Heparin reduces neuroinflammation and transsynaptic neuronal apoptosis in a model of subarachnoid hemorrhage

Supra-Prophylactic Doses of Enoxaparin Reduces Fibrin Deposition Without Exacerbation of Intracerebral Hemorrhage in a Rat Model of Penetrating Traumatic Brain Injury

Deep vein thrombosis and pulmonary embolism prophylaxis is an important part of trauma care. Despite an increased risk of thrombotic complications, the use of venous thrombosis chemoprophylaxis in penetrating traumatic brain injury (pTBI) patients is met with reluctance from neurosurgeons because of concern for the exacerbation of intracerebral hemorrhage. The objective of this study was to provide initial pre-clinical evidence of the effects of Lovenox (LVX) administration following pTBI with significant intracerebral hemorrhage. Sprague-Dawley rats received a penetrating ballistic-like brain injury. Animals were randomly divided into two groups following injury: LVX (25 mg/kg) or vehicle (VEH, saline). LVX or vehicle was administered subcutaneously beginning 24 h after the injury and continued daily for 7 days post-injury. A neurological assessment was performed daily and magnetic resonance imaging (MRI) was performed at baseline, 1, 2, 3, and 7 days post-injury. Following the final MRI, brains were isolated and prepared for histological analysis. Thromboelastography demonstrated dramatic anticoagulation effects which were confirmed by significant increases in partial thromboplastin time (p < 0.001). Daily neurological assessment revealed no worsening of functional deficits following LVX treatment. MRI analysis demonstrated no differences in cerebral edema or intracranial hemorrhage volumes between treatment groups at any tested post-injury time points. However, LVX elicited a significant reduction in fibrin deposition in the ipsilateral striatum and lesion site at 7 days post-injury (p < 0.05). Serum levels of beta-amyloid were decreased at 7 days following LVX treatment (p < 0.05) which may indicate neuroprotective effects but was not correlated to brain levels. The results presented indicate that administration of LVX at a dose capable of inducing anticoagulation is safe in a rodent model of pTBI without exacerbation of intracerebral hemorrhage within the first 7 days of injury.

Multifaceted role of thrombin in subarachnoid hemorrhage: Focusing on cerebrospinal fluid circulation disorder

Subarachnoid hemorrhage (SAH) is a severe neurological condition characterized by high morbidity and mortality. The unfavorable prognosis of SAH is closely associated with early brain injury (EBI) and delayed cerebral ischemia (DCI), wherein thrombin plays a role as part of the secondary injury components following hemorrhage in these two pathological processes. Additionally, thrombin contributes to disruptions in the circulation of cerebrospinal fluid (CSF), thereby giving rise to a spectrum of sequelae following SAH, including cerebral edema, hydrocephalus, cognitive impairments, and depressive symptoms. This review aims to provide a comprehensive understanding of the pathological role of thrombin in EBI, DCI, and CSF circulation following SAH, with a specific focus on its impact on the glymphatic-meningeal lymphatic system-a crucial mechanism for waste clearance and neurohomeostatic regulation. Additionally, this review offers an overview of current pharmacological interventions and treatment modalities targeting pathogenic mechanisms, aiming to mitigate brain injury and promote neurological recovery post-SAH.

Glycosaminoglycans' for brain health: Harnessing glycosaminoglycan based biomaterials for treating central nervous system diseases and in-vitro modeling

Dysfunction of the central nervous system (CNS) following traumatic brain injuries (TBI), spinal cord injuries (SCI), or strokes remains challenging to address using existing medications and cell-based therapies. Although therapeutic cell administration, such as stem cells and neuronal progenitor cells (NPCs), have shown promise in regenerative properties, they have failed to provide substantial benefits. However, the development of living cortical tissue engineered grafts, created by encapsulating these cells within an extracellular matrix (ECM) mimetic hydrogel scaffold, presents a promising functional replacement for damaged cortex in cases of stroke, SCI, and TBI. These grafts facilitate neural network repair and regeneration following CNS injuries. Given that natural glycosaminoglycans (GAGs) are a major constituent of the CNS, GAG-based hydrogels hold potential for the next generation of CNS healing therapies and in vitro modeling of CNS diseases. Brain-specific GAGs not only offer structural and biochemical signaling support to encapsulated neural cells but also modulate the inflammatory response in lesioned brain tissue, facilitating host integration and regeneration. This review briefly discusses different roles of GAGs and their related proteoglycan counterparts in healthy and diseases brain and explores current trends and advancements in GAG-based biomaterials for treating CNS injuries and modeling diseases. Additionally, it examines injectable, 3D bioprintable, and conductive GAG-based scaffolds, highlighting their clinical potential for in vitro modeling of patient-specific neural dysfunction and their ability to enhance CNS regeneration and repair following CNS injury in vivo.

Pharmacotherapy in SAH: Clinical Trial Lessons

Subarachnoid Haemorrhage (SAH) is a medical emergency with potentially devastating outcomes. It is without doubt that over the past decades, there has been a radical change in the approach towards patients with SAH, both in terms of the surgical as well as of the pharmacological treatments offered. The present review aims to outline the principal data regarding the best practice in the pharmacotherapy of SAH, as well as to sum up the emerging evidence from the latest clinical trials. To date, nimodipine is the only evidence-based treatment of vasospasm. However, extensive research is currently underway to identify novel substances with magnesium sulphate, cilostazol, clazosentan and fasudil, demonstrating promising results. Antifibrinolytic therapy could help reduce mortality, and anticoagulants, in spite of their associated hazards, could actually reduce the incidence of delayed cerebral ischemia. The effectiveness of triple-H therapy has been challenged, yet evidence on the optimal regimen is still pending. Statins may benefit some patients by reducing the incidence of vasospasm and delayed ischemic events. As several clinical trials are underway, it is expected that in the years to come, more therapeutic options will be added to the attending physician's armamentarium.

Compartmental Cerebrospinal Fluid Events Occurring after Subarachnoid Hemorrhage: An "Heparin Oriented" Systematic Review

Subarachnoid hemorrhage (SAH) represents a severe acute event with high morbidity and mortality due to the development of early brain injury (EBI), secondary delayed cerebral ischemia (DCI), and shunt-related hydrocephalus. Secondary events (SSE) such as neuroinflammation, vasospasm, excitotoxicity, blood-brain barrier disruption, oxidative cascade, and neuronal apoptosis are related to DCI. Despite improvement in management strategies and therapeutic protocols, surviving patients frequently present neurological deficits with neurocognitive impairment. The aim of this paper is to offer to clinicians a practical review of the actually documented pathophysiological events following subarachnoid hemorrhage. To reach our goal we performed a literature review analyzing reported studies regarding the mediators involved in the pathophysiological events following SAH occurring in the cerebrospinal fluid (CSF) (hemoglobin degradation products, platelets, complement, cytokines, chemokines, leucocytes, endothelin-1, NO-synthase, osteopontin, matricellular proteins, blood-brain barrier disruption, microglia polarization). The cascade of pathophysiological events secondary to SAH is very complex and involves several interconnected, but also distinct pathways. The identification of single therapeutical targets or specific pharmacological agents may be a limited strategy able to block only selective pathophysiological paths, but not the global evolution of SAH-related events. We report furthermore on the role of heparin in SAH management and discuss the rationale for use of intrathecal heparin as a pleiotropic therapeutical agent. The combination of the anticoagulant effect and the ability to interfere with SSE theoretically make heparin a very interesting molecule for SAH management.

Myelin sheath injury and repairment after subarachnoid hemorrhage

Subarachnoid hemorrhage (SAH) can lead to damage to the myelin sheath in white matter. Through classification and analysis of relevant research results, the discussion in this paper provides a deeper understanding of the spatiotemporal change characteristics, pathophysiological mechanisms and treatment strategies of myelin sheath injury after SAH. The research progress for this condition was also systematically reviewed and compared related to myelin sheath in other fields. Serious deficiencies were identified in the research on myelin sheath injury and treatment after SAH. It is necessary to focus on the overall situation and actively explore different treatment methods based on the spatiotemporal changes in the characteristics of the myelin sheath, as well as the initiation, intersection and common action point of the pathophysiological mechanism, to finally achieve accurate treatment. We hope that this article can help researchers in this field to further clarify the challenges and opportunities in the current research on myelin sheath injury and treatment after SAH.

Early evolution of glial morphology and inflammatory cytokines following hypoxic-ischemic injury in the newborn piglet brain

Neuroinflammation is a hallmark of hypoxic-ischemic injury and can be characterized by the activation of glial cells and the expression of inflammatory cytokines and chemokines. Interleukin (IL)-1β and tumor necrosis factor (TNF)α are among the best-characterized early response cytokines and are often expressed concurrently. Several types of central nervous system cells secrete IL-1β and TNFα, including microglia, astrocytes, and neurons, and these cytokines convey potent pro-inflammatory actions. Chemokines also play a central role in neuroinflammation by controlling inflammatory cell trafficking. Our aim was to characterise the evolution of early neuroinflammation in the neonatal piglet model of hypoxic-ischemic encephalopathy (HIE). Piglets (< 24 h old) were exposed to HI insult, and recovered to 2, 4, 8, 12 or 24H post-insult. Brain tissue from the frontal cortex and basal ganglia was harvested for assessment of glial cell activation profiles and transcription levels of inflammatory markers in HI piglets with comparison to a control group of newborn piglets. Fluorescence microscopy was used to observe microglia, astrocytes, neurons, degenerating neurons and possibly apoptotic cells, and quantitative polymerase chain reaction was used to measure gene expression of several cytokines and chemokines. HI injury was associated with microglial activation and morphological changes to astrocytes at all time points examined. Gene expression analyses of inflammation-related markers revealed significantly higher expression of pro-inflammatory cytokines tumor necrosis factor-α (TNFα) and interleukin 1 beta (IL-1β), chemokines cxc-chemokine motif ligand (CXCL)8 and CXCL10, and anti-inflammatory cytokine transforming growth factor (TGF)β in every HI group, with some region-specific differences noted. No significant difference was observed in the level of C-X-C chemokine receptor (CCR)5 over time. This high degree of neuroinflammation was associated with a reduction in the number of neurons in piglets at 12H and 24H in the frontal cortex, and the putamen at 12H. This reduction of neurons was not associated with increased numbers of degenerating neurons or potentially apoptotic cells. HI injury triggered a robust early neuroinflammatory response associated with a reduction in neurons in cortical and subcortical regions in our piglet model of HIE. This neuroinflammatory response may be targeted using novel therapeutics to reduce neuropathology in our piglet model of neonatal HIE.

A Systematic Review and Meta-Analysis on the Therapeutic Efficacy of Heparin and Low Molecular Weight Heparins in Animal Studies of Traumatic Brain Injury

The identification of effective pharmacotherapies for traumatic brain injury (TBI) remains a major challenge. Treatment with heparin and its derivatives is associated with neuroprotective effects after experimental TBI; however, the optimal dosage and method of administration, modes of action, and effects on hemorrhage remain unclear. Therefore, this review aimed to systematically evaluate, analyze, and summarize the available literature on the use of heparin and low molecular weight heparins (LMWHs) as treatment options for experimental TBI. We searched two online databases (PubMed and ISI Web of Science) to identify relevant studies. Data pertaining to TBI paradigm, animal subjects, drug administration, and all pathological and behavior outcomes were extracted. Eleven studies met our pre-specified inclusion criteria, and for outcomes with sufficient numbers, data from seven publications were analyzed in a weighted mean difference meta-analysis using a random-effects model. Study quality and risk of bias were also determined. Meta-analysis revealed that heparin and its derivatives decreased brain edema, leukocyte rolling, and vascular permeability, and improved neurological function. Further, treatment did not aggravate hemorrhage. These findings must be interpreted with caution, however, because they were determined from a limited number of studies with substantial heterogeneity. Also, overall study quality was low based on absences of data reporting, and potential publication bias was identified. Importantly, we found that there are insufficient data to evaluate the variables we had hoped to investigate. The beneficial effects of heparin and LMWHs, however, suggest that further pre-clinical studies are warranted.

Dexras1 Induces Dysdifferentiation of Oligodendrocytes and Myelin Injury by Inhibiting the cAMP-CREB Pathway after Subarachnoid Hemorrhage

White matter damage (WMD), one of the research hotspots of subarachnoid hemorrhage (SAH), mainly manifests itself as myelin injury and oligodendrocyte differentiation disorder after SAH, although the specific mechanism remains unclear. Dexamethasone-induced Ras-related protein 1(Dexras1) has been reported to be involved in nervous system damage in autoimmune encephalitis and multiple sclerosis. However, whether Dexras1 participates in dysdifferentiation of oligodendrocytes and myelin injury after SAH has yet to be examined, which is the reason for creating the research content of this article. Here, intracerebroventricular lentiviral administration was used to modulate Dexras1 levels in order to determine its functional influence on neurological injury after SAH. Immunofluorescence, transmission electron microscopy, and Western blotting methods, were used to investigate the effects of Dexras1 on demyelination, glial cell activation, and differentiation of oligodendrocyte progenitor cells (OPCs) after SAH. Primary rat brain neurons were treated with oxyhemoglobin to verify the association between Dexras1 and cAMP-CREB. The results showed that Dexras1 levels were significantly increased upon in vivo SAH model, accompanied by OPC differentiation disturbances and myelin injury. Dexras1 overexpression significantly worsened OPC dysdifferentiation and myelin injury after SAH. In contrast, Dexras1 knockdown ameliorated myelin injury, OPC dysdifferentiation, and glial cell activation. Further research of the underlying mechanism discovered that the cAMP-CREB pathway was inhibited after Dexras1 overexpression in the in vitro model of SAH. This study is the first to confirm that Dexras1 induced oligodendrocyte dysdifferentiation and myelin injury after SAH by inhibiting the cAMP-CREB pathway. This present research may reveal novel therapeutic targets for the amelioration of brain injury and neurological dysfunction after SAH.

Microglial TLR4 is Critical for Neuronal Injury and Cognitive Dysfunction in Subarachnoid Hemorrhage

Background

Toll-like receptor 4 (TLR4) activation causes excessive production of proinflammatory mediators and an increased expression of costimulatory molecules that leads to neuroinflammation after subarachnoid hemorrhage (SAH). Although TLR4-mediated inflammatory pathways have long been studied in neuroinflammation, the specific glia implicated in initiation and propagation of neuroinflammation in SAH have not been well elucidated. In this study, we investigated the involvement of glial TLR4 including microglia and astrocytes in brain damage and poor neurological outcome.

Methods

In this study, global TLR4 knockout, cell-specific TLR4 knockout, and floxxed control male and female mice were used. The mice were injected with 60 μl autologous blood near the mesencephalon to induce SAH; animals were euthanized on postoperative day 7 for immunohistochemistry of glia and apoptotic cells. Microglial morphology was evaluated by using immunofluorescence density quantification to determine correlations between morphology and neuroinflammation. Microglial depletion was accomplished with the intracerebroventricular administration of clodronate liposomes. Cognitive function was assessed with Barnes maze.

Results

On postoperative day 7 after SAH induction, neuronal apoptosis was markedly reduced in the clodronate liposome group compared with phosphate-buffered saline control liposomes, and cognitive performance in the clodronate group was improved, as well. Differences in microglial activation, assessed by morphometric analysis, and neuronal apoptosis were significantly greater in wildtype knockouts compared with cell-specific and global TLR4 knockouts. The mice lacking TLR4 on astrocytes and neurons showed no differences compared with wildtype mice on any end points.

Conclusions

Our data suggest that microglial depletion with the intracerebroventricular administration of clodronate can improve the cognitive function in an SAH mouse model, and TLR4 is critical for microglial activation and neuronal injury. Only microglial TLR4 is necessary for brain damage and poor cognitive outcome rather than astrocyte or neuronal TLR4. Thus, microglial TLR4 could be a potent therapeutic target to treat SAH-associated neuronal injury and protect against cognitive dysfunction.

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.

The Role of Heparin and Glycocalyx in Blood-Brain Barrier Dysfunction

The blood-brain barrier (BBB) functions as a dynamic boundary that protects the central nervous system from blood and plays an important role in maintaining the homeostasis of the brain. Dysfunction of the BBB is a pathophysiological characteristic of multiple neurologic diseases. Glycocalyx covers the luminal side of vascular endothelial cells(ECs). Damage of glycocalyx leads to disruption of the BBB, while inhibiting glycocalyx degradation maintains BBB integrity. Heparin has been recognized as an anticoagulant and it protects endothelial glycocalyx from destruction. In this review, we summarize the role of glycocalyx in BBB formation and the therapeutic potency of heparin to provide a theoretical basis for the treatment of neurological diseases related to BBB breakdown.

The Structure and Function of the Glycocalyx and Its Connection With Blood-Brain Barrier

The vascular endothelial glycocalyx is a dense, bush-like structure that is synthesized and secreted by endothelial cells and evenly distributed on the surface of vascular endothelial cells. The blood-brain barrier (BBB) is mainly composed of pericytes endothelial cells, glycocalyx, basement membranes, and astrocytes. The glycocalyx in the BBB plays an indispensable role in many important physiological functions, including vascular permeability, inflammation, blood coagulation, and the synthesis of nitric oxide. Damage to the fragile glycocalyx can lead to increased permeability of the BBB, tissue edema, glial cell activation, up-regulation of inflammatory chemokines expression, and ultimately brain tissue damage, leading to increased mortality. This article reviews the important role that glycocalyx plays in the physiological function of the BBB. The review may provide some basis for the research direction of neurological diseases and a theoretical basis for the diagnosis and treatment of neurological diseases.

The ERK/CREB/PTN/syndecan-3 pathway involves in heparin-mediated neuro-protection and neuro-regeneration against cerebral ischemia-reperfusion injury following cardiac arrest

BACKGROUND

Heparin, a commonly used anticoagulant, has been found to improve cerebral ischemia-reperfusion injury (CIR-CA) following cardiopulmonary resuscitation (CPR). Here, we aimed to explore the role of pleiotrophin (PTN)/syndecan-3 pathway in heparin therapy for CIR-CA.

MATERIALS AND METHODS

The CA-CPR model was constructed in Sprague-Dawley (SD) rats, which were treated with low molecular weight heparin, and the neurological changes and brain histopathological changes were evaluated. For in-vitro experiments, the ischemic injury model of primary neurons was established by oxygen and glucose deprivation (OGD), and the neuron regeneration was detected via the Cell counting Kit-8 (CCK8) method, flow cytometry and microscopy. CREB antagonist (KG-501), ERK antagonist (PD98059) and si-PTN were used respectively to inhibit the expression of CREB, ERK and PTN in cells, so as to explore the role of heparin in regulating neuronal regeneration.

RESULTS

Compared with the sham rats, the neurological deficits and cerebral edema of CA-CPR rats were significantly improved after heparin treatment. Heparin also attenuated OGD-mediated neuronal apoptosis and promoted neurite outgrowth in vitro. Moreover, heparin attenuated CA-CPR-mediated neuronal apoptosis and microglial neuroinflammation. In terms of the mechanism, heparin upregulated the expression of ERK, CREB, NF200, BDNF, NGF, PTN and syndecan-3 in the rat brains. Inhibition of ERK, CREB and interference with PTN expression notably weakened the heparin-mediated neuroprotective effects and restrained the expression of ERK/CREB and PTN/syndecan-3 pathway.

CONCLUSION

Heparin attenuates the secondary brain injury induced by CA-CPR through regulating the ERK/CREB-mediated PTN/syndecan-3 pathway.

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.

Hippocampal Transcriptome Changes After Subarachnoid Hemorrhage in Mice

After subarachnoid hemorrhage (SAH), up to 95% of surviving patients suffer from post-SAH syndrome, which includes cognitive deficits with impaired memory, executive functions, and emotional disturbances. Although these long-term cognitive deficits are thought to result from damage to temporomesial-hippocampal areas, the underlying mechanisms remain unknown. To fill this gap in knowledge, we performed a systematic RNA sequencing screen of the hippocampus in a mouse model of SAH. SAH was induced by perforation of the circle of Willis in mice. Four days later, hippocampal RNA was obtained from SAH and control (sham perforation) mice. Next-generation RNA sequencing was used to determine differentially expressed genes in the whole bilateral hippocampi remote from the SAH bleeding site. Functional analyses and clustering tools were used to define molecular pathways. Differential gene expression analysis detected 642 upregulated and 398 downregulated genes (false discovery rate <0.10) in SAH compared to Control group. Functional analyses using IPA suite, Gene Ontology terms, REACTOME pathways, and MsigDB Hallmark gene set collections revealed suppression of oligodendrocytes/myelin related genes, and overexpression of genes related to complement system along with genes associated with innate and adaptive immunity, and extracellular matrix reorganization. Interferon regulatory factors, TGF-β1, and BMP were identified as major orchestrating elements in the hippocampal tissue response. The MEME-Suite identified binding motifs of Krüppel-like factors, zinc finger transcription factors, and interferon regulatory factors as overrepresented DNA promoter motifs. This study provides the first systematic gene and pathway database of the hippocampal response after SAH. Our findings suggest that damage of the entorhinal cortex by subarachnoid blood may remotely trigger specific hippocampal responses, which include suppression of oligodendrocyte function. Identification of these novel pathways may allow for development of new therapeutic approaches for post-SAH cognitive deficits.

Low-Dose Intravenous Heparin Infusion After Aneurysmal Subarachnoid Hemorrhage is Associated With Decreased Risk of Delayed Neurological Deficit and Cerebral Infarction

BACKGROUND

Patients who survive aneurysmal subarachnoid hemorrhage (aSAH) are at risk for delayed neurological deficits (DND) and cerebral infarction. In this exploratory cohort comparison analysis, we compared in-hospital outcomes of aSAH patients administered a low-dose intravenous heparin (LDIVH) infusion (12 U/kg/h) vs those administered standard subcutaneous heparin (SQH) prophylaxis for deep vein thrombosis (DVT; 5000 U, 3 × daily).

OBJECTIVE

To assess the safety and efficacy of LDIVH in aSAH patients.

METHODS

We retrospectively analyzed 556 consecutive cases of aSAH patients whose aneurysm was secured by clipping or coiling at a single institution over a 10-yr period, including 233 administered the LDIVH protocol and 323 administered the SQH protocol. Radiological and outcome data were compared between the 2 cohorts using multivariable logistic regression and propensity score-based inverse probability of treatment weighting (IPTW).

RESULTS

The unadjusted rate of cerebral infarction in the LDIVH cohort was half that in SQH cohort (9 vs 18%; P = .004). Multivariable logistic regression showed that patients in the LDIVH cohort were significantly less likely than those in the SQH cohort to have DND (odds ratio (OR) 0.53 [95% CI: 0.33, 0.85]) or cerebral infarction (OR 0.40 [95% CI: 0.23, 0.71]). Analysis following IPTW showed similar results. Rates of hemorrhagic complications, heparin-induced thrombocytopenia and DVT were not different between cohorts.

CONCLUSION

This cohort comparison analysis suggests that LDIVH infusion may favorably influence the outcome of patients after aSAH. Prospective studies are required to further assess the benefit of LDIVH infusion in patients with aSAH.

Risk of postprocedural intracerebral hemorrhage in patients with ruptured cerebral aneurysms after treatment with antiplatelet agents

OBJECTIVE

Endovascular treatment of ruptured cerebral aneurysms frequently requires antiplatelet medication to prevent thromboembolism. This might raise concern regarding the risk of postprocedural hemorrhage (pH), e.g. from placement of intracranial probes. We explored the risk of PH associated with standard antiplatelet therapy (sAP: acetylsalicylic acid, and/or clopidogrel) in the context of aneurysmal subarachnoid hemorrhage (aSAH).

METHODS

We retrospectively reviewed a total of 146 consecutive cases with cerebral aneurysms treated between 1/2011-12/2015, and distinguished between minor (0.5 cm³) - 4 cm³) or major (> 4 cm³) PH occurring within four weeks after intervention. A separate analysis included hemorrhages related to placement of intracranial probes and drainages in the subgroup of 99 cases with such surgical interventions (pPH). Clinical outcome was assessed via Glasgow Outcome Scale (GOS) twelve months after aSAH.

RESULTS

A total of 49 cases (33.6%) in the overall sample sustained PH, there were 19 cases of pPH. Multifactorial analyses yielded sAP as an independent predictor for minor, but not major PH (p < 0.001 vs. p = 0.829), with comparable results for pPH (p = 0.001 vs. p = 0.184). sAP did not influence the clinical outcome in either group.

CONCLUSIONS

sAP was associated with a higher rate of minor PH and, more specifically, of minor pPH. However, it was neither accompanied by the occurrence of major hemorrhages nor by unfavorable clinical outcome. Future prospective studies should confirm these observations and hemorrhage risks associated with extended anticoagulation regimes after complex interventions and intra-arterial vasospasm therapy should be explored in order to facilitate interdisciplinary decision-making in aSAH.

The Role of Thrombin in Brain Injury After Hemorrhagic and Ischemic Stroke

Thrombin is increased in the brain after hemorrhagic and ischemic stroke primarily due to the prothrombin entry from blood either with a hemorrhage or following blood-brain barrier disruption. Increasing evidence indicates that thrombin and its receptors (protease-activated receptors (PARs)) play a major role in brain pathology following ischemic and hemorrhagic stroke (including intracerebral, intraventricular, and subarachnoid hemorrhage). Thrombin and PARs affect brain injury via multiple mechanisms that can be detrimental or protective. The cleavage of prothrombin into thrombin is the key step of hemostasis and thrombosis which takes place in every stroke and subsequent brain injury. The extravascular effects and direct cellular interactions of thrombin are mediated by PARs (PAR-1, PAR-3, and PAR-4) and their downstream signaling in multiple brain cell types. Such effects include inducing blood-brain-barrier disruption, brain edema, neuroinflammation, and neuronal death, although low thrombin concentrations can promote cell survival. Also, thrombin directly links the coagulation system to the immune system by activating interleukin-1α. Such effects of thrombin can result in both short-term brain injury and long-term functional deficits, making extravascular thrombin an understudied therapeutic target for stroke. This review examines the role of thrombin and PARs in brain injury following hemorrhagic and ischemic stroke and the potential treatment strategies which are complicated by their role in both hemostasis and brain.

Microvascular platelet aggregation and thrombosis after subarachnoid hemorrhage: A review and synthesis

Delayed cerebral ischemia (DCI) after aneurysmal subarachnoid hemorrhage (SAH) has been associated with numerous pathophysiological sequelae, including large artery vasospasm and microvascular thrombosis. The focus of this review is to provide an overview of experimental animal model studies and human autopsy studies that explore the temporal-spatial characterization and mechanism of microvascular platelet aggregation and thrombosis following SAH, as well as to critically assess experimental studies and clinical trials highlighting preventative therapeutic options against this highly morbid pathophysiological process. Upon review of the literature, we discovered that microvascular platelet aggregation and thrombosis occur after experimental SAH across multiple species and SAH induction techniques in a similar time frame to other components of DCI, occurring in the cerebral cortex and hippocampus across both hemispheres. We discuss the relationship of these findings to human autopsy studies. In the final section of this review, we highlight the important therapeutic options for targeting microvascular platelet aggregation and thrombosis, and emphasize why therapeutic targeting of this neurovascular pathology may improve patient care. We encourage ongoing research into the pathophysiology of SAH and DCI, especially in regard to microvascular platelet aggregation and thrombosis and the translation to randomized clinical trials.

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.

Continuous infusion of low-dose unfractionated heparin after aneurysmal subarachnoid hemorrhage: a preliminary study of cognitive outcomes

OBJECTIVE

Cognitive dysfunction occurs in up to 70% of aneurysmal subarachnoid hemorrhage (aSAH) survivors. Low-dose intravenous heparin (LDIVH) infusion using the Maryland protocol was recently shown to reduce clinical vasospasm and vasospasm-related infarction. In this study, the Montreal Cognitive Assessment (MoCA) was used to evaluate cognitive changes in aSAH patients treated with the Maryland LDIVH protocol compared with controls.

METHODS

A retrospective analysis of all patients treated for aSAH between July 2009 and April 2014 was conducted. Beginning in 2012, aSAH patients were treated with LDIVH in the postprocedural period. The MoCA was administered to all aSAH survivors prospectively during routine follow-up visits, at least 3 months after aSAH, by trained staff blinded to treatment status. Mean MoCA scores were compared between groups, and regression analyses were performed for relevant factors.

RESULTS

No significant differences in baseline characteristics were observed between groups. The mean MoCA score for the LDIVH group (n = 25) was 26.4 compared with 22.7 in controls (n = 22) (p = 0.013). Serious cognitive impairment (MoCA ≤ 20) was observed in 32% of controls compared with 0% in the LDIVH group (p = 0.008). Linear regression analysis demonstrated that only LDIVH was associated with a positive influence on MoCA scores (β = 3.68, p =0.019), whereas anterior communicating artery aneurysms and fevers were negatively associated with MoCA scores. Multivariable linear regression analysis resulted in all 3 factors maintaining significance. There were no treatment complications.

CONCLUSIONS

This preliminary study suggests that the Maryland LDIVH protocol may improve cognitive outcomes in aSAH patients. A randomized controlled trial is needed to determine the safety and potential benefit of unfractionated heparin in aSAH patients.

Neuroanesthesiology Update

We provide a synopsis of innovative research, recurring themes, and novel experimental findings pertinent to the care of neurosurgical patients and critically ill patients with neurological diseases. We cover the following broad topics: general neurosurgery, spine surgery, stroke, traumatic brain injury, monitoring, and anesthetic neurotoxicity.

Heparin: The Silver Bullet of Aneurysmal Subarachnoid Hemorrhage?

Various neurological diseases have recently been associated with neuroinflammation and worsening outcomes. Subarachnoid hemorrhage has been shown to generate a potent neuroinflammatory response. Heparin is a potential effective anti-inflammatory agent to prevent initial injury as well as delayed neurological decline. Different mechanisms of action for heparin have been proposed including, but not limited to the binding and neutralization of oxyhemoglobin, decreased transcription and signal transduction of endothelin-1, inhibition of binding to vessel wall selectins and vascular leakage into the subarachnoid space as well as direct binding and neutralization of inflammatory molecules. With a reasonably safe side-effect profile, heparin has shown significant promise in small series in human studies of aneurysmal subarachnoid hemorrhage in decreasing both initial and delayed neurological injury. Further studies are needed to validate various neuroprotective features of heparin in subarachnoid hemorrhage as well as other disease states.

Effects of pumpless extracorporeal lung assist on hemodynamics, gas exchange and inflammatory cascade response during experimental lung injury

Pumpless extracorporeal lung assist (pECLA) has been reported to efficiently remove the systemic CO₂ production and provide mild to moderate oxygenation, thereby allowing for ventilator settings and modes prioritizing oxygenation and lung protection. However, an adequate bypass flow, the capacity to provide respiratory support and the effect on the inflammatory cascade response and tissue perfusion require further study to be determined. After induction of acute lung injury (ALI) by oleic acid injection, pECLA was implemented in 12 anaesthetized and mechanically ventilated dogs for 48 h. Improved oxygenation [partial oxygen pressure (PaO₂) and oxygen saturation (SaO₂) was measured by arterial blood gas analysis, and increased by 29 and 18%, respectively] and CO₂ elimination (partial CO₂ pressure decreased by 43.35%) were obtained after pECLA implementation. A maximum arterio-venous shunt flow of up to 25% of the foundational CO resulted in stable hemodynamics. The pECLA procedure did not elicit any further increase in the concentration of tumor necrosis factor-α, interleukin (IL)-6, IL-8 and endothelin-1 compared with that in the group subjected to oleic acid injection only. In addition, the pECLA procedure had no effect on lactate levels and urine production. In conclusion, pECLA is an efficient and promising strategy for providing a mild to moderate oxygenation and adequate decarboxylation, while avoiding excessive inflammatory cascade response and tissue hypoperfusion in an experimental ALI model.

Expression of caspase-3, Bax and Bcl-2 in hippocampus of rats with diabetes and subarachnoid hemorrhage

The expression of caspase-3, Bax and Bcl-2 in hippocampus of rats with diabetes and subarachnoid hemorrhage (SAH) were investigated. Diabetes mellitus model was established by intraperitoneal injection of STZ. On the basis of diabetes mellitus model, SAH animal model was established by injecting fresh autologous femoral artery blood into cerebellomedullary cisten. Rats were divided into blank control group, diabetes control group and diabetes + SAH group. TUNEL method was used to detect cell apoptosis of hippocampus. Expression levels of caspase-3, Bax and Bcl-2 were detected by real-time quantitative reverse transcription PCR and western blot analysis at mRNA and protein levels, respectively. Apoptotic cells were not detected in blank control group and diabetes group, and number of apoptotic cells was the highest in the diabetic SAH group. Expression levels of caspase-3, Bax and Bcl-2 mRNA and protein were significantly higher in diabetes + SAH group than in blank control group and diabetes group. In conclusion, Hippocampal neuron apoptosis was induced by diabetes + SAH and expression levels of caspase-3, Bax and Bcl-2 were also increased. Our study provided experimental basis for further studies of the relationship between SAH and cell apoptosis.

High-Dose Nadroparin Following Endovascular Aneurysm Treatment Benefits Outcome After Aneurysmal Subarachnoid Hemorrhage

BACKGROUND

Delayed cerebral ischemia (DCI) is one of the major causes of delayed morbidity and mortality in patients with aneurysmal subarachnoid hemorrhage (aSAH).

OBJECTIVE

To evaluate the effect of high-dose nadroparin treatment following endovascular aneurysm treatment on the occurrence of DCI and clinical outcome.

METHODS

Medical records of 158 adult patients with an aSAH were retrospectively analyzed. Those patients treated endovascularly for their ruptured aneurysm were included in this study. They received either high-dose (twice daily 5700 AxaIE) or low-dose (once daily 2850 AxaIE) nadroparin treatment after occlusion of the aneurysm. Medical charts were reviewed and imaging was scored by 2 independent neuroradiologists. Data with respect to in-hospital complications, peri-procedural complications, discharge location, and mortality were collected.

RESULTS

Ninety-three patients had received high-dose nadroparin, and 65 patients prophylactic low-dose nadroparin. There was no significant difference in clinical DCI occurrence between patients treated with high-dose (34%) and low-dose (31%) nadroparin. More patients were discharged to home in patients who received high-dose nadroparin (40%) compared to low-dose (17%; odds ratio [OR] 3.13, 95% confidence interval [95% CI]: 1.36-7.24). Furthermore, mortality was lower in the high-dose group (5%) compared to the low-dose group (23%; OR 0.19, 95% CI: 0.07-0.55), also after adjusting for neurological status on admission (OR 0.21, 95% CI: 0.07-0.63).

CONCLUSION

Patients who were treated with high-dose nadroparin after endovascular treatment for aneurysmal SAH were more often discharged to home and showed lower mortality. High-dose nadroparin did not, however, show a decrease in the occurrence of clinical DCI after aSAH. A randomized controlled trial seems warranted.

Heparanase: Potential roles in multiple sclerosis

Heparanase is a heparan sulfate degrading enzyme that cleaves heparan sulfate (HS) chains present on HS proteoglycans (HSPGs), and has been well characterized for its roles in tumor metastasis and inflammation. However, heparanase is emerging as a contributing factor in the genesis and severity of a variety of neurodegenerative diseases and conditions. This is in part due to the wide variety of HSPGs on which the presence or absence of HS moieties dictates protein function. This includes growth factors, chemokines, cytokines, as well as components of the extracellular matrix (ECM) which in turn regulate leukocyte infiltration into the CNS. Roles for heparanase in stroke, Alzheimer's disease, and glioma growth have been described; roles for heparanase in other disease such as multiple sclerosis (MS) are less well established. However, given its known roles in inflammation and leukocyte infiltration, it is likely that heparanase also contributes to MS pathology. In this review, we will briefly summarize what is known about heparanase roles in the CNS, and speculate as to its potential role in regulating disease progression in MS and its animal model EAE (experimental autoimmune encephalitis), which may justify testing of heparanase inhibitors for MS treatment.

High Compliance with Scheduled Nimodipine Is Associated with Better Outcome in Aneurysmal Subarachnoid Hemorrhage Patients Cotreated with Heparin Infusion

Introduction

We sought to determine whether compliance with scheduled nimodipine in subarachnoid hemorrhage patients impacted patient outcomes, with the intent of guiding future nimodipine management in patients who experience nimodipine-induced hypotension.

Methods

We performed a retrospective analysis of 118 consecutive aneurysmal subarachnoid hemorrhage patients treated with the Maryland Low-Dose IV Heparin Infusion Protocol. Patients were categorized into three independent nimodipine compliance groups: ≥1 dose held, ≥1 dose split, and no missed or split-doses. A split-dose was defined as 30 mg of nimodipine administered every 2 h. Our primary outcome was discharge to home. Bivariate and multivariable logistic regression analyses were used to assess predictors of discharge disposition as a function of nimodipine compliance.

Results

Of the 118 patients, 20 (17%) received all nimodipine doses, 6 (5%) received split-doses but never had a full dose held, and 92 (78%) had ≥1 dose held. Forty-five percent of patients were discharged to home, including 75% who received all doses, 67% who received ≥1 split-doses, and 37% with ≥1 missed doses (p = 0.003). Multivariable analysis showed that, along with age and World Federation of Neurosurgical Societies grade, nimodipine compliance was an independent predictor of clinical outcome; compared to missing one or more nimodipine doses, full dosing compliance was associated with increased odds of discharge to home (odds ratio 5.20; 95% confidence intervals 1.46–18.56).

Conclusion

In aneurysmal subarachnoid hemorrhage patients with modified Fisher scores 2 through 4 who are cotreated with a low-dose heparin infusion, full compliance with nimodipine dosing was associated with increased odds of discharge to home.

Heparin and Heparin-Derivatives in Post-Subarachnoid Hemorrhage Brain Injury: A Multimodal Therapy for a Multimodal Disease

Pharmacologic efforts to improve outcomes following aneurysmal subarachnoid hemorrhage (aSAH) remain disappointing, likely owing to the complex nature of post-hemorrhage brain injury. Previous work suggests that heparin, due to the multimodal nature of its actions, reduces the incidence of clinical vasospasm and delayed cerebral ischemia that accompany the disease. This narrative review examines how heparin may mitigate the non-vasospastic pathological aspects of aSAH, particularly those related to neuroinflammation. Following a brief review of early brain injury in aSAH and heparin’s general pharmacology, we discuss potential mechanistic roles of heparin therapy in treating post-aSAH inflammatory injury. These roles include reducing ischemia-reperfusion injury, preventing leukocyte extravasation, modulating phagocyte activation, countering oxidative stress, and correcting blood-brain barrier dysfunction. Following a discussion of evidence to support these mechanistic roles, we provide a brief discussion of potential complications of heparin usage in aSAH. Our review suggests that heparin’s use in aSAH is not only safe, but effectively addresses a number of pathologies initiated by aSAH.

Amelioration of amyloid-β-induced deficits by DcR3 in an Alzheimer's disease model

Background

Microglia mediate amyloid-beta peptide (Aβ)-induced neuroinflammation, which is one of the key events in the pathogenesis of Alzheimer’s disease (AD). Decoy receptor 3 (DcR3)/TNFRSF6B is a pleiotropic immunomodulator that promotes macrophage differentiation toward the M2 anti-inflammatory phenotype. Based on its role as an immunosupressor, we examined whether DcR3 could alleviate neuroinflammation and AD-like deficits in the central nervous system.

Method

We crossed human APP transgenic mice (line J20) with human DcR3 transgenic mice to generate wild-type, APP, DcR3, and APP/DcR3 mice for pathological analysis. The Morris water maze, fear conditioning test, open-field, and elevated-plus maze were used to access their cognitive behavioral changes. Furthermore, the pathological and immune profiles were examined by immunostaining, ELISA, Q-PCR, and IP. In vitro assays were designed to examine DcR3-mediated innate cytokine profile alteration and the potential protective mechanism.

Results

We reported that DcR3 ameliorates hippocampus-dependent memory deficits and reduces amyloid plaque deposition in APP transgenic mouse. The protective mechanism of DcR3 mediates through interacting with heparan sulfate proteoglycans and activating IL-4⁺YM1⁺ M2a-like microglia that reduces Aβ-induced proinflammatory cytokines and promotes phagocytosis ability of microglia.

Conclusion

The neuroprotective effect of DcR3 is mediated via modulating microglia activation into anti-inflammatory M2a phenotype, and upregulating DcR3 expression in the brain may be a potential therapeutic approach for AD.

Electronic supplementary material

The online version of this article (doi:10.1186/s13024-017-0173-0) contains supplementary material, which is available to authorized users.

Effect of heparin on secondary brain injury in patients with subarachnoid hemorrhage: an additional ‘H’ therapy in vasospasm treatment

Objective

Secondary brain injury leads to high morbidity and mortality rates in patients with aneurysmal subarachnoid hemorrhage (aSAH). However, evidence-based treatment strategies are sparse. Since heparin has various effects on neuroinflammation, microthromboembolism and vasomotor function, our objective was to determine whether heparin can be used as a multitarget prophylactic agent to ameliorate morbidity in SAH.

Methods

Between June 1999 and December 2014, 718 patients received endovascular treatment after rupture of an intracranial aneurysm at our institution; 197 of them were treated with continuous unfractionated heparin in therapeutic dosages after the endovascular procedure. We performed a matched pair analysis to evaluate the effect of heparin on cerebral vasospasm (CVS), cerebral infarction (CI), and outcome.

Results

The rate of severe CVS was significantly reduced in the heparin group compared with the control group (14.2% vs 25.4%; p=0.005). CI and multiple ischemic lesions were less often present in patients with heparin treatment. These effects were enhanced if patients were treated with heparin for >48 hours, but the difference was not significant. Favorable outcome at 6-month follow-up was achieved in 69% in the heparin group and in 65% in the control group.

Conclusions

Patients receiving unfractionated continuous heparin after endovascular aneurysm occlusion have a significant reduction in the rate of severe CVS, have CI less often, and tend to have a favorable outcome more often. Our findings support the potential beneficial effects of heparin as a multitarget therapy in patients with SAH, resulting in an additional ‘H’ therapy in vasospasm treatment.

Novel Treatments in Neuroprotection for Aneurysmal Subarachnoid Hemorrhage

OPINION STATEMENT

New neuroprotective treatments aimed at preventing or minimizing "delayed brain injury" are attractive areas of investigation and hold the potential to have substantial beneficial effects on aneurysmal subarachnoid hemorrhage (aSAH) survivors. The underlying mechanisms for this "delayed brain injury" are multi-factorial and not fully understood. The most ideal treatment strategies would have the potential for a pleotropic effect positively modulating multiple implicated pathophysiological mechanisms at once. My personal management (RFJ) of patients with aneurysmal subarachnoid hemorrhage closely follows those treatment recommendations contained in modern published guidelines. However, over the last 5 years, I have also utilized a novel treatment strategy, originally developed at the University of Maryland, which consists of a 14-day continuous low-dose intravenous heparin infusion (LDIVH) beginning 12 h after securing the ruptured aneurysm. In addition to its well-known anti-coagulant properties, unfractionated heparin has potent anti-inflammatory effects and through multiple mechanisms may favorably modulate the neurotoxic and neuroinflammatory processes prominent in aneurysmal subarachnoid hemorrhage. In my personal series of patients treated with LDIVH, I have found significant preservation of neurocognitive function as measured by the Montreal Cognitive Assessment (MoCA) compared to a control cohort of my patients treated without LDIVH (RFJ unpublished data presented at the 2015 AHA/ASA International Stroke Conference symposium on neuroinflammation in aSAH and in abstract format at the 2015 AANS/CNS Joint Cerebrovascular Section Annual Meeting). It is important for academic physicians involved in the management of these complex patients to continue to explore new treatment options that may be protective against the potentially devastating "delayed brain injury" following cerebral aneurysm rupture. Several of the treatment options included in this review show promise and could be carefully adopted as the level of evidence for each improves. Other proposed neuroprotective treatments like statins and magnesium sulfate were previously thought to be very promising and to varying degrees were adopted at numerous institutions based on somewhat limited human evidence. Recent clinical trials and meta-analysis have shown no benefit for these treatments, and I currently no longer utilize either treatment as prophylaxis in my practice.

Aneurysmal Subarachnoid Hemorrhage and Neuroinflammation: A Comprehensive Review

Aneurysmal subarachnoid hemorrhage (SAH) can lead to devastating outcomes including vasospasm, cognitive decline, and even death. Currently, treatment options are limited for this potentially life threatening injury. Recent evidence suggests that neuroinflammation plays a critical role in injury expansion and brain damage. Red blood cell breakdown products can lead to the release of inflammatory cytokines that trigger vasospasm and tissue injury. Preclinical models have been used successfully to improve understanding about neuroinflammation following aneurysmal rupture. The focus of this review is to provide an overview of how neuroinflammation relates to secondary outcomes such as vasospasm after aneurysmal rupture and to critically discuss pharmaceutical agents that warrant further investigation for the treatment of subarachnoid hemorrhage. We provide a concise overview of the neuroinflammatory pathways that are upregulated following aneurysmal rupture and how these pathways correlate to long-term outcomes. Treatment of aneurysm rupture is limited and few pharmaceutical drugs are available. Through improved understanding of biochemical mechanisms of injury, novel treatment solutions are being developed that target neuroinflammation. In the final sections of this review, we highlight a few of these novel treatment approaches and emphasize why targeting neuroinflammation following aneurysmal subarachnoid hemorrhage may improve patient care. We encourage ongoing research into the pathophysiology of aneurysmal subarachnoid hemorrhage, especially in regards to neuroinflammatory cascades and the translation to randomized clinical trials.

Inducible nitric oxide synthase (NOS-2) in subarachnoid hemorrhage: Regulatory mechanisms and therapeutic implications

Aneurysmal subarachnoid hemorrhage (SAH) typically carries a poor prognosis. Growing evidence indicates that overabundant production of nitric oxide (NO) may be responsible for a large part of the secondary injury that follows SAH. Although SAH modulates the activity of all three isoforms of nitric oxide synthase (NOS), the inducible isoform, NOS-2, accounts for a majority of NO-mediated secondary injuries after SAH. Here, we review the indispensable physiological roles of NO that must be preserved, even while attempting to downmodulate the pathophysiologic effects of NO that are induced by SAH. We examine the effects of SAH on the function of the various NOS isoforms, with a particular focus on the pathological effects of NOS-2 and on the mechanisms responsible for its transcriptional upregulation. Finally, we review interventions to block NOS-2 upregulation or to counteract its effects, with an emphasis on the potential therapeutic strategies to improve outcomes in patients afflicted with SAH. There is still much to be learned regarding the apparently maladaptive response of NOS-2 and its harmful product NO in SAH. However, the available evidence points to crucial effects that, on balance, are adverse, making the NOS-2/NO/peroxynitrite axis an attractive therapeutic target in SAH.

Melatonin attenuates neurogenic pulmonary edema via the regulation of inflammation and apoptosis after subarachnoid hemorrhage in rats

Neurogenic pulmonary edema (NPE) is a serious non-neurological complication that can occur after a subarachnoid hemorrhage (SAH) and is associated with decreased survival and a poor neurological outcome. Melatonin is a strong antioxidant that has beneficial effects against SAH in rats, including reduced mortality and reduced neurological deficits. The molecular mechanisms underlying these clinical effects in the SAH model, however, have not been clearly identified. This study was undertaken to determine the influence of melatonin on SAH-induced NPE and the potential mechanism of these effects using the filament perforation model of SAH in male Sprague Dawley rats. Either melatonin (150 mg/kg) or a vehicle was given via an intraperitoneal injection 2 hr after an SAH induction. Lung samples were extracted 24 hr after SAH. The results show that the melatonin treatment attenuated SAH-induced NPE by preventing alveolar-capillary barrier dysfunctions via inhibiting the disruption of tight junction proteins (ZO-1 and occludin). Moreover, the treatment downregulated the levels of mature interleukin (IL) -1β, myeloperoxidase (MPO), and matrix metallopeptidase (MMP) 9 expression/activation, which were increased in the lung; also, melatonin treatment improved neurological deficits. Furthermore, the melatonin treatment markedly reduced caspase-3 activity and the number of TUNEL-positive cells in the lung. Taken together, these findings show that administration of melatonin attenuates NPE by preventing alveolar-capillary barrier dysfunctions via repressing the inflammatory response and by anti-apoptosis effects after SAH.

Enoxaparin ameliorates post-traumatic brain injury edema and neurologic recovery, reducing cerebral leukocyte endothelial interactions and vessel permeability in vivo

BACKGROUND

Traumatic brain injury (TBI) confers a high risk of venous thrombosis, but early prevention with heparinoids is often withheld, fearing cerebral hematoma expansion. Yet, studies have shown heparinoids not only to be safe but also to limit brain edema and contusion size after TBI. Human TBI data also suggest faster radiologic and clinical neurologic recovery with earlier heparinoid administration. We hypothesized that enoxaparin (ENX) after TBI blunts in vivo leukocyte (LEU) mobilization to injured brain and cerebral edema, while improving neurologic recovery without increasing the size of the cerebral hemorrhagic contusion.

METHODS

CD1 male mice underwent either TBI by controlled cortical impact (CCI, 1-mm depth, 6 m/s) or sham craniotomy. ENX (1 mg/kg) or vehicle (VEH, 0.9% saline, 1 mL/kg) was administered at 2, 8, 14, 23, and 32 hours after TBI. At 48 hours, intravital microscopy was used to visualize live LEUs interacting with endothelium and microvascular leakage of fluorescein isothiocyanate-albumin. Neurologic function (Neurological Severity Score, NSS), activated clotting time, hemorrhagic contusion size, as well as brain and lung wet-to-dry ratios were evaluated post mortem. Analysis of variance with Bonferroni correction was used for statistical comparisons between groups.

RESULTS

Compared with VEH, ENX significantly reduced in vivo LEU rolling on endothelium (72.7 ± 28.3 LEU/100 μm/min vs. 30.6 ± 18.3 LEU/100 μm/min, p = 0.02) and cerebrovascular albumin leakage (34.5% ± 8.1% vs. 23.8% ± 5.5%, p = 0.047). CCI significantly increased ipsilateral cerebral hemisphere edema, but ENX treatment reduced post-CCI edema to near control levels (81.5% ± 1.5% vs. 77.6% ± 0.6%, p < 0.01). Compared with VEH, ENX reduced body weight loss at 24 hours (8.7% ± 1.2% vs. 5.8% ± 1.1%, p < 0.01) and improved NSS at 24 hours (14.5 ± 0.5 vs. 16.2 ± 0.4, p < 0.01) and 48 hours (15.1 ± 0.4 vs. 16.7 ± 0.5, p < 0.01) after injury. There were no significant differences in activated clotting time, hemorrhagic contusion size, and lung water content between the groups.

CONCLUSION

ENX reduces LEU recruitment to injured brain, diminishing visible microvascular permeability and edema. ENX may also accelerate neurologic recovery without increasing cerebral contusion size. Further study in humans is necessary to determine safety, appropriate dosage, and timing of ENX administration early after TBI.

Early brain injury after aneurysmal subarachnoid hemorrhage: a multimodal neuromonitoring study

Introduction

There is a substantial amount of evidence from animal models that early brain injury (EBI) may play an important role for secondary brain injury after aneurysmal subarachnoid hemorrhage (aSAH). Cerebral microdialysis (CMD) allows online measurement of brain metabolites, including the pro-inflammatory cytokine interleukin-6 (IL-6) and matrix metalloproteinase-9 (MMP-9), which is indicative for disruption of the blood-brain barrier.

Methods

Twenty-six consecutive poor-grade aSAH patients with multimodal neuromonitoring were analyzed for brain hemodynamic and metabolic changes, including CMD-IL-6 and CMD-MMP-9 levels. Statistical analysis was performed by using a generalized estimating equation with an autoregressive function.

Results

The baseline cerebral metabolic profile revealed brain metabolic distress and an excitatory response which improved over the following 5 days (P <0.001). Brain tissue hypoxia (brain tissue oxygen tension of less than 20 mm Hg) was common (more than 60% of patients) in the first 24 hours of neuromonitoring and improved thereafter (P <0.05). Baseline CMD-IL-6 and CMD-MMP-9 levels were elevated in all patients (median = 4,059 pg/mL, interquartile range (IQR) = 1,316 to 12,456 pg/mL and median = 851 pg/mL, IQR = 98 to 25,860 pg/mL) and significantly decreased over days (P <0.05). A higher pro-inflammatory response was associated with the development of delayed cerebral ischemia (P = 0.04), whereas admission disease severity and early brain tissue hypoxia were associated with higher CMD-MMP-9 levels (P <0.03). Brain metabolic distress and increased IL-6 levels were associated with poor functional outcome (modified Rankin Scale of more than 3, P ≤0.01). All models were adjusted for probe location, aneurysm securing procedure, and disease severity as appropriate.

Conclusions

Multimodal neuromonitoring techniques allow insight into pathophysiologic changes in the early phase after aSAH. The results may be used as endpoints for future interventions targeting EBI in poor-grade aSAH patients.

Methemoglobin is an endogenous toll-like receptor 4 ligand-relevance to subarachnoid hemorrhage

Neuroinflammation is a well-recognized consequence of subarachnoid hemorrhage (SAH), and may be responsible for important complications of SAH. Signaling by Toll-like receptor 4 (TLR4)-mediated nuclear factor κB (NFκB) in microglia plays a critical role in neuronal damage after SAH. Three molecules derived from erythrocyte breakdown have been postulated to be endogenous TLR4 ligands: methemoglobin (metHgb), heme and hemin. However, poor water solubility of heme and hemin, and lipopolysaccharide (LPS) contamination have confounded our understanding of these molecules as endogenous TLR4 ligands. We used a 5-step process to obtain highly purified LPS-free metHgb, as confirmed by Fourier Transform Ion Cyclotron Resonance mass spectrometry and by the Limulus amebocyte lysate assay. Using this preparation, we show that metHgb is a TLR4 ligand at physiologically relevant concentrations. metHgb caused time- and dose-dependent secretion of the proinflammatory cytokine, tumor necrosis factor α (TNFα), from microglial and macrophage cell lines, with secretion inhibited by siRNA directed against TLR4, by the TLR4-specific inhibitors, Rs-LPS and TAK-242, and by anti-CD14 antibodies. Injection of purified LPS-free metHgb into the rat subarachnoid space induced microglial activation and TNFα upregulation. Together, our findings support the hypothesis that, following SAH, metHgb in the subarachnoid space can promote widespread TLR4-mediated neuroinflammation.

Glibenclamide for the treatment of ischemic and hemorrhagic stroke

Ischemic and hemorrhagic strokes are associated with severe functional disability and high mortality. Except for recombinant tissue plasminogen activator, therapies targeting the underlying pathophysiology of central nervous system (CNS) ischemia and hemorrhage are strikingly lacking. Sur1-regulated channels play essential roles in necrotic cell death and cerebral edema following ischemic insults, and in neuroinflammation after hemorrhagic injuries. Inhibiting endothelial, neuronal, astrocytic and oligodendroglial sulfonylurea receptor 1-transient receptor potential melastatin 4 (Sur1-Trpm4) channels and, in some cases, microglial KATP (Sur1-Kir6.2) channels, with glibenclamide is protective in a variety of contexts. Robust preclinical studies have shown that glibenclamide and other sulfonylurea agents reduce infarct volumes, edema and hemorrhagic conversion, and improve outcomes in rodent models of ischemic stroke. Retrospective studies suggest that diabetic patients on sulfonylurea drugs at stroke presentation fare better if they continue on drug. Additional laboratory investigations have implicated Sur1 in the pathophysiology of hemorrhagic CNS insults. In clinically relevant models of subarachnoid hemorrhage, glibenclamide reduces adverse neuroinflammatory and behavioral outcomes. Here, we provide an overview of the preclinical studies of glibenclamide therapy for CNS ischemia and hemorrhage, discuss the available data from clinical investigations, and conclude with promising preclinical results that suggest glibenclamide may be an effective therapeutic option for ischemic and hemorrhagic stroke.

Neurovascular events after subarachnoid hemorrhage: focusing on subcellular organelles

Subarachnoid hemorrhage (SAH) is a devastating condition with high morbidity and mortality rates due to the lack of effective therapy. Early brain injury (EBI) and cerebral vasospasm (CVS) are the two most important pathophysiological mechanisms for brain injury and poor outcomes for patients with SAH. CVS has traditionally been considered the sole cause of delayed ischemic neurological deficits after SAH. However, the failure of antivasospastic therapy in patients with SAH supported changing the research target from CVS to other mechanisms. Currently, more attention has been focused on global brain injury within 3 days after ictus, designated as EBI. The dysfunction of subcellular organelles, such as endoplasmic reticulum stress, mitochondrial failure, and autophagy-lysosomal system activation, has developed during EBI and delayed brain injury after SAH. To our knowledge, there is a lack of review articles addressing the direction of organelle dysfunction after SAH. In this review, we discuss the roles of organelle dysfunction in the pathogenesis of SAH and present the opportunity to develop novel therapeutic strategies of SAH via modulating the functions of organelles.

Early brain injury, an evolving frontier in subarachnoid hemorrhage research

Subarachnoid hemorrhage (SAH), predominantly caused by a ruptured aneurysm, is a devastating neurological disease that has a morbidity and mortality rate higher than 50%. Most of the traditional in vivo research has focused on the pathophysiological or morphological changes of large-arteries after intracisternal blood injection. This was due to a widely held assumption that delayed vasospasm following SAH was the major cause of delayed cerebral ischemia and poor outcome. However, the results of the CONSCIOUS-1 trial implicated some other pathophysiological factors, independent of angiographic vasospasm, in contributing to the poor clinical outcome. The term early brain injury (EBI) has been coined and describes the immediate injury to the brain after SAH, before onset of delayed vasospasm. During the EBI period, a ruptured aneurysm brings on many physiological derangements such as increasing intracranial pressure (ICP), decreased cerebral blood flow (CBF), and global cerebral ischemia. These events initiate secondary injuries such as blood-brain barrier disruption, inflammation, and oxidative cascades that all ultimately lead to cell death. Given the fact that the reversal of vasospasm does not appear to improve patient outcome, it could be argued that the treatment of EBI may successfully attenuate some of the devastating secondary injuries and improve the outcome of patients with SAH. In this review, we provide an overview of the major advances in EBI after SAH research.

Cannabinoid receptor type 2 agonist attenuates apoptosis by activation of phosphorylated CREB-Bcl-2 pathway after subarachnoid hemorrhage in rats

Early brain injury (EBI) which comprises of vasogenic edema and apoptotic cell death is an important component of subarachnoid hemorrhage (SAH) pathophysiology. This study evaluated whether cannabinoid receptor type 2 (CB2R) agonist, JWH133, attenuates EBI after SAH and whether CB2R stimulation reduces pro-apoptotic caspase-3 via up-regulation of cAMP response element-binding protein (CREB)-Bcl-2 signaling pathway. Male Sprague-Dawley rats (n=123) were subjected to SAH by endovascular perforation. Rats received vehicle or JWH133 at 1h after SAH. Neurological deficits and brain water content were evaluated at 24h after SAH. Western blot was performed to quantify phosphorylated CREB (pCREB), Bcl-2, and cleaved caspase-3 levels. Neuronal cell death was evaluated with terminal deoxynucleotidyl transferase-mediated uridine 5'-triphosphate-biotin nick end-labeling staining. Additionally, CREB siRNA was administered to manipulate the proposed pathway. JWH133 (1.0mg/kg) improved neurological deficits and reduced brain water content in left hemisphere 24h after SAH. JWH133 significantly increased activated CREB (pCREB) and Bcl-2 levels and significantly decreased cleaved caspase-3 levels in left hemisphere 24h after SAH. CREB siRNA reversed the effects of treatment. TUNEL positive neurons in the cortex were reduced with JWH133 treatment. Thus, CB2R stimulation attenuated EBI after SAH possibly through activation of pCREB-Bcl-2 pathway.

The harmful effects of subarachnoid hemorrhage on extracerebral organs

Subarachnoid hemorrhage (SAH) is a devastating neurological disorder. Patients with aneurysmal SAH develop secondary complications that are important causes of morbidity and mortality. Aside from secondary neurological injuries, SAH has been associated with nonneurologic medical complications, such as neurocardiogenic injury, neurogenic pulmonary edema, hyperglycemia, and electrolyte imbalance, of which cardiac and pulmonary complications are most common. The related mechanisms include activation of the sympathetic nervous system, release of catecholamines and other hormones, and inflammatory responses. Extracerebral complications are directly related to the severity of SAH-induced brain injury and indicate the clinical outcome in patients. This review provides an overview of the extracerebral complications after SAH. We also aim to describe the manifestations, underlying mechanisms, and the effects of those extracerebral complications on outcome following SAH.