Microglial Neuroinflammation Research Articles

Neuroinflammation of Microglial Regulation in Alzheimer's Disease: Therapeutic Approaches.

Alzheimer's disease (AD) is a complex degenerative disease of the central nervous system that is clinically characterized by a progressive decline in memory and cognitive function. The pathogenesis of AD is intricate and not yet fully understood. Neuroinflammation, particularly microglial activation-mediated neuroinflammation, is believed to play a crucial role in increasing the risk, triggering the onset, and hastening the progression of AD. Modulating microglial activation and regulating microglial energy metabolic disorder are seen as promising strategies to intervene in AD. The application of anti-inflammatory drugs and the targeting of microglia for the prevention and treatment of AD has emerged as a new area of research interest. This article provides a comprehensive review of the role of neuroinflammation of microglial regulation in the development of AD, exploring the connection between microglial energy metabolic disorder, neuroinflammation, and AD development. Additionally, the advancements in anti-inflammatory and microglia-regulating therapies for AD are discussed.

Edaravone dexborneol promotes M2 microglia polarization against lipopolysaccharide-induced inflammation via suppressing TLR4/MyD88/NF-κB pathway.

Edaravone dexborneol (ED) is a novel neuroprotective compound that consists of two active ingredients, edaravone and ( +)-borneol in a 4:1 ratio, which has been shown the anti-inflammatory properties in animal models of ischemic stroke, cerebral hemorrhage, and autoimmune encephalomyelitis. However, the effect of ED on the polarization of microglia in neuroinflammation has not been elucidated. This study was to investigate the effects of ED on the polarization of microglia induced by lipopolysaccharide (LPS) and potential mechanisms. BV-2 microglial cells were incubated with ED (100, 200, and 400 µM) for 2h, followed by lipopolysaccharide (LPS, 1µg/ml) for 12h. The researchers used the Griess method, western blot, immunocytochemistry, and subcellular fractionation to assess the effects and potential mechanisms of ED on neuroinflammatory reactions. The expression of ROS and the activities of antioxidant enzymes (SOD, GPx, and CAT) in LPS-induced BV-2 cells were also measured using the DCFH-DA fluorescent probe and colorimetric methods, respectively. It was observed that ED significantly declined the levels of TLR4/NF-κB pathway-associated proteins (TLR4, MyD88, p65, p-p65, IκBα, p-IκBα, IKKβ, p-IKKβ) and therefore inhibited LPS-induced production of NO, IL-1β, and TNF-α. Moreover, ED markedly downregulated the M1 marker (iNOS) and upregulated the M2 marker (Arginase-1, Ym-1). In addition, ED also reduced ROS generation and enhanced GPx activity. ED induced the polarization of LPS-stimulated microglia from M1 to M2 against inflammation by negatively regulating the TLR4/MyD88/NF-κB signaling pathway. Additionally, ED performed antioxidative function by depleting the intracellular excessive ROS caused by LPS through the enhancement of the enzymatic activity of GPx. ED may be a potential agent to attenuate neuroinflammation via regulating the polarization of microglia.

Neurotoxic Microglial Activation via IFNγ-Induced Nrf2 Reduction Exacerbating Alzheimer's Disease.

Microglial neuroinflammation appears to be neuroprotective in the early pathological stage, yet neurotoxic, which often precedes neurodegeneration in Alzheimer's disease (AD). However, it remains unclear how the microglial activities transit to the neurotoxic state during AD progression, due to complex neuron-glia interactions. Here, the mechanism of detrimental microgliosis in AD by employing 3D human AD mini-brains, brain tissues of AD patients, and 5XFAD mice is explored. In the human and animal AD models, amyloid-beta (Aβ)-overexpressing neurons and reactive astrocytes produce interferon-gamma (IFNγ) and excessive oxidative stress. IFNγ results in the downregulation of mitogen-activated protein kinase (MAPK) and the upregulation of Kelch-like ECH-associated Protein 1 (Keap1) in microglia, which inactivate nuclear factor erythroid-2-related factor 2 (Nrf2) and sensitize microglia to the oxidative stress and induces a proinflammatory microglia via nuclear factor kappa B (NFκB)-axis. The proinflammatory microglia in turn produce neurotoxic nitric oxide and proinflammatory mediators exacerbating synaptic impairment, phosphorylated-tau accumulation, and discernable neuronal loss. Interestingly, recovering Nrf2 in the microglia prevents the activation of proinflammatory microglia and significantly blocks the tauopathy in AD minibrains. Taken together, it is envisioned that IFNγ-driven Nrf2 downregulation in microglia as a key target to ameliorate AD pathology.

Targeting aberrant glycosylation to modulate microglial response and improve cognition in models of Alzheimer’s disease

Altered glycosylation profiles have been correlated with potential drug targets in various diseases, including Alzheimer’s disease (AD). In this area, the linkage between bisecting N-acetylglucosamine (GlcNAc), a product of N-acetylglucosaminyltransferase III (GnT-III), and AD has been recognized, however, our understanding of the cause and the causative role of this aberrant glycosylation in AD are far from completion. Moreover, the effects and mechanisms of glycosylation-targeting interventions on memory and cognition, and novel targeting strategies are worth further study. Here, we showed the characteristic amyloid pathology-induced and age-related changes of GnT-III, and identified transcription factor 7-like 2 as the key transcription factor responsible for the abnormal expression of GnT-III in AD. Upregulation of GnT-III aggravated cognitive dysfunction and Alzheimer-like pathologies. In contrast, loss of GnT-III could improve cognition and alleviate pathologies. Furthermore, we found that an increase in bisecting GlcNAc modified ICAM-1 resulted in impairment of microglial responses, and genetic inactivation of GnT-III protected against AD mechanistically by blocking the aberrant glycosylation of ICAM-1 and subsequently modulating microglial responses, including microglial motility, phagocytosis ability, homeostatic/reactive state and neuroinflammation. Moreover, by target-based screening of GnT-III inhibitors from FDA-approved drug library, we identified two compounds, regorafenib and dihydroergocristine mesylate, showing pharmacological potential leading to modulation of aberrant glycosylation and microglial responses, and rescue of memory and cognition deficits.

Mixed Metal Components in PM2.5 Contribute to Chemokine Receptor CCR5-Mediated Neuroinflammation and Neuropathological Changes in the Mouse Olfactory Bulb.

Particulate matter, especially PM2.5, can invade the central nervous system (CNS) via the olfactory pathway to induce neurotoxicity. The olfactory bulb (OB) is the key component integrating immunoprotection and olfaction processing and is necessarily involved in the relevant CNS health outcomes. Here we show that a microglial chemokine receptor, CCR5, is the target of environmentally relevant PM2.5 in the OB to trigger neuroinflammation and then neuropathological injuries. Mechanistically, PM2.5-induced CCR5 upregulation results in the pro-inflammatory paradigm of microglial activation, which subsequently activates TLR4-NF-κB neuroinflammation signaling and induces neuropathological changes that are closely related to neurodegenerative disorders (e.g., Aβ deposition and disruption of the blood-brain barrier). We specifically highlight that manganese and lead in PM2.5 are the main contributors to CCR5-mediated microglial activation and neuroinflammation in synergy with aluminum. Our results uncover a possible pathway of PM2.5-induced neuroinflammation and identify the principal neurotoxic components, which can provide new insight into efficiently diminishing the adverse health effects of PM2.5.

New Insights into Microglia as Therapeutic Targets in Alzheimer’s Disease

Abstract: Alzheimer's disease (AD) is the most common neurodegenerative disease, accounting for 60–70% of dementia cases globally. Inflammation of the central nervous system (CNS) caused by microglia is a common characteristic of neurodegenerative illnesses such as Parkinson's disease and AD. Research has recently examined the relationship between neurodegenerative diseases and CNS microglia. Microglial cells comprise 10–15% of all CNS cells and are brain-resident myeloid cells mediating critical processes to support the CNS. Microglia have a variety of receptors that operate as molecular sensors, detecting exogenous and endogenous CNS injuries and triggering an immune response. Microglia serve as brain guardians by boosting phagocytic clearance and providing trophic support to enable tissue repair and maintain cerebral homeostasis, in addition to their traditional immune cell activity. At rest, microglia manage CNS homeostasis by phagocytic action, which removes pathogens and cell debris. Microglia cells that have been "resting" convert into active cells that create inflammatory mediators, protecting neurons and protecting against invading pathogens. Neuronal damage and neurodegenerative disorders are caused by excessive inflammation. Different microglial cells reply at different phases of the disease can lead to new therapy options and reduced inflammatory activity. This review focuses on the potential function of microglia, microglia subtypes, and M1/M2 phenotypic changes associated with neurodegenerative disorders. Microglial membrane receptors, the involvement of microglia in neuroinflammation, microglial targets in AD and the double role of microglia in AD pathogenesis are also discussed in this review.

Hyperforin ameliorates neuroinflammation and white matter lesions by regulating microglial VEGFR2 /SRC pathway in vascular cognitive impairment mice.

To explore the neuroprotective potential of hyperforin and elucidate its underlying molecular mechanisms involved in its therapeutic effects against vascular cognitive impairment (VCI). The active compounds and possible targets of Hypericum perforatum L. that may be effective against VCI were found by network pharmacology in this research. We utilized bilateral common carotid artery occlusion (BCCAO) surgery to induce a VCI mouse model. Morris water maze (MWM) and Y-maze tests were used to assess VCI mice's cognitive abilities following treatment with hyperforin. To evaluate white matter lesions (WMLs), we utilized Luxol fast blue (LFB) stain and immunofluorescence (IF). Neuroinflammation was assessed using IF, western blot (WB), and enzyme-linked immunosorbent assay (ELISA). The effects of hyperforin on microglia were investigated by subjecting the BV2 microglial cell line to oxygen-glucose deprivation/reperfusion (OGD/R) stimulation. The expressions of VEGFR2 , p-SRC, SRC, VEGFA, and inflammatory markers including IL-10, IL-1β, TNF-α, and IL-6 were subsequently assessed. The VEGFR2 /SRC signaling pathway is essential for mediating the protective properties of hyperforin against VCI according to network pharmacology analysis. Invivo findings demonstrated that hyperforin effectively improved BCCAO-induced cognitive impairment. Furthermore, staining results showed that hyperforin attenuated WMLs and reduced microglial activation in VCI mice. The hyperforin treatment group's ELISA results revealed a substantial decrease in IL-1β, IL-6, and TNF-α levels. According to the results of invitro experiments, hyperforin decreased the release of pro-inflammatory mediators (TNF-α, IL-6, and IL-1β) and blocked microglial M1-polarization by modulating the VEGFR2 /SRC signaling pathway. Hyperforin effectively modulated microglial M1 polarization and neuroinflammation by inhibiting the VEGFR2 /SRC signaling pathways, thereby ameliorating WMLs and cognitive impairment in VCI mice.

Attenuation of neuronal ferroptosis in intracerebral hemorrhage by inhibiting HDAC1/2: Microglial heterogenization via the Nrf2/HO1 pathway.

The class I histone deacetylases (HDACs) implicate in microglial heterogenization and neuroinflammation following Intracerebral hemorrhage (ICH). Ferroptosis has also been reported in the ICH model. However, the relationship between HDAC1/2's role in microglial heterogenization and neuronal ferroptosis remains unclear. In both invivo and invitro models of ICH, we used Romidepsin (FK228), a selective HDAC1/2 inhibitor, to investigate its effects on microglial heterogenization and neuronal ferroptosis. In the invitro ICH model using Hemin, a transwell system was utilized to examine how microglia-driven inflammation and ICH-triggered neuronal ferroptosis interact. Immunostaining, Western blotting and RT-qPCR were used to evaluate the microglial heterogenization and neuronal ferroptosis. Microglial heterogenization, neuronal ferroptosis, and neurological dysfunctions were assessed invivo ICH mice model performed by autologous blood injection. HDAC1/2 inhibition altered microglial heterogenization after ICH, as showing the reducing neuroinflammation and shifting microglia towards an anti-inflammatory phenotype by immunostaining and qPCR results. HDAC1/2 inhibition reduced ferroptosis, characterized by high ROS and low GPx4 expression in HT22 cells, and reduced iron and lipid deposition post-ICH invivo. Additionally, the Nrf2/HO1 signaling pathway, especially acetyl-Nrf2, activated in the invivo ICH model due to HDAC1/2 inhibition, plays a role in regulating microglial heterogenization. Furthermore, HDAC1/2 inhibition improved sensorimotor and histological outcomes post-ICH, offering a potential mechanism against ICH. Inhibition of HDAC1/2 reduces neuro-ferroptosis by modifying the heterogeneity of microglia via the Nrf2/HO1 pathway, with a particular focus on acetyl-Nrf2. Additionally, this inhibition aids in the faster removal of hematomas and lessens prolonged neurological impairments, indicating novel approach for treating ICH.

Pretreated MSCs with IronQ Transplantation Attenuate Microglia Neuroinflammation via the cGAS-STING Signaling Pathway.

Intracerebral hemorrhage (ICH), a devastating form of stroke, is characterized by elevated morbidity and mortality rates. Neuroinflammation is a common occurrence following ICH. Mesenchymal stem cells (MSCs) have exhibited potential in treating brain diseases due to their anti-inflammatory properties. However, the therapeutic efficacy of MSCs is limited by the intense inflammatory response at the transplantation site in ICH. Hence, enhancing the function of transplanted MSCs holds considerable promise as a therapeutic strategy for ICH. Notably, the iron-quercetin complex (IronQ), a metal-quercetin complex synthesized through coordination chemistry, has garnered significant attention for its biomedical applications. In our previous studies, we have observed that IronQ exerts stimulatory effects on cell growth, notably enhancing the survival and viability of peripheral blood mononuclear cells (PBMCs) and MSCs. This study aimed to evaluate the effects of pretreated MSCs with IronQ on neuroinflammation and elucidate its underlying mechanisms. The ICH mice were induced by injecting the collagenase I solution into the right brain caudate nucleus. After 24 hours, the ICH mice were randomly divided into four subgroups, the model group (Model), quercetin group (Quercetin), MSCs group (MSCs), and pretreated MSCs with IronQ group (MSCs+IronQ). Neurological deficits were re-evaluated on day 3, and brain samples were collected for further analysis. TUNEL staining was performed to assess cell DNA damage, and the protein expression levels of inflammatory factors and the cGAS-STING signaling pathway were investigated and analyzed. Pretreated MSCs with IronQ effectively mitigate neurological deficits and reduce neuronal inflammation by modulating the microglial polarization. Moreover, the pretreated MSCs with IronQ suppress the protein expression levels of the cGAS-STING signaling pathway. These findings suggest that pretreated MSCs with IronQ demonstrate a synergistic effect in alleviating neuroinflammation, thereby improving neurological function, which is achieved through the inhibition of the cGAS-STING signaling pathway.

APOE from patient-derived astrocytic extracellular vesicles alleviates neuromyelitis optica spectrum disorder in a mouse model.

Neuromyelitis optica spectrum disorder (NMOSD) is an autoimmune astrocytopathy of the central nervous system, mediated by antibodies against aquaporin-4 water channel protein (AQP4-Abs), resulting in damage of astrocytes with subsequent demyelination and axonal damage. Extracellular communication through astrocyte-derived extracellular vesicles (ADEVs) has received growing interest in association with astrocytopathies. However, to what extent ADEVs contribute to NMOSD pathogenesis remains unclear. Here, through proteomic screening of patient-derived ADEVs, we observed an increase in apolipoprotein E (APOE)-rich ADEVs in patients with AQP4-Abs-positive NMOSD. Intracerebral injection of the APOE-mimetic peptide APOE130-149 attenuated microglial reactivity, neuroinflammation, and brain lesions in a mouse model of NMOSD. The protective effect of APOE in NMOSD pathogenesis was further established by the exacerbated lesion volume in APOE-deficient mice, which could be rescued by exogenous APOE administration. Genetic knockdown of the APOE receptor lipoprotein receptor-related protein 1 (LRP1) could block the restorative effects of APOE130-149 administration. The transfusion ADEVs derived from patients with NMOSD and healthy controls also alleviated astrocyte loss, reactive microgliosis, and demyelination in NMOSD mice. The slightly larger beneficial effect of patient-derived ADEVs as compared to ADEVs from healthy controls was further augmented in APOE-/- mice. These results indicate that APOE from astrocyte-derived extracellular vesicles could mediate disease-modifying astrocyte-microglia cross-talk in NMOSD.

Running exercise alleviates hippocampal neuroinflammation and shifts the balance of microglial M1/M2 polarization through adiponectin/AdipoR1 pathway activation in mice exposed to chronic unpredictable stress.

Running exercise has been shown to alleviate depressive symptoms. However, the mechanism underlying the antidepressant effects of running exercise is not fully understood. The imbalance of M1/M2 microglia phenotype/polarization and concomitant dysregulation of neuroinflammation play crucial roles in the pathogenesis of depression. Running exercise increases circulating levels of adiponectin which is known to cross the blood‒brain barrier and suppress inflammatory responses. AdipoR1 is an adiponectin receptor that is involved in regulating microglial phenotypes and activation states. However, whether running exercise regulates hippocampal microglial phenotypes and neuroinflammation through adiponectin/AdipoR1 to exert its antidepressant effects remains unclear. In the current study, 4 weeks of running exercise significantly alleviated the depressive-like behaviors of chronic unpredictable stress (CUS)-exposed mice. Moreover, running exercise decreased the microglial numbers and altered microglial morphology in three subregions of the hippocampus to restore the M1/M2 balance; these effects were accompanied by regulation of pro-/anti-inflammatory cytokine production and secretion in CUS-exposed mice. These effects may involve elevation of peripheral tissue (adipose tissue and muscle) and plasma adiponectin levels, and hippocampal AdipoR1 levels as well as activation of the AMPK-NF-κB/STAT3 signaling pathway by running exercise. When an adeno-associated virus was used to knock down hippocampal AdipoR1, mice showed depressive-like behaviors and alterations in microglia and inflammatory factor expression in the hippocampus that were similar to those observed in CUS-exposed mice. Together, these results suggest that running exercise maintains the M1/M2 balance and inhibits neuroinflammation in the hippocampus of CUS-exposed mice. These effects might occur via adiponectin/AdipoR1-mediated activation of the AMPK-NF-κB/STAT3 signaling pathway.

Citrate synthase lysine K215 hypoacetylation contributes to microglial citrate accumulation and pro-inflammatory functions after traumatic brain injury.

This study aimed to investigate the relationship between microglial metabolism and neuroinflammation by examining the impact of citrate accumulation in microglia and its potential regulation through Cs K215 hypoacetylation. Experimental approaches included assessing Cs enzyme activity through Cs K215Q mutation and investigating the inhibitory effects of hesperidin, a natural flavanone glycoside, on citrate synthase. Microglial phagocytosis and expression of pro-inflammatory cytokines were also examined in relation to Cs K215Q mutation and hesperidin treatment. Cs K215Q mutation and hesperidin exhibited significant inhibitory effects on Cs enzyme activity, microglial citrate accumulation, phagocytosis, and pro-inflammatory cytokine expression. Interestingly, Sirt3 knockdown aggravated microglial pro-inflammatory functions during neuroinflammation, despite its proven role in Cs deacetylation. Cs K215Q mutation and hesperidin effectively inhibited microglial pro-inflammatory functions without reversing the metabolic reprogramming. These findings suggest that targeting Cs K215 hypoacetylation and utilizing hesperidin may hold promise for modulating neuroinflammation in microglia.

Dihydrotestosterone reduces neuroinflammation in spinal cord injury through NF-κB and MAPK pathway.

Neuroinflammation induced by microglia following spinal cord injury (SCI) leads to secondary neurologic injury. Androgens including testosterone and dihydrotestosterone (DHT) show as endogenous neuroprotective factors against multiple neurologic diseases, while their therapeutic role in SCI-induced neuroinflammation and underlying mechanism remains elusive. In the study, we aimed to investigate the role of DHT against microglia-induced neuroinflammation in SCI and evaluate its protective treatment. BV2 cells were activated by neuroinflammation via LPS in vitro. Adult male C57BL/6 mice were used to establish the SCI model. BV2 cells and SCI mice were administrated DHT. Microglia activation, pro-inflammatory factors, p38 and p65 phosphorylation, glial scar, fibrotic scar, histology, and locomotor function recovery were measured, respectively. We demonstrated that DHT administration attenuates neuroinflammation in microglia through inhibition of p38 and p65 pathways. Moreover, DHT reduces microglia and astrocyte accumulation, cord fibrosis and histologic damage. Besides, DHT ameliorates locomotor functional recovery after SCI. DHT is verified to play a neuroprotective role in SCI, which fights against neuroinflammation by inhibition of p38 and p65 pathways. Therefore, Mel is defined as a promising factor in protecting neural tissue after SCI.

Enhanced meningeal lymphatic drainage ameliorates lipopolysaccharide-induced brain injury in aged mice

BackgroundSepsis-associated encephalopathy (SAE) is an acute cerebral dysfunction caused by sepsis. Neuroinflammation induced by sepsis is considered a potential mechanism of SAE; however, very little is known about the role of the meningeal lymphatic system in SAE.MethodsSepsis was established in male C57BL/6J mice by intraperitoneal injection of 5 mg/kg lipopolysaccharide, and the function of meningeal lymphatic drainage was assessed. Adeno-associated virus 1-vascular endothelial growth factor C (AAV1-VEGF-C) was injected into the cisterna magna to induce meningeal lymphangiogenesis. Ligation of deep cervical lymph nodes (dCLNs) was performed to induce pre-existing meningeal lymphatic dysfunction. Cognitive function was evaluated by a fear conditioning test, and inflammatory factors were detected by enzyme-linked immunosorbent assay.ResultsThe aged mice with SAE showed a significant decrease in the drainage of OVA-647 into the dCLNs and the coverage of the Lyve-1 in the meningeal lymphatic, indicating that sepsis impaired meningeal lymphatic drainage and morphology. The meningeal lymphatic function of aged mice was more vulnerable to sepsis in comparison to young mice. Sepsis also decreased the protein levels of caspase-3 and PSD95, which was accompanied by reductions in the activity of hippocampal neurons. Microglia were significantly activated in the hippocampus of SAE mice, which was accompanied by an increase in neuroinflammation, as indicated by increases in interleukin-1 beta, interleukin-6 and Iba1 expression. Cognitive function was impaired in aged mice with SAE. However, the injection of AAV1-VEGF-C significantly increased coverage in the lymphatic system and tracer dye uptake in dCLNs, suggesting that AAV1-VEGF-C promotes meningeal lymphangiogenesis and drainage. Furthermore, AAV1-VEGF-C reduced microglial activation and neuroinflammation and improved cognitive dysfunction. Improvement of meningeal lymphatics also reduced sepsis-induced expression of disease-associated genes in aged mice. Pre-existing lymphatic dysfunction by ligating bilateral dCLNs aggravated sepsis-induced neuroinflammation and cognitive impairment.ConclusionThe meningeal lymphatic drainage is damaged in sepsis, and pre-existing defects in this drainage system exacerbate SAE-induced neuroinflammation and cognitive dysfunction. Promoting meningeal lymphatic drainage improves SAE. Manipulation of meningeal lymphangiogenesis could be a new strategy for the treatment of SAE.

Dermorphin [D-Arg2, Lys4] (1-4) Amide Alleviates Frostbite-Induced Pain by Regulating TRP Channel-Mediated Microglial Activation and Neuroinflammation.

Cold injury or frostbite is a common medical condition that causes serious clinical complications including sensory abnormalities and chronic pain ultimately affecting overall well-being. Opioids are the first-choice drug for the treatment of frostbite-induced chronic pain; however, their notable side effects, including sedation, motor incoordination, respiratory depression, and drug addiction, present substantial obstacle to their clinical utility. To address this challenge, we have exploited peripheral mu-opioid receptors as potential target for the treatment of frostbite-induced chronic pain. In this study, we investigated the effect of dermorphin [D-Arg2, Lys4] (1-4) amide (DALDA), a peripheral mu-opioid receptor agonist, on frostbite injury and hypersensitivity induced by deep freeze magnet exposure in rats. Animals with frostbite injury displayed significant hypersensitivity to mechanical, thermal, and cold stimuli which was significant ameliorated on treatment with different doses of DALDA (1, 3, and 10 mg/kg) and ibuprofen (100 mg/kg). Further, molecular biology investigations unveiled heightened oxido-nitrosative stress, coupled with a notable upregulation in the expression of TRP channels (TRPA1, TRPV1, and TRPM8), glial cell activation, and neuroinflammation (TNF-α, IL-1β) in the sciatic nerve, dorsal root ganglion (DRG), and spinal cord of frostbite-injured rats. Treatment with DALDA leads to substantial reduction in TRP channels, microglial activation, and suppression of the inflammatory cascade in the ipsilateral L4-L5 DRG and spinal cord of rats. Overall, findings from the present study suggest that activation of peripheral mu-opioid receptors mitigates chronic pain in rats by modulating the expression of TRP channels and suppressing glial cell activation and neuroinflammation.

Activation of the CD200/CD200R1 axis improves cognitive impairment by enhancing hippocampal neurogenesis via suppression of M1 microglial polarization and neuroinflammation in hypoxic-ischemic neonatal rats

Following hypoxic-ischemic brain damage (HIBD), there is a decline in cognitive function; however, there are no effective treatment strategies for this condition in neonates. This study aimed to evaluate the role of the cluster of differentiation 200 (CD200)/CD200R1 axis in cognitive function following HIBD using an established model of HIBD in postnatal day 7 rats. Western blotting analysis was conducted to evaluate the protein expression levels of CD200, CD200R1, proteins associated with the PI3K/Akt-NF-κB pathway, and inflammatory factors such as TNF-α, IL-1β, and IL-6 in the hippocampus. Additionally, double-immunofluorescence labeling was utilized to evaluate M1 microglial polarization and neurogenesis in the hippocampus. To assess the learning and memory function of the experimental rats, the Morris water maze (MWM) test was conducted. HIBDleads to a decrease in the expression of CD200 and CD200R1 proteins in the neonatal rat hippocampus, while simultaneously increasing the expression of TNF-α, IL-6, and IL-1β proteins, ultimately resulting in cognitive impairment. The administration of CD200Fc, a fusion protein of CD200, was found to enhance the expression of p-PI3K and p-Akt, but reduce the expression of p-NF-κB. Additionally, CD200Fc inhibited M1 polarization of microglia, reduced neuroinflammation, improved hippocampal neurogenesis, and mitigated cognitive impairment caused by HIBD in neonatal rats. In contrast, blocking the interaction between CD200 and CD200R1 with the anti-CD200R1 antibody (CD200R1 Ab) exerted the opposite effect. Furthermore, the PI3K specific activator, 740Y-P, significantly increased the expression of p-PI3K and p-Akt, but reduced p-NF-κB expression. It also inhibited M1 polarization of microglia, reduced neuroinflammation, and improved hippocampal neurogenesis and cognitive function in neonatal rats with HIBD. Our findings illustrate that activation of the CD200/CD200R1 axis inhibits the NF-κB-mediated M1 polarization of microglia to improve HIBD-induced cognitive impairment and hippocampal neurogenesis disorder via the PI3K/Akt signaling pathway.

Therapeutic Effects of Aβ-Specific Regulatory T Cells in Alzheimer's Disease: A Study in 5xFAD Mice.

The aging global population is placing an increasing burden on healthcare systems, and the social impact of Alzheimer's disease (AD) is on the rise. However, the availability of safe and effective treatments for AD remains limited. Adoptive Treg therapy has been explored for treating neurodegenerative diseases, including AD. To facilitate the clinical application of Treg therapy, we developed a Treg preparation protocol and highlighted the therapeutic effects of Tregs in 5xFAD mice. CD4+CD25+ Tregs, isolated after Aβ stimulation and expanded using a G-rex plate with a gas-permeable membrane, were adoptively transferred into 5xFAD mice. Behavioral analysis was conducted using Y-maze and passive avoidance tests. Additionally, we measured levels of Aβ, phosphorylated tau (pTAU), and nitric oxide synthase 2 (NOS2) in the hippocampus. Real-time RT-PCR was employed to assess the mRNA levels of pro- and anti-inflammatory markers. Our findings indicate that Aβ-specific Tregs not only improved cognitive function but also reduced Aβ and pTAU accumulation in the hippocampus of 5xFAD mice. They also inhibited microglial neuroinflammation. These effects were observed at doses as low as 1.5 × 103 cells/head. Collectively, our results demonstrate that Aβ-specific Tregs can mitigate AD pathology in 5xFAD mice.

JE-133 Suppresses LPS-Induced Neuroinflammation Associated with the Regulation of JAK/STAT and Nrf2 Signaling Pathways.

Neuroinflammation plays an important role in the pathogenesis of neurodegenerative diseases, and interrupting the microglial-mediated neuroinflammation has been suggested as a promising strategy to delay or prevent the progression of neurodegeneration. In this study, we investigated the effects of JE-133, an optically active isochroman-2H-chromene conjugate containing a 1,3-disubstituted isochroman unit, on lipopolysaccharide (LPS)-induced microglial neuroinflammation and underlying mechanisms both in vitro and in vivo. First, JE-133 treatment decreased LPS-induced overproduction of interleukin-1 beta (IL-1β), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), nitrite, and nitric oxide synthase (iNOS) in BV2 microglial cells. Further study revealed that JE-133 downregulated the phosphorylation level of JAK/STAT and upregulated the protein level of Nrf2/HO-1 in LPS-stimulated BV2 microglial cells and verified that JE-133 directly bound to Keap1 by a pull-down assay. Next, JE-133 administration also inhibited neuroinflammation in vivo, as indicated by a reduced CD11b protein level and an overexpressed mRNA level of the pro-inflammatory cytokine TNF-α in the hippocampus of LPS-injected mice. Moreover, the regulative effects of JE-133 on the JAK/STAT and Nrf2/HO-1 pathways were also verified in the hippocampus of LPS-injected mice. Taken together, our study for the first time reports that JE-133 exhibits inhibitory effects against LPS-stimulated neuroinflammation both in vitro and in vivo, which might be associated with the simultaneous regulation of the JAK/STAT and Nrf2 pathways. Our findings may provide important clues for the discovery of effective drug leads/candidates against neuroinflammation-associated neurodegeneration.

Oxycodone alleviates LPS-induced neuroinflammation by regulating the CREB/miR-181c/PDCD4 axis.

Neuroinflammation plays a critical role in various neurological disorders. Oxycodone has anti-inflammatory properties. The purpose of this work was to look into the effect of oxycodone in controlling lipopolysaccharide (LPS)-induced neuroinflammation in microglia. LPS-induced HMC3 cells were subjected to oxycodone (2.5, 5, 10 and 20 μg/mL). The mRNA and protein expressions were examined by qRT-PCR and western blotting. TNF-α, IL-1β, IL-6, and IL-8 levels were assessed by ELISA. MTT assay was adopted to measure cell viability. The interactions between CREB, miR-181c and PDCD4 were analyzed by dual-luciferase reporter assay, ChIP and/or RIP assays. Oxycodone treatment alleviated LPS-induced inflammation in HMC3 cells and increased p-CREB level, but reduced PDCD4 and iNOS levels in LPS-treated cells. Mechanistically, oxycodone mitigated LPS-induced neuroinflammation by upregulating miR-181c. In addition, CREB promoted miR-181c expression by directly binding to the MIR181C promoter, and miR-181c inhibited PDCD4 expression by directly binding to PDCD4 3'UTR. As expected, oxycodone alleviated LPS-induced neuroinflammation by regulating the CREB/miR-181c/PDCD4 axis. Oxycodone attenuated LPS-induced neuroinflammation in microglia by regulating the CREB/miR-181c/PDCD4 axis. These findings proved that oxycodone is a potential drug for treating neuroinflammation and elucidate the mechanisms involved.

Promotion of neuroinflammation by the glymphatic system: a new insight into ethanol extracts from Alisma orientale in alleviating obesity-associated cognitive impairment.

Obesity is one of the critical risk factors for cognitive dysfunction. The glymphatic system (GS) plays a key role in the pathogenesis of cognitive deficits. Alisma orientale has been shown to have anti-inflammatory and antihyperlipidemic effects, whereas its effects and underlying mechanisms on obesity-associated cognitive impairment (OACI) are unclear. This work aims to decipher the mechanism of ethanol extracts from Alisma orientale (EEAO) in restoring cognitive impairment in HFD-induced obese mice through a GS approach. The restoration of abnormal glucose/lipid metabolism and excess adipose deposition by EEAO were assayed by biochemical analysis and visually displayed by a micro-CT scanner and Oil Red O staining. Biochemical assays and Western blotting (WB) were used to measure cerebral blood flow (CBF), free fatty acid (FFAs) levels and the structural integrity of the blood-brain barrier (BBB). Microglial activation and neuroinflammation were assessed with immunohistochemistry staining, ELISA and WB. Moreover, GS function was determined by immunofluorescence staining, fluorescence tracer imaging and WB. Finally, the neuropathological features and cognitive functions were detested with immunohistochemistry staining, immunofluorescence and Morris Water Maze. EEAO not only alleviated body weight, cerebral lipid accumulation and serum FFAs in HFD-induced obese mice, but also increased CBF and BBB integrity. EEAO suppressed microglial activation and lipid deposition in the hippocampus and reduced the level of inflammatory cytokines including IL-6, IL-1β and TNF-α in brain tissue. Interestingly, long-term HFD-induced GS dysfunction was significantly restored after EEAO intervention, and neuropathological lesions and cognitive deficits were also markedly rescued. EEAO rescued the cognitive deficits of OACI by inhibiting neuroinflammation and restoring GS dysfunction, indicating a potential remedy for OACI.