Activated microglia facilitate the transmission of α-synuclein in Parkinson's disease

The role of interleukin (IL)-2 cytokine family in Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder, which primarily impacts the nervous system, marked by its immune and inflammatory characteristics. The interleukin-2 (IL-2) cytokine family has a crucial role in regulating both neuroinflammation and immune activity, positioning it as one of the critical immune pathways in PD. Balancing pro-inflammatory and anti-inflammatory signals in PD heavily depends on the IL-2 cytokine family, that includes IL-2, IL-4, IL-7, IL-9, IL-15 and IL-21. This balance is vital for neuron survival and resistance to degeneration. Disruptions in IL-2 signaling can upset the equilibrium among regulatory T cells (Tregs) and pro-inflammatory T cells, such as Th1 and Th17, further aggravating the chronic neuroinflammation typical of PD. In PD, a decline in IL-2 or receptor dysfunction can hinder Treg activity, leading to increased inflammation and neurodegeneration. Similarly, IL-15 and IL-21 supports cytotoxic immune cell function, including natural killer (NK) cells and CD8+ T cells, which may exacerbate neuronal damage by sustaining pro-inflammatory processes. Moreover, IL-4 and IL-7 have anti-inflammatory roles in maintaining T cell homeostasis, and their dysregulation can contribute to interruption of the blood-brain barrier and increased infiltration of immune cells into the central nervous system. Targeting the IL-2 cytokine family in Parkinson's disease has shown therapeutic potential by expanding Tregs, which reduce neuroinflammation and promote dopaminergic neuron survival. Recombinant IL-2 and IL-2/anti-IL-2 complexes have demonstrated efficacy in animal models, enhancing Treg function and leading to improved neuroprotection. Additionally, IL-4-based therapies have been explored for their ability to shift microglia toward a neuroprotective phenotype, further enhancing neuronal survival by modulating inflammatory responses and cellular metabolism. Current research is exploring how to optimize cytokine delivery while minimizing immune side effects, with the goal of developing more targeted therapies for PD.

Intercellular communication via exosomes: A new paradigm in the pathophysiology of neurodegenerative disorders

Neurodegenerative disorders are one of the leading causes of death and disability and pose a great economic burden on healthcare systems. Generally, these neurodegenerative disorders have a progressive deterioration in neural function and structure, and deposition of misfolded proteins commonly occurs, such as amyloid-β in AD and α-synuclein in PD. However, there exists a special class of exosomes, which acts like a transmitter and enhances communication between cells. The present review discusses the significant role of exosomes in neurodegenerative diseases, with a focus on Amyotrophic lateral Sclerosis (ALS), AD, PD, and Huntington's disease (HD). In this review, the biogenesis of exosomes is discussed from multivesicular bodies and onwards to their release into the extracellular environment. The present review focuses on recent data concerning the possible use of modified exosomes as ND therapy. Indeed, future work is needed to explain the processes driving exosome biogenesis and cargo selection, while opening new routes by the use of exosome-based therapeutics in neurodegenerative disease diagnosis and treatment.

Activation of α7nAch receptors ameliorates α-synuclein pathology in the brain and gut of a subacute MPTP mouse model of Parkinson's disease

Parkinson's disease (PD) is a neurological disorder that causes a gradual decrease in mobility. Abnormal α-synuclein (α-syn) levels and aggregation contribute to PD development. The dissemination of α-synuclein pathology via the gut-brain axis has emerged as a critical aspect in α-synucleinopathies, including PD. Recently, α7 nicotinic acetylcholine receptor (α7nAchR) agonists have been proposed as promising agents for treating PD, owing to their biological properties such as anti-inflammatory effects. This study aims to investigate whether activation of α7nAchR improves α-synuclein pathology in the brain and gut of a mouse model of PD. We found that α7nAchR agonists, GTS-21 and PNU-282987, induced behavioral recovery and improved nigrostriatal dopaminergic neurotransmission in a subacute MPTP mouse model of PD. In addition, GTS-21 and PNU-282987 facilitated α-syn clearance in the brain and distal colon, as evidenced by a considerable reduction in the accumulation of pathogenic forms of α-syn. Accordingly, GTS-21 and PNU-282987 were found to promote the AMPK-mTOR autophagy signaling pathway. Furthermore, GTS-21 and PNU-282987 exerted anti-inflammatory effects, reducing the levels of proinflammatory mediators such as inducible nitric oxide synthase, interleukin-6, and tumor necrosis factor-α in both the brain and gut. To validate the specific effects of α7nAchR agonists, subacute MPTP mice were pretreated with methyllycaconitine (MLA), a selective α7nAchR antagonist before GTS-21 administration. Pretreatment with MLA abolished the GTS-21-elicited behavioral recovery, α-syn clearance, and anti-inflammatory effects in the brain and gut. Therefore, α7nAchR activation may be a potential candidate strategy for the treatment of PD by altering α-syn aggregation in the brain and gut.

Exploring the therapeutic potential of Chinese herbs on comorbid type 2 diabetes mellitus and Parkinson's disease: A mechanistic study

ETHNOPHARMACOLOGICAL RELEVANCE

Type 2 diabetes mellitus (T2DM) and Parkinson's disease (PD) are chronic conditions that affect the aging population, with increasing prevalence globally. The rising prevalence of comorbidity between these conditions, driven by demographic shifts, severely impacts the quality of life of patients, posing a significant burden on healthcare resources. Chinese herbal medicine has been used to treat T2DM and PD for millennia. Pharmacological studies have demonstrated that medicinal herbs effectively lower blood glucose levels and exert neuroprotective effects, suggesting their potential as adjunctive therapy for concurrent management of T2DM and PD.

AIM OF THE STUDY

To elucidate the shared mechanisms underlying T2DM and PD, particularly focusing on the potential mechanisms by which medicinal herbs (including herbal formulas, single herbs, and active compounds) may treat these diseases, to provide valuable insights for developing therapeutics targeting comorbid T2DM and PD.

MATERIALS AND METHODS

Studies exploring the mechanisms underlying T2DM and PD, as well as the treatment of these conditions with medicinal herbs, were extracted from several electronic databases, including PubMed, Web of Science, Google Scholar, and China National Knowledge Infrastructure (CNKI).

RESULTS

Numerous studies have shown that inflammation, oxidative stress, insulin resistance, impaired autophagy, gut microbiota dysbiosis, and ferroptosis are shared mechanisms underlying T2DM and PD mediated through the NLRP3 inflammasome, NF-κB, MAPK, Keap1/Nrf2/ARE, PI3K/AKT, AMPK/SIRT1, and System XC--GSH-GPX4 signaling pathways. Thirty-four medicinal herbs, including 2 herbal formulas, 4 single herbs, and 28 active compounds, have been reported to potentially exert anti-T2DM and anti-PD effects by targeting these shared mechanisms.

CONCLUSIONS

Traditional Chinese medicine effectively combats T2DM and PD through shared pathological mechanisms, highlighting their potential for application in treating these comorbid conditions.

Rotenone exposure causes features of Parkinson`s disease pathology linked with muscle atrophy in developing zebrafish embryo

Parkinson's disease (PD) is associated with both genetic and environmental factors; however, sporadic forms of PD account for > 90 % of cases, and PD prevalence has doubled in the past 25 years. Depending on the importance of the environmental factors, various neurotoxins are used to induce PD both in vivo and in vitro. Unlike other neurodegenerative diseases, PD can be induced in vivo using specific neurotoxic chemicals. However, no chemically induced PD model is available because of the sporadic nature of PD. Rotenone is a pesticide that accelerates the induction of PD and exhibits the highest toxicity in fish, unlike other pesticides. Therefore, in this study, we aimed to establish a model exhibiting PD pathologies such as dysfunction of DArgic neuron, aggregation of ɑ-synuclein, and behavioral abnormalities, which are known features of PD pathology, by rotenone exposure at an environmentally relevant concentration (30 nM) in developing zebrafish embryos. Our results provide direct evidence for the association between PD and muscle degeneration by confirming rotenone-induced muscle atrophy. Therefore, we conclude that the rotenone-induced model presents non-motor and motor defects with extensive studies related to muscle atrophy.

Alpha-Synuclein and Microglia in Parkinson's Disease: From Pathogenesis to Therapeutic Prospects

Parkinson's disease (PD) is a neurodegenerative disorder characterized by both motor symptoms and non-motor features. A hallmark of PD is the misfolding and accumulation of alpha-synuclein (α-syn), which triggers neuroinflammation and drives neurodegeneration. Microglia, brain cells that play a central role in neuroinflammatory responses and help clear various unnecessary molecules within the brain, thus maintaining the brain's internal environment, respond to α-syn through mechanisms involving inflammation, propagation, and clearance. This review delves into the complex interplay between α-syn and microglia, elucidating how these interactions drive PD pathogenesis. Furthermore, we discuss emerging therapeutic strategies targeting the α-syn-microglia axis, with a focus on modulating microglial functions to mitigate neuroinflammation, enhance clearance, and prevent α-syn propagation, emphasizing their potential to slow PD progression.

Combating Parkinson's disease with plant-derived polyphenols: Targeting oxidative stress and neuroinflammation

Parkinson's disease (PD) is a devastating neurodegenerative disorder predominantly affecting the elderly, characterized by the loss of dopaminergic neurons in the substantia nigra. Reactive oxygen species (ROS) generation plays a central role in the pathogenesis of PD and other neurodegenerative diseases. An imbalance between cellular antioxidant activity and ROS production leads to oxidative stress, contributing to disease progression. Dopamine metabolism, mitochondrial dysfunction, and neuroinflammation in dopaminergic neurons have been implicated in the pathogenesis of Parkinson's disease. Consequently, there is a pressing need for therapeutic interventions capable of scavenging ROS. Current pharmacological approaches, such as L-dihydroxyphenylalanine (levodopa or L-DOPA) and other drugs, provide symptomatic relief but are limited by severe side effects. Researchers worldwide have been exploring alternative compounds with less toxicity to address the multifaceted challenges associated with Parkinson's disease. In recent years, plant-derived polyphenolic compounds have gained significant attention as potential therapeutic agents. These compounds exhibit neuroprotective effects by targeting pathophysiological responses, including oxidative stress and neuroinflammation, in Parkinson's disease. The objective of this review is to summarize the current understanding of the neuroprotective effects of various polyphenols in Parkinson's disease, focusing on their antioxidant and anti-inflammatory properties, and to discuss their potential as therapeutic candidates. This review highlights the progress made in elucidating the molecular mechanisms of action of these polyphenols, identifying potential therapeutic targets, and optimizing their delivery and bioavailability. Well-designed clinical trials are necessary to establish the efficacy and safety of polyphenol-based interventions in the management of Parkinson's disease.

Modulating α-synuclein propagation and decomposition: Implications in Parkinson's disease therapy

α-Synuclein (α-Syn) is closely related to the pathogenesis of Parkinson's disease (PD). Under pathological conditions, the conformation of α-syn changes and different forms of α-syn lead to neurotoxicity. According to Braak stages, α-syn can propagate in different brain regions, inducing neurodegeneration and corresponding clinical manifestations through abnormal aggregation of Lewy bodies (LBs) and lewy axons in different types of neurons in PD. So far, PD lacks early diagnosis biomarkers, and treatments are mainly targeted at some clinical symptoms. There is no effective therapy to delay the progression of PD. This review first summarized the role of α-syn in physiological and pathological states, and the relationship between α-syn and PD. Then, we focused on the origin, secretion, aggregation, propagation and degradation of α-syn as well as the important regulatory factors in these processes systematically. Finally, we reviewed some potential drug candidates for alleviating the abnormal aggregation of α-syn in order to provide valuable targets for the treatment of PD to cope with the occurrence and progression of this disease.

Golexanolone reduces glial activation in the striatum and improves non-motor and some motor alterations in a rat model of Parkinson's disease

Background

Parkinson's disease (PD) affects more than 6 million people worldwide. Along with motor impairments, patients and animal models exhibiting PD symptoms also experience cognitive impairment, fatigue, anxiety, and depression. Currently, there are no drugs available for PD that alter the progression of the disease. A body of evidence suggests that increased GABA levels contribute to the reduced expression of tyrosine hydroxylase (TH) and accompanying behavioral deficits. TH expression may be restored by blocking GABAA receptors. We hypothesized that golexanolone (GR3027), a well-tolerated GABAA receptor-modulating steroid antagonist (GAMSA), may improve Parkinson's symptoms in a rat model of PD.

Objectives

The aims of this study were to assess whether golexanolone can ameliorate motor and non-motor symptoms in a rat model of PD and to identify some underlying mechanisms.

Methods

We used the unilateral 6-OHDA rat model of PD. The golexanolone treatment started 4 weeks after surgery. Motor symptoms were assessed using Motorater and CatWalk tests. We also analyzed fatigue (using a treadmill test), anhedonia (via the sucrose preference test), anxiety (with an open field test), and short-term memory (using a Y maze). Glial activation and key proteins involved in PD pathogenesis were analyzed using immunohistochemistry and Western blot.

Results

Rats with PD showed motor incoordination and impaired locomotor gait, increased fatigue, anxiety, depression, and impaired short-term memory. Golexanolone treatment led to improvements in motor incoordination, certain aspects of locomotor gait, fatigue, anxiety, depression, and short-term memory. Notably, golexanolone reduced the activation of microglia and astrocytes, mitigated TH loss at 5 weeks after surgery, and prevented the increase of α-synuclein levels at 10 weeks.

Conclusions

Golexanolone may be useful in improving both motor and non-motor symptoms that adversely affect the quality of life in PD patients, such as anxiety, depression, fatigue, motor coordination, locomotor gait, and certain cognitive alterations.

Emergence of the brain-border immune niches and their contribution to the development of neurodegenerative diseases

Historically, the central nervous system (CNS) was regarded as 'immune-privileged', possessing its own distinct immune cell population. This immune privilege was thought to be established by a tight blood-brain barrier (BBB) and blood-cerebrospinal-fluid barrier (BCSFB), which prevented the crossing of peripheral immune cells and their secreted factors into the CNS parenchyma. However, recent studies have revealed the presence of peripheral immune cells in proximity to various brain-border niches such as the choroid plexus, cranial bone marrow (CBM), meninges, and perivascular spaces. Furthermore, emerging evidence suggests that peripheral immune cells may be able to infiltrate the brain through these sites and play significant roles in driving neuronal cell death and pathology progression in neurodegenerative disease. Thus, in this review, we explore how the brain-border immune niches may contribute to the pathogenesis of neurodegenerative disorders such as Alzheimer's disease (AD), Parkinson's disease (PD), and multiple sclerosis (MS). We then discuss several emerging options for harnessing the neuroimmune potential of these niches to improve the prognosis and treatment of these debilitative disorders using novel insights from recent studies.

Plasma exosomes impair microglial degradation of α-synuclein through V-ATPase subunit V1G1

INTRODUCTION

Microglia are the main phagocytes in the brain and can induce neuroinflammation. Moreover, they are critical to alpha-synuclein (α-syn) aggregation and propagation. Plasma exosomes derived from patients diagnosed with Parkinson's disease (PD-exo) reportedly evoked α-syn aggregation and inflammation in microglia. In turn, microglia internalized and released exosomal α-syn, enhancing α-syn propagation. However, the specific mechanism through which PD-exo influences α-syn degradation remains unknown.

METHODS

Exosomes were extracted from the plasma of patients with PD by differential ultracentrifugation, analyzed using electron microscopy (EM) and nanoparticle flow cytometry, and stereotaxically injected into the unilateral striatum of the mice. Transmission EM was employed to visualize lysosomes and autophagosomes in BV2 cells, and lysosome pH was measured with LysoSensor Yellow/Blue DND-160. Cathepsin B and D, lysosomal-associated membrane protein 1 (LAMP1), ATP6V1G1, tumor susceptibility gene 101 protein, calnexin, α-syn, ionized calcium binding adaptor molecule 1, and NLR family pyrin domain containing 3 were evaluated using quantitative polymerase chain reaction or western blotting, and α-syn, LAMP1, and ATP6V1G1 were also observed by immunofluorescence. Small interfering ribonucleic acid against V1G1 was transfected into BV2 cells and primary microglia using Lipofectamine® 3000. A PD mouse model was established via injection with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) into mice. A lentiviral-mediated strategy to overexpress ATP6V1G1 in the brain of MPTP-treated mice was employed. Motor coordination was assessed using rotarod and pole tests, and neurodegeneration in the mouse substantia nigra and striatum tissues was determined using immunofluorescence histochemical and western blotting of tyrosine hydroxylase.

RESULTS

PD-exo decreased the expression of V1G1, responsible for the acidification of intra- and extracellular milieu. This impairment of lysosomal acidification resulted in the accumulation of abnormally swollen lysosomes and decreased lysosomal enzyme activities, impairing lysosomal protein degradation and causing α-syn accumulation. Additionally, V1G1 overexpression conferred the mice neuroprotection during MPTP exposure.

CONCLUSION

Pathogenic protein accumulation is a key feature of PD, and compromised V-type ATPase dysfunction might participate in PD pathogenesis. Moreover, V1G1 overexpression protects against neuronal toxicity in an MPTP-based PD mouse model, which may provide opportunities to develop novel therapeutic interventions for PD treatment.

Anti-inflammatory effects of myristic acid mediated by the NF-κB pathway in lipopolysaccharide-induced BV-2 microglial cells

Parkinson's disease (PD) is a serious neurodegenerative disorder wherein changes in metabolites related to lipids, glutathione, and energy metabolism occur. Currently, metabolite changes in PD have been reported, yet their role in the prognosis of disease remains poorly understood. Functional metabolites can be used to diagnose diseases, especially PD, and can exert neuroprotective effects. This study used a PD animal model and a lipopolysaccharide (LPS)-mediated inflammatory response model (using the BV-2 mouse microglial cell line) to identify functional metabolites that can identify important metabolic disorders during PD, and comprehensively evaluated their profiles using a metabolomics-based approach. Our results showed that co-treatment with myristic acid and heptadecanoic acid downregulated the expression of interleukin (IL)-1β, IL-6, and tumor necrosis factor-α in BV-2 cells. Additionally, myristic acid and 10 μM heptadecanoic acid significantly inhibited the LPS-induced inflammatory response through the nuclear factor-κB pathway in BV-2 microglial cells, which provides a potential approach for PD treatment. Myristic acid and heptadecanoic acid were the active metabolites found by active metabolomics technology, but at present, there is no research report about their function for PD treatment, and our findings offer a novel research strategy for PD diagnosis and treatment.

Microglia-specific knock-out of NF-κB/IKK2 increases the accumulation of misfolded α-synuclein through the inhibition of p62/sequestosome-1-dependent autophagy in the rotenone model of Parkinson's disease

Parkinson's disease (PD) is the most common neurodegenerative movement disorder worldwide, with a greater prevalence in men than women. The etiology of PD is largely unknown, although environmental exposures and neuroinflammation are linked to protein misfolding and disease progression. Activated microglia are known to promote neuroinflammation in PD, but how environmental agents interact with specific innate immune signaling pathways in microglia to stimulate conversion to a neurotoxic phenotype is not well understood. To determine how nuclear factor kappa B (NF-κB) signaling dynamics in microglia modulate neuroinflammation and dopaminergic neurodegeneration, we generated mice deficient in NF-κB activation in microglia (CX3CR1-Cre::IKK2fl/fl ) and exposed them to 2.5 mg/kg/day of rotenone for 14 days, followed by a 14-day post-lesioning incubation period. We postulated that inhibition of NF-κB signaling in microglia would reduce overall inflammatory injury in lesioned mice. Subsequent analysis indicated decreased expression of the NF-κB-regulated autophagy gene, sequestosome 1 (p62), in microglia, which is required for targeting ubiquitinated α-synuclein (α-syn) for lysosomal degradation. Knock-out animals had increased accumulation of misfolded α-syn within microglia, despite an overall reduction in neurodegeneration. Interestingly, this occurred more prominently in males. These data suggest that microglia play key biological roles in the degradation and clearance of misfolded α-syn and this process works in concert with the innate immune response associated with neuroinflammation. Importantly, the accumulation of misfolded α-syn protein aggregates alone did not increase neurodegeneration following exposure to rotenone but required the NF-κB-dependent inflammatory response in microglia.

Necrosulfonamide exerts neuroprotective effect by inhibiting necroptosis, neuroinflammation, and α-synuclein oligomerization in a subacute MPTP mouse model of Parkinson's disease

Parkinson's disease (PD) is an incurable movement disorder characterized by dopaminergic cell loss, neuroinflammation, and α-synuclein pathology. Herein, we investigated the therapeutic effects of necrosulfonamide (NSA), a specific inhibitor of mixed lineage kinase domain-like protein (MLKL), in a subacute 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD. MLKL is an executor of necroptosis, a programmed cell death pathway that causes inflammation. Repeated administration of NSA resulted in the recovery of impaired motor performance and dopaminergic degeneration. Furthermore, NSA inhibited the phosphorylation, ubiquitylation, and oligomerization of MLKL, all of which are associated with MLKL cell death-inducing activity in dopaminergic cells in the substantia nigra (SN). NSA also inhibited microglial activation and reactive astrogliosis as well as the MPTP-induced expression of proinflammatory molecules such as tumor necrosis factor-α, interleukin-1β, inducible nitric oxide synthase, and cystatin F. Furthermore, NSA inhibited α-synuclein oligomerization and phosphorylation in the SN of MPTP-treated mice by inhibiting the activity of glycogen synthase kinase 3β and matrix metalloproteinase-3. In conclusion, NSA has anti-necroptotic, anti-inflammatory, and anti-synucleinopathic effects on PD pathology. Therefore, NSA is a potential therapeutic candidate for PD.

Suppression of neuroinflammation and α-synuclein oligomerization by rotarod walking exercise in subacute MPTP model of Parkinson's disease

Parkinson's disease (PD) belongs to an α-synucleinopathy and manifests motor dysfunction attributed to nigrostriatal dopaminergic degeneration. In clinical practice, the beneficial role of physical therapy such as motor skill learning training has been recognized in PD-linked motor defects. Nevertheless, the disease-modifying effects of motor skill learning training on PD-related pathology remain unclear. Here, we investigated the disease-modifying effects of rotarod walking exercise (RWE), a modality of motor skill learning training, in a subacute 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD. In motor function and dopaminergic degeneration, RWE improved MPTP-induced deficits. In addition, RWE enhanced the expression of neurotrophic factors BDNF/GDNF, PGC1-α, Nurr1, and p-AMPK, thereby recovering dopaminergic neuronal cell death. Moreover, RWE inhibited microglial activation and the expression of pro-inflammatory markers, such as p-IκBα, iNOS, IL-1β, TNF-α, and cathepsin D, while elevating anti-inflammatory IL-10 and TGF-β. RWE also decreased oxidative stress markers in the substantia nigra, such as 4-HNE and 8-OHdG-positive cells, while increasing Nrf2-controlled antioxidant enzymes. Regarding the effect of RWE on α-synuclein, it reduced the monomer/oligomer forms of α-synuclein and phosphorylation at serine 129. Further mechanistic studies revealed that RWE suppressed the expression of matrix metalloproteinase-3 and p-GSK3β (Y216), which play key roles in α-synuclein aggregation. These data collectively suggest that inhibition of neuroinflammation and α-synuclein oligomerization by RWE may contribute to the improvement of PD pathology.

Intrastriatal injection of Parkinson's disease intestine and vagus lysates initiates α-synucleinopathy in rat brain

Parkinson's disease (PD) is characterized by the selective loss of dopaminergic neurons in the midbrain and the pathological accumulation of misfolded α-synuclein (α-syn) in the brain. A growing body of evidence suggests that the formation of misfolded α-syn and aggregation may begin in the peripheral nervous system, specifically the enteric nervous system, and then propagate to the central nervous system via the vagus nerve. However, the PD-like neuropathology induced by the intestine and vagus nerve extracts is rarely investigated. In this work, we injected lysates of the intestine and vagus obtained from a diagnosed PD patient, which contained abnormal α-syn aggregates, into the rat striatum unilaterally. Strikingly, such an injection induced dopaminergic neurodegeneration and α-syn depositions in the striatum, substantia nigra, and other brain regions, including the frontal cortex, somatosensory cortex, hypothalamus, brain stem, and cerebellum. Moreover, significant activation of microglia and the development of astrogliosis were observed in the substantia nigra pars compacta of the injected rats. These findings provide essential information for our understanding of PD pathogenesis, as we established for the first time that the α-syn aggregates in the intestine and vagus of a PD patient were sufficient to induce prion-like propagation of endogenous α-syn pathology in wild-type rats.

BDNF-modified human umbilical cord mesenchymal stem cells-derived dopaminergic-like neurons improve rotation behavior of Parkinson's disease rats through neuroprotection and anti-neuroinflammation

Parkinson's disease (PD) is a neurodegenerative disease still without any cure. Brain-derived neurotrophic factor (BDNF) has shown therapeutic potential in PD, which is limited by its short half-life and inability to penetrate the blood-brain barrier. Stem cells not only present migration, differentiation and neurotrophy characteristics, but also can be used as delivery vectors for BDNF. This study aimed to investigate the therapeutic effects and possible mechanisms of BDNF-modified human umbilical cord mesenchymal stem cells (hUC-MSCs)-derived dopaminergic (DAergic)-like neurons in the PD rats. Results showed that transplantation of BDNF-modified hUC-MSCs-derived DAergic-like neurons improved the apomorphine induced rotation behavior of PD rats, increased the dopamine concentration and the expression of glial fibrillary acidic protein (GFAP) and ionized calcium-binding adaptor molecule-1 (Iba-1) in the striatum, promoted the expression of tyrosine hydroxylase (TH), nuclear receptor-related factor 1 (Nurr1), pituitary homeobox 3 (Pitx3), BDNF, tyrosine kinase B (TrkB), phosphatidylinositol-3-hydroxykinase (PI3K), phosphorylated protein kinase B (p-Akt), heat shock protein 60 (Hsp60), toll-like receptor 4 (TLR4) and myeloid differentiation factor 88 (MyD88) and inhibited the neural apoptosis in the substantia nigra (SN) and striatum. Results suggest that BDNF-modified hUC-MSCs-derived DAergic-like neurons improve the rotation of PD rats might through neuroprotection and anti-neuroinflammation by regulating the BDNF-TrkB-PI3K/Akt and Hsp60-TLR4/MyD88 signaling pathways, respectively.

Exosomes, autophagy and ER stress pathways in human diseases: Cross-regulation and therapeutic approaches

Exosomal release pathway and autophagy together maintain homeostasis and survival of cells under stressful conditions. Autophagy is a catabolic process through which cell entities, such as malformed biomacromolecules and damaged organelles, are degraded and recycled via the lysosomal-dependent pathway. Exosomes, a sub-type of extracellular vesicles (EVs) formed by the inward budding of multivesicular bodies (MVBs), are mostly involved in mediating communication between cells. The unfolded protein response (UPR) is an adaptive response that is activated to sustain survival in the cells faced with the endoplasmic reticulum (ER) stress through a complex network that involves protein synthesis, exosomes secretion and autophagy. Disruption of the critical crosstalk between EVs, UPR and autophagy may be implicated in various human diseases, including cancers and neurodegenerative diseases, yet the molecular mechanism(s) behind the coordination of these communication pathways remains obscure. Here, we review the available information on the mechanisms that control autophagy, ER stress and EV pathways, with the view that a better understanding of their crosstalk and balance may improve our knowledge on the pathogenesis and treatment of human diseases, where these pathways are dysregulated.

Modulation of Inflammatory Mediators and Microglial Activation Through Physical Exercise in Alzheimer's and Parkinson's Diseases

Neuroinflammation is an inflammatory process in the central nervous system (CNS), in addition to being one of the main features of Alzheimer's disease (AD) and Parkinson's disease (PD). Microglia are known for their immune functions and have multiple reactive phenotypes related to the types of stages involving neurodegenerative diseases. Depending on the state of activation of microglia in the CNS, it can be neuroprotective or neurotoxic. In this context, AD is a neurodegenerative and neuroinflammatory disease characterized by the deposition of beta-amyloid plaques, formation of fibrillar tangles of tau protein, and loss of neurons due to neurotoxic activation of microglia. However, PD is characterized by the loss of dopaminergic neurons in the substantia nigra and accumulation of alpha-synuclein in the cortical regions, spinal cord, and brain stem, which occurs by microglial activation, contributing to the neuroinflammatory process. In this aspect, the activation of microglia in both pathologies triggers high levels of inflammatory markers, such as interleukins, and causes the neuroinflammatory process of the diseases. Thus, physical exercise is pointed out as neuroprotective, as it can act to strengthen neurogenesis and reduce the inflammatory process. Therefore, the present review addresses the neuroprotective effect of microglia after different types of physical exercise protocols and evaluates the activity and effects of inflammatory and anti-inflammatory parameters and mechanisms of AD and PD. This review will discuss the anti-inflammatory effects of physical exercise through microglia activation with neuroprotective activity and the role of pro-and anti-inflammatory cytokines in AD and PD.

The roles of connectivity and neuronal phenotype in determining the pattern of α-synuclein pathology in Parkinson's disease

Parkinson's disease (PD) is the most common neurodegenerative movement disorder, and motor dysfunction has been attributed to loss of dopaminergic neurons. However, motor dysfunction is only one of many symptoms experienced by patients. A neuropathological hallmark of PD is intraneuronal protein aggregates called Lewy pathology (LP). Neuropathological staging studies have shown that dopaminergic neurons are only one of the many cell types prone to manifest LP. Progressive appearance of LP in multiple brain regions, as well as peripheral nerves, has led to the popular hypothesis that LP and misfolded forms of one of its major components - α-synuclein (aSYN) - can spread through synaptically connected circuits. However, not all brain regions or neurons within connected circuits develop LP, suggesting that cell autonomous factors modulate the development of pathology. Here, we review studies about how LP develops and progressively engages additional brain regions. We focus on how connectivity constrains progression and discuss cell autonomous factors that drive pathology development. We propose a mixed model of cell autonomous factors and trans-synaptic spread as mediators of pathology progression and put forward this model as a framework for future experiments exploring PD pathophysiology.

Exosomes in the Field of Neuroscience: A Scientometric Study and Visualization Analysis

Exosomes have received great attention for their diagnostic, therapeutic, and prognostic roles in the field of neuroscience over the past decade. This scientometric study aimed to quantitatively and qualitatively evaluate knowledge structure, hot topics, and research trends of studies about exosomes in the field of neuroscience using visualization tools. Web of Science Core collection databases were searched for relevant publications between 2005 and 2021. The Carrot2 online system, BICOMB, gCLUTO, and Ucinet software were utilized for key word analysis, and co-citations analyses were conducted in Citespace and VOSviewer. Altogether, 21 high-frequency key words were collected from 856 included articles, and 5 clusters were identified through biclustering analyses. The strategic diagram and social network analysis further determined research hotspots and trends. Co-citation analysis results revealed a few crucial works that contributed to the development of research on exosomes in the field of neuroscience. Moreover, the important sources that had contributed to the development of this field were identified. Our findings suggested that Alzheimer's disease-related research remained a hot topic in this field till now, and recent researchers had extended their scopes to more cognitive impairments. Importantly, researches related to exosomes in multiple sclerosis and Parkinson's disease were promising. While exosomes in acute central nervous system injury had not been sufficiently investigated, with continuous improvement in exosome-based delivery technology, this subject might make a breakthrough in terms of therapeutic innovations in the immediate future.

The role of Tumour Necrosis Factor in neuroinflammation associated with Parkinson's disease and targeted therapies

Neurodegenerative disorders Parkinson's disease is a progressive neurodegenerative disorder associated with neuroinflammatory responses that lead to the neurodegeneration of the dopaminergic neurons. These neuroinflammatory mechanisms involve various cytokines produced by the activated glial cells. Tumour Necrosis factor α (TNF α) is one of the major mediators of the neuroinflammation associated with neurodegeneration. TNF α has a dual role of neuroprotection and neurotoxicity in the brain. The effective pathways of TNF involve various signalling pathways transduced by the receptors TNFR1 and TNFR2. Effective therapeutic strategies have been produced targeting the neurotoxic behaviour of the Tumour Necrosis Factor and the associated neurodegeneration which includes the use of Dominant Negative Tumour Necrosis Factor (DN-TNF) inhibitors like XENP 345 and XPro®1595 and peroxisome proliferator receptor gamma (PPAR-γ) agonists.

Emerging Potential of Exosomal Non-coding RNA in Parkinson’s Disease: A Review

Exosomes are extracellular vesicles that are released by cells and circulate freely in body fluids. Under physiological and pathological conditions, they serve as cargo for various biological substances such as nucleotides (DNA, RNA, ncRNA), lipids, and proteins. Recently, exosomes have been revealed to have an important role in the pathophysiology of several neurodegenerative illnesses, including Parkinson’s disease (PD). When secreted from damaged neurons, these exosomes are enriched in non-coding RNAs (e.g., miRNAs, lncRNAs, and circRNAs) and display wide distribution characteristics in the brain and periphery, bridging the gap between normal neuronal function and disease pathology. However, the current status of ncRNAs carried in exosomes regulating neuroprotection and PD pathogenesis lacks a systematic summary. Therefore, this review discussed the significance of ncRNAs exosomes in maintaining the normal neuron function and their pathogenic role in PD progression. Additionally, we have emphasized the importance of ncRNAs exosomes as potential non-invasive diagnostic and screening agents for the early detection of PD. Moreover, bioengineered exosomes are proposed to be used as drug carriers for targeted delivery of RNA interference molecules across the blood-brain barrier without immune system interference. Overall, this review highlighted the diverse characteristics of ncRNA exosomes, which may aid researchers in characterizing future exosome-based biomarkers for early PD diagnosis and tailored PD medicines.

α-Synuclein in Parkinson's disease and advances in detection

Parkinson's disease (PD) is a threatening neurodegenerative disorder that seriously affects patients' life quality. Substantial evidence links the overexpression and abnormal aggregation of alpha-synuclein (α-Syn) to PD. α-Syn has been identified as a characteristic biomarker of PD, which indicates its great value of diagnosis and designing effective therapeutic strategy. This article systematically summarizes the pathogenic process of α-Syn based on recent researches, outlines and compares commonly used analysis and detection technologies of α-Syn. Specifically, the detection of α-Syn by new electrochemical, photochemical, and crystal biosensors is mainly examined. Furthermore, the speculation of future study orientation is discussed, which provides reference for the further research and application of α-Syn as biomarker.

Exosomes in Parkinson: Revisiting Their Pathologic Role and Potential Applications

Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized by bradykinesia, rigidity, and tremor. Considerable progress has been made to understand the exact mechanism leading to this disease. Most of what is known comes from the evidence of PD brains' autopsies showing a deposition of Lewy bodies-containing a protein called α-synuclein (α-syn)-as the pathological determinant of PD. α-syn predisposes neurons to neurotoxicity and cell death, while the other associated mechanisms are mitochondrial dysfunction and oxidative stress, which are underlying precursors to the death of dopaminergic neurons at the substantia nigra pars compacta leading to disease progression. Several mechanisms have been proposed to unravel the pathological cascade of these diseases; most of them share a particular similarity: cell-to-cell communication through exosomes (EXOs). EXOs are intracellular membrane-based vesicles with diverse compositions involved in biological and pathological processes, which their secretion is driven by the NLR family pyrin domain-containing three proteins (NLRP3) inflammasome. Toxic biological fibrils are transferred to recipient cells, and the disposal of damaged organelles through generating mitochondrial-derived vesicles are suggested mechanisms for developing PD. EXOs carry various biomarkers; thus, they are promising to diagnose different neurological disorders, including neurodegenerative diseases (NDDs). As nanovesicles, the applications of EXOs are not only restricted as diagnostics but also expanded to treat NDDs as therapeutic carriers and nano-scavengers. Herein, the aim is to highlight the potential incrimination of EXOs in the pathological cascade and progression of PD and their role as biomarkers and therapeutic carriers for diagnosing and treating this neuro-debilitating disorder.

CREB1K292 and HINFPK330 as Putative Common Therapeutic Targets in Alzheimer's and Parkinson's Disease

Integration of omics data and deciphering the mechanism of a biological regulatory network could be a promising approach to reveal the molecular mechanism involved in the progression of complex diseases, including Alzheimer's and Parkinson's. Despite having an overlapping mechanism in the etiology of Alzheimer's disease (AD) and Parkinson's disease (PD), the exact mechanism and signaling molecules behind them are still unknown. Further, the acetylation mechanism and histone deacetylase (HDAC) enzymes provide a positive direction toward studying the shared phenomenon between AD and PD pathogenesis. For instance, increased expression of HDACs causes a decrease in protein acetylation status, resulting in decreased cognitive and memory function. Herein, we employed an integrative approach to analyze the transcriptomics data that established a potential relationship between AD and PD. Data preprocessing and analysis of four publicly available microarray datasets revealed 10 HUB proteins, namely, CDC42, CD44, FGFR1, MYO5A, NUMA1, TUBB4B, ARHGEF9, USP5, INPP5D, and NUP93, that may be involved in the shared mechanism of AD and PD pathogenesis. Further, we identified the relationship between the HUB proteins and transcription factors that could be involved in the overlapping mechanism of AD and PD. CREB1 and HINFP were the crucial regulatory transcription factors that were involved in the AD and PD crosstalk. Further, lysine acetylation sites and HDAC enzyme prediction revealed the involvement of 15 and 27 potential lysine residues of CREB1 and HINFP, respectively. Our results highlighted the importance of HDAC1(K292) and HDAC6(K330) association with CREB1 and HINFP, respectively, in the AD and PD crosstalk. However, different datasets with a large number of samples and wet lab experimentation are required to validate and pinpoint the exact role of CREB1 and HINFP in the AD and PD crosstalk. It is also possible that the different datasets may or may not affect the results due to analysis parameters. In conclusion, our study potentially highlighted the crucial proteins, transcription factors, biological pathways, lysine residues, and HDAC enzymes shared between AD and PD at the molecular level. The findings can be used to study molecular studies to identify the possible relationship in the AD-PD crosstalk.

TRAP1 in Oxidative Stress and Neurodegeneration

Tumor necrosis factor receptor-associated protein 1 (TRAP1), also known as heat shock protein 75 (HSP75), is a member of the heat shock protein 90 (HSP90) chaperone family that resides mainly in the mitochondria. As a mitochondrial molecular chaperone, TRAP1 supports protein folding and contributes to the maintenance of mitochondrial integrity even under cellular stress. TRAP1 is a cellular regulator of mitochondrial bioenergetics, redox homeostasis, oxidative stress-induced cell death, apoptosis, and unfolded protein response (UPR) in the endoplasmic reticulum (ER). TRAP1 has attracted increasing interest as a therapeutical target, with a special focus on the design of TRAP1 specific inhibitors. Although TRAP1 was extensively studied in the oncology field, its role in central nervous system cells, under physiological and pathological conditions, remains largely unknown. In this review, we will start by summarizing the biology of TRAP1, including its structure and related pathways. Thereafter, we will continue by debating the role of TRAP1 in the maintenance of redox homeostasis and protection against oxidative stress and apoptosis. The role of TRAP1 in neurodegenerative disorders will also be discussed. Finally, we will review the potential of TRAP1 inhibitors as neuroprotective drugs.