Tissue plasminogen activator (t-PA) promotes neutrophil degranulation and MMP-9 release

Effects of Lithium Ions on tPA-Induced Hemorrhagic Transformation under Stroke

Thrombolytic therapy with the tissue plasminogen activator (tPA) is a therapeutic option for acute ischemic stroke. However, this approach is subject to several limitations, particularly the increased risk of hemorrhagic transformation (HT). Lithium salts show neuroprotective effects in stroke, but their effects on HT mechanisms are still unknown. In our study, we use the models of photothrombosis (PT)-induced brain ischemia and oxygen-glucose deprivation (OGD) to investigate the effect of Li+ on tPA-induced changes in brain and endothelial cell cultures. We found that tPA did not affect lesion volume or exacerbate neurological deficits but disrupted the blood-brain barrier. We demonstrate that poststroke treatment with Li+ improves neurological status and increases blood-brain barrier integrity after thrombolytic therapy. Under conditions of OGD, tPA treatment increased MMP-2/9 levels in endothelial cells, and preincubation with LiCl abolished this MMP activation. Moreover, we observed the effect of Li+ on glycolysis in tPA-treated endothelial cells, which we hypothesized to have an effect on MMP expression.

Tissue-plasminogen activator effects on the phenotype of splenic myeloid cells in acute inflammation

Tissue-plasminogen activator (tPA) is a serine protease well known for its fibrinolytic function. Recent studies indicate that tPA could also modulate inflammation via plasmin generation and/or by receptor mediated signalling in vitro. However, the contribution of tPA in inflammatory processes in vivo has not been fully addressed. Therefore, using tPA-deficient mice, we have analysed the effect of lipopolysaccharide (LPS) challenge on the phenotype of myeloid cells including neutrophils, macrophages and dendritic cells (DCs) in spleen. We found that LPS treatment upregulated the frequency of major histocompatibility class two (MHCII+) macrophages but also, paradoxically, induced a deep downregulation of MHCII molecule level on macrophages and on conventional dendritic cells 2 (cDC2). Expression level of the CD11b integrin, known as a tPA receptor, was upregulated by LPS on MHCII+ macrophages and cDC2, suggesting that tPA effects could be amplified during inflammation. In tPA-/- mice under inflammatory conditions, expression of costimulatory CD86 molecules on MHCII+ macrophages was decreased compared to WT mice, while in steady state the expression of MHCII molecules was higher on macrophages. Finally, we reported that tPA deficiency slightly modified the phenotype of DCs and T cells in acute inflammatory conditions. Overall, our findings indicate that in vivo, LPS injection had an unexpectedly bimodal effect on MHCII expression on macrophages and DCs that consequently might affect adaptive immunity. tPA could also participate in the regulation of the T cell response by modulating the levels of CD86 and MHCII molecules on macrophages.

Neutrophil activation in patients treated with endovascular therapy is associated with unfavorable outcomes and mitigated by intravenous thrombolysis

BACKGROUND

Accumulating evidence indicates that neutrophil activation (NA) contributes to microvascular thromboinflammation in acute ischemic stroke (AIS) due to a large vessel occlusion. Preclinical data have suggested that intravenous thrombolysis (IVT) before endovascular therapy (EVT) could dampen microvascular thromboinflammation. In this study we investigated the association between NA dynamics and stroke outcome, and the impact of IVT on NA in patients with AIS treated with EVT.

METHODS

A single-center prospective study was carried out, including patients treated with EVT for whom three blood samples (before, within 1 hour, 24 hours post-EVT) were drawn to measure plasma myeloperoxidase (MPO) concentration as a marker of NA. Unfavorable outcome was defined as a modified Rankin score of 3-6 at 3 months.

RESULTS

Between 2016 and 2020, 179 patients were included. The plasma MPO concentration peaked significantly 1 hour post-EVT (median increase 21.0 ng/mL (IQR -2.1-150)) and returned to pre-EVT baseline values 24 hours after EVT (median change from baseline -0.8 ng/mL (IQR -7.6-6.7)). This peak was strongly associated with unfavorable outcomes at 3 months (aOR 0.53 (95% CI 0.34 to 0.84), P=0.007). IVT before EVT abolished this 1 hour post-EVT MPO peak. Changes in plasma MPO concentration (baseline to 1 hour post-EVT) were associated with unfavorable outcomes only in patients not treated with IVT before EVT (aOR 0.54 (95% CI 0.33 to 0.88, P=0.013). However, we found no significant heterogeneity in the associations between changes in plasma MPO concentration and outcomes.

CONCLUSIONS

A peak in plasma MPO concentration occurs early after EVT and is associated with unfavorable outcomes. IVT abolished the post-EVT MPO peak and may modulate the association between NA and outcomes.

Transient plasticity response is regulated by histone deacetylase inhibitor in oxygen-glucose deprivation condition

BACKGROUND

The pathological form of synaptic plasticity, ischemic long-term potentiation (iLTP), induced by oxygen and glucose deprivation (OGD), is implicated in the acute phase of stroke with the potentiation of N-methyl-D-aspartate receptor (NMDAR). While there has been widespread attention on the excitatory system, a recent study reported that γ-aminobutyric acid (GABA)ergic system is also involved in iLTP. Valproic acid (VPA), a histone deacetylase inhibitor, protects against ischemic damage. However, whether VPA regulates early phase plasticity in ischemic stroke remains unknown. The present study aims to investigate the potential role and mechanism of VPA in ischemic stroke.

METHODS

A brief exposure of OGD on the hippocampal slices and the induction of photothrombotic ischemia (PTI) were used as ex vivo and in vivo models of ischemic stroke, respectively.

RESULTS

Using extracellular recordings, iLTP was induced in the hippocampal Schaffer collateral pathway following OGD exposure. VPA treatment abolished hippocampal iLTP via GABAA receptor enhancement and extracellular signal-regulated kinase (ERK) phosphorylation. Administration of VPA reduced brain infarct volume and motor dysfunction in mice with PTI. Moreover, VPA protected against ischemic injury by upregulating the GABAergic system and ERK phosphorylation, as well as by reducing of matrix metalloproteinase in a PTI-induced ischemic stroke model.

CONCLUSIONS

Together, this study revealed the protection of VPA in ex vivo OGD-induced pathological form of neuroplasticity and in vivo PTI-induced brain damage and motor dysfunction through rescuing GABAergic deficiency and the pathological hallmarks of ischemia.

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.

Bibliometric and visualization analysis of matrix metalloproteinases in ischemic stroke from 1992 to 2022

Background

Matrix metalloproteinases (MMPs) are important players in the complex pathophysiology of ischemic stroke (IS). Recent studies have shown that tremendous progress has been made in the research of MMPs in IS. However, a comprehensive bibliometric analysis is lacking in this research field. This study aimed to introduce the research status as well as hotspots and explore the field of MMPs in IS from a bibliometric perspective.

Methods

This study collected 1,441 records related to MMPs in IS from 1979 to 2022 in the web of science core collection (WoSCC) database, among them the first paper was published in 1992. CiteSpace, VOSviewer, and R package "bibliometrix" software were used to analyze the publication type, author, institution, country, keywords, and other relevant data in detail, and made descriptive statistics to provide new ideas for future clinical and scientific research.

Results

The change in the number of publications related to MMPs in IS can be divided into three stages: the first stage was from 1992 to 2012, when the number of publications increased steadily; the second stage was from 2013 to 2017, when the number of publications was relatively stable; the third stage was from 2018 to 2022, when the number of publications began to decline. The United States and China, contributing more than 64% of publications, were the main drivers for research in this field. Universities in the United States were the most active institutions and contributed the most publications. STROKE is the most popular journal in this field with the largest publications as well as the most co-cited journal. Rosenberg GA was the most prolific writer and has the most citations. "Clinical," "Medical," "Neurology," "Immunology" and "Biochemistry molecular biology" were the main research areas of MMPs in IS. "Molecular regulation," "Metalloproteinase-9 concentration," "Clinical translation" and "Cerebral ischemia-reperfusion" are the primary keywords clusters in this field.

Conclusion

This is the first bibliometric study that comprehensively mapped out the knowledge structure and development trends in the research field of MMPs in IS in recent 30 years, which will provide a reference for scholars studying this field.

Delivery of mitochondria-containing extracellular vesicles to the BBB for ischemic stroke therapy

INTRODUCTION

Ischemic stroke-induced mitochondrial dysfunction in brain endothelial cells (BECs) leads to breakdown of the blood-brain barrier (BBB) causing long-term neurological dysfunction. Restoration of mitochondrial function in injured BECs is a promising therapeutic strategy to alleviate stroke-induced damage. Mounting evidence demonstrate that selected subsets of cell-derived extracellular vehicles (EVs), such as exosomes (EXOs) and microvesicles (MVs), contain functional mitochondrial components. Therefore, development of BEC-derived mitochondria-containing EVs for delivery to the BBB will (1) alleviate mitochondrial dysfunction and limit long-term neurological dysfunction in ischemic stroke and (2) provide an alternative therapeutic option for treating numerous other diseases associated with mitochondrial dysfunction.

AREA COVERED

This review will discuss (1) how EV subsets package different types of mitochondrial components during their biogenesis, (2) mechanisms of EV internalization and functional mitochondrial responses in the recipient cells, and (3) EV biodistribution and pharmacokinetics - key factors involved in the development of mitochondria-containing EVs as a novel BBB-targeted stroke therapy.

EXPERT OPINION

Mitochondria-containing MVs have demonstrated therapeutic benefits in ischemic stroke and other pathologies associated with mitochondrial dysfunction. Delivery of MV mitochondria to the BBB is expected to protect the BBB integrity and neurovascular unit post-stroke. MV mitochondria quality control, characterization, mechanistic understanding of its effects in vivo, safety and efficacy in different preclinical models, large-scale production, and establishment of regulatory guidelines are foreseeable milestones to harness the clinical potential of MV mitochondria delivery.

Matrix Metalloproteinases in Cardioembolic Stroke: From Background to Complications

Matrix metalloproteinases (MMPs) are endopeptidases participating in physiological processes of the brain, maintaining the blood-brain barrier integrity and playing a critical role in cerebral ischemia. In the acute phase of stroke activity, the expression of MMPs increase and is associated with adverse effects, but in the post-stroke phase, MMPs contribute to the process of healing by remodeling tissue lesions. The imbalance between MMPs and their inhibitors results in excessive fibrosis associated with the enhanced risk of atrial fibrillation (AF), which is the main cause of cardioembolic strokes. MMPs activity disturbances were observed in the development of hypertension, diabetes, heart failure and vascular disease enclosed in CHA₂DS₂VASc score, the scale commonly used to evaluate the risk of thromboembolic complications risk in AF patients. MMPs involved in hemorrhagic complications of stroke and activated by reperfusion therapy may also worsen the stroke outcome. In the present review, we briefly summarize the role of MMPs in the ischemic stroke with particular consideration of the cardioembolic stroke and its complications. Moreover, we discuss the genetic background, regulation pathways, clinical risk factors and impact of MMPs on the clinical outcome.

Endotypes of chronic rhinosinusitis based on inflammatory and remodeling factors

BACKGROUND

Previous studies on the endotyping of chronic rhinosinusitis (CRS) that were based on inflammatory factors have broadened our understanding of the disease. However, the endotype of CRS combined with inflammatory and remodeling features has not yet been clearly elucidated.

OBJECTIVE

We sought to identify the endotypes of patients with CRS according to inflammatory and remodeling factors.

METHODS

Forty-eight inflammatory and remodeling factors in the nasal mucosal tissues of 128 CRS patients and 24 control subjects from northern China were analyzed by Luminex, ELISA, and ImmunoCAP. Sixteen factors were used to perform the cluster analysis. The characteristics of each cluster were analyzed using correlation analysis and validated by immunofluorescence staining.

RESULTS

Patients were classified into 5 clusters. Clusters 1 and 2 showed non-type 2 signatures with low biomarker concentrations, except for IL-19 and IL-27. Cluster 3 involved a low type 2 endotype with the highest expression of neutrophil factors, such as granulocyte colony-stimulating factor, IL-8, and myeloperoxidase, and remodeling factors, such as matrix metalloproteinases and fibronectin. Cluster 4 exhibited moderate type 2 inflammation. Cluster 5 exhibited high type 2 inflammation, which was associated with relatively higher levels of neutrophil and remodeling factors. The proportion of CRS with nasal polyps, asthma, allergies, anosmia, aspirin sensitivity, and the recurrence of CRS increased from clusters 1 to 5.

CONCLUSION

Diverse inflammatory mechanisms result in distinct CRS endotypes and remodeling profiles. The explicit differentiation and accurate description of these endotypes will guide targeted treatment decisions.

S100b in acute ischemic stroke clots is a biomarker for post-thrombectomy intracranial hemorrhages

Background and purpose

Post-thrombectomy intracranial hemorrhages (PTIH) are dangerous complications of acute ischemic stroke (AIS) following mechanical thrombectomy. We aimed to investigate if S100b levels in AIS clots removed by mechanical thrombectomy correlated to increased risk of PTIH.

Methods

We analyzed 122 thrombi from 80 AIS patients in the RESTORE Registry of AIS clots, selecting an equal number of patients having been pre-treated or not with rtPA (40 each group). Within each subgroup, 20 patients had developed PTIH and 20 patients showed no signs of hemorrhage. Gross photos of each clot were taken and extracted clot area (ECA) was measured using ImageJ. Immunohistochemistry for S100b was performed and Orbit Image Analysis was used for quantification. Immunofluorescence was performed to investigate co-localization between S100b and T-lymphocytes, neutrophils and macrophages. Chi-square or Kruskal-Wallis test were used for statistical analysis.

Results

PTIH was associated with higher S100b levels in clots (0.33 [0.08-0.85] vs. 0.07 [0.02-0.27] mm², H1 = 6.021, P = 0.014^*), but S100b levels were not significantly affected by acute thrombolytic treatment (P = 0.386). PTIH was also associated with patients having higher NIHSS at admission (20.0 [17.0-23.0] vs. 14.0 [10.5-19.0], H1 = 8.006, P = 0.005) and higher number of passes during thrombectomy (2 [1-4] vs. 1 [1-2.5], H1 = 5.995, P = 0.014^*). S100b co-localized with neutrophils, macrophages and with T-lymphocytes in the clots.

Conclusions

Higher S100b expression in AIS clots, higher NIHSS at admission and higher number of passes during thrombectomy are all associated with PTIH. Further investigation of S100b expression in AIS clots by neutrophils, macrophages and T-lymphocytes could provide insight into the role of S100b in thromboinflammation.

Platelet-to-Neutrophil Ratio is Related to Hemorrhagic Transformation in Patients With Acute Cerebral Infarction

BACKGROUND

As a common complication of cerebral infarction, hemorrhagic transformation (HT) often indicates a worse clinical outcome. The aim of this study was to explore the relationship between the platelet-to-neutrophil ratio (PNR) and HT in patients with acute cerebral infarction.

METHODS

Patients with HT after acute cerebral infarction were enrolled in the HT group. Matched patients with acute cerebral infarction without HT were enrolled at the same time. All patients included in this study did not receive reperfusion therapy. The PNR was obtained on the second day of admission. Multivariate logistic analysis was used to evaluate the relationship between the PNR and HT.

RESULTS

We collected data from a total of 137 patients: 61 patients with HT and 76 patients without HT. After adjusting for confounders, the PNR was independently associated with HT (odds ratio=0.922, 95% confidence interval: 0.891-0.955, P <0.05). The receiver operating characteristic curve demonstrated that the PNR could better predict HT (area under the curve=0.808, 95% confidence interval: 0.735-0.882, P <0.05). When the cut-off value of the PNR was 50.4765, the sensitivity was 70.5%, and the specificity was 82.9%. After stratifying the PNR to 50.4765, logistic analysis was performed again. The risk of HT in patients with a low PNR was 12.995 times that of patients with a high PNR. In patients without atrial fibrillation, the PNR was still independently related to HT.

CONCLUSIONS

The PNR is a predictor of HT, and patients with a low PNR have a higher risk of HT.

Annexin V-Modified Platelet-Biomimetic Nanomedicine for Targeted Therapy of Acute Ischemic Stroke

Thromboembolic stroke is typically characterized by the activation of platelets, resulting in thrombus in the cerebral vascular system, leading to high morbidity and mortality globally. Intravenous thrombolysis by tissue plasminogen activator (tPA) administration within 4.5 h from the onset of symptoms is providing a standard therapeutic strategy for ischemic stroke, but this reagent simultaneously shows potential serious adverse effects, e.g., hemorrhagic transformation. Herein, a novel delivery platform based on Annexin V and platelet membrane is developed for tPA (APLT-PA) to enhance targeting efficiency, therapeutic effects, and reduce the risk of intracerebral hemorrhage in acute ischemic stroke. After preparation by extrusion of platelet membrane and subsequent insertion of Annexin V to liposomes, APLT-PA exhibits a high targeting efficiency to activated platelet in vitro and thrombosis site in vivo, due to the binding to phosphatidylserine (PS) and activated platelet membrane proteins. One dose of APLT-PA leads to obvious thrombolysis and significant improvement of neurological function within 7 days in mice with photochemically induced acute ischemic stroke. This study provides a novel, safe platelet-biomimetic nanomedicine for precise thrombolytic treatment of acute ischemic stroke, and offers new theories for the design and exploitation of cell-mimetic nanomedicine for diverse biomedical applications.

Neuroinflammation, Stroke, Blood-Brain Barrier Dysfunction, and Imaging Modalities

Maintaining blood-brain barrier (BBB) integrity is crucial for the homeostasis of the central nervous system. Structurally comprising the BBB, brain endothelial cells interact with pericytes, astrocytes, neurons, microglia, and perivascular macrophages in the neurovascular unit. Brain ischemia unleashes a profound neuroinflammatory response to remove the damaged tissue and prepare the brain for repair. However, the intense neuroinflammation occurring during the acute phase of stroke is associated with BBB breakdown, neuronal injury, and worse neurological outcomes. Here, we critically discuss the role of neuroinflammation in ischemic stroke pathology, focusing on the BBB and the interactions between central nervous system and peripheral immune responses. We highlight inflammation-driven injury mechanisms in stroke, including oxidative stress, increased MMP (matrix metalloproteinase) production, microglial activation, and infiltration of peripheral immune cells into the ischemic tissue. We provide an updated overview of imaging techniques for in vivo detection of BBB permeability, leukocyte infiltration, microglial activation, and upregulation of cell adhesion molecules following ischemic brain injury. We discuss the possibility of clinical implementation of imaging modalities to assess stroke-associated neuroinflammation with the potential to provide image-guided diagnosis and treatment. We summarize the results from several clinical studies evaluating the efficacy of anti-inflammatory interventions in stroke. Although convincing preclinical evidence suggests that neuroinflammation is a promising target for ischemic stroke, thus far, translating these results into the clinical setting has proved difficult. Due to the dual role of inflammation in the progression of ischemic damage, more research is needed to mechanistically understand when the neuroinflammatory response begins the transition from injury to repair. This could have important implications for ischemic stroke treatment by informing time- and context-specific therapeutic interventions.

Risk of Venous Thromboembolism in Hospitalized Patients with Acute Ischemic Stroke Versus Other Neurological Conditions

BACKGROUND

The mechanism of increased risk of venous thromboembolism (VTE) after acute ischemic stroke (AIS) is unclear. In this study, we aimed to evaluate the risk of VTE in hospitalizations due to AIS as compared to those due to non-vascular neurological conditions. We also aimed to assess any potential association between VTE risk and the use of intravenous thrombolysis (rtPA) among hospitalizations with AIS.

MATERIALS AND METHODS

In this case-control study, data were obtained from the Nationwide Inpatient Sample 2016-2018. Propensity score matching was used to adjust for the baseline differences between the groups. Logistic regression analysis was used to compare the risk of VTE.

RESULTS

We identified 1,541,685 hospitalizations due to AIS and 1,453,520 hospitalizations due to non-vascular neurological diagnoses that served as controls. After propensity score matching, 640,560 cases with AIS and corresponding well-matched controls were obtained. Hospitalizations due to AIS had higher odds of VTE as compared to the controls [odds ratio (OR) 1.50, 95% confidence interval (CI) 1.40-1.60, P<0.001]. Among hospitalizations with AIS, 184,065 (11.9%) got rtPA. The odds of VTE were lower among the AIS hospitalizations that received rtPA as compared to those that did not (OR 0.89, 95% CI 0.79-0.99, P0.035).

CONCLUSION

Hospitalizations due to AIS have a higher risk of VTE as compared to the non-vascular neurological controls. Among AIS cases, the risk of VTE is lower among patients treated with rtPA. These epidemiological findings support the hypothesis that the risk of VTE after AIS might be partly mediated by an intrinsic pro-coagulant state.

CSF and serum inflammatory response and association with outcomes in spontaneous intracerebral hemorrhage with intraventricular extension: an analysis of the CLEAR-III Trial

Background

Intracerebral hemorrhage (ICH) results in a cascade of inflammatory cell activation with recruitment of peripheral leukocytes to the brain parenchyma and surrounding the hematoma. We hypothesized that in patients with ICH and intraventricular hemorrhage (IVH), a robust cerebrospinal fluid (CSF) inflammatory response occurs with leukocyte subtypes being affected by alteplase treatment and contributing to outcomes.

Methods

Serum and CSF cell counts from patients in the phase 3 Clot Lysis: Evaluating Accelerated Resolution of Intraventricular Hemorrhage (CLEAR III) trial were analyzed. CSF leukocytes were corrected for the presence of red blood cells. Trends in cell counts were plotted chronologically. Associations were evaluated between serum and CSF leukocyte subtypes and adjudicated functional outcome (modified Rankin Scale; mRS) at 30 and 180 days and bacterial infection according to treatment with intraventricular alteplase versus saline.

Results

A total of 279 and 292 patients had ≥3 differential cell counts from serum and CSF, respectively. CSF leukocyte subtypes evolved during IVH resolution with a significantly augmented inflammatory response for all subtypes in alteplase- compared to saline-treated patients. CSF leukocyte subtypes were not associated with detrimental effect on functional outcomes in the full cohort, but all were associated with poor 30-day outcome in saline-treated patients with IVH volume ≥20 mL. Higher serum lymphocytes were associated with good functional outcomes (mRS 0–3) in the entire cohort and saline-treated but not alteplase-treated group. Conversely, increased serum neutrophil-to-lymphocyte ratio (NLR) in the entire cohort and saline group was associated with worse functional outcomes. Higher median serum lymphocytes were associated with the absence of infection at 7 days.

Conclusions

Aseptic CSF inflammation after IVH involves all leukocyte subtypes. Serum lymphocytes may be associated with better outcomes by mitigating infection. Alteplase augments the inflammatory response without affecting outcomes.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-021-02224-w.

RP11-362K2.2:RP11-767I20.1 Genetic Variation Is Associated with Post-Reperfusion Therapy Parenchymal Hematoma. A GWAS Meta-Analysis

Stroke is one of the most common causes of death and disability. Reperfusion therapies are the only treatment available during the acute phase of stroke. Due to recent clinical trials, these therapies may increase their frequency of use by extending the time-window administration, which may lead to an increase in complications such as hemorrhagic transformation, with parenchymal hematoma (PH) being the more severe subtype, associated with higher mortality and disability rates. Our aim was to find genetic risk factors associated with PH, as that could provide molecular targets/pathways for their prevention/treatment and study its genetic correlations to find traits sharing genetic background. We performed a GWAS and meta-analysis, following standard quality controls and association analysis (fastGWAS), adjusting age, NIHSS, and principal components. FUMA was used to annotate, prioritize, visualize, and interpret the meta-analysis results. The total number of patients in the meta-analysis was 2034 (216 cases and 1818 controls). We found rs79770152 having a genome-wide significant association (beta 0.09, p-value 3.90 × 10⁻⁸) located in the RP11-362K2.2:RP11-767I20.1 gene and a suggestive variant (rs13297983: beta 0.07, p-value 6.10 × 10⁻⁸) located in PCSK5 associated with PH occurrence. The genetic correlation showed a shared genetic background of PH with Alzheimer’s disease and white matter hyperintensities. In addition, genes containing the ten most significant associations have been related to aggregated amyloid-β, tau protein, white matter microstructure, inflammation, and matrix metalloproteinases.

Eosinophil-to-Neutrophil Ratio Predicts Poor Prognosis of Acute Ischemic Stroke Patients Treated With Intravenous Thrombolysis

Background and Purpose: The eosinophil-to-neutrophil ratio (ENR) was recently reported as a novel inflammatory marker in acute ischemic stroke (AIS). However, few studies reported the predictive value of ENR in AIS patients, especially for those with intravenous thrombolysis.

Methods: Two hundred sixty-six AIS patients receiving intravenous thrombolysis were retrospectively recruited in this study and followed up for 3 months and 1 year. The Modified Rankin Scale (mRS) and the time of death were recorded. Poor outcome was defined as mRS 3–6. After excluding patients who were lost to follow-up, the remaining 250 patients were included in the 3-month prognosis analysis and the remaining 223 patients were included in the 1-year prognosis analysis.

Results: ENR levels in the patients were lower than those in the healthy controls. The optimal cutoff values for the ability of ENR × 10² to predict 3-month poor outcome were 0.74 with 67.8% sensitivity and 77.3% specificity. Patients with ENR × 10² ≥ 0.74 have a lower baseline National Institutes of Health Stroke Scale (NIHSS) score (median: 7 vs. 11, p < 0.001). After multivariate adjustment, patients with ENR × 10² ≥ 0.74 were more likely to come to a better 3-month outcome (OR = 0.163; 95% CI, 0.076–0.348, p < 0.001). At the 1-year follow-up, the patients with ENR × 10² ≥ 0.74 showed a lower risk of mortality (HR = 0.314; 95% CI, 0.135–0.731; p = 0.007).

Conclusions: A lower ENR is independently associated with a 3-month poor outcome and a 3-month and 1-year mortality in AIS patients treated with intravenous thrombolysis.

Systemic Immune-Inflammation Index Predicts 3-Month Functional Outcome in Acute Ischemic Stroke Patients Treated with Intravenous Thrombolysis

Background and Purpose

Systemic immune-inflammation index (SII), a novel inflammation index derived from counts of circulating platelets, neutrophils and lymphocytes, has been studied in developing incident cancer. However, the clinical value of SII in acute ischemic stroke (AIS) patients had not been further investigated. Therefore, we aimed to explore the association between SII and severity of stroke as well as 3-month outcome of AIS patients.

Methods

A total of 216 AIS patients receiving intravenous thrombolysis (IVT) and 875 healthy controls (HCs) were retrospectively recruited. Blood samples were collected within 24h after admission. Severity of stroke was assessed by the National Institute of Health stroke scale (NIHSS) scores on admission and poor 3-month functional outcome was defined as Modified Rankin Scale (mRS) > 2.

Results

SII levels in AIS patients were higher than in HCs. The cut-off value of SII is 545.14×10⁹/L. Patients with SII > 545.14×10⁹/L had higher NIHSS scores (median: 5 vs 9, p < 0.001), a positive correlation between SII and NIHSS was observed (rs = 0.305, p < 0.001). Multivariate logistic regression analyses showed that high SII was one of the independent risk factors for poor prognosis at 3 months of AIS patients (OR = 3.953, 95% CI = 1.702-9.179, p = 0.001). The addition of SII to the conventional prognostic model improved the reclassification (but not discrimination) of the functional outcome (net reclassification index 39.3%, p = 0.007).

Conclusion

SII is correlated with stroke severity at admission and can be a novel prognostic biomarker for AIS patients treated with IVT.

Hemorrhagic Transformation in Ischemic Stroke and the Role of Inflammation

Hemorrhagic transformation (HT) is a common complication in patients with acute ischemic stroke. It occurs when peripheral blood extravasates across a disrupted blood brain barrier (BBB) into the brain following ischemic stroke. Preventing HT is important as it worsens stroke outcome and increases mortality. Factors associated with increased risk of HT include stroke severity, reperfusion therapy (thrombolysis and thrombectomy), hypertension, hyperglycemia, and age. Inflammation and the immune system are important contributors to BBB disruption and HT and are associated with many of the risk factors for HT. In this review, we present the relationship of inflammation and immune activation to HT in the context of reperfusion therapy, hypertension, hyperglycemia, and age. Differences in inflammatory pathways relating to HT are discussed. The role of inflammation to stratify the risk of HT and therapies targeting the immune system to reduce the risk of HT are presented.

Inhibition of hypoxia inducible factor 1 by YC-1 attenuates tissue plasminogen activator induced hemorrhagic transformation by suppressing HMGB1/TLR4/NF-κB mediated neutrophil infiltration in thromboembolic stroke rats

Hemorrhagic transformation (HT) is a frequent complication of ischemic stroke after thrombolytic therapy and seriously affects the prognosis of stroke. Due to the limited therapeutic window and hemorrhagic complications, tissue plasminogen activator (t-PA) is underutilized in acute ischemic stroke. Currently, there are no clinically effective drugs to decrease the incidence of t-PA-induced HT. Hypoxia-inducible factor 1 (HIF-1) is an important transcription factor that maintains oxygen homeostasis and mediates neuroinflammation under hypoxia. However, the effect of HIF-1 on t-PA-induced HT is not clear. The aim of this study was to investigate the role of HIF-1 in t-PA-induced HT by applying YC-1, an inhibitor of HIF-1. In the present study, we found that HIF-1 expression was significantly increased in ischemic brain tissue after delayed t-PA treatment and was mainly localized in neurons and endothelial cells. Inhibition of HIF-1 by YC-1 improved infarct volume and neurological deficits. YC-1 inhibited matrix metalloproteinase protein expression, increased tight junction protein expression, and ameliorated BBB disruption and the occurrence of HT. Furthermore, YC-1 suppressed the release of inflammatory factors, neutrophil infiltration and the activation of the HMGB1/TLR4/NF-κB signaling pathway. These results demonstrated that inhibition of HIF-1 could protect BBB integrity by suppressing HMGB1/TLR4/NF-κB-mediated neutrophil infiltration, thereby reducing the risk of t-PA-induced HT. Thus, HIF-1 may be a potential therapeutic target for t-PA-induced HT.

Regulatory T cells in ischemic stroke

The pathophysiological mechanisms of neuroinflammation, angiogenesis, and neuroplasticity are currently the hotspots of researches in ischemic stroke. Regulatory T cells (Tregs), a subset of T cells that control inflammatory and immune responses in the body, are closely related to the pathogenesis of ischemic stroke. They participate in the inflammatory response and neuroplasticity process of ischemic stroke by various mechanisms, such as secretion of anti‐inflammatory factors, inhibition of pro‐inflammatory factors, induction of cell lysis, production of the factors that promote neural regeneration, and modulation of microglial and macrophage polarization. However, it remains unclear whether Tregs play a beneficial or deleterious role in ischemic stroke and the effect of Tregs in different stages of ischemic stroke. Here, we discuss the dynamic changes of Tregs at various stages of experimental and clinical stroke, the potential mechanisms under Tregs in regulating stroke and the preclinical studies of Tregs‐related treatments, in order to provide a reference for clinical treatment.

Variants of WNT7A and GPR124 are associated with hemorrhagic transformation following intravenous thrombolysis in ischemic stroke

AIMS

The canonical Wnt signaling pathway plays an essential role in blood-brain barrier integrity and intracerebral hemorrhage in preclinical stroke models. Here, we sought to explore the association between canonical Wnt signaling and hemorrhagic transformation (HT) following intravenous thrombolysis (IVT) in acute ischemic stroke (AIS) patients as well as to determine the underlying cellular mechanisms.

METHODS

355 consecutive AIS patients receiving IVT were included. Blood samples were collected on admission, and HT was detected at 24 hours after IVT. 117 single-nucleotide polymorphisms (SNPs) of 28 Wnt signaling genes and exon sequences of 4 core cerebrovascular Wnt signaling components (GPR124, RECK, FZD4, and CTNNB1) were determined using a customized sequencing chip. The impact of identified genetic variants was further studied in HEK 293T cells using cellular and biochemical assays.

RESULTS

During the study period, 80 patients experienced HT with 27 parenchymal hematoma (PH). Compared to the non-PH patients, WNT7A SNPs (rs2163910, P = .001, OR 2.727; rs1124480, P = .002, OR 2.404) and GPR124 SNPs (rs61738775, P = .012, OR 4.883; rs146016051, P < .001, OR 7.607; rs75336000, P = .044, OR 2.503) were selectively enriched in the PH patients. Interestingly, a missense variant of GPR124 (rs75336000, c.3587G>A) identified in the PH patients resulted in a single amino acid alteration (p.Cys1196Tyr) in the intracellular domain of GPR124. This variant substantially reduced the activity of WNT7B-induced canonical Wnt signaling by decreasing the ability of GPR124 to recruit cytoplasmic DVL1 to the cellular membrane.

CONCLUSION

Variants of WNT7A and GPR124 are associated with increased risk of PH in patients with AIS after intravenous thrombolysis, likely through regulating the activity of canonical Wnt signaling.

Low-soluble TREM-like transcript-1 levels early after severe burn reflect increased coagulation disorders and predict 30-day mortality

BACKGROUND

Patients with severe burns often show systemic coagulation changes in the early stage and even develop extensive coagulopathy. Previous studies have confirmed that soluble TREM-like transcript-1 (sTLT-1) mediates a novel mechanism of haemostasis and thrombosis in inflammatory vascular injury. At present, the role of sTLT-1 in patients with severe burns is not well known.

OBJECTIVE

To investigate the early association between sTLT-1 levels and markers of burn severity, coagulation disorders, endothelial permeability, shock and prognosis in patients with severe burns.

METHODS

A prospective, observational study was conducted with 60 severe burn patients (divided into a death group and a survival group according to 30-day prognosis) admitted to our hospital. Twenty-eight healthy volunteers were recruited as the control group. Blood components at 48 h after burn were analysed for sTLT-1 and biomarkers reflecting platelet activation, shock, endothelial glycocalyx damage, capillary leakage, haemostasis, fibrinolytic activity, natural anticoagulation and blood cells. We compared the three groups, analysed the correlation between sTLT-1 and biomarkers, and investigated the predictive value of sTLT-1 for 30-day prognosis.

RESULT

Compared with the surviving patients, the patients who died had a lower degree of platelet activation [lower sTLT-1, platelet factor 4 (PF-4) and platelet counts] and a higher degree of burn [higher abbreviated burn severity index score (ABSI score)], shock (higher lactate), endothelial glycocalyx damage [higher syndecan-1 and soluble thrombomodulin (sTM)] and capillary leakage [higher resuscitation fluid (0-48 h), lower albumin] as well as decreased haemostasis [higher activated partial prothrombin time (APTT), lower fibrinogen and thrombin-antithrombin III complex (TAT)], increased fibrinolytic activity [higher D-dimer and tissue-type plasminogen activator (tPA)] and decreased natural anticoagulation [lower protein C (PC) and protein S (PS)]. Higher D-dimer (P = 0.013) and lower PF-4 (P = 0.001) were significantly independently associated with lower sTLT-1. Low circulating sTLT-1 (a unit is 50 pg/mL) (odds ratio [OR] 2.08 [95% CI 1.11-3.92], P = 0.022) was an independent predictor of increased 30-day mortality.

CONCLUSION

Low sTLT-1 levels at 48 h after burn in patients with severe burns is associated with increased coagulation disorders. Low circulating sTLT-1 levels were an independent predictor of increased 30-day mortality.

Neuroinflammation in hemorrhagic transformation after tissue plasminogen activator thrombolysis: Potential mechanisms, targets, therapeutic drugs and biomarkers

Hemorrhagic transformation (HT) is a common and serious complication following ischemic stroke, especially after tissue plasminogen activator (t-PA) thrombolysis, which is associated with increased mortality and disability. Due to the unknown mechanisms and targets of HT, there are no effective therapeutic drugs to decrease the incidence of HT. In recent years, many studies have found that neuroinflammation is closely related to the occurrence and development of HT after t-PA thrombolysis, including glial cell activation in the brain, peripheral inflammatory cell infiltration and the release of inflammatory factors, involving inflammation-related targets such as NF-κB, MAPK, HMGB1, TLR4 and NLRP3. Some drugs with anti-inflammatory activity have been shown to protect the BBB and reduce the risk of HT in preclinical experiments and clinical trials, including minocycline, fingolimod, tacrolimus, statins and some natural products. In addition, the changes in MMP-9, VAP-1, NLR, sICAM-1 and other inflammatory factors are closely related to the occurrence of HT, which may be potential biomarkers for the diagnosis and prognosis of HT. In this review, we summarize the potential inflammation-related mechanisms, targets, therapeutic drugs, and biomarkers associated with HT after t-PA thrombolysis and discuss the relationship between neuroinflammation and HT, which provides a reference for research on the mechanisms, prevention and treatment drugs, diagnosis and prognosis of HT.

Direct arterial damage and neurovascular unit disruption by mechanical thrombectomy in a rat stroke model

Mechanical thrombectomy (MT) is a standard treatment for acute ischemic stroke that could cause hemorrhagic complications. We aimed to evaluate the pathology of MT-induced arterial damage and neurovascular unit (NVU) disruption in relation to tissue-type plasminogen activator (tPA) injection for acute ischemic stroke. We induced transient middle cerebral artery occlusion in male SHR/Izm rats for 2 hr. This was followed by reperfusion with/without tPA (3 mg/kg) and "rough suture" insertion that mimicked MT once or thrice (MT1 or MT3). Compared with the control group, the tPA + MT3 group presented with an increase in the cerebral infarct and hemorrhage with severer IgG leakage. Moreover, structural damage reaching the tunica media was detected in the MT3 and tPA + MT3 groups. The tPA + MT3 group presented with increased matrix metalloproteinase-9 (MMP-9) and vascular endothelial growth factor (VEGF) expression with some MMP9-positive cells expressing a neutrophil marker myeloperoxidase. Furthermore, basal lamina detachment from astrocyte foot processes was observed in the tPA + MT1 and tPA + MT3 groups. These findings suggest that MT causes direct arterial damage, as well as VEGF and MMP9 upregulation, which results in NVU disruption and hemorrhagic complications in acute ischemic stroke, especially when combined with tPA.

Analysis of the association of MPO and MMP-9 with stroke severity and outcome: Cohort study

OBJECTIVE

In acute cerebral ischemia, circulating neutrophil count and neutrophil-to-lymphocyte ratio (NLR) are positively associated with stroke severity and worse outcomes. Mediators of this effect are unknown. We aimed to investigate (1) the relationship between plasma matrix metalloproteinase-9 (MMP-9) and myeloperoxidase (MPO) concentrations with stroke severity and outcome and (2) MMP-9 and MPO release after ex vivo stimulation of neutrophils by recombinant tissue plasminogen activator (rtPA).

METHODS

We analyzed data collected in 255 patients with supratentorial cerebral infarcts recruited within 48 hours of symptoms onset irrespective of rtPA treatment. The endpoints were excellent outcome (modified Rankin Scale score 0-1), symptomatic intracerebral hemorrhage (European Cooperative Acute Stroke Study-II definition), and death at 3 months. The role of rtPA treatment on peripheral neutrophil degranulation was investigated in 18 patients within 4.5 hours and after 72 hours.

RESULTS

Neutrophil counts, NLR, and MPO plasma concentrations, but not MMP-9, were positively correlated with stroke severity. Higher neutrophil counts and NLR were independently associated with worse outcomes and higher mortality rates at month 3. Higher MPO plasma concentrations, but not MMP-9, were associated with worse outcome. Neutrophil-derived MMP-9, after ex vivo rtPA stimulation, but not MPO, were higher after 72 hours in patients treated by IV rtPA but not associated with hemorrhagic transformation.

CONCLUSIONS

Neutrophil counts, NLR, and MPO plasma concentrations are associated with worse outcome in patients with acute cerebral ischemia, in contrast to MMP-9. Further investigations are needed to deepen our knowledge on MPO's role in the deleterious effect of neutrophils because it could represent a potential therapeutic target.

Plasmin Cascade Mediates Thrombotic Events in SARS-CoV-2 Infection via Complement and Platelet-Activating Systems

Objective: Recently emerged beta-coronavirus SARS-CoV-2, has resulted in the current pandemic designated COVID-19. COVID-19 manifests as severe illness exhibiting systemic inflammatory response syndrome, acute respiratory distress syndrome (ARDS), thrombotic events, and shock, exacerbated further by co-morbidities and age. Recent clinical evidence suggests that the development of ARDS and subsequent pulmonary failure result from a complex interplay between cell types (endothelial, epithelial and immune) within the lung promoting inflammatory infiltration and a pro-coagulative state. How the complex molecular events mediated by SARS-CoV-2 in infected lung epithelial cells lead to thrombosis and pulmonary failure, is yet to be fully understood. Methods: We address these questions here, using publicly available transcriptomic data in the context of lung epithelia affected by SARS-CoV-2 and other respiratory infections, in vitro. We then extend our results to the understanding of in vivo lung, using a publicly available COVID-19 lung transcriptomic study. Results and Conclusions: Our analysis indicates that there exists a complex interplay between the fibrinolytic system particularly plasmin, and the complement and platelet-activating systems upon SARS-CoV-2 infection, with a potential for therapeutic intervention.

Extracellular matrix, regional heterogeneity of the aorta, and aortic aneurysm

Aortic aneurysm is an asymptomatic disease with dire outcomes if undiagnosed. Aortic aneurysm rupture is a significant cause of death worldwide. To date, surgical repair or endovascular repair (EVAR) is the only effective treatment for aortic aneurysm, as no pharmacological treatment has been found effective. Aortic aneurysm, a focal dilation of the aorta, can be formed in the thoracic (TAA) or the abdominal (AAA) region; however, our understanding as to what determines the site of aneurysm formation remains quite limited. The extracellular matrix (ECM) is the noncellular component of the aortic wall, that in addition to providing structural support, regulates bioavailability of an array of growth factors and cytokines, thereby influencing cell function and behavior that ultimately determine physiological or pathological remodeling of the aortic wall. Here, we provide an overview of the ECM proteins that have been reported to be involved in aortic aneurysm formation in humans or animal models, and the experimental models for TAA and AAA and the link to ECM manipulations. We also provide a comparative analysis, where data available, between TAA and AAA, and how aberrant ECM proteolysis versus disrupted synthesis may determine the site of aneurysm formation.

A review of aneurysm formation, swelling in blood vessel, in the aorta, examines distinctions between two forms of the condition and the role of proteins in the extracellular matrix which surrounds cells of the arterial wall. Rupture of aneurysms in the aorta, the body’s main artery, is a major cause of death. Researchers led by Zamaneh Kassiri at the University of Alberta, Edmonton, Canada, emphasize that aneurysms in the thoracic and abdominal regions of the aorta are distinct conditions with crucial differences in their causes. Disrupted production and assembly of the extracellular matrix and its proteins may underlie thoracic aneurysm formation. Factors triggering the degradation of extracellular matrix proteins may be more significant in abdominal aneurysms. Understanding the differing molecular mechanisms involved could help address the current lack of effective drug treatments for these dangerous conditions.

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.

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.

Fibrin Modulates Shear-Induced NETosis in Sterile Occlusive Thrombi Formed under Haemodynamic Flow

Neutrophils can release extracellular traps (NETs) in infectious, inflammatory and thrombotic diseases. NETs have been detected in deep vein thrombosis, atherothrombosis, stroke, disseminated intravascular coagulation and trauma. We have previously shown that haemodynamic forces trigger rapid NETosis within sterile occlusive thrombi in vitro. Here, we tested the effects of thrombin, fibrin and fibrinolysis on shear-induced NETosis by imaging NETs with Sytox Green during microfluidic perfusion of factor XIIa-inhibited or thrombin-inhibited human whole blood over fibrillar collagen (±tissue factor). For perfusions under venous pressure drops (19 mm Hg/mm-clot), thrombin generation did not alter the near-zero level of NET generation. In contrast, production of thrombin/fibrin led to a twofold reduction in neutrophil accumulation and a sixfold reduction in NET generation after 30 minutes of arterial perfusion (163 mm Hg/mm-clot). Exogenously added tissue type plasminogen activator (tPA) drove robust fibrinolysis; however, tPA did not trigger NETosis under venous flow. In contrast, tPA did enhance NET generation in clots subjected to arterial pressure drops. After 45 minutes of arterial perfusion, clots treated with 30 nM tPA had a threefold increase in total NET production and a twofold increase in normalized NET generation (measured as deoxyribonucleic acid:neutrophil) compared with fibrin-rich clots. Blocking fibrin polymerization resulted in similar level of NET release seen in tPA-treated clots, whereas ε-aminocaproic acid abolished the NET-enhancing effect of tPA. Therefore, fibrin suppresses NET generation and the absence of fibrin promotes NETs. We demonstrated that shear-induced NETosis was strongly inversely correlated with fibrin in sterile occlusive clots.

Simvastatin pretreatment ameliorates t-PA-induced hemorrhage transformation and MMP-9/TIMP-1 imbalance in thromboembolic cerebral ischemic rats

Background: The use of thrombolysis with tissue-plasminogen activator (t-PA) in patients with acute ischemic stroke (AIS) is limited by increased levels of matrix metalloproteinase-9 (MMP-9) and by the increased risk of hemorrhagic transformation (HT). In this study, we investigated the effects of simvastatin pretreatment on t-PA-induced MMP-9/tissue inhibitor of metalloproteinase-1 (TIMP-1) imbalance and HT aggravation in a rat AIS model. Methods: The rat AIS model was established by autologous blood emboli. Two weeks before surgery, rats were pretreated with simvastatin (60 mg/kg/d), and three hours after surgery, t-PA (10 mg/kg) was administered. MMP-9 and TIMP-1 levels in the infarcted zone and plasma were evaluated by Western blot analysis and ELISA; the level of HT was quantified by determining the hemoglobin content. RhoA activation was determined to clarify the potential effect. Results: The results suggested that pretreatment with simvastatin suppressed the increase in t-PA-induced MMP-9 levels and neutralized the elevated MMP-9/TIMP-1 ratio, but had no effect on TIMP-1 levels. Thrombolysis with t-PA after ischemia improved neurological outcome, but increased intracranial hemorrhage. Moreover, t-PA-induced HT aggravation was reduced by simvastatin pretreatment. In addition, we showed that t-PA-induced activation of RhoA was suppressed by simvastatin, and that t-PA-induced MMP-9/TIMP-1 imbalance and hemorrhage was reduced by Rho kinases (ROCK) inhibitor Y-27632. Conclusion: In this study, we showed that simvastatin pretreatment ameliorated t-PA-induced HT and MMP-9/TIMP-1 imbalance, and demonstrated that the RhoA/ROCK pathway was implicated.

Neuroinflammatory mechanisms of blood-brain barrier damage in ischemic stroke

As part of the neurovascular unit, the blood-brain barrier (BBB) is a unique, dynamic regulatory boundary that limits and regulates the exchange of molecules, ions, and cells between the blood and the central nervous system. Disruption of the BBB plays an important role in the development of neurological dysfunction in ischemic stroke. Blood-borne substances and cells have restricted access to the brain due to the presence of tight junctions between the endothelial cells of the BBB. Following stroke, there is loss of BBB tight junction integrity, leading to increased paracellular permeability, which results in vasogenic edema, hemorrhagic transformation, and increased mortality. Thus, understanding principal mediators and molecular mechanisms involved in BBB disruption is critical for the development of novel therapeutics to treat ischemic stroke. This review discusses the current knowledge of how neuroinflammation contributes to BBB damage in ischemic stroke. Specifically, we provide an updated overview of the role of cytokines, chemokines, oxidative and nitrosative stress, adhesion molecules, matrix metalloproteinases, and vascular endothelial growth factor as well as the role of different cell types in the regulation of BBB permeability in ischemic stroke.

Targeting RNS/caveolin-1/MMP signaling cascades to protect against cerebral ischemia-reperfusion injuries: potential application for drug discovery

Reactive nitrogen species (RNS) play important roles in mediating cerebral ischemia-reperfusion injury. RNS activate multiple signaling pathways and participate in different cellular events in cerebral ischemia-reperfusion injury. Recent studies have indicated that caveolin-1 and matrix metalloproteinase (MMP) are important signaling molecules in the pathological process of ischemic brain injury. During cerebral ischemia-reperfusion, the production of nitric oxide (NO) and peroxynitrite (ONOO⁻), two representative RNS, down-regulates the expression of caveolin-1 (Cav-1) and, in turn, further activates nitric oxide synthase (NOS) to promote RNS generation. The increased RNS further induce MMP activation and mediate disruption of the blood-brain barrier (BBB), aggravating the brain damage in cerebral ischemia-reperfusion injury. Therefore, the feedback interaction among RNS/Cav-1/MMPs provides an amplified mechanism for aggravating ischemic brain damage during cerebral ischemia-reperfusion injury. Targeting the RNS/Cav-1/MMP pathway could be a promising therapeutic strategy for protecting against cerebral ischemia-reperfusion injury. In this mini-review article, we highlight the important role of the RNS/Cav-1/MMP signaling cascades in ischemic stroke injury and review the current progress of studies seeking therapeutic compounds targeting the RNS/Cav-1/MMP signaling cascades to attenuate cerebral ischemia-reperfusion injury. Several representative natural compounds, including calycosin-7-O-β-D-glucoside, baicalin, Momordica charantia polysaccharide (MCP), chlorogenic acid, lutein and lycopene, have shown potential for targeting the RNS/Cav-1/MMP signaling pathway to protect the brain in ischemic stroke. Therefore, the RNS/Cav-1/MMP pathway is an important therapeutic target in ischemic stroke treatment.

Improving Cerebral Blood Flow after Arterial Recanalization: A Novel Therapeutic Strategy in Stroke

Ischemic stroke is caused by a disruption in blood supply to a region of the brain. It induces dysfunction of brain cells and networks, resulting in sudden neurological deficits. The cause of stroke is vascular, but the consequences are neurological. Decades of research have focused on finding new strategies to reduce the neural damage after cerebral ischemia. However, despite the incredibly huge investment, all strategies targeting neuroprotection have failed to demonstrate clinical efficacy. Today, treatment for stroke consists of dealing with the cause, attempting to remove the occluding blood clot and recanalize the vessel. However, clinical evidence suggests that the beneficial effect of post-stroke recanalization may be hampered by the occurrence of microvascular reperfusion failure. In short: recanalization is not synonymous with reperfusion. Today, clinicians are confronted with several challenges in acute stroke therapy, even after successful recanalization: (1) induce reperfusion, (2) avoid hemorrhagic transformation (HT), and (3) avoid early or late vascular reocclusion. All these parameters impact the restoration of cerebral blood flow after stroke. Recent advances in understanding the molecular consequences of recanalization and reperfusion may lead to innovative therapeutic strategies for improving reperfusion after stroke. In this review, we will highlight the importance of restoring normal cerebral blood flow after stroke and outline molecular mechanisms involved in blood flow regulation.

Can the benefits of rtPA treatment for stroke be improved?

Tissue-type plasminogen activator (tPA) is a serine protease well known to promote fibrinolysis. This is why: its recombinant form (rtPA) can be used, either alone or combined with thrombectomy, to promote recanalization/reperfusion following ischemic stroke. However, its overall benefits are counteracted by some of its side-effects, including incomplete lysis of clots, an increased risk of hemorrhagic transformation and the possibility of neurotoxicity. Nevertheless, better understanding of the mechanisms by which tPA influences brain function and promotes its alteration may help in the design of new strategies to improve stroke therapy.

Inflammatory Disequilibrium in Stroke

Over the past several decades, there have been substantial advances in our knowledge of the pathophysiology of stroke. Understanding the benefits of timely reperfusion has led to the development of thrombolytic therapy as the cornerstone of current management of ischemic stroke, but there remains much to be learned about mechanisms of neuronal ischemic and reperfusion injury and associated inflammation. For ischemic stroke, novel therapeutic targets have continued to remain elusive. When considering modern molecular biological techniques, advanced translational stroke models, and clinical studies, a consistent pattern emerges, implicating perturbation of the immune equilibrium by stroke in both central nervous system injury and repair responses. Stroke triggers activation of the neuroimmune axis, comprised of multiple cellular constituents of the immune system resident within the parenchyma of the brain, leptomeninges, and vascular beds, as well as through secretion of biological response modifiers and recruitment of immune effector cells. This neuroimmune activation can directly impact the initiation, propagation, and resolution phases of ischemic brain injury. To leverage a potential opportunity to modulate local and systemic immune responses to favorably affect the stroke disease curve, it is necessary to expand our mechanistic understanding of the neuroimmune axis in ischemic stroke. This review explores the frontiers of current knowledge of innate and adaptive immune responses in the brain and how these responses together shape the course of ischemic stroke.

Therapeutic Strategies to Attenuate Hemorrhagic Transformation After Tissue Plasminogen Activator Treatment for Acute Ischemic Stroke

This review focuses on the mechanisms and emerging concepts of stroke and therapeutic strategies for attenuating hemorrhagic transformation (HT) after tissue plasminogen activator (tPA) treatment for acute ischemic stroke (AIS). The therapeutic time window for tPA treatment has been extended. However, the patients who are eligible for tPA treatment are still ＜5% of all patients with AIS. The risk of serious or fatal symptomatic hemorrhage increases with delayed initiation of treatment. HT is thought to be caused by 1) ischemia/reperfusion injury; 2) the toxicity of tPA itself; 3) inflammation; and/or 4) remodeling factor-mediated effects. Modulation of these pathophysiologies is the basis of direct therapeutic strategies to attenuate HT after tPA treatment. Several studies have revealed that matrix metalloproteinases and free radicals are potential therapeutic targets. In addition, we have demonstrated that the inhibition of the vascular endothelial growth factor-signaling pathway and supplemental treatment with a recombinant angiopoietin-1 protein might be a promising therapeutic strategy for attenuating HT after tPA treatment through vascular protection. Moreover, single-target therapies could be insufficient for attenuating HT after tPA treatment and improving the therapeutic outcome of patients with AIS. We recently identified progranulin, which is a growth factor and a novel target molecule with multiple therapeutic effects. Progranulin might be a therapeutic target that protects the brain through suppression of vascular remodeling (vascular protection), neuroinflammation, and/or neuronal death (neuroprotection). Clinical trials which evaluate the effects of anti-VEGF drugs or PGRN-based treatment with tPA will be might worthwhile.

Neuroprotective effects of adjunctive treatments for acute stroke thrombolysis: a review of clinical evidence

The narrow therapeutic time window and risk of intracranial hemorrhage largely restrict the clinical application of thrombolysis in acute ischemic stroke. Adjunctive treatments added to rt-PA may be beneficial to improve the capacity of neural cell to withstand ischemia, and to reduce the hemorrhage risk as well. This review aims to evaluate the neuroprotective effects of adjunctive treatments in combination with thrombolytic therapy for acute ischemic stroke. Relevant studies were searched in the PubMed, Web of Science and EMBASE database. In this review, we first interpret the potential role of adjunctive treatments to thrombolytic therapy in acute ischemic stroke. Furthermore, we summarize the current clinical evidence for the combination of intravenous recombinant tissue plasminogen activator and various adjunctive therapies in acute ischemic stroke, either pharmacological or non-pharmacological therapy, and discuss the mechanisms of some promising treatments, including uric acid, fingolimod, minocycline, remote ischemic conditioning, hypothermia and transcranial laser therapy. Even though fingolimod, minocycline, hypothermia and remote ischemic conditioning have yielded promising results, they still need to be rigorously investigated in further clinical trials. Further trials should also focus on neuroprotective approach with pleiotropic effects or combined agents with multiple protective mechanisms.

Cerebral Vascular Disease and Neurovascular Injury in Ischemic Stroke

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

Plasma Kallikrein Inhibitors in Cardiovascular Disease: An Innovative Therapeutic Approach

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

Combination therapy with liposomal neuroprotectants and tissue plasminogen activator for treatment of ischemic stroke

For ischemic stroke treatment, extension of the therapeutic time window (TTW) of thrombolytic therapy with tissue plasminogen activator (tPA) and amelioration of secondary ischemia/reperfusion (I/R) injury are most desirable. Our previous studies have indicated that liposomal delivery of neuroprotectants into an ischemic region is effective for stroke treatment. In the present study, for solving the above problems in the clinical setting, the usefulness of combination therapy with tPA and liposomal fasudil (fasudil-Lip) was investigated in ischemic stroke model rats with photochemically induced thrombosis, with clots that were dissolved by tPA. Treatment with tPA 3 h after occlusion markedly increased blood-brain barrier permeability and activated matrix metalloproteinase (MMP)-2 and -9, which are involved in cerebral hemorrhage. However, an intravenous administration of fasudil-Lip before tPA markedly suppressed the increase in permeability and the MMP activation stemming from tPA. The combination treatment showed significantly larger neuroprotective effects, even in the case of delayed tPA administration compared with each treatment alone or the tPA/fasudil-treated group. These findings suggest that treatment with fasudil-Lip before tPA could decrease the risk of tPA-derived cerebral hemorrhage and extend the TTW of tPA and that the combination therapy could be a useful therapeutic option for ischemic stroke.-Fukuta, T., Asai, T., Yanagida, Y., Namba, M., Koide, H., Shimizu, K., Oku, N. Combination therapy with liposomal neuroprotectants and tissue plasminogen activator for treatment of ischemic stroke.

Matrix Metalloproteinase in Blood-Brain Barrier Breakdown in Dementia

The neurovascular unit, which consists of astrocytic end-feet, neurons, pericytes, and endothelial cells, plays a key role in maintaining brain homeostasis by forming the blood-brain barrier and carefully controlling local cerebral blood flow. When the blood-brain barrier is disrupted, blood components can leak into the brain, damage the surrounding tissue and lead to cognitive impairment. This disruption in the blood-brain barrier and subsequent impairment in cognition are common after stroke and during cerebral amyloid angiopathy and Alzheimer's disease. Matrix metalloproteinases are proteases that degrade the extracellular matrix as well as tight junctions between endothelial cells and have been implicated in blood-brain barrier breakdown in neurodegenerative diseases. This review will focus on the roles of MMP2 and MMP9 in dementia, primarily post-stroke events that lead to dementia, cerebral amyloid angiopathy, and Alzheimer's disease.

Neuroprotective effect of lercanidipine in middle cerebral artery occlusion model of stroke in rats

Oxidative stress, inflammation and apoptotic neuronal cell death are cardinal mechanisms involved in the cascade of acute ischemic stroke. Lercanidipine apart from calcium channel blocking activity possesses anti-oxidant, anti-inflammatory and anti-apoptotic properties. In the present study, we investigated neuroprotective efficacy and therapeutic time window of lercanidipine in a 2h middle cerebral artery occlusion (MCAo) model in male Wistar rats. The study design included: acute (pre-treatment and post-treatment) and sub-acute studies. In acute studies (pre-treatment) lercanidipine (0.25, 0.5 and 1mg/kg, i.p.) was administered 60min prior MCAo. The rats were assessed 24h post-MCAo for neurological deficit score (NDS), motor deficit paradigms (grip test and rota rod) and cerebral infarction via 2,3,5-triphenyltetrazolium chloride (TTC) staining. The most effective dose was found to be at 0.5mg/kg, i.p., which was considered for further studies. Regional cerebral blood flow (rCBF) was monitored till 120min post-reperfusion to assess vasodilatory property of lercanidipine (0.5mg/kg, i.p.) administered at two different time points: 60min post-MCAo and 15min post-reperfusion. In acute studies (post-treatment) lercanidipine (0.5mg/kg, i.p.) was administered 15min, 120min and 240min post-reperfusion. Based on NDS and cerebral infarction via TTC staining assessed 24h post-MCAo, effectiveness was evident upto 120min. For sub-acute studies same dose/vehicle was repeated for next 3days and magnetic resonance imaging (MRI) was performed 96h after the last dose. Biochemical markers estimated in rat brain cortex 24h post-MCAo were oxidative stress (malondialdehyde, reduced glutathione, nitric oxide, superoxide dismutase), blood brain barrier damage (matrix metalloproteinases-2 and -9) and apoptotic (caspase-3 and -9). Lercanidipine significantly reduced NDS, motor deficits and cerebral infarction volume as compared to the control group. Lercanidipine (60min post-MCAo) significantly increased rCBF (86%) as compared to vehicle treated MCAo group (64%) 120min post-reperfusion, but failed to show vasodilatation with 15min post-reperfusion group. Lercanidipine (13.78±2.78%) significantly attenuated percentage infarct volume as evident from diffusion-weighted (DWI) and T2-weighted images as compared to vehicle treated MCAo group (25.90±2.44%) investigated 96h post-MCAo. The apparent diffusion coefficient (ADC) was also significantly improved in lercanidipine group as compared to control group. Biochemical alterations were significantly ameliorated by lercanidipine till 120min post-reperfusion group and MMP-9 inhibition observed even with 240min group. Thus, lercanidipine revealed significant neuroprotective effect mediated through attenuation of oxidative stress, inflammation and apoptosis.

Update on the effects of treatment with recombinant tissue-type plasminogen activator (rt-PA) in acute ischemic stroke

INTRODUCTION

Acute ischemic stroke (AIS) represents a major cause of death and disability all over the world. The recommended therapy aims at dissolving the clot to re-establish quickly the blood flow to the brain and reduce neuronal injury. Intravenous administration of recombinant tissue-type plasminogen activator (rt-PA) is clinically used with this goal.

AREAS COVERED

A description of beneficial and detrimental effects of rt-PA treatment is addressed. An overview of new therapies against AIS, such as new thrombolytics, sonolysis and sonothrombolysis, endovascular procedures, and association therapies is provided. Updates on the pathophysiological process leading to intracranial hemorrhage (ICH) is also discussed.

EXPERT OPINION

rt-PA treatment in AIS patients is beneficial to recovery outcomes. To weaken risks and improve benefits, it might be relevant to consider: i) a definitive identification of risk factors for symptomatic ICH; ii). a better organization of the health care system to reduce time-to-treatment and enhance discharge management. The pharmacological improvement of new thrombolytic drugs (such as tenecteplase and desmoteplase) targeting harmful and maximally exploiting beneficial effects might further reduce mortality and disability in AIS.

Implications of MMP9 for Blood Brain Barrier Disruption and Hemorrhagic Transformation Following Ischemic Stroke

Numerous studies have documented increases in matrix metalloproteinases (MMPs), specifically MMP-9 levels following stroke, with such perturbations associated with disruption of the blood brain barrier (BBB), increased risk of hemorrhagic complications, and worsened outcome. Despite this, controversy remains as to which cells release MMP-9 at the normal and pathological BBB, with even less clarity in the context of stroke. This may be further complicated by the influence of tissue plasminogen activator (tPA) treatment. The aim of the present review is to examine the relationship between neutrophils, MMP-9 and tPA following ischemic stroke to elucidate which cells are responsible for the increases in MMP-9 and resultant barrier changes and hemorrhage observed following stroke.