Pathological and Therapeutic Advances in Parkinson's Disease: Mitochondria in the Interplay

Implications of p53 in mitochondrial dysfunction and Parkinson's disease

Purpose: To study the underlying molecular mechanisms of p53 in the mitochondrial dysfunction and the pathogenesis of Parkinson's disease (PD), and provide a potential therapeutic target for PD treatment.

Methods: We review the contributions of p53 to mitochondrial changes leading to apoptosis and the subsequent degeneration of dopaminergic neurons in PD.

Results: P53 is a multifunctional protein implicated in the regulation of diverse cellular processes via transcription-dependent and transcription-independent mechanisms. Mitochondria are vital subcellular organelles for that maintain cellular function, and mitochondrial defect and impairment are primary causes of dopaminergic neuron degeneration in PD. Increasing evidence has revealed that mitochondrial dysfunction-associated dopaminergic neuron degeneration is tightly regulated by p53 in PD pathogenesis. Neurodegenerative stress triggers p53 activation, which induces mitochondrial changes, including transmembrane permeability, reactive oxygen species production, Ca2+ overload, electron transport chain defects and other dynamic alterations, and these changes contribute to neurodegeneration and are linked closely with PD occurrence and development. P53 inhibition has been shown to attenuate mitochondrial dysfunction and protect dopaminergic neurons from degeneration under conditions of neurodegenerative stress.

Conclusions: p53 appears to be a potential target for neuroprotective therapy of PD.

Mitochondrial transfer of α-synuclein mediates carbon disulfide-induced mitochondrial dysfunction and neurotoxicity

Exposure to carbon disulfide (CS2) is a recognized risk factor in the pathogenesis of Parkinson's disease, yet the underlying mechanisms of deleterious effects on mitochondrial integrity have remained elusive. Here, through establishing CS2 exposure models in rat and SH-SY5Y cells, we demonstrated that highly expressed α-synuclein (α-Syn) is transferred to mitochondria via membrane proteins such as Tom20 and leads to mitochondrial dysfunction and mitochondrial oxidative stress, which ultimately causes neuronal injury. We first found significant mitochondrial damage and oxidative stress in CS2-exposed rat midbrain and SH-SY5Y cells and showed that mitochondrial oxidative stress was the main factor of mitochondrial damage by Mitoquinone intervention. Further experiments revealed that CS2 exposure led to the accumulation of α-Syn in mitochondria and that α-Syn co-immunoprecipitated with mitochondrial membrane proteins. Finally, the use of an α-Syn inhibitor (ELN484228) and small interfering RNA (siRNA) effectively mitigated the accumulation of α-Syn in neurons, as well as the inhibition of mitochondrial membrane potential, caused by CS2 exposure. In conclusion, our study identifies the translocation of α-Syn to mitochondria and the impairment of mitochondrial function, which has important implications for the broader understanding and treatment of neurodegenerative diseases associated with environmental toxins.

PET brain imaging in neurological disorders

Brain disorders are a series of conditions with damage or loss of neurons, such as Parkinson's disease (PD), Alzheimer's disease (AD), or drug dependence. These individuals have gradual deterioration of cognitive, motor, and other central nervous system functions affected. This degenerative trajectory is intricately associated with dysregulations in neurotransmitter systems. Positron Emission Tomography (PET) imaging, employing radiopharmaceuticals and molecular imaging techniques, emerges as a crucial tool for detecting brain biomarkers. It offers invaluable insights for early diagnosis and distinguishing brain disorders. This article comprehensively reviews the application and progress of conventional and novel PET imaging agents in diagnosing brain disorders. Furthermore, it conducts a thorough analysis on merits and limitations. The article also provides a forward-looking perspective in the future development directions of PET imaging agents for diagnosing brain disorders and proposes potential innovative strategies. It aims to furnish clinicians and researchers with an all-encompassing overview of the latest advancements and forthcoming trends in the utilization of PET imaging for diagnosing brain disorders.

The Interplay of Mitochondrial Bioenergetics and Dopamine Agonists as an Effective Disease-Modifying Therapy for Parkinson's Disease

Parkinson's disease (PD) is a progressive neurological ailment with a slower rate of advancement that is more common in older adults. The biggest risk factor for PD is getting older, and those over 60 have an exponentially higher incidence of this condition. The failure of the mitochondrial electron chain, changes in the dynamics of the mitochondria, and abnormalities in calcium and ion homeostasis are all symptoms of Parkinson's disease (PD). Increased mitochondrial reactive oxygen species (mROS) and an energy deficit are linked to these alterations. Levodopa (L-DOPA) is a medication that is typically used to treat most PD patients, but because of its negative effects, additional medications have been created utilizing L-DOPA as the parent molecule. Ergot and non-ergot derivatives make up most PD medications. PD is successfully managed with the use of dopamine agonists (DA). To get around the motor issues produced by L-DOPA, these dopamine derivatives can directly excite DA receptors in the postsynaptic membrane. In the past 10 years, two non-ergoline DA with strong binding properties for the dopamine D2 receptor (D2R) and a preference for the dopamine D3 receptor (D3R) subtype, ropinirole, and pramipexole (PPx) have been developed for the treatment of PD. This review covers the most recent research on the efficacy and safety of non-ergot drugs like ropinirole and PPx as supplementary therapy to DOPA for the treatment of PD.

Mitochondrial homeostasis regulation: A promising therapeutic target for Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disease characterized by progressive loss of dopaminergic (DA) neurons in the substantia nigra pars compacta (SNc) and the presence of Lewy bodies (LBs) or Lewy neurites (LNs) which consist of α-synuclein (α-syn) and a complex mix of other biomolecules. Mitochondrial dysfunction is widely believed to play an essential role in the pathogenesis of PD and other related neurodegenerative diseases. But mitochondrial dysfunction is subject to complex genetic regulation. There is increasing evidence that PD-related genes directly or indirectly affect mitochondrial integrity. Therefore, targeted regulation of mitochondrial function has great clinical application prospects in the treatment of PD. However, lots of PD drugs targeting mitochondria have been developed but their clinical therapeutic effects are not ideal. This review aims to reveal the role of mitochondrial dysfunction in the pathogenesis of neurodegenerative diseases based on the mitochondrial structure and function, which may highlight potential interventions and therapeutic targets for the development of PD drugs to recover mitochondrial dysfunction in neurodegenerative diseases.

What Can Inflammation Tell Us about Therapeutic Strategies for Parkinson's Disease?

Parkinson's disease (PD) is a common neurodegenerative disorder with a complicated etiology and pathogenesis. α-Synuclein aggregation, dopaminergic (DA) neuron loss, mitochondrial injury, oxidative stress, and inflammation are involved in the process of PD. Neuroinflammation has been recognized as a key element in the initiation and progression of PD. In this review, we summarize the inflammatory response and pathogenic mechanisms of PD. Additionally, we describe the potential anti-inflammatory therapies, including nod-like receptor pyrin domain containing protein 3 (NLRP3) inflammasome inhibition, nuclear factor κB (NF-κB) inhibition, microglia inhibition, astrocyte inhibition, nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibition, the peroxisome proliferator-activated receptor γ (PPARγ) agonist, targeting the mitogen-activated protein kinase (MAPK) pathway, targeting the adenosine monophosphate-activated protein kinase (AMPK)-dependent pathway, targeting α-synuclein, targeting miRNA, acupuncture, and exercise. The review focuses on inflammation and will help in designing new prevention strategies for PD.

miR-221 and Parkinson's disease: A biomarker with therapeutic potential

Parkinson's disease (PD) is a neurodegenerative disorder characterized by the loss of dopaminergic neurons in the substantia nigra, leading to various motor and non-motor symptoms. Several cellular and molecular mechanisms such as alpha-synuclein (α-syn) accumulation, mitochondrial dysfunction, oxidative stress and neuroinflammation are involved in the pathogenesis of this disease. MicroRNAs (miRNAs) play important roles in post-transcriptional gene regulation. They are typically about 21-25 nucleotides in length and are involved in the regulation of gene expression by binding to the messenger RNA (mRNA) molecules. miRNAs like miR-221 play important roles in various biological processes, including development, cell proliferation, differentiation and apoptosis. miR-221 promotes neuronal survival against oxidative stress and neurite outgrowth and neuronal differentiation. Additionally, the role of miR-221 in PD has been investigated in several studies. According to the results of these studies, (1) miR-221 protects PC12 cells against oxidative stress induced by 6-hydroxydopamine; (2) miR-221 prevents Bax/caspase-3 signalling activation by stopping Bim; (3) miR-221 has moderate predictive power for PD; (4) miR-221 directly targets PTEN, and PTEN over-expression eliminates the protective action of miR-221 on p-AKT expression in PC12 cells; and (5) miRNA-221 controls cell viability and apoptosis by manipulating the Akt signalling pathway in PD. This review study suggested that miR-221 has the potential to be used as a clinical biomarker for PD diagnosis and stage assignment.

Role of F-actin-mediated endocytosis and exercise in mitochondrial transplantation in an experimental Parkinson's disease mouse model

Dopaminergic neurons gradually deteriorate in Parkinson's Disease (PD), which is characterized by the intracellular accumulation of Lewy bodies that are enriched with α-synuclein protein. Mitochondrial dysfunction is one of the primary contributors to this and is considered as the central player in the pathogenesis of PD. Recently, improving mitochondrial function has been extensively explored as a therapeutic strategy in various preclinical PD models. Mitochondrial transplantation is one such naïve yet highly efficient technique that has been well explored in diseases like diabetes, NAFLD, and cardiac ischemia but not in PD. Here, we compared the effects of transplanting normal allogenic mitochondria to those of transplanting exercise-induced allogenic mitochondria isolated from the liver into the PD mouse model. It is already known that normal Mitochondrial Transplant (MT) reduces the PD pathology, but our research found out that exercise-induced mitochondria were more effective in treating the PD pathology because they had higher respiratory capacities. Additionally, compared to a standard transplant, this therapy significantly boosted the rate of mitochondrial biogenesis and the quantity of mitochondrial subunits in PD mice. Further, we also explored the mechanism of mitochondrial uptake into the cells and found that F-actin plays a key role in the internalization of mitochondria. This study is the first to demonstrate the relevance of exercise-induced allogenic MT and the function of F-actin in the internalization of mitochondria in PD mice.

Screening of Crucial Cytosolicproteins Interconnecting the Endoplasmic Reticulum and Mitochondria in Parkinson's Disease and the Impact of Anti-Parkinson Drugs in the Preservation of Organelle Connectivity

Mitochondrial dysfunction is well-established in Parkinson's disease (PD); however, its dysfunctions associating with cell organelle connectivity remain unknown. We aimed to establish the crucial cytosolic protein involved in organelle connectivity between mitochondria and the endopalmic reticulum (ER) through a computational approach by constructing an organelle protein network to extract functional clusters presenting the crucial PD protein connecting organelles. Then, we assessed the influence of anti-parkinsonism drugs (n = 35) on the crucial protein through molecular docking and molecular dynamic simulation and further validated its gene expression in PD participants under, istradefylline (n = 25) and amantadine (n = 25) treatment. Based on our investigation, D-aspartate oxidase (DDO )protein was found to be the critical that connects both mitochondria and the ER. Further, molecular docking showed that istradefylline has a high affinity (-9.073 kcal/mol) against DDO protein, which may disrupt mitochondrial-ER connectivity. While amantadine (-4.53 kcal/mol) shows negligible effects against DDO that contribute to conformational changes in drug binding, Successively, DDO gene expression was downregulated in istradefylline-treated PD participants, which elucidated the likelihood of an istradefylline off-target mechanism. Overall, our findings illuminate the off-target effects of anti-parkinsonism medications on DDO protein, enabling the recommendation of off-target-free PD treatments.

Microtubule acetylation dyshomeostasis in Parkinson's disease

The inter-neuronal communication occurring in extensively branched neuronal cells is achieved primarily through the microtubule (MT)-mediated axonal transport system. This mechanistically regulated system delivers cargos (proteins, mRNAs and organelles such as mitochondria) back and forth from the soma to the synapse. Motor proteins like kinesins and dynein mechanistically regulate polarized anterograde (from the soma to the synapse) and retrograde (from the synapse to the soma) commute of the cargos, respectively. Proficient axonal transport of such cargos is achieved by altering the microtubule stability via post-translational modifications (PTMs) of α- and β-tubulin heterodimers, core components constructing the MTs. Occurring within the lumen of MTs, K40 acetylation of α-tubulin via α-tubulin acetyl transferase and its subsequent deacetylation by HDAC6 and SIRT2 are widely scrutinized PTMs that make the MTs highly flexible, which in turn promotes their lifespan. The movement of various motor proteins, including kinesin-1 (responsible for axonal mitochondrial commute), is enhanced by this PTM, and dyshomeostasis of neuronal MT acetylation has been observed in a variety of neurodegenerative conditions, including Alzheimer's disease and Parkinson's disease (PD). PD is the second most common neurodegenerative condition and is closely associated with impaired MT dynamics and deregulated tubulin acetylation levels. Although the relationship between status of MT acetylation and progression of PD pathogenesis has become a chicken-and-egg question, our review aims to provide insights into the MT-mediated axonal commute of mitochondria and dyshomeostasis of MT acetylation in PD. The enzymatic regulators of MT acetylation along with their synthetic modulators have also been briefly explored. Moving towards a tubulin-based therapy that enhances MT acetylation could serve as a disease-modifying treatment in neurological conditions that lack it.

GSK-3β: An exuberating neuroinflammatory mediator in Parkinson's disease

Neuroinflammation is a critical degradative condition affecting neurons in the brain. Progressive neurodegenerative conditions such as Alzheimer's disease and Parkinson's disease (PD) have been strongly linked to neuroinflammation. The trigger point for inflammatory conditions in the cells and body is the physiological immune system. The immune response mediated by glial cells and astrocytes can rectify the physiological alterations occurring in the cell for the time being but prolonged activation leads to pathological progression. The proteins mediating such an inflammatory response, as per the available literature, are undoubtedly GSK-3β, NLRP3, TNF, PPARγ, and NF-κB, along with a few other mediatory proteins. NLRP3 inflammasome is undeniably a principal instigator of the neuroinflammatory response, but the regulatory pathways controlling its activation are still unclear, besides less clarity for the interplay between different inflammatory proteins. Recent reports have suggested the involvement of GSK-3β in regulating NLRP3 activation, but the exact mechanistic pathway remains vague. In the current review, we attempt to provide an elaborate description of crosstalk between inflammatory markers and GSK-3β mediated neuroinflammation progression, linking it to regulatory transcription factors and posttranslational modification of proteins. The recent clinical therapeutic advances targeting these proteins are also discussed in parallel to provide a comprehensive view of the progress made in PD management and lacunas still existing in the field.

Calcium/calmodulin-dependent serine protein kinase exacerbates mitochondrial calcium uniporter-related mitochondrial calcium overload by phosphorylating α-synuclein in Parkinson's disease

α-Synuclein phosphorylation and mitochondrial calcium homeostasis are important mechanisms underlying mitochondrial dysfunction in Parkinson's disease, but the network regulating these mechanisms remains unclear. We identified the role of key phosphokinases and the pathological effects of α-synuclein phosphorylation on mitochondrial calcium influx and mitochondrial function in Parkinson's disease. The function of the key phosphokinase, calcium/calmodulin-dependent serine protein kinase, was investigated through loss- and gain-of-function experiments using a cell model of Parkinson's disease. The regulation of mitochondrial calcium uniporter-mediated mitochondrial calcium influx by calcium/calmodulin-dependent serine protein kinase was explored using a cellular model of Parkinson's disease. Coimmunoprecipitation experiments and α-synuclein mutation were used to explore the mechanism through which calcium/calmodulin-dependent serine protein kinase regulates mitochondrial calcium uniporter-mediated mitochondrial calcium influx and exacerbates mitochondrial damage in Parkinson's disease. Here, we show the pathogenic role of calcium/calmodulin-dependent serine protein kinase in Parkinson's disease progression. Calcium/calmodulin-dependent serine protein kinase phosphorylated α-synuclein to activate mitochondrial calcium uniporter and thus increase mitochondrial calcium influx, and these effects were blocked by α-synuclein S129A mutant expression. Furthermore, the calcium/calmodulin-dependent serine protein kinase inhibitor CASK-IN-1 exerted neuroprotective effects in Parkinson's disease. Collectively, our results suggest that calcium/calmodulin-dependent serine protein kinase phosphorylates α-synuclein to activate the mitochondrial calcium uniporter and thereby causes mitochondrial calcium overload and mitochondrial damage in Parkinson's disease. We elucidated a new role of calcium/calmodulin-dependent serine protein kinase in Parkinson's disease and revealed the potential therapeutic value of targeting calcium/calmodulin-dependent serine protein kinase in Parkinson's disease treatment.

Diagnostic metabolomic profiling of Parkinson's disease biospecimens

BACKGROUND

Reliable and sensitive biomarkers are needed for enhancing and predicting Parkinson's disease (PD) diagnosis.

OBJECTIVE

To investigate comprehensive metabolomic profiling of biochemicals in CSF and serum for determining diagnostic biomarkers of PD.

METHODS

Fifty subjects, symptomatic with PD for ≥5 years, were matched to 50 healthy controls (HCs). We used ultrahigh-performance liquid chromatography linked to tandem mass spectrometry (UHPLC-MS/MS) for measuring relative concentrations of ≤1.5 kDalton biochemicals. A reference library created from authentic standards facilitated chemical identifications. Analytes underwent univariate analysis for PD association, with false discovery rate-adjusted p-value (≤0.05) determinations. Multivariate analysis (for identifying a panel of biochemicals discriminating PD from HCs) used several biostatistical methods, including logistic LASSO regression.

RESULTS

Comparing PD and HCs, strong differentiation was achieved from CSF but not serum specimens. With univariate analysis, 21 CSF compounds exhibited significant differential concentrations. Logistic LASSO regression led to selection of 23 biochemicals (11 shared with those determined by the univariate analysis). The selected compounds, as a group, distinguished PD from HCs, with Area-Under-the-Receiver-Operating-Characteristic (ROC) curve of 0.897. With optimal cutoff, logistic LASSO achieved 100% sensitivity and 96% specificity (and positive and negative predictive values of 96% and 100%). Ten-fold cross-validation gave 84% sensitivity and 82% specificity (and 82% positive and 84% negative predictive values). From the logistic LASSO-chosen regression model, 2 polyamine metabolites (N-acetylcadaverine and N-acetylputrescine) were chosen and had the highest fold-changes in comparing PD to HCs. Another chosen biochemical, acisoga (N-(3-acetamidopropyl)pyrrolidine-2-one), also is a polyamine metabolism derivative.

CONCLUSIONS

UHPLC-MS/MS assays provided a metabolomic signature highly predictive of PD. These findings provide further evidence for involvement of polyamine pathways in the neurodegeneration of PD.