Isoflurane enhanced hemorrhagic transformation by impairing antioxidant enzymes in hyperglycemic rats with middle cerebral artery occlusion

Halcinonide activates smoothened to ameliorate ischemic stroke injury

OBJECTIVES

The Shh pathway may shed new light on developing new cell death inhibitors for the therapy of ischemic stroke. We aimed to examine whether the Shh co-reporter SMO or its agonist halcinonide can upregulate Bcl-2 to suppress neuronal cell death, ultimately improving behavioral deficits and reducing cerebral infarction in an ischemic stroke model.

METHODS

Halcinonide or genetic manipulation of SMO was conducted in PC12 cells to examine their impacts on oxidative or OGD/R stress, and the chemical, along with AAV-SMO or AAV-EGFP were tested in MCAO rats to investigate their potential protective effects against neuronal damages due to cerebral I/R injury. The amounts or activities of L-LA, LDH, ROS, MDA, SOD, MPO, GSSG, and GSH were detected using the corresponding biochemical kits. The levels of TNF-α and IL-6 were analyzed by ELISA.

RESULTS

The results show that halcinonide alleviated neurological score and cerebral infarction, and the abnormal changes in L-LA, LDH, MDA, SOD, MPO, GSH, GSSG, TNF-α, and IL-6 were also reversed in MCAO rats. Through expression or knockout of SMO, we discovered that SMO worked similarly to halcinonide, protecting neuronal cells from oxidative or OGD/R stress, and AAV-SMO prevented cerebral damages of MCAO rats caused by ischemia and reperfusion. Halcinonide inhibited Bcl-2/Bax-mediated apoptosis, at least partially by promoting the Shh signaling pathway through enhancing SMO expression in vivo and in vitro.

CONCLUSION

This study identified a new target and a candidate chemical for therapy of ischemic stroke, hopefully reducing its morbidity and mortality.

Hepatocyte growth factor-modified hair follicle stem cells ameliorate cerebral ischemia/reperfusion injury in rats

BACKGROUND

Hair follicle stem cells (HFSCs) are considered as a promising cell type in the stem cell transplantation treatment of neurological diseases because of their rich sources, easy access, and the same ectoderm source as the nervous system. Hepatocyte growth factor (HGF) is a pleiotropic cytokine that shows neuroprotective function in ischemic stroke. Here we assessed the therapeutic effects of HFSCs on ischemic stroke injury and the synthetic effect of HGF along with HFSCs.

METHODS

Rat HFSCs were intravenously transplanted into a middle cerebral artery ischemia/reperfusion (I/R) rat model. Neurological scoring and TTC staining were performed to assess the benefits of HFSC transplantation. Inflammatory cytokines, blood-brain barrier integrity and angiogenesis within penumbra were estimated by Western blot and immunohistochemistry. The differentiation of HFSCs was detected by immunofluorescence method 2 weeks after transplantation.

RESULTS

HFSC transplantation could significantly inhibit the activation of microglia, improve the integrity of blood-brain barrier and reduce brain edema. Moreover, the number of surviving neurons and microvessels density in the penumbra were upregulated by HFSC transplantation, leading to better neurological score. The combination of HFSCs and HGF could significantly improve the therapeutic benefit.

CONCLUSION

Our results indicate for the first time that HGF modified HFSCs can reduce I/R injury and promote the neurological recovery by inhibiting inflammatory response, protecting blood-brain barrier and promoting angiogenesis.

Inhibition of BRD4 decreases fibrous scarring after ischemic stroke in rats by inhibiting the phosphorylation of Smad2/3

AIMS

Fibrous scarring may play a much more important role in preventing secondary expansion of tissue damage and hindering repair and regeneration than glial scarring after central nervous system (CNS) injury. However, relatively little is known about how fibrous scars form and how fibrous scar formation is regulated after CNS injury. Bromodomain-containing protein 4 (BRD4) is involved in fibrosis in many tissues, and transforming growth factor-β1 (TGF-β1)/Smad2/3 signaling is one of the critical pathways of fibrosis. However, it is unclear whether and how BRD4 affects fibrous scar formation after ischemicbraininjury. In the present study, whether BRD4 can regulate the formation of fibrous scars after ischemic stroke via TGF-β1/Smad2/3 signaling was assessed.

MATERIALS AND METHODS

Primary meningeal fibroblasts isolated from neonatal SD rats were treated with TGF-β1, SB431542 (a TGF-β1 receptor inhibitor) and JQ1 (a small-molecule BET inhibitor that can also inhibit BRD4). BRD4 was knocked down in adult Sprague-Dawley (SD) rats by using adenovirus before middle cerebral artery occlusion/reperfusion (MCAO/R) injury. The proliferation and migration of meningeal fibroblasts in vitro were evaluated with the Cell Counting Kit-8 (CCK-8) assay and scratch test, respectively. Neurological function was assessed with Longa scores, modified Bederson Scores and modified neurological severity scores (mNSSs). The infarct volume was assessed with TTC staining. The protein expression of synaptophysin (SY), BRD4, Smad2/3, p-Smad2/3, α-smooth muscle actin (α-SMA), collagen-1 (COL1) and fibronectin (FN) in vivo and in vitro was examined with immunocytochemistry, immunofluorescence, and Western blotting.

KEY FINDINGS

BRD4 expression was upregulated in a TGF-β1-induced meningeal fibroblast fibrosis model and was downregulated by the TGF-β1 receptor inhibitor SB431542 in vitro. JQ1, a small-molecule BET inhibitor, inhibited BRD4 and decreased TGF-β1-induced meningeal fibroblast proliferation, migration and activation. Furthermore, MCAO/R injury induced fibrosis and upregulated BRD4 expression in the cerebral infarct center. BRD4 knockdown by adenovirus inhibited fibrous scarring, promoted synaptic survival, decreased the infarct volume, and improved neurological function after MCAO/R injury. Moreover, inhibition of BRD4, either by JQ1 in vitro or adenovirus in vivo, decreased the phosphorylation of Smad2/3.

CONCLUSIONS

This study is the first to indicate that inhibition of BRD4 delays fibrous scarring after ischemic stroke through mechanisms involving the phosphorylation of Smad2/3.

TGR5 activation attenuates neuroinflammation via Pellino3 inhibition of caspase-8/NLRP3 after middle cerebral artery occlusion in rats

BACKGROUND

Nucleotide-binding oligomerization domain-like receptor pyrin domain-containing protein 3 (NLRP3) plays an important role in mediating inflammatory responses during ischemic stroke. Bile acid receptor Takeda-G-protein-receptor-5 (TGR5) has been identified as an important component in regulating brain inflammatory responses. In this study, we investigated the mechanism of TGR5 in alleviating neuroinflammation after middle cerebral artery occlusion (MCAO).

METHODS

Sprague-Dawley rats were subjected to MCAO and TGR5 agonist INT777 was administered intranasally 1 h after MCAO. Small interfering RNAs (siRNA) targeting TGR5 and Pellino3 were administered through intracerebroventricular injection 48 h before MCAO. Infarct volumes and neurologic scores were evaluated, and ELISA, flow cytometry, immunofluorescence staining, immunoblotting, and co-immunoprecipitation were used for the evaluations.

RESULTS

Endogenous TGR5 and Pellino3 levels increased after MCAO. TGR5 activation by INT777 significantly decreased pro-inflammatory cytokine, cleaved caspase-8, and NLRP3 levels, thereby reducing brain infarctions; both short- and long-term neurobehavioral assessments showed improvements. Ischemic damage induced the interaction of TGR5 with Pellino3. Knockdown of either TGR5 or Pellino3 increased the accumulation of cleaved caspase-8 and NLRP3, aggravated cerebral impairments, and abolished the anti-inflammatory effects of INT777 after MCAO.

CONCLUSIONS

TGR5 activation attenuated brain injury by inhibiting neuroinflammation after MCAO, which could be mediated by Pellino3 inhibition of caspase-8/NLRP3.

Agomelatine Attenuates Isoflurane-Induced Inflammation and Damage in Brain Endothelial Cells

Background and Purpose

Neurotoxicity of anesthetics has been widely observed by clinicians. It is reported that inflammation and oxidative stress are involved in the pathological process. In the present study, we aimed to assess the therapeutic effects of agomelatine against isoflurane-induced inflammation and damage to brain endothelial cells.

Materials and Methods

MTT assay was used to detect cell viability in order to determine the optimized concentration of agomelatine. The bEnd.3 brain endothelial cells were treated with 2% isoflurane in the presence or absence of agomelatine (5, 10 μM) for 24 h. LDH release was evaluated and the ROS levels were checked using DHE staining assay. The expressions of IL-6, IL-8, TNF-α, VEGF, TF, VCAM-1, and ICAM-1 were evaluated using real-time PCR and ELISA. Real-time PCR and Western blot analysis were used to determine the expression level of Egr-1.

Results

The decreased cell viability promoted LDH release and elevated ROS levels induced by isoflurane were significantly reversed by the introduction of agomelatine in a dose-dependent manner. The expression levels of IL-6, IL-8, TNF-α, VEGF, TF, VCAM-1, and ICAM-1 were elevated by stimulation with isoflurane, which were significantly suppressed by the administration of agomelatine. The up-regulation of transcriptional factor Egr-1 induced by isoflurane was down-regulated by agomelatine.

Conclusion

Agomelatine might attenuate isoflurane-induced inflammation and damage via down-regulating Egr-1 in brain endothelial cells.

Protective effects of grape seed procyanidin on isoflurane-induced cognitive impairment in mice

Context: Oxidative imbalance-induced cognitive impairment is among the most urgent clinical concerns. Isoflurane has been demonstrated to impair cognitive function via an increase in oxidative stress. GSP has strong antioxidant capacities, suggesting potential cognitive benefits.Objective: This study investigates whether GSP pre-treatment can alleviate isoflurane-induced cognitive dysfunction in mice.Materials and methods: C57BL/6J mice were pre-treated with either GSP 25-100 mg/kg/d for seven days or GSP 100-400 mg/kg as a single dose before the 6 h isoflurane anaesthesia. Cognitive functioning was examined using the fear conditioning tests. The levels of SOD, p-NR2B and p-CREB in the hippocampus were also analysed.Results: Pre-treatment with either a dose of GSP 50 mg/kg/d for seven days or a single dose of GSP 200 mg/kg significantly increased the % freezing time in contextual tests on the 1st (72.18 ± 12.39% vs. 37.60 ± 8.93%; 78.27 ± 8.46% vs. 52.72 ± 2.64%), 3rd (93.80 ± 7.62% vs. 52.94 ± 14.10%; 87.65 ± 10.86% vs. 52.89 ± 1.73%) and 7th (91.36 ± 5.31% vs. 64.09 ± 14.46%; 93.78 ± 3.92% vs. 79.17 ± 1.79%) day after anaesthesia. In the hippocampus of mice exposed to isoflurane, GSP 200 mg/kg increased the total SOD activity on the 1st and 3rd day and reversed the decreased activity of the NR2B/CREB pathway.Discussion and conclusions: These findings suggest that GSP improves isoflurane-induced cognitive dysfunction by protecting against perturbing antioxidant enzyme activities and NR2B/CREB pathway. Therefore, GSP may possess a potential prophylactic role in isoflurane-induced and other oxidative stress-related cognitive decline.

The Combination of Astragalus membranaceus and Ligustrazine Protects Against Thrombolysis-Induced Hemorrhagic Transformation Through PKCδ/Marcks Pathway in Cerebral Ischemia Rats

Astragalus membranaceus (Ast) and ligustrazine (Lig) have a protective effect on lower hemorrhagic transformation induced by pharmaceutical thrombolysis. The cerebral ischemia rat model was induced with autologous blood clot injections. A combination of Ast and Lig, or a protein kinase C delta (PKCδ) inhibitor—rottlerin, or a combination of Ast, Lig, and rottlerin was administered immediately after recombinant tissue plasminogen activator injection. The cerebral infarct area, neurological deficits, cerebral hemorrhage status, neuronal damage and tight junctions’ changes in cerebral vessels, and the messenger RNA and protein levels of PKCδ, myristoylated alanine-rich C kinase substrate (Marcks), and matrix metallopeptidase 9 (MMP9) were determined after 3 h and 24 h of thrombolysis. The ultrastructure of the neuronal damage and tight junctions was examined under a transmission electron microscope. The expression levels of PKCδ, Marcks, and MMP9 were assessed by immunohistochemistry, western blot, and quantitative real-time polymerase chain reaction . Administration of Ast and Lig not only significantly decreased neurological deficit scores, infarct volumes, and cerebral hemorrhage but also inhibited the disruption due to neuronal dysfunction and the tight junction integrity in the cerebral vessel. Treatment with a combination of Ast and Lig effectively protected ischemia-induced microhemorrhage transformation through PKCδ/Marcks pathway suppression.

Post-treatment With Qing-Ying-Tang, a Compound Chinese Medicine Relives Lipopolysaccharide-Induced Cerebral Microcirculation Disturbance in Mice

Objective: Lipopolysaccharide (LPS) causes microvascular dysfunction, which is a key episode in the pathogenesis of endotoxemia. This work aimed to investigate the effect of Qing-Ying-Tang (QYT), a compound Chinese medicine in cerebral microcirculation disturbance and brain damage induced by LPS.

Methods: Male C57/BL6 mice were continuously transfused with LPS (7.5 mg/kg/h) through the left femoral vein for 2 h. QYT (14.3 g/kg) was given orally 2 h after LPS administration. The dynamics of cerebral microcirculation were evaluated by intravital microscopy. Brain tissue edema was assessed by brain water content and Evans Blue leakage. Cytokines in plasma and brain were evaluated by flow cytometry. Confocal microscopy and Western blot were applied to detect the expression of junction and adhesion proteins, and signaling proteins concerned in mouse brain tissue.

Results: Post-treatment with QYT significantly ameliorated LPS-induced leukocyte adhesion to microvascular wall and albumin leakage from cerebral venules and brain tissue edema, attenuated the increase of MCP-1, MIP-1α, IL-1α, IL-6, and VCAM-1 in brain tissue and the activation of NF-κB and expression of MMP-9 in brain. QYT ameliorated the downregulation of claudin-5, occludin, JAM-1, ZO-1, collagen IV as well as the expression and phosphorylation of VE-cadherin in mouse brain.

Conclusions: This study demonstrated that QYT protected cerebral microvascular barrier from disruption after LPS by acting on the transcellular pathway mediated by caveolae and paracellular pathway mediated by junction proteins. This result suggests QYT as a potential strategy to deal with endotoxemia.

Anti-inflammation conferred by stimulation of CD200R1 via Dok1 pathway in rat microglia after germinal matrix hemorrhage

CD200 has been reported to be neuroprotective in neurodegenerative diseases. However, the potential protective effects of CD200 in germinal matrix hemorrhage (GMH) have not been investigated. We examined the anti-inflammatory mechanisms of CD200 after GMH. A total of 167 seven-day-old rat pups were used. The time-dependent effect of GMH on the levels of CD200 and CD200 Receptor 1 (CD200R1) was evaluated by western blot. CD200R1 was localized by immunohistochemistry. The short-term (24 h) and long-term (28 days) outcomes were evaluated after CD200 fusion protein (CD200Fc) treatment by neurobehavioral assessment. CD200 small interfering RNA (siRNA) and downstream of tyrosine kinase 1 (Dok1) siRNA were injected intracerebroventricularly. Western blot was employed to study the mechanisms of CD200 and CD200R1. GMH induced significant developmental delay and caused impairment in both cognitive and motor functions in rat pups. CD200Fc ameliorated GMH-induced damage. CD200Fc increased expression of Dok1 and decreased IL-1beta and TNF-alpha levels. CD200R1 siRNA and Dok1 siRNA abolished the beneficial effects of CD200Fc, as demonstrated by enhanced expression levels of IL-1beta and TNF-alpha. CD200Fc inhibited GMH-induced inflammation and this effect may be mediated by CD200R1/Dok1 pathway. Thus, CD200Fc may serve as a potential treatment to ameliorate brain injury for GMH patients.

Subarachnoid hemorrhage enhances the expression of TDP-43 in the brain of experimental rats and human subjects

The transactive response DNA-binding protein of 43 (TDP-43) may be involved in neurodegenerative disease and in the response to brain injury; however, alterations in the expression of TDP-43 following subarachnoid hemorrhage (SAH) require further investigation. The present study reported a notable elevation in the expression of TDP-43 within the cerebrospinal fluid (CSF) of patients with aneurysmal SAH and increased brain expression of TDP-43 in a rat model of SAH. The TDP-43 protein and a derivative migrated at 43 and 24 kDa, respectively, as observed via the immunoblotting of concentrated CSF samples obtained from patients with SAH; no signal was detected in the CSF from healthy controls. SAH in rats was induced by intravascular suture puncture. The expression levels of TDP-43 in rat cortical lysates following SAH were increased at 0.5 h, peaked at 48 h and remained significantly elevated at 72 h post-injury, compared with sham controls. TDP-43 immunolabeling indication localization within neurons, astrocytes and microglia in the experimental rats. Collectively, the findings of the present study indicated the early involvement of TDP-43 in the brain in response to SAH, and that expression levels of TDP-43 in the CSF may serve as a prognostic biomarker among patients with this condition.

Phosphorylated recombinant HSP27 protects the brain and attenuates blood-brain barrier disruption following stroke in mice receiving intravenous tissue-plasminogen activator

Loss of integrity of the blood-brain barrier (BBB) in ischemic stroke victims initiates a devastating cascade of events causing brain damage. Maintaining the BBB is important to preserve brain function in ischemic stroke. Unfortunately, recombinant tissue plasminogen activator (tPA), the only effective fibrinolytic treatment at the acute stage of ischemic stroke, also injures the BBB and increases the risk of brain edema and secondary hemorrhagic transformation. Thus, it is important to identify compounds that maintain BBB integrity in the face of ischemic injury in patients with stroke. We previously demonstrated that intravenously injected phosphorylated recombinant heat shock protein 27 (prHSP27) protects the brains of mice with transient middle cerebral artery occlusion (tMCAO), an animal stroke-model. Here, we determined whether prHSP27, in addition to attenuating brain injury, also decreases BBB damage in hyperglycemic tMCAO mice that had received tPA. After induction of hyperglycemia and tMCAO, we examined 4 treatment groups: 1) bovine serum albumin (BSA), 2) prHSP27, 3) tPA, 4) tPA plus prHSP27. We examined the effects of prHSP27 by comparing the BSA and prHSP27 groups and the tPA and tPA plus prHSP27 groups. Twenty-four hours after injection, prHSP27 reduced infarct volume, brain swelling, neurological deficits, the loss of microvessel proteins and endothelial cell walls, and mortality. It also reduced the rates of hemorrhagic transformation, extravasation of endogenous IgG, and MMP-9 activity, signs of BBB damage. Therefore, prHSP27 injection attenuated brain damage and preserved the BBB in tPA-injected, hyperglycemic tMCAO experimental stroke-model mice, in which the BBB is even more severely damaged than in simple tMCAO mice. The attenuation of brain damage and BBB disruption in the presence of tPA suggests the effectiveness of prHSP27 and tPA as a combination therapy. prHSP27 may be a novel therapeutic agent for ischemic stroke patients whose BBBs are injured following tPA injections.

Hydrogen inhalation improves mouse neurological outcomes after cerebral ischemia/reperfusion independent of anti-necroptosis

This study aimed to investigate the role of necroptosis in the neuroprotection of hydrogen in a mouse model of cerebral ischemia/reperfusion (I/R) injury. C57BL mice were randomly divided into sham group, I/R group, hydrogen/oxygen group (HO), nitrogen/oxygen group (NO). Middle cerebral artery occlusion (MCAO) for 1 hour followed by reperfusion was introduced to animals which were allowed to inhale 66.7% hydrogen/33.3% oxygen for 90 minutes since the beginning of reperfusion. Mice in NO group inhaled 66.7% nitrogen/33.3% oxygen. 24 hours after MCAO, brain infarction, brain water content and neurological function were evaluated. The protein expression of mixed lineage kinase domain like protein (MLKL) was detected at 3, 6, 12, 24 and 72 hours after reperfusion in HO group and the protein and mRNA expression of MLKL at 24 hours after MCAO in four groups. Hydrogen inhalation significantly reduced infarct volume, attenuated brain edema and improved neurobehavioral deficit in MCAO mice. The MLKL expression increased after MCAO and peaked at 6-24 hours after reperfusion. However, hydrogen inhalation had no significant effect on the MLKL expression at transcriptional and translational levels after MCAO. This study indicates high concentration hydrogen improves mouse neurological outcome after cerebral I/R injury independent of anti-necroptosis.

Neuroprotective Effect of Protein Phosphatase 2A/Tristetraprolin Following Subarachnoid Hemorrhage in Rats

Early brain injury (EBI) following subarachnoid hemorrhage (SAH) can lead to inflammation and neuronal dysfunction. There is a need for effective strategies to mitigate these effects and improve the outcome of patients who experience SAH. The mRNA-destabilizing protein tristetraprolin (TTP) is an anti-inflammatory factor that induces the decay of cytokine transcripts and has been implicated in diseases such as glioma. However, the mechanism of action of TTP in EBI after SAH is unclear. The present study investigated the effects of TTP regulation via phosphorylation in a rat model of SAH by protein phosphatase (PP)2A, which is a pleiotropic enzyme complex with multiple substrate phospho-proteins. We hypothesized that inhibitory phosphorylation of TTP by PP2A would reduce neuroinflammation and apoptosis. To evaluate the function of each factor, the PP2A agonist FTY720, short interfering (si)RNAs targeting TTP and PP2A were administered to rats by intracerebroventricular injection 24 h before SAH. Rats were evaluated with SAH grade, neurological score, brain water content and by western blotting, and terminal deoxynucleotidyltransferase dUTP nick-end labeling. We found that endogenous PP2A and TTP levels were increased after SAH. FTY720 induced PP2A activation would lead to dephosphorylation and activation of TTP and decreased production of tumor necrosis factor (TNF)-α, interleukin (IL)-6, and IL-8. SiRNA-mediated TTP knockdown abolished anti-inflammatory effects of FTY720 treatment, indicating that PP2A was associated with TTP activation in vivo. Decreased TNF-α, IL-6, and IL-8 levels were associated with improvement of neurological function, reduction of brain edema, suppression of caspase-3, and up-regulation of B cell lymphoma-2. These results demonstrated that PP2A activation could enhance the anti-inflammatory and anti-apoptotic effects of TTP, by which it might shed light on the development of an effective therapeutic strategy against EBI following SAH.

In vivo imaging of prodromal hippocampus CA1 subfield oxidative stress in models of Alzheimer disease and Angelman syndrome

Hippocampus oxidative stress is considered pathogenic in neurodegenerative diseases, such as Alzheimer disease (AD), and in neurodevelopmental disorders, such as Angelman syndrome (AS). Yet clinical benefits of antioxidant treatment for these diseases remain unclear because conventional imaging methods are unable to guide management of therapies in specific hippocampus subfields in vivo that underlie abnormal behavior. Excessive production of paramagnetic free radicals in nonhippocampus brain tissue can be measured in vivo as a greater-than-normal 1/T₁ that is quenchable with antioxidant as measured by quench-assisted (Quest) MRI. Here, we further test this approach in phantoms, and we present proof-of-concept data in models of AD-like and AS hippocampus oxidative stress that also exhibit impaired spatial learning and memory. AD-like models showed an abnormal gradient along the CA1 dorsal-ventral axis of excessive free radical production as measured by Quest MRI, and redox-sensitive calcium dysregulation as measured by manganese-enhanced MRI and electrophysiology. In the AS model, abnormally high free radical levels were observed in dorsal and ventral CA1. Quest MRI is a promising in vivo paradigm for bridging brain subfield oxidative stress and behavior in animal models and in human patients to better manage antioxidant therapy in devastating neurodegenerative and neurodevelopmental diseases.-Berkowitz, B. A., Lenning, J., Khetarpal, N., Tran, C., Wu, J. Y., Berri, A. M., Dernay, K., Haacke, E. M., Shafie-Khorassani, F., Podolsky, R. H., Gant, J. C., Maimaiti, S., Thibault, O., Murphy, G. G., Bennett, B. M., Roberts, R. In vivo imaging of prodromal hippocampus CA1 subfield oxidative stress in models of Alzheimer disease and Angelman syndrome.

Hyperbaric Oxygen Preconditioning Attenuates Hemorrhagic Transformation Through Reactive Oxygen Species/Thioredoxin-Interacting Protein/Nod-Like Receptor Protein 3 Pathway in Hyperglycemic Middle Cerebral Artery Occlusion Rats

OBJECTIVES

To clarify whether hyperbaric oxygen preconditioning can attenuate hyperglycemia-enhanced hemorrhagic transformation and to establish a role for Nod-like receptor protein 3 inflammasome in the pathophysiology of hemorrhagic transformation.

DESIGN

Controlled prospective animal study.

SETTING

University research laboratory.

SUBJECTS

Male Sprague-Dawley rats weighing 260-280 g.

INTERVENTIONS

Rats received 1-hour-long hyperbaric oxygen preconditioning for five consecutive days. Hyperglycemic middle cerebral artery occlusion model was induced at 24 hours after the last hyperbaric oxygen exposure. Reactive oxygen species scavenger (N-acetyl-L-cysteine), thioredoxin-interacting protein small interfering RNA, and Nod-like receptor protein 3 small interfering RNA were given in different groups separately to verify the possible pathway.

MEASUREMENTS AND MAIN RESULTS

Rats were randomly divided into sham, middle cerebral artery occlusion, middle cerebral artery occlusion + dextrose, middle cerebral artery occlusion + dextrose + normobaric oxygen preconditioning, middle cerebral artery occlusion + dextrose + hyperbaric oxygen, middle cerebral artery occlusion + dextrose + hyperbaric oxygen + N-acetyl-L-cysteine, middle cerebral artery occlusion + dextrose + hyperbaric oxygen + control small interfering RNA, middle cerebral artery occlusion + dextrose + hyperbaric oxygen + thioredoxin-interacting protein small interfering RNA, and middle cerebral artery occlusion + dextrose + hyperbaric oxygen + Nod-like receptor protein 3 small interfering RNA groups. Hyperglycemia was induced by administration of 50% dextrose (6 mL/kg) intraperitoneally 30 minutes before middle cerebral artery occlusion. Control small interfering RNA/thioredoxin-interacting protein small interfering RNA or Nod-like receptor protein 3 small interfering RNA (500 pmol/5 μL) were injected intracerebroventricularly 72 hours before middle cerebral artery occlusion for intervention. The neurologic scores, infarction and hemorrhage volumes, the expression of Nod-like receptor protein 3, and its downstream targets were analyzed. Hyperbaric oxygen preconditioning decreased both infarction and hemorrhage volumes and improved neurobehavioral function. In addition, hyperbaric oxygen preconditioning provided additional protective effects in hemorrhagic transformation, which was independent of infarction volume. The benefits of hyperbaric oxygen preconditioning on hyperglycemic middle cerebral artery occlusion rats were reversed after blocking the reactive oxygen species/thioredoxin-interacting protein/Nod-like receptor protein 3 pathway.

CONCLUSIONS

Nod-like receptor protein 3 inflammasome played an important role in hyperglycemia-enhanced hemorrhagic transformation. Hyperbaric oxygen preconditioning attenuated hemorrhagic transformation through reactive oxygen species/thioredoxin-interacting protein/Nod-like receptor protein 3 pathway.

Hyperbaric Oxygen Reduces Infarction Volume and Hemorrhagic Transformation Through ATP/NAD+/Sirt1 Pathway in Hyperglycemic Middle Cerebral Artery Occlusion Rats

BACKGROUND AND PURPOSE

Energy depletion is a critical factor leading to cell death and brain dysfunction after ischemic stroke. In this study, we investigated whether energy depletion is involved in hyperglycemia-induced hemorrhagic transformation after ischemic stroke and determined the pathway underlying the beneficial effects of hyperbaric oxygen (HBO).

METHODS

After 2-hour middle cerebral artery occlusion, hyperglycemia was induced by injecting 50% dextrose (6 mL/kg) intraperitoneally at the onset of reperfusion. Immediately after it, rats were exposed to HBO at 2 atmospheres absolutes for 1 hour. ATP synthase inhibitor oligomycin A, nicotinamide phosphoribosyl transferase inhibitor FK866, or silent mating type information regulation 2 homolog 1 siRNA was administrated for interventions. Infarct volume, hemorrhagic volume, and neurobehavioral deficits were recorded; the level of blood glucose, ATP, and nicotinamide adenine dinucleotide and the activity of nicotinamide phosphoribosyl transferase were monitored; the expression of silent mating type information regulation 2 homolog 1, acetylated p53, acetylated nuclear factor-κB, and cleaved caspase 3 were detected by Western blots; and the activity of matrix metalloproteinase-9 was assayed by zymography.

RESULTS

Hyperglycemia deteriorated energy metabolism and reduced the level of ATP and nicotinamide adenine dinucleotide and exaggerated hemorrhagic transformation, blood-brain barrier disruption, and neurological deficits after middle cerebral artery occlusion. HBO treatment increased the levels of the ATP and nicotinamide adenine dinucleotide and consequently increased silent mating type information regulation 2 homolog 1, resulting in attenuation of hemorrhagic transformation, brain infarction, as well as improvement of neurological function in hyperglycemic middle cerebral artery occlusion rats.

CONCLUSIONS

HBO induced activation of ATP/nicotinamide adenine dinucleotide/silent mating type information regulation 2 homolog 1 pathway and protected blood-brain barrier in hyperglycemic middle cerebral artery occlusion rats. HBO might be promising approach for treatment of acute ischemic stroke patients, especially patients with diabetes mellitus or treated with r-tPA (recombinant tissue-type plasminogen activator).

The cerebral circulation and cerebrovascular disease III: Stroke

In this paper, our review series on cerebrovascular disease anatomy, physiology, and pathology ends with a thorough discussion of the most significant cerebrovascular pathology: stroke. This discussion proceeds through two layers of organization. First, stroke is divided up into its main etiologic categories (ischemic stroke/transient ischemic attack, hemorrhagic stroke, and ischemic to hemorrhagic transformation). Then, the epidemiological, pathophysiological, clinical, and therapeutic (employed currently as well as emerging) aspects of each etiology are explored; emphasis is placed upon the therapeutic aspects. Finally, once we have covered all aspects of each etiologic category, we end our review with a defense of the thesis that there is much hope for the future of stroke treatment to be derived from familiarity with the literature on emerging therapies.

Therapeutic Strategies to Attenuate Hemorrhagic Transformation After Tissue Plasminogen Activator Treatment for Acute Ischemic Stroke

This review focuses on the mechanisms and emerging concepts of stroke and therapeutic strategies for attenuating hemorrhagic transformation (HT) after tissue plasminogen activator (tPA) treatment for acute ischemic stroke (AIS). The therapeutic time window for tPA treatment has been extended. However, the patients who are eligible for tPA treatment are still ＜5% of all patients with AIS. The risk of serious or fatal symptomatic hemorrhage increases with delayed initiation of treatment. HT is thought to be caused by 1) ischemia/reperfusion injury; 2) the toxicity of tPA itself; 3) inflammation; and/or 4) remodeling factor-mediated effects. Modulation of these pathophysiologies is the basis of direct therapeutic strategies to attenuate HT after tPA treatment. Several studies have revealed that matrix metalloproteinases and free radicals are potential therapeutic targets. In addition, we have demonstrated that the inhibition of the vascular endothelial growth factor-signaling pathway and supplemental treatment with a recombinant angiopoietin-1 protein might be a promising therapeutic strategy for attenuating HT after tPA treatment through vascular protection. Moreover, single-target therapies could be insufficient for attenuating HT after tPA treatment and improving the therapeutic outcome of patients with AIS. We recently identified progranulin, which is a growth factor and a novel target molecule with multiple therapeutic effects. Progranulin might be a therapeutic target that protects the brain through suppression of vascular remodeling (vascular protection), neuroinflammation, and/or neuronal death (neuroprotection). Clinical trials which evaluate the effects of anti-VEGF drugs or PGRN-based treatment with tPA will be might worthwhile.

Effect of pregabalin administration upon reperfusion in a rat model of hyperglycemic stroke: Mechanistic insights associated with high-mobility group box 1

Hyperglycemia, which reduces the efficacy of treatments and worsens clinical outcomes, is common in stroke. Ability of pregabalin to reduce neuroexcitotoxicity may provide protection against stroke, even under hyperglycemia. We investigated its protective effect against hyperglycemic stroke and its possible molecular mechanisms. Male Wistar rats administered dextrose to cause hyperglycemia, underwent middle cerebral artery occlusion for 1 h and subsequent reperfusion. Rats were treated with an intraperitoneal injection of 30 mg/kg pregabalin or an equal amount of normal saline at the onset of reperfusion (n = 16 per group). At 24 h after reperfusion, neurological deficit, infarct volume, and apoptotic cell count were assessed. Western blot analysis was performed to determine protein expression of high-mobility group box 1 (HMGB1), toll-like receptor-4 (TLR-4), phosphorylated nuclear factor-kappa B (p-NF-κB), interleukin-1beta (IL-1β), tumor necrosis factor-alpha (TNF-α), phosphorylated inducible and endothelial nitric oxide synthase (p-iNOS, p-eNOS), Bcl-2, Bax, Cytochrome C, and caspase-3 in the brain. Pregabalin-treated rats showed significantly improved neurological function (31% decrease in score), reduced infarct size (by 33%), fewer apoptotic cells (by 63%), and lower expression levels of HMGB1, TLR4, p-NF-κB, IL-1β, and TNF- α, compared with control rats. Decreased p-iNOS and increased p-eNOS expressions were also observed. Expression of Bax, Cytochrome C, and cleaved caspase-3/caspase3 was significantly downregulated, while Bcl-2 expression was increased by pregabalin treatment. Pregabalin administration upon reperfusion decreased neuronal death and improved neurological function in hyperglycemic stroke rats. Cogent mechanisms would include attenuation of HMGB1/TLR-4-mediated inflammation and favorable modulation of the NOS.

Tetramethylpyrazine-2'-O-sodium ferulate attenuates blood-brain barrier disruption and brain oedema after cerebral ischemia/reperfusion

Disruption of blood-brain barrier (BBB) and subsequent oedema are major causes of the pathogenesis in ischaemic stroke with which the current clinical therapy remains unsatisfied. In this study, we examined the therapeutic effect of tetramethylpyrazine-2'-O-sodium ferulate (TSF)-a novel analogue of tetramethylpyrazine in alleviating BBB breakdown and brain oedema after cerebral ischaemia/reperfusion (I/R). Then, we explored the potential mechanism of the protection on BBB disruption in cerebral I/R rat models. Male Sprague-Dawley rats (250-300 g) were subjected to 120 min middle cerebral artery occlusion (MCAO), followed by 48 h reperfusion. TSF (10.8, 18 and 30 mg kg^-1) and ozagrel (18 mg kg^-1) were administrated by intravenous injection immediately for the first time and then received the same dose every 24 h for 2 days. We found that TSF treatment significantly attenuated the cerebral water content, infarction volume and improved neurological outcomes in MCAO rats compared to I/R models. Moreover, we investigated the effect of TSF on the BBB for that cerebral oedema is closely related to the permeability of the BBB. We found that the permeability of BBB was improved significantly in TSF groups compared to I/R model group by Evans blue leakage testing. Furthermore, the expressions of tight junction (TJ) proteins junction adhesion molecule-1 and occludin significantly decreased, but the protein expression of matrix metalloproteinase-9 (MMP-9) and aquaporin 4 (AQP4) increased after cerebral I/R, all of which were alleviated by TSF treatment. In conclusion, TSF significantly reduced BBB permeability and brain oedema, which were correlated with regulating the expression of TJ proteins, MMP-9 and AQP4. These findings provide a novel approach to the treatment of ischaemic stroke.

Acute Hyperglycemia Does Not Affect Brain Swelling or Infarction Volume After Middle Cerebral Artery Occlusion in Rats

Stroke disproportionally affects diabetic and hyperglycemic patients with increased incidence and is associated with higher morbidity and mortality due to brain swelling. In this study, the intraluminal suture middle cerebral artery occlusion (MCAO) model was used to examine the effects of blood glucose on brain swelling and infarct volume in acutely hyperglycemic rats and normo-glycemic controls. Fifty-four rats were distributed into normo-glycemic sham surgery, hyperglycemic sham surgery, normo-glycemic MCAO, and hyperglycemic MCAO. To induce hyperglycemia, 15 min before MCAO surgery, animals were injected with 50 % dextrose. Animals were subjected to 90 min of MCAO and sacrificed 24 h after reperfusion for hemispheric brain swelling and infarct volume calculations using standard equations. While normo-glycemic and hyperglycemic animals after MCAO presented with significantly higher brain swelling and larger infarcts than their respective controls, no statistical difference was observed for either brain swelling or infarct volume between normo-glycemic shams and hyperglycemic shams or normo-glycemic MCAO animals and hyperglycemic MCAO animals. The findings of this study suggest that blood glucose does not have any significant effect on hemispheric brain swelling or infarct volume after MCAO in rats.

Progranulin Reduced Neuronal Cell Death by Activation of Sortilin 1 Signaling Pathways After Subarachnoid Hemorrhage in Rats

OBJECTIVES

Progranulin has been reported to have neuroprotective actions in cultured neurons. This study investigated the effect of recombinant rat progranulin on early brain injury after subarachnoid hemorrhage.

DESIGN

Controlled in vivo laboratory study.

SETTING

Animal research laboratory.

SUBJECTS

Two hundred thirty adult male Sprague-Dawley rats weighing 280-320 g.

INTERVENTIONS

Subarachnoid hemorrhage was induced in rats by endovascular perforation. Rat recombinant progranulin (1 and 3 ng) was administrated intracerebroventricularly at 1.5 hours after subarachnoid hemorrhage. Progranulin small interfering RNA was administrated by intracerebroventricularly at 1 day before subarachnoid hemorrhage induction. Subarachnoid hemorrhage grade, neurologic score, and brain water content were measured at 24 and 72 hours after subarachnoid hemorrhage. Neural apoptosis was evaluated by double immunofluorescence staining using terminal deoxynucleotidyl transferase-mediated uridine 5'-triphosphate-biotin nick-end labeling and neuronal nuclei. For mechanistic study, the expression of progranulin, phosphorylated Akt, Akt, p-Erk, Erk, Bcl-2, and cleaved caspase-3 were analyzed by Western blot at 24 hours after subarachnoid hemorrhage. siRNA for sortilin 1 (a progranulin receptor) was used to intervene the downstream pathway.

MEASUREMENTS AND MAIN RESULTS

The expression of progranulin decreased and reached the lowest point at 24 hours after subarachnoid hemorrhage. Administration of rat recombinant progranulin decreased brain water content and improved neurologic functions at both 24 and 72 hours after subarachnoid hemorrhage, while knockdown of endogenous progranulin aggravated neurologic deficits after subarachnoid hemorrhage. Rat recombinant progranulin treatment reduced neuronal apoptosis, while progranulin deficiency promoted neuronal apoptosis at 24 hours after subarachnoid hemorrhage. Rat recombinant progranulin promoted Akt activation, increased Bcl-2 level, but reduced caspase-3 level. Knockdown of progranulin binding factor sortilin 1 abolished the beneficial effects of rat recombinant progranulin at 24 hours after subarachnoid hemorrhage.

CONCLUSION

Rat recombinant progranulin alleviated neuronal death via sortilin 1-mediated and Akt-related antiapoptosis pathway. Rat recombinant progranulin may have potentials to ameliorate early brain injury for subarachnoid hemorrhage patients.

Docosahexaenoic acid attenuates hyperglycemia-enhanced hemorrhagic transformation after transient focal cerebral ischemia in rats

Hemorrhagic transformation (HT) is a feared complication of cerebral ischemic infarction, especially following the use of thrombolytic therapy. In this study, we examined whether docosahexaenoic acid (DHA; 22:6n-3), an omega-3 essential fatty acid family member, can protect the brain from injury and whether DHA can decrease the risk of HT enhanced by hyperglycemia after focal ischemic injury. Male Sprague-Dawley rats were injected with 50% dextrose (6ml/kg intraperitoneally) to induce hyperglycemia 10min before 1.5h of filament middle cerebral artery occlusion (MCAO) was performed. Treatment with DHA (10mg/kg) 5min before reperfusion reduced HT and further improved the 7-day neurological outcome. It also reduced infarct volume, which is consistent with the restricted DWI and T2WI hyperintensive area. Reduced Evans Blue extravasation and increased expression of collagen IV indicated the improved integrity of the blood-brain barrier (BBB) in DHA-treated rats. Moreover, DHA reduced the expression of the intercellular adhesion molecule-1 (ICAM-1) in the ischemic injured brain. Therefore, we conclude that DHA attenuated hyperglycemia-enhanced HT and improved neurological function by preserving the integrity of BBB and reducing inflammation.

In Vitro Induction of Endothelial Apoptosis of the Post-Hypoxic Blood-Brain Barrier by Isoflurane but Not by Sevoflurane and Midazolam

BACKGROUND

The effects of anesthetics on the injured brain continue to be the subject of controversial discussion. Since isoflurane has recently been shown to induce apoptosis of cerebral endothelial cells, this study compared different anesthetic compounds regarding their potential to induce cerebro-vascular apoptosis.

METHODS

The in vitro model of the blood-brain barrier used in this study consisted of astrocyte-conditioned human umbilical vein endothelial cells (AC-HUVEC) has been used. After 24 h of deep hypoxia and reoxygenation or control treatment, AC-HUVEC were exposed to 0, 0.5, 1.0, or 2.0 times the minimum alveolar concentration of isoflurane or sevoflurane, or 0, 75, 150, or 300 nM of midazolam for 2 h. After 24 h, AC-HUVEC were harvested, and the degree of apoptosis was assessed by means of Western blots for the Bax and Bcl-2 ratio and, for controls and the highest concentration groups, terminal deoxynucleotidyl-mediated dUTP-biotin nick end labeling (TUNEL).

RESULTS

Without hypoxic pretreatment, 2.0 MAC of isoflurane slightly increased TUNEL intensity compared to control and sevoflurane, but without any significant changes in the Bax and Bcl-2 ratio. After hypoxic pretreatment, exposure to isoflurane led to a multifold increase in the Bax and Bcl-2 ratio in a dose dependent manner, which was also significantly higher than the ratio observed in the 2 MAC sevoflurane group. TUNEL intensity in the post-hypoxic 2 MAC isoflurane group was increased by a factor of 11 vs. control and by 40 vs. sevoflurane. Sevoflurane and midazolam did not significantly alter these markers of apoptosis, when compared to the control group.

CONCLUSIONS

Isoflurane administered after hypoxia elevates markers of apoptosis in endothelial cells transdifferentiated to the cerebro-vascular endothelium. Endothelial apoptosis may be a previously underestimated mechanism of anesthetic neurotoxicity. Administration of high concentrations of isoflurane in experimental settings may have negative effects on the blood-brain barrier.

Role of NADPH oxidase in total salvianolic acid injection attenuating ischemia-reperfusion impaired cerebral microcirculation and neurons: implication of AMPK/Akt/PKC

OBJECTIVE

TSI is a new drug derived from Chinese medicine for treatment of ischemic stroke in China. The aim of this study was to verify the therapeutic effect of TSI in a rat model of MCAO, and further explore the mechanism for its effect.

METHODS

Male Sprague-Dawley rats were subjected to right MCAO for 60 minutes followed by reperfusion. TSI (1.67 mg/kg) was administrated before reperfusion via femoral vein injection. Twenty-four hours after reperfusion, the fluorescence intensity of DHR 123 in, leukocyte adhesion to and albumin leakage from the cerebral venules were observed. Neurological scores, TTC staining, brain water content, Nissl staining, TUNEL staining, and MDA content were assessed. Bcl-2/Bax, cleaved caspase-3, NADPH oxidase subunits p47(phox)/p67(phox)/gp91(phox), and AMPK/Akt/PKC were analyzed by Western blot.

RESULTS

TSI attenuated I/R-induced microcirculatory disturbance and neuron damage, activated AMPK, inhibited NADPH oxidase subunits membrane translocation, suppressed Akt phosphorylation, and PKC translocation.

CONCLUSIONS

TSI attenuates I/R-induced brain injury in rats, supporting its clinic use for treatment of acute ischemic stroke. The role of TSI may benefit from its antioxidant activity, which is most likely implemented via inactivation of NADPH oxidase through a signaling pathway implicating AMPK/Akt/PKC.

Electroacupuncture pretreatment attenuates blood‑brain barrier disruption following cerebral ischemia/reperfusion

Disruption of the blood-brain barrier (BBB) and subsequent brain edema are major contributors to the pathogenesis of ischemic stroke, however, current clinical therapeutic methods remains unsatisfactory. Electroacupuncture (EA) pretreatment has a protective effect against cerebral ischemia/reperfusion (I/R). However, the underlying mechanisms remain to be fully elucidated. In the present study, the effect of EA pretreatment on BBB disruption was investigated in a focal I/R rat model. Male Sprague-Dawley rats (280-320 g) were pretreated with EA at the acupoint 'Baihui' (GV20) 30 min/day, for five days consecutively prior to focal cerebral I/R, which was induced by middle cerebral artery occlusion (MCAO) for 2 h. The results demonstrated that the infarction volume, brain water content and neurological deficits increased in the MCAO model rats at 3 h and 24 h post-reperfusion, and were attenuated significantly by EA pretreatment. Furthermore, electron microscopy examination confirmed a reduction in brain edema reduction in the EA pretreated rats. Western blot analysis revealed that the tight junction proteins between endothelial cells, including claudin-5, occludin, were significantly degraded, while the protein expression of phosphorylated (p-)caveolin-1 and p-Akt increased following reperfusion, all of which were alleviated by EA pretreatment. However, no significant differences were observed in the expression of caveolin-1 or Akt. Overall, the results demonstrated that EA pretreatment significantly reduced BBB permeability and brain edema, which were correlated with alleviation of the degradation of tight junction proteins and inhibition of the expression of p-caveolin-1 in the endothelial cells.

Hyperbaric oxygen preconditioning attenuates hemorrhagic transformation through increasing PPARγ in hyperglycemic MCAO rats

Hyperbaric oxygen preconditioning (HBO-PC) has been demonstrated to attenuate hemorrhagic transformation (HT) after middle cerebral artery occlusion (MCAO) in hyperglycemic rats. However, the mechanisms remain to be illustrated. Recently, HBO-PC has been shown to activate peroxisome proliferator-activated receptor-gamma (PPARγ) by increasing 15d-PGJ2 in primary cultured neurons. We hypothesize that HBO-PC reduces HT by suppressing inflammation through increasing 15d-PGJ2 and activating PPARγ in hyperglycemic MCAO rats. HBO (2.5ATA) was administered for 1h daily for 5 consecutive days. The PPARγ inhibitor GW9662 was administered intraperitoneally to designated animals. Infarction volume, hemorrhage volume, neurological scores and mortality were analyzed. The levels of 15d-PGJ2, PPARγ, TNF-α and IL-1β, tight junction proteins as well as the activity of MMP-2 and MMP-9 were evaluated 24h after MCAO. HBO-PC reduced HT, improved neurological function, down-regulated inflammatory molecules and inhibited the activation of MMP-9 by increasing 15d-PGJ2 and PPARγ at 24h after MCAO. The results suggested that HBO-PC might be an alternative measure to decrease HT in ischemic stroke.

The combination of astragalus membranaceus and ligustrazine ameliorates micro-haemorrhage by maintaining blood-brain barrier integrity in cerebrally ischaemic rats

ETHNOPHARMACOLOGICAL RELEVANCE

Haemorrhagic transformation is an asymptomatic event that frequently occurs after following ischaemic stroke, particularly when pharmaceutical thrombolysis is used. However, the mechanism responsible for haemorrhagic transformation remains unknown, and therapeutics have not been identified. In this study, we administered a combination of astragalus membranaceus and ligustrazine to rats with cerebral ischaemia that had undergone thrombolysis. We analysed the effect of this combination on the attenuation of haemorrhagic transformation and the maintenance of blood-brain barrier integrity.

METHODS

A rat model of focal cerebral ischaemia was induced with autologous blood clot injections. Thrombolysis was performed via the intravenous injection of rt-PA. Astragalus membranaceus, ligustrazine or a combination of Astragalus membranaceus and ligustrazine was administered immediately after the clot injection. The cerebral infarct area, neurological deficits, blood-brain barrier integrity, and cerebral haemorrhage status were determined after 3, 6 and 24h of ischaemia. The ultrastructure of the blood-brain barrier was examined with a transmission electron microscope. The expression of tight junction proteins, including claudin-1, claudin-5, occludin, and zonula occludens-1, and matrix metallopeptidase-9 activation was further evaluated in terms of their roles in the protective effects of the combination drug on the integrity of the blood-brain barrier.

RESULTS

Ischaemia-induced Evans blue leakage and cerebral haemorrhage were markedly reduced in the combination drug-treated rats compared to the rats treated with either astragalus membranaceus or ligustrazine alone (p<0.05). The disruption of the ultrastructure of the blood-brain barrier and the neurological deficits were ameliorated by the combination treatment (p<0.05). The reductions in the expression of laudin-1, claudin-5, occludin, and ZO-1 were smaller in the rats that received the combination treatment. In addition, MMP-9 activity was suppressed in the combination-treated rats compared to the controls (p<0.05).

CONCLUSIONS

Treatment with a combination of astragalus membranaceus and ligustrazine alleviated ischaemia-induced micro-haemorrhage transformation by maintaining the integrity of the blood-brain barrier.

Recombinant milk fat globule-EGF factor-8 reduces oxidative stress via integrin β3/nuclear factor erythroid 2-related factor 2/heme oxygenase pathway in subarachnoid hemorrhage rats

BACKGROUND AND PURPOSE

Milk fat globule-EGF factor-8 (MFGE8) has been reported to be neuroprotective in ischemic stroke. However, the effects of MFGE8 in early brain injury after subarachnoid hemorrhage (SAH) have not been investigated. We investigated the role of MFGE8 in early brain injury and the potential mechanisms in antioxidation after SAH.

METHODS

Two dosages (1 μg and 3.3 μg) of recombinant human MFGE8 were injected intracerebroventricularly at 1.5 hours after SAH. SAH grades, neurological scores, and brain water content were measured at 24 and 72 hours. For mechanistic study, MFGE8 siRNA, integrin β3 siRNA, and heme oxygenase (HO) inhibitor SnPP IX were used for intervention. The oxidative stress and expression of MFGE8, integrin β3, HO-1, extracellular signal-regulated kinase, and nuclear factor erythroid 2-related factor 2 were measured by Western blots 24 hours after SAH.

RESULTS

The expression of MFGE8 and HO-1 increased and peaked 24 hours after SAH. Administration of recombinant human MFGE8 decreased brain water content and improved neurological functions both at 24 hours and at 72 hours after SAH. Recombinant human MFGE8 reduced oxidative stress and enhanced the expression of extracellular signal-regulated kinase, nuclear factor erythroid 2-related factor 2, and HO-1; and the effects were abolished by integrin β3 siRNA and HO inhibitor SnPP IX.

CONCLUSIONS

Recombinant MFGE8 attenuated oxidative stress that may be mediated by integrin β3/nuclear factor erythroid 2-related factor 2/HO pathway after SAH. Recombinant MFGE8 may serve as an alternative treatment to ameliorate early brain injury for SAH patients.

Follistatin-like 1 attenuates apoptosis via disco-interacting protein 2 homolog A/Akt pathway after middle cerebral artery occlusion in rats

BACKGROUND AND PURPOSE

Follistatin-like 1 (FSTL1), an extracellular glycoprotein, has been reported to decrease apoptosis in ischemic cardiac diseases, but its effect in ischemic stroke has not been examined. We hypothesized that recombinant FSTL1 attenuates neuronal apoptosis through its receptor disco-interacting protein 2 homolog A (DIP2A) and the Akt pathway after middle cerebral artery occlusion (MCAO) in rats.

METHODS

One hundred forty male Sprague-Dawley rats were subjected to 2 hours of MCAO followed by reperfusion. In a subset of animals, the time course and location of FSTL1 and DIP2A were detected by Western blot and immunofluorescence double staining. Another set of animals were intracerebroventricularly given either recombinant FSTL1 1 hour after reperfusion or FSTL1-small interfering RNA (siRNA) 48 hours before reperfusion. Additionally, DIP2A was knockdown by siRNA in some animals. Infarction volume and neurological deficits were measured, and the expression of FSTL1, DIP2A, phosphorylated Akt, cleaved caspase-3, and terminal deoxynucleotidyl transferase dUTP nick end labeling were quantified using Western blot.

RESULTS

The expression of FSTL1 and DIP2A was increased in neurons and peaked 24 hours after MCAO. Recombinant FSTL1 reduced brain infarction and improved neurological deficits 24 and 72 hours after MCAO via activation of its receptor DIP2A and downstream phosphorylation of Akt. These effects were reversed by DIP2A-siRNA and FSTL1-siRNA.

CONCLUSIONS

Recombinant FSTL1 decreases neuronal apoptosis and improves neurological deficits through phosphorylation of Akt by activation of its receptor DIP2A after MCAO in rats. Thus, FSTL1 may have potentials as a treatment for patients with ischemic stroke.

Isoflurane reduces the ischemia reperfusion injury surge: a longitudinal study with MRI

BACKGROUND

Recent studies show neuroprotective benefits of isoflurane (ISO) administered during cerebral ischemia. However, the available studies evaluated cerebral injury only at a single time point following the intervention and thus the longitudinal effect of ISO on ischemic tissues remains to be investigated.

OBJECTIVE

The objective of the present study was to investigate the longitudinal effect of ISO treatment in counteracting the deleterious effect of ischemia by evoking the transcription factor, hypoxia inducible factor-1 (HIF-1), and vascular endothelial growth factor (VEGF).

METHODS

Focal cerebral ischemia was induced in 70 rats by filament medial cerebral artery occlusion (MCAo) method. MCAo rats were randomly assigned to control (90 min ischemia) and MCAo+ISO (90 min ischemia+2% ISO) groups. Infarct volume, edema, intracerebral hemorrhage (ICH), and regional cerebral blood flow (rCBF) were measured in eight in vivo sequential MR imaging sessions for 3 weeks. Western blot analysis and immunofluorescence were used to determine the expression level of HIF-1α (the regulatable subunit of HIF-1) and VEGF proteins.

RESULTS

ISO inhalation during ischemia significantly decreased the surge of infarct volume, edema, ICH, and reduced the mortality rate (p<0.01). ISO transiently altered the rCBF, significantly enhanced the expression of HIF-1α and VEGF, and decreased the immune cell infiltration. Locomotor dysfunction was ameliorated at a significantly faster pace, and the benefit was seen to persist up to three weeks.

CONCLUSION

Treatment with ISO during ischemia limits the deadly surge in the dynamics of ischemia reperfusion injury with no observed long-term inverse effect.

Recommendations for preclinical research in hemorrhagic transformation

Hemorrhagic transformation (HT) is an important complication of ischemic stroke and is responsible for most of the mortality associated with acute reperfusion therapy. Although many important publications address the preclinical models of ischemic stroke, there are no current recommendations on the conduct of research aimed at understanding the mechanisms and consequences of HT. The purpose of this review is to present the various models used in HT research, the clinical correlates, and the experimental variables known to influence the quantitation of HT in preclinical investigation. Lastly, recommendations for the conduct of preclinical research in HT are provided.

Delayed hyperbaric oxygen therapy promotes neurogenesis through reactive oxygen species/hypoxia-inducible factor-1α/β-catenin pathway in middle cerebral artery occlusion rats

BACKGROUND AND PURPOSE

Hyperbaric oxygen (HBO) has been reported to be neuroprotective and to improve neurofunctional outcomes in acute stroke. However, it is not clear whether delayed HBO enhances endogenous neurogenesis and promotes neurofunctional recovery. The aim of this study is to evaluate the effects of delayed HBO therapy on neurogenesis and its potential mechanisms.

METHODS

One hundred eleven male Sprague-Dawley rats that survived for 7 days from 2 hours of middle cerebral artery occlusion and reperfusion were used. Delayed and multiple HBO were administrated beginning at 7 days after middle cerebral artery occlusion and lasting for 42 days with 3 HBO-free intervals (5 days each). Motor sensory deficits were measured by foot-fault test, and learning and memory abilities were evaluated by Morris water maze. Neurogenesis was examined by double immunostaining of bromodeoxyuridine and doublecortin, bromodeoxyuridine and neuronal nuclei at day 42. For mechanism studies, inhibitors for reactive oxygen species (ROS), hypoxia-inducible factor (HIF)-1α, and β-catenin were administrated, and the levels of ROS, HIF-1α, β-catenin, lymphoid enhancer-binding factor-1, T-cell factor-1, neurogenin-1, doublecortin, and synapsin-1 were assessed by ELISA or Western blot at day 14.

RESULTS

Delayed HBO treatment promoted neurogenesis and improved neurofunctional recovery at day 42, and the improvements were reversed by inhibition of ROS and HIF-1α. Delayed HBO significantly increased ROS and HIF-1α, and upregulated the expression of neurogenin-1, doublecortin, and synapsin-1. Inhibition of ROS and HIF-1α removed the effects of delayed HBO.

CONCLUSIONS

Delayed HBO enhanced endogenous neurogenesis and improved neurofunctional recovery in the late-chronic phase of stroke possibly mediated by ROS/HIF-1α/β-catenin pathway. Delayed HBO may serve as an alternative treatment to improve long-term recovery of stroke survivors.

Hemorrhagic transformation after ischemic stroke in animals and humans

Hemorrhagic transformation (HT) is a common complication of ischemic stroke that is exacerbated by thrombolytic therapy. Methods to better prevent, predict, and treat HT are needed. In this review, we summarize studies of HT in both animals and humans. We propose that early HT (<18 to 24 hours after stroke onset) relates to leukocyte-derived matrix metalloproteinase-9 (MMP-9) and brain-derived MMP-2 that damage the neurovascular unit and promote blood-brain barrier (BBB) disruption. This contrasts to delayed HT (>18 to 24 hours after stroke) that relates to ischemia activation of brain proteases (MMP-2, MMP-3, MMP-9, and endogenous tissue plasminogen activator), neuroinflammation, and factors that promote vascular remodeling (vascular endothelial growth factor and high-moblity-group-box-1). Processes that mediate BBB repair and reduce HT risk are discussed, including transforming growth factor beta signaling in monocytes, Src kinase signaling, MMP inhibitors, and inhibitors of reactive oxygen species. Finally, clinical features associated with HT in patients with stroke are reviewed, including approaches to predict HT by clinical factors, brain imaging, and blood biomarkers. Though remarkable advances in our understanding of HT have been made, additional efforts are needed to translate these discoveries to the clinic and reduce the impact of HT on patients with ischemic stroke.

AQP5 is differentially regulated in astrocytes during metabolic and traumatic injuries

Water movement plays vital roles in both physiological and pathological conditions in the brain. Astrocytes are responsible for regulating this water movement and are the major contributors to brain edema in pathological conditions. Aquaporins (AQPs) in astrocytes play critical roles in the regulation of water movement in the brain. AQP1, 3, 4, 5, 8, and 9 have been reported in the brain. Compared with AQP1, 4, and 9, AQP3, 5, and 8 are less studied. Among the lesser known AQPs, AQP5, which has multiple functions identified outside the central nervous system, is also indicated to be involved in hypoxia injury in astrocytes. In our study, AQP5 expression could be detected both in primary cultures of astrocytes and neurons, and AQP5 expression in astrocytes was confirmed in 1- to 4-week old primary cultures of astrocytes. AQP5 was localized on the cytoplasmic membrane and in the cytoplasm of astrocytes. AQP5 expression was downregulated during ischemia treatment and upregulated after scratch-wound injury, which was also confirmed in a middle cerebral artery occlusion model and a stab-wound injury model in vivo. The AQP5 increased after scratch injury was polarized to the migrating processes and cytoplasmic membrane of astrocytes in the leading edge of the scratch-wound, and AQP5 over-expression facilitated astrocyte process elongation after scratch injury. Taken together, these results indicate that AQP5 might be an important water channel in astrocytes that is differentially expressed during various brain injuries.

Rosiglitazone attenuates hyperglycemia-enhanced hemorrhagic transformation after transient focal ischemia in rats

Hemorrhagic transformation (HT) has been claimed to represent the most feared complication of treatment with intravenous tissue plasminogen activator (t-PA) therapy. In this study, we tested the effect of rosiglitazone on HT in a rat focal cerebral ischemia model. Male Sprague-Dawley rats received an injection of 50% dextrose (6ml/kg intraperitoneally) and were subjected to middle cerebral artery occlusion (MCAO) 10 min later, with the regional cerebral blood flow monitored in vivo by laser-Doppler-flowmetry. Two groups were included: rosiglitazone treatment and vehicle group. In the treatment group, after 1.5h of ischemia, rosiglitazone (2mg/kg) was administered at the onset of reperfusion. Neurobehavioral scores, infarct volume, hemoglobin leakage, hemorrhage rate, the expression of collagen IV and glucose transporter 1 (GLUT1) were measured at 24h after ischemia. Rosiglitazone improved neurobehavioral deficits, reduced infarct volume and hemorrhage rate, and inhibited hemoglobin leakage, when compared with the vehicle group. In addition, it increased the expression of collagen IV and GLUT1 compared to the vehicle group. Our results suggest that rosiglitazone attenuated the hyperglycemia-induced HT after MCAO, possibly by preservation of GLUT1 expression.

Method parameters' impact on mortality and variability in rat stroke experiments: a meta-analysis

Background

Even though more than 600 stroke treatments have been shown effective in preclinical studies, clinically proven treatment alternatives for cerebral infarction remain scarce. Amongst the reasons for the discrepancy may be methodological shortcomings, such as high mortality and outcome variability, in the preclinical studies. A common approach in animal stroke experiments is that A) focal cerebral ischemia is inflicted, B) some type of treatment is administered and C) the infarct sizes are assessed. However, within this paradigm, the researcher has to make numerous methodological decisions, including choosing rat strain and type of surgical procedure. Even though a few studies have attempted to address the questions experimentally, a lack of consensus regarding the optimal methodology remains.

Methods

We therefore meta-analyzed data from 502 control groups described in 346 articles to find out how rat strain, procedure for causing focal cerebral ischemia and the type of filament coating affected mortality and infarct size variability.

Results

The Wistar strain and intraluminal filament procedure using a silicone coated filament was found optimal in lowering infarct size variability. The direct and endothelin methods rendered lower mortality rate, whereas the embolus method increased it compared to the filament method.

Conclusions

The current article provides means for researchers to adjust their middle cerebral artery occlusion (MCAo) protocols to minimize infarct size variability and mortality.

Hyperbaric oxygen preconditioning attenuates hyperglycemia-enhanced hemorrhagic transformation by inhibiting matrix metalloproteinases in focal cerebral ischemia in rats

Hyperglycemia dramatically aggravates brain infarct and hemorrhagic transformation (HT) after ischemic stroke. Oxidative stress and matrix metalloproteinases (MMPs) play an important role in the pathophysiology of HT. Hyperbaric oxygen preconditioning (HBO-PC) has been proved to decrease oxidative stress and has been demonstrated to be neuroprotective in experimental stroke models. The present study determined whether HBO-PC would ameliorate HT by a pre-ischemic increase of reactive oxygen species (ROS) generation, and a suppression of MMP-2 and MMP-9 in hyperglycemic middle cerebral artery occlusion (MCAO) rats. Rats were pretreated with HBO (100% O₂, 2.5 atmosphere absolutes) 1 h daily for 5 days before MCAO. Acute hyperglycemia was induced by an injection of 50% dextrose. Neurological deficits, infarction volume and hemorrhagic volume were assessed 24 h and 7 days after ischemia. ROS scavenger n-acetyl cysteine (NAC), hypoxia-inducible factor-1α (HIF-1α), inhibitor 2-methoxyestradiol (2ME2) and activator cobalt chloride (CoCl₂), and MMP inhibitor SB-3CT were administrated for mechanism study. The activity of MMP-2 and MMP-9, and the expression HIF-1α were measured. HBO-PC improved neurological deficits, and reduced hemorrhagic volume; the expression of HIF-1α was significantly decreased, and the activity of MMP-2 and MMP-9 was reduced by HBO-PC compared with vehicle group. Our results suggested that HBO-PC attenuated HT via decreasing HIF-1α and its downstream MMP-2 and MMP-9 in hyperglycemic MCAO rats.

Cerebralcare Granule® attenuates blood-brain barrier disruption after middle cerebral artery occlusion in rats

Disruption of blood-brain barrier (BBB) and subsequent edema are major contributors to the pathogenesis of ischemic stroke, for which the current clinical therapy remains unsatisfied. Cerebralcare Granule® (CG) is a compound Chinese medicine widely used in China for treatment of cerebrovascular diseases. CG has been demonstrated efficacy in attenuating the cerebral microcirculatory disturbance and hippocampal neuron injury following global cerebral ischemia. However, the effects of CG on BBB disruption following cerebral ischemia have not been investigated. In this study, we examined the therapeutic effect of CG on the BBB disruption in a focal cerebral ischemia/reperfusion (I/R) rat model. Male Sprague-Dawley rats (250 to 300 g) were subjected to 1h middle cerebral artery occlusion (MCAO). CG (0.4 g/kg or 0.8 g/kg) was administrated orally 3h after reperfusion for the first time and then once daily up to 6 days. The results showed that Evans blue extravasation, brain water content, albumin leakage, infarction volume and neurological deficits increased in MCAO model rats, and were attenuated significantly by CG treatment. T2-weighted MRI and electron microscopy further confirmed the brain edema reduction in CG-treated rats. Treatment with CG improved cerebral blood flow (CBF). Western blot analysis and confocal microscopy showed that the tight junction proteins claudin-5, JAM-1, occludin and zonula occluden-1 between endothelial cells were significantly degradated, but the protein expression of caveolin-1, the principal marker of caveolae in endothelial cells, increased after ischemia, all of which were alleviated by CG treatment. In conclusion, the post-treatment with CG significantly reduced BBB permeability and brain edema, which were correlated with preventing the degradation of the tight junction proteins and inhibiting the expression of caveolin-1 in the endothelial cells. These findings provide a novel approach to the treatment of ischemic stroke.

Isoflurane induces endothelial apoptosis of the post-hypoxic blood-brain barrier in a transdifferentiated human umbilical vein endothelial cell model

Isoflurane is a popular volatile anesthetic agent used in humans as well as in experimental animal research. In previous animal studies of the blood-brain barrier (BBB), observations towards an increased permeability after exposure to isoflurane are reported. In this study we investigated the effect of a 2-hour isoflurane exposure on apoptosis of the cerebral endothelium following 24 hours of hypoxia in an in vitro BBB model using astrocyte-conditioned human umbilical vein endothelial cells (AC-HUVECs). Apoptosis of AC-HUVECs was investigated using light microscopy of the native culture for morphological changes, Western blot (WB) analysis of Bax and Bcl-2, and a TUNEL assay. Treatment of AC-HUVECs with isoflurane resulted in severe cellular morphological changes and a significant dose-dependent increase in DNA fragmentation, which was observed during the TUNEL assay analysis. WB analysis confirmed increases in pro-apoptotic Bax levels at 4 hours and 24 hours and decreases in anti-apoptotic Bcl-2 in a dose-dependent manner compared with the control group. These negative effects of isoflurane on the BBB after a hypoxic challenge need to be taken into account not only in experimental stroke research, but possibly also in clinical practice.

Mixed cerebrovascular disease and the future of stroke prevention

Stroke prevention efforts typically focus on either ischemic or hemorrhagic stroke. This approach is overly simplistic due to the frequent coexistence of ischemic and hemorrhagic cerebrovascular disease. This coexistence, termed “mixed cerebrovascular disease”, offers a conceptual framework that appears useful for stroke prevention strategies. Mixed cerebrovascular disease incorporates clinical and subclinical syndromes, including ischemic stroke, subclinical infarct, white matter disease of aging (leukoaraiosis), intracerebral hemorrhage, and cerebral microbleeds. Reliance on mixed cerebrovascular disease as a diagnostic entity may assist in stratifying risk of hemorrhagic stroke associated with platelet therapy and anticoagulants. Animal models of hemorrhagic cerebrovascular disease, particularly models of cerebral amyloid angiopathy and hypertension, offer novel means for identifying underlying mechanisms and developing focused therapy. Phosphodiesterase (PDE) inhibitors represent a class of agents that, by targeting both platelets and vessel wall, provide the kind of dual actions necessary for stroke prevention, given the spectrum of disorders that characterizes mixed cerebrovascular disease.

Hyperbaric oxygen preconditioning attenuates hyperglycemia enhanced hemorrhagic transformation after transient MCAO in rats

BACKGROUND

Hemorrhagic transformation (HT) can be a devastating complication of ischemic stroke. Hyperbaric oxygen preconditioning (HBO-PC) has been shown to improve blood-brain barrier (BBB) permeability in stroke models. The purpose of this study is to examine whether HBO-PC attenuates HT after focal cerebral ischemia, and to investigate whether the mechanism of HBO-PC against HT includes up-regulation of antioxidants in hyperglycemic rats.

METHODS

Male Sprague-Dawley rats (280-320 g) were divided into the following groups: sham, middle cerebral artery occlusion (MCAO) for 2 h, and MCAO treated with HBO-PC. HBO-PC was conducted giving 100% oxygen at 2.5 atm absolute (ATA), for 1 h at every 24 h interval for 5 days. At 24 h after the last session of HBO-PC, rats received an injection of 50% glucose (6 ml/kg intraperitoneally) and were subjected to MCAO 15 min later. At 24 h after MCAO, neurological behavior tests, infarct volume, blood-brain barrier permeability, and hemoglobin content were measured to evaluate the effect of HBO-PC. Western blot analysis of nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) was evaluated at multiple time-points before and after MCAO.

RESULTS

HBO-PC improved neurological behavior test, and reduced infarction volume, HT and Evans blue extravasation in the ipsilateral hemisphere at 24 h after MCAO. Western blot analysis failed to demonstrate up-regulation of Nrf2 in HBO-PC group before and after MCAO. Paradoxically, HBO-PC decreased HO-1 expression at 24 h after MCAO, as compared with htMCAO group.

CONCLUSIONS

HBO-PC improved neurological deficits, infarction volume, BBB disruption, and HT after focal cerebral ischemia. However, its mechanism against focal cerebral ischemia and HT may not include activation of Nrf2 and subsequent HO-1 expression.

Valproic acid improves locomotion in vivo after SCI and axonal growth of neurons in vitro

Previous studies have found that valproic acid (VPA), a histone deacetylases (HDAC) inhibitor, improves outcomes in a rat model of spinal cord injury (SCI). The study here aimed to further illuminate the neuroprotective effects of VPA against SCI, both in vivo and in vitro. First, spinal cord injury was performed in rats using NYU impactor. Delayed VPA injection (8 h following SCI) significantly accelerated locomotor recovery. VPA therapy also suppressed SCI-induced hypoacetylation of histone and promoted expressions of BDNF and GDNF. Next, the influence of VPA on axonal growth inhibited by a myelin protein was tested. Neurons from embryonic spinal cord or hippocampus were cultured on plates coated with Nogo-A peptide, and escalating concentrations of VPA were added into the cultures. VPA treatment, in a concentration dependent manner, allowed neurons to overcome Nogo-A inhibition of neurite outgrowth. Meanwhile, VPA exposure increased the level of histone acetylation and expression of BDNF in spinal neurons. Cumulatively, these findings indicate that VPA is possibly a promising medication and deserves translational trials for spinal cord injury.