Delayed matrix metalloproteinase inhibition reduces intracerebral hemorrhage after embolic stroke in rats

SGLT2 inhibitor dapagliflozin alleviates intramyocardial hemorrhage and adverse ventricular remodeling via suppressing hepcidin in myocardial ischemia-reperfusion injury

Intramyocardial hemorrhage (IMH), a reperfusion therapy-associated complication, is the extravasation of red blood cells caused by severe microvascular injury. IMH is an independent predictor of adverse ventricular remodeling (AVR) after acute myocardial infarction (AMI). Hepcidin, a major regulator of iron uptake and systemic distribution, is a key factor affecting AVR. However, the role of cardiac hepcidin in the development of IMH has not been completely elucidated. This study aimed to explore if sodium-dependent glucose co-transporter 2 inhibitor (SGLT2i) exerts therapeutic effects on IMH and AVR by suppressing hepcidin and to elucidate the underlying mechanisms. SGLT2i alleviated IMH and AVR in the ischemia-reperfusion injury (IRI) mouse model. Additionally, SGLT2i downregulated the cardiac levels of hepcidin in IRI mice, suppressed M1-type macrophage polarization, and promoted M2-type macrophage polarization. The effects of hepcidin knockdown on macrophage polarization were similar to those of SGLT2i in RAW264.7 cells. SGLT2i treatment or hepcidin knockdown inhibited the expression of MMP9, an inducer of IMH and AVR, in RAW264.7 cells. Regulation of macrophage polarization and reduction of MMP9 expression by SGLT2i and hepcidin knockdown is achieved through activation of pSTAT3. In conclusion, this study demonstrated that SGLT2i alleviated IMH and AVR by regulating macrophage polarization. The potential mechanism through which SGLT2i exerted its therapeutic effect seems to involve the downregulation of MMP9 via the hepcidin-STAT3 pathway.

Receptor-interacting protein 3-phosphorylated Ca2+ /calmodulin-dependent protein kinase II and mixed lineage kinase domain-like protein mediate intracerebral hemorrhage-induced neuronal necroptosis

Necroptosis-mediated cell death is an important mechanism in intracerebral hemorrhage (ICH)-induced secondary brain injury (SBI). Our previous study has demonstrated that receptor-interacting protein 1 (RIP1) mediated necroptosis in SBI after ICH. However, further mechanisms, such as the roles of receptor-interacting protein 3 (RIP3), mixed lineage kinase domain-like protein (MLKL), and Ca²⁺ /calmodulin-dependent protein kinase II (CaMK II), remain unclear. We hypothesized that RIP3, MLKL, and CaMK II might participate in necroptosis after ICH, including their phosphorylation. The ICH model was induced by autologous blood injection. First, we found the activation of necroptosis after ICH in brain tissues surrounding the hematoma (propidium iodide staining). Meanwhile, the phosphorylation and expression of RIP3, MLKL, and CaMK II were differently up-regulated (western blotting and immunofluorescent staining). The specific inhibitors could suppress RIP3, MLKL, and CaMK II (GSK'872 for RIP3, necrosulfonamide for MLKL, and KN-93 for CaMK II). We found the necroptosis surrounding the hematoma and the concrete interactions in RIP3-MLKL/RIP3-CaMK II also both decreased after the specific intervention (co-immunoprecipitation). Then we conducted the short-/long-term neurobehavioral tests, and the rats with specific inhibition mostly had better performance. We also found less blood-brain barrier (BBB) injury, and less neuron loss (Nissl staining) in intervention groups, which supported the neurobehavioral tests. Besides, oxidative stress and inflammation were also alleviated with intervention, which had significant less reactive oxygen species (ROS), tumor necrosis factor (TNF)-α, lactate dehydrogenase (LDH), Iba1, and GFAP surrounding the hematoma. These results confirmed that RIP3-phosphorylated MLKL and CaMK II participate in ICH-induced necroptosis and could provide potential targets for the treatment of ICH patients.

Remote ischemic conditioning attenuates blood-brain barrier disruption after recombinant tissue plasminogen activator treatment via reducing PDGF-CC

Treatment of acute ischemic stroke with the recombinant tissue plasminogen activator (rtPA) is associated with increased blood-brain barrier (BBB) disruption and hemorrhagic transformation. Remote ischemic conditioning (RIC) has demonstrated neuroprotective effects against acute ischemic stroke. However, whether and how RIC regulates rtPA-associated BBB disruption remains unclear. Here, a rodent model of thromboembolic stroke followed by rtPA thrombolysis at different time points was performed with or without RIC. Brain infarction, neurological outcomes, BBB permeability, and intracerebral hemorrhage were assessed. The platelet-derived growth factor CC (PDGF-CC)/PDGFRα pathway in the brain tissue, PDGF-CC levels in the skeletal muscle and peripheral blood were also measured. Furthermore, impact of RIC on serum PDGF-CC levels were measured in healthy subjects and AIS patients. Our results showed that RIC substantially reduced BBB injury, intracerebral hemorrhage, cerebral infarction, and neurological deficits after stroke, even when rtPA was administrated in a delayed therapeutic time window. Mechanistically, RIC significantly decreased PDGFRα activation in ischemic brain tissue and reduced blood PDGF-CC levels, which partially resulted from PDGF-CC reduction in the skeletal muscle of RIC-applied hindlimbs and platelets. Intravenous or intraventricular recombinant PDGF-CC supplementation abolished RIC protective effects on BBB integrity. Moreover, similar changes of PDGF-CC in serum by RIC were also observed in healthy humans and acute ischemic stroke patients. Together, our study demonstrates that RIC can attenuate rtPA-aggravated BBB disruption after ischemic stroke via reducing the PDGF-CC/PDGFRα pathway and thus supports RIC as a potential approach for BBB disruption prevention or treatment following thrombolysis.

Acute Inflammation in Cerebrovascular Disease: A Critical Reappraisal with Focus on Human Studies

Recent attention has been focused on the field of inflammatory biomarkers associated with vascular disorders, regarding diagnosis, prognosis, and possible therapeutical targets. In this study, we aimed to perform a comprehensive review of the literature regarding the use of inflammatory biomarkers in stroke patients. We searched studies that evaluated inflammation biomarkers associated with Cerebrovascular Disease (CVD), namely, ischemic Stroke (IS), Intracerebral Hemorrhage (ICH) and Cerebral Venous Thrombosis (CVT). As of today, neutrophil–lymphocyte ratio (NLR) seems the be the most widely studied and accepted biomarker for cerebrovascular disease due to its easy access and availability. Although demonstrated as a prognostic risk factor, in IS, ICH and CVT, its diagnostic role is still under investigation. Several other prognostic factors could be used or even combined together into a diagnostic or prognostic index. Multiple inflammatory biomarkers appear to be involved in IS, ICH, and CVT. Blood inflammatory cells, easily measured and accessible at admission may provide information regarding accurate diagnosis and prognosis. Although not yet a reality, increasing evidence exists to suggest that these may become potential therapeutic targets, likely influencing or mitigating complications of CVD and improving prognosis. Nevertheless, further larger, well-designed randomized clinical trials are still needed to follow up this hypothesis.

Matrix Metalloproteinase-9 Expression is Enhanced by Ischemia and Tissue Plasminogen Activator and Induces Hemorrhage, Disability and Mortality in Experimental Stroke

Matrix metalloproteinase-9 (MMP-9) degrades collagen and other cellular matrix proteins. After acute ischemic stroke, increased MMP-9 levels are correlated with hemorrhage, lack of reperfusion and stroke severity. Nevertheless, definitive data that MMP-9 itself causes poor outcomes in ischemic stroke are limited. In a model of experimental ischemic stroke with reperfusion, we examined whether ischemia and recombinant tissue plasminogen activator (r-tPA) therapy affected MMP-9 expression, and we used specific inhibitors to test if MMP-9 affects brain injury and recovery. After stroke, MMP-9 expression increased significantly in the ischemic vs. non-ischemic hemisphere of the brain (p < 0.001). MMP-9 expression in the ischemic, but not the non-ischemic hemisphere, was further increased by r-tPA treatment (p < 0.001). To determine whether MMP-9 expression contributed to stroke outcomes after r-tPA treatment, we tested three different antibody MMP-9 inhibitors. When compared to treatment with r-tPA and saline, treatment with r-tPA and MMP-9 antibody inhibitors significantly reduced brain hemorrhage by 11.3 to 38.6-fold (p < 0.01), brain swelling by 2.8 to 4.3-fold (p < 0.001) and brain infarction by 2.5 to 3.9-fold (p < 0.0001). Similarly, when compared to treatment with r-tPA and saline, treatment with r-tPA and an MMP-9 antibody inhibitor significantly improved neurobehavioral outcomes (p < 0.001), decreased weight loss (p < 0.001) and prolonged survival (p < 0.01). In summary, both prolonged ischemia and r-tPA selectively enhanced MMP-9 expression in the ischemic hemisphere. When administered with r-tPA, specific MMP-9 inhibitors markedly reduced brain hemorrhage, swelling, infarction, disability and death, which suggests that blocking the deleterious effects of MMP-9 may improve outcomes after ischemic stroke.

The Protective Role of Immunomodulators on Tissue-Type Plasminogen Activator-Induced Hemorrhagic Transformation in Experimental Stroke: A Systematic Review and Meta-Analysis

Background: Recanalization with tissue plasminogen activator (tPA) is the only approved agent available for acute ischemic stroke. But delayed treatment of tPA may lead to lethal intracerebral hemorrhagic transformation (HT). Numerous studies have reported that immunomodulators have good efficacy on tPA-induced HT in ischemic stroke models. The benefits of immunomodulators on tPA-associated HT are not clearly defined. Here, we sought to conduct a systematic review and meta-analysis of preclinical studies to further evaluate the efficacy of immunomodulators.

Methods: The PubMed, Web of Science, and Scopus electronic databases were searched for studies. Studies that reported the efficacy of immunomodulators on tPA-induced HT in animal models of stroke were included. Animals were divided into two groups: immunomodulators plus tPA (intervention group) or tPA alone (control group). The primary outcome was intracerebral hemorrhage, and the secondary outcomes included infarct volume and neurobehavioral score. Study quality was assessed by the checklist of CAMARADES. We used standardized mean difference (SMD) to assess the impact of interventions. Regression analysis and subgroup analysis were performed to identify potential sources of heterogeneity and evaluate the impact of the study characteristics. The evidence of publication bias was evaluated using trim and fill method and Egger’s test.

Results: We identified 22 studies that met our inclusion criteria involving 516 animals and 42 different comparisons. The median quality checklist score was seven of a possible 10 (interquartile range, 6–8). Immunomodulators improved cerebral hemorrhage (1.31 SMD, 1.09–1.52); infarct volume (1.35 SMD, 0.95–1.76), and neurobehavioral outcome (0.9 SMD, 0.67–1.13) in experimental stroke. Regression analysis and subgroup analysis indicated that control of temperature and time of assessment were important factors that influencing the efficacy of immunomodulators.

Conclusion: Our findings suggested that immunomodulators had a favorable effect on tPA-associated intracerebral hemorrhage, cerebral infarction, and neurobehavioral impairments in animal models of ischemic stroke.

Matrix metalloproteinases and ADAMs in stroke

Stroke is a leading cause of death and disability worldwide. However, after years of in-depth research, the pathophysiology of stroke is still not fully understood. Increasing evidence shows that matrix metalloproteinases (MMPs) and "a disintegrin and metalloproteinase" (ADAMs) participate in the neuro-inflammatory cascade that is triggered during stroke but also in recovery phases of the disease. This review covers the involvement of these proteins in brain injury following cerebral ischemia which has been widely studied in recent years, with efforts to modulate this group of proteins in neuroprotective therapies, together with their implication in neurorepair mechanisms. Moreover, the review also discusses the role of these proteins in specific forms of neurovascular disease, such as small vessel diseases and intracerebral hemorrhage. Finally, the potential use of MMPs and ADAMs as guiding biomarkers of brain injury and repair for decision-making in cases of stroke is also discussed.

Blood-Brain Barrier Protection as a Therapeutic Strategy for Acute Ischemic Stroke

The blood-brain barrier (BBB) is a vital component of the neurovascular unit (NVU) containing tight junctional (TJ) proteins and different ion and nutrient transporters which maintain normal brain physiology. BBB disruption is a major pathological hallmark in the course of ischemic stroke which is regulated by the actions of different factors working at different stages of cerebral ischemia including matrix metalloproteinases (MMPs), inflammatory modulators, vesicular trafficking, oxidative pathways, and junctional-cytoskeletal interactions. These components interact further to disrupt maintenance of both the paracellular and transport barriers of the central nervous system (CNS) to worsen ischemic brain injury and the propensity for hemorrhagic transformation (HT) associated with injury and/or thrombolytic therapy with tissue-type plasminogen activator (tPA). We propose that these complex molecular pathways should be evaluated further so that they could be targeted alone or in combination to protect the BBB during cerebral ischemia. These types of novel interventions should be guided by advanced imaging techniques for better diagnosis of BBB damage which may exert significant therapeutic benefit including the extension of therapeutic window of tPA. This review will focus on the different stages and mechanisms of BBB damage in acute ischemic stroke and novel therapeutic strategies to target those pathways for better therapeutic outcome in stroke.

tPA Modulation of the Blood-Brain Barrier: A Unifying Explanation for the Pleiotropic Effects of tPA in the CNS

The plasminogen activation (PA) system is best known for its role in fibrinolysis. However, it has also been shown to regulate many nonfibrinolytic functions in the central nervous system (CNS). In particular, tissue-type plasminogen activator (tPA) is reported to have pleiotropic activities in the CNS, regulating events such as neuronal plasticity, excitotoxicity, and cerebrovascular barrier integrity, whereas urokinase-type plasminogen activator is mainly associated with tissue remodeling and cell migration. It has been suggested that the role tPA plays in controlling barrier integrity may provide a unifying mechanism for the reported diverse, and often opposing, functions ascribed to tPA in the CNS. Here we will review the possibility that the pleiotropic effects reported for tPA in physiologic and pathologic processes in the CNS may be a consequence of its role in the neurovascular unit in regulation of cerebrovascular responses and subsequently parenchymal homeostasis. We propose that this might offer an explanation for the ongoing debate regarding the neurotoxic versus neuroprotective roles of tPA.

Increased Plasma Matrix Metalloproteinase-9 Levels Contribute to Intracerebral Hemorrhage during Thrombolysis after Concomitant Stroke and Influenza Infection

BACKGROUND

Thrombolysis is the only approved therapy for acute stroke. However, life-threatening complications such as intracerebral hemorrhage (ICH) can develop after intravenous administration of tissue plasminogen activator (tPA). Both infection and thrombolysis during cerebral ischemia disrupt the blood-brain barrier (BBB). tPA can induce matrix metalloproteinase-9 (MMP-9), which is known to be involved in BBB disruption. However, it has still not been investigated whether preexisting influenza virus infection during thrombolysis after acute stroke affects systemic levels of MMP-9 and its inhibitor TIMP-1 and whether increased systemic MMP-9 levels affect ICH. This study aimed to investigate the influence of influenza virus infection on plasma levels of MMP-9 and TIMP-1 after thrombolysis in acute stroke, and to determine whether the infection correlates with intracerebral bleeding.

METHODS

C57BL/6 mice were infected by administering 1 × 105 plaque-forming units of human influenza (H1N1) virus intranasally. After 3 days of infection the middle cerebral artery was occluded for 45 min and then reperfused. Intravenous tPA (10 mg/kg) treatment was started 10 min after stroke onset. Twenty-four hours after stroke onset, mice were deeply anesthetized with ketamine, venous blood was drawn from the caval vein and centrifuged at 2,000 rpm, and the supernatant was collected and frozen at -80°C. Plasma levels of MMP-9 and TIMP-1 were quantified by using ELISA.

RESULTS

After stroke, plasma MMP-9 was significantly increased in mice with a concomitant influenza infection that were treated with tPA (9.99 ± 0.62 ng/ml, n = 7) as compared to noninfected control mice that were treated with tPA (4.74 ± 0.48 ng/ml, n = 8). Moreover, plasma levels of TIMP-1, an inhibitor of MMP-9, were also significantly increased in mice treated with tPA after concomitant infection and stroke (42.17 ± 7.02 ng/ml, n = 7) as compared to noninfected control mice that were treated with tPA after stroke (20.22 ± 2.12 ng/ml, n = 8). MMP-9 values significantly correlated with intracerebral hemoglobin levels in animals treated with tPA after stroke (p = 0.028, r = 0.76, n = 8) and after concomitant stroke and infection (p = 0.039, r = 0.78, n = 7).

CONCLUSION

Preexisting influenza A virus infection led to increased plasma MMP-9 and TIMP-1 levels in mice undergoing thrombolysis after induced stroke. MMP-9 levels closely correlated with intracerebral bleeding after thrombolysis during concomitant infection and stroke. Thus, our data indicate that thrombolysis may be dangerous during influenza infection. MMP-9 inhibitors might be considered to reduce the side effects of thrombolysis during concomitant infection and stroke.

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.

Recommendations for preclinical research in hemorrhagic transformation

Hemorrhagic transformation (HT) is an important complication of ischemic stroke and is responsible for most of the mortality associated with acute reperfusion therapy. Although many important publications address the preclinical models of ischemic stroke, there are no current recommendations on the conduct of research aimed at understanding the mechanisms and consequences of HT. The purpose of this review is to present the various models used in HT research, the clinical correlates, and the experimental variables known to influence the quantitation of HT in preclinical investigation. Lastly, recommendations for the conduct of preclinical research in HT are provided.

Recombinant tissue plasminogen activator enhances microglial cell recruitment after stroke in mice

The effect of recombinant human tissue plasminogen activator (rtPA) on neuroinflammation after stroke remains largely unknown. Here, we tested the effect of rtPA on expression of cellular adhesion molecules, chemokines, and cytokines, and compared those with levels of inflammatory cell recruitment, brain injury, and mortality over 3 days after transient middle cerebral artery occlusion (MCAO) in mice. Mortality was dramatically increased after rtPA treatment compared with saline treatment during the first day of reperfusion. Among the animals that survived, rtPA significantly increased CCL3 expression, microglia recruitment, and cerebral infarction 6 hours after MCAO. In contrast, the extent of neutrophils and macrophages infiltration in the brain was similar in both saline- and rtPA-treated animals. Recombinant human tissue plasminogen activator induced Il1b and Tnf expression, 6 and 72 hours after MCAO, respectively, and dramatically reduced interleukin 6 (IL-6) level 24 hours after reperfusion. A dose response study confirmed the effect of rtPA on CCL3 and Il1b expressions. The effect was similar at the doses of 1 and 10 mg/kg. In conclusion, we report for the first time that rtPA amplified microglia recruitment early after stroke in association with a rapid CCL3 production. This early response may take part in the higher susceptibility of rtPA-treated animals to reperfusion injury.

Analysis of the expression of nine secreted matrix metalloproteinases and their endogenous inhibitors in the brain of mice subjected to ischaemic stroke

Matrix metalloproteinases (MMPs) are a family of more than twenty secreted and cell-surface endopeptidases. Among them, MMP2, MMP3 and MMP9 are involved in blood-brain barrier injury and neuronal death after cerebral ischaemia. On the other hand, very little is known about the expression of the other secreted MMPs. Herein, we compared the global changes in MMP1, MMP2, MMP3, MMP7, MMP8, MMP9, MMP10, MMP12 and MMP13, and their endogenous inhibitors TIMP1 and TIMP2, both at the mRNA and protein levels, during the hyperacute (6 h), acute (24 h) and subacute (72 h) stages following transient focal cerebral ischaemia and treatment with recombinant tissue plasminogen activator (rtPA). We observed a significant increase in MMP1, MMP2, MMP9, MMP10, MMP13 and TIMP1 levels during the acute stage of reperfusion, which was further amplified during the subacute stage for MMP1, MMP2, MMP10 and TIMP1. In general, no change of MMP3, MMP7, MMP8, MMP12 and TIMP2 was observed. However, rtPA treatment induced a rapid increase in MMP1/TIMP2, MMP2/TIMP2, MMP8/TIMP2 and MMP9/TIMP2 ratios during the hyperacute stage of reperfusion compared to saline treatment, which may have potential implications in the early disruption of the blood-brain barrier after rtPA treatment.

Hemostasis and alterations of the central nervous system

Modulation of coagulation has been successfully applied to ischemic disorders of the central nervous system (CNS). Some components of the coagulation system have been identified in the CNS, yet with limited exception their functions have not been clearly defined. Little is known about how events within the cerebral tissues affect hemostasis. Nonetheless, the interaction between cerebral cells and vascular hemostasis and the possibility that endogenous coagulation factors can participate in functions within the neurovascular unit provide intriguing possibilities for deeper insight into CNS functions and the potential for treatment of CNS injuries. Here, we consider the expression of coagulation factors in the CNS, the coagulopathy associated with focal cerebral ischemia (and its relationship to hemorrhagic transformation), the use of recombinant tissue plasminogen activator (rt-PA) in ischemic stroke and its study in animal models, the impact of rt-PA on neuron and CNS structure and function, and matrix protease generation and matrix degradation and hemostasis. Interwoven among these topics is evidence for interactions of coagulation factors with and within the CNS. How activation of hemostasis occurs in the cerebral tissues and how the brain responds are difficult questions that offer many research possibilities.

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.

Treatment with Evasin-3 reduces atherosclerotic vulnerability for ischemic stroke, but not brain injury in mice

Neutrophilic inflammation might have a pathophysiological role in both carotid plaque rupture and ischemic stroke injury. Here, we investigated the potential benefits of the CXC chemokine-binding protein Evasin-3, which potently inhibits chemokine bioactivity and related neutrophilic inflammation in two mouse models of carotid atherosclerosis and ischemic stroke, respectively. In the first model, the chronic treatment with Evasin-3 as compared with Vehicle (phosphate-buffered saline (PBS)) was investigated in apolipoprotein E-deficient mice implanted of a 'cast' carotid device. In the second model, acute Evasin-3 treatment (5 minutes after cerebral ischemia onset) was assessed in mice subjected to transient left middle cerebral artery occlusion. Although CXCL1 and CXCL2 were upregulated in both atherosclerotic plaques and infarcted brain, only CXCL1 was detectable in serum. In carotid atherosclerosis, treatment with Evasin-3 was associated with reduction in intraplaque neutrophil and matrix metalloproteinase-9 content and weak increase in collagen as compared with Vehicle. In ischemic stroke, treatment with Evasin-3 was associated with reduction in ischemic brain neutrophil infiltration and protective oxidants. No other effects in clinical and histological outcomes were observed. We concluded that Evasin-3 treatment was associated with reduction in neutrophilic inflammation in both mouse models. However, Evasin-3 administration after cerebral ischemia onset failed to improve poststroke outcomes.

High-density lipoprotein-based therapy reduces the hemorrhagic complications associated with tissue plasminogen activator treatment in experimental stroke

BACKGROUND AND PURPOSE

We have previously reported that intravenous injection of high-density lipoproteins (HDLs) was neuroprotective in an embolic stroke model. We hypothesized that HDL vasculoprotective actions on the blood-brain barrier (BBB) may decrease hemorrhagic transformation-associated with tissue plasminogen activator (tPA) administration in acute stroke.

METHODS

We used tPA alone or in combination with HDLs in vivo in 2 models of focal middle cerebral artery occlusion (MCAO) (embolic and 4-hour monofilament MCAO) and in vitro in a model of BBB. Sprague-Dawley rats were submitted to MCAO, n=12 per group. The rats were then randomly injected with tPA (10 mg/kg) or saline with or without human plasma purified-HDL (10 mg/kg). The therapeutic effects of HDL and BBB integrity were assessed blindly 24 hours later. The integrity of the BBB was also tested using an in vitro model of human cerebral endothelial cells under oxygen-glucose deprivation.

RESULTS

tPA-treated groups had significantly higher mortality and rate of hemorrhagic transformation at 24 hours in both MCAO models. Cotreatment with HDL significantly reduced stroke-induced mortality versus tPA alone (by 42% in filament MCAO, P=0.009; by 73% in embolic MCAO, P=0.05) and tPA-induced intracerebral parenchymal hematoma (by 92% in filament MCAO, by 100% in embolic MCAO; P<0.0001). This was consistent with an improved BBB integrity. In vitro, HDLs decreased oxygen-glucose deprivation-induced BBB permeability (P<0.05) and vascular endothelial cadherin disorganization.

CONCLUSIONS

HDL injection decreased tPA-induced hemorrhagic transformation in rat models of MCAO. Both in vivo and in vitro results support the vasculoprotective action of HDLs on BBB under ischemic conditions.

Vascular protection to increase the safety of tissue plasminogen activator for stroke

Thrombolytic therapy with tissue plasminogen activator (tPA) remains the most effective treatment for acute ischemic stroke, but can cause vascular damage leading to edema formation and hemorrhagic transformation (HT). In this review, we discuss how tPA contributes to the pathogenesis of vascular damage and highlight evidence to support combination therapy of tPA with pharmacological agents that are vascular protective. There is an unmet need to develop therapeutic interventions which target the underlying mechanisms of vascular damage after acute ischemic stroke in order to prevent HT and improve the safety and impact of tPA.

Matrix metalloproteinase 9 and cellular fibronectin plasma concentrations are predictors of the composite endpoint of length of stay and death in the intensive care unit after severe traumatic brain injury

BACKGROUND

The relationship between severe traumatic brain injury (TBI) and blood levels of matrix metalloproteinase-9 (MMP-9) or cellular fibronectin (c-Fn) has never been reported. In this study, we aimed to assess whether plasma concentrations of MMP-9 and c-Fn could have predictive values for the composite endpoint of intensive care unit (ICU) length of stay (LOS) of survivors and mortality after severe TBI. Secondary outcomes were the state of consciousness measured with the Glasgow Coma Scale (GCS) of survivors at 14 days and Glasgow Outcome Scale Extended (GOSE) at 3 months.

METHODS

Forty-nine patients with abbreviated injury scores of the head region ≥ 4 were included. Blood was sampled at 6, 12, 24 and 48 hours after injury. MMP-9 and c-Fn concentrations were measured by ELISA. The values of MMP-9 and c-Fn, and, for comparison, the value of the GCS on the field of the accident (fGCS), as predictors of the composite outcome of ICU LOS and death were assessed by logistic regression.

RESULTS

There was a linear relationship between maximal MMP-9 concentration, measured during the 6-12-hour period, and maximal c-Fn concentration, measured during the 24-48-hour period. The risk of staying longer than 9 days in the ICU or of dying was increased in patients with a maximal early MMP-9 concentration ≥ 21.6 ng/ml (OR = 5.0; 95% CI: 1.3 to 18.6; p = 0.02) or with a maximal late c-Fn concentration ≥ 7.7 μg/ml (OR = 5.4; 95% CI: 1.4 to 20.8; p = 0.01). A similar risk association was observed with fGCS ≤8 (OR, 4.4; 95% CI, 1.2-15.8; p = 0.02). No relationship was observed between MMP-9, c-Fn concentrations or fGCS and the GCS at 14 days of survivors and GOSE at 3 months.

CONCLUSIONS

Plasma MMP-9 and c-Fn concentrations in the first 48 hours after injury are predictive for the composite endpoint of ICU LOS and death after severe TBI but not for consciousness at 14 days and outcome at 3 months.

Does inhibiting Sur1 complement rt-PA in cerebral ischemia?

Hemorrhagic transformation (HT) associated with recombinant tissue plasminogen activator (rt-PA) complicates and limits its use in stroke. Here, we provide a focused review on the involvement of matrix metalloproteinase 9 (MMP-9) in rt-PA-associated HT in cerebral ischemia, and we review emerging evidence that the selective inhibitor of the sulfonylurea receptor 1 (Sur1), glibenclamide (U.S. adopted name, glyburide), may provide protection against rt-PA-associated HT in cerebral ischemia. Glyburide inhibits activation of MMP-9, ameliorates edema formation, swelling, and symptomatic hemorrhagic transformation, and improves preclinical outcomes in several clinically relevant models of stroke, both without and with rt-PA treatment. A retrospective clinical study comparing outcomes in diabetic patients with stroke treated with rt-PA showed that those who were previously on and were maintained on a sulfonylurea fared significantly better than those whose diabetes was managed without sulfonylureas. Inhibition of Sur1 with injectable glyburide holds promise for ameliorating rt-PA-associated HT in stroke.

Matrix metalloproteinase-10 effectively reduces infarct size in experimental stroke by enhancing fibrinolysis via a thrombin-activatable fibrinolysis inhibitor-mediated mechanism

BACKGROUND

The fibrinolytic and matrix metalloproteinase (MMP) systems cooperate in thrombus dissolution and extracellular matrix proteolysis. The plasminogen/plasmin system activates MMPs, and some MMPs have been involved in the dissolution of fibrin by targeting fibrin(ogen) directly or by collaborating with plasmin. MMP-10 has been implicated in inflammatory/thrombotic processes and vascular integrity, but whether MMP-10 could have a profibrinolytic effect and represent a promising thrombolytic agent is unknown.

METHODS AND RESULTS

The effect of MMP-10 on fibrinolysis was studied in vitro and in vivo, in MMP-10-null mice (Mmp10(-/-)), with the use of 2 different murine models of arterial thrombosis: laser-induced carotid injury and ischemic stroke. In vitro, we showed that MMP-10 was capable of enhancing tissue plasminogen activator-induced fibrinolysis via a thrombin-activatable fibrinolysis inhibitor inactivation-mediated mechanism. In vivo, delayed fibrinolysis observed after photochemical carotid injury in Mmp10(-/-) mice was reversed by active recombinant human MMP-10. In a thrombin-induced stroke model, the reperfusion and the infarct size in sham or tissue plasminogen activator-treated animals were severely impaired in Mmp10(-/-) mice. In this model, administration of active MMP-10 to wild-type animals significantly reduced blood reperfusion time and infarct size to the same extent as tissue plasminogen activator and was associated with shorter bleeding time and no intracranial hemorrhage. This effect was not observed in thrombin-activatable fibrinolysis inhibitor-deficient mice, suggesting thrombin-activatable fibrinolysis inhibitor inactivation as one of the mechanisms involved in the MMP-10 profibrinolytic effect.

CONCLUSIONS

A novel profibrinolytic role for MMP-10 in experimental ischemic stroke is described, opening new pathways for innovative fibrinolytic strategies in arterial thrombosis.

Solulin reduces infarct volume and regulates gene-expression in transient middle cerebral artery occlusion in rats

Background

Thrombolysis after acute ischemic stroke has only proven to be beneficial in a subset of patients. The soluble recombinant analogue of human thrombomodulin, Solulin, was studied in an in vivo rat model of acute ischemic stroke.

Methods

Male SD rats were subjected to 2 hrs of transient middle cerebral artery occlusion (tMCAO). Rats treated with Solulin intravenously shortly before reperfusion were compared to rats receiving normal saline i.v. with respect to infarct volumes, neurological deficits and mortality. Gene expression of IL-6, IL-1β, TNF-α, MMP-9, CD11B and GFAP were semiquantitatively analyzed by rtPCR of the penumbra.

Results

24 hrs after reperfusion, rats were neurologically tested, euthanized and infarct volumes determined. Solulin significantly reduced mean total (p = 0.001), cortical (p = 0.002), and basal ganglia (p = 0.036) infarct volumes. Hippocampal infarct volumes (p = 0.191) were not significantly affected. Solulin significantly downregulated the expression of IL-1β (79%; p < 0.001), TNF-α (59%; p = 0.001), IL-6 (47%; p = 0.04), and CD11B (49%; p = 0.001) in the infarcted cortex compared to controls.

Conclusions

Solulin reduced mean total, cortical and basal ganglia infarct volumes and regulated a subset of cytokines and proteases after tMCAO suggesting the potency of this compound for therapeutic interventions.

Matrix metalloproteinases as drug targets in ischemia/reperfusion injury

Deficient blood supply (ischemia) is a common consequence of some surgical procedures and certain pathologies. Once blood circulation is re-established (reperfusion), a complex series of events results in recruitment of inflammatory cells, rearrangement of the extracellular matrix and induction of cell death, which lead to organ dysfunction. Although ischemia/reperfusion (I/R) injury is an important cause of death, there is no effective therapy targeting the molecular mechanism of disease progression. Matrix metalloproteinases (MMPs), which are important regulators of many cellular activities, have a central role in disease progression after I/R injury, as suggested by numerous studies using MMP inhibitors or MMP-deficient mice. Here, we review the involvement of MMP activity in the various processes following I/R injury and the therapeutic potential of MMP inhibition.

Activation of sulfonate ester based matrix metalloproteinase proinhibitors by hydrogen peroxide

This study details the development of matrix metalloproteinase inhibitor prodrugs (proMMPi) that are activated in the presence of reactive-oxygen species (ROS). Conventional matrix metalloproteinase inhibitors (MMPi) utilize a zinc-binding group (ZBG) that chelates to the catalytic zinc(II) ion of matrix metalloproteinases (MMPs) to inhibit their activity. To create ROS-sensitive prodrugs, sulfonate esters were used as a protecting group for the ZBG to block their metal binding ability. Surprisingly, these sulfonate esters were found to be cleaved by H(2)O(2) only when the ZBG contained an N-oxide donor atom moiety. Sulfonate ester derivatives of full-length MMPi based on these ROS-triggerable systems were synthesized. It was found that proMMPi with sulfonate ester protecting groups showed relatively high rates of cleavage in the presence of H(2)O(2) to release the active MMPi. In vitro MMP inhibition studies confirmed a significant increase in inhibitory activity of proMMPi upon addition of H(2)O(2), demonstrating the use of sulfonate esters to act as cleavable triggers for ROS-activated prodrugs.

Mmp-9, a potential target for cerebral ischemic treatment

Matrix metalloproteinase-9 (MMP-9) which is a member of matrix metalloproteinases family that normally remodel the extracellular matrix, has been shown to play an important role in both animal models of cerebral ischemia and human stroke. The expression of MMP-9 is elevated after cerebral ischemia which is involved in accelerating matrix degradation, disrupting the blood-brain barrier, increasing the infarct size and relating to hemorrhagic transformation. Recently, many drugs, such as tetracycline derivatives, cyclooxygenase inhibitors, ACEI inhibitors and AT1 receptor blockers, etc., have been found to attenuate the elevated expression levels of MMP-9 after ischemia and to reduce the damage of cerebral ischemic. This article reviews the physiological features of MMP-9 and its important role in the genesis, propagation, and therapeutics of cerebral ischemic diseases.

Tissue plasminogen activator-mediated PDGF signaling and neurovascular coupling in stroke

The use of tissue plasminogen activator (tPA) as a thrombolytic treatment in ischemic stroke is limited largely due to concerns for hemorrhagic complications. The underlying mechanisms are still unknown, but evidence is beginning to emerge that tPA interacts with key regulators of the neurovascular unit (NVU), and that these interactions may contribute to the undesirable side effects associated with the use of tPA in ischemic stroke. Understanding these connections and tPA's normal function within the NVU may offer new insights into future therapeutic approaches.