Mechanisms Of Cerebral Ischemia Research Articles

The Interrelation between Reactive Oxygen Species and Autophagy in Neurological Disorders.

Neurological function deficits due to cerebral ischemia or neurodegenerative diseases such as Alzheimer's disease (AD) and Parkinson's disease (PD) have long been considered a thorny issue in clinical treatment. Recovery after neurologic impairment is fairly limited, which poses a major threat to health and quality of life. Accumulating evidences support that ROS and autophagy are both implicated in the onset and development of neurological disorders. Notably, oxidative stress triggered by excess of ROS not only puts the brain in a vulnerable state but also enhances the virulence of other pathogenic factors, just like mitochondrial dysfunction, which is described as the culprit of nerve cell damage. Nevertheless, autophagy is proposed as a subtle cellular defense mode against destructive stimulus by timely removal of damaged and cytotoxic substance. Emerging evidence suggests that the interplay of ROS and autophagy may establish a determinant role in the modulation of neuronal homeostasis. However, the underlying regulatory mechanisms are still largely unexplored. This review sets out to afford an overview of the crosstalk between ROS and autophagy and discusses relevant molecular mechanisms in cerebral ischemia, AD, and PD, so as to provide new insights into promising therapeutic targets for the abovementioned neurological conditions.

Protective Effect of Aliskiren in Experimental Ischemic Stroke: Up-Regulated p-PI3K, p-AKT, Bcl-2 Expression, Attenuated Bax Expression

Aliskiren (ALK), a pharmacological renin inhibitor, is an effective antihypertensive drug and has potent anti-apoptotic activity, but it is currently unknown whether ALK is able to attenuate brain damage caused by acute cerebral ischemia independent of its blood pressure-lowering effects. This study aimed to investigate the role of ALK and its potential mechanism in cerebral ischemia. C57/BL6 mice were subjected to transient middle cerebral artery occlusion (tMCAO) and treated for 5days with Vehicle or ALK (10 or 25mg/kg per day via intragastric administration), whereas Sham-operated animals served as controls. Treatment with ALK significantly improved neurological deficits, infarct volume, brain water content and Nissl bodies after stroke (P<0.05), which did not affect systemic blood pressure. Furthermore, the protection of ALK was also related to decreased levels of apoptosis in mice by enhanced activation of phosphatidylinositol 3-kinase (PI3K)/AKT pathway, increased level of Bcl-2 and reduced Bax expression (P<0.05). In addition, ALK's effects were reversed by PI3K inhibitors LY294002 (P<0.05). Our data indicated that ALK protected the brain from reperfusion injuries without affecting blood pressure, and this effect may be through PI3K/AKT signaling pathway.

YiQiFuMai Powder Injection Ameliorates Cerebral Ischemia by Inhibiting Endoplasmic Reticulum Stress-Mediated Neuronal Apoptosis.

YiQiFuMai (YQFM) powder injection as a modern preparation derived from Sheng Mai San, a traditional Chinese medicine, has been widely used in the treatment of cardiovascular and cerebrovascular diseases. However, its neuroprotective effect and underlying mechanism in cerebral ischemia remain to be explored. The present study was designed to investigate the neuroprotective effect of YQFM on endoplasmic reticulum (ER) stress-mediated neuronal apoptosis in the permanent middle cerebral artery occlusion- (MCAO-) injured mice and the oxygen-glucose deprivation- (OGD-) induced pheochromocytoma (PC12) cells. The results showed that single administration of YQFM (1.342 g/kg, i.p.) could reduce the brain infarction and improve the neurological deficits and the cerebral blood flow (CBF) after MCAO for 24 h in mice. Moreover, incubation with YQFM (100, 200, and 400 μg/mL) could increase the cell viability, decrease the caspase-3 activity, and inhibit the cell apoptosis in OGD-induced PC12 cells for 12 h. In addition, YQFM treatment could significantly modulate cleaved caspase-3 and Bcl-2 expressions and inhibit the expressions of ER stress-related marker proteins and signaling pathways in vivo and in vitro. In conclusion, our findings provide the first evidence that YQFM ameliorates cerebral ischemic injury linked with modulating ER stress-related signaling pathways, which provided some new insights for its prevention and treatment of cerebral ischemia diseases.

Incidence and Mechanisms of Cerebral Ischemia After Transcatheter Aortic Valve Implantation Compared With Surgical Aortic Valve Replacement

The most likely mechanisms of neurologic injury after transcatheter aortic valve implantation (TAVI) and aortic valve replacement (AVR) are cerebral embolization and hypoperfusion. We set out to determine potential mechanisms of neurologic injury after TAVI compared with AVR. One hundred twenty-seven consecutive high-risk patients with severe aortic stenosis (AS) who underwent TAVI (n= 85) or AVR (n= 42) were studied. Transcranial Doppler ultrasound (TCD), cerebral oximetry, diffusion-weighted magnetic resonance imaging (DW-MRI) (before, 6 days, and 3 months after procedure), and neurocognitive assessment before and at 3 months were performed. Neurologic injury was not significantly different between TAVI and AVR at 1 (1.1% vs 2.2%, p= 0.25) and 3 months (4.7% vs 2.2%, p= 1). At 3 months, overall cognitive score was higher in AVR compared with TAVI when adjusted for baseline score; the estimated difference between groups was 0.63 (95% confidence interval 0.87% to 1.17%; p= 0.02). Cerebral embolic load was 212 (123 to 344) during AVR and 134 (76 to 244) during TAVI (p= 0.07). Cerebral oxygen desaturation during AVR (7.56 ± 2.16) was higher compared with TAVI (5.93 ± 2.47) (p < 0.01). Ischemic lesions measured by DW-MRI occurred in 76% of TAVI and 71% of AVR patients at 6 days (p= 0.69) and 63% and 39% at 3 months (p= 0.11). No significant association was found between cerebral emboli, cerebral oxygen desaturation, brain ischemic lesions, and general cognitive score. At 3 months follow-up, overall cognitive score was higher in AVR compared with TAVI, adjusted for baseline score. However, there was no difference in cerebral embolic load, ischemic lesions, and oxygen desaturation.

Nerve Protective Effect of Asiaticoside against Ischemia-Hypoxia in Cultured Rat Cortex Neurons.

BackgroundAsiaticoside is one of the main functional components of the natural plant Centella asiatica urban. Studies have reported it has several functions such as anti-depression and nerve cell protection. Asiaticoside can reduce the cerebral infarct size in acute focal cerebral ischemia in a mouse model and asiatic acid glycosides can significantly improve neurobehavioral scores. Currently, there is a lack of understanding of asiaticoside in regard to its neural protective mechanism in cerebral ischemia. This study aimed to solve this problem by using an ischemia-hypoxia cell model in vitro.Material/MethodsAn in vitro ischemia hypoxia cell model was successfully established by primary cultured newborn rat cortical neurons. After being treated by asiaticoside for 24 h, cell survival rate, lactate dehydrogenase release quantity, and B-cell lymphoma gene-2 (BCL-2), Bax, and caspase-3 protein expressions was detected.ResultsAfter 10 nmol/L or 100 nmol/L of asiaticoside were given to the cells, cell survival rate increased significantly and presented concentration dependence. Asiaticoside can reduce lactate dehydrogenase release. Lactate dehydrogenase release in model cells is gradually reduced with the increase of asiaticoside concentration. The lactate dehydrogenase release in asiaticoside 10 nmol/L group, asiaticoside 100 nmol/L group and ischemia hypoxia group were 26.75±1.05, 22.36±2.87 and 52.35±5.46%, respectively (p<0.05). It was also found that asiaticoside could modulate the expression of apoptotic factors, including bcl-2, Bax, and caspase-3.ConclusionsAsiaticoside helps to protect in vitro ischemia hypoxia neurons. This nerve cell protection may be mediated by the BCL-2 protein.

Neuroimaging patterns of ischemic stroke after percutaneous coronary intervention

We sought to determine neuroimaging patterns, ischemic mechanisms, and functional outcomes of ischemic stroke related to percutaneous coronary intervention (PCI) over a 16-year period. Stroke is a feared complication of PCI, associated with poor patient outcomes. The majority of strokes that occur after PCI are ischemic rather than hemorrhagic. However, mechanisms of cerebral ischemia in this setting are incompletely understood. We performed a retrospective single-center cohort study of patients with radiologically confirmed ischemic stroke occurring after PCI (PCI-stroke), between January 1, 1994 and December 31, 2009. Using brain imaging, infarctions were subclassified by radiological pattern and arterial territory as embolic, small subcortical, or hemodynamic. Modified Rankin Scale scores were used to assess functional outcome at 3 and 6 months. Radiologically confirmed PCI-stroke was identified in 35 patients. The majority of strokes (91%) revealed an embolic pattern, while the remaining strokes were small subcortical infarctions (9%). Watershed strokes with exclusive borderzone involvement, indicative of a hemodynamic mechanism, were not identified, despite the presence of periprocedural hypotension in 23% of patients. The middle cerebral artery (MCA) territory was affected most frequently (80%), and all patients suffering a complete MCA territorial infarction (14%) died in the hospital. Functional outcome among survivors of PCI-stroke was typically favorable in those who had single rather than multiple vascular territory involvement. The vast majority of radiologically confirmed ischemic strokes related to PCI are embolic. MCA territory strokes are most common and uniformly fatal when the entire MCA territory is affected. Functional outcomes in survivors of PCI-stroke are improved when only a single arterial territory is affected.

Systemic inflammation impairs tissue reperfusion through endothelin-dependent mechanisms in cerebral ischemia.

Systemic inflammation contributes to diverse acute and chronic brain pathologies, and extensive evidence implicates inflammation in stroke susceptibility and poor outcome. Here we investigate whether systemic inflammation alters cerebral blood flow during reperfusion after experimental cerebral ischemia. Serial diffusion and perfusion-weighted MRI was performed after reperfusion in Wistar rats given systemic (intraperitoneal) interleukin-1β or vehicle before 60-minute transient middle cerebral artery occlusion. The expression and location of endothelin-1 was assessed by polymerase chain reaction, ELISA, and immunofluorescence. Systemic interleukin-1 caused a severe reduction in cerebral blood flow and increase in infarct volume compared with vehicle. Restriction in cerebral blood flow was observed alongside activation of the cerebral vasculature and upregulation of the vasoconstricting peptide endothelin-1 in the ischemic penumbra. A microthrombotic profile was also observed in the vasculature of rats receiving interleukin-1. Blockade of endothelin-1 receptors reversed this hypoperfusion, reduced tissue damage, and improved functional outcome. These data suggest patients with a raised inflammatory profile may have persistent deficits in perfusion after reopening of an occluded vessel. Future therapeutic strategies to interrupt the mechanism identified could lead to enhanced recovery of penumbra in patients with a heightened inflammatory burden and a better outcome after stroke.

Progress on the protective effect of compounds from natural medicines on cerebral ischemia

The treatment of cerebral ischemic disease by natural medicines has a long history, and has accumulated a rich theoretical knowledge and treatment experience. The objective of this review is to critically evaluate the experimental research situation of the protective effect of the individual compounds from natural medicine on cerebral ischemia in the past ten years, emphasizing the major mechanisms underlying cerebral ischemic pathophysiology. Sixteen representative compounds from natural medicines which are often used to treat stroke are discussed. The results indicate that these components possess a protective effect on cerebral ischemia, and that these components have different mechanisms, including inhibiting excitotoxicity by ginkgolide B, antiapoptosis of breviscapine, influencing astrocytic activation and proliferation of tanshinone IIA, in?uencing free radicals by ginsenoside Rd, impairing blood-brain barrier disruption by baicalin, and the anti-inflammatory activity of tetramethylpyrazine. Moreover, some components have multiple neuroprotective mechanisms. Therefore, the combination of individual compounds from natural medicines, considering the mechanisms of cerebral ischemia, may be beneficial to patients with cerebral ischemia in the future. This approach will provide a direction for the further application and exploitation of new drug development in the treatment of cerebral ischemia.

P2X7 receptors in cerebral ischemia

Cerebral ischemia is one of the most common diseases resulting in death and disability in aged people. It leads immediately to rapid energy failure, ATP depletion, and ionic imbalance, which increase extracellular ATP levels and accordingly activate P2X7 receptors. These receptors are ATP-gated cation channels and widely distributed in nerve cells, especially in the immunocompetent cells of the brain. Currently, interest in the roles of P2X7 receptors in ischemic brain injury is growing. In this review, we discuss recent research progress on the actions of P2X7 receptors, their possible mechanisms in cerebral ischemia, and the potential therapeutic value of P2X7 receptor antagonists which may provide a new target both for clinical and for research purposes.

Current mechanisms in stroke

Stroke is one of the leading causes of mortality and adult disability in the world1,2,3. The occurrence of stroke and stroke-related illness is expected to triple by 20504, due to our vulnerable aging population and ongoing epidemics of diabetes and obesity1,5. Disabilities associated with stroke survivors have had a significant social and economic impact on societies worldwide2. According to the World Health Organization, about 15 million people worldwide suffer a stroke every year. Furthermore, stroke and its related illnesses cost the healthcare system billions of dollars each year, thus becoming significant financial burden and causing economic hardship in the world. While stroke is a major public health concern, the cellular and molecular mechanisms underlying brain damage following stroke are not yet fully elucidated. A series of pathophysiological events are triggered during stroke, and eventually lead to intracellular ionic imbalance and cell death6,7. Glutamate mechanisms have dominated in stroke research for the last two to three decades8. Although glutamate receptor antagonists are effective in reducing stroke-related neuronal injury in the laboratory setting, clinical trials of anti-excitotoxic therapies have failed to benefit stroke patients9. Thus, researchers have started looking beyond glutamate mechanisms in cerebral ischemia and stroke. Recent convincing and promising results, especially from in vivo animal studies, suggest non-glutamate mechanisms are also important in causing ionic imbalance and cell death during cerebral ischemia8,10. Along with the traditional model of excitotoxicity focused on glutamate-receptor-mediated mechanisms, non-glutamate mechanisms are gaining considerable attention in recent years8,10. The latter include acid-sensing ion channels11,12, TRP channels13,14, KATP channels15,16, hemichannels17,18, volume-regulated anion channels19, adenosine receptors, sodium-calcium exchangers, and other ion exchangers and nonselective cation channels. In this special issue of stroke research, we aim to cover the revised models of neuronal injury involving glutamate mechanisms and several newly identified non-glutamate mechanisms in stroke. We will discuss the current understanding of pathophysiological roles of ion channels and exchangers involved in non-glutamate mechanisms in cerebral ischemia and stroke, as well as the potential for therapeutic intervention. We will describe new studies using recently developed experimental models for stroke research. The primary scope of our reviews is to highlight findings from in vivo studies involving new strategies and drug developments for stroke treatment. The in vivo experimental approaches cover state of the art techniques currently used in the fields including molecular, genomic, proteomic, in vivo functional and behavioural assessments. We intend to highlight novel therapeutic strategies targeting non-glutamate mechanisms to prevent neuronal damage in stroke and to promote neuronal survival, regeneration and functional recovery after stroke, thus providing long-term economic, social, and healthcare benefits worldwide.

Neuroprotection by Manganese Superoxide Dismutase (MnSOD) Mimics: Antioxidant Effect and Oxidative Stress Regulation in Acute Experimental Stroke

Manganese superoxide dismutase (MnSOD), one of the most crucial antioxidant enzymes in the central nervous system, is thought to be one of the major mechanisms by which cells counteract the injuries of reactive oxygen species after cerebral ischemia. In this study, we used a novel synthesized compound (MnTm4PyP) with highly effective superoxide dismutase activity to study the therapeutic potential of MnSOD and the possible underlying mechanisms in cerebral ischemia. Primary cultured cortical neurons were used to examine the protective effect of the compounds. Mice with middle cerebral artery occlusion were used as ischemic stroke animal model. Animals were pretreated with MnTm4PyP intravenously 30 min before surgery. At 24 h after surgery, neurological behavior and histological function were observed. Infarcted cortex tissues and cultured neurons were collected for investigation of the oxidative stress signaling pathways. In vitro studies revealed that MnSOD mimic MnTm4PyP pretreatment significantly increased viability of neurons after injury by H(2) O(2) . Intracellular superoxide radical levels were eliminated. In vivo experiments demonstrated MnTm4PyP pretreatment reduced infarct volume and improved neurological function. The MnSOD mimic alleviated oxidative stress and apoptosis. MnSOD is an effective therapeutic target in ischemic stroke prevention because of its antioxidant effects and oxidative stress regulation.

Leonurine protects brain injury by increased activities of UCP4, SOD, CAT and Bcl-2, decreased levels of MDA and Bax, and ameliorated ultrastructure of mitochondria in experimental stroke

BackgroundIt has been proved that pre-treatment with leonurine could protect brain tissue against ischemic injury by exerting antioxidant effects and regulating mitochondrial function. Whether this protective effect applies to acute phase after cerebral ischemia, we therefore investigate the potential neuroprotective role of leonurine and the underlying mechanisms in cerebral ischemia. Methods: Focal cerebral ischemia was induced in adult male Sprague-Dawley rats by permanent middle cerebral artery occlusion (MCAO). Leonurine was administered intraperitoneally at 7.5 or 15mg/kg/d at 2h after surgery, then once daily thereafter. Neurological deficit, brain water content, and infarct volume were measured at 24h, 72h, and 7d after stroke. Superoxide dismutase (SOD), catalase (CAT) activities, and malondialdehyde (MDA) content were also measured by spectrophotometer to evaluate oxidative reactions, and the expression of uncoupling protein 4 (UCP4), Bcl-2, and Bax were detected by reverse transcription-polymerase chain reaction (RT-PCR), immunohistochemical staining (IHC), and western blot, while the ultrastructure of the mitochondria were observed under transmission electron microscope. Results: Leonurine significantly alleviated neurological deficit, decreased brain water content and infarct volume after ischemic stroke, which was accompanied by decreased levels of MDA and Bax, increased activities of SOD, CAT, UCP4, and Bcl-2, and restored ultrastructure of mitochondria. Conclusions: The results showed that leonurine protected brain injury by increased activities of UCP4, SOD, CAT and Bcl-2, decreased levels of MDA and Bax, and ameliorated ultrastructure of mitochondria in experimental stroke.

Protective Effect of Luteolin in Experimental Ischemic Stroke: Upregulated SOD1, CAT, Bcl-2 and Claudin-5, Down-Regulated MDA and Bax Expression

Luteolin recently has been proved to elicit a vanity of biological effects through its antioxidant and anti-apoptosis properties. Oxidative and apoptosis damage play an important role in cerebral ischemic pathogenesis and may represent a target for treatment. The aim of this study was to evaluate the neuroprotective effects of luteolin and the underlying mechanisms in cerebral ischemia. Focal cerebral ischemia was induced in adult male Sprague-Dawley rats by permanent middle cerebral artery occlusion (pMCAO). Luteolin was injected intraperitoneally at different doses of 10 or 25mg/kg immediately after pMCAO. Experiment 1, luteolin's neuroprotective effect was analyzed. Neurological deficits, brain water content and infarct volume were evaluated at 24 and 72h after pMCAO. SOD1, Bcl-2, and Bax expression were measured by immunohistochemistry, western blot and reverse transcription-polymerase chain reaction. Experiment 2, luteolin's anti-oxidative activities were evaluated. SOD1, CAT activities, and MDA content were measured by spectrophotometer. Experiment 3, the influence of luteolin on claudin-5 was detected. Compared with MCAO group, luteolin significantly increased the activities of SOD1, CAT, Bcl-2 and claudin-5 (P<0.05), decreased the levels of MDA and Bax (P<0.05), and alleviated the neurological deficits, infarct volume and brain water content (P<0.05). The results indicated that luteolin protected the brain from ischemic damage, and this effect may be through reduction of oxidative stress and apoptosis, and upregulation of the expressions of claudin-5.

Protective effect of celastrol in rat cerebral ischemia model: Down-regulating p-JNK, p-c-Jun and NF-κB

Oxidative stress and inflammatory damage play an important role in cerebral ischemic pathogenesis and may represent a target for treatment. Celastrol has been proved to elicit a vanity of biological effects through its anti-oxidant, anti-inflammatory properties in the treatment of Alzheimer's disease, systemic lupus erythematosus, and rheumatoid arthritis. However, little is known regarding the effect of celastrol in the acute phase of ischemic stroke. This study investigated the potential protective effects of celastrol and underlying mechanisms in cerebral ischemia. We used a permanent middle cerebral artery occlusion (pMCAO) model and administered celastrol intraperitoneally immediately after stroke. At 24h after stroke, we found that celastrol dramatically reduced neurological deficit, brain water content and infarct sizes, and downregulated the expression of p-JNK, p-c-Jun and NF-κB. The results indicated that celastrol may have the possibility of protective effect against ischemic injury, and this effect may be through downregulation of the expression of p-JNK, p-c-Jun and NF-κB.

Toll-like receptors in cerebral ischemic inflammatory injury

Cerebral ischemia triggers acute inflammation, which has been associated with an increase in brain damage. The mechanisms that regulate the inflammatory response after cerebral ischemia are multifaceted. An important component of this response is the activation of the innate immune system. However, details of the role of the innate immune system within the complex array of mechanisms in cerebral ischemia remain unclear. There have been recent great strides in our understanding of the innate immune system, particularly in regard to the signaling mechanisms of Toll-like receptors (TLRs), whose primary role is the initial activation of immune cell responses. So far, few studies have examined the role of TLRs in cerebral ischemia. However, work with experimental models of ischemia suggests that TLRs are involved in the enhancement of cell damage following ischemia, and their absence is associated with lower infarct volumes. It may be possible that therapeutic targets could be designed to modulate activities of the innate immune system that would attenuate cerebral brain damage. Ischemic tolerance is a protective mechanism induced by a variety of preconditioning stimuli. Interpreting the molecular mechanism of ischemic tolerance will open investigative avenues into the treatment of cerebral ischemia. In this review, we discuss the critical role of TLRs in mediating cerebral ischemic injury. We also summarize evidence demonstrating that cerebral preconditioning downregulates pro-inflammatory TLR signaling, thus reducing the inflammation that exacerbates ischemic brain injury.

Activation of sphingosine kinase 2 is an endogenous protective mechanism in cerebral ischemia

The two ubiquitously expressed sphingosine kinases (SphK) 1 and 2 are key regulators of the sphingolipid signaling pathway. Despite the formation of an identical messenger, i.e. sphingosine 1-phosphate (S1P), they exert strikingly different functions. Particularly, SphK2 is necessary for the phosphorylation of the sphingosine analog fingolimod (FTY720), which is protective in rodent stroke models. Using gene deficient mice lacking either SphK1 or SphK2, we investigated the role of the two lipid kinases in experimental stroke.We performed 2h transient middle cerebral artery occlusion (tMCAO) and analyzed lesion size and neurological function after 24h. Treatment groups received 1mg/kg FTY720. Neutrophil infiltration, microglia activation, mRNA and protein expression of SphK1, SphK2 and the S1P1 receptor after tMCAO were studied.Genetic deletion of SphK2 but not SphK1 increased ischemic lesion size and worsened neurological function after tMCAO. The protective effect of FTY720 was conserved in SphK1−/− mice but not in SphK2−/− mice.This suggests that SphK2 activity is an important endogenous protective mechanism in cerebral ischemia and corroborates that the protective effect of FTY720 is mediated via phospho-FTY720.

A Critical Review of Aspirin in the Secondary Prevention of Noncardioembolic Ischaemic Stroke

Both secondary prevention (such as lifestyle modifications, pharmacotherapy or surgery) and an understanding of the influence of risk factors (including the different aetiologic mechanisms of cerebral ischaemia) play a pivotal role in reducing the burden of recurrent stroke. Regarding the types of preventative treatments available, variations exist across all clinical studies, including differences in target populations (including the type of cerebral ischaemia), risk factors, length of follow-up, drop-out rates and outcomes, which makes translating the results of clinical trials to individual patients difficult. However, with such limitations in mind, this critical albeit nonsystematic review, which compared aspirin with other antiplatelets and in combination with other drugs, showed that the benefit from aspirin treatment is consistently shown in ischaemic stroke, while harms are limited. Furthermore, no definite superiority is apparent across different antiplatelet therapies. Dual antiplatelet regimens may expose to a slight but measurable higher risk of haemorrhagic complications, perhaps in selective groups of patients (i.e. those with severe small-vessel disease or in selective racial groups). Based on our analysis, the indication of aspirin as the first-line choice, also recommended by several acknowledged international or national guidelines, may be confirmed. However, the complex nature of patients at risk of recurrent ischaemic stroke necessitates a comprehensive approach, which should be driven by the primary care physician, whose role is central to successful actions for secondary stroke prevention.

Atorvastatin protects rat brains against permanent focal ischemia and downregulates HMGB1, HMGB1 receptors (RAGE and TLR4), NF-κB expression

Inflammatory processes play a key, mainly detrimental role in the pathophysiology of ischemic stroke. Currently, HMGB1-induced NF-κB activation pathway has been recognized as a key contributor to the proinflammatory response. It has been proved that chronic administration and pre-treatment with statins could protect brain tissue against ischemic injury. However, little is known about the effects of statins in the acute phase after cerebral ischemia. Thus, this study investigated the atorvastatin's protective role and the underlying mechanisms in cerebral ischemia. After middle cerebral artery occlusion (MCAO), atorvastatin was administered immediately. We found that atorvastatin dramatically improved neurological deficits, reduced brain water contents and infarct sizes at 24 h after stroke. Moreover, the over-expression of HMGB1, RAGE, TLR4 and NF-κB induced by ischemia was significantly attenuated by atorvastatin.

Discovery of transcriptional programs in cerebral ischemia by in silico promoter analysis

In stroke, gene transcription plays a central role in processes such as neuroinflammation and neuroregeneration. To predict new transcriptional regulatory mechanisms in cerebral ischemia, we applied a computational approach combining two kinds of information: the results of a microarray analysis in a mouse model of stroke and in silico detection of transcription factor (TF) binding sites in promoter regions of the genes on the array. By using a discriminative logistic regression model, we identified binding sites significantly associated with the up-regulation of genes. Out of 356 TF binding sites defined in TRANSFAC, we could link 32 to gene up-regulation in cerebral ischemia. These sites bind both TFs with an established and a so far unknown role in cerebral ischemia. To evaluate the results further we investigated whether two TFs, CCAAT/enhancer binding protein β (C/EBPβ) and vitamin D receptor (VDR), are activated as predicted. Immunohistochemistry demonstrated that C/EBPβ and VDR translocated to the nucleus in cerebral ischemia. Chromatin immunoprecipitation revealed increased binding of C/EBPβ to the promoter of its target gene saa3. In addition, we found evidence for the up-regulation of VDR in brain samples from human stroke patients. These results confirm the activation of C/EBPβ and VDR in cerebral ischemia. Thus, our in silico analysis may provide additional information on transcriptional regulation in stroke and suggests several novel transcriptional programs for further exploration.

Proteomics Profiling of Pituitary, Adrenal Gland, and Splenic Lymphocytes in Rats with Middle Cerebral Artery Occlusion

Ischemic strokes are often accompanied by serious brain injury and poor prognosis, but the molecular mechanisms of primary and secondary injury have not been fully understood. The aim of the present study was to investigate the protein profile in the rat pituitary, adrenal gland, and splenic lymphocyte using proteomics techniques, and to elucidate potential changes in the immune neuroendocrine system following cerebral ischemia injury in rats. Out of the 41 differentially expressed protein spots identified by matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-MS-TOF), 13 proteins were closely related to the immune and/or the neuroendocrine system, and the other proteins might have different functions through other mechanisms in middle cerebral artery occlusion (MCAO) rats. The results showed that (i) the immune neuroendocrine system was obviously changed, and the changes might be important pathological mechanisms in brain injury after cerebral ischemia, and (ii) ischemic brain damage is co-regulated by several mechanisms. The results might lay the foundations for further research on pathological mechanisms in cerebral ischemia.