Selective modulation of microglia polarization to M2 phenotype for stroke treatment

INTIMP-03564; No of Pages 6 International Immunopharmacology xxx (2015) xxx–xxx

Contents lists available at ScienceDirect

International Immunopharmacology journal homepage: www.elsevier.com/locate/intimp

Review

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Selective modulation of microglia polarization to M2 phenotype for stroke treatment

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Cong-Yuan Xia a, Shuai Zhang a, Yan Gao a, Zhen-Zhen Wang a, Nai-Hong Chen a,b,⁎

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Article history: Received 21 October 2014 Received in revised form 28 January 2015 Accepted 11 February 2015 Available online xxxx

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Keywords: Stroke Ischemia Microglia M1 phenotype M2 phenotype

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Contents

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Neuroprotective effect of M2-polarized microglia in cerebral ischemia . . . . . . . 2.1. M2 phenotype facilitates phagocytosis of debris induced by cerebral ischemia 2.2. M2 phenotype promotes tissue repair . . . . . . . . . . . . . . . . . . 3. Response of microglia after cerebral ischemia . . . . . . . . . . . . . . . . . . 4. Mechanism of microglial phenotype transition. . . . . . . . . . . . . . . . . . 4.1. NF-κB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2. CREB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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1. Introduction

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Ischemic stroke is the third leading cause of death and disability worldwide. The only effective treatment for ischemic stroke is the intravenous administration of tissue plasminogen activator (tPA), which benefits only patients who accept the treatment within a narrow time window after the stroke. There is no safe and effective therapy for patients who have missed the acute phase of the stroke, resulting in functional disability in surviving patients [1,2]. Recent studies indicate that motor neuron death and suppression of hippocampal neurogenesis

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Resident microglia are the major immune cells in the brain, acting as the first defense of the central nervous system. Following cerebral ischemia, microglia respond to this injury at first and transform from surveying microglia to active state. The activated microglia play a dual role in the ischemic injury, due to distinct microglia phenotypes, including deleterious M1 and neuroprotective M2. However, microglia show transient M2 phenotype followed by a shift to M1. The high ratio of M1 to M2 is significantly related to ischemic injury. Many signal pathways participate in the alternation of microglial phenotype, presenting potential therapeutic targets for selectively modulating M2 polarization of microglia. In this review, we discuss how the M2 phenotype mediates neuroprotective effects and summarize the alternation of signaling cascades that control microglial phenotype after ischemic stroke. © 2015 Published by Elsevier B.V.

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State Key Laboratory of Bioactive Substances and Functions of Natural Medicines, Institute of Materia Medica, Neuroscience Center, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100050, China b Hunan University of Chinese Medicine, Changsha 410208, China

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⁎ Corresponding author at: Nai-Hong Chen, Beijing, China. Tel./fax: +86 10 63165177. E-mail address: [email protected] (N.-H. Chen).

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induced by activated microglia contribute to motor and cognitive dysfunction in amyotrophic lateral sclerosis (ALS), aging, and dementia [3,4]. However, administration of exogenous microglia after ischemia improves ischemia-induced learning impairment [5]. Additionally, microglia have been proved to participate in neurogenesis after a stroke [6]. Thus, modulation of endogenous microglia may be beneficial for functional recovery, presenting a target for cerebral ischemia therapy. Microglia, the brain-resident macrophages, are the major immune cells in ischemic injury [7,8]. Under physiological conditions, microglia are characterized by ramified morphology and high motility, which make it convenient to monitor the microenvironment, prune synapse and timely clear apoptotic neurons to maintain the homeostasis of the central nervous system (CNS) [9–11]. Neuron injury induced by

http://dx.doi.org/10.1016/j.intimp.2015.02.019 1567-5769/© 2015 Published by Elsevier B.V.

Please cite this article as: Xia C-Y, et al, Selective modulation of microglia polarization to M2 phenotype for stroke treatment, Int Immunopharmacol (2015), http://dx.doi.org/10.1016/j.intimp.2015.02.019

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2.1. M2 phenotype facilitates phagocytosis of debris induced by cerebral ischemia

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Clearance of apoptotic and necrotic cells by microglia is particularly important to maintain homeostasis of CNS under pathological conditions. Removal of damaged neurons can not only prevent secondary inflammatory reaction, but also make space for newborn neurons and reconstruct homeostasis benefiting the survival of newborn neurons. The best “eat-me” signal from neurons is phosphatidylserine (PS) exteriorization. Recognition of PS is equipped with an array of receptors, as shown in Table 2 [18–21]. Though M1 and M2 express these receptors, the M2 phenotype may exhibit a stronger phagocytic capacity for those dead neurons. For example, M2 microglia exhibit an elongated shape and higher level of F-actin compared with M1 cells, which promotes phagosome formation thereby elevating the capacity of phagocytosis [22,23]. However, recent studies suggest that microglia-mediated “phagoptosis” executes neuron loss as a result of phagocytosis of viable neurons after cerebral ischemia. MFG-E8 deficiency strongly inhibits phagocytic activity, reducing motor deficits and brain atrophy. [24,25]. The phagocytosis of viable neurons can be explained as follows: 1) PS

Table 1 Molecules and their roles [13–15,29,31–34,40–42,55].

associated

with

specific

microglia

t1:4

Phenotype Molecule

Role

t1:5 t1:6

M1

Pro-inflammatory, induce M1 phenotype Pro-inflammatory

t1:7 t1:8 t1:9 t1:10

t2:3

PS PS, Ox-PS PS, Ox-PS PS PS PS PS PS PS PS, Ox-PS PS PS Ox-PS

t2:4 t2:5 t2:6 t2:7 t2:8 t2:9 t2:10 t2:11 t2:12 t2:13 t2:14 t2:15 t2:16

PS, phosphatidylserine; Mer-TK, Mer tyrosine kinase; MFG-E8, milk fat globule-epidermal growth factor; Del-1, Developmental endothelial cell locus-1; β2-GPI, β2-glycoprotein I; BAI-1, brain angiogenesis inhibitor 1; TIM, T-cell-immunoglobulin-mucin; RAGE, receptor for advanced glycation endproducts; Ox-PS, oxidized phosphatidylserine.

M2

phenotype

IFN-γ IL-1β, IL-6, TNF-α ROS, iNOS CD11b, CD16, CD32 IL-4 IL-10

t1:11

TGF-β

t1:12 t1:13 t1:14 t1:15

YM1, Arg-1, IGF-1, FIZZ1 HO-1 CD206

Oxidative damage Phagocytosis, chemotaxis Anti-inflammatory, induce M2 phenotype Anti-inflammatory, inhibit the activity of Caspase-3, up-regulate the level of GSH and NGF Anti-inflammatory, regeneration, up-regulate the level of Bcl-2 and Bcl-x1 Repair and regeneration Anti-oxidation Antigen internalization and processing

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exteriorization, 2) PS recognition. Cerebral ischemia induced oxidative stress has been reported to promote the externalization of PS. Further, oxidation modification of PS makes it easier to be recognized by MFGE8 [24,26,27]. Thus, M1 microglia possessing a high level of reactive oxygen species (ROS) may contribute to neuron loss through increasing the phagocytosis of viable neurons (Table 1, Fig. 2) [11,18,24,28]. Conversely, the M2 phenotype triggers a series of anti-oxidative responses including suppressing post-ischemic level of ROS, and up-regulating Glutathione-SH (GSH) and Heme Oxygenase-1 (HO-1) levels (Table 1) [29–31]. Furthermore, M2-polarized microglia promote the survival of neurons under hypoxic conditions [15]. IL-10 provides a negative feedback in the production of pro-inflammatory mediators (IL-1β, IL-6 and TNF-α) and up-regulates the expression of nerve growth factor (NGF) and GSH, which reduce neuron death by suppressing the activity of Caspase-3 (Table 1) [29,32]. In addition, TGF-β1 mediates a direct neuroprotective function on neuronal survival based on their regulation on the expression of anti-apoptotic proteins, such as Bcl-2, Bcl-x1 (Table 1) [33,34]. Collectively, M1 microglia-mediated phagocytosis may result in neuron loss, while M2 microglia may efficiently clear debris as well as promote neuron survival, decreasing ischemic damage (Fig. 1).

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2.2. M2 phenotype promotes tissue repair

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Neuron stem cells are the potential source for brain self-repair after ischemic injury [35–37]. The survival of newborn neurons is influenced by the microenvironment. Lipopolysaccharide-induced inflammation increases microglia activation, which strongly impairs hippocampal neurogenesis in the intact and insulted brain. In addition, activation of microglia contributes to the aberrant migration of newborn neurons. The detrimental effects of activated microglia on neurogenesis may be mediated by an array of molecules, including IL-1β, IL-6, TNF-α, interferon-gamma (IFN-γ), nitric oxide (NO), and ROS. Administration of minocycline restores impaired neurogenesis by selectively ablating the function of M1-polarized microglia [4,16,17,38,39]. Conversely, activated microglia may also play a beneficial role in the regulation of neurogenesis through the production of neurotrophic mediators, such as IGF-1 and TGF-β (Table 1) [40,41]. Other markers used for identifying M2 microglia, such as Ym1 and Arg-1, prevent the degradation of extracellular matrix components (Table 1) [42]. Furthermore, microglial activation can also promote regeneration by removing disabled synapses thereby benefiting the formation of functional synapses [9,43–45]. Increasing the proportion of the M2 phenotype may reverse the neuron loss and repair neural networks, representing a therapeutic approach to prevent stroke-related functional disorders. In view of the protective function of the M2 phenotype, numerous researches have focused on the M2-polarized microglia for the treatment of cerebral ischemia. IL-4 is mostly used to induce the M2

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Ligand

Gas6, Protein S MFG-E8 MFG-E8 Del-1 β2-GPI

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75

Bridge molecule

Mer-TK Vitronectin αv Integrin αv Integrin β2-GPI receptor BAI-1 TIM-1 TIM-4 Stabilin-1 Stabilin-2 RAGE Annexins CD36

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2. Neuroprotective effect of M2-polarized microglia in cerebral ischemia

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Receptor

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71 72

t2:1 t2:2

Table 2 Summary of PS receptors involved in phagocytosis.

P

90 91

cerebral ischemia contributes to microglial activation by increasing the levels of ATP, heat shock proteins 60 (HSP60) and glutamate [12]. Microglia are de-ramified after activation and rapidly change their phenotype, mediating neuroprotective or inevitable detrimental effects. As shown in Table 1, two phenotypes have been used to identify activated microglia. M1 represents a detrimental state of microglia, characterized by high expression of pro-inflammatory mediators including interleukin-1 beta (IL-1β), interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-α), propelling the pathological process of cerebral ischemia. Conversely, the M2 phenotype prolongs neuron survival and restricts brain damage after ischemic injury associated with high levels of arginase-1 (Arg-1), interleukin-10 (IL-10), transforming growth factor beta (TGF-β) and insulin-like growth factor-1 (IGF-1) (Table 1) [13,14]. However, activated microglia show the transient M2 phenotype followed by a shift to the detrimental M1 phenotype after cerebral ischemia [15]. A selective inhibition of M1 microglia by minocycline can obviously ameliorate ischemic damage by decreasing inflammatory response [16,17]. Therefore, selectively increasing M2 polarization of microglial cells may be a potential strategy of stroke treatment. Thus, we make a review about the neuroprotective effects of the M2 phenotype, the process and the possible mechanisms of microglial polarization after cerebral ischemia.

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Fig. 1. Engulfment of apoptotic neurons. Cerebral ischemia induces neuronal apoptosis. The apoptotic neurons begin to express PS on their surfaces, which are recognized by microglial surface receptors. Oxidation modification of PS makes it easier to be recognized by PS receptor. Thus, M1 microglia possessing high level of ROS increase the phagocytosis of viable neurons, resulting in neuron loss. In contrast, M2 microglia produce anti-oxidation factors HO-1 and GSH, which may inhibit the recognition of viable neurons, promoting viable neurons repair.

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3. Response of microglia after cerebral ischemia

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After cerebral ischemia, microglia display various changes over time, including morphology, phenotype and productions. Ischemia-induced dying neurons release ATP, activating microglia through P2 receptors. Correspondingly, the expression of P2X4 and P2X7 receptors on microglia are increased significantly after ischemia [49,50]. Activated microglia are accumulated in the injury region. Many factors participate in the migration of microglia towards the injury site and ATP is one of the important mediators [13]. Extracellular ATP induces the release of endogenous ATP from microglia, attracting distant microglia to the injury site. The generation of endogenous ATP is mediated by lysosomal exocytosis, which is a Ca2 +-dependent response. In return, Ca2 + waves guide microglial migration in an ATP-dependent manner [51, 52]. After activation, microglia show a series of morphologic changes including ramified, primed, reactive, and amoeboid morphology [53]. In the border of infarct areas, microglia exhibit different morphology, while microglia mainly show de-ramified morphology in the ischemic core [54]. Similarly, microglia exhibit dynamic polarization over time, transforming from transient M2 phenotype to detrimental M1 phenotype [15]. In the acute phase, Ym1, an M2 phenotype marker, is highly

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phenotype [11]. However, M2-polarized macrophages induced by IL-4 cannot attenuate the functional outcome and lesion size caused by cerebral ischemia. Many factors influence the results, such as administration dose, ways of administration, and final fate of cells following injection [46]. Most importantly, the M2 phenotype of microglia is a result of the interaction of multi-signal cascades, while IL-4 is one aspect of the signal network [47,48]. Therefore, it is necessary to understand the mechanism of microglia polarization after cerebral ischemia.

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up-regulated in the border zone, which induces M2-type responses providing protective functions for injured brain. Interestingly, none of microglia exerts a phagocytic action engulfing neurons at 24 h after permanent ischemia. On the 7th day, a few microglia execute phagocytic function [55,56]. These data indicate that activated microglia tend to protect neurons at first after cerebral ischemia (Fig. 2). However, the mRNA expression of M2 phenotype markers (CD206, Arg-1, Ym1/2, IL-10, and TGF-β) are decreased at 7 days post-ischemic injury, M1 phenotype genes (iNOS, CD11b, CD16, CD32) remain elevated at 14 days after ischemia [15]. Moreover, microglia are susceptible to ischemiainduced injury, which may be related to P2X4 and P2X7, resulting in decreased number and suppressed activity of microglia in the ischemic core [57–59]. Thus, a low level of microglia in the ischemic area and a high ratio of M1/M2 in the peri-infarct area may promote the progress of ischemic injury.

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Ischemia changes the microenvironment of microglia and activate microglia. Current studies emphasize that crosstalk of intracellular signal regulations determine the state of microglia [12,60,61]. In the following sections, we discuss the networks and alternation of transcription factors associated with ischemia-induced polarization of microglia, as shown in Table 3.

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Ample evidence suggests that nuclear factor-κB (NF-κB) signal 209 cascade plays a detrimental role in cerebral ischemia owing to its 210 function in the regulation of pro-inflammatory mediators, including 211

Please cite this article as: Xia C-Y, et al, Selective modulation of microglia polarization to M2 phenotype for stroke treatment, Int Immunopharmacol (2015), http://dx.doi.org/10.1016/j.intimp.2015.02.019

C.-Y. Xia et al. / International Immunopharmacology xxx (2015) xxx–xxx

Fig. 2. Pathways participating in microglia response after cerebral ischemia. After cerebral ischemia, microglia present a transient M2 phenotype followed by a transition to the M1 phenotype. NF-κB and CREB compete for the same co-activators (C/EBP, CBP/p300) polarizing microglia into M1 and M2, respectively, wherein PI3K-Akt decreases nuclear amounts of NF-κB and increases CREB level by inhibiting the activity of GSK-3β. Moreover, STAT1, STAT3 and Notch pathway positively affect the activity of NF-κB, whereas the activity of NF-κB is reduced by STAT6. Increasing NF-κB activity can inhibit the expression of PPARγ, limiting M2 phenotype specific gene expression.

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4.2. CREB

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t3:1 t3:2

Table 3 Alternation of signaling pathways related to microglia phenotype after cerebral ischemia.

In contrast to the function of NF-κB signaling, cAMP-responsive element-binding protein (CREB) cooperates with C/EBPβ and amplifies the expression of M2-specific gene, such as IL-10 and Arg-1, promoting tissue repair [84]. Confounding the idea, the expression of M1 phenotype genes encoding inflammatory molecules is also regulated by C/EBPβ [85]. The dual role of C/EBPβ in the regulation of M1 and M2 phenotypes may result from the competition between CREB and NF-κB for binding C/EBP [84,86]. Another competition site of NF-κB and CREB is CREB-binding protein (CBP). Increased activity of CREB suppresses the association of CBP and NF-κB [87]. In response

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Other transcription factors may participate in regulating polarization of microglia/macrophage by influencing the activity of NF-κB. In response to LPS, activated Notch signaling elevates the production of IFN-γ through co-recruitment of p50 and c-Rel [71–74]. Notch signaling exacerbates ischemic brain damage by protracting NF-κB activation companied by sustaining inflammation and enhancing neurotoxicity induced by microglia [71,75]. Crosstalk of Notch and NF-κB inhibit the expression of peroxisome proliferator-activated receptor-γ (PPARγ) that is essential to induce M2 phenotype, leading to the decreased expression of PPARγ after stroke [76–78]. Signal transducer and activator of transcriptions (STAT1 and STAT3) elevate the expression of NF-κB/p65 [79]. Suppressing activation of STAT1 and STAT3 preclude inflammatory response induced by cerebral ischemia, ameliorating infarct and edema volume [80–82]. STAT6−/− mice subjected to endotoxin present amplified production of pro-inflammatory mediators as a result of enhanced activation of NF-κB [83].

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IL-1, IL-2, IL-6, IL-12, TNF-α, inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2) [62,63]. In addition, NF-κB regulates the expression and activation of matrix metalloproteinases (MMPs), leading to blood–brain barrier (BBB) leakage and augmented inflammation [64–66]. MMPs also facilitate proteolysis of progranulin (PGRN), inducing lysosomal storage in microglia [67,68]. In contrast, PGRN treatment attenuates neuronal injury induced by cerebral ischemia reperfusion via the reduction of NF-κB and MMP-9 activation [69], whereas more evidences suggest that NF-κB signaling plays a dual role in inflammation [63]. The Rel family members of NF-κB, including RelA (p65), RelB and c-Rel, are able to translocate into nuclei. Unlikely, NF-κB p50 and NF-κB p52 lack transcriptional domain. NF-κB p50 homodimers increase M2-polarized microglia mediators including Arg-1, Ym1, and Found in the inflammatory zone 1 (Fizz1), suppress STAT1 activity and M1 gene transcription [70]. These data indicate that transcriptional activity of NF-κB is essential for NF-κB signaling to participate in modifying the detrimental M1 phenotype.

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Phenotype

Signaling

Activity after ischemia

Reference

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M1

Notch STAT1, STAT3 GSK-3β NF-κB PPARγ STAT6 CREB

↑ ↑ ↑ ↑ ↓ ↓ ↓

[75,95] [79,81,96–98] [87,93,94] [63] [77,78] [60,98,99] [84,92]

M2

Please cite this article as: Xia C-Y, et al, Selective modulation of microglia polarization to M2 phenotype for stroke treatment, Int Immunopharmacol (2015), http://dx.doi.org/10.1016/j.intimp.2015.02.019

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Acknowledgments

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This work was supported by National Natural Science Foundation of China (No. 81274122, No. 81173578, No. 81102831, No. 81373997), National Key Sci-Tech Major Special Item (No. 2012ZX09301002-004, No. 2012ZX09103101-006), National 863 Program of China (No. 2012AA020303), Beijing Natural Science Foundation (No. 7131013), and Research Fund for the Doctoral Program of Higher Education of China (No. 20121106130001).

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References

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[1] Shichita T, Ago T, Kamouchi M, Kitazono T, Yoshimura A, Ooboshi H. Novel therapeutic strategies targeting innate immune responses and early inflammation after stroke. J Neurochem 2012;123(Suppl. 2):29–38. [2] Sughrue ME, Mehra A, Connolly Jr ES, D'Ambrosio AL. Anti-adhesion molecule strategies as potential neuroprotective agents in cerebral ischemia: a critical review of the literature. Inflamm Res 2004;53:497–508. [3] Frakes AE, Ferraiuolo L, Haidet-Phillips AM, Schmelzer L, Braun L, Miranda CJ, et al. Microglia induce motor neuron death via the classical NF-kappaB pathway in amyotrophic lateral sclerosis. Neuron 2014;81:1009–23. [4] Ekdahl CT, Claasen JH, Bonde S, Kokaia Z, Lindvall O. Inflammation is detrimental for neurogenesis in adult brain. Proc Natl Acad Sci U S A 2003;100:13632–7. [5] Imai F, Suzuki H, Oda J, Ninomiya T, Ono K, Sano H, et al. Neuroprotective effect of exogenous microglia in global brain ischemia. J Cereb Blood Flow Metab 2007;27: 488–500. [6] Ekdahl CT, Kokaia Z, Lindvall O. Brain inflammation and adult neurogenesis: the dual role of microglia. Neuroscience 2009;158:1021–9. [7] Jin R, Yang G, Li G. Inflammatory mechanisms in ischemic stroke: role of inflammatory cells. J Leukoc Biol 2010;87:779–89. [8] Prinz M, Priller J. Microglia and brain macrophages in the molecular age: from origin to neuropsychiatric disease. Nat Rev Neurosci 2014;15:300–12. [9] Kettenmann H, Kirchhoff F, Verkhratsky A. Microglia: new roles for the synaptic stripper. Neuron 2013;77:10–8. [10] Fetler L, Amigorena S. Neuroscience. Brain under surveillance: the microglia patrol. Science 2005;309:392–3.

283 284 285 286

292 293 294 295

C

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279 280

R

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272 273

N C O

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U

268 269

F

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266 267

O

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Microglia act as the first line of defense in the brain, play an irreplaceable role in maintaining brain homeostasis. In response to microenvironmental changes, microglia show dynamic phenotypes, shifting from M2 phenotype to M1 phenotype after cerebral ischemia, which may contribute to the pathology process of ischemic stroke. Compared with the M1 phenotype, the M2 phenotype has a stronger capacity to elicit phagocytosis of dead neurons to avoid secondary inflammatory response and promote tissue regeneration. This brings us to the idea that M2-polarized microglia present a therapeutic target of ischemic stroke. Based on the crosstalk of signaling cascades that control microglial phenotype, a selective activation of M2 microglia by increasing the ratio of transcriptional action of CREB versus NF-κB will be a major challenge in the future treatment of stroke.

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276

263

P

5. Conclusion

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[11] Boche D, Perry VH, Nicoll JA. Review: activation patterns of microglia and their identification in the human brain. Neuropathol Appl Neurobiol 2013;39:3–18. [12] Yenari MA, Kauppinen TM, Swanson RA. Microglial activation in stroke: therapeutic targets. Neurotherapeutics 2010;7:378–91. [13] Patel AR, Ritzel R, McCullough LD, Liu F. Microglia and ischemic stroke: a doubleedged sword. Int J Physiol Pathophysiol Pharmacol 2013;5:73–90. [14] Olah M, KB, Vinet J, Boddeke HWGM. Microglia phenotype diversity. CNS Neurol Disord Drug Targets 2011;10:108–18. [15] Hu Xiaoming, PL, Guo Yanling, Wang Haiying, Leak Rehana K, Chen Songela, et al. Microglia/macrophage polarization dynamics reveal novel mechanism of injury expansion after focal cerebral ischemia. Stroke 2012. [16] Liu Z, Fan Y, Won SJ, Neumann M, Hu D, Zhou L, et al. Chronic treatment with minocycline preserves adult new neurons and reduces functional impairment after focal cerebral ischemia. Stroke 2007;38:146–52. [17] Kobayashi K, Imagama S, Ohgomori T, Hirano K, Uchimura K, Sakamoto K, et al. Minocycline selectively inhibits M1 polarization of microglia. Cell Death Dis 2013; 4:e525. [18] Sierra A, Abiega O, Shahraz A, Neumann H. Janus-faced microglia: beneficial and detrimental consequences of microglial phagocytosis. Front Cell Neurosci 2013;7:6. [19] Erwig LP, Henson PM. Clearance of apoptotic cells by phagocytes. Cell Death Differ 2008;15:243–50. [20] Taylor PR, Martinez-Pomares L, Stacey M, Lin HH, Brown GD, Gordon S. Macrophage receptors and immune recognition. Annu Rev Immunol 2005;23:901–44. [21] Bratton DL, Henson PM. Apoptotic cell recognition: will the real phosphatidylserine receptor(s) please stand up? Curr Biol 2008;18:R76–9. [22] McWhorter FY, Wang T, Nguyen P, Chung T, Liu WF. Modulation of macrophage phenotype by cell shape. Proc Natl Acad Sci U S A 2013;110:17253–8. [23] Aderem A, Underhill DM. Mechanisms of phagocytosis in macrophages. Annu Rev Immunol 1999;17:593–623. [24] Brown GC, Neher JJ. Microglial phagocytosis of live neurons. Nat Rev Neurosci 2014; 15:209–16. [25] Neher JJ, Emmrich JV, Fricker M, Mander PK, Thery C, Brown GC. Phagocytosis executes delayed neuronal death after focal brain ischemia. Proc Natl Acad Sci U S A 2013;110:E4098–107. [26] Arroyo A, Modriansky M, Serinkan FB, Bello RI, Matsura T, Jiang J, et al. NADPH oxidase-dependent oxidation and externalization of phosphatidylserine during apoptosis in Me2SO-differentiated HL-60 cells. Role in phagocytic clearance. J Biol Chem 2002;277:49965–75. [27] Wu Y, Tibrewal N, Birge RB. Phosphatidylserine recognition by phagocytes: a view to a kill. Trends Cell Biol 2006;16:189–97. [28] Biber K, Owens T, Boddeke E. What is microglia neurotoxicity (not)? Glia 2014;62: 841–54. [29] de Bilbao F, Arsenijevic D, Moll T, Garcia-Gabay I, Vallet P, Langhans W, et al. In vivo over-expression of interleukin-10 increases resistance to focal brain ischemia in mice. J Neurochem 2009;110:12–22. [30] Schaer CA, Schoedon G, Imhof A, Kurrer MO, Schaer DJ. Constitutive endocytosis of CD163 mediates hemoglobin-heme uptake and determines the noninflammatory and protective transcriptional response of macrophages to hemoglobin. Circ Res 2006;99:943–50. [31] Choi KM, Kashyap PC, Dutta N, Stoltz GJ, Ordog T, Shea Donohue T, et al. CD206positive M2 macrophages that express heme oxygenase-1 protect against diabetic gastroparesis in mice. Gastroenterology 2010;138:2399–409 [409 e1]. [32] Protti GG, Gagliardi RJ, Forte WC, Sprovieri SR. Interleukin-10 may protect against progressing injury during the acute phase of ischemic stroke. Arq Neuropsiquiatr 2013;71:846–51. [33] Pal G, Vincze C, Renner E, Wappler EA, Nagy Z, Lovas G, et al. Time course, distribution and cell types of induction of transforming growth factor betas following middle cerebral artery occlusion in the rat brain. PLoS One 2012;7:e46731. [34] Dhandapani KM, Brann DW. Transforming growth factor-beta: a neuroprotective factor in cerebral ischemia. Cell Biochem Biophys 2003;39:13–22. [35] McKay R. Stem cells in the central nervous system. Science 1997;276:66–71. [36] Dong J, Liu B, Song L, Lu L, Xu H, Gu Y. Neural stem cells in the ischemic and injured brain: endogenous and transplanted. Cell Tissue Bank 2012;13:623–9. [37] Jin K, Minami M, Lan JQ, Mao XO, Batteur S, Simon RP, et al. Neurogenesis in dentate subgranular zone and rostral subventricular zone after focal cerebral ischemia in the rat. Proc Natl Acad Sci U S A 2001;98:4710–5. [38] Zhou J, Cheng G, Kong R, Gao DK, Zhang X. The selective ablation of inflammation in an acute stage of ischemic stroke may be a new strategy to promote neurogenesis. Med Hypotheses 2011;76:1–3. [39] Luo XG, Chen SD. The changing phenotype of microglia from homeostasis to disease. Transl Neurodegener 2012;1:9. [40] Zhang J, Li Y, Chen J, Yang M, Katakowski M, Lu M, et al. Expression of insulin-like growth factor 1 and receptor in ischemic rats treated with human marrow stromal cells. Brain Res 2004;1030:19–27. [41] Battista D, Ferrari CC, Gage FH, Pitossi FJ. Neurogenic niche modulation by activated microglia: transforming growth factor beta increases neurogenesis in the adult dentate gyrus. Eur J Neurosci 2006;23:83–93. [42] Cherry JD, Olschowka JA, O'Banion MK. Neuroinflammation and M2 microglia: the good, the bad, and the inflamed. J Neuroinflammation 2014;11:98. [43] Neumann H, Kotter MR, Franklin RJ. Debris clearance by microglia: an essential link between degeneration and regeneration. Brain 2009;132:288–95. [44] Trapp BD, Wujek JR, Criste GA, Jalabi W, Yin X, Kidd GJ, et al. Evidence for synaptic stripping by cortical microglia. Glia 2007;55:360–8. [45] Cullheim S, Thams S. The microglial networks of the brain and their role in neuronal network plasticity after lesion. Brain Res Rev 2007;55:89–96.

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to activation of TLRs, PI3K/Akt initiates the phosphorylation of interferon regulatory factor-3 (IRF-3). Activated IRF-3 translocates into nuclei, where it interacts with CBP to drive the M2 phenotype [88–90]. Currently, the relationship between IRF-3 and CREB is not clear and further studies are needed. At the same time, the transcriptional activation domain (TAD) of NF-κB RelA can also bind to CBP/p300 to form RelA/CBP/p300 complex, which is involved in NF-κB transcriptional process [91]. Thus, CREB competes with NF-κB for the same coactivators, including C/EBP and CBP, regulating M2 and M1 responses respectively (Fig. 2). However, the balance of NF-κB and CREB is significantly impaired after cerebral ischemia with down-regulated level of p-CREB and increased activity of NF-κB [63,92]. Accordingly, cerebral ischemia induces dephosphorylation and activation of Glycogen synthase kinase-3β (GSK-3β), which diminish CREB activity while potentiating capacity of NF-κB to initiate pro-inflammation [87,93,94]. Collectively, the balance of transcriptional action of NFκB and CREB play a crucial role in the polarization of microglia after cerebral ischemia.

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[80]

[81]

[82]

[83]

[84]

[85]

[86]

C

E

R

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O

C

N

F

[79]

O

[78]

R O

[77]

P

[76]

nuclear factor-kappaB-Bcl-2-interacting mediator of cell death pathway in ischemic stroke. Mol Pharmacol 2011;80:23–31. Wei Z, Chigurupati S, Arumugam TV, Jo DG, Li H, Chan SL. Notch activation enhances the microglia-mediated inflammatory response associated with focal cerebral ischemia. Stroke 2011;42:2589–94. Maniati E, Bossard M, Cook N, Candido JB, Emami-Shahri N, Nedospasov SA, et al. Crosstalk between the canonical NF-kappaB and Notch signaling pathways inhibits Ppargamma expression and promotes pancreatic cancer progression in mice. J Clin Invest 2011;121:4685–99. Herwig MC, Bergstrom C, Wells JR, Holler T, Grossniklaus HE. M2/M1 ratio of tumor associated macrophages and PPAR-gamma expression in uveal melanomas with class 1 and class 2 molecular profiles. Exp Eye Res 2013;107:52–8. Zhao Y, Patzer A, Herdegen T, Gohlke P, Culman J. Activation of cerebral peroxisome proliferator-activated receptors gamma promotes neuroprotection by attenuation of neuronal cyclooxygenase-2 overexpression after focal cerebral ischemia in rats. FASEB J 2006;20:1162–75. Qin H, Holdbrooks AT, Liu Y, Reynolds SL, Yanagisawa LL, Benveniste EN. SOCS3 deficiency promotes M1 macrophage polarization and inflammation. J Immunol 2012; 189:3439–48. Yi JH, Park SW, Kapadia R, Vemuganti R. Role of transcription factors in mediating post-ischemic cerebral inflammation and brain damage. Neurochem Int 2007;50: 1014–27. Cai F, Li CR, Wu JL, Chen JG, Liu C, Min Q, et al. Theaflavin ameliorates cerebral ischemia-reperfusion injury in rats through its anti-inflammatory effect and modulation of STAT-1. Mediat Inflamm 2006;2006:30490. Lai CS, Lee JH, Ho CT, Liu CB, Wang JM, Wang YJ, et al. Rosmanol potently inhibits lipopolysaccharide-induced iNOS and COX-2 expression through downregulating MAPK, NF-kappaB, STAT3 and C/EBP signaling pathways. J Agric Food Chem 2009; 57:10990–8. Lentsch AB, Kato A, Davis B, Wang W, Chao C, Edwards MJ. STAT4 and STAT6 regulate systemic inflammation and protect against lethal endotoxemia. J Clin Investig 2001;108:1475–82. Ruffell D, Mourkioti F, Gambardella A, Kirstetter P, Lopez RG, Rosenthal N, et al. A CREB-C/EBPbeta cascade induces M2 macrophage-specific gene expression and promotes muscle injury repair. Proc Natl Acad Sci U S A 2009;106:17475–80. Gorgoni B, Maritano D, Marthyn P, Righi M, Poli V. C/EBP gene inactivation causes both impaired and enhanced gene expression and inverse regulation of IL-12 p40 and p35 mRNAs in macrophages. J Immunol 2002;168:4055–62. Stein B, Cogswell PC, Baldwin Jr AS. Functional and physical associations between NF-kappa B and C/EBP family members: a Rel domain-bZIP interaction. Mol Cell Biol 1993;13:3964–74. Martin M, Rehani K, Jope RS, Michalek SM. Toll-like receptor-mediated cytokine production is differentially regulated by glycogen synthase kinase 3. Nat Immunol 2005;6:777–84. Gunthner R, Anders HJ. Interferon-regulatory factors determine macrophage phenotype polarization. Mediat Inflamm 2013;2013:731023. Qin BY, Liu C, Srinath H, Lam SS, Correia JJ, Derynck R, et al. Crystal structure of IRF-3 in complex with CBP. Structure 2005;13:1269–77. Panne D, McWhirter SM, Maniatis T, Harrison SC. Interferon regulatory factor 3 is regulated by a dual phosphorylation-dependent switch. J Biol Chem 2007;282: 22816–22. Mukherjee SP, Behar M, Birnbaum HA, Hoffmann A, Wright PE, Ghosh G. Analysis of the RelA:CBP/p300 interaction reveals its involvement in NF-kappaB-driven transcription. PLoS Biol 2013;11:e1001647. Guo XJ, Tian XS, Ruan Z, Chen YT, Wu L, Gong Q, et al. Dysregulation of neurotrophic and inflammatory systems accompanied by decreased CREB signaling in ischemic rat retina. Exp Eye Res 2014;125:156–63. Jover-Mengual T, Miyawaki T, Latuszek A, Alborch E, Zukin RS, Etgen AM. Acute estradiol protects CA1 neurons from ischemia-induced apoptotic cell death via the PI3K/Akt pathway. Brain Res 2010;1321:1–12. Hu X, Chen J, Wang L, Ivashkiv LB. Crosstalk among Jak-STAT, Toll-like receptor, and ITAM-dependent pathways in macrophage activation. J Leukoc Biol 2007;82: 237–43. Wang YC, He F, Feng F, Liu XW, Dong GY, Qin HY, et al. Notch signaling determines the M1 versus M2 polarization of macrophages in antitumor immune responses. Cancer Res 2010;70:4840–9. Sehara Y, Sawicka K, Hwang JY, Latuszek-Barrantes A, Etgen AM, Zukin RS. Survivin is a transcriptional target of STAT3 critical to estradiol neuroprotection in global ischemia. J Neurosci 2013;33:12364–74. De Butte-Smith M, Zukin RS, Etgen AM. Effects of global ischemia and estradiol pretreatment on phosphorylation of Akt, CREB and STAT3 in hippocampal CA1 of young and middle-aged female rats. Brain Res 2012;1471:118–28. Jang SS, Choi JH, Im DS, Park S, Park JS, Park SM, et al. The phosphorylation of STAT6 during ischemic reperfusion in rat cerebral cortex. Neuroreport 2014; 25:18–22. Nguyen VT, Benveniste EN. IL-4-Activated STAT-6 inhibits IFN-induced CD40 gene expression in macrophages/microglia. J Immunol 2000;165:6235–43.

D

[75]

[87]

T

[46] Desestret V, Riou A, Chauveau F, Cho TH, Devillard E, Marinescu M, et al. In vitro and in vivo models of cerebral ischemia show discrepancy in therapeutic effects of M2 macrophages. PLoS One 2013;8:e67063. [47] Stout RD. Editorial: macrophage functional phenotypes: no alternatives in dermal wound healing? J Leukoc Biol 2010;87:19–21. [48] Chhor V, Le Charpentier T, Lebon S, Ore MV, Celador IL, Josserand J, et al. Characterization of phenotype markers and neuronotoxic potential of polarised primary microglia in vitro. Brain Behav Immun 2013;32:70–85. [49] Franke H, Gunther A, Grosche J, Schmidt R, Rossner S, Reinhardt R, et al. P2X7 receptor expression after ischemia in the cerebral cortex of rats. J Neuropathol Exp Neurol 2004;63:686–99. [50] Wixey Julie A, HER, Carty Michelle L, Buller Kathryn M. Delayed P2X4R expression after hypoxia-ischemia is associated with microglia in the immature rat brain. J Neuroimmunol 2009;212:35–43. [51] Dou Y, Wu HJ, Li HQ, Qin S, Wang YE, Li J, et al. Microglial migration mediated by ATP-induced ATP release from lysosomes. Cell Res 2012;22:1022–33. [52] Sieger D, Moritz C, Ziegenhals T, Prykhozhij S, Peri F. Long-range Ca2+ waves transmit brain-damage signals to microglia. Dev Cell 2012;22:1138–48. [53] Torres-Platas SG, Comeau S, Rachalski A, Bo GD, Cruceanu C, Turecki G, et al. Morphometric characterization of microglial phenotypes in human cerebral cortex. J Neuroinflammation 2014;11:12. [54] Perego C, Fumagalli S, De Simoni MG. Temporal pattern of expression and colocalization of microglia/macrophage phenotype markers following brain ischemic injury in mice. J Neuroinflammation 2011;8:174. [55] Perego Carlo, SFaM-GDS. Temporal pattern of expression and colocalization of microglia/macrophage phenotype markers following brain ischemic injury in mice. J Neuroinflammation 2011. [56] Arora M, Chen L, Paglia M, Gallagher I, Allen JE, Vyas YM, et al. Simvastatin promotes Th2-type responses through the induction of the chitinase family member Ym1 in dendritic cells. Proc Natl Acad Sci U S A 2006;103:7777–82. [57] Denes A, Vidyasagar R, Feng J, Narvainen J, McColl BW, Kauppinen RA, et al. Proliferating resident microglia after focal cerebral ischaemia in mice. J Cereb Blood Flow Metab 2007;27:1941–53. [58] Eyo UB, Miner SA, Ahlers KE, Wu LJ, Dailey ME. P2X7 receptor activation regulates microglial cell death during oxygen-glucose deprivation. Neuropharmacology 2013;73:311–9. [59] Vazquez-Villoldo N, Domercq M, Martin A, Llop J, Gomez-Vallejo V, Matute C. P2X4 receptors control the fate and survival of activated microglia. Glia 2014;62:171–84. [60] Lawrence T, Natoli G. Transcriptional regulation of macrophage polarization: enabling diversity with identity. Nat Rev Immunol 2011;11:750–61. [61] Labonte AC, Tosello-Trampont AC, Hahn YS. The role of macrophage polarization in infectious and inflammatory diseases. Mol Cells 2014;37:275–85. [62] Liang Yan, YZaPS. NF-κB and its regulation on the immune system. Cell Mol Immunol 2004;1:343–50. [63] Ridder DA, Schwaninger M. NF-kappaB signaling in cerebral ischemia. Neuroscience 2009;158:995–1006. [64] Lenglet S, Montecucco F, Mach F. Role of matrix metalloproteinases in animal models of ischemic stroke. Curr Vasc Pharmacol 2013. [65] Kim SR, Jung YR, An HJ, Kim DH, Jang EJ, Choi YJ, et al. Anti-wrinkle and antiinflammatory effects of active garlic components and the inhibition of MMPs via NF-kappaB signaling. PLoS One 2013;8:e73877. [66] Lee JK, Chung J, Kannarkat GT, Tansey MG. Critical role of regulator G-protein signaling 10 (RGS10) in modulating macrophage M1/M2 activation. PLoS One 2013;8: e81785. [67] Suh HS, Choi N, Tarassishin L, Lee SC. Regulation of progranulin expression in human microglia and proteolysis of progranulin by matrix metalloproteinase-12 (MMP-12). PLoS One 2012;7:e35115. [68] Eriksen JL, Mackenzie IR. Progranulin: normal function and role in neurodegeneration. J Neurochem 2008;104:287–97. [69] Egashira Y, Suzuki Y, Azuma Y, Takagi T, Mishiro K, Sugitani S, et al. The growth factor progranulin attenuates neuronal injury induced by cerebral ischemia–reperfusion through the suppression of neutrophil recruitment. J Neuroinflammation 2013;10:105. [70] Porta C, Rimoldi M, Raes G, Brys L, Ghezzi P, Di Liberto D, et al. Tolerance and M2 (alternative) macrophage polarization are related processes orchestrated by p50 nuclear factor kappaB. Proc Natl Acad Sci U S A 2009;106:14978–83. [71] Shin Hyun Mu, LMM, Cho Ok Hyun, Gottipati Sridevi, Fauq Abdul H, Golde Todd E, et al. Notch1 augments NF-jB activity by facilitating its nuclear retention. EMBO J 2006;25:129–38. [72] Xu H, Zhu J, Smith S, Foldi J, Zhao B, Chung AY, et al. Notch-RBP-J signaling regulates the transcription factor IRF8 to promote inflammatory macrophage polarization. Nat Immunol 2012;13:642–50. [73] Palaga T, Buranaruk C, Rengpipat S, Fauq AH, Golde TE, Kaufmann SHE, et al. Notch signaling is activated by TLR stimulation and regulates macrophage functions. Eur J Immunol 2008;38:174–83. [74] Arumugam TV, Cheng YL, Choi Y, Choi YH, Yang S, Yun YK, et al. Evidence that gamma-secretase-mediated Notch signaling induces neuronal cell death via the

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[88] [89] [90]

[91]

[92]

[93]

[94]

[95]

[96]

[97]

[98]

[99]

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