Let-7a gene knockdown protects against cerebral ischemia/reperfusion injury

Systemic administration of blood-derived exosomes induced by remote ischemic post-conditioning, by delivering a specific cluster of miRNAs, ameliorates ischemic damage and neurological function

MicroRNAs, contained in exosomes or freely circulating in the plasma, might play a pivotal role in the infarct-sparing effect exerted by remote limb ischemic postconditioning (RLIP). The aims of the present study were: (1) To evaluate the effect of pure exosomes isolated from plasma of animals subjected to RLIP systemically administered to ischemic rats; (2) To finely dissect exosomes content in terms of miRNAs; (3) To select those regulatory miRNAs specifically expressed in protective exosomes and to identify molecular pathways involved in their neurobeneficial effects. Circulating exosomes were isolated from blood of animals exposed to RLIP and administered to animals exposed to tMCAO by intracerebroventricular, intraperitoneal or intranasal routes. Exosomal miRNA signature was evaluated by microarray and FISH analysis. Plasmatic exosomes isolated from plasma of RLIP rats attenuated cerebral ischemia reperfusion injury and improved neurological functions until 3 days after ischemia induction. Interestingly, miR-702-3p and miR-423-5p seem to be mainly involved in exosome protective action by modulating NOD1 and NLRP3, two key triggers of neuroinflammation and neuronal death. Collectively, the results of the present work demonstrated that plasma-released exosomes after RLIP may transfer a neuroprotective signal to the brain of ischemic animals, thus representing a potentially translatable therapeutic strategy in stroke.

Zhilong Huoxue Tongyu Capsule attenuates hemorrhagic transformation through the let-7f/TLR4 signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Hemorrhagic transformation after acute ischemic stroke is a life-threatening disease that currently has no effective chemotherapy. Zhilong Huoxue Tongyu Capsule (ZL) is an empirical prescription of traditional Chinese medicine that is used to prevent and treat cardiovascular and cerebrovascular diseases in China. However, only a few studies have addressed the mechanisms of ZL in treating hemorrhagic transformation.

AIM OF THE STUDY

To evaluate the anti-inflammatory effects of ZL on hemorrhagic transformation model rats and lipopolysaccharide (LPS)-induced RAW264.7 macrophages and to explore the underlying molecular mechanisms.

MATERIALS AND METHODS

Murine RAW264.7 cells were treated with ZL and LPS (1 μg/mL), and cell viability was detected by cell counting kit-8 assay. RT-qPCR was used to detect the expression of inflammatory chemokines, microRNA let-7a/e/i/f, toll like receptor 4 (TLR4), myeloid differentiation factor 88 (MyD88), and nuclear factor kappa-B (NF-κB) p65. The protein expression levels of TLR4, MyD88, NF-κB p65, and apoptosis related molecules were determined by Western blotting. The apoptosis rate of RAW264.7 macrophages was detected by Annexin V-FITC/PI double staining. A hemorrhagic transformation model in rats was established by intraperitoneal injection of high glucose solution combined with thread embolization. Then, the model rats were observed behaviourally, pathologically, and molecularly. The gene expression of TLR4, MyD88, and NF-κB p65 was measured by RT-qPCR and used to evaluate the protective effect of ZL against hemorrhagic transformation in rats.

RESULTS

ZL (5, 20, 40 μg/mL) was beneficial in cell proliferation. LPS (1 μg/mL) stimulated the production of inflammatory chemokines and inhibited the production of let-7a/e/i/f, with let-7f being influenced most strongly. Moreover, overexpression of let-7f decreased the gene and protein levels of TLR4, MyD88, and NF-κB p65, downregulated TLR4, and inhibited its transcriptional activity. ZL (5, 20, and 40 μg·mL-1) inhibited the production of TLR4, MyD88, and NF-κB p65 and promoted the production of let-7f in a concentration-dependent manner. Furthermore, the blockade of TLR4 antagonized the promoting effects of TLR4 pathway activation in cell inflammation and apoptosis by downregulating let-7f. Critically, it was confirmed in vivo and in vitro that ZL upregulated the expression of let-7f and inhibited the gene expression of TLR4, MyD88, and NF-κB p65 to reduce inflammatory cell infiltration, which determined the occurrence of hemorrhagic transformation.

CONCLUSIONS

ZL can reduce inflammatory response by upregulating let-7f and subsequently inhibiting the TLR4 signaling pathway, thereby decreasing the occurrence of hemorrhagic transformation.

Some miRNA expressions and their targets in ischemic stroke

Ischemic stroke (IS) is a global health challenge leading to life-long disabilities or the deaths of patients. IS is a complex disease where genetic and environmental factors are both concerned with the pathophysiology of the condition. Here, we aimed to investigate various microRNA (miRNA) expressions and their targets in IS. A rapid and accurate diagnosis of acute IS is important to perform appropriate treatment. Therefore, there is a need for a more rapid and simple tool to carry out an acute diagnosis of IS. miRNAs are small RNA molecules serving as precious biomarkers due to their easy detection and stability in blood samples. The present systematic review aimed to summarize previous studies investigating several miRNA expressions and their targets in IS.

MicroRNA as a Potential Biomarker and Treatment Strategy for Ischemia-Reperfusion Injury

Ischemia-reperfusion (I/R) injury is a progressive injury that aggravates the pathological state when the organ tissue restores blood supply after a certain period of ischemia, including the myocardial, brain, liver, kidney, and intestinal. With growing evidence that microRNAs (miRNAs) play an important role as posttranscription gene silencing mediators in many I/R injury, in this review, we highlight the microRNAs that are related to I/R injury and their regulatory molecular pathways. In addition, we discussed the potential role of miRNA as a biomarker and its role as a target in I/R injury treatment. Developing miRNAs are not without its challenges, but prudent design combined with existing clinical treatments will result in more effective therapies for I/R injury. This review is aimed at providing new research results obtained in this research field. It is hoped that new research on this topic will not only generate new insights into the pathophysiology of miRNA in I/R injury but also can provide a basis for the clinical application of miRNA in I/R.

Emerging Role of microRNAs in Stroke Protection Elicited by Remote Postconditioning

Remote ischemic conditioning (RIC) represents an innovative and attractive neuroprotective approach in brain ischemia. The purpose of this intervention is to activate endogenous tolerance mechanisms by inflicting a subliminal ischemia injury to the limbs, or to another “remote” region, leading to a protective systemic response against ischemic brain injury. Among the multiple candidates that have been proposed as putative mediators of the protective effect generated by the subthreshold peripheral ischemic insult, it has been hypothesized that microRNAs may play a vital role in the infarct-sparing effect of RIC. The effect of miRNAs can be exploited at different levels: (1) as transducers of protective messages to the brain or (2) as effectors of brain protection. The purpose of the present review is to summarize the most recent evidence supporting the involvement of microRNAs in brain protection elicited by remote conditioning, highlighting potential and pitfalls in their exploitation as diagnostic and therapeutic tools. The understanding of these processes could help provide light on the molecular pathways involved in brain protection for the future development of miRNA-based theranostic agents in stroke.

Nutraceutical regulation of miRNAs involved in neurodegenerative diseases and brain cancers

The human brain is a well-connected, intricate network of neurons and supporting glial cells. Neurodegenerative diseases arise as a consequence of extensive loss of neuronal cells leading to disruption of their natural structure and function. On the contrary, rapid proliferation and growth of glial as well as neuronal cells account for the occurrence of malignancy in brain. In both cases, the molecular microenvironment holds pivotal importance in the progression of the disease. MicroRNAs (miRNA) are one of the major components of the molecular microenvironment. miRNAs are small, noncoding RNAs that control gene expression post-transcriptionally. As compared to other tissues, the brain expresses a substantially high number of miRNAs. In the early stage of neurodegeneration, miRNA expression upregulates, while in oncogenesis, miRNA expression is gradually lost. Neurodegeneration and brain cancer is presumed to be under the influence of identical pathways of cell proliferation, differentiation and cell death which are tightly regulated by miRNAs. It has been confirmed experimentally that miRNA expression can be regulated by nutraceuticals - macronutrients, micronutrients or natural products derived from food; thereby making dietary supplements immensely significant for targeting miRNAs having altered expression patterns during neurodegeneration or oncogenesis. In this review, we will discuss in detail, about the common miRNAs involved in brain cancers and neurodegenerative diseases along with the comprehensive list of miRNAs involved separately in both pathological conditions. We will also discuss the role of nutraceuticals in the regulation of those miRNAs which are involved in both of these pathological conditions.

let-7 microRNAs: Their Role in Cerebral and Cardiovascular Diseases, Inflammation, Cancer, and Their Regulation

The let-7 family is among the first microRNAs found. Recent investigations have indicated that it is highly expressed in many systems, including cerebral and cardiovascular systems. Numerous studies have implicated the aberrant expression of let-7 members in cardiovascular diseases, such as stroke, myocardial infarction (MI), cardiac fibrosis, and atherosclerosis as well as in the inflammation related to these diseases. Furthermore, the let-7 microRNAs are involved in development and differentiation of embryonic stem cells in the cardiovascular system. Numerous genes have been identified as target genes of let-7, as well as a number of the let-7’ regulators. Further studies are necessary to identify the gene targets and signaling pathways of let-7 in cardiovascular diseases and inflammatory processes. The bulk of the let-7’ regulatory proteins are well studied in development, proliferation, differentiation, and cancer, but their roles in inflammation, cardiovascular diseases, and/or stroke are not well understood. Further knowledge on the regulation of let-7 is crucial for therapeutic advances. This review focuses on research progress regarding the roles of let-7 and their regulation in cerebral and cardiovascular diseases and associated inflammation.

RETRACTED: Knockdown EZH2 attenuates cerebral ischemia-reperfusion injury via regulating microRNA-30d-3p methylation and USP22

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor-in-Chief as there are concerns about the reliability of the results. Concerns have been raised about a portion of Figure 5B, ‘DMSO’ group appears to contain image similarities with Figure 4e, ‘Inhibitor NC’ group, published in Yang et al., 2021 doi: 10.1080/15384101.2020.1856498. A portion of Figure 5B, ‘DZNeP+miR-30d-3p antagomir’ group appears to contain image similarities with Figure 4e, ‘Inhibitor NC’ group, published in Yang et al., 2021. Figure 7/G western blot bands have the same eyebrow shaped phenotype as many other publications as detailed here (https://pubpeer.com/publications/B26AE47AC0E71E0EF339B40893B2C2).

Down-regulation of miR-let-7e attenuates LPS-induced acute lung injury in mice via inhibiting pulmonary inflammation by targeting SCOS1/NF-κB pathway

Excessive pulmonary inflammatory response is critical in the development of acute lung injury (ALI). Previously, microRNAs (miRNAs) have been recognized as an important regulator of inflammation in various diseases. However, the effects and mechanisms of miRNAs on inflammatory response in ALI remain unclear. Herein, we tried to screen miRNAs in the processes of ALI and elucidate the potential mechanism. Using a microarray assay, microRNA let-7e (let-7e) was chose as our target for its reported suppressive roles in several inflammatory diseases. Down-regulation of let-7e by antagomiR-let-7e injection attenuated LPS-induced acute lung injury. We also found that antagomiR-let-7e could obviously improve the survival rate in ALI mice. Moreover, antagomiR-let-7e treatment reduced the production of proinflammatory cytokines (i.e., TNF-α, IL-1β and IL-6) in bronchoalveolar lavage fluid (BALF) of LPS-induced ALI mice. Luciferase reporter assays confirmed that suppressor of cytokine signaling 1 (SOCS1), a powerful attenuator of nuclear factor kappa B (NF-κB) signaling pathway, was directly targeted and suppressed by let-7e in RAW264.7 cells. In addition, it was further observed that SOCS1 was down-regulated, and inversely correlated with let-7e expression levels in lung tissues of ALI mice. Finally, down-regulation of let-7e suppressed the activation of NF-κB pathway, as evidenced by the reduction of p-IκBα, and nuclear p-p65 expressions in ALI mice. Collectively, our findings indicate that let-7e antagomir protects mice against LPS-induced lung injury via repressing the pulmonary inflammation though regulation of SOCS1/NF-κB pathway, and let-7e may act as a potential therapeutic target for ALI.

Genetic polymorphisms in pri-let-7a-2 are associated with ischemic stroke risk in a Chinese Han population from Liaoning, China: a case-control study

Ischemic stroke is a complicated disease, and its pathogenesis has been attributed to the occurrence of genetic polymorphisms. Evidence has suggested that the microRNA let-7a is involved in the pathogenesis of ischemic stroke. Pri-miRNA is the primary transcript, which undergoes several processing steps to generate pre-miRNA and, later, mature miRNAs. In this case-control study, we analyzed the distribution of pri-let-7a-2 variants in patients at a high risk for ischemic stroke and the interactions of pri-let-7a-2 variants and environmental factors. Blood samples and clinical information were collected from 1086 patients with ischemic stroke and 836 healthy controls between December 2013 and December 2015 at the First Affiliated Hospital of China Medical University. We found that the rs1143770 CC genotype and the C allele were associated with a decreased risk of ischemic stroke, whereas the rs629367 CC genotype was associated with an increased risk for ischemic stroke. Moreover, these two single-nucleotide polymorphisms were in linkage disequilibrium in this study sample. We analyzed gene-environment interactions and found that rs1143770 exerted a combined effect on the pathogenesis of ischemic stroke, together with alcohol use, smoking, and a history of hypertension. Therefore, the detection of pri-let-7a-2 polymorphisms may increase the awareness of ischemic stroke risk. This study was approved by the Institutional Ethics Committee of the First Affiliated Hospital of China Medical University, China (approval No. 2012-38-1) on February 20, 2012, and was registered with the Chinese Clinical Trial Registry (registration number: ChiCTR-COC-17013559) on December 27, 2017.

MicroRNAs in gray and white matter multiple sclerosis lesions: impact on pathophysiology

Multiple sclerosis (MS) is a chronic disease of the CNS, hallmarked by inflammation and demyelination. Early stages of the disease frequently show active lesions containing numerous foamy macrophages and inflammatory cells. Disease progression is highlighted by increasing numbers of mixed active/inactive or inactive lesions showing sparse inflammation and pronounced astrogliosis. Furthermore, gray matter lesions increase in number and extent during disease progression. MicroRNAs (miRNAs) comprise a group of several thousand (in humans more than 2000), small non-coding RNA molecules with a fundamental influence on about one-third of all protein-coding genes. Furthermore, miRNAs have been detected in body fluids, including spinal fluid, and they are assumed to participate in intercellular communications. Several studies have determined miRNA profiles from dissected white and gray matter lesions of autoptic MS patients. In this review, we summarize in detail the current knowledge of individual miRNAs in gray and white matter lesions of MS patients and present the concepts of MS tissue lesion development based on the altered miRNA profiles. © 2020 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Overexpression of long non-coding RNA Rian attenuates cell apoptosis from cerebral ischemia-reperfusion injury via Rian/miR-144-3p/GATA3 signaling

Long non-coding RNAs (lncRNAs) have been identified in cerebral ischemia-reperfusion (I/R) injury nowadays. Herein, we uncovered the function and underlying mechanism of the lncRNA Rian in cerebral I/R injury. The oxygen-glucose deprivation model in N2a cells was offered to mimic cerebral I/R injury in vitro. Trypan blue staining, reactive oxygen species (ROS) production, and caspase-3 activity were used to evaluate cell apoptosis. Then, middle cerebral artery occlusion was conducted to evaluate the function of lncRNA Rian in mice. Real-time PCR and western blotting were performed to determine the expression of lncRNA Rian, miR-144-3p, GATA binding protein 3 (GATA3), caspase-3, Bax, and Bcl-2. The results showed that both Rian and GATA3 were downregulated, and miR-144-3p was upregulated in cerebral I/R injury in vitro and in vivo. Overexpression of Rian could inhibit the cell apoptosis induced by oxygen-glucose deprivation. Furthermore, overexpression of Rian distinctly reduced the infarct size, and it also improved the neurological score. Overexpression of Rian could abolish miR-144-3p-mediated I/R injury in vitro and in vivo. Besides, GATA3 was the target of miR-144-3p and GATA3 could be regulated co-operatively by miR-144-3p and Rian. Consequently, these findings showed that the Rian/miR-144-3p/GATA3 axis is an essential signaling in cerebral I/R injury. The lncRNA Rian may serve as a potential target for novel treatment in patients with ischemic stroke.

MicroRNA profiles of MS gray matter lesions identify modulators of the synaptic protein synaptotagmin-7

We established microRNA (miRNA) profiles in gray and white matter multiple sclerosis (MS) lesions and identified seven miRNAs which were significantly more upregulated in the gray matter lesions. Five of those seven miRNAs, miR‐330‐3p, miR‐4286, miR‐4488, let‐7e‐5p, miR‐432‐5p shared the common target synaptotagmin7 (Syt7). Immunohistochemistry and transcript analyses using nanostring technology revealed a maldistribution of Syt7, with Syt7 accumulation in neuronal soma and decreased expression in axonal structures. This maldistribution could be at least partially explained by an axonal Syt7 transport disturbance. Since Syt7 is a synapse‐associated molecule, this maldistribution could result in impairment of neuronal functions in MS patients. Thus, our results lead to the hypothesis that the overexpression of these five miRNAs in gray matter lesions is a cellular mechanism to reduce further endogenous neuronal Syt7 production. Therefore, miRNAs seem to play an important role as modulators of neuronal structures in MS.

Neuroprotective Influence of miR-301a Inhibition in Experimental Cerebral Ischemia/Reperfusion Rat Models Through Targeting NDRG2

The objective of this study is to find out the potential influence of miR-301a in an experimental cerebral ischemia-reperfusion (I/R) rat model through targeting NDRG2. Rats with cerebral I/R injury were constructed and classified into model, miR-301a inhibitor, miR-301a mimic, NC (negative control), siNDRG2, NDRG2, and miR-301a inhibitor + si-NDRG2 groups, as well as another sham group. Cerebral infarct volume and cell apoptosis were observed by TTC staining and TUNEL staining. The targeting relationship between miR-301a and NDRG2 was verified by luciferase assay. ELISA, qRT-PCR, and Western blot were used to detect the expressions of related molecules. Compared with sham group, rats in the model group had elevated neurological function score and infarct volume; meanwhile, the cell apoptosis rate and inflammatory response were also increased with enhanced expression of miR-301a and NDRG2 (all P < 0.05). These changes were worsened in the miR-301a mimic and si-NDRG2 groups. Conversely, those rats in the miR-301a inhibitor and NDRG2 groups presented increased NDRG2, and at the same time, other above concerning factors also exhibited opposite tendencies (all P < 0.05). Dual-luciferase reporter gene assay confirmed that NDRG2 was a target gene of miR-301a, and si-NDRG2 could reverse the neuroprotective effect of miR-301a inhibitor in rats with cerebral I/R injury. Inhibiting miR-301a has a neuroprotective effect on rats with cerebral I/R injury to ameliorate cell apoptosis and inflammatory response through possibly targeting NDRG2.

Hypothermia and brain inflammation after cardiac arrest

The cessation (ischemia) and restoration (reperfusion) of cerebral blood flow after cardiac arrest (CA) induce inflammatory processes that can result in additional brain injury. Therapeutic hypothermia (TH) has been proven as a brain protective strategy after CA. In this article, the underlying pathophysiology of ischemia-reperfusion brain injury with emphasis on the role of inflammatory mechanisms is reviewed. Potential targets for immunomodulatory treatments and relevant effects of TH are also discussed. Further studies are needed to delineate the complex pathophysiology and interactions among different components of immune response after CA and identify appropriate targets for clinical investigations.

TNFα and IL-1β modify the miRNA cargo of astrocyte shed extracellular vesicles to regulate neurotrophic signaling in neurons

Astrocytes are known to be critical regulators of neuronal function. However, relatively few mediators of astrocyte to neuron communication have been identified. Recent advancements in the biology of extracellular vesicles have begun to implicate astrocyte derived extracellular vesicles (ADEV) as mediators of astrocyte to neuron communication, suggesting that alterations in the release and/or composition of ADEVs could influence gliotransmission. TNFα and IL-1β are key mediators of glial activation and neuronal damage, but the effects of these cytokines on the release or molecular composition of ADEVs is unknown. We found that ADEVs released in response to IL-1β (ADEV-IL-1β) and TNFα (ADEV-TNFα) were enriched with miRNAs that target proteins involved in neurotrophin signaling. We confirmed that miR-125a-5p and miR-16-5p (both enriched in ADEV-IL-1β and ADEV-TNFα) targeted NTKR3 and its downstream effector Bcl2. Downregulation of these targets in neurons was associated with reductions in dendritic growth, dendritic complexity, reduced spike rates, and burst activity. Molecular interference of miR-125a-5p and miR-16-5p prevented ADEV-IL-1β from reducing dendritic complexity, spike, and burst rates. These findings suggest that astrocytes respond to inflammatory challenge by modifying the miRNA cargo of ADEVs to diminish the activity of target neurons by regulating the translational expression of proteins controlling programs essential for synaptic stability and neuronal excitability.

Synergistic neuroprotective effect of rasagiline and idebenone against retinal ischemia-reperfusion injury via the Lin28-let-7-Dicer pathway

Retinal ischemia-reperfusion (RIR) injury causes neuronal degeneration and initiates various optic nerve diseases. This study aimed to investigate the synergistic neuroprotective effect of rasagiline and idebenone against RIR injury. A combination of rasagiline and idebenone was administered intraperitoneally immediately after establishment of the RIR model. Treatment with the combination of the two drugs resulted in a significant restoration of retinal thickness and retinal ganglion cells. Apoptosis of cells in ganglion cell layers was also ameliorated, suggesting that the effect of the two drugs was synergistic and the expression of brain-derived neurotrophic factor increased. Furthermore, idebenone and rasagiline induced the expression of Lin28A and Lin28B, respectively, which resulted in a reduced expression of microRNAs in the let-7 family and an increased protein output of Dicer. The data obtained from gene overexpression and knockdown experiments indicated that let-7 and Dicer were necessary for the synergistic neuroprotective effect of the two drugs. Our findings suggested that combination therapy with rasagiline and idebenone produced a synergistic effect that ameliorated RIR injury and restored visual function. In addition, the combined treatment provided neuroprotection via enhancement of the selective regulation of let-7 by Lin28A/B. These findings implied that a treatment with the combination of rasagiline and idebenone is a feasible treatment option for optic nerve diseases.

Long non-coding RNA and microRNA-675/let-7a mediates the protective effect of melatonin against early brain injury after subarachnoid hemorrhage via targeting TP53 and neural growth factor

The objective of this study was to identify the protective effect of melatonin (MT) against early brain injury (EBI) following subarachnoid hemorrhage (SAH) and explore the underlying molecular mechanism. Real-time polymerase chain reaction (PCR) and luciferase assay were utilized to detect the effect of MT on H19 expression level, computation analysis and luciferase assay were conducted to the underlying mechanism of let-7a and miR-675. Real-time PCR, western blot analysis, immunohistochemistry, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, and flow cytometry analysis were performed to detect the effect of MT on H19, miR-675, let-7a, TP53, neural growth factor (NGF) levels, cell viability, and apoptosis status. Melatonin increased H19 expression level by enhancing H19 transcriptional efficiency in a concentration-dependent manner. MiR-675 and let-7a directly targeted P53 and NGF, respectively, and miR-675 reduced luciferase activity of wild-type but not mutant TP53 3′UTR. Meanwhile, let-7a suppressed luciferase activity of wild-type but not mutant NGF 3′UTR. H₂O₂ increased number of SA-b-gal, and while MT administration repressed the premature senescence. H₂O₂ obviously upregulated expressions of H19, miR-675, and NGF, and downregulated let-7a and TP53 levels; however, MT treatment reduced expressions of H19, miR-675, and NGF, and improved let-7a and TP53 levels. Treating with MT attenuated the neurological deficits and reduced the brain swelling. MT treatment repressed apoptosis of neurons caused by SAH. Levels of H19, miR-675, and NGF were much higher in the SAH +  MT group, while there were even higher levels of H19, miR-675, and NGF in the SAH group than in the sham group; levels of let-7a and TP53 were much lower in the SAH + MT group, while they were even lower in the SAH group than in the sham group. Our study revealed that treatment with MT protected against EBI after SAH by modulating the signaling pathways of H19-miR-675-P53-apoptosis and H19-let-7a-NGF-apoptosis.

MicroRNAs of microglia: Wrestling with central nervous system disease

Microglia serve as brain-resident myeloid cells that affect cerebral development, ischemia, neurodegeneration, and neuro-viral infection. MicroRNAs play a key role in central nervous system disease through post-transcriptional regulation. Indeed, evidence shows that microRNAs are one of the most important regulators mediating microglial activation, polarization, and autophagy, and subsequently affecting neuroinflammation and the outcome of central nervous system disease. In this review, we provide insight into the function of microRNAs, which may be an attractive strategy and influential treatment for microglia-related central nervous system dysfunction. Moreover, we comprehensively describe how microglia fight against central nervous system disease via multiple functional microRNAs.

miR-148b Regulates Proliferation and Differentiation of Neural Stem Cells via Wnt/β-Catenin Signaling in Rat Ischemic Stroke Model

Stroke is the second leading cause of death worldwide. Stroke induced proliferation and differentiation of neural stem cells (NSCs) that have been proven to participate in ischemic brain repair. However, molecular mechanisms that regulate neurogenesis have not been fully investigated. MicroRNAs play an important role in the neurological repairing process and impact stroke recovery outcome. MiRNA-148b has been reported to regulate cell proliferation in tumor cells, but its role in NSCs after ischemic stroke remains unknown. Here, we found an overexpression of MiRNA-148b in subventricular zone (SVZ) of rat ischemic brain. In original cultured ischemic NSCs, transfection of MiRNA-148b mimic or inhibitor could suppress or enhance the expression of Wnt-1, β-catenin, and Cyclin D1, hence effected wnt/β-catenin signaling. MiRNA-148b inhibitor promoted NSCs proliferation and differentiation into newborn neural and astrocytes, and this action could be silenced with knockdown of Wnt-1. In middle cerebral artery occlusion (MCAo) rats, injection of MiRNA-148b inhibitor could reduce ischemic lesion volume and improve neurological function outcome. Collectively, our data suggest that MiRNA-148b suppressed wnt/β-catenin signaling attenuates proliferation and differentiation of neural stem cells, these findings shed new light on the role of MiRNA-148b in the recovery process during the stroke and contribute to the novel therapy strategy.

Growth of malignant extracranial tumors alters microRNAome in the prefrontal cortex of TumorGraft mice

A wide array of central nervous system complications, neurological deficits, and cognitive impairments occur and persist as a result of systemic cancer and cancer treatments. This condition is known as chemo brain and it affects over half of cancer survivors. Recent studies reported that cognitive impairments manifest before chemotherapy and are much broader than chemo brain alone, thereby adding in tumor brain as a component. The molecular mechanisms of chemo brain are under-investigated, and the mechanisms of tumor brain have not been analyzed at all. The frequency and timing, as well as the long-term persistence, of chemo brain and tumor brain suggest they may be epigenetic in nature. MicroRNAs, small, single-stranded non-coding RNAs, constitute an important part of the cellular epigenome and are potent regulators of gene expression. miRNAs are crucial for brain development and function, and are affected by a variety of different stresses, diseases and conditions. However, nothing is known about the effects of extracranial tumor growth or chemotherapy agents on the brain microRNAome. We used the well-established TumorGraft ™ mouse models of triple negative (TNBC) and progesterone receptor positive (PR+BC) breast cancer, and profiled global microRNAome changes in tumor-bearing mice upon chemotherapy, as compared to untreated tumor-bearing mice and intact mice. Our analysis focused on the prefrontal cortex (PFC), based on its roles in memory, learning, and executive functions, and on published data showing the PFC is a target in chemo brain. This is the first study showing that tumor presence alone significantly impacted the small RNAome of PFC tissues. Both tumor growth and chemotherapy treatment affected the small RNAome and altered levels of miRNAs, piRNAs, tRNAs, tRNA fragments and other molecules involved in post-transcriptional regulation of gene expression. Amongst those, miRNA changes were the most pronounced, involving several miRNA families, such as the miR-200 family and miR-183/96/182 cluster; both were deregulated in tumor-bearing and chemotherapy-treated animals. We saw that miRNA deregulation was associated with altered levels of brain-derived neurotrophic factor (BDNF), which plays an important role in cognition and memory and is one of the known miRNA targets. BDNF downregulation has been associated with an array of neurological conditions and could be one of the mechanisms underlying tumor brain and chemo brain. In the future our study could serve as a roadmap for further analysis of cancer and chemotherapy's neural side effects, and differentially expressed miRNAs should be explored as potential tumor brain and chemo brain biomarkers.

Upregulation of miR-130b protects against cerebral ischemic injury by targeting water channel protein aquaporin 4 (AQP4)

Altered microRNA regulation has been implicated in the pathogenesis of various disorders, including cerebral ischemia/reperfusion injury (I/RI). However, the regulatory mechanism of miR-130b in cerebral ischemia injury has not been reported. In this study, we explored the role of miR-130b in cerebral ischemia injury and investigated its potential mechanism. Levels of miR-130b were quantified by real-time PCR, and the protein level of AQP4 was detected by Western blotting. Cell apoptosis was detected by flow cytometry. In vitro, miR-130b levels in astrocytes were found significantly downregulated after OGD. Overexpression of miR-130b by miR-130b mimic decreased LDH release and apoptosis, but promoted cell health of astrocytes with OGD, thus playing a protective role in astrocyte I/RI. The level of miR-130b was also downregulated in ischemic tissues in MCAO model compared with the sham group, and the expression of miR-130b was gradually downregulated over time after reperfusion. AQP4 was upregulated both in two models, and as the reperfusion went on, AQP4 expression gradually upregulated. Our results indicated knockdown of AQP4 could ameliorate astrocyte injury induced by OGD. Finally, we found that miR-130b regulated astrocyte expression of AQP4, and rescue experiments further proved the protective role of miR-130b was mediated by AQP4 downregulation. Our study demonstrated that miR-130b might exert a neuroprotective effect following cerebral I/RI by regulating AQP4 expression at the post-transcriptional level. Therefore, miR-130b may be a potential therapeutic target for stroke treatment.

Electroacupuncture reduces apoptotic index and inhibits p38 mitogen-activated protein kinase signaling pathway in the hippocampus of rats with cerebral ischemia/reperfusion injury

Electroacupuncture attenuates cerebral hypoxia and neuronal apoptosis induced by cerebral ischemia/reperfusion injury. To further identify the involved mechanisms, we assumed that electroacupuncture used to treat cerebral ischemia/reperfusion injury was associated with the p38 mitogen-activated protein kinase (MAPK) signaling pathway. We established rat models of cerebral ischemia/reperfusion injury using the modified Zea-Longa's method. At 30 minutes before model establishment, p38 MAPK blocker SB20358 was injected into the left lateral ventricles. At 1.5 hours after model establishment, electroacupuncture was administered at acupoints of Chize (LU5), Hegu (LI4), Zusanli (ST36), and Sanyinjiao (SP6) for 20 minutes in the affected side. Results showed that the combination of EA and SB20358 injection significantly decreased neurologic impairment scores, but no significant differences were determined among different interventional groups. Hematoxylin-eosin staining also showed reduced brain tissue injuries. Compared with the SB20358 group, the cells were regularly arranged, the structures were complete, and the number of viable neurons was higher in the SB20358 + electroacupuncture group. Terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick-end labeling assay showed a decreased apoptotic index in each group, with a significant decrease in the SB20358 + electroacupuncture group. Immunohistochemistry revealed reduced phosphorylated p38 expression at 3 days in the electroacupuncture group and SB20358 + electroacupuncture group compared with the ischemia/reperfusion group. There was no significant difference in phosphorylated p38 expression between the ischemia/reperfusion group and SB20358 group. These findings confirmed that the electroacupuncture effects on mitigating cerebral ischemia/reperfusion injury are possibly associated with the p38 MAPK signaling pathway. A time period of 3 days could promote the repair of ischemic cerebral nerves.

Downregulation of miR-122 attenuates hypoxia/reoxygenation (H/R)-induced myocardial cell apoptosis by upregulating GATA-4

MicroRNA-122 has been reported to play a potential role in the apoptosis of myocardial cells. However, the effect of miR-122 in regulating myocardial ischemic injury has not been previously addressed. This study aimed to investigate the effect and the molecular basis of miR-122 on myocardial ischemic injury. Using the hypoxia/reoxygenation (H/R) model of rat cardiomyocytes H9C2 in vitro, we found that miR-122 was highly expressed in H9C2 cells after H/R treatment. Overexpression of miR-122 by recombinant adeno-associated viral vector infection markedly promoted the apoptosis of H9C2 cells induced by H/R treatment, whereas miR-122 inhibition significantly decreased cell apoptosis. Dual-luciferase reporter assay and western blot assay revealed that GATA-4 was a direct target gene of miR-122, and miR-122 suppressed the expression of GATA-4 via binding to its 3'-UTR. We further identified that overexpression of miR-122 inhibited the expression of GATA-4 at the mRNA and protein levels, whereas the inhibition of miR-122 upregulated the expression of GATA-4. Moreover, GATA-4 was poorly expressed in H/R H9C2 cells and the apoptosis induced by H/R was associated with the decrease in GATA-4 expression. Importantly, silencing of GATA-4 apparently abrogated the inhibitory effect of anti-miR-122 on H/R-induced cell apoptosis. In conclusion, these findings indicate that downregulation of miR-122 alleviates cardiomyocyte H/R injury through upregulation of GATA-4 expression, supplying a novel molecular target for myocardial ischemic injury.