Matrix metalloproteinases and free radicals in cerebral ischemia

Microvascular endothelial cells-derived microvesicles imply in ischemic stroke by modulating astrocyte and blood brain barrier function and cerebral blood flow

BACKGROUND

Endothelial cell (EC) released microvesicles (EMVs) can affect various target cells by transferring carried genetic information. Astrocytes are the main components of the blood brain barrier (BBB) structure in the brain and participate in regulating BBB integrity and blood flow. The interactions between ECs and astrocytes are essential for BBB integrity in homeostasis and pathological conditions. Here, we studied the effects of human brain microvascular ECs released EMVs on astrocyte functions. Additionally, we investigated the effects of EMVs treated astrocytes on regulating BBB function and cerebral ischemic damage.

RESULTS

EMVs prepared from ECs cultured in normal condition (n-EMVs) or oxygen and glucose deprivation (OGD-EMVs) condition had diverse effects on astrocytes. The n-EMVs promoted, while the OGD-EMVs inhibited the proliferation of astrocytes via regulating PI3K/Akt pathway. Glial fibrillary acidic protein (GFAP) expression (marker of astrocyte activation) was up-regulated by n-EMVs, while down-regulated by OGD-EMVs. Meanwhile, n-EMVs inhibited but OGD-EMVs promoted the apoptosis of astrocytes accompanied by up/down-regulating the expression of Caspase-9 and Bcl-2. In the BBB model of ECs-astrocytes co-culture, the n-EMVs, conversely to OGD-EMVs, decreased the permeability of BBB accompanied with up-regulation of zonula occudens-1(ZO-1) and Claudin-5. In a transient cerebral ischemia mouse model, n-EMVs ameliorated, while OGD-EMVs aggravated, BBB disruption, local cerebral blood flow (CBF) reduction, infarct volume and neurological deficit score.

CONCLUSIONS

Our data suggest that EMVs diversely modulate astrocyte functions, BBB integrity and CBF, and could serve as a novel therapeutic target for ischemic stroke.

Regulation of Caveolin-1 Expression Determines Early Brain Edema After Experimental Focal Cerebral Ischemia

Background and Purpose—

Most patients with cerebral infarction die of brain edema because of the breakdown of the blood–brain barrier (BBB) in ischemic tissue. Caveolins (a group of proteins) are key modulators of vascular permeability; however, a direct role of caveolin-1 (Cav-1) in the regulation of BBB permeability during ischemic injury has yet to be identified.

Methods—

Cav-1 expression was measured by immunoblotting after photothrombotic ischemia. A direct functional role of Cav-1 in cerebral edema and BBB permeability during cerebral ischemia was investigated by genetic manipulation (gene disruption and re-expression) of Cav-1 protein expression in mice.

Results—

There was a significant correlation between the extent of BBB disruption and the Cav-1 expression. In Cav-1–deficient (Cav-1 −/− ) mice, the extent of BBB disruption after cerebral ischemia was increased compared with wild-type (Cav-1 +/+ ) mice, whereas the increase in cerebral edema volume was ameliorated by lentiviral-mediated re-expression of Cav-1. Furthermore, Cav-1 −/− mice had significantly higher degradation of tight junction proteins and proteolytic activity of matrix metalloproteinase than Cav-1 +/+ mice. Conversely, re-expression of Cav-1 in Cav-1 −/− mice restored tight junction protein expression and reduced matrix metalloproteinase proteolytic activity.

Conclusions—

These results indicate that Cav-1 is a critical determinant of BBB permeability. Strategies for regulating Cav-1 represent a novel therapeutic approach to controlling BBB disruption and subsequent neurological deterioration during cerebral ischemia.

Cocktail treatment, a promising strategy to treat acute cerebral ischemic stroke?

Up to now, over 1,000 experimental treatments found in cells and rodents have been difficult to translate to human ischemic stroke. Since ischemia and reperfusion, two separate stages of ischemic stroke, have different pathophysiological mechanisms leading to brain injury, a combination of protective agents targeting ischemia and reperfusion respectively may obtain substantially better results than a single agent. Normobaric hyperoxia (NBO) has been shown to exhibit neuro- and vaso-protective effects by improving tissue oxygenation when it is given during ischemia, however the effect of NBO would diminish when the duration of ischemia and reperfusion was extended. Therefore, during reperfusion drug treatment targeting inflammation, oxidative stress and free radical scavenger would be a useful adjuvant to extend the therapeutic window of tissue plasminogen activator, the only United States Food and Drug Administration (FDA) approved treatment for acute ischemic stroke. In this review, we discussed the neuro- and vaso-protective effects of NBO and recent finding of combining NBO with other drugs.

Peripheral ammonia and blood brain barrier structure and function after methamphetamine

An effect of the widely abuse psychostimulant, methamphetamine (Meth), is blood-brain-barrier (BBB) disruption; however, the mechanism by which Meth causes BBB disruption remains unclear. Recently it has been shown that Meth produces liver damage and consequent increases in plasma ammonia. Ammonia can mediate oxidative stress and inflammation, both of which are known to cause BBB disruption. Therefore, the current studies examined the role of peripheral ammonia in Meth-induced disruption of BBB structure and function. A neurotoxic Meth regimen (10 mg/kg, ip, q 2 h, ×4) administered to rats increased plasma ammonia and active MMP-9 in the cortex 2 h after the last Meth injection, compared to saline treated rats. At 24 h after Meth treatment, decreased immunoreactivity of BBB structural proteins, occludin and claudin-5, and increased extravasation of 10,000 Da FITC-dextran were observed, as compared to saline controls. Pretreatment with lactulose (5.3 g/kg, po, q 12 h), a drug that remains in the lumen of the intestine and promotes ammonia excretion, prevented the Meth-induced increases in plasma ammonia. These results were paralleled by the prevention of decreases in BBB structural proteins, increases in extravasation of 10,000 Da FITC-dextran and increases in active MMP-9. The results indicate that Meth-induced increases in ammonia produce BBB disruption and suggest that MMP-9 activation mediates the BBB disruption. These findings identify a novel mechanism of Meth-induced BBB disruption that is mediated by plasma ammonia and are the first to identify a peripheral contribution to Meth-induced BBB disruption.

Microglia-blood vessel interactions: a double-edged sword in brain pathologies

Microglia are long-living resident immune cells of the brain, which secure a stable chemical and physical microenvironment necessary for the proper functioning of the central nervous system (CNS). These highly dynamic cells continuously scan their environment for pathogens and possess the ability to react to damage-induced signals in order to protect the brain. Microglia, together with endothelial cells (ECs), pericytes and astrocytes, form the functional blood-brain barrier (BBB), a specialized endothelial structure that selectively separates the sensitive brain parenchyma from blood circulation. Microglia are in bidirectional and permanent communication with ECs and their perivascular localization enables them to survey the influx of blood-borne components into the CNS. Furthermore, they may stimulate the opening of the BBB, extravasation of leukocytes and angiogenesis. However, microglia functioning requires tight control as their dysregulation is implicated in the initiation and progression of numerous neurological diseases. Disruption of the BBB, changes in blood flow, introduction of pathogens in the sensitive CNS niche, insufficient nutrient supply, and abnormal secretion of cytokines or expression of endothelial receptors are reported to prime and attract microglia. Such reactive microglia have been reported to even escalate the damage of the brain parenchyma as is the case in ischemic injuries, brain tumors, multiple sclerosis, Alzheimer's and Parkinson's disease. In this review, we present the current state of the art of the causes and mechanisms of pathological interactions between microglia and blood vessels and explore the possibilities of targeting those dysfunctional interactions for the development of future therapeutics.

Oxidative DNA Damage Mediated by Intranuclear MMP Activity Is Associated with Neuronal Apoptosis in Ischemic Stroke

Evidence of the pathological roles of matrix metalloproteinases (MMPs) in various neurological disorders has made them attractive therapeutic targets. MMPs disrupt the blood-brain barrier and cause neuronal death and neuroinflammation in acute cerebral ischemia and are critical for angiogenesis during recovery. However, some challenges have to be overcome before MMPs can be further validated as drug targets in stroke injury. Identifying in vivo substrates of MMPs should greatly improve our understanding of the mechanisms of ischemic injury and is critical for providing more precise drug targets. Recent works have uncovered nontraditional roles for MMPs in the cytosol and nucleus. These have shed light on intracellular targets and biological actions of MMPs, adding additional layers of complexity for therapeutic MMP inhibition. In this review, we discussed the recent advances made in understanding nuclear location of MMPs, their regulation of intranuclear sorting, and their intranuclear proteolytic activity and substrates. In particular, we highlighted the roles of intranuclear MMPs in oxidative DNA damage, neuronal apoptosis, and neuroinflammation at an early stage of stroke insult. These novel data point to new putative MMP-mediated intranuclear actions in stroke-induced pathological processes and may lead to novel approaches to treatment of stroke and other neurological diseases.

Circulating levels of matrix metalloproteinases and tissue inhibitors of matrix metalloproteinases during Japanese encephalitis virus infection

Matrix metalloproteinases (MMPs) are widely implicated in modulating blood brain barrier (BBB) integrity and affect the entry of peripheral immune cells into the central nervous system (CNS). The expression of MMPs is tightly regulated at the level of gene transcription, conversion of pro-enzyme to active MMPs and by the action of tissue inhibitors of metalloproteinases (TIMP). The crucial role of MMPs in inflammation indicates that perturbation of the MMP/TIMP balance decisively plays an important role in pathogenesis during viral encephalitis. The study was performed to evaluate the production of MMP-2, MMP-7, MMP-9, TIMP-1 and TIMP-3 in the sera of JEV i.e. GP 78668A (GP-78) infected BALB/c mouse model of encephalitis and gel zymography was performed for MMP-2 and MMP-9 activities. The estimation of MMP-2, MMP-7, MMP-9, TIMP-1, and TIMP-3 in JEV-infected mouse serum was analyzed by ELISA along with brain histopathology and immunohistochemistry. Evan's blue dye exclusion test was done to check the BBB integrity. Gelatin gel zymography was performed for MMP-2 and MMP-9 activities. We noticed an upregulated expression of MMPs in the sera of virus infected groups compared to controls at different days post inoculation (dpi). Post hoc analysis between days also reveals significant increase (p < 0.05) in virus infected groups with disease progression. In contrast, TIMPs expressions were significantly (p < 0.005) down regulated in the virus infected group. We provide preliminary evidence for a pattern of TIMP response in JEV infection distinct from that seen in acute inflammatory CNS conditions in JE, shown in our previous findings. Increased MMP-2 and MMP-9 activities were also found in a virus infected group with disease progression and are consistent with our previous finding of MMP-2 and MMP-9 activities in the CNS which clearly demonstrate worsen role of these immune mediators in JEV infection. This study will help to identify new targets for the therapeutic treatment of inflammatory mediated CNS disorders in JEV infection and may lead to the development of potential pharmacological targets in future.

Factors controlling permeability of the blood-brain barrier

As the primary protective barrier for neurons in the brain, the blood-brain barrier (BBB) exists between the blood microcirculation system and the brain parenchyma. The normal BBB integrity is essential in protecting the brain from systemic toxins and maintaining the necessary level of nutrients and ions for neuronal function. This integrity is mediated by structural BBB components, such as tight junction proteins, integrins, annexins, and agrin, of a multicellular system including endothelial cells, astrocytes, pericytes, etc. BBB dysfunction is a significant contributor to the pathogeneses of a variety of brain disorders. Many signaling factors have been identified to be able to control BBB permeability through regulating the structural components. Among those signaling factors are inflammatory mediators, free radicals, vascular endothelial growth factor, matrix metalloproteinases, microRNAs, etc. In this review, we provide a summary of recent progress regarding these structural components and signaling factors, relating to their roles in various brain disorders. Attention is also devoted to recent research regarding impact of pharmacological agents such as isoflurane on BBB permeability and how iron ion passes across BBB. Hopefully, a better understanding of the factors controlling BBB permeability helps develop novel pharmacological interventions of BBB hyperpermeability under pathological conditions.

Association between Interleukin-10 -1082G/A Gene Polymorphism and Risk of Stroke in the North Indian Population: A Case-Control Study

BACKGROUND

Anti-inflammatory interleukin-10 (IL-10) cytokine and its genetic variations may play an important role in the pathogenesis of various human diseases including stroke.

OBJECTIVE

The aim of this present case-control study was to determine the association between IL-10 -1082G/A (rs1800896) gene polymorphism and risk of stroke in the North Indian population.

METHODS

Genotyping was carried out by using SNaPshot method (Applied Biosystems, Foster City, California, United States) for 250 ischemic stroke (IS) patients, 250 age- and sex-matched IS free controls, 100 intracerebral hemorrhage (ICH) patients, and 100 age- and sex-matched ICH free controls. IS was classified using the Trial of Org 10172 in Acute Stroke Treatment classification. Conditional logistic regression analysis with adjustment for multiple demographic and risk factor variables was used to calculate the strength of association between IL-10 (-1082G/A) polymorphism and risk of stroke.

RESULTS

Conditional logistic regression analysis showed an independent association between IL-10 -1082G/A and risk of IS under a dominant model (odds ratio [OR] = 2.39, 95% confidence interval [CI] = 1.34-4.27, P = .003) and an allelic model (OR = 2.49, 95% CI 1.71-3.63, P < .001). An independent association between IL-10 -1082G/A, under the dominant model (OR = 6.8, 95% CI 2.2-20.7, P < .001) and the allelic model (OR = 3.4, 95% CI 1.8-6.3, P < .001), and the risk of ICH was also observed.

CONCLUSION

Our results suggest that IL-10 -1082G/A gene polymorphism is an independent risk factor for the risk of IS and ICH in the North Indian population. Our findings indicate that IL-10 -1082G/A polymorphism may be used as a genetic marker for identifying individuals at increased risk of developing stroke.

Impact of 5A/6A polymorphism of matrix metalloproteinase-3 on recurrent atherosclerotic ischemic stroke in Chinese

Little is known about the impact of the 5A/6A polymorphism of matrix metalloproteinase-3 (MMP-3) on recurrence of atherosclerotic ischemic stroke in Chinese. The aim of this study was to investigate the association of MMP-3 serum level and 5A/6A genetic polymorphism with the recurrence of atherosclerotic ischemic stroke in the Chinese Han population. We analyzed 106 large artery atherosclerosis (LAA) recurrent ischemic stroke patients and 545 LAA first onset ischemic stroke patients from January 2009 to June 2014. Serum MMP-3 concentrations were measured with an enzyme-linked immunosorbent assay. The genotypes of MMP-3 promoter polymorphism (-1171 5A/6A) were determined using polymerase chain reaction-restriction fragment length polymorphism. The frequencies of MMP-3 5A/6A+5A/5A (32.08% vs. 21.47%, p = 0.02) genotype and 5A (16.98% vs. 11.01%, p = 0.01) allele in the recurrent group was significantly higher than those in the first onset group. After adjustment for vascular risk factors, multivariate logistic regression analysis suggested that the MMP-3 5A/6A+5A/5A genotype was an independent risk factor for LAA recurrent ischemic stroke (odds ratio [OR], 1.74; 95% confidence interval [CI], 1.09-2.79, p = 0.021). No significant difference was observed for the MMP-3 serum concentrations between the recurrent group and the first onset group (22.23 ± 8.31 vs. 21.49 ± 7.89 ng/ul, t = 0.88, p = 0.38). The MMP-3 (-1171 5A/6A) polymorphism may contribute to LAA recurrent ischemic stroke susceptibility. Analysis of 5A/6A polymorphism in MMP-3 may identify patients at higher risk for LAA ischemic stroke recurrence, who may be selected for intensive preventive therapy.

Oxidative stress, mitochondrial dysfunction and neurodegenerative diseases; a mechanistic insight

Mitochondria is one of the main source of oxidative stress (ROS), as it utilizes the oxygen for the energy production. ROS and RNS are normally generated by tightly regulated enzymes. Excessive stimulation of NAD(P)H and electron transport chain leads to the overproduction of ROS, results in oxidative stress, which is a good mediator to injure the cell structures, lipids, proteins, and DNA. Various oxidative events implicated in many diseases due to oxidative stress include alteration in mitochondrial proteins, mitochondrial lipids and mitochondrial DNA, Which in turn leads to the damage to nerve cell as they are metabolically very active. ROS/RNS at moderate concentrations also play roles in normal physiology of many processes like signaling pathways, induction of mitogenic response and in defense against infectious pathogens. Oxidative stress has been considered to be the main cause in the etiology of many diseases, which includes Parkinson's and Alzheimer diseases. Several PD associated genes have been found to be involved in mitochondrial function, dynamics and morphology as well. This review includes source of free radical generation, chemistry and biochemistry of ROS/RNS and mitochondrial dysfunction and the mechanism involved in neurodegenerative diseases.

Protective effect of Daming capsule against chronic cerebral ischemia

Background

Accumulating evidence has shown that chronic cerebral ischemia (CCI) is one of the major causes of vascular dementia (VD) characterized by dysregulated cholesterol homeostasis and lipoprotein disturbances. Positive value of lipid-lowering agents has been widely evaluated for the treatment of VD. In the present study, we investigated whether Daming capsule (DMC) protected against CCI-induced VD and its possible mechanisms of action. DMC is a multi-herbal formula composed of Rheum palmatum L., Cassia obtusifolia L., Salvia miltiorrhiza, and Panax ginseng C.A., which has been used to treat hyperlipidemia for years in China.

Methods

A network pharmacology method was established to reveal whether DMC contained any chemical constituent targeting CCI-related proteins. Furthermore, the potential anti-CCI effects of DMC (100 mg/kg or 200 mg/kg) administered for 30 days were investigated in vivo on rats that were subjected to permanent bilateral occlusion of the carotid arteries (2-VO). Spatial learning and memory abilities were evaluated using a Morris water maze (MWM) and morphological changes of cerebral cortex and hippocampus were assessed using hematoxylin and eosin staining. Moreover, the lipid peroxidation levels and antioxidative capabilities were measured using biochemical analysis.

Results

Our network pharmacology analysis revealed the existence of multiple CCI-related chemical-target interactions in DMC, suggesting a potential protective effect. An in vivo experiment verified that 200 mg/kg DMC improved cognitive deficits of 2-VO rats in the MWM test and attenuated pathological alterations in both the cerebral cortex and the hippocampus. Biochemical assays indicated that DMC decreased malondialdehyde levels and CCI-elevated superoxide dismutase activities, but increased the activities of glutathione peroxidase and catalase.

Conclusions

Our findings suggested that DMC protected against cognitive dysfunction and nerve injuries caused by CCI, which is most likely related to its antioxidant actions.

Matrix metalloproteinases as therapeutic targets for stroke

Matrix metalloproteinases (MMPs) are important in injury and recovery in ischemic injury. They are proteolytic enzymes that degrade all components of the extracellular matrix (ECM). They are secreted in a latent form, protecting the cell from damage, but once activated induce injury prior to rapid inactivation by four tissue inhibitors to metalloproteinases (TIMPs). Normally the constitutive enzymes, MMP-2 and membrane type MMP (MMP-14), are activated in a spatially specific manner and act close to the site of activation, while the inducible enzymes, MMP-3 and MMP-9, become active through the action of free radicals and other enzymes during neuroinflammation. Because of the complex nature of the interactions with tissues during development, injury and repair, the MMPs have multiple roles, participating in the injury process in the early stages and contributing to recovery during the later stages. This dual role complicates the planning of treatment strategies. This article is part of a Special Issue entitled SI: Cell Interactions In Stroke.

Combination approaches to attenuate hemorrhagic transformation after tPA thrombolytic therapy in patients with poststroke hyperglycemia/diabetes

To date, tissue type plasminogen activator (tPA)-based thrombolytic stroke therapy is the only FDA-approved treatment for achieving vascular reperfusion and clinical benefit, but this agent is given to only about 5% of stroke patients in the USA. This may be related, in part, to the elevated risk of symptomatic intracranial hemorrhage, and consequently limited therapeutic time window. Clinical investigations demonstrate that poststroke hyperglycemia is one of the most important risk factors that cause intracerebral hemorrhage and worsen neurological outcomes. There is a knowledge gap in understanding the underlying molecular mechanisms, and lack of effective therapeutics targeting the severe complication. This short review summarizes clinical observations and experimental investigations in preclinical stroke models of the field. The data strongly suggest that interactions of multiple pathogenic factors including hyperglycemia-mediated vascular oxidative stress and inflammation, ischemic insult, and tPA neurovascular toxicity in concert contribute to the BBB damage-intracerebral hemorrhagic transformation process. Development of combination approaches targeting the multiple pathological cascades may help to attenuate the hemorrhagic complication.

Calycosin-7-O-β-D-glucoside regulates nitric oxide /caveolin-1/matrix metalloproteinases pathway and protects blood-brain barrier integrity in experimental cerebral ischemia-reperfusion injury

ETHNOPHARMACOLOGY RELEVANCE

Astragali Radix (AR) has been used for thousands years to treat ischemic stroke. Calycosin and its glycoside form calycosin-7-O-β-D-glucoside (CG) are two representative isoflavones in Astragali Radix. However, its neurological effects and related molecular mechanisms are largely unknown. The present study aims to evaluate the neuroprotective effects of CG on blood-brain barrier (BBB) integrity of ischemic brain tissue and explore the relevant signaling mechanisms.

MATERIAL AND METHOD

Male adult Sprague-Daweley rats were subjected to 2 h of middle cerebral artery occlusion (MCAO) plus 24 h or 14 days of reperfusion. CG (26.8 mg/kg) was intraperitoneally administered into the rats at 15 min before onset of ischemia. The neuroprotective effects of CG were evaluated by measuring infarct volume, histological damage and BBB permeability. Furthermore, the effects of CG on scavenging nitric oxide (NO), and modulating matrix metalloproteinases (MMPs) and caveolin-1 (cav-1) were investigated with in vitro cultured brain microvascular endothelial cells treated with NO donor or oxygen-glucose deprivation (OGD) and/or in vivo rat model of MCAO cerebral ischemia-reperfusion injury.

RESULTS

CG treatment significantly reduced infarct volume, histological damage and BBB permeability in the in vivo MCAO ischemia-reperfusion rat model. CG treatment remarkably inhibited the expression and activities of MMPs, and secured the expression of cav-1 and tight junction proteins in the microvessels isolated from ischemic rat cortex. Furthermore, CG was revealed to scavenge NO, inhibit the activities of MMP-2 and MMP-9, and attenuate cell death in the in vitro cultured brain microvascular endothelial cells under OGD condition.

CONCLUSION

CG could protect BBB integrity in experimental cerebral ischemia-reperfusion injury via regulating NO/cav-1/MMPs pathway.

3,4-Methylenedioxymethamphetamine (MDMA, ecstasy) disrupts blood-brain barrier integrity through a mechanism involving P2X7 receptors

The recreational drug 3,4-methylenedioxymethamphetamine (MDMA; 'ecstasy') produces a neuro-inflammatory response in rats characterized by an increase in microglial activation and IL-1β levels. The integrity of the blood-brain barrier (BBB) is important in preserving the homeostasis of the brain and has been shown to be affected by neuro-inflammatory processes. We aimed to study the effect of a single dose of MDMA on the activity of metalloproteinases (MMPs), expression of extracellular matrix proteins, BBB leakage and the role of the ionotropic purinergic receptor P2X7 (P2X7R) in the changes induced by the drug. Adult male Dark Agouti rats were treated with MDMA (10 mg/kg, i.p.) and killed at several time-points in order to evaluate MMP-9 and MMP-3 activity in the hippocampus and laminin and collagen-IV expression and IgG extravasation in the dentate gyrus. Microglial activation, P2X7R expression and localization were also determined in the dentate gyrus. Separate groups were treated with MDMA and the P2X7R antagonists Brilliant Blue G (BBG; 50 mg/kg, i.p.) or A-438079 (30 mg/kg, i.p.). MDMA increased MMP-3 and MMP-9 activity, reduced laminin and collagen-IV expression and increased IgG immunoreactivity. In addition, MDMA increased microglial activation and P2X7R immunoreactivity in these cells. BBG suppressed the increase in MMP-9 and MMP-3 activity, prevented basal lamina degradation and IgG extravasation into the brain parenchyma. A-438079 also prevented the MDMA-induced reduction in laminin and collagen-IV immunoreactivity. These results indicate that MDMA alters BBB permeability through an early P2X7R-mediated event, which in turn leads to enhancement of MMP-9 and MMP-3 activity and degradation of extracellular matrix.

Non-pharmaceutical therapies for stroke: mechanisms and clinical implications

Stroke is deemed a worldwide leading cause of neurological disability and death, however, there is currently no promising pharmacotherapy for acute ischemic stroke aside from intravenous or intra-arterial thrombolysis. Yet because of the narrow therapeutic time window involved, thrombolytic application is very restricted in clinical settings. Accumulating data suggest that non-pharmaceutical therapies for stroke might provide new opportunities for stroke treatment. Here we review recent research progress in the mechanisms and clinical implications of non-pharmaceutical therapies, mainly including neuroprotective approaches such as hypothermia, ischemic/hypoxic conditioning, acupuncture, medical gases and transcranial laser therapy. In addition, we briefly summarize mechanical endovascular recanalization devices and recovery devices for the treatment of the chronic phase of stroke and discuss the relative merits of these devices.

Herbal medicines for ischemic stroke: combating inflammation as therapeutic targets

Stroke is a debilitating disease for which limited therapeutic approaches are available currently. Thus, there is an urgent need for developing novel therapies for stroke. Astrocytes, endothelial cells and pericytes constitute a neurovascular network for metabolic requirement of neurons. During ischemic stroke, these cells contribute to post-ischemic inflammation at multiple stages of ischemic cascades. Upon ischemia onset, activated resident microglia and astrocytes, and infiltrated immune cells release multiple inflammation factors including cytokines, chemokines, enzymes, free radicals and other small molecules, not only inducing brain damage but affecting brain repair. Recent progress indicates that anti-inflammation is an important therapeutic strategy for stroke. Given a long history with direct experience in the treatment of human subjects, Traditional Chinese Medicine and its related natural compounds are recognized as important sources for drug discovery. Last decade, a great progress has been made to identify active compounds from herbal medicines with the properties of modulating post-ischemic inflammation for neuroprotection. Herein, we discuss the inflammatory pathway in early stage and secondary response to injured tissues after stroke from initial artery occlusion to brain repair, and review the active ingredients from natural products with anti-inflammation and neuroprotection effects as therapeutic agents for ischemic stroke. Further studies on the post-ischemic inflammatory mechanisms and corresponding drug candidates from herbal medicine may lead to the development of novel therapeutic strategies in stroke treatment.

Rutin improves functional outcome via reducing the elevated matrix metalloproteinase-9 level in a photothrombotic focal ischemic model of rats

BACKGROUND

Blood-brain barrier (BBB) disruption mediated by proteases plays a pivotal role in neural tissue damage after acute ischemic stroke. In an animal stroke model, the activation of matrix metalloproteinases (MMPs), especially MMP-9, was significantly increased and it showed potential association with blood-brain barrier (BBB) disruption and cerebral edema. Theoretically, it is expected that early blockade of expression and activation of MMP-9 after ischemic stroke provides neuroprotective effects from secondary neural tissue damage. This study was aimed to determine the ability of rutin to influence MMP-9 expression, activity and BBB disruption using a photothrombotic focal ischemic model in rats.

METHODS

Adult male Sprague-Dawley rats, weighing between 250 and 300 g (aged 8 weeks) received focal cerebral ischemia by photothrombosis using Rose Bengal (RB) and cold light. Injured animals were divided into two groups; one group received 50mg/kg of rutin intraperitoneally, starting 1h after injury and at 12h intervals for 3 days, while animals in the control group received weight-adjusted doses of saline vehicle over the same period. In each group, the expressions and activities of MMP-9 were assessed by Western blot and gelatin zymography at 6, 24, 48, and 72 h after photothrombotic insult. The effects of rutin on BBB disruption and functional outcomes were also determined.

RESULTS

Western blot and zymographic analysis showed up-regulated MMP-9 expression and activity in the ischemic cortex. The expression and activity of MMP-9 were significantly elevated at 6h after photothrombotic insult, which remained up-regulated for at least until 72 h after injury. In the rutin-treated group, MMP-9 expression and activity were significantly attenuated at 6, 24, and 48 h compared to the control group. Relative to the control group, BBB permeability was significantly reduced in the rutin-treated group. The results of the rotarod test revealed that rutin treatment significantly improved functional outcomes.

CONCLUSIONS

Rutin treatment starting 1h after injury attenuated BBB disruption during photothrombotic focal ischemia, which was partly, at least, achieved through inhibitory effects on MMP-9 expression and activity. The results of this study suggest that rutin might be useful in clinical trials aimed to improve the outcome of patients suffering from acute ischemic stroke.

Serum prolidase enzyme activity and oxidative stress levels in patients with acute hemorrhagic stroke

BACKGROUND

It has been indicated that oxidative damage contributes to secondary brain injury in both ischemic and hemorrhagic stroke patients. Collagen is a major component of the extracellular matrix, and prolidase plays a role in collagen synthesis. The aim of this study was to evaluate the serum prolidase activity, nitric oxide (NO) levels, total antioxidant capacity (TAC) and total oxidant status (TOS) in patients with acute hemorrhagic stroke.

METHODS

Twenty-five patients with acute hemorrhagic stroke and 25 controls were enrolled. Serum prolidase activity, catalase activity, NO levels, TAC and TOS were measured spectrophotometrically. Oxidative stress index (OSI) was calculated.

RESULTS

Serum TAC levels and catalase activity were significantly lower in acute hemorrhagic stroke patients than controls (both, p < 0.001), while NO levels, TOS levels, OSI values and prolidase activity were significantly higher (all, p < 0.01). When patients with acute hemorrhagic stroke were divided according to gender, no differences were observed between females and males in respect to serum prolidase enzyme activity, NO levels, TAC levels, TOS levels and OSI values (all, p > 0.05).

CONCLUSIONS

Findings from the study suggest an association between increased oxidative stress levels, decreased antioxidant levels and increased prolidase enzyme activity in patients with acute hemorrhagic stroke compared with controls. More studies are needed to elucidate mechanistic pathways on oxidative stress in patients with acute hemorrhagic stroke.

In vivo evidence of methamphetamine induced attenuation of brain tissue oxygenation as measured by EPR oximetry

Abuse of methamphetamine (METH) is a major and significant societal problem in the US, as a number of studies have suggested that METH is associated with increased cerebrovascular events, hemorrhage or vasospasm. Although cellular and molecular mechanisms involved in METH-induced toxicity are not completely understood, changes in brain O₂ may play an important role and contribute to METH-induced neurotoxicity including dopaminergic receptor degradation. Given that O₂ is the terminal electron acceptor for many enzymes that are important in brain function, the impact of METH on brain tissue pO₂ in vivo remains largely uncharacterized. This study investigated striatal tissue pO₂ changes in male C57BL/6 mice (16-20 g) following METH administration using EPR oximetry, a highly sensitive modality to measure pO₂ in vivo, in situ and in real time. We demonstrate that 20 min after a single injection of METH (8 mg/kg i.v.), the striatal pO₂ was reduced to 81% of the pretreatment level and exposure to METH for 3 consecutive days further attenuated striatal pO₂ to 64%. More importantly, pO₂ did not recover fully to control levels even 24 h after administration of a single dose of METH and continual exposure to METH exacerbates the condition. We also show a reduction in cerebral blood flow associated with a decreased brain pO₂ indicating an ischemic condition. Our findings suggests that administration of METH can attenuate brain tissue pO₂, which may lead to hypoxic insult, thus a risk factor for METH-induced brain injury and the development of stroke in young adults.

The role of claudin-5 in blood-brain barrier (BBB) and brain metastases (review)

Metastatic brain tumours are frequently observed in patients with lung, breast and malignant melanoma and a severe complication of metastatic cancers. With improved primary cancer treatments, including surgery, radiation therapy and chemotherapy, patients are now living longer following initial treatment, compared with previous treatments. Brain metastasis (BM) remains a significant clinical issue. Since BM represents a major therapeutic challenge, it is vital that the mechanisms of interaction between tumour cells and the blood‑brain barrier (BBB), as well as the method by which tumour cells establish metastatic tumours in the brain, are understood. A key step in BM is the interaction and penetration of the BBB by cancer cells. The BBB consists of endothelial cells, pericytes, astrocytes and a number of molecular structures between these cells. The BBB relies on the tight junctions (TJs) that are present between the endothelial cells of the brain capillaries to provide a closed environment for the brain. TJs comprise a number of proteins, including occludin, claudins and junctional adhesion molecules (JAMs). Among them, claudins are the key integral proteins that regulate BBB permeability. It has previously been shown that claudin‑5, not only regulates paracellular ionic selectivity, but also plays a role in the regulation of tumour cell motility, suggesting that TJs and claudin‑5 contribute to the control of BM. This study reviews the role of claudin‑5 in the regulation of BBB permeability during the brain metastatic process.

Moderate hypoxia followed by reoxygenation results in blood-brain barrier breakdown via oxidative stress-dependent tight-junction protein disruption

Re-canalization of cerebral vessels in ischemic stroke is pivotal to rescue dysfunctional brain areas that are exposed to moderate hypoxia within the penumbra from irreversible cell death. Goal of the present study was to evaluate the effect of moderate hypoxia followed by reoxygenation (MHR) on the evolution of reactive oxygen species (ROS) and blood-brain barrier (BBB) integrity in brain endothelial cells (BEC). BBB integrity was assessed in BEC in vitro and in microvessels of the guinea pig whole brain in situ preparation. Probes were exposed to MHR (2 hours 67-70 mmHg O2, 3 hours reoxygenation, BEC) or towards occlusion of the arteria cerebri media (MCAO) with or without subsequent reperfusion in the whole brain preparation. In vitro BBB integrity was evaluated using trans-endothelial electrical resistance (TEER) and transwell permeability assays. ROS in BEC were evaluated using 2',7'-dichlorodihydrofluorescein diacetate (DCF), MitoSox and immunostaining for nitrotyrosine. Tight-junction protein (TJ) integrity in BEC, stainings for nitrotyrosine and FITC-albumin extravasation in the guinea pig brain preparation were assessed by confocal microscopy. Diphenyleneiodonium (DPI) was used to investigate NADPH oxidase dependent ROS evolution and its effect on BBB parameters in BEC. MHR impaired TJ proteins zonula occludens 1 (ZO-1) and claudin 5 (Cl5), decreased TEER, and significantly increased cytosolic ROS in BEC. These events were blocked by the NADPH oxidase inhibitor DPI. MCAO with or without subsequent reoxygenation resulted in extravasation of FITC-albumin and ROS generation in the penumbra region of the guinea pig brain preparation and confirmed BBB damage. BEC integrity may be impaired through ROS in MHR on the level of TJ and the BBB is also functionally impaired in moderate hypoxic conditions followed by reperfusion in a complex guinea pig brain preparation. These findings suggest that the BBB is susceptible towards MHR and that ROS play a key role in this process.

Candesartan reduces the hemorrhage associated with delayed tissue plasminogen activator treatment in rat embolic stroke

We have previously reported that angiotensin receptor blockade reduces reperfusion hemorrhage in a suture occlusion model of stroke, despite increasing matrix metalloproteinase (MMP-9) activity. We hypothesized that candesartan will also decrease hemorrhage associated with delayed (6 h) tissue plasminogen activator (tPA) administration after embolic stroke, widening the therapeutic time window of tPA. Adult male Wistar rats were subjected to embolic middle cerebral artery occlusion (eMCAO) and treated with either candesartan (1 mg/kg) alone early at 3 h, delayed tPA (10 mg/kg) alone at 6 h, the combination of candesartan and tPA, or vehicle control. Rats were sacrificed at 24 and 48 h post-eMCAO and brains perfused for evaluation of neurological deficits, cerebral hemorrhage in terms of hemoglobin content, occurrence rate of hemorrhage, infarct size, tissue MMP activity and protein expression. The combination therapy of candesartan and tPA after eMCAO reduced the brain hemorrhage, and improved neurological outcome compared with rats treated with tPA alone. Further, candesartan in combination with tPA increased activity of MMP-9 but decreased MMP-3, nuclear factor kappa-B and tumor necrosis factor-α expression and enhanced activation of endothelial nitric oxide synthase. An activation of MMP-9 alone is insufficient to cause increased hemorrhage in embolic stroke. Combination therapy with acute candesartan plus tPA may be beneficial in ameliorating tPA-induced hemorrhage after embolic stroke.

The oxygen free radicals control MMP-9 and transcription factors expression in the spontaneously hypertensive rat

Oxygen free radical and matrix metalloproteinases-9 (MMP-9) play an important pathophysiological role in the development of chronic hypertension. MMP-9 activities are regulated at different levels. We hypothesize that as mediators of the expression of MMP-9 the transcription factors like nuclear factor kappa B (NF-κB), c-fos and retinoic acid receptors-α (RAR-α) with binding sites to the MMP-9 promoter are overexpressed in the spontaneously hypertensive rat (SHR) in a process that is regulated by oxygen free radicals. Transcription factor NF-κB, c-fos and RAR-α expression levels were determined by immunohistochemistry in renal, cardiac and mesentery microcirculation of the SHR and its normotensive control, the Wistar Kyoto (WKY) rat. The animals were treated with a superoxide scavenger (Tempol) for eight weeks. The elevated plasma levels of thiobarbituric acid reactive substances and MMP-9 levels in the SHR were significantly decreased by Tempol treatment (P<0.05). The NF-κB, c-fos and RAR-α expression levels in renal glomerular, heart and mesentery microvessels were enhanced in the SHR and could also be reduced by Tempol compared to untreated animals (P<0.05). The enhanced MMP-9 levels in SHR microvessels co-express with transcription factors. These results suggest that elevated NF-κB, c-fos and RAR-α expressions and MMP-9 activity in the SHR are superoxide-dependent.

Involvement of free radicals in breast cancer

Researchers have recently shown an increased interest in free radicals and their role in the tumor microenvironment. Free radicals are molecules with high instability and reactivity due to the presence of an odd number of electrons in the outermost orbit of their atoms. Free radicals include reactive oxygen and nitrogen species, which are key players in the initiation and progression of tumor cells and enhance their metastatic potential. In fact, they are now considered a hallmark of cancer. However, both reactive species may contribute to improve the outcomes of radiotherapy in cancer patients. Besides, high levels of reactive oxygen species may be indicators of genotoxic damage in non-irradiated normal tissues. The purpose of this article is to review recent research on free radicals and carcinogenesis in order to understand the pathways that contribute to tumor malignancy. This review outlines the involvement of free radicals in relevant cellular events, including their effects on genetic instability through (growth factors and tumor suppressor genes, their enhancement of mitogenic signals, and their participation in cell remodeling, proliferation, senescence, apoptosis, and autophagy processes; the possible relationship between free radicals and inflammation is also explored. This knowledge is crucial for evaluating the relevance of free radicals as therapeutic targets in cancer.

Green tea polyphenols alleviate early BBB damage during experimental focal cerebral ischemia through regulating tight junctions and PKCalpha signaling

Background

It has been supposed that green tea polyphenols (GTPs) have neuroprotective effects on brain damage after brain ischemia in animal experiments. Little is known regarding GTPs’ protective effects against the blood-brain barrier (BBB) disruption after ischemic stroke. We investigated the effects of GTPs on the expression of claudin-5, occludin, and ZO-1, and the corresponding cellular mechanisms involved in the early stage of cerebral ischemia.

Methods

Male Wistar rats were subjected to a middle cerebral artery occlusion (MCAO) for 0, 30, 60, and 120 min. GTPs (400 mg/kg/day) or vehicle was administered by intragastric gavage twice a day for 30 days prior to MCAO. At different time points, the expression of claudin-5, occludin, ZO-1, and PKCα signaling pathway in microvessel fragments of cerebral ischemic tissue were evaluated.

Results

GTPs reduced BBB permeability at 60 min and 120 min after ischemia as compared with the vehicle group. Transmission electron microscopy also revealed that GTPs could reverse the opening of tight junction (TJ) barrier at 60 min and 120 min after MACO. The decreased mRNA and protein expression levels of claudin-5, occludin, and ZO-1 in microvessel fragments of cerebral ischemic tissue were significantly prevented by treatment with GTPs at the same time points after ischemia in rats. Furthermore, GTPs could attenuate the increase in the expression levels of PKCα mRNA and protein caused by cerebral ischemia.

Conclusions

These results demonstrate that GTPs may act as a potential neuroprotective agent against BBB damage at the early stage of focal cerebral ischemia through the regulation of TJ and PKCα signaling.

The alterations of matrix metalloproteinase-9 in mouse brainstem during herpes simplex virus type 1-induced facial palsy

The aim of this study is to explore the changes of matrix metalloproteinase-9 (MMP9) in the mouse brainstem during the development of facial paralysis induced by herpes simplex virus type 1 (HSV-1) and the inhibitory effect of methylprednisolone sodium succinate (MPSS) on MMP9 expression. HSV-1 was inoculated into the surface of posterior auricle of mouse to establish a paralyzed animal model. The paralyzed mice were divided randomly into three groups. In one group without any treatment, mice were killed at different time points of 6 h, 1, 2, 3, and 7 days post-induction of facial paralysis; in the other two groups, mice were injected daily with MPSS and a combination of MPSS and glucocorticoid receptor blocker (RU486) for 2 days, respectively. The expression of MMP9 in the facial nucleus of brainstem was detected by Western blot, quantitative real-time polymerase chain reaction, and immunofluorescence technique. A total of 52.07 % of mice developed unilateral facial paralysis after inoculated with HSV-1. Both mRNA and protein expression of MMP9 were present at low levels in normal facial nucleus of brainstem and were increased significantly after facial paralysis with its peak time at 2 days post-induction of facial paralysis. Expression of MMP9 of paralyzed mice was inhibited by MPSS, and the inhibition could be blocked by RU486. Our findings suggest that MMP9 in mouse brainstem is involved in the evolution of facial palsy induced by HSV-1 and may play an important role in the pathogenesis of this disease. MPSS might effectively relieve HSV-1-mediated damages by inhibitory effect on expression of MMP9 in HSV-1-induced facial paralysis.

The immune system in stroke: clinical challenges and their translation to experimental research

Stroke represents an unresolved challenge for both developed and developing countries and has a huge socio-economic impact. Although considerable effort has been made to limit stroke incidence and improve outcome, strategies aimed at protecting injured neurons in the brain have all failed. This failure is likely to be due to both the incompleteness of modelling the disease and its causes in experimental research, and also the lack of understanding of how systemic mechanisms lead to an acute cerebrovascular event or contribute to outcome. Inflammation has been implicated in all forms of brain injury and it is now clear that immune mechanisms profoundly influence (and are responsible for the development of) risk and causation of stroke, and the outcome following the onset of cerebral ischemia. Until very recently, systemic inflammatory mechanisms, with respect to common comorbidities in stroke, have largely been ignored in experimental studies. The main aim is therefore to understand interactions between the immune system and brain injury in order to develop novel therapeutic approaches. Recent data from clinical and experimental research clearly show that systemic inflammatory diseases -such as atherosclerosis, obesity, diabetes or infection - similar to stress and advanced age, are associated with dysregulated immune responses which can profoundly contribute to cerebrovascular inflammation and injury in the central nervous system. In this review, we summarize recent advances in the field of inflammation and stroke, focusing on the challenges of translation between pre-clinical and clinical studies, and potential anti-inflammatory/immunomodulatory therapeutic approaches.

Matrix metalloproteinases and blood-brain barrier disruption in acute ischemic stroke

Ischemic stroke continues to be one of the most challenging diseases in translational neurology. Tissue plasminogen activator (tPA) remains the only approved treatment for acute ischemic stroke, but its use is limited to the first hours after stroke onset due to an increased risk of hemorrhagic transformation over time resulting in enhanced brain injury. In this review we discuss the role of matrix metalloproteinases (MMPs) in blood-brain barrier (BBB) disruption as a consequence of ischemic stroke. MMP-9 in particular appears to play an important role in tPA-associated hemorrhagic complications. Reactive oxygen species can enhance the effects of tPA on MMP activation through the loss of caveolin-1 (cav-1), a protein encoded in the cav-1 gene that serves as a critical determinant of BBB permeability. This review provides an overview of MMPs' role in BBB breakdown during acute ischemic stroke. The possible role of MMPs in combination treatment of acute ischemic stroke is also examined.

Role of oxidative stress in Parkinson's disease

Parkinson's disease (PD) is a progressive neurodegenerative movement disorder associated with a selective loss of the dopamine(DA)rgic neurons in the substantia nigra pars compacta and the degeneration of projecting nerve fibers in the striatum. Because there is currently no therapy that delays the neurodegenerative process, modification of the disease course by neuroprotective therapy is an important unmet clinical need. Toward this end, understanding cellular mechanisms that render the nigral neurons particularly vulnerable have been a subject of intensive research. Increasing evidence suggests that oxidative stress plays a major role. The metabolism of DA itself contributes to oxidative stress, resulting in modification of intracellular macromolecules whose functions are important for cell survival. Mitochondrial dysfunction and the consequent increase in reactive oxygen species also trigger a sequence of events that leads to cell demise. In addition, activated microglia produce nitric oxide and superoxide during neuroinflammatory responses, and this is aggravated by the molecules released by damaged DAergic neurons such as α-synuclein, neuromelanin and matrix metalloproteinase-3. Ways to reduce oxidative stress therefore can provide a therapeutic strategy. NAD(P)H:quinone reductase (NQO1) and other antioxidant enzymes, whose gene expression are commonly under the regulation of the transcription factor Nrf2, can serve as target proteins utilized toward development of disease-modifying therapy for PD.

Ischemic postconditioning decreases cerebral edema and brain blood barrier disruption caused by relief of carotid stenosis in a rat model of cerebral hypoperfusion

Background and Purpose

Complications due to brain edema and breakdown of blood brain barrier are an important factor affecting the treatment effects of patients with severe carotid stenosis. In this study, we investigated the protective effects of ischemic postconditioning on brain edema and disruption of blood brain barrier via establishing rat model of hypoperfusion due to severe carotid stenosis.

Methods

Wistar rat model of hypoperfusion due to severe carotid stenosis was established by binding a stainless microtube to both carotid arteries. Ischemic postconditioning procedure consisted of three cycles of 30 seconds ischemia and 30 seconds reperfusion. Brain edema was evaluated by measuring cerebral water content, and blood brain barrier permeability was assayed by examining cerebral concentration of Evans' Blue (EB) and fluorescein sodium (NaF). ELISA was used to analyze the expression of MMP-9, claudin-5 and occludin. The activity and location of MMP-9 was analyzed by gelatin zymography and in situ zymography, respectively. The distribution of tight junction proteins claudin-5 and occludin was observed by immunohistochemistry.

Results

The increased brain water content and cerebral concentration of EB and NaF were suppressed by administration of ischemic postconditioning prior to relief of carotid stenosis. Zymographic studies showed that MMP-9 was mainly located in the cortex and its activity was significantly improved by relief of carotid stenosis and, but the elevated MMP-9 activity was inhibited markedly by ischemic postconditioning. Immunohistochemistry revealed that ischemic postconditioning improved the discontinuous distribution of claudin-5 and occludin. ELISA detected that the expression of up-regulated MMP-9 and down-regulated claudin-5 and occludin caused by carotid relief were all attenuated by ischemic postconditioning.

Conclusions

Ischemic postconditioning is an effective method to prevent brain edema and improve BBB permeability and could be used during relief of severe carotid stenosis.

Targets of vascular protection in acute ischemic stroke differ in type 2 diabetes

Hemorrhagic transformation is an important complication of acute ischemic stroke, particularly in diabetic patients receiving thrombolytic treatment with tissue plasminogen activator, the only approved drug for the treatment of acute ischemic stroke. The objective of the present study was to determine the effects of acute manipulation of potential targets for vascular protection [i.e., NF-κB, peroxynitrite, and matrix metalloproteinases (MMPs)] on vascular injury and functional outcome in a diabetic model of cerebral ischemia. Ischemia was induced by middle cerebral artery occlusion in control and type 2 diabetic Goto-Kakizaki rats. Treatment groups received a single dose of the peroxynitrite decomposition catalyst 5,10,15,20-tetrakis(4-sulfonatophenyl)prophyrinato iron (III), the nonspecific NF-κB inhibitor curcumin, or the broad-spectrum MMP inhibitor minocycline at reperfusion. Poststroke infarct volume, edema, hemorrhage, neurological deficits, and MMP-9 activity were evaluated. All acute treatments reduced MMP-9 and hemorrhagic transformation in diabetic groups. In addition, acute curcumin and minocycline therapy reduced edema in these animals. Improved neurological function was observed in varying degrees with treatment, as indicated by beam-walk performance, modified Bederson scores, and grip strength; however, infarct size was similar to untreated diabetic animals. In control animals, all treatments reduced MMP-9 activity, yet bleeding was not improved. Neuroprotection was only conferred by curcumin and minocycline. Uncovering the underlying mechanisms contributing to the success of acute therapy in diabetes will advance tailored stroke therapies.

Normobaric hyperoxia-based neuroprotective therapies in ischemic stroke

Stroke is a leading cause of death and disability due to disturbance of blood supply to the brain. As brain is highly sensitive to hypoxia, insufficient oxygen supply is a critical event contributing to ischemic brain injury. Normobaric hyperoxia (NBO) that aims to enhance oxygen delivery to hypoxic tissues has long been considered as a logical neuroprotective therapy for ischemic stroke. To date, many possible mechanisms have been reported to elucidate NBO’s neuroprotection, such as improving tissue oxygenation, increasing cerebral blood flow, reducing oxidative stress and protecting the blood brain barrier. As ischemic stroke triggers a battery of damaging events, combining NBO with other agents or treatments that target multiple mechanisms of injury may achieve better outcome than individual treatment alone. More importantly, time loss is brain loss in acute cerebral ischemia. NBO can be a rapid therapy to attenuate or slow down the evolution of ischemic tissues towards necrosis and therefore “buy time” for reperfusion therapies. This article summarizes the current literatures on NBO as a simple, widely accessible, and potentially cost-effective therapeutic strategy for treatment of acute ischemic stroke.

Targeting reactive nitrogen species: a promising therapeutic strategy for cerebral ischemia-reperfusion injury

Ischemic stroke accounts for nearly 80% of stroke cases. Recanalization with thrombolysis is a currently crucial therapeutic strategy for re-building blood supply, but the thrombolytic therapy often companies with cerebral ischemia-reperfusion injury, which are mediated by free radicals. As an important component of free radicals, reactive nitrogen species (RNS), including nitric oxide (NO) and peroxynitrite (ONOO(-)), play important roles in the process of cerebral ischemia-reperfusion injury. Ischemia-reperfusion results in the production of nitric oxide (NO) and peroxynitrite (ONOO(-)) in ischemic brain, which trigger numerous molecular cascades and lead to disruption of the blood brain barrier and exacerbate brain damage. There are few therapeutic strategies available for saving ischemic brains and preventing the subsequent brain damage. Recent evidence suggests that RNS could be a therapeutic target for the treatment of cerebral ischemia-reperfusion injury. Herein, we reviewed the recent progress regarding the roles of RNS in the process of cerebral ischemic-reperfusion injury and discussed the potentials of drug development that target NO and ONOO(-) to treat ischemic stroke. We conclude that modulation for RNS level could be an important therapeutic strategy for preventing cerebral ischemia-reperfusion injury.

Recombinant ADAMTS13 reduces tissue plasminogen activator-induced hemorrhage after stroke in mice

OBJECTIVE

Tissue plasminogen activator (tPA) is approved for treatment of acute ischemic stroke, but it increases the risk of cerebral hemorrhage. Accumulating evidence suggests that von Willebrand factor (VWF) plays a pivotal role in thrombus formation and microcirculatory disturbances after ischemic stroke. By cleaving VWF, ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) protects mice from stroke. Therefore, we hypothesized that recombinant ADAMTS13 (rADAMTS13) could increase the safety of tPA thrombolysis in stroke.

METHODS

We examined blood-brain barrier (BBB) permeability after intraventricular injection of tPA, VWF, and rADAMTS13 in nonischemic mice. We investigated the role of rADAMTS13 on reducing tPA-induced BBB dysfunction and cerebral hemorrhage in a mouse stroke model.

RESULTS

Intraventricular injection of tPA or VWF under nonischemic conditions resulted in a significant increase in BBB permeability. In contrast, rADAMTS13 blocked both tPA- and VWF-induced BBB opening. BBB disruption following stroke was exacerbated by intravenous administration of tPA, but this was attenuated by injection of rADAMTS13. Correspondingly, tPA-associated hemorrhage after stroke was significantly reduced by rADAMTS13. The antihemorrhagic effect of rADAMTS13 was reversed by injection of recombinant VWF. We also showed that rADAMTS13 inhibited tPA-mediated upregulation of vascular endothelial growth factor (VEGF) in vascular endothelium after stroke. The upregulation of VEGF was suppressed by either an Akt inhibitor wortmannin or a Rho kinase inhibitor fasudil. Furthermore, rADAMTS13 downregulated tPA-induced phosphorylation of Akt and activation of RhoA.

INTERPRETATION

These findings demonstrate that the VWF-cleaving protease rADAMTS13 reduced tPA-induced hemorrhage by regulating BBB integrity, and suggest that this effect may occur through the Akt/RhoA-mediated VEGF pathways.

Association between IL10, IL10RA, and IL10RB SNPs and ischemic stroke with hypertension in Korean population

The pathogenesis of stroke is associated with the immune and inflammatory responses. Cytokines, such as interleukin 10 (IL10), play an important role in the process of inflammation. To investigate whether IL10, IL10RA, and IL10RB polymorphisms are associated with the risk of ischemic stroke (IS), selected two IL10 SNPs (rs1518111 and rs1554286), three IL10RA SNPs (rs2256111, rs4252243, and rs2228054), and two IL10RB SNPs (rs999788 and rs2834167) were analyzed in 120 patients with IS and 285 control subjects. All IS patients were classified into the clinical subgroups, according to the levels of blood pressure (hypertension, present and absent), fasting plasma glucose (diabetes mellitus, present and absent), and lipids (dyslipidemia, present and absent). SNPStats and SPSS 18.0 program were used to obtain the odds ratios, 95 % confidence intervals, and P values. Multiple logistic regression models (codominant1, codominant2, dominant, recessive, and log-additive models) were performed to analyze the genetic data. Seven polymorphisms were not associated with the IS, but showed significant associations with hypertension, in the risk of IS. These results suggest that the IL10, IL10RA, and IL10RB genes may be contributed to the hypertension in the risk of IS in the Korean population.

Differential expression of extracellular matrix components in the Fallopian tubes throughout the menstrual cycle

BACKGROUND

One of the unique characteristics of the female genital tract is the extensive tissue remodeling observed throughout the menstrual cycle. Multiple components of the extracellular matrix take part in this tissue rebuilding; however, the individual components involved have not been identified.

METHODS

In the present study, the expression of extracellular matrix proteins and selected matrix metalloproteinase (MMP) activities in Fallopian tubes (FT) throughout the menstrual cycle were examined by PCR array, immunocytochemistry, zymography and bioinformatics.

RESULTS

Of the eighty-four genes analyzed, eighty-three were expressed in the FT during at least one stage of the menstrual cycle. We observed a significant increase (>/=2-fold) in ADAMTS1, ADAMTS13, COL7A1, MMP3, MMP9, PECAM1, and THBS3 in the periovulatory phase compared to the follicular phase. Meanwhile, we observed a significant decrease (>/= 2-fold) in COL7A1, ICAM1, ITGA8, MMP16, MMP9, CLEC3B, SELE and TIMP2 in the lutheal phase compared to the periovulatory phase. Immunocytochemistry showed that MMP-3 and MMP-9 were localized in the endosalpinx during all phases of the menstrual cycle. Gelatin zymograms detected non-cycle-dependent protease activity.

CONCLUSIONS

Several extracellular matrix components were regulated throughout the menstrual cycle in a cyclic pattern, suggesting a possible steroid regulation and a role in tissue remodeling and FT functions.

Matrix metalloproteinase-2-mediated occludin degradation and caveolin-1-mediated claudin-5 redistribution contribute to blood-brain barrier damage in early ischemic stroke stage

Blood-brain barrier (BBB) disruption occurs early enough to be within the thrombolytic time window, and this early ischemic BBB damage is closely associated with hemorrhagic transformation and thus emerging as a promising target for reducing the hemorrhagic complications of thrombolytic stroke therapy. However, the mechanisms underlying early ischemic BBB damage remain poorly understood. Here, we investigated the early molecular events of ischemic BBB damage using in vitro oxygen-glucose deprivation (OGD) and in vivo rat middle cerebral artery occlusion (MCAO) models. Exposure of bEND3 monolayer to OGD for 2 h significantly increased its permeability to FITC-labeled dextran and promoted the secretion of metalloproteinase-2 and -9 (MMP-2/9) and cytosolic translocation of caveolin-1 (Cav-1). This same OGD treatment also led to rapid degradation of tight junction protein occludin and dissociation of claudin-5 from the cytoskeleton, which contributed to OGD-induced endothelial barrier disruption. Using selective MMP-2/9 inhibitor SB-3CT (2-[[(4-phenoxyphenyl)sulfonyl]methyl]-thiirane) or their neutralizing antibodies or Cav-1 siRNA, we found that MMP-2 was the major enzyme mediating OGD-induced occludin degradation, while Cav-1 was responsible for claudin-5 redistribution. The interaction between Cav-1 and claudin-5 was further confirmed by coimmunoprecipitation. Consistent with these in vitro findings, we observed fluorescence tracer extravasation, increased gelatinolytic activity, and elevated interstitial MMP-2 levels in ischemic subcortical tissue after 2 h MCAO. Moreover, occludin protein loss and claudin-5 redistribution were detected in ischemic cerebromicrovessels. These data indicate that cerebral ischemia initiates two rapid parallel processes, MMP-2-mediated occludin degradation and Cav-1-mediated claudin-5 redistribution, to cause BBB disruption at early stroke stages relevant to acute thrombolysis.

Asiatic acid attenuates infarct volume, mitochondrial dysfunction, and matrix metalloproteinase-9 induction after focal cerebral ischemia

BACKGROUND AND PURPOSE

Asiatic acid (AA) has been shown to attenuate cerebral infarction in a mouse model of focal ischemia and shows promise as a neuroprotective stroke therapy. To facilitate translation of these findings to clinical studies, we determined pharmacokinetics, a dose-response relationship, the therapeutic time window, and efficacy using multiple stroke models. We also explored potential mechanisms of action.

METHODS

Escalating doses of intravenous AA were administered and serum concentrations were measured at multiple time points for the pharmacokinetic studies. Subsequently, a dose-response relationship was determined followed by administration at different intervals after the onset of ischemia to establish a therapeutic time window for neuroprotection. Outcome measurements included both histological and behavioral. Mitochondrial function and matrix metalloproteinase activity in controls and treated rats were also determined.

RESULTS

The pharmacokinetic studies showed that AA (75 mg/kg) has a half-life of 2.0 hours. AA significantly decreased infarct volume and improved neurological outcome even when administration was at time points up to 12 hours after the onset of ischemia. Infarct volume was also significantly decreased in female rats and spontaneously hypertensive rats. AA attenuated mitochondrial dysfunction and reduced matrix metalloproteinase-9 induction.

CONCLUSIONS

Our study shows AA is effective against multiple models of focal ischemia, has a long therapeutic time window, and is also effective in females and hypertensive animals. AA may mediate neuroprotection by protecting mitochondria and inhibiting matrix metalloproteinase-9 induction and activation. Taken together these data suggest that AA is an excellent candidate for development as a stroke therapy.

Neurological diseases as primary gliopathies: a reassessment of neurocentrism

Diseases of the human brain are almost universally attributed to malfunction or loss of nerve cells. However, a considerable amount of work has, during the last decade, expanded our view on the role of astrocytes in CNS (central nervous system), and this analysis suggests that astrocytes contribute to both initiation and propagation of many (if not all) neurological diseases. Astrocytes provide metabolic and trophic support to neurons and oligodendrocytes. Here, we shall endeavour a broad overviewing of the progress in the field and forward the idea that loss of homoeostatic astroglial function leads to an acute loss of neurons in the setting of acute insults such as ischaemia, whereas more subtle dysfunction of astrocytes over periods of months to years contributes to epilepsy and to progressive loss of neurons in neurodegenerative diseases. The majority of therapeutic drugs currently in clinical use target neuronal receptors, channels or transporters. Future therapeutic efforts may benefit by a stronger focus on the supportive homoeostatic functions of astrocytes.