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      LncRNA SNHG4 Attenuates Inflammatory Responses by Sponging miR-449c-5p and Up-Regulating STAT6 in Microglial During Cerebral Ischemia-Reperfusion Injury

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          Inflammatory response mediated by microglia plays a key role in cerebral ischemia-reperfusion injury. This study intends to probe the role of lncRNA SNHG4 in regulating the inflammatory response of the microglia during cerebral ischemia reperfusion.

          Materials and Methods

          Blood samples and cerebrospinal fluid samples were collected from acute cerebral infarction (ACI) patients and healthy controls. The middle cerebral artery occlusion (MCAO) models were constructed with rats. LPS induction and oxygen-glucose deprivation methods were respectively applied to simulate the activation of microglia in vitro. qRT-PCR was employed to determine the expressions of SNHG4, miR-449c-5p and related inflammatory factors in vivo and in vitro. The inflammatory responses of the microglia subject to the varied expressions of SNHG4 and miR-449c-5p were detected. Luciferase assays were conducted to verify the crosstalk involving SNHG4, miR-449c-5p and STAT6.


          Compared with the control group, the expression of SNHG4 derived from the samples of ACI patients and the microglia of MCAO group were remarkably down-regulated, but the expression of miR-449c-5p was dramatically up-regulated. Overexpression of SNHG4 and knock-down of miR-449c-5p could inhibit the expression of pro-inflammatory cytokine in the microglia and promote the expression of anti-inflammatory factors. Meanwhile, the phospho-STAT6 was up-regulated, whereas the knock-down of SNHG4 and over-expression of miR-449c-5p in microglia had the opposite effects. Luciferase assay confirmed that SNHG4 could target miR-449c-5p, while miR-449c-5p could target STAT6.


          SNHG4 can regulate STAT6 and repress inflammation by adsorbing miR-449c-5p in microglia during cerebral ischemia-reperfusion injury.

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          Most cited references 31

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          MicroRNA-124 promotes microglia quiescence and suppresses EAE by deactivating macrophages via the C/EBP-α-PU.1 pathway.

          MicroRNAs are a family of regulatory molecules involved in many physiological processes, including differentiation and activation of cells of the immune system. We found that brain-specific miR-124 is expressed in microglia but not in peripheral monocytes or macrophages. When overexpressed in macrophages, miR-124 directly inhibited the transcription factor CCAAT/enhancer-binding protein-α (C/EBP-α) and its downstream target PU.1, resulting in transformation of these cells from an activated phenotype into a quiescent CD45(low), major histocompatibility complex (MHC) class II(low) phenotype resembling resting microglia. During experimental autoimmune encephalomyelitis (EAE), miR-124 was downregulated in activated microglia. Peripheral administration of miR-124 in EAE caused systemic deactivation of macrophages, reduced activation of myelin-specific T cells and marked suppression of disease. Conversely, knockdown of miR-124 in microglia and macrophages resulted in activation of these cells in vitro and in vivo. These findings identify miR-124 both as a key regulator of microglia quiescence in the central nervous system and as a previously unknown modulator of monocyte and macrophage activation.
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            The role of inflammation in CNS injury and disease.

            For many years, the central nervous system (CNS) was considered to be 'immune privileged', neither susceptible to nor contributing to inflammation. It is now appreciated that the CNS does exhibit features of inflammation, and in response to injury, infection or disease, resident CNS cells generate inflammatory mediators, including proinflammatory cytokines, prostaglandins, free radicals and complement, which in turn induce chemokines and adhesion molecules, recruit immune cells, and activate glial cells. Much of the key evidence demonstrating that inflammation and inflammatory mediators contribute to acute, chronic and psychiatric CNS disorders is summarised in this review. However, inflammatory mediators may have dual roles, with detrimental acute effects but beneficial effects in long-term repair and recovery, leading to complications in their application as novel therapies. These may be avoided in acute diseases in which treatment administration might be relatively short-term. Targeting interleukin (IL)-1 is a promising novel therapy for stroke and traumatic brain injury, the naturally occurring antagonist (IL-1ra) being well tolerated by rheumatoid arthritis patients. Chronic disorders represent a greater therapeutic challenge, a problem highlighted in Alzheimer's disease (AD); significant data suggested that anti-inflammatory agents might reduce the probability of developing AD, or slow its progression, but prospective clinical trials of nonsteroidal anti-inflammatory drugs or cyclooxygenase inhibitors have been disappointing. The complex interplay between inflammatory mediators, ageing, genetic background, and environmental factors may ultimately regulate the outcome of acute CNS injury and progression of chronic neurodegeneration, and be critical for development of effective therapies for CNS diseases.
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              The biphasic function of microglia in ischemic stroke.

              Microglia are brain resident macrophages originated from primitive progenitor cells in the yolk sac. Microglia can be activated within hours and recruited to the lesion site. Traditionally, microglia activation is considered to play a deleterious role in ischemic stroke, as inhibition of microglia activation attenuates ischemia induced brain injury. However, increasing evidence show that microglia activation is critical for attenuating neuronal apoptosis, enhancing neurogenesis, and promoting functional recovery after cerebral ischemia. Differential polarization of microglia could likely explain the biphasic role of microglia in ischemia. We comprehensively reviewed the mechanisms involved in regulating microglia activation and polarization. The latest discoveries of microRNAs in modulating microglia function are discussed. In addition, the interaction between microglia and other cells including neurons, astrocytes, oligodendrocytes, and stem cells were also reviewed. Future therapies targeting microglia may not exclusively aim at suppressing microglia activation, but also at modulating microglia polarization at different stages of ischemic stroke. More work is needed to elucidate the cellular and molecular mechanisms of microglia polarization under ischemic environment. The roles of microRNAs and transplanted stem cells in mediating microglia activation and polarization during brain ischemia also need to be further studied.

                Author and article information

                Drug Des Devel Ther
                Drug Des Devel Ther
                Drug Design, Development and Therapy
                11 September 2020
                : 14
                : 3683-3695
                [1 ]Department of Pharmacology, School of Pharmacy, China Medical University , Shenyang, Liaoning 110001, People’s Republic of China
                [2 ]Department of Anesthesiology, The First Affiliated Hospital of China Medical University , Shenyang, Liaoning 110001, People’s Republic of China
                Author notes
                Correspondence: Min-jie Wei; Ling Pei Email koxu078nzod@163.com; lingpei49@sina.com
                © 2020 Zhang et al.

                This work is published and licensed by Dove Medical Press Limited. The full terms of this license are available at https://www.dovepress.com/terms.php and incorporate the Creative Commons Attribution – Non Commercial (unported, v3.0) License ( http://creativecommons.org/licenses/by-nc/3.0/). By accessing the work you hereby accept the Terms. Non-commercial uses of the work are permitted without any further permission from Dove Medical Press Limited, provided the work is properly attributed. For permission for commercial use of this work, please see paragraphs 4.2 and 5 of our Terms ( https://www.dovepress.com/terms.php).

                Page count
                Figures: 7, Tables: 2, References: 40, Pages: 13
                There is no funding to report.
                Original Research

                Pharmacology & Pharmaceutical medicine

                snhg4, stat6, mir-449c-5p, ischemia-reperfusion injury


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