Photochemical stroke model: flunarizine prevents sensorimotor deficits after neocortical infarcts in rats

Therapeutic effects of mirodenafil, a phosphodiesterase 5 inhibitor, on stroke models in rats

Mirodenafil is a phosphodiesterase 5 (PDE5) inhibitor with high specificity for its target and good blood-brain barrier permeability. The drug, which is currently used for treatment of erectile dysfunction, reduces Aβ and pTau levels and improves cognitive function in mouse models of Alzheimer's disease. In the present study, we investigated the effect of mirodenafil in the transient and permanent middle cerebral artery occlusion (tMCAO and pMCAO) models of stroke in rats. Starting 24 ​h after cerebral artery occlusion, mirodenafil was administered subcutaneously at doses of 0.5, 1, and 2 ​mg/kg per day for 9 days in the tMCAO model and for 28 days in the pMCAO model. Mirodenafil significantly increased sensorimotor and cognitive recovery of tMCAO and pMCAO rats compared to saline control rats, and significantly decreased the amount of degenerative cells and cleaved caspase-3 and cleaved PARP immunoreactive cells. Effects were seen in a dose-dependent manner up to 1 ​mg/kg mirodenafil. The benefits of mirodenafil treatment increased with longer treatment duration, and the largest improvements over control were typically observed on the last assessment day. There was no effect of mirodenafil on infarct volume in both tMCAO and pMCAO rats. In an experiment to determine the treatment window for mirodenafil effects, a protective effect was observed when treatment was delayed 72 ​h after MCAO, although the most improvement was observed with shorter treatment windows. Using pMCAO and tMCAO rat models of stroke, we determined that mirodenafil improves the recovery of sensorimotor and cognitive functions after MCAO and protects cortical cells from apoptosis and degeneration. Greater benefit was observed with longer duration of treatment, and improvement was seen even when treatment was delayed.

Analysis of the brain transcriptome, microbiome and metabolome in ketogenic diet and experimental stroke

The ketogenic diet (KD) has been shown to be effective in treating various brain pathologies. In this study, we conducted detailed transcriptomic and metabolomic profiling of rat brains after KD and ischemic stroke in order to investigate the effects of KD and its underlying mechanisms. We evaluated the effect of a two-month KD on gene expression in intact brain tissue and after middle cerebral artery occlusion (MCAO). We analyzed the effects of KD on gut microbiome composition and blood metabolic profile as well as investigated the correlation between severity of neurological deficits and KD-induced changes. We found transcriptional reprogramming in the brain after stroke and KD treatment. The KD altered the expression of genes involved in the regulation of glucose and fatty acid metabolism, mitochondrial function, the immune response, Wnt-associated signaling, stem cell development, and neurotransmission, both in intact rats and after MCAO. The KD led to a significant change in the composition of gut microbiome and the levels of amino acids, acylcarnitines, polyunsaturated fatty acids, and oxylipins in the blood. However, the KD slightly worsened the neurological functions after MCAO, so that the therapeutic effect of the diet remained unproven.

"Baihui" (DU20)-penetrating "Qubin" (GB7) acupuncture on blood-brain barrier integrity in rat intracerebral hemorrhage models via the RhoA/ROCK II/MLC 2 signaling pathway

BACKGROUND

Blocking the RhoA/ROCK II/MLC 2 (Ras homolog gene family member A/Rho kinase II/myosin light chain 2) signaling pathway can initiate neuroprotective mechanisms against neurological diseases such as stroke, cerebral ischemia, and subarachnoid hemorrhage. Nevertheless, it is not clear whether and how disrupting the RhoA/ROCK II/MLC 2 signaling pathway changes the pathogenic processes of the blood-brain barrier (BBB) after intracerebral hemorrhage (ICH). The present investigation included the injection of rat caudal vein blood into the basal ganglia area to replicate the pathophysiological conditions caused by ICH.

METHODS

Scalp acupuncture (SA) therapy was performed on rats with ICH at the acupuncture point "Baihui"-penetrating "Qubin," and the ROCK selective inhibitor fasudil was used as a positive control to evaluate the inhibitory effect of acupuncture on the RhoA/ROCK II/MLC 2 signaling pathway. Post-assessments included neurological deficits, brain edema, Evans blue extravasation, Western blot, quantitative polymerase chain reaction, and transmission electron microscope imaging.

RESULTS

We found that ROCK II acts as a promoter of the RhoA/ROCK II/MLC 2 signaling pathway, and its expression increased at 6 h after ICH, peaked at 3 days, and then decreased at 7 days after ICH, but was still higher than the pre-intervention level. According to some experimental results, although 3 days is the peak, 7 days is the best time point for acupuncture treatment. Starting from 6 h after ICH, the neurovascular structure and endothelial cell morphology around the hematoma began to change. Based on the changes in the promoter ROCK II, a 7-day time point was selected as the breakthrough point for treating ICH model rats in the main experiment. The results of this experiment showed that both SA at "Baihui"-penetrating "Qubin" and treatment with fasudil could improve the expression of endothelial-related proteins by inhibiting the RhoA/ROCK II/MLC 2 signaling pathway and reduce neurological dysfunction, brain edema, and BBB permeability in rats.

CONCLUSION

This study found that these experimental data indicated that SA at "Baihui"-penetrating "Qubin" could preserve BBB integrity and neurological function recovery after ICH by inhibiting RhoA/ROCK II/MLC 2 signaling pathway activation and by regulating endothelial cell-related proteins.

Effects of Lithium Ions on tPA-Induced Hemorrhagic Transformation under Stroke

Thrombolytic therapy with the tissue plasminogen activator (tPA) is a therapeutic option for acute ischemic stroke. However, this approach is subject to several limitations, particularly the increased risk of hemorrhagic transformation (HT). Lithium salts show neuroprotective effects in stroke, but their effects on HT mechanisms are still unknown. In our study, we use the models of photothrombosis (PT)-induced brain ischemia and oxygen-glucose deprivation (OGD) to investigate the effect of Li+ on tPA-induced changes in brain and endothelial cell cultures. We found that tPA did not affect lesion volume or exacerbate neurological deficits but disrupted the blood-brain barrier. We demonstrate that poststroke treatment with Li+ improves neurological status and increases blood-brain barrier integrity after thrombolytic therapy. Under conditions of OGD, tPA treatment increased MMP-2/9 levels in endothelial cells, and preincubation with LiCl abolished this MMP activation. Moreover, we observed the effect of Li+ on glycolysis in tPA-treated endothelial cells, which we hypothesized to have an effect on MMP expression.

Methods for evaluating gait associated dynamic balance and coordination in rodents

Balance is the dynamic and unconscious control of the body's centre of mass to maintain postural equilibrium. Regulated by the vestibular system, head movement and acceleration are processed by the brain to adjust joints. Several conditions result in a loss of balance, including Alzheimer's Disease, Parkinson's Disease, Menière's Disease and cervical spondylosis, all of which are caused by damage to certain parts of the vestibular pathways. Studies about the impairment of the vestibular system are challenging to carry out in human trials due to smaller study sizes limiting applications of the results and a lacking understanding of the human balance control mechanism. In contrast, more controlled research can be performed in animal studies which have fewer confounding factors than human models and allow specific conditions that affect balance to be replicated. Balance control can be studied using rodent balance-related behavioural tests after spinal or brain lesions, such as the Basso, Beattie and Bresnahan (BBB) Locomotor Scale, Foot Fault Scoring System, Ledged Beam Test, Beam Walking Test, and Ladder Beam Test, which are discussed in this review article along with their advantages and disadvantages. These tests can be performed in preclinical rodent models of femoral nerve injury, stroke, spinal cord injury and neurodegenerative diseases.

Positive Neuroprotective Effect of Argon Inhalation after Photochemically Induced Ischemic Stroke Model in Rats

We studied the effect of 2-h inhalation of argon-oxygen mixture (Ar 70%/O2 30%) after photochemically induced stroke and on days 2 and 3 after stroke modeling on the severity of neurological deficit and brain damage (by MRI data) in Wistar rats. Neurological deficit was assessed within 14 days using the limb placement test. MRI and histological study of the brain with an assessment of the size of damage were performed on day 14 after ischemia. Significant differences were obtained in limb placement scores on days 3, 7, and 14, as well as in the volume of ischemic focus by MRI in comparison with the control (ischemia+N2 70%/O2 30%). Inhalation of argon-oxygen mixture for 2 h a day over 3 days after photoinduced stroke decreased the volume of brain damage by 2 times and reduced the severity of neurological deficit.

Extracellular vesicles of human glial cells exert neuroprotective effects via brain miRNA modulation in a rat model of traumatic brain injury

Stem cell-based therapeutic approaches for neurological disorders are widely studied. Paracrine factors secreted by stem cells in vitro and delivered intranasally might allow bypassing the disadvantages associated with a surgical cell delivery procedure with likely immune rejection of a transplant. In this study, we investigated the therapeutic effect of the extracellular vesicles secreted by glial progenitor cells (GPC-EV) derived from human induced pluripotent stem cell in a traumatic brain injury model. Intranasal administration of GPC-EV to Wistar rats for 6 days improved sensorimotor functions assessed over a 14-day observation period. Beside, deep sequencing of microRNA transcriptome of GPC-EV was estimate, and was revealed 203 microRNA species that might be implicated in prevention of various brain pathologies. Modulation of microRNA pools might contribute to the observed decrease in the number of astrocytes that inhibit neurorecovery processes while enhancing neuroplasticity by decreasing phosphorylated Tau forms, preventing inflammation and apoptosis associated with secondary damage to brain tissue. The course of GPC-EV administration was promoted the increasing protein levels of NF-κB in studied areas of the rat brain, indicating NF-κB dependent mechanisms as a plausible route of neuroprotection within the damaged area. This investigation showed that GPC-EV may be representing a therapeutic approach in traumatic brain injury, though its translation into the clinic would require an additional research and development.

Inhibition of insulin-regulated aminopeptidase confers neuroprotection in a conscious model of ischemic stroke

Stroke is a leading cause of mortality and morbidity with a paucity of effective pharmacological treatments. We have previously identified insulin-regulated aminopeptidase (IRAP) as a potential target for the development of a new class of drugs for the treatment of stroke, as global deletion of this gene in mice significantly protected against ischemic damage. In the current study, we demonstrate that small molecular weight IRAP inhibitors reduce infarct volume and improve neurological outcome in a hypertensive animal model of ischemic stroke. The effects of two structurally distinct IRAP inhibitors (HFI419 or SJM164) were investigated in a model of stroke where the middle cerebral artery was transiently occluded with endothelin-1 in the conscious spontaneously hypertensive rat. IRAP inhibitor was administered into the lateral ventricle at 2 or 6 h after stroke, with subsequent doses delivered at 24, 48 and 70 h post-stroke. Functional outcomes were assessed prior to drug treatment, and on day 1 and 3 post-stroke. Histological analyses and neuroinflammatory cytokine profiling were conducted at 72 and 24 h post-stroke respectively. IRAP inhibitor treatment following stroke significantly reduced infarct volume and improved neurological and motor deficits. These protective effects were maintained even when the therapeutic window was extended to 6 h. Examination of the cellular architecture at 72 h post-stroke demonstrated that IRAP expression was upregulated in CD11b positive cells and activated astrocytes. Furthermore, IRAP inhibitor treatment significantly increased gene expression for interleukin 6 and C-C motif chemokine ligand 2 in the ischemic core. This study provides proof-of-principle that selective inhibition of IRAP activity with two structurally distinct IRAP inhibitors reduces infarct volume and improves functional outcome even when the first dose is administered 6 h post-stroke. This is the first direct evidence that IRAP inhibitors are a class of drug with potential use in the treatment of ischemic stroke.

Immunocytoprotection after reperfusion with Kv1.3 inhibitors has an extended treatment window for ischemic stroke

Introduction: Mechanical thrombectomy has improved treatment options and outcomes for acute ischemic stroke with large artery occlusion. However, as the time window of endovascular thrombectomy is extended there is an increasing need to develop immunocytoprotective therapies that can reduce inflammation in the penumbra and prevent reperfusion injury. We previously demonstrated, that by reducing neuroinflammation, KV1.3 inhibitors can improve outcomes not only in young male rodents but also in female and aged animals. To further explore the therapeutic potential of KV1.3 inhibitors for stroke therapy, we here directly compared a peptidic and a small molecule KV1.3 blocker and asked whether KV1.3 inhibition would still be beneficial when started at 72 hours after reperfusion. Methods: Transient middle cerebral artery occlusion (tMCAO, 90-min) was induced in male Wistar rats and neurological deficit assessed daily. On day-8 infarction was determined by T2-weighted MRI and inflammatory marker expression in the brain by quantitative PCR. Potential interactions with tissue plasminogen activator (tPA) were evaluated in-vitro with a chromogenic assay. Results: In a direct comparison with administration started at 2 hours after reperfusion, the small molecule PAP-1 significantly improved outcomes on day-8, while the peptide ShK-223 failed to reduce infarction and neurological deficits despite reducing inflammatory marker expression. PAP-1 still provided benefits when started 72 hours after reperfusion. PAP-1 does not reduce the proteolytic activity of tPA. Discussion: Our studies suggest that KV1.3 inhibition for immunocytoprotection after ischemic stroke has a wide therapeutic window for salvaging the inflammatory penumbra and requires brain-penetrant small molecules.

Three-Hour Argon Inhalation Has No Neuroprotective Effect after Open Traumatic Brain Injury in Rats

In vivo studies of the therapeutic effects of argon in traumatic brain injury (TBI) are limited, and their results are contradictory. The aim of this study was to evaluate the effect of a three-hour inhalation of argon (70%Ar/30%O2) after an open TBI on the severity of the neurological deficit and the degree of brain damage in rats. The experiments were performed on male Wistar rats (n = 35). The TBI was simulated by the dosed open brain contusion injury. The animals were divided into three groups: sham-operated (SO, n = 7); TBI + 70%N2/30%O2 (TBI, n = 14); TBI + 70%Ar/30%O2 (TBI + iAr, n = 14). The Neurological status was assessed over a 14-day period (using the limb-placing and cylinder tests). Magnetic resonance imaging (MRI) scans and a histological examination of the brain with an assessment of the volume of the lesions were performed 14 days after the injury. At each of the time points (days 1, 7, and 14), the limb-placing test score was lower in the TBI and TBI + iAr groups than in the SO group, while there were no significant differences between the TBI and TBI + iAr groups. Additionally, no differences were found between these groups in the cylinder test scores (day 13). The volume of brain damage (tissue loss) according to both the MRI and histological findings did not differ between the TBI and TBI + iAr groups. A three-hour inhalation of argon (70%Ar/30%O2) after a TBI had no neuroprotective effect.

Chronic Nicotine Exposure Increases Hematoma Expansion Following Collagenase-Induced Intracerebral Hemorrhage in Rats

Spontaneous intracerebral hemorrhage (sICH) is a deadly stroke subtype, and tobacco use increases sICH risk. However epidemiological studies show that, there are no confirmatory studies showing the effect of tobacco use on sICH outcome. Therefore, we evaluated the effect of chronic nicotine exposure (as a surrogate for tobacco use) on outcomes following sICH. Young male and female rats were randomly assigned to either nicotine (4.5 mg/kg b.w. per day) or vehicle (saline) treatment (2–3 weeks) groups. sICH was induced by injecting collagenase into the right striatum. Neurological score and hematoma volume were determined 24 h post-sICH. The hematoma volumes in nicotine-treated male and female rats were significantly higher by 42% and 48% when compared to vehicle-treated male and female rats, respectively. Neurological deficits measured in terms of neurological score for the nicotine-treated male and female groups were significantly higher when compared to the respective vehicle-treated male and female groups. Our results show that chronic nicotine exposure increases hematoma volume post-sICH in rats of both sexes. Identifying the mechanism of nicotine-dependent increase in hematoma growth post-sICH will be crucial to understanding the detrimental effect of tobacco use on the severity of bleeding following intracerebral hemorrhage.

The potassium channel Kv1.3 as a therapeutic target for immunocytoprotection after reperfusion

OBJECTIVE

The voltage-gated potassium channel Kv1.3, which is expressed on activated, disease-associated microglia and memory T cells, constitutes an attractive target for immunocytoprotection after endovascular thrombectomy (EVT). Using young male mice and rats we previously demonstrated that the Kv1.3 blocker PAP-1 when started 12 h after reperfusion dose-dependently reduces infarction and improves neurological deficit on day 8. However, these proof-of-concept findings are of limited translational value because the majority of strokes occur in patients over 65 and, when considering overall lifetime risk, in females. Here, we therefore tested whether Kv1.3 deletion or delayed pharmacological therapy would be beneficial in females and aged animals.

METHODS

Transient middle cerebral artery occlusion (tMCAO, 60 min) was induced in 16-week-old and 80-week-old male and female wild-type C57BL/6J and Kv1.3-/- mice. Stroke outcomes were assessed daily with the 14-score tactile and proprioceptive limp placing test and on day 8 before sacrifice by T2-weighted MRI. Young and old female mice were treated twice daily with 40 mg/kg PAP-1 starting 12 h after reperfusion. Microglia/macrophage activation and T-cell infiltration were evaluated in whole slide scans.

RESULTS

Kv1.3 deletion provided no significant benefit in young females but improved outcomes in young males, old males, and old females compared with wild-type controls of the same sex. Delayed PAP-1 treatment improved outcomes in both young and old females. In old females, Kv1.3 deletion and PAP-1 treatment significantly reduced Iba-1 and CD3 staining intensity in the ipsilateral hemisphere.

INTERPRETATION

Our preclinical studies using aged and female mice further validate Kv1.3 inhibitors as potential adjunctive treatments for reperfusion therapy in stroke by providing both genetic and pharmacological verification.

Neferine Protects Against Brain Damage in Permanent Cerebral Ischemic Rat Associated with Autophagy Suppression and AMPK/mTOR Regulation

Neferine is the major alkaloid compound isolated from the seed embryos of lotus. Neferine has many pharmacological effects, such as anti-inflammatory, antioxidative stress, and antiapoptotic effects, and it maintains autophagic balance. The purpose of this study was to explore the mechanism by which neferine attenuates autophagy after permanent cerebral ischemia in rats. We performed permanent cerebral ischemia in rats by middle cerebral artery occlusion (pMCAO) for 12 h with or without administration of neferine or nimodipine, a calcium (Ca²⁺) channel blocker. Neuroprotective effects were determined by evaluating the infarct volume and neurological deficits. Autophagy and its signaling pathway were determined by evaluating the expression of phosphorylated AMP-activated protein kinase alpha (AMPKα), phosphorylated mammalian target of rapamycin (mTOR), beclin-1, microtubule-associated protein 1A/1B-light chain 3 class II (LC3-II), and p62 by western blotting. Autophagosomes were evaluated by transmission electron microscopy. Neferine treatment significantly reduced infarct volumes and improved neurological deficits. Neferine significantly attenuated the upregulation of autophagy-associated proteins such as LC3-II, beclin-1, and p62 as well as autophagosome formation, all of which were induced by pMCAO. Neferine exerted remarkable protection against cerebral ischemia, possibly via the regulation of autophagy mediated by the Ca²⁺-dependent AMPK/mTOR pathway.

Scalp Acupuncture Protects Against Neuronal Ferroptosis by Activating The p62-Keap1-Nrf2 Pathway in Rat Models of Intracranial Haemorrhage

Intracerebral haemorrhage (ICH) can be a catastrophic event; even if the initial stages of the pathology were well-managed, a number of patients experience varied residual neurological deficits following the insult. Ferroptosis is a recently identified type of cell demise which is tightly linked to the neurological impairment associated with ICH. In the current work, the prophylactic impact of scalp acupuncture (SA) therapy on autologous blood injection murine models of ICH was investigated in order to establish whether SA could mitigate the secondary damage arising following ICH by moderating ferroptosis. The pathophysiological mechanisms associated with this process were also explored. Ludmila Belayev tests were utilised for the characterisation of neurological damage. Haematoxylin–eosin staining was employed in order to determine the cerebral impact of the induced ICH. Malondialdehyde (MDA) and iron titres in peri-haemorrhagic cerebral tissues were appraised using purchased assay kits. Transmission electron microscopy delineated mitochondrial appearances within nerve cell bodies from the area of haemorrhage. Western blotting techniques were utilised to assay the degree of protein expression of NeuN, sequestosome 1 (p62), nuclear factor erythroid 2-related factor 2 (Nrf2), Kelch-like ECH-associated protein 1 (Keap1), glutathione peroxidase 4 (GPX4) and ferritin heavy chain 1 (FTH1). The frequencies of Nrf2, GPX4 and FTH1 positive cells, respectively, were documented with immunohistochemical staining. The results demonstrated that therapy with SA after ICH mitigated MDA and iron sequestration, diminished the appearance of contracted mitochondria with increased outer mitochondrial membrane diameter within the nerve cell bodies, and suppressed neuronal ferroptosis. The pathways responsible for these effects may encompass amplified p62, Nrf2, GPX4 and FTH1 expression, together with decreased Keap1 expression. Application of SA reduced identified neurobehavioural abnormalities after ICH; no disparities were observed between the consequences of SA therapy and deferoxamine delivery. It can be surmised that intervention with SA enhanced recovery after ICH by triggering the antioxidant pathway, p62/Keap1/Nrf2, and causing FTH1 and GPX4 upregulation, factors that participate in diminishing excess iron and thus in mitigating lipid peroxidation insults arising from ferroptosis following ICH.

Plasmin-resistant PSD-95 inhibitors resolve effect-modifying drug-drug interactions between alteplase and nerinetide in acute stroke

Neuroprotection for acute ischemic stroke is achievable with the eicosapeptide nerinetide, an inhibitor of the protein-protein interactions of the synaptic scaffolding protein PSD-95. However, nerinetide is subject to proteolytic cleavage if administered after alteplase, a standard-of-care thrombolytic agent that nullifies nerinetide's beneficial effects. Here, we showed, on the basis of pharmacokinetic data consistent between rats, primates, and humans, that in a rat model of embolic middle cerebral artery occlusion (eMCAO), nerinetide maintained its effectiveness when administered before alteplase. Because of its short plasma half-life, it can be followed by alteplase within minutes without reducing its neuroprotective effectiveness. In addition, the problem of protease sensitivity is solved by substituting cleavage-prone amino acids from their l- to their d-enantiomeric form. Treatment of rats subjected to eMCAO with such an agent, termed d-Tat-l-2B9c, eliminated protease sensitivity and maintained neuroprotective effectiveness. Our data suggest that both the clinical-stage PSD-95 inhibitor nerinetide and protease-resistant agents such as d-Tat-l-2B9c may be practically integrated into existing stroke care workflows and standards of care.

Linking 7-Nitrobenzo-2-oxa-1,3-diazole (NBD) to Triphenylphosphonium Yields Mitochondria-Targeted Protonophore and Antibacterial Agent

Appending lipophilic cations to small molecules has been widely used to produce mitochondria-targeted compounds with specific activities. In this work, we obtained a series of derivatives of the well-known fluorescent dye 7-nitrobenzo-2-oxa-1,3-diazole (NBD). According to the previous data [Denisov et al. (2014) Bioelectrochemistry, 98, 30-38], alkyl derivatives of NBD can uncouple isolated mitochondria at concentration of tens of micromoles despite a high pK_a value (~11) of the dissociating group. Here, a number of triphenylphosphonium (TPP) derivatives linked to NBD via hydrocarbon spacers of varying length (C5, C8, C10, and C12) were synthesized (mitoNBD analogues), which accumulated in the mitochondria in an energy-dependent manner. NBD-C10-TPP (C10-mitoNBD) acted as a protonophore in artificial lipid membranes (liposomes) and uncoupled isolated mitochondria at micromolar concentrations, while the derivative with a shorter linker (NBD-C5-TPP, or C5-mitoNBD) exhibited no such activities. In accordance with this data, C10-mitoNBD was significantly more efficient than C5-mitoNBD in suppressing the growth of Bacillus subtilis. C10-mitoNBD and C12-mitoNBD demonstrated the highest antibacterial activity among the investigated analogues. C10-mitoNBD also exhibited the neuroprotective effect in the rat model of traumatic brain injury.

Preclinical animal studies in ischemic stroke: Challenges and some solutions

Despite the impressive efficacies demonstrated in preclinical research, hundreds of potentially neuroprotective drugs have failed to provide effective neuroprotection for ischemic stroke in human clinical trials. Lack of a powerful animal model for human ischemic stroke could be a major reason for the failure to develop successful neuroprotective drugs for ischemic stroke. This review recapitulates the available cerebral ischemia animal models, provides an anatomical comparison of the circle of Willis of each species, and describes the functional assessment tests used in these ischemic stroke models. The distinct differences between human ischemic stroke and experimental stroke in available animal models is explored. Innovative animal models more closely resembling human strokes, better techniques in functional outcome assessment and better experimental designs generating clearer and stronger evidence may help realise the development of truly neuroprotective drugs that will benefit human ischemic stroke patients. This may involve use of newer molecules or revisiting earlier studies with new experimental designs. Translation of any resultant successes may then be tested in human clinical trials with greater confidence and optimism.

Dichloromethane extraction from Piper nigrum L. and P. longum L. to mitigate ischemic stroke by activating the AKT/mTOR signaling pathway to suppress autophagy

Dichloromethane fraction (DF) of Piper nigrum L. and P. longum L. (PnL and PlL), has been found to exert a protective effect against ischemic stroke in rats. However, the regulatory mechanism exerted by PnL and PIL have not been fully elucidated. In this study, we found that DF greatly ameliorated cerebral ischemic injury in a rat model of permanent middle cerebral artery occlusion (pMCAO). The neurological score, behavioral assessment, brain infarct volume, phosphorylation of AKT (p-AKT), phosphorylation mTOR (p-mTOR), and Atg7 protein levels were determined. Additionally, we discovered that DF pretreatment reduced infarct volume, neurological score, and brain damage. Furthermore, DF therapy caused the downregulation of Atg7 and p-AKT expression, as well as the upregulation of p-mTOR expression. In conclusion, our findings indicated that DF treatment can reduce brain damage and inhibit apoptosis and autophagy by activating the Akt-mTOR signaling pathway in ischemic stroke.

Pre-clinical to Clinical Translational Failures and Current Status of Clinical Trials in Stroke Therapy: A Brief Review

In stroke (cerebral ischemia), despite continuous efforts both at the experimental and clinical level, the only approved pharmacological treatment has been restricted to tissue plasminogen activator (tPA). Stroke is the leading cause of functional disability and mortality throughout worldwide. Its pathophysiology starts with energy pump failure, followed by complex signaling cascade that ultimately ends in neuronal cell death. Ischemic cascade involves excessive glutamate release followed by raised intracellular sodium and calcium influx along with free radicals' generation, activation of inflammatory cytokines, NO synthases, lipases, endonucleases and other apoptotic pathways leading to cell edema and death. At the pre-clinical stage, several agents have been tried and proven as an effective neuroprotectant in animal models of ischemia. However, these agents failed to show convincing results in terms of efficacy and safety when the trials were conducted in humans following stroke. This article highlights the various agents which have been tried in the past but failed to translate into stroke therapy along with key points that are responsible for the lagging of experimental success to translational failure in stroke treatment.

The combination of mannitol and temozolomide increases the effectiveness of stem cell treatment in a chronic stroke model

BACKGROUND

The blood-brain barrier (BBB) presents a significant challenge to the therapeutic efficacy of stem cells in chronic stroke. Various methods have been developed to increase BBB permeability, but these are associated with adverse effects and are, therefore, not clinically applicable. We recently identified that combination drug treatment of mannitol and temozolomide improved BBB permeability in vitro. Here, we investigated whether this combination could increase the effectiveness of stem cell treatment in an animal model of chronic ischemic stroke.

METHODS

Chronic stroke was induced in rats by middle cerebral artery occlusion (MCAo). After then, rats were administered human umbilical cord-derived mesenchymal stromal cells (hUC-MSCs) by intravenous injection with or without combination drug treatment of mannitol and temozolomide. To evaluate the therapeutic efficacy, behavioral and immunohistochemical tests were performed, and the differences among control, stem cell only, combination drug only and stem cell with combination drug treatment were analyzed.

RESULTS

Although no hUC-MSCs were detected in any group, treatment with stem cells and combination drug of mannitol and temozolomide increased the intracerebral delivery of hCD63-positive microvesicles compared with stem cell only treatment. Furthermore, treatment with stem cells and drug combination ameliorated behavioral deficits and increased bromodeoxyuridine-, doublecortin- and Reca-1-positive cells in the perilesional area as compared with other groups.

DISCUSSION

The combination drug treatment of mannitol and temozolomide allowed for the efficient delivery of hUC-MSC-derived microvesicles into the brain in a chronic stroke rat model. This attenuated behavioral deficits, likely by improving neural regeneration and angiogenesis. Thus, combination drug treatment of mannitol and temozolomide could be a novel therapeutic option for patients with chronic ischemic stroke.

CPCGI confers neuroprotection by enhancing blood circulation and neurological function in cerebral ischemia/reperfusion rats

The current study used a rat middle cerebral artery occlusion (MCAO) model with the aim to explore the effects of compound porcine cerebroside and ganglioside injection (CPCGI) on brain ischemia/reperfusion injury in rats. Improvement in the infarct‑side microcirculation and the overall recovery of neurological function were detected by triphenyltetrazolium chloride staining, laser speckle blood flow monitoring, latex perfusion, immunofluorescence and immunoblotting. The results revealed that administration of CPCGI for 7 consecutive days following ischemic stroke contributed to the recovery of neurological function and the reduction of cerebral infarct volume in rats. Blood flow monitoring results demonstrated that the administration of CPCGI effectively promoted cerebral blood flow following stroke, and contributed to the protection of the ischemic side blood vessels. In addition, CPCGI treatment increased the numbers of new blood vessels in the peripheral ischemic region, and upregulated the expression levels of vascular endothelial growth factor, angiopoietin 1 and its receptor TEK receptor tyrosine kinase, fibroblast growth factor and Wnt signaling pathway‑associated proteins. Taken together, the present results indicated that CPCGI improved the blood circulation and neurological function following cerebral ischemia/reperfusion in rats.

Expression of tissue inhibitor of metalloproteinases and matrix metalloproteinases in the ischemic brain of photothrombosis model mice

Middle cerebral artery occlusion (MCAO) is the most widely used animal model of ischemic stroke. This model well recapitulates the pathological features of most human cases; however, MCAO is technically difficult to achieve in mice and has some disadvantages for investigating the molecular mechanisms of pathological progression in stroke. The recently developed photothrombosis model may be more suitable for research on the molecular mechanisms of ischemic stroke in mice. Yet, similarities and differences between the photothrombosis and MCAO models are not well characterized. In the present study, we examined the expression of tissue inhibitor of metalloproteinases (TIMPs) and matrix metalloproteinases (MMPs) in the brains of photothrombosis model mice. Our results indicated that the gene expression of TIMP-1 was upregulated in endothelial cells in the pathological area surrounding the infarction, similar to the MCAO model. Yet, pathologically induced changes in TIMP-1 were not affected by treatment with aspirin or etodolac. Whereas MMP-2 and MMP-8 mRNA were upregulated after infarction in both models, MMP-9 expression, which is induced in the infarct area in the MCAO model, was unchanged in the photothrombosis model. These findings suggest that the expression patterns of TIMP-1 and MMP-9 are regulated independently in photothrombosis model mice.

A heparan sulfate-based matrix therapy reduces brain damage and enhances functional recovery following stroke

Alteration of the extracellular matrix (ECM) is one of the major events in the pathogenesis of brain lesions following ischemic stroke. Heparan sulfate mimetics (HSm) are synthetic pharmacologically active polysaccharides that promote ECM remodeling and tissue regeneration in various types of lesions. HSm bind to growth factors, protect them from enzymatic degradation and increase their bioavailability, which promotes tissue repair. As the ECM is altered during stroke and HSm have been shown to restore the ECM, we investigated the potential of HSm4131 (also named RGTA-4131®) to protect brain tissue and promote regeneration and plasticity after a stroke. Methods: Ischemic stroke was induced in rats using transient (1 h) intraluminal middle cerebral artery occlusion (MCAo). Animals were assigned to the treatment (HSm4131; 0.1, 0.5, 1.5, or 5 mg/kg) or vehicle control (saline) groups at different times (1, 2.5 or 6 h) after MCAo. Brain damage was assessed by MRI for the acute (2 days) and chronic (14 days) phases post-occlusion. Functional deficits were evaluated with a battery of sensorimotor behavioral tests. HSm4131-^99mTc biodistribution in the ischemic brain was analyzed between 5 min and 3 h following middle cerebral artery reperfusion. Heparan sulfate distribution and cellular reactions, including angiogenesis and neurogenesis, were evaluated by immunohistochemistry, and growth factor gene expression (VEGF-A, Ang-2) was quantified by RT-PCR. Results: HSm4131, administered intravenously after stroke induction, located and remained in the ischemic hemisphere. HSm4131 conferred long-lasting neuroprotection, and significantly reduced functional deficits with no alteration of physiological parameters. It also restored the ECM, and increased brain plasticity processes, i.e., angiogenesis and neurogenesis, in the affected brain hemisphere. Conclusion: HSm represent a promising ECM-based therapeutic strategy to protect and repair the brain after a stroke and favor functional recovery.

Using the behavioral flexibility operant task to detect long-term deficits in rats following middle cerebral artery occlusion

Stroke is a leading cause of death and disability and currently only has one FDA approved pharmacological treatment (tissue plasminogen activator), which is only administered to a fraction of stroke patients due to contraindications. New treatments are desperately needed but most treatments fail in clinical trials, even after showing benefit in animal models of stroke. To increase the translatability of animal stroke research to humans, sensitive functional measures for both the acute and chronic stages in animal models of stroke are needed. The objective of this study was to determine the sensitivity of certain behavioral tasks, up to seven weeks following occlusion of the middle cerebral artery (MCAo) in rats. A battery of behavioral tasks, including rotorod, cylinder, and limb-placement, was conducted weekly for seven weeks. Also, a behavioral flexibility operant task was introduced at the end of the study to measure cognitive deficits. All functional outcome measures showed significant differences between stroke and control groups, indicating that these tasks are sensitive enough to detect deficits in a long-term MCAo study in rats. This provides useful information for those trying to increase translatability in their own stroke research by providing long-term sensitive testing paradigms in a relevant stroke model.

Indole-3-carbinol improves neurobehavioral symptoms in a cerebral ischemic stroke model

Stroke is one of the most common causes of death worldwide and also responsible for permanent disability. Ischemic stroke has been found to affect 80% of stroke patients. Recombinant tissue plasminogen activator (rtPA) is the widely used drug for the ischemic stroke with narrow therapeutic window. Indole-3-carbinol (I3C) is a natural compound obtained from brassica species having antithrombotic activity. Middle cerebral artery occlusion (MCAO) model was used followed by reperfusion after 2 h of ischemia for the evaluation of the I3C against ischemic stroke. After reperfusion, I3C (12.5, 25, and 50 mg/kg) was given by oral route once daily and continued up to the 14th day. Behavioral studies including postural reflex, forelimb placing, and cylinder tests showed I3C attenuated the MCAO-induced increase in average score and asymmetry score efficiently. Mean cerebral blood flow (CBF) was improved by treatment with I3C (12.5 mg/kg) by 60% of baseline at 6 h. I3C inhibited ADP-induced platelet aggregation and reduced ischemic volume significantly. It also inhibited in vitro the ADP-induced platelet aggregation in healthy human volunteers. I3C improves behavioral scores and mean CBF after focal cerebral ischemia in rats. Furthermore, I3C showed prophylactic anti-thrombotic activity against carrageenan induced tail thrombosis. Therefore, preclinical evidence points to I3C as a potential candidate for use in cerebral ischemic stroke.

Baihui (DU20)-penetrating-Qubin (GB7) acupuncture inhibits apoptosis in the perihemorrhagic penumbra

Baihui (DU20)-penetrating-Qubin (GB7) acupuncture can inhibit inflammatory reactions and activate signaling pathways related to proliferation after intracerebral hemorrhage. However, there is no research showing the relationship between this treatment and cell apoptosis. Rat models of intracerebral hemorrhage were established by injecting 60 μL of autologous blood into the right side of the caudate-putamen. Six hours later, the needle traveled subcutaneously from the Baihui acupoint to Qubin acupoint. The needle was alternately rotated (180 ± 10 turns/min) manually along clockwise and counter-clockwise directions. Stimulation lasted for 7 days, and was performed three times each for 6 minutes with 6-minute intervals between stimulations. Rats intraperitoneally receiving Sonic hedgehog pathway activator, purmorphamine (1 mg/kg per day), served as positive controls. Motor and sensory function were assessed using the Ludmila Belayev test. Extent of pathological changes were measured in the perihemorrhagic penumbra using hematoxylin-eosin staining. Apoptosis was examined by terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end labeling assay. Expression of smoothened (Smo) and glioma-associated homolog 1 (Gli1) was determined by western blot assay. Our results showed that Baihui-penetrating-Qubin acupuncture promoted recovery of motor and sensory function, reduced the apoptotic cell percentage in the perihemorrhagic penumbra, and up-regulated Smo and Gli1 expression. We conclude that Baihui-penetrating-Qubin acupuncture can mitigate hemorrhage and promote functional recovery of the brain in a rat model of intracerebral hemorrhage, possibly by activating the Sonic hedgehog pathway.

Inhibition of the potassium channel Kv1.3 reduces infarction and inflammation in ischemic stroke

Objective

Inhibitors of the voltage‐gated K⁺ channel Kv1.3 are currently in development as immunomodulators for the treatment of autoimmune diseases. As Kv1.3 is also expressed on microglia and has been shown to be specifically up‐regulated on “M1‐like” microglia, we here tested the therapeutic hypothesis that the brain‐penetrant small‐molecule Kv1.3‐inhibitor PAP‐1 reduces secondary inflammatory damage after ischemia/reperfusion.

Methods

We studied microglial Kv1.3 expression using electrophysiology and immunohistochemistry, and evaluated PAP‐1 in hypoxia‐exposed organotypic hippocampal slices and in middle cerebral artery occlusion (MCAO) with 8 days of reperfusion in both adult male C57BL/6J mice (60 min MCAO) and adult male Wistar rats (90 min MCAO). In both models, PAP‐1 administration was started 12 h after reperfusion.

Results

We observed Kv1.3 staining on activated microglia in ischemic infarcts in mice, rats, and humans and found higher Kv1.3 current densities in acutely isolated microglia from the infarcted hemisphere than in microglia isolated from the contralateral hemisphere of MCAO mice. PAP‐1 reduced microglia activation and increased neuronal survival in hypoxia‐exposed hippocampal slices as effectively as minocycline. In mouse MCAO, PAP‐1 dose‐dependently reduced infarct area, improved neurological deficit score, and reduced brain levels of IL‐1β and IFN‐γ without affecting IL‐10 and brain‐derived nerve growth factor (BDNF) levels or inhibiting ongoing phagocytosis. The beneficial effects on infarct area and neurological deficit score were reproduced in rats providing confirmation in a second species.

Interpretation

Our findings suggest that Kv1.3 constitutes a promising therapeutic target for preferentially inhibiting “M1‐like” inflammatory microglia/macrophage functions in ischemic stroke.

Neuroprotective effect of neuroserpin in non-tPA-induced intracerebral hemorrhage mouse models

BACKGROUND

The neuroprotective effects of neuroserpin (NSP) have been well documented in both patients and animal models with cerebral ischemia; however, have never been investigated in hemorrhagic stroke. The aim of this study is to verify the neuroprotection of NSP in the non-tPA-induced intracerebral hemorrhage (ICH) mouse model.

METHODS

C57BL/6J male mice (n = 198) were involved in this study. ICH models were established with infusion of autologous blood into the brain parenchyma. We then detected NSP expression in ICH brains by morphological methods and western blotting analysis. We measured the brain water content and detected blood-brain barrier (BBB) permeability to verify the neuroprotective effects of NSP.

RESULTS

We found that NSP protein expression was upregulated in ICH models, with a peak at 48 h after ICH induction. NSP local administration reduced the brain edema and the BBB permeability in ICH models. The neurological deficits were also ameliorated. Thus, the neuroprotection of NSP in ICH state was confirmed. Additionally, we also found that the distribution pattern of occludin-expressing cells was obviously changed by the ICH procedure but partly recovered after NSP administration. This finding indicated that protecting and/or repairing the injured vascular endothelial cells may be a potential mechanism involved in NSP neuroprotection, which needs further verification.

CONCLUSIONS

Our results supported the fact that NSP may be considered as a potential therapy for ICH for the neuroprotective effects including amelioration of the edema.

Mild therapeutic hypothermia protects against cerebral ischemia/reperfusion injury by inhibiting miR-15b expression in rats

OBJECTIVE

Mild hypothermia has a protective effect on ischemic stroke, but the mechanisms remain elusive. Here, we investigated microRNA (miRNA) profiles and the specific role of miRNAs in ischemic stroke treated with mild hypothermia.

MATERIALS AND METHODS

Male adult Sprague Dawley rats were subjected to focal transient cerebral ischemia. Mild hypothermia was induced by applying ice packs around the neck and head of the animals. miRNAs expression profiles were detected in ischemic stroke treated with mild therapeutic hypothermia through miRNA chips. Reverse transcription-polymerase chain reaction (RT-PCR) was used to verify the change of miRNA array. Western blot and adenosine triphosphate (ATP) assay kits were used to detect the changes of protein expression and ATP levels, respectively. miR-15b mimic and its control were injected into the right lateral ventricle 60 min before the induction of ischemia.

RESULTS

The results showed that mild hypothermia affected miRNAs profiles expression. We verified the expression of miR-15b and miR-598-3p by miRNA RT-PCR. miR-15b mimic inhibited the expression of its target, ADP ribosylation factor-like 2 (Arl2) protein, and decreased ATP levels in PC12 cells. Compared with the control, miR-15b mimic increased the infarct volume and aggravated the neurological function under normothermia or hypothermia treatment. Furthermore, the expression of Arl2 was decreased in the miR-15b mimic group under normothermia or hypothermia treatment.

CONCLUSIONS

Mild therapeutic hypothermia affected miRNA profiles and protected against cerebral ischemia/reperfusion by inhibiting miR-15b expression in rats. miR-15b may be a potential target for therapeutic intervention in stroke.

The prolyl 4-hydroxylase inhibitor GSK360A decreases post-stroke brain injury and sensory, motor, and cognitive behavioral deficits

There is interest in pharmacologic preconditioning for end-organ protection by targeting the HIF system. This can be accomplished by inhibition of prolyl 4-hydroxylase (PHD). GSK360A is an orally active PHD inhibitor that has been previously shown to protect the failing heart. We hypothesized that PHD inhibition can also protect the brain from injuries and resulting behavioral deficits that can occur as a result of surgery. Thus, our goal was to investigate the effect of pre-stroke surgery brain protection using a verified GSK360A PHD inhibition paradigm on post-stroke surgery outcomes. Vehicle or an established protective dose (30 mg/kg, p.o.) of GSK360A was administered to male Sprague-Dawley rats. Initially, GSK360A pharmacokinetics and organ distribution were determined, and then PHD-HIF pharmacodynamic markers were measured (i.e., to validate the pharmacological effects of the GSK360A administration regimen). Results obtained using this validated PHD dose-regimen indicated significant improvement by GSK360A (30mg/kg); administered at 18 and 5 hours prior to transient middle cerebral artery occlusion (stroke). GSK360A exposure and plasma, kidney and brain HIF-PHD pharmacodynamics endpoints (e.g., erythropoietin; EPO and Vascular Endothelial Growth Factor; VEGF) were measured. GSK360A provided rapid exposure in plasma (7734 ng/ml), kidney (45–52% of plasma level) and brain (1–4% of plasma level), and increased kidney EPO mRNA (80-fold) and brain VEGF mRNA (2-fold). We also observed that GSK360A increased plasma EPO (300-fold) and VEGF (2-fold). Further assessments indicated that GSK360A reduced post-stroke surgery neurological deficits (47–64%), cognitive dysfunction (60–75%) and brain infarction (30%) 4 weeks later. Thus, PHD inhibition using GSK360A pretreatment produced long-term post-stroke brain protection and improved behavioral functioning. These data support PHD inhibition, specifically by GSK360A, as a potential strategy for pre-surgical use to reduce brain injury and functional decline due to surgery-related cerebral injury.

The Influence of Proinflammatory Factors on the Neuroprotective Efficiency of Multipotent Mesenchymal Stromal Cells in Traumatic Brain Injury

We studied the neuroprotective potential of multipotent mesenchymal stromal cells in traumatic brain injury and the effect of inflammatory preconditioning on neuroprotective properties of stem cells under in vitro conditions. To this end, the effects of cell incubation with LPS or their co-culturing with leukocytes on production of cytokines IL-1α, IL-6, TNFα, and MMP-2 and MMP-9 by these cells were evaluated. Culturing under conditions simulating inflammation increased the production of all these factors by multipotent mesenchymal stromal cells. However, acquisition of the inflammatory phenotype by stromal cells did not reduce their therapeutic effectiveness in traumatic brain injury. Moreover, in some variants of inflammatory preconditioning, multipotent mesenchymal stromal cells exhibited more pronounced neuroprotective properties reducing the volume of brain lesion and promoting recovery of neurological functions after traumatic brain injury.

Combining Injectable Plasma Scaffold with Mesenchymal Stem/Stromal Cells for Repairing Infarct Cavity after Ischemic Stroke

Stroke survivors are typically left with structural brain damage and associated functional impairment in the chronic phase of injury, for which few therapeutic options exist. We reported previously that transplantation of human embryonic stem cell (hESC)-derived neural stem cells together with Matrigel scaffolding into the brains of rats after focal ischemia reduced infarct volume and improved neurobehavioral performance. Matrigel is a gelatinous protein mixture extracted from mouse sarcoma cells, thus would not be approved for use as a scaffold clinically. In this study, we generated a gel-like scaffold from plasma that was controlled by changing the concentration of CaCl₂. In vitro study confirmed that 10-20 mM CaCl₂ and 10-40% plasma did not affect the viability and proliferation of human and rat bone marrow mesenchymal stem/stromal cells (BMSCs) and neural stem cells (NSCs). We transplanted plasma scaffold in combination of BMSCs into the cystic cavity after focal cerebral ischemia, and found that the atrophy volume was dramatically reduced and motor function was significantly improved in the group transplanted with scaffold/BMSCs compared with the groups treated with vehicle, scaffold or BMSCs only. Our data suggest that plasma-derived scaffold in combination of BMSCs is feasible for tissue engineering approach for the stroke treatment.

Alternative activation-skewed microglia/macrophages promote hematoma resolution in experimental intracerebral hemorrhage

Microglia/macrophages (MMΦ) are highly plastic phagocytes that can promote both injury and repair in diseased brain through the distinct function of classically activated and alternatively activated subsets. The role of MMΦ polarization in intracerebral hemorrhage (ICH) is unknown. Herein, we comprehensively characterized MMΦ dynamics after ICH in mice and evaluated the relevance of MMΦ polarity to hematoma resolution. MMΦ accumulated within the hematoma territory until at least 14days after ICH induction. Microglia rapidly reacted to the hemorrhagic insult as early as 1-1.5h after ICH and specifically presented a "protective" alternatively activated phenotype. Substantial numbers of activated microglia and newly recruited monocytes also assumed an early alternatively activated phenotype, but the phenotype gradually shifted to a mixed spectrum over time. Ultimately, markers of MMΦ classic activation dominated at the chronic stage of ICH. We enhanced MMΦ alternative activation by administering intraperitoneal injections of rosiglitazone, and subsequently observed elevations in CD206 expression on brain-isolated CD11b⁺ cells and increases in IL-10 levels in serum and perihematomal tissue. Enhancement of MMΦ alternative activation correlated with hematoma volume reduction and improvement in neurologic deficits. Intraventricular injection of alternative activation signature cytokine IL-10 accelerated hematoma resolution, whereas microglial phagocytic ability was abolished by IL-10 receptor neutralization. Our results suggest that MMΦ respond dynamically to brain hemorrhage by exhibiting diverse phenotypic changes at different stages of ICH. Alternative activation-skewed MMΦ aid in hematoma resolution, and IL-10 signaling might contribute to regulation of MMΦ phagocytosis and hematoma clearance in ICH.

Effect of Single and Double Administration of Human Umbilical Cord Blood-Derived Mesenchymal Stem Cells Following Focal Cerebral Ischemia in Rats

Stem cell therapies are administered during the acute phase of stroke to preserve the penumbral tissues from ischemic injury. However, the effect of repeated cell therapy during the acute phase remains unclear. In this study, we investigated and compared the functional outcome of single (two days post-injury) and repeated (two and nine days post-injury) treatment with human umbilical cord derived mesenchymal stem cells (hUCB-MSCs) after middle cerebral artery occlusion (MCAO). The rotarod and limb placement tests were utilized to investigate functional outcomes, while infarct volume and tissue damage were measured by immunofluorescent staining for neovascularization, neurogenesis, apoptosis, and inflammation in the penumbral zones. We observed notable motor dysfunction and a significant decrease in infarcted brain volume, as well as increases in neurons and vessels in both single and repeated hUCB-MSC treatments compared to the control group. Interestingly, repeated administration of hUCB-MSCs was not found to elicit additional or synergistic improvements over monotherapy. This study suggests that a clearer understanding of the therapeutic window after stroke will facilitate the development of more efficient treatment protocols in the clinical application of stem cell therapy.

The potassium channel KCa3.1 constitutes a pharmacological target for neuroinflammation associated with ischemia/reperfusion stroke

Activated microglia/macrophages significantly contribute to the secondary inflammatory damage in ischemic stroke. Cultured neonatal microglia express the K⁺ channels Kv1.3 and KCa3.1, both of which have been reported to be involved in microglia-mediated neuronal killing, oxidative burst and cytokine production. However, it is questionable whether neonatal cultures accurately reflect the K⁺ channel expression of activated microglia in the adult brain. We here subjected mice to middle cerebral artery occlusion with eight days of reperfusion and patch-clamped acutely isolated microglia/macrophages. Microglia from the infarcted area exhibited higher densities of K⁺ currents with the biophysical and pharmacological properties of Kv1.3, KCa3.1 and Kir2.1 than microglia from non-infarcted control brains. Similarly, immunohistochemistry on human infarcts showed strong Kv1.3 and KCa3.1 immunoreactivity on activated microglia/macrophages. We next investigated the effect of genetic deletion and pharmacological blockade of KCa3.1 in reversible middle cerebral artery occlusion. KCa3.1^-/- mice and wild-type mice treated with the KCa3.1 blocker TRAM-34 exhibited significantly smaller infarct areas on day-8 after middle cerebral artery occlusion and improved neurological deficit. Both manipulations reduced microglia/macrophage activation and brain cytokine levels. Our findings suggest KCa3.1 as a pharmacological target for ischemic stroke. Of potential, clinical relevance is that KCa3.1 blockade is still effective when initiated 12 h after the insult.

Neuroprotective properties of mitochondria-targeted antioxidants of the SkQ-type

In 2008, using a model of compression brain ischemia, we presented the first evidence that mitochondria-targeted antioxidants of the SkQ family, i.e. SkQR1 [10-(6′-plastoquinonyl)decylrhodamine], have a neuroprotective action. It was shown that intraperitoneal injections of SkQR1 (0.5–1 μmol/kg) 1 day before ischemia significantly decreased the damaged brain area. Later, we studied in more detail the anti-ischemic action of this antioxidant in a model of experimental focal ischemia provoked by unilateral intravascular occlusion of the middle cerebral artery. The neuroprotective action of SkQ family compounds (SkQR1, SkQ1, SkQTR1, SkQT1) was manifested through the decrease in trauma-induced neurological deficit in animals and prevention of amyloid-β-induced impairment of long-term potentiation in rat hippocampal slices. At present, most neurophysiologists suppose that long-term potentiation underlies cellular mechanisms of memory and learning. They consider inhibition of this process by amyloid-β1-42as anin vitromodel of memory disturbance in Alzheimer’s disease. Further development of the above studies revealed that mitochondria-targeted antioxidants could retard accumulation of hyperphosphorylated τ-protein, as well as amyloid-β1-42, and its precursor APP in the brain, which are involved in developing neurodegenerative processes in Alzheimer’s disease.

Mimetics of brain-derived neurotrophic factor loops 1 and 4 are active in a model of ischemic stroke in rats

BACKGROUND

Two dimeric dipeptides, bis-(N-monosuccinyl-l-seryl-l-lysine)hexamethylenediamide (GSB-106) and bis-(N-monosuccinyl-l-methionyl-l-serine) heptamethylenediamide (GSB-214), were designed based on the brain-derived neurotrophic factor (BDNF) loop 4 and loop 1 β-turn sequences, respectively. Earlier, both of these dipeptides were shown to exhibit neuroprotective activity in vitro (10-5-10-8 M). The present study aimed to investigate the mechanisms of action of these peptides and their neuroprotective activity in an experimental stroke model.

METHODS

We used western blot and HT-22 hippocampal neuronal cell line to investigate whether these peptides induced phosphorylation of the TrkB receptor and the AKT and ERK kinases. Rat middle cerebral artery occlusion (MCAO) was used as a stroke model. GSB-106 and GSB-214 were administered intraperitoneally (0.1 mg (1.3×10-7 mol)/kg) 4 hours after MCAO and daily for 7 days. The cerebral infarct volumes were measured with 2,3,5-triphenyltetrazolium chloride staining 21 days after MCAO.

RESULTS

Both compounds were shown to elevate the TrkB phosphorylation level while having different post-receptor signaling patterns. GSB-106 activated the PI3K/AKT and MAPK/ERK pathways simultaneously, whereas GSB-214 activated the PI3K/AKT only. In experimental stroke, the reduction of cerebral infarct volume by GSB-106 (∼66%) was significantly greater than that of GSB-214 (∼28% reduction), which could be explained by the fundamental role of the MAPK/ERK pathway in neurogenesis and neuroplasticity. Notably, between these two dipeptides, only GSB-106 exhibited antidepressant activity, as was found previously.

CONCLUSION

The results provided support for the beneficial pharmacological properties of BDNF loop 4 mimetic GSB-106, thereby suggesting a potential role for this dipeptide as a therapeutic agent.

Neuroprotective effects of Danggui-Jakyak-San on rat stroke model through antioxidant/antiapoptotic pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Dangui-Jakyak-San (DJ) is a traditional Korean medicinal polyherb, prescribed typically in patients with insufficient blood supply in Eastern Asia. The DJ also has been reported to have neuroprotective effects in vitro and in vivo studies.

AIM OF STUDY

The therapeutic potential of DJ was examined in stroke rat model, in comparison with donepezil, a reversible acetylcholinesterase inhibitor.

MATERIALS AND METHODS

Ischemic stroke rat model was induced by surgery of permanent occlusion of middle cerebral artery (pMCAO). The model was orally administered with distilled water (pMCAO control), donepezil at 10mg/kg (Donepezil) and DJ at 200, 100 and 50mg/kg (DJ 200, DJ 100 and DJ 50, respectively). Sham had the same surgery excepting for the pMCAO, and it was administered with distilled water (sham control).

RESULTS

After the administration for 28 days, the groups of DJ exhibited dose-dependent reduction in infarct/defect volumes with improvement in sensorimotor and cognitive motor function, comparing to pMCAO control. The DJ treatments seemed to enhance antiapoptotic and antioxidant effects; increases in antiapoptotic expressions (STAT3 and Pim-1) and decreases in lipid peroxidation (MDA) together with increases in contents of endogenous antioxidant (GSH) and activities of antioxidant enzymes (catalase and SOD). The histopathological analyses revealed significant reduction in neuronal apoptosis (caspase-3 and PARP) and neuronal degradation with atrophy and degeneration, in the DJ treatments. Furthermore, the oxidative stresses (nitrotyrosine as an iNOS factor and 4-HNE as a marker of lipid peroxidation) were observed mild. Although the similar neuroprotective effects were observed, the body weight loss was scarcely alleviated in Donepezil comparing to pMCAO control.

CONCLUSION

These suggest that DJ ameliorate the neurological dysfunction of cerebral ischemia through augmentation of antioxidant defense system and up-regulation of STAT3 and Pim-1.

Translational Hurdles in Stroke Recovery Studies

Emerging understanding of brain plasticity has opened new avenues for the treatment of stroke. The promising preclinical evidence with neuroprotective drugs has not been confirmed in clinical trials, thus nowadays, researchers, pharmaceutical companies, and funding bodies hesitate to initiate these expensive trials with restorative therapies. Since many of the previous failures can be traced to low study quality, a number of guidelines such as STAIR and STEPS were introduced to rectify these shortcomings. However, these guidelines stem from the study design for neuroprotective drugs and one may question whether they are appropriate for restorative approaches, which rely heavily on behavioral testing. Most of the recovery studies conducted in stroke patients have been small-scale, proof-of-concept trials. Consequently, the overall effect sizes of pooled phase II trials have proved unreliable and unstable in most meta-analyses. Although the methodological quality of trials in humans is improving, most studies still suffer from methodological flaws and do not meet even the minimum of evidence-based standards for reporting randomized controlled trials. The power problem of most phase II trials is mostly attributable to a lack of proper stratification with robust prognostic factors at baseline as well as the incorrect assumption that all patients will exhibit the same proportional amount of spontaneous neurological recovery poststroke. In addition, most trials suffer from insufficient treatment contrasts between the experimental and control arm and the outcomes have not been sufficiently responsive to detect small but clinically relevant changes in neurological impairments and activities. This narrative review describes the main factors that bias recovery studies, both in experimental animals and stroke patients.

In Situ Microparticles Loaded with S-Nitrosoglutathione Protect from Stroke

Treatment of stroke, especially during the first hours or days, is still lacking. S-nitrosoglutathione (GSNO), a cerebroprotective agent with short life time, may help if administered early with a sustain delivery while avoiding intensive reduction in blood pressure. We developed in situ forming implants (biocompatible biodegradable copolymer) and microparticles (same polymer and solvent emulsified with an external oily phase) of GSNO to lengthen its effects and allow cerebroprotection after a single subcutaneous administration to Wistar rats. Arterial pressure was recorded for 3 days (telemetry, n = 14), whole-blood platelet aggregation up to 13 days (aggregometry, n = 58), and neurological score, cerebral infarct size and edema volume for 2 days after obstruction of the middle cerebral artery by autologous blood clots (n = 30). GSNO-loaded formulations (30 mg/kg) induced a slighter and longer hypotension (-10 vs. -56 ± 6 mmHg mean arterial pressure, 18 h vs. 40 min) than free GSNO at the same dose. The change in pulse pressure (-50%) lasted even up to 42 h for microparticles. GSNO-loaded formulations (30 mg/kg) prevented the transient 24 h hyper-aggregability observed with free GSNO and 7.5 mg/kg-loaded formulations. When injected 2 h after stroke, GSNO-loaded microparticles (30 mg/kg) reduced neurological score at 24 (-62%) and 48 h (-75%) vs. empty microparticles and free GSNO 7.5 mg/kg and, compared to free GSNO, divided infarct size by 10 and edema volume by 8 at 48 h. Corresponding implants reduced infarct size and edema volume by 2.5 to 3 times. The longer (at least 2 days) but slight effects on arterial pressures show sustained delivery of GSNO-loaded formulations (30 mg/kg), which prevent transient platelet hyper-responsiveness and afford cerebroprotection against the consequences of stroke. In conclusion, in situ GSNO-loaded formulations are promising candidates for the treatment of stroke.

Neuroprotective Effect of Xueshuantong for Injection (Lyophilized) in Transient and Permanent Rat Cerebral Ischemia Model

Xueshuantong for Injection (Lyophilized) (XST), a Chinese Materia Medica standardized product extracted from Panax notoginseng (Burk.), is used extensively for the treatment of cerebrovascular diseases such as acutely cerebral infarction clinically in China. In the present study, we evaluated the acute and extended protective effects of XST in different rat cerebral ischemic model and explored its effect on peroxiredoxin (Prx) 6-toll-like receptor (TLR) 4 signaling pathway. We found that XST treatment for 3 days could significantly inhibit transient middle cerebral artery occlusion (MCAO) induced infarct volume and swelling percent and regulate the mRNA expression of interleukin-1β (IL-1β), IL-17, IL-23p19, tumor necrosis factor-α (TNFα), and inducible nitric oxide synthase (iNOS) in brain. Further study demonstrated that treatment with XST suppressed the protein expression of peroxiredoxin (Prx) 6-toll-like receptor (TLR) 4 and phosphorylation level of p38 and upregulated the phosphorylation level of STAT3. In permanent MCAO rats, XST could reduce the infarct volume and swelling percent. Moreover, our results revealed that XST treatment could increase the rats' weight and improve a batch of functional outcomes. In conclusion, the present data suggested that XST could protect against ischemia injury in transient and permanent MCAO rats, which might be related to Prx6-TLR4 pathway.

The Effect of Donor-Dependent Administration of Human Umbilical Cord Blood-Derived Mesenchymal Stem Cells following Focal Cerebral Ischemia in Rats

Stroke is an ischemic disease caused by clotted vessel-induced cell damage. It is characterized by high morbidity and mortality and is typically treated with a tissue plasminogen activator (tPA). However, this therapy is limited by temporal constraints. Recently, several studies have focused on cell therapy as an alternative treatment. Most researches have used fixed donor cell administration, and hence, the effect of donor-dependent cell administration is unknown. In this study, we administered 3 types of donor-derived human umbilical cord blood mesenchymal stem cells (hUCB-MSCs) in the ischemic boundary zone of the ischemic stroke rat model. We then performed functional and pathological characterization using rotarod, the limb placement test, and immunofluorescent staining. We observed a significant decrease in neuron number, and notable stroke-like motor dysfunction, as assessed by the rotarod test (~40% decrease in time) and the limb placement test (4.5 point increase) in control rats with ischemic stroke. The neurobehavioral performance of the rats with ischemic stroke that were treated with hUCB-MSCs was significantly better than that of rats in the vehicle-injected control group. Regardless of which donor cells were used, hUCB-MSC transplantation resulted in an accumulation of neuronal progenitor cells, and angiogenic and tissue repair factors in the ischemic boundary zone. The neurogenic and angiogenic profiles of the 3 types of hUCB-MSCs were very similar. Our results suggest that intraparenchymal administration of hUCB-MSCs results in significant therapeutic effects in the ischemic brain regardless of the type of donor.

Neuronal cell reconstruction with umbilical cord blood cells in the brain hypoxia-ischemia

Background: Brain hypoxia-ischemia is a human neonatal injury that is considered a candidate for stem cell therapy. Methods: The possible therapeutic potential of human umbilical cord blood (HUCB) stem cells was evaluated in 14-day-old rats subjected to the right common carotid occlusion, a model of neonatal brain hypoxia-ischemia. Seven days after hypoxia-ischemia, rats received either saline solution or 4 × 10⁵ HUCB cells i.v. Rats in control group did not receive any injection. After two weeks, rats were assessed using two motor tests. Subsequently, rats were scarified for histological and immunohistochemical analyses. Results: Our immunohistochemical findings demonstrated selective migration of the injected HUCB cells to the ischemic area as well as reduction in infarct volume. Seven days after surgery, we found significant recovery in the behavioral performance in the test group (12.7 +/- 0.3) compared to the sham group (10.0 +/-0.05), a trend which continued to day 14 (15.3 ± 0.3 vs. 11.9 ± 0.5, P<0.05). Postural and motor asymmetries at days 7 and 14 in the test group showed a significant decrease in the percentage of right turns in comparison to the sham group (75% and 59% vs. 97% and 96%, P<0.05). Conclusion: The results show the potential of HUCB stem cells in reduction of neurologic deficits associated with neonatal hypoxia-ischemia.

Pre-differentiation of human neural stem cells into GABAergic neurons prior to transplant results in greater repopulation of the damaged brain and accelerates functional recovery after transient ischemic stroke

INTRODUCTION

Despite attempts to prevent brain injury during the hyperacute phase of stroke, most sufferers end up with significant neuronal loss and functional deficits. The use of cell-based therapies to recover the injured brain offers new hope. In the current study, we employed human neural stem cells (hNSCs) isolated from subventricular zone (SVZ), and directed their differentiation into GABAergic neurons followed by transplantation to ischemic brain.

METHODS

Pre-differentiated GABAergic neurons, undifferentiated SVZ-hNSCs or media alone were stereotaxically transplanted into the rat brain (n=7/group) 7 days after endothelin-1 induced stroke. Neurological outcome was assessed by neurological deficit scores and the cylinder test. Transplanted cell survival, cellular phenotype and maturation were assessed using immunohistochemistry and confocal microscopy.

RESULTS

Behavioral assessments revealed accelerated improvements in motor function 7 days post-transplant in rats treated with pre-differentiated GABAergic cells in comparison to media alone and undifferentiated hNSC treated groups. Histopathology 28 days-post transplant indicated that pre-differentiated cells maintained their GABAergic neuronal phenotype, showed evidence of synaptogenesis and up-regulated expression of both GABA and calcium signaling proteins associated with neurotransmission. Rats treated with pre-differentiated cells also showed increased neurogenic activity within the SVZ at 28 days, suggesting an additional trophic role of these GABAergic cells. In contrast, undifferentiated SVZ-hNSCs predominantly differentiated into GFAP-positive astrocytes and appeared to be incorporated into the glial scar.

CONCLUSION

Our study is the first to show enhanced exogenous repopulation of a neuronal phenotype after stroke using techniques aimed at GABAergic cell induction prior to delivery that resulted in accelerated and improved functional recovery.