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.

Comparison of results obtained using clot-fibrinolysis waveform analysis and global fibrinolysis capacity assay with rotational thromboelastography

Global fibrinolysis assays detect the fibrinolysis time of clot dissolution using tissue-type plasminogen activator (tPA). Two such assays, clot-fibrinolysis waveform analysis (CFWA) and global fibrinolysis capacity (GFC) assay, were recently developed. These were compared with rotational thromboelastography (ROTEM). Healthy donor blood samples were divided into four groups based on tPA-spiked concentrations: 0, 100, 500, and 1000 ng/mL. CFWA and GFC fibrinolysis times, including 4.1 µg/mL and 100 ng/mL tPA in the assays, were determined, denoted as CFWA-Lys and GFC-Lys, respectively. Statistical differences were recognized between tPA concentrations of 0 and 500/1000 ng/mL for CFWA-Lys, and 0 and 100/500/1000 ng/mL for GFC-Lys. The correlation coefficients with lysis onset time (LOT) of extrinsic pathway evaluation and intrinsic pathway evaluation in ROTEM were statistically significant at 0.610 and 0.590 for CFWA-Lys, and 0.939 and 0.928 for GFC-Lys, respectively (p-values < 0.0001 for all correlations). Both assays showed significant correlations with ROTEM; however, the GFC assay proved to have better agreement with ROTEM compared with the CFWA assay. These assays have the potential to reflect a hyperfibrinolysis status with high tPA concentrations.

L-Palmitoylcarnitine potentiates plasmin and tPA to inhibit thrombosis

L-Palmitoylcarnitine (L-PC) is an important endogenous fatty acid metabolite. Its classical biological functions are involved in the regulations of membrane molecular dynamics and the β-oxidation of fatty acids. Decreased plasma long-chain acylcarnitines showed the association of venous thrombosis, implying anticoagulant activity of the metabolites and inspiring us to investigate if and how L-PC, a long-chain acylcarnitine, takes part in coagulation. Here we show that L-PC exerted anti-coagulant effects by potentiating the enzymatic activities of plasmin and tissue plasminogen activator (tPA). L-PC directly interacts with plasmin and tPA with an equilibrium dissociation constant (KD) of 6.47 × 10-9 and 4.46 × 10-9 M, respectively, showing high affinities. In mouse model, L-PC administration significantly inhibited FeCl3-induced arterial thrombosis. It also mitigated intracerebral thrombosis and inflammation in a transient middle cerebral artery occlusion (tMCAO) mouse model. L-PC induced little bleeding complications. The results show that L-PC has anti-thrombotic function by potentiating plasmin and tPA.

Site-specific PEGylation of recombinant tissue-type plasminogen activator

Tissue-type plasminogen activator (tPA) is the gold standard for emergency treatment of ischemic stroke, which is the third leading cause of death worldwide. Major challenges of tPA therapy are its rapid elimination by plasminogen activator inhibitor-1 (PAI-1) and hepatic clearance, leading to the use of high doses and consequent serious side effects, including internal bleeding, swelling and low blood pressure. In this regard, we developed three polyethylene glycol (PEG)ylated tPA bioconjugates based on the recombinant human tPA drug Alteplase using site-specific conjugation strategies. The first bioconjugate with PEGylation at the N-terminus of tPA performed by reductive alkylation showed a reduced proteolytic activity of 68 % compared to wild type tPA. PEGylation at the single-free cysteine of tPA with linear and branched PEG revealed similar proteolytic activities as the wild-type protein. Moreover, both bioconjugates with PEG-cysteine-modification showed 2-fold slower inhibition kinetics by PAI-1. All bioconjugates increased in hydrodynamic size as a critical requirement for half-life extension.

Association of Intravenous Thrombolysis with Delayed Reperfusion After Incomplete Mechanical Thrombectomy

PURPOSE

Treatment of distal vessel occlusions causing incomplete reperfusion after mechanical thrombectomy (MT) is debated. We hypothesized that pretreatment with intravenous thrombolysis (IVT) may facilitate delayed reperfusion (DR) of residual vessel occlusions causing incomplete reperfusion after MT.

METHODS

Retrospective analysis of patients with incomplete reperfusion after MT, defined as extended thrombolysis in cerebral infarction (eTICI) 2a-2c, and available perfusion follow-up imaging at 24 ± 12 h after MT. DR was defined as absence of any perfusion deficit on time-sensitive perfusion maps, indicating the absence of any residual occlusion. The association of IVT with the occurrence of DR was evaluated using a logistic regression analysis adjusted for confounders. Sensitivity analyses based on IVT timing (time between IVT start and the occurrence incomplete reperfusion following MT) were performed.

RESULTS

In 368 included patients (median age 73.7 years, 51.1% female), DR occurred in 225 (61.1%). Atrial fibrillation, higher eTICI grade, better collateral status and longer intervention-to-follow-up time were all associated with DR. IVT did not show an association with the occurrence of DR (aOR 0.80, 95% CI 0.44-1.46, even in time-sensitive strata, aOR 2.28 [95% CI 0.65-9.23] and aOR 1.53 [95% CI 0.52-4.73] for IVT to incomplete reperfusion following MT timing <80 and <100 min, respectively).

CONCLUSION

A DR occurred in 60% of patients with incomplete MT at ~24 h and did not seem to occur more often in patients receiving pretreatment IVT. Further research on potential associations of IVT and DR after MT is required.

Enhanced Expression of Plasminogen Activators and Inhibitor in the Healing of Tympanic Membrane Perforation in Rats

The significance of plasminogen activation during the tympanic membrane (TM) healing is known mainly from studies performed on knock-out mice. In the previous study, we reported activation of genes coding proteins of plasminogen activation and inhibition system in rat's TM perforation healing. The aim of the present study was the evaluation of protein products expressed by these genes and their tissue distribution using Western blotting and immunofluorescent method, respectively, during 10-day observation period after injury. Otomicroscopical and histological evaluation were employed to assess the healing process. The expression of urokinase plasminogen activator (uPA) and its receptor (uPAR) were significantly upregulated in the proliferation phase, with subsequent gradual attenuation during remodeling phase of healing process, when keratinocyte migration was weakening. The expression of plasminogen activator inhibitor type 1 (PAI-1) also showed the highest levels during the proliferation phase. The increase of tissue plasminogen activator (tPA) expression was observed during the whole observation period, with the highest activity during the remodeling phase. Immunofluorescence of these proteins was present mainly in migrating epithelium. Our study found that plasminogen activation (uPA, uPAR, tPA) and inhibitory (PAI-1) molecules form a well-structured regulatory system of the epithelial migration that is critical to the healing of TM after its perforation.

A modified mouse model of haemorrhagic transformation associated with tPA administration after thromboembolic stroke

Objective

To establish a new mouse model of haemorrhagic transformation associated with delayed tissue-type plasminogen activator (tPA) treatment to provide a novel tool to study therapeutic strategies for haemorrhagic transformation.

Methods

Male C57BL/6 mice were subjected to carotid artery thrombosis stimulated with ferric chloride. The thrombus was then mechanically detached to induce migration toward the intracranial circulation. To induce haemorrhagic transformation, mice were intravenously injected with 10 mg/kg tPA 4.5 h after the onset of ischaemia and were sacrificed 24 h after tPA treatment.

Results

In this new model, administration of tPA 4.5 h after stroke exacerbated the risk of intracerebral haemorrhage. Thrombolysis with tPA also exacerbated cerebral infarction, brain oedema, blood-brain barrier breakdown, and neurological deficits. However, cerebral blood flow was not significantly affected.

Conclusion

The present model is reproducible, easy to perform, and mimics the clinical situation of haemorrhagic transformation after tPA treatment in humans. This modified model can be used as a new tool to test experimental drugs for haemorrhagic transformation associated with delayed tPA administration after an ischaemic stroke.

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 choroid plexus: a door between the blood and the brain for tissue-type plasminogen activator

Background

In the vascular compartment, the serine protease tissue-type plasminogen activator (tPA) promotes fibrinolysis, justifying its clinical use against vasculo-occlusive diseases. Accumulating evidence shows that circulating tPA (endogenous or exogenous) also controls brain physiopathological processes, like cerebrovascular reactivity, blood–brain barrier (BBB) homeostasis, inflammation and neuronal fate. Whether this occurs by direct actions on parenchymal cells and/or indirectly via barriers between the blood and the central nervous system (CNS) remains unclear. Here, we postulated that vascular tPA can reach the brain parenchyma via the blood-cerebrospinal fluid barrier (BCSFB), that relies on choroid plexus (CP) epithelial cells (CPECs).

Methods

We produced various reporter fusion proteins to track tPA in primary cultures of CPECs, in CP explants and in vivo in mice. We also investigated the mechanisms underlying tPA transport across the BCSFB, with pharmacological and molecular approaches.

Results

We first demonstrated that tPA can be internalized by CPECs in primary cultures and in ex vivo CPs explants. In vivo, tPA can also be internalized by CPECs both at their basal and apical sides. After intra-vascular administration, tPA can reach the cerebral spinal fluid (CSF) and the brain parenchyma. Further investigation allowed discovering that the transcytosis of tPA is mediated by Low-density-Lipoprotein Related Protein-1 (LRP1) expressed at the surface of CPECs and depends on the finger domain of tPA. Interestingly, albumin, which has a size comparable to that of tPA, does not normally cross the CPs, but switches to a transportable form when grafted to the finger domain of tPA.

Conclusions

These findings provide new insights on how vascular tPA can reach the brain parenchyma, and open therapeutic avenues for CNS disorders.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12987-022-00378-0.

Parvalbumin interneuron-derived tissue-type plasminogen activator shapes perineuronal net structure

Background

Perineuronal nets (PNNs) are specialized extracellular matrix structures mainly found around fast-spiking parvalbumin (FS-PV) interneurons. In the adult, their degradation alters FS-PV-driven functions, such as brain plasticity and memory, and altered PNN structures have been found in neurodevelopmental and central nervous system disorders such as Alzheimer’s disease, leading to interest in identifying targets able to modify or participate in PNN metabolism. The serine protease tissue-type plasminogen activator (tPA) plays multifaceted roles in brain pathophysiology. However, its cellular expression profile in the brain remains unclear and a possible role in matrix plasticity through PNN remodeling has never been investigated.

Result

By combining a GFP reporter approach, immunohistology, electrophysiology, and single-cell RT-PCR, we discovered that cortical FS-PV interneurons are a source of tPA in vivo. We found that mice specifically lacking tPA in FS-PV interneurons display denser PNNs in the somatosensory cortex, suggesting a role for tPA from FS-PV interneurons in PNN remodeling. In vitro analyses in primary cultures of mouse interneurons also showed that tPA converts plasminogen into active plasmin, which in turn, directly degrades aggrecan, a major structural chondroitin sulfate proteoglycan (CSPG) in PNNs.

Conclusions

We demonstrate that tPA released from FS-PV interneurons in the central nervous system reduces PNN density through CSPG degradation. The discovery of this tPA-dependent PNN remodeling opens interesting insights into the control of brain plasticity.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12915-022-01419-8.

Efficacy of Chinese herbal medicine for tPA thrombolysis in experimental stroke: A systematic review and meta-analysis

BACKGROUND

Tissue-type plasminogen activator (tPA) remains the sole FDA approved thrombolytic drug for ischemic stroke. But delayed thrombolytic therapy with tPA may increase the risk of hemorrhagic transformation. Many Chinese herbal medicines have been used as tPA helpers to enhance the capacity of tPA and minimize the risk of hemorrhagic transformation. The efficacy of Chinese herbal medicines on tPA thrombolysis is not systematically analyzed.

METHODS

We searched the following three databases up to January 2022: Web of Science, PubMed, and Scopus. Studies that reported the efficacy and safety of Chinese herbal medicines on tPA thrombolysis in experimental stroke were included. The efficacy outcomes were neurological score and infarct volume, the safety outcomes were cerebral hemorrhage and blood brain barrier (BBB) damage. We used the checklist of CAMARADES to assess the quality of included studies. Standardized mean difference (SMD) with 95% confidence intervals were used to assess all the outcomes. Subgroup analyses were performed to explore the sources of heterogeneity. Trim and fill method and Egger's test were used to assess the potential publication bias. Sensitivity analyses were used to identify the stability of the results.

RESULTS

A total of nine studies including 11 Chinese herbal medicines fulfilled the inclusion criteria and were subsequently analyzed. The pooled data demonstrated that Chinese herbal medicines improved neurological score (2.23 SMD, 1.42-3.04), infarct volume (1.08 SMD, 0.62-1.54), attenuated cerebral hemorrhage (1.87 SMD, 1.34-2.4), and BBB dysfunction (1.9 SMD, 1.35-2.45) following tPA thrombolysis in experimental stroke. Subgroup analysis indicated that the route of drug delivery, dosage of tPA, and stroke model used may be factors inducing heterogeneity and influencing the efficacy.

CONCLUSION

Treatment with Chinese herbal medicines significantly improved neurological score and infarct volume, reduced cerebral hemorrhage and BBB damage after tPA thrombolysis. This study supports Chinese herbal medicine as an adjuvant therapy in reducing the side effects of tPA thrombolysis after acute ischemic stroke. The results should be interpreted with more caution since this article was based on animal studies.

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.

Biomarkers of endothelial dysfunction and outcomes in coronavirus disease 2019 (COVID-19) patients: A systematic review and meta-analysis

BACKGROUND

Several studies have reported that the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can directly infect endothelial cells, and endothelial dysfunction is often found in severe cases of coronavirus disease 2019 (COVID-19). To better understand the prognostic values of endothelial dysfunction in COVID-19-associated coagulopathy, we conducted a systematic review and meta-analysis to assess biomarkers of endothelial cells in patients with COVID-19.

METHODS

A literature search was conducted on online databases for observational studies evaluating biomarkers of endothelial dysfunction and composite poor outcomes in COVID-19 patients.

RESULTS

A total of 1187 patients from 17 studies were included in this analysis. The estimated pooled means for von Willebrand Factor (VWF) antigen levels in COVID-19 patients was higher compared to healthy control (306.42 [95% confidence interval (CI) 291.37-321.48], p < 0.001; I²:86%), with the highest VWF antigen levels was found in deceased COVID-19 patients (448.57 [95% CI 407.20-489.93], p < 0.001; I²:0%). Meta-analysis showed that higher plasma levels of VWF antigen, tissue-type plasminogen activator (t-PA), plasminogen activator inhibitor-1 antigen (PAI-1) antigen, and soluble thrombomodulin (sTM) were associated with composite poor outcome in COVID-19 patients ([standardized mean difference (SMD) 0.74 [0.33-1.16], p < 0.001; I²:80.4%], [SMD 0.55 [0.19-0.92], p = 0.003; I²:6.4%], [SMD 0.33 [0.04-0.62], p = 0.025; I²:7.9%], and [SMD 0.55 [0.10-0.99], p = 0.015; I²:23.6%], respectively).

CONCLUSION

The estimated pooled means show increased levels of VWF antigen in COVID-19 patients. Several biomarkers of endothelial dysfunction, including VFW antigen, t-PA, PAI-1, and sTM, are significantly associated with increased composite poor outcomes in patients with COVID-19.

PROSPERO REGISTRATION NUMBER

CRD42021228821.

Neuroserpin: structure, function, physiology and pathology

Neuroserpin is a serine protease inhibitor identified in a search for proteins implicated in neuronal axon growth and synapse formation. Since its discovery over 30 years ago, it has been the focus of active research. Many efforts have concentrated in elucidating its neuroprotective role in brain ischemic lesions, the structural bases of neuroserpin conformational change and the effects of neuroserpin polymers that underlie the neurodegenerative disease FENIB (familial encephalopathy with neuroserpin inclusion bodies), but the investigation of the physiological roles of neuroserpin has increased over the last years. In this review, we present an updated and critical revision of the current literature dealing with neuroserpin, covering all aspects of research including the expression and physiological roles of neuroserpin, both inside and outside the nervous system; its inhibitory and non-inhibitory mechanisms of action; the molecular structure of the monomeric and polymeric conformations of neuroserpin, including a detailed description of the polymerisation mechanism; and the involvement of neuroserpin in human disease, with particular emphasis on FENIB. Finally, we briefly discuss the identification by genome-wide screening of novel neuroserpin variants and their possible pathogenicity.

Efficacy of Sanqi (Radix Notoginseng) in treating cerebral hemorrhage in rats with traumatic brain injury

OBJECTIVE

To evaluate the protective efficacy of Sanqi (Radix Notoginseng) on cerebral hemorrhage in a rat model of traumatic brain injury (TBI) by investigating plasminogen activator inhibitor-1 (PAI-1), tissue-type plasminogen activator (t-PA), nuclear factor-κB (NF-κB, p-p65), nitric oxide (NO), endothelin (ET), cluster differentiation (CD61CD62), and coagulation.

METHODS

The free-fall method was used to create a rat model of TBI. Forty-eight rats were randomly divided into six groups: the blank group, sham group, model group, low-dose Sanqi (Radix Notoginseng) group, middle-dose Sanqi (Radix Notoginseng) group, and high-dose Sanqi (Radix Notoginseng) group. At 24 h after the model was created, we investigated brain MRI, brain tissue morphology using HE staining, flow cytometry, and immunohistochemical changes.

RESULTS

Cerebral hemorrhage was aggravated in TBI rats (observed in brain specimens, brain MRI, and brain tissue HE). Cerebral immunohistochemistry results demonstrated that the expression of t-PA, PAI-1 and p-p65 increased significantly in TBI rats, while t-PA/PAI-1 had a significant decrease. In addition, CD61CD62, D2D, and ET were significantly increased in TBI rats, and PT and APTT were significantly prolonged; in contrast, NO was significantly decreased. Sanqi (Radix Notoginseng) decreased cerebral hemorrhage in TBI rats (observed in brain MRI and brain tissue HE), and increased t-PA/PAI-1, CD61CD62 significantly. It also significantly decreased the expression of t-PA, PAI-1, and p-p65 in brain immunohistochemistry and significantly decreased PT, APTT, D2D, and ET. However, there were no differences in NO between the model group and the Sanqi (Radix Notoginseng) group.

CONCLUSION

Sanqi (Radix Notoginseng) can decrease the expression of p-p65, increase t-PA/PAI-1, and stem traumatic intracranial hemorrhage in a TBI rat model.

Single- and two- chain tissue type plasminogen activator treatments differentially influence cerebral recovery after stroke

Tissue type Plasminogen Activator (tPA), named alteplase (Actilyse®) under its commercial form, is currently the only pharmacological treatment approved during the acute phase of ischemic stroke, used either alone or combined with thrombectomy. Interestingly, the commercial recombinant tPA (rtPA) contains two physiological forms of rtPA: the single chain rtPA (sc-rtPA) and the two-chains rtPA (tc-rtPA), with differential properties demonstrated in vitro. Using a relevant mouse model of thromboembolic stroke, we have investigated the overall effects of these two forms of rtPA when infused early after stroke onset (i.e. 20 min) on recanalization, lesion volumes, alterations of the integrity of the blood brain barrier and functional recovery. Our data reveal that there is no difference in the capacity of sc-rtPA and tc-rtPA to promote fibrinolysis and reperfusion of the tissue. However, compared to sc-rtPA, tc-rtPA is less efficient to reduce lesion volumes and to improve functional recovery, and is associated with an increased opening of the blood brain barrier. These data indicate better understanding of differential effects of these tPA forms might be important to ultimately improve stroke treatment.

Thrombosis and Haemostasis challenges in COVID-19 - Therapeutic perspectives of heparin and tissue-type plasminogen activator and potential toxicological reactions-a mini review

The coronavirus disease (COVID)-19 pandemic is a major challenge for the health systems worldwide. Acute respiratory distress syndrome (ARDS), is one of the most common complications of the COVID-19 infection. The activation of the coagulation system plays an important role in the pathogenesis of ARDS. The development of lung coagulopathy involves thrombin generation and fibrinolysis inhibition.

Unfractionated heparin and its recently introduced counterpart low molecular weight heparin (LMWH), are widely used anticoagulants with a variety of clinical indications allowing for limited and manageable physio-toxicologic side effects while the use of protamine sulfate, heparin's effective antidote, has made their use even safer. Tissue-type plasminogen activator (tPA) is approved as intravenous thrombolytic treatment. The present narrative review discusses the use of heparin and tPA in the treatment of COVID-19-induced ARDS and their related potential physio-toxicologic side effects. The article is a quick review of articles on anticoagulation in COVID infection and the potential toxicologic reactions associated with these drugs.

Diabetes Mellitus/Poststroke Hyperglycemia: a Detrimental Factor for tPA Thrombolytic Stroke Therapy

Intravenous administration of tissue-type plasminogen activator (IV tPA) therapy has long been considered a mainstay in ischemic stroke management. However, patients respond to IV tPA therapy unequally with some subsets of patients having worsened outcomes after treatment. In particular, diabetes mellitus (DM) is recognized as a clinically important vascular comorbidity that leads to lower recanalization rates and increased risks of hemorrhagic transformation (HT). In this short-review, we summarize the recent advances in understanding of the underlying mechanisms involved in post-IV tPA worsening of outcome in diabetic stroke. Potential pathologic factors that are related to the suboptimal tPA recanalization in diabetic stroke include higher plasma plasminogen activator inhibitor (PAI)-1 level, diabetic atherogenic vascular damage, glycation of the tPA receptor annexin A2, and alterations in fibrin clot density. While factors contributing to the exacerbation of HT in diabetic stroke include hyperglycemia, vascular oxidative stress, and inflammation, tPA neurovascular toxicity and imbalance in extracellular proteolysis are discussed. Besides, impaired collaterals in DM also compromise the efficacy of IV tPA therapy. Additionally, several tPA combination approaches developed from experimental studies that may help to optimize IV tPA therapy are also briefly summarized. In summary, more research efforts are needed to improve the safety and efficacy of IV tPA therapy in ischemic stroke patients with DM/poststroke hyperglycemia.

The Plasminogen Activation System Promotes Neurorepair in the Ischemic Brain

The plasminogen activation (PA) system was originally thought to exclusively promote the degradation of fibrin by catalyzing the conversion of plasminogen into plasmin via two serine proteinases: tissue-type plasminogen activator (tPA) and urokinase-type plasminogen activator (uPA). However, experimental evidence accumulated over the last 30 years indicates that tPA and uPA are also found in the central nervous system (CNS), where they have a plethora of functions that not always require plasmin generation or fibrin degradation. For example, plasminogen-dependent and - independent effects of tPA and uPA play a central role in the pathophysiological events that underlie one of the leading causes of mortality and disability in the world: cerebral ischemia. Indeed, recent work indicates that while the rapid release of tPA from the presynaptic compartment following the onset of cerebral ischemia protects the synapse from the deleterious effects of the ischemic injury, the secretion of uPA and its binding to its receptor (uPAR) during the recovery phase promotes the repair of synapses that have been lost to the acute ischemic insult. This restorative role of uPA has high translational significance because to this date there is no effective approach to induce neurorepair in the ischemic brain. Here we will discuss recent evidence that bridges the gap between basic research in the field of the PA system and the bedside of ischemic stroke patients, indicating that uPA and uPAR are potential targets for the development of therapeutic strategies to promote neurological recovery among ischemic stroke survivors.

The effectiveness of activated recombinant factor VII treatment

Background:

Diffuse alveolar hemorrhage (DAH) is a rare and frequently life-threatening complication of a variety of conditions. DAH may result from coagulation disorders, inhaled toxins, or infections. We report a series of patients who developed DAH after receiving a tissue-type plasminogen activator (tPA) for acute cerebral infarction. We aimed to find risk factors of DAH in patients receiving tPA and the effectiveness of activated recombinant factor VII (rFVIIa) treatment for the same.

Case Description:

A total of 1023 acute ischemic stroke (AIS) patients who received tPA in our department from January 2006 to December 2018 were enrolled in this study. Four of the 1023 patients (0.39%) developed DAH. The modified Rankin scale was used to assess clinical severity. Infarction volume was assessed upon follow-up using DWI (diffusion-weighted imaging). Atherothrombotic brain infarction cases were excluded from the study. The age, sex, occlusion site, area of infarction, emphysema, intracranial hemorrhage, and neurological outcomes were analyzed. Patients who developed DAH were more likely to have a history of emphysema. We administered rFVIIa to three DAH patients with good prognosis.

Conclusion:

The inclusion/exclusion criteria of tPA were based on the AHA/ASA Guidelines for the early management of patients with AIS.These patients had no evidence of infections, bronchoscopy, autoimmune diseases, HIV, and transplantations. Our study suggests that systemic administration of rFVIIa for DAH is effective. Emphysema may be a risk factor for the development of DAH following tPA. When we use tPA for emphysema patients, we must be careful about DAH enough.

Impact of complete recanalization on clinical recovery in cardioembolic stroke patients with M2 occlusion

BACKGROUND AND PURPOSE

We investigated the impact of complete recanalization beyond partial recanalization in distal (M2) middle cerebral artery (MCA) occlusion.

METHODS

Data regarding M2 occlusion patients treated with endovascular thrombectomy (EVT) and/or intravenous thrombolysis (tPA) were reviewed from our prospective EVT registry and multicenter tPA (YAMATO study) data bank. Complete recanalization was modified thrombolysis with cerebral infarction score (TICI) of 3 at the end of EVT or similar appearances of both MCAs on magnetic resonance angiography (MRA) within 1.5 h after tPA. Partial recanalization was defined as TICI ≥2b or > 50% recanalization on MRA. At 3 months, favorable outcome was defined as a modified Rankin Scale score ≤ 2.

RESULT

Data on 121 patients were analyzed. EVT-alone was in 38 patients; combined EVT and tPA in 28; and tPA-alone in 55. Complete recanalization was achieved in 27 (22%), partial recanalization in 48 (40%), and no-to-limited recanalization in 46 (38%). At 3 months, 51% of patients had favorable outcomes, and this rate was significantly higher in the complete recanalization group than in the partial and no-to-limited recanalization groups (75% vs. 41% vs. 49%, p = .043). Multivariate regression analysis showed that complete recanalization was an independent parameter related to favorable outcomes (odds ratio 4.78, 95% CI: 1.16-19.73, p = .030). However, combined complete and partial recanalization was not associated with favorable outcomes (odds ratio 1.49, 95% CI 0.53-4.22, p = .449).

CONCLUSION

Complete recanalization, but not partial recanalization, at the end of EVT and tPA therapy is associated with favorable outcomes in patients with M2 occlusion.

Changes in strand 6B and helix B during neuroserpin inhibition: Implication in severity of clinical phenotype

Neuroserpin (NS) is predominantly expressed in brain and inhibits tissue-type plasminogen activator (tPA) with implications in brain development and memory. Nature of conformational change in pathological variants in strand 6B and helix B of NS that cause a relatively mild to severe epilepsy (and/or dementia) remains largely elusive. MD simulation with wild type (WT) NS, strand 6B and helix B variants indicated that substitution in this region affects the conformation of the strands 5B, 5A and reactive centre loop. Therefore, we designed variants of NS in strand 6B (I46D and F48S) and helix B (A54F, L55A and L55P) to investigate their role in tPA inhibition mechanism and propensity to aggregate. An interaction analysis showed disturbance of a hydrophobic patch centered at strands 5B, 6B and helix B in I46D and F48S but not in A54F, L55A, L55P and WT NS. Purified I46D, F48S and L55P variants showed decrease in fluorescence emission intensity but have similar α-helical content, however results of A54F and L55A were comparable to WT NS. Analysis of tPA inhibition showed marginal effect on A54F and L55A variant with tPA-NS complex formation. In contrast, I46D, F48S and L55P variants showed massive decrease in tPA inhibition, with no tPA-NS complex formation. Analysis of native PAGE under under polymerization condition showed prompt conversion of I46D, F48S and L55P to latent conformation but not A54F and L55A variants. Identification of these novel conformational changes will aid in the understanding of variable clinical phenotype of shutter region NS variants and other serpins.

Role of Tissue-Type Plasminogen Activator in Remodeling of the Ductus Arteriosus

Vascular remodeling (e.g., intimal thickening) is necessary for complete closure of the ductus arteriosus (DA). Smooth muscle cells are reported to contribute to DA remodeling. In contrast, the contribution of endothelial cells remains largely unknown. Recent data showed that tissue-type plasminogen activator (t-PA) was highly expressed in the endothelial cells of rat and human DA. It is well known that t-PA is an activator of the blood fibrinolytic system, but t-PA-induced localized proteolysis has been reported to play an important role in vascular development. We found that t-PA-induced plasminogen-plasmin conversion promoted matrix metalloproteinase-2 activation in endothelial cells of rat DA. Gelatinase activity was noted at the internal elastic laminae (IEL) of rat and human DA on in situ gelatin zymography. The in vivo injection of plasminogen to pre-term rats increased gelatinase activation, IEL disruption, and the subsequent intimal thickening formation in the pre-term rat DA. Human DA results partly supported the rat DA findings, suggesting that t-PA-mediated DA remodeling may also be present in the human DA. Current pharmacotherapy for patent DA (PDA) mainly focuses on increasing vascular constriction. Elucidating the molecular mechanisms of DA remodeling may help to expand the range of therapeutic strategies for PDA.

Clinical features and efficacy of reperfusion therapy in minor ischemic stroke patients with atrial fibrillation

The efficacy of reperfusion therapy (RT) using intravenous infusion of recombinant tissue plasminogen activator and/or endovascular therapy for minor ischemic stroke (MIS) has not yet been established. The present study aimed to elucidate the clinical features of MIS patients with atrial fibrillation (AF) and examine whether they could be potential candidates for RT. Data of MIS patients, defined as those with a score ≤ 5 on the National Institute of Health Stroke Scale, were extracted from patients admitted to our hospital between 2006 and 2018, and clinical characteristics were compared between the AF and non-AF groups. Thereafter, the impact of RT on outcomes in the AF- group was evaluated using the modified Rankin scale (mRS) score 3 months after onset and compared to that of standard medical therapy (SMT) using propensity score matching (PSM). Of 10,483 stroke patients, 3003 were shortlisted, and 457 AF patients and 2546 non-AF patients were finally selected. Patients in the AF group had more RT (13.3% vs. 5.7%, p < 0.001) than those in the non-AF group. Using PSM, 53 patients each were extracted from the AF-RT and AF-SMT groups. The frequencies of mRS = 0 or 1 for the AF-RT and AF-SMT groups were 69.8% and 64.2% (p = 0.536), respectively, with a significant difference in mRS = 0 (56.5% vs. 34.0%, p = 0.019). The present study found that MIS patients with AF underwent more RT than those without AF and that RT compared favorably with SMT for them; further study is warranted to examine whether these patients could be good candidates for RT.

Efficacy and safety of mechanical thrombectomy for M2 segment of middle cerebral artery: a systematic review and meta-analysis

BACKGROUND AND PURPOSE

The efficacy and safety of mechanical thrombectomy (MT) for M2 segment occlusion of middle cerebral artery in patients with acute ischemic stroke (AIS) was investigated.

METHODS

We searched PubMed and EMBASE from inception to 16 April 2019 for relevant studies, calculated the pool relative risks (RRs) of 3-month functional independence (modified Rankin scale score 0-2), death and symptomatic intracerebral hemorrhage (sICH) in MT for M2 segment occlusion in patients with AIS versus those of M1 segment or best medical care.

RESULTS

Nine studies enrolling 2152 patients compared MT for patients with AIS of M2 segment occlusion and those of M1 segment occlusion. MT for M2 occlusion had a higher rate of 3-month functional independence compared to the patients with M1 occlusion. (RR 1.27, 95% CI 1.11-1.44, P < 0.001) and decreased death (RR 0.74; 95% CI 0.58-0.96, P = 0.022) with similar risk of sICH (RR 1.11; 95% CI 0.65-1.87, P = 0.707). Four studies enrolling 1016 patients compared MT and best medical care for patients with AIS of M2 occlusion. MT for M2 occlusion benefit more than best medical care on 3-month functional independence (RR 1.43, 95% CI 1.08-1.90, P = 0.011) and death (RR 0.46; 95% CI 0.22-0.96, P = 0.022) with similar risk of sICH (RR 1.65; 95% CI 0.66-4.13; P = 0.286).

CONCLUSION

MT for M2 segment benefit patients with AIS on 3-month functional independence compared with that of M1 segment or medical care, without increasing the risk of sICH.

Fibrinolysis protease receptors promote activation of astrocytes to express pro-inflammatory cytokines

Background

Astrocytes contribute to the crosstalk that generates chronic neuro-inflammation in neurological diseases; however, compared with microglia, astrocytes respond to a more limited continuum of innate immune system stimulants. Recent studies suggest that the fibrinolysis system may regulate inflammation. The goal of this study was to test whether fibrinolysis system components activate astrocytes and if so, elucidate the responsible biochemical pathway.

Methods

Primary cultures of astrocytes and microglia were prepared from neonatal mouse brains. The ability of purified fibrinolysis system proteins to elicit a pro-inflammatory response was determined by measuring expression of the mRNAs encoding tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and chemokine (C-C motif) ligand 2 (CCL2). IκBα phosphorylation also was measured. Plasminogen activation in association with cells was detected by chromogenic substrate hydrolysis. The activity of specific receptors was tested using neutralizing antibodies and reagents.

Results

Astrocytes expressed pro-inflammatory cytokines when treated with plasminogen but not when treated with agonists for Toll-like Receptor-4 (TLR4), TLR2, or TLR9. Microglia also expressed pro-inflammatory cytokines in response to plasminogen; however, in these cells, the response was observed only when tissue-type plasminogen activator (tPA) was added to activate plasminogen. In astrocytes, endogenously produced urokinase-type plasminogen activator (uPA) converted plasminogen into plasmin in the absence of tPA. Plasminogen activation was dependent on the plasminogen receptor, α-enolase, and the uPA receptor, uPAR. Although uPAR is capable of directly activating cell-signaling, the receptor responsible for cytokine expression and IκBα phosphorylation response to plasmin was Protease-activated Receptor-1 (PAR-1). The pathway, by which plasminogen induced astrocyte activation, was blocked by inhibiting any one of the three receptors implicated in this pathway with reagents such as εACA, α-enolase-specific antibody, uPAR-specific antibody, the uPA amino terminal fragment, or a pharmacologic PAR-1 inhibitor.

Conclusions

Plasminogen may activate astrocytes for pro-inflammatory cytokine expression through the concerted action of at least three distinct fibrinolysis protease receptors. The pathway is dependent on uPA to activate plasminogen, which is expressed endogenously by astrocytes in culture but also may be provided by other cells in the astrocytic cell microenvironment in the CNS.

Improving the solubility, activity, and stability of reteplase using in silico design of new variants

Reteplase (recombinant plasminogen activator, r-PA) is a thrombolytic agent recombined from tissue-type plasminogen activator (t-PA), which has several prominent features such as strong thrombolytic ability and E. coli expressibility. Despite these outstanding features, it demonstrates reduced fibrin binding affinity, reduced stimulation of protease activity, and lower solubility, hence higher aggregation propensity, compared to t-PA. The present study was devoted to design r-PA variants with comparable structural stability, enhanced biological activity, and high solubility. For this purpose, computational molecular modeling techniques were utilized. The supercharging technique was applied for r-PA to designing new species of the protein. Based on the results from in silico evaluation of selected mutations in comparison to the wild-type r-PA, the designed supercharged mutant (S7 variant) exhibited augmented stability, decreased solvation energy, as well as enhanced binding affinity to fibrin. The data also implied increased plasminogen cleavage activity of the new variant. These findings have implications to therapies which involve removal of intravascular blood clots, including the treatment of acute myocardial infarction.

Comparative anti-thrombotic activity and haemorrhagic adverse effect of nattokinase and tissue-type plasminogen activator

Anti-thrombotic activity and safety of nattokinase, an enzyme produced by Bacillus subtilis during soybean fermentation, were investigated in comparison with tissue-type plasminogen activator (t-PA). Carotid arterial thrombosis was produced with a FeCl₃-soaked paper, followed by intravenous injection of nattokinase or t-PA. Nattokinase and t-PA delayed thrombus formation, near-fully (> 90%) inhibiting at 75 and 8.5 mg/kg, respectively. As adverse effects, t-PA induced petechial haemorrhage at 10 mg/kg in the lungs and thymus, and extensive bleeding at 20 mg/kg. Nattokinase also caused pulmonary haemorrhage from 300 mg/kg. Collectively, the standard safety margins (SSMs) for t-PA and nattokinase were calculated to be 1.2 and 4.0, respectively. Combinational treatment with dexamethasone (2 mg/kg) increased the efficacy and safety of t-PA and nattokinase, widening their SSMs to 2.4 and 8.0, respectively. The results indicate that nattokinase delayed thrombus formation and dissolved thrombi, and that nattokinase could be a good candidate anti-thrombotic agent with relatively-low haemorrhagic risk.

Is it dangerous to treat spontaneous intracerebral hemorrhage by minimally invasive surgery plus local thrombolysis in patients with coexisting unruptured intracranial aneurysms?

OBJECTIVES

Limited evidence supports the presumed increased frequency of hemorrhage caused by the unruptured intracranial aneurysms which coexist in patients with spontaneous intracerebral hemorrhage treated with minimally invasive surgery plus local thrombolysis. Subsequently, we sought to determine the safety of local thrombolysis for this particular subset of patients.

PATIENTS AND METHODS

We reviewed the medical records of patients treated with minimally invasive surgery plus local thrombolysis for intracerebral hemorrhage between November 2013 to December 2015 in an intensive care unit of a tertiary care hospital. Depending upon the vascular images, unruptured intracranial aneurysms were identified. The primary outcome was any of postoperative intracranial rebleeding. The second outcome included the 30-day death and 6-month follow up graded by Modified Rank Scale. Blind abstractors reviewed the medical data and binary logistic regression was performed to investigate the risk factors of poor prognosis.

RESULTS

We identified a cohort of consecutive 188 patients, of whom 23 (12.2%) harbored unruptured intracranial aneurysms. There were 28 aneurysms documented in this study, among which 3 were in the posterior circulation. And in total, 20 (11.3%) cases suffered from postoperative hematoma growth, of which 4 were with aneurysms. Additionally,the 30-day mortality after stroke in patients with aneurysms was 8.69% (2/23), comparable to 13.33% in without (22/165,p = 0.744). The proportion of the favorable outcome at 6-month follow-up in patients with aneurysms was comparable to that in without (47.8% versus 48.5%,p = 1.000) Insignificant associations were demonstrated between the unruptured intracranial aneurysms and postoperative intracranial rehemorrhage (p = 0.092), 30-day death(p = 0.588) and poor long-term prognosis (p = 0.332), respectively.

CONCLUSION

Our findings suggest that unruptured intracranial aneurysms seem to represent no increased risks of poor outcome after local thrombolysis for intracerbral hematomas.

Tissue-type plasminogen activator regulates p35-mediated Cdk5 activation in the postsynaptic terminal

Neuronal depolarization induces the synaptic release of tissue-type plasminogen activator (tPA). Cyclin-dependent kinase-5 (Cdk5) is a member of the family of cyclin-dependent kinases that regulates cell migration and synaptic function in postmitotic neurons. Cdk5 is activated by its binding to p35 (also known as Cdk5r1), a membrane-anchored protein that is rapidly degraded by the proteasome. Here, we show that tPA prevents the degradation of p35 in the synapse by a plasminogen-dependent mechanism that requires open synaptic N-methyl-D-aspartate (NMDA) receptors. We show that tPA treatment increases the abundance of p35 and its binding to Cdk5 in the postsynaptic density (PSD). Furthermore, our data indicate that tPA-induced p35-mediated Cdk5 activation does not induce cell death, but instead prevents NMDA-induced ubiquitylation of postsynaptic density protein-95 (PSD-95; also known as Dlg4) and the removal of GluR1 (also known as Gria1)-containing α-amino-3-hydroxy-5-methyl-4-isoxazoleproprionic acid (AMPA) receptors from the PSD. These results show that the interaction between tPA and synaptic NMDA receptors regulates the expression of AMPA receptor subunits in the PSD via p35-mediated Cdk5 activation. This is a novel role for tPA as a regulator of Cdk5 activation in cerebral cortical neurons.

The ratio of concentrations of aminocaproic acid and tranexamic acid that prevent plasmin activation of platelets does not provide equivalent inhibition of plasmatic fibrinolysis

Aminocaproic acid (EACA) availability has recently been decreased whereas tranexamic acid (TXA) is still available as an antifibrinolytic agent to decrease blood loss associated with procedures involving cardiopulmonary bypass (CPB) by inhibiting plasmin mediated platelet activation. Given that the clinical inclination is to substitute TXA for EACA, we sought to compare the antifibrinolytic efficacy of the two agents using the clinically accepted molar ratio of EACA:TXA (7.9:1) that prevents platelet activation in a viscoelastic based system under a variety of conditions in human plasma; 25-50% therapeutic concentration (EACA 32.5-65 µg/ml, TXA 5-10 µg/ml) in the presence of 1500-3000 IU tissue-type plasminogen activator, with 0-50% dilution of plasma with buffer. In all equipotent concentrations, TXA provided superior antifibrinolytic action compared to EACA. It is hoped that this work will serve as a rationale to further investigate these and other similar agents, especially now in a time of unpredictable unavailability of key medications needed to optimize patient care. It is also our wish that these data assist perfusionists, anesthesiologists and cardiothoracic surgeons with their consideration of using an antifibrinolytic agent when managing complex patients with hypercoagulable states (e.g., ventricular assist device explant, infective endocarditis) undergoing CPB.

Tissue-type plasminogen activator protects the postsynaptic density in the ischemic brain

Cerebral ischemia causes the presynaptic release of tissue-type plasminogen activator (tPA). The postsynaptic density (PSD) is a postsynaptic structure that provides a matrix where signaling transduction of excitatory synapses takes place. The postsynaptic density protein-95 (PSD-95) is the most abundant scaffolding protein in the postsynaptic density (PSD), where it modulates the postsynaptic response to the presynaptic release of glutamate by regulating the anchoring of glutamate receptors to the PSD. We found that tPA induces the local translation of PSD-95 mRNA and the subsequent recruitment of PSD-95 protein to the PSD, via plasminogen-independent activation of TrkB receptors. Our data show that PSD-95 is removed from the PSD during the early stages of cerebral ischemia, and that this effect is abrogated by either the release of neuronal tPA, or intravenous administration of recombinant tPA (rtPA). We report that the effect of tPA on PSD-95 is associated with inhibition of the phosphorylation and recruitment of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors to the PSD, known to amplify the effect of the excitotoxic injury, and that this is followed by TrkB-mediated protection of dendritic spines from the harmful effects of the hypoxic insult. These data reveal that tPA is a synaptic protector in the ischemic brain.

Cell permeable HMGB1-binding heptamer peptide ameliorates neurovascular complications associated with thrombolytic therapy in rats with transient ischemic stroke

Background

Blood–brain barrier (BBB) breakdown and inflammatory responses are the major causes of tissue-type plasminogen activator (tPA)-induced hemorrhagic transformation (HT), while high-mobility group box 1 (HMGB1) exacerbates inflammatory damage to BBB during the process of brain ischemia/reperfusion. This study aimed to investigate the change of HMGB1 after thrombolytic therapy and whether blocking HMGB1 could ameliorate the neurovasculature complications secondary to tPA treatment in stroke rats.

Methods

Sera from acute stroke patients and rats with thrombolytic therapy were collected to investigate HMGB1 secretion. Male Sprague-Dawley rats with 2 h or 4.5 h middle cerebral artery occlusion were continuously infused with tPA followed by administration of membrane permeable HMGB1-binding heptamer peptide (HBHP). The mortality rate, neurological score, HT, brain swelling, BBB permeability, and inflammatory factors were determined.

Results

The results revealed that HMGB1 levels were elevated in both stroke patients and rats after tPA treatment. Blocking HMGB1 signaling by HBHP in the rat model of 4.5 h brain ischemia significantly attenuated tPA-related complications, including mortality rate, the degree of hemorrhage, brain swelling, neurological deficits, BBB impairment, microglia activation, and the expressions of inflammatory cytokines.

Conclusions

tPA treatment might induce HMGB1 secretion while blocking HMGB1 with HBHP could markedly reduce the risk of thrombolysis-associated brain hemorrhage and mortality through attenuating BBB damage and inflammatory reactions. These results indicate that HMGB1 may potentiate the risk of HT in tPA administration and that blocking HMGB1 signaling would be helpful in preventing complications brought by thrombolysis in ischemic stroke.

Trial registration

http://www.chictr.org.cn. Unique identifier: ChiCTR-OOC-16010052. Registered 30 November 2016.

Electronic supplementary material

The online version of this article (10.1186/s12974-018-1267-5) contains supplementary material, which is available to authorized users.

Generation and characterization of tissue-type plasminogen activator transgenic rats

To address a species difference in the responsiveness to human recombinant tissue-type plasminogen activator (rt-PA) between rats and humans, tPA transgenic (Tg) rats were generated and characterized. In the rats, transcriptional regulation of tPA was designed under the control of the endogenous tPA promoter. There were no significant differences in hematological parameters between the tPA Tg and non Tg rats. Plasma tPA concentration was significantly increased and serum free PAI-1 was significantly decreased in the tPA Tg rats. Significant overexpression of tPA mRNA in five major organs was also confirmed in the tPA Tg rats. In contrast, the extent of tPA mRNA induction by pathophysiological stimuli (focal cerebral ischemia) was comparable in the two strains. Earlier increase in the plasma D-Dimer level was observed in the tPA Tg rats in a model of thromboembolism compared with the non Tg rats. On the other hand, there was no statistically significant prolongation of bleeding time in a rat model of bleeding between the two strains. rt-PA showed dose-related blood flow restoration in a rat model of thromboembolic stroke in the tPA Tg rats from a dose (1 mg/kg, i.v.) similar to clinical doses for human stroke patients. In conclusion, tPA Tg rats, in which tPA is overexpressed and endogenous fibrinolytic activity is enhanced without hemostatic abnormality, were generated. tPA Tg rats would be beneficial for the pharmacological and the toxicological evaluation of rt-PA and other various fibrinolytic enhancers.

PAI1 blocks NMDA receptor-mediated effects of tissue-type plasminogen activator on cell signaling and physiology

The fibrinolysis proteinase tissue-type plasminogen activator (tPA, also known as PLAT) triggers cell signaling and regulates cell physiology. In PC12 cells, Schwann cells and macrophages, the N-methyl-D-aspartate receptor (NMDA-R) mediates tPA signaling. Plasminogen activator inhibitor-1 (PAI1, also known as SERPINE1) is a rapidly acting inhibitor of tPA enzyme activity. Although tPA-initiated cell signaling is not dependent on its enzyme active site, we show that tPA signaling is neutralized by PAI1. In PC12 cells, PAI1 blocked the ERK1/2 activation mediated by tPA as well as neurite outgrowth. In Schwann cells, PAI1 blocked tPA-mediated ERK1/2 activation and cell migration. In macrophages, PAI1 blocked the ability of tPA to inhibit IκBα phosphorylation and cytokine expression. The cell signaling activity of tPA-PAI1 complex was rescued when the complex was formed with PAI1R^76E, which binds to LRP1 with decreased affinity, by pre-treating cells with the LRP1 antagonist receptor-associated protein and upon LRP1 gene silencing. The inhibitory role of LRP1 in tPA-PAI1 complex-initiated cell signaling was unanticipated given the reported role of LRP1 as an NMDA-R co-receptor in signaling responses elicited by free tPA or α₂-macroglobulin. We conclude that PAI1 functions as an in-hibitor not only of the enzyme activity of tPA but also of tPA receptor-mediated activities.

Retinal Endovascular Surgery with Tissue Plasminogen Activator Injection for Central Retinal Artery Occlusion

Purpose

To report 2 cases of central retinal artery occlusion (CRAO) who underwent retinal endovascular surgery with injection of tissue plasminogen activator (tPA) into the retinal artery and showed a remarkable improvement in visual acuity and retinal circulation.

Methods

Standard 25-G vitrectomy was performed under local anesthesia. Simultaneously, tPA (80,000 units/mL) solution was injected into the retinal artery of the optic disc for 2–3 min using a microneedle. Changes in visual acuity, fundus photography, optical coherence tomography (OCT), fluorescein angiography, and laser speckle flowgraphy (LSFG) results were examined.

Results

Both cases could be treated within 12 h after the onset of CRAO. Case 1 was a 47-year-old woman. Her visual acuity improved from counting fingers before operation to 0.08 logMAR 1 month after the surgery. However, thinning of the retina at the macula was observed by OCT. Case 2 was a 70-year-old man. His visual acuity improved from counting fingers to 0.1 logMAR 2 months after the surgery. Both fluorescein angiography and LSFG showed improvement in retinal circulation after the surgery in case 2.

Conclusions

Retinal endovascular surgery with injection of tPA into the retinal artery was feasible and may be a way to improve visual acuity and retinal circulation when performed in the acute phase of CRAO.

Plasminogen activator system homeostasis and its dysregulation by ethanol in astrocyte cultures and the developing brain

In utero alcohol exposure can cause fetal alcohol spectrum disorders (FASD), characterized by structural brain abnormalities and long-lasting behavioral and cognitive dysfunction. Neuronal plasticity is affected by in utero alcohol exposure and can be modulated by extracellular proteolysis. Plasmin is a major extracellular serine-protease whose activation is tightly regulated by the plasminogen activator (PA) system. In the present study we explored the effect of ethanol on the expression of the main components of the brain PA system in sex-specific cortical astrocyte primary cultures in vitro and in the cortex and hippocampus of post-natal day (PD) 9 male and female rats. We find that ethanol alters the PA system in astrocytes and in the developing brain. In particular, the expression of tissue-type PA (tPA), encoded by the gene Plat, is consistently upregulated by ethanol in astrocytes in vitro and in the cortex and hippocampus in vivo. Astrocytes exhibit endogenous plasmin activity that is increased by ethanol and recombinant tPA and inhibited by tPA silencing. We also find that tPA is expressed by astrocytes of the developing cortex and hippocampus in vivo. All components of the PA system investigated, with the exception of Neuroserpin/Serpini1, are expressed at higher levels in astrocyte cultures than in the developing brain, suggesting that astrocytes are major producers of these proteins in the brain. In conclusion, astrocyte PA system may play a major role in the modulation of neuronal plasticity; ethanol-induced upregulation of tPA levels and plasmin activity may be responsible for altered neuronal plasticity in FASD.

LDL receptor blockade reduces mortality in a mouse model of ischaemic stroke without improving tissue-type plasminogen activator-induced brain haemorrhage: towards pre-clinical simulation of symptomatic ICH

Background

Symptomatic intracerebral haemorrhage (sICH) following tissue-type plasminogen activator (rt-PA) administration is the most feared and lethal complication of thrombolytic therapy for ischaemic stroke, creating a significant obstacle for a broader uptake of this beneficial treatment. rt-PA also undermines cerebral vasculature stability in a multimodal process which involves engagement with LDL receptor-related protein 1 (LRP-1), potentially underlying the development of sICH.

Aims and methods

We aimed to simulate rt-PA-induced haemorrhagic transformation (HT) in a mouse model of stroke and to assess if it drives symptomatic neurological deterioration and whether it is attenuated by LDL receptor blockade. rt-PA (10 mg/kg) or its vehicle, with or without the LDL receptor antagonist, receptor-associated protein (RAP; 2 mg/kg), were intravenously injected at reperfusion after 0.5 or 4 h of middle cerebral artery occlusion (MCAo). Albumin and haemoglobin content were measured in the perfused mouse brains 24 h post MCAo as indications of blood–brain barrier (BBB) compromise and HT, respectively.

Results

rt-PA did not elevate brain albumin and haemoglobin levels in sham mice or in mice subjected to 0.5 h MCAo. In contrast, administration of rt-PA after prolonged MCAo (4 h) caused a marked increase in HT (but similar changes in brain albumin) compared to vehicle, mimicking the clinical shift from a safe to detrimental intervention. Interestingly, this HT did not correlate with functional deficit severity at 24 h, suggesting that it does not play a symptomatic role in our mouse stroke model. Co-administration of RAP with or without rt-PA reduced mortality and neurological scores but did not effectively decrease brain albumin and haemoglobin levels.

Conclusion

Despite the proven causative relationship between severe HT and neurological deterioration in human stroke, rt-PA-triggered HT in mouse MCAo does not contribute to neurological deficit or simulate sICH. Model limitations, such as the long duration of occlusion required, the type of HT achieved and the timing of deficit assessment may account for this mismatch. Our results further suggest that blockade of LDL receptors improves stroke outcome irrespective of rt-PA, blood–brain barrier breakdown and HT.

Preventing graft restenosis after coronary artery bypass grafting with tissue-type plasminogen activator

Objective

To explore the feasibility and safety of using tissue-type plasminogen activator (t-PA) to prevent graft restenosis after coronary artery bypass grafting (CABG).

Methods

In this prospective observational study, 37 patients underwent CABG between June 2009 and May 2013. These patients were grouped according to the anti-coagulation strategy after surgery: t-PA (n = 12) and conventional treatments (n = 25). In the t-PA group, the patients received acetylsalicylic acid (ASA) and clopidogrel plus intravenous infusion of t-PA (0.25 mg/kg/day) starting at 24 h after surgery and that lasted for 3 days. In the conventional group, the patients received only ASA and clopidogrel. 64-row spiral computed tomographic coronary angiography was performed at 1 week, 1, and 3 months after surgery to evaluate the patency of the graft vessel.

Results

The mean stenosis severity of the saphenous vein grafts was lower in the t-PA group compared with the conventional group at 3 months after surgery (p < 0.05), but there was no significant difference at 1 week and 1 month (p > 0.05). The patency rate of the grafts was not significantly different between the two groups at 1 week, 1, and 3 months after surgery (p > 0.05).

Conclusion

Early application of t-PA after CABG was feasible and safe, and might help prevent early restenosis of SV grafts. Additional clinical randomized trials are necessary to address this issue.

Nationwide "Hospital Emergent Capability Accreditation by Level-Stroke" Improves Stroke Treatment in Taiwan

Background and Purpose

Recombinant tissue plasminogen activator (rtPA) is one of the proven therapies that improve the outcome of patients with acute ischemic stroke (AIS). In 2009, the Ministry of Health and Welfare, Executive Yuan, Republic of China, launched the project “Hospital Emergent Capability Accreditation by Level-Stroke (HECAL-Stroke)” to improve AIS treatment in Taiwan. The current study was performed to determine whether the project launched by the government was effective in promoting rtPA therapy among AIS patients.

Methods

All participating hospitals were verified and designated as “heavy duty (HD),” “moderate duty (MoD),” or “medium duty (MeD)” according to the stroke center criteria. Four annual indices (rates of treatment, protocol adherence, in-time treatment, and complications) were recorded from 2009 to 2014 as outcome measures. The data were analyzed using the χ² test for significance.

Results

The number of certified hospitals progressively increased from 74 to 112 during the 6-year period and finally consisted of 33 HD, 9 MoD and 70 MeD hospitals in 2014. The annual intravenous rtPA treatment rate increased significantly from 3.0% in 2009 to 4.5% in 2014. The protocol adherence rates were 95.7% in the HD group, 92.4% in the MoD group and 72.8% in the MeD group. The annual in-time treatment rate significantly improved from 26.0% in 2009 to 60.1% in 2014. The overall symptomatic intracranial hemorrhagic rate after rtPA treatment was 8.6%.

Conclusions

Initiation of the HECAL-Stroke project by the government significantly improved rtPA treatment in Taiwan.

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

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

Ancrod revisited: viscoelastic analyses of the effects of Calloselasma rhodostoma venom on plasma coagulation and fibrinolysis

Fibrinogen depletion via catalysis by snake venom enzymes as a therapeutic strategy to prevent or treat thrombotic disorders was utilized for over four decades, with ancrod being the quintessential agent. However, ancrod eventually was found to not be of clinical utility in large scale stroke trial, resulting in the eventual discontinuation of the administration of the drug for any indication. It was hypothesized that ancrod, possessing thrombin-like activity, may have unappreciated robust coagulation kinetics. Using thrombelastographic methods, a comparison of equivalent tissue factor initiated thrombin generation and Calloselasma rhodostoma venom (rich in ancrod activity) on plasmatic coagulation kinetics was performed. The venom resulted in thrombi that formed nearly twice as fast compared to thrombin formed clots, and there was no difference in fibrinolytic kinetics initiated by tissue-type plasminogen activator. In plasma containing iron and carbon monoxide modified fibrinogen, which may be found in patients at risk of stroke, the coagulation kinetic differences observed with venom was still more vigorous than that seen with thrombin. These phenomena may provide insight into the clinical failure of ancrod, and may serve as an impetus to revisit the concept of fibrinogen depletion via fibrinogenolytic enzymes, not those with thrombin-like activity.

Isoflurane preconditioning inhibits the effects of tissue-type plasminogen activator on brain endothelial cell in an in vitro model of ischemic stroke

Tissue-type plasminogen activator (tPA) is the only treatment for ischemic stroke. However, tPA could induce the intracranial hemorrhage (ICH), which is the main cause of death in ischemic stroke patient after tPA treatment. At present, there is no treatment strategy to ameliorate tPA-induced brain injury after ischemia. Therefore, we investigated the effect of pre-treated isoflurane, which is a volatile anesthetic and has beneficial effects on neurological dysfunction, brain edema and infarct volume in ischemic stroke model. In this study, we used oxygen/glucose deprivation and reperfusion (OGD/R) condition to mimic an ischemic stroke in vitro. Matrix metalloproteinases (MMP) activity was measured in endothelial cell media. Also, neuronal cell culture was performed to investigate the effect of pretreated isoflurane on the neuronal cell survival after tPA-induced injury during OGD/R. Isoflurane pretreatment prevented tPA-induced MMP-2 and MMP-9 activity and suppressed tPA-triggered LRP/NF-κB/Cox-2 signaling after OGD/R. Neuronal cells, incubated with endothelial cell conditioned medium (EC-CM) after tPA + OGD/R, showed upregulation of pro-apoptotic molecules. However, neurons incubated with isoflurane-pretreated EC-CM showed increased anti-apoptotic molecules. Our findings suggest that isoflurane pretreatment could attenuate tPA-exaggerated brain ischemic injury, by reducing tPA-induced LRP/NF-κB/Cox-2 in endothelial cells, endothelial MMP-2 and MMP-9 activation, and subsequent pro-apoptotic molecule in neurons after OGD/R.

Cost-effectiveness of stent-retriever thrombectomy in combination with IV t-PA compared with IV t-PA alone for acute ischemic stroke in the UK

OBJECTIVE

To evaluate the cost-effectiveness of neurothrombectomy with a stent retriever (Solitaire * Revascularization Device) in treating acute ischemic stroke patients from the UK healthcare provider perspective.

METHODS

A Markov model was developed to simulate health outcomes and costs of two therapies over a lifetime time horizon: stent-retriever thrombectomy in combination with intravenous tissue-type plasminogen activator (IV t-PA), and IV t-PA alone. The model incorporated an acute phase (0-90 days) and a rest of life phase (90+ days). Health states were defined by the modified Rankin Scale score. During the rest of life phase, patients remained in the same health state until a recurrent stroke or death. Clinical effectiveness and safety data were taken from the SWIFT PRIME study. Resource use and health state utilities were informed by published data.

RESULTS

Combined stent-retriever thrombectomy and IV t-PA led to improved quality-of-life and increased life expectancy compared to IV t-PA alone. The higher treatment costs associated with the use of stent-retriever thrombectomy were offset by long-term cost savings due to improved patient health status, leading to overall cost savings of £33 190 per patient and a net benefit of £79 402. Deterministic and probabilistic sensitivity analyses demonstrated that the results were robust to a wide range of parameter inputs.

LIMITATIONS

The acute and long-term costs resource use data were taken from a study based on a patient population that was older and may have had additional comorbidities than the SWIFT PRIME population, resulting in costs that may not be representative of the cohort within this model. In addition, the estimates may not reflect stroke care today as no current evidence is available; however, the cost estimates were deemed reasonable by clinical opinion.

CONCLUSIONS

Combined stent-retriever neurothrombectomy and IV t-PA is a cost-effective treatment for acute ischemic stroke compared with IV t-PA alone.

The Plasminogen Activation System Promotes Dendritic Spine Recovery and Improvement in Neurological Function After an Ischemic Stroke

Advances in neurocritical care and interventional neuroradiology have led to a significant decrease in acute ischemic stroke (AIS) mortality. In contrast, due to the lack of an effective therapeutic strategy to promote neuronal recovery among AIS survivors, cerebral ischemia is still a leading cause of disability in the world. Ischemic stroke has a harmful impact on synaptic structure and function, and plasticity-mediated synaptic recovery is associated with neurological improvement following an AIS. Dendritic spines (DSs) are specialized dendritic protrusions that receive most of the excitatory input in the brain. The deleterious effect of cerebral ischemia on DSs morphology and function has been associated with impaired synaptic transmission and neurological deterioration. However, these changes are reversible if cerebral blood flow is restored on time, and this recovery has been associated with neurological improvement following an AIS. Tissue-type plasminogen activator (tPA) and urokinase-type plasminogen activator (uPA) are two serine proteases that, besides catalyzing the conversion of plasminogen into plasmin in the intravascular and pericellular environment, respectively, are also efficient inductors of synaptic plasticity. Accordingly, recent evidence indicates that both, tPA and uPA, protect DSs from the metabolic stress associated with the ischemic injury, and promote their morphological and functional recovery during the recovery phase from an AIS. Here, we will review data indicating that plasticity-induced changes in DSs and the associated post-synaptic density play a pivotal role in the recovery process from AIS, making special emphasis on the role of tPA and uPA in this process.

The Plasminogen Activation System Promotes Dendritic Spine Recovery and Improvement in Neurological Function After an Ischemic Stroke

Advances in neurocritical care and interventional neuroradiology have led to a significant decrease in acute ischemic stroke (AIS) mortality. In contrast, due to the lack of an effective therapeutic strategy to promote neuronal recovery among AIS survivors, cerebral ischemia is still a leading cause of disability in the world. Ischemic stroke has a harmful impact on synaptic structure and function, and plasticity-mediated synaptic recovery is associated with neurological improvement following an AIS. Dendritic spines (DSs) are specialized dendritic protrusions that receive most of the excitatory input in the brain. The deleterious effect of cerebral ischemia on DSs morphology and function has been associated with impaired synaptic transmission and neurological deterioration. However, these changes are reversible if cerebral blood flow is restored on time, and this recovery has been associated with neurological improvement following an AIS. Tissue-type plasminogen activator (tPA) and urokinase-type plasminogen activator (uPA) are two serine proteases that, besides catalyzing the conversion of plasminogen into plasmin in the intravascular and pericellular environment, respectively, are also efficient inductors of synaptic plasticity. Accordingly, recent evidence indicates that both, tPA and uPA, protect DSs from the metabolic stress associated with the ischemic injury, and promote their morphological and functional recovery during the recovery phase from an AIS. Here, we will review data indicating that plasticity-induced changes in DSs and the associated post-synaptic density play a pivotal role in the recovery process from AIS, making special emphasis on the role of tPA and uPA in this process.

The story of an exceptional serine protease, tissue-type plasminogen activator (tPA)

The only acute treatment of ischemic stroke approved by the health authorities is tissue recombinant plasminogen activator (tPA)-induced thrombolysis. Under physiological conditions, tPA, belonging to the serine protease family, is secreted by endothelial and brain cells (neurons, astrocytes, microglia, oligodendrocytes). Although revascularisation induced by tPA is beneficial during a stroke, research over the past 20 years shows that tPA can also be deleterious for the brain parenchyma. Thus, in this review of the literature, after a brief history on the discovery of tPA, we reviewed current knowledge of mechanisms by which tPA can influence brain function in physiological and pathological conditions.

Chronic kidney disease and intravenous thrombolysis in acute stroke: A systematic review and meta-analysis

BACKGROUND

The association between chronic kidney disease (CKD) and hemorrhagic complications or clinical outcomes in patients treated with intravenous (IV) thrombolytic agents is controversial.

METHODS

We searched multiple databases for studies on the association between CKD and symptomatic intracerebral hemorrhage (ICH) and/or clinical outcomes in acute stroke patients treated with IV tissue plasminogen activator (tPA). Observational studies that evaluated the association between CKD and outcomes after adjusting for other confounding factors were eligible. We assessed study quality and performed a meta-analysis. The main outcome was symptomatic ICH. The secondary outcomes were poor functional status at 3 months using the modified Rankin Scale, mortality at 3 months, and any ICH.

RESULTS

Seven studies were selected based on our eligibility criteria. Of 7168 patients treated with IV tPA, 2001 (27.9%) had CKD. Patients with CKD had a higher risk of symptomatic ICH and mortality [pooled odds ratio (OR) 1.56, 95% confidence interval (CI) 1.05-2.33 and pooled OR 1.70, 95% CI 1.03-2.81, respectively]. Patients with CKD were likely to have an increased risk of poor outcome at 3 months. There was no significant association between CKD and any ICH.

CONCLUSIONS

Chronic kidney disease may significantly affect symptomatic hemorrhagic complications and poor clinical outcomes following administration of IV tPA.

Tissue Plasminogen Activator Expression Is Restricted to Subsets of Excitatory Pyramidal Glutamatergic Neurons

Although the extracellular serine protease tissue plasminogen activator (tPA) is involved in pathophysiological processes such as learning and memory, anxiety, epilepsy, stroke, and Alzheimer's disease, information about its regional, cellular, and subcellular distribution in vivo is lacking. In the present study, we observed, in healthy mice and rats, the presence of tPA in endothelial cells, oligodendrocytes, mastocytes, and ependymocytes, but not in pericytes, microglial cells, and astrocytes. Moreover, blockage of the axo-dendritic transport unmasked tPA expression in neurons of cortical and hippocampal areas. Interestingly, combined electrophysiological recordings, single-cell reverse transcription polymerase chain reaction (RT-PCR), and immunohistological analyses revealed that the presence of tPA is restricted to subsets of excitatory pyramidal glutamatergic neurons. We further evidenced that tPA is stored in synaptobrevin-2-positive glutamatergic synaptic vesicles. Based on all these data, we propose the existence of tPA-ergic neurons in the mature brain.

Role of mesenchymal stem cell-derived fibrinolytic factor in tissue regeneration and cancer progression

Tissue regeneration during wound healing or cancer growth and progression depends on the establishment of a cellular microenvironment. Mesenchymal stem cells (MSC) are part of this cellular microenvironment, where they functionally modulate cell homing, angiogenesis, and immune modulation. MSC recruitment involves detachment of these cells from their niche, and finally MSC migration into their preferred niches; the wounded area, the tumor bed, and the BM, just to name a few. During this recruitment phase, focal proteolysis disrupts the extracellular matrix (ECM) architecture, breaks cell-matrix interactions with receptors, and integrins, and causes the release of bioactive fragments from ECM molecules. MSC produce a broad array of proteases, promoting remodeling of the surrounding ECM through proteolytic mechanisms. The fibrinolytic system, with its main player plasmin, plays a crucial role in cell migration, growth factor bioavailability, and the regulation of other protease systems during inflammation, tissue regeneration, and cancer. Key components of the fibrinolytic cascade, including the urokinase plasminogen activator receptor (uPAR) and plasminogen activator inhibitor-1 (PAI-1), are expressed in MSC. This review will introduce general functional properties of the fibrinolytic system, which go beyond its known function of fibrin clot dissolution (fibrinolysis). We will focus on the role of the fibrinolytic system for MSC biology, summarizing our current understanding of the role of the fibrinolytic system for MSC recruitment and the functional consequences for tissue regeneration and cancer. Aspects of MSC origin, maintenance, and the mechanisms by which these cells contribute to altered protease activity in the microenvironment under normal and pathological conditions will also be discussed.