Endothelial nitric oxide synthase mediates endogenous protection against subarachnoid hemorrhage-induced cerebral vasospasm

Exploring medical gas therapy in hemorrhagic stroke treatment: A narrative review

Hemorrhagic stroke (HS) is a neurological disorder caused by the rupture of cerebral blood vessels, resulting in blood seeping into the brain parenchyma and causing varying degrees of neurological impairment, including intracerebral hemorrhage (ICH) and subarachnoid hemorrhage (SAH). Current treatment methods mainly include hematoma evacuation surgery and conservative treatment. However, these methods have limited efficacy in enhancing neurological function and prognosis. The current challenge in treating HS lies in inhibiting the occurrence and progression of secondary brain damage after bleeding, which is a key factor affecting the prognosis of HS patients. Studies have shown that medical gas therapy is gaining more attention and has demonstrated various levels of neuroprotective effects on central nervous system disorders, such as hyperbaric oxygen, hydrogen sulfide, nitric oxide, carbon monoxide, and other inhalable gas molecules. These medical gas molecules primarily improve brain tissue damage and neurological dysfunction by regulating inflammation, oxidative stress, apoptosis, and other processes. However, many of these medical gasses also possess neurotoxic properties. Therefore, the use of medical gases in HS deserves further exploration and research. In this review, we will elucidate the therapeutic effects and study the advances in medical gas molecules in HS.

Role of adenosine A3 receptor and endothelial nitric oxide synthase in patients with traumatic hemorrhagic shock

BACKGROUND

The aim of this research is to access the expression of adenosine A3 receptor (ADORA3) and nitric oxide synthase 3 (NOS3) genes and serum levels of ADORA3 and NOS3 in patients with multiple trauma with hemorrhagic shock.

MATERIALS AND METHODS

The study was performed at Erciyes University between November 2022 and March 2024, in a prospective and controlled manner. Patients diagnosed with traumatic hemorrhagic shock and requiring transfusion in the emergency department were selected as the patients group. Gene expressions were analyzed using quantitative real-time PCR analysis in total RNA samples and serum levels of NOS3 and ADORA3 were detected using ELISA measurements.

RESULTS

In patients with multiple trauma, adenosine A3 receptor (ADORA3) gene expression showed a significant increase at discharge when compared to healthy controls (P < 0.05). However, serum levels of ADORA3 showed significant decreases at all stages (i.e. at admission, at 24 h, and at discharge) of patients. Although no significant changes were detected in NOS3 gene expression, marked decreases in serum NOS3 levels were observed at admission and at 24 h in multiple trauma patients (P < 0.05). ADORA3 and NOS3 gene expressions were found to be significantly diminished in nonsurvivors.

CONCLUSION

The study emphasizes the importance of ADORA3 and NOS3 gene expressions in influencing shock progression in multiple trauma patients. The increase in ADORA3 gene expression may play a role in restoring vascular reactivity after traumatic shock. Decreased serum NOS3 and ADORA3 levels can contribute to the shock progression in the pathophysiology of multiple trauma.

The Promising Key Factors Mediating Secondary Neuronal Damage in the Perihematomal Region of Intracerebellar Hemorrhage of Mice

ABSTRACT

The underlying mechanisms of secondary neuronal damage following intracerebellar hemorrhage (ICbH) have not yet been clearly understood. Our previous study reported apoptotic neuronal damage in the perihematomal region (PH) in mice. However, the possible key factors causing secondary neuronal damage in ICbH are not yet known. Therefore, we aimed to study the vital factors in the mediation of secondary neuronal damage following ICbH induced by collagenase type VII (0.4 U/μL of saline) into the cerebellum of mice. The mice were grouped into four groups: (1) control group ( n = 12), (2) day-1 group ( n = 12), (3) day-3 group ( n = 12), and (4) day-7 group ( n = 12). All mice underwent behavior assessment following induction of ICbH and were subsequently sacrificed on days 1, 3, and 7. Perihaematoma samples were collected to study morphological changes, immunohistochemistry, nitric oxide (NO) estimation, and oxidative stress markers, respectively. Mouse behavior was disturbed following ICbH on days 3 and 7 compared to the control. In addition, neuronal damage was found in the PH region. Glial fibrillary acidic protein (GFAP) and excitatory amino acid transporter 1 (EAAT1) were highly expressed on day 7, while gamma-aminobutyric acid receptor subunit alpha-1 (GABA A α1)-containing receptor subunit was detected on days 1 and 3. NO increased on day 1 post-induction and decreased on days 3 and 7. The expressions of superoxide dismutase (SOD), catalase (CAT), neuronal nitric oxide synthases (nNOSs), glutathione peroxidase 1, and cyclooxygenase-2 (COX-2) were significantly increased on day 3. Morphological studies of the PH and tissue showed that neuronal damage occurred from day 1 onward and peaked on day 3, associated with alterations in NO, reactive astrocytes (GFAP), glutamate transport regulation (EAAT1), and GABA receptor. Briefly, significant changes in the key markers in the PH regions at different time points are possibly crucial factors facilitating secondary neuronal damage in the PH region. Identifying the time window of these vital changes could help prevent secondary damage and optimize the treatment to occur at proper time points.

Clinical usage of ischemic tolerance-where are its limits?

Ischemic tolerance is a robust internal defense mechanism of all living organisms. The effectiveness of this mechanism has been repeatedly demonstrated in experiments, but a comprehensive review of the clinical applicability of this phenomenon in practice has not yet been published. The results in clinical practice sound ambiguous and unconvincing in comparison with the results of experimental studies. Also, in many localities, the effect of ischemic tolerance was not clinically proven. For the reasons mentioned, the authors analyze the possible causes of the mentioned discrepancies and provide a comprehensive insight into the possible relevant clinical use of this phenomenon in practice for different groups of patients.

MiRNA expression profiling reveals a potential role of microRNA-148b-3p in cerebral vasospasm in subarachnoid hemorrhage

Cerebral vasospasm (CVS) is an important contributor to delayed cerebral ischemia following aneurysmal subarachnoid hemorrhage (aSAH), leading to high morbidity and long-term disability. While several microRNAs (miRNAs) have been implicated in vasospasm, the underlying mechanisms for CVS remain poorly understood. Our study aims to identify miRNAs that may contribute to the development of CVS. Whole-blood samples were obtained during or outside of vasospasm from aSAH patients whose maximal vasospasm was moderate or severe. MiRNAs were isolated from serial whole-blood samples, and miRNA sequencing was performed. Differentially expressed miRNAs were identified and the expression levels in patients' samples were verified using real-time qPCR. The biological functions of identified miRNA were evaluated in human brain endothelial cells (HBECs). MiRNA profiling revealed significant upregulation of miR-148b-3p in patients during CVS. We demonstrated that miR-148b-3p directly targeted and decreased the expression of ROCK1, affecting cell proliferation, migration, and invasion of HBECs through the ROCK-LIMK-Cofilin pathway. We propose that the upregulation of miRNA-148b-3p plays a role in the development of CVS by regulating actin cytoskeletal dynamics in HBECs, which is crucial for vascular function. Our study highlights miR-148b-3p as a potential diagnostic marker as well as therapeutic target for CVS following aSAH.

Protective Effects of Adropin in Experimental Subarachnoid Hemorrhage

PURPOSE

We aimed to investigate early effects of exogenously administered adropin (AD) on neurological function, endothelial nitric oxide synthase (eNOS) expression, nitrite/nitrate levels, oxidative stress, and apoptosis in subarachnoid hemorrhage (SAH).

METHODS

Following intracerebroventricular AD administration (10 µg/5 µl at a rate of 1 µl/min) SAH model was carried out in Sprague-Dawley rats by injection of autologous blood into the prechiasmatic cistern. The effects of AD were assessed 24 h following SAH. The modified Garcia score was employed to evaluate functional insufficiencies. Adropin and caspase-3 proteins were measured by ELISA, while nitrite/nitrate levels, total antioxidant capacity (TAC) and reactive oxygen/nitrogen species (ROS/RNS) were assayed by standard kits. eNOS expression and apoptotic neurons were detected by immunohistochemical analysis.

RESULTS

The SAH group performed notably lower on the modified Garcia score compared to sham and SAH + AD groups. Adropin administration increased brain eNOS expression, nitrite/nitrate and AD levels compared to SHAM and SAH groups. SAH produced enhanced ROS/RNS generation and reduced antioxidant capacity in the brain. Adropin boosted brain TAC and diminished ROS/RNS production in SAH rats and no considerable change amongst SHAM and SAH + AD groups were detected. Apoptotic cells were notably increased in intensity and number after SAH and were reduced by AD administration.

CONCLUSIONS

Adropin increases eNOS expression and reduces neurobehavioral deficits, oxidative stress, and apoptotic cell death in SAH model. Presented results indicate that AD provides protection in early brain injury associated with SAH.

Beyond nimodipine: advanced neuroprotection strategies for aneurysmal subarachnoid hemorrhage vasospasm and delayed cerebral ischemia

The clinical management of aneurysmal subarachnoid hemorrhage (SAH)-associated vasospasm remains a challenge in neurosurgical practice, with its prevention and treatment having a major impact on neurological outcome. While considered a mainstay, nimodipine is burdened by some non-negligible limitations that make it still a suboptimal candidate of pharmacotherapy for SAH. This narrative review aims to provide an update on the pharmacodynamics, pharmacokinetics, overall evidence, and strength of recommendation of nimodipine alternative drugs for aneurysmal SAH-associated vasospasm and delayed cerebral ischemia. A PRISMA literature search was performed in the PubMed/Medline, Web of Science, ClinicalTrials.gov, and PubChem databases using a combination of the MeSH terms "medical therapy," "management," "cerebral vasospasm," "subarachnoid hemorrhage," and "delayed cerebral ischemia." Collected articles were reviewed for typology and relevance prior to final inclusion. A total of 346 articles were initially collected. The identification, screening, eligibility, and inclusion process resulted in the selection of 59 studies. Nicardipine and cilostazol, which have longer half-lives than nimodipine, had robust evidence of efficacy and safety. Eicosapentaenoic acid, dapsone and clazosentan showed a good balance between effectiveness and favorable pharmacokinetics. Combinations between different drug classes have been studied to a very limited extent. Nicardipine, cilostazol, Rho-kinase inhibitors, and clazosentan proved their better pharmacokinetic profiles compared with nimodipine without prejudice with effective and safe neuroprotective role. However, the number of trials conducted is significantly lower than for nimodipine. Aneurysmal SAH-associated vasospasm remains an area of ongoing preclinical and clinical research where the search for new drugs or associations is critical.

Subarachnoid hemorrhage-associated brain injury and neurobehavioral deficits are reversed with synthetic adropin treatment through sustained Ser1179 phosphorylation of endothelial nitric oxide synthase

Background

Subarachnoid hemorrhage (SAH) is a life-threatening vascular condition without satisfactory treatment options. The secreted peptide adropin is highly expressed in the human brain and has neuroprotective effects in brain injury models, including actions involving the cerebrovasculature. Here, we report an endothelial nitric oxide synthase (eNOS)-dependent effect of synthetic adropin treatment that reverses the deleterious effects of SAH.

Methods

We tested the molecular, cellular, and physiological responses of cultured brain microvascular endothelial cells and two mouse models of SAH to treatment using synthetic adropin peptide or vehicle.

Results

SAH decreases adropin expression in cultured brain microvascular endothelial cells and in murine brain tissue. In two validated mouse SAH models, synthetic adropin reduced cerebral edema, preserved tight junction protein expression, and abolished microthrombosis at 1 day post-SAH. Adropin treatment also prevented delayed cerebral vasospasm, decreased neuronal apoptosis, and reduced sensorimotor deficits at seven days post-SAH. Delaying initial treatment of adropin until 24 h post-SAH preserved the beneficial effect of adropin in preventing vasospasm and sensorimotor deficits. Mechanistically, adropin treatment increased eNOS phosphorylation (Ser1179) at 1 & 7 days post-SAH. Treating eNOS-/- mice with adropin failed to prevent vasospasm or behavioral deficits, indicating a requirement of eNOS signaling.

Conclusions

Adropin is an effective treatment for SAH, reducing cerebrovascular injury in both the acute (1 day) and delayed (7 days) phases. These findings establish the potential of adropin or adropin mimetics to improve outcomes following subarachnoid hemorrhage.

Conditioning-based therapeutics for aneurysmal subarachnoid hemorrhage - A critical review

Aneurysmal subarachnoid hemorrhage (SAH) carries significant mortality and morbidity, with nearly half of SAH survivors having major cognitive dysfunction that impairs their functional status, emotional health, and quality of life. Apart from the initial hemorrhage severity, secondary brain injury due to early brain injury and delayed cerebral ischemia plays a leading role in patient outcome after SAH. While many strategies to combat secondary brain injury have been developed in preclinical studies and tested in late phase clinical trials, only one (nimodipine) has proven efficacious for improving long-term functional outcome. The causes of these failures are likely multitude, but include use of therapies targeting only one element of what has proven to be multifactorial brain injury process. Conditioning is a therapeutic strategy that leverages endogenous protective mechanisms to exert powerful and remarkably pleiotropic protective effects against injury to all major cell types of the CNS. The aim of this article is to review the current body of evidence for the use of conditioning agents in SAH, summarize the underlying neuroprotective mechanisms, and identify gaps in the current literature to guide future investigation with the long-term goal of identifying a conditioning-based therapeutic that significantly improves functional and cognitive outcomes for SAH patients.

Peripheral macrophages in the development and progression of structural cerebrovascular pathologies

The human cerebrovascular system is responsible for maintaining neural function through oxygenation, nutrient supply, filtration of toxins, and additional specialized tasks. While the cerebrovascular system has resilience imparted by elaborate redundant collateral circulation from supportive tertiary structures, it is not infallible, and is susceptible to developing structural vascular abnormalities. The causes of this class of structural cerebrovascular diseases can be broadly categorized as 1) intrinsic developmental diseases resulting from genetic or other underlying aberrations (arteriovenous malformations and cavernous malformations) or 2) extrinsic acquired diseases that cause compensatory mechanisms to drive vascular remodeling (aneurysms and arteriovenous fistulae). Cerebrovascular diseases of both types pose significant risks to patients, in some cases leading to death or disability. The drivers of such diseases are extensive, yet inflammation is intimately tied to all of their progressions. Central to this inflammatory hypothesis is the role of peripheral macrophages; targeting this critical cell type may lead to diagnostic and therapeutic advancement in this area. Here, we comprehensively review the role that peripheral macrophages play in cerebrovascular pathogenesis, provide a schema through which macrophage behavior can be understood in cerebrovascular pathologies, and describe emerging diagnostic and therapeutic avenues in this area.

ABO blood types may affect transient neurological events after surgical revascularization in patients with moyamoya disease: a retrospective single center study

BACKGROUND

Moyamoya disease (MMD) is a cerebrovascular disease with unknown cause. Patients with MMD disease usually experience transient neurological events (TNEs) after revascularization surgery. This retrospective single-center study was aimed to explore the risk factors of postoperative TNEs after surgical revascularization in patients with MMD.

METHODS

We selected 324 patients who underwent surgical revascularization between January 2017 and September 2022 in our center. The perioperative characteristics of the patients were recorded and the outcome was TNEs after surgery. An analysis of risk factors contributing to postoperative TNEs by using logistic regression model.

RESULTS

Three hundred twelve patients were enrolled, and the incidence of postoperative TNEs was 34% in our study. Males were more likely to suffer from postoperative TNEs (OR = 2.344, p = 0.002). Preoperative ischemic presentation (OR = 1.849, p = 0.048) and intraoperative hypotension (OR = 2.332, p = 0.002) were associated with postoperative TNEs. Compared to patients with blood type O, patients with blood type A (OR = 2.325, p = 0.028), B (OR = 2.239, p = 0.027) and AB (OR = 2.938, p = 0.019) had a significantly higher incidence of postoperative TNEs. A risk prediction model for postoperative TNEs was established, and the established risk prediction area under the receiver operating characteristic curve (ROC) of the model was 0.741.

CONCLUSIONS

Males, preoperative ischemic presentation and intraoperative hypotension were associated with postoperative TNEs. We also found a possible link between postoperative TNEs and ABO blood types after surgical revascularization for moyamoya patients.

Candidate neuroinflammatory markers of cerebral autoregulation dysfunction in human acute brain injury

The loss of cerebral autoregulation (CA) is a common and detrimental secondary injury mechanism following acute brain injury and has been associated with worse morbidity and mortality. However patient outcomes have not as yet been conclusively proven to have improved as a result of CA-directed therapy. While CA monitoring has been used to modify CPP targets, this approach cannot work if the impairment of CA is not simply related to CPP but involves other underlying mechanisms and triggers, which at present are largely unknown. Neuroinflammation, particularly inflammation affecting the cerebral vasculature, is an important cascade that occurs following acute injury. We hypothesise that disturbances to the cerebral vasculature can affect the regulation of CBF, and hence the vascular inflammatory pathways could be a putative mechanism that causes CA dysfunction. This review provides a brief overview of CA, and its impairment following brain injury. We discuss candidate vascular and endothelial markers and what is known about their link to disturbance of the CBF and autoregulation. We focus on human traumatic brain injury (TBI) and subarachnoid haemorrhage (SAH), with supporting evidence from animal work and applicability to wider neurologic diseases.

Early Brain Injury After Subarachnoid Hemorrhage: Incidence and Mechanisms

Aneurysmal subarachnoid hemorrhage is a devastating condition causing significant morbidity and mortality. While outcomes from subarachnoid hemorrhage have improved in recent years, there continues to be significant interest in identifying therapeutic targets for this disease. In particular, there has been a shift in emphasis toward secondary brain injury that develops in the first 72 hours after subarachnoid hemorrhage. This time period of interest is referred to as the early brain injury period and comprises processes including microcirculatory dysfunction, blood-brain-barrier breakdown, neuroinflammation, cerebral edema, oxidative cascades, and neuronal death. Advances in our understanding of the mechanisms defining the early brain injury period have been accompanied by improved imaging and nonimaging biomarkers for identifying early brain injury, leading to the recognition of an elevated clinical incidence of early brain injury compared with prior estimates. With the frequency, impact, and mechanisms of early brain injury better defined, there is a need to review the literature in this area to guide preclinical and clinical study.

Value of sildenafil treatment for the prevention of vasospasm‑related delayed ischemic neurological deficits and delayed brain infarction following aneurysmal subarachnoid hemorrhage

Cerebral vasospasm (CV) or delayed cerebral ischemia (DCI) constitutes the main reason for the unfavorable outcomes of patients with aneurysmal subarachnoid hemorrhage (aSAH). The present retrospective cohort study, through an evaluation with computed tomography (CT) perfusion (CTP), aimed to examine the utility of an intravenous or oral administration of sildenafil in preventing DCI that develops due to vasospasm in these patients. A retrospective cohort study was conducted, which included 34 patients in a tertiary care hospital. Of these patients, 18 were males (52.9%), and the median age was 54.4 years. Of these patients, 18 (52.9%) had undergone surgery, and 16 (47.1%) had an endovascular procedure. CTP was performed on the 3rd to the 6th day. The clinical outcome was documented at 30 days using a CT scan and a complete neurological evaluation, including the Glasgow Coma Scale assessment. There was a statistically significant difference in the number of patients who developed an ischemic event at 1 month between those who did not receive sildenafil compared to those who received sildenafil (P<0.05). In addition, the multivariate analysis revealed that cerebral blood flow was an independent factor for detecting an ischemic event in 1 month (P=0.001). On the whole, the findings of the present study indicate that the intravenous or oral administration of sildenafil may be beneficial for the prevention of DCI.

Influence of neurovascular anatomy on perforation site in different mouse strains using the filament perforation model for induction of subarachnoid hemorrhage

BACKGROUND

Filament perforation is a widely-used method to induce subarachnoid hemorrhage (SAH) in mice. Whereas the perforation site has been assumed to be in the branching of middle cerebral artery (MCA) and anterior cerebral artery (ACA), we recently observed more proximal perforations.

METHODS

Filament perforation was performed in CD1- (n = 10) and C57Bl/6N-mice (n = 9) ex vivo. The filament was left in place and the perforation site was microscopically assessed. Digital subtraction angiography (DSA) was performed in CD1- (n = 9) and C57Bl/6J-mice (n = 29) and anatomical differences of the internal carotid artery (ICA) were determined.

RESULTS

Whereas in C57Bl/6N-mice perforation occurred in the proximal intracranial ICA in 89% (n = 8), in CD1-mice the perforation site was in the proximal ICA in 50% (n = 5), in the branching between MCA and ACA in 40% (n = 4), and in the proximal ACA in 10% (n = 1). DSA revealed a stronger angulation (p<0.001) of the ICA in CD1-mice (163.5±2.81°) compared to C57Bl/6J-mice (124.5±5.49°). Body weight and ICA-angle showed no significant correlation in C57Bl/6J- (r = -0.06, pweight/angle = 0.757) and CD1-mice (r = -0.468, pweight/angle = 0.242).

CONCLUSION

Filament perforation in mice occurs not only at the hitherto presumed branching between MCA and ACA, but seems to depend on mouse strain and anatomy as the proximal intracranial ICA may also be perforated frequently.

Endothelial NO synthase 786T/T polymorphism increases hemorrhagic transformation after endovascular thrombectomy

BACKGROUND AND PURPOSE

This study examined whether the 786 NOS3 polymorphism is associated with the risk of hemorrhagic transformation (HT) in stroke patients with anterior large vessel occlusion (ALVO) treated using endovascular thrombectomy (EVT).

METHODS

We performed an observational cohort study that included 118 patients with ALVO who underwent EVT. HT was assessed in follow-up CT and MRI. HT and non-HT patients were compared in terms of the 786 NOS3 polymorphism, flow mediated dilation (FMD) values within 3 days after the stroke, and collateral status based on three grading scales. Demographics, vascular risk factors, additional radiological data including ASPECT score, thrombus length and infarct size, and EVT procedure and outcome variables were also included.

RESULTS

Radiological HT occurred in 55 (46.6%) patients and the 786T/T NOS3 polymorphism was associated with HT (unadjusted OR of 2.33, 95%CI: 1.05-5.20, adjusted OR of 3.14, 95%CI: 1.16-8.54). Collateral status and systemic endothelial function assessed by FMD were not mediators of this relationship as no differences were seen in the median FMD percentage values or collateral status between NOS3 genotypes.

CONCLUSIONS

Our results suggest that genetic variations affecting the NO pathway, such as the 786 NOS3 polymorphism, may contribute to individual variability in the occurrence of HT and these results support involvement of this pathway in the pathogenesis of ischemia-reperfusion injury after EVT.

SIRT1 mediates hypoxic postconditioning- and resveratrol-induced protection against functional connectivity deficits after subarachnoid hemorrhage

Functional connectivity (FC) is a sensitive metric that provides a readout of whole cortex coordinate neural activity in a mouse model. We examine the impact of experimental SAH modeled through endovascular perforation, and the effectiveness of subsequent treatment on FC, through three key questions: 1) Does the endovascular perforation model of SAH induce deficits in FC; 2) Does exposure to hypoxic conditioning provide protection against these FC deficits and, if so, is this neurovascular protection SIRT1-mediated; and 3) does treatment with the SIRT1 activator resveratrol alone provide protection against these FC deficits? Cranial windows were adhered on skull-intact mice that were then subjected to either sham or SAH surgery and either left untreated or treated with hypoxic post-conditioning (with or without EX527) or resveratrol for 3 days. Mice were imaged 3 days post-SAH/sham surgery, temporally aligned with the onset of major SAH sequela in mice. Here we show that the endovascular perforation model of SAH induces global and network-specific deficits in FC by day 3, corresponding with the time frame of DCI in mice. Hypoxic conditioning provides SIRT1-mediated protection against these network-specific FC deficits post-SAH, as does treatment with resveratrol. Conditioning-based strategies provide multifaceted neurovascular protection in experimental SAH.

Vitamin D as therapeutic modulator in cerebrovascular diseases: a mechanistic perspectives

Vitamin D deficiency has been linked to several major chronic diseases, such as cardiovascular and neurodegenerative diseases, diabetes, and cancer, linked to oxidative stress, inflammation, and aging. Vitamin D deficiency appears to be particularly harmful to the cardiovascular system, as it can cause endothelial dysfunctioning and vascular abnormalities through the modulation of various downstream mechanisms. As a result, new research indicates that therapeutic approaches targeting vitamin D inadequacies or its significant downstream effects, such as impaired autophagy, abnormal pro-inflammatory and pro-oxidant reactions, may delay the onset and severity of major cerebrovascular disorders such as stroke and neurologic malformations. Vitamin D modulates the various molecular pathways, i.e., Nitric Oxide, PI3K-Akt Pathway, cAMP pathway, NF-kB Pathway, Sirtuin 1, Nrf2, FOXO, in cerebrovascular disorder. The current review shows evidence for vitamin D's mitigating or slowing the progression of these cerebrovascular disorders, which are significant causes of disability and death worldwide.

Melatonin affects hypoxia-inducible factor 1α and ameliorates delayed brain injury following subarachnoid hemorrhage via H19/miR-675/HIF1A/TLR4

This study aimed to investigate the molecular mechanism of how melatonin (MT) interferes with hypoxia-inducible factor 1α (HIF1A) and toll-like receptor 4 (TLR4) expression, which is implicated in the management of delayed brain injury (DBI) after subarachnoid hemorrhage (SAH). Luciferase assay, real-time PCR, Western-blot analysis and immunohistochemistry (IHC) assays were utilized to explore the interaction among H19, miR-675, HIF1A and TLR4, and to evaluate the effect of MT on the expression of above transcripts in different groups. MT enhanced H19 expression by promoting the transcription efficiency of H19 promoter, and HIF1A was identified as a target of miR-675. HIF1A enhanced TLR4 expression via promoting the transcription efficiency of TLR4 promoter. Furthermore, administration of MT up-regulated miR-675 but suppressed the expressions of HIF1A and TLR4. Treatment with MT alleviated neurobehavioral deficits and apoptosis induced by SAH. According to the result of IHC, HIF1A and TLR4 protein levels in the SAH group were much higher than those in the SAH+MT group. Therefore, the administration of MT increased the levels of H19 and miR-675 which have been inhibited by SAH. In a similar way, treatment with MT decreased the levels of HIF1A and TLR4 which have been enhanced by SAH. MT could down-regulate the expression of HIF1A and TLR4 via the H19/miR-675/HIF1A/TLR4 signaling pathway, while TLR4 is crucial to the release of pro-inflammatory cytokines. Therefore, the treatment with MT could ameliorate post-SAH DBI.Running title: Melatonin ameliorates post-SAH DBI via H19/miR-675/HIF1A/TLR4 signaling pathways

Ratio of Nitric Oxide Metabolite Levels in Cerebrospinal Fluid and Serum, and Their Correlation with Severity and Outcome in Patients with Subarachnoid Haemorrhage

BACKGROUND

Nitric oxide (NO) is involved in a multitude of physiological processes in the central nervous system (CNS). Given the ubiquitous nature of NO and its involvement in various vital processes, nitric oxide metabolite (NOx) has been investigated as a biomarker in CNS diseases. This study aims to investigate the ratio of NOx levels and serum in cerebrospinal fluid (CSF) in patients with spontaneous subarachnoid haemorrhage (SAH). The associations among these markers with clinical outcomes were also studied.

METHODS

A prospective cohort study was conducted over a 2-year period (May 2013-May 2015) to investigate the levels of NOx in the CSF and serum of patients with radiologically confirmed aneurysmal SAH. NOx samples and all relevant data were collected from the patients on admission and serially over 5 days. On admission, NOx levels were compared between the groups of patients, who were divided as per the World Federation Neurosurgeons Score (WFNS) grading scale, Fisher scale, occurrence of vasospasm on transcranial doppler (TCD), and Glasgow outcome scale (GOS) upon discharge and at 6 months follow-up. The ratios of CSF-to-serum were calculated and correlated with SAH severity and the outcome parameters listed above.

RESULTS

The patients (N = 40) had a mean (SD) age of 58.2 (11.8) years old. The majority (65%) had a higher severity of SAH (WFNS score 3-5). On evaluation of the CT scan findings, 74% had outcomes equivalent to 4 on the Fisher scale. Vasospasm was detected via TCD in nearly half (45%) of the cohort during the study period; 80% were noted to have a poor outcome (GOS 1-3) at discharge; this persisted at 6 months follow-up. Comparison of NOx levels in the CSF/serum ratio was based on the incidence of vasospasm and severity of outcome (GOS) for day-1 and day-4. Statistically significant results were evident for patients with better outcomes, high severity grading, and the presence of vasospasm (P-values: 0.031, 0.034 and 0.043, respectively).

CONCLUSION

Elevated NOx levels in CSF and serum and reductions in the ratio of NOx in CSF/serum were found to be associated with severity, occurrence of vasospasm and clinical outcome in aneurysmal SAH patients. This indicates the possible role of NOx as a biomarker to assess severity and prognosis in patients with SAH.

Sirtuin 1 Mediates Protection Against Delayed Cerebral Ischemia in Subarachnoid Hemorrhage in Response to Hypoxic Postconditioning

Background Many therapies designed to prevent delayed cerebral ischemia (DCI) and improve neurological outcome in aneurysmal subarachnoid hemorrhage (SAH) have failed, likely because of targeting only one element of what has proven to be a multifactorial disease. We previously demonstrated that initiating hypoxic conditioning before SAH (hypoxic preconditioning) provides powerful protection against DCI. Here, we expanded upon these findings to determine whether hypoxic conditioning delivered at clinically relevant time points after SAH (hypoxic postconditioning) provides similarly robust DCI protection. Methods and Results In this study, we found that hypoxic postconditioning (8% O₂ for 2 hours) initiated 3 hours after SAH provides strong protection against cerebral vasospasm, microvessel thrombi, and neurological deficits. By pharmacologic and genetic inhibition of SIRT1 (sirtuin 1) using EX527 and global Sirt1^-/- mice, respectively, we demonstrated that this multifaceted DCI protection is SIRT1 mediated. Moreover, genetic overexpression of SIRT1 using Sirt1-Tg mice, mimicked the DCI protection afforded by hypoxic postconditioning. Finally, we found that post-SAH administration of resveratrol attenuated cerebral vasospasm, microvessel thrombi, and neurological deficits, and did so in a SIRT1-dependent fashion. Conclusions The present study indicates that hypoxic postconditioning provides powerful DCI protection when initiated at clinically relevant time points, and that pharmacologic augmentation of SIRT1 activity after SAH can mimic this beneficial effect. We conclude that conditioning-based therapies administered after SAH hold translational promise for patients with SAH and warrant further investigation.

Pathophysiology of Delayed Cerebral Ischemia After Subarachnoid Hemorrhage: A Review

Delayed cerebral ischemia is a major predictor of poor outcomes in patients who suffer subarachnoid hemorrhage. Treatment options are limited and often ineffective despite many years of investigation and clinical trials. Modern advances in basic science have produced a much more complex, multifactorial framework in which delayed cerebral ischemia is better understood and novel treatments can be developed. Leveraging this knowledge to improve outcomes, however, depends on a holistic understanding of the disease process. We conducted a review of the literature to analyze the current state of investigation into delayed cerebral ischemia with emphasis on the major themes that have emerged over the past decades. Specifically, we discuss microcirculatory dysfunction, glymphatic impairment, inflammation, and neuroelectric disruption as pathological factors in addition to the canonical focus on cerebral vasospasm. This review intends to give clinicians and researchers a summary of the foundations of delayed cerebral ischemia pathophysiology while also underscoring the interactions and interdependencies between pathological factors. Through this overview, we also highlight the advances in translational studies and potential future therapeutic opportunities.

Nitric Oxide-Dependent Pathways as Critical Factors in the Consequences and Recovery after Brain Ischemic Hypoxia

Brain ischemia is one of the leading causes of disability and mortality worldwide. Nitric oxide (NO^•), a molecule that is involved in the regulation of proper blood flow, vasodilation, neuronal and glial activity constitutes the crucial factor that contributes to the development of pathological changes after stroke. One of the early consequences of a sudden interruption in the cerebral blood flow is the massive production of reactive oxygen and nitrogen species (ROS/RNS) in neurons due to NO^• synthase uncoupling, which leads to neurotoxicity. Progression of apoptotic or necrotic neuronal damage activates reactive astrocytes and attracts microglia or lymphocytes to migrate to place of inflammation. Those inflammatory cells start to produce large amounts of inflammatory proteins, including pathological, inducible form of NOS (iNOS), which generates nitrosative stress that further contributes to brain tissue damage, forming vicious circle of detrimental processes in the late stage of ischemia. S-nitrosylation, hypoxia-inducible factor 1α (HIF-1α) and HIF-1α-dependent genes activated in reactive astrocytes play essential roles in this process. The review summarizes the roles of NO^•-dependent pathways in the early and late aftermath of stroke and treatments based on the stimulation or inhibition of particular NO^• synthases and the stabilization of HIF-1α activity.

Role of endothelial nitric oxide synthase for early brain injury after subarachnoid hemorrhage in mice

The first few hours and days after subarachnoid hemorrhage (SAH) are characterized by cerebral ischemia, spasms of pial arterioles, and a significant reduction of cerebral microperfusion, however, the mechanisms of this early microcirculatory dysfunction are still unknown. Endothelial nitric oxide production is reduced after SAH and exogenous application of NO reduces post-hemorrhagic microvasospasm. Therefore, we hypothesize that the endothelial NO-synthase (eNOS) may be involved in the formation of microvasospasms, microcirculatory dysfunction, and unfavorable outcome after SAH. SAH was induced in male eNOS deficient (eNOS^-/-) mice by endovascular MCA perforation. Three hours later, the cerebral microcirculation was visualized using in vivo 2-photon-microscopy. eNOS^-/- mice had more severe SAHs, more severe ischemia, three time more rebleedings, and a massively increased mortality (50 vs. 0%) as compared to wild type (WT) littermate controls. Three hours after SAH eNOS^-/- mice had fewer perfused microvessels and 40% more microvasospasms than WT mice. The current study indicates that a proper function of eNOS plays a key role for a favorable outcome after SAH and helps to explain why patients suffering from hypertension or other conditions associated with impaired eNOS function, have a higher risk of unfavorable outcome after SAH.

Remote Ischemic Conditioning in Emergency Medicine-Clinical Frontiers and Research Opportunities

Time-critical acute ischemic conditions such as ST-elevation myocardial infarction and acute ischemic stroke are staples in Emergency Medicine practice. While timely reperfusion therapy is a priority, the resultant acute ischemia/reperfusion injury contributes to significant mortality and morbidity. Among therapeutics targeting ischemia/reperfusion injury (IRI), remote ischemic conditioning (RIC) has emerged as the most promising.RIC, which consists of repetitive inflation and deflation of a pneumatic cuff on a limb, was first demonstrated to have protective effect on IRI through various neural and humoral mechanisms. Its attractiveness stems from its simplicity, low-cost, safety, and efficacy, while at the same time it does not impede reperfusion treatment. There is now good evidence for RIC as an effective adjunct to reperfusion in ST-elevation myocardial infarction patients for improving clinical outcomes. For other applications such as acute ischemic stroke, subarachnoid hemorrhage, traumatic brain injury, cardiac arrest, and spinal injury, there is varying level of evidence.This review aims to describe the RIC phenomenon, briefly recount its historical development, and appraise the experimental and clinical evidence for RIC in selected emergency conditions. Finally, it describes the practical issues with RIC clinical application and research in Emergency Medicine.

Role of SIRT1 in Isoflurane Conditioning-Induced Neurovascular Protection against Delayed Cerebral Ischemia Secondary to Subarachnoid Hemorrhage

We recently reported that isoflurane conditioning provided multifaceted protection against subarachnoid hemorrhage (SAH)-induced delayed cerebral ischemia (DCI), and this protection was through the upregulation of endothelial nitric oxide synthase (eNOS). SIRT1, an NAD-dependent deacetylase, was shown to be one of the critical regulators of eNOS. The aim of our current study is to examine the role of SIRT1 in isoflurane conditioning-induced neurovascular protection against SAH-induced DCI. Mice were divided into four groups: sham, SAH, or SAH with isoflurane conditioning (with and without EX-527). Experimental SAH via endovascular perforation was performed. Anesthetic conditioning was performed with isoflurane 2% for 1 h, 1 h after SAH. EX-527, a selective SIRT1 inhibitor, 10 mg/kg was injected intraperitoneally immediately after SAH in the EX-527 group. SIRT1 mRNA expression and activity levels were measured. Vasospasm, microvessel thrombosis, and neurological outcome were assessed. SIRT1 mRNA expression was downregulated, and no difference in SIRT1 activity was noted after isoflurane exposure. Isoflurane conditioning with and without EX-527 attenuated vasospasm, microvessel thrombosis and improved neurological outcomes. Our data validate our previous findings that isoflurane conditioning provides strong protection against both the macro and micro vascular deficits induced by SAH, but this protection is likely not mediated through the SIRT1 pathway.

Anesthetic and subanesthetic doses of isoflurane conditioning provides strong protection against delayed cerebral ischemia in a mouse model of subarachnoid hemorrhage

Delayed cerebral ischemia (DCI) is identified as one of the significant contributors to poor patient outcome after aneurysmal subarachnoid hemorrhage (SAH). We previously reported that a supratherapeutic dose of isoflurane conditioning (2%) provided robust protection against SAH-induced DCI. The aim of our current study is to compare the efficacy of the supratherapeutic dose of isoflurane to that typically used to establish general anesthesia or sedation. After IRB approval for animal studies, ten to fourteen-week-old wild-type male mice (C57BL/6) were divided into five groups - sham, SAH alone, or SAH with isoflurane conditioning (0.5%, 1%, and 2%). Conditioning was performed with one-hour of isoflurane initiated one-hour after induction of SAH via endovascular perforation technique. Vasospasm measurement in the middle cerebral artery was assessed 72 h after SAH. Neurological assessment was performed at baseline and for next three days after SAH. It was identified that all tested doses of isoflurane conditioning (0.5%, 1%, and 2%) significantly attenuated large artery vasospasm and markedly improved neurological deficits following SAH. No significant differences in neurovascular outcome were noted between the three doses of isoflurane conditioning. Our data show that isoflurane dosing typically used for general anesthesia (1%) or sedation (0.5%) provide similar levels of DCI protection in SAH as that provided by a supratherapeutic dose (2%). This result has important implications for future translational studies. Additional studies examining the therapeutic potential of anesthetic conditioning for SAH are therefore warranted.

Remote Ischemic Pre-conditioning in Subarachnoid Hemorrhage: A Prospective Pilot Trial

BACKGROUND

Cerebral injury from aneurysmal subarachnoid hemorrhage (aSAH) is twofold. The initial hemorrhage causes much of the injury; secondary injury can occur from delayed cerebral ischemia (DCI). Remote ischemic preconditioning (RIPC) is a mechanism of organ protection in response to transient ischemia within a distant organ. This pilot trial sought to apply RIPC in patients with aSAH to evaluate its effect on secondary cerebral injury and resultant outcomes.

METHODS

Patients were randomized to the high-pressure occlusion group (HPO) or the low-pressure occlusion group (LPO). Lower extremity RIPC treatment was initiated within 72 h of symptom onset and every other day for 14 days or until Intensive Care Unit (ICU) discharge. In HPO, each treatment consisted of 4 five-minute cycles of manual blood pressure cuff inflation with loss of distal pulses. LPO received cuff inflation with lower pressures while preserving distal pulses. Retrospectively matched controls were also analyzed. Efficacy of treatment was measured by total days spent in vasospasm out of study enrollment days, hospital and ICU length of stay (LOS), cerebral infarction, one and six month modified Rankin score, and mortality.

RESULTS

The final analysis included 33 patients with 11 in each group. Patient demographics, aneurysm location, admission airway status, Glasgow Coma Scale (GCS), modified Rankin score, Hunt and Hess score, modified Fisher Score and aneurysm management were not significantly different between groups. Hospital and ICU LOS was shorter in LPO compared to the control (p = 0·0468 and p = 0·0409, respectively). Total vasospasm days/study enrollment days, cerebral infarction, one and six month modified Rankin score, and mortality were not significantly different between the groups.

CONCLUSIONS

This pilot trial did demonstrate feasibility and safety. The shortened LOS in the LPO may implicate a protective role of RIPC and warrants future study.

Role of Endothelial Nitric Oxide Synthase in Isoflurane Conditioning-Induced Neurovascular Protection in Subarachnoid Hemorrhage

Background

Delayed cerebral ischemia remains a common and profound risk factor for poor outcome after subarachnoid hemorrhage (SAH). The aim of our current study is to define the role of endothelial nitric oxide synthase (eNOS) in isoflurane conditioning‐induced neurovascular protection after SAH.

Methods and Results

Ten‐ to 14‐week‐old male wild‐type mice (C57BL/6) as controls and eNOS knockout male mice (strain # 002684) were obtained for the study. Animals underwent either sham surgery, SAH surgery, or SAH with isoflurane conditioning. Anesthetic post conditioning was performed with isoflurane 2% for 1 hour, 1 hour after SAH. Normothermia was maintained with the homeothermic blanket. In a separate cohort, nitric oxide synthase was inhibited by a pan nitric oxide synthase inhibitor, L‐nitroarginine methyl ester. Vasospasm measurement was assessed 72 hours after SAH and neurological function was assessed daily. Isoflurane‐induced changes in the eNOS protein expression were measured. eNOS protein expression was significantly increased by isoflurane conditioning in naïve mice as well as mice subjected to SAH. Vasospasm of the middle cerebral artery and neurological deficits were evident following SAH versus sham surgery, both in wild‐type mice and eNOS knockout mice. Isoflurane conditioning attenuated vasospasm and neurological deficits in wild‐type mice. This delayed cerebral ischemia protection was lost in L‐nitroarginine methyl ester ‐administered mice and eNOS knockout mice.

Conclusions

Our data indicate isoflurane conditioning provides robust protection against SAH‐induced vasospasm and neurological deficits, and that this delayed cerebral ischemia protection is critically mediated via isoflurane‐induced augmentation of eNOS.

SIRT1 mediates hypoxic preconditioning induced attenuation of neurovascular dysfunction following subarachnoid hemorrhage

BACKGROUND AND PURPOSE

Vasospasm and delayed cerebral ischemia (DCI) contribute significantly to the morbidity/mortality associated with aneurysmal subarachnoid hemorrhage (SAH). While considerable research effort has focused on preventing or reversing vasospasm, SAH-induced brain injury occurs in response to a multitude of concomitantly acting pathophysiologic mechanisms. In this regard, the pleiotropic epigenetic responses to conditioning-based therapeutics may provide an ideal SAH therapeutic strategy. We previously documented the ability of hypoxic preconditioning (PC) to attenuate vasospasm and neurological deficits after SAH, in a manner that depends on the activity of endothelial nitric oxide synthase. The present study was undertaken to elucidate whether the NAD-dependent protein deacetylase sirtuin isoform SIRT1 is an upstream mediator of hypoxic PC-induced protection, and to assess the efficacy of the SIRT1-activating polyphenol Resveratrol as a pharmacologic preconditioning therapy.

METHODS

Wild-type C57BL/6J mice were utilized in the study and subjected to normoxia or hypoxic PC. Surgical procedures included induction of SAH via endovascular perforation or sham surgery. Multiple endpoints were assessed including cerebral vasospasm, neurobehavioral deficits, SIRT1 expression via quantitative real-time PCR for mRNA, and western blot for protein quantification. Pharmacological agents utilized in the study include EX-527 (SIRT1 inhibitor), and Resveratrol (SIRT1 activator).

RESULTS

Hypoxic PC leads to rapid and sustained increase in cerebral SIRT1 mRNA and protein expression. SIRT1 inhibition blocks the protective effects of hypoxic PC on vasospasm and neurological deficits. Resveratrol pretreatment dose-dependently abrogates vasospasm and attenuates neurological deficits following SAH - beneficial effects that were similarly blocked by pharmacologic inhibition of SIRT1.

CONCLUSION

SIRT1 mediates hypoxic preconditioning-induced protection against neurovascular dysfunction after SAH. Resveratrol mimics this neurovascular protection, at least in part, via SIRT1. Activation of SIRT1 is a promising, novel, pleiotropic therapeutic strategy to combat DCI after SAH.

Review Cerebral Ischemic Tolerance and Preconditioning: Methods, Mechanisms, Clinical Applications, and Challenges

Stroke is one of the leading causes of morbidity and mortality worldwide, and it is increasing in prevalence. The limited therapeutic window and potential severe side effects prevent the widespread clinical application of the venous injection of thrombolytic tissue plasminogen activator and thrombectomy, which are regarded as the only approved treatments for acute ischemic stroke. Triggered by various types of mild stressors or stimuli, ischemic preconditioning (IPreC) induces adaptive endogenous tolerance to ischemia/reperfusion (I/R) injury by activating a multitude cascade of biomolecules, for example, proteins, enzymes, receptors, transcription factors, and others, which eventually lead to transcriptional regulation and epigenetic and genomic reprogramming. During the past 30 years, IPreC has been widely studied to confirm its neuroprotection against subsequent I/R injury, mainly including local ischemic preconditioning (LIPreC), remote ischemic preconditioning (RIPreC), and cross preconditioning. Although LIPreC has a strong neuroprotective effect, the clinical application of IPreC for subsequent cerebral ischemia is difficult. There are two main reasons for the above result: Cerebral ischemia is unpredictable, and LIPreC is also capable of inducing unexpected injury with only minor differences to durations or intensity. RIPreC and pharmacological preconditioning, an easy-to-use and non-invasive therapy, can be performed in a variety of clinical settings and appear to be more suitable for the clinical management of ischemic stroke. Hoping to advance our understanding of IPreC, this review mainly focuses on recent advances in IPreC in stroke management, its challenges, and the potential study directions.

Neurobehavioral Deficits After Subarachnoid Hemorrhage in Mice: Sensitivity Analysis and Development of a New Composite Score

Background

Because of the failure of numerous clinical trials, various recommendations have been made to improve the usefulness of preclinical studies. Specifically, the STAIR (Stroke Therapy Academic Industry Roundtable) recommendations highlighted functional outcome as a critical measure. Recent reviews of experimental subarachnoid hemorrhage (SAH) studies have brought to light the numerous neurobehavioral scoring systems that are used in preclinical SAH studies. To gain insight into the utility of these scoring systems, as well as to identify a scoring system that best captures the deficits caused by SAH in mice, we designed the current study.

Methods and Results

Adult male C57BL/6J mice were used. One cohort of mice was randomly allocated to either sham or SAH and had functional testing performed on days 1 to 3 post‐SAH using the modified Bederson Score, Katz Score, Garcia Neuroscore, and Parra Neuroscore, as well as 21 individual subtests. A new composite neuroscore was developed using the 8 most diagnostically accurate subtests. To validate the use of the developed composite neuroscore, another cohort of mice was randomly assigned to either the sham or SAH group and neurobehavior was evaluated on days 1 to 3, 5, and 7 after injury. Receiver operating characteristic curves were used to analyze the diagnostic accuracy of each scoring system, as well as the subtests. Of the 4 published scoring systems, the Parra Neuroscore was diagnostically accurate for SAH injury in mice versus the modified Bederson and Katz Scores, but not the Garcia Neuroscore. However, the newly developed composite neuroscore was found to be statistically more diagnostically accurate than even the Parra Neuroscore.

Conclusions

The findings of this study promote use of the newly developed composite neuroscore for experimental SAH studies in mice.

Liver structural transformation after partial hepatectomy and repeated partial hepatectomy in rats: A renewed view on liver regeneration

BACKGROUND

The phenomenon of liver regeneration after partial hepatectomy (PH) is still a subject of considerable interest due to the increasing frequency of half liver transplantation on the one hand, and on the other hand, new surgical approaches which allow removal of massive space-occupying hepatic tumors, which earlier was considered as inoperable. Interestingly, the mechanisms of liver regeneration are extensively studied after PH but less attention is paid to the architectonics of the regenerated organ. Because of this, the question "How does the structure of regenerated liver differ from normal, regular liver?" has not been fully answered yet. Furthermore, almost without any attention is left the liver's structural transformation after repeated hepatectomy (of the re-regenereted liver).

AIM

To compare the architectonics of the lobules and circulatory bed of normal, re-generated and re-regenerated livers.

METHODS

The livers of 40 adult, male, albino Wistar rats were studied. 14 rats were subjected to PH - the 1st study group (SG1); 10 rats underwent repeated PH - the 2nd study group (SG2); 16 rats were subjected to sham operation - control group (CG); The livers were studied after 9 months from PH, and after 6 months from repeated PH. Cytological (Schiff reaction for the determination of DNA concen-tration), histological (H&E, Masson trichrome, CK8 Immunohistochemical marker, transparent slides after Indian Ink injection, ), morphometrical (hepatocytes areas, perimeters and ploidy) and Electron Microscopical (Scanning Electron Microscopy of corrosion casts) methods were used.

RESULTS

In the SG1 and SG2, the area of hepatocytes and their perimeter are increased compared to the CG (P < 0.05). However, the areas and perimeters of the hepatocytes of the SG1 and SG2 groups reveal a lesser difference. In regenerated (SG1) and re-regenerated (SG2) livers, the hepatocytes form the remodeled lobules, which size (300-1200 µm) exceeds the sizes of the lobules from CG (300-600 µm). The remodeled lobules (especially the "mega-lobules" with the sizes 1000-1200 µm) contain the transformed meshworks of the sinusoids, the part of which is dilated asymmetrically. This meshwork might have originated from the several portal venules (interlobular and/or inlet). The boundaries between the adjacent lobules (including mega-lobules) are widened and filled by connective tissue fibers, which gives the liver parenchyma a nodular look. In SG2 the unevenness of sinusoid diameters, as well as the boundaries between the lobules (including the mega-lobules) are more vividly expressed in comparison with SG1. The liver tissue of both SG1 and SG2 is featured by the slightly expressed ductular reaction.

CONCLUSION

Regenerated and re-regenerated livers in comparison with normal liver contain hypertrophied hepatocytes with increased ploidy which together with transformed sinusoidal and biliary meshworks form the remodeled lobulli.

Protective Effects of Obstructive Sleep Apnea on Outcomes After Subarachnoid Hemorrhage: A Nationwide Analysis

BACKGROUND

Obstructive sleep apnea (OSA) is typically associated with an increased risk of cardiovascular and cerebrovascular disease. Recent studies, however, have suggested that hypercapnia and chronic intermittent hypoxia may potentially provide protection against ischemic events like stroke.

OBJECTIVE

To evaluate the impact of OSA with presentation, hospital course, and treatment outcomes of patients with subarachnoid hemorrhage (SAH).

METHODS

Data for patients with SAH between the years 2011 and 2015 were extracted from the Nationwide Inpatient Sample (NIS) and stratified based on diagnosis codes for OSA. Univariate analysis was used to assess the prevalence of comorbidities in OSA patients diagnosed with SAH and several covariates, including patient demographics, aneurysmal treatment, in-hospital morality rate, length of stay, and costs. Multivariate logistic regression models analyzed the relationship between several comorbidities, including OSA, tobacco use, and hypertension, and poor outcomes after SAH.

RESULTS

Data from 49 265 SAH patients were used in this study, of which 2408 (4.9%) also had a concomitant OSA diagnosis. Patients with OSA compared to all other SAH patients had a significantly lower in-hospital mortality rate, as well as statistically significant lower odds of vasospasm, stroke, and poor outcomes. Additionally, hypercholesterolemia, obesity, and tobacco use disorder were also associated with more favorable outcomes.

CONCLUSION

SAH patients with OSA are significantly less likely to have a poor outcome when compared to non-OSA patients, despite having an increased risk of several comorbidities.

Proposed Definition of Experimental Secondary Ischemia for Mouse Subarachnoid Hemorrhage

Inconsistency in outcome parameters for delayed cerebral ischemia (DCI) makes it difficult to compare results between mouse studies, in the same way inconsistency in outcome parameters in human studies has for long obstructed adequate comparison. The absence of an established definition may in part be responsible for the failed translational results. The present article proposes a standardized definition for DCI in experimental mouse models, which can be used as outcome measure in future animal studies. We used a consensus-building approach to propose a definition for "experimental secondary ischemia" (ESI) in experimental mouse subarachnoid hemorrhage that can be used as an outcome measure in preclinical studies. We propose that the outcome measure should be as follows: occurrence of focal neurological impairment or a general neurological impairment compared with a control group and that neurological impairment should occur secondarily following subarachnoid hemorrhage (SAH) induction compared with an initial assessment following SAH induction. ESI should not be used if the condition can be explained by general anesthesia or if other means of assessments sufficiently explain function impairment. If neurological impairment cannot reliably be evaluated, due to scientific setup. Verification of a significant secondary impairment of the cerebral perfusion compared with a control group is mandatory. This requires longitudinal examination in the same animal. The primary aim is that ESI should be distinguished from intervention-related ischemia or neurological deficits, in order establish a uniform definition for experimental SAH in mice that is in alignment with outcome measures in human studies.

Non-steroidal anti-inflammatory drugs in the pathophysiology of vasospasms and delayed cerebral ischemia following subarachnoid hemorrhage: a critical review

Aneurysmal subarachnoid hemorrhage (aSAH) is a life-threatening condition associated with the development of early brain injury (EBI) and delayed cerebral ischemia (DCI). Pharmacological treatment of vasospasm following aSAH currently mainly comprises nimodipine administration. In the past few years, many drugs that can potentially benefit cases of subarachnoid hemorrhage have become available. The objective of this review is to critically assess the effects of non-steroidal anti-inflammatory drugs (NSAIDs) following aSAH. A systematic literature review was conducted following PRISMA guidelines. The search was aimed at studies addressing aSAH and NSAIDs during the 2010 to 2019 period, and it yielded 13 articles. Following the application of search criteria, they were divided into two groups, one containing 6 clinical articles and the other containing 7 experimental articles on animal models of aSAH. Inflammatory cerebral changes after aneurysm rupture contribute to the development of EBI, DCI and cerebral vasospasm. It appears that NSAIDs (especially coxibs) are even more effective in reducing vasospasm than nimodipine. Other beneficial effects of NSAIDs include reduction in mortality, improved functional outcome and increased hypoaggregability. However, despite these positive effects, there is only one randomized, double-blind, placebo-controlled trial showing a tendency towards a better outcome with lower incidence of vasospasm or mortality in patients following aSAH.

Delayed Cerebral Ischemia After Subarachnoid Hemorrhage: Experimental-Clinical Disconnect and the Unmet Need

BACKGROUND

Delayed cerebral ischemia (DCI) is among the most dreaded complications following aneurysmal subarachnoid hemorrhage (SAH). Despite advances in neurocritical care, DCI remains a significant cause of morbidity and mortality, prolonged intensive care unit and hospital stay, and high healthcare costs. Large artery vasospasm has classically been thought to lead to DCI. However, recent failure of clinical trials targeting vasospasm to improve outcomes has underscored the disconnect between large artery vasospasm and DCI. Therefore, interest has shifted onto other potential mechanisms such as microvascular dysfunction and spreading depolarizations. Animal models can be instrumental in dissecting pathophysiology, but clinical relevance can be difficult to establish.

METHODS

Here, we performed a systematic review of the literature on animal models of SAH, focusing specifically on DCI and neurological deficits.

RESULTS

We find that dog, rabbit and rodent models do not consistently lead to DCI, although some degree of delayed vascular dysfunction is common. Primate models reliably recapitulate delayed neurological deficits and ischemic brain injury; however, ethical issues and cost limit their translational utility.

CONCLUSIONS

To facilitate translation, clinically relevant animal models that reproduce the pathophysiology and cardinal features of DCI after SAH are urgently needed.

Neuroinflammation and Microvascular Dysfunction After Experimental Subarachnoid Hemorrhage: Emerging Components of Early Brain Injury Related to Outcome

Aneurysmal subarachnoid hemorrhage has a high mortality rate and, for those who survive this devastating injury, can lead to lifelong impairment. Clinical trials have demonstrated that cerebral vasospasm of larger extraparenchymal vessels is not the sole contributor to neurological outcome. Recently, the focus of intense investigation has turned to mechanisms of early brain injury that may play a larger role in outcome, including neuroinflammation and microvascular dysfunction. Extravasated blood after aneurysm rupture results in a robust inflammatory response characterized by activation of microglia, upregulation of cellular adhesion molecules, recruitment of peripheral immune cells, as well as impaired neurovascular coupling, disruption of the blood-brain barrier, and imbalances in endogenous vasodilators and vasoconstrictors. Each of these phenomena is either directly or indirectly associated with neuronal death and brain injury. Here, we review recent studies investigating these various mechanisms in experimental models of subarachnoid hemorrhage with special emphasis on neuroinflammation and its effect on microvascular dysfunction. We discuss the various therapeutic targets that have risen from these mechanistic studies and suggest the utility of a multi-targeted approach to preventing delayed injury and improving outcome after subarachnoid hemorrhage.

A Comparison of Pathophysiology in Humans and Rodent Models of Subarachnoid Hemorrhage

Non-traumatic subarachnoid hemorrhage (SAH) affects an estimated 30,000 people each year in the United States, with an overall mortality of ~30%. Most cases of SAH result from a ruptured intracranial aneurysm, require long hospital stays, and result in significant disability and high fatality. Early brain injury (EBI) and delayed cerebral vasospasm (CV) have been implicated as leading causes of morbidity and mortality in these patients, necessitating intense focus on developing preclinical animal models that replicate clinical SAH complete with delayed CV. Despite the variety of animal models currently available, translation of findings from rodent models to clinical trials has proven especially difficult. While the explanation for this lack of translation is unclear, possibilities include the lack of standardized practices and poor replication of human pathophysiology, such as delayed cerebral vasospasm and ischemia, in rodent models of SAH. In this review, we summarize the different approaches to simulating SAH in rodents, in particular elucidating the key pathophysiology of the various methods and models. Ultimately, we suggest the development of standardized model of rodent SAH that better replicates human pathophysiology for moving forward with translational research.

Minocycline protects against delayed cerebral ischemia after subarachnoid hemorrhage via matrix metalloproteinase-9 inhibition

Objective

Delayed cerebral ischemia (DCI) is an independent risk factor for poor outcome after aneurysmal subarachnoid hemorrhage (SAH) and is multifactorial in etiology. While prior studies have suggested a role for matrix metalloproteinase-9 (MMP-9) in early brain injury after SAH, its contribution to the pathophysiology of DCI is unclear.

Methods

In the first experiment, wild-type (WT) and MMP-9^-/- mice were subjected to sham or endovascular perforation SAH surgery. In separate experiments, WT and MMP-9^-/-mice were administered vehicle or minocycline either pre- or post-SAH. All mice underwent assessment of multiple components of DCI including vasospasm, neurobehavioral function, and microvessel thrombosis. In another experiment, rabbits were subjected to sham or cisterna magna injection SAH surgery, and administered vehicle or minocycline followed by vasospasm assessment.

Results

MMP-9 expression and activity was increased after SAH. Genetic (MMP-9^-/- mice) and pharmacological (pre-SAH minocycline administration) inhibition of MMP-9 resulted in decreased vasospasm and neurobehavioral deficits. A therapeutically feasible strategy of post-SAH administration of minocycline resulted in attenuation of multiple components of DCI. Minocycline administration to MMP-9^-/- mice did not yield additional protection. Consistent with experiments in mice, both pre- and post-SAH administration of minocycline attenuated SAH-induced vasospasm in rabbits.

Interpretation

MMP-9 is a key player in the pathogenesis of DCI. The consistent attenuation of multiple components of DCI with both pre- and post-SAH administration of minocycline across different species and experimental models of SAH, combined with the excellent safety profile of minocycline in humans suggest that a clinical trial in SAH patients is warranted.

Acute Effect of Intravenous Sildenafil on Cerebral Blood Flow in Patients with Vasospasm After Subarachnoid Hemorrhage

BACKGROUND

The phosphodiesterase-5 inhibitor sildenafil has been shown to attenuate delayed cerebral ischemia (DCI) and improve neurologic function in experimental subarachnoid hemorrhage (SAH). We recently demonstrated that it could improve cerebral vasospasm (CVS) in humans after SAH. However, successful therapies for DCI must also restore cerebral blood flow (CBF) and/or autoregulatory capacity. In this study, we tested the effects of sildenafil on CBF in SAH patients at-risk for DCI.

METHODS

Six subjects with angiographically confirmed CVS received 30-mg of intravenous sildenafil (mean 9 ± 2 days after aneurysmal SAH). Each underwent (15)O-PET imaging to measure global and regional CBF at baseline and post-sildenafil.

RESULTS

Mean arterial pressure declined by 10 mm Hg on average post-sildenafil (8 %, p = 0.01), while ICP was unchanged. There was no change in global CBF (mean 34.5 ± 7 ml/100g/min at baseline vs. 33.9 ± 8.0 ml/100g/min post-sildenafil, p = 0.84). The proportion of brain regions with low CBF (<25 ml/100g/min) was also unchanged after sildenafil infusion.

CONCLUSIONS

Infusion of sildenafil does not lead to a change in global or regional perfusion despite a significant reduction in cerebral perfusion pressure. While this could reflect the ineffectiveness of sildenafil-induced proximal vasodilatation to alter brain perfusion, it also suggests that cerebral autoregulatory function was preserved in this group. Future studies should assess whether sildenafil can restore or enhance autoregulation after SAH.

The role of nitric oxide in stroke

Stroke is considered to be an acute cerebrovascular disease, including ischemic stroke and hemorrhagic stroke. The high incidence and poor prognosis of stroke suggest that it is a highly disabling and highly lethal disease which can pose a serious threat to human health. Nitric oxide (NO), a common gas in nature, which is often thought as a toxic gas, because of its intimate relationship with the pathological processes of many diseases, especially in the regulation of blood flow and cell inflammation. However, recent years have witnessed an increased interest that NO plays a significant and positive role in stroke as an essential gas signal molecule. In view of the fact that the neuroprotective effect of NO is closely related to its concentration, cell type and time, only in the appropriate circumstances can NO play a protective effect. The purpose of this review is to summarize the roles of NO in ischemic stroke and hemorrhagic stroke.

A novel fluorescent imaging technique for assessment of cerebral vasospasm after experimental subarachnoid hemorrhage

Various techniques have been developed to study changes in the cerebral vasculature in numerous neuropathological processes including subarachnoid hemorrhage (SAH). One of the most widely employed techniques uses India ink-gelatin casting, which presents numerous challenges due to its high viscosity, rapid solidification, and its impact on immunohistochemical analysis. To overcome these limitations, we developed a novel technique for assessing cerebral vasospasm using cerebrovascular perfusion with ROX, SE (5-Carboxy-X-Rhodamine, Succinimidyl Ester), a fluorescent labeling dye. We found that ROX SE perfusion achieves excellent delineation of the cerebral vasculature, was qualitatively and quantitatively superior to India ink-gelatin casting for the assessment of cerebral vasospasm, permits outstanding immunohistochemical examination of non-vasospasm components of secondary brain injury, and is a more efficient and cost-effective experimental technique. ROX SE perfusion is therefore a novel and highly useful technique for studying cerebrovascular pathology following experimental SAH.

Acute cardiac support with intravenous milrinone promotes recovery from early brain injury in a murine model of severe subarachnoid haemorrhage

Early brain injury/ischaemia (EBI) is a serious complication early after subarachnoid haemorrhage (SAH) that contributes to development of delayed cerebral ischaemia (DCI). This study aimed to determine the role of inotropic cardiac support using milrinone (MIL) on restoring acute cerebral hypoperfusion attributable to EBI and improving outcomes after experimental SAH. Forty-three male C57BL/6 mice were assigned to either sham surgery (SAH-sham), SAH induced by endovascular perforation plus postconditioning with 2% isoflurane (Control), or SAH plus isoflurane combined with MIL with and without hypoxia-inducible factor inhibitor (HIF-I) pretreatment. Cardiac output (CO) during intravenous MIL infusion (0.25-0.75 μg/kg/min) between 1.5 and 2.5 hours after SAH induction was monitored with Doppler echocardiography. Magnetic resonance imaging (MRI)-continuous arterial spin labelling was used for quantitative cerebral blood flow (CBF) measurements. Neurobehavioral function was assessed daily by neurological score and open field test. DCI was analyzed 3 days later by determining infarction on MRI. Mild reduction of cardiac output (CO) and global cerebral blood flow (CBF) depression were notable early after SAH. MIL increased CO in a dose-dependent manner (P<.001), which was accompanied by improved hypoperfusion, incidence of DCI and functional recovery than Control (P<.05). The neuroprotective effects afforded by MIL or Control were attenuated by hypoxia-inducible factor (HIF) inhibition (P<.05). These results suggest that MIL improves acute hypoperfusion by its inotropic effect, leading to neurobehavioral improvement in mice after severe SAH, in which HIF may be acting as a critical mediator.

Inotropic support against early brain injury improves cerebral hypoperfusion and outcomes in a murine model of subarachnoid hemorrhage

Early brain injury/ischemia is a recent therapeutic target that contributes to triggering delayed cerebral ischemia (DCI) in the setting of subarachnoid hemorrhage (SAH). This study aimed to determine the role of dobutamine for inotropic cardiac support in improving cerebral blood flow (CBF) and outcomes after experimental SAH, mediated by hypoxia-inducible factor (HIF). Thirty-one mice were subjected to SAH by endovascular perforation, and assigned to either 2% isoflurane postconditioning performed between 1 and 2.5h after SAH induction or concomitant intravenous dobutamine infusion (15μg/kg/min) with or without HIF inhibitor 2-methoxyestradiol (2ME2) (10mg/kg) administered intraperitoneally. Neurobehavioral function was assessed daily by neurological scores and open field testing. DCI was defined 3days later by detecting a new infarction on MRI. Global CBF depression was notable early after SAH, but dobutamine showed significant improvement in CBF, lower incidence of DCI, and better recovery of neuroscores and open field test variables compared with isoflurane postconditioning (P<0.05). CBF over the entire brain on day 1 predicted DCI with a cut-off of 36.5ml/100g/min (80% specificity and 67% sensitivity), with a better area under the curve (0.83 versus 0.75) than the hemispheric CBF measured on the perforated side. The dobutamine-mediated outcomes were attenuated (P<0.05) by 2ME2 pretreatment. The data suggest that cardiac support with dobutamine improves global CBF depression induced by early brain injury, leading to reduced prevalence of DCI and better functional outcomes after experimental SAH, in which HIF may be acting as a critical mediator.

Nitric oxide inhalation reduces brain damage, prevents mortality, and improves neurological outcome after subarachnoid hemorrhage by resolving early pial microvasospasms

Subarachnoid hemorrhage is a stroke subtype with particularly bad outcome. Recent findings suggest that constrictions of pial arterioles occurring early after hemorrhage may be responsible for cerebral ischemia and - subsequently - unfavorable outcome after subarachnoid hemorrhage. Since we recently hypothesized that the lack of nitric oxide may cause post-hemorrhagic microvasospasms, our aim was to investigate whether inhaled nitric oxide, a treatment paradigm selectively delivering nitric oxide to ischemic microvessels, is able to dilate post-hemorrhagic microvasospasms; thereby improving outcome after experimental subarachnoid hemorrhage. C57BL/6 mice were subjected to experimental SAH. Three hours after subarachnoid hemorrhage pial artery spasms were quantified by intravital microscopy, then mice received inhaled nitric oxide or vehicle. For induction of large artery spasms mice received an intracisternal injection of autologous blood. Inhaled nitric oxide significantly reduced number and severity of subarachnoid hemorrhage-induced post-hemorrhage microvasospasms while only having limited effect on large artery spasms. This resulted in less brain-edema-formation, less hippocampal neuronal loss, lack of mortality, and significantly improved neurological outcome after subarachnoid hemorrhage. This suggests that spasms of pial arterioles play a major role for the outcome after subarachnoid hemorrhage and that lack of nitric oxide is an important mechanism of post-hemorrhagic microvascular dysfunction. Reversing microvascular dysfunction by inhaled nitric oxide might be a promising treatment strategy for subarachnoid hemorrhage.

Scutellarin attenuates vasospasm through the Erk5-KLF2-eNOS pathway after subarachnoid hemorrhage in rats

Angiographic vasospasm, especially in the early phases (<72h) of subarachnoid hemorrhage (SAH), is one of the major complications after an aneurysm rupture and is often the cause of delayed neurological deterioration. Scutellarin (SCU), a flavonoid extracted from the traditional Chinese herb Erigeron breviscapus, has been widely accepted as an antioxidant, but the effect of SCU on vasospasm after SAH remains elusive. Endovascular perforation was conducted to induce SAH in Sprague-Dawley rats. Then, the underlying mechanism of the anti-vasospasm effect of SCU was investigated using a modified Garcia scale, India ink angiography, cross-sectional area analysis, immunohistochemistry staining and western blot. SCU (50μM, 100mg/kg) alleviated angiographic vasospasm and improved neurological function 48h after SAH and enhanced the expression of endothelial nitric oxide synthase (eNOS) at the intima of cerebral arteries. In addition, SCU upregulated the expression of phosphorylated extracellular-regulated kinase 5 (p-Erk5) and Kruppel-like factor 2 (KLF2) at 48h after SAH. However, the effects of SCU were reversed by the Erk5 inhibitor XMD8-92. Our results indicate that SCU could attenuate vasospasm and neurological deficits via modulating the Erk5-KLF2-eNOS pathway after SAH, which may provide an experimental basis for the clinical use of SCU treatment in SAH patients.