High Serum Levels of Endothelin-1 Predict Severe Cerebral Edema in Patients With Acute Ischemic Stroke Treated With t-PA

Updates in Management of Large Hemispheric Infarct

This review delves into updates in management of large hemispheric infarction (LHI), a condition affecting up to 10% of patients with supratentorial strokes. While traditional management paradigms have endured, recent strides in research have revolutionized the approach to acute therapies, monitoring, and treatment. Notably, advancements in triage methodologies and the application of both pharmacological and mechanical abortive procedures have reshaped the acute care trajectory for patients with LHI. Moreover, ongoing endeavors have sought to refine strategies for the optimal surveillance and mitigation of complications, notably space-occupying mass effect, which can ensue in the aftermath of LHI. By amalgamating contemporary guidelines with cutting-edge clinical trial findings, this review offers a comprehensive exploration of the current landscape of acute and ongoing patient care for LHI, illuminating the evolving strategies that underpin effective management in this critical clinical domain.

Relationship between serum endothelin-1 and in-stent restenosis following vertebral artery stenting

The study objective was to investigate the relations between serum endothelin-1 and in-stent restenosis in vertebral artery stenting. Sixty-eight patients undergoing re-examination of vertebral artery stenting in the Department of Cerebrovascular Disease, Hangzhou Third People's Hospital, between April 2019 and October 2022, were invited to participate. According to the presence of vertebral artery stenting, patients were divided into the restenosis (n = 19) or non-restenosis (n = 49) groups. General clinical data and endothelin-1 levels were compared between the groups. Logistic regression analysis was used to explore the relations between endothelin-1 level and risk for in-stent restenosis. Receiver operating characteristic curves were drawn to test the diagnostic value of serum endothelin-1 level for in-stent restenosis. Compared with the non-restenosis group, restenosis group levels of low-density lipoprotein, triglycerides, and endothelin-1 were significantly higher (p < 0.05) Multivariate logistic regression analysis showed that endothelin-1, stent length, and low-density lipoprotein were independently associated with in-stent restenosis (odds ratio = 1.502, 95% confidence interval: 0.042 ~ 0.212, p = 0.000; odds ratio = 1.899, 95% confidence interval: 1.116 ~ 2.237, p = 0.000; odds ratio = 1.899, 95% confidence interval: 1.228 ~ 3.337, p = 0.001, respectively). Area under the curve for serum endothelin-1 in the diagnosis of vertebral artery in-stent restenosis was 0.938. The best diagnostic cut-off value was 11.94 ng/L. Sensitivity was 89.5%. Specificity was 85.7%. These cumulative data indicate that endothelin-1 level is independently associated with in-stent restenosis.

Definition, prediction, prevention and management of patients with severe ischemic stroke and large infarction

ABSTRACT

Severe ischemic stroke carries a high rate of disability and death. The severity of stroke is often assessed by the degree of neurological deficits or the extent of brain infarct, defined as severe stroke and large infarction, respectively. Critically severe stroke is a life-threatening condition that requires neurocritical care or neurosurgical intervention, which includes stroke with malignant brain edema, a leading cause of death during the acute phase, and stroke with severe complications of other vital systems. Early prediction of high-risk patients with critically severe stroke would inform early prevention and treatment to interrupt the malignant course to fatal status. Selected patients with severe stroke could benefit from intravenous thrombolysis and endovascular treatment in improving functional outcome. There is insufficient evidence to inform dual antiplatelet therapy and the timing of anticoagulation initiation after severe stroke. Decompressive hemicraniectomy (DHC) <48 h improves survival in patients aged <60 years with large hemispheric infarction. Studies are ongoing to provide evidence to inform more precise prediction of malignant brain edema, optimal indications for acute reperfusion therapies and neurosurgery, and the individualized management of complications and secondary prevention. We present an evidence-based review for severe ischemic stroke, with the aims of proposing operational definitions, emphasizing the importance of early prediction and prevention of the evolution to critically severe status, summarizing specialized treatment for severe stroke, and proposing directions for future research.

Candidate neuroinflammatory markers of cerebral autoregulation dysfunction in human acute brain injury

The loss of cerebral autoregulation (CA) is a common and detrimental secondary injury mechanism following acute brain injury and has been associated with worse morbidity and mortality. However patient outcomes have not as yet been conclusively proven to have improved as a result of CA-directed therapy. While CA monitoring has been used to modify CPP targets, this approach cannot work if the impairment of CA is not simply related to CPP but involves other underlying mechanisms and triggers, which at present are largely unknown. Neuroinflammation, particularly inflammation affecting the cerebral vasculature, is an important cascade that occurs following acute injury. We hypothesise that disturbances to the cerebral vasculature can affect the regulation of CBF, and hence the vascular inflammatory pathways could be a putative mechanism that causes CA dysfunction. This review provides a brief overview of CA, and its impairment following brain injury. We discuss candidate vascular and endothelial markers and what is known about their link to disturbance of the CBF and autoregulation. We focus on human traumatic brain injury (TBI) and subarachnoid haemorrhage (SAH), with supporting evidence from animal work and applicability to wider neurologic diseases.

Secondary Cerebellar Cortex Injury in Albino Male Rats after MCAO: A Histological and Biochemical Study

The present study focused on secondary injury following the middle cerebral artery (MCA) occlusion in rats not linked to the MCA’s feeding zone. This entity has been very rarely studied. Additionally, this study investigated the rates of expression of five fundamental angiogenic biomarkers called endoglin, vascular endothelial growth factors-A (VEGF-A), endothelin-1 (ET-1), 2granulocyte colony-stimulating factor (G-CSF), and angiopoietin-using the MCA occlusion (MCAO) model. The random allocation of twelve adult male albino rats was in two groups. As a sham control group, six rats were used. This group was subjected to a sham operation without MCAO. The MCAO group consisted of six rats that were subjected to MCAO operation. After three days, the rats were sacrificed. The cerebellar specimens were immediately processed for light microscopic examination. An angiogenic biomarkers multiplex assay from multiplex was used to assess endoglin levels, VEGF-A, ET-1, angiopoietin-2, and G-CSF in serum samples. Hematoxylin and eosin-stained sections showed that the cerebellar cortex of rats of the MCAO group was more affected than the sham control group. Furthermore, Nissl stain and immunohistochemical analysis revealed an apparent increase in the number of positive immunoreactive in the cerebellar cortex and an evident decrease in Nissl granules in Purkinje cells of the MCAO rats, in contrast to the control rats. In addition, there was a significant increase in angiogenic factors VEGF-A, ET-1, angiopoietin-2, and endoglin. Interestingly, there was an increase in the G-CSF but a non-significant in the MCAO rats compared to the control rats. Furthermore, there was a significant correlation between the angiopoietin-2 and ET-1, and between G-CSF and ET-1. VEGF-A also exhibited significant positive correlations with the G-CSF serum level parameter, Endoglin, and ET-1. Rats subjected to MCAO are a suitable model to study secondary injury away from MCA’s feeding zone. Additionally, valuable insights into the association and interaction between altered angiogenic factors and acute ischemic stroke induced by MCAO in rats.

Predicting hemorrhagic transformation after large vessel occlusion stroke in the era of mechanical thrombectomy

Serum biomarkers are associated with hemorrhagic transformation and brain edema after cerebral infarction. However, whether serum biomarkers predict hemorrhagic transformation in large vessel occlusion stroke even after mechanical thrombectomy, which has become widely used, remains uncertain. In this prospective study, we enrolled patients with large vessel occlusion stroke in the anterior circulation. We analyzed 91 patients with serum samples obtained on admission. The levels of matrix metalloproteinase-9 (MMP-9), amyloid precursor protein (APP) 770, endothelin-1, S100B, and claudin-5 were measured. We examined the association between serum biomarkers and hemorrhagic transformation within one week. Fifty-four patients underwent mechanical thrombectomy, and 17 patients developed relevant hemorrhagic transformation (rHT, defined as hemorrhagic changes ≥ hemorrhagic infarction type 2). Neither MMP-9 (no rHT: 46 ± 48 vs. rHT: 15 ± 4 ng/mL, P = 0.30), APP770 (80 ± 31 vs. 85 ± 8 ng/mL, P = 0.53), endothelin-1 (7.0 ± 25.7 vs. 2.0 ± 2.1 pg/mL, P = 0.42), S100B (13 ± 42 vs. 12 ± 15 pg/mL, P = 0.97), nor claudin-5 (1.7 ± 2.3 vs. 1.9 ± 1.5 ng/mL, P = 0.68) levels on admission were associated with subsequent rHT. When limited to patients who underwent mechanical thrombectomy, the level of claudin-5 was higher in patients with rHT than in those without (1.2 ± 1.0 vs. 2.1 ± 1.7 ng/mL, P = 0.0181). APP770 levels were marginally higher in patients with a midline shift ≥ 5 mm than in those without (79 ± 29 vs. 97 ± 41 ng/mL, P = 0.084). The predictive role of serum biomarkers has to be reexamined in the mechanical thrombectomy era because some previously reported serum biomarkers may not predict hemorrhagic transformation, whereas the level of APP770 may be useful for predicting brain edema.

Matrix metalloproteinase-9 as a messenger in the cross talk between obstructive sleep apnea and comorbid systemic hypertension, cardiac remodeling, and ischemic stroke: a literature review

STUDY OBJECTIVES

OSA is a common sleep disorder. There is a strong link between sleep-related breathing disorders and cardiovascular and cerebrovascular diseases. Matrix metalloproteinase-9 (MMP-9) is a biological marker for extracellular matrix degradation, which plays a significant role in systemic hypertension, myocardial infarction and postmyocardial infarction heart failure, and ischemic stroke. This article reviews MMP-9 as an inflammatory mediator and a potential messenger between OSA and OSA-induced comorbidities.

METHODS

We reviewed the MEDLINE database (PubMed) for publications on MMP-9, OSA, and cardiovascular disease, identifying 1,592 studies and including and reviewing 50 articles for this work.

RESULTS

There is strong evidence that MMP-9 and tissue inhibitor of metalloproteinase-1 levels are elevated in patients with OSA (mainly MMP-9), systemic hypertension, myocardial infarction, and postmyocardial infarction heart failure. Our study showed variable results that could be related to the sample size or to laboratory methodology.

CONCLUSIONS

MMP-9 and its endogenous inhibitor, tissue inhibitor of metalloproteinase-1, are a common denominator in OSA, systemic hypertension, myocardial infarction, and heart failure. This characterization makes MMP-9 a target for developing novel selective inhibitors that can serve as adjuvant therapy in patients with OSA, which may ameliorate the cardiovascular and cerebrovascular mortality associated with OSA.

Association of Matrix Metalloproteinase 9 and Cellular Fibronectin and Outcome in Acute Ischemic Stroke: A Systematic Review and Meta-Analysis

Introduction: The role of matrix metalloproteinase 9 (MMP-9) and cellular fibronectin (c-Fn) in acute ischemic stroke is controversial. We systematically reviewed the literature to investigate the association of circulating MMP-9 and c-Fn levels and MMP-9 rs3918242 polymorphism with the risk of three outcome measures after stroke.

Methods: We searched English and Chinese databases to identify eligible studies. Outcomes included severe brain edema, hemorrhagic transformation, and poor outcome (modified Rankin scale score ≥3). We estimated standardized mean differences (SMDs) and pooled odds ratios (ORs) with 95% confidence intervals (CIs).

Results: Totally, 28 studies involving 7,239 patients were included in the analysis of circulating MMP-9 and c-Fn levels. Meta-analysis indicated higher levels of MMP-9 in patients with severe brain edema (SMD, 0.76; 95% CI, 0.18–1.35; four studies, 419 patients) and hemorrhagic transformation (SMD, 1.00; 95% CI, 0.41–1.59; 11 studies, 1,709 patients) but not poor outcome (SMD, 0.30; 95% CI, −0.12 to 0.72; four studies, 759 patients). Circulating c-Fn levels were also significantly higher in patients with severe brain edema (SMD, 1.55; 95% CI, 1.18–1.93; four studies, 419 patients), hemorrhagic transformation (SMD, 1.75; 95% CI, 0.72–2.78; four studies, 458 patients), and poor outcome (SMD, 0.46; 95% CI, 0.16–0.76; two studies, 210 patients). Meta-analysis of three studies indicated that the MMP-9 rs3918242 polymorphism may be associated with hemorrhagic transformation susceptibility under the dominant model (TT + CT vs. CC: OR, 0.621; 95% CI, 0.424–0.908; P = 0.014). No studies reported the association between MMP-9 rs3918242 polymorphism and brain edema or functional outcome after acute stroke.

Conclusion: Our meta-analysis showed that higher MMP-9 levels were seen in stroke patients with severe brain edema and hemorrhagic transformation but not poor outcome. Circulating c-Fn levels appear to be associated with all three outcomes including severe brain edema, hemorrhagic transformation, and poor functional outcome. The C-to-T transition at the MMP-9 rs3918242 gene appears to reduce the risk of hemorrhagic transformation.

The Relationship Between Cerebral Reperfusion And Regional Expression Of Matrix Metalloproteinase-9 In Rat Brain Following Focal Cerebral Ischemia

We investigated the effect of full and partial mechanical reperfusion on MMP-9 expression in rat brain following middle cerebral artery occlusion, mimicking mechanical thrombectomy. Using percentage hemispheric lesion volume and oedema as measures, partial reperfusion reduced extent of brain damage caused by MCA occlusion, but the protective effect was less pronounced than with complete reperfusion. Using ELISA quantification in fresh frozen tissue, confirmed by immunofluorescence in perfusion fixed tissue, increased MMP-9 expression was observed in infarcted tissue. MMP-9 was increased in lesioned tissue of the anterior and posterior temporal cortex and underlying striatal tissue, but also the normal appearing frontal cortex. No significant increase in MMP-9 in the hippocampus was observed, nor in the unlesioned contralateral hemisphere. Both partial reperfusion and full reperfusion reduced the regional MMP expression significantly. The highest levels of MMP-9 were observed in lesioned brain regions in the non-reperfused group. MMP-9 expression was evident in microvessels and in neuronal cell bodies of affected tissue. This study shows that MMP-9 brain levels are reduced relative to the extent of reperfusion. These observations suggest targeting early increases in MMP-9 expression as a possible neuroprotective therapeutic strategy and highlight the rat MCA occlusion model as an ideal model in which to study candidate therapeutics.

The presence of leukoaraiosis enhances the association between sTWEAK and hemorrhagic transformation

Objective

To investigate whether elevated serum levels of sTWEAK (soluble tumor necrosis factor‐like inducer of apoptosis) might be involved in a higher frequency of symptomatic hemorrhagic transformation (HT) through the presence of leukoaraiosis (LA) in patients with acute ischemic stroke (IS) undergoing reperfusion therapies.

Methods

This is a retrospective observational study. The primary endpoint was to study the sTWEAK‐LA‐HT relationship by comparing results with biomarkers associated to HT and evaluating functional outcome at 3‐months. Clinical factors, neuroimaging variables and biomarkers associated to inflammation, endothelial/atrial dysfunction or blood‐brain barrier damage were also investigated.

Results

We enrolled 875 patients (mean age 72.3 ± 12.2 years; 46.0% women); 710 individuals underwent intravenous thrombolysis, 87 endovascular therapy and 78 both. HT incidence was 32%; LA presence was 75.4%. Patients with poor functional outcome at 3‐months showed higher sTWEAK levels at admission (9844.2 [7460.4–12,542.0] vs. 2717.3 [1489.7–5852.3] pg/mL, P < 0.0001). By means of logistic regression models, PDGF‐CC and sTWEAK were associated with mechanisms linked simultaneously to HT and LA. Serum sTWEAK levels at admission ≥6700 pg/mL were associated with an odds ratio of 13 for poor outcome at 3‐months (OR: 13.6; CI 95%: 8.2–22.6, P < 0.0001).

Conclusions

Higher sTWEAK levels are independently associated with HT and poor functional outcome in patients with IS undergoing reperfusion therapies through the presence of LA. sTWEAK could become a therapeutic target to reduce HT incidence in patients with IS.

Blood Biomarkers of Parenchymal Damage in Ischemic Stroke Patients Treated With Revascularization Therapies

Purpose

Postischemic reperfusion injury may exacerbate cerebral damage and capillary dysfunction, leading to brain edema (BE), hemorrhagic transformation (HT), necrosis, and injury from free radicals with subsequent infarct growth (IG). Several plasmatic biomarkers involved in the ischemic cascade have been studied in relation to radiological and clinical outcomes of reperfusion injury in ischemic stroke with heterogeneous results. This article provides a brief overview of the contribution of circulating biomarkers to the pathophysiology of parenchymal damage in ischemic stroke patients treated with revascularization therapies.

Methods

We included full reports with measurements of plasma markers in patients with acute ischemic stroke treated with revascularization therapies.

Findings

Our research included a large number of observational studies investigating a possible role of circulating biomarkers in the development of parenchymal damage after acute stroke treatments. To make the results clearer, we divided the review in 4 sections, exploring the relation of different biomarkers with each of the indicators of parenchymal damage (HT, BE, IG, recanalization).

Discussion and conclusion

Definite conclusions are difficult to draw because of heterogeneity across studies. However, our review seems to confirm an association between some circulating biomarkers (particularly matrix metalloproteinase-9) and occurrence of parenchymal damage in ischemic stroke patients treated with revascularization therapies.

Early Prediction of Malignant Brain Edema After Ischemic Stroke

Background and Purpose- Malignant brain edema after ischemic stroke has high mortality but limited treatment. Therefore, early prediction is important, and we systematically reviewed predictors and predictive models to identify reliable markers for the development of malignant edema. Methods- We searched Medline and Embase from inception to March 2018 and included studies assessing predictors or predictive models for malignant brain edema after ischemic stroke. Study quality was assessed by a 17-item tool. Odds ratios, mean differences, or standardized mean differences were pooled in random-effects modeling. Predictive models were descriptively analyzed. Results- We included 38 studies (3278 patients) with 24 clinical factors, 7 domains of imaging markers, 13 serum biomarkers, and 4 models. Generally, the included studies were small and showed potential publication bias. Malignant edema was associated with younger age (n=2075; mean difference, -4.42; 95% CI, -6.63 to -2.22), higher admission National Institutes of Health Stroke Scale scores (n=807, median 17-20 versus 5.5-15), and parenchymal hypoattenuation >50% of the middle cerebral artery territory on initial computed tomography (n=420; odds ratio, 5.33; 95% CI, 2.93-9.68). Revascularization (n=1600, odds ratio, 0.37; 95% CI, 0.24-0.57) were associated with a lower risk for malignant edema. Four predictive models all showed an overall C statistic >0.70, with a risk of overfitting. Conclusions- Younger age, higher National Institutes of Health Stroke Scale, and larger parenchymal hypoattenuation on computed tomography are reliable early predictors for malignant edema. Revascularization reduces the risk of malignant edema. Future studies with robust design are needed to explore optimal cutoff age and National Institutes of Health Stroke Scale scores and to validate and improve existing models.

Protective Effects of a New C-Jun N-terminal Kinase Inhibitor in the Model of Global Cerebral Ischemia in Rats

c-Jun N-terminal kinase (JNK) is activated by various brain insults and is implicated in neuronal injury triggered by reperfusion-induced oxidative stress. Some JNK inhibitors demonstrated neuroprotective potential in various models, including cerebral ischemia/reperfusion injury. The objective of the present work was to study the neuroprotective activity of a new specific JNK inhibitor, IQ-1S (11H-indeno[1,2-b]quinoxalin-11-one oxime sodium salt), in the model of global cerebral ischemia (GCI) in rats compared with citicoline (cytidine-5'-diphosphocholine), a drug approved for the treatment of acute ischemic stroke and to search for pleiotropic mechanisms of neuroprotective effects of IQ-1S. The experiments were performed in a rat model of ischemic stroke with three-vessel occlusion (model of 3VO) affecting the brachiocephalic artery, the left subclavian artery, and the left common carotid artery. After 7-min episode of GCI in rats, 25% of animals died, whereas survived animals had severe neurological deficit at days 1, 3, and 5 after GCI. At day 5 after GCI, we observing massive loss of pyramidal neurons in the hippocampal CA1 area, increase in lipid peroxidation products in the brain tissue, and decrease in local cerebral blood flow (LCBF) in the parietal cortex. Moreover, blood hyperviscosity syndrome and endothelial dysfunction were found after GCI. Administration of IQ-1S (intragastrically at a dose 50 mg/kg daily for 5 days) was associated with neuroprotective effect comparable with the effect of citicoline (intraperitoneal at a dose of 500 mg/kg, daily for 5 days).The neuroprotective effect was accompanied by a decrease in the number of animals with severe neurological deficit, an increase in the number of animals with moderate degree of neurological deficit compared with control GCI group, and an increase in the number of unaltered neurons in the hippocampal CA1 area along with a significant decrease in the number of neurons with irreversible morphological damage. In rats with IQ-1S administration, the LCBF was significantly higher (by 60%) compared with that in the GCI control. Treatment with IQ-1S also decreases blood viscosity and endothelial dysfunction. A concentration-dependent decrease (IC50 = 0.8 ± 0.3 μM) of tone in isolated carotid arterial rings constricted with phenylephrine was observed after IQ-1S application in vitro. We also found that IQ-1S decreased the intensity of the lipid peroxidation in the brain tissue in rats with GCI. 2.2-Diphenyl-1-picrylhydrazyl scavenging for IQ-1S in acetonitrile and acetone exceeded the corresponding values for ionol, a known antioxidant. Overall, these results suggest that the neuroprotective properties of IQ-1S may be mediated by improvement of cerebral microcirculation due to the enhanced vasorelaxation, beneficial effects on blood viscosity, attenuation of the endothelial dysfunction, and antioxidant/antiradical IQ-1S activity.

Deficiency of Bmal1 disrupts the diurnal rhythm of haemostasis

BACKGROUND

Mice deficient in the circadian clock gene BMAL1 (Brain and Muscle ARNT-like protein-1) exhibit a hypercoagulable state and an enhanced arterial and venous thrombogenicity, which aggravates with age. We investigated the effect of BMAL1 deficiency in mice at a different age on the diurnal rhythm of factors involved in coagulation and fibrinolysis.

MATERIALS AND METHODS

Hepatic, cardiac and brain tissues were isolated from 10- and 25-weeks-old Bmal1-deficient (BMAL1-/-) and wild-type (BMAL1+/+) mice at ZT2 and at ZT14 to analyze the mRNA expression level of genes involved in coagulation and fibrinolysis.

RESULTS

Body weight and brain weight were significantly lower in all BMAL1-/- versus BMAL1+/+ mice. Bmal1 deficiency disturbed the diurnal rhythm of plasminogen activator inhibitor-1 (PAI-1) in liver and plasma, but not in cardiac or brain tissues. BMAL1+/+ livers showed diurnal fluctuations in factor (F)VII, FVII, protein S and anti-thrombin gene expression, which were not observed in BMAL1-/- tissues. Interestingly, tissue plasminogen activator (t-PA) expression was significantly upregulated in all BMAL1-/- versus BMAL1+/+ brains at both time points. Plasma t-PA-PAI-1 complex levels were however similar for all groups.

CONCLUSION

Bmal1 deficiency affected the biphasic rhythm of coagulation and fibrinolysis factors predominantly in the liver. In the brain, Bmal1-dependent control of t-PA gene expression was documented for the first time.

Cerebrovascular Gene Expression in Spontaneously Hypertensive Rats After Transient Middle Cerebral Artery Occlusion

Hypertension is a major risk factor for stroke, which is one of the leading global causes of death. In the search for new and effective therapeutic targets in stroke research, we need to understand the influence of hypertension in the vasculature following stroke. We used Affymetrix whole-transcriptome expression profiling as a tool to address gene expression differences between the occluded and non-occluded middle cerebral arteries (MCAs) from spontaneously hypertensive rats (SHRs) and normotensive Wistar-Kyoto (WKY) rats after transient middle cerebral artery occlusion (tMCAO), to provide clues about the pathological mechanisms set in play after stroke. Verified by quantitative PCR, expression of Ccl2, Edn1, Tgfβ2, Olr1 and Serpine1 was significantly increased in the occluded compared to non-occluded MCAs from both SHRs and WKY rats. Additionally, expression of Mmp9, Icam1, Hif1α and Timp1 was increased in the occluded compared to non-occluded MCAs isolated from WKY rats. In comparison between occluded MCAs from SHRs versus occluded MCAs from WKY rats, expression of Ccl2, Olr1 and Serpine1 was significantly increased in SHR MCAs. However, the opposite was observed regarding expression of Edn1. Thus these data suggest that Ccl2, Edn1, Tgfβ2, Olr1 and Serpine1 may be possible mediators of the vascular changes in the occluded MCAs from both SHRs and WKY rats after tMCAO. The aforementioned genes possess biological functions that are consistent with early stroke injuries. In conclusion, these genes may be potential targets in future strategies for acute stroke treatments that can be used in patients with and without hypertension.

A Single-Nucleotide Polymorphism in 3'-Untranslated Region of Endothelin-1 Reduces Risk of Dementia After Ischemic Stroke

BACKGROUND Ischemic stroke is widely recognized as a major health problem and social burden worldwide, and it usually leads to dementia. In this study, we aimed to better understand the pathogenesis in the development of dementia following ischemic stroke. MATERIAL AND METHODS We exploited miRNA database to search for the target for miR-125a and validated the found target using luciferase assay. Further, we performed real-time PCR and Western blot analysis to examine the expression of miR-125a and its target in the tissue samples. In addition, a polymorphism was genotyped and its association with post-stroke dementia was analyzed. RESULTS We identified enthothelin-1 (ET-1) as a target of miR-125a, and this relationship was validated using luciferase assay. Furthermore, transfection of miR-125a inhibitor substantially upregulated the expression of ET-1, while miR-125a and ET-1 siRNA caused downregulation of ET-1 in endothelial cells. In addition, we found that a polymorphism (rs12976445) interferes with the expression of miR-125a, which in turn caused an increase in the expression of ET-1 in human endothelial cells. Logistic regression analysis showed that rs12976445 is significantly associated with the risk of dementia after ischemic stroke. CONCLUSIONS Our study demonstrated the pathogenesis mechanism during the development of dementia after ischemic stroke by investigating the relationship between miR-125a and its target ET-1, promising a potential pathological solution for post-stroke dementia in the future.

Ischemic stroke outcome: A review of the influence of post-stroke complications within the different scenarios of stroke care

Stroke remains one of the main causes of death and disability worldwide. The challenge of predicting stroke outcome has been traditionally assessed from a general point of view, where baseline non-modifiable factors such as age or stroke severity are considered the most relevant factors. However, after stroke occurrence, some specific complications such as hemorrhagic transformations or post stroke infections, which lead to a poor outcome, could be developed. An early prediction or identification of these circumstances, based on predictive models including clinical information, could be useful for physicians to individualize and improve stroke care. Furthermore, the addition of biological information such as blood biomarkers or genetic polymorphisms over these predictive models could improve their prognostic value. In this review, we focus on describing the different post-stroke complications that have an impact in short and long-term outcome across different time points in its natural history and on the clinical-biological information that might be useful in their prediction.

Implications of MMP9 for Blood Brain Barrier Disruption and Hemorrhagic Transformation Following Ischemic Stroke

Numerous studies have documented increases in matrix metalloproteinases (MMPs), specifically MMP-9 levels following stroke, with such perturbations associated with disruption of the blood brain barrier (BBB), increased risk of hemorrhagic complications, and worsened outcome. Despite this, controversy remains as to which cells release MMP-9 at the normal and pathological BBB, with even less clarity in the context of stroke. This may be further complicated by the influence of tissue plasminogen activator (tPA) treatment. The aim of the present review is to examine the relationship between neutrophils, MMP-9 and tPA following ischemic stroke to elucidate which cells are responsible for the increases in MMP-9 and resultant barrier changes and hemorrhage observed following stroke.

High Altitude and Acute Mountain Sickness and Changes in Circulating Endothelin-1, Interleukin-6, and Interleukin-17a

INTRODUCTION

Hypoxia induces an inflammatory response, which is enhanced by exercise. High altitude (HA) leads to endothelial activation and may be proinflammatory. The relationship between endothelial activation, inflammation, and acute mountain sickness (AMS) and its severity has never been examined.

METHODS

Forty-eight trekkers were studied during a progressive trek at 3833, 4450, and 5129 m at rest postascent (exercise), and then again at rest 24 hours later. Twenty of the subjects were also tested at rest pre- and postexercise at sea level (SL) at 6 weeks preascent. We examined plasma levels of the interleukin 6 (IL-6), 17a (IL-17a), and endothelin-1 (ET-1) along with oxygen saturation (SpO2) and Lake Louise scores (LLS).

RESULTS

ET-1 (5.7 ± 2.1 vs. 4.3 ± 1.9 pg/mL; p < 0.001), IL-6 (3.3 ± 3.3 vs. 2.4 ± 2.3 pg/mL; p = 0.007), and IL-17a (1.3 ± 3.0 vs. 0.46 ± 0.4 pg/mL; p < 0.001) were all overall significantly higher at HA versus SL. There was a paired increase in ET-1 and IL-6 with exercise versus rest at SL, 3833, 4450, and 5129 m (p < 0.05). There was a negative correlation between LLS and SpO2 (r = -0.32; 95% confidence interval [CI] -0.21 to -0.42; p < 0.001) and a positive correlation between LLS and IL-6 (r = 0.16; 0.0-0.27; p = 0.007) and ET-1 levels (r = 0.29; 0.18-0.39; p < 0.001. Altitude, ET-1, IL-6, and SpO2 were all univariate predictors of AMS. On multivariate analysis, ET-1 (p = 0.002) and reducing SpO2 (p = 0.02) remained as the only independent predictors (overall r(2) = 0.16; p < 0.001) of AMS. ET-1 (p = 03) and SpO2 were (p = 0.01) also independent predictors of severe AMS (overall r(2) = 0.19; p < 0.001).

CONCLUSIONS

HA leads to endothelial activation and an inflammatory response. The rise in ET-1 and IL-6 is heavily influenced by the degree of exercise and hypoxia. ET-1 is an independent predictor of both AMS and its severity.

Selective astrocytic endothelin-1 overexpression contributes to dementia associated with ischemic stroke by exaggerating astrocyte-derived amyloid secretion

Endothelin-1 (ET-1) is synthesized by endothelial cells and astrocytes in stroke and in brains of Alzheimer's disease patients. Our transgenic mice with ET-1 overexpression in the endothelial cells (TET-1) showed more severe blood-brain barrier (BBB) breakdown, neuronal apoptosis, and glial reactivity after 2-hour transient middle cerebral artery occlusion (tMCAO) with 22-hour reperfusion and more severe cognitive deficits after 30 minutes tMCAO with 5 months reperfusion. However, the role of astrocytic ET-1 in contributing to poststroke cognitive deficits after tMCAO is largely unknown. Therefore, GET-1 mice were challenged with tMCAO to determine its effect on neurologic and cognitive deficit. The GET-1 mice transiently displayed a sensorimotor deficit after reperfusion that recovered shortly, then more severe deficit in spatial learning and memory was observed at 3 months after ischemia compared with that of the controls. Upregulation of TNF-α, cleaved caspase-3, and Thioflavin-S-positive aggregates was observed in the ipsilateral hemispheres of the GET-1 brains as early as 3 days after ischemia. In an in vitro study, ET-1 overexpressing astrocytic cells showed amyloid secretion after hypoxia/ischemia insult, which activated endothelin A (ETA) and endothelin B (ETB) receptors in a PI3K/AKT-dependent manner, suggesting role of astrocytic ET-1 in dementia associated with stroke by astrocyte-derived amyloid production.

Monitoring biomarkers of cellular injury and death in acute brain injury

BACKGROUND

Molecular biomarkers have revolutionalized diagnosis and treatment of many diseases, such as troponin use in myocardial infarction. Urgent need for high-fidelity biomarkers in neurocritical care has resulted in numerous studies reporting potential candidate biomarkers.

METHODS

We performed an electronic literature search and systematic review of English language articles on cellular/molecular biomarkers associated with outcome and with disease-specific secondary complications in adult patients with acute ischemic stroke (AIS), intracerebral hemorrhage (ICH), subarachnoid hemorrhage (SAH), traumatic brain injury (TBI), and post-cardiac arrest hypoxic ischemic encephalopathic injuries (HIE).

RESULTS

A total of 135 articles were included. Though a wide variety of potential biomarkers have been identified, only neuron-specific enolase has been validated in large cohorts and shows 100% specificity for poor outcome prediction in HIE patients not treated with therapeutic hypothermia. There are many promising candidate blood and CSF biomarkers in SAH, AIS, ICH, and TBI, but none yet meets criteria for routine clinical use.

CONCLUSION

Current studies vary significantly in patient selection, biosample collection/processing, and biomarker measurement protocols, thereby limiting the generalizability of overall results. Future large prospective studies with standardized treatment, biosample collection, and biomarker measurement and validation protocols are necessary to identify high-fidelity biomarkers in neurocritical care.

Early-stage minimally invasive procedures decrease perihematomal endothelin-1 levels and improve neurological functioning in a rabbit model of intracerebral hemorrhage

INTRODUCTION

To determine the effects of minimally invasive surgery (MIS) at various stages after intracerebral hemorrhage (ICH) on perihematomal endothelin (ET)-1 levels and neurological functioning.

METHODS

Sixty rabbits were randomly distributed into a model control group (MC group, 30 rabbits) or a MIS group (MI group, 30 rabbits). An ICH model was established in all animals. In the MI group, ICH was evacuated by MIS at 6, 12, 18, 24, and 48 hours (six rabbits at each time point) after the ICH was established. The animals in the MC group underwent the same procedures for ICH evacuation, but with a sham operation without hematoma aspiration. All the animals were sacrificed 7 days after the ICH was established. Neurological deficit scores were determined, and the perihematomal brain tissue was removed to determine the ET-1 levels, blood-brain barrier (BBB) permeability, and brain water content (BWC).

RESULTS

The neurological deficit scores, perihematomal ET-1 levels, BBB permeability, and BWC all decreased significantly in the MI group compared to the MC group. Performing the MIS for evacuating the ICH at 6 hours resulted in the most remarkable decreases in these indices, followed by a significant difference observed at 12 hours within the MI subgroups.

CONCLUSIONS

Performing MIS at 6-12 hours after ICH resulted in the most significant decreases in neurological deficit scores, ET-1 levels, BBB permeability, and brain edema. The optimal time window for performing MIS for ICH evacuation might be within 6-12 hours after hemorrhage.

Endothelin-1-mediated vasoconstriction alters cerebral gene expression in iron homeostasis and eicosanoid metabolism

Endothelins are potent vasoconstrictors and signaling molecules. Their effects are broad, impacting processes ranging from neurovascular and cardiovascular health to cell migration and survival. In stroke, traumatic brain injury or subarachnoid hemorrhage, endothelin-1 (ET-1) is induced resulting in cerebral vasospasm, ischemia, reperfusion and the activation of various pathways. Given the central role that ET-1 plays in these patients and to identify the downstream molecular events specific to transient vasoconstriction, we studied the consequences of ET-1-mediated vasoconstriction of the middle cerebral artery in a rat model. Our observations demonstrate that ET-1 can lead to increases in gene expression, including genes associated with the inflammatory response (Ifnb, Il6, Tnf) and oxidative stress (Hif1a, Myc, Sod2). We also observed inductions (>2 fold) of genes involved in eicosanoid biosynthesis (Pla2g4a, Pla2g4b, Ptgs2, Ptgis, Alox12, Alox15), heme metabolism (Hpx, Hmox1, Prdx1) and iron homeostasis (Hamp, Tf). Our findings demonstrate that mRNA levels for the hormone hepcidin (Hamp) are induced in the brain in response to ET-1, providing a novel target in the treatment of multiple conditions. These changes on the ipsilateral side were also accompanied by corresponding changes in a subset of genes in the contralateral hemisphere. Understanding ET-1-mediated events at the molecular level may lead to better treatments for neurological diseases and provide significant impact on neurological function, morbidity and mortality.

Overactivation of corticotropin-releasing factor receptor type 1 and aquaporin-4 by hypoxia induces cerebral edema

Cerebral edema is a potentially life-threatening illness, but knowledge of its underlying mechanisms is limited. Here we report that hypobaric hypoxia induces rat cerebral edema and neuronal apoptosis and increases the expression of corticotrophin releasing factor (CRF), CRF receptor type 1 (CRFR1), aquaporin-4 (AQP4), and endothelin-1 (ET-1) in the cortex. These effects, except for the increased expression of CRF itself, could all be blocked by pretreatment with an antagonist of the CRF receptor CRFR1. We also show that, in cultured primary astrocytes: (i) both CRFR1 and AQP4 are expressed; (ii) exogenous CRF, acting through CRFR1, triggers signaling of cAMP/PKA, intracellular Ca(2+), and PKCε; and (iii) the up-regulated cAMP/PKA signaling contributes to the phosphorylation and expression of AQP4 to enhance water influx into astrocytes and produces an up-regulation of ET-1 expression. Finally, using CHO cells transfected with CRFR1(+) and AQP4(+), we show that transfected CRFR1(+) contributes to edema via transfected AQP4(+). In conclusion, hypoxia triggers cortical release of CRF, which acts on CRFR1 to trigger signaling of cAMP/PKA in cortical astrocytes, leading to activation of AQP4 and cerebral edema.

Potential serum biomarkers in the pathophysiological processes of stroke

Stroke is a leading cause of death and serious long-term disability. Ischemic stroke is the major subtype of stroke. Currently, its diagnosis is mainly dependent upon clinical symptoms and neuroimaging techniques. Despite these clinical and imaging modalities, often strokes are not recognized after initial onset. As early intervention of medical or surgical therapy is often associated with improved outcomes, there is an urgent need to improve the speed and accuracy of stroke diagnosis. Stroke is a complex pathophysiological process involving; energy failure, imbalance of ion homeostasis, acidosis, intracellular calcium overload, neuronal excitotoxicity, free radical-mediated lipid oxidation, inflammatory cell infiltration, and glial cell activation. These events ultimately lead to neuronal apoptotic cell death or necrosis. In this review, we have summarized the serum biomarkers according to the pathophysiological processes of stroke, which have been intensively studied in clinical trials of stroke over the past five years, and also used Medline's 'related article' option to identify further articles. We focused on the potential biomarkers pertaining to vascular injury, metabolic changes, oxidative injury, and inflammation, and newly studied biomarkers, and discussed how these biomarkers could be used for the diagnosis or determining the prognosis of stroke.

New insights into the mechanism of action of endothelin-1 on cerebral microcirculation

EVALUATION OF: Faraco G, Moraga A, Moore J, Anrather J, Pickel VM, Iadecola C. Circulating endothelin-1 alters critical mechanisms regulating cerebral microcirculation. Hypertension 62(4), 759–766 (2013). This article reviews a study by Faraco and colleagues that attempts to elucidate the mechanism of modulation of the cerebral blood flow by endothelin (ET) 1. ET1 is one of the most powerful vasoconstrictors and plays an important role in cerebrovascular disease and traumatic brain injury. However, the details of the mechanism of action of ET1 are still unknown. The study used a mouse model with a skull window through which the cortical cerebral blood flow was measured with a laser Doppler probe while various agents were applied. The role of reactive oxygen species and integrity of the blood–brain barrier were also assessed. In addition, the location of the ET receptor was determined by incubation of cortex samples with specific antibodies. ET1 increased mean arterial pressure and attenuated the cerebral blood flow increase stimulated by neuronal activity or the endothelium-dependent acethylcholine but not by A23187. ET1 suppresses the endothelial production of nitric oxide by modulating the endothelial nitric oxide synthase phosphorylation through Rho-associated protein kinase. This effect was mediated by an ETA receptor coupled to phospholipase C via GTP-binding protein and was not related to oxidative stress. The ETA receptor was found in the smooth muscle cells of the pial arterioles and cerebral endothelial cells. The resultant vascular dysfunction may increase the risk of brain ischemia by attenuating the cerebrovascular reserve. Improved understanding of the mechanism of action of ET1 on cerebral microcirculation is likely to stimulate the development of new and promising pharmacological targets.

Therapeutic hypothermia after recanalization in patients with acute ischemic stroke

BACKGROUND AND PURPOSE

Therapeutic hypothermia improves outcomes in experimental stroke models, especially after ischemia-reperfusion injury. We investigated the clinical and radiological effects of therapeutic hypothermia in acute ischemic stroke patients after recanalization.

METHODS

A prospective cohort study at 2 stroke centers was performed. We enrolled patients with acute ischemic stroke in the anterior circulation with an initial National Institutes of Health Stroke Scale≥10 who had successful recanalization (≥thrombolysis in cerebral ischemia, 2b). Patients at center A underwent a mild hypothermia (34.5°C) protocol, which included mechanical ventilation, and 48-hour hypothermia and 48-hour rewarming. Patients at center B were treated according to the guidelines without hypothermia. Cerebral edema, hemorrhagic transformation, good outcome (3-month modified Rankin Scale, ≤2), mortality, and safety profiles were compared. Potential variables at baseline and during the therapy were analyzed to evaluate for independent predictors of good outcome.

RESULTS

The hypothermia group (n=39) had less cerebral edema (P=0.001), hemorrhagic transformation (P=0.016), and better outcome (P=0.017) compared with the normothermia group (n=36). Mortality, hemicraniectomy rate, and medical complications were not statistically different. After adjustment for potential confounders, therapeutic hypothermia (odds ratio, 3.0; 95% confidence interval, 1.0-8.9; P=0.047) and distal occlusion (odds ratio, 7.3; 95% confidence interval; 1.3-40.3; P=0.022) were the independent predictors for good outcome. Absence of cerebral edema (odds ratio, 5.4; 95% confidence interval, 1.6-18.2; P=0.006) and no medical complications (odds ratio, 9.3; 95% confidence interval, 2.2-39.9; P=0.003) were also independent predictors for good outcome during the therapy.

CONCLUSIONS

In patients with ischemic stroke, after successful recanalization, therapeutic hypothermia may reduce risk of cerebral edema and hemorrhagic transformation, and lead to improved clinical outcomes.

proMetalloproteinase-10 is associated with brain damage and clinical outcome in acute ischemic stroke

BACKGROUND

Matrix metalloproteinases (MMPs) mediate tissue injury during stroke but also neurovascular remodeling and we have shown that MMP-10 is involved in atherothrombosis.

OBJECTIVE

The purpose of this study was to examine the relationship between proMMP-10 and clinical outcome, assessing inflammatory and proteolytic markers, in patients with acute ischemic stroke.

METHODS

We prospectively studied 76 patients with ischemic stroke treated with tPA within the first 3 h from symptom onset, compared with 202 non-tPA-treated ischemic stroke patients and 83 asymptomatic subjects. Stroke severity was assessed with the National Institutes of Health Stroke Scale (NIHSS). Hemorrhagic transformation (HT) and severe brain edema were diagnosed by cranial CT. Good functional outcome was defined as a modified Rankin scale score ≤ 2 at 90 days. Serum levels of MMP-9, proMMP-10, TIMP-1, tumor necrosis factor-α (TNFα), interleukin-6 and cellular fibronectin were measured at admission. The effect of TNFα on endothelial proMMP-10 was assessed in vitro.

RESULTS

Serum proMMP-10 concentration in ischemic stroke patients, non-treated or treated with t-PA, which was higher than age-matched healthy subjects (P < 0.0001), was independently associated with higher infarct volume, severe brain edema, neurological deterioration and poor functional outcome at 3 months (all P < 0.05), but not with HT. proMMP-10 levels were also independently and positively associated with circulating levels of TNFα (P < 0.0001), which induced its endothelial expression in vitro, both mRNA and protein. MMP-9, however, was only associated with HT and severe edema (all P < 0.05).

CONCLUSIONS

Increased serum proMMP-10 after acute ischemic stroke, associated with TNFα, is a new marker of brain damage and poor outcome.

Platelet derived growth factor-CC isoform is associated with hemorrhagic transformation in ischemic stroke patients treated with tissue plasminogen activator

OBJECTIVE

Platelet derived growth factor-CC (PDGF-CC) isoform is activated by tissue plasminogen activator (tPA) regulating blood brain barrier permeability after ischemia. We aimed to study the association of PDGF isoforms serum levels with hemorrhagic transformation (HT) and edema after thrombolytic treatment in ischemic stroke.

METHODS

We studied 129 patients with ischemic stroke treated with tPA within the first 4.5 h (h) from stroke onset. CT was performed on admission and at 24-36 h. On the 2nd CT, HT was classified according to ECASS II criteria, and severe brain edema was diagnosed if extensive swelling causing any shifting of the structures of the midline was detected. PDGF-AA, PDGF-AB, PDGF-BB and PDGF-CC serum levels were analyzed by ELISA on admission (before tPA bolus), at 24 and 72 h.

RESULTS

Patients who developed HT showed only higher levels of PDGF-CC isoform on admission and at 24 h (all p < 0.0001). In the multivariate analysis, PDGF-CC levels on admission (OR, 1.02; CI 95%, 1.00-1.04) and at 24 h (OR, 1.05; CI 95%, 1.02-1.08) were independently associated with HT after adjustment by confounding factors. On the other hand, patients with severe edema showed also higher levels of PDGF-CC on admission and at 24 h (p < 0.0001), but this statistical association was lost in the logistic regression analysis. PDGF-CC levels ≥ 175 ng/mL at 24 h predict the development of PH with a sensitivity of 90% and specificity of 88% (area under the curve 0.936; p < 0.0001).

CONCLUSION

Increased PDGF-CC levels after tPA treatment is associated with HT.

Towards the identification of blood biomarkers for acute stroke in humans: a comprehensive systematic review

AIMS

Identification of biomarkers for stroke will aid our understanding of its aetiology, provide diagnostic and prognostic indicators for patient selection and stratification, and play a significant role in developing personalized medicine. We undertook the largest systematic review conducted to date in an attempt to characterize diagnostic and prognostic biomarkers in acute ischaemic and haemorrhagic stroke and those likely to predict complications following thrombolysis.

METHODS

A comprehensive literature search was carried out to identify diagnostic and prognostic stroke blood biomarkers. Mean differences (MDs) and 95% confidence intervals (CIs) were calculated for each biomarker.

RESULTS

We identified a total of 141 relevant studies, interrogating 136 different biomarkers. Three biomarkers (C-reactive protein, P-selectin and homocysteine) significantly differentiated between ischaemic stroke and healthy control subjects. Furthermore, glial fibrillary acidic protein levels were significantly different between haemorrhagic stroke and ischaemic stroke patients (MD 224.58 ng l⁻¹; 95% CI 25.84, 423.32; P= 0.03), high levels of admission glucose were a strong predictor of poor prognosis after ischaemic stroke and symptomatic intracerebral haemorrhage post-thrombolysis, glutamate was found to be an indicator of progressive (unstable) stroke (MD 172.65 µmol l⁻¹, 95% CI 130.54, 214.75; P= 0.00001), D-dimer predicted in-hospital death (MD 0.67 µg ml⁻¹, 95% CI 0.35, 1.00; P= 0.0001), and high fibrinogen levels were associated with poor outcome at 3 months (MD 47.90 mg l⁻¹, 95% CI 14.88, 80.93; P= 0.004) following ischaemic stroke.

CONCLUSIONS

Few biomarkers currently investigated have meaningful clinical value. Admission glucose may be a strong marker of poor prognosis following acute thrombolytic treatment. However, molecules released in the bloodstream before, during or after stroke may have potential to be translated into sensitive blood-based tests.

Neuroprotection afforded by antagonists of endothelin-1 receptors in experimental stroke

Endothelin-1 (ET-1) is involved on the development of cerebral edema in acute ischemic stroke. As edema is a therapeutic target in cerebral ischemia, our aim was to study the effect of antagonists for ET-1 receptors (Clazosentan® and BQ-788, specific antagonists for receptors A and B, respectively) on the development of edema, infarct volume and sensorial-motor deficits in rats subjected to ischemia by occlusion of the middle cerebral artery (MCAO). We used Wistar rats (280-320 g) submitted to ischemia by intraluminal transient (90 min) MCAO. After ischemia, rats were randomized into 4 groups (n = 6) treated with; 1) control group (saline), 2) Clazosentan® group (10 mg/kg iv), 3) BQ-788 group (3 mg/kg iv), and 4) combined treatment (Clazosentan® 10 mg/kg plus BQ-788 3 mg/kg iv). We observed that rats treated with Clazosentan® showed a reduction of edema, measured by MRI, at 72 h (hours) and at day 7 (both p < 0.0001), and a decrease in the serum levels of ET-1 at 72 h (p < 0.0001) and at day 7 (p = 0.009). The combined treatment also induced a reduction of edema at 24 h (p = 0.004), 72 h (p < 0.0001) and at day 7 (p < 0.0001), a reduction on infarct volume, measured by MRI, at 24 and 72 h, and at day 7 (all p < 0.01), and a better sensorimotor recovery at 24 and 72 h, and at day 7 (all p < 0.01). Moreover, Clazosentan® induced a decrease in AQP4 expression, while BQ-788 induced an increase in AQP9 expression. These results suggest that antagonists for ET-1 receptors may be a good therapeutic target for cerebral ischemia.

Kininogen deficiency protects from ischemic neurodegeneration in mice by reducing thrombosis, blood-brain barrier damage, and inflammation

Thrombosis and inflammation are hallmarks of ischemic stroke still unamenable to therapeutic interventions. High-molecular-weight kininogen (KNG) is a central constituent of the contact-kinin system which represents an interface between thrombotic and inflammatory circuits and is critically involved in stroke development. Kng(-/-) mice are protected from thrombosis after artificial vessel wall injury and lack the proinflammatory mediator bradykinin. We investigated the consequences of KNG deficiency in models of ischemic stroke. Kng(-/-) mice of either sex subjected to transient middle cerebral artery occlusion developed dramatically smaller brain infarctions and less severe neurologic deficits without an increase in infarct-associated hemorrhage. This protective effect was preserved at later stages of infarction as well as in elderly mice. Targeting KNG reduced thrombus formation in ischemic vessels and improved cerebral blood flow, and reconstitution of KNG-deficient mice with human KNG or bradykinin restored clot deposition and infarct susceptibility. Moreover, mice deficient in KNG showed less severe blood-brain barrier damage and edema formation, and the local inflammatory response was reduced compared with controls. Because KNG appears to be instrumental in pathologic thrombus formation and inflammation but dispensable for hemostasis, KNG inhibition may offer a selective and safe strategy for combating stroke and other thromboembolic diseases.

Minimally invasive procedures reduce perihematomal endothelin-1 levels and the permeability of the BBB in a rabbit model of intracerebral hematoma

To observe the effects of minimally invasive procedures for the evacuation of intracerebral hematomas on perihematomal ET-1 expression and their correlation with blood-brain barrier (BBB) permeability. Forty-five rabbits (2.8-3.4 kg body weight) were randomly divided into a normal control group (NC group, 15 rabbits), a model control group (MC group, 15 rabbits) and a minimally invasive group (MI group, 15 rabbits). A model of intracerebral hemorrhage (ICH) was prepared in the MC and MI groups by infusing autologous arterial blood into the rabbits' brains; the same procedure was also performed in the NC group but without infusing blood into the rabbits' brains. The intracerebral hematomas were evacuated by a stereotactic procedure in the minimally invasive group 6 h after the model was established. The neurological functions, ET-1 expression and the perihematomal BBB permeability were determined and analyzed in all of the animals. The number of endothelial cells with ET-1-positive expression and the perihematomal BBB permeability significantly increased 1, 3, and 7 days after the ICH model was prepared successfully, as compared to the NC group. In the MI group, however, both measurements decreased markedly compared with the MC group at the same time point. A positive correlation between the number of endothelial cells with ET-1-positive expression and BBB permeability was observed. Increased BBB permeability might be associated with perihematomal ET-1 levels. Minimally invasive procedures for the evacuation of intracerebral hematomas could significantly decrease BBB permeability in perihematomal brain tissues, likely by reducing the production of ET-1.

Exposure to severe urban air pollution influences cognitive outcomes, brain volume and systemic inflammation in clinically healthy children

Exposure to severe air pollution produces neuroinflammation and structural brain alterations in children. We tested whether patterns of brain growth, cognitive deficits and white matter hyperintensities (WMH) are associated with exposures to severe air pollution. Baseline and 1 year follow-up measurements of global and regional brain MRI volumes, cognitive abilities (Wechsler Intelligence Scale for Children-Revised, WISC-R), and serum inflammatory mediators were collected in 20 Mexico City (MC) children (10 with white matter hyperintensities, WMH(+), and 10 without, WMH(-)) and 10 matched controls (CTL) from a low polluted city. There were significant differences in white matter volumes between CTL and MC children - both WMH(+) and WMH(-) - in right parietal and bilateral temporal areas. Both WMH(-) and WMH(+) MC children showed progressive deficits, compared to CTL children, on the WISC-R Vocabulary and Digit Span subtests. The cognitive deficits in highly exposed children match the localization of the volumetric differences detected over the 1 year follow-up, since the deficits observed are consistent with impairment of parietal and temporal lobe functions. Regardless of the presence of prefrontal WMH, Mexico City children performed more poorly across a variety of cognitive tests, compared to CTL children, thus WMH(+) is likely only partially identifying underlying white matter pathology. Together these findings reveal that exposure to air pollution may perturb the trajectory of cerebral development and result in cognitive deficits during childhood.

Neuroprotection by glutamate oxaloacetate transaminase in ischemic stroke: an experimental study

As ischemic stroke is associated with an excessive release of glutamate into the neuronal extracellular space, a decrease in blood glutamate levels could provide a mechanism to remove it from the brain tissue, by increasing the brain-blood gradient. In this regard, the ability of glutamate oxaloacetate transaminase (GOT) to metabolize glutamate in blood could represent a potential neuroprotective tool for ischemic stroke. This study aimed to determine the neuroprotective effects of GOT in an animal model of cerebral ischemia by means of a middle cerebral arterial occlusion (MCAO) following the Stroke Therapy Academic Industry Roundtable (STAIR) group guidelines. In this animal model, oxaloacetate-mediated GOT activation inhibited the increase of blood and cerebral glutamate after MCAO. This effect is reflected in a reduction of infarct size, smaller edema volume, and lower sensorimotor deficits with respect to controls. Magnetic resonance spectroscopy confirmed that the increase of glutamate levels in the brain parenchyma after MCAO is inhibited after oxaloacetate-mediated GOT activation. These findings show the capacity of the GOT to remove glutamate from the brain by means of blood glutamate degradation, and suggest the applicability of this enzyme as an efficient and novel neuroprotective tool against ischemic stroke.

Juguloarterial endothelin-1 gradients after severe traumatic brain injury

BACKGROUND

Endothelin-1 (ET-1) is a potent vasoconstrictor and is thought to be responsible for secondary ischemia and vasogenic edema after traumatic brain injury (TBI). Both CSF and plasma concentrations have been shown to be increased after TBI, but there is little evidence to confirm an intracranial site of production.

METHODS

Using paired arterial and jugular venous bulb sampling, we measured arterial and jugular levels of ET-1 and its precursor, big endothelin (Big ET), and calculated juguloarterial (JA) gradients for the first 5 days post-TBI.

RESULTS

Arterial levels of both Big ET and ET-1 were maximal on day 1 post-TBI, and decreased thereafter (P < 0.05). Arterial levels of Big ET and ET-1 showed correlation across all 5 days of the study (r(2) = 0.25, P < 0.001). While there was no significant JA gradient for Big ET, significant gradients were observed for ET-1 on days 1-4 post-TBI (P < 0.05). There was no correlation between JA gradients for Big ET and ET-1 (r(2) < 0.1, P > 0.9). These data suggest parenchymal production of ET-1 by brain tissue with spill over into the blood, rather than local intraluminal cleavage of Big ET in the cerebral vasculature. Systemic ET-1 levels and JA gradients of ET-1 were unrelated to the injury severity, APACHE II score, Marshall Grade, the presence of subarachnoid or subdural hemorrhage, or eventual outcome.

CONCLUSIONS

These findings confirm the synthesis of Big ET and its cleavage to ET-1 within the brain after TBI. More work is needed to elucidate the pathophysiological role and the outcome impact of ET-1 generation after TBI.

Endothelial dysfunction induced by antibodies against angiotensin AT1 receptor in immunized rats

AIM

To investigate the association between autoantibodies against angiotensin AT1 receptor (AT1-AAs) and endothelial dysfunction in vivo.

METHODS

Rat models with AT1 receptor antibodies (AT1-Abs) were established by active immunization for nine months. Lactate dehydrogenase (LDH) activity was regarded as an indicator of cell necrotic death. Endothelin-1 (ET-1) in the sera of rats was determined and endothelium-dependent vasodilatation was detected in isolated thoracic aorta. Endothelial intercellular adhesion molecule-1 (ICAM-1) expression in aorta endothelium was assessed using confocal microscopy. Coronary artery endothelial ultrastructure was observed.

RESULTS

IgGs in the immunized group significantly increased the LDH activity (0.84±0.17 vs 0.39±0.12, P<0.01 vs vehicle group IgGs)in incubated human umbilical vein endothelial cells through AT1 receptor. Higher content of ET-1 occurred in the immunized rats than that of the vehicle group, and reached two peaks at month 3 (27±4 ng/L, P<0.01) and month 7 (35±5 ng/L, P<0.01), respectively. In addition, aortic endothelium-dependent vasodilatation was attenuated; endothelial ICAM-1 level was markedly increased and cardiac capillary endothelium was damaged following immunization.

CONCLUSION

Our study demonstrated that AT1-Abs contributed to endothelial dysfunction in vivo, which was a potential mechanism through which the antibodies play vital roles in related diseases.

Postmenopausal women with osteoporosis may be associated with high endothelin-1

AIM

We aimed to find out if there was any difference of the endothelin-1 (ET-1) and asymmetric dimethylarginine (ADMA) levels between osteoporotic and non-osteoporotic healthy postmenopausal women and whether there were any associations between ET-1 and ADMA levels and bone mineral density (BMD).

METHODS

A total of 75 healthy postmenopausal women were enrolled in the study. BMD was measured at lumbar spine (LS) and femur neck (FN). Serum ET-1 and ADMA levels were measured by ELISA. In this population, 41 (54%) women had BMD t-scores > or = 2.5 at the LS and/or FN defined as osteoporosis and 34 (46%) of them had normal BMDs (non-osteoporotic group).

RESULTS

The mean value of ET-1 serum level in patients was 0.42 +/- 0.30, 0.28 +/- 0.12 fmol/ml in osteoporotic and non-osteoporotic groups, respectively (p = 0.018). In non-osteoporotic group, there was an only significant positive correlation was found between BMD (g/cm(2)) and total t-scores at the lumbar region and ET-1 level. In osteoporotic group, no correlation was found between BMD and total t-scores and ET-1 levels. Serum ADMA level was not significantly different between osteoporotic and non-osteoporotic postmenopausal women (p > 0.05).

CONCLUSIONS

ET-1 may be a physiologic regulator in non-osteoporotic healthy postmenopausal women. Osteoporotic postmenopausal women had higher ET-1 levels than non-osteoporotic postmenopausal women. ADMA seems not to have effect on bone in postmenopausal women.

Oxidized low-density lipoprotein-induced matrix metalloproteinase-9 expression via PKC-delta/p42/p44 MAPK/Elk-1 cascade in brain astrocytes

After ischemic injury to brain, disruption of the blood-brain barrier (BBB) raises the possibility of exposing the central nervous system (CNS) to oxidized low-density lipoprotein (oxLDL), a risk factor implicated in neurodegenerative diseases. Matrix metalloproteinases (MMPs), especially MMP-9, contribute to extracellular matrix (ECM) remodeling during the CNS diseases. However, the molecular mechanisms underlying oxLDL-induced MMP-9 expression in astrocytes remained unclear. Here, we reported that oxLDL induced MMP-9 expression via a PKC-delta/p42/p44 MAPK-dependent Elk-1 activation in rat brain astrocyte (RBA)-1 cells, revealed by gelatin zymography, RT-PCR, and Western blotting analyses. These responses were attenuated by pretreatment with pharmacological inhibitors and transfection with dominant negative mutants. Moreover, Elk-1-mediated MMP-9 gene transcription was confirmed by transfection with an Elk-1 binding site-mutated MMP-9 promoter construct (mt-Ets-MMP9), which blocked oxLDL-stimulated MMP-9 luciferase activity. Understanding the regulatory mechanisms by which oxLDL induced MMP-9 expression in astrocytes might provide a new therapeutic strategy of brain diseases.

The complexity of neurobiological processes in acute ischemic stroke

There is an urgent need for improved diagnostics and therapeutics for acute ischemic stroke. This is the focus of numerous research projects involving in vitro studies, animal models and clinical trials, all of which are based on current knowledge of disease mechanisms underlying acute focal cerebral ischemia. Insight in the chain of events occurring during acute ischemic injury is essential for understanding current and future diagnostic and therapeutic approaches. In this review, we summarize the actual knowledge on the pathophysiology of acute ischemic stroke. We focus on the ischemic cascade, which is a complex series of neurochemical processes that are unleashed by transient or permanent focal cerebral ischemia and involves cellular bioenergetic failure, excitotoxicity, oxidative stress, blood-brain barrier dysfunction, microvascular injury, hemostatic activation, post-ischemic inflammation and finally cell death of neurons, glial and endothelial cells.

Regulation of glial inflammatory mediators synthesis: possible role of endothelins

Endothelins are well known as modulators of inflammation in the periphery, but little is known about their possible role in brain inflammation. Stimulation of astrocyte prostaglandin, an inflammatory mediator, synthesis was shown so far only by endothelin 3 (ET-3). By contrast, several studies showed no change or slight decrease of basal nitric oxide synthesis after treatment of astrocytes with endothelin 1 (ET-1) and ET-3. However, a significant increase in astrocytic and microglial nitric oxide synthase (NOS) was observed after exposure to ET-1 and ET-3 in a model of forebrain ischaemia. Here we demonstrate that all three endothelins (ET-1, ET-2, ET-3) significantly enhanced the synthesis of prostaglandin E(2) and nitric oxide in glial cells. Each of the selective antagonists for ETA and ETB receptors (BQ123 and BQ788 respectively), significantly inhibited endothelins-induced production of both nitric oxide and prostaglandin E(2). These results suggest a regulatory mechanism of endothelins, interacting with both endothelin receptors, on glial inflammation. Therefore, inhibition of endothelin receptors may have a therapeutic potential in pathological conditions of the brain, when an uncontrolled inflammatory response is involved.