Relationship between transmembrane signal transduction pathway and DNA repair and the mechanism after global cerebral ischemia-reperfusion in rats

Objective

To investigate the protein levels of phospho-ERK and phospho-APE/Ref-1 in hippocampal neurons after global cerebral ischemia reperfusion in rats, and observe the relationship between transmembrane signal transduction and repair of DNA damage. The role of ERK signal transduction pathway following global cerebral ischemia reperfusion in rats is further discussed.

Methods

Ninety healthy male SD rats were divided into 3 groups randomly: Sham group (S group), Ischemia reperfusion group (IR group) and Pd98059 pretreatment/ischemia reperfusion group (PD group). Global cerebral ischemia reperfusion model was established by four-vessel occlusion (4-VO) method, and reperfusion was performed 5 minutes following ischemia. Protein levels of phospho-ERK and phospho-APE/Ref-1 were detected using immunohistochemical method at 2 h, 6 h, 12 h, 24 h, 48 h and 72 h after reperfusion, and neuron apoptosis was observed by HE and TUNEL staining.

Results

In CA1 region of IR group, TUNEL positive cells began to appear at 6 h after IR, and reached the apex during 24 h to 48 h. However, TUNEL positive was most strongly exhibited in PD group. In IR group, phospho-ERK was obviously detected in CA3 region at 2 h after IR, and its level was gradually decreased from 6 h until totally absent at 48 h. Besides, phospho-ERK expression in PD group was weaker than that in IR group. For phospho-APE/Ref-1, its expression began to appear in CA1 region in IR group at 2 h after IR, with no obvious changes during 2 h to 12 h. Phospho-APE/Ref-1 expression began to decrease at 24 h and this decrease continued thereafter. Expression level of phospho-APE/Ref-1 in PD group was lower than that in IR group. Results showed the concurrence of decreased phospho-ERK expression level and increased neuron apoptosis after cerebral ischemia reperfusion, the former of which was consistent with the decrease of phospho-APE/Ref-1 expression. Also, the greater the inhibition of ERK phosphorylation was, the greater decrease of APE/Ref-1 expression occurred.

Conclusion

Activation of ERK signal transduction pathway increased the expression of phospho-APE/Ref-1, and thus faciliated the repair of DNA damage. So, activation of ERK signal transduction pathway may protect neurons from apoptosis after cerebral ischemia reperfusion.     

Surgical flow disconnection of cerebral pial dual-channel arteriovenous fistula with a large varix: the role of anti-platelet agent or anti-coagulation therapy

Introduction

Intracranial pial arteriovenous fistula (AVF) is a rare cerebrovascular lesion, and the literature is sparse. Most authors insist that simple disconnection of arteriovenous shunting is enough to treat intracral single-channel pial AVF in most cases, either by microsurgery or endovascular embolization without resection of entire vascular malformation.

Discussion

We report an insidious onset of peri-lesional edema formation after abrupt disconnection of AVF shunting with surgical arterial ligation. Treatment entailed anti-platelet and anti-coagulation agent to slow down thrombus formation in intracranial dual-channel pial AVF. We suggest that slowing down thrombus formation in the large varix with anti-platelet and/or anti-coagulation agents seems to be necessary in case of abrupt disconnection of shunting in intracranial single- or dual-channel pial AVF to prevent postoperative cerebral edema or infarction.     

Duplicate preconditioning with sevoflurane in vitro improves neuroprotection in rat brain via activating the extracellular signal-regulated protein kinase

Objective

Sevoflurane preconditioning has been demonstrated to reduce cerebral ischemia-reperfusion (IR) injury, but the underlying mechanisms have not been fully elucidated. Besides, different protocols would usually lead to different results. The objective of this study was to determine whether dual exposure to sevoflurane improves the effect of anesthetic preconditioning against oxygen and glucose deprivation (OGD) injury in vitro.

Methods

Rat hippocampal slices under normoxic conditions (95% O₂/5% CO₂) were pre-exposed to sevoflurane 1, 2 and 3 minimum alveolar concentration (MAC) for 30 min, once or twice, with 15-min washout after each exposure. The slices were then subjected to 13-min OGD treatment (95% N₂/5% CO₂, glucose-free), followed by 30-min reoxygenation. The population spikes (PSs) were recorded in the CA1 region of rat hippocampus. The percentage of PS amplitude at the end of 30-min reoxygenation to that before OGD treatment was calculated, since it could indicate the recovery degree of neuronal function. In addition, to assess the role of mitogen-activated protein kinases (MAPKs) in preconditioning, U0126, an inhibitor of extracellular signal-regulated protein kinase (MEK-ERK1/2, ERK1/2 MAPK), and SB203580, an inhibitor of p38 MAPK, were separately added 10 min before sevoflurane exposure.

Results

Preconditioning once with sevoflurane 1, 2, and 3 MAC increased the percentage of PS amplitude at the end of 30-min reoxygenation to that before OGD treatment, from (15.13±3.79)% (control) to (31.88±5.36)%, (44.00±5.01)%, and (49.50±6.25)%, respectively, and twice preconditioning with sevoflurane 1, 2, and 3 MAC increased the percentage to (38.53±4.36)%, (50.74±7.05)% and (55.86±6.23)%, respectively. The effect of duplicate preconditioning with sevoflurane 3 MAC was blocked by U0126 [(16.23±4.62)%].

Conclusion

Sevoflurane preconditioning can induce neuroprotection against OGD injury in vitro, and preconditioning twice enhances this effect. Besides, the activation of extracellular signal-regulated protein kinase (MEK-ERK1/2, ERK1/2 MAPK) may be involved in this process.     

Treatment of Intracerebral Hemorrhage with Tranexamic Acid After Thrombolysis with Tissue Plasminogen Activator

Background

Thrombolytic treatment with intravenous tissue plasminogen activator (iv tPA) is the only FDA-approved therapy for acute ischemic stroke. There are risks associated with thrombolytics, including intracranial and extracranial hemorrhage and hypersensitivity reactions. Established treatment for post-tPA hemorrhage includes administration of blood products including cryoprecipitate, fresh frozen plasma, and platelets which have poorly established efficacy. Tranexamic acid (TXA) and epsilon-aminocaproic acid (EACA) have been studied as hemostatic therapies in post-operative hemorrhage, menorrhagia, intracranial hemorrhage (ICH), subarachnoid hemorrhage, and trauma patients. There is no reported literature on the use of TXA to reverse thrombolytic therapy with tPA.

Methods

This is a case report of a Jehovah??s Witness patient who was unwilling to receive blood products after developing symptomatic ICH following iv tPA. He consequently received TXA for reversal of thrombolytic therapy.

Results

The patient received a total of 1.675?g of iv TXA within 3?h of finishing the iv tPA. Repeat brain imaging with computed tomography and magnetic resonance imaging revealed no further expansion of hemorrhages.

Conclusion

TXA is an inexpensive medication which competitively inhibits the activation of plasminogen and can be given to reverse thrombolysis in the setting of hemorrhage after iv thrombolytic therapy.     

Role of Endothelin-1 in Human Aneurysmal Subarachnoid Hemorrhage: Associations with Vasospasm and Delayed Cerebral Ischemia

Background

Endothelin-1 (ET-1) is a potent vasoconstrictor implicated in the pathogenesis of vasospasm and delayed cerebral ischemia (DCI) in aneurysmal subarachnoid hemorrhage (aSAH) patients. The aim of this study was to investigate the relationship between cerebrospinal fluid (CSF) ET-1 levels and angiographic vasospasm and DCI.

Methods

Patients with aSAH were consented (n?=?106). Cerebral vasospasm was determined by angiography. DCI was determined by transcranial Doppler (TCD) results and/or angiogram results with corresponding clinical deterioration. CSF ET-1 levels over 14?days after the initial insult was quantified by ELISA. ET-1 analysis included a group-based trajectory analysis and ET-1 exposure rate during 24, 48, and 72?h prior to, as well as 72?h post angiography, or clinical deterioration.

Results

Trajectory analysis revealed two distinct groups of subjects with 56% of patients in the low ET-1 trajectory group (mean at day 1?=?0.31?pg/ml; SE?=?0.04; mean at day 14?=?0.41?pg/ml; SE?=?0.15) and 44% of patients in the high ET-1 trajectory group (mean at day 1?=?0.65?pg/ml; SE?=?0.08; mean at day 14?=?0.61?pg/ml; SE?=?0.06). Furthermore, we observed that ET-1 exposure rate 72?h before angiography and clinical spasm was a significant predictor of both angiographic vasospasm and DCI, whereas, ET-1 exposure after angiography and clinical spasm was not associated with either angiographic vasospasm or DCI.

Conclusion

Based on these results we conclude that ET-1 concentrations are elevated in a sub-group of patients and that the acute (72?h prior to angiography and clinical neurological deterioration), but not chronic, elevations in CSF ET-1 concentrations are indicative of the pathogenic alterations of vasospasm and DCI in aSAH patients.     

Characterization of neuroblastoma bone invasion/metastasis in established bone metastatic model of SY5Y and KCNR cell lines

Objects

To determine the mechanism of neuroblastoma (NB) bone invasion/metastasis, it is necessary to investigate the bone invasion/metastasis-related factors in the bone invasion/metastasis process. Some evidence has suggested that various proteins were involved in bone osteolytic response. The invasion/metastasis property and gene expression of NB, however, are still unknown.

Methods

Single-cell suspensions of SY5Y and KCNR cells were injected directly into the femur of nude mice. Radiological and histological analyses, immunohistochemistry analyses, and western blot assay were performed to characterize bone metastasis mechanism in these bone metastasis models.

Results

SY5Y and KCNR NB cells result in osteolytic responses in bone metastasis model. Osteoprotegerin (OPG), receptor activator of NF-kappaB ligand (RANKL), parathyroid hormone-related peptide (PTHrP), endothelin 1 (ET-1), and CXCR4 were examined and compared among in vitro, in vivo, and normal bone, respectively. PTHrP, OPG, RANKL, and ET-1 except CXCR4 in SY5Y and KCNR NB cells xenografts were strikingly upregulated compared with normal bone and NB cells. However, significantly stronger expression of PTHrP and RANKL was presented than ET-1 and OPG; furthermore, the ratios of expression of PTHrP, RANKL to OPG, and ET-1 were also markedly increased in vivo versus in vitro.

Conclusions

Our study provided evidence that NB cell may enhance bone invasion through PTHrP, OPG, RANKL, and ET-1, especially PTHrP and RANKL which may display stronger effects. CXCR4 appeared not participating in bone invasion, but in tumor growth, and homing to bone. Targeting PTHrP, OPG, ET-1, and RANKL may provide a new insight and method for patient therapy by inhibiting NB bone metastasis and invasiveness.     

Endogenous Inhibition of the Nociceptive Flexion Reflex (NFR) and Pain Ratings During the Menstrual Cycle in Healthy Women

Background

The menstrual cycle influences pain, with symptoms often increasing during the premenstrual (late-luteal) phase. Deficiencies in endogenous inhibition of afferent nociception at the spinal level might contribute to menstrual phase-related changes in pain.

Purpose

This study assessed whether conditioned pain modulation (CPM) of spinal nociception differs between mid-follicular and late-luteal phases.

Methods

CPM was evoked by a blood pressure cuff affixed to the right forearm and inflated to induce ischemia in 41 healthy women during both menstrual phases. Suprathreshold electric stimuli were delivered to the left sural nerve to evoke pain and the nociceptive flexion reflex (NFR) before, during, and after forearm ischemia.

Results

Forearm ischemia produced CPM of electrocutaneous pain and NFR, but inhibition did not differ across mid-follicular and late-luteal phases.

Conclusions

Mechanisms contributing to changes in experimental pain across mid-follicular and late-luteal phases in healthy women are not due to deficits in CPM of spinal nociception.     

Interactive Influences of Ethnicity, Endothelin-1 Gene, and Everyday Discrimination Upon Nocturnal Ambulatory Blood Pressure

Background

Everyday discrimination scale scores are associated with increased ambulatory blood pressure (BP) and reduced nocturnal dipping, and the endothelin-1 (ET-1)/Lys198Asn polymorphism is associated with increased resting BP and exaggerated BP reactivity among African Americans compared to European Americans. Combined influences of these factors on BP control are unknown.

Purpose

This study tested the hypothesis of a three-way interaction between ethnicity, ET-1 carrier status, and everyday discrimination upon ambulatory BP and nocturnal dipping.

Methods

Baseline laboratory anthropometrics and the everyday discrimination scale were completed by 352 (175 African American) young adult normotensives, followed by 24-h ambulatory BP monitoring.

Results

For nocturnal dipping, multiple regression models controlling for age, sex, ethnicity, and body mass index revealed significant three-way ET-1?×?everyday discrimination?×?ethnicity interactions. Specifically, among African American ET-1 T-allele carriers, increases in everyday discrimination led to reduced nocturnal dipping.

Conclusions

African Americans that carry the ET-1/Lys198Asn T-allele and report higher everyday discrimination scores may be at particular risk for reduced nocturnal dipping.     

Bedside Diagnosis of Mitochondrial Dysfunction After Malignant Middle Cerebral Artery Infarction

Background

The study explores whether the cerebral biochemical pattern in patients treated with hemicraniectomy after large middle cerebral artery infarcts reflects ongoing ischemia or non-ischemic mitochondrial dysfunction.

Methods

The study includes 44 patients treated with decompressive hemicraniectomy (DCH) due to malignant middle cerebral artery infarctions. Chemical variables related to energy metabolism obtained by microdialysis were analyzed in the infarcted tissue and in the contralateral hemisphere from the time of DCH until 96 h after DCH.

Results

Reperfusion of the infarcted tissue was documented in a previous report. Cerebral lactate/pyruvate ratio (L/P) and lactate were significantly elevated in the infarcted tissue compared to the non-infarcted hemisphere (p < 0.05). From 12 to 96 h after DCH the pyruvate level was significantly higher in the infarcted tissue than in the non-infarcted hemisphere (p < 0.05).

Conclusion

After a prolonged period of ischemia and subsequent reperfusion, cerebral tissue shows signs of protracted mitochondrial dysfunction, characterized by a marked increase in cerebral lactate level with a normal or increased cerebral pyruvate level resulting in an increased LP-ratio. This biochemical pattern contrasts to cerebral ischemia, which is characterized by a marked decrease in cerebral pyruvate. The study supports the hypothesis that it is possible to diagnose cerebral mitochondrial dysfunction and to separate it from cerebral ischemia by microdialysis and bed-side biochemical analysis.     

Activation of extracellular signal-regulated kinase in the anterior cingulate cortex contributes to the induction of long-term potentiation in rats

Objective

To explore the role of the extracellular signal-regulated kinase (ERK)/cAMP response element binding protein (CREB) pathway in the induction of long-term potentiation (LTP) in the anterior cingulate cortex (ACC) that may be implicated in pain-related negative emotion.

Methods

LTP of field potential was recorded in ACC slice and the expressions of phospho-ERK (pERK) and phospho-CREB (pCREB) were examined using immunohistochemistry method.

Results

LTP could be induced stably in ACC slice by high frequency stimulation (2-train, 100 Hz, 1 s), while APv (an antagonist of NMDA receptor) could block the induction of LTP in the ACC, indicating that LTP in this experiment was NMDA receptor-dependent. Bath application of PD98059 (50 μmol/L), a selective MEK inhibitor, at 30 min before tetanic stimulation could completely block the induction of LTP. Moreover, the protein level of pERK in the ACC was transiently increased after LTP induction, starting at 5 min and returning to basal at 1 h after tetanic stimulation. The protein level of pCREB was also increased after LTP induction. The up-regulation in pERK and pCREB expressions could be blocked by pretreatment of PD98059. Double immunostaining showed that after LTP induction, most pERK was co-localized with pCREB.

Conclusion

NMDA receptor and ERK-CREB pathway are necessary for the induction of LTP in rat ACC and may play important roles in pain emotion.     

Safety and efficacy using a detachable tip microcatheter in the embolization of pediatric arteriovenous malformations

Purpose

The treatment of deep-seeded pediatric brain arteriovenous malformations (AVMs) remains a challenging task. We describe our experience using a new detachable tip microcatheter in the embolization of brain arteriovenous malformations, pial arteriovenous fistulas, and vein of Galen malformations. We describe the safety and efficacy using a new detachable tip microcatheter in the treatment of pediatric deep brain arteriovenous malformations, pial malformations, and vein of Galen malformations.

Methods

During a period of 9 months from March 2013 through January 2014, 11 pediatric patients in 14 procedures with 27 total injections were selected for treatment with a detachable tip under Food and Drug Administration (FDA) compassionate use exemption and were admitted to our department for treatment of their brain AVM using a liquid embolic agent and a detachable tip microcatheter. The ages of the patients ranged from 3 months to 18 years old.

Results

Of the 27 total injections done, the tip detached in seven cases. For the 16 n-BCA injections, the tip detached six times (37.5 %), and for the 11 Onyx injections, the tip detached one time (9 %). There were no cases of premature microcatheter detachment during normal vessel navigation.

Conclusions

The introduction of these detachable tip microcatheters allows for a safe and relaxed injection that permits a true circumferential occlusion, and may further permit filling a larger amount of angioarchitecture without the risk of distal migration, or vessel damage during the usual rapid removal of non detachable micocatheters.     

Accumulation of exogenous polyamines in gerbil brain after ischemia

Regionally selective delayed neuronal degeneration is a characteristic sequel of cerebral ischemia. Recent evidence indicates that changes in brain polyamine metabolism may be critical for nerve cell survival after ischemia. Within hours after ischemia, intracellular putrescine levels are greatly increased and remain elevated for days, whereas only minor changes are noted in the levels of the polyamines spermine and spermidine. In contrast, the extracellular levels of all polyamines are low after ischemia. Injections of polyamines following ischemia, however, can protect neurons in the gerbil brain from delayed cell death, with spermine being the most potent of the polyamines. In the present study, therefore, we sought to determine if increased polyamine uptake occurs in the brain after ischemia. In the hippocampal slice preparation, temperature-dependent uptake was unique for spermine, but not for spermidine or putrescine. Uptake of [¹⁴C]spermine was transiently increased after ischemia, peaking at 150% of control by 12–13 h and subsiding by 24 h. Intravenous injections of [³H]spermidine resulted in a postischemic accumulation of this polyamine throughout the forebrain parenchyma. We conclude that:

1. Active cellular uptake of spermine is transiently increased early after ischemia;
2. A nonspecific accumulation of exogenous polyamines occurs early after ischemia probably owing to a compromised blood-brain barrier, and
3. The findings indicate that exogenous polyamines can exert their effect directly in the brain after ischemia.

     

Using parametric regressors to disentangle properties of multi-feature processes

Background

Existing brain imaging studies, investigating sexual arousal via the presentation of erotic pictures or film excerpts, have mainly used blocked designs with long stimulus presentation times.

Methods

To clarify how experimental functional magnetic resonance imaging (fMRI) design affects stimulus-induced brain activity, we compared brief event-related presentation of erotic vs. neutral stimuli with blocked presentation in 10 male volunteers.

Results

Brain activation differed depending on design type in only 10% of the voxels showing task related brain activity. Differences between blocked and event-related stimulus presentation were found in occipitotemporal and temporal regions (Brodmann Area (BA) 19, 37, 48), parietal areas (BA 7, 40) and areas in the frontal lobe (BA 6, 44).

Conclusion

Our results suggest that event-related designs might be a potential alternative when the core interest is the detection of networks associated with immediate processing of erotic stimuli. Additionally, blocked, compared to event-related, stimulus presentation allows the emergence and detection of non-specific secondary processes, such as sustained attention, motor imagery and inhibition of sexual arousal.     

Decreased postnatal neurogenesis in the hippocampus combined with stress experience during adolescence is accompanied by an enhanced incidence of behavioral pathologies in adult mice

Background

Although long-term potentiation (LTP) of synaptic strength is very persistent, current studies have provided evidence that various manipulations or pharmacological treatment when applied shortly after LTP induction can reverse it. This kind of reversal of synaptic strength is termed as depotentiation and may have a function to increase the flexibility and storage capacity of neuronal networks. Our previous studies have demonstrated that an increase in extracellular levels of adenosine and subsequent activation of adenosine A₁ receptors are important for the induction of depotentiation; however, the signaling downstream of adenosine A₁ receptors to mediate depotentiation induction remains elusive.

Results

We confirm that depotentiation induced by low-frequency stimulation (LFS) (2 Hz, 10 min, 1200 pulses) was dependent on adenosine A₁ receptor activation, because it was mimicked by bath-applied adenosine A₁ receptor agonist N ⁶-cyclopentyladenosine (CPA) and was inhibited by the selective adenosine A₁ receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX). Pretreatment of the hippocampal slices with the selective p38 mitogen-activated protein kinase (MAPK) inhibitors, 4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl]-5-(4-pyrudyl)-1H-imidazole (SB203580) or trans-1-(4-hydroxycyclohexyl)-4-(fluorophenyl)-5-(2-methoxypyrimidin-4-yl)imidazole (SB239063), prevented the induction of depotentiation by LFS and CPA. In agreement with electrophysiological observation, both LFS- and CPA-induced depotentiation are associated with an increase in p38 MAPK activation, which are blocked by DPCPX or SB203580 application.

Conclusion

These results suggest that activation of adenosine A₁ receptor and in turn triggering p38 MAPK signaling may contribute to the LFS-induced depotentiation at hippocampal CA1 synapses.     

Cerebral Ischemia and Neurogenesis: A Two-time Comparison

Background

This study compares the effect of mild and severe cerebral ischemia on neuronal damage and neurogenesis.

Methods

Sixteen Sprague–Dawley rats, anesthetized with 0.8 vol% halothane in O₂/air, were subjected to forebrain ischemia by bilateral common carotid artery occlusion plus hemorrhagic hypotension (mean arterial blood pressure = 40 mmHg) for 8 (mild) or 13 (severe) min. Four non-ischemic animals were investigated as naïve controls. Bromodeoxyuridine (50 mg/kg), a marker of new cells, was administrated for seven consecutive postischemic days. After 28 days, animals were perfused with 4% paraformaldehyde and the brains were sliced. Histopathological damage of the hippocampus and the volume of the dentate gyrus were assessed by HE-staining. With immunohistochemistry BrdU-positve cells were detected in the dentate gyrus. The amount of new generated neurons was identified by double-immunofluorescence-staining of BrdU and neuronal marker (NeuN).

Results

In the CA-1 region of the hippocampus, mild ischemia induced damage up to 10% (HE-index 0.8 ± 1.2) and severe ischemia up to 50% (HE-index 2.1 ± 1.4). There was no histopathological damage in naïve control animals. The amount of new neurons was increased by 250% after mild insult and by 160% after severe insult compared to the naïve control animals.

Conclusions

These data indicate that histopathological damage depends on the severity of the ischemic insult and that forebrain ischemia activates generation of new neurons. A mild ischemic challenge appears to be a more potent neurogenic stimulus than severe ischemia. The new neurons survive at least 28 days. This may relate to delayed histopathological and functional recovery after cerebral ischemia.     

Continuous Electroencephalography (cEEG) Changes Precede Clinical Changes in a Case of Progressive Cerebral Edema

Background

Continuous electroencephalogram (cEEG) is tightly linked to cerebral metabolism and is sensitive to cerebral ischemia and hypoxia. The severity of cerebral ischemia can be seen on cEEG as changes in morphology, amplitude, or frequency, and cEEG may detect neuronal dysfunction at a reversible stage.

Methods

Case report and imaging.

Results

We present a case of focal cerebral edema with changes seen on cEEG 24 h before clinical signs of increased intracranial pressure. cEEG showed developing asymmetry in the left hemisphere followed by burst suppression. The right hemisphere showed similar progression to burst suppression. Complete suppression of both hemispheres was noted 6 h before clinical signs of herniation. Computed tomography (CT) head confirmed a large left parietal intracerebral hematoma with mass effect.

Conclusions

cEEG has applications in monitoring cerebral dysfunction in addition to detecting seizure activity in the intensive care unit. It may serve a vital role in multi-modality monitoring for early recognition of neurological complications from brain injuries that may not be noticed clinically, which is paramount to early intervention.     

Aggravated inflammation and increased expression of cysteinyl leukotriene receptors in the brain after focal cerebral ischemia in AQP4-deficient mice

Objective Aquaporin-4（AQP4）,the main water channel protein in the brain,plays a critical role in water homeostasis and brain edema.Here,we investigated its role in the inflammatory responses after focal cerebral ischemia. Methods In AQP4-knockout（KO） and wild-type mice,focal cerebral ischemia was induced by 30 min of middle cerebral arterial occlusion（MCAO）.Ischemic neuronal injury and cellular inflammatory responses,as well as the expression and localization of cysteinyl leukotriene CysLT₂ and CysLT₁ receptors,were determined at 24 and 72 h after MCAO. Results AQP4-KO mice showed more neuronal loss,more severe microglial activation and neutrophil infiltration,but less astrocyte proliferation in the brain after MCAO than wild-type mice.In addition,the protein levels of both CysLT₁, and CysLT₂ receptors were up-regulated in the ischemic brain,and the up-regulation was more pronounced in AQP4-KO mice.The CysLT₁,and CysLT₂ receptors were primarily localized in neurons,microglia and neutrophils;those localized in microglia and neutrophils were enhanced in AQP4-KO mice.Conclusion AQP4 may play an inhibitory role in postischemic inflammation.     

Sexual attraction enhances glutamate transmission in mammalian anterior cingulate cortex

Background

Neural stem cells (NSCs) are present in the adult mammalian brain and sustain life-long adult neurogenesis in the dentate gyrus of the hippocampus. In culture, fibroblast growth factor-2 (FGF-2) is sufficient to maintain the self-renewal of adult NSCs derived from the adult rat hippocampus. The underlying signalling mechanism is not fully understood.

Results

In the established adult rat NSC culture, FGF-2 promotes self-renewal by increasing proliferation and inhibiting spontaneous differentiation of adult NSCs, accompanied with activation of MAPK and PLC pathways. Using a molecular genetic approach, we demonstrate that activation of FGF receptor 1 (FGFR1), largely through two key cytoplasmic amino acid residues that are linked to MAPK and PLC activation, suffices to promote adult NSC self-renewal. The canonical MAPK, Erk1/2 activation, is both required and sufficient for the NSC expansion and anti-differentiation effects of FGF-2. In contrast, PLC activation is integral to the maintenance of adult NSC characteristics, including the full capacity for neuronal and oligodendroglial differentiation.

Conclusion

These studies reveal two amino acid residues in FGFR1 with linked downstream intracellular signal transduction pathways that are essential for maintaining adult NSC self-renewal. The findings provide novel insights into the molecular mechanism regulating adult NSC self-renewal, and pose implications for using these cells in potential therapeutic applications.     

Endophilin isoforms have distinct characteristics in interactions with N-type Ca2+ channels and dynamin I

Objective Formation of the endophilin II-Ca 2+ channel complex is Ca 2+ -dependent in clathrin-mediated endocytosis. However, little is known about whether the other two endophilin isoforms have the same features. The present study aimed to investigate the characteristics of the interactions of all three isoforms with Ca 2+ channels and dynamin I. Methods N-type Ca 2+ channel C-terminal fragments (NCFs) synthesized with a 3 H-leucine-labeled kit, were incubated with endophilin-GST fusion proteins, followed by pull-down assay. Results were counted on a scintillation counter. In addition, the different endophilin isoforms were each co-transfected with dynamin I into 293T cells, followed by flow cytometry and co-immunoprecipitation assay. Immunostaining was performed and an image analysis program was used to evaluate the overlap coefficient of cells expressing endophilin and dynamin I. Results All three isoforms interacted with NCF. Endophilins I and II demonstrated clear Ca 2+ -dependent interactions with NCF, whereas endophilin III did not. Co-immunoprecipitation showed that, compared to endophilin I/II, the interaction between endophilin III and dynamin I was significantly increased. Similar results were obtained from flow cytometry. Furthermore, endophilin III had a higher overlap coefficient with dynamin I in co-transfected 293T cells. Conclusion Endophilin isoforms have distinct characteristics in interactions with NCF and dynamin I. Endophilin III binding to NCF is Ca 2+ -independent, implying that it plays a different role in clathrin-mediated endocytosis.     

Endothelin-1 induces LIMK2-mediated programmed necrotic neuronal death independent of NOS activity

Background

Recently, we have reported that LIM kinase 2 (LIMK2) involves programmed necrotic neuronal deaths induced by aberrant cyclin D1 expression following status epilepticus (SE). Up-regulation of LIMK2 expression induces neuronal necrosis by impairment of dynamin-related protein 1 (DRP1)-mediated mitochondrial fission. However, we could not elucidate the upstream effecter for LIMK2-mediated neuronal death. Thus, we investigated the role of endothelin-1 (ET-1) in LIMK2-mediated neuronal necrosis, since ET-1 involves neuronal death via various pathways.

Results

Following SE, ET-1 concentration and its mRNA were significantly increased in the hippocampus with up-regulation of ET_B receptor expression. BQ788 (an ET_B receptor antagonist) effectively attenuated SE-induced neuronal damage as well as reduction in LIMK2 mRNA/protein expression. In addition, BQ788 alleviated up-regulation of Rho kinase 1 (ROCK1) expression and impairment of DRP1-mediated mitochondrial fission in CA1 neurons following SE. BQ788 also attenuated neuronal death and up-regulation of LIMK2 expression induced by exogenous ET-1 injection.

Conclusion

These findings suggest that ET-1 may be one of the upstream effectors for programmed neuronal necrosis through abnormal LIMK2 over-expression by ROCK1.