Effect of propofol post-treatment on blood-brain barrier integrity and cerebral edema after transient cerebral ischemia in rats

Anesthetics in pathological cerebrovascular conditions

The increasing prevalence of pathological cerebrovascular conditions, including stroke, hypertensive encephalopathy, and chronic disorders, underscores the importance of anesthetic considerations for affected patients. Preserving cerebral oxygenation and blood flow during anesthesia is paramount to prevent neurological deterioration. Furthermore, protecting vulnerable neurons from damage is crucial for optimal outcomes. Recent research suggests that anesthetic agents may provide a potentially therapeutic approach for managing pathological cerebrovascular conditions. Anesthetics target neural mechanisms underlying cerebrovascular dysfunction, thereby modulating neuroinflammation, protecting neurons against ischemic injury, and improving cerebral hemodynamics. However, optimal strategies regarding mechanisms, dosage, and indications remain uncertain. This review aims to clarify the physiological effects, mechanisms of action, and reported neuroprotective benefits of anesthetics in patients with various pathological cerebrovascular conditions. Investigating anesthetic effects in cerebrovascular disease holds promise for developing novel therapeutic strategies.

Update on the intriguing roles of AQP4 expression and redistribution in the progression and treatment of glioma

Aquaporin 4 (AQP4) is abundant in the human brain and has an important role in brain homeostasis and diseases. AQP4 expression has been found to be associated with glioma malignancies. However, the complete understanding of the biological processes and curative importance of AQP4 in glioma remains unclear. The impact of AQP4 subcellular mislocalization on glioma progression and the precise mechanisms regarding AQP4 translocation in glioma need further investigation. In this review, we update recent findings about disturbed AQP4 expression in glioma and explore targeting AQP4 to modulate the glioma progression. Thereafter we discuss some possible mechanisms of action of AQP4 translocations in glioma. The present article offers an appropriate introduction to the potential involvement of AQP4 in the emergence and progression of glioma. Both comprehensive research into the mechanisms and systematically intervention studies focusing on AQP4 are essential. By embracing this strategy, we can obtain a new and insightful outlook on managing cancerous glioma. Although the observations summarized in this review should be confirmed with more studies, we believe that they could provide critical information for the design of more focused research that will allow for systematic and definitive evaluation of the role of AQP4 in glioma treatments.

Research progress of propofol in alleviating cerebral ischemia/reperfusion injury

Ischemic stroke is a leading cause of adult disability and death worldwide. The primary treatment for cerebral ischemia patients is to restore blood supply to the ischemic region as quickly as possible. However, in most cases, more severe tissue damage occurs, which is known as cerebral ischemia/reperfusion (I/R) injury. The pathological mechanisms of brain I/R injury include mitochondrial dysfunction, oxidative stress, excitotoxicity, calcium overload, neuroinflammation, programmed cell death and others. Propofol (2,6-diisopropylphenol), a short-acting intravenous anesthetic, possesses not only sedative and hypnotic effects but also immunomodulatory and neuroprotective effects. Numerous studies have reported the protective properties of propofol during brain I/R injury. In this review, we summarize the potential protective mechanisms of propofol to provide insights for its better clinical application in alleviating cerebral I/R injury.

An overview of hyperbaric oxygen preconditioning against ischemic stroke

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

Mild hypothermia combined with dexmedetomidine reduced brain, lung, and kidney damage in experimental acute focal ischemic stroke

BACKGROUND

Sedatives and mild hypothermia alone may yield neuroprotective effects in acute ischemic stroke (AIS). However, the impact of this combination is still under investigation. We compared the effects of the combination of mild hypothermia or normothermia with propofol or dexmedetomidine on brain, lung, and kidney in experimental AIS. AIS-induced Wistar rats (n = 30) were randomly assigned, after 24 h, to normothermia or mild hypothermia (32-35 °C) with propofol or dexmedetomidine. Histologic injury score and molecular biomarkers were evaluated not only in brain, but also in lung and kidney. Hemodynamics, ventilatory parameters, and carotid Doppler ultrasonography were analyzed for 60 min.

RESULTS

In brain: (1) hypothermia compared to normothermia, regardless of sedative, decreased tumor necrosis factor (TNF)-α expression and histologic injury score; (2) normothermia + dexmedetomidine reduced TNF-α and histologic injury score compared to normothermia + propofol; (3) hypothermia + dexmedetomidine increased zonula occludens-1 expression compared to normothermia + dexmedetomidine. In lungs: (1) hypothermia + propofol compared to normothermia + propofol reduced TNF-α and histologic injury score; (2) hypothermia + dexmedetomidine compared to normothermia + dexmedetomidine reduced histologic injury score. In kidneys: (1) hypothermia + dexmedetomidine compared to normothermia + dexmedetomidine decreased syndecan expression and histologic injury score; (2) hypothermia + dexmedetomidine compared to hypothermia + propofol decreased histologic injury score.

CONCLUSIONS

In experimental AIS, the combination of mild hypothermia with dexmedetomidine reduced brain, lung, and kidney damage.

AQP4 knockout promotes neurite outgrowth via upregulating GAP43 expression in infant rats with hypoxic-ischemic brain injury

Neonatal hypoxic-ischemic encephalopathy (NHIE) induces severe cerebral damage and neurological dysfunction, with seldom effective therapy. Aquaporin-4 (AQP4) is involved in aggravating brain damage induced by NHIE. This study aimed to investigate the role of AQP4 underlying the pathogenesis of NHIE. Neonatal Sprague-Dawley rats were used to establish neonatal hypoxic-ischemic (HI) models, and the expression of AQP4 in the cortex, hippocampus, and lung tissues was detected by real-time quantitative polymerase chain reaction as well as Western blot. Primary cortical neurons were cultured for the oxygen-glucose deprivation (OGD) model, and siRNA was used to silence the expression of AQP4. Immunostaining of Tuj1 was performed to observe the axonal growth. CRISPER/Cas9 technology was used to knock out AQP4. The results demonstrated that AQP4 was upregulated in the cortex, hippocampus, and lung tissues in neonatal rats with HI and OGD neurons. Besides, silencing AQP4 promoted axonal growth of OGD neurons, and AQP4 knockout notably improved long-term neurobehavioral impairment. Furthermore, GAP43 was found closely correlated with AQP4 via GeneMANIA prediction. Significant downregulation of GAP43 was induced in OGD neurons, while AQP4 knockout markedly upregulated its expression in rats. This indicated that the depletion of AQP4 may enhance axonal regeneration and promote the long-term neurobehavioral recovery associated with the upregulation of GAP43 expression.

The Water Transport System in Astrocytes–Aquaporins

Highlights

(AQPs) are transmembrane proteins responsible for fast water movement across cell membranes, including those of astrocytes.

The expression and subcellular localization of AQPs in astrocytes are highly dynamic under physiological and pathological conditions.

Besides their primary function in water homeostasis, AQPs participate in many ancillary functions including glutamate clearance in tripartite synapses and cell migration.

Abstract

Astrocytes have distinctive morphological and functional characteristics, and are found throughout the central nervous system. Astrocytes are now known to be far more than just housekeeping cells in the brain. Their functions include contributing to the formation of the blood–brain barrier, physically and metabolically supporting and communicating with neurons, regulating the formation and functions of synapses, and maintaining water homeostasis and the microenvironment in the brain. Aquaporins (AQPs) are transmembrane proteins responsible for fast water movement across cell membranes. Various subtypes of AQPs (AQP1, AQP3, AQP4, AQP5, AQP8 and AQP9) have been reported to be expressed in astrocytes, and the expressions and subcellular localizations of AQPs in astrocytes are highly correlated with both their physiological and pathophysiological functions. This review describes and summarizes the recent advances in our understanding of astrocytes and AQPs in regard to controlling water homeostasis in the brain. Findings regarding the features of different AQP subtypes, such as their expression, subcellular localization, physiological functions, and the pathophysiological roles of astrocytes are presented, with brain edema and glioma serving as two representative AQP-associated pathological conditions. The aim is to provide a better insight into the elaborate “water distribution” system in cells, exemplified by astrocytes, under normal and pathological conditions.

DL-3n-Butylphthalide Improves Blood-Brain Barrier Integrity in Rat After Middle Cerebral Artery Occlusion

Objective: DL-3n-butylphthalide (NBP) has beneficial effects in different stages of ischemic stroke. Our previous studies have demonstrated that NBP promoted angiogenesis in the perifocal region of the ischemic brain. However, the molecular mechanism of NBP for blood–brain barrier protection in acute ischemic stroke was unclear. Here, we explored the neuroprotective effects of NBP on blood–brain barrier integrity in the acute phase of ischemic stroke in a rat model.

Methods: Adult male Sprague–Dawley rats (n = 82) underwent 2 h of transient middle cerebral artery occlusion and received 90 mg/kg of NBP for 3 days. Brain edema, infarct volume, surface blood flow, and neurological severity score were evaluated. Blood–brain barrier integrity was evaluated by Evans blue leakage and changes in tight junction proteins. We further examined AQP4 and eNOS expression, MMP-9 enzyme activity, and possible signaling pathways for the role of NBP after ischemic stroke.

Results: NBP treatment significantly increased eNOS expression and surface blood flow in the brain, reduced brain edema and infarct volume, and improved neurological severity score compared to the control group (p < 0.05). Furthermore, NBP attenuated Evans blue and IgG leakage and increased tight junction protein expression compared to the control after 1 and 3 days of ischemic stroke (p < 0.05). Finally, NBP decreased AQP4 expression, MMP-9 enzyme activity, and increased MAPK expression during acute ischemic stroke.

Conclusion: NBP protected blood–brain barrier integrity and attenuated brain injury in the acute phase of ischemic stroke by decreasing AQP4 expression and MMP-9 enzyme activity. The MAPK signaling pathway may be associated in this process.

Targeted Temperature Management Suppresses Hypoxia-Inducible Factor-1α and Vascular Endothelial Growth Factor Expression in a Pig Model of Cardiac Arrest

BACKGROUND

The hypoxia-inducible factor-1α (HIF-1α)/vascular endothelial growth factor (VEGF)/VEGF receptor subtype 2 (VEGFR-2) pathway has been implicated in ischemia/reperfusion injury. The aim of this study was to clarify whether whole-body hypothermic targeted temperature management (HTTM) inhibits the HIF-1α/VEGF/VEGFR-2 pathway in a swine model of cardiac arrest (CA) and cardiopulmonary resuscitation (CPR).

METHODS

Twenty-four domestic male Beijing Landrace pigs were used in this study. CA was electrically induced with ventricular fibrillation and left untreated for 8 min. Return of spontaneous circulation (ROSC) was achieved in 16 pigs, which were randomly assigned either to normothermia at 38 °C or to HTTM at 33 °C (each group: n = 8). HTTM was intravascularly induced immediately after ROSC. The core temperature was reduced to 33 °C and maintained for 12 h after ROSC. The serum levels of HIF-1α, VEGF, VEGFR-2, and neuron-specific enolase (NSE) were measured with enzyme immunoassay kits 0.5, 6, 12, and 24 h after ROSC. The expression of HIF-1α, VEGF, and VEGFR-2 in cerebral cortical tissue was measured by RT-PCR and Western blot analysis 24 h after ROSC. Neurological deficit scores and brain cortical tissue water content were evaluated 24 h after ROSC.

RESULTS

The serum levels of HIF-1α, VEGF, and VEGFR-2 were significantly increased under normothermia within 24 h after ROSC. However, these increases were significantly reduced by HTTM. HTTM also decreased cerebral cortical HIF-1α, VEGF, and VEGFR-2 mRNA and protein expression 24 h after ROSC (all p < 0.05). HTTM pigs had better neurological outcomes and less brain edema than normothermic pigs.

CONCLUSION

The HIF-1α/VEGF/VEGFR-2 system is activated following CA and CPR. HTTM protects against cerebral injury after ROSC, which may be part of the mechanism by which it inhibits the expression of components of the HIF-1α/VEGF/VEGFR-2 signaling pathway.

Fatal Status Epilepticus in Dravet Syndrome

Dravet Syndrome (DS) is burdened by high epilepsy-related premature mortality due to status epilepticus (SE). We surveyed centres within Europe through the Dravet Italia Onlus and EpiCARE network (European Reference Network for Rare and Complex Epilepsies). We collated responses on seven DS SCN1A+ patients who died following refractory SE (mean age 6.9 year, range 1.3–23.4 year); six were on valproate, clobazam, and stiripentol. All patients had previous SE. Fatal SE was always triggered by fever: either respiratory infection or one case of hexavalent vaccination. SE lasted between 80 min and 9 h and all patients received IV benzodiazepines. Four patients died during or within hours of SE; in three patients, SE was followed by coma with death occurring after 13–60 days. Our survey supports the hypothesis that unresponsive fever is a core characteristic feature of acute encephalopathy. We highlight the need for management protocols for prolonged seizures and SE in DS.

Diabetes exacerbates brain pathology following a focal blast brain injury: New role of a multimodal drug cerebrolysin and nanomedicine

Blast brain injury (bBI) is a combination of several forces of pressure, rotation, penetration of sharp objects and chemical exposure causing laceration, perforation and tissue losses in the brain. The bBI is quite prevalent in military personnel during combat operations. However, no suitable therapeutic strategies are available so far to minimize bBI pathology. Combat stress induces profound cardiovascular and endocrine dysfunction leading to psychosomatic disorders including diabetes mellitus (DM). This is still unclear whether brain pathology in bBI could exacerbate in DM. In present review influence of DM on pathophysiology of bBI is discussed based on our own investigations. In addition, treatment with cerebrolysin (a multimodal drug comprising neurotrophic factors and active peptide fragments) or H-290/51 (a chain-breaking antioxidant) using nanowired delivery of for superior neuroprotection on brain pathology in bBI in DM is explored. Our observations are the first to show that pathophysiology of bBI is exacerbated in DM and TiO₂-nanowired delivery of cerebrolysin induces profound neuroprotection in bBI in DM, not reported earlier. The clinical significance of our findings with regard to military medicine is discussed.

Hypertonic saline downregulates endothelial cell-derived VEGF expression and reduces blood-brain barrier permeability induced by cerebral ischaemia via the VEGFR2/eNOS pathway

The aim of the present study was to explore the possible mechanisms by which hypertonic saline (HS) effectively ameliorates cerebral oedema via the vascular endothelial growth factor receptor 2 (VEGFR2)-mediated endothelial nitric oxide synthase (eNOS) pathway of endothelial cells in rats. A middle cerebral artery occlusion (MCAO) model in Sprague-Dawley rats and an oxygen-glucose deprivation (OGD) model in cells were used in the present study. Evans blue (EB) staining and a horseradish peroxidase flux assay were performed to evaluate the protective effect of 10% HS on the blood-brain barrier (BBB). The expression levels of vascular endothelial growth factor (VEGF), VEGFR2, zonula occludens 1 (ZO1) and occludin were quantified. The results demonstrated that 10% HS effectively reduced EB extravasation in the peri-ischaemic brain tissue. At 24 h after MCAO, the protein expression levels of VEGF and VEGFR2 in the peri-ischaemic brain tissue were downregulated following treatment with 10% HS. In vitro experiments demonstrated that the permeability of a monolayer endothelial cell barrier was decreased significantly following HS treatment. In addition, VEGF and VEGFR2 protein expression levels were increased in endothelial cells under hypoxic conditions, but that effect was suppressed by HS treatment. Furthermore, HS inhibited the downregulation of ZO1 and occludin effectively, possibly through the VEGFR2/phospholipase C γ1 (PLCγ1)/eNOS signalling pathway. In conclusion, 10% HS may alleviate cerebral oedema through reducing ischaemia-induced BBB permeability, as a consequence of inhibiting VEGFR2/PLCγ1/eNOS-mediated downregulation of ZO1 and occludin.

Propofol improved hypoxia-impaired integrity of blood-brain barrier via modulating the expression and phosphorylation of zonula occludens-1

Aims

Hypoxia may damage blood‐brain barrier (BBB). The neuroprotective effect of propofol has been reported. We aimed to identify whether and how propofol improved hypoxia‐induced impairment of BBB integrity.

Methods

Mouse brain microvascular endothelial cells (MBMECs) and astrocytes were cocultured to establish in vitro BBB model. The effects of hypoxia and propofol on BBB integrity were examined. Further, zonula occludens‐1 (ZO‐1) expression and phosphorylation, hypoxia‐inducible factor‐1α (HIF‐1α) and vascular endothelial growth factor (VEGF) expression, intracellular calcium concentration and Ca²⁺/calmodulin‐dependent protein kinase II (CAMKII) activation were measured.

Results

Hypoxia‐impaired BBB integrity, which was protected by propofol. Hypoxia‐reduced ZO‐1 expression, while induced ZO‐1 phosphorylation. These effects were attenuated by propofol. The expression of HIF‐1α and VEGF was increased by hypoxia and was alleviated by propofol. The hypoxia‐mediated suppression of ZO‐1 and impaired BBB integrity was reversed by HIF‐α inhibitor and VEGF inhibitor. In addition, hypoxia increased the intracellular calcium concentration and induced the phosphorylation of CAMKII, which were mitigated by propofol. The hypoxia‐induced phosphorylation of ZO‐1 and impaired BBB integrity was ameliorated by calcium chelator and CAMKII inhibitor.

Conclusion

Propofol could protect against hypoxia‐mediated impairment of BBB integrity. The underlying mechanisms may involve the expression and phosphorylation of ZO‐1.

Bu Yang Huan Wu decoction prevents reperfusion injury following ischemic stroke in rats via inhibition of HIF-1 α, VEGF and promotion β-ENaC expression

ETHNOPHARMACOLOGICAL RELEVANCE

Bu Yang Huan Wu Decoction (BYHW) is a famous traditional Chinese medicine (TCM) formula used in China for the treatment of cerebral ischemic stroke. But the protective effects and underlining mechanisms of BYHW remain unclear.

AIM OF THE STUDY

This study was designed to investigate the protective effects and underlining signaling mechanisms of BYHW on brain tissues in a rat model of cerebral ischemic reperfusion (I/R) injury.

MATERIALS AND METHODS

Liquid chromatography was used to verify the composition of BYHW. The cerebral edema and infarct volume were measured by magnetic resonance imaging (MRI). The morphology and ultrastructure of ischemic penumbra brain tissues were observed by hematoxylin-eosin (HE) and transmission electron microscopy (TEM). The expression levels of HIF-1 α, VEGF and β-ENaC were tested using immunohistochemistry technique, western blot and quantitative PCR analysis, respectively.

RESULTS

Administration of BYHW significantly decreased cerebral edema, rat neurological function scores, reduced brain infarct volume. At the same time, BYHW had protective effect on the blood-brain barrier (BBB), which improved the morphology and ultrastructure of ischemic penumbra brain tissues. BYHW treatment significantly decreased the protein and mRNA levels of HIF-1 α and VEGF compared with the model treatment. In addition, BYHW treatment significantly up-regulated the protein and mRNA levels of β-ENaC.

CONCLUSIONS

BYHW protected against cerebral I/R injury in MCAO rats through inhibiting the activation of the HIF-1 α /VEGF pathway and stabilizing ion channel of β-ENaC in brain, indicating that BYHW shows potential for stroke treatment in acute stage.

Hypothermia and brain inflammation after cardiac arrest

The cessation (ischemia) and restoration (reperfusion) of cerebral blood flow after cardiac arrest (CA) induce inflammatory processes that can result in additional brain injury. Therapeutic hypothermia (TH) has been proven as a brain protective strategy after CA. In this article, the underlying pathophysiology of ischemia-reperfusion brain injury with emphasis on the role of inflammatory mechanisms is reviewed. Potential targets for immunomodulatory treatments and relevant effects of TH are also discussed. Further studies are needed to delineate the complex pathophysiology and interactions among different components of immune response after CA and identify appropriate targets for clinical investigations.

The potential roles of aquaporin 4 in malignant gliomas

Aquaporin 4 (AQP4) is the major water channel expressed in the central nervous system and is primarily expressed in astrocytes. Recently, accumulated evidence has pointed to AQP4 as a key molecule that could play a critical role in glioma development. Discoveries of the role of AQP4 in cell migration suggest that AQP4 could be a significant factor regarding glioma malignancies. However, the AQP4 expression levels in glioma have not been fully elucidated; furthermore, the correlation of AQP4 expression with glioma malignancy remains controversial. Here, we review the expression pattern and predictive significance of AQP4 in malignant glioma. The molecular mechanism of AQP4 as it pertains to the migration and invasion of human glioma cells has been summarized. In addition, the important roles of AQP4 in combating drug resistance as well as potential pharmacological blockers of AQP4 have been systematically discussed. More research should be conducted to elucidate the potential roles of AQP4 in malignant glioma for identifying the tumor type, progression stages and optimal treatment strategies. The observed experimental results strongly emphasize the importance of this topic for future investigations.

Limb remote ischemic postconditioning protects integrity of the blood-brain barrier after stroke

Integrity of the blood-brain barrier structure is essential for maintaining the internal environment of the brain. Development of cerebral infarction and brain edema is strongly associated with blood-brain barrier leakage. Therefore, studies have suggested that protecting the blood-brain barrier may be an effective method for treating acute stroke. To examine this possibility, stroke model rats were established by middle cerebral artery occlusion and reperfusion. Remote ischemic postconditioning was immediately induced by three cycles of 10-minute ischemia/10-minute reperfusion of bilateral hind limbs at the beginning of middle cerebral artery occlusion reperfusion. Neurological function of rat models was evaluated using Zea Longa’s method. Permeability of the blood-brain barrier was assessed by Evans blue leakage. Infarct volume and brain edema were evaluated using 2,3,5-triphenyltetrazolium chloride staining. Expression of matrix metalloproteinase-9 and claudin-5 mRNA was determined by real-time quantitative reverse transcription-polymerase chain reaction. Expression of matrix metalloproteinase-9 and claudin-5 protein was measured by western blot assay. The number of matrix metalloproteinase-9- and claudin-5-positive cells was analyzed using immunohistochemistry. Our results showed that remote ischemic postconditioning alleviated disruption of the blood-brain barrier, reduced infarct volume and edema, decreased expression of matrix metalloproteinase-9 mRNA and protein and the number of positive cells, increased expression of claudin-5 mRNA and protein and the number of positive cells, and remarkably improved neurological function. These findings confirm that by suppressing expression of matrix metalloproteinase-9 and claudin-5 induced by acute ischemia/reperfusion, remote ischemic postconditioning reduces blood-brain barrier injury, mitigates ischemic injury, and exerts protective effects on the brain.

The role of aquaporin-4 in synaptic plasticity, memory and disease

Since the discovery of aquaporins, it has become clear that the various mammalian aquaporins play critical physiological roles in water and ion balance in multiple tissues. Aquaporin-4 (AQP4), the principal aquaporin expressed in the central nervous system (CNS, brain and spinal cord), has been shown to mediate CNS water homeostasis. In this review, we summarize new and exciting studies indicating that AQP4 also plays critical and unanticipated roles in synaptic plasticity and memory formation. Next, we consider the role of AQP4 in Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), Parkinson's disease (PD), multiple sclerosis (MS), neuromyelitis optica (NMO), epilepsy, traumatic brain injury (TBI), and stroke. Each of these conditions involves changes in AQP4 expression and/or distribution that may be functionally relevant to disease physiology. Insofar as AQP4 is exclusively expressed on astrocytes, these data provide new evidence of "astrocytopathy" in the etiology of diverse neurological diseases.

Hypertonic saline alleviates experimentally induced cerebral oedema through suppression of vascular endothelial growth factor and its receptor VEGFR2 expression in astrocytes

BACKGROUND

Cerebral oedema is closely related to the permeability of blood-brain barrier, vascular endothelial growth factor (VEGF) and its receptor vascular endothelial growth factor receptor 2 (VEGFR2) all of which are important blood-brain barrier (BBB) permeability regulatory factors. Zonula occludens 1 (ZO-1) and claudin-5 are also the key components of BBB. Hypertonic saline is widely used to alleviate cerebral oedema. This study aimed to explore the possible mechanisms underlying hypertonic saline that ameliorates cerebral oedema effectively.

METHODS

Middle cerebral artery occlusion (MCAO) model in Sprague-Dawley (SD) rats and of oxygen-glucose deprivation model in primary astrocytes were used in this study. The brain water content (BWC) was used to assess the effect of 10 % HS on cerebral oedema. The assessment of Evans blue (EB) extravasation was performed to evaluate the protective effect of 10 % HS on blood-brain barrier. The quantification of VEGF, VEGFR2, ZO-1 and claudin-5 was used to illustrate the mechanism of 10 % HS ameliorating cerebral oedema.

RESULTS

BWC was analysed by wet-to-dry ratios in the ischemic hemisphere of SD rats; it was significantly decreased after 10 % HS treatment (P < 0.05). We also investigated the blood-brain barrier protective effect by 10 % HS which reduced EB extravasation effectively in the peri-ischemic brain tissue. In parallel to the above notably at 24 h following MCAO, mRNA and protein expression of VEGF and VEGFR2 in the peri-ischemic brain tissue was down-regulated after 10 % HS treatment (P < 0.05). Along with this, in vitro studies showed increased VEGF and VEGFR2 mRNA and protein expression in primary astrocytes under hypoxic condition (P < 0.05), but it was suppressed after HS treatment (P < 0.05). In addition, HS inhibited the down-regulation of ZO-1, claudin-5 effectively.

CONCLUSIONS

The results suggest that 10 % HS could alleviate cerebral oedema possibly through reducing the ischemia induced BBB permeability as a consequence of inhibiting VEGF-VEGFR2-mediated down-regulation of ZO-1, claudin-5.

Hyperbaric oxygen preconditioning ameliorates blood-brain barrier damage induced by hypoxia through modulation of tight junction proteins in an in vitro model

Aim

To explore the effects of hyperbaric oxygen preconditioning (HBOP) on the permeability of blood-brain barrier (BBB) and expression of tight junction proteins under hypoxic conditions in vitro.

Methods

A BBB in vitro model was constructed using the hCMEC/D3 cell line and used when its trans-endothelial electrical resistance (TEER) reached 80-120 Ω · cm² (tested by Millicell-Electrical Resistance System). The cells were randomly divided into the control group cultured under normal conditions, the group cultured under hypoxic conditions (2%O₂) for 24 h (hypoxia group), and the group first subjected to HBOP for 2 h and then to hypoxia (HBOP group). Occludin and ZO-1 expression were analyzed by immunofluorescence assay.

Results

Normal hCMEC/D3 was spindle-shaped and tightly integrated. TEER was significantly reduced in the hypoxia (P = 0.001) and HBOP group (P = 0.014) compared to control group, with a greater decrease in the hypoxia group. Occludin membranous expression was significantly decreased in the hypoxia group (P = 0.001) compared to the control group, but there was no change in the HBOP group. ZO-1 membranous expression was significantly decreased (P = 0.002) and cytoplasmic expression was significantly increased (P = 0.001) in the hypoxia group compared to the control group, although overall expression levels did not change. In the HBOP group, there was no significant change in ZO-1 expression compared to the control group.

Conclusion

Hyperbaric oxygen preconditioning protected the integrity of BBB in an in vitro model through modulation of occludin and ZO-1 expression under hypoxic conditions.

Progress in AQP Research and New Developments in Therapeutic Approaches to Ischemic and Hemorrhagic Stroke

Cerebral edema often manifests after the development of cerebrovascular disease, particularly in the case of stroke, both ischemic and hemorrhagic. Without clinical intervention, the influx of water into brain tissues leads to increased intracranial pressure, cerebral herniation, and ultimately death. Strategies to manage the development of edema constitute a major unmet therapeutic need. However, despite its major clinical significance, the mechanisms underlying cerebral water transport and edema formation remain elusive. Aquaporins (AQPs) are a class of water channel proteins which have been implicated in the regulation of water homeostasis and cerebral edema formation, and thus represent a promising target for alleviating stroke-induced cerebral edema. This review examines the significance of relevant AQPs in stroke injury and subsequently explores neuroprotective strategies aimed at modulating AQP expression, with a particular focus on AQP4, the most abundant AQP in the central nervous system.

The effect of propofol on the expression of rabbit ischemia reperfusion injury-related proteins

To investigate the effect of propofol on the expression of rabbit ischemia-reperfusion injury-related proteins and the mechanism involved. Thirty healthy adult New Zealand rabbit were selected. After establishment of liver I/R model, the rabbits were divided into group A (sham operation group), group B (control group using saline), and group C (propofol group) with ten rabbits in each group. The total protein concentration, differentially expressed protein spots and the difference of apoptotic proteins expression levels among the three groups were compared. The total protein concentrations in group A, B, and C were 0.778, 0.835, and 0.765 μg/μl, respectively, and the protein concentration in group B was significantly higher than group A and C (p < 0.05), with no significant difference between group A and C (p > 0.05); results analyzed by PDQuest software showed that the average number of protein spots and matching ratio had no significant difference among the three groups (p > 0.05); MALDI-TOF-MS mass spectrometry identified 16 differentially expressed protein spots; the numbers of Caspase-3 positive cells in group B and C were significantly higher than those in group A, and the numbers of Bcl-2 and Bax positive cells in group B and C were significantly lower than those in group A (p < 0.05); the number of Capase-3 positive cells in group C was significantly higher than those in group B, and the number of Bcl-2 positive cells in group C was significantly lower than those in group B (p < 0.05). The numbers of Bax positive cells had no significant difference between group B and C (p > 0.05); densities of Caspase-3, Bcl-2 and Bax in group B and C were significantly higher than those in group A (p < 0.05); Western blotting results from the comparison of the number of positive cells between group B and C was in accordance to the result obtained from immunohistochemistry. After I/R injury in rabbit, there was deregulation of various proteins such as Caspase-3, Bcl-2 and Bax, which was an important factor contributing to liver injury even systematic disease. Propofol could regulate the expression of I/R injury-related proteins and inhibit the attack of free radical to liver, having a remarkable advantage in preventing I/R injury and controlling the development of I/R injury. This study provides an effective theoretical basis for the prevention and treatment of I/R injury.

Changes in Rat Brain MicroRNA Expression Profiles Following Sevoflurane and Propofol Anesthesia

BACKGROUND

Sevoflurane and propofol are widely used anesthetics for surgery. Studies on the mechanisms of general anesthesia have focused on changes in protein expression properties and membrane lipid. MicroRNAs (miRNAs) regulate neural function by altering protein expression. We hypothesize that sevoflurane and propofol affect miRNA expression profiles in the brain, expect to understand the mechanism of anesthetic agents.

METHODS

Rats were randomly assigned to a 2% sevoflurane group, 600 μg·kg - 1·min - 1 propofol group, and a control group without anesthesia (n = 4, respectively). Treatment group was under anesthesia for 6 h, and all rats breathed spontaneously with continuous monitoring of respiration and blood gases. Changes in rat cortex miRNA expression profiles were analyzed by miRNA microarrays and validated by quantitative real-time polymerase chain reaction (qRT-PCR). Differential expression of miRNA using qRT-PCR among the control, sevoflurane, and propofol groups were compared using one-way analysis of variance (ANOVA).

RESULTS

Of 677 preloaded rat miRNAs, the microarray detected the expression of 277 miRNAs in rat cortex (40.9%), of which 9 were regulated by propofol and (or) sevoflurane. Expression levels of three miRNAs (rno-miR-339-3p, rno-miR-448, rno-miR-466b-1FNx01) were significantly increased following sevoflurane and six (rno-miR-339-3p, rno-miR-347, rno-miR-378FNx01, rno-miR-412FNx01, rno-miR-702-3p, and rno-miR-7a-2FNx01) following propofol. Three miRNAs (rno-miR-466b-1FNx01, rno-miR-3584-5p and rno-miR-702-3p) were differentially expressed by the two anesthetic treatment groups.

CONCLUSIONS

Sevoflurane and propofol anesthesia induced distinct changes in brain miRNA expression patterns, suggesting differential regulation of protein expression. Determining the targets of these differentially expressed miRNAs may help reveal both the common and agent-specific actions of anesthetics on neurological and physiological function.

Bone marrow stromal cells inhibits HMGB1-mediated inflammation after stroke in type 2 diabetic rats

High-mobility group box 1 (HMGB1), a ligand of receptor for advanced glycation endproducts (RAGE), functions as a proinflammatory factor. It is mainly involved in inflammatory activation and contributes to the initiation and progression of stroke. By using a model of transient middle cerebral artery occlusion (MCAo) in type 2 diabetic rats, we investigated the changes of pro-inflammation mediators, blood-brain barrier (BBB) leakage and functional outcome after stroke. Type 2 diabetic rats did not show an increased lesion volume, but exhibited significantly increased expression of HMGB1 and RAGE, BBB leakage, as well as decreased functional outcome after stroke compared with control rats. Injection of bone marrow stromal cells (BMSCs) into type 2 diabetic rats significantly reduced the expression of HMGB1 and RAGE, attenuated BBB leakage, and improved functional outcome after stroke. BMSCs-treated type 2 diabetic rats inhibited inflammation and improved functional outcome after stroke. Furthermore, in vitro data support the hypothesis that BMSCs-induced reduction of HMGB1 and RAGE in T2DM-MCAo rats contributed to attenuated inflammatory response in the ischemic brain, which may lead to the beneficial effects of BMSCs treatment. Further investigation of BMSCs treatment in type 2 diabetic stroke is warranted.

Propofol Suppressed Hypoxia/Reoxygenation-Induced Apoptosis in HBVSMC by Regulation of the Expression of Bcl-2, Bax, Caspase3, Kir6.1, and p-JNK

Recent studies have found that propofol may protect brain from cerebral ischemic-reperfusion injury. However, the underlying mechanism remains unclear. The effects of propofol were evaluated in HBVSMC after hypoxia/reoxygenation (H/R). Cell viability and levels of SOD, LDH, and MDA were measured. Apoptosis was detected by flow cytometry. The levels of Bax, Bcl-2, Caspase3, Sur2b, Kir6.1, JNK, p-JNK, mTOR, and p-mTOR proteins were measured by western blotting. H/R decreased cell viability and SOD activity and increased LDH leakage and MDA content in HBVSMC, all of which were significantly reversed by propofol. Propofol suppressed the levels of H/R-induced apoptosis. The expression of Bcl-2 and p-mTOR was significantly downregulated and the expression levels of Bax, Caspase3, Kir6.1, and p-JNK were upregulated following H/R injury. The ratio of p-JNK/JNK was increased; however, that of p-mTOR/mTOR decreased correspondingly. The effects on the expression of these proteins were reversed by propofol treatment. SP600125 enhanced and Everolimus attenuated the effect of propofol. These findings suggested that the protective effect of propofol against H/R injury in the HBVSMC was through the inhibition of apoptosis by inducing the expression of Bcl-2 and p-mTOR as well as inhibiting the expression levels of Bax, Caspase3, Kir6.1, and p-JNK.

Propofol Pretreatment Fails to Provide Neuroprotection Following a Surgically Induced Brain Injury Rat Model

Neurosurgical procedures are associated with unintentional damage to the brain during surgery, known as surgically induced brain injuries (SBI), which have been implicated in orchestrating structural and neurobehavioral deterioration. Propofol, an established hypnotic anesthetic agent, has been shown to ameliorate neuronal injury when given after injury in a number of experimental brain studies. We tested the hypothesis that propofol pretreatment confers neuroprotection against SBI and will reduce cerebral edema formation and neurobehavioral deficits in our rat population. Sprague-Dawley rats were treated with low- and high-dose propofol 30 min before SBI. At 24 h post injury, brain water content and neurobehavioral assessment was conducted based on previously established models. In vehicle-treated rats, SBI resulted in significant cerebral edema and higher neurological deficit scores compared with sham-operated rats. Low- or high-dose propofol therapy neither reduced cerebral edema nor improved neurologic function. The results suggest that propofol pretreatment fails to provide neuroprotection in SBI rats. However, it is possible that a SBI model with less magnitude of injury or that propofol re-dosing, given the short-acting pharmacokinetic property of propofol, may be needed to provide definitive conclusions.

Effects of propofol and sevoflurane on aquaporin-4 and aquaporin-9 expression in patients performed gliomas resection

Post-operative cerebral edema is a threat for patients performed gliomas resection. Some studies have shown that general anesthesia drugs, such as, propofol had neuroprotective effect. Aquaporin-4 (AQP4) and Aquaporin-9 (AQP9) play an important role in maintaining brain water homeostasis under various conditions. The aim of this study was to compare the effect of propofol or sevoflurane on expression of AQP4 and AQP9 in patients performed gliomas resection. 30 patients performed gliomas resection were included in this study. The patients were randomly divided into two groups: propofol group and sevoflurane group. Fresh human gliomas specimens were obtained and hematoxylin eosin (HE) staining, immunohistochemical staining and Western blot analysis were used for observation of the expression of AQP4 and AQP9. The immunohistochemical staining of the sections showed that the percentage of AQP4 positive cells in the propofol group (14.3±4.61%) was significantly lower than that in sevoflurane group (37.3±10.01%) (n=15, P<0.05). There was no significant difference in the percentage of AQP9 positive cells in propofol group and sevoflurane group (25.8±2.67 versus 28.1±7.81%, n=15, P>0.05). Western blot analysis confirmed the immunohistochemistry results. AQP4 protein level in propofol group was significantly lower than that in sevoflurane group (1.4±0.13 versus 1.7±0.12, P<0.05). Western blot analysis did not show any difference of expression of AQP9 protein between the propofol group and sevoflurane group (2.0±0.13 versus 2.1±0.13, P>0.05, n=6). AQP4 expression was lower in patients of propofol group than that in sevoflurane group. Our results suggested that propofol could inhibit the expression of AQP4.

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.

Effect of isoflurane post-treatment on tPA-exaggerated brain injury in a rat ischemic stroke model

Background

Intravenous tissue-type plasminogen activator (tPA) is recognized as the standard treatment for ischemic stroke. However, its narrow therapeutic window and association with an increased risk of intracranial hemorrhage have required caution when used. In this context, several approaches are required to deal with the shortcomings of such a double-edged drug. Anesthetics are known to protect against ischemic reperfusion injury, and their protective role in ischemic post-conditioning is crucial for reducing ischemia-related injury. The aim of this study was to assess the effect of isoflurane post-treatment on intracranial hemorrhage and cerebral infarction after tPA treatment for transient cerebral ischemia.

Methods

Cerebral ischemia was modeled in male Sprague-Dawley rats (n = 32) by occluding the right middle cerebral artery for 1 h, followed by intravenous tPA administration. Rats were randomly divided into control and isoflurane post-treatment group, and isoflurane post-treatment group was post-treated by administering 1.5% isoflurane for 1 h from the start of reperfusion. Twenty-four h after reperfusion, neurobehavioral changes were assessed. The extent of cerebral infarction and intracranial hemorrhage were also assessed by quantification of infarction volume and cerebral hemoglobin concentration from brain tissue, respectively.

Results

Neurobehavioral testing showed better functional outcomes in the isoflurane post-treatment group than the control group. The extent of cerebral infarction and intracranial hemorrhage were both reduced in isoflurane post-treatment group compared to control group.

Conclusions

Isoflurane post-treatment may mitigate infarction volume and intracranial hemorrhage in tPA-exaggerated brain injury. Our findings provide an encouraging novel approach for enhancing clinical outcomes in tPA-exaggerated brain injury.

Protective Effects and Mechanisms of Salvianolic Acid B Against H₂O₂-Induced Injury in Induced Pluripotent Stem Cell-Derived Neural Stem Cells

Induced pluripotent stem cells (iPSCs) have the potential to differentiate into neural lineages. Salvianolic acid B (Sal B) is a commonly used, traditional Chinese medicine for enhancing neuroprotective effects, and has antioxidant, anti-inflammatory, and antiapoptotic properties. Here, we explore the potential mechanism of Sal B in protecting iPSC-derived neural stem cells (NSCs) against H2O2-induced injury. iPSCs were induced into NSCs, iPSC-derived NSCs were treated with 50 μM Sal B for 24.5 h and 500 μM H2O2 for 24 h. The resulting effects were examined by flow cytometry analysis, quantitative reverse-transcription polymerase chain reaction, and western blotting. Upon H2O2 exposure, Sal B significantly promoted cell viability and stabilization of the mitochondrial membrane potential. Sal B also visibly decreased the cell apoptotic ratio. In addition, Sal B markedly reduced expression of matrix metalloproteinase (MMP)-2 and -9, and phosphospecific signal transducer and activator of transcription 3 (p-STAT3), and increased the level of tissue inhibitor of metalloproteinase (TIMP)-2 in iPSC-derived NSCs induced by H2O2. These results suggest that Sal B protects iPSC-derived NSCs against H2O2-induced oxidative stress. The mechanisms of this stress tolerance may be attributed to modulation of the MMP/TIMP system and inhibition of the STAT3 signaling pathway.

Pharmacologic Treatment Reduces Pressure Times Time Dose and Relative Duration of Intracranial Hypertension

INTRODUCTION

Past work has shown the importance of the "pressure times time dose" (PTD) of intracranial hypertension (intracranial pressure [ICP] > 19 mm Hg) in predicting outcome after severe traumatic brain injury. We used automated data collection to measure the effect of common medications on the duration and dose of intracranial hypertension.

METHODS

Patients >17 years old, admitted and requiring ICP monitoring between 2008 and 2010 at a single, large urban tertiary care facility, were retrospectively enrolled. Timing and dose of ICP-directed therapy were recorded from paper and electronic medical records. The ICP data were collected automatically at 6-second intervals and averaged over 5 minutes. The percentage of time of intracranial hypertension (PTI) and PTD (mm Hg h) were calculated.

RESULTS

A total of 98 patients with 664 treatment instances were identified. Baseline PTD ranged from 27 (before administration of propofol and fentanyl) to 150 mm Hg h (before mannitol). A "small" dose of hypertonic saline (HTS; ≤250 mL 3%) reduced PTD by 38% in the first hour and 37% in the second hour and reduced the time with ICP >19 by 38% and 39% after 1 and 2 hours, respectively. A "large" dose of HTS reduced PTD by 40% in the first hour and 63% in the second (PTI reduction of 36% and 50%, respectively). An increased dose of propofol or fentanyl infusion failed to decrease PTD but reduced PTI between 14% (propofol alone) and 30% (combined increase in propofol and fentanyl, after 2 hours). Barbiturates failed to decrease PTD but decreased PTI by 30% up to 2 hours after administration. All reductions reported are significantly changed from baseline, P < .05.

CONCLUSION

Baseline PTD values before drug administration reflects varied patient criticality, with much higher values seen before the use of mannitol or barbiturates. Treatment with HTS reduced PTD and PTI burden significantly more than escalation of sedation or pain management, and this effect remained significant at 2 hours after administration.

Metallothionein-II inhibits lipid peroxidation and improves functional recovery after transient brain ischemia and reperfusion in rats

After transient cerebral ischemia and reperfusion (I/R), damaging mechanisms, such as excitotoxicity and oxidative stress, lead to irreversible neurological deficits. The induction of metallothionein-II (MT-II) protein is an endogenous mechanism after I/R. Our aim was to evaluate the neuroprotective effect of MT-II after I/R in rats. Male Wistar rats were transiently occluded at the middle cerebral artery for 2 h, followed by reperfusion. Rats received either MT (10 μg per rat i.p.) or vehicle after ischemia. Lipid peroxidation (LP) was measured 22 h after reperfusion in frontal cortex and hippocampus; also, neurological deficit was evaluated after ischemia, using the Longa scoring scale. Infarction area was analyzed 72 hours after ischemia. Results showed increased LP in frontal cortex (30.7%) and hippocampus (26.4%), as compared to control group; this effect was fully reversed by MT treatment. Likewise, we also observed a diminished neurological deficit assessed by the Longa scale in those animals treated with MT compared to control group values. The MT-treated group showed a significant (P < 0.05) reduction of 39.9% in the infarction area, only at the level of hippocampus, as compared to control group. Results suggest that MT-II may be a novel neuroprotective treatment to prevent ischemia injury.