, in turn, led to translocation of p47phox from the cytosol to the membrane-associated gp91phox (NOX2) subunit, activation of the NOX2 enzyme complex, and production of ROS. Thus, LRRK2 kinase activity may drive cellular ROS production in PD through the regulation of NOX2 activity.

Regulating cardiolipin to maintain mitochondrial homeostasis is a promising strategy for addressing Parkinson's disease (PD). Through a comprehensive screening and validation process involving multiple models, ginsenoside Rg3 (Rg3) as a compound capable of enhancing cardiolipin levels is identified. This augmentation in cardiolipin levels fosters mitochondrial homeostasis by bolstering mitochondrial unfolded protein response, promoting mitophagy, and enhancing mitochondrial oxidative phosphorylation. Consequently, this cascade enhances the survival of tyrosine hydroxylase positive (TH+) dopaminergic neurons, leading to an amelioration in motor performance within PD mouse models. Using limited proteolysis-small-molecule mapping combined with molecular docking analysis, it has confirmed Growth Factor Receptor-Bound Protein 2 (GRB2) as a molecular target for Rg3. Furthermore, these investigations reveal that Rg3 facilitates the interaction between GRB2 and TRKA (Neurotrophic Tyrosine Kinase, Receptor, Type 1), thus promotes EVI1 (Ecotropic Virus Integration Site 1 Protein Homolog) phosphorylation by ERK, subsequently increases CRLS1 (Cardiolipin Synthase 1) gene expression and boosts cardiolipin synthesis. The absence of GRB2 or CRLS1 significantly attenuates the beneficial effects of Rg3 on PD symptoms. Finally, Tenofovir Disoproxil Fumarate (TDF) that also promotes the binding between GRB2 and TRKA is further identified. The identified compounds, Rg3 and TDF, exhibit promising potential for the prevention of PD by bolstering cardiolipin expression and reinstating mitochondrial homeostasis.

The heterogeneity of protein-rich inclusions and its significance in neurodegeneration is poorly understood. Standard patient-derived iPSC models develop inclusions neither reproducibly nor in a reasonable time frame. Here, we developed screenable iPSC "inclusionopathy" models utilizing piggyBac or targeted transgenes to rapidly induce CNS cells that express aggregation-prone proteins at brain-like levels. Inclusions and their effects on cell survival were trackable at single-inclusion resolution. Exemplar cortical neuron α-synuclein inclusionopathy models were engineered through transgenic expression of α-synuclein mutant forms or exogenous seeding with fibrils. We identified multiple inclusion classes, including neuroprotective p62-positive inclusions versus dynamic and neurotoxic lipid-rich inclusions, both identified in patient brains. Fusion events between these inclusion subtypes altered neuronal survival. Proteome-scale α-synuclein genetic- and physical-interaction screens pinpointed candidate RNA-processing and actin-cytoskeleton-modulator proteins like RhoA whose sequestration into inclusions could enhance toxicity. These tractable CNS models should prove useful in functional genomic analysis and drug development for proteinopathies.