Activation of the JAK-STAT signaling pathway in the rat basilar artery after subarachnoid hemorrhage

The minor allele of rs17427875 in long non-coding RNA-HOXA11-AS influences the prognosis of subarachnoid hemorrhage (SAH) via modulating miR-15a and STAT3 expression

Background: HOAX11-AS was reported to promote the progression of liver cancer via the signaling pathway of miR-15a-3p/STAT3. In this study, we investigated the effect of rs17427875 on the prognosis of subarachnoid hemorrhage (SAH) and its underlying molecular mechanisms.

Methods: 158 SAH patients were recruited and grouped according to their genotypes rs17427875. Peripheral blood and cerebrospinal fluid (CSF) samples were collected for subsequent analysis. Quantitative real-time PCR, luciferase assays, Western blot and ELISA were performed to analyze the correlations between the expression of lncRNA-HOXA11-AS, miR-15a, TNF-α and NF-κB.

Results: The survival rate was remarkably higher in SAH patients carrying the AA genotype of rs17427875 when compared with those carrying the AT genotype. The expression of miR-15a was significantly repressed in the peripheral blood and CSF of SAH patients carrying the AT allele when compared with that in patients carrying the AA allele. MiR-15a showed a remarkable efficacy in inhibiting the luciferase activity of wild type lncRNA-HOXA11-AS and STAT3 in THP-1 cells. P-HOXA11-AS-T showed a stronger ability to suppress the expression of miR-15a and activate the expression of STAT3, TNF-α and NF-κB in THP-1 cells when compared with P-HOXA11-AS-A.

Conclusions: The findings demonstrated that the presence of the minor allele of rs17427875 in lncRNA-HOXA11-AS could increase the expression level of lncRNA-HOXA11-AS, thus elevating the expression level of STAT3 via down-regulating miR-15a, and increased STAT3 expression could aggravate inflammation to cause poor prognosis of SAH. Therefore, the rs17427875 polymorphism can be used as a potential biomarker for the prognosis of SAH.

The blood-brain barrier and the neurovascular unit in subarachnoid hemorrhage: molecular events and potential treatments

The response of the blood-brain barrier (BBB) following a stroke, including subarachnoid hemorrhage (SAH), has been studied extensively. The main components of this reaction are endothelial cells, pericytes, and astrocytes that affect microglia, neurons, and vascular smooth muscle cells. SAH induces alterations in individual BBB cells, leading to brain homeostasis disruption. Recent experiments have uncovered many pathophysiological cascades affecting the BBB following SAH. Targeting some of these pathways is important for restoring brain function following SAH. BBB injury occurs immediately after SAH and has long-lasting consequences, but most changes in the pathophysiological cascades occur in the first few days following SAH. These changes determine the development of early brain injury as well as delayed cerebral ischemia. SAH-induced neuroprotection also plays an important role and weakens the negative impact of SAH. Supporting some of these beneficial cascades while attenuating the major pathophysiological pathways might be decisive in inhibiting the negative impact of bleeding in the subarachnoid space. In this review, we attempt a comprehensive overview of the current knowledge on the molecular and cellular changes in the BBB following SAH and their possible modulation by various drugs and substances.

Microglia activation, classification and microglia-mediated neuroinflammatory modulators in subarachnoid hemorrhage

Subarachnoid hemorrhage is a devastating disease with significant mortality and morbidity, despite advances in treating cerebral aneurysms. There has been recent progress in the intensive care management and monitoring of patients with subarachnoid hemorrhage, but the results remain unsatisfactory. Microglia, the resident immune cells of the brain, are increasingly recognized as playing a significant role in neurological diseases, including subarachnoid hemorrhage. In early brain injury following subarachnoid hemorrhage, microglial activation and neuroinflammation have been implicated in the development of disease complications and recovery. To understand the disease processes following subarachnoid hemorrhage, it is important to focus on the modulators of microglial activation and the pro-inflammatory/anti-inflammatory cytokines and chemokines. In this review, we summarize research on the modulators of microglia-mediated inflammation in subarachnoid hemorrhage, including transcriptome changes and the neuroinflammatory signaling pathways. We also describe the latest developments in single-cell transcriptomics for microglia and summarize advances that have been made in the transcriptome-based classification of microglia and the implications for microglial activation and neuroinflammation.

Peroxisome proliferator‑activated receptor β/δ regulates cerebral vasospasm after subarachnoid hemorrhage via modulating vascular smooth muscle cells phenotypic conversion

Cerebral vasospasm (CVS) is a common complication of subarachnoid hemorrhage (SAH) with high deformity rates and cerebral vascular smooth muscle cells (VSMCs) phenotypic switch is considered to be involved in the regulation of CVS. However, to the best of the authors' knowledge, its underlying molecular mechanism remains to be elucidated. Peroxisome proliferator‑activated receptor β/δ (PPARβ/δ) has been demonstrated to be involved in the modulation of vascular cells proliferation and maintains the autoregulation function of blood vessels. The present study investigated the potential effect of PPARβ/δ on CVS following SAH. A model of SAH was established by endovascular perforation on male adult Sprague‑Dawley rats, and the adenovirus PPARβ/δ (Ad‑PPARβ/δ) was injected via intracerebroventricular administration prior to SAH. The expression levels of phenotypic markers α‑smooth muscle actin and embryonic smooth muscle myosin heavy chain were measured via western blotting or immunofluorescence staining. The basilar artery diameter and vessel wall thickness were evaluated under fluorescence microscopy. SAH grade, neurological scores, brain water content and brain swelling were measured to study the mechanisms of PPARβ/δ on vascular smooth muscle phenotypic transformation. It was revealed that the expression levels of synthetic proteins were upregulated in rats with SAH and this was accompanied by CVS. Activation of PPARβ/δ using Ad‑PPARβ/δ markedly upregulated the contractile proteins elevation, restrained the synthetic proteins expression and attenuated SAH‑induced CVS by regulating the phenotypic switch in VSMCs at 72 h following SAH. Furthermore, the preliminary study demonstrated that PPARβ/δ downregulated ERK activity and decreased the expression of phosphorylated (p‑)ETS domain‑containing protein Elk‑1 and p‑p90 ribosomal S6 kinase, which have been demonstrated to serve an important role in VSMC phenotypic change. Additionally, it was revealed that Ad‑PPARβ/δ could positively improve CVS by ameliorating the diameter of the basilar artery and mitigating the thickness of the vascular wall. Furthermore, subsequent experiments demonstrated that Ad‑PPARβ/δ markedly reduced the brain water content and brain swelling and improved the neurological outcome. Taken together, the present study identified PPARβ/δ as a useful regulator for the VSMCs phenotypic switch and attenuating CVS following SAH, thereby providing novel insights into the therapeutic strategies of delayed cerebral ischemia.

Gene expression profiling of brain endothelial cells after experimental subarachnoid haemorrhage

Subarachnoid haemorrhage (SAH) is a type of hemorrhagic stroke that is associated with high morbidity and mortality. New effective treatments are needed to improve outcomes. The pathophysiology of SAH is complex and includes early brain injury and delayed cerebral ischemia, both of which are characterized by blood–brain barrier (BBB) impairment. We isolated brain endothelial cells (BECs) from mice subjected to SAH by injection of blood into the prechiasmatic cistern. We used gene expression profiling to identify 707 unique genes (2.8% of transcripts, 403 upregulated, 304 downregulated, 24,865 interrogated probe sets) that were significantly differentially expressed in mouse BECs after SAH. The pathway involving prostaglandin synthesis and regulation was significantly upregulated after SAH, including increased expression of the Ptgs2 gene and its corresponding COX-2 protein. Celecoxib, a selective COX-2 inhibitor, limited upregulation of Ptgs2 in BECs. In this study, we have defined the gene expression profiling of BECs after experimental SAH and provide further insight into BBB pathophysiology, which may be relevant to other neurological diseases such as traumatic brain injury, brain tumours, ischaemic stroke, multiple sclerosis, and neurodegenerative disorders.

The Role of Oxidative Stress in Early Brain Injury after Subarachnoid Hemorrhage

This review focuses on the problem of oxidative stress in early brain injury (EBI) after spontaneous subarachnoid hemorrhage (SAH). EBI involves complex pathophysiological mechanisms, including oxidative stress. In the first section, we describe the main sources of free radicals in EBI. There are several sources of excessive generation of free radicals from mitochondrial free radicals’ generation and endoplasmic reticulum stress, to hemoglobin and enzymatic free radicals’ generation. The second part focuses on the disruption of antioxidant mechanisms in EBI. The third section describes some newly found molecular mechanisms and pathway involved in oxidative stress after EBI. The last section is dedicated to the pathophysiological mechanisms through which free radicals mediate early brain injury.

Development of an Early Prediction Model for Subarachnoid Hemorrhage With Genetic and Signaling Pathway Analysis

Subarachnoid hemorrhage (SAH) is devastating disease with high mortality, high disability rate, and poor clinical prognosis. It has drawn great attentions in both basic and clinical medicine. Therefore, it is necessary to explore the therapeutic drugs and effective targets for early prediction of SAH. Firstly, we demonstrate that LCN2 can effectively intervene or treat SAH from the perspective of cell signaling pathway. Next, three potential genes that we explored have been validated by manually reviewed experimental evidences. Finally, we turn out that the SAH early ensemble learning predictive model performs better than the classical LR, SVM, and Naïve-Bayes models.

Inflammatory Pathways Following Subarachnoid Hemorrhage

Aneurysmal subarachnoid hemorrhage (SAH) is an acute cerebrovascular emergency resulting from the rupture of a brain aneurysm. Despite only accounting for 5% of all strokes, SAH imposes a significant health burden on society due to its relatively young age at onset. Those who survive the initial bleed are often afflicted with severe disabilities thought to result from delayed cerebral ischemia (DCI). Consequently, elucidating the underlying mechanistic pathways implicated in DCI development following SAH remains a priority. Neuroinflammation has recently been implicated as a promising new theory for the development of SAH complications. However, despite this interest, clinical trials have failed to provide consistent evidence for the use of anti-inflammatory agents in SAH patients. This may be explained by the complexity of SAH as a plethora of inflammatory pathways have been shown to be activated in the disease. By determining how these pathways may overlap and interact, we hope to better understand the developmental processes of SAH complications and how to prevent them. The goal of this review is to provide insight into the available evidence regarding the molecular pathways involved in the development of inflammation following SAH and how SAH complications may arise as a result of these inflammatory pathways.

Interleukin-6, MCP-1, IP-10, and MIG are sequentially expressed in cerebrospinal fluid after subarachnoid hemorrhage

Background

Interleukin-6 (IL-6), an inflammatory cytokine, plays important roles in cerebrospinal fluid (CSF) after subarachnoid hemorrhage (SAH). Chemokines are chemoattractant cytokines that regulate trafficking of monocytes/macrophages and lymphocytes to sites of inflammation. However, no studies have been reported regarding the temporal expression of these cytokines in CSF after SAH.

Findings

The concentrations of IL-6, monocyte chemoattractant protein-1 (MCP-1), interferon-γ-inducible protein-10 (IP-10), and monokine induced by interferon-γ (MIG) in the CSF of ten patients with SAH were measured using ELISA kits over a period of 14 days. All aneurysms were located in the anterior circulation. CSF samples from patients with unruptured aneurysms were used as controls. The concentration of IL-6 significantly increased during the acute stage of the disease. The concentration of MCP-1 increased from days 1 to 5, peaking on day 3, and decreased thereafter. The concentrations of IP-10 and MIG progressively increased, peaked on day 5, and then gradually decreased. There were strong correlations between the maximum levels of IL-6 and MCP-1 and IP-10 and MIG on day 5. The maximum level of IL-6 was much higher in poor outcome patients than in good outcome patients.

Conclusions

The present investigation demonstrated that increases in IL-6 levels may induce the expression of MCP-1 in CSF after SAH, followed by increases in the expression of IP-10 and MIG. Dynamic changes in the levels of these cytokines may induce inflammation and may be closely associated with the development of delayed ischemic neurological deficits after SAH.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-016-0675-7) contains supplementary material, which is available to authorized users.

Expression of suppressor of cytokine signaling 3 in cerebrospinal fluid after subarachnoid hemorrhage

BACKGROUND

IL-6 is a proinflammatory cytokine reported to play an important role in the induction of cerebral vasospasm after subarachnoid hemorrhage (SAH). Suppressor of cytokine signaling 3 (SOCS3) is known to act as an inhibitor of signal transduction of IL-6. However, there have been no reports on the expression of SOCS3 in cerebrospinal fluid (CSF) after SAH.

FINDINGS

The concentration of IL-6 was measured serially up until day 10, in CSF of eight patients with SAH. CSF samples obtained from patients suffering from an unruptured aneurysm were used as controls. The expression of SOCS3 in CSF was further examined by immunoprecipitation methods. Concentrations of IL-6 in CSF increased immediately after the onset of SAH and remained chronically elevated over control values. SOCS3 was significantly expressed in CSF on days 1 to 3 after SAH.

CONCLUSIONS

Our findings suggest that SOCS3 regulates IL-6 signaling as an antagonist in CSF, immediately following SAH. As the expression of SOCS3 decreases after day 5, IL-6 signals might then be more easily transmitted, presumably resulting in cerebral vasospasm.

Signal transduction in cerebral arteries after subarachnoid hemorrhage-a phosphoproteomic approach

After subarachnoid hemorrhage (SAH), pathologic changes in cerebral arteries contribute to delayed cerebral ischemia and poor outcome. We hypothesize such changes are triggered by early intracellular signals, targeting of which may prevent SAH-induced vasculopathy. We performed an unbiased quantitative analysis of early SAH-induced phosphorylations in cerebral arteries and evaluated identified signaling components as targets for prevention of delayed vasculopathy and ischemia. Labeled phosphopeptides from rat cerebral arteries were quantified by high-resolution tandem mass spectrometry. Selected SAH-induced phosphorylations were validated by immunoblotting and monitored over a 24-hour time course post SAH. Moreover, inhibition of key phosphoproteins was performed. Major SAH-induced phosphorylations were observed on focal adhesion complexes, extracellular regulated kinase 1/2 (ERK1/2), calcium calmodulin-dependent kinase II, signal transducer and activator of transcription (STAT3) and c-Jun, the latter two downstream of ERK1/2. Inhibition of ERK1/2 6-hour post SAH prevented increases in cerebrovascular constrictor receptors, matrix metalloprotease-9, wall thickness, and improved neurologic outcome. STAT3 inhibition partially mimicked these effects. The study shows that quantitative mass spectrometry is a strong approach to study in vivo vascular signaling. Moreover, it shows that targeting of ERK1/2 prevents delayed pathologic changes in cerebral arteries and improves outcome, and identifies SAH-induced signaling components downstream and upstream of ERK1/2.

Sulforaphane enhances the activity of the Nrf2-ARE pathway and attenuates inflammation in OxyHb-induced rat vascular smooth muscle cells

AIM

A growing body of evidence indicates that the nuclear factor erythroid 2-related factor 2-antioxidant response element (Nrf2-ARE) pathway plays a protective role in many physiological stress processes such as inflammatory damage, oxidative stress, and the accumulation of toxic metabolites, which are all involved in the cerebral vasospasm following subarachnoid hemorrhage (SAH). We hypothesized that the Nrf2-ARE pathway might have a protective role in cerebral vasospasm following SAH.

MATERIALS AND METHODS

In our study, we investigate whether the oxyhemoglobin (OxyHb) can induce the activation of the Nrf2-ARE pathway in vascular smooth muscle cells (VSMCs), and evaluate the modulatory effects of sulforaphane (SUL) on OxyHb-induced inflammation in VSMCs.

RESULTS

As a result, both the protein level and the mRNA level of the nuclear Nrf2 were significantly increased, while the mRNA levels of two Nrf2-regulated gene products, both heme oxygenase-1 and NAD(P)H: quinone oxidoreductase-1, were also up-regulated in VSMCs induced with OxyHb. A marked increase of inflammatory cytokines such as IL-1β, IL-6 and TNF-α release was observed at 48 h after cells were treated with OxyHb. SUL enhanced the activity of the Nrf2-ARE pathway and suppressed cytokine release.

CONCLUSIONS

Our results indicate that the Nrf2-ARE pathway was activated in OxyHb-induced VSMCs. SUL suppressed cytokine release via the activation of the Nrf2-ARE pathway in OxyHb-induced VSMCs.

Vascular KCNQ (Kv7) potassium channels as common signaling intermediates and therapeutic targets in cerebral vasospasm

Cerebral vasospasm after subarachnoid hemorrhage (SAH) is characterized by prolonged severe constriction of the basilar artery, which often leads to ischemic brain damage. Locally elevated concentrations of spasmogenic substances induce persistent depolarization of myocytes in the basilar artery, leading to continuous influx of calcium (Ca) through voltage-sensitive Ca channels and myocyte contraction. Potassium (K) channel openers may have therapeutic utility to oppose membrane depolarization, dilate the arteries, and reduce ischemia. Here, we examined the involvement of vascular Kv7 K channels in the pathogenesis of cerebral vasospasm and tested whether Kv7 channel openers are effective therapeutic agents in a rat model of SAH. Patch-clamp experiments revealed that 3 different spasmogens (serotonin, endothelin, and vasopressin) suppressed Kv7 currents and depolarized freshly isolated rat basilar artery myocytes. These effects were significantly reduced in the presence of a Kv7 channel opener, retigabine. Retigabine (10 μM) also significantly blocked L-type Ca channels, reducing peak inward currents by >50%. In the presence of a selective Kv7 channel blocker, XE991, the spasmogens did not produce additive constriction responses measured using pressure myography. Kv7 channel openers (retigabine or celecoxib) significantly attenuated basilar artery spasm in rats with experimentally induced SAH. In conclusion, we identify Kv7 channels as common targets of vasoconstrictor spasmogens and as candidates for therapeutic intervention for cerebral vasospasm.

Genetics of cerebral vasospasm

Cerebral vasospasm (CV) is a major source of morbidity and mortality in aneurysmal subarachnoid hemorrhage (aSAH). It is thought that an inflammatory cascade initiated by extravasated blood products precipitates CV, disrupting vascular smooth muscle cell function of major cerebral arteries, leading to vasoconstriction. Mechanisms of CV and modes of therapy are an active area of research. Understanding the genetic basis of CV holds promise for the recognition and treatment for this devastating neurovascular event. In our review, we summarize the most recent research involving key areas within the genetics and vasospasm discussion: (1) Prognostic role of genetics—risk stratification based on gene sequencing, biomarkers, and polymorphisms; (2) Signaling pathways—pinpointing key inflammatory molecules responsible for downstream cellular signaling and altering these mediators to provide therapeutic benefit; and (3) Gene therapy and gene delivery—using viral vectors or novel protein delivery methods to overexpress protective genes in the vasospasm cascade.

Influence of experimental subarachnoid hemorrhage on nicotine-induced contraction of the rat basilar artery in relation to arachidonic acid metabolites signaling pathway

BACKGROUND

Smoking is one of the most important risk factors for cerebral circulatory disorders. The purpose of this study was to investigate the influence of experimental subarachnoid hemorrhage (SAH) on nicotine-induced contraction (arachidonic acid metabolites) in the basilar arteries of rats.

METHODS

Rats were killed at 1 hour and 1 week after blood injection, and the basilar artery was isolated and cut into a spiral strip.

RESULTS

Testing of cyclooxygenase-1 (COX-1) and 5-lipoxygenase (5-LOX) inhibitors revealed no significant differences in their effects on normal and SAH (1 hour and 1 week). Phospholipase C (PLC) inhibitor (1-(6-((17beta-3-methoxyestra-1,3,5(10)-trien-17yl)amino)hexyl)-1H-pyrrole-2,5,-dione [U-73122]) slightly inhibited contraction of SAH (1 hour and 1 week) when compared to controls. Phospholipase A2 (PLA2) inhibitor (manoalide) and cytosolic PLA2 (cPLA2) inhibitor (arachidonyltrifluoromenthylketone [AACOCF3]) more strongly attenuated contraction in SAH (1 hour and 1 week) than in controls. Secreted PLA2 (sPLA2) inhibitor (indoxam), PLC inhibitor (2-nitro-4-carboxyphenyl N, N-diphenylcarbamate [NCDC]), and COX-2 inhibitors (nimesulide, (5-methanesulfonamido-6-(2,4-difluorothiophenyl)-1-indanone) [L-745337], and celecoxib) only slightly inhibited contraction of SAH (1 week) when compared to normal and SAH (1 hour). The calcium-independent PLA2 (iPLA2) inhibitor bromoenol lactone (BEL) showed greater inhibition of contraction in SAH (1 hour) when compared to normal and SAH (1 week).

CONCLUSIONS

One week after exposure to SAH, PLC, sPLA2, and COX-2 activity were enhanced and cPLA2 activity was inhibited. One hour after exposure to SAH, PLC activity was enhanced and cPLA2 and iPLA2 activity was inhibited. Such changes of inflammatory arachidonic acid metabolites by smoking after SAH may play important roles in fatal cerebral circulatory disorders, suggesting important implications for the etiology and pathogenesis of SAH.

The potential role of JAK2/STAT3 pathway on the anti-apoptotic effect of recombinant human erythropoietin (rhEPO) after experimental traumatic brain injury of rats

Previous studies indicate that administration of recombinant human erythropoietin (rhEPO) protects cortical neurons following traumatic brain injury (TBI). The mechanisms of rhEPO's neuroprotection are complex and interacting, including anti-apoptosis. Here we aim to demonstrate the role of janus kinase 2/signal transducer and activator of transcription 3 (JAK2/STAT3) pathway on the anti-apoptotic effect of rhEPO in Feeney free falling TBI model. Activation of JAK2/STAT3 in pericontusional cortex was analyzed among rats in Sham, TBI, TBI+rhEPO, TBI+rhEPO+AG490 groups (rhEPO: 5000 U/kg day; JAK2 inhibitor AG490: 5 mg/kg day, intraperitoneal) through Western blotting, electrophoretic mobility shift assay. Bcl-2 and Bcl-xl expression (Q-PCR, Western blotting) and cell apoptosis (TUNEL) in pericontusional cortex were also detected in each group. As a result, we found that TBI could activate JAK2 and STAT3, and increase cell apoptosis in pericontusional cortex. RhEPO enhanced the expression of p-JAK2 and p-STAT3, up-regulated the mRNA and protein levels of Bcl-2 and Bcl-xl, followed by increased cell survival. Moreover, AG490 attenuated rhEPO's neuroprotection by down-regulating rhEPO-induced activation of JAK2/STAT3, and inhibiting Bcl-2 and Bcl-xl. These results suggest the essential role of JAK2/STAT3 pathway on the anti-apoptotic benefit of post-TBI rhEPO treatment.

Significance of brain tissue oxygenation and the arachidonic acid cascade in stroke

The significance of the hypoxia component of stroke injury is highlighted by hypermetabolic brain tissue enriched with arachidonic acid (AA), a 22:6n-3 polyunsaturated fatty acid. In an ischemic stroke environment in which cerebral blood flow is arrested, oxygen-starved brain tissue initiates the rapid cleavage of AA from the membrane phospholipid bilayer. Once free, AA undergoes both enzyme-independent and enzyme-mediated oxidative metabolism, resulting in the formation of number of biologically active metabolites which themselves contribute to pathological stroke outcomes. This review is intended to examine two divergent roles of molecular dioxygen in brain tissue as (1) a substrate for life-sustaining homeostatic metabolism of glucose and (2) a substrate for pathogenic metabolism of AA under conditions of stroke. Recent developments in research concerning supplemental oxygen therapy as an intervention to correct the hypoxic component of stroke injury are discussed.

Activation of JAK2/STAT pathway in cerebral cortex after experimental traumatic brain injury of rats

The janus kinase/signal transducer and activator of transcription (JAK/STAT) is one of the main pathways downstream of cytokine receptors and growth factor receptors by transducing signals from cell surface to the nucleus. In this study, we aimed to survey the role of JAK2/STAT pathway in the progress of TBI. Right parietal cortical contusion in rats was induced by the Feeney free falling model. The activation of JAK2, STAT1 and STAT3 in pericontusional cortex was determined by Western blotting, electrophoretic mobility shift assay (EMSA), immunohistochemistry and immunofluorescence. Moreover, we assessed the neurological recovery (using Neurological Severity Scores (NSS)) of rats under the pretreatment of a JAK2 inhibitor, AG490. Western blotting revealed that expression of p-JAK2, p-STAT1 and p-STAT3 increased immediately, peaked at 3h after TBI and decreased thereafter, and the activation could be inhibited by AG490. Immunohistochemical study showed that JAK2/STAT pathway was activated in both neurons and astrocytes at 3h after TBI. STAT3-specific binding activity was obviously enhanced after TBI and down-regulated after AG490 administration. The higher NSS of TBI+AG490 group revealed a worse behavior recovery when compared with TBI+DMSO group. Our results suggest that the JAK2/STAT pathway is activated in pericontusional cortex of rats, and may be involved in the neurological function recovery after TBI.

Impaired vascular responses of insulin-resistant rats after mild subarachnoid hemorrhage

Insulin resistance (IR) impairs cerebrovascular responses to several stimuli in Zucker obese (ZO) rats. However, cerebral artery responses after subarachnoid hemorrhage (SAH) have not been described in IR. We hypothesized that IR worsens vascular reactions after a mild SAH. Hemolyzed blood (300 μl) or saline was infused (10 μl/min) into the cisterna magna of 11-13-wk-old ZO (n = 25) and Zucker lean (ZL) rats (n = 25). One day later, dilator responses of the basilar artery (BA) and its side branch (BA-Br) to acetylcholine (ACh, 10(-6) M), cromakalim (10(-7) M, 10(-6) M), and sodium nitroprusside (10(-7) M) were recorded with intravital videomicroscopy. The baseline diameter of the BA was increased both in the ZO and ZL rats 24 h after the hemolysate injection. Saline-injected ZO animals showed reduced dilation to ACh (BA = 9 ± 3 vs. 22 ± 4%; and BA-Br = 23 ± 5 vs. 37 ± 7%) compared with ZL rats. Hemolysate injection blunted the response to ACh in both the ZO (BA = 4 ± 2%; and BA-Br = 12 ± 3%) and ZL (BA = 7 ± 2%; and BA-Br = 11 ± 3%) rats. Cromakalim (10(-6) M)-induced dilation was significantly reduced in the hemolysate-injected ZO animals compared with the saline control (BA = 13 ± 3 vs. 26 ± 5%; and BA-Br = 28 ± 8 vs. 44 ± 9%) and in the hemolysate-injected ZL rats compared with their saline control (BA = 24 ± 4 vs. 32 ± 4%; but not BA-Br = 39 ± 6 vs. 59 ± 9%). No significant difference in sodium nitroprusside reactivity was observed. Western blot analysis of the BA showed a lower baseline level of neuronal nitric oxide synthase expression and an enhanced cyclooxygenase-2 level in the hemolysate-injected ZO animals. In summary, cerebrovascular reactivity to both endothelium-dependent and -independent stimuli is severely compromised by SAH in IR animals.

Monitoring of the inflammatory response after aneurysmal subarachnoid haemorrhage in the clinical setting: review of literature and report of preliminary clinical experience

BACKGROUND

Clinical and experimental studies showed a marked inflammatory response in aneurysmal subarachnoid haemorrhage (SAH), and it has been proposed to play a key role in the development of cerebral vasospasm (CVS). Inflammatory response and occurrence of CVS may represent a common pathogenic pathway allowing point of care diagnostics of CVS. Therefore, monitoring of the inflammatory response might be useful in the daily clinical setting of an ICU. The aim of the current report is to give a summary about factors contributing to the complex pathophysiology of inflammatory response in SAH and to discuss possible monitoring modalities.

METHODS

Review and analysis of the existing literature and definition of own study protocols.

RESULTS

In cerebrospinal fluid, interleukin (IL)-6 has been found to be significantly higher in patients with CVS during the peri-vasospasm period. While systemic inflammatory response syndrome, high C-reactive protein levels and leukocyte counts has been linked with the occurrence of CVS, less has been reported about cytokines levels in the jugular bulb of the internal jugular vein and in the peripheral blood. Preliminary evaluation of own data suggests, that IL-6 values in the peripheral blood and the arterio-jugular differences of IL-6 are increased with the inflammatory response after SAH.

CONCLUSION

Monitoring of the inflammatory response, in particular IL-6, might be a useful tool for the daily clinical management of patients with SAH and CVS.

The neuroprotective effects of cyclooxygenase-2 inhibition in a mouse model of aneurysmal subarachnoid hemorrhage

The CNS inflammatory reaction occurring after aneurysmal subarachnoid hemorrhage (SAH) involves the upregulation of numerous cytokines and prostaglandins. Cyclooxygenase (COX) inhibition is a well-established pharmacological anti-inflammatory agent. Previous studies have shown marked increases in COX-2 expression in neurons, astrocytes, microglia, and endothelial cells following brain injury. COX-2 inhibition has been shown to be beneficial following various types of brain injury. This experiment investigates the role of COX-2 activity in early brain injury following SAH. CD-1 mice were subjected to an endovascular perforation model of SAH or SHAM surgery. Following experimental SAH animals were treated with the specific COX-2 inhibitor, NS398, in dosages of either 10 or 30 mg/kg. Neurological performance and brain edema were evaluated 24 and 72 h after SAH. NS398 at 30 mg/kg significantly reduced SAH-induced neurological deterioration. NS 398 at 30 mg/kg resulted in a trend toward the reduction of SAH-induced cerebral edema. Treatment had no effect on mortality. This experiment provides preliminary evidence that COX-2 inhibition is an effective pharmacological intervention for the prevention of brain edema and the preservation of neurological function following SAH.

Expression of NF-E2-related factor 2 (Nrf2) in the basilar artery after experimental subarachnoid hemorrhage in rabbits: a preliminary study

It has been suggested that the pathogenesis of vasospasm is complex including endothelial damage, oxidative stress, inflammatory damage, and the accumulation of toxic metabolites. Recently, a growing body of evidence indicates that nuclear factor erythroid 2-related factor 2 (Nrf2) plays a unique role in many physiological stress processes. In this study, a total of 48 rabbits were assigned randomly to four groups: control group, SAH day 3, day 5, and day 7 groups. The animals in SAH day 3, day 5, and day 7 groups were subjected to injection of autologous blood into cisterna magna twice on day 0 and day 2 and were killed on days 3, 5, and 7, respectively. Cross-sectional area of basilar artery was measured and the Nrf2 expression was assessed by immunohistochemistry and Western blot analysis. The mRNA levels of Nrf2 were also determined by RT-PCR. The basilar arteries exhibited vasospasm after SAH and became more severe on days 3 and 5. The elevated expression of Nrf2 was detected after SAH and peaked on days 3 and 5. Nrf2 is increasingly expressed in a parallel time course to the development of cerebral vasospasm in a rabbit experimental model of SAH.

Effects of recombinant human erythropoietin (rhEPO) on JAK2/STAT3 pathway and endothelial apoptosis in the rabbit basilar artery after subarachnoid hemorrhage

Previous studies have shown that recombinant human erythropoietin (rhEPO) can attenuate the degree of cerebral vasospasm following experimental subarachnoid hemorrhage (SAH). However, the mechanisms for this beneficial effect are still poorly understood. SAH-induced endothelial apoptosis may trigger, aggravate, and maintain cerebral vasospasm. We, therefore, tried to analyze whether rhEPO administration influenced the endothelial cell apoptosis in the basilar artery after SAH. Another aim of the current study was to investigate the modulation of rhEPO on the activity of Janus kinase 2 (JAK2) and signal transducer and activator of transcription 3 (STAT3), which played an important role in the signaling of apoptosis. A total of 48 rabbits were randomly divided into four groups; control group, SAH group, SAH+vehicle group, and SAH+rhEPO group. All SAH animals were subjected to injection of autologous blood into cisterna magna twice on day 0 and day 2. The rhEPO was administered i.p. starting 5 min after the induction of SAH on day 0 and repeated every 8 h for 120 h. The basilar arteries were extracted on day 5 after SAH. As a result, we found that administration of rhEPO could activate JAK2 and STAT3 in the basilar artery and decrease the apoptosis index of endothelial cells following SAH. Moreover, the anti-apoptotic genes such as bcl-2 and bcl-xL were up-regulated after the injections of rhEPO. In conclusion, the therapeutic effect of rhEPO on the subsequent vasospasm after SAH may relate to its inhibition on the endothelial apoptosis in the cerebral arteries, which may be mediated in part by JAK2/STAT3 signaling pathway.

IL-4 suppresses dendritic cell response to type I interferons

Cytokines play an important role in modulating the development and function of dendritic cells (DCs). Type I IFNs activate DCs and drive anti-viral responses, whereas IL-4 is the prototype of a Th2 cytokine. Evidence suggests that type I IFNs and IL-4 influence each other to modulate DC functions. We found that two type I IFNs, IFN-alpha and IFN-beta, stimulated a similar costimulatory profile in myeloid resting DCs. IL-4 suppressed the response of myeloid DCs to both type I IFNs in vitro and in vivo by impairing the up-regulation of MHC and costimulatory molecules and the production of cytokines, such as IL-6 and IL-15, and anti-viral genes, such as Mx-1, upon type I IFN stimulation. In dissecting the mechanism underlying this inhibition, we characterized the positive feedback loop that is triggered by IFN-alpha in primary DCs and found that IL-4 inhibited the initial phosphorylation of STAT1 and STAT2 (the transducers of signaling downstream of IFN-alpha and -beta receptors (IFNARs)) and reduced the up-regulation of genes involved in the amplification of the IFN response such as IRF-7, STAT1, STAT2, IFN-beta, and the IFNARs in vitro and in vivo. Therefore, IL-4 renders myeloid DCs less responsive to paracrine type I IFNs and less potent in sustaining the autocrine positive loop that normally amplifies the effects of type I IFNs. This inhibition could explain the increased susceptibility to viral infections observed during Th2-inducing parasitoses.

Activation of c-jun in the rat basilar artery after subarachnoid hemorrhage

Subarachnoid hemorrhage (SAH) initiates a series of cellular and molecular events, some of which involve a mitogen activated protein kinase, c-jun N-terminal kinase (JNK). However, precise details regarding activation of c-jun in the vessel wall after SAH largely remain to be elucidated. In this study, we therefore investigated the localization and time-dependent expression of c-jun in the rat basilar artery after SAH in a rat single-hemorrhage model featuring infusion of autologous arterial blood. Basilar arteries were obtained at 2, 6 and 12h and 1, 2, 4 and 7 days after SAH, as well as from controls. Western blot analysis with c-jun, phosphorylated c-jun at Ser(63), and actin antibodies revealed that c-jun was immediately phosphorylated at Ser(63) within 2h, thereafter gradually becoming dephosphorylated, while total c-jun and actin levels remained almost unchanged. Immunohistochemistry demonstrated phosphorylation of c-jun at Ser(63) to occur in smooth muscle cells of the basilar artery 2h after SAH. These results indicate that c-jun is activated in the basilar artery immediately after the onset of SAH, presumably resulting in transcription of immediate early genes and smooth muscle cell proliferation.

Expression of Toll-like receptor 4 in the basilar artery after experimental subarachnoid hemorrhage in rabbits: a preliminary study

Inflammation and immunity play a crucial role in the pathogenesis of cerebral vasospasm after subarachnoid hemorrhage (SAH). Recently, a growing body of evidence indicates that Toll-like receptor (TLR) 4 is vital for inflammation and immunity. Therefore, this study aimed to detect the expression of TLR4 in the basilar artery in a rabbit SAH model and to clarify the potential role of TLR4 in cerebral vasospasm. A total of 48 rabbits were randomly divided into four groups: control group; day 3, day 5, and day 7 groups. Day 3, day 5, and day 7 groups were all SAH groups. The animals in day 3, day 5 and day 7 groups were subjected to injection of autologous blood into cisterna magna twice on day 0 and day 2 and were killed on days 3, 5, and 7, respectively. Cross-sectional area of basilar artery was measured and the TLR4 expression was assessed by immunohistochemistry and Western blot analysis. The basilar arteries exhibited vasospasm after SAH and became more severe on day 3 and 5. The elevated expression of TLR4 was detected after SAH and peaked on day 3 and 5. TLR4 is increasingly expressed in a parallel time course to the development of cerebral vasospasm in a rabbit experimental model of SAH.

Attenuation of experimental subarachnoid hemorrhage--induced cerebral vasospasm by the adenosine A2A receptor agonist CGS 21680

OBJECT

Impaired endothelium-dependent relaxation is present in vasospastic cerebral vessels after subarachnoid hemorrhage (SAH) and may result from deficient production of endothelial nitric oxide synthase (eNOS) or increased production and/or activity of inducible NOS (iNOS). Accumulating evidence demonstrates that adenosine A2A receptors increase the production of NO by human and porcine arterial endothelial cells, which in turn leads to vasodilation. This study was designed to examine the effects of an adenosine A2A receptor agonist, (2(4-[2-carboxyethyl]phenyl)ethylamino)-5'-N-ethylcarboxamidoadenosine (CGS 21680), in the prevention of SAH-induced vasospasm.

METHODS

. Experimental SAH was induced in Sprague-Dawley rats by injecting 0.3 ml of autologous blood into the cisterna magna of each animal. Intraperitoneal injections of CGS 21680 or vehicle were administered 5 minutes and 24 hours after induction of SAH. The degree of vasospasm was determined by averaging measurements of cross-sectional areas of the basilar artery (BA) 48 hours after SAH. Expression of eNOS and iNOS in the BA was also evaluated. Prior to perfusion-fixation, there were no significant differences among animals in the control and treated groups in any physiological parameter that was recorded. The CGS 21680 treatment significantly attenuated SAH-induced vasospasm. Induction of iNOS mRNA and protein in the BA by the SAH was significantly diminished by administration of CGS 21680. The SAH-induced suppression of eNOS mRNA and protein was also relieved by the CGS 21680 treatment.

CONCLUSIONS

This is the first evidence that adenosine A2A receptor agonism is effective in preventing SAH-induced vasospasm without significant complications. The beneficial effect of adenosine A2A receptor agonists may be, at least in part, related to the prevention of augmented expression of iNOS and the preservation of normal eNOS expression following SAH. Adenosine A2A receptor agonism holds promise in the treatment of cerebral vasospasm following SAH and merits further investigation.