Post-stroke DHA Treatment Protects Against Acute Ischemic Brain Injury by Skewing Macrophage Polarity Toward the M2 Phenotype

Identification and validation of the inflammatory response-related LncRNAs as diagnostic biomarkers for acute ischemic stroke

Ischemic stroke is one of the leading causes of deaths and disability, which is linked to inflammation. In this study, we aimed to identify inflammation-related lncRNAs as diagnostic biomarkers of acute ischemic stroke (AIS). A competing endogenous RNAs (ceRNA) network was established through whole transcriptome analysis. Gene expression datasets from the GEO database were analyzed to identify differentially expressed genes (DEGs), miRNAs and lncRNAs. Inflammation-related DEGs were determined through the intersection of the DEGs of the inflammation-related gene set from Genecards. Multiple databases like lncBase and Targetscan were analyzed to establish a ceRNA network. Several hub genes and sub-networks were obtained from a protein to protein (PPI) network. In addition, the candidate lncRNAs derived from the subnetwork were validated using mice MCAO model and clinical samples. Finally, a network comprising 20 lncRNAs, 26 miRNAs, and 43 inflammatory genes was analyzed, leading to the identification of MALAT1, SNHG8, and GAS5 as potential diagnostic biomarkers. Knockdown of MALAT1 and GAS5 resulted in decreased neurological severity score and inflammation response in mice MCAO model, indicating that these genes were significant diagnostic biomarkers for distinguishing AIS from healthy controls. These findings show that circulating MALAT1 and GAS5 have the potential to serve as clinical diagnostic biomarkers of AIS associated with inflammation.

Changes in border-associated macrophages after stroke: single-cell sequencing analysis

ABSTRACT

Border-associated macrophages are located at the interface between the brain and the periphery, including the perivascular spaces, choroid plexus, and meninges. Until recently, the functions of border-associated macrophages have been poorly understood and largely overlooked. However, a recent study reported that border-associated macrophages participate in stroke-induced inflammation, although many details and the underlying mechanisms remain unclear. In this study, we performed a comprehensive single-cell analysis of mouse border-associated macrophages using sequencing data obtained from the Gene Expression Omnibus (GEO) database (GSE174574 and GSE225948). Differentially expressed genes were identified, and enrichment analysis was performed to identify the transcription profile of border-associated macrophages. CellChat analysis was conducted to determine the cell communication network of border-associated macrophages. Transcription factors were predicted using the 'pySCENIC' tool. We found that, in response to hypoxia, border- associated macrophages underwent dynamic transcriptional changes and participated in the regulation of inflammatory-related pathways. Notably, the tumor necrosis factor pathway was activated by border-associated macrophages following ischemic stroke. The pySCENIC analysis indicated that the activity of signal transducer and activator of transcription 3 (Stat3) was obviously upregulated in stroke, suggesting that Stat3 inhibition may be a promising strategy for treating border-associated macrophages-induced neuroinflammation. Finally, we constructed an animal model to investigate the effects of border-associated macrophages depletion following a stroke. Treatment with liposomes containing clodronate significantly reduced infarct volume in the animals and improved neurological scores compared with untreated animals. Taken together, our results demonstrate comprehensive changes in border-associated macrophages following a stroke, providing a theoretical basis for targeting border-associated macrophages-induced neuroinflammation in stroke treatment.

The effect of dietary camelina, flaxseed, and canola oil supplementation on skin fatty acid profile and immune and inflammatory responses in healthy adult horses

Camelina sativa is an oilseed crop rich in α-linolenic acid (ALA), an n-3 fatty acid (FA), and is resistant to harsh climates and pests. Previously, supplementation with camelina oil (CAM) in horses had no adverse effects on basic health parameters and had comparable skin and coat parameters as both flaxseed oil (FLX) and canola oil (OLA). Further, the plasma FA profile of horses was reflective of their respective treatment oil. The objective of this study was to assess the effects of dietary CAM supplementation on skin FA profile, immune, and inflammatory responses as compared to 2 commonly used oils in the equine industry, OLA and FLX, in healthy adult horses. Twenty-four adult horses, from 2 separate herds, were enrolled in this experiment. The horses underwent a gradual 4-wk fat acclimation period to sunflower oil (approximately 0.28% ALA), then were supplemented with either CAM (approximately 34.9% ALA), OLA (approximately 12.0% ALA), or FLX (56.0% ALA) at an inclusion rate of 0.37 g/kg body weight (BW) per day for an additional 16 wk. Immune and inflammatory responses were assessed by measuring antibody concentrations across time after sensitization to keyhole limpet hemocyanin (KLH) at weeks 10 and 12, and a subsequent delayed-type hypersensitivity (DTH) challenge. Skin biopsy samples were collected at weeks 0, 8, and 16, and FA composition was determined using gas-chromatography. All data were analyzed as a repeated measures ANOVA using PROC GLIMMIX in SAS. Antibody and DTH responses to KLH did not differ among groups (P = 0.262 and 0.813, respectively), and no treatment by time effects were observed (P = 0.764 and P = 0.817, respectively). Most FA in the skin changed in composition across time, with the sum of n-3 FA increasing (P < 0.001) and the sum of n-6 FA and skin n-6:n-3 ratio decreasing over time (P < 0.001 and P < 0.001, respectively). Only dihomo-γ-linolenic acid (P = 0.025) and the sum of n-3 FA (P = 0.031) had treatment-by-week effects. At week 16, the composition of eicosapentaenoic acid in the skin was greater in FLX than OLA, but neither differed from CAM (P = 0.049). These results suggest that ALA supplementation may beneficially impact skin FA profile. However, due to the small differences in n-3 FA and n-6:n-3 ratio among CAM, FLX, and OLA, a comparable skin FA profile, immune, and inflammatory response was observed among treatments at a dose of 0.37 g oil/kg BW. Therefore, CAM may be a suitable alternative to FLX in equine diets for the delivery of ALA.

Adaptive Metabolic Responses Facilitate Blood-Brain Barrier Repair in Ischemic Stroke via BHB-Mediated Epigenetic Modification of ZO-1 Expression

Adaptive metabolic responses and innate metabolites hold promising therapeutic potential for stroke, while targeted interventions require a thorough understanding of underlying mechanisms. Adiposity is a noted modifiable metabolic risk factor for stroke, and recent research suggests that it benefits neurological rehabilitation. During the early phase of experimental stroke, the lipidomic results showed that fat depots underwent pronounced lipolysis and released fatty acids (FAs) that feed into consequent hepatic FA oxidation and ketogenesis. Systemic supplementation with the predominant ketone beta-hydroxybutyrate (BHB) is found to exert discernible effects on preserving blood-brain barrier (BBB) integrity and facilitating neuroinflammation resolution. Meanwhile, blocking FAO-ketogenesis processes by administration of CPT1α antagonist or shRNA targeting HMGCS2 exacerbated endothelial damage and aggravated stroke severity, whereas BHB supplementation blunted these injuries. Mechanistically, it is unveiled that BHB infusion is taken up by monocarboxylic acid transporter 1 (MCT1) specifically expressed in cerebral endothelium and upregulated the expression of tight junction protein ZO-1 by enhancing local β-hydroxybutyrylation of H3K9 at the promoter of TJP1 gene. Conclusively, an adaptive metabolic mechanism is elucidated by which acute lipolysis stimulates FAO-ketogenesis processes to restore BBB integrity after stroke. Ketogenesis functions as an early metabolic responder to restrain stroke progression, providing novel prospectives for clinical translation.

Transcriptome Analysis of the Striatum of Electroacupuncture-treated Naïve and Ischemic Stroke Mice

Objectives

Electroacupuncture (EA) has been demonstrated to aid stroke recovery. However, few investigations have focused on identifying the potent molecular targets of EA by comparing EA stimulation between naïve and disease models. Therefore, this study was undertaken to identify the potent molecular therapeutic mechanisms underlying EA stimulation in ischemic stroke through a comparison of mRNA sequencing data obtained from EA-treated naïve control and ischemic stroke mouse models.

Methods

Using both naïve control and middle cerebral artery occlusion (MCAO) mouse models, EA stimulation was administered at two acupoints, Baihui (GV20) and Dazhui (GV14), at a frequency of 2 Hz. Comprehensive assessments were conducted, including behavioral evaluations, RNA sequencing to identify differentially expressed genes (DEGs), functional enrichment analysis, protein-protein interaction (PPI) network analysis, and quantitative real-time PCR.

Results

EA stimulation ameliorated the ischemic insult-induced motor dysfunction in mice with ischemic stroke. Comparative analysis between control vs. MCAO, control vs. control + EA, and MCAO vs. MCAO + EA revealed 4,407, 101, and 82 DEGs, respectively. Of these, 30, 7, and 1 were common across the respective groups. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses revealed upregulated DEGs associated with the regulation of inflammatory immune response in the MCAO vs. MCAO + EA comparison. Conversely, downregulated DEGs in the control vs. control + EA comparison were linked to neuronal development. PPI analysis revealed major clustering related to the regulation of cytokines, such as Cxcl9, Pcp2, Ccl11, and Cxcl13, in the common DEGs of MCAO vs. MCAO + EA, with Esp8l1 identified as the only common downregulated DEG in both EA-treated naïve and ischemic models.

Conclusion

These findings underscore the diverse potent mechanisms of EA stimulation between naïve and ischemic stroke mice, albeit with few overlaps. However, the potent mechanisms underlying EA treatment in ischemic stroke models were associated with the regulation of inflammatory processes involving cytokines.

Ischemic Brain Injury: Involvement of Lipids in the Pathophysiology of Stroke and Therapeutic Strategies

Stroke is a devastating neurological disorder that is characterized by the sudden disruption of blood flow to the brain. Lipids are essential components of brain structure and function and play pivotal roles in stroke pathophysiology. Dysregulation of lipid signaling pathways modulates key cellular processes such as apoptosis, inflammation, and oxidative stress, exacerbating ischemic brain injury. In the present review, we summarize the roles of lipids in stroke pathology in different models (cell cultures, animal, and human studies). Additionally, the potential of lipids, especially polyunsaturated fatty acids, to promote neuroprotection and their use as biomarkers in stroke are discussed.

Opto-Lipidomics of Tissues

Lipid metabolism and signaling play pivotal functions in biology and disease development. Despite this, currently available optical techniques are limited in their ability to directly visualize the lipidome in tissues. In this study, opto-lipidomics, a new approach to optical molecular tissue imaging is introduced. The capability of vibrational Raman spectroscopy is expanded to identify individual lipids in complex tissue matrices through correlation with desorption electrospray ionization (DESI) - mass spectrometry (MS) imaging in an integrated instrument. A computational pipeline of inter-modality analysis is established to infer lipidomic information from optical vibrational spectra. Opto-lipidomic imaging of transient cerebral ischemia-reperfusion injury in a murine model of ischemic stroke demonstrates the visualization and identification of lipids in disease with high molecular specificity using Raman scattered light. Furthermore, opto-lipidomics in a handheld fiber-optic Raman probe is deployed and demonstrates real-time classification of bulk brain tissues based on specific lipid abundances. Opto-lipidomics opens a host of new opportunities to study lipid biomarkers for diagnostics, prognostics, and novel therapeutic targets.

Bioinformatics identification of potential biomarkers and therapeutic targets for ischemic stroke and vascular dementia

Ischemic stroke and vascular dementia, as common cerebrovascular diseases, with the former causing irreversible neurological damage and the latter causing cognitive and memory impairment, are closely related and have long received widespread attention. Currently, the potential causative genes of these two diseases have yet to be investigated, and effective early diagnostic tools for the diseases have not yet emerged. In this study, we screened new potential biomarkers and analyzed new therapeutic targets for both diseases from the perspective of immune infiltration. Two gene expression profiles on ischemic stroke and vascular dementia were obtained from the NCBI GEO database, and key genes were identified by LASSO regression and SVM-RFE algorithms, and key genes were analyzed by GO and KEGG enrichment. The CIBERSORT algorithm was applied to the gene expression profile species of the two diseases to quantify the 24 subpopulations of immune cells. Moreover, logistic regression modeling analysis was applied to illustrate the stability of the key genes in the diagnosis. Finally, the key genes were validated using RT-PCR assay. A total of 105 intersecting DEGs genes were obtained in the 2 sets of GEO datasets, and bioinformatics functional analysis of the intersecting DEGs genes showed that GO was mainly involved in the purine ribonucleoside triphosphate metabolic process，respiratory chain complex，DNA-binding transcription factor binding and active transmembrane transporter activity. KEGG is mainly involved in the Oxidative phosphorylation, cAMP signaling pathway. The LASSO regression algorithm and SVM-RFE algorithm finally obtained three genes, GAS2L1, ARHGEF40 and PFKFB3, and the logistic regression prediction model determined that the three genes, GAS2L1 (AUC: 0.882), ARHGEF40 (AUC: 0.867) and PFKFB3 (AUC: 0.869), had good diagnostic performance. Meanwhile, the two disease core genes and immune infiltration were closely related, GAS2L1 and PFKFB3 had the highest positive correlation with macrophage M1 (p < 0.001) and the highest negative correlation with mast cell activation (p = 0.0017); ARHGEF40 had the highest positive correlation with macrophage M1 and B cells naive (p < 0.001), the highest negative correlation with B cell memory highest correlation (p = 0.0047). RT-PCR results showed that the relative mRNA expression levels of GAS2L1, ARHGEF40, and PFKFB3 were significantly elevated in the populations of both disease groups (p < 0.05). Immune infiltration-based models can be used to predict the diagnosis of patients with ischemic stroke and vascular dementia and provide a new perspective on the early diagnosis and treatment of both diseases.

Unraveling the impact of Omega-3 polyunsaturated fatty acids on blood-brain barrier (BBB) integrity and glymphatic function

Alzheimer's disease (AD) and other forms of dementia represent major public health challenges but effective therapeutic options are limited. Pathological brain aging is associated with microvascular changes and impaired clearance systems. The application of omega-3 polyunsaturated fatty acids (n-3 or omega-3 PUFAs) is one of the most promising nutritional interventions in neurodegenerative disorders from epidemiological data, clinical and pre-clinical studies. As essential components of neuronal membranes, n-3 PUFAs have shown neuroprotection and anti-inflammatory effects, as well as modulatory effects through microvascular pathophysiology, amyloid-beta (Aβ) clearance and glymphatic pathways. This review meticulously explores these underlying mechanisms that contribute to the beneficial effects of n-3 PUFAs against AD and dementia, synthesizing evidence from both animal and interventional studies.

Anti-inflammatory effects of icariin in the acute and chronic phases of the mouse pilocarpine model of epilepsy

Neuroinflammation mediated by microglia made a significant contribution in the pathophysiology of epilepsy. Icariin (ICA), a bioactive ingredient isolated from Epimedium, has been shown to present both antioxidant and anti-inflammatory properties. This study was to explore the potential therapeutic effects of icariin on mouse pilocarpine model of epilepsy and its underlying mechanisms in vivo and in vitro. To this end, we firstly measured the serum concentrations of the proinflammatory cytokines IL-1β and IL-6 from patients with temporal lobe epilepsy and found that patients with a higher seizure frequency showed correspondingly higher inflammatory reaction. Mouse pharmacokinetic study, transmembrane transportation assay, and cell viability assay collectively demonstrated that ICA was able to cross the blood-brain barrier and has good biocompatibility. The acute and chronic epilepsy models were next established in a pilocarpine mouse model of acquired epilepsy. Icariin has been identified that it could cross the blood-brain barrier and enter the hippocampus to exhibit therapeutic effects. ICA treatment dramatically promoted microglial polarization to the M2 phenotype in epilepsy mice both in the acute and chronic phases. Reduced release of M1-associated proinflammatory factors, such as IL-1β and IL-6, corroborates the altered glial cell polarization. Furthermore, ICA alleviated seizure intensity and mortality in acute phase epileptic mice. Models in the chronic group also showed improved general condition, cognition ability, and memory function after ICA treatment. Taken together, our research strongly suggested that icariin has the potential to treat epilepsy via inhibiting neuroinflammation by promoting microglial polarization to the M2 phenotype.

Effects of food-borne docosahexaenoic acid supplementation on bone lead mobilisation, mitochondrial function and serum metabolomics in pre-pregnancy lead-exposed lactating rats

Large bone lead (Pb) resulting from high environmental exposure during childhood is an important source of endogenous Pb during pregnancy and lactation. Docosahexaenoic acid (DHA) attenuates Pb toxicity, however, the effect of DHA on bone Pb mobilisation during lactation has not been investigated. We aimed to study the effects of DHA supplementation during pregnancy and lactation on bone Pb mobilisation during lactation and its potential mechanisms. Weaning female rats were randomly divided into control (0.05% sodium acetate) and Pb-exposed (0.05% Pb acetate) groups, after a 4-week exposure by ad libitum drinking and a subsequent 4-week washout period, all female rats were mated with healthy males until pregnancy. Then exposed rats were randomly divided into Pb and Pb + DHA groups, and the latter was given a 0.14% DHA diet, while the remaining groups were given normal feed until the end of lactation. Pb and calcium levels, bone microarchitecture, bone turnover markers, mitochondrial function and serum metabolomics were analyzed. The results showed that higher blood and bone Pb levels were observed in the Pb group compared to the control, and there was a significant negative correlation between blood and bone Pb. Also, Pb increased trabecular bone loss along with slightly elevated serum C-telopeptide of type I collagen (CTX-I) levels. However, DHA reduced CTX-I levels and improved trabecular bone microarchitecture. Metabolomics showed that Pb affected mitochondrial function, which was further demonstrated in bone tissue by significant reductions in ATP levels, Na+-K+-ATPase, Ca2+-Mg2+-ATPase and CAT activities, and elevated levels of MDA, IL-1β and IL-18. However, these alterations were partially mitigated by DHA. In conclusion, DHA supplementation during pregnancy and lactation improved bone Pb mobilisation and mitochondrial dysfunction in lactating rats induced by pre-pregnancy Pb exposure, providing potential means of mitigating bone Pb mobilisation levels during lactation, but the mechanism still needs further study.

Experimental procedures for flow cytometry of wild-type mouse brain: a systematic review

Objective

The aim of this study was to systematically review the neuroimmunology literature to determine the average immune cell counts reported by flow cytometry in wild-type (WT) homogenized mouse brains.

Background

Mouse models of gene dysfunction are widely used to study age-associated neurodegenerative disorders, including Alzheimer's disease and Parkinson's disease. The importance of the neuroimmune system in these multifactorial disorders has become increasingly evident, and methods to quantify resident and infiltrating immune cells in the brain, including flow cytometry, are necessary. However, there appears to be no consensus on the best approach to perform flow cytometry or quantify/report immune cell counts. The development of more standardized methods would accelerate neuroimmune discovery and validation by meta-analysis.

Methods

There has not yet been a systematic review of 'neuroimmunology' by 'flow cytometry' via examination of the PROSPERO registry. A protocol for a systematic review was subsequently based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) using the Studies, Data, Methods, and Outcomes (SDMO) criteria. Literature searches were conducted in the Google Scholar and PubMed databases. From that search, 900 candidate studies were identified, and 437 studies were assessed for eligibility based on formal exclusion criteria.

Results

Out of the 437 studies reviewed, 58 were eligible for inclusion and comparative analysis. Each study assessed immune cell subsets within homogenized mouse brains and used flow cytometry. Nonetheless, there was considerable variability in the methods, data analysis, reporting, and results. Descriptive statistics have been presented on the study designs and results, including medians with interquartile ranges (IQRs) and overall means with standard deviations (SD) for specific immune cell counts and their relative proportions, within and between studies. A total of 58 studies reported the most abundant immune cells within the brains were TMEM119+ microglia, bulk CD4+ T cells, and bulk CD8+ T cells.

Conclusion

Experiments to conduct and report flow cytometry data, derived from WT homogenized mouse brains, would benefit from a more standardized approach. While within-study comparisons are valid, the variability in methods of counting of immune cell populations is too broad for meta-analysis. The inclusion of a minimal protocol with more detailed methods, controls, and standards could enable this nascent field to compare results across studies.

Focal ischemic stroke modifies microglia-derived exosomal miRNAs: potential role of mir-212-5p in neuronal protection and functional recovery

BACKGROUND

Ischemic stroke is a severe type of stroke with high disability and mortality rates. In recent years, microglial exosome-derived miRNAs have been shown to be promising candidates for the treatment of ischemic brain injury and exert neuroprotective effects. Mechanisms underlying miRNA dysregulation in ischemic stroke are still being explored. Here, we aimed to verify whether miRNAs derived from exosomes exert effects on functional recovery.

METHODS

MiR-212-5p agomir was employed to upregulate miR-212-5p expression in a rat model of middle cerebral artery occlusion/reperfusion (MCAO/R) as well as an oxygen-glucose deprivation/reoxygenation (OGD/R) in vitro. Western blot analysis, qRT-PCR and immunofluorescence staining and other methods were applied to explore the underlying mechanisms of action of miR-212-5p.

RESULTS

The results of our study found that intervention with miR-212-5p agomir effectively decreased infarct volume and restored motor function in MCAO/R rats. Mechanistically, miR-212-5p agomir significantly reduced the expression of PlexinA2 (PLXNA2). Additionally, the results obtained in vitro were similar to those achieved in vivo.

CONCLUSION

In conclusion, the present study indicated that PLXNA2 may be a target gene of miR-212-5p, and miR-212-5p has great potential as a target for the treatment and diagnosis of ischemic stroke.

Else_BRB_110660Docosahexaenoic acid promotes M2 microglia phenotype via activating PPARγ-mediated ERK/AKT pathway against cerebral ischemia-reperfusion injury

In ischemia-reperfusion stroke, microglia play a dual role in brain injury as well as brain repair, and promoting their switch from a pro-inflammatory M1 phenotype to an anti-inflammatory M2 phenotype is considered to be a potential therapeutic strategy. Docosahexaenoic acid (DHA) is an essential long-chain omega-3 polyunsaturated fatty acid that exhibits potent anti-inflammatory properties in the acute phase of ischemic stroke, but its effect on microglia polarization is unknown. Thus, the objective of this study was to investigate the neuroprotective effects of DHA on rat brain following ischemia-reperfusion injury, and to investigate the mechanism by which DHA regulates microglia polarization. We administered DHA 5mg/kg intraperitoneally daily for 3 d following a transient middle cerebral artery occlusion reperfusion model in rats. The protective effects of DHA on cerebral ischemia-reperfusion injury were detected by TTC staining, HE staining, Nissler staining, and TUNEL staining. Quantitative real-time PCR, immunofluorescence, western blot, and enzyme-linked immunosorbent assay were used to detect the expression of M1 and M2 microglia-associated markers and PPARγ-mediated ERK/AKT signaling pathway proteins. We found that DHA significantly improved brain injury by decreasing the expression of the M1 phenotypic marker (iNOS, CD16) and increasing the expression of the M2 phenotypic marker (Arg-1, CD206). DHA also increased the expression of peroxisome proliferator-activated receptor gamma (PPARγ) mRNA and protein, increased the expression of the pathway protein AKT, and decreased the expression of ERK1/2. In addition, DHA promoted the expression of anti-inflammatory factor IL-10 and decreased the expression of pro-inflammatory factors TNF-α and IL-1β. However, the PPARγ antagonist GW9662 greatly blocked these beneficial effects. These results suggest that DHA may activate PPARγ to inhibit ERK and activate AKT signaling pathways to regulate microglia polarization, thereby reducing neuroinflammation and promoting neurological recovery to alleviate cerebral ischemia-reperfusion injury.

FOXP3+ macrophage represses acute ischemic stroke-induced neural inflammation

Proper termination of cell-death-induced neural inflammation is the premise of tissue repair in acute ischemic stroke (AIS). Macrophages scavenge cell corpses/debris and produce inflammatory mediators that orchestrate immune responses. Here, we report that FOXP3, the key immune-repressive transcription factor of Tregs, is conditionally expressed in macrophages in stroke lesion. FOXP3 ablation in macrophages results in detrimental stroke outcomes, emphasizing the beneficial role of FOXP3+ macrophages. FOXP3+ macrophages are distinct from the M1 or M2 subsets and display superactive efferocytic capacity. With scRNAseq and analysis of FOXP3-bound-DNA isolated with CUT & RUN, we show that FOXP3 facilitates macrophage phagocytosis through enhancing cargo metabolism. FOXP3 expression is controlled by macroautophagic/autophagic protein degradation in resting macrophages, while initiation of LC3-associated phagocytosis (LAP) competitively occupies the autophagic machineries, and thus permits FOXP3 activation. Our data demonstrate a distinct set of FOXP3+ macrophages with enhanced scavenging capability, which could be a target in immunomodulatory therapy against AIS.Abbreviations: ADGRE1/F4/80: adhesion G protein-coupled receptor E1; AIF1/Iba1: allograft inflammatory factor 1; AIS: acute ischemic stroke; ARG1: arginase 1; ATP: adenosine triphosphate; BECN1/Beclin1: Beclin 1, autophagy related; BMDM: bone marrow-derived macrophages; CKO: conditional knockout; CSF1/M-CSF: colony stimulating factor 1 (macrophage); CSF2/GM-CSF: colony stimulating factor 2; CSF3/G-CSF: colony stimulating factor 3; CUT & RUN: cleavage under targets and release using nuclease; CyD: cytochalasin D; DAMP: danger/damage-associated molecular pattern; DIL: dioctadecyl-3,3,3,3-tetramethylin docarbocyanine; ELISA: enzyme linked immunosorbent assay; GO: Gene Ontology; FCGR3/CD16: Fc receptor, IgG, low affinity III; HMGB1: high mobility group box 1; IFNG/IFNγ: interferon gamma; IP: immunoprecipitation; KEGG: Kyoto Encyclopedia of Genes and Genomes; ITGAM/CD11b: integrin subunit alpha M; ITGAX/CD11c: integrin subunit alpha X; LAP: LC3-associated phagocytosis; LC-MS: liquid chromatography-mass spectrometry; LPS: lipopolysaccharide; MRC1/CD206: mannose receptor, C type 1; O4: oligodendrocyte marker O4; PBMC: peripheral blood mononuclear cells; RBC: red blood cells; PTPRC/CD45: protein tyrosine phosphatase, receptor type, C; RBFOX3/NeuN: RNA binding protein, fox 1 homolog (C. elegans) 3; RUBCN/Rubicon: RUN domain and cysteine-rich domain containing, Beclin 1-interacting protein; scRNAseq: single cell RNA sequencing; SQSTM1/p62 (sequestosome 1); TGFB/TGFβ: transforming growth factor, beta; tMCAO: transient middle cerebral artery occlusion; TNF/TNFα: tumor necrosis factor; Treg: regulatory T cell.

Exosomal Mir-3613-3p derived from oxygen-glucose deprivation-treated brain microvascular endothelial cell promotes microglial M1 polarization

BACKGROUND

Brain microvascular endothelial cell (BMEC) injury can affect neuronal survival by modulating immune responses through the microenvironment. Exosomes are important vehicles of transport between cells. However, the regulation of the subtypes of microglia by BMECs through the exosome transport of microRNAs (miRNAs) has not been established.

METHODS

In this study, exosomes from normal and oxygen-glucose deprivation (OGD)-cultured BMECs were collected, and differentially expressed miRNAs were analyzed. BMEC proliferation, migration, and tube formation were analyzed using MTS, transwell, and tube formation assays. M1 and M2 microglia and apoptosis were analyzed using flow cytometry. miRNA expression was analyzed using real-time polymerase chain reaction (RT-qPCR), and IL-1β, iNOS, IL-6, IL-10, and RC3H1 protein concentrations were analyzed using western blotting.

RESULTS

We found that miR-3613-3p was enriched in BMEC exosome by miRNA GeneChip assay and RT-qPCR analysis. miR-3613-3p knockdown enhanced cell survival, migration, and angiogenesis in the OGD-treated BMECs. In addition, BMECs secrete miR-3613-3p to transfer into microglia via exosomes, and miR-3613-3p binds to the RC3H1 3' untranslated region (UTR) to reduce RC3H1 protein levels in microglia. Exosomal miR-3613-3p promotes microglial M1 polarization by inhibiting RC3H1 protein levels. BMEC exosomal miR-3613-3p reduces neuronal survival by regulating microglial M1 polarization.

CONCLUSIONS

miR-3613-3p knockdown enhances BMEC functions under OGD conditions. Interfering with miR-3613-3p expression in BMSCs reduced the enrichment of miR-3613-3p in exosomes and enhanced M2 polarization of microglia, which contributed to reduced neuronal apoptosis.

Selective ischemic-hemisphere targeting Ginkgolide B liposomes with improved solubility and therapeutic efficacy for cerebral ischemia-reperfusion injury

Cerebral ischemia-reperfusion injury (CI/RI) remains the main cause of disability and death in stroke patients due to lack of effective therapeutic strategies. One of the main issues related to CI/RI treatment is the presence of the blood-brain barrier (BBB), which affects the intracerebral delivery of drugs. Ginkgolide B (GB), a major bioactive component in commercially available products of Ginkgo biloba, has been shown significance in CI/RI treatment by regulating inflammatory pathways, oxidative damage, and metabolic disturbance, and seems to be a candidate for stroke recovery. However, limited by its poor hydrophilicity and lipophilicity, the development of GB preparations with good solubility, stability, and the ability to cross the BBB remains a challenge. Herein, we propose a combinatorial strategy by conjugating GB with highly lipophilic docosahexaenoic acid (DHA) to obtain a covalent complex GB-DHA, which can not only enhance the pharmacological effect of GB, but can also be encapsulated in liposomes stably. The amount of finally constructed Lipo@GB-DHA targeting to ischemic hemisphere was validated 2.2 times that of free solution in middle cerebral artery occlusion (MCAO) rats. Compared to the marketed ginkgolide injection, Lipo@GB-DHA significantly reduced infarct volume with better neurobehavioral recovery in MCAO rats after being intravenously administered both at 2 h and 6 h post-reperfusion. Low levels of reactive oxygen species (ROS) and high neuron survival in vitro was maintained via Lipo@GB-DHA treatment, while microglia in the ischemic brain were polarized from the pro-inflammatory M1 phenotype to the tissue-repairing M2 phenotype, which modulate neuroinflammatory and angiogenesis. In addition, Lipo@GB-DHA inhibited neuronal apoptosis via regulating the apoptotic pathway and maintained homeostasis by activating the autophagy pathway. Thus, transforming GB into a lipophilic complex and loading it into liposomes provides a promising nanomedicine strategy with excellent CI/RI therapeutic efficacy and industrialization prospects.

Unsaturated Fatty Acids and Their Immunomodulatory Properties

Oils are an essential part of the human diet and are primarily derived from plant (or sometimes fish) sources. Several of them exhibit anti-inflammatory properties. Specific diets, such as Mediterranean diet, that are high in ω-3 polyunsaturated fatty acids (PUFAs) and ω-9 monounsaturated fatty acids (MUFAs) have even been shown to exert an overall positive impact on human health. One of the most widely used supplements in the developed world is fish oil, which contains high amounts of PUFAs docosahexaenoic and eicosapentaenoic acid. This review is focused on the natural sources of various polyunsaturated and monounsaturated fatty acids in the human diet, and their role as precursor molecules in immune signaling pathways. Consideration is also given to their role in CNS immunity. Recent findings from clinical trials utilizing various fatty acids or diets high in specific fatty acids are reviewed, along with the mechanisms through which fatty acids exert their anti-inflammatory properties. An overall understanding of diversity of polyunsaturated fatty acids and their role in several molecular signaling pathways is useful in formulating diets that reduce inflammation and increase longevity.

Omega-3 polyunsaturated fatty acids alleviate early brain injury after traumatic brain injury by inhibiting neuroinflammation and necroptosis

Presently, traumatic brain injury (TBI) is a leading contributor to disability and mortality that places a considerable financial burden on countries all over the world. Docosahexaenoic acid and eicosapentaenoic acid are two kinds of omega-3 polyunsaturated fatty acids (ω-3 PUFA), both of which have been shown to have beneficial biologically active anti-inflammatory and antioxidant effects. However, the neuroprotective effect of ω-3 PUFA in TBI has not been proven, and its probable mechanism remains obscure. We suppose that ω-3 PUFA can alleviate early brain injury (EBI) via regulating necroptosis and neuroinflammation after TBI. This research intended to examine the neuroprotective effect of ω-3 and its possible molecular pathways in a C57BL/6 mice model of EBI caused by TBI. Cognitive function was assessed by measuring the neuronal necroptosis, neuroinflammatory cytokine levels, brain water content, and neurological score. The findings demonstrate that administration of ω-3 remarkably elevated neurological scores, alleviated cerebral edema, and reduced inflammatory cytokine levels of NF-κB, interleukin-1β (IL-1β), IL-6, and TNF-α, illustrating that ω-3 PUFA attenuated neuroinflammation, necroptosis, and neuronal cell death following TBI. The PPARγ/NF-κB signaling pathway is partially responsible for the neuroprotective activity of ω-3. Collectively, our findings illustrate that ω-3 can alleviate EBI after TBI against neuroinflammation and necroptosis.

Proposed practical protocol for flow cytometry analysis of microglia from the healthy adult mouse brain: Systematic review and isolation methods’ evaluation

The aim of our study was to systematically analyze the literature for published flow cytometry protocols for microglia isolation and compare their effectiveness in terms of microglial yield, including our own protocol using sucrose for myelin removal and accutase for enzymatic digestion. For systematic review, the PubMed was searched for the terms “flow cytometry,” “microglia,” “brain,” and “mice.” Three different myelin removal methods (Percoll, sucrose, and no removal) and five protocols for enzymatic digestion (accutase, dispase II, papain, trypsin, and no enzymatic digestion) were tested for the effectiveness of microglia (CD11b⁺CD45^int cell population) isolation from the adult mouse brain using flow cytometry. Qualitative analysis of the 32 selected studies identified three most commonly used myelin removal protocols: Percoll, the use of myelin removal kit, and no removal. Nine enzymatic digestion protocols were identified, from which we selected dispase II, papain, trypsin, and no enzymatic digestion. A comparison of these myelin removal methods and digestion protocols showed the Percoll method to be preferable in removal of non-immune cells, and superior to the use of sucrose which was less effective in removal of non-immune cells, but resulted in a comparable microglial yield to Percoll myelin removal. Digestion with accutase resulted in one of the highest microglial yields, all while having the lowest variance among tested protocols. The proposed protocol for microglia isolation uses Percoll for myelin removal and accutase for enzymatic digestion. All tested protocols had different features, and the choice between them can depend on the individual focus of the research.

Docosahexaenoic Acid Alleviates Brain Damage by Promoting Mitophagy in Mice with Ischaemic Stroke

Mitophagy, the selective removal of damaged mitochondria through autophagy, is crucial for mitochondrial turnover and quality control. Docosahexaenoic acid (DHA), an essential omega-3 fatty acid, protects mitochondria in various diseases. This study aimed to investigate the neuroprotective role of DHA in ischaemic stroke models in vitro and in vivo and its involvement in mitophagy and mitochondrial dysfunction. A mouse model of ischaemic stroke was established through middle cerebral artery occlusion (MCAO). To simulate ischaemic stroke in vitro, PC12 cells were subjected to oxygen–glucose deprivation (OGD). Immunofluorescence analysis, western blotting (WB), electron microscopy (EM), functional behavioural tests, and Seahorse assay were used for analysis. DHA treatment significantly alleviated the brain infarction volume, neuronal apoptosis, and behavioural dysfunction in mice with ischaemic stroke. In addition, DHA enhanced mitophagy by significantly increasing the number of autophagosomes and LC3-positive mitochondria in neurons. The Seahorse assay revealed that DHA increased glutamate and succinate metabolism in neurons after ischaemic stroke. JC-1 and MitoSox staining, and evaluation of ATP levels indicated that DHA-induced mitophagy alleviated reactive oxygen species (ROS) accumulation and mitochondrial injury. Mechanistically, DHA improved mitochondrial dynamics by increasing the expression of dynamin-related protein 1 (Drp1), LC3, and the mitophagy clearance protein Pink1/Parkin. Mdivi-1, a specific mitophagy inhibitor, abrogated the neuroprotective effects of DHA, indicating that DHA protected neurons by enhancing mitophagy. Therefore, DHA can protect against neuronal apoptosis after stroke by clearing the damaged mitochondria through Pink1/Parkin-mediated mitophagy and by alleviating mitochondrial dysfunction.

DJ-1 activates the Atg5-Atg12-Atg16L1 complex via Sirt1 to influence microglial polarization and alleviate cerebral ischemia/reperfusion-induced inflammatory injury

BACKGROUND

After cerebral ischemia/reperfusion (I/R) injury, activated microglia can be polarized towards different phenotypes (the proinflammatory M1 phenotype or the anti-inflammatory M2 phenotype) to regulate neuroinflammation. Our previous research showed that DJ-1 has anti-inflammatory effects in cerebral I/R. Here, we examined whether the neuroprotective effect of DJ-1 is related to the autophagy-associated Atg5-Atg12-Atg161L1 complex and whether Sirt1 is involved in the influence of DJ-1 by mediating microglial polarization and ameliorating cerebral I/R injury.

METHODS

To answer these questions, we adopted the middle cerebral artery occlusion/reperfusion (MCAO/R) model to simulate I/R injury, knocked down the expression of DJ-1 with siRNA, and used the chemical inhibitor EX-527 to inhibit the expression of Sirt1. Related indexes were evaluated by Western blotting, immunoprecipitation and transmission electron microscopy.

RESULTS

Interference with DJ-1 promotes the polarization of microglia from the anti-inflammatory phenotype to the proinflammatory phenotype. Addition of a Sirt1 inhibitor following DJ-1 interference enhances the effect of DJ-1 interference on microglial polarization, decreases the level of the Atg5-Atg12-Atg16L1 complex, and inhibits autophagy.

CONCLUSION

These results suggest that DJ-1 regulates the polarization of microglia during cerebral I/R injury, possibly by activating the Atg5-Atg12-Atg16L1 complex through Sirt1 to promote autophagy.

Roles of Fatty Acids in Microglial Polarization: Evidence from In Vitro and In Vivo Studies on Neurodegenerative Diseases

Microglial polarization to the M1 phenotype (classically activated) or the M2 phenotype (alternatively activated) is critical in determining the fate of immune responses in neurodegenerative diseases (NDs). M1 macrophages contribute to neurotoxicity, neuronal and synaptic damage, and oxidative stress and are the first line of defense, and M2 macrophages elicit an anti-inflammatory response to regulate neuroinflammation, clear cell debris, and promote neuroregeneration. Various studies have focused on the ability of natural compounds to promote microglial polarization from the M1 phenotype to the M2 phenotype in several diseases, including NDs. However, studies on the roles of fatty acids in microglial polarization and their implications in NDs are a rare find. Most of the studies support the role of polyunsaturated fatty acids (PUFAs) in microglial polarization using cell and animal models. Thus, we aimed to collect data and provide a narrative account of microglial types, markers, and studies pertaining to fatty acids, particularly PUFAs, on microglial polarization and their neuroprotective effects. The involvement of only PUFAs in the chosen topic necessitates more in-depth research into the role of unexplored fatty acids in microglial polarization and their mechanistic implications. The review also highlights limitations and future challenges.

NLRP3 Inflammasome Activation: A Therapeutic Target for Cerebral Ischemia–Reperfusion Injury

Millions of patients are suffering from ischemic stroke, it is urgent to figure out the pathogenesis of cerebral ischemia–reperfusion (I/R) injury in order to find an effective cure. After I/R injury, pro-inflammatory cytokines especially interleukin-1β (IL-1β) upregulates in ischemic brain cells, such as microglia and neuron. To ameliorate the inflammation after cerebral I/R injury, nucleotide-binding oligomerization domain (NOD), leucine-rich repeat (LRR), and pyrin domain-containing protein 3 (NLRP3) inflammasome is well-investigated. NLRP3 inflammasomes are complicated protein complexes that are activated by endogenous and exogenous danger signals to participate in the inflammatory response. The assembly and activation of the NLRP3 inflammasome lead to the caspase-1-dependent release of pro-inflammatory cytokines, such as interleukin (IL)-1β and IL-18. Furthermore, pyroptosis is a pro-inflammatory cell death that occurs in a dependent manner on NLRP3 inflammasomes after cerebral I/R injury. In this review, we summarized the assembly and activation of NLRP3 inflammasome; moreover, we also concluded the pivotal role of NLRP3 inflammasome and inhibitors, targeting the NLRP3 inflammasome in cerebral I/R injury.

Nociceptor-derived Reg3γ prevents endotoxic death by targeting kynurenine pathway in microglia

Nociceptors can fine-tune local or systemic immunity, but the mechanisms of nociceptive modulation in endotoxic death remain largely unknown. Here, we identified C-type lectin Reg3γ as a nociceptor-enriched hormone that protects the host from endotoxic death. During endotoxemia, nociceptor-derived Reg3γ penetrates the brain and suppresses the expression of microglial indoleamine dioxygenase 1, a critical enzyme of the kynurenine pathway, via the Extl3-Bcl10 axis. Endotoxin-administered nociceptor-null mice and nociceptor-specific Reg3γ-deficient mice exhibit a high mortality rate accompanied by decreased brain HK1 phosphorylation and ATP production despite normal peripheral inflammation. Such metabolic arrest is only observed in the brain, and aberrant production of brain quinolinic acid, a neurotoxic metabolite of the kynurenine pathway, causes HK1 suppression. Strikingly, the central administration of Reg3γ protects mice from endotoxic death by enhancing brain ATP production. By identifying nociceptor-derived Reg3γ as a microglia-targeted hormone, this study provides insights into the understanding of tolerance to endotoxic death.

Microglia and Macrophages in Neuroprotection, Neurogenesis, and Emerging Therapies for Stroke

Stroke remains the number one cause of morbidity in the United States. Within weeks to months after an ischemic event, there is a resolution of inflammation and evidence of neurogenesis; however, years following a stroke, there is evidence of chronic inflammation in the central nervous system, possibly by the persistence of an autoimmune response to brain antigens as a result of ischemia. The mechanisms underlying the involvement of macrophage and microglial activation after stroke are widely acknowledged as having a role in ischemic stroke pathology; thus, modulating inflammation and neurological recovery is a hopeful strategy for treating the long-term outcomes after ischemic injury. Current treatments fail to provide neuroprotective or neurorestorative benefits after stroke; therefore, to ameliorate brain injury-induced deficits, therapies must alter both the initial response to injury and the subsequent inflammatory process. This review will address differences in macrophage and microglia nomenclature and summarize recent work in elucidating the mechanisms of macrophage and microglial participation in antigen presentation, neuroprotection, angiogenesis, neurogenesis, synaptic remodeling, and immune modulating strategies for treating the long-term outcomes after ischemic injury.

Dietary Docosahexaenoic Acid as a Potential Treatment for Semi-acute and Chronic Particle-Induced Pulmonary Inflammation in Balb/c Mice

Acute and chronic inflammation are vital contributing factors to pulmonary diseases which can be triggered by exposure to occupational and man-made particles; however, there are no established treatments. One potential treatment shown to have anti-inflammatory capabilities is the dietary supplement docosahexaenoic acid (DHA), an omega-3 polyunsaturated fatty acid found in fish oil. DHA's anti-inflammatory mechanisms are unclear for particle-induced inflammation; therefore, this study evaluated DHA as a prophylactic treatment for semi-acute and chronic particle-induced inflammation in vivo. Balb/c mice were fed a control or 1% DHA diet and exposed to dispersion media, an inflammatory multi-walled carbon nanotube (MWCNT), or crystalline silica (SiO₂) either once (semi-acute) or once a week for 4 weeks (chronic). The hypothesis was that DHA will decrease pulmonary inflammatory markers in response to particle-induced inflammation. Results indicated that DHA had a trending anti-inflammatory effect in mice exposed to MWCNT. There was a general decrease in inflammatory signals within the lung lavage fluid and upregulation of M2c macrophage gene expression in the spleen tissue. In contrast, mice exposed to SiO₂ while on the DHA diet significantly increased most inflammatory markers. However, DHA stabilized the phagolysosomal membrane upon prolonged treatment. This indicated that DHA treatment may depend upon certain inflammatory particle exposures as well as the length of the exposure.

Involvement of Microglia in Neurodegenerative Diseases: Beneficial Effects of Docosahexahenoic Acid (DHA) Supplied by Food or Combined with Nanoparticles

Neurodegenerative diseases represent a major public health issue and require better therapeutic management. The treatments developed mainly target neuronal activity. However, an inflammatory component must be considered, and microglia may constitute an important therapeutic target. Given the difficulty in developing molecules that can cross the blood–brain barrier, the use of food-derived molecules may be an interesting therapeutic avenue. Docosahexaenoic acid (DHA), an omega-3 polyunsaturated fatty acid (22:6 omega-3), has an inhibitory action on cell death and oxidative stress induced in the microglia. It also acts on the inflammatory activity of microglia. These data obtained in vitro or on animal models are corroborated by clinical trials showing a protective effect of DHA. Whereas DHA crosses the blood–brain barrier, nutritional intake lacks specificity at both the tissue and cellular level. Nanomedicine offers new tools which favor the delivery of DHA at the cerebral level, especially in microglial cells. Because of the biological activities of DHA and the associated nanotargeting techniques, DHA represents a therapeutic molecule of interest for the treatment of neurodegenerative diseases.

Constipation induced gut microbiota dysbiosis exacerbates experimental autoimmune encephalomyelitis in C57BL/6 mice

Background

Constipation is a common gastrointestinal dysfunction which has a potential impact on people's immune state and their quality of life. Here we investigated the effects of constipation on experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis (MS).

Methods

Constipation was induced by loperamide in female C57BL/6 mice. The alternations of gut microbiota, permeability of intestinal barrier and blood–brain barrier, and histopathology of colon were assessed after constipation induction. EAE was induced in the constipation mice. Fecal microbiota transplantation (FMT) was performed from constipation mice into microbiota-depleted mice. Clinical scores, histopathology of inflammation and demyelination, Treg/Th17 and Treg17/Teff17 imbalance both in the peripheral lymphatic organs and central nervous system, cytokines include TGF-β, GM-CSF, IL-10, IL-17A, IL-17F, IL-21, IL-22, and IL-23 in serum were assessed in different groups.

Results

Compared with the vehicle group, the constipation mice showed gut microbiota dysbiosis, colon inflammation and injury, and increased permeability of intestinal barrier and blood–brain barrier. We found that the clinical and pathological scores of the constipation EAE mice were severer than that of the EAE mice. Compared with the EAE mice, the constipation EAE mice showed reduced percentage of Treg and Treg17 cells, increased percentage of Th17 and Teff17 cells, and decreased ratio of Treg/Th17 and Treg17/Teff17 in the spleen, inguinal lymph nodes, brain, and spinal cord. Moreover, the serum levels of TGF-β, IL-10, and IL-21 were decreased while the GM-CSF, IL-17A, IL-17F, IL-22, and IL-23 were increased in the constipation EAE mice. In addition, these pathological processes could be transferred via their gut microbiota.

Conclusions

Our results verified that constipation induced gut microbiota dysbiosis exacerbated EAE via aggravating Treg/Th17 and Treg17/Teff17 imbalance and cytokines disturbance in C57BL/6 mice.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-021-02995-z.

Immune Cells in the BBB Disruption After Acute Ischemic Stroke: Targets for Immune Therapy?

Blood-Brain Barrier (BBB) disruption is an important pathophysiological process of acute ischemic stroke (AIS), resulting in devastating malignant brain edema and hemorrhagic transformation. The rapid activation of immune cells plays a critical role in BBB disruption after ischemic stroke. Infiltrating blood-borne immune cells (neutrophils, monocytes, and T lymphocytes) increase BBB permeability, as they cause microvascular disorder and secrete inflammation-associated molecules. In contrast, they promote BBB repair and angiogenesis in the latter phase of ischemic stroke. The profound immunological effects of cerebral immune cells (microglia, astrocytes, and pericytes) on BBB disruption have been underestimated in ischemic stroke. Post-stroke microglia and astrocytes can adopt both an M1/A1 or M2/A2 phenotype, which influence BBB integrity differently. However, whether pericytes acquire microglia phenotype and exert immunological effects on the BBB remains controversial. Thus, better understanding the inflammatory mechanism underlying BBB disruption can lead to the identification of more promising biological targets to develop treatments that minimize the onset of life-threatening complications and to improve existing treatments in patients. However, early attempts to inhibit the infiltration of circulating immune cells into the brain by blocking adhesion molecules, that were successful in experimental stroke failed in clinical trials. Therefore, new immunoregulatory therapeutic strategies for acute ischemic stroke are desperately warranted. Herein, we highlight the role of circulating and cerebral immune cells in BBB disruption and the crosstalk between them following acute ischemic stroke. Using a robust theoretical background, we discuss potential and effective immunotherapeutic targets to regulate BBB permeability after acute ischemic stroke.

Supplemental N-3 Polyunsaturated Fatty Acids Limit A1-Specific Astrocyte Polarization via Attenuating Mitochondrial Dysfunction in Ischemic Stroke in Mice

Ischemic stroke is one of the leading causes of death and disability for adults, which lacks effective treatments. Dietary intake of n-3 polyunsaturated fatty acids (n-3 PUFAs) exerts beneficial effects on ischemic stroke by attenuating neuron death and inflammation induced by microglial activation. However, the impact and mechanism of n-3 PUFAs on astrocyte function during stroke have not yet been well investigated. Our current study found that dietary n-3 PUFAs decreased the infarction volume and improved the neurofunction in the mice model of transient middle cerebral artery occlusion (tMCAO). Notably, n-3 PUFAs reduced the stroke-induced A1 astrocyte polarization both in vivo and in vitro. We have demonstrated that exogenous n-3 PUFAs attenuated mitochondrial oxidative stress and increased the mitophagy of astrocytes in the condition of hypoxia. Furthermore, we provided evidence that treatment with the mitochondrial-derived antioxidant, mito-TEMPO, abrogated the n-3 PUFA-mediated regulation of A1 astrocyte polarization upon hypoxia treatment. Together, this study highlighted that n-3 PUFAs prevent mitochondrial dysfunction, thereby limiting A1-specific astrocyte polarization and subsequently improving the neurological outcomes of mice with ischemic stroke.

Docosahexaenoic acid decreased inflammatory gene expression, but not 18-kDa translocator protein binding, in rat pup brain after controlled cortical impact

BACKGROUND

Traumatic brain injury is the leading cause of acquired neurologic disability in children. In our model of pediatric traumatic brain injury, controlled cortical impact (CCI) in rat pups, docosahexaenoic acid (DHA) improved lesion volume and cognitive testing as late as postinjury day (PID) 50. Docosahexaenoic acid decreased proinflammatory messenger RNA (mRNA) in microglia and macrophages at PIDs 3 and 7, but not 30. We hypothesized that DHA affected inflammatory markers differentially relative to impact proximity, early and persistently after CCI.

METHODS

To provide a temporal snapshot of regional neuroinflammation, we measured 18-kDa translocator protein (TSPO) binding using whole brain autoradiography at PIDs 3, 7, 30, and 50. Guided by TSPO results, we measured mRNA levels in contused cortex and underlying hippocampus for genes associated with proinflammatory and inflammation-resolving states at PIDs 2 and 3.

RESULTS

Controlled cortical impact increased TSPO binding at all time points, most markedly at PID 3 and in regions closest to impact, not blunted by DHA. Controlled cortical impact increased cortical and hippocampal mRNA proinflammatory markers, blunted by DHA at PID 2 in hippocampus.

CONCLUSION

Controlled cortical impact increased TSPO binding in the immature brain in a persistent manner more intensely with more severe injury, not altered by DHA. Controlled cortical impact increased PIDs 2 and 3 mRNA levels of proinflammatory and inflammation-resolving genes. Docosahexaenoic acid decreased proinflammatory markers associated with inflammasome activation at PID 2. We speculate that DHA's salutary effects on long-term outcomes result from early effects on the inflammasome. Future studies will examine functional effects of DHA on microglia both early and late after CCI.

Salvianolic Acids for Injection alleviates cerebral ischemia/reperfusion injury by switching M1/M2 phenotypes and inhibiting NLRP3 inflammasome/pyroptosis axis in microglia in vivo and in vitro

ETHNOPHARMACOLOGICAL RELEVANCE

After cerebral ischemia/reperfusion injury, pro-inflammatory M1 and anti-inflammatory M2 phenotypes of microglia are involved in neuroinflammation, in which activation of NLRP3 inflammasome and subsequent pyroptosis play essential roles. Salvianolic Acids for Injection (SAFI) is Chinese medicine injection which composed of multiple phenolic acids extracted from Radix Salviae Miltiorrhizae, and has been reported to generate neuroprotective effects after cerebral ischemic insult in clinical and animal studies.

AIM OF THE STUDY

The present study was designed to investigate whether SAFI exerts neuroprotective effects by switching microglial phenotype and inhibiting NLRP3 inflammasome/pyroptosis axis in microglia.

MATERIALS AND METHODS

The middle cerebral artery occlusion/reperfusion (MCAO/R) model in rats and oxygen-glucose deprivation/reoxygenation (OGD/R) model in co-cultured primary neurons and primary microglia were utilized. The neuroprotective effect of SAFI was evaluated through measuring neurological deficit scores, neuropathological changes, inflammatory factors, cell phenotype markers, and related proteins of NLRP3 inflammasome/pyroptosis axis.

RESULTS

The results showed that SAFI treatment was able to: (1) produce a significant increase in neurological deficit scores and decrease in infarct volumes, and alleviate histological injury and neuronal apoptosis in cerebral cortex in MCAO/R model; (2) increase neuronal viability and reduce neuronal apoptosis in the OGD model; (3) reshape microglial polarization patterns from M1-like phenotype to M2-like phenotype; (4) inhibit the activation of the NLRP3 inflammasome and the expression of proteins related to NLRP3 inflammasome/pyroptosis axis in vivo and in vitro.

CONCLUSION

These findings indicate that SAFI exert neuroprotective effect, probably via reducing neuronal apoptosis, switching microglial phenotype from M1 towards M2, and inhibiting NLRP3 inflammasome/pyroptosis axis in microglia.

High-salt diet downregulates TREM2 expression and blunts efferocytosis of macrophages after acute ischemic stroke

Background

A high-salt diet (HSD) is one of the major risk factors for acute ischemic stroke (AIS). As a potential mechanism, surplus salt intake primes macrophages towards a proinflammatory phenotype. In this study, whether HSD could blunt the efferocytic capability of macrophages after ischemic stroke, thus exacerbating post-stroke neural inflammation, was investigated.

Methods

Wild-type male C57BL/6 mice were fed with fodder containing 8% sodium chloride for 4 weeks and subjected to transient middle cerebral occlusion (tMCAO). Disease severity, macrophage polarization as well as efferocytic capability were evaluated. Bone marrow-derived macrophages were cultured in vitro, and the impact of high salinity on their efferocytic activity, as well as their expression of phagocytic molecules, were analyzed. The relationships among sodium concentration, macrophage phenotype, and disease severity in AIS patients were explored.

Results

HSD-fed mice displayed increased infarct volume and aggravated neurological deficiency. Mice fed with HSD suffered exacerbated neural inflammation as shown by higher inflammatory mediator expression and immune cell infiltration levels. Infiltrated macrophages within stroke lesions in HSD-fed mice exhibited a shift towards proinflammatory phenotype and impaired efferocytic capability. As assessed with a PCR array, the expression of triggering receptor expressed on myeloid cells 2 (TREM2), a receptor relevant to phagocytosis, was downregulated in high-salt-treated bone marrow-derived macrophages. Enhancement of TREM2 signaling restored the efferocytic capacity and cellular inflammation resolution of macrophages in a high salinity environment in vitro and in vivo. A high concentration of urine sodium in AIS patients was found to be correlated with lower TREM2 expression and detrimental stroke outcomes.

Conclusions

HSD inhibited the efferocytic capacity of macrophages by downregulating TREM2 expression, thus impeding inflammation resolution after ischemic stroke. Enhancing TREM2 signaling in monocytes/macrophages could be a promising therapeutic strategy to enhance efferocytosis and promote post-stroke inflammation resolution.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-021-02144-9.

The second phase of brain trauma can be controlled by nutraceuticals that suppress DAMP-mediated microglial activation

INTRODUCTION

A delayed second wave of brain trauma is mediated in large part by microglia that are activated to a pro-inflammatory M1 phenotype by DAMP proteins released by dying neurons. These microglia can promote apoptosis or necrosis in neighboring neurons by producing a range of pro-inflammatory cytokines and the deadly oxidant peroxynitrite. This second wave could therefore be mitigated with agents that blunt the post-traumatic M1 activation of microglia and that preferentially promote a pro-healing M2 phenotype.

AREAS COVERED

The literature on nutraceuticals that might have clinical potential in this regard.

EXPERT OPINION

The chief signaling pathway whereby DAMPs promote M1 microglial activation involves activation of toll-like receptor 4 (TLR4), NADPH oxidase, NF-kappaB, and the stress activated kinases JNK and p38. The green tea catechin EGCG can suppress TLR4 expression. Phycocyanobilin can inhibit NOX2-dependent NADPH oxidase, ferulate and melatonin can oppose pro-inflammatory signal modulation by NADPH oxidase-derived oxidants. Long-chain omega-3 fatty acids, the soy isoflavone genistein, the AMPK activator berberine, glucosamine, and ketone bodies can down-regulate NF-kappaB activation. Vitamin D activity can oppose JNK/p38 activation. A sophisticated program of nutraceutical supplementation may have important potential for mitigating the second phase of neuronal death and aiding subsequent healing.

DHA attenuated Japanese Encephalitis virus infection-induced neuroinflammation and neuronal cell death in cultured rat Neuron/glia

Japanese Encephalitis Virus (JEV) is a neurotropic virus and its Central Nervous System (CNS) infection causes fatal encephalitis with high mortality and morbidity. Microglial activation and consequences of bystander damage appear to be the dominant mechanisms for Japanese Encephalitis and complications. Docosahexaenoic acid (DHA), an essential fatty acid and a major component of brain cell membranes, possesses additional biological activities, including anti-apoptosis, anti-inflammation, and neuroprotection. Through this study, we have provided experimental evidence showing the anti-inflammatory, neuroprotective, and anti-viral effects of DHA against JEV infection in rat Neuron/glia cultures. By Neuron/glia and Neuron cultures, DHA protected against neuronal cell death upon JEV infection and reduced JEV amplification. In Neuron/glia and Microglia cultures, the effects of DHA were accompanied by the downregulation of pro-inflammatory M1 microglia, upregulation of anti-inflammatory M2 microglia, and reduction of neurotoxic cytokine expression, which could be attributed to its interference in the Toll-Like Receptor (TLR), Mitogen-Activated Protein Kinase (MAPK), and Interferon/Janus Kinase/Signal Transducers and Activators of Transcription (Stat), along with the NF-κB, AP-1, and c-AMP Response Element Binding Protein (CREB) controlled transcriptional programs. Parallel anti-inflammatory effects against JEV infection were duplicated by G Protein-Coupled Receptor (GPR120) and GPR40 agonists and a reversal of DHA-mediated anti-inflammation was seen in the presence of GPR120 antagonist, while the GPR40 was less effectiveness. Since increasing evidence indicates its neuroprotection against neurodegenerative diseases, DHA is a proposed anti-inflammatory and neuroprotective candidate for the treatment of neuroinflammation-accompanied viral pathogenesis such as Japanese Encephalitis.

Synthesis of Paeonol-Ozagrel Conjugate: Structure Characterization and In Vivo Anti-Ischemic Stroke potential

Ischemic stroke is a common neurological disease that can lead to mortality and disability. The current curative effect remains unsatisfactory because drug accumulation in the diseased areas is insufficient as a result of the unique blood–brain barrier. Therefore, much attention has been paid to develop a novel therapeutic compound, paeonol-ozagrel conjugate (POC), for ischemic stroke. Then, POC was successfully synthesized by conjugating of paeonol and ozagrel as mutual prodrug. A series of in vitro characterizations and evaluations, including high - resolution mass spectroscopy, nuclear magnetic resonance spectroscopy, partition coefficient, and assessment of cytotoxicity against PC12 cells, were performed. Pharmacokinetic study demonstrated POC is eliminated quickly (t_1/2 = 53.46 ± 19.64 min), which supported a short dosing interval. The neurological score, infarct volume, histopathological changes, oxidative stress, inflammatory cytokines levels, and TXA₂ levels also were evaluated in vivo in middle cerebral artery occlusion (MCAO) rats. All results showed that POC had a significant curative and therapeutic effect on ischemic stroke, as evaluated by the middle cerebral artery occlusion. Overall, POC can be expected to become a new drug candidate for the treatment of ischemic stroke.

Emerging Role of Microglia-Mediated Neuroinflammation in Epilepsy after Subarachnoid Hemorrhage

Epilepsy is a common and serious complication of subarachnoid hemorrhage (SAH), giving rise to increased morbidity and mortality. It's difficult to identify patients at high risk of epilepsy and the application of anti-epileptic drugs (AEDs) following SAH is a controversial topic. Therefore, it's pressingly needed to gain a better understanding of the risk factors, underlying mechanisms and the optimization of therapeutic strategies for epilepsy after SAH. Neuroinflammation, characterized by microglial activation and the release of inflammatory cytokines, has drawn growing attention due to its influence on patients with epilepsy after SAH. In this review, we discuss the risk factors for epilepsy after SAH and emphasize the critical role of microglia. Then we discuss how various molecules arising from pathophysiological changes after SAH activate specific receptors such as TLR4, NLRP3, RAGE, P2X7R and initiate the downstream inflammatory pathways. Additionally, we focus on the significant responses implicated in epilepsy including neuronal excitotoxicity, the disruption of blood-brain barrier (BBB) and the change of immune responses. As the application of AEDs for seizure prophylaxis after SAH remains controversial, the regulation of neuroinflammation targeting the key pathological molecules could be a promising therapeutic method. While neuroinflammation appears to contribute to epilepsy after SAH, more comprehensive experiments on their relationships are needed.

The immune response of T cells and therapeutic targets related to regulating the levels of T helper cells after ischaemic stroke

Through considerable effort in research and clinical studies, the immune system has been identified as a participant in the onset and progression of brain injury after ischaemic stroke. Due to the involvement of all types of immune cells, the roles of the immune system in stroke pathology and associated effects are complicated. Past research concentrated on the functions of monocytes and neutrophils in the pathogenesis of ischaemic stroke and tried to demonstrate the mechanisms of tissue injury and protection involving these immune cells. Within the past several years, an increasing number of studies have elucidated the vital functions of T cells in the innate and adaptive immune responses in both the acute and chronic phases of ischaemic stroke. Recently, the phenotypes of T cells with proinflammatory or anti-inflammatory function have been demonstrated in detail. T cells with distinctive phenotypes can also influence cerebral inflammation through various pathways, such as regulating the immune response, interacting with brain-resident immune cells and modulating neurogenesis and angiogenesis during different phases following stroke. In view of the limited treatment options available following stroke other than tissue plasminogen activator therapy, understanding the function of immune responses, especially T cell responses, in the post-stroke recovery period can provide a new therapeutic direction. Here, we discuss the different functions and temporal evolution of T cells with different phenotypes during the acute and chronic phases of ischaemic stroke. We suggest that modulating the balance between the proinflammatory and anti-inflammatory functions of T cells with distinct phenotypes may become a potential therapeutic approach that reduces the mortality and improves the functional outcomes and prognosis of patients suffering from ischaemic stroke.

Acute Injection of Omega-3 Triglyceride Emulsion Provides Very Similar Protection as Hypothermia in a Neonatal Mouse Model of Hypoxic-Ischemic Brain Injury

Therapeutic hypothermia (HT) is a currently accepted treatment for neonatal asphyxia and is a promising strategy in adult stroke therapy. We previously reported that acute administration of docosahexaenoic acid (DHA) triglyceride emulsion (tri-DHA) protects against hypoxic-ischemic (HI) injury in neonatal mice. We questioned if co-treatment with HT and tri-DHA would achieve synergic effects in protecting the brain from HI injury. Neonatal mice (10-day old) subjected to HI injury were placed in temperature-controlled chambers for 4 h of either HT (rectal temperature 31–32°C) or normothermia (NT, rectal temperature 37°C). Mice were treated with tri-DHA (0.375 g tri-DHA/kg bw, two injections) before and 1 h after initiation of HT. We observed that HT, beginning immediately after HI injury, reduced brain infarct volume similarly to tri-DHA treatment (~50%). Further, HT delayed 2 h post-HI injury provided neuroprotection (% infarct volume: 31.4 ± 4.1 vs. 18.8 ± 4.6 HT), while 4 h delayed HT did not protect against HI insult (% infarct volume: 30.7 ± 5.0 vs. 31.3 ± 5.6 HT). HT plus tri-DHA combination treatment beginning at 0 or 2 h after HI injury did not further reduce infarct volumes compared to HT alone. Our results indicate that HT offers similar degrees of neuroprotection against HI injury compared to tri-DHA treatment. HT can only be provided in tertiary care centers, requires intense monitoring and can have adverse effects. In contrast, tri-DHA treatment may be advantageous in providing a feasible and effective strategy in patients after HI injury.

Role of polyunsaturated fatty acids in ischemic stroke - A perspective of specialized pro-resolving mediators

Polyunsaturated fatty acids (PUFAs) have been proposed as beneficial for cardiovascular health. However, results from both epidemiological studies and clinical trials have been inconsistent, whereas most of the animal studies showed promising benefits of PUFAs in the prevention and treatment of ischemic stroke. In recent years, it has become clear that PUFAs are metabolized into various types of bioactive derivatives, including the specialized pro-resolving mediators (SPMs). SPMs exert multiple biofunctions, such as to limit excessive inflammatory responses, regulate lipid metabolism and immune cell functions, decrease production of pro-inflammatory factors, increase anti-inflammatory mediators, as well as to promote tissue repair and homeostasis. Inflammation has been recognised as a key contributor to the pathophysiology of acute ischemic stroke. Owing to their potent pro-resolving actions, SPMs are potential for development of novel anti-stroke therapy. In this review, we will summarize current knowledge of epidemiological studies, basic research and clinical trials concerning PUFAs in stroke prevention and treatment, with special attention to SPMs as the unsung heroes behind PUFAs.

Targeting the Immune System for Ischemic Stroke

Stroke is responsible for almost 6 million deaths and more than 10% of all mortalities each year, and two-thirds of stroke survivors remain disabled. With treatments for ischemic stroke still limited to clot lysis and/or mechanical removal, new therapeutic targets are desperately needed. In this review, we provide an overview of the complex mechanisms of innate and adaptive immune cell-mediated inflammatory injury, that exacerbates infarct development for several days after stroke. We also highlight the features of poststroke systemic immunodepression that commonly leads to infections and some mortalities, and argue that safe and effective therapies will need to balance pro- and anti-inflammatory mechanisms in a time-sensitive manner, to maximize the likelihood of an improved long-term outcome.

Acute injection of a DHA triglyceride emulsion after hypoxic-ischemic brain injury in mice increases both DHA and EPA levels in blood and brain✰

We recently reported that acute injection of docosahexaenoic acid (DHA) triglyceride emulsions (tri-DHA) conferred neuroprotection after hypoxic-ischemic (HI) injury in a neonatal mouse stroke model. We showed that exogenous DHA increased concentrations of DHA in brain mitochondria as well as DHA-derived specialized pro-resolving mediator (SPM) levels in the brain. The objective of the present study was to investigate the distribution of emulsion particles and changes in plasma lipid profiles after tri-DHA injection in naïve mice and in animals subjected to HI injury. We also examined whether tri-DHA injection would change DHA- and eicosapentaenoic acid (EPA)-derived SPM levels in the brain. To address this, neonatal (10-day-old) naïve and HI mice were injected with radiolabeled tri-DHA emulsion (0.375 g tri-DHA/kg bw), and blood clearance and tissue distribution were analyzed. Among all the organs assayed, the lowest uptake of emulsion particles was in the brain (<0.4% recovered dose) in both naïve and HI mice, while the liver had the highest uptake. Tri-DHA administration increased DHA concentrations in plasma lysophosphatidylcholine and non-esterified fatty acids. Additionally, treatment with tri-DHA after HI injury significantly elevated the levels of DHA-derived SPMs and monohydroxy-containing DHA-derived products in the brain. Further, tri-DHA administration increased resolvin E2 (RvE2, 5S,18R-dihydroxy-eicosa-6E,8Z,11Z,14Z,16E-pentaenoic acid) and monohydroxy-containing EPA-derived products in the brain. These results suggest that the transfer of DHA through plasma lipid pools plays an important role in DHA brain transport in neonatal mice subjected to HI injury. Furthermore, increases in EPA and EPA-derived SPMs following tri-DHA injection demonstrate interlinked metabolism of these two fatty acids. Hence, changes in both EPA and DHA profile patterns need to be considered when studying the protective effects of DHA after HI brain injury. Our results highlight the need for further investigation to differentiate the effects of DHA from EPA on neuroprotective pathways following HI damage. Such information could contribute to the development of specific DHA-EPA formulations to improve clinical endpoints and modulate potential biomarkers in ischemic brain injury.

Microglial Responses to Brain Injury and Disease: Functional Diversity and New Opportunities

As an integral part of the innate immune system of the brain, resident microglia must react rapidly to the onset of brain injury and neurological disease. These dynamic cells then continue to shift their phenotype along a multidimensional continuum with overlapping pro- and anti-inflammatory states, allowing them to adapt to microenvironmental changes during the progression of brain disorders. However, the ability of microglia to shift phenotype through nimble molecular, structural, and functional changes comes at a cost, as the extreme pro-inflammatory states may prevent these professional phagocytes from clearing toxic debris and secreting tissue-repairing neurotrophic factors. Evolution has strongly favored heterogeneity in microglia in both the spatial and temporal dimensions-they can assume diverse roles in different brain regions, throughout the course of brain development and aging, and during the spatiotemporal progression of brain injuries and neurological diseases. Age and sex differences add further diversity to microglia functional status under physiological and pathological conditions. This article reviews recent advances in our knowledge of microglia with emphases on molecular mediators of phenotype shifts and functional diversity. We describe microglia-targeted therapeutic opportunities, including pharmacologic modulation of phenotype and repopulation of the brain with fresh microglia. With the advent of powerful new tools, research on microglia has recently accelerated in pace and may translate into potential therapeutics against brain injury and neurological disease.

The role of peripheral monocytes and macrophages in ischemic stroke

After acute ischemic stroke (AIS), peripheral monocytes infiltrate into the lesion site within 24 h, peak at 3 to 7 days, and then differentiate into macrophages. Traditionally, monocytes/macrophages (MMs) are thought to play a deleterious role in AIS. Depletion of MMs in the acute phase can alleviate brain injury induced by ischemia. However, several studies have shown that MMs have anti-inflammatory functions, participate in angiogenesis, phagocytose necrotic neurons, and promote neurovascular repair. Therefore, MMs play dual roles in ischemic stroke, depending mainly upon the MM microenvironment and the window of time post-stroke. Because activated microglia and MMs are similar in morphology and function, previous studies have often investigated them together. However, recent studies have used special methods to distinguish MMs from microglia and have found that MMs have properties which differ from microglia. Here, we review the unique role of MMs and the interaction between MMs and neurovascular units, including neurons, astrocytes, microglia, and microvessels. Future therapeutics targeting MMs should regulate the polarization and subset transformation of the MMs at different stages of AIS rather than comprehensively suppressing MM infiltration and differentiation. In addition, more studies are needed to elucidate the cellular and molecular mechanisms of MM subsets and polarization during ischemic stroke.

Docosahexaenoic Acid Improves Diabetic Wound Healing in a Rat Model by Restoring Impaired Plasticity of Macrophage Progenitor Cells

BACKGROUND

Chronic inflammation associated with delayed diabetic wound healing is induced by disturbed polarization of macrophages derived mainly from predisposed progenitor cells in bone marrow. Docosahexaenoic acid plays a critical role in regulating the function of macrophage progenitor cells. The authors evaluated whether docosahexaenoic acid accelerates diabetic wound healing in rats.

METHODS

Streptozotocin-induced diabetic rats divided into control and docosahexaenoic acid-treated groups (n = 10) were subjected to paired dorsal skin wounds. Docosahexaenoic acid (100 mg/kg per day) was orally supplemented 2 weeks before wounding until termination. The wound healing process was recorded 0, 7, and 14 days after wounding. At day 7, blood perfusion was measured by laser Doppler perfusion imaging; angiogenesis was compared using immunofluorescent CD31 and α-smooth muscle actin staining; macrophage polarization was detected using immunofluorescence for CD68, CD206, and inducible nitric oxide synthase. Hematoxylin and eosin staining was used to examine wound healing at day 14. Activation status of macrophages derived from bone marrow cells in normal, diabetic, and docosahexaenoic acid-treated diabetic rats was determined in vitro using Western blotting and enzyme-linked immunosorbent assay.

RESULTS

Docosahexaenoic acid significantly accelerated wound healing 7 and 14 days (p < 0.01) after wounding. Increased vessel densities (1.96-fold; p < 0.001) and blood perfusion (2.56-fold; p < 0.001) were observed in docosahexaenoic acid-treated wounds. Immunofluorescence revealed more CD206 and fewer inducible nitric oxide synthase-positive macrophages (p < 0.001) in treated wounds. Furthermore, macrophages derived from diabetic rats expressed higher levels of inducible nitric oxide synthase and tumor necrosis factor-α and lower arginase-1 and interleukin-10 (p < 0.05).

CONCLUSION

Docosahexaenoic acid accelerates diabetic wound healing at least in part by restoring impaired plasticity of macrophage progenitor cells.

Neuroinflammation and fibrosis in stroke: The good, the bad and the ugly

Stroke is the leading cause of death and the main cause of disability in surviving patients. The detrimental interaction between immune cells, glial cells, and matrix components in stroke pathology results in persistent inflammation that progresses to fibrosis. A substantial effort is being directed toward understanding the exact neuroinflammatory events that take place as a result of stroke. The initiation of a potent cytokine response, along with immune cell activation and infiltration in the ischemic core, has massive acute deleterious effects, generally exacerbated by comorbid inflammatory conditions. There is secondary neuroinflammation that promotes further injury, resulting in cell death, but conversely plays a beneficial role, by promoting recovery. This highlights the need for a better understanding of the neuroinflammatory and fibrotic processes, as well as the need to identify new mechanisms and potential modulators. In this review, we summarize several aspects of stroke-induced inflammation, fibrosis, and include a discussion of cytokine inhibitors/inducers, immune cells, and fibro-inflammation signaling inhibitors in order to identify new pharmacological means of intervention.

Kv1.3 channel blockade alleviates cerebral ischemia/reperfusion injury by reshaping M1/M2 phenotypes and compromising the activation of NLRP3 inflammasome in microglia

After cerebral ischemia/reperfusion injury, pro-inflammatory M1-like and anti-inflammatory M2-like phenotypes of microglia are involved in neuroinflammation, in which NLRP3 inflammasome plays an essential role. Kv1.3 channel has been recognized as neuro-immunomodulatory target, but it is not clear as to its role in the neuroinflammation after cerebral ischemic injury. The current study aimed to investigate the issue. Middle cerebral artery occlusion/reperfusion (MCAO/R) model in rats and oxygen-glucose deprivation/ reoxygenation (OGD/R) in primary microglia were utilized to mimic disease state of ischemic stroke. Treatment with PAP-1, a Kv1.3 channel blocker, produced a significant improvement in neurological deficit scores and a decrease in infarct volume in MCAO/R model. An increased number of M2-like phenotypic microglia and a reduced number of M1-like phenotypic microglia were observed by immunofluorescent staining in the in vivo model, which was further validated by flow cytometry in vitro. Western blot showed that PAP-1 treatment profoundly reduced cleavage of caspase-1 and IL-1β in vivo and in vitro. Furthermore, PAP-1 administration reduced the number of NLRP3⁺/Iba1⁺ cells and NLRP3 protein levels in vivo, while reduced mRNA and protein expression levels of NLRP3 in vitro. Reduced mRNA expression levels of IL-1β in vitro and protein level of IL-1β in vivo were also observed. Taken together, our findings suggested that Kv1.3 channel blockade effectively alleviated cerebral ischemic injury, possibly by reshaping microglial phenotypic response from M1 towards M2, compromising the activation of NLRP3 inflammasome in microglia, and inhibiting release of IL-1β.

Pentraxin 3: A promising therapeutic target for autoimmune diseases

Pentraxin 3 (PTX3) is a prototypic humoral soluble pattern recognition molecule that exerts a pivotal role in innate immune response and inflammation, as well as in tissue damage and remodeling. Recently, emerging evidence has revealed that PTX3 is involved in the occurrence and development of various autoimmune diseases, such as rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), ankylosing spondylitis (AS), systemic sclerosis (SSc), inflammatory bowel disease (IBD), multiple sclerosis (MS) and psoriasis, etc. In this review, we have succinctly summarized the complex immunological functions of PTX3 and mostly focused on recent findings of the pleiotropic activities played by PTX3 in the pathogenesis of autoimmune diseases, aiming at hopefully offering possible future therapeutic alternatives.