Lipoprotein receptor-mediated induction of matrix metalloproteinase by tissue plasminogen activator

Acute Ischemic Stroke in the Clinic and the Laboratory: Targets for Translational Research

Ischemic stroke research has enabled significant advancements in diagnosis, treatment, and management of this debilitating disease, yet challenges remain standing in the way of better patient prognoses. In this narrative review, a fictional case illustrates challenges and uncertainties that medical professionals still face - penumbra identification, lack of neuroprotective agents, side-effects of tissue plasminogen activator, dearth of molecular biomarkers, incomplete microvascular reperfusion or no-reflow, post-recanalization hyperperfusion, blood pressure management and procedural anesthetic effects. The current state of the field is broadly reviewed per topic, with the aim to introduce a broad audience (scientist and clinician alike) to recent successes in translational stroke research and pending scientific queries that are tractable for preclinical assessment. Opportunities for co-operation between clinical and experimental stroke experts are highlighted to increase the size and frequency of strides the field makes to improve our understanding of this disease and ways of treating it.

Effect of intravenous thrombolysis before endovascular therapy on outcomes in acute ischemic stroke with large core: a systematic review and meta-analysis

OBJECTIVE

To investigate the effect of intravenous thrombolysis (IVT) before endovascular therapy (EVT) on outcomes in acute ischemic stroke of large core.

METHODS

The studies comparing functional outcomes after EVT with and without IVT were systematically searched up to October 10th, 2023. Odds ratio (OR) was pooled using random effects model. Subgroup analysis was performed stratified by study design, country or region, study date, imaging methods and time window.

RESULTS

Thirteen studies were included, enrolling 1717 patients. The pooled rate of functional independence in patients receiving IVT + EVT was 26% (95% CI 20% - 33%), significantly higher than 18% (95% CI 15% - 20%) in those receiving EVT alone (OR 1.55, 95% CI 1.13-2.12, P = 0.006; I²= 23.9%). In subgroup analysis, prior IVT increased the probability of functional independence in retrospective studies (OR 1.97, 95% 1.47-2.63, P < 0.00001; I2 = 0). Non-Asian patients benefit from IVT before EVT for functional independence (OR 2.04, 95% 1.48-2.81, P < 0.0001; I2 = 0), but Asian patients did not (OR 1.45, 95% 0.90-2.35, p = 0.13; I2 = 0). The pooled rate of symptomatic intracranial hemorrhage in patients receiving IVT + EVT was 16% (95% CI 12% - 20%), inclining to be higher than 11% (95% CI 6% - 15%) in those receiving EVT alone without significant difference (OR 1.42, 0.83-2.41, P = 0.20; I²= 12%).

CONCLUSIONS

IVT before EVT might increase the probability of functional independence in non-Asian patients with large ischemic core. The results provided clinicians with additional information on selecting eligible patients for EVT.

A promising frontier: targeting NETs for stroke treatment breakthroughs

Stroke is a prevalent global acute cerebrovascular condition, with ischaemic stroke being the most frequently occurring type. After a stroke, neutrophils accumulate in the brain and subsequently generate and release neutrophil extracellular traps (NETs). The accumulation of NETs exacerbates the impairment of the blood‒brain barrier (BBB), hampers neovascularization, induces notable neurological deficits, worsens the prognosis of stroke patients, and can facilitate the occurrence of t-PA-induced cerebral haemorrhage subsequent to ischaemic stroke. Alternative approaches to pharmacological thrombolysis or endovascular thrombectomy are being explored, and targeting NETs is a promising treatment that warrants further investigation.

LOX-1 and MMP-9 Inhibition Attenuates the Detrimental Effects of Delayed rt-PA Therapy and Improves Outcomes After Acute Ischemic Stroke

BACKGROUND

Acute ischemic stroke triggers endothelial activation that disrupts vascular integrity and increases hemorrhagic transformation leading to worsened stroke outcomes. rt-PA (recombinant tissue-type plasminogen activator) is an effective treatment; however, its use is limited due to a restricted time window and hemorrhagic transformation risk, which in part may involve activation of MMPs (matrix metalloproteinases) mediated through LOX-1 (lectin-like oxLDL [oxidized low-density lipoprotein] receptor 1). This study's overall aim was to evaluate the therapeutic potential of novel MMP-9 (matrix metalloproteinase 9) ± LOX-1 inhibitors in combination with rt-PA to improve stroke outcomes.

METHODS

A rat thromboembolic stroke model was utilized to investigate the impact of rt-PA delivered 4 hours poststroke onset as well as selective MMP-9 (JNJ0966) ±LOX-1 (BI-0115) inhibitors given before rt-PA administration. Infarct size, perfusion, and hemorrhagic transformation were evaluated by 9.4-T magnetic resonance imaging, vascular and parenchymal MMP-9 activity via zymography, and neurological function was assessed using sensorimotor function testing. Human brain microvascular endothelial cells were exposed to hypoxia plus glucose deprivation/reperfusion (hypoxia plus glucose deprivation 3 hours/R 24 hours) and treated with ±tPA and ±MMP-9 ±LOX-1 inhibitors. Barrier function was assessed via transendothelial electrical resistance, MMP-9 activity was determined with zymography, and LOX-1 and barrier gene expression/levels were measured using qRT-PCR (quantitative reverse transcription PCR) and Western blot.

RESULTS

Stroke and subsequent rt-PA treatment increased edema, hemorrhage, MMP-9 activity, LOX-1 expression, and worsened neurological outcomes. LOX-1 inhibition improved neurological function, reduced edema, and improved endothelial barrier integrity. Elevated MMP-9 activity correlated with increased edema, infarct volume, and decreased neurological function. MMP-9 inhibition reduced MMP-9 activity and LOX-1 expression. In human brain microvascular endothelial cells, LOX-1/MMP-9 inhibition differentially attenuated MMP-9 levels, inflammation, and activation following hypoxia plus glucose deprivation/R.

CONCLUSIONS

Our findings indicate that LOX-1 inhibition and ± MMP-9 inhibition attenuate negative aspects of ischemic stroke with rt-PA therapy, thus resulting in improved neurological function. While no synergistic effect was observed with simultaneous LOX-1 and MMP-9 inhibition, a distinct interaction is evident.

Progress in the Treatment of Central Nervous System Diseases Based on Nanosized Traditional Chinese Medicine

Traditional Chinese Medicine (TCM) is widely used in clinical practice to treat diseases related to central nervous system (CNS) damage. However, the blood-brain barrier (BBB) constitutes a significant impediment to the effective delivery of TCM, thus substantially diminishing its efficacy. Advances in nanotechnology and its applications in TCM (also known as nano-TCM) can deliver active ingredients or components of TCM across the BBB to the targeted brain region. This review provides an overview of the physiological and pathological mechanisms of the BBB and systematically classifies the common TCM used to treat CNS diseases and types of nanocarriers that effectively deliver TCM to the brain. Additionally, drug delivery strategies for nano-TCMs that utilize in vivo physiological properties or in vitro devices to bypass or cross the BBB are discussed. This review further focuses on the application of nano-TCMs in the treatment of various CNS diseases. Finally, this article anticipates a design strategy for nano-TCMs with higher delivery efficiency and probes their application potential in treating a wider range of CNS diseases.

The paradox of tPA in ischemic stroke: tPA knockdown following recanalization improves functional and histological outcomes

Previous studies have demonstrated that endogenous tissue-type plasminogen activator (tPA) is upregulated in the brain after an acute ischemic stroke (AIS). While mixed results were observed in genetic models, the pharmacological inhibition of endogenous tPA showed beneficial effects. Treatment with exogenous recombinant tPA exacerbated brain damage in rodent models of stroke. Despite the detrimental effects of tPA in ischemic stroke, recombinant tPA is administered to AIS patients to recanalize the occluded blood vessels because the benefits of its administration outweigh the risks associated with tPA upregulation and increased activity. We hypothesized that tPA knockdown following recanalization would ameliorate sensorimotor deficits and reduce brain injury. Young male and female rats (2-3 months old) were subjected to transient focal cerebral ischemia by occlusion of the right middle cerebral artery. Shortly after reperfusion, rats from appropriate cohorts were administered a nanoparticle formulation containing tPA shRNA or control shRNA plasmids (1 mg/kg) intravenously via the tail vein. Infarct volume during acute and chronic phases, expression of matrix metalloproteinases (MMPs) 1, 3, and 9, enlargement of cerebral ventricle volume, and white matter damage were all reduced by shRNA-mediated gene silencing of tPA following reperfusion. Additionally, recovery of somatosensory and motor functions was improved. In conclusion, our results provide evidence that reducing endogenous tPA following recanalization improves functional outcomes and reduces post-stroke brain damage.

Effects of the New Thrombolytic Compound LT3001 on Acute Brain Tissue Damage After Focal Embolic Stroke in Rats

LT3001 is a novel synthetic small molecule with thrombolytic and free radical scavenging activities. In this study, we tested the effects of LT3001 as a potential alternative thrombolytic in focal embolic ischemic stroke rat model. Stroked rats received intravenous injection of 10 mg/kg LT3001 or tPA at 1.5, 3, or 4.5 h after stroke, respectively, and the outcomes were measured at different time points after stroke by performing multi-parametric MRI, 2,3,5-triphenyltetrazolium chloride (TTC) staining, and modified neurological severity score. Lastly, we assessed the effect of LT3001 on the tPA activity in vitro, the international normalized ratio (INR), and the serum levels of active tPA and plasminogen activator inhibitor-1 (PAI-1). LT3001 treated at 1.5 h after stroke is neuroprotective by reducing the CBF lesion size and lowering diffusion and T2 lesion size measured by MRI, which is consistent with the reduction in TTC-stained infarction. When treated at 3 h after stroke, LT3001 had significantly better therapeutic effects regarding reduction of infarct size, swelling rate, and hemorrhagic transformation compared to tPA. When treated at 4.5 h after stroke, tPA, but not LT3001, significantly increased brain swelling and intracerebral hemorrhagic transformation. Lastly, LT3001 did not interfere with tPA activity in vitro, or significantly alter the INR and serum levels of active tPA and PAI-1 in vivo. Our data suggests that LT3001 is neuroprotective in focal embolic stroke rat model. It might have thrombolytic property, not interfere with tPA/PAI-1 activity, and cause less risk of hemorrhagic transformation compared to the conventional tPA. Taken together, LT3001 might be developed as a novel therapy for treating thrombotic ischemic stroke.

Intravenous alteplase before endovascular therapy for acute large vessel occlusion with large ischemic core: subanalysis of a randomized clinical trial

BACKGROUND

The efficacy of endovascular therapy (EVT) in patients with large ischemic core has been reported, but it remains unclear whether IV alteplase (IVT) has beneficial effects in addition to EVT in such patients. We evaluated the efficacy and safety of EVT with or without IVT.

METHODS

The RESCUE-Japan LIMIT was an open-label, prospective, multicenter, randomized clinical trial to evaluate the efficacy and safety of EVT in stroke patients with large ischemic core, defined as Alberta Stroke Program Early CT Score (ASPECTS) 3-5. This subanalysis evaluated the differences in the effects of EVT with medical care (EVT group) compared with medical care alone (No-EVT group) between those who received IVT (IVT stratum) and those who did not (No-IVT stratum) before EVT.

RESULTS

Among 202 enrolled patients, 147 (73%) did not receive IVT. In the No-IVT stratum, the modified Rankin Scale (mRS) score of 0-3 at 90 days was significantly higher in the EVT group than in the No-EVT group (31.1% vs 12.3%, OR 3.21 (95% CI 1.37 to 7.53)). In the IVT stratum, the mRS score of 0-3 was 30.8% in the EVT group and 13.8% in the No-EVT group (OR 2.78 (95% CI 0.72 to 10.7)) (interaction p=0.77). The incidence of symptomatic intracranial hemorrhage was not different between the two groups in the No-IVT stratum (OR 1.20 (95% CI 0.35 to 4.12)), but it was significantly higher in the EVT group than in the No-EVT group in the IVT stratum (11.5% vs 0%, p=0.03).

CONCLUSIONS

There was no difference in efficacy of EVT with or without IVT, while IVT before EVT might increase symptomatic intracranial hemorrhage in patients with large ischemic core.

TRIAL REGISTRATION INFORMATION

NCT03702413.

Neurovascular Inflammation and Complications of Thrombolysis Therapy in Stroke

Intravenous thrombolysis via tPA (tissue-type plasminogen activator) is the only approved pharmacological treatment for acute ischemic stroke, but its benefits are limited by hemorrhagic transformation. Emerging evidence reveals that tPA swiftly mobilizes immune cells which extravasate into the brain parenchyma via the cerebral vasculature, augmenting neurovascular inflammation, and tissue injury. In this review, we summarize the pronounced alterations of immune cells induced by tPA in patients with stroke and experimental stroke models. We argue that neuroinflammation, triggered by ischemia-induced cell death and exacerbated by tPA, compromises neurovascular integrity and the microcirculation, leading to hemorrhagic transformation. Finally, we discuss current and future approaches to attenuate thrombolysis-associated hemorrhagic transformation via uncoupling immune cells from the neurovascular unit.

The Role of Matrix Metalloproteinases in Hemorrhagic Transformation in the Treatment of Stroke with Tissue Plasminogen Activator

Ischemic stroke is a leading cause of disability and mortality worldwide. The only approved treatment for ischemic stroke is thrombolytic therapy with tissue plasminogen activator (tPA), though this approach often leads to a severe complication: hemorrhagic transformation (HT). The pathophysiology of HT in response to tPA is complex and not fully understood. However, numerous scientific findings suggest that the enzymatic activity and expression of matrix metalloproteinases (MMPs) in brain tissue play a crucial role. In this review article, we summarize the current knowledge of the functioning of various MMPs at different stages of ischemic stroke development and their association with HT. We also discuss the mechanisms that underlie the effect of tPA on MMPs as the main cause of the adverse effects of thrombolytic therapy. Finally, we describe recent research that aimed to develop new strategies to modulate MMP activity to improve the efficacy of thrombolytic therapy. The ultimate goal is to provide more targeted and personalized treatment options for patients with ischemic stroke to minimize complications and improve clinical outcomes.

Prognostic role of tissue plasminogen activator in coronary artery disease with or without aortic valve sclerosis

AIMS

We sought to investigate the relationship between circulating tissue plasminogen activator (t-PA) level and long-term outcomes in stable coronary artery disease patients with or without aortic valve sclerosis (AVSc).

METHODS AND RESULTS

Serum levels of t-PA were determined in 347 consecutive stable angina patients with (n = 183) or without (n = 164) AVSc. Outcomes were prospectively recorded as planned clinic evaluations every 6 months up to 7 years. The primary endpoint was a composite of cardiovascular death and rehospitalization due to heart failure. The secondary endpoint included all-cause mortality, cardiovascular death, and rehospitalization due to heart failure. Serum t-PA was significantly higher in AVSc than in non-AVSc patients (2131.22 pg/mL vs. 1495.85 pg/mL, P < 0.001). For patients with AVSc, those with t-PA level above the median (>1840.68 pg/mL) were more likely to meet the primary and secondary endpoints (all P < 0.001). After adjusting for potential confounding factors, serum t-PA level remained significantly predictive for each endpoint in the Cox proportional hazard models. The prognostic value of t-PA was good, with an AUC-ROC of 0.753 (P < 0.001). The combination of t-PA with traditional risk factors improved the risk reclassification of AVSc patients, with a net reclassification index of 0.857 and an integrated discrimination improvement of 0.217 (all P < 0.001). However, for patients without AVSc, both primary and secondary endpoints were similar, irrespective of t-PA levels.

CONCLUSIONS

Elevated circulating t-PA confers an increased risk for poor long-term clinical outcomes in stable coronary artery disease patients with AVSc.

Hemorrhagic Conversion of Acute Ischemic Stroke

Stroke is a leading cause of morbidity and mortality worldwide; a serious complication of ischemic stroke is hemorrhagic transformation. Current treatment of acute ischemic stroke includes endovascular thrombectomy and thrombolytic therapy. Both of these treatment options are linked with increased risks of hemorrhagic conversion. The diagnosis and timely management of patients with hemorrhagic conversion is critically important to patient outcomes. This review aims to discuss hemorrhagic conversion of acute ischemic stroke including discussion of the pathophysiology, review of risk factors, imaging considerations, and treatment of patients with hemorrhagic conversion.

Therapeutic effect of 7 nicotinic receptor activation after ischemic stroke in rats

Nicotinic acetylcholine α7 receptors (α7 nAChRs) have a well-known modulator effect in neuroinflammation. Yet, the therapeutical effect of α7 nAChRs activation after stroke has been scarcely evaluated to date. The role of α7 nAChRs activation with PHA 568487 on inflammation after brain ischemia was assessed with positron emission tomography (PET) using [¹⁸F]DPA-714 and [¹⁸F]BR-351 radiotracers after transient middle cerebral artery occlusion (MCAO) in rats. The assessment of brain oedema, blood brain barrier (BBB) disruption and neurofunctional progression after treatment was evaluated with T₂ weighted and dynamic contrast-enhanced magnetic resonance imaging (T₂ W and DCE-MRI) and neurological evaluation. The activation of α7 nAChRs resulted in a decrease of ischemic lesion, midline displacement and cell neurodegeneration from days 3 to 7 after ischemia. Besides, the treatment with PHA 568487 improved the neurofunctional outcome. Treated ischemic rats showed a significant [¹⁸F]DPA-714-PET uptake reduction at day 7 together with a decrease of activated microglia/infiltrated macrophages. Likewise, the activation of α7 receptors displayed an increase of [¹⁸F]BR-351-PET signal in ischemic cortical regions, which resulted from the overactivation of MMP-2. Finally, the treatment with PHA 568487 showed a protective effect on BBB disruption and blood brain vessel integrity after cerebral ischemia.

Endothelial Dysfunction in Neurodegenerative Diseases

The cerebral vascular system stringently regulates cerebral blood flow (CBF). The components of the blood-brain barrier (BBB) protect the brain from pathogenic infections and harmful substances, efflux waste, and exchange substances; however, diseases develop in cases of blood vessel injuries and BBB dysregulation. Vascular pathology is concurrent with the mechanisms underlying aging, Alzheimer's disease (AD), and vascular dementia (VaD), which suggests its involvement in these mechanisms. Therefore, in the present study, we reviewed the role of vascular dysfunction in aging and neurodegenerative diseases, particularly AD and VaD. During the development of the aforementioned diseases, changes occur in the cerebral blood vessel morphology and local cells, which, in turn, alter CBF, fluid dynamics, and vascular integrity. Chronic vascular inflammation and blood vessel dysregulation further exacerbate vascular dysfunction. Multitudinous pathogenic processes affect the cerebrovascular system, whose dysfunction causes cognitive impairment. Knowledge regarding the pathophysiology of vascular dysfunction in neurodegenerative diseases and the underlying molecular mechanisms may lead to the discovery of clinically relevant vascular biomarkers, which may facilitate vascular imaging for disease prevention and treatment.

Dexmedetomidine Increases MMP-12 and MBP Concentrations after Coronary Artery Bypass Graft Surgery with Extracorporeal Circulation Anaesthesia without Impacting Cognitive Function: A Randomised Control Trial

Postoperative neurological deficits remain a concern for patients undergoing cardiac surgeries. Even minor injuries can lead to neurocognitive decline (i.e., postoperative cognitive dysfunction). Dexmedetomidine may be beneficial given its reported neuroprotective effect. We aimed to investigate the effects of dexmedetomidine on brain injury during cardiac surgery anaesthesia. This prospective observational study analysed data for 46 patients who underwent coronary artery bypass graft surgery with extracorporeal circulation between August 2018 and March 2019. The patients were divided into two groups: control (CON) with typical anaesthesia and dexmedetomidine (DEX) with dexmedetomidine infusion. Concentrations of the biomarkers matrix metalloproteinase-12 (MMP-12) and myelin basic protein (MBP) were measured preoperatively and at 24 and 72 h postoperatively. Cognitive evaluations were performed preoperatively, at discharge, and 3 months after discharge using Addenbrooke's Cognitive Examination version III (ACE-III). The primary endpoint was the ACE-III score at discharge. Increased MMP-12 and MBP concentrations were observed in the DEX group 24 and 72 h postoperatively. No significant differences in ACE-III scores were observed between the groups at discharge; however, the values were increased when compared with initial values after 3 months (p = 0.000). The current results indicate that the administration of dexmedetomidine as an adjuvant to anaesthesia can increase MMP-12 and MBP levels without effects on neurocognitive outcomes at discharge and 3 months postoperatively.

The interplay between MMP-12 and t-PA in the brain after ischemic stroke

Tissue-type plasminogen activator (t-PA) expression is known to increase following transient focal cerebral ischemia and reperfusion. Previously, we reported downregulation of t-PA upon suppression of matrix metalloproteinase-12 (MMP-12), following transient focal cerebral ischemia and reperfusion. We now present data on the temporal expression of t-PA in the brain after transient ischemia, as well as the interaction between MMP-12 and t-PA, two proteases associated with the breakdown of the blood-brain barrier (BBB) and ischemic brain damage. We hypothesized that there might be reciprocal interactions between MMP-12 and t-PA in the brain after ischemic stroke. This hypothesis was tested using shRNA-mediated gene silencing and computational modeling. Suppression of t-PA following transient ischemia and reperfusion in rats attenuated MMP-12 expression in the brain. The overall effect of t-PA shRNA administration was to attenuate the degradation of BBB tight junction protein claudin-5, diminish BBB disruption, and reduce neuroinflammation by decreasing the expression of the microglia/macrophage pro-inflammatory M1 phenotype (CD68, iNOS, IL-1β, and TNFα). Reduced BBB disruption and subsequent lack of infiltration of macrophages (the main source of MMP-12 in the ischemic brain) could account for the decrease in MMP-12 expression after t-PA suppression. Computational modeling of in silico protein-protein interactions indicated that MMP-12 and t-PA may interact physically. Overall, our findings demonstrate that MMP-12 and t-PA interact directly or indirectly at multiple levels in the brain following an ischemic stroke. The present findings could be useful in the development of new pharmacotherapies for the treatment of stroke.

The Gelatinase Inhibitor ACT-03 Reduces Gliosis in the Rapid Kindling Rat Model of Epilepsy, and Attenuates Inflammation and Loss of Barrier Integrity In Vitro

Matrix metalloproteinases (MMPs) are endopeptidases responsible for the cleavage of intra- and extracellular proteins. Several brain MMPs have been implicated in neurological disorders including epilepsy. We recently showed that the novel gelatinase inhibitor ACT-03 has disease-modifying effects in models of epilepsy. Here, we studied its effects on neuroinflammation and blood–brain barrier (BBB) integrity. Using the rapid kindling rat model of epilepsy, we examined whether ACT-03 affected astro- and microgliosis in the brain using immunohistochemistry. Cellular and molecular alterations were further studied in vitro using human fetal astrocyte and brain endothelial cell (hCMEC/D3) cultures, with a focus on neuroinflammatory markers as well as on barrier permeability using an endothelial and astrocyte co-culture model. We observed less astro- and microgliosis in the brains of kindled animals treated with ACT-03 compared to control vehicle-treated animals. In vitro, ACT-03 treatment attenuated stimulation-induced mRNA expression of several pro-inflammatory factors in human fetal astrocytes and brain endothelial cells, as well as a loss of barrier integrity in endothelial and astrocyte co-cultures. Since ACT-03 has disease-modifying effects in epilepsy models, possibly via limiting gliosis, inflammation, and barrier integrity loss, it is of interest to further evaluate its effects in a clinical trial.

Elevated plasma syndecan-1 as glycocalyx injury marker predicts unfavorable outcomes after rt-PA intravenous thrombolysis in acute ischemic stroke

Purpose: We aimed to examine the prognostic value of syndecan-1 as a marker of glycocalyx injury in patients with acute ischemic stroke (AIS) receiving rt-PA intravenous thrombolysis.

Methods: The study included 108 patients with AIS treated with rt-PA intravenous thrombolysis and 47 healthy controls. Patients were divided into unfavorable and favorable prognosis groups based on modified Rankin Scale scores. Univariate and multivariate logistic regression analyses were used to determine risk factors affecting prognosis. Risk prediction models presented as nomograms. The predictive accuracy and clinical value of the new model were also evaluated.

Results: Plasma levels of syndecan-1 were significantly higher in patients with AIS than in controls (p < 0.05). Univariate analysis indicated that higher levels of syndecan-1 were more frequent in patients with poor prognosis than in those with good prognosis (t = −4.273, p < 0.001). Syndecan-1 alone and in combination with other factors predicted patient outcomes. After adjusting for confounding factors, syndecan-1 levels remained associated with poor prognosis [odds ratio, 1.024; 95% confidence interval (CI), 1.010–1.038]. The risk model exhibited a good fit, with an area under the receiver operating characteristic curve of 0.935 (95% CI, 0.888–0.981). The categorical net reclassification index (NRI) and continuous NRI values were >0. The integrated discrimination improvement value was 0.111 (95% CI, 0.049–0.174, p < 0.001). Decision curve analysis indicated that the model incorporating syndecan-1 levels was more clinically valuable than the conventional model.

Conclusion: Plasma syndecan-1 levels represent a potential marker of prognosis of AIS following intravenous thrombolysis. Adding syndecan-1 to the conventional model may improve risk stratification.

Endothelial Cells and the Cerebral Circulation

Endothelial cells form the innermost layer of all blood vessels and are the only vascular component that remains throughout all vascular segments. The cerebral vasculature has several unique properties not found in the peripheral circulation; this requires that the cerebral endothelium be considered as a unique entity. Cerebral endothelial cells perform several functions vital for brain health. The cerebral vasculature is responsible for protecting the brain from external threats carried in the blood. The endothelial cells are central to this requirement as they form the basis of the blood-brain barrier. The endothelium also regulates fibrinolysis, thrombosis, platelet activation, vascular permeability, metabolism, catabolism, inflammation, and white cell trafficking. Endothelial cells regulate the changes in vascular structure caused by angiogenesis and artery remodeling. Further, the endothelium contributes to vascular tone, allowing proper perfusion of the brain which has high energy demands and no energy stores. In this article, we discuss the basic anatomy and physiology of the cerebral endothelium. Where appropriate, we discuss the detrimental effects of high blood pressure on the cerebral endothelium and the contribution of cerebrovascular disease endothelial dysfunction and dementia. © 2022 American Physiological Society. Compr Physiol 12:3449-3508, 2022.

Exploring Contraindications for Thrombolysis: Risk of Hemorrhagic Transformation and Neurological Deterioration after Thrombolysis in Mice with Recent Ischemic Stroke and Hyperglycemia

(1) Intravenous thrombolysis with recombinant tissue plasminogen activator (rt-PA) in patients with acute ischemic stroke is limited because of several contraindications. In routine clinical practice, patients with a recent stroke are typically not treated with rt-PA in case of a recurrent ischemic event. The same applies to its use in the context of pulmonary artery embolism and myocardial infarction with a recent stroke. In this translational study, we evaluated whether rt-PA treatment after experimental ischemic stroke with or without additional hyperglycemia increases the risk for hemorrhagic transformation (HT) and worsens functional outcome regarding the old infarct area. (2) In total, 72 male C57BL/6N mice were used. Ischemic stroke (index stroke) was induced by transient middle cerebral artery occlusion (tMCAO). Mice received either rt-PA or saline 24 h or 14 days after index stroke to determine whether a recent ischemic stroke predisposes to HT. In addition to otherwise healthy mice, hyperglycemic mice were analyzed to evaluate diabetes as a second risk factor for HT. Mice designated to develop hyperglycemia were pre-treated with streptozotocin. (3) The neurological outcome in rt-PA and saline-treated normoglycemic mice did not differ significantly, either at 24 h or at 14 days. In contrast, hyperglycemic mice treated with rt-PA had a significantly worse neurological outcome (at 24 h, p = 0.02; at 14 days, p = 0.03). At 24 h after rt-PA or saline treatment, HT scores differed significantly (p = 0.02) with the highest scores within hyperglycemic mice treated with rt-PA, where notably only small petechial hemorrhages could be detected. (4) Thrombolysis after recent ischemic stroke does not increase the risk for HT or worsen the functional outcome in otherwise healthy mice. However, hyperglycemia as a second risk factor leads to neurological deterioration after rt-PA treatment, which cannot be explained by an increase of HT alone. Direct neurotoxic effects of rt-PA may play a role.

A biomimetic zeolite-based nanoenzyme contributes to neuroprotection in the neurovascular unit after ischaemic stroke via efficient removal of zinc and ROS

Zeolite-based nanomaterials have a large number of applications in the field of medicine due to their high porosity, biocompatibility and biological stability. In this study, we designed cerium (Ce)-doped Linde Type A (LTA) zeolite-based nanomaterials (Ce/Zeo-NMs) as a multifunctional mesoporous nanoenzyme to reduce dysfunction of the neurovascular unit (NVU) and attenuate cerebral ischaemia-reperfusion (I/R) injury. Owing to its unique adsorption capacity and mimetic catalytic activities, Ce@Zeo-NMs adsorbed excess zinc ions and exhibited scavenging activity against reactive oxygen species (ROS) induced by acute I/R, thus reshaping the oxidative and zinc microenvironment in the ischaemic brain. In vivo results demonstrated that Ce@Zeo-NMs significantly reduced ischaemic damage to the NVU by decreasing the infarct area, protecting against breakdown of the blood-brain barrier (BBB) via inhibiting the degradation of tight junction proteins (TJPs) and inhibiting activation of microglia and astrocytes in a rat model of middle cerebral artery occlusion-reperfusion (MCAO/R). Taken together, these findings indicated that Ce@Zeo-NMs may serve as a promising dual-targeting therapeutic agent for alleviating cerebral I/R injury. STATEMENT OF SIGNIFICANCE: Cerium (Ce)-doped Linde Type A zeolite-based nanomaterials (Ce/Zeo-NMs) as a multifunctional mesoporous nanoenzyme were designed for inducing neuroprotection after ischaemic stroke by reducing dysfunction of the neurovascular unit (NVU). Ce@Zeo-NMs had the ability to adsorb excessive Zn²⁺ and showed mimetic enzymatic activities. As a result, Ce@Zeo-NMs protected against cerebral ischaemia and reduced the damage of NVU by improving the integrity of blood brain barrier (BBB) and inhibiting activation of microglia and astrocytes in a rat model of middle cerebral artery occlusion-reperfusion (MCAO/R). These findings indicated that Ce@Zeo-NMs may serve as a therapeutic strategy for neuroprotection and functional recovery upon ischaemic stroke onset.

Membrane-Free Stem Cell Extract Enhances Blood–Brain Barrier Integrity by Suppressing NF-κB-Mediated Activation of NLRP3 Inflammasome in Mice with Ischemic Stroke

Membrane-free stem cell extract (MFSCE) of human adipose tissues possesses various biological activities. However, the effects of MFSCE on blood–brain barrier dysfunction and brain damage are unknown. In this study, we determined the role of MFSCE in an ischemic stroke mouse model. Mice were treated with MFSCE once daily for 4 days and 1 h before ischemic damage. Experimental ischemia was induced by photothrombosis. Pretreatment with MFSCE reduced infarct volume and edema and improved neurological, as well as motor functions. Evans blue leakage and water content in the brain tissue were reduced by MFSCE pretreatment relative to those in the vehicle group. MFSCE increased the expression of the tight junction proteins zonula occludens 1 and claudin-5, as well as vascular endothelial-cadherin, but decreased that of matrix metalloproteinase 9. Notably, MFSCE treatment decreased cell death and the level of NOD-like receptor protein 3 inflammasome, consistent with the downregulated expression of the pro-inflammatory cytokines interleukin (IL)-1β and IL-18 in the ischemic brain. These effects might have occurred via the suppression of the expression of Toll-like receptor 4 and activation of nuclear factor-κB. The results highlighted the potential of MFSCE treatment as a novel and preventive strategy for patients at a high risk of ischemic stroke.

Cross-Talk between Amyloid, Tau Protein and Free Radicals in Post-Ischemic Brain Neurodegeneration in the Form of Alzheimer’s Disease Proteinopathy

Recent years have seen remarkable progress in research into free radicals oxidative stress, particularly in the context of post-ischemic recirculation brain injury. Oxidative stress in post-ischemic tissues violates the integrity of the genome, causing DNA damage, death of neuronal, glial and vascular cells, and impaired neurological outcome after brain ischemia. Indeed, it is now known that DNA damage and repair play a key role in post-stroke white and gray matter remodeling, and restoring the integrity of the blood-brain barrier. This review will present one of the newly characterized mechanisms that emerged with genomic and proteomic development that led to brain ischemia to a new level of post-ischemic neuropathological mechanisms, such as the presence of amyloid plaques and the development of neurofibrillary tangles, which further exacerbate oxidative stress. Finally, we hypothesize that modified amyloid and the tau protein, along with the oxidative stress generated, are new key elements in the vicious circle important in the development of post-ischemic neurodegeneration in a type of Alzheimer’s disease proteinopathy.

Modulation of gene expression on a transcriptome-wide level following human neural stem cell transplantation in aged mouse stroke brains

INTRODUCTION

Neural stem cell (NSC) transplantation offers great potential for treating ischemic stroke. Clinically, ischemia followed by reperfusion results in robust cerebrovascular injury that upregulates proinflammatory factors, disrupts neurovascular units, and causes brain cell death. NSCs possess multiple actions that can be exploited for reducing the severity of neurovascular injury. Our previous studies in young adult mice showed that human NSC transplantation during the subacute stage diminishes stroke pathophysiology and improves behavioral outcome.

METHODS

We employed a well-established and commonly used stroke model, middle cerebral artery occlusion with subsequent reperfusion (MCAO/R). Here, we assessed the outcomes of hNSC transplantation 48 h post-MCAO (24 h post-transplant) in aged mouse brains in response to stroke because aging is a crucial risk factor for cerebral ischemia. Next, we tested whether administration of the integrin α5β1 inhibitor, ATN-161, prior to hNSC transplantation further affects stoke outcome as compared with NSCs alone. RNA sequencing (RNA-seq) was used to assess the impact of hNSC transplantation on differentially expressed genes (DEGs) on a transcriptome-wide level.

RESULTS

Here, we report that hNSC-engrafted brains with or without ATN-161 showed significantly reduced infarct size, and attenuated the induction of proinflammatory factors and matrix metalloproteases. RNA-seq analysis revealed DEGs and molecular pathways by which hNSCs induce a beneficial post-stroke outcome in aged stroke brains. 811 genes were differentially expressed (651 downregulated and 160 upregulated) in hNSC-engrafted stroke brains. Functional pathway analysis identified enriched and depleted pathways in hNSC-engrafted aged mouse stroke brains. Depletion of pathways following hNSC-engraftment included signaling involving neuroinflammation, acute phase response, leukocyte extravasation, and phagosome formation. On the other hand, enrichment of pathways in hNSC-engrafted brains was associated with PPAR signaling, LXR/RXR activation, and inhibition of matrix metalloproteases. Hierarchical cluster analysis of DEGs in hNSC-engrafted brains indicate decreased expression of genes encoding TNF receptors, proinflammatory factors, apoptosis factors, adhesion and leukocyte extravasation, and Toll-like receptors.

CONCLUSIONS

Our study is the first to show global transcripts differentially expressed following hNSC transplantation in the subacute phase of stroke in aged mice. The outcome of our transcriptome study would be useful to develop new therapies ameliorating early-stage stroke injury.

Roles of the tissue-type plasminogen activator in immune response

The COVID-19 pandemic has once again brought to the forefront the existence of a tight link between the coagulation/fibrinolytic system and the immunologic processes. Tissue-type plasminogen activator (tPA) is a serine protease with a key role in fibrinolysis by converting plasminogen into plasmin that can finally degrade fibrin clots. tPA is released in the blood by endothelial cells and hepatocytes but is also produced by various types of immune cells including T cells and monocytes. Beyond its role on hemostasis, tPA is also a potent modulator of inflammation and is involved in the regulation of several inflammatory diseases. Here, after a brief description of tPA structure, we review its new functions in adaptive immunity focusing on T cells and antigen presenting cells. We intend to synthesize the recent knowledge on proteolysis- and receptor-mediated effects of tPA on immune response in physiological and pathological context.

Plasminogen activator receptor assemblies in cell signaling, innate immunity, and inflammation

Tissue-type plasminogen activator (tPA) and urokinase-type plasminogen activator (uPA) are serine proteases and major activators of fibrinolysis in mammalian systems. Because fibrinolysis is an essential component of the response to tissue injury, diverse cells, including cells that participate in the response to injury, have evolved receptor systems to detect tPA and uPA and initiate appropriate cell-signaling responses. Formation of functional receptor systems for the plasminogen activators requires assembly of diverse plasma membrane proteins, including but not limited to: the urokinase receptor (uPAR); integrins; N-formyl peptide receptor-2 (FPR2), receptor tyrosine kinases (RTKs), the N-methyl-d-aspartate receptor (NMDA-R), and low-density lipoprotein receptor-related protein-1 (LRP1). The cell-signaling responses elicited by tPA and uPA impact diverse aspects of cell physiology. This review describes rapidly evolving knowledge regarding the structure and function of plasminogen activator receptor assemblies. How these receptor assemblies regulate innate immunity and inflammation is then considered.

Blood-Brain Barrier Breakdown: An Emerging Biomarker of Cognitive Impairment in Normal Aging and Dementia

The blood–brain barrier (BBB) plays a vital role in maintaining the specialized microenvironment of the neural tissue. It separates the peripheral circulatory system from the brain parenchyma while facilitating communication. Alterations in the distinct physiological properties of the BBB lead to BBB breakdown associated with normal aging and various neurodegenerative diseases. In this review, we first briefly discuss the aging process, then review the phenotypes and mechanisms of BBB breakdown associated with normal aging that further cause neurodegeneration and cognitive impairments. We also summarize dementia such as Alzheimer's disease (AD) and vascular dementia (VaD) and subsequently discuss the phenotypes and mechanisms of BBB disruption in dementia correlated with cognition decline. Overlaps between AD and VaD are also discussed. Techniques that could identify biomarkers associated with BBB breakdown are briefly summarized. Finally, we concluded that BBB breakdown could be used as an emerging biomarker to assist to diagnose cognitive impairment associated with normal aging and dementia.

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

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

Neural Stem Cells for Early Ischemic Stroke

Clinical treatments for ischemic stroke are limited. Neural stem cell (NSC) transplantation can be a promising therapy. Clinically, ischemia and subsequent reperfusion lead to extensive neurovascular injury that involves inflammation, disruption of the blood-brain barrier, and brain cell death. NSCs exhibit multiple potentially therapeutic actions against neurovascular injury. Currently, tissue plasminogen activator (tPA) is the only FDA-approved clot-dissolving agent. While tPA’s thrombolytic role within the vasculature is beneficial, tPA’s non-thrombolytic deleterious effects aggravates neurovascular injury, restricting the treatment time window (time-sensitive) and tPA eligibility. Thus, new strategies are needed to mitigate tPA’s detrimental effects and quickly mediate vascular repair after stroke. Up to date, clinical trials focus on the impact of stem cell therapy on neuro-restoration by delivering cells during the chronic stroke stage. Also, NSCs secrete factors that stimulate endogenous repair mechanisms for early-stage ischemic stroke. This review will present an integrated view of the preclinical perspectives of NSC transplantation as a promising treatment for neurovascular injury, with an emphasis on early-stage ischemic stroke. Further, this will highlight the impact of early sub-acute NSC delivery on improving short-term and long-term stroke outcomes.

Recombinant Annexin A2 Administration Improves Neurological Outcomes After Traumatic Brain Injury in Mice

Microvascular failure is one of the key pathogenic factors in the dynamic pathological evolution after traumatic brain injury (TBI). Our laboratory and others previously reported that Annexin A2 functions in blood-brain barrier (BBB) development and cerebral angiogenesis, and recombinant human Annexin A2 (rA2) protected against hypoxia plus IL-1β-induced cerebral trans-endothelial permeability in vitro, and cerebral angiogenesis impairment of AXNA2 knock-out mice in vivo. We thereby hypothesized that ANXA2 might be a cerebrovascular therapy candidate that targets early BBB integrity disruption, and subacute/delayed cerebrovascular remodeling after TBI, ultimately improve neurological outcomes. In a controlled cortex impact (CCI) mice model, we found rA2 treatment (1 mg/kg) significantly reduced early BBB disruption at 24 h after TBI; and rA2 daily treatment for 7 days augmented TBI-induced mRNA levels of pro-angiogenic and endothelial-derived trophic factors in cerebral microvessels. In cultured human brain microvascular endothelial cells (HBMEC), through MAPKs array, we identified that rA2 significantly activated Akt, ERK, and CREB, and the activated CREB might be responsible for the rA2-induced VEGF and BDNF expression. Moreover, rA2 administration significantly increased cerebral angiogenesis examined at 14 days and vessel density at 28 days after TBI in mice. Consistently, our results validated that rA2 significantly induced angiogenesis in vitro, evidenced by tube formation and scratched migration assays in HBMEC. Lastly, we demonstrated that rA2 improved long-term sensorimotor and cognitive function, and reduced brain tissue loss at 28 days after TBI. Our findings suggest that rA2 might be a novel vascular targeting approach for treating TBI.

Continuous Glibenclamide Prevents Hemorrhagic Transformation in a Rodent Model of Severe Ischemia-Reperfusion

BACKGROUND

Endovascular thrombectomy (EVT) is highly effective but may also lead to hemorrhagic transformation (HT) and edema, which may be more pronounced in severe ischemia. We sought to determine whether glibenclamide can attenuate HT and edema in a severe ischemia-reperfusion model that reflects EVT.

METHODS

Using a transient middle cerebral artery occlusion (tMCAo) rodent model of stroke, we studied two rat cohorts, one without rt-PA and a second cohort treated with rt-PA. Glibenclamide or vehicle control was administered as an intravenous bolus at reperfusion, followed by continuous subcutaneous administration with an osmotic pump.

RESULTS

Compared to vehicle control, glibenclamide improved neurological outcome (median 7, interquartile range [IQR 6-8] vs. control median 6 [IQR 0-6], p = 0.025), reduced stroke volume (323 ± 42 vs. 484 ± 60 mm3, p < 0.01), swelling volume (10 ± 4 vs. 28 ± 7%, p < 0.01) and water content (84 ± 1 vs. 85 ± 1%, p < 0.05). Glibenclamide administration also reduced HT based on ECASS criteria, densitometry (0.94 ± 0.1 vs. 1.15 ± 0.2, p < 0.01), and quantitative hemoglobin concentration (2.7 ± 1.5 vs. 6.2 ± 4.6 uL, p = 0.011). In the second cohort with rt-PA coadministration, concordant effects on HT were observed with glibenclamide.

CONCLUSIONS

Taken together, these studies demonstrated that glibenclamide reduced the amount of edema and HT after severe ischemia. This study suggests that co-administration of glibenclamide may be worth further study in severe stroke patients treated with EVT with or without IV rt-PA.

Tissue plasminogen activator worsens experimental autoimmune encephalomyelitis by complementary actions on lymphoid and myeloid cell responses

BACKGROUND

Tissue plasminogen activator (tPA) is a serine protease involved in fibrinolysis. It is released by endothelial cells, but also expressed by neurons and glial cells in the central nervous system (CNS). Interestingly, this enzyme also contributes to pathological processes in the CNS such as neuroinflammation by activating microglia and increasing blood-brain barrier permeability. Nevertheless, its role in the control of adaptive and innate immune response remains poorly understood.

METHODS

tPA effects on myeloid and lymphoid cell response were studied in vivo in the mouse model of multiple sclerosis experimental autoimmune encephalomyelitis and in vitro in splenocytes.

RESULTS

tPA-/- animals exhibited less severe experimental autoimmune encephalomyelitis than their wild-type counterparts. This was accompanied by a reduction in both lymphoid and myeloid cell populations in the spinal cord parenchyma. In parallel, tPA increased T cell activation and proliferation, as well as cytokine production by a protease-dependent mechanism and via plasmin generation. In addition, tPA directly raised the expression of MHC-II and the co-stimulatory molecules CD80 and CD86 at the surface of dendritic cells and macrophages by a direct action dependent of the activation of epidermal growth factor receptor.

CONCLUSIONS

Our study provides new insights into the mechanisms responsible for the harmful functions of tPA in multiple sclerosis and its animal models: tPA promotes the proliferation and activation of both lymphoid and myeloid populations by distinct, though complementary, mechanisms.

Effects of ML351 and tissue plasminogen activator combination therapy in a rat model of focal embolic stroke

Thrombolytic stroke therapy with tissue plasminogen activator (tPA) is limited by risks of hemorrhagic transformation (HT). We have reported that a new 12/15-lipoxygenase (12/15-LOX) inhibitor ML351 reduced tPA related HT in mice subjected to experimental stroke under anticoagulation. In this study, we asked whether ML351 can ameliorate tPA induced HT in an embolic stroke model. Rats were subjected to embolic middle cerebral artery occlusion with 2 or 3 hr ischemia and tPA infusion, with or without ML351. Regional cerebral blood flow was monitored 2 hr after ischemia and continuously monitored for 1 hr after treatment for determining reperfusion. Hemoglobin was determined in brain homogenates and infarct volume was quantified at 24 hr after stroke.12/15-LOX, cluster of differentiation 68(CD68), immunoglobulin G (IgG), and tight junction proteins expression was detected by immunohistochemistry. ML351 significantly reduced tPA related hemorrhage after stroke without affecting its thrombolytic efficacy. ML351 also reduced blood-brain barrier disruption and improved preservation of junction proteins. ML351 and tPA combination improved neurological deficit of rats even though ML351 did not further reduce the infarct volume compared to tPA alone treated animals. Pro-inflammatory cytokines were suppressed by ML351 both in vivo and in vitro experiments. We further showed that ML351 suppressed the expression of c-Jun-N-terminal kinase (JNK) in brains and microglia cultures, whereas exogenous 12-HETE attenuated this effect in vitro. In conclusion, ML351 and tPA combination therapy is beneficial in ameliorating HT after ischemic stroke. This protective effect is probably because of 12/15-LOX inhibition and suppression of JNK-mediated microglia/macrophage activation.

Endothelial LRP1 protects against neurodegeneration by blocking cyclophilin A

The low-density lipoprotein receptor–related protein 1 (LRP1) is an endocytic and cell signaling transmembrane protein. Endothelial LRP1 clears proteinaceous toxins at the blood–brain barrier (BBB), regulates angiogenesis, and is increasingly reduced in Alzheimer’s disease associated with BBB breakdown and neurodegeneration. Whether loss of endothelial LRP1 plays a direct causative role in BBB breakdown and neurodegenerative changes remains elusive. Here, we show that LRP1 inactivation from the mouse endothelium results in progressive BBB breakdown, followed by neuron loss and cognitive deficits, which is reversible by endothelial-specific LRP1 gene therapy. LRP1 endothelial knockout led to a self-autonomous activation of the cyclophilin A–matrix metalloproteinase-9 pathway in the endothelium, causing loss of tight junctions underlying structural BBB impairment. Cyclophilin A inhibition in mice with endothelial-specific LRP1 knockout restored BBB integrity and reversed and prevented neuronal loss and behavioral deficits. Thus, endothelial LRP1 protects against neurodegeneration by inhibiting cyclophilin A, which has implications for the pathophysiology and treatment of neurodegeneration linked to vascular dysfunction.

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.

tPA Mobilizes Immune Cells That Exacerbate Hemorrhagic Transformation in Stroke

RATIONALE

Hemorrhagic complications represent a major limitation of intravenous thrombolysis using tPA (tissue-type plasminogen activator) in patients with ischemic stroke. The expression of tPA receptors on immune cells raises the question of what effects tPA exerts on these cells and whether these effects contribute to thrombolysis-related hemorrhagic transformation.

OBJECTIVE

We aim to determine the impact of tPA on immune cells and investigate the association between observed immune alteration with hemorrhagic transformation in ischemic stroke patients and in a rat model of embolic stroke.

METHODS AND RESULTS

Paired blood samples were collected before and 1 hour after tPA infusion from 71 patients with ischemic stroke. Control blood samples were collected from 27 ischemic stroke patients without tPA treatment. A rat embolic middle cerebral artery occlusion model was adopted to investigate the underlying mechanisms of hemorrhagic transformation. We report that tPA induces a swift surge of circulating neutrophils and T cells with profoundly altered molecular features in ischemic stroke patients and a rat model of focal embolic stroke. tPA exacerbates endothelial injury, increases adhesion and migration of neutrophils and T cells, which are associated with brain hemorrhage in rats subjected to embolic stroke. Genetic ablation of annexin A2 in neutrophils and T cells diminishes the effect of tPA on these cells. Decoupling the interaction between mobilized neutrophils/T cells and the neurovascular unit, achieved via a S1PR (sphingosine-1-phosphate receptor) 1 modulator RP101075 and a CCL2 (C-C motif chemokine ligand 2) synthesis inhibitor bindarit, which block lymphocyte egress and myeloid cell recruitment, respectively, attenuates hemorrhagic transformation and improves neurological function after tPA thrombolysis.

CONCLUSIONS

Our findings suggest that immune invasion of the neurovascular unit represents a previously unrecognized mechanism underlying tPA-mediated brain hemorrhage, which can be overcome by precise immune modulation during thrombolytic therapy.

Disruptions of Circadian Rhythms and Thrombolytic Therapy During Ischemic Stroke Intervention

Several endogenous and exogenous factors interact to influence stroke occurrence, in turn contributing to discernable daily distribution patterns in the frequency and severity of cerebrovascular events. Specifically, strokes that occur during the morning tend to be more severe and are associated with elevated diastolic blood pressure, increased hospital stay, and worse outcomes, including mortality, compared to strokes that occur later in the day. Furthermore, disrupted circadian rhythms are linked to higher risk for stroke and play a role in stroke outcome. In this review, we discuss the interrelation among core clock genes and several factors contributing to ischemic outcomes, sources of disrupted circadian rhythms, the implications of disrupted circadian rhythms in foundational stroke scientific literature, followed by a review of clinical implications. In addition to highlighting the distinct daily pattern of onset, several aspects of physiology including immune response, endothelial/vascular and blood brain barrier function, and fibrinolysis are under circadian clock regulation; disrupted core clock gene expression patterns can adversely affect these physiological processes, leading to a prothrombotic state. Lastly, we discuss how the timing of ischemic onset increases morning resistance to thrombolytic therapy and the risk of hemorrhagic transformation.

Unravelling the Network of Nuclear Matrix Metalloproteinases for Targeted Drug Design

Matrix metalloproteinases (MMPs) are zinc-dependent endopeptidases that are responsible for the degradation of a wide range of extracellular matrix proteins, which are involved in many cellular processes to ensure the normal development of tissues and organs. Overexpression of MMPs has been observed to facilitate cellular growth, migration, and metastasis of tumor cells during cancer progression. A growing number of these proteins are being found to exist in the nuclei of both healthy and tumor cells, thus highlighting their localization as having a genuine purpose in cellular homeostasis. The mechanism underlying nuclear transport and the effects of MMP nuclear translocation have not yet been fully elucidated. To date, nuclear MMPs appear to have a unique impact on cellular apoptosis and gene regulation, which can have effects on immune response and tumor progression, and thus present themselves as potential therapeutic targets in certain types of cancer or disease. Herein, we highlight and evaluate what progress has been made in this area of research, which clearly has some value as a specific and unique way of targeting the activity of nuclear matrix metalloproteinases within various cell types.

Roadmap for Stroke: Challenging the Role of the Neuronal Extracellular Matrix

Stroke is a major challenge in modern medicine and understanding the role of the neuronal extracellular matrix (NECM) in its pathophysiology is fundamental for promoting brain repair. Currently, stroke research is focused on the neurovascular unit (NVU). Impairment of the NVU leads to neuronal loss through post-ischemic and reperfusion injuries, as well as coagulatory and inflammatory processes. The ictal core is produced in a few minutes by the high metabolic demand of the central nervous system. Uncontrolled or prolonged inflammatory response is characterized by leukocyte infiltration of the injured site that is limited by astroglial reaction. The metabolic failure reshapes the NECM through matrix metalloproteinases (MMPs) and novel deposition of structural proteins continues within months of the acute event. These maladaptive reparative processes are responsible for the neurological clinical phenotype. In this review, we aim to provide a systems biology approach to stroke pathophysiology, relating the injury to the NVU with the pervasive metabolic failure, inflammatory response and modifications of the NECM. The available data will be used to build a protein–protein interaction (PPI) map starting with 38 proteins involved in stroke pathophysiology, taking into account the timeline of damage and the co-expression scores of their RNA patterns The application of the proposed network could lead to a more accurate design of translational experiments aiming at improving both the therapy and the rehabilitation processes.

Neuroprotective Methodologies of Co-Enzyme Q10 Mediated Brain Hemorrhagic Treatment: Clinical and Pre-Clinical Findings

Cerebral brain hemorrhage is associated with the highest mortality and morbidity despite only constituting approximately 10-15% of all strokes classified into intracerebral and intraventricular hemorrhage where most of the patients suffer from impairment in memory, weakness or paralysis in arms or legs, headache, fatigue, gait abnormality and cognitive dysfunctions. Understanding molecular pathology and finding the worsening cause of hemorrhage will lead to explore the therapeutic interventions that could prevent and cure the disease. Mitochondrial ETC-complexes dysfunction has been found to increase neuroinflammatory cytokines, oxidative free radicals, excitotoxicity, neurotransmitter and energy imbalance that are the key neuropathological hallmarks of cerebral hemorrhage. Coenzyme Q10 (CoQ10), as a part of the mitochondrial respiratory chain can effectively restore these neuronal dysfunctions by preventing the opening of mitochondrial membrane transition pore, thereby counteracting cell death events as well as exerts an anti-inflammatory effect by influencing the expression of NF-kB1 dependent genes thus preventing the neuroinflammation and energy restoration. Due to behavior and biochemical heterogeneity in post cerebral brain hemorrhagic pattern different preclinical autologous blood injection models are required to precisely investigate the forthcoming therapeutic strategies. Despite emerging pre-clinical research and resultant large clinical trials for promising symptomatic treatments, there are very less pharmacological interventions demonstrated to improve post operative condition of patients where intensive care is required. Therefore, in current review, we explore the disease pattern, clinical and pre-clinical interventions under investigation and neuroprotective methodologies of CoQ10 precursors to ameliorate post brain hemorrhagic conditions.

Tissue-Type Plasminogen Activator Controlled Corticogenesis Through a Mechanism Dependent of NMDA Receptors Expressed on Radial Glial Cells

Modifications of neuronal migration during development, including processes that control cortical lamination are associated with functional deficits at adult stage. Here, we report for the first time that the lack of the serine protease tissue-type Plasminogen Activator (tPA), previously characterized as a neuromodulator and a gliotransmitter, leads to an altered cortical lamination in adult. This results in a neuronal migration defect of tPA deficient neurons which are stopped in the intermediate zone at E16. This phenotype is rescued by re-expressing a wild-type tPA in cortical neurons at E14 but not by a tPA that cannot interact with NMDAR. We thus hypothetized that the tPA produced by cortical neuronal progenitors can control their own radial migration through a mechanism dependent of NMDAR expressed at the surface of radial glial cells (RGC). Accordingly, conditional deletion of tPA in neuronal progenitors at E14 or overexpression of a dominant-negative NMDAR that cannot bind tPA in RGC also delayed neuronal migration. Moreover, the lack of tPA lead to an impaired maturation and orientation of RGC. These data provide the first demonstration that the neuronal serine protease tPA is an actor of a proper corticogenesis by its ability to control NMDAR signaling in RGC.

Release rate is a key variable affecting the therapeutic effectiveness of liposomal fasudil for the treatment of cerebral ischemia/reperfusion injury

Liposomal fasudil as a treatment for cerebral ischemia/reperfusion (I/R) injury has been demonstrated to be effective in animal models due to the high accumulation of liposomes in damaged brain tissue. However, it is still unclear what effect drug release rate has on the treatment of I/R injury, where pathology progresses dramatically in a short time. In the present study, we assessed four formulations of liposomal fasudil. The results of an in vitro drug release assay showed that the release properties of fasudil were changed by varying the lipid composition and internal phase of the liposomes. Based on these results, differences in the transition of fasudil plasma concentration were monitored after the administration of each type of liposomal fasudil in normal rats. A pharmacokinetic study showed that higher levels of drug retention in liposomal fasudil resulted in higher fasudil plasma concentration. Finally, treatment of I/R injury model rats with liposomal fasudil revealed that a mid-level release rate of fasudil from liposomes resulted in the greatest therapeutic effect among the formulations. In conclusion, these results demonstrate that an optimized drug release rate from liposomes enhances the therapeutic effect of fasudil for the treatment of cerebral I/R injury.

An increase in AMPK/e-NOS signaling and attenuation of MMP-9 may contribute to remote ischemic perconditioning associated neuroprotection in rat model of focal ischemia

Remote ischemic perconditioning (RIPerC) results in collateral enhancement and a reduction in middle cerebral artery occlusion (MCAO) induced ischemia. RIPerC likely activates multiple metabolic protective mechanisms, including effects on matrix metalloproteinases (MMPs) and protein kinases. Here we explore if RIPerC improves neuroprotection and collateral flow by modifying the activities of MMP-9 and AMPK/e-NOS. Age matched adult male Sprague Dawley rats were subjected to MCAO followed one hour later by RIPerC (3 cycles of 15 min ischemia). Animals were euthanized 24 h post-MCAO. Haematoxylin and Eosin (H&E) staining 24 h post-MCAO revealed a significant (p < 0.02) reduction in the infarction volume in RIPerC treated animals (24.9 ± 5.4%) relative to MCAO controls (42.5 ± 4.2, %). TUNEL staining showed a 42.6% reduction in the apoptotic cells with RIPerC treatment (p < 0.01). Immunoblotting in congruence with RT-PCR and Zymography showed that RIPerC significantly reduced MMP-9 expression and activity in RIPerC + MCAO group compared to MCAO group (218.3 ± 19.1% vs. 148.9 ± 12.05% (p < 0.01). Immunoblotting revealed that RIPerC was associated with a significant 2.5-fold increase in activation of p-AMPK compared to the MCAO group (p < 0.01) which was also associated with a significant increase in the e-NOS activity (p < 0.01). RIPerC resulted in reduction of infarction volume, decreased apoptotic cell death and attenuated MMP-9 activity. This together with the increased activity of p-AMPK and increase in p-eNOS may, in part explain the neuroprotection and sustained increase in blood flow observed with RIPerC following acute stroke.

Contribution of the Low-Density Lipoprotein Receptor Family to Breast Cancer Progression

The low-density lipoprotein receptor (LDLR) family comprises 14 single-transmembrane receptors sharing structural homology and common repeats. These receptors specifically recognize and internalize various extracellular ligands either alone or complexed with membrane-spanning co-receptors that are then sorted for lysosomal degradation or cell-surface recovery. As multifunctional endocytic receptors, some LDLR members from the core family were first considered as potential tumor suppressors due to their clearance activity against extracellular matrix-degrading enzymes. LDLRs are also involved in pleiotropic functions including growth factor signaling, matricellular proteins, and cell matrix adhesion turnover and chemoattraction, thereby affecting both tumor cells and their surrounding microenvironment. Therefore, their roles could appear controversial and dependent on the malignancy state. In this review, recent advances highlighting the contribution of LDLR members to breast cancer progression are discussed with focus on (1) specific expression patterns of these receptors in primary cancers or distant metastasis and (2) emerging mechanisms and signaling pathways. In addition, potential diagnosis and therapeutic options are proposed.

Human neural stem cells improve early stage stroke outcome in delayed tissue plasminogen activator-treated aged stroke brains

INTRODUCTION

Clinically, significant stroke injury results from ischemia-reperfusion (IR), which induces a deleterious biphasic opening of the blood-brain barrier (BBB). Tissue plasminogen activator (tPA) remains the sole pharmacological agent to treat ischemic stroke. However, major limitations of tPA treatment include a narrow effective therapeutic window of 4.5 h in most patients after initial stroke onset and off-target non-thrombolytic effects (e.g., the risk of increased IR injury). We hypothesized that ameliorating BBB damage with exogenous human neural stem cells (hNSCs) would improve stroke outcome to a greater extent than treatment with delayed tPA alone in aged stroke mice.

METHODS

We employed middle cerebral artery occlusion to produce focal ischemia with subsequent reperfusion (MCAO/R) in aged mice and administered tPA at a delayed time point (6 h post-stroke) via tail vein. We transplanted hNSCs intracranially in the subacute phase of stroke (24 h post-stroke). We assessed the outcomes of hNSC transplantation on pathophysiological markers of stroke 48 h post-stroke (24 h post-transplant).

RESULTS

Delayed tPA treatment resulted in more extensive BBB damage and inflammation relative to MCAO controls. Notably, transplantation of hNSCs ameliorated delayed tPA-induced escalated stroke damage; decreased expression of proinflammatory factors (tumor necrosis factor-alpha (TNF-α) and interleukin (IL)-6), decreased the level of matrix metalloprotease-9 (MMP-9), increased the level of brain-derived neurotrophic factor (BDNF), and reduced BBB damage.

CONCLUSIONS

Aged stroke mice that received delayed tPA treatment in combination with hNSC transplantation exhibited reduced stroke pathophysiology in comparison to non-transplanted stroke mice with delayed tPA. This suggests that hNSC transplantation may synergize with already existing stroke therapies to benefit a larger stroke patient population.

Neonatal cerebral hypoxia-ischemia in mice triggers age-dependent vascular effects and disabilities in adults; implication of tissue plasminogen activator (tPA)

Neonatal encephalopathy frequently results from hypoxia-ischemia (HI) or inflammation in preterm or term neonates. Neuropathology depends on cerebral development at insult time, but the poor correlation of neuromotor, cognitive, and behavioral disabilities in infancy with initial imaging and clinical records precludes early prognosis. The Rice-Vannucci HI procedure was applied to wild type and tissue plasminogen activator knockout (tPA-KO) mice as surrogates for human preterm (with five-day-old postnatal (P5) mice) or human term (with ten-day-old postnatal (P10) mice). Acute and delayed T2-magnetic resonance imaging (T2-MRI) signals and cognitive deficits in adulthood (spatial memory and social interaction) were investigated in the same animals. Early vascular tPA and matrix metalloproteinase-9 (MMP-9) activities, blood-brain barrier permeability to water or IgG, and microglial activation were assessed separately. HI in P5 or P10 mice induced early hemisphere swelling in T2-MRI scans, and a delayed atrophy of the cortex and hippocampus, but affected white matter in the P5 group only, irrespective of the wild type or tPA-KO genotype. Adults had no motor disabilities, but we did find HI-induced age-dependent deficits, preferentially social interaction and activity in P5 mice, and spatial learning in P10 mice. In P5 mice, tPA-KO prevented MMP-9 activation, IgG extravasation, microglial activation, and behavior impairments. In P10 mice, MMP-9 activation and inflammatory processes remained in the hippocampus of the tPA-KO group, and also contributed to persistent spatial learning deficits. Perinatal HI in mice mimicked the unpredictability of outcomes from imaging in human clinics. Delayed deficits appeared associated to vascular dysfunction-induced inflammation, which recalls our previous work showing major vascular maturation between P5 and P10 stages. Using omics to explore neural, glial, or brain vessel markers in neonate blood may be a promising perspective to identify pertinent prognostic tools.

Prothymosin alpha and its mimetic hexapeptide improve delayed tissue plasminogen activator-induced brain damage following cerebral ischemia

Tissue plasminogen activator (tPA) administration beyond 4.5 h of stroke symptoms is beneficial for patients but has an increased risk of cerebral hemorrhage. Thus, increasing the therapeutic window of tPA is important for stroke recovery. We previously showed that prothymosin alpha (ProTα) or its mimetic hexapeptide (P6Q) has anti-ischemic activity. Here, we examined the beneficial effects of ProTα or P6Q against delayed tPA-induced brain damage following middle cerebral artery occlusion (MCAO) or photochemically induced thrombosis in mice. Brain hemorrhage was observed by tPA administration during reperfusion at 4.5 and 6 h after MCAO. Co-administration of ProTα with tPA at 4.5 h inhibited hemorrhage and motor dysfunction 2-4 days, but not 7 days after MCAO. ProTα administration at 2 and 4.5 h after MCAO significantly inhibited tPA (4.5 h)-induced motor dysfunction and death more than 7 days. Administration of tPA caused the loss of tight junction proteins, zona occulden-1 and occludin, and up-regulation of matrix metalloproteinase-2/9, in a ProTα-reversible manner. P6Q administration abolished tPA (4.5 h)-induced hemorrhage and reversed tPA (6 h)-induced vascular damage and matrix metalloproteinase-2 and 9 up-regulation. Twice administrations of P6Q at 2 h alone and 6 h with tPA significantly improved motor dysfunction more than 7 days. In photochemically induced thrombosis ischemia, similar vascular leakage and neuronal damage (infarction and motor dysfunction) by late tPA (4.5 or 6 h) were also inhibited by P6Q. Thus, these studies suggest that co-administration with ProTα or P6Q would be beneficial to inhibit delayed tPA-induced hemorrhagic mechanisms in acute ischemic stroke.

Iron Overload Exacerbates the Risk of Hemorrhagic Transformation After tPA (Tissue-Type Plasminogen Activator) Administration in Thromboembolic Stroke Mice

Background and Purpose- Recanalization with tPA (tissue-type plasminogen activator) is the only pharmacological therapy available for patients with ischemic stroke. However, the percentage of patients who may receive this therapy is limited by the risk of hemorrhagic transformation (HT)-the main complication of ischemic stroke. Our aim is to establish whether iron overload affects HT risk, to identify mechanisms that could help to select patients and to prevent this devastating complication. Methods- Mice fed with control or high-iron diet were subjected to thromboembolic stroke, with or without tPA therapy at different times after occlusion. Blood samples were collected for determination of malondialdehyde, matrix metalloproteinases, and fibronectin. Brain samples were collected 24 hours after occlusion to determine brain infarct and edema size, hemorrhage extension, IgG extravasation, and inflammatory and oxidative markers (neutrophil infiltration, 4-hydroxynonenal, and matrix metalloproteinase-9 staining). Results- Despite an increased rate of recanalization, iron-overload mice showed less neuroprotection after tPA administration. Importantly, iron overload exacerbated the risk of HT after early tPA administration, accelerated ischemia-induced serum matrix metalloproteinase-9 increase, and enhanced basal serum lipid peroxidation. High iron increased brain lipid peroxidation at most times and neutrophil infiltration at the latest time studied. Conclusions- Our data showing that iron overload increases the death of the compromised tissues, accelerates the time of tPA-induced reperfusion, and exacerbates the risk of HT may have relevant clinical implications for a safer thrombolysis. Patients with stroke with iron overload might be at high risk of HT after fibrinolysis, and, therefore, clinical studies must be performed to confirm our results.