Inhibition of MyD88 Signaling Skews Microglia/Macrophage Polarization and Attenuates Neuronal Apoptosis in the Hippocampus After Status Epilepticus in Mice

MyD88-mediated signaling is critical for the generation of seizure responses and cognitive impairment in a model of anti-N-methyl-D-aspartate receptor encephalitis

OBJECTIVE

We previously demonstrated that interleukin-1 receptor-mediated immune activation contributes to seizure severity and memory loss in anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis. In the present study, we assessed the role of the myeloid differentiation primary response gene 88 (MyD88), an adaptor protein in Toll-like receptor signaling, in the key phenotypic characteristics of anti-NMDAR encephalitis.

METHODS

Monoclonal anti-NMDAR antibodies or control antibodies were infused into the lateral ventricle of MyD88 knockout mice (MyD88-/-) and control C56BL/6J mice (wild type [WT]) via osmotic minipumps for 2 weeks. Seizure responses were measured by electroencephalography. Upon completion of the infusion, the motor, anxiety, and memory functions of the mice were assessed. Astrocytic (glial fibrillary acidic protein [GFAP]) and microglial (ionized calcium-binding adaptor molecule 1 [Iba-1]) activation and transcriptional activation for the principal inflammatory mediators involved in seizures were determined using immunohistochemistry and quantitative real-time polymerase chain reaction, respectively.

RESULTS

As shown before, 80% of WT mice infused with anti-NMDAR antibodies (n = 10) developed seizures (median = 11, interquartile range [IQR] = 3-25 in 2 weeks). In contrast, only three of 14 MyD88-/- mice (21.4%) had seizures (0, IQR = 0-.25, p = .01). The WT mice treated with antibodies also developed memory loss in the novel object recognition test, whereas such memory deficits were not apparent in MyD88-/- mice treated with anti-NMDAR antibodies (p = .03) or control antibodies (p = .04). Furthermore, in contrast to the WT mice exposed to anti-NMDAR antibodies, the MyD88-/- mice had a significantly lower induction of chemokine (C-C motif) ligand 2 (CCL2) in the hippocampus (p = .0001, Sidak tests). There were no significant changes in the expression of GFAP and Iba-1 in the MyD88-/- mice treated with anti-NMDAR or control antibodies.

SIGNIFICANCE

These findings suggest that MyD88-mediated signaling contributes to the seizure and memory phenotype in anti-NMDAR encephalitis and that CCL2 activation may participate in the expression of these features. The removal of MyD88 inflammation may be protective and therapeutically relevant.

Ferroptosis and Pyroptosis in Epilepsy

Epilepsy is sudden, recurrent, and transient central nervous system dysfunction caused by abnormal discharge of neurons in the brain. Ferroptosis and pyroptosis are newly discovered ways of programmed cell death. One of the characteristics of ferroptosis is the oxidative stress generated by lipid peroxides. Similarly, pyroptosis has unique pro-inflammatory properties. As both oxidative stress and neuroinflammation are significant contributors to the pathogenesis of epilepsy, increasing evidence shows that ferroptosis and pyroptosis are closely related to epilepsy. This article reviews the current comprehension of ferroptosis and pyroptosis and elucidates potential mechanisms by which ferroptosis and pyroptosis may contribute to epilepsy. In addition, we also highlight the possible interactions between ferroptosis and pyroptosis because they reportedly coexist in many diseases, and increasing studies have demonstrated the convergence of pathways between the two. This is of great significance for explaining the occurrence and development of epilepsy and provides a new therapeutic perspective for the treatment of epilepsy.

Targeted nanotheranostics for the treatment of epilepsy through in vivo hijacking of locally activated macrophages

Epilepsy refers to a disabling neurological disorder featured by the long-term and unpredictable occurrence of seizures owing to abnormal excessive neuronal electrical activity and is closely linked to unresolved inflammation, oxidative stress, and hypoxia. The difficulty of accurate localization and targeted drug delivery to the lesion hinders the effective treatment of this disease. The locally activated inflammatory cells in the epileptogenic region offer a new opportunity for drug delivery to the lesion. In this work, CD163-positive macrophages in the epileptogenic region were first harnessed as Trojan horses after being hijacked by targeted albumin manganese dioxide nanoparticles, which effectively penetrated the brain endothelial barrier and delivered multifunctional nanomedicines to the epileptic foci. Hence, accumulative nanoparticles empowered the visualization of the epileptogenic lesion through microenvironment-responsive MR T1-weight imaging of manganese dioxide. Besides, these manganese-based nanomaterials played a pivotal role in shielding neurons from cell apoptosis mediated by oxidative stress and hypoxia. Taken together, the present study provides an up-to-date approach for integrated diagnosis and treatment of epilepsy and other hypoxia-associated inflammatory diseases. STATEMENT OF SIGNIFICANCE: The therapeutic effects of antiepileptic drugs (AEDs) are hindered by insufficient drug accumulation in the epileptic site. Herein, we report an efficient strategy to use locally activated macrophages as carriers to deliver multifunctional nanoparticles to the brain lesion. As MR-responsive T1 contrast agents, multifunctional BMC nanoparticles can be harnessed to accurately localize the epileptogenic region with high sensitivity and specificity. Meanwhile, catalytic nanoparticles BMC can synergistically scavenge ROS, generate O2 and regulate neuroinflammation for the protection of neurons in the brain.

The exploration of neuroinflammatory mechanism by which CRHR2 deficiency induced anxiety disorder

Inflammation stimulates the hypothalamic-pituitary adrenal (HPA) axis and triggers glial neuroinflammatory phenotypes, which reduces monoamine neurotransmitters by activating indoleamine 2,3-dioxygenase enzyme. These changes can induce psychiatric diseases, including anxiety. Corticotropin releasing hormone receptor 2 (CRHR2) in the HPA axis is involved in the etiology of anxiety. Omega(n)-3 polyunsaturated fatty acids (PUFAs) can attenuate anxiety through anti-inflammation and HPA axis modulation. However, the underlying molecular mechanism by CRHR2 modulates anxiety and its correlation with neuroinflammation remain unclear. Here, we first constructed a crhr2 zebrafish mutant line, and evaluated anxiety-like behaviors, gene expression associated with the HPA axis, neuroinflammatory response, neurotransmitters, and PUFAs profile in crhr2+/+ and crhr2-/- zebrafish. The crhr2 deficiency decreased cortisol levels and up-regulated crhr1 and down-regulated crhb, crhbp, ucn3l and proopiomelanocortin a (pomc a) in zebrafish. Interestingly, a significant increase in the neuroinflammatory markers, translocator protein (TSPO) and the activation of microglia M1 phenotype (CD11b) were found in crhr2-/- zebrafish. As a consequence, the expression of granulocyte-macrophage colony-stimulating factor, pro-inflammatory cytokines vascular endothelial growth factor, and astrocyte A1 phenotype c3 were up-regulated. While microglia anti-inflammatory phenotype (CD206), central anti-inflammatory cytokine interleukin-4, arginase-1, and transforming growth factor-β were downregulated. In parallel, crhr2-deficient zebrafish showed an upregulation of vdac1 protein, a TSPO ligand, and its downstream caspase-3. Furthermore, 5-HT/5-HIAA ratio was decreased and n-3 PUFAs deficiency was identified in crhr2-/- zebrafish. In conclusion, anxiety-like behavior displayed by crhr2-deficient zebrafish may be caused by the HPA axis dysfunction and enhanced neuroinflammation, which resulted in n-3 PUFAs and monoamine neurotransmitter reductions.

The immune system and metabolic products in epilepsy and glioma-associated epilepsy: emerging therapeutic directions

Epilepsy has a profound impact on quality of life. Despite the development of new antiseizure medications (ASMs), approximately one-third of affected patients have drug-refractory epilepsy and are nonresponsive to medical treatment. Nearly all currently approved ASMs target neuronal activity through ion channel modulation. Recent human and animal model studies have implicated new immunotherapeutic and metabolomic approaches that may benefit patients with epilepsy. In this Review, we detail the proinflammatory immune landscape of epilepsy and contrast this with the immunosuppressive microenvironment in patients with glioma-related epilepsy. In the tumor setting, excessive neuronal activity facilitates immunosuppression, thereby contributing to subsequent glioma progression. Metabolic modulation of the IDH1-mutant pathway provides a dual pathway for reversing immune suppression and dampening seizure activity. Elucidating the relationship between neurons and immunoreactivity is an area for the prioritization and development of the next era of ASMs.

Leukocyte differential gene expression prognostic value for high versus low seizure frequency in temporal lobe epilepsy

BACKGROUND

This study was performed to test the hypothesis that systemic leukocyte gene expression has prognostic value differentiating low from high seizure frequency refractory temporal lobe epilepsy (TLE).

METHODS

A consecutive series of patients with refractory temporal lobe epilepsy was studied. Based on a median baseline seizure frequency of 2.0 seizures per month, low versus high seizure frequency was defined as ≤ 2 seizures/month and > 2 seizures/month, respectively. Systemic leukocyte gene expression was analyzed for prognostic value for TLE seizure frequency. All differentially expressed genes were analyzed, with Ingenuity® Pathway Analysis (IPA®) and Reactome, to identify leukocyte gene expression and biological pathways with prognostic value for seizure frequency.

RESULTS

There were ten males and six females with a mean age of 39.4 years (range: 16 to 62 years, standard error of mean: 3.6 years). There were five patients in the high and eleven patients in the low seizure frequency cohorts, respectively. Based on a threshold of twofold change (p < 0.001, FC > 2.0, FDR < 0.05) and expression within at least two pathways from both Reactome and Ingenuity® Pathway Analysis (IPA®), 13 differentially expressed leukocyte genes were identified which were all over-expressed in the low when compared to the high seizure frequency groups, including NCF2, HMOX1, RHOB, FCGR2A, PRKCD, RAC2, TLR1, CHP1, TNFRSF1A, IFNGR1, LYN, MYD88, and CASP1. Similar analysis identified four differentially expressed genes which were all over-expressed in the high when compared to the low seizure frequency groups, including AK1, F2R, GNB5, and TYMS.

CONCLUSIONS

Low and high seizure frequency TLE are predicted by the respective upregulation and downregulation of specific leukocyte genes involved in canonical pathways of neuroinflammation, oxidative stress and lipid peroxidation, GABA (γ-aminobutyric acid) inhibition, and AMPA and NMDA receptor signaling. Furthermore, high seizure frequency-TLE is distinguished prognostically from low seizure frequency-TLE by differentially increased specific leukocyte gene expression involved in GABA inhibition and NMDA receptor signaling. High and low seizure frequency patients appear to represent two mechanistically different forms of temporal lobe epilepsy based on leukocyte gene expression.

Immunology of Retinitis Pigmentosa and Gene Therapy-Associated Uveitis

The underlying immune state of inherited retinal degenerations (IRDs) and retinitis pigmentosa (RP) has been an emerging area of interest, wherein the consequences have never been greater given the widespread recognition of gene therapy-associated uveitis (GTU) in gene therapy clinical trials. Whereas some evidence suggests that the adaptive immune system may play a role, the majority of studies indicate that the innate immune system is likely the primary driver of neuroinflammation in RP. During retinal degeneration, discrete mechanisms activate resident microglia and promote infiltrating macrophages that can either be protective or detrimental to photoreceptor cell death. This persistent stimulation of innate immunity, overlaid by the introduction of viral antigens as part of gene therapy, has the potential to trigger a complex microglia/macrophage-driven proinflammatory state. A better understanding of the immune pathophysiology in IRD and GTU will be necessary to improve the success of developing novel treatments for IRDs.

Identification and verification of ferroptosis-related genes in the pathology of epilepsy: insights from CIBERSORT algorithm analysis

Background

Epilepsy is a neurological disorder characterized by recurrent seizures. A mechanism of cell death regulation, known as ferroptosis, which involves iron-dependent lipid peroxidation, has been implicated in various diseases, including epilepsy.

Objective

This study aimed to provide a comprehensive understanding of the relationship between ferroptosis and epilepsy through bioinformatics analysis. By identifying key genes, pathways, and potential therapeutic targets, we aimed to shed light on the underlying mechanisms involved in the pathogenesis of epilepsy.

Materials and methods

We conducted a comprehensive analysis by screening gene expression data from the Gene Expression Omnibus (GEO) database and identified the differentially expressed genes (DEGs) related to ferroptosis. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were performed to gain insights into the biological processes and pathways involved. Moreover, we constructed a protein-protein interaction (PPI) network to identify hub genes, which was further validated using the receiver operating characteristic (ROC) curve analysis. To explore the relationship between immune infiltration and genes, we employed the CIBERSORT algorithm. Furthermore, we visualized four distinct interaction networks-mRNA-miRNA, mRNA-transcription factor, mRNA-drug, and mRNA-compound-to investigate potential regulatory mechanisms.

Results

In this study, we identified a total of 33 differentially expressed genes (FDEGs) associated with epilepsy and presented them using a Venn diagram. Enrichment analysis revealed significant enrichment in the pathways related to reactive oxygen species, secondary lysosomes, and ubiquitin protein ligase binding. Furthermore, GSVA enrichment analysis highlighted significant differences between epilepsy and control groups in terms of the generation of precursor metabolites and energy, chaperone complex, and antioxidant activity in Gene Ontology (GO) analysis. Furthermore, during the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, we observed differential expression in pathways associated with amyotrophic lateral sclerosis (ALS) and acute myeloid leukemia (AML) between the two groups. To identify hub genes, we constructed a protein-protein interaction (PPI) network using 30 FDEGs and utilized algorithms. This analysis led to the identification of three hub genes, namely, HIF1A, TLR4, and CASP8. The application of the CIBERSORT algorithm allowed us to explore the immune infiltration patterns between epilepsy and control groups. We found that CD4-naïve T cells, gamma delta T cells, M1 macrophages, and neutrophils exhibited higher expression in the control group than in the epilepsy group.

Conclusion

This study identified three FDEGs and analyzed the immune cells in epilepsy. These findings pave the way for future research and the development of innovative therapeutic strategies for epilepsy.

Electroacupuncture alleviates neuropathic pain caused by SNL by promoting M2 microglia polarization through PD-L1

As a common clinical disease, neuropathic pain is difficult to be cured with drugs. The occurrence and progression of pain is closely related to the response of spinal microglia. Aspartof the regulation of microglialactivity,PD-L1 playsacriticalrole. Loss of PD-L1 promoted the polarization of M1-like microglia. Increased expression of PD-L1 promoted M2-like polarization. Electroacupuncture has a significant analgesic effect in clinical practice, but its specific mechanism remains to be further explored. In this study, we verified the role of PD-L1 in EA analgesia and the underlying molecular mechanism through spinal nerve ligation (SNL) in rats and lipopolysaccharide (LPS)-treated BV2 microglial cells. Forbehavioralstudiesofrats,mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL) were measured, and spinal cord neuros were examined under transmission electron microscopyto determine changes to their myelin structure. The expression levels of PD-L1 and M1/M2-specific markers in rat spinal cord and BV2 microglial cells were measured by enzyme-linked immunosorbent assay, flow cytometry, immunofluorescence staining and Western blot analysis. Our study showed that EA increased the pain threshold, reduced the destruction of myelin structure, promoted the expression of PD-L1 and PD-1, inhibited the MAPK signaling pathway, and promoted the conversion of microglial polarization from the M1 phenotype to the M2 phenotype in SNL rats. PD-L1 knockdown reversed these effects of EA. In addition, PD-L1 knockdown activated the MAPK signaling pathway, promoted microglial polarization to the M1 phenotype, decreased the expression of anti-inflammatory mediators and increased the expression of proinflammatory factors in LPS-stimulated BV2 microglial cells. Our results showed that EA may regulate the excitability of primary afferent neurons through PD-L1 and then inhibit the MAPK signaling pathway to promote the transformation of activated M1 microglia into M2 microglia, reduce inflammatory reactions, and finally achieve analgesic effects. A therapy targeting PD-L1 may be an effective strategy for treating neuropathic pain.

The applications of the pilocarpine animal model of status epilepticus: 40 years of progress (1983-2023)

Status epilepticus is a neurological disorder that can result in various neuropathological conditions and presentations. Various studies involving animal models have been accomplished to understand and replicating its prominent manifestations including characteristics of related clinical cases. Up to these days, there are variety of methods and techniques to be utilized in inducing this disorder that can be chemically or electrically applied which depending on the experimental designs and targets of the studies. In particular, the chemically induced pilocarpine animal model of status epilepticus is a reliable choice which has evolved for 40 years from its initial discovery back in 1983. Although the development of the model can be considered as a remarkable breakthrough in understanding status epilepticus, several aspects of the model have been improved, throughout the years. Among the major issues in developing this model are the morbidity and mortality rates during induction process. Several modifications have been introduced in the process by different studies to tackle the related problems including application of dose fractionation, adaptation of pilocarpine to lithium-pilocarpine model and utilization of various drugs. Despite all challenges and drawbacks, this model has proven its pertinent and relevance with improvements that have been adapted since it was introduced 40 years ago. In this review, we emphasize on the evolution of this animal model from the beginning until now (1983 - 2023) and the related issues that have made this model still a popular choice in status epilepticus studies.

Melatonin regulates microglial polarization to M2 cell via RhoA/ROCK signaling pathway in epilepsy

BACKGROUND

Melatonin (MEL), an endogenous hormone, has been widely investigated in neurological diseases. Microglia (MG), a resident immunocyte localizing in central nervous system is reported to play important functions in the animal model of temporal lobe epilepsy (TLE). Some evidence showed that MEL influenced activation of MG, but the detailed model of action that MEL plays in remains uncertain.

METHODS

In this study, we established a model of TLE in mice by stereotactic injection of kainic acid (KA). We treated the mice with MEL. Lipopolysaccharide, ROCK2-knockdown (ROCK-KD) and -overexpression (ROCK-OE) of lentivirus-treated cells were used in cell experiments to simulate an in vitro inflammatory model.

RESULTS

The results of electrophysiological tests showed that MEL reduced frequency and severity of seizure. The results of behavioral tests indicated MEL improved cognition, learning, and memory ability. Histological evidences demonstrated a significant reduction of neuronal death in the hippocampus. In vivo study showed that MEL changed the polarization status of MG from a proinflammatory M1 phenotype to an anti-inflammatory M2 phenotype by inversely regulating the RhoA/ROCK signaling pathway. In cytological study, we found that MEL had a significant protective effect in LPS-treated BV-2 cells and ROCK-KD cells, while the protective effect of MEL was significantly attenuated in ROCK-OE cells.

CONCLUSION

MEL played an antiepileptic role in the KA-induced TLE modeling mice both in behavioral and histological levels, and changed MG polarization status by regulating the RhoA/ROCK signaling pathway.

Beneficial Effects of Probiotic Bifidobacterium longum in a Lithium-Pilocarpine Model of Temporal Lobe Epilepsy in Rats

Epilepsy is a challenging brain disorder that is often difficult to treat with conventional therapies. The gut microbiota has been shown to play an important role in the development of neuropsychiatric disorders, including epilepsy. In this study, the effects of Bifidobacterium longum, a probiotic, on inflammation, neuronal degeneration, and behavior are evaluated in a lithium-pilocarpine model of temporal lobe epilepsy (TLE) induced in young adult rats. B. longum was administered orally at a dose of 10⁹ CFU/rat for 30 days after pilocarpine injection. The results show that B. longum treatment has beneficial effects on the TLE-induced changes in anxiety levels, neuronal death in the amygdala, and body weight recovery. In addition, B. longum increased the expression of anti-inflammatory and neuroprotective genes, such as Il1rn and Pparg. However, the probiotic had little effect on TLE-induced astrogliosis and microgliosis and did not reduce neuronal death in the hippocampus and temporal cortex. The study suggests that B. longum may have a beneficial effect on TLE and may provide valuable insights into the role of gut bacteria in epileptogenesis. In addition, the results show that B. longum may be a promising drug for the comprehensive treatment of epilepsy.

Adiponectin Attenuates Splenectomy-Induced Cognitive Deficits by Neuroinflammation and Oxidative Stress via TLR4/MyD88/NF-κb Signaling Pathway in Aged Rats

Perioperative neurocognitive disorder (PND) is a common adverse event after surgical trauma in elderly patients. The pathogenesis of PND is still unclear. Adiponectin (APN) is a plasma protein secreted by adipose tissue. We have reported that a decreased APN expression is associated with PND patients. APN may be a promising therapeutic agent for PND. However, the neuroprotective mechanism of APN in PND is still unclear. In this study, 18 month old male Sprague-Dawley rats were assigned to six groups: the sham, sham + APN (intragastric (i.g.) administration of 10 μg/kg/day for 20 days before splenectomy), PND (splenectomy), PND + APN, PND + TAK-242 (intraperitoneal (i.p.) administration of 3 mg/kg TAK-242), and PND + APN + lipopolysaccharide (LPS) (i.p. administration of 2 mg/kg LPS). We first found that APN gastric infusion significantly improved learning and cognitive function in the Morris water maze (MWM) test after surgical trauma. Further experiments indicated that APN could inhibit the Toll-like receptor 4 (TLR4)/myeloid differentiation factor 88 (MyD88)/nuclear factor kappa B (NF-κb) p65 pathway to decrease the degree of oxidative damage (malondialdehyde (MDA) and superoxide dismutase (SOD)), microglia-mediated neuroinflammation (ionized calcium binding adapter molecule 1 (IBA1), caspase-1, tumor necrosis factor (TNF)-α, interleukin-1β (IL-1β), and interleukin-6 (IL-6)), and apoptosis (p53, Bcl2, Bax, and caspase 3) in hippocampus. By using LPS-specific agonist and TAK-242-specific inhibitor, the involvement of TLR4 engagement was confirmed. APN intragastric administration exerts a neuroprotective effect against cognitive deficits induced by peripheral trauma, and the possible mechanisms include the inhibition of neuroinflammation, oxidative stress, and apoptosis, mediated by the suppression of the TLR4/MyD88/NF-κb signaling pathway. We propose that oral APN may be a promising candidate for PND treatment.

Curcumin promotes microglial M2 polarization and suppresses chronic constriction: Injury-induced neuropathic pain in a rat model of peripheral neuropathy

OBJECTIVES

Glia (i.e., astrocyte and microglia) activation in the central nervous system plays a critical role in developing neuropathic pain. Microglia can be activated into proinflammatory (M1) and anti-inflammatory (M2) phenotypes. Switching microglial polarization from M1 to M2 phenotypes represents a novel therapeutic strategy for neuropathic pain. Curcumin has been widely used for its anti-inflammatory and immunomodulatory effects. This study investigated effects of curcumin on astrocyte activation and microglia polarization in the cuneate nucleus (CN) and development of neuropathic pain behavior after chronic constriction injury (CCI) of the median nerve.

METHODS

Rats were fed with curcumin once daily at a dose of 40, 80, or 120 mg/kg 30 min before and until 7 d after median nerve CCI. Subsequently, mechanical allodynia and thermal hyperalgesia were evaluated using von Frey filaments and plantar tests, respectively. The levels of astrocyte marker, monoclonal glial fibrillary acidic protein; microglia marker, ionized calcium-binding adapter molecule 1; M1 marker, CD86; and M2 marker, CD206 in the cuneate nucleus were determined. Enzyme-linked immunosorbent assay was applied to measure cytokine concentrations.

RESULTS

Curcumin administration dose-dependently reduced mechanical allodynia and thermal hyperalgesia and decreased monoclonal glial fibrillary acidic protein and ionized calcium-binding adapter molecule 1 immunoreactivity in the ipsilateral cuneate nucleus after CCI. On ultrastructural observation, curcumin treatment was associated with fewer features of activated astrocytes and microglia. Furthermore, CCI rats given curcumin exhibited a decline in CD86 immunoreactivity and proinflammatory cytokine levels but an increase in CD206 immunoreactivity and release of anti-inflammatory cytokines.

CONCLUSIONS

In our findings, curcumin switches microglial phenotypes from M1 to M2 by suppressing astrocytic activation, reducing proinflammatory cytokine release, promoting anti-inflammatory cytokine production, and contributing to relief of neuropathic pain.

Microglial activation and over pruning involved in developmental epilepsy

To understand the potential role of microglia in synaptic pruning following status epilepticus (SE), we examined the time course of expression of Iba-1, and immune and neuroinflammatory regulators, including CD86, CD206, and CX3CR1, and TLR4/NF-κB after SE induced by pilocarpine in rats. Behavioral tests, TUNEL (terminal deoxynucleotidyl transferase dUTP nick end labeling) staining, immunohistochemical staining, Western blotting, PCR, and fluorescence double staining assessments were performed. The expression of Iba-1 protein was lowest in the control group, and peaked after 2 days (p < 0.001). CD86 and CD206 mRNA levels increased gradually in the microglia of the epilepsy group after 12 hours, 1 day, 2 days, and 3 days; peak expression was on the second day. The expression of the chemokine receptor CX3CR1 in microglia increased to varying degrees after SE, and expression of the presynaptic protein synapsin decreased. The expression of TLR4/NF-κB in microglia positively correlated with Iba-1 protein expression. These findings indicate that the TLR4/NF-κB signaling pathway may be involved in the activation and polarization of microglia in epilepsy and in excess synaptic pruning, which could lead to an increase in brain injury.

Neuroprotection of cannabidiol in epileptic rats: Gut microbiome and metabolome sequencing

AIMS

Epilepsy is a neurological disease occurring worldwide. Alterations in the gut microbial composition may be involved in the development of Epilepsy. The study aimed to investigate the effects of cannabidiol (CBD) on gut microbiota and the metabolic profile of epileptic rats.

MATERIALS AND METHODS AND RESULTS

A temporal lobe epilepsy rat model was established using Li-pilocarpine. CBD increased the incubation period and reduced the epileptic state in rats. Compared to epileptic rats, the M1/M2 ratio of microglia in the CBD group was significantly decreased. The expression of IL-1β, IL-6, and TNF-α in the CBD group decreased, while IL-10, IL-4, and TGF-β1 increased. 16S rDNA sequencing revealed that the ANOSIM index differed significantly between the groups. At the genus level, Helicobacter, Prevotellaceae_UCG-001, and Ruminococcaceae_UCG-005 were significantly reduced in the model group. CBD intervention attenuated the intervention effects of Li-pilocarpine. Roseburia, Eubacterium_xylanophilum_group, and Ruminococcus_2 were strongly positively correlated with proinflammatory cytokine levels. CBD reversed dysregulated metabolites, including glycerophosphocholine and 4-ethylbenzoic acid.

CONCLUSION

CBD could alleviate the dysbiosis of gut microbiota and metabolic disorders of epileptic rats. CBD attenuated Epilepsy in rats might be related to gut microbial abundance and metabolite levels.

SIGNIFICANCE AND IMPACT OF STUDY

The study may provide a reliable scientific clue to explore the regulatory pathway of CBD in alleviating Epilepsy.

Tailoring Materials for Epilepsy Imaging: From Biomarkers to Imaging Probes

Excising epileptic foci (EF) is the most efficient approach for treating drug-resistant epilepsy (DRE). However, owing to the vast heterogeneity of epilepsies, EF in one-third of patients cannot be accurately located, even after exhausting all current diagnostic strategies. Therefore, identifying biomarkers that truly represent the status of epilepsy and fabricating probes with high targeting specificity are prerequisites for identifying the "concealed" EF. However, no systematic summary of this topic has been published. Herein, the potential biomarkers of EF are first summarized and classified into three categories: functional, molecular, and structural aberrances during epileptogenesis, a procedure of nonepileptic brain biasing toward epileptic tissue. The materials used to fabricate these imaging probes and their performance in defining the EF in preclinical and clinical studies are highlighted. Finally, perspectives for developing the next generation of probes and their challenges in clinical translation are discussed. In general, this review can be helpful in guiding the development of imaging probes defining EF with improved accuracy and holds promise for increasing the number of DRE patients who are eligible for surgical intervention.

Targeting Myd88 using peptide-loaded mesenchymal stem cell membrane-derived synthetic vesicles to treat systemic inflammation

Mesenchymal stem cells (MSC) secrete extracellular vesicles (EV) with a regenerative profile, and an increasing number of studies have focused on the utilization of MSC-EV for therapeutic drug delivery. However, EV are usually produced by cells in low quantities and are packed with numerous cytoplasmic components, which may be unfavorable for further drug loading. In this study, we developed a simple process for generating membrane vesicles directly from the cells, which we refer to as synthetic eukaryotic vesicles (SyEV). We hypothesized that MSC-derived SyEV can be efficiently loaded with an anti-inflammatory drug and the loaded vesicles can strongly suppress the systemic inflammation induced by bacterial outer membrane vesicles (OMV). SyEV were generated from MSC membranes through serial extrusion of the cells, ionic stress, and subsequent vesiculation of the membrane sheets, leading to high yield and purity of the SyEV with few cytosolic components remaining. When these SyEV were given to macrophages or mice exposed to OMV, the release of pro-inflammatory cytokines was similarly attenuated comparable to treatment with natural EV. We then loaded the SyEV with large numbers of peptides targeting Myd88 and observed enhanced therapeutic potential of the loaded vesicles in OMV-induced macrophages. Further, in vivo experiments showed that the peptide-encapsulated MSC-SyEV suppressed cytokine production synergistically. Taken together, these findings suggest that SyEV-based therapeutics is a highly interesting platform for delivering an advanced therapeutic drug for the treatment of systemic inflammation without severe side effects.

Distinct Cell-specific Roles of NOX2 and MyD88 in Epileptogenesis

It is well established that temporal lobe epilepsy (TLE) is often related to oxidative stress and neuroinflammation. Both processes subserve alterations observed in epileptogenesis and ultimately involve distinct classes of cells, including astrocytes, microglia, and specific neural subtypes. For this reason, molecules associated with oxidative stress response and neuroinflammation have been proposed as potential targets for therapeutic strategies. However, these molecules can participate in distinct intracellular pathways depending on the cell type. To illustrate this, we reviewed the potential role of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 2 (NOX2) and myeloid differentiation primary response 88 (MyD88) in astrocytes, microglia, and neurons in epileptogenesis. Furthermore, we presented approaches to study genes in different cells, employing single-cell RNA-sequencing (scRNAseq) transcriptomic analyses, transgenic technologies and viral serotypes carrying vectors with specific promoters. We discussed the importance of identifying particular roles of molecules depending on the cell type, endowing more effective therapeutic strategies to treat TLE.

Microglia Phenotypes in Aging and Neurodegenerative Diseases

Neuroinflammation is a hallmark of many neurodegenerative diseases (NDs) and plays a fundamental role in mediating the onset and progression of disease. Microglia, which function as first-line immune guardians of the central nervous system (CNS), are the central drivers of neuroinflammation. Numerous human postmortem studies and in vivo imaging analyses have shown chronically activated microglia in patients with various acute and chronic neuropathological diseases. While microglial activation is a common feature of many NDs, the exact role of microglia in various pathological states is complex and often contradictory. However, there is a consensus that microglia play a biphasic role in pathological conditions, with detrimental and protective phenotypes, and the overall response of microglia and the activation of different phenotypes depends on the nature and duration of the inflammatory insult, as well as the stage of disease development. This review provides a comprehensive overview of current research on the various microglia phenotypes and inflammatory responses in health, aging, and NDs, with a special emphasis on the heterogeneous phenotypic response of microglia in acute and chronic diseases such as hemorrhagic stroke (HS), Alzheimer’s disease (AD), and Parkinson’s disease (PD). The primary focus is translational research in preclinical animal models and bulk/single-cell transcriptome studies in human postmortem samples. Additionally, this review covers key microglial receptors and signaling pathways that are potential therapeutic targets to regulate microglial inflammatory responses during aging and in NDs. Additionally, age-, sex-, and species-specific microglial differences will be briefly reviewed.

Upregulation of FAM129B protects cardiomyocytes from hypoxia/reoxygenation-induced injury by inhibiting apoptosis, oxidative stress, and inflammatory response via enhancing Nrf2/ARE activation

Family with sequence similarity 129, member B (FAM129B) has been identified as a novel cytoprotective protein that facilitates the survival of detrimentally stimulated cells. However, whether FAM129B is involved in regulating cardiomyocyte survival after myocardial ischemia-reperfusion injury is unknown. The goal of this work was to evaluate the potential role of FAM129B in regulating hypoxia/reoxygenation (H/R)-induced cardiomyocyte injury in vitro. We demonstrated that exposure to H/R markedly downregulated the expression of FAM129B in cardiomyocytes. Functional experiments revealed that the upregulation of FAM129B improved H/R-exposed cardiomyocyte viability, and ameliorated H/R-induced cardiomyocyte apoptosis, the generation of reactive oxygen species (ROS), and pro-inflammatory cytokine release. The upregulation of FAM129B significantly increased the nuclear expression of nuclear factor-erythroid 2-related factor 2 (Nrf2), and reinforced Nrf2/antioxidant response element (ARE) activation in H/R-exposed cardiomyocytes. Moreover, FAM129B modulates Nrf2/ARE signaling in a Kelchlike ECH-associated protein 1-dependent manner. Notably, the inhibition of Nrf2 significantly blocked FAM129B-overexpression-induced cardioprotective effects in H/R-exposed cardiomyocytes. In summary, the findings of our work demonstrate that the upregulation of FAM129B ameliorates H/R-induced cardiomyocyte injury via enhancing Nrf2/ARE activation. Thus, our study indicates that FAM129B may play a role in myocardial ischemia-reperfusion injury and has the potential to be used as a cardioprotective target.

Mechanism of cell death pathways in status epilepticus and related therapeutic agents

The most severe form of epilepsy, status epilepticus (SE), causes brain damage and results in the development of recurring seizures. Currently, the management of SE remains a clinical challenge because patients do not respond adequately to conventional treatments. Evidence suggests that neural cell death worsens the occurrence and progression of SE. The main forms of cell death are apoptosis, necroptosis, pyroptosis, and ferroptosis. Herein, these mechanisms of neuronal death in relation to SE and the alleviation of SE by potential modulators that target neuronal death have been reviewed. An understanding of these pathways and their possible roles in SE may assist in the development of SE therapies and in the discovery of new agents.

The Role of the Negative Regulation of Microglia-Mediated Neuroinflammation in Improving Emotional Behavior After Epileptic Seizures

Objective

Studies have long shown that uncontrolled inflammatory responses in the brain play a key role in epilepsy pathogenesis. Microglias play an important role in epileptic-induced neuroinflammation, but their role after epileptic seizures is still poorly understood. Alleviating epilepsy and its comorbidities has become a key area of interest for pediatricians.

Methods

A pilocarpine-induced rat model of epilepsy was established. The rats were randomly divided into four groups: a control group, epilepsy group, TLR4 inhibitor group (epilepsy+TAK-242), and NF-κB antagonist group (epilepsy+BAY11–7082).

Results

1. The results of TUNEL staining showed that the expression in rats in the epilepsy group was the most obvious and was significantly different from that in rats in the control, EP+BAY and EP+TAK groups. 2. The expression of TLR4 and NF-κB was highest in rats in the epilepsy group and was significantly different from that in rats in the control, EP+BAY and EP+TAK groups. 3. The fluorescence intensity and number of IBA-1-positive cells in rats in the epilepsy group were highest and significantly different from those in rats in the control, EP+BAY and EP+TAK groups. Western blot analysis of IBA-1 showed that the expression in rats in the epilepsy group was the highest and was statistically significant. 4. CD68 was the highest in rats in the epilepsy group and was statistically significant. 5. In the open-field experiment, the central region residence time of rats in the EP group was delayed, the central region movement distance traveled was prolonged, the total distance traveled was prolonged, and the average speed was increased. Compared with rats in the EP group, rats in the EP+BAY and EP+ TAK groups exhibited improvements to different degrees.

Conclusion

At the tissue level, downregulation of the TLR4/NF-κB inflammatory pathway in epilepsy could inhibit microglial activation and the expression of the inflammatory factor CD68, could inhibit hyperphagocytosis, and inhibit the occurrence and exacerbation of epilepsy, thus improving cognitive and emotional disorders after epileptic seizures.

Intestinal Flora Composition Determines Microglia Activation and Improves Epileptic Episode Progress

In response to environmental stimuli, immune memory mediates the plasticity of myeloid cells. Immune training and immune tolerance are two aspects of plasticity. Microglia that are immunologically trained or immunologically tolerant are endowed with a tendency to differentiate into alternative dominant phenotypes (M1/M2). Male C57BL/6 mice (immune-training group, immune-tolerant group, and control group) were used to establish the kainic acid epilepsy model. The seizure grade, duration, latency, hippocampal potential, and energy density were used to evaluate seizures, and the changes in the polarization of microglia were detected by western blot. 16S rDNA sequencing showed that the abundance of Ruminococcus in the immune-tolerant group was the dominant flora. Our research connections Intestinal microorganisms, brain immune status, and epilepsy behavior together. Pro-inflammatory M1 phenotype and anti-inflammatory M2 phenotype mediate and enhance and suppress subsequent inflammation, respectively. We conclude that intestinal microorganisms influence the occurrence and development of epilepsy by regulating the polarization of microglia.

Targeting macrophagic SHP2 for ameliorating osteoarthritis via TLR signaling

Osteoarthritis (OA), in which M1 macrophage polarization in the synovium exacerbates disease progression, is a major cause of cartilage degeneration and functional disabilities. Therapeutic strategies of OA designed to interfere with the polarization of macrophages have rarely been reported. Here, we report that SHP099, as an allosteric inhibitor of src-homology 2-containing protein tyrosine phosphatase 2 (SHP2), attenuated osteoarthritis progression by inhibiting M1 macrophage polarization. We demonstrated that M1 macrophage polarization was accompanied by the overexpression of SHP2 in the synovial tissues of OA patients and OA model mice. Compared to wild-type (WT) mice, myeloid lineage conditional Shp2 knockout (cKO) mice showed decreased M1 macrophage polarization and attenuated severity of synovitis, an elevated expression of cartilage phenotype protein collagen II (COL2), and a decreased expression of cartilage degradation markers collagen X (COL10) and matrix metalloproteinase 3 (MMP3) in OA cartilage. Further mechanistic analysis showed thatSHP099 inhibited lipopolysaccharide (LPS)-induced Toll-like receptor (TLR) signaling mediated by nuclear factor kappa B (NF-κB) and PI3K–AKT signaling. Moreover, intra-articular injection of SHP099 also significantly attenuated OA progression, including joint synovitis and cartilage damage. These results indicated that allosteric inhibition of SHP2 might be a promising therapeutic strategy for the treatment of OA.

Salmonid MyD88 is a key adapter protein that activates innate effector mechanisms through the TLR5M/TLR5S signaling pathway and protects against Piscirickettsia salmonis infection

The membrane-anchored and soluble Toll-like Receptor 5 -TLR5M and TLR5S, respectively-from teleost recognize bacterial flagellin and induce the pro-inflammatory cytokines expression in a MyD88-dependent manner such as the TLR5 mammalian orthologous receptor. However, it has not been demonstrated whether the induced signaling pathway by these receptors activate innate effector mechanisms MyD88-dependent in salmonids. Therefore, in this work we study the MyD88 dependence on the induction of TLR5M/TLR5S signaling pathway mediated by flagellin as ligand on the activation of some innate effector mechanisms. The intracellular and extracellular Reactive Oxygen Species (ROS) production and conditioned supernatants production were evaluated in RTS11 cells, while the challenge with Piscirickettsia salmonis was evaluated in SHK-1 cells. Our results demonstrate that flagellin directly stimulates ROS production and indirectly stimulates it through the production of conditioned supernatants, both in a MyD88-dependent manner. Additionally, flagellin stimulation prevents the cytotoxicity induced by infection with P. salmonis in a MyD88-dependent manner. In conclusion we demonstrate that MyD88 is an essential adapter protein in the activation of the TLR5M/TLR5S signaling pathway mediated by flagellin in salmonids, which leads downstream to the induction of innate effector mechanisms, promoting immuno-protection against a bacterial challenge with P. salmonis.

Blockade of Myd88 signaling by a novel MyD88 inhibitor prevents colitis-associated colorectal cancer development by impairing myeloid-derived suppressor cells

Background. In cancer, myeloid-derived suppressor cells (MDSCs) are known to escape the host immune system by developing a highly suppressive environment. However, little is known about the molecular mechanism behind MDSC-mediated tumor cell evasion of the immune system. Toll-like receptor (TLR) signaling elicited in the tumor microenvironment has the potential to induce MDSC differentiations in different organs. Therefore, MDSC elimination by blocking the action of myeloid differentiation factor 88 (MyD88), which is a key adaptor-signaling molecule that affects TLR activity, seems to be an ideal tumor immunotherapy. Previous studies have proven that blocking MyD88 signaling with a novel MyD88 inhibitor (TJ-M2010-5, synthesized by Zhou’s group) completely prevented colitis-associated colorectal cancer (CAC) development in mice. Methods. In the present study, we investigated the impact of the novel MyD88 inhibitor on the number, phenotype, and function of MDSC in the mice model of CAC. Results. We showed that CAC growth inhibition was involved in diminished MDSC generation, expansion, and suppressive function and that MDSC-mediated immune escape was dependent on MyD88 signaling pathway activation. MyD88 inhibitor treatment decreased the accumulation of CD11b⁺Gr1⁺ MDSCs in mice with CAC, thereby reducing cytokine (GM-CSF, G-CSF, IL-1β, IL-6 and TGF-β) secretion associated with MDSC accumulation, and reducing the expression of molecules (iNOS, Arg-1 and IDO) associated with the suppressive capacity of MDSCs. In addition, MyD88 inhibitor treatment reduced the differentiation of MDSCs from myeloid cells and the suppressive capacity of MDSCs on the proliferation of activated CD4⁺ T cells in vitro. Conclusion. MDSCs are primary cellular targets of a novel MyD88 inhibitor during CAC development. Our findings prove that MyD88 signaling is involved in the regulation of the immunosuppressive functions of MDSCs. The novel MyD88 inhibitor TJ-M2010-5 is a new and effective agent that modulates MyD88 signaling to overcome MDSC suppressive functions, enabling the development of successful antitumor immunotherapy.

ω-3 DPA Protected Neurons from Neuroinflammation by Balancing Microglia M1/M2 Polarizations through Inhibiting NF-κB/MAPK p38 Signaling and Activating Neuron-BDNF-PI3K/AKT Pathways

Microglia M1 phenotype causes HPA axis hyperactivity, neurotransmitter dysfunction, and production of proinflammatory mediators and oxidants, which may contribute to the etiology of depression and neurodegenerative diseases. Eicosapentaenoic acid (EPA) may counteract neuroinflammation by increasing n-3 docosapentaenoic acid (DPA). However, the cellular and molecular mechanisms of DPA, as well as whether it can exert antineuroinflammatory and neuroprotective effects, are unknown. The present study first evaluated DPA’s antineuroinflammatory effects in lipopolysaccharide (LPS)-activated BV2 microglia. The results showed that 50 μM DPA significantly decreased BV2 cell viability after 100 ng/mL LPS stimulation, which was associated with significant downregulation of microglia M1 phenotype markers and proinflammatory cytokines but upregulation of M2 markers and anti-inflammatory cytokine. Then, DPA inhibited the activation of mitogen-activated protein kinase (MAPK) p38 and nuclear factor-κB (NF-κB) p65 pathways, which results were similar to the effects of NF-κB inhibitor, a positive control. Second, BV2 cell supernatant was cultured with differentiated SH-SY5Y neurons. The results showed that the supernatant from LPS-activated BV2 cells significantly decreased SH-SY5Y cell viability and brain-derived neurotrophic factor (BDNF), TrkB, p-AKT, and PI3K expression, which were significantly reversed by DPA pretreatment. Furthermore, DPA neuroprotection was abrogated by BDNF-SiRNA. Therefore, n-3 DPA may protect neurons from neuroinflammation-induced damage by balancing microglia M1 and M2 polarizations, inhibiting microglia-NF-κB and MAPK p38 while activating neuron-BDNF/TrkB-PI3K/AKT pathways.

Quantitative proteomic analysis after neuroprotective MyD88 inhibition in the retinal degeneration 10 mouse

Progressive photoreceptor death occurs in blinding diseases such as retinitis pigmentosa. Myeloid differentiation primary response protein 88 (MyD88) is a central adaptor protein for innate immune system Toll-like receptors (TLR) and induces cytokine secretion during retinal disease. We recently demonstrated that inhibiting MyD88 in mouse models of retinal degeneration led to increased photoreceptor survival, which was associated with altered cytokines and increased neuroprotective microglia. However, the identity of additional molecular changes associated with MyD88 inhibitor-induced neuroprotection is not known. In this study, we used isobaric tags for relative and absolute quantification (iTRAQ) labelling followed by LC-MS/MS for quantitative proteomic analysis on the rd10 mouse model of retinal degeneration to identify protein pathways changed by MyD88 inhibition. Quantitative proteomics using iTRAQ LC-MS/MS is a high-throughput method ideal for providing insight into molecular pathways during disease and experimental treatments. Forty-two proteins were differentially expressed in retinas from mice treated with MyD88 inhibitor compared with control. Notably, increased expression of multiple crystallins and chaperones that respond to cellular stress and have anti-apoptotic properties was identified in the MyD88-inhibited mice. These data suggest that inhibiting MyD88 enhances chaperone-mediated retinal protection pathways. Therefore, this study provides insight into molecular events contributing to photoreceptor protection from modulating inflammation.

miR-106b-5p upregulation is associated with microglial activation and inflammation in the mouse hippocampus following status epilepticus

To investigate the association of miR-106b-5p with neuroinflammation and microglial activation in a status epilepticus (SE) mouse model. We examined changes in the expression of microRNA-106b-5p (miRNA-106b-5p), repulsive guidance molecule A (RGMa), triggering receptor expressed on myeloid cells 2 (TREM2), and the microglia-related markers interleukin (IL)-1β, IL-4, IL-6, IL-10, inducible nitric oxide synthase (iNOS), and arginase-1 (Arg-1) in the mouse hippocampus of the lithium-pilocarpine-induced SE mouse model. Eighty-four female C57BL/6 mice were randomly divided into a normal control group (n = 12), and six SE groups (n = 12/group), which were monitored at 6 h and at 1, 3, 7, 14, and 21 days (d) post-SE induction. Unlike in the dentate gyrus, immunohistochemical staining revealed prominent neuronal swelling at 6 h, significant neuronal loss and apoptosis on day 3, and recovery by day 14 in the hippocampal cornu ammonis (CA)1 and CA3 pyramidal cells in SE mice. We noted elevated levels of miRNA-106b-5p and all microglia-related markers, which peaked at 3 days post-SE, except IL-4, which peaked at 7 days post-SE, indicating inflammation and microglial activation. RGMa and TREM2 levels decreased at 6 h post-SE. All markers but miRNA-106b-5p, RGMa, and TREM2 returned to baseline levels at 21 days post-SE. Dual luciferase reporter gene assay showed that microRNA-106b-5p can interact with RGMa. We observed that miR-106b-5p level increased while both RGMa and TREM2 levels decreased post-SE and showed associations with microglial activation and inflammation in the mouse hippocampus, suggesting their potential as SE therapeutic targets.

Antishock Characteristics of Erythrocyte-mediated Endoplasmic Reticulum Stress in Macrophages in Severe Hemorrhagic Shock Environment Based on TLR9-cGAS-STING-IFN Signal Axis

This study aimed to investigate the protective effects of erythrocyte-mediated endoplasmic reticulum (ER) stress in macrophages in hemorrhagic shock. An hemorrhagic shock model was established in male BALB/c mice. Animals were randomly divided into three groups (n = 8): control group (A), erythrocyte reinfusion group (B), and TLR9 inhibition group (C). Eight healthy BALB/c mice were also included as group N (n = 8). Mice in group A were not treated, while mice in groups B and C were transfused with red blood cells separated from the blood of mice in group N. Flow cytometry was used to detect the expression of erythrocyte surface protein TLR9 in each group. Immunofluorescence assay was used to analyze the distribution and relative expression of protein STING in macrophages. Flow cytometry was used to analyze the expression of STING, ATF6, and IRE1 in macrophages. Enzyme-linked immunosorbent assay was used to analyze the levels of inflammatory signal molecules, including IFN-α, IFN-β, IL-6, CCL4, CCL5, and IL-6. FITC-Annexin V was used to analyze the apoptosis of immune cells (macrophages) in mouse blood samples and to detect the concentration of calcium ions in erythrocyte cytoplasm. The results showed that the expression of erythrocyte surface protein TLR9; the distribution of STING-positive cells in macrophages; the expressions of STING, ATF6, and IRE1 in macrophages; the levels of inflammatory signal molecules; the apoptosis rate of macrophages; and the intracellular calcium concentration in erythrocytes in group B were higher than those in group A, followed by group C. These results suggest that TLR9 regulates ER stress in macrophages of mice with hemorrhagic shock through the TLR9-cGAS-STING-IFN signaling pathway. Increased expression of TLR9 enhanced macrophage activity, reduced apoptosis, enhanced inflammatory response and immune response, and restored electrolyte level, which might be a therapeutic option for the treatment of hemorrhagic shock.

Silencing of circIgf1r plays a protective role in neuronal injury via regulating astrocyte polarization during epilepsy

Epilepsy is a common brain disorder, repeated seizures of epilepsy may lead to a series of brain pathological changes such as neuronal or glial damage. However, whether circular RNAs are involved in neuronal injury during epilepsy is not fully understood. Here, we screened circIgf1r in the status epilepticus model through circRNA sequencing, and found that it was upregulated after the status epilepticus model through QPCR analysis. Astrocytes polarizing toward neurotoxic A1 phenotype and neurons loss were observed after status epilepticus. Through injecting circIgf1r siRNA into the lateral ventricle, it was found that knocking down circIgf1r in vivo would induce the polarization of astrocytes to phenotype A2 and reduce neuronal loss. The results in vitro further confirmed that inhibiting the expression of circIgf1r in astrocytes could protect neurons by converting reactive astrocytes from A1 to the protective A2. In addition, knocking down circIgf1r in astrocytes could functionally promote astrocyte autophagy and relieve the destruction of 4-AP-induced autophagy flux. In terms of mechanism, circIgf1r promoted the polarization of astrocytes to phenotype A1 by inhibiting autophagy. Taken together, our results reveal circIgf1r may serve as a potential target for the prevention and treatment of neuron damage after epilepsy.

Diisopropylfluorophosphate-induced status epilepticus drives complex glial cell phenotypes in adult male mice

Organophosphate pesticides and nerve agents (OPs), are characterized by cholinesterase inhibition. In addition to severe peripheral symptoms, high doses of OPs can lead to seizures and status epilepticus (SE). Long lasting seizure activity and subsequent neurodegeneration promote neuroinflammation leading to profound pathological alterations of the brain. The aim of this study was to characterize neuroinflammatory responses at key time points after SE induced by the OP, diisopropylfluorophosphate (DFP). Immunohistochemistry (IHC) analysis and RT-qPCR on cerebral tissue are often insufficient to identity and quantify precise neuroinflammatory alterations. To address these needs, we performed RT-qPCR quantification after whole brain magnetic-activated cell-sorting (MACS) of CD11B (microglia/infiltrated macrophages) and GLAST (astrocytes)-positive cells at 1, 4, 24 h and 3 days post-SE. In order to compare these results to those obtained by IHC, we performed, classical Iba1 (microglia/infiltrated macrophages) and GFAP (astrocytes) IHC analysis in parallel, focusing on the hippocampus, a brain region affected by seizure activity and neurodegeneration. Shortly after SE (1-4 h), an increase in pro-inflammatory (M1-like) markers and A2-specific markers, proposed as neurotrophic, were observed in CD11B and GLAST-positive isolated cells, respectively. Microglial cells successively expressed immuno-regulatory (M2b-like) and anti-inflammatory (M2a-like) at 4 h and 24 h post-SE induction. At 24 h and 3 days, A1-specific markers, proposed as neurotoxic, were increased in isolated astrocytes. Although IHC analysis presented no modification in terms of percentage of marked area and cell number at 1 and 4 h after SE, at 24 h and 3 days after SE, microglial and astrocytic activation was visible by IHC as an increase in Iba1 and GFAP-positive area and Iba1-positive cells in DFP animals when compared to the control. Our work identified sequential microglial and astrocytic phenotype activation. Although the role of each phenotype in SE cerebral outcomes requires further study, targeting specific markers at specific time point could be a beneficial strategy for DFP-induced SE treatment.

Apoptosis-antagonizing transcription factor is involved in rat post-traumatic epilepsy pathogenesis

The present study aimed to explore the pathogenesis behind post-traumatic epilepsy (PTE). In the present study, a chloride ferric injection-induced rat PTE model was established. The expression levels of apoptosis-antagonizing transcription factor (AATF), cleaved caspase-3, p53, Bcl-2 and Bax were measured by western blotting or immunofluorescence staining (IF). The expression of AATF in vivo was downregulated by microinjection of lentiviral-mediated short-hairpin RNA. Compared with control and sham groups, at day 5 after PTE, neuron apoptosis was significantly increased and the expression levels of AATF, p53, cleaved caspase-3 and Bax were significantly upregulated. In addition, IF revealed co-localization of AATF and cleaved caspase-3 in the cortex. Additionally, AATF was expressed mainly in neurons and astrocytes. Following AATF inhibition, the expression levels of p53 and cleaved caspase-3 were significantly reduced as compared with the control group. Taken together, these findings suggested that following PTE, AATF is involved in neuronal apoptosis and may serve as a potential target for its alleviation.

d-Serine Intervention In The Medial Entorhinal Area Alters TLE-Related Pathology In CA1 Hippocampus Via The Temporoammonic Pathway

Entrainment of the hippocampus by the medial entorhinal area (MEA) in Temporal Lobe Epilepsy (TLE), the most common type of drug-resistant epilepsy in adults, is believed to be mediated primarily through the perforant pathway (PP), which connects stellate cells in layer (L) II of the MEA with granule cells of the dentate gyrus (DG) to drive the hippocampal tri-synaptic circuit. Using immunohistochemistry, high-resolution confocal microscopy and the rat pilocarpine model of TLE, we show here that the lesser known temporoammonic pathway (TAP) plays a significant role in transferring MEA pathology to the CA1 region of the hippocampus independently of the PP. The pathology observed was region-specific and restricted primarily to the CA1c subfield of the hippocampus. As shown previously, daily intracranial infusion of d-serine (100 μm), an antagonist of GluN3-containing triheteromeric N-Methyl d-aspartate receptors (t-NMDARs), into the MEA prevented loss of LIII neurons and epileptogenesis. This intervention in the MEA led to the rescue of hippocampal CA1 neurons that would have otherwise perished in the epileptic animals, and down regulation of the expression of astrocytes and microglia thereby mitigating the effects of neuroinflammation. Interestingly, these changes were not observed to a similar extent in other regions of vulnerability like the hilus, DG or CA3, suggesting that the pathology manifest in CA1 is driven predominantly through the TAP. This work highlights TAP's role in the entrainment of the hippocampus and identifies specific areas for therapeutic intervention in dealing with TLE.

Microglial contributions to aberrant neurogenesis and pathophysiology of epilepsy

Microglia are dynamic cells that constitute the brain's innate immune system. Recently, research has demonstrated microglial roles beyond immunity, which include homeostatic roles in the central nervous system. The function of microglia is an active area of study, with insights into changes in neurogenesis and synaptic pruning being discovered in both health and disease. In epilepsy, activated microglia contribute to several changes that occur during epileptogenesis. In this review, we focus on the effects of microglia on neurogenesis and synaptic pruning, and discuss the current state of anti-seizure drugs and how they affect microglia during these processes. Our understanding of the role of microglia post-seizure is still limited and may be pivotal in recognizing new therapeutic targets for seizure intervention.

Intracerebral overexpression of miR-669c is protective in mouse ischemic stroke model by targeting MyD88 and inducing alternative microglial/macrophage activation

Background

Ischemic stroke is a devastating disease without a cure. The available treatments for ischemic stroke, thrombolysis by tissue plasminogen activator, and thrombectomy are suitable only to a fraction of patients and thus novel therapeutic approaches are urgently needed. The neuroinflammatory responses elicited secondary to the ischemic attack further aggravate the stroke-induced neuronal damage. It has been demonstrated that these responses are regulated at the level of non-coding RNAs, especially miRNAs.

Methods

We utilized lentiviral vectors to overexpress miR-669c in BV2 microglial cells in order to modulate their polarization. To detect whether the modulation of microglial activation by miR-669c provides protection in a mouse model of transient focal ischemic stroke, miR-669c overexpression was driven by a lentiviral vector injected into the striatum prior to induction of ischemic stroke.

Results

Here, we demonstrate that miR-669c-3p, a member of chromosome 2 miRNA cluster (C2MC), is induced upon hypoxic and excitotoxic conditions in vitro and in two different in vivo models of stroke. Rather than directly regulating the neuronal survival in vitro, miR-669c is capable of attenuating the microglial proinflammatory activation in vitro and inducing the expression of microglial alternative activation markers arginase 1 (Arg1), chitinase-like 3 (Ym1), and peroxisome proliferator-activated receptor gamma (PPAR-γ). Intracerebral overexpression of miR-669c significantly decreased the ischemia-induced cell death and ameliorated the stroke-induced neurological deficits both at 1 and 3 days post injury (dpi). Albeit miR-669c overexpression failed to alter the overall Iba1 protein immunoreactivity, it significantly elevated Arg1 levels in the ischemic brain and increased colocalization of Arg1 and Iba1. Moreover, miR-669c overexpression under cerebral ischemia influenced several morphological characteristics of Iba1 positive cells. We further demonstrate the myeloid differentiation primary response gene 88 (MyD88) transcript as a direct target for miR-669c-3p in vitro and show reduced levels of MyD88 in miR-669c overexpressing ischemic brains in vivo.

Conclusions

Collectively, our data provide the evidence that miR-669c-3p is protective in a mouse model of ischemic stroke through enhancement of the alternative microglial/macrophage activation and inhibition of MyD88 signaling. Our results accentuate the importance of controlling miRNA-regulated responses for the therapeutic benefit in conditions of stroke and neuroinflammation.

Qiang Xin 1 Formula Suppresses Excessive Pro-Inflammatory Cytokine Responses and Microglia Activation to Prevent Cognitive Impairment and Emotional Dysfunctions in Experimental Sepsis

Sepsis commonly leads to acute and long-term cognitive and affective impairments which are associated with increased mortality in patients. Neuroinflammation characterized by excessive cytokine release and immune cell activation underlies the behavioral changes associated with sepsis. We previously reported that the administration of a traditional Chinese herbal Qiang Xin 1 (QX1) formula improves survival in septic mice. This study was performed to better understand the effects and the mechanisms of QX1 formula treatment on behavioral changes in a preclinical septic model induced by cecal ligation and puncture. Oral administration of QX1 formula significantly improved survival, alleviated overall cognitive impairment and emotional dysfunction as assessed by the Morris water maze, novel object recognition testing, elevated plus maze and open field testing in septic mice. QX1 formula administration dramatically inhibited short and long-term excessive pro-inflammatory cytokine production both peripherally and centrally, and was accompanied by diminished microglial activation in septic mice. Biological processes including synaptic transmission, microglia cell activation, cytokine production, microglia cell polarization, as well as inflammatory responses related to signaling pathways including the MAPK signaling pathway and the NF-κB signaling pathway were altered prominently by QX1 formula treatment in the hippocampus of septic mice. In addition, QX1 formula administration decreased the expression of the M1 phenotype microglia gene markers such as Cd32, Socs3, and Cd68, while up-regulated M2 phenotype marker genes including Myc, Arg-1, and Cd206 as revealed by microarray analysis and Real-time PCR. In conclusion, QX1 formula administration attenuates cognitive deficits, emotional dysfunction, and reduces neuroinflammatory responses to improve survival in septic mice. Diminished microglial activation and altered microglial polarization are involved in the neuroprotective mechanism of QX1 formula.

Botulinum toxin type A promotes microglial M2 polarization and suppresses chronic constriction injury-induced neuropathic pain through the P2X7 receptor

Background

Switching microglial polarization from the pro-inflammatory M1 phenotype to the anti-inflammatory M2 phenotype represents a novel therapeutic strategy for neuropathic pain (NP). This study aims to investigate whether botulinum toxin type A (BTX-A) regulates microglial M1/M2 polarization by inhibiting P2X7 expression in a rat model of NP.

Results

The BTX-A administration elevated pain threshold, induced microglial polarization toward the M2 phenotype, and decreased P2X7 protein level in a rat model of NP induced by chronic compression injury (CCI). Lipopolysaccharide (LPS) was used to activate HAPI rat microglial cells as an in vitro inflammatory model and we demonstrated that BTX-A promoted microglial M2 polarization in LPS-stimulated HAPI microglial cells through suppressing P2X7.

Conclusions

Our results indicate that BTX-A promotes microglial M2 polarization and suppresses CCI-induced NP through inhibiting P2X7 receptor. These findings provide new insights into the mechanism of BTX-A in relieving NP.

Dynorphin activation of kappa opioid receptor promotes microglial polarization toward M2 phenotype via TLR4/NF-κB pathway

Background

Microglia-mediated neuroinflammation is associated with epilepsy. Switching microglial polarization from the pro-inflammatory M1 phenotype to the anti-inflammatory M2 phenotype represents a novel therapeutic strategy for mitigating epileptogenesis. We previously found that dynorphins protected against epilepsy via activation of kappa opioid receptor (KOR). Here, this study aims to investigate the role and the mechanism of dynorphin in regulating microglial polarization.

Methods

A pilocarpine-induced rat model of epilepsy was established and lipopolysaccharide (LPS)-activated BV-2 microglial cells were used as an inflammatory model to explore the mechanism of dynorphin regulating microglial polarization.

Results

Overexpression of the dynorphin precursor protein prodynorphin (PDYN) alleviated the pilocarpine-induced neuronal apoptosis, promoted microglial polarization to the M2 phenotype, and inhibited pilocarpine-induced Toll-like receptor 4 (TLR4)/nuclear factor-kappa B (NF-κB) pathway in the hippocampi of epileptic rats. Dynorphin activation of KOR promoted microglial M2 polarization via inhibiting TLR4/NF-κB pathway in LPS-stimulated BV-2 microglial cells. Moreover, dynorphin/KOR regulated microglial M2 polarization inhibited apoptosis of the primary mouse hippocampal neurons.

Conclusion

In conclusion, dynorphin activation of KOR promotes microglia polarization toward M2 phenotype via inhibiting TLR4/NF-κB pathway.

Increased Neuroprotective Microglia and Photoreceptor Survival in the Retina from a Peptide Inhibitor of Myeloid Differentiation Factor 88 (MyD88)

Myeloid differentiation factor 88 (MyD88) is an adaptor protein for the Toll-like receptor (TLR) and interleukin 1 receptor (IL-1R) families of innate immunity receptors that mediate inflammatory responses to cellular injury. TLR/IL1R/MyD88 signaling is known to contribute to retinal degeneration, although how MyD88 regulates neuronal survival, and the effect of MyD88 on the inflammatory environment in the retina, is mostly unknown. In this study, we tested the hypothesis that blocking MyD88-mediated signaling early in retinal degeneration promotes transition of microglia towards a neuroprotective anti-inflammatory phenotype, resulting in enhanced photoreceptor survival. We also tested whether systemic delivery of a pharmacologic MyD88 inhibitor has therapeutic potential. The rd10 mouse model of retinal degeneration was injected intraperitoneally with increasing doses of a MyD88 blocking peptide or control peptide early in degeneration, and inflammatory responses and photoreceptor survival were measured at specific time points using flow cytometry, cytokine profiling, and electroretinograms. Our results demonstrated that rd10 mice injected with a low dose of MyD88 inhibitor peptide showed increased rod photoreceptor function and reduced apoptosis compared with control peptide and uninjected mice. MyD88 inhibition also resulted in fewer microglia/macrophage cells in the photoreceptor layer whereas total peripheral and retinal macrophage were not changed. Furthermore, increased number of cells expressing the Arg1 marker of neuroprotective microglia in the photoreceptor layer and higher MCP-1 and anti-inflammatory cytokine IL-27 were associated with photoreceptor survival. Therefore, these data suggest that the MyD88 inhibitor modified the retina environment to become less inflammatory, leading to improved photoreceptor function and survival.

Microglial polarization in posttraumatic epilepsy: Potential mechanism and treatment opportunity

Owing to the complexity of the pathophysiological mechanisms driving epileptogenesis following traumatic brain injury (TBI), effective preventive treatment approaches are not yet available for posttraumatic epilepsy (PTE). Neuroinflammation appears to play a critical role in the pathogenesis of the acquired epilepsies, including PTE, but despite a large preclinical literature demonstrating the ability of anti-inflammatory treatments to suppress epileptogenesis and chronic seizures, no anti-inflammatory treatment approaches have been clinically proven to date. TBI triggers robust inflammatory cascades, suggesting that they may be relevant for the pathogenesis of PTE. A major cell type involved in such cascades is the microglial cells-brain-resident immune cells that become activated after brain injury. When activated, these cells can oscillate between different phenotypes, and such polarization states are associated with the release of various pro- and anti-inflammatory mediators that may influence brain repair processes, and also differentially contribute to the development of PTE. As the molecular mechanisms and key signaling molecules associated with microglial polarization in brain are discovered, strategies are now emerging that can modulate this polarization, promoting this as a potential therapeutic strategy for PTE. In this review, we discuss the relevant literature regarding the polarization of brain-resident immune cells following TBI and attempt to put into perspective a role in epilepsy pathogenesis. Finally, we explore potential strategies that could polarize microglia/macrophages toward a neuroprotective phenotype to mitigate PTE development.

Electroacupuncture Pretreatment Alleviates Cerebral Ischemic Injury Through α7 Nicotinic Acetylcholine Receptor-Mediated Phenotypic Conversion of Microglia

Electroacupuncture (EA) pretreatment alleviates cerebral ischemic injury through α7 nicotinic acetylcholine receptor (α7nAChR). We attempted to investigate whether the phenotypic conversion of microglia was involved in the therapeutic effect of EA pretreatment in cerebral ischemia through α7nAChR. Adult male Sprague-Dawley (SD) rats were subjected to middle cerebral artery occlusion (MCAO) after EA or α7nAChR agonist N-(3R)-1-azabicyclo[2.2.2]oct-3-yl-furo[2,3-c]pyridine-5-carboxamide hydrochloride (PHA-543,613 hydrochloride) and antagonist α-bungarotoxin (α-BGT) pretreatment. Primary microglia were subjected to drug pretreatment and oxygen-glucose deprivation (OGD). The expressions of the classical activated phenotype (M1) microglia markers induced nitric oxide synthase (iNOS), interleukin-1β (IL-1β), and cluster of differentiation 86 (CD86); the alternative activated phenotype (M2) microglia markers arginase-1 (Arg-1), transforming growth factor-β1 (TGF-β1), and cluster of differentiation 206 (CD206); and the pro-inflammatory cytokines tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and anti-inflammatory cytokines interleukin-4 (IL-4) and interleukin-10 (IL-10) in the ischemic penumbra or in the supernatant of primary microglia were analyzed. The infarction volume and neurological scores were assessed 72 h after reperfusion. The cell viability and lactate dehydrogenase (LDH) release of neurons co-cultured with microglia were analyzed using cell counting kit-8 (CCK-8) and LDH release assays. EA pretreatment decreased the expressions of M1 markers (iNOS, IL-1β, and CD86) and pro-inflammatory cytokines (TNF-α and IL-6), whereas it increased the expressions of M2 markers (Arg-1, TGF-β1, and CD206) and anti-inflammatory cytokines (IL-4 and IL-10) by activating α7nAChR. EA pretreatment also significantly reduced the infarction volume and improved the neurological deficit. The activation of α7nAChR in microglia relieved the inflammatory response of primary microglia subjected to OGD and attenuated the injury of neurons co-cultured with microglia. In conclusion, EA pretreatment alleviates cerebral ischemic injury through α7nAChR-mediated phenotypic conversion of microglia, which may be a new mechanism for the EA pretreatment-induced neuroprotection against cerebral ischemia.

Heterogeneous macrophages: Supersensors of exogenous inducing factors

As heterogeneous immune cells, macrophages mount effective responses to various internal and external changes during disease progression. Macrophage polarization, rather than macrophage heterogenization, is often used to describe the functional differences between macrophages. While macrophage polarization partially contributes to heterogeneity, it does not completely explain the concept of macrophage heterogeneity. At the same time, there are abundant and sophisticated endogenous and exogenous substances that can affect macrophage heterogeneity. While the research on endogenous factors has been systematically reviewed, the findings on exogenous factors have not been well summarized. Hence, we reviewed the characteristics and inducing factors of heterogeneous macrophages to reveal their functional plasticity as well as their targeting manoeuvreability. In the process of constructing and analysing a network organized by disease-related cells and molecules, paying more attention to heterogeneous macrophages as mediators of this network may help to explore a novel entry point for early prevention of and intervention in disease.

Clemastine Alleviates Depressive-Like Behavior Through Reversing the Imbalance of Microglia-Related Pro-inflammatory State in Mouse Hippocampus

Backgrounds: Abundant reports indicate that neuroinflammatory signaling contributes to behavioral complications associated with depression and may be related to treatment response. The glial cells, especially microglia and astrocytes in brain regions of hippocampus and medial prefrontal cortex (mPFC), are major components of CNS innate immunity. Moreover, purinergic receptor P2X, ligand-gated ion channel 7 (P2X7R) was recently reckoned as a pivotal regulator in central immune system. Besides, it was pointed out that clemastine, a first-generation histamine receptor H1 (HRH1) antagonist with considerable safety profile and pharmacological effect, may suppress immune activation through modulating P2X7R. Herein, we investigated the potential anti-neuroinflammatory effects of clemastine on chronic unpredictable mild stress (CUMS)-induced depressive-like behavior in a mouse model.

Methods: Male BALB/c mice were subjected to CUMS for 4 weeks, some of them were injected with clemastine fumarate solution. After the stress procedure, behavioral tests including Sucrose Preference Tests (SPTs), Tail Suspension Tests (TSTs) and locomotor activities were performed to evaluate depressive-like phenotype. Subsequently, expression of cytokines and microglia-related inflammatory biomarkers were assessed.

Results: In the present research, we found that clemastine significantly reversed both the declination of SPT percentage and the extension of TST immobility durations in depression mouse model without affecting locomotor activity. Also, we observed that clemastine regulated the imbalance of pro-inflammatory cytokines including interleukin-1 beta (IL-1β) and tumor necrosis factor alpha (TNF-α) in the hippocampus and serum of depressive-like mice. Additionally, clemastine significantly suppressed microglial M1-like activation specifically in the hippocampus, and also improved hippocampal astrocytic loss. Furthermore, clemastine downregulated hippocampal P2X7R without interfering with the expression of HRH1.

Conclusion: As a safe and efficient anti-allergic agent, clemastine could impressively alleviate stress-related depressive-like phenotype in mice. Further evidence supported that it was because of the potential function of clemastine in modulating the expression of P2X7 receptor possibly independent of HRH1, therefore suppressing the microglial M1-like activation and pro-inflammatory cytokines release in brain regions of hippocampus rather than mPFC.