Leukocyte-derived matrix metalloproteinase-9 mediates blood-brain barrier breakdown and is proinflammatory after transient focal cerebral ischemia

Neutrophils in traumatic brain injury (TBI): friend or foe?

Our knowledge of the pathophysiology about traumatic brain injury (TBI) is still limited. Neutrophils, as the most abundant leukocytes in circulation and the first-line transmigrated immune cells at the sites of injury, are highly involved in the initiation, development, and recovery of TBI. Nonetheless, our understanding about neutrophils in TBI is obsolete, and mounting evidences from recent studies have challenged the conventional views. This review summarizes what is known about the relationships between neutrophils and pathophysiology of TBI. In addition, discussions are made on the complex roles as well as the controversial views of neutrophils in TBI.

Mesenchymal stem cells attenuate blood-brain barrier leakage after cerebral ischemia in mice

Background

Ischemic stroke induced matrixmetallo-proteinase-9 (MMP-9) upregulation, which increased blood-brain barrier permeability. Studies demonstrated that mesenchymal stem cell therapy protected blood-brain barrier disruption from several cerebrovascular diseases. However, the underlying mechanism was largely unknown. We therefore hypothesized that mesenchymal stem cells reduced blood-brain barrier destruction by inhibiting matrixmetallo-proteinase-9 and it was related to intercellular adhesion molecule-1 (ICAM-1).

Methods

Adult ICR male mice (n = 118) underwent 90-min middle cerebral artery occlusion and received 2 × 10⁵ mesenchymal stem cell transplantation. Neurobehavioral outcome, infarct volume, and blood-brain barrier permeability were measured after ischemia. The relationship between myeloperoxidase (MPO) activity and ICAM-1 release was further determined.

Results

We found that intracranial injection of mesenchymal stem cells reduced infarct volume and improved behavioral function in experimental stroke models (p < 0.05). IgG leakage, tight junction protein loss, and inflammatory cytokines IL-1β, IL-6, and TNF-α reduced in mesenchymal stem cell-treated mice compared to the control group following ischemia (p < 0.05). After transplantation, MMP-9 was decreased in protein and activity levels as compared with controls (p < 0.05). Furthermore, myeloperoxidase-positive cells and myeloperoxidase activity were decreased in mesenchymal stem cell-treated mice (p < 0.05).

Conclusion

The results showed that mesenchymal stem cell therapy attenuated blood-brain barrier disruption in mice after ischemia. Mesenchymal stem cells attenuated the upward trend of MMP-9 and potentially via downregulating ICAM-1 in endothelial cells. Adenosine 5′-monophosphate (AMP)-activated protein kinase (AMPK) pathway may influence MMP-9 expression of neutrophils and resident cells, and ICAM-1 acted as a key factor in the paracrine actions of mesenchymal stem cell.

Neuroimmune Axes of the Blood-Brain Barriers and Blood-Brain Interfaces: Bases for Physiological Regulation, Disease States, and Pharmacological Interventions

Central nervous system (CNS) barriers predominantly mediate the immune-privileged status of the brain, and are also important regulators of neuroimmune communication. It is increasingly appreciated that communication between the brain and immune system contributes to physiologic processes, adaptive responses, and disease states. In this review, we discuss the highly specialized features of brain barriers that regulate neuroimmune communication in health and disease. In section I, we discuss the concept of immune privilege, provide working definitions of brain barriers, and outline the historical work that contributed to the understanding of CNS barrier functions. In section II, we discuss the unique anatomic, cellular, and molecular characteristics of the vascular blood-brain barrier (BBB), blood-cerebrospinal fluid barrier, and tanycytic barriers that confer their functions as neuroimmune interfaces. In section III, we consider BBB-mediated neuroimmune functions and interactions categorized as five neuroimmune axes: disruption, responses to immune stimuli, uptake and transport of immunoactive substances, immune cell trafficking, and secretions of immunoactive substances. In section IV, we discuss neuroimmune functions of CNS barriers in physiologic and disease states, as well as pharmacological interventions for CNS diseases. Throughout this review, we highlight many recent advances that have contributed to the modern understanding of CNS barriers and their interface functions.

Perinatal Asphyxia and Brain Development: Mitochondrial Damage Without Anatomical or Cellular Losses

Perinatal asphyxia remains a significant cause of neonatal mortality and is associated with long-term neurodegenerative disorders. In the present study, we evaluated cellular and subcellular damages to brain development in a model of mild perinatal asphyxia. Survival rate in the experimental group was 67%. One hour after the insult, intraperitoneally injected Evans blue could be detected in the fetuses' brains, indicating disruption of the blood-brain barrier. Although brain mass and absolute cell numbers (neurons and non-neurons) were not reduced after perinatal asphyxia immediately and in late brain development, subcellular alterations were detected. Cortical oxygen consumption increased immediately after asphyxia, and remained high up to 7 days, returning to normal levels after 14 days. We observed an increased resistance to mitochondrial membrane permeability transition, and calcium buffering capacity in asphyxiated animals from birth to 14 days after the insult. In contrast to ex vivo data, mitochondrial oxygen consumption in primary cell cultures of neurons and astrocytes was not altered after 1% hypoxia. Taken together, our results demonstrate that although newborns were viable and apparently healthy, brain development is subcellularly altered by perinatal asphyxia. Our findings place the neonate brain mitochondria as a potential target for therapeutic protective interventions.

Immune responses in stroke: how the immune system contributes to damage and healing after stroke and how this knowledge could be translated to better cures?

Stroke is one of the leading causes of death and disability worldwide. The long-standing dogma that stroke is exclusively a vascular disease has been questioned by extensive clinical findings of immune factors that are associated mostly with inflammation after stroke. These have been confirmed in preclinical studies using experimental animal models. It is now accepted that inflammation and immune mediators are critical in acute and long-term neuronal tissue damage and healing following thrombotic and ischaemic stroke. Despite mounting information delineating the role of the immune system in stroke, the mechanisms of how inflammatory cells and their mediators are involved in stroke-induced neuroinflammation are still not fully understood. Currently, there is no available treatment for targeting the acute immune response that develops in the brain during cerebral ischaemia. No new treatment has been introduced to stroke therapy since the discovery of tissue plasminogen activator therapy in 1996. Here, we review current knowledge of the immunity of stroke and identify critical gaps that hinder current therapies. We will discuss advances in the understanding of the complex innate and adaptive immune responses in stroke; mechanisms of immune cell-mediated and factor-mediated vascular and tissue injury; immunity-induced tissue repair; and the importance of modulating immunity in stroke.

The Dynamics of Impaired Blood-Brain Barrier Restoration in a Rat Model of Co-morbid Injury

Defect in brain microperfusion is increasingly recognized as an antecedent event to Alzheimer's disease (AD) and ischemia. Nevertheless, studies on the role of impaired microperfusion as a pathological trigger to neuroinflammation, Aβ deposition as well as blood-brain barrier (BBB) disruption, and the etiological link between AD and ischemia are lacking. In this study, we employ in vivo sequential magnetic resonance imaging (MRI) and computed tomography (CT) imaging in a co-morbid rat model of β-amyloid toxicity (Aβ) and ischemia (ET1) with subsequent histopathology of striatal lesion core and penumbra at 1, 7, and 28 days post injury. Within 24 h, cerebral injury resulted in increased BBB permeability due to the dissolution of β-dystroglycan (β-DG) and basement membrane laminin by active matrix metalloproteinase9 (MMP9). As a result, net flow of circulating IgG down a hydrostatic gradient into the parenchyma led to vasogenic edema and impaired perfusion, thus increasing the apparent hyperintensity in true fast imaging with steady-state free precession (true FISP) imaging and acute hypoperfusion in CT. This was followed by a slow recruitment of reactive astroglia to the affected brain and depolarization of aquaporin4 (AQP4) expression resulting in cytotoxic edema-in an attempt to resolve vasogenic edema. On d28, functional BBB was restored in ET1 rats as observed by astrocytic MMP9 release, β-DG stabilization, and new vessel formation. This was confirmed by reduced hyperintensity on true FISP imaging and normalized cerebral blood flow in CT. While, Aβ toxicity alone was not detrimental enough, Aβ+ET1 rats showed delayed differential expression of MMP9, late recruitment of astroglial cells, protracted loss of AQP4 depolarization, and thus delayed BBB restoration and cerebral perfusion.

[Pathogenetic aspects of the development of acute focal cerebral ischemia]

Current concepts on the main mechanisms of brain damage in ischemic stroke are considered. Chemical regulation of physiological and pathological processes of maintaining cellular pool is supported by a multistep system that included compounds of different structure and complexity. A complex assessment and comparison of the processes taking place during the development of acute local cerebral ischemia (necrosis, apoptosis, autoimmune inflammatory reaction, neuroplasticity) can help in the objectification and prognosis of individual characteristics of the course and outcome of ischemic stroke. Understanding of the cascade of events that occur during the acute ischemic damage is critical for determining current and future diagnostic and therapeutic approaches.

Serum Matrix Metalloproteinase-9 and Cognitive Impairment After Acute Ischemic Stroke

Background

The impact of serum matrix metalloproteinases‐9 (MMP‐9) on cognitive impairment after ischemic stroke is unclear. We aimed to investigate the association between serum MMP‐9 in the short‐term acute phase of ischemic stroke and cognitive impairment at 3 months.

Methods and Results

Our study was based on a subsample from the CATIS (China Antihypertensive Trial in Acute Ischemic Stroke); a total of 558 patients with serum MMP‐9 levels from 7 of 26 participating sites of the trial were included in this analysis. Cognitive impairment severity was categorized as severe, mild, or none (Mini‐Mental State Examination score, <23, 23–26, or ≥27, respectively; Montreal Cognitive Assessment score, <20, 20–24, or ≥25, respectively). Cognitive impairment was defined as a score of <27 for Mini‐Mental State Examination or <25 for Montreal Cognitive Assessment. According to Mini‐Mental State Examination score, 143 participants (25.6%) had mild cognitive impairment and 153 (27.4%) had severe cognitive impairment at 3 months. After adjustment for age, National Institutes of Health stroke score, education, and other covariates, the odds ratio for the highest quartile of serum MMP‐9 compared with the lowest quartile was 3.20 (95% confidence interval, 1.87–5.49) for cognitive impairment. Multiple‐adjusted spline regression model showed a linear association between MMP‐9 levels and cognitive impairment (P<0.001 for linearity). Sensitivity and subgroup analyses further confirmed these results. Similar significant findings were observed when cognitive impairment was defined by Montreal Cognitive Assessment score.

Conclusions

Increased serum MMP‐9 levels in the short‐term phase of ischemic stroke were associated with 3‐month cognitive impairment, independently of established risk factors.

Cell-free DNA as a biomarker in stroke: Current status, problems and perspectives

There is currently no proposed stroke biomarker with consistent application in clinical practice. A number of studies have examined cell-free DNA (cfDNA), which circulates in biological fluids during stroke, as a potential biomarker of this disease. The data available suggest that dynamically-determined levels of blood cfDNA may provide new prognostic information for assessment of stroke severity and outcome. However, such an approach has its own difficulties and limitations. This review covers the potential role of cfDNA as a biomarker in stroke, and includes evidence from both animal models and clinical studies, protocols used to analyze cfDNA, and hypotheses on the origin of cfDNA.

Matrix Metalloproteinase-9 Mediates the Deleterious Effects of α2-Antiplasmin on Blood-Brain Barrier Breakdown and Ischemic Brain Injury in Experimental Stroke

During acute brain ischemia, α2-antiplasmin markedly enhances brain injury, blood-brain barrier breakdown and matrix metalloproteinase-9 (MMP-9) expression. Although α2-antiplasmin inhibits fibrin thrombus-degradation, and MMP-9 is a collagen-degrading enzyme altering blood-brain barrier, both have similar deleterious effects on the ischemic brain. We examined the hypothesis that MMP-9 is an essential downstream mediator of α2-antiplasmin's deleterious effects during brain ischemia. Middle cerebral artery thromboembolic stroke was induced in a randomized, blinded fashion in mice with increased blood levels of α2-antiplasmin. There was a robust increase in MMP-9 expression (immunofluorescence) in the ischemic vs. the non-ischemic hemisphere of MMP-9^+/+ but not MMP-9^-/- mice, 24 h after stroke. Brain swelling and hemorrhage were significantly increased in the ischemic vs. the non-ischemic hemisphere of MMP-9^+/+ mice. By comparison to MMP-9^+/+ mice, the ischemic hemispheres of MMP-9^-/- mice showed a ∼6-fold reduction in brain swelling (p < 0.001) and a ∼9-fold reduction in brain hemorrhage. Brain infarction (p < 0.0001) and TUNEL-positive cell death (p < 0.001) were significantly diminished in the ischemic hemisphere of MMP-9^-/- mice vs. MMP-9^+/+ mice. Ischemic breakdown of the blood-brain barrier and fibrin deposition were also significantly reduced in MMP-9^-/- mice vs. MMP-9^+/+ mice (p < 0.05), as measured by quantitative immunofluorescence. We conclude that MMP-9 deficiency ablates many of the deleterious effects of high α2-antiplasmin levels, significantly reducing blood-brain barrier breakdown, TUNEL-positive cell death, brain hemorrhage, swelling and infarction. This suggests that the two molecules may be in a shared pathway in which MMP-9 is essential downstream for the deleterious effects of α2-antiplasmin in ischemic stroke.

Brain-immune interactions in perinatal hypoxic-ischemic brain injury

Perinatal hypoxia-ischemia remains the primary cause of acute neonatal brain injury, leading to a high mortality rate and long-term neurological deficits, such as behavioral, social, attentional, cognitive and functional motor deficits. An ever-increasing body of evidence shows that the immune response to acute cerebral hypoxia-ischemia is a major contributor to the pathophysiology of neonatal brain injury. Hypoxia-ischemia provokes an intravascular inflammatory cascade that is further augmented by the activation of resident immune cells and the cerebral infiltration of peripheral immune cells response to cellular damages in the brain parenchyma. This prolonged and/or inappropriate neuroinflammation leads to secondary brain tissue injury. Yet, the long-term effects of immune activation, especially the adaptive immune response, on the hypoxic-ischemic brain still remain unclear. The focus of this review is to summarize recent advances in the understanding of post-hypoxic-ischemic neuroinflammation triggered by the innate and adaptive immune responses and to discuss how these mechanisms modulate the brain vulnerability to injury. A greater understanding of the reciprocal interactions between the hypoxic-ischemic brain and the immune system will open new avenues for potential immunomodulatory therapy in the treatment of neonatal brain injury.

Blood-brain barrier dysfunction and recovery after ischemic stroke

The blood-brain barrier (BBB) plays a vital role in regulating the trafficking of fluid, solutes and cells at the blood-brain interface and maintaining the homeostatic microenvironment of the CNS. Under pathological conditions, such as ischemic stroke, the BBB can be disrupted, followed by the extravasation of blood components into the brain and compromise of normal neuronal function. This article reviews recent advances in our knowledge of the mechanisms underlying BBB dysfunction and recovery after ischemic stroke. CNS cells in the neurovascular unit, as well as blood-borne peripheral cells constantly modulate the BBB and influence its breakdown and repair after ischemic stroke. The involvement of stroke risk factors and comorbid conditions further complicate the pathogenesis of neurovascular injury by predisposing the BBB to anatomical and functional changes that can exacerbate BBB dysfunction. Emphasis is also given to the process of long-term structural and functional restoration of the BBB after ischemic injury. With the development of novel research tools, future research on the BBB is likely to reveal promising potential therapeutic targets for protecting the BBB and improving patient outcome after ischemic stroke.

Anti-Inflammatory Targets for the Treatment of Reperfusion Injury in Stroke

While the mainstay of acute stroke treatment includes revascularization via recombinant tissue plasminogen activator or mechanical thrombectomy, only a minority of stroke patients are eligible for treatment, as delayed treatment can lead to worsened outcome. This worsened outcome at the experimental level has been attributed to an entity known as reperfusion injury (R/I). R/I is occurred when revascularization is delayed after critical brain and vascular injury has occurred, so that when oxygenated blood is restored, ischemic damage is increased, rather than decreased. R/I can increase lesion size and also worsen blood barrier breakdown and lead to brain edema and hemorrhage. A major mechanism underlying R/I is that of poststroke inflammation. The poststroke immune response consists of the aberrant activation of glial cell, infiltration of peripheral leukocytes, and the release of damage-associated molecular pattern (DAMP) molecules elaborated by ischemic cells of the brain. Inflammatory mediators involved in this response include cytokines, chemokines, adhesion molecules, and several immune molecule effectors such as matrix metalloproteinases-9, inducible nitric oxide synthase, nitric oxide, and reactive oxygen species. Several experimental studies over the years have characterized these molecules and have shown that their inhibition improves neurological outcome. Yet, numerous clinical studies failed to demonstrate any positive outcomes in stroke patients. However, many of these clinical trials were carried out before the routine use of revascularization therapies. In this review, we cover mechanisms of inflammation involved in R/I, therapeutic targets, and relevant experimental and clinical studies, which might stimulate renewed interest in designing clinical trials to specifically target R/I. We propose that by targeting anti-inflammatory targets in R/I as a combined therapy, it may be possible to further improve outcomes from pharmacological thrombolysis or mechanical thrombectomy.

Non-invasive near-infrared fluorescence imaging of the neutrophil response in a mouse model of transient cerebral ischaemia

Near-infrared fluorescence (NIRF) imaging enables non-invasive monitoring of molecular and cellular processes in live animals. Here we demonstrate the suitability of NIRF imaging to investigate the neutrophil response in the brain after transient middle cerebral artery occlusion (tMCAO). We established procedures for ex vivo fluorescent labelling of neutrophils without affecting their activation status. Adoptive transfer of labelled neutrophils in C57BL/6 mice before surgery resulted in higher fluorescence intensities over the ischaemic hemisphere in tMCAO mice with NIRF imaging when compared with controls, corroborated by ex vivo detection of labelled neutrophils using fluorescence microscopy. NIRF imaging showed that neutrophils started to accumulate immediately after tMCAO, peaking at 18 h, and were still visible until 48 h after reperfusion. Our data revealed accumulation of neutrophils also in extracranial tissue, indicating damage in the external carotid artery territory in the tMCAO model. Antibody-mediated inhibition of α4-integrins did reduce fluorescence signals at 18 and 24, but not at 48 h after reperfusion, compared with control treatment animals. Antibody treatment reduced cerebral lesion volumes by 19%. In conclusion, the non-invasive nature of NIRF imaging allows studying the dynamics of neutrophil recruitment and its modulation by targeted interventions in the mouse brain after transient experimental cerebral ischaemia.

Pericytes as Inducers of Rapid, Matrix Metalloproteinase-9-Dependent Capillary Damage during Ischemia

Blood-brain barrier disruption (BBB) and release of toxic blood molecules into the brain contributes to neuronal injury during stroke and other cerebrovascular diseases. While pericytes are builders and custodians of the BBB in the normal brain, their impact on BBB integrity during ischemia remains unclear. We imaged pericyte-labeled transgenic mice with in vivo two-photon microscopy to examine the relationship between pericytes and blood plasma leakage during photothrombotic occlusion of cortical capillaries. Upon cessation of capillary flow, we observed that plasma leakage occurred with three times greater frequency in regions where pericyte somata adjoined the endothelium. Pericyte somata covered only 7% of the total capillary length in cortex, indicating that a disproportionate amount of leakage occurred from a small fraction of the capillary bed. Plasma leakage was preceded by rapid activation of matrix metalloproteinase (MMP) at pericyte somata, which was visualized at high resolution in vivo using a fluorescent probe for matrix metalloproteinase-2/9 activity, fluorescein isothiocyanate (FITC)-gelatin. Coinjection of an MMP-9 inhibitor, but not an MMP-2 inhibitor, reduced pericyte-associated FITC-gelatin fluorescence and plasma leakage. These results suggest that pericytes contribute to rapid and localized proteolytic degradation of the BBB during cerebral ischemia.

SIGNIFICANCE STATEMENT

Pericytes are a key component of the neurovascular unit and are essential for normal BBB function. However, during acute ischemia, we find that pericytes are involved in creating rapid and heterogeneous BBB disruption in the capillary bed. The mechanism by which pericytes contribute to BBB damage warrants further investigation, as it may yield new therapeutic targets for acute stroke injury and other neurological diseases involving capillary flow impairment.

Metformin ameliorates BSCB disruption by inhibiting neutrophil infiltration and MMP-9 expression but not direct TJ proteins expression regulation

Blood-spinal cord barrier (BSCB) disruption is a major process for the secondary injury of spinal cord injury (SCI) and is considered to be a therapeutic target for SCI. Previously, we demonstrated that metformin could improve functional recovery after SCI; however, the effect of metformin on BSCB is still unknown. In this study, we found that metformin could prevent the loss of tight junction (TJ) proteins at day 3 after SCI in vivo, but in vitro there was no significant difference of these proteins between control and metformin treatment in endothelial cells. This indicated that metformin-induced BSCB protection might not be mediated by up-regulating TJ proteins directly, but by inhibiting TJ proteins degradation. Thus, we investigated the role of metformin on MMP-9 and neutrophils infiltration. Neutrophils infiltration is the major source of the enhanced MMP-9 in SCI. Our results showed that metformin decreased MMP-9 production and blocked neutrophils infiltration at day 1 after injury, which might be related to ICAM-1 down-regulation. Also, our in vitro study showed that metformin inhibited TNF-α-induced MMP-9 up-regulation in neutrophils, which might be mediated via an AMPK-dependent pathway. Together, it illustrated that metformin prevented the breakdown of BSCB by inhibiting neutrophils infiltration and MMP-9 production, but not by up-regulating TJ proteins expression. Our study may help to better understand the working mechanism of metformin on SCI.

Immune responses in perinatal brain injury

The perinatal period has often been described as immune deficient. However, it has become clear that immune responses in the neonate following exposure to microbes or as a result of tissue injury may be substantial and play a role in perinatal brain injury. In this article we will review the immune cell composition under normal physiological conditions in the perinatal period, both in the human and rodent. We will summarize evidence of the inflammatory responses to stimuli and discuss how neonatal immune activation, both in the central nervous system and in the periphery, may contribute to perinatal hypoxic-ischemic brain injury.

Predictive value of serum transthyretin for outcome in acute ischemic stroke

Introduction

The impact of choroid plexus with its blood–cerebrospinal fluid barrier in the ischemic stroke pathology is poorly explored. Transthyretin (TTR) is a protein synthesized in liver and just in choroid plexus.

Objectives

The current study was designed to assess the prognostic value of serum TTR for functional outcome (at the time of hospital discharge) and long-term (one-year) overall mortality in ischemic stroke patients.

Patients and methods

We conducted a prospective observational study. Patients (n = 81) with acute (< 24 hours of symptoms onset) ischemic stroke consecutively admitted to Stroke Unit were included. An unfavorable outcome was defined as a modified Rankin Scale (mRS) score ≥ 3. The relationships between serum TTR levels and clinical outcome were analyzed using multivariate analysis. One-year mortality was analyzed by Kaplan–Meier survival curves stratified by mean value of TTR.

Results

Compared with patients with mRS <3, patients with an unfavorable outcome at hospital discharge had significantly lower TTR levels on admission (P < 0.0001). In non-survivals serum TTR levels were significantly lower compared with patients who survive one year of observation (P = 0.009). Using multivariate analysis, transthyretin emerged as an independent predictor for unfavorable outcome at the day of hospital discharge (adjusted odds ratio = 0.96; 95% CI: 0.9–0.99, P <0.05). A one-year mortality of patients with the lower TTR levels was significantly higher than in patients with TTR levels above mean value (P = 0.02).

Conclusions

Serum level of TTR at admission was a predictor of functional outcome after ischemic stroke and was also associated with one-year mortality in stroke survivals.

3H-1,2-Dithiole-3-thione as a novel therapeutic agent for the treatment of ischemic stroke through Nrf2 defense pathway

Cerebral ischemic stroke accounts for more than 80% of all stroke cases. During cerebral ischemia, reactive oxygen species produced in brain tissue induce oxidative stress and inflammatory responses. D3T, the simplest compound of the cyclic, sulfur-containing dithiolethiones, is found in cruciferous vegetables and has been reported to induce antioxidant genes and glutathione biosynthesis through activation of Nrf2. In addition to antioxidant activity, D3T was also reported to possess anti-inflammatory effects. In this study, we evaluated the therapeutic potential of D3T for the treatment of ischemic stroke and investigated the mechanisms underlying the protective effects of D3T in ischemic stroke. Mice subjected to transient middle cerebral artery occlusion/reperfusion (tMCAO/R) were administered with vehicle or D3T to evaluate the effect of D3T in cerebral brain injury. We observed D3T reduced infarct size, decreased brain edema, lessened blood-brain barrier disruption, and ameliorated neurological deficits. Further investigation revealed D3T suppressed microglia (MG) activation and inhibited peripheral inflammatory immune cell infiltration of CNS in the ischemic brain. The protective effect of D3T in ischemic stroke is mediated through Nrf2 induction as D3T-attenuated brain injury was abolished in Nrf2 deficient mice subjected to tMCAO/R. In addition, in vitro results indicate the induction of Nrf2 by D3T is required for its suppressive effect on MG activation and cytokine production. In summary, we demonstrate for the first time that D3T confers protection against ischemic stroke, which is mediated through suppression of MG activation and inhibition of CNS peripheral cell infiltration, and that the protective effect of D3T in ischemic stroke is dependent on the activation of Nrf2.

Circulating matrix metalloproteinases in children with diabetic ketoacidosis

BACKGROUND AND OBJECTIVE

Matrix metalloproteinases (MMPs) mediate blood-brain barrier dysfunction in inflammatory disease states. Our objective was to compare circulating MMPs in children with diabetic ketoacidosis (DKA) to children with type 1 diabetes mellitus without DKA.

RESEARCH DESIGN AND METHODS

This was a prospective study performed at five tertiary-care pediatric hospitals. We measured plasma MMP-2, MMP-3, and MMP-9 early during DKA (time 1; within 2 h of beginning intravenous fluids) and during therapy (time 2; median 8 h; range: 4-16 h). The primary outcome was MMP levels in 34 children with DKA vs. 23 children with type 1 diabetes without DKA. Secondary outcomes included correlations between MMPs and measures of DKA severity.

RESULTS

In children with DKA compared with diabetes controls, circulating MMP-2 levels were lower (mean 77 vs. 244 ng/mL, p < 0.001), MMP-3 levels were similar (mean 5 vs. 4 ng/mL, p = 0.57), and MMP-9 levels were higher (mean 67 vs. 25 ng/mL, p = 0.002) early in DKA treatment. MMP-2 levels were correlated with pH at time 1 (r = 0.45, p = 0.018) and time 2 (r = 0.47, p = 0.015) and with initial serum bicarbonate at time 2 (r = 0.5, p = 0.008). MMP-9 levels correlated with hemoglobin A1c in DKA and diabetes controls, but remained significantly elevated in DKA after controlling for hemoglobin A1c (β = -31.3, p = 0.04).

CONCLUSIONS

Circulating MMP-2 levels are lower and MMP-9 levels are higher in children during DKA compared with levels in children with diabetes without DKA. Alterations in MMP expression could mediate BBB dysfunction occurring during DKA.

Cerebral Vascular Disease and Neurovascular Injury in Ischemic Stroke

The consequences of cerebrovascular disease are among the leading health issues worldwide. Large and small cerebral vessel disease can trigger stroke and contribute to the vascular component of other forms of neurological dysfunction and degeneration. Both forms of vascular disease are driven by diverse risk factors, with hypertension as the leading contributor. Despite the importance of neurovascular disease and subsequent injury after ischemic events, fundamental knowledge in these areas lag behind our current understanding of neuroprotection and vascular biology in general. The goal of this review is to address select key structural and functional changes in the vasculature that promote hypoperfusion and ischemia, while also affecting the extent of injury and effectiveness of therapy. In addition, as damage to the blood-brain barrier is one of the major consequences of ischemia, we discuss cellular and molecular mechanisms underlying ischemia-induced changes in blood-brain barrier integrity and function, including alterations in endothelial cells and the contribution of pericytes, immune cells, and matrix metalloproteinases. Identification of cell types, pathways, and molecules that control vascular changes before and after ischemia may result in novel approaches to slow the progression of cerebrovascular disease and lessen both the frequency and impact of ischemic events.

Epigallocatechin Gallate Extends Therapeutic Window of Recombinant Tissue Plasminogen Activator Treatment for Brain Ischemic Stroke: A Randomized Double-Blind and Placebo-Controlled Trial

OBJECTIVES

Recombinant tissue plasminogen activator (rt-PA) is a safe and effective treatment for acute brain ischemia stroke, albeit with a narrow therapeutic window. We aimed to assess the effect of epigallocatechin gallate (EGCG) in extending the rt-PA treatment window in this clinical trial among stroke patients.

METHODS

Patients were randomly assigned according to their onset-to-treatment time (OTT) and were then treated with rt-PA simultaneously with EGCG or placebo. Treatment outcome was assessed by the National Institutes of Health stroke scale (NIHSS) and plasma levels of matrix metalloproteinases (MMP)-2 and 9.

RESULTS

Administration of EGCG significantly improved treatment outcomes of patients in the delayed OTT strata, as evidenced by improved NIHSS scores. This improved treatment outcome was likely attributed to reduction in plasma levels of both MMP-2 and 9, as indicated by strong linear correlations between both MMPs and NIHSS scores in all patients.

CONCLUSIONS

Epigallocatechin gallate could potentially be used as a supplement of traditional rt-PA treatment among stroke patients, particularly those with delayed OTT, to extend the otherwise narrow therapeutic window and improve the outcome in late stroke treatment.

Plasma Kallikrein Inhibitors in Cardiovascular Disease: An Innovative Therapeutic Approach

Plasma prekallikrein is the liver-derived precursor of the trypsin-like serine protease plasma kallikrein, and circulates in plasma bound to high molecular weight kininogen. Plasma prekallikrein is activated to plasma kallikrein by activated factor XII or prolylcarboxypeptidase. Plasma kallikrein regulates the activity of multiple proteolytic cascades in the cardiovascular system such as the intrinsic pathway of coagulation, the kallikrein-kinin system, the fibrinolytic system, the renin-angiotensin system, and the complement pathways. As such, plasma kallikrein plays a central role in the pathogenesis of thrombosis, inflammation, and blood pressure regulation. Under physiological conditions, plasma kallikrein serves as a cardioprotective enzyme. However, its increased plasma concentration or hyperactivity perpetuates cardiovascular disease (CVD). In this article, we review the biochemistry and cell biology of plasma kallikrein and summarize data from preclinical and clinical studies that have established important functions of this serine protease in CVD states. Finally, we propose plasma kallikrein inhibitors as a novel class of drugs with potential therapeutic applications in the treatment of CVDs.

Matrix Metalloproteinase-9 and Recovery of Acute Ischemic Stroke

BACKGROUND

Stroke outcome can be predicted by clinical features, biochemical parameters, and some risk factors. Matrix metalloproteinase-9 (MMP-9) is involved in various stages of stroke pathology. MMP-9 inhibitors are potential stroke therapeutic agents. Little is known about the relation between MMP-9-after the acute stage-and clinical recovery.

OBJECTIVE

The study aimed to investigate the serum level of MMP-9 at stroke onset as predictor of stroke outcome and the relation between the level of MMP-9 after 30 days and stroke recovery.

METHODS

The National Institutes of Health Stroke Scale, modified Rankin Scale, and serum level of MMP-9 were assessed in 30 patients with acute ischemic stroke during the first 24 hours of onset and then a month later. None of the patients received thrombolytic therapy. Thirty normal volunteers of matched age and sex were included in the control group.

RESULTS

The serum level of MMP-9 at stroke onset was independently positively correlated with stroke outcome. The serum level of MMP-9 30 days after stroke onset was positively correlated with initial stroke severity and outcome, as well as with clinical recovery.

CONCLUSION

Higher serum level of MMP-9 at stroke onset can be a predictor of poor stroke outcome. However, beyond the acute stage, MMP-9 may play beneficial role in stroke recovery.

One-Compound-Multi-Target: Combination Prospect of Natural Compounds with Thrombolytic Therapy in Acute Ischemic Stroke

Tissue plasminogen activator (t-PA) is the only FDA-approved drug for acute ischemic stroke treatment, but its clinical use is limited due to the narrow therapeutic time window and severe adverse effects, including hemorrhagic transformation (HT) and neurotoxicity. One of the potential resolutions is to use adjunct therapies to reduce the side effects and extend t-PA&#039;s therapeutic time window. However, therapies modulating single target seem not to be satisfied, and a multitarget strategy is warranted to resolve such complex disease. Recently, large amount of efforts have been made to explore the active compounds from herbal supplements to treat ischemic stroke. Some natural compounds revealed both neuro- and bloodbrain- barrier (BBB)-protective effects by concurrently targeting multiple cellular signaling pathways in cerebral ischemia-reperfusion injury. Thus, those compounds are potential to be one-drug-multi-target agents as combined therapy with t-PA for ischemic stroke. In this review article, we summarize current progress about molecular targets involving in t-PA-mediated HT and neurotoxicity in ischemic brain injury. Based on these targets, we select 23 promising compounds from currently available literature with the bioactivities simultaneously targeting several important molecular targets. We propose that those compounds merit further investigation as combined therapy with t-PA. Finally, we discuss the potential drawbacks of the natural compounds&#039; studies and raise several important issues to be addressed in the future for the development of natural compound as an adjunct therapy.

Matrix Metalloproteinase 9 in Epilepsy: The Role of Neuroinflammation in Seizure Development

Matrix metalloproteinase 9 is a proteolytic enzyme which is recently one of the more often studied biomarkers. Its possible use as a biomarker of neuronal damage in stroke, heart diseases, tumors, multiple sclerosis, and epilepsy is being widely indicated. In epilepsy, MMP-9 is suggested to play a role in epileptic focus formation and in the stimulation of seizures. The increase of MMP-9 activity in the epileptic focus was observed both in animal models and in clinical studies. MMP-9 contributes to formation of epileptic focus, for example, by remodeling of synapses. Its proteolytic action on the elements of blood-brain barrier and activation of chemotactic processes facilitates accumulation of inflammatory cells and induces seizures. Also modification of glutamatergic transmission by MMP-9 is associated with seizures. In this review we will try to recapitulate the results of previous studies about MMP-9 in terms of its association with epilepsy. We will discuss the mechanisms of its actions and present the results revealed in animal models and clinical studies. We will also provide a comparison of the results of various studies on MMP-9 levels in the context of its possible use as a biomarker of the activity of epilepsy.

Pre-conditioning with transcranial low-level light therapy reduces neuroinflammation and protects blood-brain barrier after focal cerebral ischemia in mice

PURPOSE

Transcranial low-level light therapy (LLLT) has gained interest as a non-invasive, inexpensive and safe method of modulating neurological and psychological functions in recent years. This study was designed to examine the preventive effects of LLLT via visible light source against cerebral ischemia at the behavioral, structural and neurochemical levels.

METHODS

The mice received LLLT twice a day for 2 days prior to photothrombotic cortical ischemia.

RESULTS

LLLT significantly reduced infarct size and edema and improved neurological and motor function 24 h after ischemic injury. In addition, LLLT markedly inhibited Iba-1- and GFAP-positive cells, which was accompanied by a reduction in the expression of inflammatory mediators and inhibition of MAPK activation and NF-κB translocation in the ischemic cortex. Concomitantly, LLLT significantly attenuated leukocyte accumulation and infiltration into the infarct perifocal region. LLLT also prevented BBB disruption after ischemic events, as indicated by a reduction of Evans blue leakage and water content. These findings were corroborated by immunofluorescence staining of the tight junction-related proteins in the ischemic cortex in response to LLLT.

CONCLUSIONS

Non-invasive intervention of LLLT in ischemic brain injury may provide a significant functional benefit with an underlying mechanism possibly being suppression of neuroinflammation and reduction of BBB disruption.

Obesity and stroke: Can we translate from rodents to patients?

Obesity is a risk factor for stroke and is consequently one of the most common co-morbidities found in patients. There is therefore an identified need to model co-morbidities preclinically to allow better translation from bench to bedside. In preclinical studies, both diet-induced and genetically obese rodents have worse stroke outcome, characterised by increased ischaemic damage and an altered inflammatory response. However, clinical studies have reported an 'obesity paradox' in stroke, characterised by reduced mortality and morbidity in obese patients. We discuss the potential reasons why the preclinical and clinical studies may not agree, and review the mechanisms identified in preclinical studies through which obesity may affects stroke outcome. We suggest inflammation plays a central role in this relationship, as obesity features increases in inflammatory mediators such as C-reactive protein and interleukin-6, and chronic inflammation has been linked to worse stroke risk and outcome.

Neuroprotective effect of resveratrol against brain ischemia reperfusion injury in rats entails reduction of DJ-1 protein expression and activation of PI3K/Akt/GSK3b survival pathway

In the current study, we aimed to investigate the mechanistic role of DJ-1/PI3K/Akt survival pathway in ischemia/reperfusion (I/R) induced cerebral damage and to investigate if the resveratrol (RES) mediates its ischemic neuroptotection through this pathway. RES administration to Sham rats boosted glutathione level and superoxide dismutase activity and downregulated inducible nitric oxide synthase expression without affecting redox levels of DJ-1 forms or components of PI3K/Akt pathway including PTEN, p-Akt or p/p-GSK3b. However, RES pre-administration to I/R rats reduced infarction area, oxidative stress, inflammation and apoptosis. Concomitantly, RES ameliorated the decreased levels of oxidized forms of DJ-1 and enhancing its reduction, increased the nuclear protein expression of Nfr-2 and led to activation of PI3K/Akt survival pathway. In conclusion, overoxidation of DJ-1 is a major factor that contributes to post-I/R cerebral damage and its reduction by RES could explain the neuroprotection offered by RES.

Physiologic variations in blood plasminogen levels affect outcomes after acute cerebral thromboembolism in mice: a pathophysiologic role for microvascular thrombosis

Essentials Physiologic variations in blood plasminogen (Pg) levels may affect ischemic stroke outcomes. We tested Pg effects in a model with translational relevance to human thromboembolic stroke. A dose-response exists between Pg levels and brain injury, fibrinolysis, barrier breakdown. Higher Pg levels reduce microvascular thrombosis and improve outcomes in ischemic stroke.

SUMMARY

Background and Objectives Plasminogen appears to affect brain inflammation, cell movement, fibrinolysis, neuronal excitotoxicity, and cell death. However, brain tissue and circulating blood plasminogen may have different roles, and there is wide individual variation in blood plasminogen levels. The aim of this study was to determine the integrated effect of blood plasminogen levels on ischemic brain injury. Methods We examined thromboembolic stroke in mice with varying, experimentally determined, blood plasminogen levels. Ischemic brain injury, blood-brain barrier breakdown, matrix metalloproteinase-9 expression and microvascular thrombosis were determined. Results Within the range of normal variation, plasminogen levels were strongly associated with ischemic brain injury; higher blood plasminogen levels had dose-related, protective effects. Higher plasminogen levels were associated with increased dissolution of the middle cerebral artery thrombus. Higher plasminogen levels decreased blood-brain barrier breakdown, matrix metalloproteinase-9 expression and microvascular thrombosis in the ischemic brain. In plasminogen-deficient mice, selective restoration of blood plasminogen levels reversed the harmful effects of plasminogen deficiency on ischemic brain injury. Specific inhibition of thrombin also reversed the effect of plasminogen deficiency on ischemic injury by decreasing microvascular thrombosis, blood-brain barrier breakdown, and matrix metalloproteinase-9 expression. Conclusions Variation in blood plasminogen levels, within the range seen in normal individuals, had marked effects on experimental ischemic brain injury. Higher plasminogen levels protected against ischemic brain injury, and decreased blood-brain barrier breakdown, matrix metalloproteinase-9 expression, and microvascular thrombosis. The protective effects of blood plasminogen appear to be mediated largely through a decrease in microvascular thrombosis in the ischemic territory.

Matrix metalloproteinases in the brain and blood-brain barrier: Versatile breakers and makers

Matrix metalloproteinases are versatile endopeptidases with many different functions in the body in health and disease. In the brain, matrix metalloproteinases are critical for tissue formation, neuronal network remodeling, and blood-brain barrier integrity. Many reviews have been published on matrix metalloproteinases before, most of which focus on the two best studied matrix metalloproteinases, the gelatinases MMP-2 and MMP-9, and their role in one or two diseases. In this review, we provide a broad overview of the role various matrix metalloproteinases play in brain disorders. We summarize and review current knowledge and understanding of matrix metalloproteinases in the brain and at the blood-brain barrier in neuroinflammation, multiple sclerosis, cerebral aneurysms, stroke, epilepsy, Alzheimer's disease, Parkinson's disease, and brain cancer. We discuss the detrimental effects matrix metalloproteinases can have in these conditions, contributing to blood-brain barrier leakage, neuroinflammation, neurotoxicity, demyelination, tumor angiogenesis, and cancer metastasis. We also discuss the beneficial role matrix metalloproteinases can play in neuroprotection and anti-inflammation. Finally, we address matrix metalloproteinases as potential therapeutic targets. Together, in this comprehensive review, we summarize current understanding and knowledge of matrix metalloproteinases in the brain and at the blood-brain barrier in brain disorders.

Microglial Cells Prevent Hemorrhage in Neonatal Focal Arterial Stroke

Perinatal stroke leads to significant morbidity and long-term neurological and cognitive deficits. The pathophysiological mechanisms of brain damage depend on brain maturation at the time of stroke. To understand whether microglial cells limit injury after neonatal stroke by preserving neurovascular integrity, we subjected postnatal day 7 (P7) rats depleted of microglial cells, rats with inhibited microglial TGFbr2/ALK5 signaling, and corresponding controls, to transient middle cerebral artery occlusion (tMCAO). Microglial depletion by intracerebral injection of liposome-encapsulated clodronate at P5 significantly reduced vessel coverage and triggered hemorrhages in injured regions 24 h after tMCAO. Lack of microglia did not alter expression or intracellular redistribution of several tight junction proteins, did not affect degradation of collagen IV induced by the tMCAO, but altered cell types producing TGFβ1 and the phosphorylation and intracellular distribution of SMAD2/3. Selective inhibition of TGFbr2/ALK5 signaling in microglia via intracerebral liposome-encapsulated SB-431542 delivery triggered hemorrhages after tMCAO, demonstrating that TGFβ1/TGFbr2/ALK5 signaling in microglia protects from hemorrhages. Consistent with observations in neonatal rats, depletion of microglia before tMCAO in P9 Cx3cr1(GFP/+)/Ccr2(RFP/+) mice exacerbated injury and induced hemorrhages at 24 h. The effects were independent of infiltration of Ccr2(RFP/+) monocytes into injured regions. Cumulatively, in two species, we show that microglial cells protect neonatal brain from hemorrhage after acute ischemic stroke.

Resveratrol improves delayed r-tPA treatment outcome by reducing MMPs

OBJECTIVES

Although recombinant tissue plasminogen activator (r-tPA) is currently the most effective treatment for brain ischemic stroke, the 3-h narrow therapeutic windows severely limits its clinical efficacy. We aim to investigate the effect of resveratrol on improving treatment outcomes of delayed r-tPA administration.

MATERIALS & METHODS

Patients were randomly divided according to their onset-to-treatment time (OTT), as early OTT or delayed OTT. Then, they were either treated with r-tPA + placebo or with r-tPA + resveratrol. Twenty-four hours after the treatment, outcomes were assessed with NIH stroke scale (NIHSS), and plasma levels of MMP-2 and MMP-9 were also examined with ELISA.

RESULTS

In patients receiving delayed r-tPA treatment, co-administration of resveratrol significantly improves their treatment outcomes compared with those receiving placebo, as indicated by improved NIHSS scores. This improved outcome was be caused by resveratrol-induced reduction in plasma levels of both matrix metalloproteinase (MMP)-2 and MMP-9, as a positive correlation was observed between reductions in both MMPs and patient NIHSS scores.

CONCLUSIONS

Resveratrol could be potentially administered as an adjuvant with r-tPA treatment, which extends the clinical therapeutic window of r-tPA, therefore improving the outcome of patients receiving late stroke treatment.

Inflammatory responses in brain ischemia

Brain infarction causes tissue death by ischemia due to occlusion of the cerebral vessels and recent work has shown that post stroke inflammation contributes significantly to the development of ischemic pathology. Because secondary damage by brain inflammation may have a longer therapeutic time window compared to the rescue of primary damage following arterial occlusion, controlling inflammation would be an obvious therapeutic target. A substantial amount of experimentall progress in this area has been made in recent years. However, it is difficult to elucidate the precise mechanisms of the inflammatory responses following ischemic stroke because inflammation is a complex series of interactions between inflammatory cells and molecules, all of which could be either detrimental or beneficial. We review recent advances in neuroinflammation and the modulation of inflammatory signaling pathways in brain ischemia. Potential targets for treatment of ischemic stroke will also be covered. The roles of the immune system and brain damage versus repair will help to clarify how immune modulation may treat stroke.

Stroke Damage Is Exacerbated by Nano-Size Particulate Matter in a Mouse Model

This study examines the effects of nano-size particulate matter (nPM) exposure in the setting of murine reperfused stroke. Particulate matter is a potent source of inflammation and oxidative stress. These processes are known to influence stroke progression through recruitment of marginally viable penumbral tissue into the ischemic core. nPM was collected in an urban area in central Los Angeles, impacted primarily by traffic emissions. Re-aerosolized nPM or filtered air was then administered to mice through whole body exposure chambers for forty-five cumulative hours. Exposed mice then underwent middle cerebral artery occlusion/ reperfusion. Following cerebral ischemia/ reperfusion, mice exposed to nPM exhibited significantly larger infarct volumes and less favorable neurological deficit scores when compared to mice exposed to filtered air. Mice exposed to nPM also demonstrated increases in markers of inflammation and oxidative stress in the region of the ischemic core. The findings suggest a detrimental effect of urban airborne particulate matter exposure in the setting of acute ischemic stroke.

Therapy Effects of Bone Marrow Stromal Cells on Ischemic Stroke

Stroke is the second most common cause of death and major cause of disability worldwide. Recently, bone marrow stromal cells (BMSCs) have been shown to improve functional outcome after stroke. In this review, we will focus on the protective effects of BMSCs on ischemic brain and the relative molecular mechanisms underlying the protective effects of BMSCs on stroke.

Microglial Cells Prevent Hemorrhage in Neonatal Focal Arterial Stroke

Perinatal stroke leads to significant morbidity and long-term neurological and cognitive deficits. The pathophysiological mechanisms of brain damage depend on brain maturation at the time of stroke. To understand whether microglial cells limit injury after neonatal stroke by preserving neurovascular integrity, we subjected postnatal day 7 (P7) rats depleted of microglial cells, rats with inhibited microglial TGFbr2/ALK5 signaling, and corresponding controls, to transient middle cerebral artery occlusion (tMCAO). Microglial depletion by intracerebral injection of liposome-encapsulated clodronate at P5 significantly reduced vessel coverage and triggered hemorrhages in injured regions 24 h after tMCAO. Lack of microglia did not alter expression or intracellular redistribution of several tight junction proteins, did not affect degradation of collagen IV induced by the tMCAO, but altered cell types producing TGFβ1 and the phosphorylation and intracellular distribution of SMAD2/3. Selective inhibition of TGFbr2/ALK5 signaling in microglia via intracerebral liposome-encapsulated SB-431542 delivery triggered hemorrhages after tMCAO, demonstrating that TGFβ1/TGFbr2/ALK5 signaling in microglia protects from hemorrhages. Consistent with observations in neonatal rats, depletion of microglia before tMCAO in P9 Cx3cr1(GFP/+)/Ccr2(RFP/+) mice exacerbated injury and induced hemorrhages at 24 h. The effects were independent of infiltration of Ccr2(RFP/+) monocytes into injured regions. Cumulatively, in two species, we show that microglial cells protect neonatal brain from hemorrhage after acute ischemic stroke.

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.

Omega-3 polyunsaturated fatty acids mitigate blood-brain barrier disruption after hypoxic-ischemic brain injury

Omega-3 polyunsaturated fatty acids (n-3 PUFAs) have been shown to protect the neonatal brain against hypoxic/ischemic (H/I) injury. However, the mechanism of n-3 PUFA-afforded neuroprotection is not well understood. One major determinant of H/I vulnerability is the permeability of the blood-brain barrier (BBB). Therefore, we examined the effects of n-3 PUFAs on BBB integrity after neonatal H/I. Female rats were fed a diet with or without n-3 PUFA enrichment from day 2 of pregnancy to 14days after parturition. H/I was introduced in 7day-old offspring. We observed relatively rapid BBB penetration of the small molecule cadaverine (640Da) at 4h post-H/I and a delayed penetration of larger dextrans (3kD-40kD) 24-48h after injury. Surprisingly, the neonatal BBB was impermeable to Evans Blue or 70kD dextran leakage for up to 48h post-H/I, despite evidence of IgG extravasation at this time. As expected, n-3 PUFAs ameliorated H/I-induced BBB damage, as shown by reductions in tracer efflux and IgG extravasation, preservation of BBB ultrastructure, and enhanced tight junction protein expression. Furthermore, n-3 PUFAs prevented the elevation in matrix metalloproteinase (MMP) activity in the brain and blood after H/I. Thus, n-3 PUFAs may protect neonates against BBB damage by blunting MMPs activation after H/I.

Sex-specific effects of N-acetylcysteine in neonatal rats treated with hypothermia after severe hypoxia-ischemia

Approximately half of moderate to severely hypoxic-ischemic (HI) newborns do not respond to hypothermia, the only proven neuroprotective treatment. N-acetylcysteine (NAC), an antioxidant and glutathione precursor, shows promise for neuroprotection in combination with hypothermia, mitigating post-HI neuroinflammation due to oxidative stress. As mechanisms of HI injury and cell death differ in males and females, sex differences must be considered in translational research of neuroprotection. We assessed the potential toxicity and efficacy of NAC in combination with hypothermia, in male and female neonatal rats after severe HI injury. NAC 50mg/kg/d administered 1h after initiation of hypothermia significantly decreased iNOS expression and caspase 3 activation in the injured hemisphere versus hypothermia alone. However, only females treated with hypothermia +NAC 50mg/kg showed improvement in short-term infarct volumes compared with saline treated animals. Hypothermia alone had no effect in this severe model. When NAC was continued for 6 weeks, significant improvement in long-term neuromotor outcomes over hypothermia treatment alone was observed, controlling for sex. Antioxidants may provide insufficient neuroprotection after HI for neonatal males in the short term, while long-term therapy may benefit both sexes.

Ischemic, traumatic and neurodegenerative brain inflammatory changes

This review serves to link the role of the immune system in the neuropathology of acute ischemic stroke, traumatic brain injury and neurodegenerative disease. The blood–brain barrier delineates the CNS from the peripheral immune system. However, the blood–cerebrospinal fluid barrier acts as a gate between the periphery and the brain, permitting immune activity crosstalk and modulation. In acute ischemic stroke, traumatic brain injury and other neurodegenerative diseases, the blood–brain barrier is compromised and an influx of inflammatory cells and plasma proteins occurs, resulting in edema, demyelination, cell dysfunction and death, and neurobehavioral changes. The role of the complement system, key cytokines, microglia and other neuroglia in brain degenerative pathology will be discussed.

Rapid endothelial cytoskeletal reorganization enables early blood-brain barrier disruption and long-term ischaemic reperfusion brain injury

The mechanism and long-term consequences of early blood–brain barrier (BBB) disruption after cerebral ischaemic/reperfusion (I/R) injury are poorly understood. Here we discover that I/R induces subtle BBB leakage within 30–60 min, likely independent of gelatinase B/MMP-9 activities. The early BBB disruption is caused by the activation of ROCK/MLC signalling, persistent actin polymerization and the disassembly of junctional proteins within microvascular endothelial cells (ECs). Furthermore, the EC alterations facilitate subsequent infiltration of peripheral immune cells, including MMP-9-producing neutrophils/macrophages, resulting in late-onset, irreversible BBB damage. Inactivation of actin depolymerizing factor (ADF) causes sustained actin polymerization in ECs, whereas EC-targeted overexpression of constitutively active mutant ADF reduces actin polymerization and junctional protein disassembly, attenuates both early- and late-onset BBB impairment, and improves long-term histological and neurological outcomes. Thus, we identify a previously unexplored role for early BBB disruption in stroke outcomes, whereby BBB rupture may be a cause rather than a consequence of parenchymal cell injury.

Matrix metalloproteinases (MMPs) released from infiltrating immune cells are a major contributor to blood-brain barrier (BBB) breakdown following stroke. Here, the authors identify an early, MMP-independent BBB breakdown mechanism caused by rapid cytoskeletal rearrangements in endothelial cells, which could be inhibited by ADF.

Protective Effects of HDL Against Ischemia/Reperfusion Injury

Several lines of evidence suggest that, besides being a strong independent predictor of the occurrence of primary coronary events, a low plasma high density lipoprotein (HDL) cholesterol level is also associated with short- and long-term unfavorable prognosis in patients, who have recovered from a myocardial infarction, suggesting a direct detrimental effect of low HDL on post-ischemic myocardial function. Experiments performed in ex vivo and in vivo models of myocardial ischemia/reperfusion (I/R) injury have clearly shown that HDL are able to preserve cardiac function when given before ischemia or at reperfusion; the protective effects of HDL against I/R injury have been also confirmed in other tissues and organs, as brain and hind limb. HDL were shown to act on coronary endothelial cells, by limiting the increase of endothelium permeability and promoting vasodilation and neoangiogenesis, on white blood cells, by reducing their infiltration into the ischemic tissue and the release of pro-inflammatory and matrix-degrading molecules, and on cardiomyocytes, by preventing the activation of the apoptotic cascade. Synthetic HDL retains the cardioprotective activity of plasma-derived HDL and may become a useful adjunctive therapy to improve clinical outcomes in patients with acute coronary syndromes or undergoing coronary procedures.