Three Dimensional-Arterial Spin Labeling Evaluation of Improved Cerebral Perfusion After Limb Remote Ischemic Preconditioning in a Rat Model of Focal Ischemic Stroke

Purpose

To investigate the application value of 3D arterial spin labeling (3D-ASL) for evaluating distal limb ischemic preconditioning to improve acute ischemic stroke (AIS) perfusion.

Materials and Methods

A total of 40 patients with AISs treated in our hospital from January 2020 to December 2020 were recruited, and 15 healthy individuals who were examined in our hospital during the same period were included as the control group; all of these participants were scored on the National Institutes of Health Stroke Scale (NIHSS) and examined by MRI. Sequences included conventional sequences, diffusion-weighted imaging (DWI), magnetic resonance angiography (MRA), and 3D-ASL, and cerebral infarct volume and cerebral blood flow (CBF) in the area of the infarct lesion were measured. After 3 months of treatment, patients with AIS were scored on the modified Rankin Scale (mRS) and divided into good prognosis and poor prognosis groups. In total, 55 adult male Sprague–Dawley rats were divided randomly into three groups: 20 in the middle cerebral artery occlusion (MCAO) group, 20 in the MCAO + limb remote ischemic preconditioning (LRP) group, and 15 in the sham group. In total, 48 h after the procedures, conventional MRI, DWI, and 3D-ASL sequence data were collected, and 2,3,5-trphenyltetrazolium chloride monohydrate (TTC) staining and behavioral scoring were performed. CBF was recorded in the infarct lesion area and the corresponding contralateral area, and the affected/contralateral relative values (rCBF) were calculated to compare the differences in rCBF between different groups. The pathological changes in brain tissues were observed by HE staining, and the expression of vascular endothelial growth factor (VEGF) and platelet endothelial cell adhesion molecule-1 (PECAM-1/CD31) in brain tissues was detected by immunofluorescence and real-time quantitative polymerase chain reaction (RT-qPCR). The protein expression of VEGF was detected by western blotting.

Results

Hypertension and internal carotid atherosclerosis are high-risk factors for ischemic stroke, and CBF values in the infarct area are significantly lower than those in the corresponding areas on the contralateral side. NIHSS and mRS scores and CBF values have higher specificity and sensitivity for the prognosis of patients with AIS. LRP significantly reduces the infarct area, improves behavioral deficits in rats with cerebral ischemia, reduces neurological injury and histological damage, protects vascular structures, and promotes neovascularization. In addition, 3D-ASL showed a significant increase in brain tissue perfusion in the ischemic area after LRP, and the expression of VEGF and CD31 showed a significant positive correlation with CBF values.

Conclusion

Three dimensional (3D) ASL can be used to evaluate LRP to improve stroke perfusion, and its protective effect may be closely related to LRP-induced vascular regeneration.

Catalpol protects vascular structure and promotes angiogenesis in cerebral ischemic rats by targeting HIF-1α/VEGF

BACKGROUND

The initial factor in the occurrence, development, and prognosis of cerebral ischemia is vascular dysfunction in the brain, and vascular remodeling of the brain is the key therapeutic target and strategy for ischemic tissue repair. Catalpol is the main active component of the radix of Rehmannia glutinosa Libosch, and it exhibits potential pleiotropic protective effects in many brain-related diseases, including stroke.

PURPOSE

The present study was designed to investigate whether catalpol protects vascular structure and promotes angiogenesis in cerebral ischemic rats and to identify its possible mechanisms in vivo and in vitro.

STUDY DESIGN

Cerebral ischemic rats and oxygen-glucose deprivation-exposed brain microvascular endothelial cells were used to study the therapeutic potential of catalpol in vivo and in vitro.

METHODS

First, neurological deficits, histopathological morphology, infarct volume, vascular morphology, vessel density, and angiogenesis in focal cerebral ischemic rats were observed to test the potential treatment effects of catalpol. Then, oxygen-glucose deprivation-exposed brain microvascular endothelial cells were used to mimic the pathological changes in vessels during ischemia to study the effects and possible mechanisms of catalpol in protecting vascular structure and promoting angiogenesis.

RESULTS

The in vivo results showed that catalpol reduced neurological deficit scores and infarct volume, protected vascular structure, and promoted angiogenesis in cerebral ischemic rats. The in vitro results showed that catalpol improved oxygen-glucose deprivation-induced damage and promoted proliferation, migration, and in vitro tube formation of brain microvascular endothelial cells. The HIF-1α (hypoxia-inducible factor 1α)/VEGF (vascular endothelial growth factor) pathway was activated by catalpol both in the brains of cerebral ischemic rats and in primary brain microvascular endothelial cells, and the activating effects of catalpol were inhibited by SU1498.

CONCLUSION

The results of both the in vivo and in vitro studies proved that catalpol protects vascular structure and promotes angiogenesis in focal cerebral ischemic rats and that the mechanism is dependent on HIF-1α/VEGF.

Effects of Red Ginseng on Neural Injuries with Reference to the Molecular Mechanisms

Red ginseng, as an effective herbal medicine, has been traditionally and empirically used for the treatment of neuronal diseases. Many studies suggest that red ginseng and its ingredients protect the brain and spinal cord from neural injuries such as ischemia, trauma, and neurodegeneration. This review focuses on the molecular mechanisms underlying the neuroprotective effects of red ginseng and its ingredients. Ginsenoside Rb1 and other ginsenosides are regarded as the active ingredients of red ginseng; the anti-apoptotic, anti-inflammatory, and anti-oxidative actions of ginsenosides, together with a series of bioactive molecules relevant to the above actions, appear to account for the neuroprotective effects in vivo and/or in vitro. Moreover, in this review, the possibility is raised that more effective or stable neuroprotective derivatives based on the chemical structures of ginsenosides could be developed. Although further studies, including clinical trials, are necessary to confirm the pharmacological properties of red ginseng and its ingredients, red ginseng and its ingredients could be promising candidate drugs for the treatment of neural injuries.

Neuroprotective mechanism of the novel melatonin derivative Neu-P11 in brain ischemia related models

Stopping the ischemic cascade by targeting its components is a potential strategy for acute ischemic stroke treatment. During ischemia and especially over reperfusion, oxidative stress plays a major role in causing neuronal cell death. Melatonin has been previously reported to provide neuroprotective effects in in vivo models of stroke by a mechanism that implicates melatonin receptors. In this context, this study was planned to test the potential neuroprotective effects of the novel melatonin MT1/MT2 receptor agonist, Neu-P11, against brain ischemia in in vitro and in vivo models, and to elucidate its underlying mechanism of action. Neu-P11 proved to be a good antioxidant, to protect against glutamate-induced excitotoxicity and oxygen and glucose deprivation in hippocampal slices, and to reduce infarct volume in an in vivo stroke model. Regarding its mechanism of action, the protective effect of Neu-P11 was reverted by luzindole (melatonin receptor antagonist), AG490 (JAK2 inhibitor), LY294002 (PI3/AKT inhibitor) and PD98059 (MEK/ERK1/2 inhibitor). In conclusion, Neu-P11 affords neuroprotection against brain ischemia in in vitro and in vivo models by activating a pro-survival signaling pathway that involves melatonin receptors, JAK/STAT, PI3K/Akt and MEK/ERK1/2.

Therapeutic benefits of nanoparticles in stroke

Stroke represents one of the major causes of death and disability worldwide, for which no effective treatments are available. The thrombolytic drug alteplase (tissue plasminogen activator or tPA) is the only treatment for acute ischemic stroke but its use is limited by several factors including short therapeutic window, selective efficacy, and subsequent haemorrhagic complications. Numerous preclinical studies have reported very promising results using neuroprotective agents but they have failed at clinical trials because of either safety issues or lack of efficacy. The delivery of many potentially therapeutic neuroprotectants and diagnostic compounds to the brain is restricted by the blood-brain barrier (BBB). Nanoparticles (NPs), which can readily cross the BBB without compromising its integrity, have immense applications in the treatment of ischemic stroke. In this review, potential uses of NPs will be summarized for the treatment of ischemic stroke. Additionally, an overview of targeted NPs will be provided, which could be used in the diagnosis of stroke. Finally, the potential limitations of using NPs in medical applications will be mentioned. Since the use of NPs in stroke therapy is now emerging and is still in development, this review is far from comprehensive or conclusive. Instead, examples of NPs and their current use will be provided, as well as the potentials of NPs in an effort to meet the high demand of new therapies in stroke.

Drug delivery to the ischemic brain

Cerebral ischemia occurs when blood flow to the brain is insufficient to meet metabolic demand. This can result from cerebral artery occlusion that interrupts blood flow, limits CNS supply of oxygen and glucose, and causes an infarction/ischemic stroke. Ischemia initiates a cascade of molecular events in neurons and cerebrovascular endothelial cells including energy depletion, dissipation of ion gradients, calcium overload, excitotoxicity, oxidative stress, and accumulation of ions and fluid. Blood-brain barrier (BBB) disruption is associated with cerebral ischemia and leads to vasogenic edema, a primary cause of stroke-associated mortality. To date, only a single drug has received US Food and Drug Administration (FDA) approval for acute ischemic stroke treatment, recombinant tissue plasminogen activator (rt-PA). While rt-PA therapy restores perfusion to ischemic brain, considerable tissue damage occurs when cerebral blood flow is reestablished. Therefore, there is a critical need for novel therapeutic approaches that can "rescue" salvageable brain tissue and/or protect BBB integrity during ischemic stroke. One class of drugs that may enable neural cell rescue following cerebral ischemia/reperfusion injury is the HMG-CoA reductase inhibitors (i.e., statins). Understanding potential CNS drug delivery pathways for statins is critical to their utility in ischemic stroke. Here, we review molecular pathways associated with cerebral ischemia and novel approaches for delivering drugs to treat ischemic disease. Specifically, we discuss utility of endogenous BBB drug uptake transporters such as organic anion transporting polypeptides and nanotechnology-based carriers for optimization of CNS drug delivery. Overall, this chapter highlights state-of-the-art technologies that may improve pharmacotherapy of cerebral ischemia.

Importance of cerebral artery recanalization in patients with stroke with and without neurological improvement after intravenous thrombolysis

BACKGROUND AND PURPOSE

Recanalization status after intravenous thrombolysis (IVT) in patients with ischemic stroke is a reference point to proceed with a rescue reperfusion intervention, although early neurological improvement (NI) may preclude endovascular procedures. We aimed to evaluate the importance of restoration of blood flow at the arterial occlusion site in subgroups of patients with stroke stratified by early NI after IVT.

METHODS

The following patients were recruited from the Safe Implementation of Treatment in Stroke-International Stroke Thrombolysis Register: (1) with baseline vessel occlusion documented by computed tomographic (CT) or magnetic resonance (MR) angiography and follow-up angioimaging between 22 and 36 hours after IVT available; and (2) with dense cerebral artery sign on admission CT scan and results of follow-up CT reported. Recanalization at 24 hours was defined as absence of vessel occlusion or as resolution of dense cerebral artery sign on follow-up 22- to 36-hour imaging. NI was assessed at 2 hours and 24 hours after IVT and was defined as improvement by 20% from baseline National Institute of Health Stroke scale score. Primary outcome measure was independence, defined as modified Rankin scale score 0 to 2 after 3 months.

RESULTS

Of 28136 cases registered between December 2003 and November 2009, 5324 cases (19%) met the inclusion criteria. Patients with both NI at 2 hours post-treatment and vessel recanalization had the best chances to achieve independence at 3 months (adjusted odds ratio, 15.8; 95% confidence interval, 12.5-20.0), followed by those who had NI despite persistent occlusion (adjusted odds ratio, 4.7; 95% confidence interval, 3.6-6.1); and those without NI despite recanalization (adjusted odds ratio, 2.7; 95% confidence interval, 2.2-3.3).

CONCLUSIONS

Recanalization of an occluded artery in acute stroke is associated with favorable functional outcome both in patients with and without NI after IVT. In future evaluations of mechanical thrombectomy and other additional strategies, recanalization should be considered in patients with persisting occlusion after IVT even after significant NI.

Targeted drug delivery to treat pain and cerebral hypoxia

Limited drug penetration is an obstacle that is often encountered in treatment of central nervous system (CNS) diseases including pain and cerebral hypoxia. Over the past several years, biochemical characteristics of the brain (i.e., tight junction protein complexes at brain barrier sites, expression of influx and efflux transporters) have been shown to be directly involved in determining CNS permeation of therapeutic agents; however, the vast majority of these studies have focused on understanding those mechanisms that prevent drugs from entering the CNS. Recently, this paradigm has shifted toward identifying and characterizing brain targets that facilitate CNS drug delivery. Such targets include the organic anion-transporting polypeptides (OATPs in humans; Oatps in rodents), a family of sodium-independent transporters that are endogenously expressed in the brain and are involved in drug uptake. OATP/Oatp substrates include drugs that are efficacious in treatment of pain and/or cerebral hypoxia (i.e., opioid analgesic peptides, 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors). This clearly suggests that OATP/Oatp isoforms are viable transporter targets that can be exploited for optimization of drug delivery to the brain and, therefore, improved treatment of CNS diseases. This review summarizes recent knowledge in this area and emphasizes the potential that therapeutic targeting of OATP/Oatp isoforms may have in facilitating CNS drug delivery and distribution. Additionally, information presented in this review will point to novel strategies that can be used for treatment of pain and cerebral hypoxia.

Blood-brain barrier integrity and glial support: mechanisms that can be targeted for novel therapeutic approaches in stroke

The blood-brain barrier (BBB) is a critical regulator of brain homeostasis. Additionally, the BBB is the most significant obstacle to effective CNS drug delivery. It possesses specific charcteristics (i.e., tight junction protein complexes, influx and efflux transporters) that control permeation of circulating solutes including therapeutic agents. In order to form this "barrier," brain microvascular endothelial cells require support of adjacent astrocytes and microglia. This intricate relationship also occurs between endothelial cells and other cell types and structures of the CNS (i.e., pericytes, neurons, extracellular matrix), which implies existence of a "neurovascular unit." Ischemic stroke can disrupt the neurovascular unit at both the structural and functional level, which leads to an increase in leak across the BBB. Recent studies have identified several pathophysiological mechanisms (i.e., oxidative stress, activation of cytokine-mediated intracellular signaling systems) that mediate changes in the neurovascular unit during ischemic stroke. This review summarizes current knowledge in this area and emphasizes pathways (i.e., oxidative stress, cytokine-mediated intracellular signaling, glial-expressed receptors/targets) that can be manipulated pharmacologically for i) preservation of BBB and glial integrity during ischemic stroke and ii) control of drug permeation and/or transport across the BBB. Targeting these pathways present a novel opportunity for optimization of CNS delivery of therapeutics in the setting of ischemic stroke.

Paeoniflorin protects against ischemia-induced brain damages in rats via inhibiting MAPKs/NF-κB-mediated inflammatory responses

Paeoniflorin (PF), the principal component of Paeoniae Radix prescribed in traditional Chinese medicine, has been reported to exhibit many pharmacological effects including protection against ischemic injury. However, the mechanisms underlying the protective effects of PF on cerebral ischemia are still under investigation. The present study showed that PF treatment for 14 days could significantly inhibit transient middle cerebral artery occlusion (MCAO)-induced over-activation of astrocytes and microglia, and prevented up-regulations of pro-inflamamtory mediators (TNFα, IL-1β, iNOS, COX(2) and 5-LOX) in plasma and brain. Further study demonstrated that chronic treatment with PF suppressed the activations of JNK and p38 MAPK, but enhanced ERK activation. And PF could reverse ischemia-induced activation of NF-κB signaling pathway. Moreover, our in vitro study revealed that PF treatment protected against TNFα-induced cell apoptosis and neuronal loss. Taken together, the present study demonstrates that PF produces a delayed protection in the ischemia-injured rats via inhibiting MAPKs/NF-κB mediated peripheral and cerebral inflammatory response. Our study reveals that PF might be a potential neuroprotective agent for stroke.

Temperature affects thrombolytic efficacy using rt-PA and eptifibatide, an in vitro study

The potential for hypothermia as a neuroprotectant during stroke has led to its increase in clinical use. At the same time, combination pharmaceutical therapies for ischemic stroke using recombinant tissue plasminogen activator (rt-PA), and GP IIb-IIIa inhibitors, such as Eptifibatide (Epf ), are under study. However, there is little data on how the reactions triggered by these agents are impacted by temperature. Here, clot lysis during exposure to the combination of rt-PA and Epf is measured in an in vitro human clot model at hypothermic temperatures. The hypothesis is that lytic efficacy of rt-PA and Epf decreases with decreasing temperature. Whole blood clots from 31 volunteers were exposed to rt-PA (0.5 μg/mL) and Epf (0.63 μg/mL) in human fresh-frozen plasma (rt-PA+Epf ), rt-PA alone in plasma (rt-PA Alone), or to plasma alone (Control), at temperatures from 30°C to 37°C, for 30 minutes. Clot lysis was measured using a microscopic imaging technique; the mean fractional clot loss (FCL) at 30 minutes was used to determine lytic efficacy. Temperature had a significant impact on FCL in clots exposed to rt-PA+Epf, with the FCL being lower at 30°C to 36°C than at 37°C. The FCL remained significantly higher for rt-PA+Epf–treated clots than Controls regardless of temperature, with the exception of measurements made at 30°C when no significant differences in the FCL were observed between groups. The use of hypothermia as a neuroprotectant may negatively impact the therapeutic benefit of thrombolytic agents.

Time for a neurorestorative therapy in stroke

Stroke remains one of the main causes of death and disability worldwide. The aging of the population is likely to result in a dramatic increase in the burden of stroke. Thus, it is not surprising that the pharmaceutical industry has invested much money in the development of pharmacotherapies for ischemic stroke. Promising experimental data, however, have almost consistently failed to produce a clinically effective neuroprotective or neurorestorative drug. Only intravenous recombinant tissue plasminogen activator (rtPA) has been approved for the treatment of acute ischemic stroke. Many pharmaceutical companies have scaled down their stroke programs and despite the unmet need, activity in the field is almost frozen. Trafermin, a recombinant form of human basic fibroblast growth factor (bFGF), is a good example of a translational failure in neuroprotection. However, trafermin may also promote neuronal plasticity after cerebral insults. Thus, clinical trials with trafermin in stroke are warranted but should be based on neuronal restoration rather than acute neuroprotection.

Experimental approaches to study functional recovery following cerebral ischemia

Valid experimental models and behavioral tests are indispensable for the development of therapies for stroke. The translational failure with neuroprotective drugs has forced us to look for alternative approaches. Restorative therapies aiming to facilitate the recovery process by pharmacotherapy or cell-based therapy have emerged as promising options. Here we describe the most common stroke models used in cell-based therapy studies with particular emphasis on their inherent complications, which may affect behavioral outcome. Loss of body weight, stress, hyperthermia, immunodepression, and infections particularly after severe transient middle cerebral artery occlusion (filament model) are recognized as possible confounders to impair performance in certain behavioral tasks and bias the treatment effects. Inherent limitations of stroke models should be carefully considered when planning experiments to ensure translation of behavioral data to the clinic.

Treatment of acute middle cerebral artery occlusion with a Solitaire AB stent: preliminary experience

We report our initial experience with a Solitaire AB neurovascular remodeling stent device in performing cerebral embolectomy in seven patients presenting to our institution with acute stroke who were resistant to iv thrombolytic drug treatment. The main inclusion criteria were: National Institutes of Health Stroke Scale (NIHSS) score ≥10; treatment performed within 8 h from the onset of symptoms and no large hypodensity on CT; and occlusion of a major cerebral artery on the CT angiogram. An admission and a post-interventional NIHSS score were calculated for all patients by two different neurologists. Efficacy was assessed radiologically by post-treatment thrombolysis in myocardial infarction (TIMI) scores and clinically by a 30-day Modified Rankin Scale (MRS) score. The mean duration of neurointerventional treatment was 84 min. All interventions were successful, with TIMI scores of 2 or 3 achieved in 100% of patients. There was one procedural complication in our series owing to a self-detached stent and one patient had a small asymptomatic basal ganglia haemorrhage. There was improvement of more than 4 points on the NIHSS score in 5 (72%) of the patients following treatment, of whom 4 (57%) had a 30-day MRS score of ≤2. The use of a Solitaire stent in acute stroke was safe, time-efficient and encouraging; however, a larger sample size will be required to further evaluate the use of this device, which could benefit a significant number of stroke patients.

Protective effects and potential mechanisms of Pien Tze Huang on cerebral chronic ischemia and hypertensive stroke

Background

Stroke caused by brain ischemia is the third leading cause of adult disability. Active prevention and early treatment of stroke targeting the causes and risk factors may decrease its incidence, mortality and subsequent disability. Pien Tze Huang (PZH), a Chinese medicine formula, was found to have anti-edema, anti-inflammatory and anti-thrombotic effects that can prevent brain damage. This study aims to investigate the potential mechanisms of the preventive effects of Pien Tze Huang on brain damage caused by chronic ischemia and hypertensive stroke in rats.

Methods

The effects of Pien Tze Huang on brain protein expression in spontaneously hypertensive rat (SHR) and stroke prone SHR (SHRsp) were studied with 2-D gel electrophoresis and mass spectrometric analysis with a matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF)/TOF tandem mass spectrometer and on brain cell death with enzyme link immunosorbent assay (ELISA) and immunostaining.

Results

Pien Tze Huang decreased cell death in hippocampus and cerebellum caused by chronic ischemia and hypertensive stroke. Immunostaining of caspase-3 results indicated that Pien Tze Huang prevents brain cells from apoptosis caused by ischemia. Brain protein expression results suggested that Pien Tze Huang downregulated QCR₂ in the electron transfer chain of mitochondria preventing reactive oxygen species (ROS) damage and possibly subsequent cell death (caspase 3 assay) as caused by chronic ischemia or hypertensive stroke to hippocampus and cerebellum.

Conclusion

Pien Tze Huang showed preventive effects on limiting the damage or injury caused by chronic ischemia and hypertensive stroke in rats. The effect of Pien Tze Huang was possibly related to prevention of cell death from apoptosis or ROS/oxidative damage in mitochondria.

Targeting ischemic penumbra: part I - from pathophysiology to therapeutic strategy

Penumbra is the viable tissue around the irreversibly damaged ischemic core. The purpose of acute stroke treatment is to salvage penumbral tissue and to improve brain function. However, the majority of acute stroke patients who have treatable penumbra are left untreated. Therefore, developing an effective non-recanalizational therapeutics, such as neuroprotective agents, has significant clinical applications. Part I of this serial review on "targeting penumbra" puts special emphases on penumbral pathophysiology and the development of therapeutic strategies. Bioenergetic intervention by massive metabolic suppression and direct energy delivery would be a promising future direction. An effective drug delivery system for this purpose should be able to penetrate BBB and achieve high local tissue drug levels while non-ischemic region being largely unaffected. Selective drug delivery to ischemic stroke penumbra is feasible and deserves intensive research.