scholarly journals Minocycline promotes posthemorrhagic neurogenesis via M2 microglia polarization via upregulation of the TrkB/BDNF pathway in rats

2018 ◽  
Vol 120 (3) ◽  
pp. 1307-1317 ◽  
Author(s):  
Hongsheng Miao ◽  
Runming Li ◽  
Cong Han ◽  
Xiuzhen Lu ◽  
Hang Zhang
Keyword(s):  
Intracerebral Hemorrhage ◽  
Therapeutic Potential ◽  
Autologous Blood ◽  
Neurological Deficits ◽  
Neuroprotective Effects ◽  
Microglial Polarization ◽  
Arginase 1 ◽  
M2 Microglia ◽  
Microglia Polarization ◽  
Bdnf Pathway

Intracerebral hemorrhage (ICH) is a devastating disease worldwide with increasing mortality. The present study investigated whether minocycline was neuroprotective and induced M2 microglial polarization via upregulation of the TrkB/BDNF pathway after ICH. ICH was induced via injection of autologous blood into 150 Sprague-Dawley rats. A selective TrkB antagonist [N2–2-2-oxoazepan-3-yl amino] carbonyl phenyl benzo (b) thiophene-2-carboxamide (ANA 12)] and agonist [ N-[2-(5-hydroxy-1H-indol-3-yl) ethyl]-2-oxopiperidine-3-carboxamide (HIOC)] were used to investigate the mechanism of minocycline-induced neuroprotection. Minocycline improved ICH-induced neurological deficits and reduced M1 microglia marker protein (CD68, CD16) expression as well as M2 microglial polarization (CD206 and arginase 1 protein). Minocycline administration enhanced microglia-neuron cross talk and promoted the proliferation of neuronal progenitor cells, such as DCX- and Tuj-1-positive cells, 24 h after ICH. Minocycline also increased M2 microglia-derived brain-derived neurotrophic factors (BDNF) and the upstream TrkB pathway. ANA 12 reversed the neuroprotective effects of minocycline. HIOC exhibited the same effects as minocycline and accelerated neurogenesis after ICH. This study demonstrated for the first time that minocycline promoted M2 microglia polarization via upregulation of the TrkB/BDNF pathway and promoted neurogenesis after ICH. This study contributes to our understanding of the therapeutic potential of minocycline in ICH. NEW & NOTEWORTHY The present study gives several novel points: 1) Minocycline promotes neurogenesis after intracerebral hemorrhage in rats. 2) Minocycline induces activated M1 microglia into M2 neurotrophic phenotype. 3) M2 microglia secreting BDNF remodel the damaged neurocircuit.

scholarly journals NDP-MSH binding melanocortin-1 receptor ameliorates neuroinflammation and BBB disruption through CREB/Nr4a1/NF-κB pathway after intracerebral hemorrhage in mice

2019 ◽  
Vol 16 (1) ◽  
Author(s):  
Xuan Wu ◽  
Siming Fu ◽  
Yun Liu ◽  
Hansheng Luo ◽  
Feng Li ◽  
...  
Keyword(s):  
Intracerebral Hemorrhage ◽  
Water Content ◽  
Autologous Blood ◽  
Neurological Deficits ◽  
Secondary Brain Injury ◽  
Brain Water Content ◽  
Protective Mechanisms ◽  
Neuroprotective Effects ◽  
Melanocortin 1 Receptor ◽  
Brain Water

Abstract Background Neuroinflammation and blood-brain barrier (BBB) disruption are two vital mechanisms of secondary brain injury following intracerebral hemorrhage (ICH). Recently, melanocortin-1 receptor (Mc1r) activation by Nle4-D-Phe7-α-MSH (NDP-MSH) was shown to play a neuroprotective role in an experimental autoimmune encephalomyelitis (EAE) mouse model. This study aimed to investigate whether NDP-MSH could alleviate neuroinflammation and BBB disruption after experimental ICH, as well as the potential mechanisms of its neuroprotective roles. Methods Two hundred and eighteen male C57BL/6 mice were subjected to autologous blood-injection ICH model. NDP-MSH, an agonist of Mc1r, was administered intraperitoneally injected at 1 h after ICH insult. To further explore the related protective mechanisms, Mc1r small interfering RNA (Mc1r siRNA) and nuclear receptor subfamily 4 group A member 1 (Nr4a1) siRNA were administered via intracerebroventricular (i.c.v) injection before ICH induction. Neurological test, BBB permeability, brain water content, immunofluorescence staining, and Western blot analysis were implemented. Results The Expression of Mc1r was significantly increased after ICH. Mc1r was mainly expressed in microglia, astrocytes, and endothelial cells following ICH. Treatment with NDP-MSH remarkably improved neurological function and reduced BBB disruption, brain water content, and the number of microglia in the peri-hematoma tissue after ICH. Meanwhile, the administration of NDP-MSH significantly reduced the expression of p-NF-κB p65, IL-1β, TNF-α, and MMP-9 and increased the expression of p-CREB, Nr4a1, ZO-1, occludin, and Lama5. Inversely, the knockdown of Mc1r or Nr4a1 abolished the neuroprotective effects of NDP-MSH. Conclusions Taken together, NDP-MSH binding Mc1r attenuated neuroinflammation and BBB disruption and improved neurological deficits, at least in part through CREB/Nr4a1/NF-κB pathway after ICH.

scholarly journals Berberine exhibits neuroprotective effects through inhibited autophagy and promoted microglial M1 transferred to M2 polarization

2020 ◽  
Author(s):  
Qiang Lei ◽  
Zhiping Hu ◽  
Binbin Yang ◽  
Zheng Jiang ◽  
Fangfang Zhou
Keyword(s):  
Intracerebral Hemorrhage ◽  
Neuroprotective Effect ◽  
Neurological Deficits ◽  
Current Evidence ◽  
Secondary Injury ◽  
Neuroprotective Effects ◽  
Neurological Outcomes ◽  
Microglial Polarization ◽  
The Brain ◽  
M1 Type

Abstract Background: Intracerebral haemorrhage (ICH) induces autophagy excessive activation and microglia mainly switched into proinflammatory M1 type, which can cause severe secondary injury. Current evidence has implied that berberine has a protective effect against ischaemic stroke through mediated autophagy and microglial polarization. However, the neuroprotective effect of berberine in intracerebral hemorrhage (ICH) remains unclear.Method: In this study the effect of berberine on rats model of intracerebral hemorrhage were investigated through Immunofluorescence, qPCR, ELISA, and western blot.Result: Berberine administration significantly reduces neurological deficits and the brain water content via inhibited autophagy, promoted M1 type microglia to M2 type, and subsequently exerts anti-inflammation effects in a rat model of ICH.Conclusion: These results suggest that berberine reduced secondary injury and improved neurological outcomes in ICH model.

scholarly journals Targeting connexin 43 provides anti-inflammatory effects after intracerebral hemorrhage injury by regulating YAP signaling

2020 ◽  
Vol 17 (1) ◽  
Author(s):  
Hailong Yu ◽  
Xiang Cao ◽  
Wei Li ◽  
Pinyi Liu ◽  
Yuanyuan Zhao ◽  
...  
Keyword(s):  
Intracerebral Hemorrhage ◽  
Connexin 43 ◽  
Nuclear Translocation ◽  
Neurological Deficits ◽  
Proximity Ligation Assay ◽  
Neuroprotective Effects ◽  
Cx43 Expression ◽  
Anti Inflammatory

Abstract Background In the central nervous system (CNS), connexin 43 (Cx43) is mainly expressed in astrocytes and regulates astrocytic network homeostasis. Similar to Cx43 overexpression, abnormal excessive opening of Cx43 hemichannels (Cx43Hcs) on reactive astrocytes aggravates the inflammatory response and cell death in CNS pathologies. However, the role of excessive Cx43Hc opening in intracerebral hemorrhage (ICH) injury is not clear. Methods Hemin stimulation in primary cells and collagenase IV injection in C57BL/6J (B6) mice were used as ICH models in vitro and in vivo. After ICH injury, the Cx43 mimetic peptide Gap19 was used for treatment. Ethidium bromide (EtBr) uptake assays were used to measure the opening of Cx43Hcs. Western blotting and immunofluorescence were used to measure protein expression. qRT-PCR and ELISA were used to determine the levels of cytokines. Coimmunoprecipitation (Co-IP) and the Duolink in situ proximity ligation assay (PLA) were applied to measure the association between proteins. Results In this study, Cx43 expression upregulation and excessive Cx43Hc opening was observed in mice after ICH injury. Delayed treatment with Gap19 significantly alleviated hematoma volume and neurological deficits after ICH injury. In addition, Gap19 decreased inflammatory cytokine levels in the tissue surrounding the hematoma and decreased reactive astrogliosis after ICH injury in vitro and in vivo. Intriguingly, Cx43 transcriptional activity and expression in astrocytes were significantly increased after hemin stimulation in culture. However, Gap19 treatment downregulated astrocytic Cx43 expression through the ubiquitin-proteasome pathway without affecting Cx43 transcription. Additionally, our data showed that Gap19 increased Yes-associated protein (YAP) nuclear translocation. This subsequently upregulated SOCS1 and SOCS3 expression and then inhibited the TLR4-NFκB and JAK2-STAT3 pathways in hemin-stimulated astrocytes. Finally, the YAP inhibitor, verteporfin (VP), reversed the anti-inflammatory effect of Gap19 in vitro and almost completely blocked its protective effects in vivo after ICH injury. Conclusions This study provides new insight into potential treatment strategies for ICH injury involving astroglial Cx43 and Cx43Hcs. Suppression of abnormal astroglial Cx43 expression and Cx43Hc opening by Gap19 has anti-inflammatory and neuroprotective effects after ICH injury.

scholarly journals Neurovascular Cell Sheet Transplantation in a Canine Model of Intracranial Hemorrhage

Cell Medicine ◽  
2017 ◽  
Vol 9 (3) ◽  
pp. 73-85
Author(s):  
Woo-Jin Lee ◽  
Jong Young Lee ◽  
Keun-Hwa Jung ◽  
Soon-Tae Lee ◽  
Hyo Yeol Kim ◽  
...  
Keyword(s):  
Intracerebral Hemorrhage ◽  
Cell Transplantation ◽  
Therapeutic Potential ◽  
Autologous Blood ◽  
Cell Sheet ◽  
Neural Tissue ◽  
Direct Regeneration ◽  
Saline Control ◽  
Control Group ◽  
Cell Based Therapy

Cell-based therapy for intracerebral hemorrhage (ICH) has a great therapeutic potential. However, methods to effectively induce direct regeneration of the damaged neural tissue after cell transplantation have not been established, which, if done, would improve the efficacy of cell-based therapy. In this study, we aimed to develop a cell sheet with neurovasculogenic potential and evaluate its usefulness in a canine ICH model. We designed a composite cell sheet made of neural progenitors derived from human olfactory neuroepithelium and vascular progenitors from human adipose tissue-derived stromal cells. We also generated a physiologic canine ICH model by manually injecting and then infusing autologous blood under arterial pressure. We transplanted the sheet cells (cell sheet group) or saline (control group) at the cortex over the hematoma at subacute stages (2 weeks from ICH induction). At 4 weeks from the cell transplantation, cell survival, migration, and differentiation were evaluated. Hemispheric atrophy and neurobehavioral recovery were also compared between the groups. As a result, the cell sheet was rich in extracellular matrices and expressed neurotrophic factors as well as the markers for neuronal development. After transplantation, the cells successfully survived for 4 weeks, and a large portion of those migrated to the perihematomal site and differentiated into neurons and pericytes (20% and 30% of migrated stem cells, respectively). Transplantation of cell sheets alleviated hemorrhage-related hemispheric atrophy ( p = 0.042) and showed tendency for improving functional recovery ( p = 0.062). Therefore, we concluded that the cell sheet transplantation technique might induce direct regeneration of neural tissue and might improve outcomes of intracerebral hemorrhage.

scholarly journals IL (Interleukin)-15 Bridges Astrocyte-Microglia Crosstalk and Exacerbates Brain Injury Following Intracerebral Hemorrhage

Stroke ◽  
2020 ◽  
Vol 51 (3) ◽  
pp. 967-974 ◽  
Author(s):  
Samuel X. Shi ◽  
Yu-Jing Li ◽  
Kaibin Shi ◽  
Kristofer Wood ◽  
Andrew F. Ducruet ◽  
...  
Keyword(s):  
Brain Injury ◽  
Intracerebral Hemorrhage ◽  
Autologous Blood ◽  
Brain Slices ◽  
Neurological Deficits ◽  
Transgenic Mouse Line ◽  
Il Interleukin ◽  
Targeted Expression ◽  
Interleukin 15

Background and Purpose— Microglia are among the first cells to respond to intracerebral hemorrhage (ICH), but the mechanisms that underlie their activity following ICH remain unclear. IL (interleukin)-15 is a proinflammatory cytokine that orchestrates homeostasis and the intensity of the immune response following central nervous system inflammatory events. The goal of this study was to investigate the role of IL-15 in ICH injury. Methods— Using brain slices of patients with ICH, we determined the presence and cellular source of IL-15. A transgenic mouse line with targeted expression of IL-15 in astrocytes was generated to determine the role of astrocytic IL-15 in ICH. The expression of IL-15 was controlled by a glial fibrillary acidic protein promoter (GFAP-IL-15 tg ). ICH was induced by intraparenchymal injection of collagenase or autologous blood. Results— In patients with ICH and wild-type mice subjected to experimental ICH, we found a significant upregulation of IL-15 in astrocytes. In GFAP-IL-15 tg mice, we found that astrocyte-targeted expression of IL-15 exacerbated brain edema and neurological deficits following ICH. This aggravated ICH injury in GFAP-IL-15 tg mice is accompanied by increased microglial accumulation in close proximity to astrocytes in perihematomal tissues. Additionally, microglial expression of CD86, IL-1β, and TNF-α is markedly increased in GFAP-IL-15 tg mice following ICH. Furthermore, depletion of microglia using a colony stimulating factor 1 receptor inhibitor diminishes the exacerbation of ICH injury in GFAP-IL-15 tg mice. Conclusions— Our findings identify IL-15 as a mediator of the crosstalk between astrocytes and microglia that exacerbates brain injury following ICH.

Berberine Protects against Neurological Impairments and Blood-Brain Barrier Injury in Mouse Model of Intracerebral Hemorrhage

2021 ◽  
pp. 1-10
Author(s):  
Xiuwen Wu ◽  
Xiaopeng Liu ◽  
Liang Yang ◽  
Yuanyu Wang
Keyword(s):  
Intracerebral Hemorrhage ◽  
Blood Brain Barrier ◽  
Inflammatory Responses ◽  
Brain Barrier ◽  
Neurological Deficits ◽  
Peroxisome Proliferator ◽  
Intracerebral Injection ◽  
Neuroprotective Effects ◽  
Blood Brain ◽  
Autologous Whole Blood

<b><i>Background:</i></b> Elevation of AMP-activated protein kinase (AMPK)/peroxisome proliferator-activated receptor-γ coactivator-1α (PGC1α) signaling can suppress intracerebral hemorrhage (ICH)-induced neurological impairments. As an isoquinoline alkaloid, Berberine exerts neuroprotective effects in neurological disease models with activated AMPK/PGC1α signaling. <b><i>Aim:</i></b> We aim to study the effect of Berberine on ICH-induced brain injury and explore the potential molecular mechanism. <b><i>Methods:</i></b> ICH model was established in mice through intracerebral injection of autologous whole blood, followed by treatment with Berberine. Neurological impairments were assessed by the modified neurological severity score and behavioral assays. Brain edema and blood-brain barrier (BBB) integrity were assessed by water content in the brain, amount of extravasated Evans blue, and BBB tight junction components. Neuroinflammatory responses were assessed by inflammatory cytokine levels. AMPK/PGC1α signaling was examined by AMPK mRNA expression and phosphorylated AMPK and PGC1α protein levels. <b><i>Results:</i></b> Berberine (200 mg/kg) attenuated ICH-induced neurological deficits, motor and cognitive impairment, and BBB disruption. Berberine also suppressed ICH-induced inflammatory responses indicated by reduced production of inflammatory cytokines. Finally, Berberine drastically elevated AMPK/PGC1α signaling in the hemisphere of ICH mice. <b><i>Conclusion:</i></b> Our findings suggest that Berberine plays an important neuroprotective role against ICH-induced neurological impairments and BBB injury, probably by inhibition of inflammation and activation of AMPK/PGC1α signaling.

Neuregulin-1 Regulates the Conversion of M1/M2 Microglia Phenotype via ErbB4-dependent Inhibition of the NF-κB Pathway

2021 ◽  
Author(s):  
Yuqi Ma ◽  
Peixia Fan ◽  
Rui Zhao ◽  
Yinghua Zhang ◽  
Xianwei Wang ◽  
...  
Keyword(s):  
Inflammatory Factors ◽  
Neuregulin 1 ◽  
Microglial Polarization ◽  
M2 Microglia ◽  
Tnf Α ◽  
Microglia Polarization ◽  
Dependent Inhibition ◽  
The Central Nervous System ◽  
The Relationship

Abstract BackgroundThe inflammatory response caused by microglia in the central nervous system plays an important role in Alzheimer's disease. Neuregulin-1 (NRG1) is a member of the neuregulin family and has been demonstrated to have anti-inflammatory properties. The relationship between NRG1, microglia phenotype and neuroinflammation remains unclear.Materials and MethodsBV2 cells were used to examine the mechanism of NRG1 in regulating microglia polarization. Neuronal apoptosis, inflammatory factors TNF-α and iNOS, microglia polarization, ErbB4 and NF-κB p65 expression were assessed.ResultsWe found that exogenous NRG1 treatment or overexpression improved microglial activity and reduced the secretion of the inflammatory factors TNF-α and iNOS in vitro. The expression of Bax in SH-SY5Y neuron cells incubated with medium collected from the NRG1 treatment group decreased. Additionally, our study showed that NRG1 treatment reduced the levels of the M1 microglia markers CD120 and iNOS and increased the levels of the M2 microglia markers CD206 and Arg-1. Furthermore, we observed that NRG1 treatment attenuated Aβ-induced NF-κB activation and promoted the expression of p-ErbB4 and that knockdown of ErbB4 abrogated the effects of NRG1 on NF-κB, Bax levels and M2 microglial polarization. ConclusionNRG1 inhibits the release of inflammatory factors in microglia and regulates the switching of the M1/M2 microglia phenotype, most likely via ErbB4-dependent inhibition of the NF-κB pathway.

scholarly journals Bexarotene Enhances Macrophage Erythrophagocytosis and Hematoma Clearance in Experimental Intracerebral Hemorrhage

Stroke ◽  
2020 ◽  
Vol 51 (2) ◽  
pp. 612-618 ◽  
Author(s):  
Che-Feng Chang ◽  
Jordan Massey ◽  
Artem Osherov ◽  
Luís Henrique Angenendt da Costa ◽  
Lauren H. Sansing
Keyword(s):  
Intracerebral Hemorrhage ◽  
Functional Recovery ◽  
Autologous Blood ◽  
Neurological Deficits ◽  
Macrophage Phenotype ◽  
Timely Manner ◽  
Collagenase Injection ◽  
Necrosis Factor

Background and Purpose— Enhancement of erythrophagocytosis by macrophages in a timely manner can limit the toxic effects of erythrocyte metabolites and promote brain recovery after intracerebral hemorrhage (ICH). In the current study, we investigated the therapeutic effect of retinoid X receptor agonist, bexarotene, in facilitating erythrophagocytosis and neurobehavioral recovery in 2 mouse models of ICH. Methods— Bone marrow-derived macrophages and fluorescently labeled erythrocytes were used to study erythrophagocytosis in vitro with phenotypic changes quantified by gene expression. ICH was modeled in vivo using intrastriatal autologous blood and collagenase injection in mice with and without bexarotene treatment beginning 3 hours after ICH. In vivo phagocytosis, ability and hematoma clearance were evaluated by erythrophagocytosis assays, flow cytometry, and histological analysis. Neurological deficits and functional recovery were also quantified. Results— Bexarotene increased macrophage expression of phagocytosis receptors and erythrophagocytosis and reduced macrophage TNF (tumor necrosis factor) production in vitro. In vivo, bexarotene treatment enhanced erythrophagocytosis, reduced hematoma volume, and ultimately improved neurological recovery after ICH in 2 distinct models of ICH. Conclusions— Bexarotene administration is beneficial for recovery after ICH by enhancing hemorrhage phagocytosis, modulating macrophage phenotype, and improving functional recovery.

scholarly journals Melatonin reduces neuroinflammation and improves axonal hypomyelination by modulating M1/M2 microglia polarization via JAK2-STAT3-telomerase pathway in postnatal rats exposed to lipopolysaccharide

2021 ◽  
Author(s):  
Qiuping Zhou ◽  
Lanfen Lin ◽  
Haiyan Li ◽  
Shuqi Jiang ◽  
Huifang Wang ◽  
...  
Keyword(s):  
Inflammatory Mediators ◽  
Periventricular White Matter ◽  
Microglial Polarization ◽  
Proinflammatory Mediators ◽  
M2 Microglia ◽  
Microglia Polarization ◽  
M1 Phenotype ◽  
Anti Inflammatory ◽  
Postnatal Rats

Abstract Microglia activation and associated inflammation are implicated in the periventricular white matter damage (PWMD) in septic postnatal rats. This study investigated whether melatonin would mitigate inflammation and alleviate the axonal hypomyelination in the corpus callosum in septic postnatal rats. We further explored if this might be through modulating microglial polarization from M1 phenotype to M2 through JAK2/STAT3/telomerase pathway. We reported here that melatonin, indeed, not only can it reduce the neurobehavioral disturbances in LPS injected rats, but it can also dampen microglia mediated inflammation. Thus, in LPS + melatonin group, expression of proinflammatory mediators in M1 phenotype microglia was downregulated. As opposed to this, M2 microglia were increased which was accompanied by upregulated expression of anti-inflammatory mediators along with TERT or MT1. In parallel to this was decreased NG2 expression but increased expression of myelin and neurofilament proteins. That melatonin can improve hypomyelination was confirmed by electron microscopy. In vitro in primary microglia stimulated by LPS, melatonin decreased the expression of proinflammatory mediators significantly; but it increased expression of anti-inflammatory mediators. Additionally, the expression levels of p-JAK2 and p-STAT3 were significantly elevated in microglia after melatonin treatment. Remarkably, the melatonin effects on LPS treated microglia was blocked by melatonin receptor, JAK2, STAT3 and telomerase reverse transcriptase inhibitors, respectively. Taken together, it is concluded that melatonin can attenuate PWMD through shifting M1 microglia towards M2 via MT1/JAK2/STAT3/telomerase pathway. The results suggest a new therapeutic strategy whereby melatonin may be adopted to convert microglial polarization that would ultimately contribute to attenuation of PWMD.

Abstract 114: CX3CR1-null Microglia Fail to Transition to an M2 Phenotype after Intracerebral Hemorrhage

Stroke ◽  
2015 ◽  
Vol 46 (suppl_1) ◽  
Author(s):  
Roslyn A Taylor ◽  
Matthew D Hammond ◽  
Youxi Ai ◽  
Lauren H Sansing
Keyword(s):  
Gene Expression ◽  
Bone Marrow ◽  
Flow Cytometry ◽  
Intracerebral Hemorrhage ◽  
Microglial Polarization ◽  
Arginase 1 ◽  
The Right ◽  
Bone Marrow Chimeras ◽  
Receptor Cx3cr1 ◽  
M2 Phenotype

Introduction: Intracerebral hemorrhage (ICH) results in the activation of microglia. Microglia can polarize into either a pro-inflammatory (M1), or a reparative (M2) phenotype; the effect of microglial polarization after ICH is unknown. Microglia express the chemokine receptor CX3CR1, which has been shown to regulate microglial neurotoxicity. CX3CR1 +/GFP mice have a functional CX3CR1 and are frequently used to identify microglia. We previously reported that mice with CX3CR1-null microglia do not show functional recovery 14 days after ICH. We hypothesize that 1) microglia transition from M1 to M2 phenotypes in the acute to subacute period after ICH and 2) CX3CR1-null microglia fail to make this transition, inhibiting recovery after ICH. Methods: ICH was modeled by injecting 20ul of WT blood into the right striatum. Microglia were sorted from male CX3CR1 +/GFP mice 0.5, 1, 3, 7, and 14 days after ICH in order to specifically study microglia phenotypes. RNA was extracted and qRT-PCR was performed to analyze changes in gene expression. To study microglial CX3CR1 function, C57BL/6 (WT) and CX3CR1 GFP/GFP (CX3CR1-null) mice were irradiated and reconstituted with WT bone marrow (CD45.1) to generate bone marrow chimeras (CD45.1->WT or CD45.1->CX3CR1-null). Brains were harvested for flow cytometry 14 days after ICH. Results: At 12 hours after ICH, microglia have high IL-6 gene expression (M1). However, M2 markers arginase-1, TGF-β and SOCS3 increase over time (Fig. 1), suggesting microglia transition from M1 to M2 over the first 2 weeks after ICH. By flow cytometry, CX3CR1-null microglia had significantly less SIRPα, a receptor involved in phagocytosis of erythrocytes, and CD206, an M2 marker, than WT microglia 14 days after ICH. Conclusions: Our data show WT microglia transition from an M1 to an M2 phenotype after ICH. Our results also suggest microglial CX3CR1 is necessary for transition toward an M2 phenotype after ICH and this transition is required for recovery after ICH.

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