Ischemic transient neurological events identified by immune response to cerebral ischemia

Bioinformatics Identification of angiogenesis-related biomarkers and therapeutic targets in cerebral ischemia-reperfusion

Promoting vascular endothelial cell regeneration can enhance recovery from cerebral ischemia reperfusion injury (CIRI), but there is a lack of bioinformatic studies on angiogenesis-related biomarkers in CIRI. In this study, we utilized the GSE97537 and GSE61616 datasets from GEO to identify 181 angiogenesis-related genes (ARGs) and analyzed differentially expressed genes (DEGs) between CIRI and control groups. We converted ARGs to 169 rat homologues and intersected them with DEGs to find DE-ARGs. RF and XGBoost models were employed to identify five biomarkers (Stat3, Hmox1, Egfr, Col18a1, Ptgs2) and conducted GSEA on these biomarkers, revealing their enrichment in pathways such as ECM-receptor interaction and hematopoietic cell lineage. We also analyzed the immune microenvironment, finding significant differences in 21 immune cells between CIRI and control groups. Furthermore, we constructed lncRNA-miRNA-mRNA networks and drug-gene networks. Finally, biomarker expression was compared between the CIRI and control groups by qRT-PCR in tissue and blood samples. Overall, our bioinformatic exploration of angiogenesis-related biomarkers in CIRI provides new insights for the diagnosis and treatment of CIRI.

Quantitative analysis of selected genetic markers of induced brain stroke ischemic tolerance detected in human blood

A brain stroke is a serious disease and the second leading cause of death in the European Union. Carotid stenosis accounts for 15% of all ischemic cerebral strokes. However, there is currently no effective screening for carotid disease. Analysis of the DNA from peripheral blood is increasingly being used for several disease diagnoses. The potentially beneficial therapeutic method of inducing tissue tolerance to ischemia has so far been studied mainly in animal models. The aim of this study is to investigate changes in the gene expression of selected markers of brain ischemia during carotid endarterectomy, considered in this study as an activator of ischemic tolerance. During the carotid endarterectomy, there is a short-term occlusion of the internal carotid artery. Using the RT-qPCR method, we detected changes in the early identified gene markers of brain ischemia (ADM, CDKN1A, GADD45G, IL6, TM4SF1) in peripheral blood during sub lethal cerebral ischemia caused by carotid endarterectomy. Patients underwenting surgical procedure were divided into three groups: asymptomatic, symptomatic, and those who underwent carotid endarterectomy after an acute stroke. The results were compared to a negative/control group. Carotid endarterectomy had an impact on the expression of all monitored biomarkers. We observed statistically significant changes (p value 0.05-0.001) when comparing the groups among themselves, as well as the presence of ischemic tolerance of brain tissue to ischemic attacks. In conclusion, ADM, GADD45G, and TM4SF1 were affected in symptomatic patients, GADD45G and IL6 in acute patients, and CDKN1A and ADM in asymptomatic group after application of carotid endarterectomy.

Biomarkers for Transient Ischemic Attack: A Brief Perspective of Current Reports and Future Horizons

Cerebrovascular disease is the leading cause of long-term disability in the world and the third-leading cause of death in the United States. The early diagnosis of transient ischemic attack (TIA) is of great importance for reducing the mortality and morbidity of cerebrovascular diseases. Patients with TIA have a high risk of early subsequent ischemic stroke and the development of permanent nervous system lesions. The diagnosis of TIA remains a clinical diagnosis that highly relies on the patient's medical history assessment. There is a growing list of biomarkers associated with different components of the ischemic cascade in the brain. In this review, we take a closer look at the biomarkers of TIA and their validity with a focus on the more clinically important ones using recent evidence of their reliability for practical usage.

Modifications of gene expression detected in peripheral blood after brain ischemia treated with remote postconditioning

BACKGROUND

A stroke is an acute damage to a certain area of a nerve tissue of the brain. In developed countries, it ranks second among the most often causes of death and is also the leading cause of disability. Recent findings emphasize the significant neuroprotective effect of conditioning on the course and rate of recovery after ischemic attack; however the molecular mechanism of ischemic tolerance induced by conditioning is still not completely explored.

METHODS AND RESULTS

The purpose of this study is an identification of changes in gene expression induced by stimulation of reaction cascades after activation of the neuroprotective mechanism using an experimental rat model of global ischemia. The induction of neuroprotective cascades was stimulated by the application of early and delayed form of remote ischemic postconditioning. The quantitative qRT-PCR method was used to assess the rate of change in ADM, BDNF, CDKN1A, CREB, GADD45G, IL6, nNOS, and TM4SF1 gene expression levels 72 h after ischemic attack. The detected results confirm the neuroprotective effect of both forms of postconditioning. Participation of neuroprotection-related gene expression changes was observed once as an early one (CREB, GADD45G), once as a delayed one (ADM, IL6), or both (BDNF, CDKN1A, nNOS, TM4SF1) postconditioning forms, depending on the particular gene.

CONCLUSIONS

Our results characterize impact of ischemic tolerance on the molecular level. We predict ischemic tolerance to be consisted of complex combination of early and delayed remote postconditioning.

Identification of Candidate Blood mRNA Biomarkers in Intracerebral Hemorrhage Using Integrated Microarray and Weighted Gene Co-expression Network Analysis

Purpose

Intracerebral hemorrhage (ICH) is a serious public health hazard due to its high morbidity, disability, and mortality. Currently, the exact molecular mechanisms of ICH are unknown. We tried to identify the ICH-related candidate blood messenger RNA (mRNA) biomarkers by microarray analysis and weighted gene co-expression network analysis (WGCNA).

Materials and Methods

We collected the blood samples from patients with ICH (n = 4) and from vascular risk factor (VRF) controls (n = 4) and analyzed the mRNA expression profiles by competitive endogenous RNA (ceRNA) microarray. Differentially expressed genes (DEGs) were identified and then a weighted gene co-expression network was constructed. Modules with clinical significance were distinguished. Then, we downloaded two Gene Expression Omnibus (GEO) datasets (GSE24265 and GSE125512). Candidate mRNAs were identified by taking the intersection of the DEGs in our microarray, the interesting genes in the key module, and the DEGs in GSE24265. Functional analysis involving Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) and construction of a protein–protein interaction (PPI) network were conducted.

Results

A total of 340 DEGs in our microarray were identified between the ICH group and the control group. Among the eight gene modules established by WGCNA, the yellow module containing 191 genes was the most strongly associated with ICH. Four candidate mRNAs (C3AR1, PAWR, ARNTL2, and LDLRAD4) were identified. In the early stage of ICH (within 24 h), C3AR1, PAWR, and ARNTL2 were highly expressed in the perihematomal tissue, but with low expressions in peripheral blood; in the late stage (72 h after the first blood draw), an obvious upward trend of C3AR1 and PAWR in peripheral blood was seen. Functional analysis showed that candidate mRNAs were concerned with multiple pathways, such as the Wnt signaling pathway and calcium signaling pathway. They might affect the process of ICH through neuroinflammation, cell apoptosis, and pyroptosis.

Conclusion

We identified four candidate blood mRNAs (C3AR1, PAWR, ARNTL2, and LDLRAD4) related to ICH. They showed different expression patterns in peripheral blood and perihematomal tissues and changed with time. They might play important roles in ICH through neuroinflammation, cell apoptosis, and pyroptosis and might shed new light to novel biomarkers or therapeutic targets in ICH.

Acute Stroke Biomarkers: Are We There Yet?

Background: Distinguishing between stroke subtypes and knowing the time of stroke onset are critical in clinical practice. Thrombolysis and thrombectomy are very effective treatments in selected patients with acute ischemic stroke. Neuroimaging helps decide who should be treated and how they should be treated but is expensive, not always available and can have contraindications. These limitations contribute to the under use of these reperfusion therapies.

Aim: An alternative approach in acute stroke diagnosis is to identify blood biomarkers which reflect the body's response to the damage caused by the different types of stroke. Specific blood biomarkers capable of differentiating ischemic from hemorrhagic stroke and mimics, identifying large vessel occlusion and capable of predicting stroke onset time would expedite diagnosis and increase eligibility for reperfusion therapies.

Summary of Review: To date, measurements of candidate biomarkers have usually occurred beyond the time window for thrombolysis. Nevertheless, some candidate markers of brain tissue damage, particularly the highly abundant glial structural proteins like GFAP and S100β and the matrix protein MMP-9 offer promising results. Grouping of biomarkers in panels can offer additional specificity and sensitivity for ischemic stroke diagnosis. Unbiased “omics” approaches have great potential for biomarker identification because of greater gene, protein, and metabolite coverage but seem unlikely to be the detection methodology of choice because of their inherent cost.

Conclusion: To date, despite the evolution of the techniques used in their evaluation, no individual candidate or multimarker panel has proven to have adequate performance for use in an acute clinical setting where decisions about an individual patient are being made. Timing of biomarker measurement, particularly early when decision making is most important, requires urgent and systematic study.

Multilevel omics for the discovery of biomarkers and therapeutic targets for stroke

Despite many years of research, no biomarkers for stroke are available to use in clinical practice. Progress in high-throughput technologies has provided new opportunities to understand the pathophysiology of this complex disease, and these studies have generated large amounts of data and information at different molecular levels. The integration of these multi-omics data means that thousands of proteins (proteomics), genes (genomics), RNAs (transcriptomics) and metabolites (metabolomics) can be studied simultaneously, revealing interaction networks between the molecular levels. Integrated analysis of multi-omics data will provide useful insight into stroke pathogenesis, identification of therapeutic targets and biomarker discovery. In this Review, we detail current knowledge on the pathology of stroke and the current status of biomarker research in stroke. We summarize how proteomics, metabolomics, transcriptomics and genomics are all contributing to the identification of new candidate biomarkers that could be developed and used in clinical stroke management.

PEGylated Erythropoietin Protects against Brain Injury in the MCAO-Induced Stroke Model by Blocking NF-κB Activation

Cerebral ischemia exhibits a multiplicity of pathophysiological mechanisms. During ischemic stroke, the reactive oxygen species (ROS) concentration rises to a peak during reperfusion, possibly underlying neuronal death. Recombinant human erythropoietin (EPO) supplementation is one method of treating neurodegenerative disease by reducing the generation of ROS. We investigated the therapeutic effect of PEGylated EPO (P-EPO) on ischemic stroke. Mice were administered P-EPO (5,000 U/kg) via intravenous injection, and middle cerebral artery occlusion (MCAO) followed by reperfusion was performed to induce in vivo ischemic stroke. P-EPO ameliorated MCAO-induced neurological deficit and reduced behavioral disorder and the infarct area. Moreover, lipid peroxidation, expression of inflammatory proteins (cyclooxygenase-2 and inducible nitric oxide synthase), and cytokine levels in blood were reduced by the P-EPO treatment. In addition, higher activation of nuclear factor kappa B (NF-κB) was found in the brain after MCAO, but NF-κB activation was reduced in the P-EPO-injected group. Treatment with the NF-κB inhibitor PS-1145 (5 mg/kg) abolished the P-EPO-induced reduction of infarct volume, neuronal death, neuroinflammation, and oxidative stress. Moreover, P-EPO was more effective than EPO (5,000 U/kg) and similar to a tissue plasminogen activator (10 mg/kg). An in vitro study revealed that P-EPO (25, 50, and 100 U/mL) treatment protected against rotenone (100 nM)-induced neuronal loss, neuroinflammation, oxidative stress, and NF-κB activity. These results indicate that the administration of P-EPO exerted neuroprotective effects on cerebral ischemia damage through anti-oxidant and anti-inflammatory properties by inhibiting NF-κB activation.

Blood Biomarkers for Stroke Diagnosis and Management

Biomarkers are objective indicators used to assess normal or pathological processes, evaluate responses to treatment and predict outcomes. Many blood biomarkers already guide decision-making in clinical practice. In stroke, the number of candidate biomarkers is constantly increasing. These biomarkers include proteins, ribonucleic acids, lipids or metabolites. Although biomarkers have the potential to improve the diagnosis and the management of patients with stroke, there is currently no marker that has demonstrated sufficient sensitivity, specificity, rapidity, precision, and cost-effectiveness to be used in the routine management of stroke, thus highlighting the need for additional work. A better standardization of clinical, laboratory and statistical procedures between centers is indispensable to optimize biomarker performance. This review focuses on blood biomarkers that have shown promise for translation into clinical practice and describes some newly reported markers that could add to routine stroke care. Avenues for the discovery of new stroke biomarkers and future research are discussed. The description of the biomarkers is organized according to their expected application in clinical practice: diagnosis, treatment decision, and outcome prediction.

Blood transcriptomic biomarker as a surrogate of ischemic brain gene expression

Objectives

Blood biomarkers for cerebral tissue ischemia are lacking. The goal was to identify a blood transcriptomic signature jointly identified in the ischemic brain.

Methods

A nonhuman primate model with middle cerebral artery (MCA) territory infarction was used to study gene expression by microarray during acute ischemic cerebral stroke in the brain and the blood. Brain samples were collected in the infarcted and contralateral non‐infarcted cortex as well as blood samples before and after occlusion. Gene expression was compared between the two brain locations to find differentially expressed genes. The expressions of these genes were then compared in the blood pre‐ and post‐occlusion.

Results

Hierarchical clustering of brain expression data revealed strong independent clustering of ischemic and nonischemic brain samples. The top five enriched, up‐regulated gene sets in the brain were TNF α signaling, apoptosis, P53 pathway, hypoxia, and UV response up. A comparison of differentially expressed genes in the brain and blood revealed a significant overlap of gene expression patterns. Stringent analysis of blood expression data from pre‐ and post‐occlusion samples in each monkey identified nine genes highly differentially expressed in both the brain and the blood. Many of these up‐regulated genes belong to pathways involved in cell death and DNA damage repair.

Interpretation

Common gene expression profile can be identified in the brain and blood and clearly differentiates ischemic from nonischemic conditions. Therefore, specific blood transcriptomic signature may represent a surrogate for brain ischemic gene expression.

[Collateral circulation and Toll-like receptor 4 levels in patients with acute cerebral infarction after intravenous thrombolysis]

OBJECTIVE

To investigate the relationship between Toll-like receptor 4 (TLR4) and collateral circulation in patients with acute cerebral infarction (AIS) after thrombolytic therapy.

METHODS

This retrospective, observational cohort study was conducted among 65 patients with AIS receiving thrombolytic therapy, who were divided according to findings by computed tomographic angiography (CTA) into good collateral circulation (group A, n = 34) and poor collateral circulation (group B, n = 31). Serum samples were collected from all the patients and the levels of TLR4 were measured with ELISA.

RESULTS

The patients in group A had significantly better outcomes than those in group B. The NIHSS scores at 24 h and 30 days after thrombolytic therapy, mRS scores at 90 days and serum TLR4 levels were significantly lower in group A than in group B (P < 0.05); the percentages of patients with symptomatic intracerebral hemorrhage were comparable between the two groups. The serum levels of TLR4 were negatively correlated with the rMLC score (P < 0.05). Multivariate logistic regression analysis showed that a high level of TLR4 was associated with a poor collateral circulation after thrombolysis.

CONCLUSIONS

Good collateral circulation can increase the benefit of intravenous thrombolysis in patients with ACI, and the level of TLR4 is a predictive factor for the compensation of collateral circulation following ACI.

Repression of long non-coding RNA MEG3 restores nerve growth and alleviates neurological impairment after cerebral ischemia-reperfusion injury in a rat model

OBJECTIVE

This study was performed to investigate effect of long non-coding RNA (lncRNA) MEG3 on nerve growth and neurological impairment in a rat model after cerebral ischemia-reperfusion injury (IRI) through the Wnt/β-catenin signaling pathway.

METHODS

Rat models of middle cerebral artery occlusion (MCAO) were established to stimulate an environment of cerebral IRI. The modeled rats were subjected to negative control (NC), MEG3, si-MEG3, classical Wnt pathway inhibitor DKK1 or classical Wnt pathway activator LiCl to validate the effect of MEG3 on neurological impairment and nerve growth. Neurological deficit scoring, fault-foot test and balance beam test were performed to assess neurological impairment. TTC staining, dry-wet weight method and Evan's blue (EB) staining were employed to determine infarct area, water content of brain tissues and blood-brain barrier (BBB) permeability, respectively. Neuronal apoptosis and necrosis were observed by TUNEL staining and Fluoro-Jade C staining. ELISA was adopted to identify levels of nerve growth factors to identify neurogenesis conditions, including brain derived neurotrophic factor (BDNF), nerve growth factor (NGF) and basic fibroblast growth factor (bFGF). Nissl staining was used to detect the survival of neurons in brain tissues of rats. Western blot analysis was used to detect the expression of key proteins in Wnt/β-catenin signaling pathway in brain tissues.

RESULTS

High expression of MEG3 was identified in rat models of MACAO, the brain tissues of which manifested obvious neurological impairment, increased infarct area, water content, BBB permeability, accelerated neuronal apoptosis and necrosis, increased surviving neurons, upregulated expression of key proteins in Wnt/β-catenin signaling pathway and elevated levels of BDNF, NGF and bFGF. With the treatment of si-MEG3, the MEG3 expression was reduced; whereby, modeled rats showed ameliorated neurological impairment, reduced infarct area, water content, BBB permeability, neuronal apoptosis and necrosis and significantly enhanced neurogenesis. The treatment of MEG3 exhibited an opposite trend. After treatment with DKK1, the effect of si-MEG3 was reversed. After treatment with LiCl, the effect of MEG3 was reversed.

CONCLUSION

Based on the findings of this study, down-regulation of lncRNA MEG3 expression enhanced nerve growth and alleviated neurological impairment of rats after cerebral IRI through the activation of the Wnt/β-catenin signaling pathway.

Systematic Understanding of the Mechanism of Baicalin against Ischemic Stroke through a Network Pharmacology Approach

Ischemic stroke is accompanied by high mortality and morbidity rates. At present, there is no effective clinical treatment. Alternatively, traditional Chinese medicine has been widely used in China and Japan for the treatment of ischemic stroke. Baicalin is a flavonoid extracted from Scutellaria baicalensis that has been shown to be effective against ischemic stroke; however, its mechanism has not been fully elucidated. Based on network pharmacology, we explored the potential mechanism of baicalin on a system level. After obtaining baicalin structural information from the PubChem database, an approach combined with literature mining and PharmMapper prediction was used to uncover baicalin targets. Ischemic stroke-related targets were gathered with the help of DrugBank, Online Mendelian Inheritance in Man (OMIM), Genetic Association Database (GAD), and Therapeutic Target Database (TTD). Protein-protein interaction (PPI) networks were constructed through the Cytoscape plugin BisoGenet and analyzed by topological methods. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment were carried out via the Database for Annotation, Visualization, and Integrated Discovery (DAVID) server. We obtained a total of 386 potential targets and 5 signaling pathways, including mitogen-activated protein kinase (MAPK), phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT), hypoxia-inducible factor-1 (HIF-1), nuclear factor kappa B (NF-κB), and forkhead box (FOXO) signaling pathways. GO analysis showed that these targets were associated with antiapoptosis, antioxidative stress, anti-inflammation, and other physiopathological processes that are involved in anti-ischemic stroke effects. In summary, the mechanism of baicalin against ischemic stroke involved multiple targets and signaling pathways. Our study provides a network pharmacology framework for future research on traditional Chinese medicine.

Regulatory T CD4 + CD25+ lymphocytes increase in symptomatic carotid artery stenosis

BACKGROUND

Atherosclerosis is a multifactorial disease characterized by an immune-inflammatory remodeling of the arterial wall. Treg and Th17 subpopulations are detectable inside atherosclerotic plaque; however, their behavior in symptomatic carotid artery stenosis (CAS) is not fully elucidated. The aim of this study was to evaluate Th17 and Treg subsets and their ratio in patients affected by symptomatic and asymptomatic CAS.

METHODS

14 patients with symptomatic CAS (CAS-S group), 41 patients with asymptomatic CAS (CAS-A group), 32 subjects with traditional cardiovascular risk factors (RF group), and 10 healthy subjects (HS group) were enrolled. Th17 and Treg frequency was determined by flow cytometry and by histology and immunohistochemistry. Interleukin (IL)-10, IL-17, and metalloproteinase (MMP)-12 levels were measured by ELISA.

RESULTS

Th17 were significantly increased in CAS-A versus RF and versus HS. Tregs were significantly increased in CAS-S versus CAS-A. Tregs/Th17 ratio was significantly reduced in CAS-A versus RF and versus HS, whereas it was significantly increased in CAS-S versus CAS-A.

CONCLUSIONS

The results of this study suggest that Th17 are related to the late stages of CAS but not to plaque instability. Moreover, Treg expansion seems to represent a specific cellular pattern displayed by patients with symptomatic CAS and associated with brain injury. KEY MESSAGES Tregs expansion seems to represent a specific cellular pattern displayed by patients with symptomatic CAS and associated with CD4+ effector depletion and brain ischemic injury. Th17 lymphocytes are related to the late stages of CAS but not to plaque instability.

RNA as a stroke biomarker

A biomarker to aid in the diagnosis of ischemic stroke and its causes would be of value in acute clinical practice. It could have applications to aid in acute stroke treatment decisions for tissue plasminogen activator and/or the triage to endovascular therapy. A stroke biomarker may also be useful to identify stroke etiology and guide stroke prevention treatments. This review provides an overview of RNA as a novel biomarker for the diagnosis and assessment of ischemic stroke. Topics addressed include RNA to identify acute ischemic stroke; RNA to identify transient ischemic attack; RNA to predict large vessel, cardioembolic and small vessel cause of stroke; and RNA to predict risk of tissue plasminogen activator related hemorrhagic transformation. Emerging methods to measure RNA as a point-of-care assay include microfluidics sorting and electrochemical sensors.

Molecular magnetic resonance imaging discloses endothelial activation after transient ischaemic attack

SEE SUN ET AL DOI101093/AWW306 FOR A SCIENTIFIC COMMENTARY ON THIS ARTICLE: About 20% of patients with ischaemic stroke have a preceding transient ischaemic attack, which is clinically defined as focal neurological symptoms of ischaemic origin resolving spontaneously. Failure to diagnose transient ischaemic attack is a wasted opportunity to prevent recurrent disabling stroke. Unfortunately, diagnosis can be difficult, due to numerous mimics, and to the absence of a specific test. New diagnostic tools are thus needed, in particular for radiologically silent cases, which correspond to the recommended tissue-based definition of transient ischaemic attack. As endothelial activation is a hallmark of cerebrovascular events, we postulated that this may also be true for transient ischaemic attack, and that it would be clinically relevant to develop non-invasive in vivo imaging to detect this endothelial activation. Using transcriptional and immunohistological analyses for adhesion molecules in a mouse model, we identified brain endothelial P-selectin as a potential biomarker for transient ischaemic attack. We thus developed ultra-sensitive molecular magnetic resonance imaging using antibody-based microparticles of iron oxide targeting P-selectin. This highly sensitive imaging strategy unmasked activated endothelial cells after experimental transient ischaemic attack and allowed discriminating transient ischaemic attack from epilepsy and migraine, two important transient ischaemic attack mimics. We provide preclinical evidence that combining conventional magnetic resonance imaging with molecular magnetic resonance imaging targeting P-selectin might aid in the diagnosis of transient ischaemic attack.

Inter-rater agreement analysis of the Precise Diagnostic Score for suspected transient ischemic attack

Background

No definitive criteria are available to confirm the diagnosis of transient ischemic attack. Inter-rater agreement between physicians regarding the diagnosis of transient ischemic attack is low, even among vascular neurologists. We developed the Precise Diagnostic Score, a diagnostic score that consists of discrete and well-defined clinical and imaging parameters, and investigated inter-rater agreement in patients with suspected transient ischemic attack.

Methods

Fellowship-trained vascular neurologists, blinded to final diagnosis, independently reviewed retrospectively identical history, physical examination, routine diagnostic studies, and brain magnetic resonance imaging (diffusion and perfusion images) from consecutive patients with suspected transient ischemic attack. Each patient was rated using the 8-point Precise Diagnostic Score score, composed of a clinical score (0–4 points) and an imaging score (0–4 points). The composite Precise Diagnostic Score determines a Precise Diagnostic Score Likelihood of Brain Ischemia Scale: 0–1 = unlikely, 2 = possible, 3 = probable, 4–8 = very likely.

Results

Three raters reviewed data from 114 patients. Using Precise Diagnostic Score, all three raters scored a similar percentage of the clinical events as being “probable” or “very likely” caused by brain ischemia: 57, 55, and 58%. Agreement was high for both total Precise Diagnostic Score (intraclass correlation coefficient of 0.94) and for the Likelihood of Brain Ischemia Scale (agreement coefficient of 0.84).

Conclusions

Compared with prior studies, inter-rater agreement for the diagnosis of transient brain ischemia appears substantially improved with the Precise Diagnostic Score scoring system. This score is the first to include specific criteria to assess the clinical relevance of diffusion-weighted imaging and perfusion lesions and supports the added value of magnetic resonance imaging for assessing patients with suspected transient ischemic attack.

Gene expression profiling in stroke: relevance of blood-brain interaction

Biomarker profiling is utilized to identify diagnostic and prognostic candidates for stroke. Clinical and preclinical biomarker data suggest altered circulating immune responses may illuminate the mechanisms of stroke recovery. However, the relationship between peripheral blood biomarker profile(s) and brain profiles following stroke remains elusive. Data show that neutrophil lymphocyte ratio (NLR) predicts stroke outcome. Neutrophils release Arginase 1 (ARG1) resulting in T lymphocyte suppression in peripheral blood. Interestingly, the cellular response to stroke may have implications for known biomarker profiles. Conversely, preclinical evidence suggests that upregulation of ARG1 in microglia is a marker of M2 macrophages and may influence neuroprotection. Comparing clinical and preclinical studies creates opportunities to explore the molecular mechanisms of blood and brain biomarker interactions in stroke.

Innate and adaptive immune response in stroke: Focus on epigenetic regulation

Inflammation and immune response play a pivotal role in the pathophysiology of ischemic stroke giving their contribution to tissue damage and repair. Emerging evidence supports the involvement of epigenetic mechanisms such as methylation, histone modification and miRNAs in the pathogenesis of stroke. Interestingly, epigenetics can influence the molecular events involved in ischemic injury by controlling the switch from pro- to anti-inflammatory response, however, this is still a field to be fully explored. The knowledge of epigenetic processes could to allow for the discovery of more sensitive and specific biomarkers for risk, onset, and progression of disease as well as further novel tools to be used in both primary prevention and therapy of stroke. Indeed, studies performed in vitro and in small animal models seem to suggest a neuroprotective role of HDAC inhibitors (e.g. valproic acid) and antagomir (e.g. anti-miR-181a) in ischemic condition by modulation of both immune and inflammatory pathways. Thus, the clinical implications of altered epigenetic mechanisms for the prevention of stroke are very promising but clinical prospective studies and translational approaches are still warranted.

microRNA expression in peripheral blood cells following acute ischemic stroke and their predicted gene targets

Background

microRNA (miRNA) are important regulators of gene expression. In patients with ischemic stroke we have previously shown that differences in immune cell gene expression are present. In this study we sought to determine the miRNA that are differentially expressed in peripheral blood cells of patients with acute ischemic stroke and thus may regulate immune cell gene expression.

Methods

miRNA from peripheral blood cells of forty-eight patients with ischemic stroke and vascular risk factor controls were compared. Differentially expressed miRNA in patients with ischemic stroke were determined by microarray with qRT-PCR confirmation. The gene targets and pathways associated with ischemic stroke that may be regulated by the identified miRNA were characterized.

Results

In patients with acute ischemic stroke, miR-122, miR-148a, let-7i, miR-19a, miR-320d, miR-4429 were decreased and miR-363, miR-487b were increased compared to vascular risk factor controls. These miRNA are predicted to regulate several genes in pathways previously identified by gene expression analyses, including toll-like receptor signaling, NF-κβ signaling, leukocyte extravasation signaling, and the prothrombin activation pathway.

Conclusions

Several miRNA are differentially expressed in blood cells of patients with acute ischemic stroke. These miRNA may regulate leukocyte gene expression in ischemic stroke including pathways involved in immune activation, leukocyte extravasation and thrombosis.

ABCD2 score and BNP level in patients with TIA and cerebral stroke

Scoring systems have been designed to help physicians in early prediction of cerebral stroke following Transitional Ischemic Attack (TIA). ABCD2 system is one of these scoring systems. Considering increase of brain natriuretic peptide following cerebral ischemic stroke, BNP level may be associated with incidence of ischemic stroke following TIA. The present study evaluates ABCD2 score, BNP level in patients with TIA and incidence of cerebral stroke. This cross sectional-analytical study evaluated 78 patients with TIA. ABCD2 score was calculated for all patients based on some criteria including age, blood pressure, clinical manifestations (speech/motor disorder), symptoms duration and diabetes. BNP level was measured at the reference laboratory when the patient referred to the treatment center. The patients were followed up for 6 months considering incidence of cerebral stroke and TIA. Mean age of the patients was 66.53 +/- 13.08 years and the sample was consisted of 62.8% male and 37.2% female patients. Mean BNP level and mean ABCD2 score was 611.31 +/- 125.61 and 4.61 +/- 10.99 in all patients, respectively. During follow-up period, TIA recurrence and cerebral stroke were, respectively seen in 11.5 and 3.8% of cases. Mortality was reported in 5.1% of the patients. BNP was significantly higher in cases with recursive TIA (p = 0.03). But, there was not any difference considering ABCD2 score (p = 0.38). BNP is capable of predicting TIA recurrence following first TIA and it can be used in this case.

A new role for downstream Toll-like receptor signaling in mediating immediate early gene expression during focal cerebral ischemia

To better understand the role of downstream Toll-like receptor (TLR) signaling during acute cerebral ischemia, we performed cDNA microarrays, on brain RNA, and cytokine arrays, on serum, from wild type (WT), MyD88-/- and TRIF-mutant mice, at baseline and following permanent middle cerebral artery occlusion (pMCAO). The acute stress response pathway was among the top pathways identified by Ingenuity Pathway Analysis of microarray data. We used real-time polymerase chain reaction to confirm the expression of four immediate early genes; EGR1, EGR2, ARC, Nurr77, in this pathway, and insulin degrading enzyme (IDE). Compared to WT, baseline immediate early gene expression was increased up to10-fold in MyD88-/- and TRIF-mutant mice. However, following pMCAO, immediate early gene expression remained unchanged, from this elevated baseline in these mice, but increased up to 12-fold in WT. Furthermore, expression of IDE, which also degrades β-amyloid, decreased significantly only in TRIF-mutant mice. Finally, sE-Selectin, sICAM, sVCAM-1, and MMP-9 levels were significantly decreased only in MyD88-/- compared with WT mice. We thus report a new role for downstream TLR signaling in immediate early gene expression during acute cerebral ischemia. We also show that the TRIF pathway regulates IDE expression; a major enzyme that clears β-amyloid from the brain.

All's well that transcribes well: non-coding RNAs and post-stroke brain damage

The mammalian genome is replete with various classes of non-coding (nc) RNA genes. Many of them actively transcribe, and their relevance to CNS diseases is just beginning to be understood. CNS is one of the organs in the body that shows very high ncRNAs activity. Recent studies demonstrated that cerebral ischemia rapidly changes the expression profiles of different classes of ncRNAs: including microRNA, long noncoding RNA and piwi-interacting RNA. Several studies further showed that post-ischemic neuronal death and/or plasticity/regeneration can be altered by modulating specific microRNAs. These studies are of interest for therapeutic development as they may contribute to identifying new ncRNA targets that can be modulated to prevent secondary brain damage after stroke.

RNA in blood is altered prior to hemorrhagic transformation in ischemic stroke

OBJECTIVE

Hemorrhagic transformation (HT) is a major complication of ischemic stroke that worsens outcomes and increases mortality. Disruption of the blood-brain barrier is a central feature of HT pathogenesis, and leukocytes may contribute to this process. We sought to determine whether ischemic strokes that develop HT have differences in RNA expression in blood within 3 hours of stroke onset prior to treatment with thrombolytic therapy.

METHODS

Stroke patient blood samples were obtained prior to treatment with thrombolysis, and leukocyte RNA was assessed by microarray analysis. Strokes that developed HT (n = 11) were compared to strokes without HT (n = 33) and controls (n = 14). Genes were identified (corrected p < 0.05, fold change ≥|1.2|), and functional analysis was performed. RNA prediction of HT in stroke was evaluated using cross-validation, and in a second stroke cohort (n = 52).

RESULTS

Ischemic strokes that developed HT had differential expression of 29 genes in circulating leukocytes prior to treatment with thrombolytic therapy. A panel of 6 genes could predict strokes that later developed HT with 80% sensitivity and 70.2% specificity. Key pathways involved in HT of human stroke are described, including amphiregulin, a growth factor that regulates matrix metalloproteinase-9; a shift in transforming growth factor-β signaling involving SMAD4, INPP5D, and IRAK3; and a disruption of coagulation factors V and VIII.

INTERPRETATION

Identified genes correspond to differences in inflammation and coagulation that may predispose to HT in ischemic stroke. Given the adverse impact of HT on stroke outcomes, further evaluation of the identified genes and pathways is warranted to determine their potential as therapeutic targets to reduce HT and as markers of HT risk.

Ischemic stroke biomarkers in blood

Ischemic stroke is a leading cause of adult disability and mortality. With over 15 million strokes occurring every year in the world, methods to better identify patients at risk for stroke are needed, as are methods to improve patient diagnosis and prognosis when stroke occurs. Use of blood-based biomarkers is one method that has been evaluated to predict risk of stroke, diagnose stroke and its causes, predict stroke severity and outcome, and guide prevention therapy. Markers that have been identified include a variety of proteins, nucleic acids and lipids that relate to stroke pathophysiology. The role of blood biomarkers in ischemic stroke is still being defined, and further study is needed to develop blood biomarkers for clinical stroke use. In this review, the authors provide a summary of biomarkers that have been divided by their potential clinical application.