Sulfonylurea receptor 1 contributes to the astrocyte swelling and brain edema in acute liver failure

Long-Term Sequelae of COVID-19 in Experimental Mice

We recently reported acute COVID-19 symptoms, clinical status, weight loss, multi-organ pathological changes, and animal death in a murine hepatitis virus-1 (MHV-1) coronavirus mouse model of COVID-19, which were similar to that observed in humans with COVID-19. We further examined long-term (12 months post-infection) sequelae of COVID-19 in these mice. Congested blood vessels, perivascular cavitation, pericellular halos, vacuolation of neuropils, pyknotic nuclei, acute eosinophilic necrosis, necrotic neurons with fragmented nuclei, and vacuolation were observed in the brain cortex 12 months post-MHV-1 infection. These changes were associated with increased reactive astrocytes and microglia, hyperphosphorylated TDP-43 and tau, and a decrease in synaptic protein synaptophysin-1, suggesting the possible long-term impact of SARS-CoV-2 infection on defective neuronal integrity. The lungs showed severe inflammation, bronchiolar airway wall thickening due to fibrotic remodeling, bronchioles with increased numbers of goblet cells in the epithelial lining, and bronchiole walls with increased numbers of inflammatory cells. Hearts showed severe interstitial edema, vascular congestion and dilation, nucleated red blood cells (RBCs), RBCs infiltrating between degenerative myocardial fibers, inflammatory cells and apoptotic bodies and acute myocyte necrosis, hypertrophy, and fibrosis. Long-term changes in the liver and kidney were less severe than those observed in the acute phase. Noteworthy, the treatment of infected mice with a small molecule synthetic peptide which prevents the binding of spike protein to its respective receptors significantly attenuated disease progression, as well as the pathological changes observed post-long-term infection. Collectively, these findings suggest that COVID-19 may result in long-term, irreversible changes predominantly in the brain, lung, and heart.

Mechanism of Multi-Organ Injury in Experimental COVID-19 and Its Inhibition by a Small Molecule Peptide

Severe disease from SARS-CoV-2 infection often progresses to multi-organ failure and results in an increased mortality rate amongst these patients. However, underlying mechanisms of SARS- CoV-2-induced multi-organ failure and subsequent death are still largely unknown. Cytokine storm, increased levels of inflammatory mediators, endothelial dysfunction, coagulation abnormalities, and infiltration of inflammatory cells into the organs contribute to the pathogenesis of COVID-19. One potential consequence of immune/inflammatory events is the acute progression of generalized edema, which may lead to death. We, therefore, examined the involvement of water channels in the development of edema in multiple organs and their contribution to organ dysfunction in a Murine Hepatitis Virus-1 (MHV-1) mouse model of COVID-19. Using this model, we recently reported multi-organ pathological abnormalities and animal death similar to that reported in humans with SARS-CoV-2 infection. We now identified an alteration in protein levels of AQPs 1, 4, 5, and 8 and associated oxidative stress, along with various degrees of tissue edema in multiple organs, which correlate well with animal survival post-MHV-1 infection. Furthermore, our newly created drug (a 15 amino acid synthetic peptide, known as SPIKENET) that was designed to prevent the binding of spike glycoproteins with their receptor(s), angiotensin- converting enzyme 2 (ACE2), and carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) (SARS-CoV-2 and MHV-1, respectively), ameliorated animal death and reversed altered levels of AQPs and oxidative stress post-MHV-1 infection. Collectively, our findings suggest the possible involvement of altered aquaporins and the subsequent edema, likely mediated by the virus-induced inflammatory and oxidative stress response, in the pathogenesis of COVID- 19 and the potential of SPIKENET as a therapeutic option.

Serum sulfonylurea receptor-1 as a biomarker of clinical severity and prognosis in patients with traumatic brain injury

BACKGROUND

Sulfonylurea receptor-1 (Sur1) plays an important role in acute brain injury. We determine whether serum Sur1 concentrations are associated with traumatic severity and clinical outcome after traumatic brain injury (TBI).

METHODS

Serum Sur1 concentrations were measured in 100 healthy controls and 138 patients with moderate to severe TBI. Glasgow coma scale (GCS) and Rotterdam computed tomography (CT) classification were recorded to assess traumatic severity. Glasgow outcome scale (GOS) score of 1-3 at posttraumatic 3 months was defined as an unfavorable outcome.

RESULTS

Serum Sur1 concentrations were markedly higher in patients than in controls. Serum Sur1 concentrations of patients were highly correlated with GCS score, Rotterdam CT classification and GOS score. Patients with unfavorable outcome displayed markedly higher serum Sur1 concentrations than those presenting with favorable outcome. Under receiver operating characteristic curve, serum Sur1 concentrations significantly distinguished patients at risk of unfavorable outcome. Serum Sur1 emerged as an independent predictor for unfavorable outcome.

CONCLUSIONS

Rising serum Sur1 concentrations are highly correlated with traumatic severity and are independently associated with poor prognosis after TBI, indicating that serum Sur1 may have the potential to be a useful prognostic biomarker of TBI.

Sulfonylurea Receptor 1 in Central Nervous System Injury: An Updated Review

Sulfonylurea receptor 1 (SUR1) is a member of the adenosine triphosphate (ATP)-binding cassette (ABC) protein superfamily, encoded by Abcc8, and is recognized as a key mediator of central nervous system (CNS) cellular swelling via the transient receptor potential melastatin 4 (TRPM4) channel. Discovered approximately 20 years ago, this channel is normally absent in the CNS but is transcriptionally upregulated after CNS injury. A comprehensive review on the pathophysiology and role of SUR1 in the CNS was published in 2012. Since then, the breadth and depth of understanding of the involvement of this channel in secondary injury has undergone exponential growth: SUR1-TRPM4 inhibition has been shown to decrease cerebral edema and hemorrhage progression in multiple preclinical models as well as in early clinical studies across a range of CNS diseases including ischemic stroke, traumatic brain injury, cardiac arrest, subarachnoid hemorrhage, spinal cord injury, intracerebral hemorrhage, multiple sclerosis, encephalitis, neuromalignancies, pain, liver failure, status epilepticus, retinopathies and HIV-associated neurocognitive disorder. Given these substantial developments, combined with the timeliness of ongoing clinical trials of SUR1 inhibition, now, another decade later, we review advances pertaining to SUR1-TRPM4 pathobiology in this spectrum of CNS disease—providing an overview of the journey from patch-clamp experiments to phase III trials.

Emerging therapeutic targets for cerebral edema

INTRODUCTION

Cerebral edema is a key contributor to death and disability in several forms of brain injury. Current treatment options are limited, reactive, and associated with significant morbidity. Targeted therapies are emerging based on a growing understanding of the molecular underpinnings of cerebral edema.

AREAS COVERED

We review the pathophysiology and relationships between different cerebral edema subtypes to provide a foundation for emerging therapies. Mechanisms for promising molecular targets are discussed, with an emphasis on those advancing in clinical trials, including ion and water channels (AQP4, SUR1-TRPM4) and other proteins/lipids involved in edema signaling pathways (AVP, COX2, VEGF, and S1P). Research on novel treatment modalities for cerebral edema [including recombinant proteins and gene therapies] is presented and finally, insights on reducing secondary injury and improving clinical outcome are offered.

EXPERT OPINION

Targeted molecular strategies to minimize or prevent cerebral edema are promising. Inhibition of SUR1-TRPM4 (glyburide/glibenclamide) and VEGF (bevacizumab) are currently closest to translation based on advances in clinical trials. However, the latter, tested in glioblastoma multiforme, has not demonstrated survival benefit. Research on recombinant proteins and gene therapies for cerebral edema is in its infancy, but early results are encouraging. These newer modalities may facilitate our understanding of the pathobiology underlying cerebral edema.

Evaluation of the protective effect of curcumin on encephalopathy caused by intrahepatic and extrahepatic damage in male rats

Objective(s):

Along with increased intracranial pressure (ICP) and brain damage, brain edema is the most common cause of death in patients with hepatic encephalopathy. Curcumin can pass the blood-brain barrier and possesses anti-inflammatory and anti-oxidant properties. This study focuses on the curcumin protective effect on intrahepatic and extrahepatic damage in the brain.

Materials and Methods:

One hundred and forty-four male Albino N-Mary rats were randomly divided into 2 main groups: intrahepatic injury group and extrahepatic cholestasis group. In intra-hepatic injury group intrahepatic damage was induced by intraperitoneal (IP) injection of acetaminophen (500 mg/kg) [19] and included four subgroups: 1. Sham, 2. Acetaminophen (APAP), 3. Normal saline (Veh) which was used as curcumin solvent, and 4. Curcumin (CMN). In extrahepatic cholestasis group intrahepatic damage was caused by common bile duct litigation (BDL) and included four subgroups: 1. Sham, 2. BDL, 3. Vehicle (Veh), and 4. Curcumin (CMN). In both groups, 72 hr after induction of cholestasis, brain water content, blood-brain barrier permeability, serum ammonia, and histopathological indicators were examined and ICP was measured every 24 hr for three days.

Results:

The results showed that curcumin reduced brain edema, ICP, serum ammonia, and blood-brain barrier permeability after extrahepatic and intrahepatic damage. The maximum effect of curcumin on ICP was observed 72 hr after the injection.

Conclusion:

According to our findings, it seems that curcumin is an effective therapeutic intervention for treating encephalopathy caused by extrahepatic and intrahepatic damage.

The neurogliovascular unit in hepatic encephalopathy

Hepatic encephalopathy (HE) is a neurological complication of hepatic dysfunction and portosystemic shunting. It is highly prevalent in patients with cirrhosis and is associated with poor outcomes. New insights into the role of peripheral origins in HE have led to the development of innovative treatment strategies like faecal microbiota transplantation. However, this broadening of view has not been applied fully to perturbations in the central nervous system. The old paradigm that HE is the clinical manifestation of ammonia-induced astrocyte dysfunction and its secondary neuronal consequences requires updating. In this review, we will use the holistic concept of the neurogliovascular unit to describe central nervous system disturbances in HE, an approach that has proven instrumental in other neurological disorders. We will describe HE as a global dysfunction of the neurogliovascular unit, where blood flow and nutrient supply to the brain, as well as the function of the blood-brain barrier, are impaired. This leads to an accumulation of neurotoxic substances, chief among them ammonia and inflammatory mediators, causing dysfunction of astrocytes and microglia. Finally, glymphatic dysfunction impairs the clearance of these neurotoxins, further aggravating their effect on the brain. Taking a broader view of central nervous system alterations in liver disease could serve as the basis for further research into the specific brain pathophysiology of HE, as well as the development of therapeutic strategies specifically aimed at counteracting the often irreversible central nervous system damage seen in these patients.

Drug-induced-acute liver failure: A critical appraisal of the thioacetamide model for the study of hepatic encephalopathy

Hepatic encephalopathy (HE) following acute and chronic liver failure is defined as a complex of neuropsychiatric abnormalities, such as discrete personal changes, sleep disorder, forgetfulness, confusion, and decreasing the level of consciousness to coma. The use and design of suitable animal models that represent clinical features and pathological changes of HE are valuable to map the molecular mechanisms that result in HE. Among different types of animal models, thioacetamide (TAA) has been used extensively for the induction of acute liver injury and HE. This agent is not directly hepatotoxic but its metabolites induce liver injury through the induction of oxidative stress and produce systemic inflammation similar to that seen in acute HE patients. In this short review article, we shortly review the most important pathological findings in animal models of acute HE following the administration of TAA.

Potential Therapies for Cerebral Edema After Ischemic Stroke: A Mini Review

Stroke is the leading cause of global mortality and disability. Cerebral edema and intracranial hypertension are common complications of cerebral infarction and the major causes of mortality. The formation of cerebral edema includes three stages (cytotoxic edema, ionic edema, and vasogenic edema), which involve multiple proteins and ion channels. A range of therapeutic agents that successfully target cerebral edema have been developed in animal studies, some of which have been assessed in clinical trials. Herein, we review the mechanisms of cerebral edema and the research progress of anti-edema therapies for use after ischemic stroke.

An update on the pharmacological management and prevention of cerebral edema: current therapeutic strategies

Introduction: Cerebral edema is a common complication of multiple neurological diseases and is a strong predictor of outcome, especially in traumatic brain injury and large hemispheric infarction.Areas Covered: Traditional and current treatments of cerebral edema include treatment with osmotherapy or decompressive craniectomy at the time of clinical deterioration. The authors discuss preclinical and clinical models of a variety of neurological disease states that have identified receptors, ion transporters, and channels involved in the development of cerebral edema as well as modulation of these receptors with promising agents.Expert opinion: Further study is needed on the safety and efficacy of the agents discussed. IV glibenclamide has shown promise in preclinical and clinical trials of cerebral edema in large hemispheric infarct and traumatic brain injury. Consideration of underlying pathophysiology and pharmacodynamics is vital, as the synergistic use of agents has the potential to drastically mitigate cerebral edema and secondary brain injury thusly transforming our treatment paradigms.

Xiaochaihutang Improves the Cortical Astrocyte Edema in Thioacetamide-Induced Rat Acute Hepatic Encephalopathy by Activating NRF2 Pathway

Oxidative stress induced by high ammonia, which leads to astrocyte edema, is the key to acute hepatic encephalopathy (AHE). Nuclear factor erythroid 2-related factor 2 (NRF2) has been implicated in oxidative stress, but the mechanism of NRF2 against ammonia-induced astrocytes edema has not been fully studied. We confirmed that the NRF2 pathway is related to brain edema caused by AHE and found that Xiaochaihutang (XCHT) could effectively activate the NRF2 pathway to treat AHE. The model of AHE was established with thioacetamide (TAA) in rats. Rat behaviors were observed, brain water content, blood ammonia levels, glutamine synthetase (GS), malondialdehyde (MDA), and total superoxide dismutase (T-SOD) were determined after XCHT treatment. Furthermore, the expression of NRF2 pathway proteins and mRNA, glial fibrillary acidic protein (GFAP) and aquaporins 4 (AQP4) were examined. In order to determine whether XCHT has a direct effect on cerebral edema caused by high ammonia, we examined the effect of XCHT compound serum on cortical astrocytes in the presence of ammonia, through microscopic observation and immunofluorescence (IF). Results showed that AHE induced by TAA changed the behavior of the rats, and increased brain water content, blood ammonia levels, GS and MDA content meanwhile decreasing T-SOD, but these symptoms were improved by treatment with XCHT. XCHT protected brain edema by activating the NRF2 pathway and increasing the expression of downstream proteins and genes. Astrocytes treated with 5 mM ammonia also showed an increase in the AQP4 protein expression but a decrease in XCHT compound serum and ammonia-induced cell edema groups. This study demonstrates that the NRF2 pathway is involved in the brain edema in AHE, and XCHT may represent a useful prescription for the treatment of AHE.

Cerebral edema and liver disease: Classic perspectives and contemporary hypotheses on mechanism

Liver disease is a growing public health concern. Hepatic encephalopathy, the syndrome of brain dysfunction secondary to liver disease, is a frequent complication of both acute and chronic liver disease and cerebral edema (CE) is a key feature. While altered ammonia metabolism is a key contributor to hepatic encephalopathy and CE in liver disease, there is a growing appreciation that additional mechanisms contribute to CE. In this review we will begin by presenting three classic perspectives that form a foundation for a discussion of CE in liver disease: 1) CE is unique to acute liver failure, 2) CE in liver disease is only cytotoxic, and 3) CE in liver disease is primarily an osmotically mediated consequence of ammonia and glutamine metabolism. We will present each classic perspective along with more recent observations that call in to question that classic perspective. After highlighting these areas of debate, we will explore the leading contemporary mechanisms hypothesized to contribute to CE during liver disease.

Role of Sulfonylurea Receptor 1 and Glibenclamide in Traumatic Brain Injury: A Review of the Evidence

Cerebral edema and contusion expansion are major determinants of morbidity and mortality after TBI. Current treatment options are reactive, suboptimal and associated with significant side effects. First discovered in models of focal cerebral ischemia, there is increasing evidence that the sulfonylurea receptor 1 (SUR1)-Transient receptor potential melastatin 4 (TRPM4) channel plays a key role in these critical secondary injury processes after TBI. Targeted SUR1-TRPM4 channel inhibition with glibenclamide has been shown to reduce edema and progression of hemorrhage, particularly in preclinical models of contusional TBI. Results from small clinical trials evaluating glibenclamide in TBI have been encouraging. A Phase-2 study evaluating the safety and efficacy of intravenous glibenclamide (BIIB093) in brain contusion is actively enrolling subjects. In this comprehensive narrative review, we summarize the molecular basis of SUR1-TRPM4 related pathology and discuss TBI-specific expression patterns, biomarker potential, genetic variation, preclinical experiments, and clinical studies evaluating the utility of treatment with glibenclamide in this disease.

BIIB093 (IV glibenclamide): an investigational compound for the prevention and treatment of severe cerebral edema

Introduction: Brain swelling due to edema formation is a major cause of neurological deterioration and death in patients with large hemispheric infarction (LHI) and severe traumatic brain injury (TBI), especially contusion-TBI. Preclinical studies have shown that SUR1-TRPM4 channels play a critical role in edema formation and brain swelling in LHI and TBI. Glibenclamide, a sulfonylurea drug and potent inhibitor of SUR1-TRPM4, was reformulated for intravenous injection, known as BIIB093.Areas covered: We discuss the findings from Phase 2 clinical trials of BIIB093 in patients with LHI (GAMES-Pilot and GAMES-RP) and from a small Phase 2 clinical trial in patients with TBI. For the GAMES trials, we review data on objective biological variables, adjudicated edema-related endpoints, functional outcomes, and mortality which, despite missing the primary endpoint, supported the initiation of a Phase 3 trial in LHI (CHARM). For the TBI trial, we review data on MRI measures of edema and the initiation of a Phase 2 trial in contusion-TBI (ASTRAL).Expert opinion: Emerging clinical data show that BIIB093 has the potential to transform our management of patients with LHI, contusion-TBI and other conditions in which swelling leads to neurological deterioration and death.

Bursting at the Seams: Molecular Mechanisms Mediating Astrocyte Swelling

Brain swelling is one of the most robust predictors of outcome following brain injury, including ischemic, traumatic, hemorrhagic, metabolic or other injury. Depending on the specific type of insult, brain swelling can arise from the combined space-occupying effects of extravasated blood, extracellular edema fluid, cellular swelling, vascular engorgement and hydrocephalus. Of these, arguably the least well appreciated is cellular swelling. Here, we explore current knowledge regarding swelling of astrocytes, the most abundant cell type in the brain, and the one most likely to contribute to pathological brain swelling. We review the major molecular mechanisms identified to date that contribute to or mitigate astrocyte swelling via ion transport, and we touch upon the implications of astrocyte swelling in health and disease.

Hyperammonemia in Hepatic Encephalopathy

The precise mechanism underlying the neurotoxicity of Hepatic Encephalopathy (HE) is remains unclear. The dominant view has been that gut-derived nitrogenous toxins are not extracted by the diseased liver and thereby enter the brain. Among the various toxins proposed, the case for ammonia is most compelling. Events that lead to increased levels of blood or brain ammonia have been shown to worsen HE, whereas reducing blood ammonia levels alleviates HE. Clinical, pathological, and biochemical changes observed in HE can be reproduced by increasing blood or brain ammonia levels in experimental animals, while exposure of cultured astrocytes to ammonium salts reproduces the morphological and biochemical findings observed in HE. However, factors other than ammonia have recently been proposed to be involved in the development of HE, including cytokines and other blood and brain immune factors. Moreover, recent studies have questioned the critical role of ammonia in the pathogenesis of HE since blood ammonia levels do not always correlate with the level/severity of encephalopathy. This review summarizes the vital role of ammonia in the pathogenesis of HE in humans, as well as in experimental models of acute and chronic liver failure. It further emphasizes recent advances in the molecular mechanisms involved in the progression of neurological complications that occur in acute and chronic liver failure.

Acute Liver Failure: Mechanisms of Disease and Multisystemic Involvement

Acute liver failure is accompanied by a pathologic syndrome common to numerous different etiologies of liver injury. This acute liver failure syndrome leads to potentially widespread devastating end-organ consequences. Systemic dysregulation and dysfunction is likely propagated via inflammation as well as underlying hepatic failure itself. Decoding the mechanisms of the disease process and multisystemic involvement of acute liver failure offers potential for targeted treatment opportunities and improved clinical outcomes in this sick population.

The protective roles of L-borneolum, D-borneolum and synthetic borneol in cerebral ischaemia via modulation of the neurovascular unit

OBJECTIVE

Borneol has been used to treat stroke in China since ancient times. In our previous research, we demonstrated the effect of borneol on cerebral ischaemia injury via meta-analysis. The neurovascular unit (NVU) is the structural basis of the preservation of the brain microenvironment and is believed to be a promising target in treating stroke. In this research, we explored the roles of three kinds of borneol, namely, L-borneolum (B1), D-borneolum (B2) and synthetic borneol (B3), in the NVU with permanent middle cerebral artery occluded (pMCAO) rats.

METHODS

The Longa scoring method was used to evaluate nerve function deficits in the pMCAO rats. Awakening time, brain water content, brain index and brain edema rate were also measured. TTC staining was used to calculate the cerebral infarction rate. The morphology of the ischaemia penumbra brain tissue was observed via HE staining, and the neuronal denatured cell index (DCI) was calculated. An enzyme-linked immunosorbent assay (ELISA) was used to determine the levels of vascular endothelial growth factor VEGF and TNF-α in the serum. Moreover, the ultrastructures of the neurons and of the blood-brain barrier (BBB) were observed using transmission electron microscopy. The expression levels of Claudin-5, Bcl-2 and Bax in the ischaemia penumbra of pMCAO rats were detected using real-time PCR and immunohistochemistry.

RESULTS

Pretreatment with B1, B2 and B3 delayed the recovery time (P < 0.01). B1 remarkably ameliorated neurological deficits 24 h after cerebral ischaemia (P < 0.05). Moreover, B1 and B3 were both able to ameliorate brain edema and the area of cerebral infarction. In addition, B1, B2 and B3 all increased serum VEGF levels and decreased serum TNF-α levels (P < 0.01). For the ultrastructure determination, the BBB and the nerve centre were significantly improved by B1, B2 and B3. The mechanistic exploration revealed that B2 and B3 protected the brain by reducing the Bax/Bcl-2 ratio (P < 0.05, P < 0.01, respectively). Immunohistochemistry suggested that B1, B2 and B3 could also enhance the expression of Claudin-5 (P < 0.01).

CONCLUSION

The three kinds of borneol demonstrated different protective effects on cerebral ischaemia injury. L-Borneolum displayed the most prominent anti-cerebral ischaemia effect among them. The mechanism was most likely executed via anti-apoptosis and anti-inflammation effects and maintenance of the stability of the BBB and TJs to comprehensively improve NVU function.

Genistein inhibited ammonia induced astrocyte swelling by inhibiting NF-κB activation-mediated nitric oxide formation

Our previous study has indicated the involvement of epidermal growth factor receptor (EGFR) transactivation in ammonia-induced astrocyte swelling, which represents a major pathogenesis of brain edema in hepatic encephalopathy. In this study, we examined the effect of genistein, a naturally occurred broad-spectrum protein tyrosine kinase (PTK) inhibitor, on ammonia-induced cell swelling. We found that genistein pretreatment significantly prevented ammonia-induced astrocyte swelling. Mechanistically, ammonia triggered EGFR/extracellular signal-regulated kinase (ERK) association and subsequent ERK phosphorylation were alleviated by genistein pretreatment. Moreover, ammonia-induced NF-κB nuclear location, iNOS expression, and consequent NO production were all prevented by AG1478 and genistein pretreatment. This study suggested that genistein could alleviate ammonia-induced astrocyte swelling, which may be, at least partly, related to its PTK-inhibiting activity and repression of NF-κB mediated iNOS-derived NO accumulation.

Glibenclamide ameliorates cerebral edema and improves outcomes in a rat model of status epilepticus

Glibenclamide (GBC), a sulfonylurea receptor 1 blocker, emerges recently as a promising neuron protectant in various neurological disorders. This study aimed to determine whether GBC improves survival and neurological outcome of status epilepticus (SE). Male Sprague-Dawley rats successfully undergoing SE for 2.5 h (n = 134) were randomly assigned to GBC or vehicle group. Rats in the GBC group received a loading dose of 10 μg/kg of GBC, followed by 1.2 μg/6 h for 3 days, while same dose of vehicle was used as control. The 28-day survival rate in the GBC group (11/23) was significantly higher than that in the vehicle group (8/36). In addition, the frequency and duration of spontaneous recurrent seizures in SE rats were profoundly reduced by GBC but not by vehicle treatment. Moreover, cognitive impairment was observed in the SE rats at day 28, which was reversed by GBC treatment. Meanwhile, cerebral edema, as well as neuronal loss, was decreased in several brain areas in the GBC group. Additionally, on the molecular basis, the subunits of sulfonylurea receptor 1/transient receptor potential M4 (SUR1-TRPM4) heterodimer were both strongly upregulated after SE but partly suppressed by GBC treatment. Furthermore, gene knockdown of Trpm4 in SE rats reduced BBB disruption and neuronal loss, similar to the inhibitory effects with GBC treatment. Taken together, GBC treatment markedly improved survival and neurologic outcomes after SE. The salutary effects of GBC were correlated to the alleviation of cerebral edema and reduction in neurological injury via down-regulation of SUR1-TRPM4 channel.

[Glibenclamide as a promising agent for prevention and treatment of cerebral edema]

The article presents a review of the literature on the use of a fundamentally new technique for prevention and treatment of cerebral edema. A drug glibenclamide, which is used to treat type 2 diabetes mellitus, is able to reduce cerebral edema and neuronal damage as evidenced by the results of preclinical trials in rodents and the first results of drug application in patients. The article describes the mechanism of glibenclamide action and discusses the potential for its application.

Glibenclamide–sulfonylurea receptor 1 antagonist alleviates LPS-induced BV2 cell activation through the p38/MAPK pathway

We investigated the anti-neuroinflammatory activity and mechanism of glibenclamide, sulfonylurea receptor 1 (Sur1) antagonist, against LPS-induced microglial activationin vitro.

Glibenclamide Is Comparable to Target Temperature Management in Improving Survival and Neurological Outcome After Asphyxial Cardiac Arrest in Rats

Background

We previously have shown that glibenclamide (GBC), a sulfonylurea receptor 1–transient receptor potential M4 (SUR1‐TRPM4) channel inhibitor, improves survival and neurological outcome after asphyxial cardiac arrest and cardiopulmonary resuscitation (ACA/CPR). Here, we further compare the efficacy of GBC with target temperature management (TTM) and determine whether the efficacy of GBC is affected by TTM.

Methods and Results

Male Sprague‐Dawley rats (n=213) subjected to 10‐minute ACA/CPR were randomized to 4 groups after return of spontaneous circulation (ROSC): normothermia control (NT); GBC; TTM; and TTM+GBC. Survival, neurodeficit scores, histological injury, as well as the expressions of SUR1 and TRPM4 were evaluated. The 7‐day survival rate was 34.4% (11 of 32) in the NT group, 65% (13 of 20) in the GBC group, 50% (10 of 20) in the TTM group, and 70% (14 of 20) in the TTM+GBC group. Rats that received either GBC, TTM alone, or in combination showed less neurological deficit than NT control at 24, 48, and 72 hours and 7 days after ROSC. Moreover, TTM or GBC ameliorated neuronal degeneration and glial activation in the hippocampal CA1 region with similar efficacy, whereas the combination of them had a trend toward better effect. The subunits of SUR1‐TRPM4 heterodimers were both strongly upregulated after ACA/CPR and expressed in multiple types of brain cells, but partly suppressed by TTM.

Conclusions

GBC is comparable to TTM in improving survival and neurological outcome after ACA/CPR. When GBC is given along with TTM, less histological injury tended to be achieved.

Glibenclamide Attenuates Blood-Brain Barrier Disruption in Adult Mice after Traumatic Brain Injury

Glibenclamide is a hypoglycemic drug that is widely used for the treatment of diabetes mellitus type 2 (DM II), but it also plays a protective role following injury to the central nervous system (CNS). However, the precise mechanisms underlying its neuroprotective actions remain to be elucidated. Therefore, the present study evaluated the effects of glibenclamide on the blood-brain barrier (BBB) in a mouse model of traumatic brain injury (TBI). In the present study, 86 adult male C57BL/6 mice were exposed to a controlled cortical impact (CCI) injury and then received glibenclamide (10 μg) for 3 days. Tight junction (TJ) protein levels, BBB permeability, and tissue hemoglobin levels were evaluated following the CCI injury. Additionally, a biaxial stretch injury was applied to cell cultures of bEnd.3 cells using the Cell Injury Controller II system to explore the mechanisms by which glibenclamide inhibits apoptosis-signaling pathways. Compared with the control group, glibenclamide-treated mice exhibited decreases in brain water content (p < 0.05), tissue hemoglobin levels (p < 0.05), and Evans Blue extravasation (p < 0.01) after the CCI injury. Glibenclamide primarily attenuated apoptosis via the JNK/c-jun signaling pathway and resulted in an elevation of stretch injury-induced ZO-1 expression in bEnd.3 cells (p < 0.01).Glibenclamide downregulated the activity of the JNK/c-jun apoptosis-signaling pathway which, in turn, decreased apoptosis in endothelial cells (ECs). This may have prevented the disruption of the BBB in a mouse model of TBI.

Molecular pathophysiology of cerebral edema

Advancements in molecular biology have led to a greater understanding of the individual proteins responsible for generating cerebral edema. In large part, the study of cerebral edema is the study of maladaptive ion transport. Following acute CNS injury, cells of the neurovascular unit, particularly brain endothelial cells and astrocytes, undergo a program of pre- and post-transcriptional changes in the activity of ion channels and transporters. These changes can result in maladaptive ion transport and the generation of abnormal osmotic forces that, ultimately, manifest as cerebral edema. This review discusses past models and current knowledge regarding the molecular and cellular pathophysiology of cerebral edema.

Methylene Blue Ameliorates Ischemia/Reperfusion-Induced Cerebral Edema: An MRI and Transmission Electron Microscope Study

The neuroprotective effect of methylene blue (MB) has been identified against various brain disorders, including ischemic stroke. In the present study, we evaluated the effects of MB on postischemic brain edema using magnetic resonance imaging (MRI) and transmission electron microscopy (TEM). Adult male rats were subjected to transient focal cerebral ischemia induced by 1 h middle cerebral artery occlusion (MCAO), followed by reperfusion. MB was infused intravenously immediately after reperfusion (3 mg/kg) and again at 3 h post-occlusion (1.5 mg/kg). Normal saline was administered as vehicle control. Sequential MRIs, including apparent diffusion coefficient (ADC) and T2-weighted imaging (T2WI), were obtained at 0.5, 2.5, and 48 h after the onset of stroke. Separated groups of animals were sacrificed at 2.5 and 48 h after stroke for ultrastructural analysis by TEM. In addition, final lesion volumes were analyzed by triphenyltetrazolium chloride (TTC) staining at 48 h after stroke. Ischemic stroke induced ADC lesion volume at 0.5 h during MCAOs that were temporally recovered at 1.5 h after reperfusion. No significant difference in ADC-defined lesion was observed between vehicle and MB treatment groups. At 48 h after stroke, MB significantly reduced ADC lesion and T2WI lesion volume and attenuated cerebral swelling. Consistently, MB treatment significantly decreased TTC-defined lesion volume at 48 h after stroke. TEM revealed remarkable swollen astrocytes, astrocytic perivascular end-feet, and concurrent shrunken neurons in the penumbra at 2.5 and 48 h after MCAO. MB treatment attenuated astrocyte swelling, the perivascular astrocytic foot process, and endothelium and also alleviated neuron degeneration. This study demonstrated that MB could decrease postischemic brain edema and provided additional evidence that future clinical investigation of MB for the treatment of ischemic stroke is warrented.

Osteopontin-Rac1 on Blood-Brain Barrier Stability Following Rodent Neonatal Hypoxia-Ischemia

Osteopontin (OPN) is a neuroprotective molecule that is upregulated following rodent neonatal hypoxic-ischemic (nHI) brain injury. Because Rac1 is a regulator of blood-brain barrier (BBB) stability, we hypothesized a role for this in OPN signaling. nHI was induced by unilateral ligation of the right carotid artery followed by hypoxia (8 % oxygen for 2 h) in P10 Sprague-Dawley rat pups. Intranasal (iN) OPN was administered at 1 h post-nHI. Groups consisted of: (1) Sham, (2) Vehicle, (3) OPN, and (4) OPN + Rac1 inhibitor (NSC23766). Evans blue dye extravasation (BBB permeability) was quantified 24 h post-nHI, and brain edema at 48 h. Increased BBB permeability and brain edema following nHI was ameliorated in the OPN treatment group. However, those rat pups receiving OPN co-treatment with the Rac1 inhibitor experienced no improvement compared with vehicle. OPN protects the BBB following nHI, and this was reversed by Rac1 inhibitor (NSC23766).

Brain Volume Determination in Subarachnoid Hemorrhage Using Rats

Brain edema is routinely measured using the wet-dry method. Volume, however, is the sum total of all cerebral tissues, including water. Therefore, volumetric change following injury may not be adequately quantified using percentage of edema. We thus tested the hypothesis that dried brains can be reconstituted with water and then re-measured to determine the actual volume. Subarachnoid hemorrhage (SAH) was induced by endovascular perforation in adult male Sprague-Dawley rats (n = 30). Animals were euthanized at 24 and 72 h after evaluation of neurobehavior for determination of brain water content. Dried brains were thereafter reconstituted with equal parts of water (lost from brain edema) and centrifuged to remove air bubbles. The total volume was quantified using hydrostatic (underwater) physics principles that 1 ml water (mass) = 1 cm(3) (volume). The amount of additional water needed to reach a preset level marked on 2-ml test tubes was added to that lost from brain edema, and from the brain itself, to determine the final volume. SAH significantly increased both brain water and volume while worsening neurological function in affected rats. Volumetric measurements demonstrated significant brain swelling after SAH, in addition to the brain edema approach. This modification of the "wet-dry" method permits brain volume determination using valuable post hoc dried brain tissue.

Novel human ABCC9/SUR2 brain-expressed transcripts and an eQTL relevant to hippocampal sclerosis of aging

ABCC9 genetic polymorphisms are associated with increased risk for various human diseases including hippocampal sclerosis of aging. The main goals of this study were 1 > to detect the ABCC9 variants and define the specific 3' untranslated region (3'UTR) for each variant in human brain, and 2 > to determine whether a polymorphism (rs704180) associated with risk for hippocampal sclerosis of aging pathology is also associated with variation in ABCC9 transcript expression and/or splicing. Rapid amplification of ABCC9 cDNA ends (3'RACE) provided evidence of novel 3' UTR portions of ABCC9 in human brain. In silico and experimental studies were performed focusing on the single nucleotide polymorphism, rs704180. Analyses from multiple databases, focusing on rs704180 only, indicated that this risk allele is a local expression quantitative trait locus (eQTL). Analyses of RNA from human brains showed increased ABCC9 transcript levels in individuals with the risk genotype, corresponding with enrichment for a shorter 3' UTR which may be more stable than variants with the longer 3' UTR. MicroRNA transfection experiments yielded results compatible with the hypothesis that miR-30c causes down-regulation of SUR2 transcripts with the longer 3' UTR. Thus we report evidence of complex ABCC9 genetic regulation in brain, which may be of direct relevance to human disease. ABCC9 gene variants are associated with increased risk for hippocampal sclerosis of aging (HS-Aging--a prevalent brain disease with symptoms that mimic Alzheimer's disease). We describe novel ABCC9 variants in human brain, corresponding to altered 3'UTR length, which could lead to targeting by miR-30c. We also determined that the HS-Aging risk mutation is associated with variation in ABCC9 transcript expression.

Pathogenesis of brain edema and investigation into anti-edema drugs

Brain edema is a potentially fatal pathological state that occurs after brain injuries such as stroke and head trauma. In the edematous brain, excess accumulation of extracellular fluid results in elevation of intracranial pressure, leading to impaired nerve function. Despite the seriousness of brain edema, only symptomatic treatments to remove edema fluid are currently available. Thus, the development of novel anti-edema drugs is required. The pathogenesis of brain edema is classified as vasogenic or cytotoxic edema. Vasogenic edema is defined as extracellular accumulation of fluid resulting from disruption of the blood-brain barrier (BBB) and extravasations of serum proteins, while cytotoxic edema is characterized by cell swelling caused by intracellular accumulation of fluid. Various experimental animal models are often used to investigate mechanisms underlying brain edema. Many soluble factors and functional molecules have been confirmed to induce BBB disruption or cell swelling and drugs targeted to these factors are expected to have anti-edema effects. In this review, we discuss the mechanisms and involvement of factors that induce brain edema formation, and the possibility of anti-edema drugs targeting them.

Neuroinflammation in hepatic encephalopathy: mechanistic aspects

Hepatic encephalopathy (HE) is a major neurological complication of severe liver disease that presents in acute and chronic forms. While elevated brain ammonia level is known to be a major etiological factor in this disorder, recent studies have shown a significant role of neuroinflammation in the pathogenesis of both acute and chronic HE. This review summarizes the involvement of ammonia in the activation of microglia, as well as the means by which ammonia triggers inflammatory responses in these cells. Additionally, the role of ammonia in stimulating inflammatory events in brain endothelial cells (ECs), likely through the activation of the toll-like receptor-4 and the associated production of cytokines, as well as the stimulation of various inflammatory factors in ECs and in astrocytes, are discussed. This review also summarizes the inflammatory mechanisms by which activation of ECs and microglia impact on astrocytes leading to their dysfunction, ultimately contributing to astrocyte swelling/brain edema in acute HE. The role of microglial activation and its contribution to the progression of neurobehavioral abnormalities in chronic HE are also briefly presented. We posit that a better understanding of the inflammatory events associated with acute and chronic HE will uncover novel therapeutic targets useful in the treatment of patients afflicted with HE.

Brain edema in acute liver failure: mechanisms and concepts

Brain edema and associated increase in intracranial pressure continue to be lethal complications of acute liver failure (ALF). Abundant evidence suggests that the edema in ALF is largely cytotoxic brought about by swelling of astrocytes. Elevated blood and brain ammonia levels have been strongly implicated in the development of the brain edema. Additionally, inflammation and sepsis have been shown to contribute to the astrocyte swelling/brain edema in the setting of ALF. We posit that ammonia initiates a number of signaling events, including oxidative/nitrative stress (ONS), the mitochondrial permeability transition (mPT), activation of the transcription factor (NF-κB) and signaling kinases, all of which have been shown to contribute to the mechanism of astrocyte swelling. All of these factors also impact ion-transporters, including Na(+), K(+), Cl(-) cotransporter and the sulfonylurea receptor 1, as well as the water channel protein aquaporin-4 resulting in a perturbation of cellular ion and water homeostasis, ultimately resulting in astrocyte swelling/brain edema. All of these events are also potentiated by inflammation. This article reviews contemporary knowledge regarding mechanisms of astrocyte swelling/brain edema formation which hopefully will facilitate the identification of therapeutic targets capable of mitigating the brain edema associated with ALF.

Acute liver failure-induced hepatic encephalopathy s associated with changes in microRNA expression rofiles in cerebral cortex of the mouse [corrected]

The mechanisms that promote brain dysfunction after acute liver failure (ALF) are not clearly understood. The small noncoding RNAs known as microRNAs (miRNAs) significantly control mRNA translation and thus normal and pathological functions in the mammalian body. To understand their significance in ALF, we currently profiled the expression of miRNAs in the cerebral cortex of mice sacrificed at coma stage following treatment with azoxymethane. Of the 470 miRNAs profiled using microarrays, 37 were significantly altered (20 up-and 17 down-regulated) in their expression in the ALF group compared to sham group. In silico analysis showed that the ALF-responsive miRNAs target on average 231 mRNAs/miRNA (range: 3 to 840 targets). Pathways analysis showed that many miRNAs altered after ALF target multiple mRNAs that are part of various biological and molecular pathways. Glutamatergic synapse, Wnt signaling, MAP-kinase signaling, axon guidance, PI3-kinase-AKT signaling, T-cell receptor signaling and ubiquitin-mediated proteolysis are the top pathways targeted by the ALF-sensitive miRNAs. At least 28 ALF-responsive miRNAs target each of the above pathways. We hypothesize that alterations in miRNAs and their down-stream mRNAs of signaling pathways might play a role in the induction and progression of neurological dysfunction observed during ALF.