An overview of hyperbaric oxygen preconditioning against ischemic stroke

Ischemic stroke (IS) has become the second leading cause of morbidity and mortality worldwide, and the prevention of IS should be given high priority. Recent studies have indicated that hyperbaric oxygen preconditioning (HBO-PC) may be a protective nonpharmacological method, but its underlying mechanisms remain poorly defined. This study comprehensively reviewed the pathophysiology of IS and revealed the underlying mechanism of HBO-PC in protection against IS. The preventive effects of HBO-PC against IS may include inducing antioxidant, anti-inflammation, and anti-apoptosis capacity; activating autophagy and immune responses; upregulating heat shock proteins, hypoxia-inducible factor-1, and erythropoietin; and exerting protective effects upon the blood-brain barrier. In addition, HBO-PC may be considered a safe and effective method to prevent IS in combination with stem cell therapy. Although the benefits of HBO-PC on IS have been widely observed in recent research, the implementation of this technique is still controversial due to regimen differences. Transferring the results to clinical application needs to be taken carefully, and screening for the optimal regimen would be a daunting task. In addition, whether we should prescribe an individualized preconditioning regimen to each stroke patient needs further exploration.

The Protective and Reparative Role of Colony-Stimulating Factors in the Brain with Cerebral Ischemia/Reperfusion Injury

Stroke is a debilitating disease and has the ability to culminate in devastating clinical outcomes. Ischemic stroke followed by reperfusion entrains cerebral ischemia/reperfusion (I/R) injury, which is a complex pathological process and is associated with serious clinical manifestations. Therefore, the development of a robust and effective poststroke therapy is crucial. Granulocyte colony-stimulating factor (GCSF) and erythropoietin (EPO), originally discovered as hematopoietic growth factors, are versatile and have transcended beyond their traditional role of orchestrating the proliferation, differentiation, and survival of hematopoietic progenitors to one that fosters brain protection/neuroregeneration. The clinical indication regarding GCSF and EPO as an auspicious therapeutic strategy is conferred in a plethora of illnesses, including anemia and neutropenia. EPO and GCSF alleviate cerebral I/R injury through a multitude of mechanisms, involving antiapoptotic, anti-inflammatory, antioxidant, neurogenic, and angiogenic effects. Despite bolstering evidence from preclinical studies, the multiple brain protective modalities of GCSF and EPO failed to translate in clinical trials and thereby raises several questions. The present review comprehensively compiles and discusses key findings from in vitro, in vivo, and clinical data pertaining to the administration of EPO, GCSF, and other drugs, which alter levels of colony-stimulating factor (CSF) in the brain following cerebral I/R injury, and elaborates on the contributing factors, which led to the lost in translation of CSFs from bench to bedside. Any controversial findings are discussed to enable a clear overview of the role of EPO and GCSF as robust and effective candidates for poststroke therapy.

Infusion of Cold Saline into the Carotid Artery Does Not Affect Outcome After Intrastriatal Hemorrhage

Localized brain hypothermia (HYPO) can be achieved by infusing cold saline into the carotid artery of animals and patients. Studies suggest that HYPO improves behavioral and histological outcomes in focal ischemia models. Given that ischemic stroke and intracerebral hemorrhage (ICH) share pathophysiological overlap, we tested whether cold saline infusion is safe and neuroprotective when given during collagenase-induced ICH. Eighty-five adult male Sprague-Dawley rats were used. Experiment 1 investigated brain and body temperature changes associated with a cold saline infusion paradigm that was scaled from patients according to brain weight and blood volume (3 mL/20-minute infusion). Experiment 2 determined whether HYPO aggravated bleeding volume. Experiment 3 investigated if cerebral edema or elemental concentrations were altered by HYPO. We also collected core body temperature and activity data through telemetry. Experiment 4 investigated whether behavioral outcomes (e.g., skilled reaching) and tissue loss were influenced by HYPO. Our HYPO protocol decreased the ipsilateral striatal temperature by ∼0.20°C (p < 0.001), with no other effects. HYPO did not affect hematoma volume (p = 0.64), cerebral edema (p = 0.34), or elemental concentrations (p = 0.49) at 24 hours post-ICH. Although ICH caused persistent behavioral impairments, HYPO did not improve behavioral outcomes (measured by a neurological deficit scale, cylinder, and the staircase test; p > 0.05 for all). Brain tissue loss was not different between groups on day 28 post-ICH (p = 0.90). Although cold saline infusion appears to be safe in the acute post-ICH period, there was no evidence that this therapy improved outcome. However, our treatment protocol was relatively mild and additional interventions might help improve efficacy. Finally, our findings may also speak to the safety of this cooling approach in focal ischemia where hemorrhagic transformation is a risk; future studies on this issue are needed.

CKLF1/CCR5 axis is involved in neutrophils migration of rats with transient cerebral ischemia

BACKGROUND

Chemokine-like factor 1 (CKLF1) is a chemokine increased significantly in ischemic brain poststroke. It shows chemotaxis effects on various immune cells, but the mechanisms of CKLF1 migrating neutrophils are poorly understood. Recent studies have provided evidence that CC chemokine receptor 5 (CCR5), a receptor of CKLF1, is involved in ischemic stroke.

PURPOSES

To investigate the effects of HIF-1α guided AAV in ischemic brain, investigating the outcome of stroke, and examining the involvement of CKLF1/CCR5 axis in recruitment of neutrophils.

RESULTS

HIF-1α guided AAV knocked down CKLF1 in ischemic area and alleviated brain damage of rats. CKLF1 migrated neutrophils through CCR5, worsening inflammatory responses. Akt/GSK-3β pathway may involve in CKLF1/CCR5 axis guided neutrophils chemotaxis.

CONCLUSIONS

CKLF1/CCR5 axis is involved in neutrophils migration of rats with transient cerebral ischemia. CKLF1/CCR5 axis may be a useful target for stroke therapy.

Improvement in mitochondrial function underlies the effects of ANNAO tablets on attenuating cerebral ischemia-reperfusion injuries

ETHNOPHARMACOLOGICAL RELEVANCE

ANNAO tablets derive from Chinese classical prescriptions of Angong Niuhuang Pills with modified compositions, which have been singly or combined used for stoke associated neurological disorders. However the underlying mechanism is not yet well-defined, the present study investigated its anti-ischemic effects in rat middle cerebral artery occlusion (MCAO) model and focused on mitochondrial quality control.

MATERIALS AND METHODS

Rats were subjected to 2 h of brain ischemia followed by 1 day or up to 7 days of reperfusion. Vehicle, ANNAO tablets or Edaravone were given at 1h after the start of reperfusion for 1 day or successive 7 days in MCAO rats. For the behavior assessment, Longa test and modified Neurological Severity Scores (m NSS) test were performed. Following the behavioral assessment, we assessed the protein expressions related to mitochondrial function. Moreover, we also assessed the neuroprotective effects of ANNAO tablets by immunohistochemical analysis.

RESULTS

Compared with sham rats, ANNAO tablets improved the behavioral performance and decreased the infarction volume in the MCAO rats. Western blotting results showed that ANNAO tablets altered the expression level of multiple proteins related to mitochondrial function, elevated the ratio of Bcl-2/Bax and inhibited the apoptosis. Additionally, ANNAO tablets increased the number of NeuN positive neurons.

CONCLUSIONS

The obtained data demonstrated that ANNAO tablets exhibited an obvious anti-cerebral ischemia-reperfusion effect, which could be attributed to the improvement of mitochondrial quality control.

Reduced Apoptotic Injury by Phenothiazine in Ischemic Stroke through the NOX-Akt/PKC Pathway

Phenothiazine treatment has been shown to reduce post-stroke ischemic injury, though the underlying mechanism remains unclear. This study sought to confirm the neuroprotective effects of phenothiazines and to explore the role of the NOX (nicotinamide adenine dinucleotide phosphate oxidase)/Akt/PKC (protein kinase C) pathway in cerebral apoptosis. Sprague-Dawley rats underwent middle cerebral artery occlusion (MCAO) for 2 h and were randomly divided into 3 different cohorts: (1) saline, (2) 8 mg/kg chlorpromazine and promethazine (C+P), and (3) 8 mg/kg C+P as well as apocynin (NOX inhibitor). Brain infarct volumes were examined, and cell death/NOX activity was determined by assays. Western blotting was used to assess protein expression of kinase C-δ (PKC-δ), phosphorylated Akt (p-Akt), Bax, Bcl-XL, and uncleaved/cleaved caspase-3. Both C+P and C+P/NOX inhibitor administration yielded a significant reduction in infarct volumes and cell death, while the C+P/NOX inhibitor did not confer further reduction. In both treatment groups, anti-apoptotic Bcl-XL protein expression generally increased, while pro-apoptotic Bax and caspase-3 proteins generally decreased. PKC protein expression was decreased in both treatment groups, demonstrating a further decrease by C+P/NOX inhibitor at 6 and 24 h of reperfusion. The present study confirms C+P-mediated neuroprotection and suggests that the NOX/Akt/PKC pathway is a potential target for efficacious therapy following ischemic stroke.

Local endovascular infusion and hypothermia in stroke therapy: A systematic review

Ischemic stroke is a leading cause of death and disability worldwide, but there are no effective, widely applicable stroke therapies. Systemic hypothermia is an international mainstay of postcardiac arrest care, and the neuroprotective benefits of systemic hypothermia following cerebral ischemia have been proven in clinical trials, but logistical issues hinder clinical acceptance. As a novel solution to these logistical issues, the application of local endovascular infusion of cold saline directly to the infarct site using a microcatheter has been put forth. In small animal models, the procedure has shown incredible neuroprotective promise on the biochemical, structural, and functional levels, and preliminary trials in large animals and humans have been similarly encouraging. In addition, the procedure would be relatively cost-effective and widely applicable. The administration of local endovascular hypothermia in humans is relatively simple, as this is a normal part of endovascular intervention for neuroendovascular surgeons. Therefore, it is expected that this new therapy could easily be added to an angiography suite. However, the neuroprotective efficacy in humans has yet to be determined, which is an end goal of researchers in the field. Given the potentially massive benefits, ease of induction, and cost-effective nature, it is likely that local endovascular hypothermia will become an integral part of endovascular treatment following ischemic stroke. This review outlines relevant research, discusses neuroprotective mechanisms, and discusses possibilities for future directions.

Ginaton improves neurological function in ischemic stroke rats via inducing autophagy and maintaining mitochondrial homeostasis

PURPOSE

The present study was carried out to confirm the protective effect of extract of Ginkgo biloba (Ginaton) against ischemic neuronal damage post-treatment at 24 h after reperfusion in rats with middle cerebral artery occlusion (MCAO) and further reveal its possible mechanisms.

METHODS

Adult male Sprague-Dawley rats were modeled by MCAO for 2 h. The rats were divided into three groups: sham, model, and Ginaton (50 mg/kg). All animals received treatment once a day for 14 days from 24 h after reperfusion. Modified neurological severity score test was performed in 1, 7 and 14 days after MCAO, and beam walking test was performed only 14 days after MCAO. Hematoxylin-eosin straining was implemented to measure infarct volume and immunohistochemical analysis was performed to calculate the number of neurons in ischemic cortex penumbra. Western blot was used to evaluate the expression of autophagy (Beclin1, LC3, AMPK, mTOR, ULK), mitochondrial dynamic protein (Parkin, DRP1, OPA1) and apoptosis (Bcl-2, Bax).

RESULTS

Post-treatment with Ginaton for 14 days decreased neurological deficit score, promoted the recovery of motor function, and noticeably reduced infarct size. Besides, Ginaton also alleviated the loss of NeuN-positive cells in ischemic cortex penumbra. In ischemic cortex, Ginaton increased the expression of Beclin1 and LC3-Ⅱ, elevated the AMPK, mTOR and ULK1, and induced autophagy. Moreover, Ginaton treatment upregulated Parkin, DRP1, and OPA1, and elevated the ratio of Bcl-2/Bax in 14 days after MCAO reperfusion injury.

CONCLUSION

Ginaton exhibited obvious neuroprotective effects in MCAO rats with initial administered 24 h after MCAO. The mechanism of Ginaton included induction of autophagy via activation of the AMPK pathway, maintenance of mitochondrial homeostasis and inhibition of apoptosis.

Salidroside improves brain ischemic injury by activating PI3K/Akt pathway and reduces complications induced by delayed tPA treatment

Cerebral ischemia causes blood-brain barrier (BBB) injury and thus increases the risk of complications secondary to thrombolysis, which limited its clinical application. This study aims to clarify the role and mechanism of salidroside (SALD) in alleviating brain ischemic injury and whether pretreatment of it could improve prognosis of delayed treatment of tissue plasminogen activator (t-PA). Rats were subjected to 3 h of middle cerebral artery occlusion (MCAO) and were intraperitoneally administered with 10, 20 or 40 mg/kg SALD before ischemia. 1.5% 5-triphenyl-2H-tetrazolium chloride (TTC) staining and neurological studies were performed to observe the effectiveness of SALD. The expressions and the distribution of phosphoinositide-3-kinase/protein kinase B (PI3K/Akt) signaling were analyzed. Experiments were further conducted in isolated microvessels and human brain microvascular endothelial cells (HBMECs) to explore the protective mechanism of SALD. Finally, rats were subjected to 6 h of MCAO and 24 h of reperfusion. tPA was given with or without the pretreatment of SALD. Various approaches including gelatin zymography, western blot and immunofluorescence were used to evaluate the effect of this combination therapy. SALD could reduce cerebral ischemic injury and enhance HBMECs viability subjected to OGD. In vivo and in vitro studies showed the mechanism might be related to the activation of PI3K/Akt signaling by phosphorylating Akt on Ser473. Pretreatment of SALD could alleviate BBB injury and improve the outcome of delayed treatment of tPA. These results provide evidence that SALD might be an effective adjuvant to reduce the complications induced by delayed tPA treatment for brain ischemia.

Exacerbation of Brain Injury by Post-Stroke Exercise Is Contingent Upon Exercise Initiation Timing

Accumulating evidence has demonstrated that post-stroke physical rehabilitation may reduce morbidity. The effectiveness of post-stroke exercise, however, appears to be contingent upon exercise initiation. This study assessed the hypothesis that very early exercise exacerbates brain injury, induces reactive oxygen species (ROS) generation, and promotes energy failure. A total of 230 adult male Sprague-Dawley rats were subjected to middle cerebral artery (MCA) occlusion for 2 h, and randomized into eight groups, including two sham injury control groups, three non-exercise and three exercise groups. Exercise was initiated after 6 h, 24 h and 3 days of reperfusion. Twenty-four hours after completion of exercise (and at corresponding time points in non-exercise controls), infarct volumes and apoptotic cell death were examined. Early brain oxidative metabolism was quantified by examining ROS, ATP and NADH levels 0.5 h after completion of exercise. Furthermore, protein expressions of angiogenic growth factors were measured in order to determine whether post-stroke angiogenesis played a role in rehabilitation. As expected, ischemic stroke resulted in brain infarction, apoptotic cell death and ROS generation, and diminished NADH and ATP production. Infarct volumes and apoptotic cell death were enhanced (p < 0.05) by exercise that was initiated after 6 h of reperfusion, but decreased by late exercise (24 h, 3 days). This exacerbated brain injury at 6 h was associated with increased ROS levels (p < 0.05), and decreased (p < 0.05) NADH and ATP levels. In conclusion, very early exercise aggravated brain damage, and early exercise-induced energy failure with ROS generation may underlie the exacerbation of brain injury. These results shed light on the manner in which exercise initiation timing may affect post-stroke rehabilitation.

Neurovascular Unit Protection From Cerebral Ischemia-Reperfusion Injury by Radical-Containing Nanoparticles in Mice

BACKGROUND AND PURPOSE

Reperfusion therapy by mechanical thrombectomy is used to treat acute ischemic stroke. However, reactive oxygen species generation after reperfusion therapy causes cerebral ischemia-reperfusion injury, which aggravates cerebral infarction. There is limited evidence for clinical efficacy in stroke for antioxidants. Here, we developed a novel core-shell type nanoparticle containing 4-amino-4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (nitroxide radical-containing nanoparticles [RNPs]) and investigated its ability to scavenge reactive oxygen species and confer neuroprotection.

METHODS

C57BL/6J mice underwent transient middle cerebral artery occlusion and then received RNPs (9 mg/kg) through the common carotid artery. Infarction size, neurological scale, and blood-brain barrier damage were visualized by Evans blue extravasation 24 hours after reperfusion. RNP distribution was detected by rhodamine labeling. Blood-brain barrier damage, neuronal apoptosis, and oxidative neuronal cell damage were evaluated in ischemic brains. Multiple free radical-scavenging capacities were analyzed by an electron paramagnetic resonance-based method.

RESULTS

RNPs were detected in endothelial cells and around neuronal cells in the ischemic lesion. Infarction size, neurological scale, and Evans blue extravasation were significantly lower after RNP treatment. RNP treatment preserved the endothelium and endothelial tight junctions in the ischemic brain; neuronal apoptosis, O₂^- production, and gene oxidation were significantly suppressed. Reactive oxygen species scavenging capacities against OH, ROO, and O₂^- improved by RNP treatment.

CONCLUSIONS

An intra-arterial RNP injection after cerebral ischemia-reperfusion injury reduced blood-brain barrier damage and infarction volume by improving multiple reactive oxygen species scavenging capacities. Therefore, RNPs can provide neurovascular unit protection.

Improvement of mitochondrial function mediated the neuroprotective effect of 5-(4-hydroxy-3-dimethoxybenzylidene)-2-thioxo-4-thiazolidinone in rats with cerebral ischemia-reperfusion injuries

Deficits in mitochondrial function is a critical inducement in the major pathways that drive neuronal cell death in ischemic process particularly. Drugs target to improve the mitochondrial function may be a feasible therapeutic choice in treatment with ischemic diseases. In the present study, we investigated whether 5-(4-hydroxy-3-dimethoxybenzylidene)-2-thioxo-4-thiazolidinone (RD-1), a compound derived from rhodanine, could protect against ischemic neuronal damage via improving mitochondrial function. We tested the neuroprotective effect of RD-1 both in rats modeled by middle cerebral artery occlusion reperfusion in vivo and in primary cortical neurons subjected to hypoxia/reperfusion injury in vitro. Results showed that treatment with RD-1 for 14 days remarkably reduced infarct size, decreased neurological deficit score and accelerated the recovery of somatosensory function in vivo. Meanwhile, RD-1 also increased the cellular viability after 48 h treatment in vitro. In addition, RD-1 protected the primary cortical neurons against mitochondrial damage as evidenced by stabilizing the mitochondrial membrane potential and reducing the overproduction of reactive oxygen species. Furthermore, hypoxia/reperfusion injury induced damaged mitochondrial axonal transport and consequently neurotransmitter release disorder, which were ameliorated by RD-1 treatment. Besides, RD-1 inhibited the downregulation of proteins related with mitochondrial transport and neurotransmitter release induced by ischemic injury both in vivo and in vitro. The obtained data demonstrated the neuroprotective effect of RD-1 and the involved mechanisms were partially attributed to the improvement in mitochondrial function and the synaptic activity. Our study indicated that RD-1 may be a potential therapeutic drug for the ischemic stroke therapy.

Erythropoietin: Endogenous Protection of Ischemic Brain

The human brain requires uninterrupted delivery of blood-borne oxygen and nutrients to sustain its function. Focal ischemia, particularly, ischemic stroke, and global ischemia imposed by cardiac arrest disrupt the brain's fuel supply. The resultant ATP depletion initiates a complex injury cascade encompassing intracellular Ca²⁺ overload, glutamate excitotoxicity, oxido-nitrosative stress, extracellular matrix degradation, and inflammation, culminating in neuronal and astroglial necrosis and apoptosis, neurocognitive deficits, and even death. Unfortunately, brain ischemia has proven refractory to pharmacological intervention. Many promising treatments afforded brain protection in animal models of focal and global ischemia, but failed to improve survival and neurocognitive recovery of stroke and cardiac arrest patients in randomized clinical trials. The culprits are the blood-brain barrier (BBB) that limits transferral of medications to the brain parenchyma, and the sheer complexity of the injury cascade, which presents a daunting array of targets unlikely to respond to monotherapies. Erythropoietin is a powerful neuroprotectant capable of interrupting multiple aspects of the brain injury cascade. Preclinical research demonstrates erythropoietin's ability to suppress glutamate excitotoxicity and intracellular Ca²⁺ overload, dampen oxidative stress and inflammation, interrupt the apoptotic cascade, and preserve BBB integrity. However, the erythropoietin dosages required to traverse the BBB and achieve therapeutically effective concentrations in the brain parenchyma impose untoward side effects. Recent discoveries that hypoxia induces erythropoietin production within the brain and that neurons, astroglia, and cerebrovascular endothelium harbor membrane erythropoietin receptors, raise the exciting prospect of harnessing endogenous erythropoietin to protect the brain from the ravages of ischemia-reperfusion.

Compound porcine cerebroside and ganglioside injection attenuates cerebral ischemia-reperfusion injury in rats by targeting multiple cellular processes

BACKGROUND

Compound porcine cerebroside and ganglioside injection (CPCGI) is a neurotrophic drug used clinically to treat certain functional disorders of brain. Despite its extensive usage throughout China, the exact mechanistic targets of CPCGI are unknown. This study was carried out to investigate the protective effect of CPCGI against ischemic neuronal damage in rats with middle cerebral artery occlusion (MCAO) reperfusion injury and to investigate the neuroprotective mechanisms of CPCGI.

MATERIALS AND METHODS

Adult male Sprague-Dawley rats were subjected to MCAO surgery for 2 hours followed by reperfusion. The rats were administered CPCGI once a day for 14 days after reperfusion, and behavioral tests were performed 1, 3, 7, and 14 days post MCAO. Hematoxylin-eosin staining was used to measure infarct volume, and immunohistochemical analysis was performed to determine the number of NeuN-positive neurons in the ischemic cortex penumbra. Finally, the relative expression levels of proteins associated with apoptosis (Bcl-2, Bax, and GADD45α), synaptic function (Synaptophysin, SNAP25, Syntaxin, and Complexin-1/2), and mitochondrial function (KIFC2 and UCP3) were determined by Western blot.

RESULTS

CPCGI treatment reduced infarct size, decreased neurological deficit scores, and accelerated the recovery of somatosensory function 14 days after MCAO. In addition, CPCGI reduced the loss of NeuN-positive cells in the ischemic cortex penumbra. In the ischemic cortex, CPCGI treatment decreased GADD45α expression, increased the Bcl-2/Bax ratio, augmented Synaptophysin, SNAP25, and Complexin-1/2 expression, and increased the expression of KIFC2 and UCP3 compared with sham rats 14 days after MCAO reperfusion injury.

CONCLUSION

CPCGI displays neuroprotective properties in rats subjected to MCAO injury by inhibiting apoptosis and improving synaptic and mitochondrial function.

IMM-H004, a coumarin derivative, attenuated brain ischemia/reperfusion injuries and subsequent inflammation in spontaneously hypertensive rats through inhibition of VCAM-1

We studied the effect of IMM-H004 in treating brain I/R injury in spontaneously hypertensive rats and showed that IMM-H004 could efficiently ameliorate neurological defects and infarct volume in a time and dose dependent manner.

Effects of erythropoietin combined with tissue plasminogen activator on the rats following cerebral ischemia and reperfusion

OBJECTIVES:

Exogenously administered recombinant human erythropoietin (rhEPO) has been reported to exhibit neuroprotective effects in animal models. However, there are still have some controversies that combination of EPO and tissue plasminogen activator (tPA) in acute ischemic stroke. In the present study, we investigated the effects of local intra-arterial infusion of low-dose EPO in combination with tPA on focal cerebral ischemic stroke.

MATERIALS AND METHODS:

Sixty adult male Sprague–Dawley rats were randomly divided into five groups, including sham, vehicle, EPO, tPA, and EPO+tPA groups. Rats were subjected to middle cerebral artery occlusion (MCAO) and administrated with EPO (800 U/kg, middle cerebral artery injection), tPA (10 mg/kg, tail vein injection), EPO+tPA, or saline (vehicle) onset of reperfusion. Neurobehavioral deficits, infarct volume, brain edema, the expression of tight junction proteins (Claudin-5, Occludin), and AQP4 were assessed following 2 h ischemia and 24 h reperfusion. The number of apoptotic cells in the periinfarct region was detected by the terminal deoxyribonucleotide transferase dUTP nick end labeling (TUNEL) staining.

RESULTS:

The neurobehavioral deficits, brain infarct volume, edema volume, TUNEL-positive cells and downregulation of Claudin-5 and Occludin were alleviated by EPO or EPO plus tPA, following the ischemia/reperfusion (I/R) in rats. The EPO and EPO plus tPA both reduced the upregulation of AQP4 in the ischemic brain tissue.

CONCLUSION:

Our data demonstrate local intra-arterial infusion of low-dose EPO in combination with tPA protected against focal cerebral ischemia in rats manifested by a decrease in brain edema and blood-brain barrier (BBB) disruption after 2 h ischemia and 24 h reperfusion.

Erythropoietin for the Treatment of Subarachnoid Hemorrhage: A Feasible Ingredient for a Successful Medical Recipe

Subarachnoid hemorrhage (SAH) following aneurysm bleeding accounts for 6% to 8% of all cerebrovascular accidents. Although an aneurysm can be effectively managed by surgery or endovascular therapy, delayed cerebral ischemia is diagnosed in a high percentage of patients resulting in significant morbidity and mortality. Cerebral vasospasm occurs in more than half of all patients after aneurysm rupture and is recognized as the leading cause of delayed cerebral ischemia after SAH. Hemodynamic strategies and endovascular procedures may be considered for the treatment of cerebral vasospasm. In recent years, the mechanisms contributing to the development of vasospasm, abnormal reactivity of cerebral arteries and cerebral ischemia following SAH, have been investigated intensively. A number of pathological processes have been identified in the pathogenesis of vasospasm, including endothelial injury, smooth muscle cell contraction from spasmogenic substances produced by the subarachnoid blood clots, changes in vascular responsiveness and inflammatory response of the vascular endothelium. To date, the current therapeutic interventions remain ineffective as they are limited to the manipulation of systemic blood pressure, variation of blood volume and viscosity and control of arterial carbon dioxide tension. In this scenario, the hormone erythropoietin (EPO) has been found to exert neuroprotective action during experimental SAH when its recombinant form (rHuEPO) is administered systemically. However, recent translation of experimental data into clinical trials has suggested an unclear role of recombinant human EPO in the setting of SAH. In this context, the aim of the current review is to present current evidence on the potential role of EPO in cerebrovascular dysfunction following aneurysmal subarachnoid hemorrhage.

Intraarterial administration of norcantharidin attenuates ischemic stroke damage in rodents when given at the time of reperfusion: novel uses of endovascular capabilities

OBJECT Matrix metalloprotease-9 (MMP-9) plays a critical role in infarct progression, blood-brain barrier (BBB) disruption, and vasogenic edema. While systemic administration of MMP-9 inhibitors has shown neuroprotective promise in ischemic stroke, there has been little effort to incorporate these drugs into endovascular modalities. By modifying the rodent middle cerebral artery occlusion (MCAO) model to allow local intraarterial delivery of drugs, one has the ability to mimic endovascular delivery of therapeutics. Using this model, the authors sought to maximize the protective potential of MMP-9 inhibition by intraarterial administration of an MMP-9 inhibitor, norcantharidin (NCTD). METHODS Spontaneously hypertensive rats were subjected to 90-minute MCAO followed immediately by local intraarterial administration of NCTD. The rats' neurobehavioral performances were scored according to the ladder rung walking test results and the Garcia neurological test for as long as 7 days after stroke. MRI was also conducted 24 hours after the stroke to assess infarct volume and BBB disruption. At the end of the experimental protocol, rat brains were used for active MMP-9 immunohistochemical analysis to assess the degree of MMP-9 inhibition. RESULTS NCTD-treated rats showed significantly better neurobehavioral scores for all days tested. MR images also depicted significantly decreased infarct volumes and BBB disruption 24 hours after stroke. Inhibition of MMP-9 expression in the ischemic region was depicted on immunohistochemical analysis, wherein treated rats showed decreased active MMP-9 staining compared with controls. CONCLUSIONS Intraarterial NCTD significantly improved outcome when administered at the time of reperfusion in a spontaneously hypertensive rat stroke model. This study suggests that supplementing endovascular revascularization with local neuroprotective drug therapy may be a viable therapeutic strategy.

AKT/GSK3β-dependent autophagy contributes to the neuroprotection of limb remote ischemic postconditioning in the transient cerebral ischemic rat model

BACKGROUND

Limb remote ischemic postconditioning (RIPostC) has been recognized as an applicable strategy in protecting against cerebral ischemic injury. However, the time window for application of limb RIPostC and the mechanisms behind RIPostC are still unclear.

AIMS

In this study, we investigated the protective efficacy and the role of autophagy in limb RIPostC using a transient middle cerebral artery occlusion rat model.

RESULTS

Limb RIPostC applied in the early phase of reperfusion reduced infarct size and improved neurological function. Autophagy levels in penumbral tissues were elevated in neurons of limb RIPostC rats, with an increase in the phosphorylation of AKT and glycogen synthase kinase 3β (GSK3β). Blocking the AKT/GSK3β pathway via the AKT inhibitor LY294002 prior to limb RIPostC suppressed the RIPostC-induced autophagy and resulted in the activation of caspase-3 in RIPostC rats, suggesting a critical role for AKT/GSK3β-dependent autophagy in reducing cell death after cerebral ischemia.

CONCLUSIONS

These results aid optimization of the time window for RIPostC use and offer novel insight into, and a better understanding of, the protective mechanism of autophagy in limb RIPostC.

A new middle cerebral artery occlusion model for intra-arterial drug infusion in rats

With the wide application of intra-arterial therapy for cerebrovascular disorders, preclinical intra-arterial drug-delivery studies based on middle cerebral artery occlusion (MCAO) models have become urgent. In the present study, a novel stroke model was developed for intra-arterial drug delivery: MCAO and drug delivery were accomplished using a microcatheter device. MCAO was induced in Sprague-Dawley rats using the microcatheter device (cMCAO group, n=10) or a nylon suture (sMCAO group, n=10). After 24-h occlusion, neurological deficit and infarct volume were compared between the groups. Drug-delivery models used in stroke studies were compared with the present model to verify the drug-delivery ability of the microcatheter device. MCAO was induced using the microcatheter device in 21 Sprague-Dawley rats. At 4h after occlusion, 2% Evans blue dye was infused using different methods, and 1h later, the dye was extracted from each hemisphere and spectrophotometrically quantified. All cMCAO group rats showed neurological deficits; none developed subarachnoid hemorrhage or died before sacrifice. Neurological deficits and infarct volumes were similar in the cMCAO and sMCAO groups. Significantly more dye leakage occurred in the ischemic hemispheres of the rats that received the dye via the microcatheter device. Compared to other intra-arterial drug-delivery models used in stroke studies, the present model was easily established, had a high success rate, caused minimal surgical injury, and enabled highly efficient drug delivery. Thus, the present model is an efficient tool for investigating the effect of intra-arterial drug delivery on ischemic cerebral tissue.

Intra-artery infusion of recombinant human erythropoietin reduces blood-brain barrier disruption in rats following cerebral ischemia and reperfusion

OBJECTIVES

Intra-artery infusion of recombinant human erythropoietin (rhEPO) has recently been reported to confer neuroprotection against cerebral ischemia-reperfusion injury in animal models; however, the molecular mechanisms are still under investigation. The present study focused on the specific mechanism involved in blood-brain barrier (BBB) disruption.

METHODS

Thirty-six male and nine female Sprague Dawley rats were subjected to middle cerebral artery (MCA) occlusion to induce focal cerebral ischemia, and administrated rhEPO at a dose of 800 U/kg through MCA infusion at the beginning of reperfusion. Neurobehavioral deficits, brain edema, and infarct volume were evaluated after 2 h of ischemia and 24 h of reperfusion. BBB permeability was assessed by quantifying the extravasation of Evans blue (EB) dye. The expression of tight junction proteins and matrix metalloproteinases (MMPs) (Claudin-5, Occludin, MMP-2, and MMP-9) in microvessels were detected by immunofluorescence and western blot. The activities of MMPs in the cerebral microvessels were determined by gelatin zymography.

RESULTS

Treatment with rhEPO through the MCA strongly alleviated infarct volume, brain edema, and improved neurobehavioral outcomes in male and female rats. In addition, rhEPO remarkably suppressed the EB extravasation induced by brain ischemia. Furthermore, rhEPO prevented degradation of Claudin-5 and Occludin, and reduced the expression and activity of MMP-2 and MMP-9 in isolated brain microvessels.

CONCLUSIONS

Treatment with rhEPO through MCA infusion prevented brain edema formation and infarction through inhibition of MMP-mediated BBB disruption in acute ischemic stroke.

AKT-related autophagy contributes to the neuroprotective efficacy of hydroxysafflor yellow A against ischemic stroke in rats

Hydroxysafflor yellow A (HSYA) has been approved clinically for treating cardiac patients in China since 2005. Recent studies have indicated that HSYA may be neuroprotective at 24 h in experimental stroke models. Autophagy is a vital degradation pathway of damaged intracellular macromolecules or organelles to maintain homeostasis in physiological or pathological conditions. The purpose of this study is to investigate the neuroprotection of HSYA at 72 h and its mechanism via activating the autophagy pathway using an acute ischemic-reperfusion stroke rat model. Rats were treated with HSYA (2 mg/kg) during 90 min middle cerebral artery occlusion/72 h reperfusion by intravenous administration at four different time points (15 min post-ischemia, 15 min, 24 h, and 48 h post reperfusion), mimicking the potential treatment for acute ischemic stroke. HSYA administration reduced infarction volume and improved various neurological functions at 72 h of reperfusion. The possible molecular mechanism was investigated. We found that HSYA activated the AKT-autophagy pathway in penumbra tissue, which occurred in neuronal-specific cells. Moreover, blocking the AKT-autophagy pathway by an AKT inhibitor abolished HSYA-induced neuroprotection after cerebral ischemia. HSYA may be a promising drug for treating acute ischemic stroke and the AKT-dependent autophagy pathway contributes to the HSYA-afforded neuroprotection.

Overexpression of mitochondrial uncoupling protein 2 inhibits inflammatory cytokines and activates cell survival factors after cerebral ischemia

Mitochondria play a critical role in cell survival and death after cerebral ischemia. Uncoupling proteins (UCPs) are inner mitochondrial membrane proteins that disperse the mitochondrial proton gradient by translocating H⁺ across the inner membrane in order to stabilize the inner mitochondrial membrane potential (ΔΨ_m) and reduce the formation of reactive oxygen species. Previous studies have demonstrated that mice transgenically overexpressing UCP2 (UCP2 Tg) in the brain are protected from cerebral ischemia, traumatic brain injury and epileptic challenges. This study seeks to clarify the mechanisms responsible for neuroprotection after transient focal ischemia. Our hypothesis is that UCP2 is neuroprotective by suppressing innate inflammation and regulating cell cycle mediators. PCR gene arrays and protein arrays were used to determine mechanisms of damage and protection after transient focal ischemia. Our results showed that ischemia increased the expression of inflammatory genes and suppressed the expression of anti-apoptotic and cell cycle genes. Overexpression of UCP2 blunted the ischemia-induced increase in IL-6 and decrease in Bcl2. Further, UCP2 increased the expression of cell cycle genes and protein levels of phospho-AKT, PKC and MEK after ischemia. It is concluded that the neuroprotective effects of UCP2 against ischemic brain injury are associated with inhibition of pro-inflammatory cytokines and activation of cell survival factors.