Effects of tissue plasminogen activator and annexin A2 combination therapy on long-term neurological outcomes of rat focal embolic stroke

Advancing stroke recovery: unlocking the potential of cellular dynamics in stroke recovery

Stroke stands as a predominant cause of mortality and morbidity worldwide, and there is a pressing need for effective therapies to improve outcomes and enhance the quality of life for stroke survivors. In this line, effective efferocytosis, the clearance of apoptotic cells, plays a crucial role in neuroprotection and immunoregulation. This process involves specialized phagocytes known as "professional phagocytes" and consists of four steps: "Find-Me," "Eat-Me," engulfment/digestion, and anti-inflammatory responses. Impaired efferocytosis can lead to secondary necrosis and inflammation, resulting in adverse outcomes following brain pathologies. Enhancing efferocytosis presents a potential avenue for improving post-stroke recovery. Several therapeutic targets have been identified, including osteopontin, cysteinyl leukotriene 2 receptor, the µ opioid receptor antagonist β-funaltrexamine, and PPARγ and RXR agonists. Ferroptosis, defined as iron-dependent cell death, is now emerging as a novel target to attenuate post-stroke tissue damage and neuronal loss. Additionally, several biomarkers, most importantly CD163, may serve as potential biomarkers and therapeutic targets for acute ischemic stroke, aiding in stroke diagnosis and prognosis. Non-pharmacological approaches involve physical rehabilitation, hypoxia, and hypothermia. Mitochondrial dysfunction is now recognized as a major contributor to the poor outcomes of brain stroke, and medications targeting mitochondria may exhibit beneficial effects. These strategies aim to polarize efferocytes toward an anti-inflammatory phenotype, limit the ingestion of distressed but viable neurons, and stimulate efferocytosis in the late phase of stroke to enhance post-stroke recovery. These findings highlight promising directions for future research and development of effective stroke recovery therapies.

Fibrinolytic Agents in Thromboembolic Diseases: Historical Perspectives and Approved Indications

Fibrinolytic agents catalyze the conversion of the inactive proenzyme plasminogen into the active protease plasmin, degrading fibrin within the thrombus and recanalizing occluded vessels. The history of these medications dates to the discovery of the first fibrinolytic compound, streptokinase, from bacterial cultures in 1933. Over time, researchers identified two other plasminogen activators in human samples, namely urokinase and tissue plasminogen activator (tPA). Subsequently, tPA was cloned using recombinant DNA methods to produce alteplase. Several additional derivatives of tPA, such as tenecteplase and reteplase, were developed to extend the plasma half-life of tPA. Over the past decades, fibrinolytic medications have been widely used to manage patients with venous and arterial thromboembolic events. Currently, alteplase is approved by the U.S. Food and Drug Administration (FDA) for use in patients with pulmonary embolism with hemodynamic compromise, ST-segment elevation myocardial infarction (STEMI), acute ischemic stroke, and central venous access device occlusion. Reteplase and tenecteplase have also received FDA approval for treating patients with STEMI. This review provides an overview of the historical background related to fibrinolytic agents and briefly summarizes their approved indications across various thromboembolic diseases.

Naoxueshu oral liquid promotes hematoma absorption by targeting CD36 in M2 microglia via TLR4/MyD88/NF-κB signaling pathway in rats with intracerebral hemorrhage

ETHNOPHARMACOLOGICAL RELEVANCE

Intracerebral hemorrhage (ICH) is a major public health issue that leads to elevated rates of death and disability and has few proven treatments. Naoxueshu oral liquid (NXS), a TCM patent drug, is widely used in patients with ICH. Although a series of clinical studies have confirmed the efficacy and safety of NXS, the underlying mechanism of hematoma absorption is unclear.

AIM OF THE STUDY

Our work aimed to elucidate the effect and mechanism of NXS on hematoma absorption in rats with ICH.

MATERIALS AND METHODS

Induction of ICH model in the rats with intracerebral injection of collagenase VII, followed by treatment with NXS and Edaravone as a control neuroprotection medication. Neural functional recovery was assessed using mNSS, foot fault test, corner test, forelimb grip-traction test, and adhesive removal test. Hematoma absorption was assessed by the spectrophotometric hemoglobin assay with Drabkin's reagent. The protein expression of CD36, M2 microglia marker (CD206 and YM-1) and TLR4/MyD88/NF-κB pathway related proteins were determined by Western blot and immunofluorescence.

RESULTS

NXS could significantly ameliorate the ICH recovery of neural and locomotor function as well as reduce hemorrhage volume. NXS could increase the expression of CD36 expressed in M2 microglia and promote M2 microglia polarization. Simultaneously, NXS significantly suppressed protein expressions of TLR4, MyD88, and NF-κB following ICH in rats. The results indicated that lipopolysaccharide (LPS), TLR4 specific agonist, could partially reverse the change in ICH rats administrated with NXS.

CONCLUSIONS

NXS promotes hematoma absorption by targeting CD36 expression in M2 microglia via TLR4/MyD88/NF-κB signaling pathway in rats with ICH. Collectively, current research provides a novel theoretical basis for the clinical application of NXS.

Gomisin N attenuated cerebral ischemia-reperfusion injury through inhibition of autophagy by activating the PI3K/AKT/mTOR pathway

BACKGROUND

Ischemic stroke is a major global cause of mortality and permanent disability.  Studies have shown that autophagy is essential to maintain cell homeostasis and inevitably lead to neuronal damage after cerebral ischemia. Gomisin N (GN), lignin isolated from Schisandra chinensis, possesses multiple pharmacological activities. However, there is no research on the potential of GN for neuroprotection in ischemic stroke.

PURPOSE

The current work aimed to explore the potential therapeutic possibilities of GN on ischemic stroke and investigate the underlying molecular mechanisms.

STUDY DESIGN

The neuroprotective effects of GN on PC12 cells induced by oxygen glucose deprivation/reoxygenation (OGD/R) and mice with middle cerebral artery occlusion/reperfusion (MCAO/R) injury were investigated.

METHODS

On day 3 after ischemia, the infarct volume and neurological function were assessed. The level of autophagy was measured in vivo and in vitro using Transmission electron microscopy (TEM) and Monodansylcadaverine (MDC) staining. The interaction between GN and PI3K/AKT/mTOR pathway was investigated by molecular docking. Additionally, the expressions of critical proteins in the PI3K/AKT/mTOR signaling pathway and autophagy markers were determined by western blotting.

RESULTS

In compared to the Model group, GN might considerably improve the neurological and locomotor function following a stroke, as well as lower the volume of the cerebral infarct volume and the number of autophagosomes. GN therapy may suppress autophagy by activating the PI3K/Akt/mTOR signaling pathway in the penumbra. In vitro, MDC and TEM results showed that GN treatment obviously suppressed autophagy. Meanwhile, GN downregulated LC3II/LC3I expression ratio while upregulated the p62 expression level. In further studies, GN dramatically boosted the expression ratios of p-PI3K/PI3K, p-AKT/AKT, and p-mTOR/mTOR proteins in PC12 cells following OGD/R damage. However, the PI3K inhibitor (LY294002) reversed the increase of p-PI3K/PI3K, p-AKT/AKT, and p-mTOR/mTOR expression ratio induced by GN administration. Also, LY294002 significantly partially attenuated GN induced reduction of autophagy and increase of cell viability compared with GN treatment alone.

CONCLUSIONS

Here, we first demonstrate the neuroprotective effects of GN on MCAO mice and OGD/R induced PC12 cells injury. A possible mechanism by which GN prevents ischemic stroke is proposed: GN could restrain autophagy by stimulating the PI3K/AKT/mTOR signaling pathways. More effects and mechanisms of GN on the rehabilitation of ischemic stroke are worthy to be explored in the future.

Annexin A2 promotes angiogenesis after ischemic stroke via annexin A2 receptor - AKT/ERK pathways

Promoting angiogenesis to restore circulation to the ischemic tissue is still an important therapeutic target in stroke. Our group and others previously reported that the Ca²⁺-regulated, phospholipid-and membrane-binding protein-Annexin A2 (ANXA2) functions in cerebrovascular integrity and retinal neoangiogenesis. Here, we hypothesized that ANXA2 may regulate angiogenesis after stroke, ultimately improve neurological outcomes. Compared with wild type (WT) mice, the density of microvessels in brain and the number of new vessels sprouting from aortic ring were significantly increased in Anxa2 knock-in (Anxa2 KI) mice. After focal cerebral ischemia, proliferation of brain endothelial cells in Anxa2 KI mice was significantly elevated at 7 days post-stroke, which further improved behavioral recovery. To assess the pro-angiogenic mechanisms of ANXA2, we used brain endothelial cells cultures to investigate its effects on cell tube-numbers and migration. Recombinant ANXA2 increased tube-numbers and migration of brain endothelial cells either under normal condition or after oxygen glucose deprivation (OGD) injury. Co-immunoprecipitation experiments demonstrated that these protective effects of recombinant ANXA2 were regulated by interaction with ANXA2 receptor (A2R), a protein found in cancer cells that can interact with ANXA2 to promote cell migration and proliferation, and the ability of ANXA2-A2R to activate AKT/ERK pathways. Inhibition of AKT/ERK diminished recombinant ANXA2-induced angiogenesis in vitro. Taken together, our study indicates that ANXA2 might be involved in angiogenesis after ischemic stroke. Further investigation of ANXA2-A2R will provide a new therapeutic target for stroke.

Antagonism of histamine H3 receptor promotes angiogenesis following focal cerebral ischemia

Our previous study showed that H3 receptor antagonists reduced neuronal apoptosis and cerebral infarction in the acute stage after cerebral ischemia, but through an action independent of activation of histaminergic neurons. Because enhanced angiogenesis facilitates neurogenesis and neurological recovery after ischemic stroke, we herein investigated whether antagonism of H3R promoted angiogenesis after brain ischemia. Photothrombotic stroke was induced in mice. We showed that administration of H3R antagonist thioperamide (THIO, 10 mg·kg-1·d-1, i.p., from D1 after cerebral ischemia) significantly improved angiogenesis assessed on D14, and attenuated neurological defects on D28 after cerebral ischemia. Compared with wild-type mice, Hrh3-/- mice displayed more blood vessels in the ischemic boundary zone on D14, and THIO administration did not promote angiogenesis in these knockout mice. THIO-promoted angiogenesis in mice was reversed by i.c.v. injection of H3R agonist immepip, but not by H1 and H2 receptor antagonists, histidine decarboxylase inhibitor α-fluoromethylhistidine, or histidine decarboxylase gene knockout (HDC-/-), suggesting that THIO-promoted angiogenesis was independent of activation of histaminergic neurons. In vascular endothelial cells (bEnd.3), THIO (10-9-10-7 M) dose-dependently facilitated cell migration and tube formation after oxygen glucose deprivation (OGD), and H3R knockdown caused similar effects. We further revealed that H3R antagonism reduced the interaction between H3R and Annexin A2, while knockdown of Annexin A2 abrogated THIO-promoted angiogenesis in bEnd.3 cells after OGD. Annexin A2-overexpressing mice displayed more blood vessels in the ischemic boundary zone, which was reversed by i.c.v. injection of immepip. In conclusion, this study demonstrates that H3R antagonism promotes angiogenesis after cerebral ischemia, which is independent of activation of histaminergic neurons, but related to the H3R on vascular endothelial cells and its interaction with Annexin A2. Thus, H3R antagonists might be promising drug candidates to improve angiogenesis and neurological recovery after ischemic stroke.

Erythrocyte Membrane-Enveloped Salvianolic Acid B Nanoparticles Attenuate Cerebral Ischemia-Reperfusion Injury

Purpose

Ischemic stroke is the second leading cause of death and the third leading cause of disability worldwide. Salvianolic acid B (SAB), a water-soluble phenolic acid derived from the traditional Chinese medicine Salvia miltiorrhiza, exerted protective effects on cerebral ischemia-reperfusion injury. However, the efficacy of SAB is seriously hindered by poor blood brain barrier (BBB) permeability and short biological half-life in plasma. Brain targeted biomimetic nanoparticle delivery systems offer much promise in overcoming these limitations.

Methods

A brain targeted biomimetic nanomedicine (RR@SABNPs) was developed, which comprised of SAB loaded bovine serum albumin nanoparticles and functionalized red blood cell membrane (RBCM) with Arg-Gly-Asp (RGD). The characterization parameters, including particle size, zeta potential, morphology, Encapsulation Efficiency (EE), Drug Loading (DL), release behavior, stability, and biocompatibility, were investigated. Moreover, the middle cerebral artery occlusion/reperfusion (MCAO/R) mouse model was used to assess the therapeutic efficacy of RR@SABNPs on ischemic stroke. Finally, the reactive oxygen species (ROS) levels and mitochondrial membrane potential (MMP) were detected by DHE and JC‑1 staining in oxygen-glucose deprivation/reperfusion (OGD/R) and H₂O₂ injured PC12 cells.

Results

RR@SABNPs exhibited spheric morphology with core-shell structures and good stability and biocompatibility. Meanwhile, RR@SABNPs can significantly prolong SAB circulation time by overcoming the reticuloendothelial system (RES) and actively targeting ischemic BBB. Moreover, RR@SABNPs had comprehensive protective effects on MCAO/R model mice, manifested as a reduced infarct volume and improved neurological and sensorimotor functions, and significantly scavenged excess ROS and maintained MMP.

Conclusion

The designed brain targeted biomimetic nanomedicine RR@SABNPs can significantly prolong the half-time of SAB, deliver SAB into the ischemic brain and exhibit good therapeutic effects on MCAO/R model mice.

Investigation on the potential targets of Astragaloside IV against intracerebral hemorrhage based on network pharmacology and experimental validation

Intracerebral hemorrhage (ICH) is a life-threatening type of stroke that affects millions of individuals worldwide. Astragaloside IV (AS-IV), the main bioactive ingredient in Radix Astragali, has been linked to a variety of pharmacologic actions, including stroke. However, the effects and potential mechanisms of AS-IV on hematoma absorption after ICH are still unknown. The study aims to identify potential targets and regulation mechanisms of AS-IV on hematoma absorption after ICH. Network pharmacology, molecular docking, pharmacodynamic study, and western blot were used in this study to explore the potential mechanisms. The results showed that AS-IV could improve the hematoma absorption and neurological outcomes in collagenase VII induced rat ICH models. Molecular docking results had shown that PI3K and AKT were the potential targets of AS-IV against ICH. The experimental validation showed that AS-IV could reduce phosphorylation expression of PI3K and AKT, thereby inhibiting the NF-κB and increasing CD36 expression. This study demonstrated that AS-IV could play a critical role on hematoma absorption after ICH by regulating the PI3K/AKT signaling pathway and promoting CD36 phagocytosis, which provided a new thought for the drug development of ICH.

Danhong injection combined with tPA protects the BBB through Notch-VEGF signaling pathway on long-term outcomes of thrombolytic therapy

Current therapy for ischemic stroke primarily relies on tissue plasminogen activator (tPA), but it is limited by narrow treatment time window, bleeding complications and neurotoxicity. The preliminary study of tPA plus Danhong injection (DHI) shows that it can significantly reduce the side effects of tPA and improve its thrombolytic effect, but the mechanism of this action has not been further studied. In this study, the rats were randomly divided into sham group, vehicle group, DHI group (4 mL/kg), tPA group (5 mg/kg) and DHI+tPA group (4 mL/kg+ 2.5 mg/kg), administered intravenously 4.5 h since focal embolic stroke modeling. After 3 days and 7 days of cerebral ischemia, the neurological function of each treatment group was significantly improved compared with the vehicle group. The combination of DHI and tPA significantly reduced Evans blue (EB) penetration as well as the expressions of the proteins MMP-9, PAI-1 and P-selectin, while upregulating the expressions of claudin-5, occludin, and ZO-1 mRNA. Furthermore, the effect of continuous 7-day treatment was more conspicuous than 3-day treatment. Then, it significantly reduced the expressions of the proteins DLL-4 and VEGFR-2, increased the expressions of Notch-1, HIF-1α and HES-1 mRNA, and promoted the expressions of VEGF/HIF-1α-positive cells at 14 days following stroke. Hematoxylin-eosin (HE) staining and transmission electron microscopy (TEM) also showed that it improved pathological changes of ischemic brain tissue and the cerebral cortex micro-structure. These indicate that DHI combined with tPA may significantly ameliorate blood-brain barrier (BBB) disruption by activating Notch-VEGF signaling pathway to promote angiogenesis for long-term outcomes.

[Spontaneous fibrinolysis and possibilities of its acceleration in pulmonary embolism]

This review contains the data concerning the mechanisms of spontaneous fibrinolysis in pulmonary vessels and possibilities of its acceleration in pulmonary embolism. The spontaneous fibrinolysis system is known to be sequential and multifactorial, with the interaction of accelerators (t-PA and u-PA) and inhibitors (alpha-2-antiplasmin, PAI-1, TAFI). The fibrinolytic processes take place in case of prevailing reactions of accelerating factors over inhibiting ones. The endothelium of pulmonary vessels possesses pronounced antithrombogenic and profibrinolytic properties, therefore, the processes of fibrinolysis in the pulmonary vascular bed normally occur more intensively than in the vessels of the systemic circulation. The membrane proteins of the endothelium annexins A2 activate plasminogen, whereas thrombomodulin inhibits the activity of PAI-1. The main approaches to increase the fibrinolysis intensity in conditions of pulmonary embolism may be aimed at elevating the activity of fibrinolytic enzymes (enhancing the synthesis of annexins A2, the use of NMDA-receptor antagonists) and suppressing its inhibitors (the use of monoclonal antibodies to alpha-2-antiplasmin, as well as plasminogen activator inhibitor-1 (PAI-1) and thrombin-activatable fibrinolysis inhibitor (TAFI). Promising directions for future research can be the synthesis of a new generation of tissue-type plasminogen activators, and investigations of the possibility of clinical application of antithrombin and thrombomodulin, angiotensin converting enzyme inhibitors and cortisol antagonists. To meet these challenges, it is necessary to develop new models of venous thrombosis and acute pulmonary embolism in different animal species, with the assessment of the changes in the venous haemodynamics and pulmonary microcirculation on the background of administration of a new class of fibrinolytic agents.

Annexin A2 in Fibrinolysis, Inflammation and Fibrosis

As a cell surface tissue plasminogen activator (tPA)-plasminogen receptor, the annexin A2 (A2) complex facilitates plasmin generation on the endothelial cell surface, and is an established regulator of hemostasis. Whereas A2 is overexpressed in hemorrhagic disease such as acute promyelocytic leukemia, its underexpression or impairment may result in thrombosis, as in antiphospholipid syndrome, venous thromboembolism, or atherosclerosis. Within immune response cells, A2 orchestrates membrane repair, vesicle fusion, and cytoskeletal organization, thus playing a critical role in inflammatory response and tissue injury. Dysregulation of A2 is evident in multiple human disorders, and may contribute to the pathogenesis of various inflammatory disorders. The fibrinolytic system, moreover, is central to wound healing through its ability to remodel the provisional matrix and promote angiogenesis. A2 dysfunction may also promote tissue fibrogenesis and end-organ fibrosis.

Integrative Multi-omics Analysis to Characterize Human Brain Ischemia

Stroke is a major cause of death and disability. A better comprehension of stroke pathophysiology is fundamental to reduce its dramatic outcome. The use of high-throughput unbiased omics approaches and the integration of these data might deepen the knowledge of stroke at the molecular level, depicting the interaction between different molecular units. We aimed to identify protein and gene expression changes in the human brain after ischemia through an integrative approach to join the information of both omics analyses. The translational potential of our results was explored in a pilot study with blood samples from ischemic stroke patients. Proteomics and transcriptomics discovery studies were performed in human brain samples from six deceased stroke patients, comparing the infarct core with the corresponding contralateral brain region, unveiling 128 proteins and 2716 genes significantly dysregulated after stroke. Integrative bioinformatics analyses joining both datasets exposed canonical pathways altered in the ischemic area, highlighting the most influential molecules. Among the molecules with the highest fold-change, 28 genes and 9 proteins were selected to be validated in five independent human brain samples using orthogonal techniques. Our results were confirmed for NCDN, RAB3C, ST4A1, DNM1L, A1AG1, A1AT, JAM3, VTDB, ANXA1, ANXA2, and IL8. Finally, circulating levels of the validated proteins were explored in ischemic stroke patients. Fluctuations of A1AG1 and A1AT, both up-regulated in the ischemic brain, were detected in blood along the first week after onset. In summary, our results expand the knowledge of ischemic stroke pathology, revealing key molecules to be further explored as biomarkers and/or therapeutic targets.

Autoantibodies to Annexin A2 and cerebral thrombosis: Insights from a mouse model

Introduction

Antiphospholipid syndrome (APS) is an autoimmune disorder manifested by thromboembolic events, recurrent spontaneous abortions and elevated titers of circulating antiphospholipid antibodies. In addition, the presence of antiphospholipid antibodies seems to confer a fivefold higher risk for stroke or transient ischemic attack. Although the major antigen of APS is β₂ glycoprotein I, it is now well established that antiphospholipid antibodies are heterogeneous and bind to various targets. Recently, antibodies to Annexin A2 (ANXA2) have been reported in APS. This is of special interest since data indicated ANXA2 as a key player in fibrinolysis. Therefore, in the present study we assessed whether anti-ANXA2 antibodies play a pathological role in thrombosis associated disease.

Materials and Methods

Mice were induced to produce anti-ANXA2 antibodies by immunization with ANXA2 (iANXA2) and control mice were immunized with adjuvant only. A middle cerebral artery occlusion stroke model was applied to the mice. The outcome of stroke severity was assessed and compared between the two groups.

Results

Our results indicate that antibodies to ANXA2 lead to a more severe stroke as demonstrated by a significant larger stroke infarct volume (iANXA2 133.9 ± 3.3 mm³ and control 113.7 ± 7.4 mm³; p = 0.017) and a more severe neurological outcome (iANXA2 2.2 ± 0.2, and control 1.5 ± 0.18; p = 0.03).

Conclusions

This study supports the hypothesis that auto-antibodies to ANXA2 are an independent risk factor for cerebral thrombosis. Consequently, we propose screening for anti-ANXA2 antibodies should be more widely used and patients that exhibit the manifestations of APS should be closely monitored by physicians.

tPA Mobilizes Immune Cells That Exacerbate Hemorrhagic Transformation in Stroke

RATIONALE

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

OBJECTIVE

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

METHODS AND RESULTS

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

CONCLUSIONS

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

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.

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.

miR-145-5p/Nurr1/TNF-α Signaling-Induced Microglia Activation Regulates Neuron Injury of Acute Cerebral Ischemic/Reperfusion in Rats

Nurr1 is a member of the nuclear receptor 4 family of orphan nuclear receptors that is decreased in inflammatory responses and leads to neurons death in Parkinson’s disease. Abnormal expression of Nurr1 have been attributed to various signaling pathways, but little is known about microRNAs (miRNAs) regulation of Nurr1 in ischemia/reperfusion injury. To investigate the post transcriptional regulatory networks of Nurr1, we used a miRNA screening approach and identified miR-145-5p as a putative regulator of Nurr1. By using computer predictions, we identified and confirmed a miRNA recognition element in the 3′UTR of Nurr1 that was responsible for miR-145-5p-mediated suppression. We next demonstrated that overexpression of Nurr1 inhibited TNF-α expression in microglia by trans-repression and finally attenuated ischemia/reperfusion-induced inflammatory and cytotoxic response of neurons. Results of further in vivo study revealed that anti-miR-145-5p administration brought about increasing expression of Nurr1 and reduction of infarct volume in acute cerebral ischemia. Administration of anti-miR-145-5p promotes neurological outcome of rats post MCAO/R. It might be an effective therapeutic strategy to relieve neurons injury upon ischemia/reperfusion of rats through interrupting the axis signaling of miR-145-5p- Nurr1-TNF-α in acute phase.

Peripheral sensory stimulation is neuroprotective in a rat photothrombotic ischemic stroke model

Ischemic stroke is one of the leading causes of death and disability in the world. Thrombolytic therapy using recombinant tissue plasminogen activator (rtPA), the only FDA-approved drug for acute ischemia, is limited by a narrow therapeutic time window and risk of hemorrhage. There is a serious need for a neuroprotective therapy which is clinically viable. We earlier demonstrated that peripheral sensory stimulation (PSS) is a potential therapeutic intervention for hyperacute ischemia resulting in recovery of neurovascular functions when administered immediately following ischemia onset in a rat model. Here, we investigated the potential neuroprotective effect of PSS during the hyperacute phase of stroke in a rat photothrombotic ischemia (PTI) model. We employed electrocorticography (ECoG) to image cortical neural activity responses pre-and post-ischemia. Results showed that the neural activity including somatosensory evoked potentials (SSEPs) and alpha-to-delta ratio (ADR) were restored following administration of PSS. Further, immunohistochemistry and TTC staining also indicated the neuroprotective effect of PSS intervention, protecting more neurons and reduced infarct. Overall, the study demonstrated that PSS administered immediately following ischemia induction in a rat PTI model can significantly promote neuroprotection via inhibition of peri-infarct expansion and enhanced cortical neural activity functions, suggesting effective recovery. Future work utilizing multimodal imaging to probe changes in neurovascular functions, will explore application of PSS as an adjuvant intervention for improving rtPA thrombolysis therapy.

Annexin A2 Plus Low-Dose Tissue Plasminogen Activator Combination Attenuates Cerebrovascular Dysfunction After Focal Embolic Stroke of Rats

Previous studies showed recombinant annexin A2 (rA2) in combination with low-dose tissue-type plasminogen activator (tPA) improved thrombolytic efficacy and long-term neurological outcomes after embolic focal ischemia in rats. The objective of this study was to investigate the effects and mechanisms of the combination in early BBB integrity and cerebrovascular patency in the rat focal embolic stroke model. Ischemic brain infarct volume and hemorrhagic transformation were quantified at 24 h after stroke. At an earlier time point, 16 h after stroke, BBB integrity was evaluated by IgG extravasation, and the involved mechanisms were assessed for tight junction ZO-1 and adhesion junction ve-cadherin protein expression, matrix metalloproteinase activation, extracellular matrix collagen IV and endothelial barrier antigen expression, and activation of microglia/macrophages and astrocytes. While at the same time point, cerebrovascular patency was assessed by intravascular fibrin and platelet depositions. At 24 h after stroke, the combination showed significant reduction in brain infarction and intracerebral hemorrhage. At 16 h after stroke onset, the combination therapy significantly reduced BBB disruption, and improved preservation of the junction proteins ZO-1 and ve-cadherin, decreased activation of matrix metalloproteinase, inhibited degradation of extracellular matrix collagen IV and endothelial barrier antigen, and reduced microglia/macrophage and astrocytes activations. Meanwhile, the combination also significantly improved cerebrovascular patency by reducing intravascular fibrin and platelet depositions in the peri-infarct brain tissues. These results suggest the beneficial effects of the rA2 plus low-dose tPA combination may be mediated in part by the amelioration of BBB disruption and improvement of cerebrovascular patency.

Improved thrombolytic effect with focused ultrasound and neuroprotective agent against acute carotid artery thrombosis in rat

Combination therapy with focused ultrasound (FUS) and a neuroprotective agent, BNG-1, was examined in an acute carotid thrombotic occlusion model using LED irradiation in rat to improve the thrombolytic effect of rt-PA. Seven treatment groups included (A) intravenous bolus injection of 0.45 mg/kg rt-PA, (B) intravenous bolus injection of 0.9 mg/kg, (C) sonothrombolysis with FUS alone, (D) oral administration of 2 g/kg BNG-1 for 7 days alone, (E) A + D, (F) A + C, and (G) A + C + D. Four comparison groups were made including (H) 0.45 mg/kg rt-PA 20% bolus +80% IV fusion + FUS, (I) 0.9 mg/kg rt-PA with 10% bolus + 90% intravenous fusion, (J) B + C, (K) B + D. At 7 days after carotid occlusion, small-animal carotid ultrasound and 7 T MR angiography showed the recanalization rate of ≤50% stenosis was 50% in group B and 83% in group I, but 0% in groups A and C and 17% in group D. Combination therapy improved recanalization rate to 50–63% in groups E and F, to 67–83% in groups J and K, and to 100% in groups G and H. Our study demonstrated combination therapy with different remedies can be a feasible strategy to improve the thrombolytic effect of rt-PA.

Traumatic Brain Injury Induces Genome-Wide Transcriptomic, Methylomic, and Network Perturbations in Brain and Blood Predicting Neurological Disorders

The complexity of the traumatic brain injury (TBI) pathology, particularly concussive injury, is a serious obstacle for diagnosis, treatment, and long-term prognosis. Here we utilize modern systems biology in a rodent model of concussive injury to gain a thorough view of the impact of TBI on fundamental aspects of gene regulation, which have the potential to drive or alter the course of the TBI pathology. TBI perturbed epigenomic programming, transcriptional activities (expression level and alternative splicing), and the organization of genes in networks centered around genes such as Anax2, Ogn, and Fmod. Transcriptomic signatures in the hippocampus are involved in neuronal signaling, metabolism, inflammation, and blood function, and they overlap with those in leukocytes from peripheral blood. The homology between genomic signatures from blood and brain elicited by TBI provides proof of concept information for development of biomarkers of TBI based on composite genomic patterns. By intersecting with human genome-wide association studies, many TBI signature genes and network regulators identified in our rodent model were causally associated with brain disorders with relevant link to TBI. The overall results show that concussive brain injury reprograms genes which could lead to predisposition to neurological and psychiatric disorders, and that genomic information from peripheral leukocytes has the potential to predict TBI pathogenesis in the brain.

CD47 deficiency improves neurological outcomes of traumatic brain injury in mice

CD47 is a receptor for signal-regulatory protein alpha (SIRPα) in self-recognition by the innate immune system, and a receptor of thrombospondin-1 (TSP-1) contributing to vascular impairment in response to stress. However, the roles of CD47 in traumatic brain injury (TBI) have not been investigated. In this study we aimed to test our hypothesis that CD47 mediates early neutrophil brain infiltration and late brain vascular remodeling after TBI. Mice were subjected to TBI using a controlled cortical impact (CCI) device. We examined early phase neutrophil infiltration, and late phase brain vessel density, pro-angiogenic markers VEGF and Ang-1 protein expression, neurological function deficits and lesion volumes for up to three weeks after TBI. Our results show that mice deficient in CD47 (CD47 Knockout) had significantly less brain neutrophil infiltration at 24h, upregulated VEGF expression in peri-lesion cortex at 7 and 14days, and increased blood vessel density at 21days after TBI, compared to wild type (WT) mice. CD47 knockout also significantly decreased sensorimotor function deficits and reduced brain lesion volume at 21days after TBI. We conclude that CD47 may play pathological roles in brain neutrophil infiltration, progression of brain tissue damage, impairment of cerebrovascular remodeling and functional recovery after TBI.

Combination Low-Dose Tissue-Type Plasminogen Activator Plus Annexin A2 for Improving Thrombolytic Stroke Therapy

Risk of hemorrhagic transformation, incomplete reperfusion, neurotoxicity, and a short treatment time window comprises major challenges for tissue plasminogen activator (tPA) thrombolytic stroke therapy. Improving tPA therapy has become one of the highest priorities in the stroke field. This mini review article focuses on our recent efforts aimed at evaluating a novel combination approach of low-dose tPA plus recombinant annexin A2 (rA2, a tPA, and plasminogen co-receptor), which might enhance tPA thrombolytic efficacy, while reducing its associated complications related to intracerebral hemorrhagic transformation. Results of our experimental studies using a focal embolic stroke model in rats support the feasibility of the combination approach and suggest the potential for successful clinical translation.

Low dose tPA plus annexin A2 combination attenuates tPA delayed treatment-associated hemorrhage and improves recovery in rat embolic focal stroke

We previously have shown that tissue type plasminogen activator (tPA) in combination with its receptor annexin A2 (rA2) protein significantly improved tPA thrombolytic efficacy. In this study we aimed to examine the therapeutic effects of the combination when treated at delayed 4-hour window after stroke compared to standard conventional tPA alone in an embolic focal stroke rat model. We compared effects of intravenous tPA alone (10 mg/kg) versus a combination of low-dose tPA (5 mg/kg) plus 10 mg/kg rA2. Totally 152 rats were used. Our results showed that: (1) at 24 h after stroke, the combination slightly reduced brain infarction compared to saline (9.2% reduction), and tPA (7.4% reduction), although the reductions did not reach statistical significance; while the combination significantly reduced (22.2% reduction) the conventional tPA-elevated intracerebral hemorrhagic (ICH) transformation; (2) at 7 days after stroke, the combination significantly attenuated conventional tPA alone-elevated iron deposition at peri-lesion area (68.2% reduction); (3) at 28 days after stroke, the combination significantly improved performance of adhesive tape-removal test, which was accompanied by a significantly higher micro vessel density at peri- infarct areas compared to conventional tPA alone group.In conclusion, compared to conventional tPA alone, when treated at delayed 4-hour after stroke, the combination of low-dose tPA plus rA2 therapy provides a safer profile by lowering risk of ICH transformation and improves neurological function recovery after stroke.

Comparative Analysis of Different Methods of Ischemia/Reperfusion in Hyperglycemic Stroke Outcomes: Interaction with tPA

Acute hyperglycemia (HG) exacerbates reperfusion injury and aggravates tissue plasminogen activator (tPA)-induced hemorrhagic transformation (HT). Previous experimental hyperglycemic stroke studies employed very high blood glucose levels and exclusively used suture occlusion model to induce ischemia. Only few studies evaluated HG in embolic stroke and mostly involving the use of 10-fold higher dose of tPA than that is used in patients. However, the interaction between acute HG and low (human) dose tPA in different experimental models of stroke has never been reported. We first tested the impact of the severity of acute HG on stroke outcome. Building upon our findings, we then compared the impact of mild acute HG on neurovascular injury in rats subjected to suture or thromboembolic occlusion with and without low dose tPA. We assessed cerebral blood flow, neurobehavioral outcomes, infarction, hemorrhage, and edema. tPA did not change the infarct size in either control or hyperglycemic animals when compared to no tPA groups. HG increased HT and worsened functional outcomes in both suture and embolic occlusion models. The combination of HG and tPA exacerbated the vascular injury and worsened the neurological deficits more than each individual treatment in both models. Our findings show that the interaction between HG and even low dose tPA has detrimental effects on the cerebrovasculature and functional outcomes independent of the method of reperfusion.

Modulation of mitochondrial function and autophagy mediates carnosine neuroprotection against ischemic brain damage

BACKGROUND AND PURPOSE

Despite the rapidly increasing global burden of ischemic stroke, no therapeutic options for neuroprotection against stroke currently exist. Recent studies have shown that autophagy plays a key role in ischemic neuronal death, and treatments that target autophagy may represent a novel strategy in neuroprotection. We investigated whether autophagy is regulated by carnosine, an endogenous pleiotropic dipeptide that has robust neuroprotective activity against ischemic brain damage.

METHODS

We examined the effect of carnosine on mitochondrial dysfunction and autophagic processes in rat focal ischemia and in neuronal cultures.

RESULTS

Autophagic pathways such as reduction of phosphorylated mammalian target of rapamycin (mTOR)/p70S6K and the conversion of microtubule-associated protein 1 light chain 3 (LC3)-I to LC3-II were enhanced in the ischemic brain. However, treatment with carnosine significantly attenuated autophagic signaling in the ischemic brain, with improvement of brain mitochondrial function and mitophagy signaling. The protective effect of carnosine against autophagy was also confirmed in primary cortical neurons.

CONCLUSIONS

Taken together, our data suggest that the neuroprotective effect of carnosine is at least partially mediated by mitochondrial protection and attenuation of deleterious autophagic processes. Our findings shed new light on the mechanistic pathways that this exciting neuroprotective agent influences.