The adhesion and migration of microglia to β-amyloid (Aβ) is decreased with aging and inhibited by Nogo/NgR pathway

Three-dimensional human neural culture on a chip recapitulating neuroinflammation and neurodegeneration

Neuroinflammation has either beneficial or detrimental effects, depending on risk factors and neuron-glia interactions in neurological disorders. However, studying neuroinflammation has been challenging due to the complexity of cell-cell interactions and lack of physio-pathologically relevant neuroinflammatory models. Here, we describe our three-dimensional microfluidic multicellular human neural culture model, referred to as a 'brain-on-a-chip' (BoC). This elucidates neuron-glia interactions in a controlled manner and recapitulates pathological signatures of the major neurological disorders: dementia, brain tumor and brain edema. This platform includes a chemotaxis module offering a week-long, stable chemo-gradient compared with the few hours in other chemotaxis models. Additionally, compared with conventional brain models cultured with mixed phenotypes of microglia, our BoC can separate the disease-associated microglia out of heterogeneous population and allow selective neuro-glial engagement in three dimensions. This provides benefits of interpreting the neuro-glia interactions while revealing that the prominent activation of innate immune cells is the risk factor leading to synaptic impairment and neuronal loss, validated in our BoC models of disorders. This protocol describes how to fabricate and implement our human BoC, manipulate in real time and perform end-point analyses. It takes 2 d to set up the device and cell preparations, 1-9 weeks to develop brain models under disease conditions and 2-3 d to carry out analyses. This protocol requires at least 1 month training for researchers with basic molecular biology techniques. Taken together, our human BoCs serve as reliable and valuable platforms to investigate pathological mechanisms involving neuroinflammation and to assess therapeutic strategies modulating neuroinflammation in neurological disorders.

Enhanced microglial dynamics and paucity of tau seeding in the amyloid plaque microenvironment contributes to cognitive resilience in Alzheimer's disease

Asymptomatic Alzheimer's disease (AsymAD) describes the status of subjects with preserved cognition but with identifiable Alzheimer's disease (AD) brain pathology (i.e. Aβ-amyloid deposits, neuritic plaques, and neurofibrillary tangles) at autopsy. In this study, we investigated the postmortem brains of a cohort of AsymAD cases to gain insight into the underlying mechanisms of resilience to AD pathology and cognitive decline. Our results showed that AsymAD cases exhibit an enrichment of core plaques and decreased filamentous plaque accumulation, as well as an increase in microglia surrounding this last type. In AsymAD cases we found less pathological tau aggregation in dystrophic neurites compared to AD and tau seeding activity comparable to healthy control subjects. We used spatial transcriptomics to further characterize the plaque niche and found autophagy, endocytosis, and phagocytosis within the top upregulated pathways in the AsymAD plaque niche, but not in AD. Furthermore, we found ARP2, an actin-based motility protein crucial to initiate the formation of new actin filaments, increased within microglia in the proximity of amyloid plaques in AsymAD. Our findings support that the amyloid-plaque microenvironment in AsymAD cases is characterized by microglia with highly efficient actin-based cell motility mechanisms and decreased tau seeding compared to AD. These two mechanisms can potentially provide protection against the toxic cascade initiated by Aβ that preserves brain health and slows down the progression of AD pathology.

The RhoA-ROCK1/ROCK2 Pathway Exacerbates Inflammatory Signaling in Immortalized and Primary Microglia

Neuroinflammation is a unifying factor among all acute central nervous system (CNS) injuries and chronic neurodegenerative disorders. Here, we used immortalized microglial (IMG) cells and primary microglia (PMg) to understand the roles of the GTPase Ras homolog gene family member A (RhoA) and its downstream targets Rho-associated coiled-coil-containing protein kinases 1 and 2 (ROCK1 and ROCK2) in neuroinflammation. We used a pan-kinase inhibitor (Y27632) and a ROCK1- and ROCK2-specific inhibitor (RKI1447) to mitigate a lipopolysaccharide (LPS) challenge. In both the IMG cells and PMg, each drug significantly inhibited pro-inflammatory protein production detected in media (TNF-α, IL-6, KC/GRO, and IL-12p70). In the IMG cells, this resulted from the inhibition of NF-κB nuclear translocation and the blocking of neuroinflammatory gene transcription (iNOS, TNF-α, and IL-6). Additionally, we demonstrated the ability of both compounds to block the dephosphorylation and activation of cofilin. In the IMG cells, RhoA activation with Nogo-P4 or narciclasine (Narc) exacerbated the inflammatory response to the LPS challenge. We utilized a siRNA approach to differentiate ROCK1 and ROCK2 activity during the LPS challenges and showed that the blockade of both proteins may mediate the anti-inflammatory effects of Y27632 and RKI1447. Using previously published data, we show that genes in the RhoA/ROCK signaling cascade are highly upregulated in the neurodegenerative microglia (MGnD) from APP/PS-1 transgenic Alzheimer's disease (AD) mice. In addition to illuminating the specific roles of RhoA/ROCK signaling in neuroinflammation, we demonstrate the utility of using IMG cells as a model for primary microglia in cellular studies.

Unveiling the modulation of Nogo receptor in neuroregeneration and plasticity: Novel aspects and future horizon in a new frontier

Neurodegenerative diseases (NDs) such as Alzheimer's, Parkinson's, Multiple Sclerosis, Hereditary Spastic Paraplegia, and Amyotrophic Lateral Sclerosis have emerged as the most dreaded diseases due to a lack of precise diagnostic tools and efficient therapies. Despite the fact that the contributing factors of NDs are still unidentified, mounting evidence indicates the possibility that genetic and cellular changes may lead to the significant production of abnormally misfolded proteins. These misfolded proteins lead to damaging effects thereby causing neurodegeneration. The association between Neurite outgrowth factor (Nogo) with neurological diseases and other peripheral diseases is coming into play. Three isoforms of Nogo have been identified Nogo-A, Nogo-B and Nogo-C. Among these, Nogo-A is mainly responsible for neurological diseases as it is localized in the CNS (Central Nervous System), whereas Nogo-B and Nogo-C are responsible for other diseases such as colitis, lung, intestinal injury, etc. Nogo-A, a membrane protein, had first been described as a CNS-specific inhibitor of axonal regeneration. Several recent studies have revealed the role of Nogo-A proteins and their receptors in modulating neurite outgrowth, branching, and precursor migration during nervous system development. It may also modulate or affect the inhibition of growth during the developmental processes of the CNS. Information about the effects of other ligands of Nogo protein on the CNS are yet to be discovered however several pieces of evidence have suggested that it may also influence the neuronal maturation of CNS and targeting Nogo-A could prove to be beneficial in several neurodegenerative diseases.

Molecular Mechanisms of Neuroinflammation in Aging and Alzheimer's Disease Progression

Aging is the most prominent risk factor for late-onset Alzheimer's disease. Aging associates with a chronic inflammatory state both in the periphery and in the central nervous system, the evidence thereof and the mechanisms leading to chronic neuroinflammation being discussed. Nonetheless, neuroinflammation is significantly enhanced by the accumulation of amyloid beta and accelerates the progression of Alzheimer's disease through various pathways discussed in the present review. Decades of clinical trials targeting the 2 abnormal proteins in Alzheimer's disease, amyloid beta and tau, led to many failures. As such, targeting neuroinflammation via different strategies could prove a valuable therapeutic strategy, although much research is still needed to identify the appropriate time window. Active research focusing on identifying early biomarkers could help translating these novel strategies from bench to bedside.

Sulforaphene, a CDK5 Inhibitor, attenuates cognitive deficits in a transgenic mouse model of Alzheimer's disease via reducing Aβ Deposition, tau hyperphosphorylation and synaptic dysfunction

BACKGROUND

Alzheimer's disease (AD) is the most common form of neurodegenerative disorder characterized by progressive loss of memory and cognitive functions. There are two pathological hallmarks, including accumulation of amyloid plaques composed of β-amyloid peptide (Aβ) and deposits of neurofibrillatory tangles (NFT). Cyclin-dependent kinase 5 (CDK5), a serine/threonine kinase, plays an important role in synaptic plasticity and cognitive behavior. Sulforaphene (SF) has been demonstrated to exert anti-AD activity in AD rat model. In this study, we aimed to evaluate the cognitive deficits improving effects of SF on in TgCRND8 mice and to elucidate the underlying molecular mechanisms.

METHODS

TgCRND8 mice were intragastrically treated with SF (25 and 50 mg/kg) for 4 months from 3-month-old. The cognitive functions were assessed using Morris Water Maze Test. Cultured primary mouse neurons were pre-treated with SF, followed by co-treatment with Aβ1-42 oligomers. CDK5 inhibitor (roscovitine) was used to determine the involvement of CDK5/p25 pathway in the anti-AD effects of SF in primary neurons.

RESULTS

Our results showed that SF treatment significantly ameliorated the cognitive deficits in TgCRND8 mice and protected primary mouse neurons against Aβ1-42 induced neurotoxicity. SF could modulate the expression of Aβ production related markers, and suppress the phosphorylation of tau protein at specific sites in the TgCRND8 mice. In addition, SF enhanced the expressions of synaptic plasticity related markers and CDK5. SF also markedly suppressed the CDK5/p25 activity.

CONCLUSIONS

SF is a potent CDK5 inhibitor and a potential therapeutic agent for treatment and prevention of AD. Moreover, SF inhibited the overexpression of CDK5 in primary neurons of mouse.

Modulation of the Microglial Nogo-A/NgR Signaling Pathway as a Therapeutic Target for Multiple Sclerosis

Current therapeutics targeting chronic phases of multiple sclerosis (MS) are considerably limited in reversing the neural damage resulting from repeated inflammation and demyelination insults in the multi-focal lesions. This inflammation is propagated by the activation of microglia, the endogenous immune cell aiding in the central nervous system homeostasis. Activated microglia may transition into polarized phenotypes; namely, the classically activated proinflammatory phenotype (previously categorized as M1) and the alternatively activated anti-inflammatory phenotype (previously, M2). These transitional microglial phenotypes are dynamic states, existing as a continuum. Shifting microglial polarization to an anti-inflammatory status may be a potential therapeutic strategy that can be harnessed to limit neuroinflammation and further neurodegeneration in MS. Our research has observed that the obstruction of signaling by inhibitory myelin proteins such as myelin-associated inhibitory factor, Nogo-A, with its receptor (NgR), can regulate microglial cell function and activity in pre-clinical animal studies. Our review explores the microglial role and polarization in MS pathology. Additionally, the potential therapeutics of targeting Nogo-A/NgR cellular mechanisms on microglia migration, polarization and phagocytosis for neurorepair in MS and other demyelination diseases will be discussed.

The role of microglia in Alzheimer's disease and progress of treatment

Microglia are permanent immune cells of the central nervous system. Microglia play an important role in the pathological process of Alzheimer's disease (AD). They are mainly involved in the uptake and clearance of amyloid-β (Aβ), as well as the formation of neuroinflammation. We found that overactivated microglia increase Aβ and Tau, and Aβ and Tau in turn act as activators of microglia. Additionally, various cytokines and proteins, high cholesterol, and telomere shortening are all associated with microglia activation. More activated microglia induce the release of inflammatory and anti-inflammatory factors to regulate inflammation, while microglia express multiple homologous receptors that bind to neuroimmunomodulators to prevent microglia overactivation. Moreover, aging of the body promotes neuroinflammation by increasing the response to IFN-γ (interferon-γ), and aging of the microglia themselves promotes AD by inducing the accumulation of large amounts of iron and reducing autophagy by regulating protein levels. Cognitive dysfunction occurs when activated microglia induce an increase in beta oligomers, promoting the production of pro-inflammatory factors that alter the shape, composition, and density of synapses. Based on their correlation, microglia-mediated AD therapy as well as the corresponding targets and drugs are discussed. In contrast to similar reviews, this article also summarizes some novel microglia-mediated AD treatment methods over the recent years.

p38 Inhibition Decreases Tau Toxicity in Microglia and Improves Their Phagocytic Function

Alzheimer’s disease (AD) and other tauopathies are histopathologically characterized by tau aggregation, along with a chronic inflammatory response driven by microglia. Over the past few years, the role of microglia in AD has been studied mainly in relation to amyloid-β (Aβ) pathology. Consequently, there is a substantial knowledge gap concerning the molecular mechanisms involved in tau-mediated toxicity and neuroinflammation, thus hindering the development of therapeutic strategies. We previously demonstrated that extracellular soluble tau triggers p38 MAPK activation in microglia. Given the activation of this signaling pathway in AD and its involvement in neuroinflammation processes, here we evaluated the effect of p38 inhibition on primary microglia cultures subjected to tau treatment. Our data showed that the toxic effect driven by tau in microglia was diminished through p38 inhibition. Furthermore, p38 blockade enhanced microglia-mediated tau phagocytosis, as reflected by an increase in the number of lysosomes. In conclusion, these results contribute to our understanding of the functions of p38 in the central nervous system (CNS) beyond tau phosphorylation in neurons and provide further insights into the potential of p38 inhibition as a therapeutic strategy to halt neuroinflammation in tauopathies.

Nogo receptor impairs the clearance of fibril amyloid-β by microglia and accelerates Alzheimer's-like disease progression

Alzheimer's disease (AD) is characterized by the progressive accumulation of β‐amyloid (Aβ)‐containing amyloid plaques, and microglia play a critical role in mediating Aβ clearance. Mounting evidence has confirmed that the ability of microglia in clearing Aβ decreased with aging and AD progress, but the underlying mechanisms are unclear. Previously, we have demonstrated that Nogo receptor (NgR), a receptor for three axon growth inhibitors associated with myelin, can decrease adhesion and migration of microglia to fibrils Aβ with aging. However, whether NgR expressed on microglia affect microglia phagocytosis of fibrils Aβ with aging remains unclear. Here, we found that aged but not young microglia showed increased NgR expression and decreased Aβ phagocytosis in APP/PS1 transgenic mice. NgR knockdown APP/PS1 mice showed simultaneous reduced amyloid burden and improved spatial learning and memory, which were associated with increased Aβ clearance. Importantly, Nogo‐P4, an agonist of NgR, enhanced the protein level of p‐Smad2/3, leading to a significant transcriptional inhibition of CD36 gene expression, which in turn decreased the microglial phagocytosis of Aβ. Moreover, ROCK accounted for Nogo‐P4‐induced activation of Smad2/3 signaling. Finally, the decreasing effect of NgR on microglial Aβ uptake was confirmed in a mouse model of intra‐hippocampal fAβ injection. Our findings suggest that NgR may play an important role in the regulation of Aβ homeostasis, and has potential as a therapeutic target for AD.

The Regulatory Role of Reticulons in Neurodegeneration: Insights Underpinning Therapeutic Potential for Neurodegenerative Diseases

In the last few decades, cytoplasmic organellar dysfunction, such as that of the endoplasmic reticulum (ER), has created a new area of research interest towards the development of serious health maladies including neurodegenerative diseases. In this context, the extensively dispersed family of ER-localized proteins, i.e. reticulons (RTNs), is gaining interest because of its regulative control over neural regeneration. As most neurodegenerative diseases are pathologically manifested with the accretion of misfolded proteins with subsequent induction of ER stress, the regulatory role of RTNs in neural dysfunction cannot be ignored. With the limited information available in the literature, delineation of the functional connection between rising consequences of neurodegenerative diseases and RTNs need to be elucidated. In this review, we provide a broad overview on the recently revealed regulatory roles of reticulons in the pathophysiology of several health maladies, with special emphasis on neurodegeneration. Additionally, we have also recapitulated the decisive role of RTN4 in neurite regeneration and highlighted how neurodegeneration and proteinopathies are mechanistically linked with each other through specific RTN paralogues. With the recent findings advocating zebrafish Rtn4b (a mammalian Nogo-A homologue) downregulation following central nervous system (CNS) lesion, RTNs provides new insight into the CNS regeneration. However, there are controversies with respect to the role of Rtn4b in zebrafish CNS regeneration. Given these controversies, the connection between the unique regenerative capabilities of zebrafish CNS by distinct compensatory mechanisms and Rtn4b signalling pathway could shed light on the development of new therapeutic strategies against serious neurodegenerative diseases.

A Novel Role of Nogo Proteins: Regulating Macrophages in Inflammatory Disease

Nogo proteins, also known as Reticulon-4, have been identified as myelin-derived inhibitors of neurite outgrowth in the central nervous system (CNS). There are three Nogo variants, Nogo-A, Nogo-B and Nogo-C. Recent studies have shown that Nogo-A/B is abundant in macrophages and may have a wider effect on inflammation. In this review, we focus mainly on the possible roles of Nogo-A/B on polarization and recruitment of macrophages and their involvement in a variety of inflammatory diseases. We then discuss the Nogo receptor1 (NgR1), a common receptor for Nogo proteins that is also abundant in microglia/macrophage in the CNS. Interaction of Nogo and NgR1 in microglia/macrophage may affect the adhesion and polarization of macrophages that are involved in multiple neurodegenerative diseases, including Alzheimer's disease and multiple sclerosis. Overall, this review provides insights into the roles of Nogo proteins in regulating macrophage functions and suggests that, potentially, Nogo proteins maybe a new target in the treatment of inflammatory diseases.

Artemisinin improves neurocognitive deficits associated with sepsis by activating the AMPK axis in microglia

Sepsis is life-threatening organ dysfunction due to dysregulated systemic inflammatory and immune response to infection, often leading to cognitive impairments. Growing evidence shows that artemisinin, an antimalarial drug, possesses potent anti-inflammatory and immunoregulatory activities. In this study we investigated whether artemisinin exerted protective effect against neurocognitive deficits associated with sepsis and explored the underlying mechanisms. Mice were injected with LPS (750 μg · kg-1 · d-1, ip, for 7 days) to establish an animal model of sepsis. Artemisinin (30 mg · kg-1 · d-1, ip) was administered starting 4 days prior LPS injection and lasting to the end of LPS injection. We showed that artemisinin administration significantly improved LPS-induced cognitive impairments assessed in Morris water maze and Y maze tests, attenuated neuronal damage and microglial activation in the hippocampus. In BV2 microglial cells treated with LPS (100 ng/mL), pre-application of artemisinin (40 μΜ) significantly reduced the production of proinflammatory cytokines (i.e., TNF-α, IL-6) and suppressed microglial migration. Furthermore, we revealed that artemisinin significantly suppressed the nuclear translocation of NF-κB and the expression of proinflammatory cytokines by activating the AMPKα1 pathway; knockdown of AMPKα1 markedly abolished the anti-inflammatory effects of artemisinin in BV2 microglial cells. In conclusion, atemisinin is a potential therapeutic agent for sepsis-associated neuroinflammation and cognitive impairment, and its effect is probably mediated by activation of the AMPKα1 signaling pathway in microglia.

Opposing functions of β-arrestin 1 and 2 in Parkinson's disease via microglia inflammation and Nprl3

Although β-arrestins (ARRBs) regulate diverse physiological and pathophysiological processes, their functions and regulation in Parkinson's disease (PD) remain poorly defined. In this study, we show that the expression of β-arrestin 1 (ARRB1) and β-arrestin 2 (ARRB2) is reciprocally regulated in PD mouse models, particularly in microglia. ARRB1 ablation ameliorates, whereas ARRB2 knockout aggravates, the pathological features of PD, including dopaminergic neuron loss, neuroinflammation and microglia activation in vivo, and microglia-mediated neuron damage in vitro. We also demonstrate that ARRB1 and ARRB2 produce adverse effects on inflammation and activation of the inflammatory STAT1 and NF-κB pathways in primary cultures of microglia and macrophages and that two ARRBs competitively interact with the activated form of p65, a component of the NF-κB pathway. We further find that ARRB1 and ARRB2 differentially regulate the expression of nitrogen permease regulator-like 3 (Nprl3), a functionally poorly characterized protein, as revealed by RNA sequencing, and that in the gain- and loss-of-function studies, Nprl3 mediates the functions of both ARRBs in microglia inflammatory responses. Collectively, these data demonstrate that two closely related ARRBs exert opposite functions in microglia-mediated inflammation and the pathogenesis of PD which are mediated at least in part through Nprl3 and provide novel insights into the understanding of the functional divergence of ARRBs in PD.

Repressor Element 1 Silencing Transcription Factor (REST) Governs Microglia-Like BV2 Cell Migration via Progranulin (PGRN)

Microglia activation contributes to Alzheimer's disease (AD) etiology, and microglia migration is a fundamental function during microglia activation. The repressor element-1 silencing transcription factor (REST), a powerful transcriptional factor, was found to play a neuroprotective role in AD. Despite its possible role in disease progression, little is known about whether REST participates in microglia migration. In this study, we aimed to explore the function of REST and its molecular basis during microglia migration under Aβ_1-42-treated pathological conditions. When treated by Aβ_1-42 REST was upregulated through JAK2/STAT3 signal pathway in BV2 cells. And transwell coculture system was used to evaluate cell migration function of microglia-like BV2. Small interfering RNA (siRNA) targeting progranulin (PGRN) were delivered into BV2 cells, and results showed that PGRN functions to promote BV2 migration. REST expression was inhibited by sh-RNA, which induced BV2 cell migration obviously. On the contrary, REST was overexpressed by REST recombinant plasmid transfection, which repressed BV2 cell migration, indicating that REST may act as a repressor of cell migration. To more comprehensively examine the molecular basis, we analyzed the promoter sequence of PGRN and found that it has the potential binding site of REST. Moreover, knocking-down of REST can increase the expression of PGRN, which confirms the inhibiting effect of REST on PGRN expression. Further detection of double luciferase reporter gene also confirmed the inhibition of REST on the activity of PGRN promoter, indicating that REST may be an inhibitory transcription factor of PGRN which governs microglia-like BV2 cell migration. In conclusion, the present study demonstrates that transcription factor REST may act as a repressor of microglia migration through PGRN.

CD36 in Alzheimer's Disease: An Overview of Molecular Mechanisms and Therapeutic Targeting

CD36 is a membrane protein with wide distribution in the human body, is enriched in the monocyte-macrophage system and endothelial cells, and is involved in the cellular uptake of long chain fatty acids (LCFA) and oxidized low-density lipoproteins. It is also a scavenger receptor, binding hydrophobic amyloid fibrils found in the Alzheimer's disease (AD) brain. In neurobiology research, it has been mostly studied in relationship with chronic ischemia and stroke, but it was also related to amyloid clearance by microglial phagocytosis. In AD animal models, amyloid binding to CD36 has been consistently correlated with a pro-inflammatory response. Therapeutic approaches have two main focuses: CD36 blockade with monoclonal antibodies or small molecules, which is beneficial in terms of the inflammatory milieu, and upregulation of CD36 for increased amyloid clearance. The balance of the two approaches, centered on microglia, is poorly understood. Furthermore, CD36 evaluation in AD clinical studies is still at a very early stage and there is a gap in the knowledge regarding the impact of LCFA on AD progression and CD36 expression and genetic phenotype. This review summarizes the role played by CD36 in the pathogenic amyloid cascade and explore the translatability of preclinical data towards clinical research.

The age-related microglial transformation in Alzheimer's disease pathogenesis

Neuroinflammatory responses mediated by microglia, the resident immune cells of the central nervous system, have long been a subject of study in the field of Alzheimer's disease (AD). Microglia express a wide range of receptors that act as molecular sensors, through which they can fulfill their various functions. In this review, we first analyzed the changes in the expression levels of microglial membrane receptors SR-A, TREM2, CD36, CD33, and CR3 in aging and AD and described the different roles of these receptors in amyloid-beta clearance and inflammatory responses. Two classical hallmarks of AD are extracellular amyloid-beta deposits and intracellular aggregated phosphorylated tau. In AD, microglia reaction was initially thought to be triggered by amyloid deposits. New evidence showed it also associated with increased phosphorylation of tau. However, which first appeared and induced activated microglia is not clear. Then we summarized diverse opinions on it. Besides, as AD is tightly linked to aging, and microglia changes dramatically on aging, yet the relative impacts of both aging and microglia are less frequently considered, so at last, we discussed the roles of aging microglia in AD. We hope to provide a reference for subsequent research.

miR-124 participates in the proliferation and differentiation of brain glioma stem cells through regulating Nogo/NgR expression

The effect of miR-124 on the proliferation and differentiation of brain glioma stem cells and Nogo/NgR signaling pathway were investigated. miR-124 mimic, miR-124 inhibitor and miR-control expression vector were designed and produced to transfect U87 glioma stem cells. The results of transfection were tested via RT-qPCR and the expression of protein was detected by western blot analysis. Cell proliferation was detected by MTT proliferation and the proportion of CD133⁺ cells was detected by immunomagnetic beads to determine cell differentiation. The correlation between miR-124 and Nogo-A, and NgR protein expression was analyzed by Spearman correlation analysis. The relative expression of miR-124 in cells of miR-124 mimic group was significantly higher than that of miR-124 inhibitor and miR-control groups (P<0.05). The relative expression of Nogo-A and NgR protein in cells of the miR-124 mimic group was significantly lower than that of miR-124 inhibitor and miR-control groups (P<0.05). Absorbance values of the cells in the miR-124 mimic and miR-control groups were significantly lower than those in the miR-124 inhibitor group at each time point (P<0.05), while the values of the cells in the miR-124 mimic group were significantly lower than that in miR-control group (P<0.05). The level of CD133⁺ cells in miR-124 mimic group was significantly lower than that in miR-124 inhibitor and miR-control groups (P<0.05), while the level of CD133⁺ cells in miR-124 inhibitor group was higher than that in miR-control group (P<0.05). Correlation analysis revealed that there was a negative correlation between miR-124 and the expression of Nogo-A and NgR protein (P<0.05). miR-124 may participate in the differentiation of brain glioma stem cells through the Nogo/NgR pathway, which may bring a new direction for the clinical treatment of brain glioma.

Involvement of RhoA/ROCK Signaling in Aβ-Induced Chemotaxis, Cytotoxicity and Inflammatory Response of Microglial BV2 Cells

Reactive microglia clustering around amyloid plaques in brain is a histopathological feature of Alzheimer's disease (AD) and reflects the contribution of neuroinflammation in AD pathogenesis. β-Amyloid peptide (Aβ) has been shown to induce a range of microglial responses including chemotaxis, cytotoxicity and inflammation, but the underlying mechanism is poorly understood. Considering the fundamental role of RhoA/ROCK signaling in cell migration and its broad implication in AD and neuroinflammation, we hypothesized that RhoA/ROCK signaling might be involved in Aβ-induced microglial responses. From in vivo mouse models including APP/PS1 transgene and fibrillar Aβ stereotactic injection, we observed the elevated expression level of RhoA in reactive microglia. Through a series in vitro cell migration, cytotoxicity and biochemistry assays, we found that RhoA/ROCK signaling plays an essential role in Aβ-induced responses of microglial BV2 cells. Small molecular agents Fasudil and Y27632 showed prominent beneficial effects, which implies the therapeutic potential of RhoA/ROCK signaling inhibitors in AD treatment.

The Cytoskeleton as a Modulator of Aging and Neurodegeneration

The cytoskeleton consists of filamentous protein polymers that form organized structures, contributing to a multitude of cell life aspects. It includes three types of polymers: the actin microfilaments, the microtubules and the intermediate filaments. Decades of research have implicated the cytoskeleton in processes that regulate cellular and organismal aging, as well as neurodegeneration associated with injury or neurodegenerative disease, such as Alzheimer's disease, Parkinson's disease, Huntington's disease, Amyotrophic Lateral Sclerosis, or Charcot Marie Tooth disease. Here, we provide a brief overview of cytoskeletal structure and function, and discuss experimental evidence linking cytoskeletal function and dynamics with aging and neurodegeneration.