Apoptosis and necrosis after reversible focal ischemia: an in situ DNA fragmentation analysis

Mobile phone specific radiation disturbs cytokinesis and causes cell death but not acute chromosomal damage in buccal cells: Results of a controlled human intervention study

Several human studies indicate that mobile phone specific electromagnetic fields may cause cancer in humans but the underlying molecular mechanisms are currently not known. Studies concerning chromosomal damage (which is causally related to cancer induction) are controversial and those addressing this issue in mobile phone users are based on the use of questionnaires to assess the exposure. We realized the first human intervention trial in which chromosomal damage and acute toxic effects were studied under controlled conditions. The participants were exposed via headsets at one randomly assigned side of the head to low and high doses of a UMTS signal (n = 20, to 0.1 W/kg and n = 21 to 1.6 W/kg Specific Absorption Rate) for 2 h on 5 consecutive days. Before and three weeks after the exposure, buccal cells were collected from both cheeks and micronuclei (MN, which are formed as a consequence of structural and numerical chromosomal aberrations) and other nuclear anomalies reflecting mitotic disturbance and acute cytotoxic effects were scored. We found no evidence for induction of MN and of nuclear buds which are caused by gene amplifications, but a significant increase of binucleated cells which are formed as a consequence of disturbed cell divisions, and of karyolitic cells, which are indicative for cell death. No such effects were seen in cells from the less exposed side. Our findings indicate that mobile phone specific high frequency electromagnetic fields do not cause acute chromosomal damage in oral mucosa cells under the present experimental conditions. However, we found clear evidence for disturbance of the cell cycle and cytotoxicity. These effects may play a causal role in the induction of adverse long term health effects in humans.

Granzymes in health and diseases: the good, the bad and the ugly

Granzymes are a family of serine proteases, composed of five human members: GA, B, H, M and K. They were first discovered in the 1980s within cytotoxic granules released during NK cell- and T cell-mediated killing. Through their various proteolytic activities, granzymes can trigger different pathways within cells, all of which ultimately lead to the same result, cell death. Over the years, the initial consideration of granzymes as mere cytotoxic mediators has changed due to surprising findings demonstrating their expression in cells other than immune effectors as well as new intracellular and extracellular activities. Additional roles have been identified in the extracellular milieu, following granzyme escape from the immunological synapse or their release by specific cell types. Outside the cell, granzyme activities mediate extracellular matrix alteration via the degradation of matrix proteins or surface receptors. In certain contexts, these processes are essential for tissue homeostasis; in others, excessive matrix degradation and extensive cell death contribute to the onset of chronic diseases, inflammation, and autoimmunity. Here, we provide an overview of both the physiological and pathological roles of granzymes, highlighting their utility while also recognizing how their unregulated presence can trigger the development and/or worsening of diseases.

Similarities in the Electrographic Patterns of Delayed Cerebral Infarction and Brain Death After Aneurysmal and Traumatic Subarachnoid Hemorrhage

While subarachnoid hemorrhage is the second most common hemorrhagic stroke in epidemiologic studies, the recent DISCHARGE-1 trial has shown that in reality, three-quarters of focal brain damage after subarachnoid hemorrhage is ischemic. Two-fifths of these ischemic infarctions occur early and three-fifths are delayed. The vast majority are cortical infarcts whose pathomorphology corresponds to anemic infarcts. Therefore, we propose in this review that subarachnoid hemorrhage as an ischemic-hemorrhagic stroke is rather a third, separate entity in addition to purely ischemic or hemorrhagic strokes. Cumulative focal brain damage, determined by neuroimaging after the first 2 weeks, is the strongest known predictor of patient outcome half a year after the initial hemorrhage. Because of the unique ability to implant neuromonitoring probes at the brain surface before stroke onset and to perform longitudinal MRI scans before and after stroke, delayed cerebral ischemia is currently the stroke variant in humans whose pathophysiological details are by far the best characterized. Optoelectrodes located directly over newly developing delayed infarcts have shown that, as mechanistic correlates of infarct development, spreading depolarizations trigger (1) spreading ischemia, (2) severe hypoxia, (3) persistent activity depression, and (4) transition from clustered spreading depolarizations to a negative ultraslow potential. Furthermore, traumatic brain injury and subarachnoid hemorrhage are the second and third most common etiologies of brain death during continued systemic circulation. Here, we use examples to illustrate that although the pathophysiological cascades associated with brain death are global, they closely resemble the local cascades associated with the development of delayed cerebral infarcts.

Current trends in luminescence-based assessment of apoptosis

Apoptosis, the most extensively studied type of cell death, is known to play a crucial role in numerous processes such as elimination of unwanted cells or cellular debris, growth, control of the immune system, and prevention of malignancies. Defective regulation of apoptosis can trigger various diseases and disorders including cancer, neurological conditions, autoimmune diseases and developmental disorders. Knowing the nuances of the cell death type induced by a compound can help decipher which therapy is more effective for specific diseases. The detection of apoptotic cells using classic methods has brought significant contribution over the years, but innovative methods are quickly emerging and allow more in-depth understanding of the mechanisms, aside from a simple quantification. Due to increased sensitivity, time efficiency, pathway specificity and negligible cytotoxicity, these innovative approaches have great potential for both in vitro and in vivo studies. This review aims to shed light on the importance of developing and using novel nanoscale methods as an alternative to the classic apoptosis detection techniques.

Gonadal Degeneration Is Mediated by Apoptotic Processes in the Semelparous Gray Side-Gilled Sea Slug Pleurobranchaea maculata

AbstractSpecies undergoing postreproductive death experience great changes in their reproductive organs, which are driven by numerous physiological processes. To assess whether apoptotic processes are involved in the dynamics of the reproductive organs of Pleurobranchaea maculata, the gonadal structure of this semelparous side-gilled sea slug was studied using light and scanning electron microscopy. Apoptotic cells at different gonadal developmental stages were detected by in situ TUNEL assay. Apoptosis was primarily focused on spermatogonia during gonadal cell proliferation, probably as a regulatory mechanism that maintains homeostasis in reproductive cells. Visible gonadal degeneration at the end of the reproductive period is accompanied by apoptosis of the basal lamina cells of the acini, suggesting that apoptotic processes are involved in the gonadal degeneration observed in P. maculata.

Pharmacological therapy to cerebral ischemia-reperfusion injury: Focus on saponins

Secondary insult from cerebral ischemia-reperfusion injury (CIRI) is a major risk factor for poor prognosis of cerebral ischemia. Saponins are steroid or triterpenoid glycosides with various pharmacological activities that are effective in treating CIRI. By browsing the literature from 2001 to 2021, 55 references involving 24 kinds of saponins were included. Saponins were shown to relieve CIRI by inhibiting oxidation stress, neuroinflammation, and apoptosis, restoring BBB integrity, and promoting neurogenesis and angiogenesis. This review summarizes and classifies several common saponins and their mechanisms in relieving CIRI. Information provided in this review will benefit researchers to design, research and develop new medicines to treat CIRI-related conditions with saponins.

Migraine Aura, Transient Ischemic Attacks, Stroke, and Dying of the Brain Share the Same Key Pathophysiological Process in Neurons Driven by Gibbs–Donnan Forces, Namely Spreading Depolarization

Neuronal cytotoxic edema is the morphological correlate of the near-complete neuronal battery breakdown called spreading depolarization, or conversely, spreading depolarization is the electrophysiological correlate of the initial, still reversible phase of neuronal cytotoxic edema. Cytotoxic edema and spreading depolarization are thus different modalities of the same process, which represents a metastable universal reference state in the gray matter of the brain close to Gibbs–Donnan equilibrium. Different but merging sections of the spreading-depolarization continuum from short duration waves to intermediate duration waves to terminal waves occur in a plethora of clinical conditions, including migraine aura, ischemic stroke, traumatic brain injury, aneurysmal subarachnoid hemorrhage (aSAH) and delayed cerebral ischemia (DCI), spontaneous intracerebral hemorrhage, subdural hematoma, development of brain death, and the dying process during cardio circulatory arrest. Thus, spreading depolarization represents a prime and simultaneously the most neglected pathophysiological process in acute neurology. Aristides Leão postulated as early as the 1940s that the pathophysiological process in neurons underlying migraine aura is of the same nature as the pathophysiological process in neurons that occurs in response to cerebral circulatory arrest, because he assumed that spreading depolarization occurs in both conditions. With this in mind, it is not surprising that patients with migraine with aura have about a twofold increased risk of stroke, as some spreading depolarizations leading to the patient percept of migraine aura could be caused by cerebral ischemia. However, it is in the nature of spreading depolarization that it can have different etiologies and not all spreading depolarizations arise because of ischemia. Spreading depolarization is observed as a negative direct current (DC) shift and associated with different changes in spontaneous brain activity in the alternating current (AC) band of the electrocorticogram. These are non-spreading depression and spreading activity depression and epileptiform activity. The same spreading depolarization wave may be associated with different activity changes in adjacent brain regions. Here, we review the basal mechanism underlying spreading depolarization and the associated activity changes. Using original recordings in animals and patients, we illustrate that the associated changes in spontaneous activity are by no means trivial, but pose unsolved mechanistic puzzles and require proper scientific analysis.

The Critical Role of Spreading Depolarizations in Early Brain Injury: Consensus and Contention

BACKGROUND

When a patient arrives in the emergency department following a stroke, a traumatic brain injury, or sudden cardiac arrest, there is no therapeutic drug available to help protect their jeopardized neurons. One crucial reason is that we have not identified the molecular mechanisms leading to electrical failure, neuronal swelling, and blood vessel constriction in newly injured gray matter. All three result from a process termed spreading depolarization (SD). Because we only partially understand SD, we lack molecular targets and biomarkers to help neurons survive after losing their blood flow and then undergoing recurrent SD.

METHODS

In this review, we introduce SD as a single or recurring event, generated in gray matter following lost blood flow, which compromises the Na⁺/K⁺ pump. Electrical recovery from each SD event requires so much energy that neurons often die over minutes and hours following initial injury, independent of extracellular glutamate.

RESULTS

We discuss how SD has been investigated with various pitfalls in numerous experimental preparations, how overtaxing the Na⁺/K⁺ ATPase elicits SD. Elevated K⁺ or glutamate are unlikely natural activators of SD. We then turn to the properties of SD itself, focusing on its initiation and propagation as well as on computer modeling.

CONCLUSIONS

Finally, we summarize points of consensus and contention among the authors as well as where SD research may be heading. In an accompanying review, we critique the role of the glutamate excitotoxicity theory, how it has shaped SD research, and its questionable importance to the study of early brain injury as compared with SD theory.

Intravenous Administration of Human Amniotic Mesenchymal Stem Cells in the Subacute Phase of Cerebral Infarction in a Mouse Model Ameliorates Neurological Disturbance by Suppressing Blood Brain Barrier Disruption and Apoptosis via Immunomodulation

Neuro-inflammation plays a key role in the pathophysiology of brain infarction. Cell therapy offers a novel therapeutic option due to its effect on immunomodulatory effects. Amniotic stem cells, in particular, show promise owing to their low immunogenicity, tumorigenicity, and easy availability from amniotic membranes discarded following birth. We have successfully isolated and expanded human amniotic mesenchymal stem cells (hAMSCs). Herein, we evaluated the therapeutic effect of hAMSCs on neurological deficits after brain infarction as well as their immunomodulatory effects in a mouse model in order to understand their mechanisms of action. One day after permanent occlusion of the middle cerebral artery (MCAO), hAMSCs were intravenously administered. RT-qPCR for TNFα, iNOS, MMP2, and MMP9, immunofluorescence staining for iNOS and CD11b/c, and a TUNEL assay were performed 8 days following MCAO. An Evans Blue assay and behavioral tests were performed 2 days and several months following MCAO, respectively. The results suggest that the neurological deficits caused by cerebral infarction are improved in dose-dependent manner by the administration of hAMSCs. The mechanism appears to be through a reduction in disruption of the blood brain barrier and apoptosis in the peri-infarct region through the suppression of pro-inflammatory cytokines and the M2-to-M1 phenotype shift.

Comparison of Anti-oncotic Effect of TRPM4 Blocking Antibody in Neuron, Astrocyte and Vascular Endothelial Cell Under Hypoxia

In stroke and other neurological diseases, Transient Receptor Potential Melastatin 4 (TRPM4) has been reported to cause oncotic cell death which is due to an excessive influx of sodium ions. Following stroke, hypoxia condition activates TRPM4 channel, and the sodium influx via TRPM4 is further enhanced by an increased TRPM4 expression. However, the effect of TRPM4 inhibition on oncotic cell death, particularly during the acute stage, remains largely unknown. Recently, we have developed a polyclonal antibody M4P that specifically inhibits TRPM4 channel. M4P blocks the channel via binding to a region close to the channel pore from extracellular space. Using M4P, we evaluated the acute effect of blocking TRPM4 in neurons, astrocytes, and vascular endothelial cells. In a rat stroke model, M4P co-localized with neuronal marker NeuN and endothelial marker vWF, whereas few GFAP positive astrocytes were stained by M4P in the ipsilateral hemisphere. When ATP was acutely depleted in cultured cortical neurons and microvascular endothelial cells, cell swelling was induced. Application of M4P significantly blocked TRPM4 current and attenuated oncosis. TUNEL assay, PI staining and western blot on cleaved Caspase-3 revealed that M4P could ameliorate apoptosis after 24 h hypoxia exposure. In contrast, acute ATP depletion in cultured astrocytes failed to demonstrate an increase of cell volume, and application of M4P or control IgG had no effect on cell volume change. When TRPM4 was overexpressed in astrocytes, acute ATP depletion successfully induced oncosis which could be suppressed by M4P treatment. Our results demonstrate that comparing to astrocytes, neurons, and vascular endothelial cells are more vulnerable to hypoxic injury. During the acute stage of stroke, blocking TRPM4 channel could protect neurons and vascular endothelial cells from oncotic cell death.

Lower cardiac output is associated with neurodegeneration among older adults with normal cognition but not mild cognitive impairment

Subclinical cardiac dysfunction is associated with smaller total brain volume on magnetic resonance imaging (MRI). To study whether cardiac output relates to regional measurements of grey and white matter structure, older adults (n = 326) underwent echocardiogram to quantify cardiac output (L/min) and brain MRI. Linear regressions related cardiac output to grey matter volumes measured on T₁ and white matter hyperintensities assessed on T₂-FLAIR. Voxelwise analyses related cardiac output to diffusion tensor imaging adjusting for demographic, genetic, and vascular risk factors. Follow-up models assessed a cardiac output x diagnosis interaction with stratification (normal cognition, mild cognitive impairment). Cardiac output interacted with diagnosis, such that lower cardiac output related to smaller total grey matter (p = 0.01), frontal lobe (p = 0.01), and occipital lobe volumes (p = 0.01) among participants with normal cognition. When excluding participants with cardiovascular disease and atrial fibrillation, associations emerged with smaller parietal lobe (p = 0.005) and hippocampal volume (p = 0.05). Subtle age-related cardiac changes may disrupt neuronal homeostasis and impact grey matter integrity prior to cognitive impairment.

HIF‑1α attenuates neuronal apoptosis by upregulating EPO expression following cerebral ischemia‑reperfusion injury in a rat MCAO model

Hypoxia-inducible factor-1α (HIF-1α) is a key transcriptional factor in response to hypoxia and is involved in ischemic stroke. In the present study, the potential for HIF-1α to inhibit neuronal apoptosis through upregulating erythropoietin (EPO) was investigated in a transient middle cerebral artery occlusion (tMCAO) rat stroke model. For this purpose, a recombinant adenovirus expressing HIF-1α was engineered (Ad-HIF-1α). Control adenovirus (Ad group), Ad-HIF-1α (Ad-HIF-1α group) or Ad-HIF-1α in addition to erythropoietin mimetic peptide-9 (EMP9), an EPO-receptor (-R) antagonist (Ad-HIF-1α+EMP9 group), were used for an intracranial injection into rat ischemic penumbra 1 h following MCAO. All rats demonstrated functional improvement following tMCAO, while the improvement rate was faster in rats treated by Ad-HIF-1α compared with all other groups. The EPO-R inhibitor partially reversed the benefits of Ad-HIF-1α. Apoptosis induced by tMCAO was significantly inhibited by Ad-HIF-1α (P<0.05). The expression of HIF-1α, evaluated by immunohistochemistry either in neurons or astrocytes, was upregulated by Ad-HIF-1α. Both EPO mRNA and protein expression were increased by Ad-HIF-1α, however, there was no significant change of EPO-R either on an mRNA level or protein level. Furthermore, EMP9 did not change the EPO expression which was upregulated by Ad-HIF-1α. Activated caspase 3 in neurons was suppressed by Ad-HIF-1α. Activated caspase 3 downregulated by HIF-1α was partially blocked by EMP9. Altogether, the present data demonstrated that HIF-1α attenuates neuronal apoptosis partially through upregulating EPO following cerebral ischemia in rat. Thus, upregulating HIF-1α subsequent to a stroke may be a potential treatment for ischemic stroke.

Morphological and immunohistochemical analysis of proteins CASPASE 3 and XIAP in rats subjected to cerebral ischemia and chronic alcoholism

PURPOSE

To evaluate histopathological and ultrastructural changes and expression of proteins related to apoptosis CASPASE 3 and XIAP after experimental induction of temporary focal cerebral ischemia (90 minutes) due to obstruction of the middle cerebral artery in alcoholism model.

METHODS

Forty adult Wistar rats were used, subdivided into 5 experimental groups: control group (C); Sham group (S); Ischemic group (I); Alcoholic group (A); and Ischemic and Alcoholized group (I+A): animals submitted to the same treatment of group A and after four weeks were submitted to focal cerebral ischemia during 90 minutes, followed by reperfusion of 48 hours. Were processed for histopathological analysis and immunohistochemistry (for the protein expression of CASPASE -3 and XIAP).

RESULTS

Greater histopathological changes were observed in the animals of groups I and I+A in the three areas analyzed. The neuronal loss was higher in the medial striatum region of the animals of groups I and I + A. The protein expression of CASPASE -3 was higher than that of XIAP in the groups I and I + A for both proteins.

CONCLUSION

The expression of XIAP was slightly higher where the histopathological changes and expression of CASPASE -3 was less evident.

Inflammatory Profiles of the Interleukin Family and Network in Cerebral Hemorrhage

Cerebral hemorrhage is a series of devastating cerebrovascular diseases with high mortality, morbidity and recurrence rate. Localized and systemic immuno-reactions are involved. Aggregation of immunocytes, which were both recruited from the peripheral circulation and resident in the central nervous system, is induced and activated by hematoma-related blood components. Subsequently, various cytokines, chemokines, free radicals and toxic chemicals are secreted to participant host defense responses. Among these, neuro-inflammation plays critical roles in both the pathologic processes of secondary injuries and recovery of neural damages. Numerous treatment strategies have been proposed, aiming at controlling the balance between anti- and proinflammation. Here, we summarized our current understanding and potential clinical applications for cytokines of the interleukin family in the pathogenesis of hemorrhagic stroke. In addition, we conducted protein-protein network, gene ontology and KEGG analysis on the interleukins using online bioinformatic tools to further elaborate the comprehensive mechanisms of interleukins in cerebral hemorrhage.

Oncotic Cell Death in Stroke

Oncotic cell death or oncosis represents a major mechanism of cell death in ischaemic stroke, occurring in many central nervous system (CNS) cell types including neurons, glia and vascular endothelial cells. In stroke, energy depletion causes ionic pump failure and disrupts ionic homeostasis. Imbalance between the influx of Na⁺ and Cl^- ions and the efflux of K⁺ ions through various channel proteins and transporters creates a transmembrane osmotic gradient, with ensuing movement of water into the cells, resulting in cell swelling and oncosis. Oncosis is a key mediator of cerebral oedema in ischaemic stroke, contributing directly through cytotoxic oedema, and indirectly through vasogenic oedema by causing vascular endothelial cell death and disruption of the blood-brain barrier (BBB). Hence, inhibition of uncontrolled ionic flux represents a novel and powerful strategy in achieving neuroprotection in stroke. In this review, we provide an overview of oncotic cell death in the pathology of stroke. Importantly, we summarised the therapeutically significant pathways of water, Na⁺, Cl^- and K⁺ movement across cell membranes in the CNS and their respective roles in the pathobiology of stroke.

The emerging link between O-GlcNAcylation and neurological disorders

O-linked β-N-acetylglucosaminylation (O-GlcNAcylation) is involved in the regulation of many cellular cascades and neurological diseases such as Alzheimer's disease (AD), Parkinson's disease (PD), and stroke. In the brain, the expression of O-GlcNAcylation is notably heightened, as is that of O-linked N-acetylglucosaminyltransferase (OGT) and β-N-acetylglucosaminidase (OGA), the presence of which is prominent in many regions of neurological importance. Most importantly, O-GlcNAcylation is believed to contribute to the normal functioning of neurons; conversely, its dysregulation participates in the pathogenesis of neurological disorders. In neurodegenerative diseases, O-GlcNAcylation of the brain's key proteins, such as tau and amyloid-β, interacts with their phosphorylation, thereby triggering the formation of neurofibrillary tangles and amyloid plaques. An increase of O-GlcNAcylation by pharmacological intervention prevents neuronal loss. Additionally, O-GlcNAcylation is stress sensitive, and its elevation is cytoprotective. Increased O-GlcNAcylation ameliorated brain damage in victims of both trauma-hemorrhage and stroke. In this review, we summarize the current understanding of O-GlcNAcylation's physiological and pathological roles in the nervous system and provide a foundation for development of a therapeutic strategy for neurological disorders.

Spreading depolarization is not an epiphenomenon but the principal mechanism of the cytotoxic edema in various gray matter structures of the brain during stroke

Spreading depolarization (SD) is a phenomenon of various cerebral gray matter structures that only occurs under pathological conditions. In the present paper, we summarize the evidence from several decades of research that SD and cytotoxic edema in these structures are largely overlapping terms. SD/cytotoxic edema is a toxic state that - albeit initially reversible - leads eventually to cellular death when it is persistent. Both hemorrhagic and ischemic stroke are among the most prominent causes of SD/cytotoxic edema. SD/cytotoxic edema is the principal mechanism that mediates neuronal death in these conditions. This applies to gray matter structures in both the ischemic core and the penumbra. SD/cytotoxic edema is often a single terminal event in the core whereas, in the penumbra, a cluster of repetitive prolonged SDs is typical. SD/cytotoxic edema also propagates widely into healthy surrounding tissue as short-lasting, relatively harmless events so that regional electrocorticographic monitoring affords even remote detection of ischemic zones. Ischemia cannot only cause SD/cytotoxic edema but it can also be its consequence through inverse neurovascular coupling. Under this condition, ischemia does not start simultaneously in different regions but spreads in the tissue driven by SD/cytotoxic edema-induced microvascular constriction (= spreading ischemia). Spreading ischemia prolongs SD/cytotoxic edema. Thus, it increases the likelihood for the transition from SD/cytotoxic edema into cellular death. Vasogenic edema is the other major type of cerebral edema with relevance to ischemic stroke. It results from opening of the blood-brain barrier. SD/cytotoxic edema and vasogenic edema are distinct processes with important mutual interactions. This article is part of the Special Issue entitled 'Cerebral Ischemia'.

Recording, analysis, and interpretation of spreading depolarizations in neurointensive care: Review and recommendations of the COSBID research group

Spreading depolarizations (SD) are waves of abrupt, near-complete breakdown of neuronal transmembrane ion gradients, are the largest possible pathophysiologic disruption of viable cerebral gray matter, and are a crucial mechanism of lesion development. Spreading depolarizations are increasingly recorded during multimodal neuromonitoring in neurocritical care as a causal biomarker providing a diagnostic summary measure of metabolic failure and excitotoxic injury. Focal ischemia causes spreading depolarization within minutes. Further spreading depolarizations arise for hours to days due to energy supply-demand mismatch in viable tissue. Spreading depolarizations exacerbate neuronal injury through prolonged ionic breakdown and spreading depolarization-related hypoperfusion (spreading ischemia). Local duration of the depolarization indicates local tissue energy status and risk of injury. Regional electrocorticographic monitoring affords even remote detection of injury because spreading depolarizations propagate widely from ischemic or metabolically stressed zones; characteristic patterns, including temporal clusters of spreading depolarizations and persistent depression of spontaneous cortical activity, can be recognized and quantified. Here, we describe the experimental basis for interpreting these patterns and illustrate their translation to human disease. We further provide consensus recommendations for electrocorticographic methods to record, classify, and score spreading depolarizations and associated spreading depressions. These methods offer distinct advantages over other neuromonitoring modalities and allow for future refinement through less invasive and more automated approaches.

Inhibition of cerebral ischemia/reperfusion injury-induced apoptosis: nicotiflorin and JAK2/STAT3 pathway

Nicotiflorin is a flavonoid extracted from Carthamus tinctorius. Previous studies have shown its cerebral protective effect, but the mechanism is undefined. In this study, we aimed to determine whether nicotiflorin protects against cerebral ischemia/reperfusion injury-induced apoptosis through the JAK2/STAT3 pathway. The cerebral ischemia/reperfusion injury model was established by middle cerebral artery occlusion/reperfusion. Nicotiflorin (10 mg/kg) was administered by tail vein injection. Cell apoptosis in the ischemic cerebral cortex was examined by hematoxylin-eosin staining and terminal deoxynucleotidyl transferase dUTP nick end labeling assay. Bcl-2 and Bax expression levels in ischemic cerebral cortex were examined by immunohistochemial staining. Additionally, p-JAK2, p-STAT3, Bcl-2, Bax, and caspase-3 levels in ischemic cerebral cortex were examined by western blot assay. Nicotiflorin altered the shape and structure of injured neurons, decreased the number of apoptotic cells, down-regulates expression of p-JAK2, p-STAT3, caspase-3, and Bax, decreased Bax immunoredactivity, and increased Bcl-2 protein expression and immunoreactivity. These results suggest that nicotiflorin protects against cerebral ischemia/reperfusion injury-induced apoptosis via the JAK2/STAT3 pathway.

Cytotoxicity Evaluation of Essential Oil and its Component from Zingiber officinale Roscoe

Zingiber officinale Roscoe has been widely used as a folk medicine to treat various diseases, including cancer. This study aims to re-examine the therapeutic potential of co-administration of natural products and cancer chemotherapeutics. Candidate material for this project, α-zingiberene, was extracted from Zingiber officinale Roscoe, and α-zingiberene makes up 35.02 ± 0.30% of its total essential oil. α-Zingiberene showed low IC50 values, 60.6 ± 3.6, 46.2 ± 0.6, 172.0 ± 6.6, 80.3 ± 6.6 (μg/mL) in HeLa, SiHa, MCF-7 and HL-60 cells each. These values are a little bit higher than IC50 values of general essential oil in those cells. The treatment of α-zingiberene produced nucleosomal DNA fragmentation in SiHa cells, and the percentage of sub-diploid cells increased in a concentration-dependent manner in SiHa cells, hallmark features of apoptosis. Mitochondrial cytochrome c activation and an in vitro caspase-3 activity assay demonstrated that the activation of caspases accompanies the apoptotic effect of α-zingiberene, which mediates cell death. These results suggest that the apoptotic effect of α-zingiberene on SiHa cells may converge caspase-3 activation through the release of mitochondrial cytochrome c into cytoplasm. It is considered that anti-proliferative effect of α-zingiberene is a result of apoptotic effects, and α-zingiberene is worth furthermore study to develop it as cancer chemotherapeutics.

Sphingosine kinase 1/sphingosine-1-phosphate regulates the expression of interleukin-17A in activated microglia in cerebral ischemia/reperfusion

BACKGROUND

Microglial activation is one of the causative factors of neuroinflammation in cerebral ischemia/reperfusion (IR). Sphingosine kinase 1 (Sphk1), a key enzyme responsible for phosphorylating sphingosine into sphingosine-1-phosphate (S1P), plays an important role in the regulation of proinflammatory cytokines in activated microglia. Recent research demonstrated that S1P increased IL-17A-secretion and then worsened CNS (central nervous system) inflammation. Thus, in the present study, we sought to use microglial cells as the object of study to discuss the molecular mechanisms in Sphk1/S1P-regulated IL-17A-secretion in IR.

METHODS

We used immunofluorescence and confocal microscopy to detect whether Sphk1 is expressed in microglia after cerebral IR or oxygen-glucose deprivation (OGDR). Western blot analysis was used to estimate the total Sphk1 protein level at different time points after OGDR. To detect cytokine secretion in microglial supernatants in response to OGDR, we measured the concentration of IL-17A in the culture supernatants using an enzyme-linked immunosorbent assay (ELISA). To evaluate whether microglia subjected to OGDR exhibited neuronal injury, we used a commercially available terminal transferase-mediated deoxyuridine triphosphate-biotin nick end labeling (TUNEL) kit to detect apoptotic neurons.

RESULTS

Sphk1 was expressed in microglia in response to cerebral IR or OGDR at appointed time. Pre-injection with PF-543, an inhibitor of Sphk1, before IR clearly reduced the expression of Sphk1 in microglia relative to brain IR alone. The number of TUNEL-positive neurons was also decreased in the PF-543-pretreated animals before IR compared to the animals with IR alone. When S1P was administered in OGDR microglia, IL-17A expression and neuronal apoptosis were increased compared to OGDR alone and the administration of S1P alone. ELISA further confirmed the above results. Moreover, the inhibition of Sphk1 by siRNA reduced IL-17A production and relieved neuronal apoptosis in OGDR microglia.

CONCLUSION

These results indicated that Sphk1/S1P regulates the expression of IL-17A in activated microglia, inducing neuronal apoptosis in cerebral ischemia/reperfusion. The microglial Sphk1/S1P pathway may thus be a potential therapeutic target to control neuroinflammation in brain IR.

RGD-decorated redox-responsived-α-tocopherol polyethylene glycol succinate–poly(lactide) nanoparticles for targeted drug delivery

A novel kind of copolymer, TPGS-SS-PLA, was successfully synthesized and applied in targeted drug delivery.

Combination of methylprednisolone and rosiglitazone promotes recovery of neurological function after spinal cord injury

Methylprednisolone exhibits anti-inflammatory antioxidant properties, and rosiglitazone acts as an anti-inflammatory and antioxidant by activating peroxisome proliferator-activated receptor-γ in the spinal cord. Methylprednisolone and rosiglitazone have been clinically used during the early stages of secondary spinal cord injury. Because of the complexity and diversity of the inflammatory process after spinal cord injury, a single drug cannot completely inhibit inflammation. Therefore, we assumed that a combination of methylprednisolone and rosiglitazone might promote recovery of neurological function after secondary spinal cord injury. In this study, rats were intraperitoneally injected with methylprednisolone (30 mg/kg) and rosiglitazone (2 mg/kg) at 1 hour after injury, and methylprednisolone (15 mg/kg) at 24 and 48 hours after injury. Rosiglitazone was then administered once every 12 hours for 7 consecutive days. Our results demonstrated that a combined treatment with methylprednisolone and rosiglitazone had a more pronounced effect on attenuation of inflammation and cell apoptosis, as well as increased functional recovery, compared with either single treatment alone, indicating that a combination better promoted recovery of neurological function after injury.

Morphological characteristics of eosinophilic neuronal death after transient unilateral forebrain ischemia in Mongolian gerbils

Various types of eosinophilic neurons (ENs) are found in the post-ischemic brain. The aim of the present study was to elucidate the temporal and spatial profile of ENs, the expression of TUNEL staining and ultrastructural characteristics in the core and peripheral regions of the cortex post-ischemia. Unilateral forebrain ischemia was induced in Mongolian gerbils by transient common carotid artery occlusions, and the brains from 3 h to 2 weeks post-ischemia were prepared for morphometric, electron microscopy (EM) and TUNEL staining of the ENs. Light microscopy showed that ENs with minimally abnormal nuclei and swollen cell bodies appeared at 3 h in the ischemic core and at 12 h in the periphery. Thereafter, ENs with pyknosis and irregular atrophic cytoplasm peaked at 12 h, pyknosis with scant cytoplasm peaked at 4 days, and TUNEL-positive staining was observed in the ischemic core. In the ischemic periphery, ENs had slightly atrophic cytoplasm and sequentially developed pyknosis, karyorrhexis and karyolysis over 1 week. These cells were also positive for TUNEL. In EM, severe organelle dilation and vacuolization preceded chromatin fragmentation in the ischemic core, while chromatin fragmentation and homogenization were the vital characteristics in the ischemic periphery. There might be two region-dependent pathways for EN changes in the post-ischemic brain: pyknosis with cytoplasmic shrinkage in the core and nuclear disintegration with slightly atrophic cytoplasm in the periphery. These pathways were comparable to necrosis and proceeded from non-classical apoptosis to necrosis, respectively.

Effects of Repetitive Transcranial Magnetic Stimulation on Behavioral Recovery during Early Stage of Traumatic Brain Injury in Rats

Repetitive transcranial magnetic stimulation (rTMS) is a promising technique that modulates neural networks. However, there were few studies evaluating the effects of rTMS in traumatic brain injury (TBI). Herein, we assessed the effectiveness of rTMS on behavioral recovery and metabolic changes using brain magnetic resonance spectroscopy (MRS) in a rat model of TBI. We also evaluated the safety of rTMS by measuring brain swelling with brain magnetic resonance imaging (MRI). Twenty male Sprague-Dawley rats underwent lateral fluid percussion and were randomly assigned to the sham (n=10) or the rTMS (n=10) group. rTMS was applied on the fourth day after TBI and consisted of 10 daily sessions for 2 weeks with 10 Hz frequency (total pulses=3,000). Although the rTMS group showed an anti-apoptotic effect around the peri-lesional area, functional improvements were not significantly different between the two groups. Additionally, rTMS did not modulate brain metabolites in MRS, nor was there any change of brain lesion or edema after magnetic stimulation. These data suggest that rTMS did not have beneficial effects on motor recovery during early stages of TBI, although an anti-apoptosis was observed in the peri-lesional area.

O-GlcNAcylation regulates ischemia-induced neuronal apoptosis through AKT signaling

Apoptosis plays an important role in neural development and neurological disorders. In this study, we found that O-GlcNAcylation, a unique protein posttranslational modification with O-linked β-N-acetylglucosamine (GlcNAc), promoted apoptosis through attenuating phosphorylation/activation of AKT and Bad. By using co-immunoprecipitation and mutagenesis techniques, we identified O-GlcNAc modification at both Thr308 and Ser473 of AKT. O-GlcNAcylation-induced apoptosis was attenuated by over-expression of AKT. We also found a dynamic elevation of protein O-GlcNAcylation during the first four hours of cerebral ischemia, followed by continuous decline after middle cerebral artery occlusion (MCAO) in the mouse brain. The elevation of O-GlcNAcylation coincided with activation of cell apoptosis. Finally, we found a negative correlation between AKT phosphorylation and O-GlcNAcylation in ischemic brain tissue. These results indicate that cerebral ischemia induces a rapid increase of O-GlcNAcylation that promotes apoptosis through down-regulation of AKT activity. These findings provide a novel mechanism through which O-GlcNAcylation regulates ischemia-induced neuronal apoptosis through AKT signaling.

The stroke-migraine depolarization continuum

The term spreading depolarization (SD) refers to waves of abrupt, sustained mass depolarization in gray matter of the CNS. SD, which spreads from neuron to neuron in affected tissue, is characterized by a rapid near-breakdown of the neuronal transmembrane ion gradients. SD can be induced by hypoxic conditions--such as from ischemia--and facilitates neuronal death in energy-compromised tissue. SD has also been implicated in migraine aura, where SD is assumed to ascend in well-nourished tissue and is typically benign. In addition to these two ends of the "SD continuum," an SD wave can propagate from an energy-depleted tissue into surrounding, well-nourished tissue, as is often the case in stroke and brain trauma. This review presents the neurobiology of SD--its triggers and propagation mechanisms--as well as clinical manifestations of SD, including overlaps and differences between migraine aura and stroke, and recent developments in neuromonitoring aimed at better diagnosis and more targeted treatments.

The PBDE metabolite 6-OH-BDE 47 affects melanin pigmentation and THRβ MRNA expression in the eye of zebrafish embryos

Polybrominated diphenyl ethers and their hydroxyl-metabolites (OH-BDEs) are commonly detected contaminants in human serum in the US population. They are also considered to be endocrine disruptors, and are specifically known to affect thyroid hormone regulation. In this study, we investigated and compared the effects of a PBDE and its OH-BDE metabolite on developmental pathways regulated by thyroid hormones using zebrafish as a model. Exposure to 6-OHBDE 47 (10–100 nM), but not BDE 47 (1–50 μM), led to decreased melanin pigmentation and increased apoptosis in the retina of zebrafish embryos in a concentration-dependent manner in short-term exposures (4 – 30 hours). Six-OH-BDE 47 exposure also significantly decreased thyroid hormone receptor β (THRβ) mRNA expression, which was confirmed using both RT-PCR and in situ hybridization (whole mount and paraffin- section). Interestingly, exposure to the native thyroid hormone, triiodothyronine (T3) also led to similar responses: decreased THRβ mRNA expression, decreased melanin pigmentation and increased apoptosis, suggesting that 6-OH-BDE 47 may be acting as a T3 mimic. To further investigate short-term effects that may be regulated by THRβ, experiments using a morpholino gene knock down and THRβ mRNA over expression were conducted. Knock down of THRβ led to decreases in melanin pigmentation and increases in apoptotic cells in the eye of zebrafish embryos, similar to exposure to T3 and 6-OH-BDE 47, but THRβ mRNA overexpression rescued these effects. Histological analysis of eyes at 22 hpf from each group revealed that exposure to T3 or to 6-OH-BDE 47 was associated with a decrease of melanin and diminished proliferation of cells in layers of retina near the choroid. This study suggests that 6-OH-BDE 47 disrupts the activity of THRβ in early life stages of zebrafish, and warrants further studies on effects in developing humans.

IL-33 expression in the cerebral cortex following experimental subarachnoid hemorrhage in rats

Subarachnoid hemorrhage (SAH) is a pervasive and devastating condition in which inflammatory and apoptotic pathways contribute to poor outcome. Interleukin-33 (IL-33) plays a crucial role in the inflammatory and apoptotic pathways through binding of the transmembrane ST2 receptor. This study investigated the expression and cellular localization of IL-33 in the cerebral cortex after SAH in order to clarify the role of IL-33 after SAH. Sprague-Dawley rats were randomly divided into sham and SAH groups and evaluated 2, 6, and 12 h and 1, 2, 3, and 5 days after the surgery, with SAH animals subjected to prechiasmatic cistern SAH. IL-33 expression was measured by western blot analysis, real-time PCR, immunohistochemistry, and immunofluorescence. The mRNA levels of tumor necrosis factor (TNF)-α and IL-1β were also assessed. The expression of IL-33, IL-1β, and TNF-α was markedly elevated in the SAH as compared to the sham group; IL-33 was mainly localized in neurons and astrocytes and not microglia after SAH. Moreover, a significant positive association was observed between IL-33 and IL-1β expression. These findings indicate that IL-33 might play an important role in the inflammatory response following SAH.

L-3-n-butylphthalide protects against vascular dementia via activation of the Akt kinase pathway

As a neuroprotective drug for the treatment of ischemic stroke, 3-n-butylphthalide, a celery seed extract, has been approved by the State Food and Drug Administration of China as a clinical therapeutic drug for ischemic stroke patients. L-3-n-butylphthalide possesses significant efficacy in the treatment of acute ischemic stroke. The activated Akt kinase pathway can prevent the death of nerve cells and exhibit neuroprotective effects in the brain after stroke. This study provides the hypothesis that l-3-n-butylphthalide has a certain therapeutic effect on vascular dementia, and its mechanism depends on the activation of the Akt kinase pathway. A vascular dementia mouse model was established by cerebral repetitive ischemia/reperfusion, and intragastrically administered l-3-n-butylphthalide daily for 28 consecutive days after ischemia/reperfusion, or 7 consecutive days before ischemia/reperfusion. The Morris water maze test showed significant impairment of spatial learning and memory at 4 weeks after operation, but intragastric administration of l-3-n-butylphthalide, especially pretreatment with l-3-n-butylphthalide, significantly reversed these changes. Thionine staining and western blot analylsis showed that preventive and therapeutic application of l-3-n-butylphthalide can reduce loss of pyramidal neurons in the hippocampal CA1 region and alleviate nerve damage in mice with vascular dementia. In addition, phosphorylated Akt expression in hippocampal tissue increased significantly after l-3-n- butylphthalide treatment. Experimental findings demonstrate that l-3-n-butylphthalide has preventive and therapeutic effects on vascular dementia, and its mechanism may be mediated by upregulation of phosphorylated Akt in the hippocampus.

IMM-H004, a novel courmarin derivative, protects against oxygen-and glucose-deprivation/restoration-induced apoptosis in PC12 cells

7-Hydroxy-5-methoxy-4-methyl-3-(4-methylpiperazin-1-yl)-coumarin (IMM-H004) is a novel coumarin derivative synthesized in our laboratory. The purpose of the current study was to determine the neuroprotective effects of IMM-H004 on PC12 cells and its potential mechanism of action. PC12 cells were subject to oxygen and glucose deprivation (OGD) followed by the restoration of oxygen and glucose (R), which mimics ischemia and reperfusion in vivo. Cell viability was determined by MTT assay. DNA fragmentation was analyzed by DNA ladder. ROS and mitochondrial membrane potential were measured by fluorescent microscope and quantified by Image-Pro Express 6.0 software. ATP was measured by luciferin-luciferase assay. The activation of signal-regulated molecules was assessed by the Western blot analysis. OH formation was determined using the Electron Spin Resonance (ESR) trapping technique in combination with 5, 5-dimethyl-1-pyrroline-N-oxide. OGD/R reduced cell viability and induced cell apoptosis, which were both dose-dependently attenuated by IMM-H004. The accumulation of intracellular reactive oxygen species (ROS) and reduced mitochondrial membrane potential observed in PC12 cells treated with OGD/R, which switch on the mitochondrion-dependent apoptotic pathway, were reversed by IMM-H004. ATP production in OGD/R-treated PC12 cells was elevated by IMM-H004, which suggests that it restored the functions of the mitochondria. OGD/R-induced cytochrome c release from the mitochondria reduced the ratio of apoptotic proteins, Bcl-2/Bax, and induced caspase-3 activation and DNA fragmentation. These changes were significantly inhibited by IMM-H004. IMM-H004 also significantly inhibited OH formation, determined by electron spin resonance, which indicates that it is a potent free-radical scavenger. This study has demonstrated that IMM-H004 protects PC12 cells against OGD/R-induced apoptosis, at least in part, by scavenging excessive ROS and inhibiting the mitochondrion-dependent apoptotic pathway.

Dual leucine zipper kinase is required for excitotoxicity-induced neuronal degeneration

Loss of dual leucine zipper kinase results in attenuated JNK/c-Jun stress response pathway activation and reduced neuronal degeneration after kainic acid–induced excitotoxic seizures.

Excessive glutamate signaling is thought to underlie neurodegeneration in multiple contexts, yet the pro-degenerative signaling pathways downstream of glutamate receptor activation are not well defined. We show that dual leucine zipper kinase (DLK) is essential for excitotoxicity-induced degeneration of neurons in vivo. In mature neurons, DLK is present in the synapse and interacts with multiple known postsynaptic density proteins including the scaffolding protein PSD-95. To examine DLK function in the adult, DLK-inducible knockout mice were generated through Tamoxifen-induced activation of Cre-ERT in mice containing a floxed DLK allele, which circumvents the neonatal lethality associated with germline deletion. DLK-inducible knockouts displayed a modest increase in basal synaptic transmission but had an attenuation of the JNK/c-Jun stress response pathway activation and significantly reduced neuronal degeneration after kainic acid–induced seizures. Together, these data demonstrate that DLK is a critical upstream regulator of JNK-mediated neurodegeneration downstream of glutamate receptor hyper-activation and represents an attractive target for the treatment of indications where excitotoxicity is a primary driver of neuronal loss.

Neuroprotective effect of TAT PTD-Ngb fusion protein on primary cortical neurons against hypoxia-induced apoptosis

Hypoxic-ischemic injury increases neuroglobin (Ngb) expression in the brain. In our previous study, we have generated a transactivator-of-transcription protein-transduction domain-neuroglobin fusion protein (TAT PTD-Ngb) that successfully mediated exogenous Ngb expression in the primary neurons. In this study, we further investigated the role of TAT PTD-Ngb in protecting neurons against hypoxia-induced apoptosis and explored the possible mechanism. The primary cultured neurons were divided into four groups: (1) the normal group (no hypoxic injury); (2) the vehicle group (vehicle treatment and hypoxia injury); (3) the TAT PTD-Ngb group (TAT PTD-Ngb treatment and hypoxia injury); and (4) the Ngb group (Ngb treatment and hypoxia injury). Translocation of TAT PTD-Ngb into neurons was detected using fluorescent immunostaining against His-tag as early as 30 min after incubation. MTT assay showed that the TAT PTD-Ngb group had significantly increased cell viability compared to the vehicle or Ngb group after hypoxia. The result of transmission electron microscopy (TEM) also displayed rescued ultrastructure in TAT PTD-Ngb neurons compared to that of apoptotic neurons. In addition, TAT PTD-Ngb neurons showed significantly increased expression of anti-apoptotic Bcl-2 protein and decreased activities of caspase-3 and caspase-9 in response to hypoxia. These results suggest that TAT PTD-Ngb fusion protein protects primary cortical neurons against hypoxia-induced injury possibly through suppressing mitochondria apoptotic pathway.

Peroxisome proliferator-activated receptor-γ agonist rosiglitazone reduces secondary damage in experimental spinal cord injury

OBJECTIVE

To investigate the neuroprotective effects of rosiglitazone in a rat traumatic spinal cord injury (SCI) model.

METHODS

Adult Sprague-Dawley rats (n = 12/group) underwent laminectomy (sham), SCI, SCI and rosiglitazone treatment (2 mg/kg twice daily for 7 days), or SCI and saline injection (vehicle). SCI was induced via dural application of an aneurysm clip. Spinal cord apoptosis and levels of tumour necrosis factor-α (TNFα), interleukin (IL)-1β, myeloperoxidase (MPO) and the apoptosis-associated proteins B-cell leukaemia/lymphoma 2 (Bcl-2) and Bcl-2 associated X protein (Bax) were examined 24 h after SCI. Locomotor function was evaluated 3, 7, 10, 14 and 21 days after SCI.

RESULTS

At 24 h after SCI, apoptosis and TNFα, IL-1β and MPO concentrations were significantly lower in the rosiglitazone group than in the vehicle and SCI groups. SCI resulted in an increase in Bax and a decrease in Bcl-2, which was reversed by rosiglitazone treatment. Rats in the rosiglitazone group had significantly better functional recovery than those in the vehicle and SCI groups.

CONCLUSION

Rosiglitazone significantly improved functional recovery, probably via attenuation of the local inflammatory reaction and reduced apoptosis.

Neuroprotection by GDNF in the ischemic brain

The glial cell line-derived neurotrophic factor (GDNF) was first identified as a survival factor for midbrain dopaminergic neurons, but additional studies provided evidences for a role as a trophic factor for other neurons of the central and peripheral nervous systems. GDNF regulates cellular activity through interaction with glycosyl-phosphatidylinositol-anchored cell surface receptors, GDNF family receptor-α1, which might signal through the transmembrane Ret tyrosine receptors or the neural cell adhesion molecule, to promote cell survival, neurite outgrowth, and synaptogenesis. The neuroprotective effect of exogenous GDNF has been shown in different experimental models of focal and global brain ischemia, by local administration of the trophic factor, using viral vectors carrying the GDNF gene and by transplantation of GDNF-expressing cells. These different strategies and the mechanisms contributing to neuroprotection by GDNF are discussed in this review. Importantly, neuroprotection by GDNF was observed even when administered after the ischemic injury.

Is spreading depolarization characterized by an abrupt, massive release of gibbs free energy from the human brain cortex?

In the evolution of the cerebral cortex, the sophisticated organization in a steady state far away from thermodynamic equilibrium has produced the side effect of two fundamental pathological network events: ictal epileptic activity and spreading depolarization. Ictal epileptic activity describes the partial disruption, and spreading depolarization describes the near-complete disruption of the physiological double Gibbs-Donnan steady state. The occurrence of ictal epileptic activity in patients has been known for decades. Recently, unequivocal electrophysiological evidence has been found in patients that spreading depolarizations occur abundantly in stroke and brain trauma. The authors propose that the ion changes can be taken to estimate relative changes in Gibbs free energy from state to state. The calculations suggest that in transitions from the physiological state to ictal epileptic activity to spreading depolarization to death, the cortex releases Gibbs free energy in a stepwise fashion. Spreading depolarization thus appears as a twilight state close to death. Consistently, electrocorticographic recordings in the core of focal ischemia or after cardiac arrest display a smooth transition from the initial spreading depolarization component to the later ultraslow negative potential, which is assumed to reflect processes in cellular death.

Over-expression of map kinase phosphatase-1 (MKP-1) suppresses neuronal death through regulating JNK signaling in hypoxia/re-oxygenation

A pivotal role of c-jun N-terminal kinase (JNK) on neuronal apoptosis has been demonstrated in a rodent stroke model. MAP kinase phosphatase 1 (MKP-1) is an archetypal member of the dual-specificity protein phosphatase (DUSP) family, which inactivates mitogen-activated protein kinase (MAPK) including JNK through dephosphorylation. MKP-1, one of immediate early genes in stress conditions, was induced at transcriptional level in hypoxia/re-oxygenation (H/R) in neuroblastoma N1E115 cells, however the activation of JNK was not suppressed in the acute phase of re-oxygenation. Small interference RNA-mediated knock-down of MKP-1 enhanced phospho-JNK and neuronal death that is rescued by JNK inhibitor in H/R. Conversely, conditional over-expression of MKP-1 suppressed phospho-JNK, the expression of proapoptotic genes, and neuronal death in H/R. Further the immunoreactivity of MKP-1 was detected in the neurons and partially co-localized with that of phospho-JNK in the surrounding zone of ischemia in rat MCA-O (middle cerebral artery occlusion) reperfusion model. These findings indicate that over-expression of MKP-1 could suppress neuronal death possibly through regulating JNK signaling in vitro and be a prominent neuroprotective target for the treatment of acute cerebral infarction.

Mechanism of functional recovery after repetitive transcranial magnetic stimulation (rTMS) in the subacute cerebral ischemic rat model: neural plasticity or anti-apoptosis?

Repetitive transcranial magnetic stimulation (rTMS) has been studied increasingly in recent years to determine whether it has a therapeutic benefit on recovery after stroke. However, the underlying mechanisms of rTMS in stroke recovery remain unclear. Here, we evaluated the effect of rTMS on functional recovery and its underlying mechanism by assessing proteins associated with neural plasticity and anti-apoptosis in the peri-lesional area using a subacute cerebral ischemic rat model. Twenty cerebral ischemic rats were randomly assigned to the rTMS or the sham group at post-op day 4. A total of 3,500 impulses with 10 Hz frequency were applied to ipsilesional cortex over a 2-week period. Functional outcome was measured before (post-op day 4) and after rTMS (post-op day 18). The rTMS group showed more functional improvement on the beam balance test and had stronger Bcl-2 and weaker Bax expression on immunohistochemistry compared with the sham group. The expression of NMDA and MAP-2 showed no significant difference between the two groups. These results suggest that rTMS in subacute cerebral ischemia has a therapeutic effect on functional recovery and is associated with an anti-apoptotic mechanism in the peri-ischemic area rather than with neural plasticity.

Signal transducers and activators of transcription: STATs-mediated mitochondrial neuroprotection

Cerebral ischemia is defined as little or no blood flow in cerebral circulation, characterized by low tissue oxygen and glucose levels, which promotes neuronal mitochondria dysfunction leading to cell death. A strategy to counteract cerebral ischemia-induced neuronal cell death is ischemic preconditioning (IPC). IPC results in neuroprotection, which is conferred by a mild ischemic challenge prior to a normally lethal ischemic insult. Although many IPC-induced mechanisms have been described, many cellular and subcellular mechanisms remain undefined. Some reports have suggested key signal transduction pathways of IPC, such as activation of protein kinase C epsilon, mitogen-activated protein kinase, and hypoxia-inducible factors, that are likely involved in IPC-induced mitochondria mediated-neuroprotection. Moreover, recent findings suggest that signal transducers and activators of transcription (STATs), a family of transcription factors involved in many cellular activities, may be intimately involved in IPC-induced ischemic tolerance. In this review, we explore current signal transduction pathways involved in IPC-induced mitochondria mediated-neuroprotection, STAT activation in the mitochondria as it relates to IPC, and functional significance of STATs in cerebral ischemia.

The role of spreading depression, spreading depolarization and spreading ischemia in neurological disease

The term spreading depolarization describes a wave in the gray matter of the central nervous system characterized by swelling of neurons, distortion of dendritic spines, a large change of the slow electrical potential and silencing of brain electrical activity (spreading depression). In the clinic, unequivocal electrophysiological evidence now exists that spreading depolarizations occur abundantly in individuals with aneurismal subarachnoid hemorrhage, delayed ischemic stroke after subarachnoid hemorrhage, malignant hemispheric stroke, spontaneous intracerebral hemorrhage or traumatic brain injury. Spreading depolarization is induced experimentally by various noxious conditions including chemicals such as potassium, glutamate, inhibitors of the sodium pump, status epilepticus, hypoxia, hypoglycemia and ischemia, but it can can also invade healthy, naive tissue. Resistance vessels respond to it with tone alterations, causing either transient hyperperfusion (physiological hemodynamic response) in healthy tissue or severe hypoperfusion (inverse hemodynamic response, or spreading ischemia) in tissue at risk for progressive damage, which contributes to lesion progression. Therapies that target spreading depolarization or the inverse hemodynamic response may potentially treat these neurological conditions.