Extension of Tissue Plasminogen Activator Treatment Window by Granulocyte-Colony Stimulating Factor in a Thromboembolic Rat Model of Stroke

2-BFI protects against ischemic stroke by selectively acting on NR2B-containing NMDA receptors

BACKGROUND AND PURPOSE

The intricate roles of NMDA receptors, specifically those containing the NR2A or NR2B subunit, in ischemic stroke pathology necessitate targeted therapeutic investigations. Building on our prior discovery showcasing the neuroprotective potential of 2-(benzofuran-2-yl)-2-imidazoline (2-BFI), an imidazoline I2 receptor ligand, in inhibiting NMDA receptor currents during ischemic stroke, this study aims to elucidate the specific impact of 2-BFI on NR2A- and NR2B-containing NMDARs.

EXPERIMENTAL APPROACH

Through whole-cell patch-clamp techniques, we observed an inhibition by 2-BFI on NR2A-containing NMDAR currents (IC50 = 238.6 μM) and NR2B-containing NMDAR currents (IC50 = 18.47 μM). Experiments with HEK293 cells expressing exogenous receptor subunits revealed a significantly higher affinity of 2-BFI towards NR2B-containing NMDARs. In vivo studies involved the co-administration of 2-BFI and the NR2A subunit antagonist NVP-AAM077 in rats subjected to transient middle cerebral artery occlusion (tMCAO). Key results 2-BFI exhibited a pronounced preference for inhibiting NR2B-containing NMDAR currents, leading to a notable mitigation of cerebral ischemic injury when administered in conjunction with NVP-AAM077 in the tMCAO rat model. Furthermore, alterations in the expression of downstream proteins specific to NR2B-containing NMDA receptors were observed, suggesting targeted molecular effects. Conclusion and implications This study unveils the neuroprotective potential of 2-BFI in ischemic stroke by selectively inhibiting NR2B-containing NMDA receptors. These findings lay the foundation for precise therapeutic strategies, showcasing the differential roles of NR2A and NR2B subunits and paving the way for advancements in targeted interventions for ischemic stroke treatment.

Hemorrhagic Transformation After Tissue Plasminogen Activator Treatment in Acute Ischemic Stroke

Hemorrhagic transformation (HT) is a common complication after thrombolysis with recombinant tissue-type plasminogen activator (rt-PA) in ischemic stroke. In this article, recent research progress of HT in vivo and in vitro studies was reviewed. We have discussed new potential mechanisms and possible experimental models of HT development, as well as possible biomarkers and treatment methods. Meanwhile, we compared and analyzed rodent models, large animal models and in vitro BBB models of HT, and the limitations of these models were discussed. The molecular mechanism of HT was investigated in terms of BBB disruption, rt-PA neurotoxicity and the effect of neuroinflammation, matrix metalloproteinases, reactive oxygen species. The clinical features to predict HT were represented including blood biomarkers and clinical factors. Recent progress in neuroprotective strategies to improve HT after stroke treated with rt-PA is outlined. Further efforts need to be made to reduce the risk of HT after rt-PA therapy and improve the clinical prognosis of patients with ischemic stroke.

Colony-Stimulating Factors on Mobilizing CD34+ Cells and Improving Neurological Functions in Patients With Stroke: A Meta-Analysis and a Systematic Review

Background and Purpose: CSF therapy is considered a promising therapeutic approach for stroke. We performed a meta-analysis to explore the safety and efficacy of CSF in published clinical stroke studies. Methods: We searched articles online and manually. Two reviewers selected studies independently, selecting data based on study quality, characteristics of intervention (administration time, observation time, type, dose, and injection approach of CSF), and the baseline characteristics of patients (age, sex, hypertension, diabetes, smoker, and lipids) were extracted. Main prognosis outcomes were measured as all-cause death in severe adverse events (SAE) and recurrent stroke in SAE. Secondary outcomes were measured as CD34+ cell counts in periphery blood at day 5, National Institutes of Health Stroke Scale (NIHSS), and Barthel index (BI), Side effects of CSF were taken as the indicator of safety. STATA13 software was used to perform the meta-analysis.Keywords: Stroke, Colony-stimulating factor, Meta-analysis, therapy, Neurological Diseases Results: This meta-analysis involved 485 patients from eight studies. Among them, 475 patients from seven studies were gauged SAE (all-cause death), 393 patients from six studies were checked SAE (recurrent stroke); 137 patients from three studies underwent CD34⁺ measurement, 389 patients from six studies were tested NIHSS and 307 patients from five studies accessed BI. Compared with the control group, both all-causes death (RR= 1.73, 95%CI= (0.61, 4.92), P=0.735, I²=0.0%) and recurrent stroke (RR= 0.43, 95%CI= (0.14, 1.32), P=0.214, I²=33.1%) present no statistical differences, indicating that the application of CSF does not statistically alter the prognosis of patients with stroke. The application of CSF effectively enhanced CD34+ cell counts in periphery blood at day 5 (SMD= 1.23, 95%CI= (0.54, 1.92), P=0.04, I²=69.0%) but did not statistically impact NIHSS (SMD= -0.40, 95%CI= (-0.93, 0.13), P ≤ 0.001, I²=79.7%) or BI (SMD= 0.04, 95%CI= (-0.38, 0.46), P=0.068, I²=54.3%). Conclusion: Our study consolidates the security of CSF administration for its exerting no effect on detrimental outcomes. It has proven to be effective in elevating CD34+ cell counts in periphery blood at day 5, indicating CSF may participate in stroke recovery, but its efficacy in stroke recovery remains detected.

Neuroinflammation in Ischemic Stroke: Focus on MicroRNA-mediated Polarization of Microglia

Ischemic stroke is one of the most common causes of death and disability worldwide. Neuroinflammation is a major pathological event involved in the process of ischemic injury and repair. In particular, microglia play a dual role in neuroinflammation. During the acute phase of stroke onset, M2 microglia are the dominant phenotype and exert protective effects on neuronal cells, whereas permanent M1 microglia contribute to prolonged inflammation and are detrimental to brain tissue. Emerging evidence indicates that microRNAs (miRNAs) may have regulatory effects on microglia-associated inflammation. Thus, we briefly reviewed the dynamic response of microglia after a stroke and assessed how specific miRNAs affect the behavior of reactive microglia. We concluded that miRNAs may be useful novel therapeutic targets to improve stroke outcomes and modulate neuroinflammation.

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.

Opioid antagonists as potential therapeutics for ischemic stroke

Chronic use of prescription opioids exacerbates risk and severity of ischemic stroke. Annually, 6 million people die from stroke worldwide and there are no neuroprotective or neurorestorative agents to improve stroke outcomes and promote recovery. Prescribed opioids such as morphine have been shown to alter tight junction protein expression, resulting in the disruption of the blood brain barrier (BBB), ultimately leading to stroke pathogenesis. Consequently, protection of the BBB has been proposed as a therapeutic strategy for ischemic stroke. This perspective addresses the deficiency in stroke pharmacological options and examines a novel application and repurposing of FDA-approved opioid antagonists as a prospective neuroprotective therapeutic strategy to minimize BBB damage, reduce stroke severity, and promote neural recovery. Future directions discuss potential drug design and delivery methods to enhance these novel therapeutic targets.

Structural Biology and Protein Engineering of Thrombolytics

Myocardial infarction and ischemic stroke are the most frequent causes of death or disability worldwide. Due to their ability to dissolve blood clots, the thrombolytics are frequently used for their treatment. Improving the effectiveness of thrombolytics for clinical uses is of great interest. The knowledge of the multiple roles of the endogenous thrombolytics and the fibrinolytic system grows continuously. The effects of thrombolytics on the alteration of the nervous system and the regulation of the cell migration offer promising novel uses for treating neurodegenerative disorders or targeting cancer metastasis. However, secondary activities of thrombolytics may lead to life-threatening side-effects such as intracranial bleeding and neurotoxicity. Here we provide a structural biology perspective on various thrombolytic enzymes and their key properties: (i) effectiveness of clot lysis, (ii) affinity and specificity towards fibrin, (iii) biological half-life, (iv) mechanisms of activation/inhibition, and (v) risks of side effects. This information needs to be carefully considered while establishing protein engineering strategies aiming at the development of novel thrombolytics. Current trends and perspectives are discussed, including the screening for novel enzymes and small molecules, the enhancement of fibrin specificity by protein engineering, the suppression of interactions with native receptors, liposomal encapsulation and targeted release, the application of adjuvants, and the development of improved production systems.

tPA Helpers in the Treatment of Acute Ischemic Stroke: Are They Ready for Clinical Use?

Tissue plasminogen activator (tPA) is the only therapeutic agent approved to treat patients with acute ischemic stroke. The clinical benefits of tPA manifest when the agent is administered within 4.5 hours of stroke onset. However, tPA administration, especially delayed administration, is associated with increased intracranial hemorrhage (ICH), hemorrhagic transformation (HT), and mortality. In the ischemic brain, vascular remodeling factors are upregulated and microvascular structures are destabilized. These factors disrupt the blood brain barrier (BBB). Delayed recanalization of the vessels in the presence of relatively matured infarction appears to damage the BBB, resulting in HT or ICH, also known as reperfusion injury. Moreover, tPA itself activates matrix metalloproteases, further aggravating BBB disruption. Therefore, attenuation of edema, HT, or ICH after tPA treatment is an important therapeutic strategy that may enable clinicians to extend therapeutic time and increase the probability of excellent outcomes. Recently, numerous agents with various mechanisms have been developed to interfere with various steps of ischemia/ reperfusion injuries or BBB destabilization. These agents successfully reduce infarct volume and decrease the incidence of ICH and HT after delayed tPA treatment in various animal stroke models. However, only some have entered into clinical trials; the results have been intriguing yet unsatisfactory. In this narrative review, I describe such drugs and discuss the problems and future directions. These “tPA helpers” may be clinically used in the future to increase the efficacy of tPA in patients with acute ischemic stroke.

Stand alone or join forces? Stem cell therapy for stroke

INTRODUCTION

Stroke is a major cause of mortality and disability with a narrow therapeutic window. Stem cell therapy may enhance the stroke recovery.

AREAS COVERE

Regenerative medicine via stem cells stands as a novel therapy for stroke. In particular, bone marrow-derived mesenchymal stem cells (MSCs) have neuroprotective and anti-inflammatory properties that improve brain function after stroke. Here, we discuss the safety, efficacy, and mechanism of action underlying the therapeutic effects of bone marrow-derived MSCs. We also examine the discrepant transplant protocols between preclinical studies and clinical trials. Laboratory studies show the safety and efficacy of bone marrow-derived MSCs in stroke models. However, while safe, MSCs remain to be fully evaluated as effective in clinical trials. Furthermore, recognizing the multiple cell death processes associated with stroke, we next discuss the potential therapeutic benefits of a combination therapy. With preliminary results and on-going clinical trials, a careful assessment of dosing, timing, and delivery route regimens will further direct the future of stem cell therapy for neurological disorders, including stroke.

EXPERT OPINION

Bone marrow-derived MSCs appear to be the optimal stem cell source for stroke therapy. Optimizing dosing, timing, and delivery route should guide the clinical application of bone marrow-derived MSCs.