Primary Microglial Cells Research Articles

Dihydro-resveratrol ameliorates NLRP3 inflammasome-mediated neuroinflammation via Bnip3-dependent mitophagy in Alzheimer's disease.

Dihydro-resveratrol (DHR), a polyphenol derivative, that has been demonstrated to suppress inflammation-mediated injury. However, it is still unknown whether it has anti-neuroinflammatory and neuroprotective effects, and a therapeutic action in Alzheimer's disease (AD). The anti-inflammatory and anti-Alzheimer's disease actions of dihydro-resveratrol were investigated using lipopolysaccharide (LPS) and AD mice models, and primary microglial cells. The changes in behaviour in mice were detected by the Morris water maze test and open-field test. Flow cytometry assay, western blotting, immunofluorescence assays and co-immunoprecipitation were used to investigate the changes in the NLRP3 inflammasome activation and mitophagy. In this study, in vivo observations indicated that the administration of dihydro-resveratrol (DHR) dramatically restored spatial learning, memory ability, autophagy and mitophagy, attenuated NLRP3 inflammasome activation, neuroinflammation and amyloid precursor protein pathology in LPS mice and AD mice. In addition, the inhibition of autophagy and mitophagy, or the activation of NLRP3 in vivo greatly abolished DHR-generated therapeutic efficacy on neuroinflammation, amyloid precursor protein pathology and cognitive loss. Further examination indicated that the application of DHR after the LPS and ATP exposure significantly inhibited the NLRP3 inflammasome activation, neuroinflammation and enhanced autophagic and mitophagic activation in microglia. Additionally, in vitro results show that DHR protects microglial cells against LPS and ATP-induced cytotoxicity by inhibiting NLRP3 inflammasome through activating Bnip3-dependent mitophagy and ULK phosphorylation. In summary, these findings suggest that dihydro-resveratrol (DHR) possesses potent anti-neuroinflammatory property and can act as a potential therapeutic agent for the treatment of AD.

Tetramerization of PKM2 Alleviates Traumatic Brain Injury by Ameliorating Mitochondrial Damage in Microglia.

Traumatic brain injury (TBI) is a leading cause of death and disability worldwide. Microglial activation and neuroinflammation are key cellular events that determine the outcome of TBI, especially neuronal and cognitive function. Studies have suggested that the metabolic characteristics of microglia dictate their inflammatory response. The pyruvate kinase isoform M2 (PKM2), a key glycolytic enzyme, is involved in the regulation of various cellular metabolic processes, including mitochondrial metabolism. This suggests that PKM2 may also participate in the regulation of microglial activation during TBI. Therefore, the present study aimed to evaluate the role of PKM2 in regulating microglial activation and neuroinflammation and its effects on cognitive function following TBI. A controlled cortical impact (CCI) mouse model and inflammation-induced primary mouse microglial cells in vitro were used to investigate the potential effects of PKM2 inhibition and regulation. PKM2 was significantly increased during the acute and subacute phases of TBI and was predominantly detected in microglia rather than in neurons. Our results demonstrate that shikonin and TEPP-46 can inhibit microglial inflammation, improving mitochondria, improving mouse behavior, reducing brain defect volume, and alleviating pathological changes after TBI. There is a difference in the intervention of shikonin and TEPP-46 on PKM2. Shikonin directly inhibits General PKM2; TEPP-46 can promote the expression of PKM2 tetramer. In vitro experiments, TEPP-46 can promote the expression of PKM2 tetramer, enhance the interaction between PKM2 and MFN2, improve mitochondria, alleviate neuroinflammation. General inhibition and tetramerization activation of PKM2 attenuated cognitive function caused by TBI, whereas PKM2 tetramerization exhibited a better treatment effect. Our experiments demonstrated the non-metabolic role of PKM2 in the regulation of microglial activation following TBI. Both shikonin and TEPP-46 can inhibit pro-inflammatory factors, but only TEPP-46 can promote PKM2 tetramerization and upregulate the release of anti-inflammatory factors from microglia.

The dopamine analogue CA140 alleviates AD pathology, neuroinflammation, and rescues synaptic/cognitive functions by modulating DRD1 signaling or directly binding to Abeta

BackgroundWe recently reported that the dopamine (DA) analogue CA140 modulates neuroinflammatory responses in lipopolysaccharide-injected wild-type (WT) mice and in 3-month-old 5xFAD mice, a model of Alzheimer’s disease (AD). However, the effects of CA140 on Aβ/tau pathology and synaptic/cognitive function and its molecular mechanisms of action are unknown.MethodsTo investigate the effects of CA140 on cognitive and synaptic function and AD pathology, 3-month-old WT mice or 8-month-old (aged) 5xFAD mice were injected with vehicle (10% DMSO) or CA140 (30 mg/kg, i.p.) daily for 10, 14, or 17 days. Behavioral tests, ELISA, electrophysiology, RNA sequencing, real-time PCR, Golgi staining, immunofluorescence staining, and western blotting were conducted.ResultsIn aged 5xFAD mice, a model of AD pathology, CA140 treatment significantly reduced Aβ/tau fibrillation, Aβ plaque number, tau hyperphosphorylation, and neuroinflammation by inhibiting NLRP3 activation. In addition, CA140 treatment downregulated the expression of cxcl10, a marker of AD-associated reactive astrocytes (RAs), and c1qa, a marker of the interaction of RAs with disease-associated microglia (DAMs) in 5xFAD mice. CA140 treatment also suppressed the mRNA levels of s100β and cxcl10, markers of AD-associated RAs, in primary astrocytes from 5xFAD mice. In primary microglial cells from 5xFAD mice, CA140 treatment increased the mRNA levels of markers of homeostatic microglia (cx3cr1 and p2ry12) and decreased the mRNA levels of a marker of proliferative region-associated microglia (gpnmb) and a marker of lipid-droplet-accumulating microglia (cln3). Importantly, CA140 treatment rescued scopolamine (SCO)-mediated deficits in long-term memory, dendritic spine number, and LTP impairment. In aged 5xFAD mice, these effects of CA140 treatment on cognitive/synaptic function and AD pathology were regulated by dopamine D1 receptor (DRD1)/Elk1 signaling. In primary hippocampal neurons and WT mice, CA140 treatment promoted long-term memory and dendritic spine formation via effects on DRD1/CaMKIIα and/or ERK signaling.ConclusionsOur results indicate that CA140 improves neuronal/synaptic/cognitive function and ameliorates Aβ/tau pathology and neuroinflammation by modulating DRD1 signaling in primary hippocampal neurons, primary astrocytes/microglia, WT mice, and aged 5xFAD mice.

A multifunctional carbon quantum dot overcoming the BBB for modulating amyloid aggregation and scavenging reactive oxygen species

The abnormal aggregation of β-amyloid (Aβ), the accumulation of reactive oxygen species (ROS), and the presence of the blood-brain barrier (BBB) cause the prevention and treatment of Alzheimer's disease (AD) extremely difficult. In this study, we report multifunctional carbon quantum dots (CQDs) with red emission (RCQDs) for targeting Aβ42, modulating Aβ42 aggregation, overcoming the BBB, and scavenging ROS. RCQDs demonstrate exceptional targeting affinity for Aβ42 species, and exhibit high inhibition and disaggregation efficiencies against Aβ42 aggregates. Moreover, RCQDs possess outstanding scavenging abilities against the ROS in cells, thus resulting in the mitigation of cellular oxidative damages. RCQDs also exhibited strong penetration through the BBB in both in vitro and in vivo models, highlighting their potential for brain-targeted treatment. Further investigations using primary microglial cells confirm the anti-neuroinflammation properties of RCQDs. This study unprecedently demonstrates the therapeutic potential of unmodified pure CQDs for overcoming the BBB, targeting Aβ42 species, modulating Aβ42 aggregation and scavenging ROS, offering a promising candidate for the treatment of AD.

LRRK2 kinase activity restricts NRF2-dependent mitochondrial protection in microglia.

Mounting evidence supports a critical role for central nervous system (CNS) glial cells in neuroinflammation and neurodegenerative diseases, including Alzheimer's disease (AD), Parkinson's Disease (PD), Multiple Sclerosis (MS), as well as neurovascular ischemic stroke. Previously, we found that loss of the PD-associated gene leucine-rich repeat kinase 2 (Lrrk2) in macrophages, peripheral innate immune cells, induced mitochondrial stress and elevated basal expression of type I interferon (IFN) stimulated genes (ISGs) due to chronic mitochondrial DNA engagement with the cGAS/STING DNA sensing pathway. Here, we report that loss of LRRK2 results in a paradoxical response in microglial cells, a CNS-specific macrophage population. In primary murine microglia and microglial cell lines, loss of Lrrk2 reduces tonic IFN signaling leading to a reduction in ISG expression. Consistent with reduced type I IFN, mitochondria from Lrrk2 KO microglia are protected from stress and have elevated metabolism. These protective phenotypes involve upregulation of NRF2, an important transcription factor in the response to oxidative stress and are restricted by LRRK2 kinase activity. Collectively, these findings illustrate a dichotomous role for LRRK2 within different immune cell populations and give insight into the fundamental differences between immune regulation in the CNS and the periphery.

Naringenin-loaded poly(3-hydroxybutyrate-co-3-hydroxyvalerate)-based devices have an anti-inflammatory activity on microglia

Retinal degenerative diseases, such as retinitis pigmentosa, represent a significant fraction of the burden of blindness. This kind of diseases involves the activation of microglial cells which causes neuroinflammation. Flavonoids, such as naringenin (Nar), are able to modulate the pro-inflammatory behavior of the microglia cells but their low bioavailability often hinders this activity. In this context, the aim of this research activity was the development of implantable drug delivery systems through Nar encapsulation into a polymeric matrix, as a valuable way to increase its bioavailability. For this purpose, a blend between microbial poly(3-hydroxybutyrate-co-3-hydroxyvaerate) (PHBV) and poly(d,l-lactide-co-glycolide (PLGA) was processed by means of two different fabrication techniques, i.e., melt-spinning and wet-spinning, to fabricate rods designed for ocular implantation. The two developed kinds of rod had different morphology and thermal properties, as demonstrated by scanning electron microscopy, thermogravimetric analysis, and differential scanning calorimetry. In addition, an increase in Nar concentration in the starting polymeric mixture (1–5 wt% respect to device weight) determined a higher drug encapsulation efficiency, with a resulting drug loading increasing from 0.5 to 3.5 % and from 0.4 to 4.4 % for melt- and wet-spun rods, respectively. A significant effect of processing technique and drug loading on the resulting release kinetics was also observed, with the devices loaded with a higher percentage of Nar reaching a 100 % cumulative drug release after 38 and 73 days in the case of wet- and melt-spun rods, respectively. In addition, the wet-spun rods showed a first order drug release kinetics while the melt-spun rods a zero order one. The bioactivity of the wet-spun rods was tested on lipopolysaccharide-activated BV2 as well as primary murine microglia cells, thus demonstrating the ability of the released flavonoid to favor cell maturation from a pro-inflammatory to an anti-inflammatory phenotype.

Modulation of neuroinflammation by interleukin-10 in mouse microglial cells

Abstract Microglia are resident macrophages of the central nervous system that are important for maintaining brain homeostasis. Persistent activation of microglia is associated with neuroinflammation in neurodegenerative disorders. Interest in immortalized microglia cell lines as cell culture models to study their biology and role in neuroinflammation has increased in the past decade, with mouse microglial BV-2 cells emerging as an in vitro model for neuronal inflammation similar to primary mouse microglial cells. We report here IL-10 pretreatment of BV-2 cells compared to primary microglia from CD-1 mice. A 45-plex Luminex immunoassay was used to measure IL-10 pretreatment attenuation of TNF-a, IL-6, CCL5/RANTES, and G-CSF secretion from cells treated with IFN-g and LPS. In addition, we demonstrate the effects of small molecule inhibitors MLN4924, tofacitinib (CP 690550), and Cardamonin on IL-10 pretreatment. MLN4924 inhibits the NFkB pathway and decreased secretion of multiple cytokines and chemokines, including TNF-a, IL-6, CCL2/MCP-1, CCL5, CCL3/MIP-1a, and CCL4/MIP-1b. Tofacitinib inhibits the Jak1/Tyk2-STAT3 pathway, decreasing STAT-3 TYR705 phosphorylation, but had little effect on IL-10 cytokine suppression. Interestingly, IL-10 pretreatment increased secretion of IL-1ra, an M2b microglia phenotype marker, and chemokines CCL2 and CCL3. Multiplex immunoassays are a valuable tool for investigating the mechanisms of neuroinflammation in primary and immortalized cell lines.

Atractylodes lancea (Thunb.) DC. [Asteraceae] rhizome-derived exosome-like nanoparticles suppress lipopolysaccharide-induced inflammation in murine microglial cells.

Exosome-like nanoparticles (ELNs) mediate interspecies intercellular communications and modulate gene expression. In this study, we isolated and purified ELNs from the dried rhizome of Atractylodes lancea (Thunb.) DC. [Asteraceae] (ALR-ELNs), a traditional natural medicine, and investigated their potential as neuroinflammatory therapeutic agents. ALR-ELN samples were isolated and purified using differential centrifugation, and their physical features and microRNA contents were analyzed through transmission electron microscopy and RNA sequencing, respectively. BV-2 microglial murine cells and primary mouse microglial cells were cultured in vitro, and their ability to uptake ALR-ELNs was explored using fluorescence microscopy. The capacity of ALR-ELNs to modulate the anti-inflammatory responses of these cells to lipopolysaccharide (LPS) exposure was assessed through mRNA and protein expression analyses. Overall, BV-2 cells were found to internalize ALR-ELNs, which comprised three microRNAs (ath-miR166f, ath-miR162a-5p, and ath-miR162b-5p) that could have anti-inflammatory activity. Pretreatment of BV-2 cells with ALR-ELN prevented the pro-inflammatory effects of LPS stimulation by significantly reducing the levels of nitric oxide, interleukin-1β, interleukin-6, and tumor necrosis factor-α. Notably, the mRNA levels of Il1b, Il6, iNos, ccl2, and cxcl10 in BV-2 cells, which increased upon LPS exposure, were significantly reduced following ALR-ELN treatment. Moreover, the mRNA levels of heme oxygenase 1, Irf7, ccl12, and Irg1 also increased significantly following ALR-ELN treatment. In addition, pretreatment of primary mouse microglial cells with ALR-ELN prevented the pro-inflammatory effects of LPS stimulation by significantly reducing the levels of nitric oxide. Our findings indicate that ALR-ELNs exhibit anti-inflammatory effects on murine microglial cells. Further validation may prove ALR-ELNs as a promising neuroinflammatory therapeutic agent.

Neuroprotective Effect of Lithospermum officinale Callus Extract on Inflamed Primary Microglial Cells.

Plants that have therapeutic features for humans or animals are commonly referred to as "medicinal plants". They produce secondary metabolites with antioxidant, antimicrobial and/or anti-cancer effects. Lithospermum officinale, known as European stone seed, is a famous medicinal herb. However, due to the pyrrolizidine alkaloids (PzAl) in the root extract of L.officinal, there are therapeutic limitations to this herb. This research was devoted to the evaluation of the anti-inflammatory capacity of methanolic extracts of L. officinale callus (LoE) (fresh cells) on rat microglial cells, the immune cells of the Central Nervous System, which play an essential role in the responses to neuroinflammation. Primary microglia were obtained from neonatal Wistar rats (1 to 3-days old), and then treated with various concentration of CfA and methanolic extracts of 17 and 31-day-old L. officinale callus before LPS-stimulation. In addition to HPLC analysis of the extracts, viability, nitric oxide production, and evaluation of pro-inflammatory genes and cytokines in the inflamed microglia were investigated by MTT, Griess methos, qrt-PCR, and ELISA. Methanolic extract of the 17-day-old callus of L. officinale exhibited anti-inflammatory effects on LPS-stimulated microglial cells much higher than observed for CfA. The data were further supported by the decreased expression of Nos2, Tnf-α, and Cox-2 mRNA and the suppression of TNF-α and IL-1β release in the activated microglial cells pretreated with the effective dose of LoE (0.8 mg mL-1). It was assumed that the better anti-neuroinflammatory performance of LoE than CfA in LPS-activated primary microglia could be a result of the synergism of the components of the extract and the lipophilic nature of RsA as the main phenolic acid of LoE. Considering that LoE shows a high antioxidant capacity and lacks PzAl, it is anticipated that LoE extract might be considered a reliable substitute to play a key role in the preparation of neuroprotective pharmaceutical formulas, which require in vivo research and further experiments.

Neuroprotective and Anti-Inflammatory Activities of Hybrid Small-Molecule SA-10 in Ischemia/Reperfusion-Induced Retinal Neuronal Injury Models.

To induce I/R injury and inflammation, we subjected R28 and primary microglial cells to oxygen glucose deprivation (OGD) for 6 h in vitro or treated these cells with a cocktail of TNF-α, IL-1β and IFN-γ for 1 h, followed by the addition of SA-10 (10 µM). Inhibition of microglial activation, ROS scavenging, cytoprotective and anti-inflammatory activities were measured. In vivo I/R-injured mouse retinas were treated with either PBS or SA-10 (2%) intravitreally, and pattern electroretinogram (ERG), spectral-domain optical coherence tomography, flash ERG and retinal immunocytochemistry were performed. SA-10 significantly inhibited microglial activation and inflammation in vitro. Compared to the control, the compound SA-10 significantly attenuated cell death in both microglia (43% vs. 13%) and R28 cells (52% vs. 17%), decreased ROS (38% vs. 68%) production in retinal microglia cells, preserved neural retinal function and increased SOD1 in mouse eyes. SA-10 is protective to retinal neurons by decreasing oxidative stress and inflammatory cytokines.

Lead inhibits microglial cell migration via suppression of store-operated calcium entry

Lead (Pb) is a non-biodegradable environmental pollutant that can lead to neurotoxicity by inducing neuroinflammation. Microglial activation plays a key role in neuroinflammation, and microglial migration is one of its main features. However, whether Pb affects microglial migration has not yet been elucidated. Herein, the effect of Pb on microglial migration was investigated using BV-2 microglial cells and primary microglial cells. The results showed that cell activation markers (TNF-α and CD206) in BV-2 cells were increased after Pb treatment. The migration ability of microglia was inhibited by Pb. Both store-operated calcium entry (SOCE) and the Ca2+ release-activated Ca2+ (CRAC) current were downregulated by microglia treatment with Pb in a dose-dependent manner. However, there was no statistical difference in the protein levels of stromal interaction molecule (STIM) 1, STIM2, or Ca2+ release-activated Ca2+ channel protein (Orai) 1 in microglia. The external Ca2+ influx and cell migration ability were restored to a certain extent after overexpression of either STIM1 or its CRAC activation domain in microglia. These results indicated that Pb inhibits microglial migration by downregulation of SOCE and impairment of the function of STIM1.

Anti-inflammatory effects of quinolinyl analog of resveratrol targeting TLR4 in MCAO/R ischemic stroke rat model

BackgroundAmong adults, stroke is the main causes of mortality and permanent disability. Neuroinflammation is one of the main causes of stoke-mediated neuronal death. Our previous study revealed that (E)-5-(2-(Quinolin-4-yl) vinyl) benzene-1, 3-diol (RV01), a quinolinyl analog of resveratrol, inhibits microglia-induced neuroinflammation and safeguards neurons from inflammatory harm. The preventive role of RV01 in ischemic stroke and its underlying cellular mechanisms and molecular targets remain poorly understood. PurposeTo investigate whether RV01 alleviates ischemia-reperfusion (I/R) injury by inhibiting microglia-mediated neuroinflammation and determine the potential molecular mechanisms and targets by which RV01 inhibits the I/R-mediated microglia activation. MethodsRat middle cerebral artery occlusion and reperfusion (MCAO/R) and BV-2 or primary microglial cells oxygen-glucose deprivation and reperfusion (OGD/R) models were established. The neurological behavior scores, 2, 3, 5-triphenyl tetrazolium chloride staining and immunofluorescence were used to detect the neuroprotective effect of RV01 in the MCAO/R rats. In addition, the mRNA expression levels of IL-6, TNF-α, and IL-1β were detected to reveal the antineuroinflammatory effect of RV01. Moreover, a western blot assay was performed to explore the protein expression changes in NF-κB-mediated neuroinflammation. Finally, we identified TLR4 as an RV01 target through molecular docking, drug sensitivity target stability analysis, cellular thermal shift analysis, and surface plasmon resonance techniques. ResultsRV01 reduced the infarct volume and neurological deficits, increased the rotarod duration, and decreased the number of rightward deflections in the MCAO/R rats. RV01 inhibited the NF-κB signaling pathway in vitro and in vivo, as demonstrated by the reduction in the transcription factor p65-mediated expression of several inflammatory factors including IL-6, TNF-α, and IL-1β. Further studies showed that its protective effect was associated with targeting the TLR4 protein. Notably, the anti-inflammatory effect of RV01 was markedly reinforced by the TLR4 knockdown, but inhibited by the overexpression of TLR4. Results revealed that the conditioned medium derived from the RV01-treated BV-2 cells significantly decreased the OGD/R-mediated neuronal damage. ConclusionOur results are the first to reveal the protective effects of RV01 on cerebral ischemia, depending on its inhibitory effect on the NF-κB pathway by targeting TLR4. RV01 could be a potential protective agent in ischemic stroke treatment.

Isolation and Culture of Mouse Primary Microglia and Oligodendrocyte Precursor Cells.

Microglia and oligodendrocyte precursor cells (OPCs) are critical glia subsets in the central nervous system (CNS) and are actively engaged in a body of diseases, such as stroke, Alzheimer's disease, multiple sclerosis, etc. Microglia and OPC serve as compelling tools for the study of CNS diseases as well as the repair and damage of myelin sheath in vitro. In this protocol, we summarized a method which is capable of using the same batch of new-born mice to isolate and culture microglia and OPCs. It integrates the characteristics of practicality, convenience, and efficiency, providing a convenient, easy, and reliable technique for research.

Inhibition of CXCR2 as a therapeutic target for chronic post-surgical pain: Insights from animal and cell models.

Studies have shown that chemokines can stimulate the migration and activation of microglia to cause chronic post-surgical pain (CPSP). However, the involvement of C-X-C motif chemokine receptor 2 (CXCR2) as a new chemotactic factor in regulating CPSP and its underlying mechanism remains unclear. This study is to investigate the role of CXCR2 in the development of CPSP and reveal the underlying mechanism. A rat model of skin/muscle incision and retraction was established, and treated with or without SB225002 (a selective inhibitor of CXCR2). In addition, the primary microglia cells induced by lipopolysaccharide were applied as an in vitro model for CPSP and treated individually with si-negative control (NC), si-CXCR2, si-CXCR2+Interleukin (IL)-6 (an agonist of the janus kinase (JAK)/signal transducers and activators of transcription (STAT)3 signaling pathway), si-CXCR2+IL-6+si-NC, or si-CXCR2+IL-6+si-exchange protein 1 directly activated by cAMP (EPAC1). Results from the database analysis showed that CXCR2 and JAK/STAT3 signaling pathway-related genes, including JAK1, STAT3, and EPAC1, were mainly involved in the development of CPSP. Inhibition of CXCR2 expression not only inhibited the reduction of foot pain threshold in CPSP models but also led to a decreased expression of CXCR2 and the phosphorylation levels of JAK and STAT3 in both animal and cell models. Furthermore, inhibition of EPAC1 expression can hinder the regulatory function of CXCR2. This study indicated that the high expression of CXCR2 activates the JAK1/STAT3 signaling pathway, enhances EPAC1 activation in microglial cells, and exacerbates CPSP.

Extracellular vesicles of Weizmannia coagulans lilac-01 reduced cell death of primary microglia and increased mitochondrial content in dermal fibroblasts in vitro.

We investigated the properties of extracellular vesicles from the probiotic Weizmannia coagulans lilac-01 (Lilac-01EVs). The phospholipids in the Lilac-01EV membrane were phosphatidylglycerol and mitochondria-specific cardiolipin. We found that applying Lilac-01EVs to primary rat microglia in vitro resulted in a reduction in primary microglial cell death (P<.05). Lilac-01EVs, which contain cardiolipin and phosphatidylglycerol, may have the potential to inhibit cell death in primary microglia. The addition of Lilac-01EVs to senescent human dermal fibroblasts suggested that Lilac-01 EVs increase the mitochondrial content without affecting their membrane potential in these cells.

Low-dose Esketamine suppresses NLRP3-mediated apoptotic and pyroptotic cell death in microglial cells to ameliorate LPS-induced depression via ablating GSK-3β

Esketamine is verified as a potential therapeutic drug for the treatment of depression, but it is still unclear the detailed underlying mechanisms by which Esketamine ameliorates depression-related symptoms, which seriously limits the utilization of this drug in clinical practices. In this study, the C57BL6/J mice and mouse primary microglial cells were subjected to lipopolysaccharide (LPS)-induced depressive models in vivo and in vitro, and our results confirmed that LPS-induced neuroinflammation, pyroptotic and apoptotic death contributed to the development of LPS-induced depressive symptoms. Then, the following experiments verified that low-dose Esketamine treatment decreased the expression levels of IL-6, TNF-α and IL-18 to restrain cellular inflammation, downregulated NLRP3, cleaved Caspase-1, IL-1β and GSDMD-N to hamper pyroptotic cell death, and inhibited cleaved caspase-3 and Bax, but upregulated Bcl-2 to restrict apoptotic cell death in the LPS-treated mice hippocampus tissues and mouse microglial cells, leading to the suppression of depression development. However, high-dose Esketamine did not have those effects. Next, by conducting mechanical experiments, we verified that low-dose Esketamine downregulated GSK-3β to inactivate NLRP3 inflammasome, and the effects of low-dose Esketamine on cell pyroptosis, neuroinflammation and apoptosis in the LPS-treated microglial cells were all abrogated by overexpressing GSK-3β and NLRP3. Taken together, low-dose Esketamine ameliorated LPS-induced depressive symptoms in mice through regulating the GSK-3β/NLRP3 pathway, and our work suggested that appropriate doses of Esketamine were essential for the treatment of depression in clinic.

M6A methyltransferase METTL3 contributes to sympathetic hyperactivity post-MI via promoting TRAF6-dependent mitochondrial ROS production

ObjectivesN6-methyladenosine (m6A) is the most prevalent post-translational modification in eukaryotic mRNA. Recently, m6A editing modified by methyltransferase-like enzyme 3 (METTL3), the core m6A methyltransferase, has been demonstrated to be involved in cardiac sympathetic hyperactivity. This study aimed to clarify the effects and underlying mechanisms of METTL3 in the paraventricular nucleus (PVN) in mediating sympathetic activity following myocardial infarction (MI). MethodsWe established rat MI models by left anterior descending coronary artery ligation. m6A quantification was performed.The expression of METTL3 and its downstream gene, tumor necrosis factor (TNF) receptor-associated factor 6 (TRAF6), were determined. The functional role of METTL3 in sympathetic hyperactivity and electrical conduction stability were verified by assessing renal sympathetic nerve activity (RSNA), norepinephrine (NE) levels, and programmed electrical stimulation. Rescue experiments were also conducted. The mechanism by which m6A is involved in mitochondrial reactive oxygen species (mROS) production, mediated by TRAF6/ECSIT pathway, was explored in lipopolysaccharide (LPS) treated primary microglial cells. ResultsMETTL3 was predominantly localized in the microglia and significantly increased within the PVN at 3 days post-MI. Inhibition of METTL3 decreased m6A levels, TRAF6 expression, and mROS production; downregulated sympathoexcitation, indicated by attenuated NE concentration and RSNA; decreased the incidence of ventricular tachycardia or fibrillation; and improved cardiac function. Mechanistically, downregulation of METTL3 prevented TRAF6 translocation to the mitochondria in the microglia and subsequent TRAF6/ECSIT pathway activation, resulting in decreased mROS production. ConclusionsThis study demonstrates that METTL3-mediated m6A modification promotes sympathetic hyperactivity through TRAF6/ECSIT pathway and mitochondrial oxidative stress in the PVN, thereby leading to ventricular arrhythmias post-MI.

Circular RNA PTP4A2 regulates microglial polarization through STAT3 to promote neuroinflammation in ischemic stroke.

Microglial polarization plays a critical role in neuroinflammation and may be a potential therapeutic target for ischemic stroke. This study was to explore the role and underlying molecular mechanism of Circular RNA PTP4A2 (circPTP4A2) in microglial polarization after ischemic stroke. C57BL/6J mice underwent transient middle cerebral artery occlusion (tMCAO), while primary mouse microglia and BV2 microglial cells experienced oxygen glucose deprivation/reperfusion (OGD/R) to mimic ischemic conditions. CircPTP4A2 shRNA lentivirus and Colivelin were used to knock down circPTP4A2 and upregulate signal transducer and activator of transcription 3 (STAT3) phosphorylation, respectively. Microglial polarization was assessed using immunofluorescence staining and Western blot. RNA pull-down and RNA binding protein immunoprecipitation (RIP) were applied to detect the binding between circPTP4A2 and STAT3. The levels of circPTP4A2 were significantly increased in plasma and peri-infarct cortex in tMCAO mice. CircPTP4A2 knockdown reduced infarct volume, increased cortical cerebral blood flow (CBF), and attenuated neurological deficits. It also decreased pro-inflammatory factors levels in peri-infarct cortex and plasma, and increased anti-inflammatory factors concentrations 24 h post-stroke. In addition, circPTP4A2 knockdown suppressed M1 microglial polarization and promoted M2 microglial polarization in both tMCAO mice and OGD/R-induced BV2 microglial cells. Moreover, circPTP4A2 knockdown inhibited the phosphorylation of STAT3 induced by oxygen-glucose deprivation. In contrast, increased phosphorylation of STAT3 partly counteracted the effects of circPTP4A2 knockdown. RNA pull-down and RIP assays further certified the binding between circPTP4A2 and STAT3. These results revealed regulatory mechanisms of circPTP4A2 that stimulated neuroinflammation by driving STAT3-dependent microglial polarization in ischemic brain injury. CircPTP4A2 knockdown reduced cerebral ischemic injury and promoted microglial M2 polarization, which could be a novel therapeutic target for ischemic stroke.

Modulation of TRPM8 alters the phagocytic activity of microglia and induces changes in sub-cellular organelle functions

In this work, we investigated the presence and function of TRPM8, a non-selective and cold-sensitive Ca2+-permeable ion channel in the primary microglia cell as well as in microglia cell line BV2. We demonstrate that primary microglia as well as BV2 express TRPM8 endogenously. Both pharmacological activation or inhibition of TRPM8 causes enhanced uptake of bacterial particles at early time points of infection. In BV2, TRPM8 activation and/or LPS-signaling alters its surface expression and cytosolic ROS production. TRPM8 modulation in the absence and presence of LPS causes differential regulation of cytosolic pH and lysosomal pH. Notably, TRPM8 modulation also alters the correlation between lysosomal pH and cytosolic pH depending on TRPM8 modulation and the presence or absence of LPS. Collectively our data suggest that TRPM8 is involved in the regulation of subcellular organelle, i.e. mitochondrial and lysosomal functions. Data also suggest that primarily TRPM8 activation, but often deviation from endogenous TRPM8 function is linked with better innate immune function mediated by microglial cells. We suggest that TRPM8-mediated regulations of sub-cellular organelle functions are more context-dependent manner. Such understanding is relevant in the context of microglial cell functions and innate immunity.

Anti-inflammatory effects of Arnica montana (mother tincture and homeopathic dilutions) in various cell models

Ethnopharmacological relevanceThe plant Arnica montana L. has been shown to alleviate inflammation, pain and swelling associated with trauma, and post-operative clinical conditions, yet the mechanism of action is not well understood. Aim of the studyThe study was designed to investigate the effect of Arnica montana (A. montana) mother tincture and homeopathic dilutions on inflammation markers, oxidative stress and cell migration in diverse cell culture models. Materials and methodsWe tested A. montana mother tincture and a range of homeopathic dilutions in different human and murine cell culture models to demonstrate their anti-inflammatory properties by measuring the inflammatory markers: tumor necrosis factor alpha (TNFα), interleukin-6 (IL-6), cyclooxygenase-2 (COX-2), monocyte chemoattractant protein-1 (MCP-1), intercellular adhesion molecule (ICAM-1), reactive oxygen species (ROS) and cell migration. The inflammatory markers were measured by ELISA assays. The intracellular oxidative stress (ROS) in microglial cells was measured using Deep Red CellROX probe. The cell migration was examined by wound healing using the Oris Cell migration assay. ResultsThese data showed the ability of A. montana (mother tincture and mainly 1C dilution) to significantly reduce TNFα production in inflamed macrophages compared with vehicle (control). They significantly reduced both IL-6 and MCP-1 in inflamed human microglial cells and significantly decreased COX-2 expression in inflamed murine fibroblasts. Moreover, A. montana mother tincture reduced the cell migration whereas 9C dilution significantly enhanced the migration of fibroblast cells compared with vehicle. The expression of ICAM-1 was significantly reduced with A. montana mother tincture and 1C, 3C, 5C, and 9C dilutions in inflamed human endothelial cells compared with vehicle. A. montana mother tincture and 1C, 3C, 5C and 9C dilutions induced a significant and consistent effect on ROS production in inflamed murine microglial cells. A. montana 1C had the largest impact on ROS production. ConclusionsMother tincture and 1C dilution of A. montana showed anti-inflammatory properties assessed by measurement of several markers (pro-inflammatory cytokines, adhesion molecule, ROS) in various human and murine cell models. In addition, A. montana 3C, 5C, 9C dilutions have anti-inflammatory and antioxidant effects as highlighted on both primary endothelial cells and murine microglial cells.