Blood-brain barrier disruption in humans is independently associated with increased matrix metalloproteinase-9

Lack of IL-6 increases blood-brain barrier permeability in fungal meningitis

The pathogenesis of increased blood-brain barrier permeability during Cryptococcus meningitis is still largely unknown. Interleukin (IL-6) is a multifunctional cytokine, and numerous studies have shown that IL-6 influences the integrity of the blood-brain barrier. In this study we investigated the role of IL-6 in Cryptococcus meningitis. First, wild-type or IL-6(-/-) mice were injected with Cryptococcus neoformans (C. neoformans) and the survival time in both groups was recorded. Second, the number of fungi was measured in the brains of IL-6(-/-) wild-type mice. Finally, the blood-brain barrier permeability index was detected in infected IL-6(-/-) mice treated with recombinant human IL-6. The blood-brain barrier permeability index was measured in infected wild-type mice treated with anti-IL-6 antibodies as well. The survival of IL-6(-/-) mice injected with C. neoformans was significantly lower than that of identically challenged wild-type mice. The infected IL-6(-/-) mice had significantly larger brain fungal burdens than wild-type mice. Furthermore, increased blood-brain barrier index was found in infected IL-6(-/-) mice when compared with that in infected control mice. Similar results were obtained when mice challenged with C. neoformans were treated systemically with neutralizing anti-IL-6 antibodies, resulting in an elevation of vascular permeability. Our data revealed that IL-6 reduced the blood-brain barrier permeability during Cryptococcus meningitis, and it might provide an explanation for the significantly lower survival of infected IL-6(-/-) mice.

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

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

Role of Matrix Metalloproteinases in the Pathogenesis of Traumatic Brain Injury

Traumatic brain injury (TBI) is a major cause of mortality and morbidity worldwide. Studies revealed that the pathogenesis of TBI involves upregulation of MMPs. MMPs form a large family of closely related zinc-dependent endopeptidases, which are primarily responsible for the dynamic remodulation of the extracellular matrix (ECM). Thus, they are involved in several normal physiological processes like growth, development, and wound healing. During pathophysiological conditions, MMPs proteolytically degrade various components of ECM and tight junction (TJ) proteins of BBB and cause BBB disruption. Impairment of BBB causes leakiness of the blood from circulation to brain parenchyma that leads to microhemorrhage and edema. Further, MMPs dysregulate various normal physiological processes like angiogenesis and neurogenesis, and also they participate in the inflammatory and apoptotic cascades by inducing or regulating the specific mediators and their receptors. In this review, we explore the roles of MMPs in various physiological/pathophysiological processes associated with neurological complications, with special emphasis on TBI.

Brain endothelial dysfunction in cerebral adrenoleukodystrophy

See Aubourg (doi:10.1093/awv271) for a scientific commentary on this article.X-linked adrenoleukodystrophy is caused by mutations in the ABCD1 gene leading to accumulation of very long chain fatty acids. Its most severe neurological manifestation is cerebral adrenoleukodystrophy. Here we demonstrate that progressive inflammatory demyelination in cerebral adrenoleukodystrophy coincides with blood-brain barrier dysfunction, increased MMP9 expression, and changes in endothelial tight junction proteins as well as adhesion molecules. ABCD1, but not its closest homologue ABCD2, is highly expressed in human brain microvascular endothelial cells, far exceeding its expression in the systemic vasculature. Silencing of ABCD1 in human brain microvascular endothelial cells causes accumulation of very long chain fatty acids, but much later than the immediate upregulation of adhesion molecules and decrease in tight junction proteins. This results in greater adhesion and transmigration of monocytes across the endothelium. PCR-array screening of human brain microvascular endothelial cells after ABCD1 silencing revealed downregulation of both mRNA and protein levels of the transcription factor c-MYC (encoded by MYC). Interestingly, MYC silencing mimicked the effects of ABCD1 silencing on CLDN5 and ICAM1 without decreasing the levels of ABCD1 protein itself. Together, these data demonstrate that ABCD1 deficiency induces significant alterations in brain endothelium via c-MYC and may thereby contribute to the increased trafficking of leucocytes across the blood-brain barrier as seen in cerebral adrenouleukodystrophy.

Serum tissue inhibitor of matrix metalloproteinase-1 levels are associated with mortality in patients with malignant middle cerebral artery infarction

Background

In the last years, circulating matrix metalloproteinases (MMP)-9 levels have been associated with functional outcome in ischemic stroke patients. However the prognostic value of circulating levels of tissue inhibitor of matrix metalloproteinases (TIMP)-1 and MMP-10 in functional outcome of ischemic stroke patients has been scarcely studied. In addition, to our knowledge, serum MMP-9, MMP-10 and TIMP-1 levels in patients with malignant middle cerebral artery infarction (MMCAI) for mortality prediction have not been studied, and these were the objectives of this study.

Methods

This was a multicenter, observational and prospective study carried out in six Spanish Intensive Care Units. We included patients with severe MMCAI defined as Glasgow Coma Scale (GCS) lower than 9. We measured circulating levels of MMP-9, MMP-10, TIMP-1, in 50 patients with severe MMCAI at diagnosis and in 50 healthy subjects. Endpoint was 30-day mortality.

Results

Patients with severe MMCAI showed higher serum levels of MMP-9 (p = 0.001), MMP-10 (p < 0.001), and TIMP-1 (p = 0.02) than healthy subjects. Non-surviving MMCAI patients (n = 26) compared to survivor ones (n = 24) showed higher circulating levels of TIMP-1 (p < 0.001), MMP-10 (p = 0.02) and PAI-1(p = 0.02), and lower MMP-9 levels (p = 0.04). Multiple binomial logistic regression analysis showed that serum TIMP-1 levels > 239 ng/mL are associated with 30-day mortality (OR = 5.82; 95 % CI = 1.37-24.73; P = 0.02) controlling for GCS and age. The area under the curve for TIMP-1 as predictor of 30-day mortality was 0.81 (95 % CI = 0.67-0.91; P < 0.001). We found an association between circulating levels of TIMP-1 and MMP-10 (rho = 0.45; P = 0.001), plasminogen activator inhibitor (PAI)-1 (rho = 0.53; P < 0.001), and tumor necrosis factor (TNF)-alpha (rho = 0.70; P < 0.001).

Conclusions

The most relevant and new findings of our study, were that serum TIMP-1 levels in MMCAI patients were associated with mortality, and could be used as a prognostic biomarker of mortality in MMCAI patients.

Clinical Implications of Sulcal Enhancement on Postcontrast Fluid Attenuated Inversion Recovery Images in Patients with Acute Stroke Symptoms

Objective

Hyperintense acute reperfusion marker (HARM) without diffusion abnormalities is occasionally found in patients with an acute stroke. This study was to determine the prevalence and clinical implications of HARM without diffusion abnormalities.

Materials and Methods

There was a retrospective review of magnetic resonance images 578 patients with acute strokes and identified those who did not have acute infarction lesions, as mapped by diffusion-weighted imaging (DWI). These patients were classified into an imaging-negative stroke and HARM without diffusion abnormalities groups, based on the DWI findings and postcontrast fluid attenuated inversion recovery images. The National Institutes of Health Stroke Scale (NIHSS) scores at admission, 1 day, and 7 days after the event, as well as clinical data and risk factors, were compared between the imaging-negative stroke and HARM without diffusion abnormalities groups.

Results

Seventy-seven acute stroke patients without any DWI abnormalities were found. There were 63 patients with an imaging-negative stroke (accounting for 10.9% of 578) and 13 patients with HARM without diffusion abnormalities (accounting for 2.4% of 578). The NIHSS scores at admission were higher in HARM without diffusion abnormalities group than in the imaging-negative stroke group (median, 4.5 vs. 1.0; p < 0.001), but the scores at 7 days after the event were not significantly different between the two groups (median, 0 vs. 0; p = 1). The patients with HARM without diffusion abnormalities were significantly older, compared with patients with an imaging-negative stroke (mean, 73.1 years vs. 55.9 years; p < 0.001).

Conclusion

Patients with HARM without diffusion abnormalities are older and have similarly favorable short-term neurological outcomes, compared with the patients with imaging-negative stroke.

Unbalanced Metalloproteinase-9 and Tissue Inhibitors of Metalloproteinases Ratios Predict Hemorrhagic Transformation of Lesion in Ischemic Stroke Patients Treated with Thrombolysis: Results from the MAGIC Study

Background

Experimentally, metalloproteinases (MMPs) play a detrimental role related to the severity of ischemic brain lesions. Both MMPs activity and function in tissues reflect the balance between MMPs and tissue inhibitors of metalloproteinases (TIMPs). We aimed to evaluate the role of MMPs/TIMPs balance in the setting of rtPA-treated stroke patients.

Methods

Blood was taken before and 24-h after rtPA from 327 patients (mean age 68 years, median NIHSS 11) with acute ischemic stroke. Delta median values of each MMP/TIMP ratio [(post rtPA MMP/TIMP-baseline MMP/TIMP)/(baseline MMP/TIMP)] were analyzed related to symptomatic intracranial hemorrhage (sICH) according to NINDS criteria, relevant hemorrhagic transformation (HT) defined as confluent petechiae within the infarcted area or any parenchymal hemorrhage, stroke subtypes (according to Oxfordshire Community Stroke Project) and 3-month death. The net effect of each MMP/TIMP ratio was estimated by a logistic regression model including major clinical determinants of outcomes

Results

Adjusting for major clinical determinants, only increase in MMP9/TIMP1 and MMP9/TIMP2 ratios remained significantly associated with sICH (odds ratio [95% confidence interval], 1.67 [1.17–2.38], p = 0.005; 1.74 [1.21–2.49], p = 0.003, respectively). Only relative increase in MMP9/TIMP1 ratio proved significantly associated with relevant HT (odds ratio [95% confidence interval], 1.74 [1.17–2.57], p = 0.006) with a trend toward significance for MMP9/TIMP2 ratio (p = 0.007).

Discussion

Our data add substantial clinical evidence about the role of MMPs/TIMPs balance in rtPA-treated stroke patients. These results may serve to generate hypotheses on MMPs inhibitors to be administered together with rtPA in order to counteract its deleterious effect.

Fingolimod alters inflammatory mediators and vascular permeability in intracerebral hemorrhage

Intracerebral hemorrhage (ICH) leads to high rates of death and disability. The pronounced inflammatory reactions that rapidly follow ICH contribute to disease progression. Our recent clinical trial demonstrated that oral administration of an immune modulator fingolimod restrained secondary injury derived from initial hematoma, but the mechanisms remain unknown. In this study, we aim to investigate the effects of fingolimod on inflammatory mediators and vascular permeability in the clinical trial of oral fingolimod for intracerebral hemorrhage (ICH). The results showed that fingolimod decreased the numbers of circulating CD4(+) T, CD8(+) T, CD19(+) B, NK, and NKT cells and they recovered quickly after the drug was stopped. The plasma ICAM level was decreased and IL-10 was increased by fingolimod. Interestingly, fingolimod protected vascular permeability as indicated by a decreased plasma level of MMP9 and the reduced rT1%. In conclusion, modulation of systemic inflammation by fingolimod demonstrates that it is an effective therapeutic agent for ICH. Fingolimod may prevent perihematomal edema enlargement by protecting vascular permeability.

Anti-NR2A/B Antibodies and Other Major Molecular Mechanisms in the Pathogenesis of Cognitive Dysfunction in Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease that affects approximately 1–45.3 per 100,000 people worldwide. Although deaths as a result of active and renal diseases have been substantially declining amongst SLE patients, disease involving the central nervous system (CNS), collectively termed neuropsychiatric systemic lupus erythematosus (NPSLE), remains one of the important causes of death in these patients. Cognitive dysfunction is one of the most common manifestations of NPSLE, which comprises deficits in information-processing speed, attention and executive function, in conjunction with preservation of speech. Albeit a prevalent manifestation of NPSLE, the pathogenetic mechanisms of cognitive dysfunction remain unclear. Recent advances in genetic studies, molecular techniques, neuropathology, neuroimaging and cognitive science have gleaned valuable insights into the pathophysiology of lupus-related cognitive dysfunction. In recent years, a role for autoantibodies, molecular and cellular mechanisms in cognitive dysfunction, has been emerging, challenging our previous concept of the brain as an immune privileged site. This review will focus on the potential pathogenic factors involved in NPSLE, including anti-N-methyl-d-aspartate receptor subunit NR2A/B (anti-NR2A/B) antibodies, matrix metalloproteinase-9, neutrophil extracellular traps and pro-inflammatory mediators. Better understanding of these mechanistic processes will enhance identification of new therapeutic modalities to halt the progression of cognitive decline in SLE patients.

Propofol post-conditioning protects the blood brain barrier by decreasing matrix metalloproteinase-9 and aquaporin-4 expression and improves the neurobehavioral outcome in a rat model of focal cerebral ischemia-reperfusion injury

Propofol, an intravenous anesthetic, inhibits neuronal apoptosis induced by ischemic stroke, protects the brain from ischemia/reperfusion injury and improves neuronal function. However, whether propofol is able to protect the blood brain barrier (BBB) and the underlying mechanisms have remained to be elucidated. In the present study, a rat model of cerebral ischemia/reperfusion was established, using a thread embolism to achieve middle cerebral artery occlusion. Rats were treated with propofol (propofol post-conditioning) or physiological saline (control) administered by intravenous injection 30 min following reperfusion. Twenty-four hours following reperfusion, neurobehavioral manifestations were assessed. The levels of cephaloedema, damage to the BBB and expression levels of matrix metalloproteinase-9 (MMP-9), aquaporin-4 (AQP-4) and phosphorylated c-Jun N-terminal kinase (pJNK) were determined in order to evaluate the effects of propofol on the BBB. In comparison to the cerebral ischemia/reperfusion group, the levels of brain water content and Evans blue content, as well as the expression levels of MMP-9, AQP-4 and pJNK were significantly reduced in the propofol post-conditioning group. These results indicated that propofol post-conditioning improved the neurobehavioral manifestations and attenuated the BBB damage and cephaloedema induced following cerebral ischemia/reperfusion. This effect may be due to the inhibition of MMP-9 and AQP-4 expression, and the concurrent decrease in JNK phosphorylation.

In vitro cerebrovascular modeling in the 21st century: current and prospective technologies

The blood-brain barrier (BBB) maintains the brain homeostasis and dynamically responds to events associated with systemic and/or rheological impairments (e.g., inflammation, ischemia) including the exposure to harmful xenobiotics. Thus, understanding the BBB physiology is crucial for the resolution of major central nervous system CNS) disorders challenging both health care providers and the pharmaceutical industry. These challenges include drug delivery to the brain, neurological disorders, toxicological studies, and biodefense. Studies aimed at advancing our understanding of CNS diseases and promoting the development of more effective therapeutics are primarily performed in laboratory animals. However, there are major hindering factors inherent to in vivo studies such as cost, limited throughput and translational significance to humans. These factors promoted the development of alternative in vitro strategies for studying the physiology and pathophysiology of the BBB in relation to brain disorders as well as screening tools to aid in the development of novel CNS drugs. Herein, we provide a detailed review including pros and cons of current and prospective technologies for modelling the BBB in vitro including ex situ, cell based and computational (in silico) models. A special section is dedicated to microfluidic systems including micro-BBB, BBB-on-a-chip, Neurovascular Unit-on-a-Chip and Synthetic Microvasculature Blood-brain Barrier.

Monitoring biomarkers of cellular injury and death in acute brain injury

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Matrix Metalloproteinase-8 is a Novel Pathogenetic Factor in Focal Cerebral Ischemia

The neutrophil collagenase matrix metalloproteinase-8 (MMP8) is a recently identified member of MMPs that have important roles in various inflammation-related disorders. Previously, we identified MMP8 as a new neuroinflammatory mediator in activated microglia by regulating TNF-α productivity. Here, we present evidence that MMP8 is a critical factor for brain damage in transient focal cerebral ischemia by modulating neuroinflammation likely microglial activation and TNF-α production. Biochemical analyses showed upregulation of MMP8 expression at mRNA and protein levels in transient middle cerebral artery occlusion/reperfusion (M/R)-challenged brains. Furthermore, double immunolabeling showed that MMP8 expression was upregulated in the activated microglia of M/R-challenged brains. Assessment of infarct volume, neurological score, and survival/death of neural cells revealed that administration of an MMP8 inhibitor (M8I) immediately after reperfusion reduced brain damage. Histological analyses showed that microglial activation and TNF-α expression in ischemic conditions was abrogated by exposure to M8I, as demonstrated in our previous study using cultured microglia. These outcomes from a pharmacological approach were reaffirmed by a genetic approach using a lentiviral system. Intracerebroventricular microinjection of MMP8-specific shRNA lentivirus reduced the extent of ischemia-induced brain damage, as assessed by infarct volume, neurological score, microglial activation, and TNF-α expression. These results suggest a novel pathogenetic role of MMP8 and implicate modulation of its activity as a tractable strategy for therapies against cerebral ischemia.

The effects of previous statin treatment on plasma matrix metalloproteinase-9 level in Chinese stroke patients undergoing thrombolysis

It is unclear whether previous statin therapy influences the prognosis, hemorrhagic transformation, and plasma matrix metalloproteinases (MMP)-9 levels in Chinese stroke patients receiving intravenous thrombolysis. We conduct a prospective cohort study of 193 patients treated with intravenous thrombolysis. All the enrolled patients were divided into 2 groups (the control group and the statin group), according to the previous history of statin use. The plasma MMP-9 levels were detected before and at 6 hours, 12 hours, 24 hours, and 72 hours after intravenous thrombolysis. The clinical outcome of stroke was measured in terms of the functional outcome and occurrence of symptomatic intracerebral hemorrhage. The MMP-9 levels increased after thrombolysis in statin group and control group. No significant intergroup difference was found in the MMP-9 levels before and at 6 hours after thrombolysis, but the levels were significantly lower in the statin group than in the control group at 12, 24, and 72 hours (P < .001) after thrombolysis. Similarly, no significant intergroup difference was noted in the occurrence of symptomatic intracranial hemorrhage as was the case with the modified Rankin scale (assessed by the Mann-Whitney U test) at 7 days (P = .428) and 90 days (P = .419) after thrombolysis. Our results indicate that pretreatment with statin can inhibit the thrombolysis-induced increase in plasma MMP-9 levels but does not significantly affect the prognosis of acute ischemic stroke patients undergoing intravenous thrombolysis.

Matrix metalloproteinase-9: dual role and temporal profile in intracerebral hemorrhage

BACKGROUND

Clinical outcome after intracerebral hemorrhage (ICH) remains poor. Recent trials in ICH, focusing on hematoma reduction, have not yielded significant clinical improvement. The modulation of matrix metalloproteinase (MMP)-9 may represent a potential therapeutic target for reducing perihematomal edema (PHE) and improving clinical outcome.

METHODS

We searched Cochrane Library, Ovid/Medline, and PubMed databases using combinations of the following MeSH search terms: "intracerebral hemorrhage," "matrix metalloproteinase," "minocycline," "inhibition," and "neuroprotection".

RESULTS

MMP-9 levels in animal models have largely shown detrimental correlations with mortality, clinical outcome, hematoma volume, and PHE. Animal models and clinical studies have established a timeline for MMP-9 expression and corresponding PHE that include an initial peak on days 1-3 and a secondary peak on day 7. Clinical studies evaluating MMP-9 levels in the acute phase (days 1-3) and subacute phase (day 7) of ICH suggest that MMP-9 may be detrimental in the acute phase through destruction of basal lamina, activation of vascular endothelial growth factor, and activation of apoptosis but assist in recovery in the subacute phase through angiogenesis.

CONCLUSIONS

MMP-9 inhibition represents a potentially effective target for neuroprotection in ICH. However, as a ubiquitous protein, the inhibition of pathologic processes must be balanced against the preservation of neuroprotective angiogenesis. As the opposing roles of MMP-9 may have similar mechanisms, the most important factor may be the timing of MMP-9 inhibition. Further studies are necessary to delineate these mechanisms and their temporal relationship.

Effects of edaravone, a free radical scavenger, on circulating levels of MMP-9 and hemorrhagic transformation in patients with intravenous thrombolysis using low-dose alteplase

BACKGROUND

Matrix metalloproteinase-9 (MMP-9) plays a key role for the blood-brain barrier disruption and intravenous tissue plasminogen activator (iv-tPA) therapy increases MMP-9. Edaravone, a free radical scavenger, reduces MMP-9-related blood-brain barrier disruption. We aimed to investigate whether edaravone would suppress the MMP-9 increase after iv-tPA using low-dose alteplase (0.6 mg/kg).

SUBJECTS

Patients hospitalized within 12 hours after ischemic stroke onset between April 2008 and June 2013 were retrospectively examined. Patients with slight deficits (National Institutes of Health Stroke Scale score ≤ 4), stroke caused by arterial dissection, severe inflammatory disease or autoimmune disease, or regular use of steroid were excluded. Serum concentrations of high-sensitivity C-reactive protein, interleukin-6, MMP-2, and MMP-9 were serially measured at admission, after 24 hours, day 7, and day 14. General linear models were used to compare changes in concentrations of these biomarkers over time.

RESULTS

A total of 63 patients (38 men, aged 74.48 ± 13.8 years) were studied. Patients were divided into 2 groups according to the iv-tPA therapy, that is, tPA group (n = 32) and non-tPA group (n = 31). Edaravone was administered routinely except for contraindication (90.6% in the tPA group and 87.1% in the non-tPA group). Significant interaction of group × time factor was observed only in MMP-9 concentrations by repeated-measure analysis of variance (P = .004). Association between iv-tPA therapy and subsequent hemorrhagic transformation was highly significant, but MMP-9 concentrations at any point did not predictive of subsequent hemorrhagic transformation (area under the receiver operating characteristic curve, .681).

CONCLUSIONS

Low-dose iv-tPA increases MMP-9 concentration even in combination with Edaravone. The effect of higher dosage of Edaravone on circulating MMP-9 concentration and subsequent hemorrhagic transformation should be investigated.

Circulating matrix metalloproteinase-9 level is associated with cerebral white matter hyperintensities in non-stroke individuals

BACKGROUNDS

The pathogenesis of cerebral white matter hyperintensities (WMH) has been poorly understood. Our aim was to investigate the association of circulating proteins, the biomarkers of inflammation, blood-brain barrier (BBB) dysfunction, and thrombosis with WMH in non-stroke individuals.

METHODS

Demographic, laboratory, and brain magnetic resonance imaging parameters were prospectively analyzed in 137 subjects. The relationship between plasma interleukin-6, tumor necrosis factor-α, matrx-metalloproteinase-9 (MMP-9), plasminogen activator inhibitor-1 and overt WMH (Fazekas grading score ≥2) was analyzed.

RESULTS

In univariate analysis, old age, high blood pressure, history of hypertension, and elevated plasma MMP-9 level were associated with overt WMH. In multivariate analysis, plasma MMP-9 still maintained a significant association with WMH. Plasma MMP-9 level was weakly but significantly associated with WMH volume (r = 0.232, p = 0.006). All the other circulating proteins examined failed to demonstrate a significant relationship with WMH.

CONCLUSIONS

Plasma MMP-9 is associated with pathophysiology of WMH development.

Drug delivery to the ischemic brain

Cerebral ischemia occurs when blood flow to the brain is insufficient to meet metabolic demand. This can result from cerebral artery occlusion that interrupts blood flow, limits CNS supply of oxygen and glucose, and causes an infarction/ischemic stroke. Ischemia initiates a cascade of molecular events in neurons and cerebrovascular endothelial cells including energy depletion, dissipation of ion gradients, calcium overload, excitotoxicity, oxidative stress, and accumulation of ions and fluid. Blood-brain barrier (BBB) disruption is associated with cerebral ischemia and leads to vasogenic edema, a primary cause of stroke-associated mortality. To date, only a single drug has received US Food and Drug Administration (FDA) approval for acute ischemic stroke treatment, recombinant tissue plasminogen activator (rt-PA). While rt-PA therapy restores perfusion to ischemic brain, considerable tissue damage occurs when cerebral blood flow is reestablished. Therefore, there is a critical need for novel therapeutic approaches that can "rescue" salvageable brain tissue and/or protect BBB integrity during ischemic stroke. One class of drugs that may enable neural cell rescue following cerebral ischemia/reperfusion injury is the HMG-CoA reductase inhibitors (i.e., statins). Understanding potential CNS drug delivery pathways for statins is critical to their utility in ischemic stroke. Here, we review molecular pathways associated with cerebral ischemia and novel approaches for delivering drugs to treat ischemic disease. Specifically, we discuss utility of endogenous BBB drug uptake transporters such as organic anion transporting polypeptides and nanotechnology-based carriers for optimization of CNS drug delivery. Overall, this chapter highlights state-of-the-art technologies that may improve pharmacotherapy of cerebral ischemia.

Genetic variations of MMP9 gene and intracerebral hemorrhage outcome: a cohort study in Chinese Han population

OBJECTIVE

To investigate the association between genetic variations of matrix metalloproteinase 9 (MMP9) gene and intracerebral hemorrhage (ICH) outcome in Chinese Han population.

METHODS

The clinical data and peripheral blood samples from the patients with ICH were collected. The patients were followed up for 3 months, and poor outcome was defined as death or dependency (modified Rankin scale score of 3-6). MassARRAY Analyser was used to genotype the tagger single nucleotide polymorphisms (SNPs) of MMP9 gene. Construction of haplotypes and genetic comparisons were performed by employing PLINK 1.0.7 software.

RESULTS

181 patients with ICH were recruited between September 2009 and October 2010. Information on genetic variations and follow-up assessments were available for 169 (93.4%) patients. Independent patients at 90 days were younger than those who died or dependent (57.82 ± 13.47 vs. 66.99 ± 11.49 years, p<0.01). In addition, independent patients had lower National Institutes of Health Stroke Scale (NIHSS) score (4[1-6] vs. 13[9-19], p<0.01). There were no significant associations (all p>0.05) between MMP9 genetic variations (alleles, genotypes and haplotypes) and ICH outcome after adjustment for conventional risk factors.

CONCLUSIONS

The genetic variations of MMP9 gene were not significantly associated with ICH outcome at 90 days in Chinese Han population.

Physical exercise training and neurovascular unit in ischemic stroke

Physical exercise could exert a neuroprotective effect in both clinical studies and animal experiments. A series of related studies have indicated that physical exercise could reduce infarct volume, alleviate neurological deficits, decrease blood-brain barrier dysfunction, promote angiogenesis in cerebral vascular system and increase the survival rate after ischemic stroke. In this review, we summarized the protective effects of physical exercise on neurovascular unit (NVU), including neurons, astrocytes, pericytes and the extracellular matrix. Furthermore, it was demonstrated that exercise training could decrease the blood-brain barrier dysfunction and promote angiogenesis in cerebral vascular system. An awareness of the exercise intervention benefits pre- and post stroke may lead more stroke patients and people with high-risk factors to accept exercise therapy for the prevention and treatment of stroke.

Attenuation of urokinase activity during experimental ischaemia protects the cerebral barrier from damage through regulation of matrix metalloproteinase-2 and NAD(P)H oxidase

Ischaemic injury impairs the integrity of the blood-brain barrier (BBB). In this study, we investigated the molecular causes of this defect with regard to the putative correlations among NAD(P)H oxidase, plasminogen-plasmin system components, and matrix metalloproteinases. Hence, the activities of NAD(P)H oxidase, matrix metalloproteinase-2, urokinase-type plasminogen activator (uPA), and tissue-type plasminogen activator (tPA), and superoxide anion levels, were assessed in human brain microvascular endothelial cells (HBMECs) exposed to oxygen-glucose deprivation (OGD) alone or OGD followed by reperfusion (OGD + R). The integrity of an in vitro model of BBB comprising HBMECs and astrocytes was studied by measuring transendothelial electrical resistance and the paracellular flux of albumin. OGD with or without reperfusion (OGD ± R) radically perturbed barrier function while concurrently enhancing uPA, tPA and NAD(P)H oxidase activities and superoxide anion release in HBMECs. Pharmacological inactivation of NAD(P)H oxidase attenuated OGD ± R-mediated BBB damage through modulation of matrix metalloproteinase-2 and tPA, but not uPA activity. Overactivation of NAD(P)H oxidase in HBMECs via cDNA electroporation of its p22-phox subunit confirmed the involvement of tPA in oxidase-mediated BBB disruption. Interestingly, blockade of uPA or uPA receptor preserved normal BBB function by neutralizing both NAD(P)H oxidase and matrix metalloproteinase-2 activities. Hence, selective targeting of uPA after ischaemic strokes may protect cerebral barrier integrity and function by concomitantly attenuating basement membrane degradation and oxidative stress.

Potential roles of HDAC inhibitors in mitigating ischemia-induced brain damage and facilitating endogenous regeneration and recovery

Ischemic stroke is a leading cause of death and disability worldwide, with few available treatment options. The pathophysiology of cerebral ischemia involves both early phase tissue damage, characterized by neuronal death, inflammation, and blood-brain barrier breakdown, followed by late phase neurovascular recovery. It is becoming clear that any promising treatment strategy must target multiple points in the evolution of ischemic injury to provide substantial therapeutic benefit. Histone deacetylase (HDAC) inhibitors are a class of drugs that increase the acetylation of histone and non-histone proteins to activate transcription, enhance gene expression, and modify the function of target proteins. Acetylation homeostasis is often disrupted in neurological conditions, and accumulating evidence suggests that HDAC inhibitors have robust protective properties in many preclinical models of these disorders, including ischemic stroke. Specifically, HDAC inhibitors such as trichostatin A, valproic acid, sodium butyrate, sodium 4-phenylbutyrate, and suberoylanilide hydroxamic acid have been shown to provide robust protection against excitotoxicity, oxidative stress, ER stress, apoptosis, inflammation, and bloodbrain barrier breakdown. Concurrently, these agents can also promote angiogenesis, neurogenesis and stem cell migration to dramatically reduce infarct volume and improve functional recovery after experimental cerebral ischemia. In the following review, we discuss the mechanisms by which HDAC inhibitors exert these protective effects and provide evidence for their strong potential to ultimately improve stroke outcome in patients.

Potential serum biomarkers in the pathophysiological processes of stroke

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

Role of Rho kinase in lysophosphatidic acid-induced altering of blood-brain barrier permeability

Lysophosphatidic acid (LPA) the simplest of the water-soluble phospholipids, is produced by activated platelets, macrophage and endothelial cells. It also evokes various biological responses. When LPA concentrations reach high levels, brain injury, including stroke and intracerebral hemorrhage (ICH), occurs. Previous studies have shown that LPA is crucial in increasing blood-brain barrier (BBB) permeability, and the Rho/Rho kinase (ROCK) signaling pathway is involved in the regulation of endothelial permeability. However, the exact mechanism by which the Rho/ROCK pathway mediates BBB disruption induced by LPA remains to be determined. In the present study, we observed that LPA induced the increase of BBB permeability in the right striatum after 10 µl LPA (100 µM) was injected into the ipsilateral caudate nucleus of rats. The ROCK was involved in the expression of proteolytic enzymes, matrix metalloproteinase (MMP)-9 and urokinase-type plasminogen activator (uPA), leading to LPA-induced BBB disruption. ROCK inhibitor (Y27632) markedly inhibited the expression of proteolytic enzymes induced by LPA as well as the BBB disruption after it was co-injected with LPA. Thus, results of the present study suggest that LPA increases BBB permeability, which may be due to the Rho/ROCK signaling pathway and the subsequent production of proteolytic enzymes MMP-9 and uPA.

Proteomic Protease Substrate Profiling of tPA Treatment in Acute Ischemic Stroke Patients: A Step Toward Individualizing Thrombolytic Therapy at the Bedside

Tissue plasminogen activator (tPA) is the only FDA-approved medical therapy for acute ischemic stroke. But as a serine peptidase, intravenous tPA can affect the expression of other proteases that may be implicated in blood-brain barrier breakdown. Such parallel cascades of cell signaling may be involved in intracranial hemorrhage, the major side effect of tPA. Here, we describe an initial attempt in proteomic substrate profiling, i.e., degradomics in human plasma within the context of acute stroke. Plasma from acute stroke patients were analyzed pre- and post-intravenous tPA using tandem mass spectrometry and protein array profiling to identify substrates and proteases of interest. In non-tPA-treated stroke plasma, degradomic patterns indicated a rapid induction of protease activity within 3 h of stroke onset that mostly stabilized by 24 h. But in tPA-treated patients, pre- and post-tPA samples from the same patient demonstrated distinct degradomic patterns that persisted even up to 3-5 days after stroke onset. Matching control patients without strokes had little change in degradomic profiles over time. Our findings demonstrate that tPA treatment changes the plasma degradomic profiles in acute stroke patients. These composite proteolytic profiles may provide a glimpse of the pleiotropic effects of tPA on cellular signaling cascades at the bedside. This study supports the feasibility of performing pharmaco-proteomics at the bedside, which may ultimately allow us to dissect mechanisms of thrombolysis-related therapeutic efficacy in stroke.

C-reactive protein and long-term ischemic stroke prognosis

C-reactive protein (CRP) is an inflammatory biomarker of inflammation and may reflect progression of vascular disease. Conflicting evidence suggests CRP may be a prognostic biomarker of ischemic stroke outcome. Most studies that have examined the relationship between CRP and ischemic stroke outcome have used mortality or subsequent vascular event as the primary outcome measure. Given that nearly half of stroke patients experience moderate to severe functional impairments, using a biomarker like CRP to predict functional recovery rather than mortality may have clinical utility for guiding acute stroke treatments. The primary aim of this study was to systematically and critically review the relationship between CRP and long-term functional outcome in ischemic stroke patients to evaluate the current state of the literature. PubMed and MEDLINE databases were searched for original studies which assessed the relationship between acute CRP levels measured within 24 hours of symptom onset and long-term functional outcome. The search yielded articles published between 1989 and 2012. Included studies used neuroimaging to confirm ischemic stroke diagnosis, high-sensitivity CRP assay, and a functional outcome scale to assess prognosis beyond 30 days after stroke. Study quality was assessed using the REMARK recommendations. Five studies met all inclusion criteria. Results indicate a significant association between elevated baseline high sensitivity CRP and unfavorable long-term functional outcome. Our results emphasize the need for additional research to characterize the relationship between acute inflammatory markers and long-term functional outcome using well-defined diagnostic criteria. Additional studies are warranted to prospectively examine the relationship between high sensitivity CRP measures and long-term outcome.

TIMP-1 polymorphisms in a Chinese Han population with intracerebral hemorrhage

Remodeling of extracellular matrix (ECM) and breakdown of blood-brain barrier (BBB) are crucial events in the pathogenesis of intracerebral hemorrhage (ICH). Matrix metalloproteinases (MMPs), particularly MMP-9 and MMP-2, are the most important degrading enzymes in the ECM and BBB. These proteolytic effects are controlled predominantly by tissue inhibitors of metalloproteinases (TIMPs). TIMP-1 is the main endogenous inhibitor of MMP-9. Two polymorphisms in the TIMP-1 gene (rs4898 and rs2070584) were selected through a literature review and successfully genotyped in a study sample of 410 ICH patients and 305 controls. Differences in genotype and allele frequencies of identified polymorphisms were determined. Furthermore, the serum levels of TIMP-1 were measured in a subgroup of 96 ICH patients on days 1 after ICH onset and 76 controls. Analyses showed that C allele of rs2070584 was significantly associated with the development of ICH in male subjects (p = 0.037, OR = 1.535, 95%CI 1.025-2.300). Multiple logistic regression analysis under three genetic models demonstrated both rs4898 and rs2070584 were not risk factors for ICH in female subjects. Furthermore, serum levels of TIMP-1 were significantly higher in ICH patients than those in normal controls. However, the serum levels of TIMP-1 showed a nonsignificant decrease, depending on the alleles and genotypes of rs2070584 both in male and female cases. In conclusion, this is the first association study of the TIMP-1 gene variants with ICH. Our data suggest that C allele of rs2070584 is a risk factor for ICH development in the Chinese male population. However, the precise function of this variant needs further investigation.

Ischemic stroke biomarkers in blood

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

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Disruption of the blood-brain barrier after generalized tonic-clonic seizures correlates with cerebrospinal fluid MMP-9 levels

Background

Increasing evidence suggests seizures cause blood–brain barrier (BBB) dysfunction including decreased seizure threshold and higher onset potential of future seizures. However, the mechanisms underlying BBB damage in seizures remains poorly understood. Evidence in human and animal models shows BBB disruption is associated with activation of matrix metalloproteinase-9 (MMP-9) after cerebral ischemia and inflammation. The objective of this study was to determine whether MMP-9 concentrations in cerebral spinal fluid (CSF) are associated with BBB disruption in patients after epileptic seizures.

Methods

Thirty-one patients with generalized tonic-clonic (GTC) seizures were included in the study: 20 had recurrent GTC seizures (RS), and 11 had a single GTC seizure (SS) episode. Twenty-five adult non-seizure patients were used as controls. CSF samples were collected by lumbar puncture within 24 h after seizure cessation (range: 3–15 h, mean 6.2 h). CSF MMP-9 levels were determined by an enzyme-linked immunosorbent assay (ELISA). MMP enzyme activity was measured by gelatin zymography. The CSF/serum albumin ratio (albumin quotient, QAlb) was used as a measure of blood–brain barrier permeability.

Results

We found significantly higher CSF MMP-9 concentrations in seizure patients compared with controls (P < 0.001). CSF MMP-9 levels and QAlb values were higher in RS patients compared with SS and controls. Moreover, CSF MMP-9 concentration showed strong correlation between QAlb values (r = 0.76, P < 0.0001) and between CSF leukocyte counts (r = 0.77, P < 0.0001) in patients after seizures. Gelatin zymography showed MMP-9 proteolytic activity only in GTC seizure patients.

Conclusions

Our results suggest MMP-9 plays a role in BBB dysfunction, characterized by invasion of leukocytes into the CSF during seizures.

TIMP-1 attenuates blood-brain barrier permeability in mice with acute liver failure

Blood-brain barrier (BBB) dysfunction in acute liver failure (ALF) results in increased BBB permeability that often precludes the patients from obtaining a life-saving liver transplantation. It remains controversial whether matrix metalloproteinase-9 (MMP-9) from the injured liver contributes to the deregulation of BBB function in ALF. We selectively upregulated a physiologic inhibitor of MMP-9 (TIMP-1) with a single intracerebroventricular injection of TIMP-1 cDNA plasmids at 48 and 72 hours, or with pegylated-TIMP-1 protein. Acute liver failure was induced with tumor necrosis factor-α and D-(+)-galactosamine in mice. Permeability of BBB was assessed with sodium fluorescein (NaF) extravasation. We found a significant increase in TIMP-1 within the central nervous system (CNS) after the administration of TIMP-1 cDNA plasmids and that increased TIMP-1 within the CNS resulted in an attenuation of BBB permeability, a reduction in activation of epidermal growth factor receptor and p38 mitogen-activated protein kinase signals, and a restoration of the tight junction protein occludin in mice with experimental ALF. Pegylated TIMP-1 provided similar protection against BBB permeability in mice with ALF. Our results provided a proof of principle that MMP-9 contributes to the BBB dysfunction in ALF and suggests a potential therapeutic role of TIMP-1 in ALF.

Early exercise protects the blood-brain barrier from ischemic brain injury via the regulation of MMP-9 and occludin in rats

Early exercise within 24 h after stroke can reduce neurological deficits after ischemic brain injury. However, the mechanisms underlying this neuroprotection remain poorly understood. Ischemic brain injury disrupts the blood-brain barrier (BBB) and then triggers a cascade of events, leading to secondary brain injury and poor long-term outcomes. This study verified the hypothesis that early exercise protected the BBB after ischemia. Adult rats were randomly assigned to sham, early exercise (EE) or non-exercise (NE) groups. The EE and NE groups were subjected to ischemia induced by middle cerebral artery occlusion (MCAO). The EE group ran on a treadmill beginning 24 h after ischemia, 30 min per day for three days. After three-days’ exercise, EB extravasation and electron microscopy were used to evaluate the integrity of the BBB. Neurological deficits, cerebral infarct volume and the expression of MMP-9, the tissue inhibitors of metalloproteinase-1 (TIMP-1), and occludin were determined. The data indicated that early exercise significantly inhibited the ischemia-induced reduction of occludin, and an increase in MMP-9 promoted TIMP-1 expression (p < 0.01), attenuated the BBB disruption (p < 0.05) and neurological deficits (p < 0.01) and diminished the infarct volume (p < 0.01). Our results suggest that the neuroprotection conferred by early exercise was likely achieved by improving the function of the BBB via the regulation of MMP-9 and occludin.

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.

The inhibitory effect of S-nitrosoglutathione on blood-brain barrier disruption and peroxynitrite formation in a rat model of experimental stroke

The hallmark of stroke injury is endothelial dysfunction leading to blood-brain barrier (BBB) leakage and edema. Among the causative factors of BBB disruption are accelerating peroxynitrite formation and the resultant decreased bioavailability of nitric oxide (NO). S-nitrosoglutathione (GSNO), an S-nitrosylating agent, was found not only to reduce the levels of peroxynitrite but also to protect the integrity of BBB in a rat model of cerebral ischemia and reperfusion (IR). A treatment with GSNO (3 μmol/kg) after IR reduced 3-nitrotyrosine levels in and around vessels and maintained NO levels in brain. This mechanism protected endothelial function by reducing BBB leakage, increasing the expression of Zonula occludens-1 (ZO-1), decreasing edema, and reducing the expression of matrix metalloproteinase-9 and E-selectin in the neurovascular unit. An administration of the peroxynitrite-forming agent 3-morpholino sydnonimine (3 μmol/kg) at reperfusion increased BBB leakage and decreased the expression of ZO-1, supporting the involvement of peroxynitrite in BBB disruption and edema. Mechanistically, the endothelium-protecting action of GSNO was invoked by reducing the activity of nuclear factor kappa B and increasing the expression of S-nitrosylated proteins. Taken together, the results support the ability of GSNO to improve endothelial function by reducing nitroxidative stress in stroke.

Matrix metalloproteinase-9 in homocysteine-induced intestinal microvascular endothelial paracellular and transcellular permeability

Although elevated levels of homocysteine (Hcy), known as hyperhomocysteinemia (HHcy), is associated with inflammatory bowel disease (IBD), the mechanism of Hcy action is unclear. In the present study, we tested the hypothesis that HHcy activates matrix metalloproteinase-9 (MMP-9), which in turn enhances permeability of human intestinal microvascular endothelial cell (HIMEC) layer by decreasing expression of endothelial junction proteins and increasing caveolae formation. HIMECs were grown in Transwells and treated with 500 µM Hcy in the presence or absence of MMP-9 activity inhibitor. Hcy-induced permeability to FITC-conjugated bovine serum albumin (FITC-BSA) was assessed by measuring fluorescence intensity of solutes in the Transwells' lower chambers. The cell-cell interaction and cell barrier function was estimated by measuring trans-endothelial electrical impedance. Confocal microscopy and flow cytometry were used to study cell junction protein expressions. Hcy-induced changes in transcellular transport of HIMECs were estimated by observing formation of functional caveolae defined as caveolae labeled by cholera toxin and antibody against caveolin-1 and one that have taken up FITC-BSA. Hcy instigated HIMEC monolayer permeability through activation of MMP-9. The increased paracellular permeability was associated with degradation of vascular endothelial cadherin and zona occludin-1 and transcellular permeability through increased caveolae formation in HIMECs. Elevation of Hcy content increases permeability of HIMEC layer affecting both paracellular and transcellular transport pathways, and this increased permeability was alleviated by inhibition of MMP-9 activity. These findings contribute to clarification of mechanisms of IBD development.

Blood-brain barrier disruption after cardiac surgery

BACKGROUND AND PURPOSE

CNS complications are often seen after heart surgery, and postsurgical disruption of the BBB may play an etiologic role. The objective of this study was to determine the prevalence of MR imaging-detected BBB disruption (HARM) and DWI lesions after cardiac surgery.

MATERIALS AND METHODS

All patients had an MRI after cardiac surgery. For half the patients (group 1), we administered gadolinium 24 hours after surgery and obtained high-resolution DWI and FLAIR images 24-48 hours later. We administered gadolinium to the other half (group 2) at the time of the postoperative scan, 2-4 days after surgery. Two stroke neurologists evaluated the images.

RESULTS

Of the 19 patients we studied, none had clinical evidence of a stroke or delirium at the time of the gadolinium administration or the scan, but 9 patients (47%) had HARM (67% in group 1; 30% in group 2; P = .18) and 14 patients (74%) had DWI lesions (70% in group 1; 78% in group 2; P = 1.0). Not all patients with DWI lesions had HARM, and not all patients with HARM had DWI lesions (P = .56).

CONCLUSIONS

Almost half the patients undergoing cardiac surgery have evidence of HARM, and three-quarters have acute lesions on DWI after surgery. BBB disruption is more prevalent in the first 24 hours after surgery. These findings suggest that MR imaging can be used as an imaging biomarker to assess therapies that may protect the BBB in patients undergoing heart surgery.

Ischemic postconditioning diminishes matrix metalloproteinase 9 expression and attenuates loss of the extracellular matrix proteins in rats following middle cerebral artery occlusion and reperfusion

AIMS

Ischemic postconditioning (IPostC) has been proved to have neuroprotective effects for cerebral ischemia, but the underlying mechanism remains elusive. This study aimed at validating the neuroprotective effects of IPostC and investigating whether the neuroprotection of IPostC is associated with matrix metalloproteinase 9 (MMP9) and the extracellular matrix proteins, laminin and fibronectin, following cerebral ischemia/reperfusion in rats.

METHODS

The rats in middle cerebral artery occlusion (MCAO) group underwent MCAO and reperfusion, and the animals in MCAO + IPostC group were treated by occluding bilateral common carotid arteries for 10 seconds and then reperfusing for 10 seconds for five episodes at the beginning of MCAO. Apoptosis was detected with terminal deoxynucleotidyl transferase dUTP nick end labeling staining. The expression of MMP9, laminin, and fibronectin was measured with immunofluorescence and enzyme-linked immunosorbent assay.

RESULTS

IPostC reduced brain edema and infarct volume and improved the neurological function. Furthermore, IPostC decreased cell apoptosis compared with the MCAO group. Compared to the MCAO group, IPostC treatment reduced MMP9 expression. Moreover, the results showed that the expression of laminin and fibronectin significantly increased in the MCAO + IPostC group compared to the MCAO group.

CONCLUSION

These findings indicated that diminishment of MMP9 expression and the attenuation of degradation of laminin and fibronectin may be involved in the protective mechanisms of postconditioning against cerebral ischemia/reperfusion injury.

ATP-binding cassette transporters in immortalised human brain microvascular endothelial cells in normal and hypoxic conditions

Background

Rapid reperfusion following ischemia is the most effective therapy in stroke therapy. However, the success may be compromised by ischemia & reperfusion (I/R) injury and at the human blood–brain barrier (BBB), therefore the effects on transendothelial transport are of special interest. Current studies suggest the ATP-binding cassette (ABC) transporters to be regulated upon ischemic stroke in a way that impedes the effects of drug therapy. The immortalised human brain microvascular endothelial cell line hCMEC/D3 provides most of the unique properties of the BBB with respect to transport and might be a reliable in vitro model to study transendothelial transport after I/R.

Methods

We exposed hCMEC/D3 cells to 24 hours of hypoxia alone and to hypoxia followed by 60 min of reoxygenisation as an in vitro model for I/R. Western blot showed mild upregulation of hypoxia inducible factor (HIF-1α) after hypoxia alone and RNA lysates were analysed with a well-established real-time RT-PCR-based TaqMan low-density array detecting 47 of 48 known human ABC transporters.

Results

No significant increases of ABC mRNA expression levels were detected neither in hypoxic nor in I/R samples. However, slight decrease of ABCC1 in hypoxic and I/R samples and of ABCA10 and ABCD3 in I/R samples was observed.

Conclusion

Our data suggests that hCMEC/D3 cell line and – at the moment – in vitro models in general are a poor basis for stroke research but may be enhanced by co-culturing more cells of the neurovascular unit inducing an overall ischemic response at the BBB.

Albumin induces upregulation of matrix metalloproteinase-9 in astrocytes via MAPK and reactive oxygen species-dependent pathways

BACKGROUND

Astrocytes are an integral component of the blood-brain barrier (BBB) which may be compromised by ischemic or traumatic brain injury. In response to trauma, astrocytes increase expression of the endopeptidase matrix metalloproteinase (MMP)-9. Compromise of the BBB leads to the infiltration of fluid and blood-derived proteins including albumin into the brain parenchyma. Albumin has been previously shown to activate astrocytes and induce the production of inflammatory mediators. The effect of albumin on MMP-9 activation in astrocytes is not known. We investigated the molecular mechanisms underlying the production of MMP-9 by albumin in astrocytes.

METHODS

Primary enriched astrocyte cultures were used to investigate the effects of exposure to albumin on the release of MMP-9. MMP-9 expression was analyzed by zymography. The involvement of mitogen-activated protein kinase (MAPK), reactive oxygen species (ROS) and the TGF-β receptor-dependent pathways were investigated using pharmacological inhibitors. The production of ROS was observed by dichlorodihydrofluorescein diacetate fluorescence. The level of the MMP-9 inhibitor tissue inhibitor of metalloproteinase (TIMP)-1 produced by astrocytes was measured by ELISA.

RESULTS

We found that albumin induces a time-dependent release of MMP-9 via the activation of p38 MAPK and extracellular signal regulated kinase, but not Jun kinase. Albumin-induced MMP-9 production also involves ROS production upstream of the MAPK pathways. However, albumin-induced increase in MMP-9 is independent of the TGF-β receptor, previously described as a receptor for albumin. Albumin also induces an increase in TIMP-1 via an undetermined mechanism.

CONCLUSIONS

These results link albumin (acting through ROS and the p38 MAPK) to the activation of MMP-9 in astrocytes. Numerous studies identify a role for MMP-9 in the mechanisms of compromise of the BBB, epileptogenesis, or synaptic remodeling after ischemia or traumatic brain injury. The increase in MMP-9 produced by albumin further implicates both astrocytes and albumin in the acute and long-term complications of acute CNS insults, including cerebral edema and epilepsy.

Chemokines and their receptors in intracerebral hemorrhage

Intracerebral hemorrhage (ICH) is a devastating clinical event which results in a high rate of disability and death. At present, no effective treatment is available for ICH. Accumulating evidence suggests that inflammatory responses contribute significantly to the ICH-induced secondary brain outcomes. During ICH, inflammatory cells accumulate at the ICH site attracted by gradients of chemokines. This review summarizes recent progress in ICH studies and the chemoattractants that act during the injury and focuses on and introduces the basic biology of the chemokine monocyte chemoattractant protein-1 (MCP1) and its role in the progression of ICH. Better understanding of MCP1 signaling cascade and the compensation after its inhibition could shed light on the development of effective treatments for ICH.

Anticoagulants affect matrix metalloproteinase 9 levels in blood samples of stroke patients and healthy controls

OBJECTIVES

Matrix metalloproteinase-9 (MMP-9) represents a promising marker for acute stroke management. In clinical studies MMP-9 has been quantified by ELISA using differing protocols. We aimed to establish a valid protocol by evaluation of preanalytics.

DESIGN AND METHODS

Blood from stroke patients (n=28) and healthy controls (n=28) was drawn into tubes containing different anticoagulants (EDTA, citrate, lithium-heparin (heparin) and heparin with proteinase inhibitors) and processed after 0, 60 and 240 min. MMP-9 plasma protein and mRNA from mononuclear leukocytes were determined.

RESULTS

In regard to anticoagulants used, samples showed different MMP-9 protein baseline values and kinetics. Stable MMP-9 protein concentrations were only measured from EDTA samples. Particularly in samples with proteinase inhibitors protein and mRNA concentrations increased over time. Kinetics did not differ between patients and controls.

CONCLUSIONS

Preanalytics plays a key role for determination of MMP-9. EDTA seems to be a valid anticoagulant for MMP-9 protein measurement.

Beneficial effects of mood stabilizers lithium, valproate and lamotrigine in experimental stroke models

The mood stabilizers lithium, valproate and lamotrigine are traditionally used to treat bipolar disorder. However, accumulating evidence suggests that these drugs have broad neuroprotective properties and may therefore be promising therapeutic agents for the treatment of neurodegenerative diseases, including stroke. Lithium, valproate and lamotrigine exert protective effects in diverse experimental stroke models by acting on their respective primary targets, ie, glycogen synthase kinase-3, histone deacetylases and voltage-gated sodium channels, respectively. This article reviews the most recent findings regarding the underlying mechanisms of these phenomena, which will pave the way for clinical investigations that use mood stabilizers to treat stroke. We also propose several future research avenues that may extend our understanding of the benefits of lithium, valproate and lamotrigine in improving stroke outcomes.

Circulating CD133+CD34+ progenitor cells inversely correlate with soluble ICAM-1 in early ischemic stroke patients

Background and Purpose

Both endothelial progenitor cells (EPC) and markers of neuroinflammation are candidate biomarkers for stroke severity and outcome prediction. A relationship between EPC and neuroinflammatory markers in early stroke is not fully elucidated. The objectives were to investigate correlations between EPC and neuroinflammation markers (adhesion molecules ICAM-1, VCAM-1, E-selectin, tumor necrosis factor (TNF)-α, interleukin (IL)-6, endothelin (ET)-1, markers of tissue injury (matrix metalloproteinases (MMP)-9 and tissue inhibitor of matrix metalloproteinases (TIMP)-1) in early stroke patients.

Methods

We prospectively recruited symptomatic patients with ischemic cerebrovascular disease. We assessed stroke severity by using of acute (diffusion-weighted imaging (DWI) and final lesion volumes (fluid attenuated inversion recovery (FLAIR). We measured serum soluble ICAM-1, VCAM-1, E-selectin, MMP-9, TIMP-1 and plasma TNF-α, IL-6, ET-1 by ELISA, and quantified EPC in mononuclear fraction of peripheral blood on days 1 and 3 in 17 patients (mean(SD) age 62(14), with admission National Institutes of Health Stroke Scale (NIHSS) 10(8)) selected from 175 patients with imaging confirmed ischemic stroke. Non-parametric statistics, univariate and multivariate analysis were used.

Results

Only ICAM-1 inversely correlated with EPC subset CD133+CD34+ on day 1 (Spearman r = -0.6, p < 0.01) and on day 3 (r = -0.967, p < 0.001). This correlation remained significant after adjustment for age and NIHSS (beta -0.992, p < 0.004), for glucose and systolic blood pressure (beta -0.86, p < 0.005), and for white blood cells and hematocrit (beta -1.057, p < 0.0001) on day 3. MMP-9 (r = 0.509, p < 0.04) and MMP-9/TIMP-1 (r = 0.59, p < 0.013) on day 1 correlated with acute lesion volume. Both IL-6 (r = 0.624, p < 0.01) and MMP-9/TIMP-1 (r = 0.56, p < 0.02) correlated with admission NIHSS.

Conclusion

Our study showed that high ICAM-1 is associated with low CD133+CD34+subset of EPC. Biomarkers of neuroinflammation may predict tissue injury and stroke severity in early ischemia.

Blood biomarkers of ischemic stroke

This review provides a summary of the protein and RNA biomarkers that have been studied for the diagnosis and assessment of ischemic stroke. Many of the biomarkers identified relate to the pathophysiology of ischemic stroke, including ischemia of CNS tissue, acute thrombosis and inflammatory response. These biomarkers are summarized by their intended clinical application in ischemic stroke including diagnosis, prediction of stroke severity and outcome, and stratification of patients for stroke therapy. Among the biomarkers discussed are recent whole genome studies using RNA expression profiles to diagnose ischemic stroke and stroke etiology. Though many candidate blood based biomarkers for ischemic stroke have been identified, none are currently used in clinical practice. With further well designed study and careful validation, the development of blood biomarkers to improve the care of patients with ischemic stroke may be achieved.

Phosphatidylinositol-3-kinase gamma plays a central role in blood-brain barrier dysfunction in acute experimental stroke

BACKGROUND AND PURPOSE

Phosphoinositide 3-kinase (PI3K)-γ is linked to inflammation and oxidative stress. This study was conducted to investigate the role of the PI3Kγ in the blood-brain barrier dysfunction and brain damage induced by focal cerebral ischemia/reperfusion.

METHODS

Wild-type and PI3Kγ knockout mice were subjected to middle cerebral artery occlusion (60 minutes) followed by reperfusion. Evans blue leakage, brain edema, infarct volumes, and neurological deficits were examined. Oxidative stress, neutrophil infiltration, and matrix metallopeptidase-9 were assessed. Activation of nuclear factor-κB and expression of proinflammatory and pro-oxidative genes were studied.

RESULTS

PI3Kγ deficiency significantly reduced blood-brain barrier permeability and brain edema formation, which were time-dependently correlated with preventing the degradation of the tight junction protein, claudin-5, and the basal lamina protein, collagen IV, and the phosphorylation of myosin light chain in brain microvessels. PI3Kγ deficiency suppressed ischemia/reperfusion-induced nuclear factor-κB p65 (Ser536) phosphorylation and the expression of the pro-oxidant enzyme NADPH oxidase (Nox1, Nox2, and Nox4) and proinflammatory adhesion molecules (E- and P-selectin, intercellular adhesion molecule-1) at different time points. These molecular changes were associated with significant inhibition of oxidative stress (superoxide production and malondialdehyde content), neutrophil infiltration, and matrix metallopeptidase-9 expression/activity in PI3Kγ knockout mice. Eventually, PI3Kγ deficiency significantly reduced infarct volumes and neurological scores at 24 hours after ischemia/reperfusion.

CONCLUSIONS

Our results provide the first direct demonstration that PI3Kγ plays a significant role in ischemia/reperfusion-induced blood-brain barrier disruption and brain damage. Future studies need to explore PI3Kγ as a potential target for stroke therapy.

Translational Stroke Research of the Combination of Thrombolysis and Antioxidant Therapy

Stroke is an enormous public health problem with an imperative need for more effective therapy. Recombinant tissue plasminogen activator is the only licensed drug for acute stroke, but its efficacy may be limited by the toxicity of the compound and by reperfusion injury. The coadministration of neuroprotective drugs could augment the value of thrombolytic therapy, but the evidence in support of this approach is scarce. The use of the free radical trapping NXY-059, either with or without recombinant tissue plasminogen activator, was not successful in Phase III studies. However, these results could reflect its weak antioxidant capacity, poor blood–brain barrier penetration, and lack of synergism with recombinant tissue plasminogen activator as well as the overly broad treatment window used in the reported trials. This article contends that further translational research should explore newer antioxidant drugs in combination with thrombolytic agents, but only if the combination yields additive or synergistic effects in preclinical thromboembolic models or in biomarker-assisted Phase II studies. Edaravone and novel nitrones endowed with a better pharmacokinetic profile or multitarget and thrombolytic activity are discussed as well as the latest research data on uric acid, a strong endogenous antioxidant in blood that is early consumed after acute stroke. The coadministration of uric acid and recombinant tissue plasminogen activator has shown to provide synergistic neuroprotection in experimental thromboembolic models and to lessen several biomarkers of oxidative stress in patients with acute stroke. The clinical efficacy of uric acid is currently under investigation in a Phase III trial that follows current recommendations of also evaluating surrogate biomarkers of treatment effects.