Microglia and astrocyte dysfunction in parkinson's disease

Regulation of P-Glycoprotein in the Brain

Maintenance of the tightly regulated homeostatic environment of the brain is facilitated by the blood-brain barrier (BBB). P-glycoprotein (P-gp), an ATP-binding cassette transporter, is expressed on the luminal surface of the endothelial cells in the BBB, and actively exports a wide variety of substrates to limit exposure of the vulnerable brain environment to waste buildup and neurotoxic compounds. Downregulation of P-gp expression and activity at the BBB have been reported with ageing and in neurodegenerative diseases. Upregulation of P-gp at the BBB contributes to poor therapeutic outcomes due to altered pharmacokinetics of CNS-acting drugs. The regulation of P-gp is highly complex, but unravelling the mechanisms involved may help the development of novel and nuanced strategies to modulate P-gp expression for therapeutic benefit. This review summarises the current understanding of P-gp regulation in the brain, encompassing the transcriptional, post-transcriptional and post-translational mechanisms that have been identified to affect P-gp expression and transport activity.

The Crosstalk between the Blood–Brain Barrier Dysfunction and Neuroinflammation after General Anaesthesia

As we know, with continuous medical progress, the treatment of many diseases can be conducted via surgery, which often relies on general anaesthesia for its satisfactory performance. With the widespread use of general anaesthetics, people are beginning to question the safety of general anaesthesia and there is a growing interest in central nervous system (CNS) complications associated with anaesthetics. Recently, abundant evidence has suggested that both blood–brain barrier (BBB) dysfunction and neuroinflammation play roles in the development of CNS complications after anaesthesia. Whether there is a crosstalk between BBB dysfunction and neuroinflammation after general anaesthesia, and whether this possible crosstalk could be a therapeutic target for CNS complications after general anaesthesia needs to be clarified by further studies.

The Interplay between Ghrelin and Microglia in Neuroinflammation: Implications for Obesity and Neurodegenerative Diseases

Numerous studies have shown that microglia are capable of producing a wide range of chemokines to promote inflammatory processes within the central nervous system (CNS). These cells share many phenotypical and functional characteristics with macrophages, suggesting that microglia participate in innate immune responses in the brain. Neuroinflammation induces neurometabolic alterations and increases in energy consumption. Microglia may constitute an important therapeutic target in neuroinflammation. Recent research has attempted to clarify the role of Ghre signaling in microglia on the regulation of energy balance, obesity, neuroinflammation and the occurrence of neurodegenerative diseases. These studies strongly suggest that Ghre modulates microglia activity and thus affects the pathophysiology of neurodegenerative diseases. This review aims to summarize what is known from the current literature on the way in which Ghre modulates microglial activity during neuroinflammation and their impact on neurometabolic alterations in neurodegenerative diseases. Understanding the role of Ghre in microglial activation/inhibition regulation could provide promising strategies for downregulating neuroinflammation and consequently for diminishing negative neurological outcomes.

The role of microglial autophagy in Parkinson's disease

Parkinson's disease (PD) is the second most common neurodegenerative disease. Studies have shown that abnormal accumulation of α-synuclein (α-Syn) in the substantia nigra is a specific pathological characteristic of PD. Abnormal accumulation of α-Syn in PD induces the activation of microglia. Microglia, which are immune cells in the central nervous system, are involved in the function and regulation of inflammation in PD by autophagy. The role of microglial autophagy in the pathophysiology of PD has become a hot-pot issue. This review outlines the pathways of microglial autophagy, and explores the key factor of microglial autophagy in the mechanism of PD and the possibility of microglial autophagy as a potential therapeutic target for PD.

Natural Compounds Such as Hericium erinaceus and Coriolus versicolor Modulate Neuroinflammation, Oxidative Stress and Lipoxin A4 Expression in Rotenone-Induced Parkinson's Disease in Mice

BACKGROUND

A growing body of research suggests that oxidative stress and neuroinflammation are early pathogenic features of neurodegenerative disorders. In recent years, the vitagene system has emerged as a potential target, as it has been shown to have a high neuroprotective power. Therefore, the discovery of molecules capable of activating this system may represent a new therapeutic target to limit the deleterious consequences induced by oxidative stress and neuroinflammation, such as neurodegeneration. Lipoxins are derived from arachidonic acid, and their role in the resolution of systemic inflammation is well established; however, they have become increasingly involved in the regulation of neuroinflammatory and neurodegenerative processes. Our study aimed at activating the NF-E2-related factor 2 (Nrf2)/heme oxygenase 1 (HO-1) redox system and increasing lipoxin A4 for the modulation of antioxidant stress and neuroinflammation through the action of two fungi in a rotenone-induced Parkinson's model.

METHODS

During the experiment, mice received Hericium erinaceus, Coriolus versicolor or a combination of the two (200 mg/kg, orally) concomitantly with rotenone (5 mg/kg, orally) for 28 days.

RESULTS

The results obtained highlighted the ability of these two fungi and, in particular, their ability through their association to act on neuroinflammation through the nuclear factor-kB pathway and on oxidative stress through the Nrf2 pathway. This prevented dopaminergic neurons from undergoing apoptosis and prevented the alteration of typical Parkinson's disease (PD) markers and α-synuclein accumulation. The action of Hericium erinaceus and Coriolus versicolor was also able to limit the motor and non-motor alterations characteristic of PD.

CONCLUSIONS

Since these two mushrooms are subject to fewer regulations than traditional drugs, they could represent a promising nutraceutical choice for preventing PD.

Cathepsin L-containing exosomes from α-synuclein-activated microglia induce neurotoxicity through the P2X7 receptor

Uncontrolled microglial activation is pivotal to the pathogenesis of Parkinson's disease (PD), which can secrete Cathepsin L (CTSL) to affect the survival of neurons in the PD patients; however, the precise mechanism has yet to be determined. We demonstrated for the first time that CTSL was mostly released by exosomes derived from α-Syn-activated microglia, resulting in neuronal damage and death. The elevation of CTSL activity was blocked by GW4869, suggesting a critical role for exosomes in mediating CTSL release. Furthermore, the P2X7R/PI3K/AKT signalling pathway was identified as the underlying molecular mechanism since specific antagonists of this signalling pathway, P2X7R knockdown and exosome release inhibitors significantly reduced the injury to cultured mouse cortical neurons. Our study suggests that increased extracellular release of CTSL from α-Syn-activated microglia through exosomes amplifies and aggravates of the neurotoxic effect of microglia, implying that CTSL may be involved in a fresh mechanism of PD pathogenesis, and serve as a potential biomarker and a target for PD drug development.

Phikud Navakot extract attenuates lipopolysaccharide-induced inflammatory responses through inhibition of ERK1/2 phosphorylation in a coculture system of microglia and neuronal cells

ETHNOPHARMACOLOGICAL RELEVANCE

Phikud Navakot (PN), a mixture of nine herbal plants, is an ancient Thai traditional medicine used for relieving circulatory disorders and dizziness. PN has also shown anti-inflammatory effects in rats with acute myocardial infarction. Moreover, phytochemical-inhibiting neuroinflammation, including gallic acid, vanillic acid, ferulic acid, and rutin were detected in PN extract; however, the anti-neuroinflammatory activity of PN extract and its components in a coculture system of microglia and neuronal cells is limited.

OBJECTIVE

To investigate the anti-neuroinflammatory activities of PN on lipopolysaccharide (LPS)-induced inflammation in a coculture system of microglia and neuronal cells.

METHODS

ELISA and qRT-PCR were used to assess cytokine expression. The phosphorylation of mitogen-activated protein kinases (MAPKs) was determined by Western blotting. Microglia-mediated neuroinflammation was evaluated using a BV-2 microglia-N2a neuron transwell co-culture.

RESULTS

PN extract and its component, gallic acid, decreased LPS-induced the mRNA expression of interleukin-6 (IL-6) and inducible nitric oxide synthase (iNOS), as well as IL-6 protein levels in both microglial monoculture and coculture systems. This was accompanied by a reduction in neurodegeneration triggered by microglia in N2a neurons with increased neuronal integrity markers (βIII tubulin and tyrosine hydroxylase (TH)). These effects were caused by the ability of PN extract to inhibit extracellular signal-regulated protein kinases 1 and 2 (ERK1/2) activation.

CONCLUSION

This is the first study to show that PN extract inhibits neurodegeneration in LPS-activated BV-2 microglia by targeting ERK signaling activity.

Implications of glial metabolic dysregulation in the pathophysiology of neurodegenerative diseases

Glial cells are the most abundant cells of the brain, outnumbering neurons. These multifunctional cells are crucial for maintaining brain homeostasis by providing trophic and nutritional support to neurons, sculpting synapses, and providing an immune defense. Glia are highly plastic and undergo both structural and functional alterations in response to changes in the brain microenvironment. Glial phenotypes are intimately regulated by underlying metabolic machinery, which dictates the effector functions of these cells. Altered brain energy metabolism and chronic neuroinflammation are common features of several neurodegenerative diseases. Microglia and astrocytes are the major glial cells fueling the ongoing neuroinflammatory process, exacerbating neurodegeneration. Distinct metabolic perturbations in microglia and astrocytes, including altered carbohydrate, lipid, and amino acid metabolism have been documented in neurodegenerative diseases. These disturbances aggravate the neurodegenerative process by potentiating the inflammatory activation of glial cells. This review covers the recent advances in the molecular aspects of glial metabolic changes in the pathophysiology of neurodegenerative diseases. Finally, we discuss studies exploiting glial metabolism as a potential therapeutic avenue in neurodegenerative diseases.

Neuroinflammation and Parkinson's Disease-From Neurodegeneration to Therapeutic Opportunities

Parkinson’s disease (PD) is the second most prevalent neurodegenerative disorder worldwide. Clinically, it is characterized by a progressive degeneration of dopaminergic neurons (DAn), resulting in severe motor complications. Preclinical and clinical studies have indicated that neuroinflammation can play a role in PD pathophysiology, being associated with its onset and progression. Nevertheless, several key points concerning the neuroinflammatory process in PD remain to be answered. Bearing this in mind, in the present review, we cover the impact of neuroinflammation on PD by exploring the role of inflammatory cells (i.e., microglia and astrocytes) and the interconnections between the brain and the peripheral system. Furthermore, we discuss both the innate and adaptive immune responses regarding PD pathology and explore the gut–brain axis communication and its influence on the progression of the disease.

Anti-Inflammatory and Neuroprotective Effects of Morin in an MPTP-Induced Parkinson’s Disease Model

Neurodegenerative diseases such as Parkinson’s disease (PD) are known to be related to oxidative stress and neuroinflammation, and thus, modulating neuroinflammation offers a possible means of treating PD-associated pathologies. Morin (2′,3,4′,5,7-pentahydroxy flavone) is a flavonol with anti-oxidative and anti-inflammatory effects found in wines, herbs, and fruits. The present study was undertaken to determine whether a morin-containing diet has protective effects in an MPTP-induced mouse model of PD. Mice were fed a control or morin diet for 34 days, and then MPTP (30 mg/kg, i.p.) was administered daily for 5 days to induce a PD-like pathology. We found that dietary morin prevented MPTP-induced motor dysfunction and ameliorated dopaminergic neuronal damage in striatum (STR) and substantia nigra (SN) in our mouse model. Furthermore, MPTP-induced neuroinflammation was significantly reduced in mice fed morin. In vitro studies showed that morin effectively suppressed glial activations in primary microglia and astrocytes, and biochemical analysis and a docking simulation indicated that the anti-inflammatory effects of morin were mediated by blocking the extracellular signal-regulated kinase (ERK)-p65 pathway. These findings suggest that morin effectively inhibits glial activations and has potential use as a functional food ingredient with therapeutic potential for the treatment of PD and other neurodegenerative diseases associated with neuroinflammation.

Research Progress on the Role of RNA m6A Modification in Glial Cells in the Regulation of Neurological Diseases

Glial cells are the most abundant and widely distributed cells that maintain cerebral homeostasis in the central nervous system. They mainly include microglia, astrocytes, and the oligodendrocyte lineage cells. Moreover, glial cells may induce pathological changes, such as inflammatory responses, demyelination, and disruption of the blood–brain barrier, to regulate the occurrence and development of neurological diseases through various molecular mechanisms. Furthermore, RNA m6A modifications are involved in various pathological processes associated with glial cells. In this review, the roles of glial cells in physiological and pathological states, as well as advances in understanding the mechanisms by which glial cells regulate neurological diseases under RNA m6A modification, are summarized, hoping to provide new perspectives on the deeper mechanisms and potential therapeutic targets for neurological diseases.

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.

Enriched environment priors to TET1 hippocampal administration for regulating psychiatric behaviors via glial reactivity in chronic cerebral hypoperfusion models

BACKGROUND

Chronic cerebral hypoperfusion (CCH) has been gradually regarded as a common etiologic mechanism for cognitive and psychiatric disturbances. Ten-eleven translocation methylcytosine dioxygenase 1 (TET1) played an important role in adult hippocampal neurogenesis (AHN), neuronal circuits formation, cognition and psychiatric disorders. Enriched environment (EE) showed a beneficial effect on cognition and depression via effectively regulating AHN and glial reactivity. This study aimed to assess which strategy was feasible to improve cognition and psychiatric disturbances by comparing the TET1 hippocampal microinjection and EE in CCH models and to investigate the possible mechanisms.

METHOD

CCH rats were established via permanent bilateral common carotid artery occlusion (2-VO). Rats were stereotaxically injected with the human catalytic domain of TET1 (hTET1) to overexpress the hTET1 in the hippocampus 10 days before 2-VO. 3 days after 2-VO, rats were subjected to standard environment or EE with free access to food and water. Behavioral tests were used to appraise depression and cognition before sacrifice. Epigenetic molecules, adult neurogenesis, synaptic proteins expression, and glial activation were analyzed using immunofluorescent staining, qRT-PCR and western blot.

RESULTS

In the present study, we found both EE and genetical treatment with overexpressing hTET1 were sufficient for stimulating AHN. However, promoting ANH could not deal with the cognitive dysfunction and depressive-like behaviors in CCH rats. Notably, a healthy local brain environment with elevated BDNF and astrocytes was conducive to improving cognitive dysfunction. Meanwhile, astrocytes were involved in the cognitive regulating process of neurons, presynaptic function and microglia. In general, we held that depressive disturbances were determined by BDNF levels, neuronal and presynaptic function, as well as glial activation containing astrocytes and microglia. To further support this point, we investigated severe depressive symptoms that were strongly correlated with the activation of astroglia and microglia. Importantly, causal mediation analysis showed significant mediation by the presence of reactive glial cells in the relation between neural plasticity and depressive symptoms. Finally, we showed EE performed better than hTET1 treatment for cognitive deficits and depression. EE with less glial reactivity was much more resistant to depression, while hTET1 with more glial activation was more vulnerable to depressive disorders.

CONCLUSIONS

EE was likely to be superior to TET1 hippocampal administration for cognition and psychiatric behaviors in CCH rats. Furthermore, a healthy local brain environment with elevated BDNF and astrocytes was conducive to improving cognitive dysfunction. More glial activation, and more vulnerable to depressive disorders. These results were important for our understanding of disease mechanisms and provided valuable tools for the overall management of CCH patients.

Neurodegeneration and Neuroinflammation in Parkinson's Disease: a Self-Sustained Loop

PURPOSE OF REVIEW

Neuroinflammation plays a significant role in Parkinson's disease (PD) etiology along with mitochondrial dysfunction and impaired proteostasis. In this context, mechanisms related to immune response can act as modifiers at different steps of the neurodegenerative process and justify the growing interest in anti-inflammatory agents as potential disease-modifying treatments in PD. The discovery of inherited gene mutations in PD has allowed researchers to develop cellular and animal models to study the mechanisms of the underlying biology, but the original cause of neuroinflammation in PD is still debated to date.

RECENT FINDINGS

Cell autonomous alterations in neuronal cells, including mitochondrial damage and protein aggregation, could play a role, but recent findings also highlighted the importance of intercellular communication at both local and systemic level. This has given rise to debate about the role of non-neuronal cells in PD and reignited intense research into the gut-brain axis and other non-neuronal interactions in the development of the disease. Whatever the original trigger of neuroinflammation in PD, what appears quite clear is that the aberrant activation of glial cells and other components of the immune system creates a vicious circle in which neurodegeneration and neuroinflammation nourish each other. In this review, we will provide an up-to-date summary of the main cellular alterations underlying neuroinflammation in PD, including those induced by environmental factors (e.g. the gut microbiome) and those related to the genetic background of affected patients. Starting from the lesson provided by familial forms of PD, we will discuss pathophysiological mechanisms linked to inflammation that could also play a role in idiopathic forms. Finally, we will comment on the potential clinical translatability of immunobiomarkers identified in PD patient cohorts and provide an update on current therapeutic strategies aimed at overcoming or preventing inflammation in PD.

An Improved Method to Generate Human Induced Astrocytes

A major improvement in the generation of astrocytes directly from human fibroblasts will now facilitate the study of how aging impacts on astrocyte function and whether this contributes to neurodegenerative disorders.

Clickable Biomaterials for Modulating Neuroinflammation

Crosstalk between the nervous and immune systems in the context of trauma or disease can lead to a state of neuroinflammation or excessive recruitment and activation of peripheral and central immune cells. Neuroinflammation is an underlying and contributing factor to myriad neuropathologies including neurodegenerative diseases like Alzheimer's disease and Parkinson's disease; autoimmune diseases like multiple sclerosis; peripheral and central nervous system infections; and ischemic and traumatic neural injuries. Therapeutic modulation of immune cell function is an emerging strategy to quell neuroinflammation and promote tissue homeostasis and/or repair. One such branch of 'immunomodulation' leverages the versatility of biomaterials to regulate immune cell phenotypes through direct cell-material interactions or targeted release of therapeutic payloads. In this regard, a growing trend in biomaterial science is the functionalization of materials using chemistries that do not interfere with biological processes, so-called 'click' or bioorthogonal reactions. Bioorthogonal chemistries such as Michael-type additions, thiol-ene reactions, and Diels-Alder reactions are highly specific and can be used in the presence of live cells for material crosslinking, decoration, protein or cell targeting, and spatiotemporal modification. Hence, click-based biomaterials can be highly bioactive and instruct a variety of cellular functions, even within the context of neuroinflammation. This manuscript will review recent advances in the application of click-based biomaterials for treating neuroinflammation and promoting neural tissue repair.

Hypoxia and Alpha-Synuclein: Inextricable Link Underlying the Pathologic Progression of Parkinson's Disease

Parkinson's disease (PD) is the second most common neurodegenerative disease after Alzheimer's disease, with typical motor symptoms as the main clinical manifestations. At present, there are about 10 million patients with PD in the world, and its comorbidities and complications are numerous and incurable. Therefore, it is particularly important to explore the pathogenesis of PD and find possible therapeutic targets. Because the etiology of PD is complex, involving genes, environment, and aging, finding common factors is the key to identifying intervention targets. Hypoxia is ubiquitous in the natural environment and disease states, and it is considered to be closely related to the etiology of PD. Despite research showing that hypoxia increases the expression and aggregation of alpha-synuclein (α-syn), the most important pathogenic protein, there is still a lack of systematic studies on the role of hypoxia in α-syn pathology and PD pathogenesis. Considering that hypoxia is inextricably linked with various causes of PD, hypoxia may be a co-participant in many aspects of the PD pathologic process. In this review, we describe the risk factors for PD, and we discuss the possible role of hypoxia in inducing PD pathology by these risk factors. Furthermore, we attribute the pathological changes caused by PD etiology to oxygen uptake disorder and oxygen utilization disorder, thus emphasizing the possibility of hypoxia as a critical link in initiating or promoting α-syn pathology and PD pathogenesis. Our study provides novel insight for exploring the pathogenesis and therapeutic targets of PD.

Nutrition and Gut–Brain Pathways Impacting the Onset of Parkinson’s Disease

An emerging body of literature suggests that long-term gut inflammation may be a silent driver of Parkinson’s disease (PD) pathogenesis. Importantly, specific nutritive patterns might improve gut health for PD risk reduction. Here, we review the current literature on the nutritive patterns and inflammatory markers as a predictor for early detection of PD. This knowledge might be used to foster the detection of early nutritive patterns and preclinical biomarkers to potentially alter PD development and progression.

Astrocytes in Neurodegeneration: Inspiration From Genetics

Despite the discovery of numerous molecules and pathologies, the pathophysiology of various neurodegenerative diseases remains unknown. Genetics participates in the pathogenesis of neurodegeneration. Neural dysfunction, which is thought to be a cell-autonomous mechanism, is insufficient to explain the development of neurodegenerative disease, implying that other cells surrounding or related to neurons, such as glial cells, are involved in the pathogenesis. As the primary component of glial cells, astrocytes play a variety of roles in the maintenance of physiological functions in neurons and other glial cells. The pathophysiology of neurodegeneration is also influenced by reactive astrogliosis in response to central nervous system (CNS) injuries. Furthermore, those risk-gene variants identified in neurodegenerations are involved in astrocyte activation and senescence. In this review, we summarized the relationships between gene variants and astrocytes in four neurodegenerative diseases, including Alzheimer’s disease (AD), amyotrophic lateral sclerosis (ALS), frontotemporal dementia (FTD), and Parkinson’s disease (PD), and provided insights into the implications of astrocytes in the neurodegenerations.

Gypenoside XVII, an Active Ingredient from Gynostemma Pentaphyllum, Inhibits C3aR-Associated Synaptic Pruning in Stressed Mice

Gynostemma pentaphyllum is a herbal medicine widely used in Asian countries, and its saponin extracts have been shown to possess potent anti-inflammatory effects. Gypenoside XVII, an active ingredient isolated from Gynostemma pentaphyllum, has been found to alleviate the inflammation induced by LPS in the BV2 microglia, according to our preliminary study. This study aims to evaluate whether Gypenoside XVII could attenuate depression-like symptoms in vivo and tries to demonstrate the involvement of the complement regulation in its antidepressant-like effect. The results showed that Gypenoside XVII significantly attenuated depression-like behaviors in the forced swimming test, tail suspension test and sucrose preference test. It also alleviated the acute stress-induced hyperactivity of serum corticosterone levels. Additionally, Gypenoside XVII significantly inhibited the activation of microglia and the expression of C3 in mice exposed to chronic unpredictable mild stress (CUMS). Meanwhile, the activation of C3aR/STAT3 signaling and the expression of proinflammatory cytokines was reversed by Gypenoside XVII. Moreover, CUMS induced excessive synaptic pruning by activating microglia, while Gypenoside XVII restored it in the prefrontal cortex. Our data demonstrated that Gypenoside XVII, the active ingredient of Gynostemma pentaphyllum, produced the antidepressant-like effects in mice, which was mediated by the inhibition of complement C3/C3aR/STAT3/cytokine signaling in the prefrontal cortex.

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.

Microglia-induced autophagic death of neurons via IL-6/STAT3/miR-30d signaling following hypoxia/ischemia

BACKGROUND

There is a relationship between autophagy and the occurrence, maintenance, and progression of several neurodegenerative diseases. The activation of microglia after ischemia contributes to neuronal injury via proinflammatory cytokines and neurotoxic elements. The purpose of this study was to evaluate the function of autophagy in the microglia-mediated death of neuronal cells.

METHODS AND RESULTS

Microglial activation by oxygen/glucose deprivation induced both apoptosis and autophagy in neuron-like PC12 cells. Microglia-derived interleukin (IL)-6 induced PC12 cell apoptosis in vitro; however, this effect was inhibited by the autophagy inhibitor chloroquine. Further analysis demonstrated that miR-30d in PC12 cells suppressed microglia-induced PC12 apoptosis and autophagy by directly targeting autophagy protein 5. Moreover, microglia-derived IL-6 activated signal transducer and activator of transcription 3 (STAT3), which can then directly repress miR-30d genes via a conserved STAT3-binding site in its promoter, thereby promoting PC12 cell autophagy and apoptosis.

CONCLUSIONS

Our study identified IL-6-dependent autophagy-related signaling between microglia and neurons, which contributed to neuronal apoptosis. Importantly, we also provided potential therapeutic targets for ischemic treatment via the interruption of proinflammatory signaling.

The Impact of Alcohol-Induced Dysbiosis on Diseases and Disorders of the Central Nervous System

The human digestive tract contains a diverse and abundant microbiota that is important for health. Excessive alcohol use can disrupt the balance of these microbes (known as dysbiosis), leading to elevated blood endotoxin levels and systemic inflammation. Using QIAGEN Ingenuity Pathway Analysis (IPA) bioinformatics tool, we have confirmed that peripheral endotoxin (lipopolysaccharide) mediates various cytokines to enhance the neuroinflammation signaling pathway. The literature has identified alcohol-mediated neuroinflammation as a possible risk factor for the onset and progression of neurodegenerative diseases, including Alzheimer's disease (AD) and Parkinson's disease (PD), and psychiatric disorders such as addiction to alcohol and other drugs. In this review, we discuss alcohol-use-induced dysbiosis in the gut and other body parts as a causal factor in the progression of Central Nervous System (CNS) diseases including neurodegenerative disease and possibly alcohol use disorder.

Sensitive and Low-Bias Transcriptome Sequencing Using Agarose PCR

Transcriptome sequencing has emerged as an important research tool for exploring the mysteries of life at the single-cell level. However, its wide application is limited by the bias associated with the amplification reactions which is essential for library building of trace RNA. In this study, low-melting-point agarose was added to the amplification reactions to take advantage of its molecular crowding effect and polymer cross-linked structure to improve the sensitivity of the reactions and reduce bias. To further evaluate the performance of the method, it was applied to transcriptome sequencing of microregion samples from brain tissue sections of mice with Parkinson's disease at the single cell level. The results showed that agarose PCR had better performance than in-tube PCR. Further application of agarose PCR to transcriptome library sequencing could obtain data closer to that of unamplified. With the addition of low melting point agarose, the sensitivity of the amplification reaction was significantly increased, while homogeneity was increased by approximately 2-fold. Not only that, but this work also provides 11% sensitivity improvement for spatial transcriptomic study on Parkinson's disease-associated gene detection. The agarose PCR provides a new tool for efficient and homogeneous amplification of trace samples and can be widely used for spatial transcriptome library sequencing and studies.

6-methoxyflavone suppresses neuroinflammation in lipopolysaccharide- stimulated microglia through the inhibition of TLR4/MyD88/p38 MAPK/NF-κB dependent pathways and the activation of HO-1/NQO-1 signaling

BACKGROUND

Microglia-related neuroinflammation is associated with a variety of neurodegenerative diseases. Flavonoids have demonstrated different pharmacological effects, such as antioxidation, neuroprotection and anti-inflammation However, the effect of flavonoid 6-methoxyflavone (6-MeOF) on microglia-mediated neuroinflammation remain unknown.

PURPOSE

The current study aim to study the antineuroinflammatory effects of 6-MeOF in lipopolysaccharide- (LPS-) induced microglia in vitro and in vivo.

METHODS

Pretreatment of BV2 microglia cells with 6-MeOF for 1 h then stimulated with LPS (100 ng/ml) for 24 h. The expression levels of pro-inflammatory factors, NO and reactive oxygen species (ROS) were performed by the enzyme-linked immunosorbent assay (ELISA), Griess assay and flow cytometry. Western blotting was used to assess MAPK, NF-κB signal transducer and antioxidant enzymes-related proteins. Analysis of ROS and microglial morphology was confirmed in the zebrafish and mice brain, respectively.

RESULTS

Our results demonstrated that 6-MeOF dose-dependently prevent cell death and decreased the levels of pro-inflammatory mediators in LPS-stimulated BV2 microglia cells. Phosphorylated NF-κB/IκB and TLR4/MyD88/p38 MAPK/JNK proteins after exposure to 6-MeOF was suppressed in LPS-activated BV-2 microglial cells. 6-MeOF also presented antioxidant activity by reduction of NO, ROS, iNOS and COX-2 and the induction of the level of HO-1 and NQO1 expressions in LPS-activated BV2 microglial cells. Furthermore, we demonstrated that 6-MeOF inhibited LPS-induced NO generation in an experimental zebrafish model and prevent the LPS-induced microgliosis in the prefrontal cortex and substantia nigra of mice.

CONCLUSION

These results explored that 6-MeOF possesses potential as anti-inflammatory and anti-oxidant agents against microglia-associated neuroinflammatory disorders.

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.

Altered expression of the immunoregulatory ligand-receptor pair CD200-CD200R1 in the brain of Parkinson's disease patients

Neuroinflammation, in which activated microglia are involved, appears to contribute to the development of Parkinson’s disease (PD). However, the role of microglial activation and the mechanisms governing this process remain uncertain. We focused on one inhibitory mechanism involved in the control of microglial activation, the microglia inhibitory receptor CD200R1, and its ligand CD200, mainly expressed by neurons. The human CD200R1 gene encodes two membrane-associated and two soluble protein isoforms and the human CD200 gene encodes full-length proteins (CD200full) but also truncated (CD200tr) proteins which act as CD200R1 antagonists. Little is known about their expression in the human brain under pathological conditions. We used human peripheral blood monocytes and monocyte-derived microglia-like cells from control subjects to characterize the expression of the CD200R1 mRNA variants, which showed stimulus-specific responses. We provide evidence of increased CD200R1 (mRNA variants and protein isoforms) and CD200 expression (CD200tr mRNA) in brain tissue of PD patients, mainly in the hippocampus, as well as increased CD200 expression (CD200full and CD200tr mRNAs) in iPSCs-derived dopaminergic neurons generated from skin fibroblasts of PD patients. Our results suggest that CD200-CD200R1 signalling is altered in PD, which may affect the microglial function and constitute a potential target in therapeutic strategies for PD.

Microvascular Changes in Parkinson’s Disease- Focus on the Neurovascular Unit

Vascular alterations emerge as a common denominator for several neurodegenerative diseases. In Parkinson’s disease (PD), a number of observations have been made suggesting that the occurrence of vascular pathology is an important pathophysiological aspect of the disease. Specifically, pathological activation of pericytes, blood-brain barrier (BBB) disruption, pathological angiogenesis and vascular regression have been reported. This review summarizes the current evidence for the different vascular alterations in patients with PD and in animal models of PD. We suggest a possible sequence of vascular pathology in PD ranging from early pericyte activation and BBB leakage to an attempt for compensatory angiogenesis and finally vascular rarefication. We highlight different pathogenetic mechanisms that play a role in these vascular alterations including perivascular inflammation and concomitant metabolic disease. Awareness of the contribution of vascular events to the pathogenesis of PD may allow the identification of targets to modulate those mechanisms. In particular the BBB has for decades only been viewed as an obstacle for drug delivery, however, preservation of its integrity and/or modulation of the signaling at this interface between the blood and the brain may prove to be a new avenue to take in order to develop disease-modifying strategies for neurodegenerative disorders.

LRRK2 Inhibition Mitigates the Neuroinflammation Caused by TLR2-Specific α-Synuclein and Alleviates Neuroinflammation-Derived Dopaminergic Neuronal Loss

Evidence suggests that crosstalk occurs between microglial leucine-rich repeat kinase 2 (LRRK2)-a regulator of neuroinflammation-and neuron-released α-synuclein (αSyn)-a promoter of microglial activation and neuroinflammatory responses-in neuroinflammation-mediated Parkinson's disease (PD) progression. Therefore, we examined whether LRRK2 inhibition reduces the responses of microglia to neuroinflammation caused by neuron-released αSyn. We examined the neuroinflammatory responses provoked by Toll-like receptor 2 (TLR2)-positive αSyn of neuronal cells using an LRRK2 inhibitor in the mouse glioma cells, rat primary microglia, and human microglia cell line; and the effects of LRRK2 inhibitor in the co-culture of ectopic αSyn-expressing human neuroblastoma cells and human microglia cells and in mouse models by injecting αSyn. We analyzed the association between LRRK2 activity and αSyn oligomer and TLR2 levels in the substantia nigra tissues of human patients with idiopathic PD (iPD). The TLR2-specific αSyn elevated LRRK2 activity and neuroinflammation, and the LRRK2 inhibitor ameliorated neuroinflammatory responses in various microglia cells, alleviated neuronal degeneration along with neuroinflammation in the co-culture, and blocked the further progression of locomotor failure and dopaminergic neuronal degeneration caused by TLR2-specific αSyn in mice. Furthermore, LRRK2 phosphorylation was increased in patients with iPD showing αSyn-specific high TLR2 level. These results suggest the application of LRRK2 inhibitors as a novel therapeutic approach against αSyn-mediated PD progression.

MED1/BDNF/TrkB pathway is involved in thalamic hemorrhage-induced pain and depression by regulating microglia

Central post-stroke pain (CPSP) and associated depression remain poorly understood and pharmacological treatments are unsatisfactory. Recently, microglia activation was suggested to be involved in CPSP pathophysiology. The goal of this study was to investigate the effectiveness of a co-ultramicronized combination of N-palmitoylethanolamide and luteolin (PEALut) in a mouse model of thalamic hemorrhage (TH)-induced CPSP. TH was established through the collagenase-IV injection in thalamic ventral-posterolateral-nucleus. PEALut effects in CPSP-associated behaviors were evaluated during a 28-days observation period. We found that repeated administrations of co-ultra PEALut significantly reduced mechanical hypersensitivity after TH, as compared to vehicle, by reducing the early microglial activation in the perilesional site. Moreover, PEALut prevented the development of depressive-like behavior (21 days post-TH). These effects were associated with the restoration of synaptic plasticity in LEC-DG pathway and monoamines levels found impaired in TH mice. Hippocampal MED1 and TrkB expressions were significantly increased in TH compared to sham mice 21 days post-TH, whereas BDNF levels were decreased. PEALut restored MED1/TrkB/BDNF expression in mice. Remarkably, we found significant overexpression of MED1 in the human autoptic brain specimens after stroke, indicating a translational potential of our findings. These results pave the way for better-investigating depression in TH- induced CPSP, together with the involvement of MED1/TrkB/BDNF pathway, proposing PEALut as an adjuvant treatment.

Functional genomics elucidates regulatory mechanisms of Parkinson's disease-associated variants

BACKGROUND

Genome-wide association studies (GWASs) have identified multiple risk loci for Parkinson's disease (PD). However, identifying the functional (or potential causal) variants in the reported risk loci and elucidating their roles in PD pathogenesis remain major challenges. To identify the potential causal (or functional) variants in the reported PD risk loci and to elucidate their regulatory mechanisms, we report a functional genomics study of PD.

METHODS

We first integrated chromatin immunoprecipitation sequencing (ChIP-Seq) (from neuronal cells and human brain tissues) data and GWAS-identified single-nucleotide polymorphisms (SNPs) in PD risk loci. We then conducted a series of experiments and analyses to validate the regulatory effects of these (i.e., functional) SNPs, including reporter gene assays, allele-specific expression (ASE), transcription factor (TF) knockdown, CRISPR-Cas9-mediated genome editing, and expression quantitative trait loci (eQTL) analysis.

RESULTS

We identified 44 SNPs (from 11 risk loci) affecting the binding of 12 TFs and we validated the regulatory effects of 15 TF binding-disrupting SNPs. In addition, we also identified the potential target genes regulated by these TF binding-disrupting SNPs through eQTL analysis. Finally, we showed that 4 eQTL genes of these TF binding-disrupting SNPs were dysregulated in PD cases compared with controls.

CONCLUSION

Our study systematically reveals the gene regulatory mechanisms of PD risk variants (including widespread disruption of CTCF binding), generates the landscape of potential PD causal variants, and pinpoints promising candidate genes for further functional characterization and drug development.

Evidence of Inflammation in Parkinson’s Disease and Its Contribution to Synucleinopathy

Accumulation of alpha-synuclein (αSyn) protein in neurons is a renowned pathological hallmark of Parkinson’s disease (PD). In addition, accumulating evidence indicates that activated inflammatory responses are involved in the pathogenesis of PD. Thus, achieving a better understanding of the interaction between inflammation and synucleinopathy in relation to the PD process will facilitate the development of promising disease-modifying therapies. In this review, the evidence of inflammation in PD is discussed, and human, animal, and laboratory studies relevant to the relationship between inflammation and αSyn are explored as well as new therapeutic targets associated with this relationship.

Targeting α-Synuclein in Parkinson's Disease by Induced Pluripotent Stem Cell Models

Parkinson's disease (PD) is a progressive, neurodegenerative disorder characterized by motor and non-motor symptoms. To date, no specific treatment to halt disease progression is available, only medication to alleviate symptoms can be prescribed. The main pathological hallmark of PD is the development of neuronal inclusions, positive for α-synuclein (α-syn), which are termed Lewy bodies (LBs) or Lewy neurites. However, the cause of the inclusion formation and the loss of neurons remain largely elusive. Various genetic determinants were reported to be involved in PD etiology, including SNCA, DJ-1, PRKN, PINK1, LRRK2, and GBA. Comprehensive insights into pathophysiology of PD critically depend on appropriate models. However, conventional model organisms fall short to faithfully recapitulate some features of this complex disease and as a matter-of-fact access to physiological tissue is limiting. The development of disease models replicating PD that are close to human physiology and dynamic enough to analyze the underlying molecular mechanisms of disease initiation and progression, as well as the generation of new treatment options, is an important and overdue step. Recently, the establishment of induced pluripotent stem cell (iPSC)-derived neural models, particularly from genetic PD-variants, developed into a promising strategy to investigate the molecular mechanisms regarding formation of inclusions and neurodegeneration. As these iPSC-derived neurons can be generated from accessible biopsied samples of PD patients, they carry pathological alterations and enable the possibility to analyze the differences compared to healthy neurons. This review focuses on iPSC models carrying genetic PD-variants of α-syn that will be especially helpful in elucidating the pathophysiological mechanisms of PD. Furthermore, we discuss how iPSC models can be instrumental in identifying cellular targets, potentially leading to the development of new therapeutic treatments. We will outline the enormous potential, but also discuss the limitations of iPSC-based α-syn models.

Human Umbilical Cord Mesenchymal Stem Cells Improve Locomotor Function in Parkinson’s Disease Mouse Model Through Regulating Intestinal Microorganisms

Parkinson’s disease (PD) is a progressive neurological disorder characterized by loss of neurons that synthesize dopamine, and subsequent impaired movement. Umbilical cord mesenchymal stem cells (UC-MSCs) exerted neuroprotection effects in a rodent model of PD. However, the mechanism underlying UC-MSC-generated neuroprotection was not fully elucidated. In the present study, we found that intranasal administration of UC-MSCs significantly alleviated locomotor deficits and rescued dopaminergic neurons by inhibiting neuroinflammation in a PD mouse model induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP, a toxic agent which selectively destroys nigrostriatal neurons but does not affect dopaminergic neurons elsewhere). Furthermore, UC-MSC treatment altered gut microbiota composition characterized by decreased phylum Proteobacteria, class Gammaproteobacteria, family Enterobacteriaceae, and genus Escherichia-Shigella. In addition, the neurotransmitter dopamine in the striatum and 5-hydroxytryptamine in the colon were also modulated by UC-MSCs. Meanwhile, UC-MSCs significantly maintained intestinal goblet cells, which secrete mucus as a mechanical barrier against pathogens. Furthermore, UC-MSCs alleviate the level of TNF-α and IL-6 as well as the conversion of NF-κB expression in the colon, indicating that inflammatory responses were blocked by UC-MSCs. PICRUSt showed that some pathways including bacterial invasion of epithelial cells, fluorobenzoate degradation, and pathogenic Escherichia coli infection were significantly reversed by UC-MSCs. These data suggest that the beneficial effects were detected following UC-MSC intranasal transplantation in MPTP-treated mice. There is a possible neuroprotective role of UC-MSCs in MPTP-induced PD mice by cross talk between the brain and gut.

Neuroprotection and Disease Modification by Astrocytes and Microglia in Parkinson Disease

Oxidative stress and neuroinflammation are common bases for disease onset and progression in many neurodegenerative diseases. In Parkinson disease, which is characterized by the degeneration of dopaminergic neurons resulting in dopamine depletion, the pathogenesis differs between hereditary and solitary disease forms and is often unclear. In addition to the pathogenicity of alpha-synuclein as a pathological disease marker, the involvement of dopamine itself and its interactions with glial cells (astrocyte or microglia) have attracted attention. Pacemaking activity, which is a hallmark of dopaminergic neurons, is essential for the homeostatic maintenance of adequate dopamine concentrations in the synaptic cleft, but it imposes a burden on mitochondrial oxidative glucose metabolism, leading to reactive oxygen species production. Astrocytes provide endogenous neuroprotection to the brain by producing and releasing antioxidants in response to oxidative stress. Additionally, the protective function of astrocytes can be modified by microglia. Some types of microglia themselves are thought to exacerbate Parkinson disease by releasing pro-inflammatory factors (M1 microglia). Although these inflammatory microglia may further trigger the inflammatory conversion of astrocytes, microglia may induce astrocytic neuroprotective effects (A2 astrocytes) simultaneously. Interestingly, both astrocytes and microglia express dopamine receptors, which are upregulated in the presence of neuroinflammation. The anti-inflammatory effects of dopamine receptor stimulation are also attracting attention because the functions of astrocytes and microglia are greatly affected by both dopamine depletion and therapeutic dopamine replacement in Parkinson disease. In this review article, we will focus on the antioxidative and anti-inflammatory effects of astrocytes and their synergism with microglia and dopamine.

Recent advances in preventing neurodegenerative diseases

The worldwide health-care burden of neurodegenerative diseases is on the rise-a crisis created through a combination of increased caseload and lack of effective treatments. The limitations of pharmacotherapy in these disorders have led to an urgent shift toward research and clinical trials for the development of novel compounds, interventions, and methods that target shared features across the spectrum of neurodegenerative diseases. Research targets include neuronal cell death, mitochondrial dysfunction, protein aggregation, and neuroinflammation. In the past few years, there has been a growth in understanding of the pathophysiologic mechanisms of neurodegenerative disorders such as Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, multiple sclerosis, and Huntington's disease. This increase in knowledge has led to the discovery of numerous novel neuroprotective therapeutic targets. In this context, we reviewed and summarized recent advancements in neuroprotective strategies in neurodegenerative diseases.

Calpain activation and progression of inflammatory cycles in Parkinson's disease

Parkinson's disease (PD) is a progressive, neurodegenerative condition of the central nervous system (CNS) affecting 6.3 million people worldwide with no curative treatments. Current therapies aim to mitigate PD's effects and offer symptomatic relief for patients. Multiple pathways are involved in the pathogenesis of PD, leading to neuroinflammation and the destruction of dopaminergic neurons in the CNS. This review focuses on PD pathology and the role of calpain, a neutral protease, as a regulator of various immune cells such as T-cells, microglia and astrocytes which lead to persistent neuroinflammatory responses and neuronal loss in both the brain and spinal cord (SC). Calpain plays a significant role in the cleavage and aggregation of toxic α-synuclein (α-syn), a presynaptic neural protein, and other organelles, contributing to mitochondrial dysfunction and oxidative stress. α-Syn aggregation results in the formation of Lewy bodies (LB) that further contribute to neuronal damage through lipid bilayer penetration, calcium ion (Ca2+) influx, oxidative stress and damage to the blood brain barrier (BBB). Dysfunctional mitochondria destabilize cytosolic Ca2+ concentrations, raising intracellular Ca2+; this leads to excessive calpain activation and persistent inflammatory responses. α-Syn aggregation also results in the disruption of dopamine synthesis through phosphorylation of tyrosine hydroxylase (TH), a key enzyme involved in the conversion of tyrosine to levodopa (L-DOPA), the amino acid precursor to dopamine. Decreased dopamine levels result in altered dopamine receptor (DR) signaling, ultimately activating pro-inflammatory T-cells to further contribute to the inflammatory response. All of these processes, together, result in neuroinflammation, degeneration and ultimately neuronal death seen in PD. 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP-a prodrug to the neurotoxin 1-methyl-4-phenylpyridinium (MPP+)), rotenone (an environmental neurotoxin), and 6-hydroxydopamine (6-OHDA - a neurotoxic synthetic organic compound) induce PD-like conditions when injected into rodents. All three agents work through similar mechanisms and lead to degeneration of dopaminergic neurons in the substantia nigra (SN) and more recently discovered in motor neurons of the spinal cord (SC). These neurotoxins also increase calpain activity, furthering the neuroinflammatory response. Hence, calpain inhibitors have been posited as potential therapeutics for PD to prevent calpain-related inflammation and neurodegenerative responses in not only the SN but the SC as well.

Neuroprotective Effects of Resveratrol in In vivo and In vitro Experimental Models of Parkinson's Disease: a Systematic Review

Parkinson's disease (PD) is currently the second most common neurodegenerative disease, being characterized by motor and non-motor symptoms. The therapeutic options available for its treatment are limited, do not slow the progression of the disease, and have serious side effects. For this reason, many studies have sought to find compounds with neuroprotective properties that bring additional benefits to current therapy. In this context, resveratrol is a phenolic compound, found in many plant species, capable of crossing the blood-brain barrier and having multiple biological properties. Experimental studies in vitro and in vivo have shown that it can prevent or slow the progression of a variety of diseases, including PD. In this systematic review, we summarize the effects of resveratrol in experimental in vivo and in vitro models of PD and discuss the molecular mechanisms involved in its action. The bibliographic search was performed in the databases of PubMed, Web of Science, SciELO, and Google Scholar, and based on the inclusion criteria, 41 articles were selected and discussed. Most of the included studies have demonstrated neuroprotective effects of resveratrol. In general, resveratrol prevented behavioral and/or neurological disorders, improved antioxidant defenses, reduced neuroinflammatory processes, and inhibited apoptosis. In summary, this systematic review offers important scientific evidence of neuroprotective effects of resveratrol in PD and also provide valuable information about its mechanism of action that can support future clinical studies.

Neuroinflammation in perioperative neurocognitive disorders: From bench to the bedside

The perioperative neurocognitive disorders (PNDs) are one of the most common complications in elderly patients characterized by various forms of cognitive decline after anesthesia and surgery. Although the etiology for PNDs remained unclear, neuroinflammation has been characterized as one of the major causes, especially in the elderly patients. The activation of glial cells including microglia and astrocytes plays a significant role in the inflammatory responses in central nerve system (CNS). Although carefully designed, clinical studies on PNDs showed controversial results. Meanwhile, preclinical studies provided evidence from various levels, including behavior performance, protein levels, and gene expression. In this review, we summarize high‐quality studies and recent advances from both clinical and preclinical studies and provide a broad view from the onset of PNDs to its potential therapeutic targets. Future studies are needed to investigate the signaling pathways in PNDs for prevention and treatment, as well as the relationship of PNDs and future neurocognitive dysfunction.

Profile of the RNA in exosomes from astrocytes and microglia using deep sequencing: implications for neurodegeneration mechanisms

Glial cells play an important role in signal transduction, energy metabolism, extracellular ion homeostasis and neuroprotection of the central nervous system. However, few studies have explained the potential effects of exosomes from glial cells on central nervous system health and disease. In this study, the genes expressed in exosomes from astrocytes and microglia were identified by deep RNA sequencing. Kyoto Encyclopedia of Genes and Genomes analysis indicated that several pathways in these exosomes are responsible for promoting neurodegenerative diseases, including Alzheimer’s disease, Parkinson’s disease and Huntington’s disease. Gene ontology analysis showed that extracellular exosome, mitochondrion and growth factor activity were enriched in exosomes from the unique astrocyte group, while extracellular exosome and mitochondrion were enriched in exosomes from the unique microglia group. Next, combined with the screening of hub genes, the protein-protein interaction network analysis showed that exosomes from astrocytes influence neurodegenerative diseases through metabolic balance and ubiquitin-dependent protein balance, whereas exosomes from microglia influence neurodegenerative diseases through immune inflammation and oxidative stress. Although there were differences in RNA expression between exosomes from astrocytes and microglia, the groups were related by the hub genes, ubiquitin B and heat shock protein family A (Hsp70) member 8. Ubiquitin B appeared to be involved in pleiotropic regulatory functions, including immune regulation, inflammation inhibition, protein catabolism, intracellular protein transport, exosomes and oxidative stress. The results revealed the clinical significance of exosomes from glia in neurodegenerative diseases. This study was approved by the Animal Ethics Committee of Nantong University, China (approval No. S20180102-152) on January 2, 2018.

Gut microbiota relieves inflammation in the substantia nigra of chronic Parkinson's disease by protecting the function of dopamine neurons

The composition of the intestinal flora of patients with Parkinson's disease (PD) can change. However, whether reshaping the gut microbial composition can treat PD remains to be seen. The present study evaluated the effect of intestinal flora in the treatment of PD in a C57BL/6 mouse PD model induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Chronic, low-dose, MPTP-treated mice exhibited upregulated gene expression levels of TNF-α and IL-1β in the substantia nigra (SN) of the mice, and induced intestinal microbial disorders. This indicated that the chronic low-dose MPTP model could be used to evaluate the progress of early intestinal pathology and intestinal flora imbalance in PD. After transplantation of faecal bacteria to MPTP-induced PD mice, the level of inflammation in the SN of the mice was reduced, and motor dysfunction was alleviated. Notably, faecal microbiota transplantation (FMT) upregulated the abundance of Blautia but downregulated Anaerostipes, Bifidobacterium, ASF356 and Ruminococcus in the gut of PD mice. In addition, FMT reduced the activation of microglia and astrocytes in the SN and reduced the expression levels of GSK3β, IL-1β, inducible nitric oxide synthase and phosphorylated PTEN in the SN. Overall, the present study demonstrated that gut microbial dysfunction is associated with the pathogenesis of PD, and that FMT can protect PD mice by inhibiting neuroinflammation.

Therapeutic Strategies for Immune Transformation in Parkinson's Disease

Dysregulation of innate and adaptive immunity can lead to alpha-synuclein (α-syn) misfolding, aggregation, and post-translational modifications in Parkinson's disease (PD). This process is driven by neuroinflammation and oxidative stress, which can contribute to the release of neurotoxic oligomers that facilitate dopaminergic neurodegeneration. Strategies that promote vaccines and antibodies target the clearance of misfolded, modified α-syn, while gene therapy approaches propose to deliver intracellular single chain nanobodies to mitigate α-syn misfolding, or to deliver neurotrophic factors that support neuronal viability in an otherwise neurotoxic environment. Additionally, transformative immune responses provide potential targets for PD therapeutics. Anti-inflammatory drugs represent one strategy that principally affects innate immunity. Considerable research efforts have focused on transforming the balance of pro-inflammatory effector T cells (Teffs) to favor regulatory T cell (Treg) activity, which aims to attenuate neuroinflammation and support reparative and neurotrophic homeostasis. This approach serves to control innate microglial neurotoxic activities and may facilitate clearance of α-syn aggregates accordingly. More recently, changes in the intestinal microbiome have been shown to alter the gut-immune-brain axis leading to suppressed leakage of bacterial products that can promote peripheral inflammation and α-syn misfolding. Together, each of the approaches serves to interdict chronic inflammation associated with disordered immunity and neurodegeneration. Herein, we examine research strategies aimed at improving clinical outcomes in PD.

Multi-omic insights into Parkinson's Disease: From genetic associations to functional mechanisms

Genome-Wide Association Studies (GWAS) have elucidated the genetic components of Parkinson's Disease (PD). However, because the vast majority of GWAS association signals fall within non-coding regions, translating these results into an interpretable, mechanistic understanding of the disease etiology remains a major challenge in the field. In this review, we provide an overview of the approaches to prioritize putative causal variants and genes as well as summarise the primary findings of previous studies. We then discuss recent efforts to integrate multi-omics data to identify likely pathogenic cell types and biological pathways implicated in PD pathogenesis. We have compiled full summary statistics of cell-type, tissue, and phentoype enrichment analyses from multiple studies of PD GWAS and provided them in a standardized format as a resource for the research community (https://github.com/RajLabMSSM/PD_omics_review). Finally, we discuss the experimental, computational, and conceptual advances that will be necessary to fully elucidate the effects of functional variants and genes on cellular dysregulation and disease risk.