In Vivo Inhibition of miR-155 Promotes Recovery after Experimental Mouse Stroke

Neurovascular Unit: A critical role in ischemic stroke

Ischemic stroke (IS), a common cerebrovascular disease, results from a sudden blockage of a blood vessel in the brain, thereby restricting blood supply to the area in question, and making a significantly negative impact on human health. Unfortunately, current treatments, that are mainly based on a recanalization of occluded blood vessels, are insufficient or inaccessible to many stroke patients. Recently, the profound influence of the neurovascular unit (NVU) on recanalization and the prognosis of IS have become better understood; in‐depth studies of the NVU have also provided novel approaches for IS treatment. In this article, we review the intimate connections between the changes in the NVU and IS outcomes, and discuss possible new management strategies having practical significance to IS. We discuss the concept of the NVU, as well as its roles in IS blood‐brain barrier regulation, cell preservation, inflammatory immune response, and neurovascular repair. Besides, we also summarize the influence of noncoding RNAs in NVU, and IS therapies targeting the NVU. We conclude that both the pathophysiological and neurovascular repair processes of IS are strongly associated with the homeostatic state of the NVU and that further research into therapies directed at the NVU could expand the range of treatments available for IS.

Regulatory microRNAs and vascular cognitive impairment and dementia

Vascular cognitive impairment and dementia (VCID) is defined as a progressive dementia disease related to cerebrovascular injury and often occurs in aged populations. Despite decades of research, effective treatment for VCID is still absent. The pathological processes of VCID are mediated by the molecular mechanisms that are partly modulated at the post-transcriptional level. As small endogenous non-coding RNAs, microRNAs (miRs) can regulate target gene expression through post-transcriptional gene silencing. miRs have been reported to play an important role in the pathology of VCID and have recently been suggested as potential novel pharmacological targets for the development of new diagnosis and treatment strategies in VCID. In this review, we summarize the current understanding of VCID, the possible role of miRs in the regulation of VCID and attempt to envision future therapeutic strategies. Since manipulation of miR levels by either pharmacological or genetic approaches has shown therapeutic effects in experimental VCID models, we also emphasize the potential therapeutic value of miRs in clinical settings.

miR-210 Participates in Hepatic Ischemia Reperfusion Injury by Forming a Negative Feedback Loop With SMAD4

BACKGROUND AND AIMS

Hepatic ischemia-reperfusion (IR) injury is a major complication of liver transplantation, resection, and hemorrhagic shock. Hypoxia is a key pathological event associated with IR injury. MicroRNA-210 (miR-210) has been characterized as a micromanager of hypoxia pathway. However, its function and mechanism in hepatic IR injury is unknown.

APPROACH AND RESULTS

In this study, we found miR-210 was induced in liver tissues from patients subjected to IR-related surgeries. In a murine model of hepatic IR, the level of miR-210 was increased in hepatocytes but not in nonparenchymal cells. miR-210 deficiency remarkably alleviated liver injury, cell inflammatory responses, and cell death in a mouse hepatic IR model. In vitro, inhibition of miR-210 decreased hypoxia/reoxygenation (HR)-induced cell apoptosis of primary hepatocytes and LO2 cells, whereas overexpression of miR-210 increased cells apoptosis during HR. Mechanistically, miR-210 directly suppressed mothers against decapentaplegic homolog 4 (SMAD4) expression under normoxia and hypoxia condition by directly binding to the 3' UTR of SMAD4. The pro-apoptotic effect of miR-210 was alleviated by SMAD4, whereas short hairpin SMAD4 abrogated the anti-apoptotic role of miR-210 inhibition in primary hepatocytes. Further studies demonstrated that hypoxia-induced SMAD4 transported into nucleus, in which SMAD4 directly bound to the promoter of miR-210 and transcriptionally induced miR-210, thus forming a negative feedback loop with miR-210.

CONCLUSIONS

Our study implicates a crucial role of miR-210-SMAD4 interaction in hepatic IR-induced cell death and provides a promising therapeutic approach for liver IR injury.

Plasma Exosomal MiRNAs Expression Profile in Mesial Temporal Lobe Epilepsy With Hippocampal Sclerosis: Case-Control Study and Analysis of Potential Functions

Background

To explore an expression profile in plasma exosomal miRNAs of mesial temporal lobe epilepsy with hippocampal sclerosis (mTLE + HS) patients and investigate the associated clinical significance and putative pathways involved.

Methods

Plasma exosomal miRNAs were measured in six mTLE + HS patients who were confirmed with pre-surgical stereo-electroencephalography and six without hippocampal sclerosis (mTLE−HS) using Illumina HiSeq 2500. Then six dysregulated miRNAs were chosen for validation in an independent sample of 18 mTLE + HS patients and 18 mTLE−HS controls using RT-qPCR. Receiver operating characteristic curve was conducted to evaluate the diagnostic value of miRNAs in HS. Bioinformatic analyses were conducted to reveal in which pathways these miRNAs were involved.

Results

We revealed that a total of 42 exosomal miRNAs were differentially expressed in mTLE + HS. Among them, 25 were increased and 17 decreased. After validation, hsa-miR-129-5p, -214-3p, -219a-5p, and -34c-5p were confirmed as being upregulated, while hsa-miR-421 and -184 were significantly downregulated in mTLE + HS. Moreover, hsa-miR-184 had the best diagnostic value for discriminating mTLE + HS with 88.9% sensitivity and 83.3% specificity. These six miRNAs regulated several genes from neurotrophin-, hippo-, p53-, TGF- beta-, HIF- 1-, mTOR-related pathways.

Conclusion

Six miRNAs were dysregulated in mTLE + HS patients and targeted several genes. This result might facilitate pathological mechanistic studies of miRNAs in HS and represent potential diagnostic biomarkers. These provided the rationale for further confirmation studies in larger cohorts of prospective patients.

The role of resveratrol as a natural modulator in glia activation in experimental models of stroke

OBJECTIVE

Stroke is one of the most important causes of death and disability in modern and developing societies. In a stroke, both the glial cells and neurons develop apoptosis due to decreased cellular access to glucose and oxygen. Resveratrol (3, 5, 4'-trihydroxy-trans-stilbene) as a herbal compound shows neuroprotective and glioprotective effects. This article reviews how resveratrol can alleviate symptoms after stroke to help neurons to survive by modulating some signaling pathways in glia.

MATERIALS AND METHODS

Various databases such as ISI Web of Knowledge, Scopus, Medline, PubMed, and Google Scholar, were searched from 2000 to February 2020 to gather the required articles using appropriate keywords.

RESULTS

Resveratrol enhances anti-inflammatory and decreases inflammatory cytokines by affecting the signaling pathways in microglia such as AMP-activated protein kinase (5' adenosine monophosphate-activated protein kinase, AMPK), SIRT1 (sirtuin 1) and SOCS1 (suppressor of cytokine signaling 1). Furthermore, through miR-155 overexpressing in microglia, resveratrol promotes M2 phenotype polarization. Resveratrol also increases AMPK and inhibits GSK-3β (glycogen synthase kinase 3 beta) activity in astrocytes, which release energy, makes ATP available to neurons and reduces reactive oxygen species (ROS). Besides, resveratrol increases oligodendrocyte survival, which can lead to maintaining post-stroke brain homeostasis.

CONCLUSION

These results suggest that resveratrol can be considered a novel therapeutic agent for the reduction of stroke symptoms that can not only affect neuronal function but also play an important role in reducing neurotoxicity by altering glial activity and signaling.

Role of non-coding RNAs in age-related vascular cognitive impairment: An overview on diagnostic/prognostic value in Vascular Dementia and Vascular Parkinsonism

Age is the pivotal risk factor for different common medical conditions such as cardiovascular diseases, cancer and dementia. Among age-related disorders, cardiovascular and cerebrovascular diseases, represent the leading causes of premature mortality strictly related to vascular ageing, a pathological condition characterized by endothelial dysfunction, atherosclerosis, hypertension, heart disease and stroke. These features negatively impact on the brain, owing to altered cerebral blood flow, neurovascular coupling and impaired endothelial permeability leading to cerebrovascular diseases (CVDs) as Vascular Dementia (VD) and Parkinsonism (VP). It is an increasing opinion that neurodegenerative disorders and cerebrovascular diseases are associated from a pathogenetic point of view, and in this review, we discuss how cerebrovascular dysfunctions, due to epigenetic alterations, are linked with neuronal degeneration/dysfunction that lead to cognitive impairment. The relation between neurodegenerative and cerebrovascular diseases are reviewed with a focus on role of ncRNAs in age-related vascular diseases impairing the endothelium in the blood-brain barrier with consequent dysfunction of cerebral blood flow. In this review we dissert about different regulatory mechanisms of gene expression implemented by ncRNAs in the pathogenesis of age-related neurovascular impairment, aiming to highlight the potential use of ncRNAs as biomarkers for diagnostic/prognostic purposes as well as novel therapeutic targets.

Can miRNAs Be Considered as Diagnostic and Therapeutic Molecules in Ischemic Stroke Pathogenesis?-Current Status

Ischemic stroke is one of the leading causes of death worldwide. Clinical manifestations of stroke are long-lasting and causing economic burden on the patients and society. Current therapeutic modalities to treat ischemic stroke (IS) are unsatisfactory due to the intricate pathophysiology and poor functional recovery of brain cellular compartment. MicroRNAs (miRNA) are endogenously expressed small non-coding RNA molecules, which can act as translation inhibitors and play a pivotal role in the pathophysiology associated with IS. Moreover, miRNAs may be used as potential diagnostic and therapeutic tools in clinical practice; yet, the complete role of miRNAs is enigmatic during IS. In this review, we explored the role of miRNAs in the regulation of stroke risk factors viz., arterial hypertension, metabolic disorders, and atherosclerosis. Furthermore, the role of miRNAs were reviewed during IS pathogenesis accompanied by excitotoxicity, oxidative stress, inflammation, apoptosis, angiogenesis, neurogenesis, and Alzheimer's disease. The functional role of miRNAs is a double-edged sword effect in cerebral ischemia as they could modulate pathological mechanisms associated with risk factors of IS. miRNAs pertaining to IS pathogenesis could be potential biomarkers for stroke; they could help researchers to identify a particular stroke type and enable medical professionals to evaluate the severity of brain injury. Thus, ascertaining the role of miRNAs may be useful in deciphering their diagnostic role consequently it is plausible to envisage a suitable therapeutic modality against IS.

Neuroinvasive Listeria monocytogenes infection triggers accumulation of brain CD8+ tissue-resident memory T cells in a miR-155-dependent fashion

Background

Brain inflammation is a key cause of cognitive decline after central nervous system (CNS) infections. A thorough understanding of immune responses to CNS infection is essential for developing anti-inflammatory interventions that improve outcomes. Tissue-resident memory T cells (T_RM) are non-recirculating memory T cells that provide surveillance of previously infected tissues. However, in addition to protecting the brain against reinfection, brain T_RM can contribute to post-infectious neuroinflammation. We hypothesized that accumulation of CD8⁺T_RM in the brain could be reduced by inhibiting microRNA (miR)-155, a microRNA that influences development of cytotoxic CD8⁺ T lymphocytes during infection.

Methods

C57BL/6J mice were infected by intraperitoneal injection with a lethal inoculum of Listeria monocytogenes (Lm) then treated with antibiotics. Flow cytometry was used to quantify specific populations of brain leukocytes 28–29 days (d) post-infection (p.i.). To test the degree to which miR-155 altered leukocyte influxes into the brain, infected mice were injected with a miR-155 inhibitor or locked nucleic acid (LNA) scramble control 2d, 4d, 6d, and 8d p.i. along with antibiotic treatment. Bacterial loads in spleen and liver and body weights were measured up to 7d p.i. Brain leukocytes were analyzed 14d and 28d p.i. Confirmatory studies were performed in mutated mice lacking miR-155 (miR-155^−/−)

Results

Lm infection significantly increased the numbers of brain CD3⁺CD8⁺ lymphocytes at 28d p.i. These cells were extravascular, and displayed markers characteristic of T_RM, with the predominant phenotype of CD44⁺CD62L^-CD69⁺CX3CR1⁻. Further analysis showed that > 75% of brain T_RM also expressed CD49a, PD-1, Ly6C, CD103, and CD127. Mice injected with miR-155 inhibitor lost less weight through 7d p.i. than did control mice, whereas bacterial loads in brain, liver, and spleen were not different from controls. By 28d p.i., the numbers of brain CD8⁺ T_RM cells were significantly decreased in mice treated with the inhibitor compared with controls. Similarly, miR-155^−/− mice showed significantly reduced numbers of brain CD8⁺T_RM cells by 28d p.i.

Conclusions

Brain CD8⁺ T_RM populations are established during neuroinvasive Lm infection. Accumulation of brain CD8⁺ T_RM cells is reduced by blocking miR-155 and in miR-155^−/− mice, indicating that this molecule has a critical role in development of these specialized cells. Administering anti-miR-155 during infection could provide a novel avenue for reducing post-infectious neuroinflammation.

MicroRNAs as sentinels and protagonists of carotid artery thromboembolism

Stroke is the leading cause of serious disability in the world and a large number of ischemic strokes are due to thromboembolism from unstable carotid artery atherosclerotic plaque. As it is difficult to predict plaque rupture and surgical treatment of asymptomatic disease carries a risk of stroke, carotid disease continues to present major challenges with regard to clinical decision-making and revascularization. There is therefore an imminent need to better understand the molecular mechanisms governing plaque instability and rupture, as this would allow for the development of biomarkers to identify at-risk asymptomatic carotid plaque prior to disease progression and stroke. Further, it would aid in creation of therapeutics to stabilize carotid plaque. MicroRNAs (miRNAs) have been implicated as key protagonists in various stages of atherosclerotic plaque initiation, development and rupture. Notably, they appear to play a crucial role in carotid artery thromboembolism. As the molecular pathways governing the role of miRNAs are being uncovered, we are learning that their involvement is complex, tissue- and stage-specific, and highly selective. Notably, miRNAs can be packaged and secreted in extracellular vesicles (EVs), where they participate in cell-cell communication. The measurement of EV-encapsulated miRNAs in the circulation may inform disease mechanisms occurring in the plaque itself, and therefore may serve as sentinels of unstable plaque as well as therapeutic targets.

miR-211-5p alleviates focal cerebral ischemia-reperfusion injury in rats by down-regulating the expression of COX2

The present study was to investigate the role of microRNA (miR)-211-5p on cerebral ischemia-reperfusion injury (CIRI) and clarify its underlying mechanisms. Middle cerebral artery occlusion/reperfusion (MCAO/R) was operated on male Sprague Dawley (SD) rats, oxygen-glucose deprivation/reperfusion (OGD/R) was conducted on pheochromocytoma-12 (PC12) cells. Here, we found that miR-211-5p and Cyclooxygenase (COX2) expressions were altered in the plasma, cortex and hippocampus of MCAO/R-treated rats, as well as in the OGD/R-treaded PC12 cells. In vivo, overexpression of miR-211-5p resulted in decrease of infarct volumes, neurological deficit scores and histopathological damage. In vitro, miR-211-5p overexpression significantly decreased cell apoptosis and Lactate dehydrogenase (LDH) release rate, increased cell viability. Furthermore, our data showed that miR-211-5p overexpression markedly reduced the expressions of COX2 mRNA and protein, and the contents of Prostaglandin D2 (PGD2), PGE2, tumor necrosis factor-α (TNF-α) and Interleukin-1β (IL-1β). In addition, inhibition of COX2 significantly rescued the effects of miR-211-5p inhibitor. At last, dual luciferase experimental data showed that miR-211-5p regulated the mRNA stability of COX2 by directly binding to the 3'-untranslated region (3'-UTR) of COX2. In conclusion, our data suggested the neuroprotective effects of miR-211-5p on CIRI by targeting COX2.

Resveratrol promoted the M2 polarization of microglia and reduced neuroinflammation after cerebral ischemia by inhibiting miR-155

Purpose: Neuroinflammation was demonstrated to play an important role in the brain injury induced by cerebral ischemia, which was mainly mediated by microglia. MicroRNA-155 (MiR-155) was reported to promote the M1 polarization of microglia and increase neuroinflammation. Resveratrol was identified to have the ability to promote the M2 polarization of microglia and reduce inflammation. Whether resveratrol can promote the M2 polarization of microglia and further inhibit neuroinflammation after cerebral ischemia, and its correlation with miR-155 is unclear. To clarify this, we conducted this study to explore the potential of resveratrol as an effective strategy to treat cerebral ischemia induced neuroinflammation.Materials and methods:The cerebral ischemia mouse model was first constructed by middle cerebral artery occlusion (MCAO). Then resveratrol was intraperitoneally injected at 0 h, 8 h and 18 h after cerebral ischemia. Subsequently, the relative expression of miR-155 and the signature genes of M1 and M2 microglia in injured brain were measured by RT-PCR, and the concentration of pro-inflammatory and anti-inflammatory cytokines were detected by ELISA. Further, the in vitro experiments were also conducted to explore the effect of resveratrol on the inflammation mediated by LPS activated BV2 microglia.Results: Results indicated that the relative expression of miR-155 in ischemia brain and activated BV2 microglia was elevated, while resveratrol reduced the expression of miR-155. Resveratrol promoted the M2 polarization of microglia and reduced neuroinflammation in injured brain and activated BV2 microglia.Conclusions: In conclusion, this research indicated that resveratrol promoted the M2 polarization of microglia and reduced neuroinflammation after cerebral ischemia by inhibiting miR-155.

δ-Opioid Receptors, microRNAs, and Neuroinflammation in Cerebral Ischemia/Hypoxia

Hypoxia and ischemia are the main underlying pathogenesis of stroke and other neurological disorders. Cerebral hypoxia and/or ischemia (e.g., stroke) can lead to neuronal injury/death and eventually cause serious neurological disorders or even death in the patients. Despite knowing these serious consequences, there are limited neuroprotective strategies against hypoxic and ischemic insults in clinical settings. Recent studies indicate that microRNAs (miRNAs) are of great importance in regulating cerebral responses to hypoxic/ischemic stress in addition to the neuroprotective effect of the δ-opioid receptor (DOR). Moreover, new discovery shows that DOR can regulate miRNA expression and inhibit inflammatory responses to hypoxia/ischemia. We, therefore, summarize available data in current literature regarding the role of DOR and miRNAs in regulating the neuroinflammatory responses in this article. In particular, we focus on microglia activation, cytokine production, and the relevant signaling pathways triggered by cerebral hypoxia/ischemia. The intent of this review article is to provide a novel clue for developing new strategies against neuroinflammatory injury resulting from cerebral hypoxia/ischemia.

Epigenetic mechanisms of neurodegenerative diseases and acute brain injury

Epigenetic modifications are emerging as major players in the pathogenesis of neurodegenerative disorders and susceptibility to acute brain injury. DNA and histone modifications act together with non-coding RNAs to form a complex gene expression machinery that adapts the brain to environmental stressors and injury response. These modifications influence cell-level operations like neurogenesis and DNA repair to large, intricate processes such as brain patterning, memory formation, motor function and cognition. Thus, epigenetic imbalance has been shown to influence the progression of many neurological disorders independent of aberrations in the genetic code. This review aims to highlight ways in which epigenetics applies to several commonly researched neurodegenerative diseases and forms of acute brain injury as well as shed light on the benefits of epigenetics-based treatments.

miR-155 Knockdown Protects against Cerebral Ischemia and Reperfusion Injury by Targeting MafB

Background

Studies have elucidated that the variable expression levels of miRNAs influence the inflammatory process in ischemic stroke. Nevertheless, the impact and potential mechanism of miR-155 in cerebral ischemia-reperfusion injury (CIRI) keep to be incompletely known.

Methods

The levels of miR-155 and MafB were determined via qRT-PCR, western blot, or immunohistochemistry assays in plasma of patients with CIRI, oxygen glucose deprivation/reoxygenation (OGD/R) induced SH-SY5Y cells, and mouse models with middle cerebral artery occlusion (MCAO). The association between miR-155 and MafB was validated via dual-luciferase reporter and western blot assays. Cell viability, apoptosis, invasion, and migration were evaluated through MTT, flow cytometry, Transwell and wound healing assays. Infarction volume was measured in MCAO mouse brain tissues by TTC assay. The expression of inflammatory mediators was measured by ELISA in cells and brain tissues.

Results

miR-155 level was upregulated whereas MafB was downregulated in the plasma of patients with CIRI, OGD/R-induced SH-SY5Y cells, also as mouse models with MCAO injury. Mechanistically, miR-155 directly targeted 3'UTR of MafB and restrained MafB expression in OGD/R injury SH-SY5Y cells. Downregulation of miR-155 attenuated OGD/R-induced injury through increasing proliferation, inhibiting apoptosis, enhancing invasion and migration abilities, and constraining the expression of inflammatory mediators (IL-1β, IL-6, and TNF-α) and inflammatory enzymes (iNOS and COX-2) in SH-SY5Y cells following OGD/R, while MafB inhibition reversed the protective effects. In vivo, downregulating miR-155 reduced the infarction volume in the MACO mouse brain. Furthermore, miR-155 knockdown inhibited the IL-1β, IL-6, and TNF-α) and inflammatory enzymes (iNOS and COX-2) in SH-SY5Y cells following OGD/R, while MafB inhibition reversed the protective effects.

Conclusion

Our results suggest that miR-155 knockdown alleviated ischemia-reperfusion injury by targeting MafB to improve the neurological function and inhibit inflammation response, highlighting a novel therapeutic strategist for CIRI.

Intranasal Administration of PACAP Is an Efficient Delivery Route to Reduce Infarct Volume and Promote Functional Recovery After Transient and Permanent Middle Cerebral Artery Occlusion

Intranasal (IN) administration appears to be a suitable route for clinical use as it allows direct delivery of bioactive molecules to the central nervous system, reducing systemic exposure and sides effects. Nevertheless, only some molecules can be transported to the brain from the nasal cavity. This led us to compare the efficiency of an IN, intravenous (IV), and intraperitoneal (IP) administration of pituitary adenylate cyclase-activating polypeptide (PACAP) after transient or permanent middle cerebral artery occlusion (MCAO) in C57BL/6 mice. The results show that the neuroprotective effect of PACAP is much more efficient after IN administration than IV injection while IP injection had no effect. IN administration of PACAP reduced the infarct volume when injected within 6 h after the reperfusion and improved functional recovery up to at least 1 week after the ischemia.

A Novel Cerebroprotein Hydrolysate, CH1, Ameliorates Chronic Focal Cerebral Ischemia Injury by Promoting White Matter Integrity via the Shh/Ptch-1/Gli-1 Signaling Pathway

PURPOSE

Strokes are devastating as there are no current therapies to prevent long-term neurological deficits. Previous studies reported that cerebroprotein hydrolysate (CH) plays a role in neuronal protection in acute phase after ischemic stroke, while the long-term effects of CH upon brain plasticity and neurological outcomes after stroke are still uncertain. To address these gaps, we assessed the effect of a new cerebroprotein hydrolysate, CH1, on long-term gray and white matter integrity as well as axonal plasticity in the late phase after ischemic stroke and the potential mechanisms.

METHODS

Adult male mice were subjected to permanent distal middle cerebral artery occlusion (dMCAO), followed by daily intraperitoneal injection of CH1 for 14 days. Motor function was measured weekly through behavioral neurological evaluations. Gray matter intensity and white matter intensity were examined by immunofluorescence staining. The sonic hedgehog (Shh) inhibitor cyclopamine (CYC) was injected to determine the involvement of the Shh pathway in the therapeutic effects of CH1.

RESULTS

We found that intraperitoneal delivery of CH1, compared to vehicle administration, significantly improved long-term neurological outcomes at various times and promoted neuronal viability at 14 days but not at 28 days after stroke. Importantly, CH1 mitigated stroke-induced white matter injury and facilitated axonal plasticity in the late stage after stroke.

CONCLUSION

These results unveil a previously unappreciated role for CH in the repair of white matter and brain plasticity after stroke.

Association of miR-155 and Angiotensin Receptor Type 1 Polymorphisms with the Risk of Ischemic Stroke in a Chinese Population

There is increasing evidence suggesting that dysregulation of miR-155 and its target angiotensin receptor type 1 (AT1R) are linked to the incidence of ischemic stroke (IS), but the underlying mechanisms remain to be clarified. In this study, we therefore sought to investigate how miR-155 and AT1R polymorphisms affect IS risk. We included 579 IS patients and 509 age-matched controls in the present analysis, genotyping individuals for the rs767649 polymorphism in miR-155, as well as for the rs1492099 and rs275653 polymorphisms in AT1R via iMLDR-TM genotyping technology. The allele and genotype frequencies for the assessed polymorphisms were comparable in IS patients and controls, without any detectable association between AT1R haplotype and IS risk. We conducted additional trial of ORG 10172 in acute stroke treatment-mediated stratification, which indicated that the AT1R rs1492099 T allele was linked to a decreased risk of large-artery atherosclerosis (LAA) stroke. We further found that those with the AT1R rs275653 AA genotype had a decreased risk of small-artery occlusion (SAO) strokes. We further confirmed elevated miR-155 expression in IS patients, but observed no link between the rs767649 polymorphism and expression of this microRNA. Similarly, rs1492099 and rs275653 polymorphisms did not impact AT1R expression levels. The miR-155 rs767649 polymorphism does not seem to be a key determinant of IS risk, whereas the AT1R rs1492099 polymorphism is linked to reduced LAA-stroke risk, and the rs275653 AA genotype is potentially protective against SAO strokes.

Wnt canonical pathway activator TWS119 drives microglial anti-inflammatory activation and facilitates neurological recovery following experimental stroke

Background

Ischemic stroke is a leading cause of disability worldwide and characteristically accompanied by downregulation of the Wnt/β-catenin signaling. Activation of Wnt/β-catenin signaling emerges to attenuate neuroinflammation after ischemic stroke; however, its effect on modulating microglial polarization is largely unknown. Here, we explored whether Wnt/β-catenin pathway activator TWS119 facilitated long-term neurological recovery via modulating microglia polarization after experimental stroke.

Methods

Ischemic stroke mice model was induced by permanent distal middle cerebral artery occlusion plus 1 h hypoxia. TWS119 was administrated from day 1 to 14 after stroke. Neurological deficits were monitored up to 21 days after stroke. Angiogenesis, neural plasticity, microglial polarization, and microglia-associated inflammatory cytokines were detected in the peri-infarct cortex at days 14 and 21 after stroke. Primary microglia and mouse brain microvascular endothelial cell lines were employed to explore the underlying mechanism in vitro.

Results

TWS119 mitigated neurological deficits at days 14 and 21 after experimental stroke, paralleled by acceleration on angiogenesis and neural plasticity in the peri-infarct cortex. Mechanistically, cerebral ischemia induced production of microglia-associated proinflammatory cytokines and priming of activated microglia toward pro-inflammatory polarization, whereas TWS119 ameliorated microglia-mediated neuroinflammatory status following ischemic stroke and promoted angiogenesis by modulating microglia to anti-inflammatory phenotype. The beneficial efficacy of TWS119 in microglial polarization was largely reversed by selective Wnt/β-catenin pathway blockade in vitro, suggesting that TWS119-enabled pro-inflammatory to anti-inflammatory phenotype switch of microglia was possibly mediated by Wnt/β-catenin signaling.

Conclusions

Wnt/β-catenin pathway activator TWS119 ameliorated neuroinflammatory microenvironment following chronic cerebral ischemia via modulating microglia towards anti-inflammatory phenotype, and facilitates neurological recovery in an anti-inflammatory phenotype polarization-dependent manner. Activation of Wnt/β-catenin pathway following ischemic stroke might be a potential restorative strategy targeting microglia-mediated neuroinflammation.

Weighted gene co-expression network analysis to explore the mechanism of heroin addiction in human nucleus accumbens

Heroin dependence is a complex behavioral disease, and a chronic encephalopathy with the important feature of relapse. The purpose of the study was to identify the regulatory mechanism of the nucleus accumbens (NAc) in heroin dependence. We used weighted gene co-expression network analysis to analyze the GSE87823 data package, which included 27 heroin users and 22 controls of human NAc tissue. Modules were correlated with basic information of samples and enrichment analyses used to identify biological function and transcription factors and online tools were used to perform the gene ontology of significant genes. We identified one gene module from the total data (blue) and the male data (turquoise), respectively. The overlap genes of top 10 hub genes in significant modules (PRR11, SLC35E1, LPP, ZNF721, ZNF611, LRRFIP1) were selected to identify as candidate genes in the regulation mechanism of NAc in heroin dependence. Then, we accorded the results to further explore that miRNA-hsa-miR-155-5p in male and total may be a potential marker. The candidate genes may serve as novel prognostic markers and treatment targets. Hsa-miR-155-5p may be a promising regulatory point for the treatment of heroin addiction.

Inhibition of microRNA-711 limits angiopoietin-1 and Akt changes, tissue damage, and motor dysfunction after contusive spinal cord injury in mice

Spinal cord injury (SCI) causes neuronal cell death and vascular damage, which contribute to neurological dysfunction. Given that many biochemical changes contribute to such secondary injury, treatment approaches have increasingly focused on combined therapies or use of multi-functional drugs. MicroRNAs (miRs) are small (20-23 nucleotide), non-protein-coding RNAs and can negatively regulate target gene expression at the post-transcriptional level. As individual miRs can potentially modulate expression of multiple relevant proteins after injury, they are attractive candidates as upstream regulators of the secondary SCI progression. In the present study we examined the role of miR-711 modulation after SCI. Levels of miR-711 were increased in injured spinal cord early after SCI, accompanied by rapid downregulation of its target angiopoietin-1 (Ang-1), an endothelial growth factor. Changes of miR-711 were also associated with downregulation of the pro-survival protein Akt (protein kinase B), another target of miR-711, with sequential activation of glycogen synthase kinase 3 and the pro-apoptotic BH3-only molecule PUMA. Central administration of a miR-711 hairpin inhibitor after SCI limited decreases of Ang-1/Akt expression and attenuated apoptotic pathways. Such treatment also reduced neuronal/axonal damage, protected microvasculature and improved motor dysfunction following SCI. In vitro, miR-711 levels were rapidly elevated by neuronal insults, but not by activated microglia and astrocytes. Together, our data suggest that post-traumatic miR-711 elevation contributes to neuronal cell death after SCI, in part by inhibiting Ang-1 and Akt pathways, and may serve as a novel therapeutic target.

MicroRNAs in central nervous system diseases: A prospective role in regulating blood-brain barrier integrity

Given the essential role of the blood-brain barrier (BBB) in the central nervous system (CNS), cumulative investigations have been performed to elucidate how modulation of BBB structural and functional integrity affects the pathogenesis of CNS diseases such as stroke, traumatic brain injuries, dementia, and cerebral infection. Recent studies have demonstrated that microRNAs (miRNAs) contribute to the maintenance of the BBB and thereby mediate CNS homeostasis. This review summarizes emerging studies that demonstrate cerebral miRNAs regulate BBB function in CNS disorders, emphasizing the direct role of miRNAs in BBB molecular composition. Evidence presented in this review will encourage a deeper understanding of the mechanisms by which miRNAs regulate BBB function, and facilitate the development of new miRNAs-based therapies in patients with CNS diseases.

MiR-20b Down-Regulates Intestinal Ferroportin Expression In Vitro and In Vivo

Ferroportin (FPN) is the only known cellular iron exporter in mammalian. However, post-transcriptional regulation of intestinal FPN has not yet been completely understood. In this study, bioinformatics algorithms (TargetScan, PicTar, PITA, and miRanda) were applied to predict, screen and obtain microRNA-17 family members (miR-17, miR-20a, miR-20b, and miR-106a) targeting FPN, ‘seed sequence’ and responding binding sites on the 3′untranslated region (3′UTR) region of FPN. Dual-luciferase reporter assays revealed miRNA-17 family members’ mimics decreased the luciferase activity, whereas their inhibitors increased the luciferase activity. Compared with the FPN 3′UTR wild type reporter, co-transfection of a miRNA-17 family members’ over-expression plasmids and FPN 3′UTR mutant reporters enhanced the luciferase activity in HCT116 cells. Transfection with miR-20b overexpression plasmid significantly enhanced its expression, and it inhibited endogenous FPN protein expression in Caco-2 cells. Additionally, tail-vein injection of miR-20b resulted in increasing duodenal miR-20b expression, decreasing duodenal FPN protein expression, which was closely related to lower plasma iron level in mice. Taken together, these data suggest that the miR-20b is identified to regulate intestinal FPN expression in vitro and in vivo, which will provide a potential target for intestinal iron exportation.

The extensive role of miR-155 in malignant and non-malignant diseases

MicroRNAs (miRNAs) have rapidly emerged as key molecules in cancer initiation and development, showing the capability to regulate pivotal oncogenic pathways. MiR-155 has gathered an increased attention especially in oncology, but also in non-malignanat pathologies. Nowadays, this noncoding RNA is one of the most important miRNAs in cancer, due to the extensive signaling network associated with it, implication in immune system regulation and also deregulation in disease states. Therefore, numerous research protocols are focused on preclinical modulation of miR-155 for therapeutic purposes, or investigation of its dynamic expression for diagnostic/prognostic assessments, with the final intention of bringing this miRNA into the clinical setting. This review comprehensively presents the extended role of miR-155 in cancer and other pathologies, where its expression is dysregulated. Finally, we assess the future steps toward miR-155 based therapeutics.

Long noncoding RNA BFAL1 mediates enterotoxigenic Bacteroides fragilis-related carcinogenesis in colorectal cancer via the RHEB/mTOR pathway

Long noncoding RNAs (lncRNAs) contribute to many steps in carcinogenesis and often serve as biomarkers or therapeutic targets for tumor diagnosis and therapy. Although the role of lncRNAs in tumor formation is becoming clear, whether lncRNAs mediate gut microbiota-induced colorectal cancer (CRC) is largely unknown. Enterotoxigenic Bacteroides fragilis (ETBF) is a well-known tumor-inducing bacterium in the human gut; however, its tumorigenic effect remains to be explored. In the present study, we revealed the mechanism by which a lncRNA participates in gut bacteria-induced carcinogenesis: Bacteroides fragilis-associated lncRNA1 (BFAL1) in CRC tissues mediates ETBF carcinogenesis. BFAL1 was highly expressed in CRC tissues compared with that in adjacent normal tissues. In vitro, BFAL1 was upregulated in ETBF-treated CRC cells. Mechanistically, ETBF promoted tumor growth via BFAL1 by activating the Ras homolog, which is the MTORC1 binding/mammalian target of the rapamycin (RHEB/mTOR) pathway. Furthermore, BFAL1 regulated RHEB expression by competitively sponging microRNAs miR-155-5p and miR-200a-3p. Clinically, both high expression of BFAL1 and high abundance of ETBF in CRC tissues predicted poor outcomes for patients with CRC. Thus, BFAL1 is a mediator of ETBF-induced carcinogenesis and may be a potential therapeutic target for ETBF-induced CRC.

The Involvement and Therapy Target of Immune Cells After Ischemic Stroke

After ischemic stroke, the integrity of the blood-brain barrier is compromised. Peripheral immune cells, including neutrophils, T cells, B cells, dendritic cells, and macrophages, infiltrate into the ischemic brain tissue and play an important role in regulating the progression of ischemic brain injury. In this review, we will discuss the role of different immune cells after stroke in the secondary inflammatory reaction and focus on the phenotypes and functions of macrophages in ischemic stroke, as well as briefly introduce the anti-ischemic stroke therapy targeting macrophages.

The role of microglia in ischemic preconditioning

Ischemic preconditioning (IPC) is an experimental phenomenon in which a brief ischemic stimulus confers protection against a subsequent prolonged ischemic event. Initially thought to be due to mechanistic changes in neurons, our understanding of IPC has evolved to encompass a global reprogramming of the Central Nervous System (CNS) after transient ischemia/reperfusion that requires innate immune signaling pathways including Toll-like receptors (TLRs) and Type I interferons. Microglia are the CNS resident neuroimmune cells that express these key innate immune receptors. Studies suggest that microglia are required for IPC-mediated neuronal and axonal protection. Multiple paradigms targeting TLRs have converged on a distinctive Type I interferon response in microglia that is critical for preconditioning-mediated protection against ischemia. These pathways can be targeted through administration of TLR agonists, cytokines including interferon-β, and pharmaceutical agents that induce preconditioning through cross-tolerance mechanisms. Transcriptomic analyses and single cell RNA studies point to specific gene expression signatures in microglia that functionally shift these mutable cells to an immunomodulatory or protective phenotype. Although there are technological challenges and gaps in knowledge to overcome, the targeting of specific molecular signaling pathways in microglia is a promising direction for development of novel and effective pharmacotherapies for stroke. Studies on preconditioning in animal models, including nonhuman primates, show promise as prophylactic preconditioning treatments for selected at risk patient populations. In addition, our growing understanding of the mechanisms of IPC-mediated protection is identifying novel cellular and molecular targets for therapeutic interventions that could apply broadly to both acute stroke and chronic vascular cognitive impairment patients.

MicroRNA-199a-3p and MicroRNA-199a-5p Take Part to a Redundant Network of Regulation of the NOS (NO Synthase)/NO Pathway in the Endothelium

Objective- Members of the microRNA (miR)-199a family, namely miR-199a-5p and miR-199a-3p, have been recently identified as potential regulators of cardiac homeostasis. Also, upregulation of miR-199a expression in cardiomyocytes was reported to influence endothelial cells. Whether miR-199a is expressed by endothelial cells and, if so, whether it directly regulates endothelial function remains unknown. We investigate the implication of miR-199a products on endothelial function by focusing on the NOS (nitric oxide synthase)/NO pathway. Approach and Results- Bovine aortic endothelial cells were transfected with specific miRNA inhibitors (locked-nucleic acids), and potential molecular targets identified with prediction algorithms were evaluated by Western blot or immunofluorescence. Ex vivo experiments were performed with mice treated with antagomiRs targeting miR-199a-3p or -5p. Isolated vessels and blood were used for electron paramagnetic resonance or myograph experiments. eNOS (endothelial NO synthase) activity (through phosphorylations Ser1177/Thr495) is increased by miR-199a-3p/-5p inhibition through an upregulation of the PI3K (phosphoinositide 3-kinase)/Akt (protein kinase B) and calcineurin pathways. SOD1 (superoxide dismutase 1) and PRDX1 (peroxiredoxin 1) upregulation was also observed in locked-nucleic acid-treated cells. Moreover, miR-199a-5p controls angiogenesis and VEGFA (vascular endothelial growth factor A) production and upregulation of NO-dependent relaxation were observed in vessels from antagomiR-treated mice. This was correlated with increased circulated hemoglobin-NO levels and decreased superoxide production. Angiotensin infusion for 2 weeks also revealed an upregulation of miR-199a-3p/-5p in vascular tissues. Conclusions- Our study reveals that miR-199a-3p and miR-199a-5p participate in a redundant network of regulation of the NOS/NO pathway in the endothelium. We highlighted that inhibition of miR-199a-3p and -5p independently increases NO bioavailability by promoting eNOS activity and reducing its degradation, thereby supporting VEGF-induced endothelial tubulogenesis and modulating vessel contractile tone.

Rapamycin Increases Collateral Circulation in Rodent Brain after Focal Ischemia as detected by Multiple Modality Dynamic Imaging

Rationale: Brain collaterals contribute to improving ischemic stroke outcomes. However, dynamic and timely investigations of collateral blood flow and collateral restoration in whole brains of living animals have rarely been reported.

Methods: Using multiple modalities of imaging, including synchrotron radiation angiography, laser speckle imaging, and micro-CT imaging, we dynamically explored collateral circulation throughout the whole brain in the rodent middle cerebral artery occlusion model.

Results: We demonstrated that compared to control animals, 4 neocollaterals gradually formed between the intra- and extra-arteries in the skull base of model animals after occlusion (p<0.05). Two main collaterals were critical to the supply of blood from the posterior to the middle cerebral artery territory in the deep brain (p<0.05). Abundant small vessel and capillary anastomoses were detected on the surface of the cortex between the posterior and middle cerebral artery and between the anterior and middle cerebral artery (p<0.05). Collateral perfusion occurred immediately (≈15 min) and was maintained for up to 14 days after occlusion. Further study revealed that administration of rapamycin at 15 min after MCAO dilated the existing collateral vessels and promoted collateral perfusion.

Principal conclusions: Our results provide evidence of collateral functional perfusion in the skull base, deep brain, and surface of the cortex. Rapamycin was capable of enlarging the diameter of collaterals, potentially extending the time window for ischemic stroke therapy.

MicroRNA-155 induces protection against cerebral ischemia/reperfusion injury through regulation of the Notch pathway in vivo

microRNA (miR)-155 has been demonstrated to participate in the regulation of endothelium during cerebral ischemia. In the present study, it was aimed to investigate the molecular mechanism of miR-155 in the regulation of cerebral ischemia/reperfusion (I/R) injury with middle cerebral artery occlusion (MCAO) in mice. The MCAO model was established in C57BL/6 mice. Transfection of miR-155 mimics and miR-155 inhibitors was performed to alter the expression of miR-155. The level of miR-155 was measured by RT-qPCR analysis. The western blotting results demonstrated that deletion of miR-155 increased the expression of Notch1, intracellular Notch receptor domain (NICD) and hairy and enhancer of split-1 (Hes1) levels. In addition, the percentage of terminal deoxynucleotidyl-transferase-mediated dUTP nick end labeling-positive cells and caspase-3 levels were decreased following treatment with a miR-155 inhibitor compared with the Pre-IR group. Notably, disrupting miR-155 also increased nitric oxide (NO) production and the expression of endothelial NO synthase (eNOS), leading to downregulation of brain water content and Evans blue levels. However, overexpression of miR-155 restored all these changes to similar levels observed in the cerebral I/R injury group. The expressions of Notch1, NICD and Hes1 were also decreased to the cerebral I/R injury condition. In conclusion, a novel mechanism was identified for abrogating normal NO production and eNOS expression via the aberrant expression of the Notch signaling pathway, a mechanism that may be modulated by miR-155. Together, these results reveal important functions of miR-155 in regulating the Notch signaling pathway of the nervous system, and a potential role for miR-155 as a crucial therapy target for cerebral stroke.

Downregulation of microRNA-155 stimulates sevoflurane-mediated cardioprotection against myocardial ischemia/reperfusion injury by binding to SIRT1 in mice

OBJECTIVE

The inhaled sevoflurane has been demonstrated to protect against myocardial ischemia/reperfusion (I/R) injury. However, the relative mechanisms of sevoflurane-mediated cardioprotection remain largely unknown. This study intends to explore the effect of miR-155 on the sevoflurane-mediated cardioprotection by regulating Sirtuin 1 (SIRT1) in mouse models of myocardial I/R.

METHODS

Left anterior descending coronary artery ligation was used to induce models of myocardial I/R in mice. The I/R mice were treated with sevoflurane, sevoflurane + mimics negative control (NC) or sevoflurane + miR-155 mimics. The expression of microRNA-155 (miR-155) and SIRT1 was examined by quantitative real-time polymerase chain reaction and Western blot assay. Then cardiac functions and hemodynamic alterations were evaluated. Evans blue-2,3,5-triphenyltetrazolium chloride and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay staining methods were adopted to evaluate infarct size and cardiomyocyte apoptosis, respectively.

RESULTS

In the I/R mice, miR-155 was expressed at a high level and SIRT1 at a low level. SIRT1 was confirmed to be a target gene of miR-155. The treatment of sevoflurane could reduce miR-155 expression and increased SIRT1 expression in the myocardial tissues, under which conditions, cardiac functions were promoted, accompanied by reduced infarct size and inhibited cardiomyocyte apoptosis. In response to miR-155 upregulation, the sevoflurane-treated I/R mice showed reduced cardiac functions, and increased infarct size and cardiomyocyte apoptosis.

CONCLUSION

The findings obtained in this study provide evidence suggesting that miR-155 targets and negatively regulates SIRT1 expression, a mechanism by which the protection of sevoflurane is inhibited against myocardial I/R in mice.

Circulating miR-103a-3p contributes to angiotensin II-induced renal inflammation and fibrosis via a SNRK/NF-κB/p65 regulatory axis

Although angiotensin II (AngII) is known to cause renal injury and fibrosis, the underlying mechanisms remain poorly characterized. Here we show that hypertensive nephropathy (HN) patients and AngII-infused mice exhibit elevated levels of circulating miR103a-3p. We observe a positive correlation between miR-103a-3p levels and AngII-induced renal dysfunction. miR-103a-3p suppresses expression of the sucrose non-fermentable-related serine/threonine-protein kinase SNRK in glomerular endothelial cells, and glomeruli of HN patients and AngII-infused mice show reduced endothelial expression of SNRK. We find that SNRK exerts anti-inflammatory effects by interacting with activated nuclear factor-κB (NF-κB)/p65. Overall, we demonstrate that AngII increases circulating miR-103a-3p levels, which reduces SNRK levels in glomerular endothelial cells, resulting in the over-activation of NF-κB/p65 and, consequently, renal inflammation and fibrosis. Together, our work identifies miR-103a-3p/SNRK/NF-κB/p65 as a regulatory axis of AngII-induced renal inflammation and fibrosis.

Angiotensin II is known to cause renal inflammation and fibrosis. Here Lu et al. show that levels of circulating miR-103a-3p are elevated in hypertensive nephropathy patients and in an animal model of angiotensin II-induced renal dysfunction, and that miR-103a-3p suppresses SNRK expression leading to the activation of the pro-inflammatory NF-κB pathway in glomerular endothelial cells.

Cortical tissue loss and major structural reorganization as result of distal middle cerebral artery occlusion in the chronic phase of nude mice

The stroke model of distal middle cerebral artery occlusion is considered a reliable stroke model with high reproducibility and low mortality rate. Thus, it is preferred for assessments of therapeutic strategies, in particular for neurorepair and regeneration studies. However, present literature has reported only on the lesion behavior and behavioral deficits during the acute and subacute phase of maximally three weeks. We have here aimed to characterize the lesion expansion and consequent, potential tissue displacements using structural magnetic resonance imaging modalities, histology, and behavioral tests, during the chronic time window of 12 weeks following stroke induction. We found a severe cortical thinning resulting in 15% tissue loss of the ipsilateral cortex by 6 weeks. After two weeks, massive hippocampus displacement was found, into the cortical tissue void and, in this process, pushing the corpus callosum to the brain surface showing an almost radial direction towards the surface. These massive chronic morphological changes and rearrangements, not known from other stroke models, have relevant consequences for decision of stem cell graft placement for cerebral regeneration to assure persistent graft vitality during a longitudinal investigation in the chronic phase.

MicroRNAs in Neuroinflammation: Implications in Disease Pathogenesis, Biomarker Discovery and Therapeutic Applications

The central nervous system can respond to threat via the induction of an inflammatory response. Under normal circumstances this response is tightly controlled, however uncontrolled neuroinflammation is a hallmark of many neurological disorders. MicroRNAs are small non-coding RNA molecules that are important for regulating many cellular processes. The ability of microRNAs to modulate inflammatory signaling is an area of ongoing research, which has gained much attention in recent years. MicroRNAs may either promote or restrict inflammatory signaling, and either exacerbate or ameliorate the pathological consequences of excessive neuroinflammation. The aim of this review is to summarize the mode of regulation for several important and well-studied microRNAs in the context of neuroinflammation, including miR-155, miR-146a, miR-124, miR-21 and let-7. Furthermore, the pathological consequences of miRNA deregulation during disorders that feature neuroinflammation are discussed, including Multiple Sclerosis, Alzheimer’s disease, Parkinson’s disease, Prion diseases, Japanese encephalitis, Herpes encephalitis, ischemic stroke and traumatic brain injury. There has also been considerable interest in the use of altered microRNA signatures as biomarkers for these disorders. The ability to modulate microRNA expression may even serve as the basis for future therapeutic strategies to help treat pathological neuroinflammation.

Nucleic Acid Therapies for Ischemic Stroke

Stroke remains a leading cause of disability and death worldwide despite significant scientific and therapeutic advances. Therefore, there is a critical need to improve stroke prevention and treatment. In this review, we describe several examples that leverage nucleic acid therapeutics to improve stroke care through prevention, acute treatment, and recovery. Aptamer systems are under development to increase the safety and efficacy of antithrombotic and thrombolytic treatment, which represent the mainstay of medical stroke therapy. Antisense oligonucleotide therapy has shown some promise in treating stroke causes that are genetically determined and resistant to classic prevention approaches such as elevated lipoprotein (a) and cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL). Targeting microRNAs may be attractive because they regulate factors involved in neuronal cell death and reperfusion-associated injury, as well as neurorestorative pathways. Lastly, microRNAs may aid reliable etiologic classification of stroke subtypes, which is important for effective secondary stroke prevention.

Emerging Roles of miRNAs in Brain Development and Perinatal Brain Injury

In human beings the immature brain is highly plastic and depending on the stage of gestation is particularly vulnerable to a range of insults that if sufficiently severe, can result in long-term motor, cognitive and behavioral impairment. With improved neonatal care, the incidence of major motor deficits such as cerebral palsy has declined with prematurity. Unfortunately, however, milder forms of injury characterized by diffuse non-cystic white matter lesions within the periventricular region and surrounding white matter, involving loss of oligodendrocyte progenitors and subsequent axonal hypomyelination as the brain matures have not. Existing therapeutic options for treatment of preterm infants have proved inadequate, partly owing to an incomplete understanding of underlying post-injury cellular and molecular changes that lead to poor neurodevelopmental outcomes. This has reinforced the need to improve our understanding of brain plasticity, explore novel solutions for the development of protective strategies, and identify biomarkers. Compelling evidence exists supporting the involvement of microRNAs (miRNAs), a class of small non-coding RNAs, as important post-transcriptional regulators of gene expression with functions including cell fate specification and plasticity of synaptic connections. Importantly, miRNAs are differentially expressed following brain injury, and can be packaged within exosomes/extracellular vesicles, which play a pivotal role in assuring their intercellular communication and passage across the blood-brain barrier. Indeed, an increasing number of investigations have examined the roles of specific miRNAs following injury and regeneration and it is apparent that this field of research could potentially identify protective therapeutic strategies to ameliorate perinatal brain injury. In this review, we discuss the most recent findings of some important miRNAs in relation to the development of the brain, their dysregulation, functions and regulatory roles following brain injury, and discuss how these can be targeted either as biomarkers of injury or neuroprotective agents.

MicroRNAs and Regeneration in Animal Models of CNS Disorders

microRNAs (miRNAs) are recently identified small RNA molecules that regulate gene expression and significantly influence the essential cellular processes associated with CNS repair after trauma and neuropathological conditions including stroke and neurodegenerative disorders. A number of specific miRNAs are implicated in regulating the development and propagation of CNS injury, as well as its subsequent regeneration. The review focuses on the functions of the miRNAs and their role in brain recovery following CNS damage. The article introduces a brief description of miRNA biogenesis and mechanisms of miRNA-induced gene suppression, followed by an overview of miRNAs involved in the processes associated with CNS repair, including neuroprotection, neuronal plasticity and axonal regeneration, vascular reorganization, neuroinflammation, and endogenous stem cell activation. Specific emphasis is placed on the role of multifunctional miRNA miR-155, as it appears to be involved in multiple neurorestorative processes during different CNS pathologies. In association with our own studies on miR-155, I introduce a new and unexplored approach to cerebral regeneration: regulation of brain tissue repair through a direct modulation of specific miRNA activity. The review concludes with discussion on the challenges and the future potential of miRNA-based therapeutic approaches to CNS repair.

MicroRNAs in brain development and cerebrovascular pathophysiology

MicroRNAs (miRNAs) are a class of highly conserved non-coding RNAs with 21-25 nucleotides in length and play an important role in regulating gene expression at the posttranscriptional level via base-paring with complementary sequences of the 3'-untranslated region of the target gene mRNA, leading to either transcript degradation or translation inhibition. Brain-enriched miRNAs act as versatile regulators of brain development and function, including neural lineage and subtype determination, neurogenesis, synapse formation and plasticity, neural stem cell proliferation and differentiation, and responses to insults. Herein, we summarize the current knowledge regarding the role of miRNAs in brain development and cerebrovascular pathophysiology. We review recent progress of the miRNA-based mechanisms in neuronal and cerebrovascular development as well as their role in hypoxic-ischemic brain injury. These findings hold great promise, not just for deeper understanding of basic brain biology but also for building new therapeutic strategies for prevention and treatment of pathologies such as cerebral ischemia.

Neutral Sphingomyelinase Inhibition Alleviates LPS-Induced Microglia Activation and Neuroinflammation after Experimental Traumatic Brain Injury

Neuroinflammation is one of the key secondary injury mechanisms triggered by traumatic brain injury (TBI). Microglial activation, a hallmark of brain neuroinflammation, plays a critical role in regulating immune responses after TBI and contributes to progressive neurodegeneration and neurologic deficits following brain trauma. Here we evaluated the role of neutral sphingomyelinase (nSMase) in microglial activation by examining the effects of the nSMase inhibitors altenusin and GW4869 in vitro (using BV2 microglia cells and primary microglia), as well as in a controlled cortical injury (CCI) model in adult male C57BL/6 mice. Pretreatment of altenusin or GW4869 prior to lipopolysaccharide (LPS) stimulation for 4 or 24 hours, significantly downregulated gene expression of the pro-inflammatory mediators TNF-α, IL-1β, IL-6, iNOS, and CCL2 in microglia and reduced the release of nitric oxide and TNF-α These nSMase inhibitors also attenuated the release of microparticles and phosphorylation of p38 MAPK and ERK1/2. In addition, altenusin pretreatment also reduced the gene expression of multiple inflammatory markers associated with microglial activation after experimental TBI, including TNF-α, IL-1β, IL-6, iNOS, CCL2, CD68, NOX2, and p22phox Overall, our data demonstrate that nSMase inhibitors attenuate multiple inflammatory pathways associated with microglial activation in vitro and after experimental TBI. Thus, nSMase inhibitors may represent promising therapeutics agents targeting neuroinflammation.

Inhibition of microRNA-155 attenuates sympathetic neural remodeling following myocardial infarction via reducing M1 macrophage polarization and inflammatory responses in mice

Inflammation plays an important role in sympathetic neural remodeling induced by myocardial infarction (MI). MiR-155 is a vital regulator of inflammatory responses, and macrophage-secreted miR-155 promotes cardiac fibrosis and hypertrophy. However, whether miR-155 influences MI-induced sympathetic neural remodeling is not clear. Therefore, we examined the role of miR-155 in MI-induced sympathetic neural remodeling and the related mechanisms in both an mouse model and in lipopolysaccharide (LPS)-stimulated bone marrow-derived macrophages (BMDMs). Our data showed that miR-155 expression was significantly enhanced in the myocardial tissues of MI mice compared to sham mice. Also, MI up-regulated the electrophysiological parameters, M1 macrophage polarization, inflammatory responses, and suppressor of cytokine signaling 1 (SOCS1) expression, which coincided with the increased expression of sympathetic nerve remodeling markers(nerve growth factor, tyrosine hydroxylase and growth-associated protein 43). Except for SOCS1, these proteins were attenuated by miR-155 antagomir. In vitro, LPS-stimulation promoted miR-155 expression in BMDMs. Consistent with the in vivo findings, miR-155 antagomir diminished the LPS-induced M1 macrophage polarization, nuclear factor (NF)-κB activation, and the expression of pro-inflammatory factors and nerve growth factor; but it increased the expression of SOCS1. Inversely, miR-155 agomir significantly potentiated LPS-induced pathophysiological effects in BMDMs. MiR-155 agomir-induced effects were reversed by the NF-κB inhibitor. Mechanistically, treatment with siRNA against SOCS1 augmented the aforementioned LPS-mediated activities, which were antagonized by the addition of miR-155 antagomir. In conclusion, miR-155 inhibition downregulated NGF expression via decreasing M1 macrophage polarization and inflammatory responses dependent on the SOCS1/NF-κB pathway, subsequently diminishing MI-induced sympathetic neural remodeling and ventricular arrhythmias (VAs).

Inhibition of miR-155 Limits Neuroinflammation and Improves Functional Recovery After Experimental Traumatic Brain Injury in Mice

Micro-RNAs (miRs) are short, noncoding RNAs that negatively regulate gene expression at the post-transcriptional level and have been implicated in the pathophysiology of secondary damage after traumatic brain injury (TBI). Among miRs linked to inflammation, miR-155 has been implicated as a pro-inflammatory factor in a variety of organ systems. We examined the expression profile of miR-155, following experimental TBI (controlled cortical impact) in adult male C57Bl/6 mice, as well as the effects of acute or delayed administration of a miR-155 antagomir on post-traumatic neuroinflammatory responses and neurological recovery. Trauma robustly increased miR-155 expression in the injured cortex over 7 days. Similar TBI-induced miR-155 expression changes were also found in microglia/macrophages isolated from the injured cortex at 7 days post-injury. A miR-155 hairpin inhibitor (antagomir; 0.5 nmol), administered intracerebroventricularly (ICV) immediately after injury, attenuated neuroinflammatory markers at both 1 day and 7 days post-injury and reduced impairments in spatial working memory. Delayed ICV infusion of the miR-155 antagomir (0.5 nmol/day), beginning 24 h post-injury and continuing for 6 days, attenuated neuroinflammatory markers at 7 days post-injury and improved motor, but not cognitive, function through 28 days. The latter treatment limited NADPH oxidase 2 expression changes in microglia/macrophages in the injured cortex and reduced cortical lesion volume. In summary, TBI causes a robust and persistent neuroinflammatory response that is associated with increased miR-155 expression in microglia/macrophages, and miR-155 inhibition reduces post-traumatic neuroinflammatory responses and improves neurological recovery. Thus, miR-155 may be a therapeutic target for TBI-related neuroinflammation.

Panax notoginseng Saponins Attenuate Oxygen-Glucose Deprivation/Reoxygenation-Induced Injury in Human SH-SY5Y Cells by Regulating the Expression of Inflammatory Factors through miR-155

Panax notoginseng saponins (PNS) have been widely used in China to treat stroke. Accumulating evidence has found that microRNA (miR)-155 plays critical roles in the pathology of ischemic stroke. Here we investigated whether PNS plays a protective effect against oxygen-glucose deprivation/reoxygenation (OGD/R)-induced focal inflammation and injury in SH-SY5Y cells by regulating miR-155 expression. Treatment with PNS at a concentration less than 160 µg/mL had no effect on the proliferation of SH-SY5Y cell. In OGD/R-induced SH-SY5Y cells, 160 µg/mL PNS treatment promoted cell proliferation and cell cycle progression, as well as decreased inhibited apoptosis and miR-155 expression. However, overexpression of miR-155 attenuated the promotion effects of PNS on cell proliferation and cell cycle, apoptosis inhibition in OGD/R-induced SH-SY5Y cells. Moreover, 160 µg/mL PNS treatment decreased the levels of interleukin-1β (IL-1β), IL-6, and tumor necrosis factor-α (TNF-α) in OGD/R-induced SH-SY5Y cells, whereas overexpression of miR-155 reversed PNS-induced decreases in the levels of IL-1β, IL-6, and TNF-α in OGD/R-treated SH-SY5Y cells. In conclusion, PNS attenuated OGD/R-induced injury in human undifferentiated SH-SY5Y cells by regulating the expression of inflammatory factors through miR-155.

Non-Coding RNA in Acute Ischemic Stroke: Mechanisms, Biomarkers and Therapeutic Targets

Non-coding RNAs (ncRNAs) are a class of functional RNAs that regulate gene expression in a post-transcriptional manner. NcRNAs include microRNAs, long non-coding RNAs and circular RNAs. They are highly expressed in the brain and are involved in the regulation of physiological and pathophysiological processes, including cerebral ischemic injury, neurodegeneration, neural development, and plasticity. Stroke is one of the leading causes of death and physical disability worldwide. Acute ischemic stroke (AIS) occurs when brain blood flow stops, and that stoppage results in reduced oxygen and glucose supply to cells in the brain. In this article, we review the latest progress on ncRNAs in relation to their implications in AIS, as well as their potential as diagnostic and prognostic biomarkers. We also review ncRNAs acting as possible therapeutic targets in future precision medicine. Finally, we conclude with a brief discussion of current challenges and future directions for ncRNAs studies in AIS, which may facilitate the translation of ncRNAs research into clinical practice to improve clinical outcome of AIS.

MiR-155 deletion reduces ischemia-induced paralysis in an aortic aneurysm repair mouse model: Utility of immunohistochemistry and histopathology in understanding etiology of spinal cord paralysis

Spinal cord paralysis is relatively common after surgical repair of thoraco-abdominal aortic aneurysm (TAAA) and its etiology is unknown. The present study was designed to examine the histopathology of the disease and investigate whether miR-155 ablation would reduce spinal cord ischemic damage and delayed hindlimb paralysis induced by aortic cross-clamping (ACC) in our mouse model. The loss of locomotor function in ACC-paralyzed mice correlated with the presence of extensive gray matter damage and central cord edema, with minimal white matter histopathology. qRTPCR and Western blotting showed that the spinal cords of wild-type ACC mice that escaped paralysis showed lower miR-155 expression and higher levels of transcripts encoding Mfsd2a, which is implicated in the maintenance of blood-brain barrier integrity. In situ based testing demonstrated that increased miR-155 detection in neurons was highly correlated with the gray matter damage and the loss of one of its targets, Mfsd2a, could serve as a good biomarker of the endothelial cell damage. In vitro, we demonstrated that miR-155 targeted Mfsd2a in endothelial cells and motoneurons and increased endothelial cell permeability. Finally, miR-155 ablation slowed the progression of central cord edema, and reduced the incidence of paralysis by 40%. In sum, the surgical pathology findings clearly indicated that the epicenter of the ischemic-induced paralysis was the gray matter and that endothelial cell damage correlated to Mfsd2a loss is a good biomarker of the disease. MiR-155 targeting therefore offers new therapeutic opportunity for edema caused by traumatic spinal cord injury and diagnostic pathologists, by using immunohistochemistry, can clarify if this mechanism also is important in other ischemic diseases of the CNS, including stroke.

Let-7i inhibition enhances progesterone-induced functional recovery in a mouse model of ischemia

Progesterone (P4) is a potent neuroprotectant and a promising therapeutic for stroke treatment. However, the underlying mechanism(s) remain unclear. Our laboratory recently reported that brain-derived neurotrophic factor (BDNF) is a critical mediator of P4's protective actions and that P4-induced BDNF release from cortical astrocytes is mediated by a membrane-associated progesterone receptor, Pgrmc1. Here, we report that the microRNA (miRNA) let-7i is a negative regulator of Pgrmc1 and BDNF in glia and that let-7i disrupts P4-induced BDNF release and P4's beneficial effects on cell viability and markers of synaptogenesis. Using an in vivo model of ischemia, we demonstrate that inhibiting let-7i enhances P4-induced neuroprotection and facilitates functional recovery following stroke. The discovery of such factors that regulate the cytoprotective effects of P4 may lead to the development of biomarkers to differentiate/predict those likely to respond favorably to P4 versus those that do not.

Pivotal role of innate myeloid cells in cerebral post-ischemic sterile inflammation

Inflammatory responses play a multifaceted role in regulating both disability and recovery after ischemic brain injury. In the acute phase of ischemic stroke, resident microglia elicit rapid inflammatory responses by the ischemic milieu. After disruption of the blood-brain barrier, peripheral-derived neutrophils and mononuclear phagocytes infiltrate into the ischemic brain. These infiltrating myeloid cells are activated by the endogenous alarming molecules released from dying brain cells. Inflammation after ischemic stroke thus typically consists of sterile inflammation triggered by innate immunity, which exacerbates the pathologies of ischemic stroke and worsens neurological prognosis. Infiltrating immune cells sustain the post-ischemic inflammation for several days; after this period, however, these cells take on a repairing function, phagocytosing inflammatory mediators and cellular debris. This time-specific polarization of immune cells in the ischemic brain is a potential novel therapeutic target. In this review, we summarize the current understanding of the phase-dependent role of innate myeloid cells in ischemic stroke and discuss the cellular and molecular mechanisms of their inflammatory or repairing polarization from a therapeutic perspective.