CXCL12 is involved in α-synuclein-triggered neuroinflammation of Parkinson's disease

Modulating the biosynthesis and TLR4-interaction of lipopolysaccharide as an approach to counter gut dysbiosis and Parkinson's disease: role of phyto-compounds

The prevalence of the world's second leading neurodegenerative disorder Parkinson's disease (PD) is well known while its pathogenesis is still a topical issue to explore. Clinical and experimental reports suggest the prevalence of disturbed gut microflora in PD subjects, with an abundance of especially Gram-negative bacteria. The endotoxin lipopolysaccharide (LPS) released from the outer cell layer of these bacteria interacts with the toll-like receptor 4 (TLR4) present on the macrophages and it stimulates the downstream inflammatory cascade in both the gut and brain. Recent research also suggests a positive correlation between LPS, alpha-synuclein, and TLR4 levels, which indicates the contribution of a parallel LPS-alpha-synuclein-TLR4 axis in stimulating inflammation and neurodegeneration in the gut and brain, establishing a body-first type of PD. However, owing to the novelty of this paradigm, further investigation is mandatory. Modulating LPS biosynthesis and LPS-TLR4 interaction can ameliorate gut dysbiosis and PD. Several synthetic LpxC (UDP-3-O-(R-3-hydroxymyristoyl)-N-acetylglucosamine deacetylase; LPS-synthesizing enzyme) inhibitors and TLR4 antagonists are reported to show beneficial effects including neuroprotection in PD models, however, are not devoid of side effects. Plant-derived compounds have been long documented for their benefits as nutraceuticals and thus to search for effective, safer, and multitarget therapeutics, the present study focused on summarizing the evidence reporting the potential of phyto-compounds as LpxC inhibitors and TLR4 antagonists. Studies demonstrating the dual potential of phyto-compounds as the modulators of LpxC and TLR4 have not yet been reported. Also, very few preliminary studies have reported LpxC inhibition by phyto-compounds. Nevertheless, remarkable neuroprotection along with TLR4 antagonism has been shown by curcumin and juglanin in PD models. The present review thus provides a wide look at the research progressed to date in discovering phyto-compounds that can serve as LpxC inhibitors and TLR4 antagonists. The study further recommends the need for expanding the search for potential candidates that can render dual protection by inhibiting both the biosynthesis and TLR4 interaction of LPS. Such multitarget therapeutic intervention is believed to bring fruitful yields in countering gut dysbiosis, neuroinflammation, and dopaminergic neuron damage in PD patients through a single treatment paradigm.

Rapidly repeated visual stimulation induces long-term potentiation of VEPs and increased content of membrane AMPA and NMDA receptors in the V1 cortex of cats

Studies report that rapidly repeated sensory stimulation can evoke LTP-like improvement of neural response in the sensory cortex. Whether this neural response potentiation is similar to the classic LTP induced by presynaptic electrical stimulation remains unclear. This study examined the effects of repeated high-frequency (9 Hz) versus low-frequency (1 Hz) visual stimulation on visually-evoked field potentials (VEPs) and the membrane protein content of AMPA / NMDA receptors in the primary visual cortex (V1) of cats. The results showed that repeated high-frequency visual stimulation (HFS) caused a long-term improvement in peak-to-peak amplitude of V1-cortical VEPs in response to visual stimuli at HFS-stimulated orientation (SO: 90°) and non-stimulated orientation (NSO: 180°), but the effect exhibited variations depending on stimulus orientation: the amplitude increase of VEPs in response to visual stimuli at SO was larger, reached a maximum earlier and lasted longer than at NSO. By contrast, repeated low-frequency visual stimulation (LFS) had not significantly affected the amplitude of V1-cortical VEPs in response to visual stimuli at both SO and NSO. Furthermore, the membrane protein content of the key subunit GluA1 of AMPA receptors and main subunit NR1 of AMPA receptors in V1 cortex was significantly increased after HFS but not LFS when compared with that of control cats. Taken together, these results indicate that HFS can induce LTP-like improvement of VEPs and an increase in membrane protein of AMPA and NMDA receptors in the V1 cortex of cats, which is similar to but less specific to stimulus orientation than the classic LTP.

The regulating effect of curcumin on NF-κB pathway in neurodegenerative diseases: a review of the underlying mechanisms

Neurodegenerative diseases are part of the central nervous system (CNS) disorders that indicate their presence with neuronal loss, neuroinflammation, and increased oxidative stress. Several pathophysiological factors and biomarkers are involved in this inflammatory process causing these neurological disorders. The nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) is an inflammation element, which induced transcription and appears to be one of the important players in physiological procedures, especially nervous disorders. NF-κB can impact upon series of intracellular actions and induce or inhibit many inflammation-related pathways. Multiple reports have focused on the modification of NF-κB activity, controlling its expression, translocation, and signaling pathway in neurodegenerative disorders and injuries like Alzheimer's disease (AD), spinal cord injuries (SCI), and Parkinson's disease (PD). Curcumin has been noted to be a popular anti-oxidant and anti-inflammatory substance and is the foremost natural compound produced by turmeric. According to various studies, when playing an anti-inflammatory role, it interacts with several modulating proteins of long-standing disease signaling pathways and has an unprovocative consequence on pro-inflammatory cytokines. This review article determined to figure out curcumin's role in limiting the promotion of neurodegenerative disease via influencing the NF-κB signaling route. Preclinical studies were gathered from plenty of scientific platforms including PubMed, Scopus, Cochrane, and Google Scholar to evaluate this hypothesis. Extracted findings from the literature review explained the repressing impact of Curcumin on the NF-κB signaling pathway and, occasionally down-regulating the cytokine expression. Yet, there is an essential need for further analysis and specific clinical experiments to fully understand this subject.

CXCR4/CXCL12 axis: "old" pathway as "novel" target for anti-inflammatory drug discovery

Inflammation is the body's defense response to exogenous or endogenous stimuli, involving complex regulatory mechanisms. Discovering anti-inflammatory drugs with both effectiveness and long-term use safety is still the direction of researchers' efforts. The inflammatory pathway was initially identified to be involved in tumor metastasis and HIV infection. However, research in recent years has proved that the CXC chemokine receptor type 4 (CXCR4)/CXC motif chemokine ligand 12 (CXCL12) axis plays a critical role in the upstream of the inflammatory pathway due to its chemotaxis to inflammatory cells. Blocking the chemotaxis of inflammatory cells by CXCL12 at the inflammatory site may block and alleviate the inflammatory response. Therefore, developing CXCR4 antagonists has become a novel strategy for anti-inflammatory therapy. This review aimed to systematically summarize and analyze the mechanisms of action of the CXCR4/CXCL12 axis in more than 20 inflammatory diseases, highlighting its crucial role in inflammation. Additionally, the anti-inflammatory activities of CXCR4 antagonists were discussed. The findings might help generate new perspectives for developing anti-inflammatory drugs targeting the CXCR4/CXCL12 axis.

Novel Findings on CCR1 Receptor in CNS Disorders: A Pathogenic Marker Useful in Controlling Neuroimmune and Neuroinflammatory Mechanisms in Parkinson's Disease

Parkinson's disease (PD) is recognized as the second most common neurodegenerative disease worldwide. Even if PD etiopathogenesis is not yet fully understood, in recent years, it has been advanced that a chronic state of inflammation could play a decisive role in the development of this pathology, establishing the close link between PD and neuroinflammation. In the broad panorama of inflammation and its several signaling pathways, the C-C chemokine receptor type 1 (CCR1) could play a key pathogenic role in PD progression, and could constitute a valuable target for the development of innovative anti-PD therapies. In this study, we probed the neuroprotective properties of the CCR1 antagonist BX471 compound in a mouse model of MPTP-induced nigrostriatal degeneration. BX471 treatments were performed intraperitoneally at a dose of 3 mg/kg, 10 mg/kg, and 30 mg/kg, starting 24 h after the last injection of MPTP and continuing for 7 days. From our data, BX471 treatment strongly blocked CCR1 and, as a result, decreased PD features, also reducing the neuroinflammatory state by regulating glial activation, NF-κB pathway, proinflammatory enzymes, and cytokines overexpression. Moreover, we showed that BX471's antagonistic action on CCR1 reduced the infiltration of immune cells, including mast cells and lymphocyte T activation. In addition, biochemical analyses carried out on serum revealed a considerable increase in circulating levels of CCR1 following MPTP-induced PD. In light of these findings, CCR1 could represent a useful pathological marker of PD, and its targeting could be a worthy candidate for the future development of new immunotherapies against PD.

Parkinson's Disease and MicroRNAs: A Duel Between Inhibition and Stimulation of Apoptosis in Neuronal Cells

Parkinson's disease (PD) is one of the most prevalent diseases of central nervous system that is caused by degeneration of the substantia nigra's dopamine-producing neurons through apoptosis. Apoptosis is regulated by initiators' and executioners' caspases both in intrinsic and extrinsic pathways, further resulting in neuronal damage. In that context, targeting apoptosis appears as a promising therapeutic approach for treating neurodegenerative diseases. Non-coding RNAs-more especially, microRNAs, or miRNAs-are a promising target for the therapy of neurodegenerative diseases because they are essential for a number of cellular processes, including signaling, apoptosis, cell proliferation, and gene regulation. It is estimated that a substantial portion of coding genes (more than 60%) are regulated by miRNAs. These small regulatory molecules can have wide-reaching consequences on cellular processes like apoptosis, both in terms of intrinsic and extrinsic pathways. Furthermore, it was recommended that a disruption in miRNA expression levels could also result in perturbation of typical apoptosis pathways, which may be a factor in certain diseases like PD. The latest research on miRNAs and their impact on neural cell injury in PD models by regulating the apoptosis pathway is summarized in this review article. Furthermore, the importance of lncRNA/circRNA-miRNA-mRNA network for regulating apoptosis pathways in PD models and treatment is explored. These results can be utilized for developing new strategies in PD treatment.

TLR4/Rac1/NLRP3 Pathway Mediates Amyloid-β-Induced Neuroinflammation in Alzheimer's Disease

Background

Neuroinflammation plays a crucial part in the initial onset and progression of Alzheimer's disease (AD). NLRP3 inflammasome was demonstrated to get involved in amyloid-β (Aβ)-induced neuroinflammation. However, the mechanism of Aβ-triggered activation of NLRP3 inflammasome remains poorly understood.

Objective

Based on our previous data, the study aimed to identify the downstream signals that bridge the activation of TLR4 and NLRP3 inflammasome associated with Aβ.

Methods

BV-2 cells were transfected with TLR4siRNA or pretreated with a CLI-095 or NSC23766, followed by Aβ1-42 treatment. APP/PS1 mice were injected intraperitoneally with CLI-095 or NSC23766. NLRP3 inflammasome and microglia activation was detected with immunostaining and western blot. G-LISA and Rac1 pull-down activation test were performed to investigate the activation of Rac1. Real-time PCR and ELISA were used to detect the inflammatory cytokines. Aβ plaques were assessed by western blotting and immunofluorescence staining. Morris water maze test was conducted to determine the spatial memory in mice.

Results

Rac1 and NLRP3 inflammasome were activated by Aβ in both in vitro and in vivo experiments. Inhibition of TLR4 reduced the activity of Rac1 and NLRP3 inflammasome induced by Aβ1-42. Furthermore, inhibition of Rac1 blocked NLRP3 inflammasome activation mediated by TLR4. Blocking the pathway by CLI095 or NSC23766 suppressed Aβ1-42-triggered activation of microglia, reduced the expression of pro-inflammatory mediators and ameliorated the cognition deficits in APP/PS1 mice.

Conclusions

Our study demonstrated that TLR4/Rac1/NLRP3 pathway mediated Aβ-induced neuroinflammation, which unveiled a novel pathway and key contributors underlying the pathogenic mechanism of Aβ.

Collaborative plasma biomarkers for Parkinson disease development and progression: A cross-sectional and longitudinal study

BACKGROUND AND PURPOSE

Relying on a single biomarker for early diagnosis of Parkinson disease (PD) may not yield accurate results. We aimed to assess the combined diagnostic value of multiple biomarkers, including plasma CCL2, plasma CXCL12, and plasma neuronal exosomal α-synuclein (α-syn) for early stage PD diagnosis and their predictive value in PD progression.

METHODS

This study included both cross-sectional and longitudinal designs. The CCL2, CXCL12, and neuronal exosomal α-syn levels were analyzed in 50 healthy controls (HCs) and 50 early stage PD patients. Then, a prospective follow-up of 30 early stage PD patients was performed.

RESULTS

In early stage PD, we observed a significant increase in CCL2, CXCL12, and plasma neuronal exosomal α-syn compared to HCs (p < 0.05). Utilizing a combined diagnostic approach of CCL2, CXCL12, and α-syn significantly improved the area under the curve (AUC = 0.89, p < 0.001). Spearman correlation analysis revealed that CCL2 levels were correlated with PD clinical stage and autonomic symptoms (p < 0.05). CXCL12 levels were associated with nonmotor symptoms (p < 0.05). Plasma neuronal exosomal α-syn levels were connected to the clinical stage, motor symptoms, and nonmotor symptoms in early stage PD (p < 0.01). In the longitudinal cohort, the Cox regression analysis showed that high CCL2 levels were associated with motor progression after a mean follow-up of 24 months.

CONCLUSIONS

Our study suggested that the combined measurement of plasma CCL2, CXCL12, and neuronal exosomal α-syn can improve early stage PD diagnosis, and CCL2 may serve as a prognostic marker for PD progression.

The Involvement of Neuroinflammation in the Onset and Progression of Parkinson's Disease

Parkinson's disease is a neurodegenerative disease exhibiting the fastest growth in incidence in recent years. As with most neurodegenerative diseases, the pathophysiology is incompletely elucidated, but compelling evidence implicates inflammation, both in the central nervous system and in the periphery, in the initiation and progression of the disease, although it is not yet clear what triggers this inflammatory response and where it begins. Gut dysbiosis seems to be a likely candidate for the initiation of the systemic inflammation. The therapies in current use provide only symptomatic relief, but do not interfere with the disease progression. Nonetheless, animal models have shown promising results with therapies that target various vicious neuroinflammatory cascades. Translating these therapeutic strategies into clinical trials is still in its infancy, and a series of issues, such as the exact timing, identifying biomarkers able to identify Parkinson's disease in early and pre-symptomatic stages, or the proper indications of genetic testing in the population at large, will need to be settled in future guidelines.

Advanced human iPSC-based preclinical model for Parkinson's disease with optogenetic alpha-synuclein aggregation

Human induced pluripotent stem cells (hiPSCs) offer advantages for disease modeling and drug discovery. However, recreating innate cellular pathologies, particularly in late-onset neurodegenerative diseases with accumulated protein aggregates including Parkinson's disease (PD), has been challenging. To overcome this barrier, we developed an optogenetics-assisted α-synuclein (α-syn) aggregation induction system (OASIS) that rapidly induces α-syn aggregates and toxicity in PD hiPSC-midbrain dopaminergic neurons and midbrain organoids. Our OASIS-based primary compound screening with SH-SY5Y cells identified 5 candidates that were secondarily validated with OASIS PD hiPSC-midbrain dopaminergic neurons and midbrain organoids, leading us to finally select BAG956. Furthermore, BAG956 significantly reverses characteristic PD phenotypes in α-syn preformed fibril models in vitro and in vivo by promoting autophagic clearance of pathological α-syn aggregates. Following the FDA Modernization Act 2.0's emphasis on alternative non-animal testing methods, our OASIS can serve as an animal-free preclinical test model (newly termed "nonclinical test") for the synucleinopathy drug development.

Preliminary study to identify CXCR4 inhibitors as potential therapeutic agents for Alzheimer's and Parkinson's diseases

Neurodegenerative disorders (NDDs) are known to exhibit genetic overlap and shared pathophysiology. This study aims to find the shared genetic architecture of Alzheimer's disease (AD) and Parkinson's disease (PD), two major age-related progressive neurodegenerative disorders. The gene expression profiles of GSE67333 (containing samples from AD patients) and GSE114517 (containing samples from PD patients) were retrieved from the Gene Expression Omnibus (GEO) functional genomics database managed by the National Center for Biotechnology Information. The web application GREIN (GEO RNA-seq Experiments Interactive Navigator) was used to identify differentially expressed genes (DEGs). A total of 617 DEGs (239 upregulated and 379 downregulated) were identified from the GSE67333 dataset. Likewise, 723 DEGs (378 upregulated and 344 downregulated) were identified from the GSE114517 dataset. The protein-protein interaction networks of the DEGs were constructed, and the top 50 hub genes were identified from the network of the respective dataset. Of the four common hub genes between two datasets, C-X-C chemokine receptor type 4 (CXCR4) was selected due to its gene expression signature profile and the same direction of differential expression between the two datasets. Mavorixafor was chosen as the reference drug due to its known inhibitory activity against CXCR4 and its ability to cross the blood-brain barrier. Molecular docking and molecular dynamics simulation of 51 molecules having structural similarity with Mavorixafor was performed to find two novel molecules, ZINC49067615 and ZINC103242147. This preliminary study might help predict molecular targets and diagnostic markers for treating Alzheimer's and Parkinson's diseases. Insight Box Our research substantiates the therapeutic relevance of CXCR4 inhibitors for the treatment of Alzheimer's and Parkinson's diseases. We would like to disclose the following insights about this study. We found common signatures between Alzheimer's and Parkinson's diseases at transcriptional levels by analyzing mRNA sequencing data. These signatures were used to identify putative therapeutic agents for these diseases through computational analysis. Thus, we proposed two novel compounds, ZINC49067615 and ZINC103242147, that were stable, showed a strong affinity with CXCR4, and exhibited good pharmacokinetic properties. The interaction of these compounds with major residues of CXCR4 has also been described.

Rac1: A Regulator of Cell Migration and A Potential Target for Cancer Therapy

Cell migration is crucial for physiological and pathological processes such as morphogenesis, wound repair, immune response and cancer invasion/metastasis. There are many factors affecting cell migration, and the regulatory mechanisms are complex. Rac1 is a GTP-binding protein with small molecular weight belonging to the Rac subfamily of the Rho GTPase family. As a key molecule in regulating cell migration, Rac1 participates in signal transduction from the external cell to the actin cytoskeleton and promotes the establishment of cell polarity which plays an important role in cancer cell invasion/metastasis. In this review, we firstly introduce the molecular structure and activity regulation of Rac1, and then summarize the role of Rac1 in cancer invasion/metastasis and other physiological processes. We also discuss the regulatory mechanisms of Rac1 in cell migration and highlight it as a potential target in cancer therapy. Finally, the current state as well as the future challenges in this area are considered. Understanding the role and the regulatory mechanism of Rac1 in cell migration can provide fundamental insights into Rac1-related cancer progression and further help us to develop novel intervention strategies for cancer therapy in clinic.

Non-Motor Symptoms of Parkinson's Disease: The Neurobiology of Early Psychiatric and Cognitive Dysfunction

Parkinson's disease (PD) is a progressive neurodegenerative disorder that has been recognized for over 200 years by its clinically dominant motor system impairment. There are prominent non-motor symptoms as well, and among these, psychiatric symptoms of depression and anxiety and cognitive impairment are common and can appear earlier than motor symptoms. Although the neurobiology underlying these particular PD-associated non-motor symptoms is not completely understood, the identification of PARK genes that contribute to hereditary and sporadic PD has enabled genetic models in animals that, in turn, have fostered ever deepening analyses of cells, synapses, circuits, and behaviors relevant to non-motor psychiatric and cognitive symptoms of human PD. Moreover, while it has long been recognized that inflammation is a prominent component of PD, recent studies demonstrate that brain-immune signaling crosstalk has significant modulatory effects on brain cell and synaptic function in the context of psychiatric symptoms. This review provides a focused update on such progress in understanding the neurobiology of PD-related non-motor psychiatric and cognitive symptoms.

CXCR4 knockout induces neuropathological changes in the MPTP-lesioned model of Parkinson's disease

C-X-C chemokine receptor type 4 (CXCR4) is highly expressed in Parkinson's disease (PD) mice's brains and is related to astrocyte signaling and microglial activation. This makes CXCR4 related to neuroinflammation and also makes CXCR4 considered to be the PD development mechanism and possible therapeutic targets. Therefore, it is worth studying the effect of CXCR4 on neuropathological changes and its potential therapeutic value for PD. This study aimed to investigate the effect of CXCR4 knockout on neuropathological changes in the mouse model of PD and its mechanism. In this study, CXCR4-WT and CXCR4^+/- C57BL mice were used to make Parkinson's model. Behavioral experiments, dopaminergic neuron markers, neuroinflammation, and blood-brain barrier damage were detected to verify the effect of CXCR4 knockout on neuropathological changes. CXCR4 knockout improved the behavioral results and tyrosine hydroxylase (TH) expression of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-lesioned mice. In the substantia nigra (SN) area of the brain of PD mouse model, the number of Iba1-positive (p = 0.0004) and GFAP-positive cells (p = 0.0349) was significantly lower in CXCR4 knockout group than CXCR4-WT group. CXCR4 knockout reduced MPTP-induced infiltration of peripheral immune cells and the expression of pro-inflammatory cytokines. CXCR4 knockout also protected blood-brain barrier (BBB) from MPTP-induced damage. In conclusion, CXCR4 knockout inhibits the degeneration of dopamine neurons, microglial and astrocyte activation, neuroinflammation, and BBB damages in the MPTP-lesioned PD mice.

The roles of chemokines following intracerebral hemorrhage in animal models and humans

Intracerebral hemorrhage (ICH) is one common yet devastating stroke subtype, imposing considerable burdens on families and society. Current guidelines are limited to symptomatic treatments after ICH, and the death rate remains significant in the acute stage. Thus, it is crucial to promote research to develop new targets on brain injury after ICH. In response to hematoma formation, amounts of chemokines are released in the brain, triggering the infiltration of resident immune cells in the brain and the chemotaxis of peripheral immune cells via the broken blood-brain barrier. During the past decades, mounting studies have focused on the roles of chemokines and their receptors in ICH injury. This review summarizes the latest advances in the study of chemokine functions in the ICH. First, we provide an overview of ICH epidemiology and underlying injury mechanisms in the pathogenesis of ICH. Second, we introduce the biology of chemokines and their receptors in brief. Third, we outline the roles of chemokines in ICH according to subgroups, including CCL2, CCL3, CCL5, CCL12, CCL17, CXCL8, CXCL12, and CX3CL1. Finally, we summarize current drug usage targeting chemokines in ICH and other cardio-cerebrovascular diseases. This review discusses the expressions of these chemokines and receptors under normal or hemorrhagic conditions and cell-specific sources. Above all, we highlight the related data of these chemokines in the progression and outcomes of the ICH disease in preclinical and clinical studies and point to therapeutic opportunities targeting chemokines productions and interactions in treating ICH, such as accelerating hematoma absorption and alleviating brain edema.

HMGB1 is a Potential and Challenging Therapeutic Target for Parkinson's Disease

Parkinson's disease (PD) is one of the most common degenerative diseases of the human nervous system and has a wide range of serious impacts on human health and quality of life. Recently, research targeting high mobility group box 1 (HMGB1) in PD has emerged, and a variety of laboratory methods for inhibiting HMGB1 have achieved good results to a certain extent. However, given that HMGB1 undergoes a variety of intracellular modifications and three different forms of extracellular redox, the possible roles of these forms in PD are likely to be different. General inhibition of all forms of HMGB1 is obviously not ideal and has become one of the biggest obstacles in the clinical application of targeting HMGB1. In this review, pure mechanistic research of HMGB1 and in vivo research targeting HMGB1 were combined, the effects of HMGB1 on neurons and immune cell responses in PD are discussed in detail, and the problems that need to be focused on in the future are addressed.

How Toll-like receptors influence Parkinson's disease in the microbiome-gut-brain axis

Recently, a large number of experimenters have found that the pathogenesis of Parkinson's disease may be related to the gut microbiome and proposed the microbiome-gut-brain axis. Studies have shown that Toll-like receptors, especially Toll-like receptor 2 (TLR2) and Toll-like receptor 4 (TLR4), are key mediators of gut homeostasis. In addition to their established role in innate immunity throughout the body, research is increasingly showing that the Toll-like receptor 2 and Toll-like receptor 4 signaling pathways shape the development and function of the gut and enteric nervous system. Notably, Toll-like receptor 2 and Toll-like receptor 4 are dysregulated in Parkinson's disease patients and may therefore be identified as the core of early gut dysfunction in Parkinson's disease. To better understand the contribution of Toll-like receptor 2 and Toll-like receptor 4 dysfunction in the gut to early α-synuclein aggregation, we discussed the structural function of Toll-like receptor 2 and Toll-like receptor 4 and signal transduction of Toll-like receptor 2 and Toll-like receptor 4 in Parkinson's disease by reviewing clinical, animal models, and in vitro studies. We also present a conceptual model of the pathogenesis of Parkinson's disease, in which microbial dysbiosis alters the gut barrier as well as the Toll-like receptor 2 and Toll-like receptor 4 signaling pathways, ultimately leading to a positive feedback loop for chronic gut dysfunction, promoting α-synuclein aggregation in the gut and vagus nerve.

Src family kinases (SFKs): critical regulators of microglial homeostatic functions and neurodegeneration in Parkinson's and Alzheimer's diseases

c-Src was the first protein kinase to be described as capable of phosphorylating tyrosine residues. Subsequent identification of other tyrosine-phosphorylating protein kinases with a similar structure to c-Src gave rise to the concept of Src family kinases (SFKs). Microglia are the resident innate immune cell population of the CNS. Under physiological conditions, microglia actively participate in brain tissue homeostasis, continuously patrolling the neuronal parenchyma and exerting neuroprotective actions. Activation of pathogen-associated molecular pattern (PAMP) and damage-associated molecular pattern (DAMP) receptors induces microglial proliferation, migration toward pathological foci, phagocytosis, and changes in gene expression, concurrent with the secretion of cytokines, chemokines, and growth factors. A significant body of literature shows that SFK stimulation positively associates with microglial activation and neuropathological conditions, including Alzheimer's and Parkinson's diseases. Here, we review essential microglial homeostatic functions regulated by SFKs, including phagocytosis, environmental sensing, and secretion of inflammatory mediators. In addition, we discuss the potential of SFK modulation for microglial homeostasis in Parkinson's and Alzheimer's diseases.

The CXCL12/CXCR4/ACKR3 Response Axis in Chronic Neurodegenerative Disorders of the Central Nervous System: Therapeutic Target and Biomarker

There has been an increase in the incidence of chronic neurodegenerative disorders of the central nervous system, including Alzheimer's and Parkinson's diseases, over the recent years mostly due to the rise in the number of elderly individuals. In addition, various neurodegenerative disorders are related to imbalances in the CXCL12/CXCR4/ACKR3 response axis. Notably, the CXC Chemokine Ligand 12 (CXCL12) is essential for the development of the central nervous system. Moreover, the expression and distribution of CXCL12 and its receptors are associated with the aggravation or alleviation of symptoms of neurodegenerative disorders. Therefore, the current review sought to highlight the specific functions of CXCL12 and its receptors in various neurodegenerative disorders, in order to provide new insights for future research.

Potential neurotoxic activity of diverse molecules released by astrocytes

Astrocytes are the main support cells of the central nervous system. They also participate in neuroimmune reactions. In response to pathological and immune stimuli, astrocytes transform to reactive states characterized by increased release of inflammatory mediators. Some of these molecules are neuroprotective and inflammation resolving while others, including reactive oxygen species (ROS), nitric oxide (NO), matrix metalloproteinase (MMP)- 9, L-glutamate, and tumor necrosis factor α (TNF), are well-established toxins known to cause damage to surrounding cells and tissues. We hypothesized that similar to microglia, the brain immune cells, reactive astrocytes can release a broader set of diverse molecules that are potentially neurotoxic. A literature search was conducted to identify such molecules using the following two criteria: 1) evidence of their expression and secretion by astrocytes and 2) direct neurotoxic action. This review describes 14 structurally diverse molecules as less-established astrocyte neurotoxins, including C-X-C motif chemokine ligand (CXCL)10, CXCL12/CXCL12(5-67), FS-7-associated surface antigen ligand (FasL), macrophage inflammatory protein (MIP)- 2α, TNF-related apoptosis inducing ligand (TRAIL), pro-nerve growth factor (proNGF), pro-brain-derived neurotrophic factor (proBDNF), chondroitin sulfate proteoglycans (CSPGs), cathepsin (Cat)B, group IIA secretory phospholipase A₂ (sPLA₂-IIA), amyloid beta peptides (Aβ), high mobility group box (HMGB)1, ceramides, and lipocalin (LCN)2. For some of these molecules, further studies are required to establish either their direct neurotoxic effects or the full spectrum of stimuli that induce their release by astrocytes. Only limited studies with human-derived astrocytes and neurons are available for most of these potential neurotoxins, which is a knowledge gap that should be addressed in the future. We also summarize available evidence of the role these molecules play in select neuropathologies where reactive astrocytes are a key feature. A comprehensive understanding of the full spectrum of neurotoxins released by reactive astrocytes is key to understanding neuroinflammatory diseases characterized by the adverse activation of these cells and may guide the development of novel treatment strategies.

Potential Molecular Mechanism of Guishao Pingchan Recipe in the Treatment of Parkinson’s Disease Based on Network Pharmacology and Molecular Docking

Objective: To investigate the potential mechanism of Guishao Pingchan Recipe (GPR) against Parkinson's disease (PD) based on network pharmacology and molecular docking. Methods: The main components of GPR were collected based on TCMSP database, Batman-TCM database, Chinese Pharmacopoeia, and Literatures. The potential therapeutic targets of PD were predicted by Drug Bank Database and Gene Cards database. Cytoscape 3.8.2 software was used to construct herb–component–target network. Then, String database was used to construct a PPI network, and DAVID database was used for gene ontology (GO) enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway annotation of targets function. Core components of GPR and hub targets were imported into AutoDock Vina for molecular docking verification and results were visualized by Pymol. Results: 13 candidate components were selected and 288 corresponding targets of GPR for treating PD were obtained. The GO enrichment analysis mainly involved 135 cell components, 187 molecular functions, and 1753 biological processes. Moreover, KEGG pathway enrichment analysis mainly involved 200 signaling pathways. Molecular docking simulation indicated a good binding ability of components and targets. Conclusion: Based on network pharmacology and molecular docking, we found that sitosterol, 4-Cholesten-3-one and stigmasterol in GPR could combine with MAPK3, APP, VEGFA, and CXCR4 and involved in the cAMP, PI3K/Akt, Rap1 signaling pathways. It is suggested that GPR may have therapeutic effects on PD through multi-component, multi-target, and multi-pathway and predict the relevant mechanism of the anti-PD effect of GPR.

Pre-clinical Studies Identifying Molecular Pathways of Neuroinflammation in Parkinson's Disease: A Systematic Review

Parkinson's disease (PD), the second most common neurodegenerative disorder, is characterized by neuroinflammation, formation of Lewy bodies, and progressive loss of dopaminergic neurons in the substantia nigra of the brain. In this review, we summarize evidence obtained by animal studies demonstrating neuroinflammation as one of the central pathogenetic mechanisms of PD. We also focus on the protein factors that initiate the development of PD and other neurodegenerative diseases. Our targeted literature search identified 40 pre-clinical in vivo and in vitro studies written in English. Nuclear factor kappa B (NF-kB) pathway is demonstrated as a common mechanism engaged by neurotoxins such as 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and 6-hydroxydopamine (6-OHDA), as well as the bacterial lipopolysaccharide (LPS). The α-synuclein protein, which plays a prominent role in PD neuropathology, may also contribute to neuroinflammation by activating mast cells. Meanwhile, 6-OHDA models of PD identify microsomal prostaglandin E synthase-1 (mPGES-1) as one of the contributors to neuroinflammatory processes in this model. Immune responses are used by the central nervous system to fight and remove pathogens; however, hyperactivated and prolonged immune responses can lead to a harmful neuroinflammatory state, which is one of the key mechanisms in the pathogenesis of PD.

Altered hydroxymethylome in the substantia nigra of Parkinson's disease

Parkinson's disease (PD) is the second most common neurodegenerative disorder, and aging and genetic and environmental exposure can contribute to its pathogenesis. DNA methylation has been suggested to play a pivotal role in neurodevelopment and neurodegenerative diseases. 5-hydroxymethylcytosine (5hmC) is generated through 5-methylcytosine (5mC) oxidization by ten-eleven translocation proteins and is particularly enriched in the brain. Although 5hmC has been linked to multiple neurological disorders, little is known about 5hmC alterations in the substantia nigra of patients with PD. To determine the specific alterations in DNA methylation and hydroxymethylation in PD brain samples, we examined the genome-wide profiles of 5mC and 5hmC in the substantia nigra of patients with PD and Alzheimer's disease (ad). We identified 4119 differentially hydroxymethylated regions (DhMRs) and no differentially methylated regions (DMRs) in the postmortem brains of patients with PD compared with those of controls. These DhMRs were PD-specific when compared with the results of AD. Gene ontology analysis revealed that several signaling pathways, such as neurogenesis and neuronal differentiation, were significantly enriched in PD DhMRs. KEGG enrichment analysis revealed substantial alterations in multiple signaling pathways, including phospholipase D (PLD), cAMP and Rap1. In addition, using a PD Drosophila model, we found that one of the 5hmC-modulated genes, PLD1, modulated α-synuclein toxicity. Our analysis suggested that 5hmC may act as an independent epigenetic marker and contribute to the pathogenesis of PD.

Parkinson's disease peripheral immune biomarker profile: a multicentre, cross-sectional and longitudinal study

BACKGROUND

Inflammations play crucial role in the pathogenesis of Parkinson's disease (PD), however, their possible value in the diagnosis or tracking of the progress of PD is still limited, because of discordant results in the literature and a lack of information regarding its reproducibility. Thus, overall longitudinal and cross-sectional studies are needed. This multicentre study was designed to investigate the association between multiple peripheral immune biomarkers and the development and progression of PD.

METHODS

This was a longitudinal and multicentre study. First, we measured the levels of five typical cytokines and five focused chemokines in 76 PD patients and 76 healthy controls (HCs) in a discovery cohort. Then, a validation cohort of 80 PD and 80 HC participants was recruited from four multicentre locations. In addition, a prospective follow-up of early-stage PD patients was performed with significant biomarkers. Finally, we performed further verification in an exploratory set of patients with idiopathic REM sleep behaviour disorder (iRBD).

RESULTS

In the discovery set, CXCL12, CX3CL1 and IL-8 levels were significantly higher in PD patients than in HCs (p < 0.05). The receiver-operating characteristic (ROC) curve for a combination of these three biomarkers produced a high area under the curve (AUC) of 0.89 (p < 0.001). Moreover, four biomarkers (the previous three and CCL15) were significantly associated with PD in the discovery and validation cohorts. Furthermore, in the prospective follow-up cohort, CX3CL1 levels were associated with motor progression after a mean interval of 43 months. In addition, CX3CL1 and IL-8 levels were higher in iRBD patients than in HCs.

CONCLUSION

We showed a correlation between a profile of four peripheral immune biomarkers and PD development and progression. Our findings may provide a basis whereby PD patients with abnormal inflammatory profiles can be identified and receive timely therapeutic interventions.

SUN11602, a bFGF mimetic, modulated neuroinflammation, apoptosis and calcium-binding proteins in an in vivo model of MPTP-induced nigrostriatal degeneration

Background

Parkinson’s disease (PD) is the second most frequent neurodegenerative disease. PD etiopathogenesis is multifactorial and not yet fully known, however, the scientific world advised the establishment of neuroinflammation among the possible risk factors. In this field, basic fibroblast growth factor/fibroblast growth factor receptor-1 (bFGF/FGFR1) could be a promising way to treat CNS-mediated inflammation; unfortunately, the use of bFGF as therapeutic agent is limited by its side effects. The novel synthetic compound SUN11602 exhibited neuroprotective activities like bFGF. With this perspective, this study aimed to evaluate the effect of SUN11602 administration in a murine model of MPTP-induced dopaminergic degeneration.

Methods

Specifically, nigrostriatal degeneration was induced by intraperitoneal injection of MPTP (80 mg/kg). SUN11602 (1 mg/kg, 2.5 mg/kg, and 5 mg/kg) was administered daily by oral gavage starting from 24 h after the first administration of MPTP. Mice were killed 7 days after MPTP induction.

Results

The results obtained showed that SUN11602 administration significantly reduced the alteration of PD hallmarks, attenuating the neuroinflammatory state via modulation of glial activation, NF-κB pathway, and cytokine overexpression. Furthermore, we demonstrated that SUN11602 treatment rebalanced Ca²⁺ overload in neurons by regulating Ca²⁺-binding proteins while inhibiting the apoptotic cascade.

Conclusion

Therefore, in the light of these findings, SUN11602 could be considered a valuable pharmacological strategy for PD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02457-3.

Neuroglial Senescence, α-Synucleinopathy, and the Therapeutic Potential of Senolytics in Parkinson’s Disease

Parkinson’s disease (PD) is the most common movement disorder and the second most prevalent neurodegenerative disease after Alzheimer’s disease. Despite decades of research, there is still no cure for PD and the complicated intricacies of the pathology are still being worked out. Much of the research on PD has focused on neurons, since the disease is characterized by neurodegeneration. However, neuroglia has become recognized as key players in the health and disease of the central nervous system. This review provides a current perspective on the interactive roles that α-synuclein and neuroglial senescence have in PD. The self-amplifying and cyclical nature of oxidative stress, neuroinflammation, α-synucleinopathy, neuroglial senescence, neuroglial chronic activation and neurodegeneration will be discussed. Finally, the compelling role that senolytics could play as a therapeutic avenue for PD is explored and encouraged.

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.

The neuroinflammatory role of glucocerebrosidase in Parkinson's disease

The lysosomal enzyme glucocerebrosidase (GCase), encoded by the GBA1 gene, is a membrane-associated protein catalyzing the cleavage of glucosylceramide (GlcCer) and glucosylsphingosine (GlcSph). Homologous GBA1 mutations cause Gaucher disease (GD) and heterologous mutations cause Parkinson's disease (PD). Importantly, heterologous GBA1 mutations are recognized as the second risk factor of PD. The pathological features of PD are Lewy neurites (LNs) and Lewy bodies (LBs) composed of pathological α-synuclein. Oxidative stress, inflammatory response, autophagic impairment, and α-synuclein accumulation play critical roles in PD pathogenic cascades, but the pathogenesis of PD has not yet been fully elucidated. What's more, PD treatment drugs can only relieve symptoms to a certain extent, but cannot alleviate neurodegenerative progression. Therefore, it's urgent to explore new targets that can alleviate the neurodegenerative process. Deficient GCase can cause lysosomal dysfunction, obstructing the metabolism of α-synuclein. Meanwhile, GCase dysfunction causes accumulation of its substrates, leading to lipid metabolism disorders. Subsequently, astrocytes and microglia are activated, releasing amounts of pro-inflammatory mediators and causing extensive neuroinflammation. All these cascades can induce neuron damage and death, eventually promoting PD pathology. This review aims to summarize these points and the potential of GCase as an original target to provide some ideas for elucidating the pathogenesis of PD.

Role of G Protein-Coupled Receptors in Microglial Activation: Implication in Parkinson's Disease

Parkinson’s disease (PD) is one of the prevalent neurodegenerative diseases associated with preferential loss of dopaminergic (DA) neurons in the substantia nigra compacta (SNc) and accumulation of α-synuclein in DA neurons. Even though the precise pathogenesis of PD is not clear, a large number of studies have shown that microglia-mediated neuroinflammation plays a vital role in the process of PD development. G protein-coupled receptors (GPCRs) are widely expressed in microglia and several of them act as regulators of microglial activation upon corresponding ligands stimulations. Upon α-synuclein insults, microglia would become excessively activated through some innate immune receptors. Presently, as lack of ideal drugs for treating PD, certain GPCR which is highly expressed in microglia of PD brain and mediates neuroinflammation effectively could be a prospective source for PD therapeutic intervention. Here, six kinds of GPCRs and two types of innate immune receptors were introduced, containing adenosine receptors, purinergic receptors, metabotropic glutamate receptors, adrenergic receptors, cannabinoid receptors, and melatonin receptors and their roles in neuroinflammation; we highlighted the relationship between these six GPCRs and microglial activation in PD. Based on the existing findings, we tried to expound the implication of microglial GPCRs-regulated neuroinflammation to the pathophysiology of PD and their potential to become a new expectation for clinical therapeutics.

Rh-CXCL-12 Attenuates Neuronal Pyroptosis after Subarachnoid Hemorrhage in Rats via Regulating the CXCR4/NLRP1 Pathway

Subarachnoid hemorrhage (SAH) is a cerebrovascular disease associated with high morbidity and mortality. CXCR4 provides neuroprotective effects, which can alleviate brain injury and inflammation induced by stroke. Previous studies have suggested that CXCR4 reduces the pyroptosis of LPS-stimulated BV2 cells. The purpose of this study was to evaluate the antipyroptosis effects and mechanisms of CXCR4 after SAH. SAH animal model was induced via endovascular perforation. A total of 136 male Sprague-Dawley rats were used. Recombinant human cysteine-X-cysteine chemokine ligand 12 (rh-CXCL-12) was administered intranasally at 1 h after SAH induction. To investigate the underlying mechanism, the inhibitor of CXCR4, AMD3100, was administered intraperitoneally at 1 h before SAH. The neurobehavior tests were assessed, followed by performing Western blot and immunofluorescence staining. The Western blot results suggested that the expressions of endogenous CXCL-12, CXCR4, and NLRP1 were increased and peaked at 24 h following SAH. Immunofluorescence staining showed that CXCR4 was expressed on neurons, microglia, and astrocytes. Rh-CXCL-12 treatment improved the neurological deficits and reduced the number of FJC-positive cells, IL-18-positive neurons, and cleaved caspase-1(CC-1)-positive neurons after SAH. Meanwhile, rh-CXCL-12 treatment increased the levels of CXCL-12 and CXCR4, and reduced the levels of NLRP1, IL-18, IL-1β, and CC-1. Moreover, the administration of AMD3100 abolished antipyroptosis effects of CXCL-12 and its regulation of CXCR4 post-SAH. The CXCR4/NLRP1 signaling pathway may be involved in CXCL-12-mediated neuronal pyroptosis after SAH. Early administration of CXCL-12 may be a preventive and therapeutic strategy against brain injury after SAH.

Integrative analysis of potential biomarkers and immune cell infiltration in Parkinson's disease

BACKGROUND

Parkinson's disease (PD) is a common neurodegenerative disease in the elderly population. However, there are no reliable diagnostic biomarkers for PD, and the pathogenesis of PD still needs further study. The aim of the current study was to identify potential biomarkers and explore the pathogenesis of PD.

METHODS

We conducted an integrative analysis of messenger RNA (mRNA), microRNA (miRNA), and long noncoding RNA (lncRNA) expression profiles of PD using data from the Gene Expression Omnibus (GEO). The GSE110720, GSE110719 and GSE133347 data sets were selected and analysed. Gene ontology (GO) enrichment and gene set variation analysis (GSVA) were performed for annotation, visualization, and integrated discovery. Protein-protein interaction (PPI) and competing endogenous RNA (ceRNA) networks were constructed, and hub genes were identified. Meanwhile, the immune infiltration analysis of hub genes was analysed. Moreover, receiver operating characteristic (ROC) curves were generated to verify the diagnostic value of the differentially expressed genes (DEGs). Finally, the genes with high area under the curve (AUC) values were verified by human samples.

RESULTS

We identified 464 DEGs closely related to PD, including 154 mRNAs, 134 miRNAs, and 176 lncRNAs. The GO analyses indicated that changes in PD were mainly enriched in receptor ligand activity and cytokine receptor binding. The KEGG enrichment analysis showed that these DEGs were significantly involved in cytokine-cytokine receptor interactions, signalling pathways regulating the pluripotency of stem cells and Th17 cell differentiation. GSVA suggested that growth factor binding, IL2-stat5 signalling, and IL6-jak-stat3 signalling were crucial in the development of PD. A total of five hub genes (NPBWR2, CXCL10, CXCL5, S1PR5, and GALR1) were selected via the PPI network. A ceRNA network of the CXCL5, CXCL10 and S1PR5 genes was constructed, and target genes of the three genes were screened. The immune infiltration analysis showed that there were significant differences in a variety of immune cells between the hub genes. The expression of DEGs was validated in clinical human samples by quantitative reverse transcription polymerase chain reaction (qRT-PCR). The expression levels of hsa-miR6895-5p, hsa-miR6791-5p, hsa-miR518f-5p, hsa-miR455-3p and TEKT4P2 were decreased, while the levels of TPTE2P6 were increased in human samples. These findings are consistent with the bioinformatics analysis results.

CONCLUSION

We found that the immune inflammatory response and immune cell regulation were involved in the pathogenesis of PD. Five hub genes involved in the immune infiltration biological processes of PD based on bioinformatics. We verified the DEGs with significant differences by qRT-PCR. These findings might provide new insight into the pathogenesis of PD and the development of diagnostic and therapeutic strategies for PD.

Influence of Simulated Deep Brain Stimulation on the Expression of Inflammatory Mediators by Human Central Nervous System Cells In Vitro

Deep brain stimulation (DBS) seems to modulate inflammatory processes. Whether this modulation leads to an induction or suppression of inflammatory mediators is still controversially discussed. Most studies of the influence of electrical stimulation on inflammation were conducted in rodent models with direct current stimulation and/or long impulses, both of which differ from the pattern in DBS. This makes comparisons with the clinical condition difficult. We established an in-vitro model that simulated clinical stimulation patterns to investigate the influence of electrical stimulation on proliferation and survival of human astroglial cells, microglia, and differentiated neurons. We also examined its influence on the expression of the inflammatory mediators C-X-C motif chemokine (CXCL)12, CXCL16, CC-chemokin-ligand-2 (CCL)2, CCL20, and interleukin (IL)-1β and IL-6 by these cells using quantitative polymerase chain reaction. In addition, protein expression was assessed by immunofluorescence double staining. In our model, electrical stimulation did not affect proliferation or survival of the examined cell lines. There was a significant upregulation of CXCL12 in the astrocyte cell line SVGA, and of IL-1β in differentiated SH-SY5Y neuronal cells at both messenger RNA and protein levels. Our model allowed a valid examination of chemokines and cytokines associated with inflammation in human brain cells. With it, we detected the induction of inflammatory mediators by electrical stimulation in astrocytes and neurons.

Neurons and Glia Interplay in α-Synucleinopathies

Accumulation of the neuronal presynaptic protein alpha-synuclein within proteinaceous inclusions represents the key histophathological hallmark of a spectrum of neurodegenerative disorders, referred to by the umbrella term a-synucleinopathies. Even though alpha-synuclein is expressed predominantly in neurons, pathological aggregates of the protein are also found in the glial cells of the brain. In Parkinson's disease and dementia with Lewy bodies, alpha-synuclein accumulates mainly in neurons forming the Lewy bodies and Lewy neurites, whereas in multiple system atrophy, the protein aggregates mostly in the glial cytoplasmic inclusions within oligodendrocytes. In addition, astrogliosis and microgliosis are found in the synucleinopathy brains, whereas both astrocytes and microglia internalize alpha-synuclein and contribute to the spread of pathology. The mechanisms underlying the pathological accumulation of alpha-synuclein in glial cells that under physiological conditions express low to non-detectable levels of the protein are an area of intense research. Undoubtedly, the presence of aggregated alpha-synuclein can disrupt glial function in general and can contribute to neurodegeneration through numerous pathways. Herein, we summarize the current knowledge on the role of alpha-synuclein in both neurons and glia, highlighting the contribution of the neuron-glia connectome in the disease initiation and progression, which may represent potential therapeutic target for a-synucleinopathies.

Pramipexole attenuates 6-OHDA-induced Parkinson's disease by mediating the Nurr1/NF-κB pathway

Neuroinflammation is the key factor associated with the progression of Parkinson's disease (PD). Pramipexole (PPX) has anti-inflammatory and antioxidant properties. This study explored the effects of PPX on PD and its related mechanisms. A PD rat model was established using 6-hydroxydopamine (6-OHDA). Thirty rats were divided into the following three groups: control, PD, and PD + PPX. The rats in the PD and PD + PPX groups were first administered 6-OHDA and then respectively treated with saline and PPX. Afterward, rotational behavior tests were performed to evaluate the efficiency of PPX. The level of tyrosine hydroxylase (TH) was measured using immunohistochemical staining. Subsequently, real-time quantitative PCR (RT-qPCR) and western blot were used to determine the expression of α-synuclein (α-syn), nuclear receptor subfamily 4 group A member 2 (Nurr1), and nuclear factor kappa B (NF-κB). PPX improved the motor behavior of PD rats caused by 6-OHDA. The number of TH-positive neurons in the PD group was significantly lower than that in the control group (P < 0.05), while PPX could rescue 6-OHDA-induced TH loss. RT-qPCR and western blot showed that Nurr1 expression was significantly downregulated in the PD group compared to that of the control group (P < 0.05), while after PPX treatment, its expression was significantly upregulated (P < 0.05). For α-syn and NF-κB, 6-OHDA significantly upregulated their expressions (P < 0.05), whereas PPX reversed them. PPX improved the motor behavior of PD through mediating the inflammatory response and regulating the Nurr1/NF-κB signaling pathway.

LINC00943 knockdown exerts neuroprotective effects in Parkinson's disease through regulates CXCL12 expression by sponging miR-7-5p

BACKGROUND

Parkinson's disease (PD) is a common neurodegenerative movement disorder, but the pathogenesis is still unclear. Long non-coding RNAs (lncRNAs) have been reported to play a prominent role in PD.

OBJECTIVE

This study is designed to explore the role and mechanism of long intergenic non-coding RNA 00943 (LINC00943) in the N-methyl-4-phenylpyridine (MPP⁺)-inducted PD model.

METHODS

LINC00943, microRNA-7-5p (miR-7-5p), and the chemokine (C-X-C motif) ligand 12 (CXCL12, also referred to as SDF-1) level were examined by real-time quantitative polymerase chain reaction (RT-qPCR). Cell viability and apoptosis were analyzed by 3-(4, 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2-H-tetrazolium bromide (MTT), and flow cytometry assays, severally. Protein levels of interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), and CXCL12 were assessed by western blot assay. The ROS generation and SOD activity were detected by the corresponding kits. The binding relationship between miR-7-5p and LINC00943 or CXCL12 was predicted by Starbase and then verified by a dual-luciferase reporter and RNA Immunoprecipitation (RIP) assays.

RESULTS

LINC00943 and CXCL12 were increased, and miR-7-5p was decreased in MPP⁺-inducted SK-N-SH cells. LINC00943 silencing promoted cell viability, and repressed apoptosis and the inflammatory response in MPP⁺-treated SK-N-SH cells. The mechanical analysis discovered that LINC00943 acted as a sponge of miR-7-5p to regulate CXCL12 expression.

CONCLUSIONS

LINC00943 knockdown could attenuate MPP⁺-triggered neuron injury by regulating the miR-7-5p/CXCL12 axis, hinting at a promising therapeutic target for PD treatment.

Nuclear factor-kappa B (NF-κB) in pathophysiology of Parkinson disease: Diverse patterns and mechanisms contributing to neurodegeneration

Parkinson's disease (PD), the most common movement disorder, comprises several pathophysiologic mechanisms including misfolded alpha-synuclein aggregation, inflammation, mitochondrial dysfunction, and synaptic loss. Nuclear Factor-Kappa B (NF-κB), as a key regulator of a myriad of cellular reactions, is shown to be involved in such mechanisms associated with PD, and the changes in NF-κB expression is implicated in PD. Alpha-synuclein accumulation, the characteristic feature of PD pathology, is known to trigger NF-κB activation in neurons, thereby propagating apoptosis through several mechanisms. Furthermore, misfolded alpha-synuclein released from degenerated neurons, activates several signaling pathways in glial cells which culminate in activation of NF-κB and production of pro-inflammatory cytokines, thereby aggravating neurodegenerative processes. On the other hand, NF-κB activation, acting as a double-edged sword, can be necessary for survival of neurons. For instance, NF-κB activation is necessary for competent mitochondrial function and deficiency in c-Rel, one of the NF-κB proteins, is known to propagate DA neuron loss via several mechanisms. Despite the dual role of NF-κB in PD, several agents by selectively modifying the mechanisms and pathways associated with NF-κB, can be effective in attenuating DA neuron loss and PD, as reviewed in this paper.

Genotype-driven therapeutic developments in Parkinson's disease

BACKGROUND

Remarkable advances have been reached in the understanding of the genetic basis of Parkinson's disease (PD), with the identification of monogenic causes (mPD) and a plethora of gene loci leading to an increased risk for idiopathic PD. The expanding knowledge and subsequent identification of genetic contributions fosters the understanding of molecular mechanisms leading to disease development and progression. Distinct pathways involved in mitochondrial dysfunction, oxidative stress, and lysosomal function have been identified and open a unique window of opportunity for individualized treatment approaches. These genetic findings have led to an imminent progress towards pathophysiology-targeted clinical trials and potentially disease-modifying treatments in the future.

MAIN BODY OF THE MANUSCRIPT

In this review article we will summarize known genetic contributors to the pathophysiology of Parkinson's disease, the molecular mechanisms leading to disease development, and discuss challenges and opportunities in clinical trial designs.

CONCLUSIONS

The future success of clinical trials in PD is mainly dependent on reliable biomarker development and extensive genetic testing to identify genetic cases. Whether genotype-dependent stratification of study participants will extend the potential application of new drugs will be one major challenge in conceptualizing clinical trials. However, the latest developments in genotype-driven treatments will pave the road to individualized pathophysiology-based therapies in the future.

Proteomics Profiling of Neuron-Derived Small Extracellular Vesicles from Human Plasma: Enabling Single-Subject Analysis

Small extracellular vesicles have been intensively studied as a source of biomarkers in neurodegenerative disorders. The possibility to isolate neuron-derived small extracellular vesicles (NDsEV) from blood represents a potential window into brain pathological processes. To date, the absence of sensitive NDsEV isolation and full proteome characterization methods has meant their protein content has been underexplored, particularly for individual patients. Here, we report a rapid method based on an immunoplate covalently coated with mouse monoclonal anti-L1CAM antibody for the isolation and the proteome characterization of plasma-NDsEV from individual Parkinson’s disease (PD) patients. We isolated round-shaped vesicles with morphological characteristics consistent with exosomes. On average, 349 ± 38 protein groups were identified by liquid chromatography–tandem mass spectrometry (LC-MS/MS) analysis, 20 of which are annotated in the Human Protein Atlas as being highly expressed in the brain, and 213 were shared with a reference NDsEV dataset obtained from cultured human neurons. Moreover, this approach enabled the identification of 23 proteins belonging to the Parkinson disease KEGG pathway, as well as proteins previously reported as PD circulating biomarkers.

Alpha-Synuclein in the Regulation of Brain Endothelial and Perivascular Cells: Gaps and Future Perspectives

Misfolded proteins, inflammation, and vascular alterations are common pathological hallmarks of neurodegenerative diseases. Alpha-synuclein is a small synaptic protein that was identified as a major component of Lewy bodies and Lewy neurites in the brain of patients affected by Parkinson's disease (PD), Lewy body dementia (LBD), and other synucleinopathies. It is mainly involved in the regulation of synaptic vesicle trafficking but can also control mitochondrial/endoplasmic reticulum (ER) homeostasis, lysosome/phagosome function, and cytoskeleton organization. Recent evidence supports that the pathological forms of α-synuclein can also reduce the release of vasoactive and inflammatory mediators from endothelial cells (ECs) and modulates the expression of tight junction (TJ) proteins important for maintaining the blood-brain barrier (BBB). This hints that α-synuclein deposition can affect BBB integrity. Border associated macrophages (BAMs) are brain resident macrophages found in association with the vasculature (PVMs), meninges (MAMs), and choroid plexus (CPMs). Recent findings indicate that these cells play distinct roles in stroke and neurodegenerative disorders. Although many studies have addressed how α-synuclein may modulate microglia, its effect on BAMs has been scarcely investigated. This review aims at summarizing the main findings supporting how α-synuclein can affect ECs and/or BAMs function as well as their interplay and effect on other cells in the brain perivascular environment in physiological and pathological conditions. Gaps of knowledge and new perspectives on how this protein can contribute to neurodegeneration by inducing BBB homeostatic changes in different neurological conditions are highlighted.

Upregulating miR-130a-5p relieves astrocyte over activation-induced neuropathic pain through targeting C-X-C motif chemokine receptor 12/C-X-C motif chemokine receptor 4 axis

OBJECTIVES

This study intends to explore the role and specific mechanism of miR-130a-5p in neuropathic pain through regulating the C-X-C motif chemokine receptor 12 (CXCL12)-C-X-C motif chemokine receptor 4 (CXCR4) pathway.

METHODS

First, mouse neuropathic pain model was constructed by spinal nerve ligation. MiR-130a-5p mimics were used to upregulate miR-130a-5p in vivo. The behaviour and pain scores of the spinal cord injury (SCI) mice were assessed. In addition, astrocytic activation as well as inflammatory response in the spinal lesions was determined.

RESULTS

The results manifested miR-130a-5p was notably downregulated in neuropathic pain model and reached the lowest point at 3 days after injury. Besides, tail vein injection of miR-130a-5p mimics inhibited the activation and inflammatory response of astrocytes, thus alleviating chronic constriction injury-induced neuropathic pain. Moreover, miR-130a-5p inactivated CXCR4 and its downstream Rac1, nuclear factor-κB (NF-κB) and extracellular regulated protein kinases signalling pathways by attenuating CXCL12.

CONCLUSION

MiR-130a-5p inactivated astrocytes by targeting CXCL12/CXCR4, thus alleviating SCI-induced neuropathic pain.

Cerebral sterile inflammation in neurodegenerative diseases

Therapeutic strategies for regulating neuroinflammation are expected in the development of novel therapeutic agents to prevent the progression of central nervous system (CNS) pathologies. An understanding of the detailed molecular and cellular mechanisms of neuroinflammation in each CNS disease is necessary for the development of therapeutics. Since the brain is a sterile organ, neuroinflammation in Alzheimer's disease (AD), Parkinson's disease (PD), and amyotrophic lateral sclerosis (ALS) is triggered by cerebral cellular damage or the abnormal accumulation of inflammatogenic molecules in CNS tissue through the activation of innate and acquired immunity. Inflammation and CNS pathologies worsen each other through various cellular and molecular mechanisms, such as oxidative stress or the accumulation of inflammatogenic molecules induced in the damaged CNS tissue. In this review, we summarize the recent evidence regarding sterile immune responses in neurodegenerative diseases.

Revisiting the Immune Balance Theory: A Neurological Insight Into the Epidemic of COVID-19 and Its Alike

As the pandemic of COVID-19 is raging around the world, the mysteriousness of severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) coronavirus is being revealed by the concerted endeavors of scientists. Although fever and pneumonia are typical symptoms, COVID-19 patients exhibit multiple neurological complications. In this interim review, we will summarize the neurological manifestations and their potential causes in COVID-19. Similar to the other two fatal respiratory coronaviruses, SARS-CoV and Middle East respiratory syndrome coronavirus (MERS-CoV), SARS-CoV-2 also shows to be neuroinvasive that may spread from the periphery to brain, probably by the retrograde axonal transport. The invaded viruses may directly disrupt the complex neural circuits, and raise a chronic activation of immune responses. In another hand, multiple organ failure in severe COVID-19 is caused by the systemic acute immune responses, and unsurprisingly caused the brain inflammation and led to encephalitis. However, in the central nervous system (CNS), the activation of resident immune cells including microglia and astrocytes may lead to chronic immune imbalance, which underlies the potential long-term effects in synaptic changes and neuropsychiatric impairments. The neuroinvasive biology also provides a possible link with the Braak staging of neurodegenerative diseases such as Parkinson's disease (PD). Although with considerable advances, the neurotropic potential and chronic neurological effects caused by SARS-CoV-2 infections merit further investigations.

Bacterial, viral, and fungal infection-related risk of Parkinson's disease: Meta-analysis of cohort and case-control studies

AIMS

Recent studies showed that patients with various bacterial, viral, and fungal infections might be at increased risk of Parkinson's disease (PD). However, the risk of PD in patients with each specific infection varied. This meta-analysis estimated the association between various infections and PD risk.

METHODS

Literature published from January 1965 to October 2019 in PubMed and EMBASE databases was searched. Data were extracted and pooled using random/fixed effects model. Sensitivity analysis and meta-regression were also performed to analyze the source of heterogeneity. Publication bias was estimated by the trim and fill.

RESULTS

Twenty-three out of 6,609 studies were included. Helicobacter pylori (HP; pooled OR = 1.653, 1.426-1.915, p < .001), hepatitis C virus (HCV; pooled OR = 1.195, 1.012-1.410, p = .035), Malassezia (pooled OR = 1.694, 1.367-2.100, p < .001), and pneumoniae (pooled OR = 1.595, 1.020-2.493, p = .041) infection were associated with increased PD risk. Influenza virus, herpes virus, hepatitis B virus, scarlet fever, mumps virus, chicken pox, pertussis, German measles, and measles were not associated with PD risk. After antiviral treatment against HCV reduced the risk of PD in patients with HCV infection (OR = 0.672, 0.571-0.791, p < .001). Significant heterogeneity exists among the included studies.

CONCLUSION

Patients with infection of HP, HCV, Malassezia, pneumoniae might be an increased risk of PD. Antiviral treatment of HCV could reduce the risk of PD.