HMGB1 Level in Cerebrospinal Fluid as a Marker of Treatment Outcome in Patients with Acute Hydrocephalus Following Aneurysmal Subarachnoid Hemorrhage

Potential significance of high-mobility group protein box 1 in cerebrospinal fluid

High-mobility group protein box 1 (HMGB1) is a cytokine with multiple functions (according to its subcellular location) that serves a marker of inflammation. CSF HMGB1 could be the part of pathological mechanisms that underlie the complications associated with CNS diseases. HMGB1 actively or passively released into the CSF is detected in the CSF in many diseases of the central nervous system (CNS) and thus may be useful as a biomarker. Pathological alterations in distant areas were observed due to lesions in a specific region, and the level of HMGB1 in the CSF was found to be elevated. Reducing the HMGB1 level via intraventricular injection of anti-HMGB1 neutralizing antibodies can improve the outcomes of CNS diseases. The results indicated that CSF HMGB1 could serve as a biomarker for predicting disease progression and may also act as a pathogenic factor contributing to pathological alterations in distant areas following focal lesions in the CNS. In this mini-review, the characteristics of HMGB1 and progress in research on CSF HMGB1 as a biomarker of CNS diseases were discussed. CSF HMGB1 is useful not only as a biomarker of CNS diseases but may also be involved in interactions between different brain regions and the spinal cord.

The Critical Role of Sirt1 in Subarachnoid Hemorrhages: Mechanism and Therapeutic Considerations

The subarachnoid hemorrhage (SAH) is an important cause of death and long-term disability worldwide. As a nicotinamide adenine dinucleotide-dependent deacetylase, silent information regulator 1 (Sirt1) is a multipotent molecule involved in many pathophysiological processes. A growing number of studies have demonstrated that Sirt1 activation may exert positive effects on SAHs by regulating inflammation, oxidative stress, apoptosis, autophagy, and ferroptosis. Thus, Sirt1 agonists may serve as potential therapeutic drugs for SAHs. In this review, we summarized the current state of our knowledge on the relationship between Sirt1 and SAHs and provided an updated overview of the downstream molecules of Sirt1 in SAHs.

High-Mobility Group Box 1 in Spinal Cord Injury and Its Potential Role in Brain Functional Remodeling After Spinal Cord Injury

High-mobility group box 1 (HMGB1) is a nonhistone nuclear protein, the functions of which depend on its subcellular location. It is actively or passively secreted into the blood and/or cerebrospinal fluid (CSF) and can be used as a prognostic indicator of disease. HMGB1 released into the bloodstream can cause pathological reactions in distant organs, and entry into the CSF can destroy the blood-brain barrier and aggravate brain injuries. HMGB1 expression has been reported to be increased in the tissues of spinal cord injury (SCI) patients and involved in the regulation of neuroinflammation, neuronal apoptosis, and ferroptosis. SCI can lead to brain changes, resulting in neuropathic pain, depression, and cognitive dysfunction, but the specific mechanism is unknown. It remains unclear whether HMGB1 plays an important role in brain functional remodeling after SCI. Damaged cells at the site of SCI passively release HMGB1, which travels to the brain via the blood, CSF, and/or axonal transport, destroys the blood-brain barrier, and causes pathological changes in the brain. This may explain the remodeling of brain function that occurs after SCI. In this minireview, we introduce the structure and function of HMGB1 and its mechanism of action in SCI. Clarifying the functions of HMGB1 may provide insight into the links between SCI and various brain regions.

Inflammatory Markers as Predictors of Shunt Dependency and Functional Outcome in Patients with Aneurysmal Subarachnoid Hemorrhage

The mechanisms underlying post-hemorrhagic hydrocephalus (PHH) development following subarachnoid hemorrhage (SAH) are not fully understood, which complicates informed clinical decisions regarding the duration of external ventricular drain (EVD) treatment and prevents the prediction of shunt-dependency in the individual patient. The aim of this study was to identify potential inflammatory cerebrospinal fluid (CSF) biomarkers of PHH and, thus, shunt-dependency and functional outcome in patients with SAH. This study was a prospective observational study designed to evaluate inflammatory markers in ventricular CSF. In total, 31 Patients with SAH who required an EVD between June 2019 and September 2021 at the Department of Neurosurgery, Rigshospitalet, Copenhagen, Denmark, were included. CSF samples were collected twice from each patient and analyzed for 92 inflammatory markers via proximity extension assay (PEA), and the prognostic ability of the markers was investigated. In total, 12 patients developed PHH, while 19 were weaned from their EVD. Their 6-month functional outcome was determined with the modified Rankin Scale. Of the 92 analyzed inflammatory biomarkers, 79 were identified in the samples. Seven markers (SCF, OPG, LAP TGFβ1, Flt3L, FGF19, CST5, and CSF1) were found to be predictors of shunt dependency, and four markers (TNFα, CXCL5, CCL20, and IL8) were found to be predictors of functional outcome. In this study, we identified promising inflammatory biomarkers that are able to predict (i) the functional outcome in patients with SAH and (ii) the development of PHH and, thus, the shunt dependency of the individual patients. These inflammatory markers may have the potential to be employed as predictive biomarkers of shunt dependency and functional outcome following SAH and could, as such, be applied in the clinic.

Inflammation and immune cell abnormalities in intracranial aneurysm subarachnoid hemorrhage (SAH): Relevant signaling pathways and therapeutic strategies

Intracranial aneurysm subarachnoid hemorrhage (SAH) is a cerebrovascular disorder associated with high overall mortality. Currently, the underlying mechanisms of pathological reaction after aneurysm rupture are still unclear, especially in the immune microenvironment, inflammation, and relevant signaling pathways. SAH-induced immune cell population alteration, immune inflammatory signaling pathway activation, and active substance generation are associated with pro-inflammatory cytokines, immunosuppression, and brain injury. Crosstalk between immune disorders and hyperactivation of inflammatory signals aggravated the devastating consequences of brain injury and cerebral vasospasm and increased the risk of infection. In this review, we discussed the role of inflammation and immune cell responses in the occurrence and development of aneurysm SAH, as well as the most relevant immune inflammatory signaling pathways [PI3K/Akt, extracellular signal-regulated kinase (ERK), hypoxia-inducible factor-1α (HIF-1α), STAT, SIRT, mammalian target of rapamycin (mTOR), NLRP3, TLR4/nuclear factor-κB (NF-κB), and Keap1/nuclear factor (erythroid-derived 2)-like 2 (Nrf2)/ARE cascades] and biomarkers in aneurysm SAH. In addition, we also summarized potential therapeutic drugs targeting the aneurysm SAH immune inflammatory responses, such as nimodipine, dexmedetomidine (DEX), fingolimod, and genomic variation-related aneurysm prophylactic agent sunitinib. The intervention of immune inflammatory responses and immune microenvironment significantly reduces the secondary brain injury, thereby improving the prognosis of patients admitted to SAH. Future studies should focus on exploring potential immune inflammatory mechanisms and developing additional therapeutic strategies for precise aneurysm SAH immune inflammatory regulation and genomic variants associated with aneurysm formation.

Janus Faced HMGB1 and Post-Aneurysmal Subarachnoid Hemorrhage (aSAH) Inflammation

Aneurysmal subarachnoid hemorrhage (aSAH), resulting majorly from the rupture of intracranial aneurysms, is a potentially devastating disease with high morbidity and mortality. The bleeding aneurysms can be successfully secured; however, the toxic and mechanical impact of the blood extravasation into the subarachnoid space damages the brain cells leading to the release of different damage-associated molecular pattern molecules (DAMPs). DAMPs upregulate the inflammation after binding their cognate receptors on the immune cells and underlies the early and delayed brain injury after aSAH. Moreover, these molecules are also associated with different post-aSAH complications, which lead to poor clinical outcomes. Among these DAMPs, HMGB1 represents a prototypical protein DAMP that has been well characterized for its proinflammatory role after aSAH and during different post-aSAH complications. However, recent investigations have uncovered yet another face of HMGB1, which is involved in the promotion of brain tissue remodeling, neurovascular repair, and anti-inflammatory effects after SAH. These different faces rely on different redox states of HMGB1 over the course of time after SAH. Elucidation of the dynamics of these redox states of HMGB1 has high biomarker as well as therapeutic potential. This review mainly highlights these recent findings along with the conventionally described normal role of HMGB1 as a nuclear protein and as a proinflammatory molecule during disease (aSAH).

Involvement of Microglia in the Pathophysiology of Intracranial Aneurysms and Vascular Malformations-A Short Overview

Aneurysms and vascular malformations of the brain represent an important source of intracranial hemorrhage and subsequent mortality and morbidity. We are only beginning to discern the involvement of microglia, the resident immune cell of the central nervous system, in these pathologies and their outcomes. Recent evidence suggests that activated proinflammatory microglia are implicated in the expansion of brain injury following subarachnoid hemorrhage (SAH) in both the acute and chronic phases, being also a main actor in vasospasm, considerably the most severe complication of SAH. On the other hand, anti-inflammatory microglia may be involved in the resolution of cerebral injury and hemorrhage. These immune cells have also been observed in high numbers in brain arteriovenous malformations (bAVM) and cerebral cavernomas (CCM), although their roles in these lesions are currently incompletely ascertained. The following review aims to shed a light on the most significant findings related to microglia and their roles in intracranial aneurysms and vascular malformations, as well as possibly establish the course for future research.

Inflammatory Markers in Cerebrospinal Fluid from Patients with Hydrocephalus: A Systematic Literature Review

OBJECTIVE

The aim of this systematic review was to evaluate existing literature on inflammatory markers in CSF from patients with hydrocephalus and identify potential markers capable of promoting hydrocephalus development and progression.

METHODS

Relevant studies published before December 3rd 2020 were identified from PubMed, Embase, and reference lists. Studies were screened for eligibility using the predefined inclusion and exclusion criteria. Data from eligible studies were extracted, and sources of bias were evaluated. We included articles written in English investigating inflammatory markers in CSF from patients with hydrocephalus and control subjects. The review was conducted according to the PRISMA guidelines by three independent reviewers.

RESULTS

Twenty-two studies analyzed CSF from 311 patients with idiopathic normal pressure hydrocephalus (iNPH), 178 with posthemorrhagic hydrocephalus (PHH), 151 with other hydrocephalus diagnoses, and 394 control subjects. Fifty-eight inflammatory markers were investigated. The CSF of iNPH patients had increased CSF levels of IL-6, IL-1β, and LRG compared with control subjects, whereas the CSF of PHH patients had increased levels of IL-6, IL-18, and VEGF. CSF from patients with "other hydrocephalus diagnoses" had elevated IFN-γ compared to control subjects, and VEGF was increased in congenital hydrocephalus, spina bifida, and hydrocephalus associated with tuberculous meningitis compared with controls.

CONCLUSION

IL-6, IL-1β, LRG, IL-18, VEGF, and IFN-γ are elevated in CSF from patients with hydrocephalus and may be involved in promotion of hydrocephalus development and progression. They may serve as novel disease biomarkers, and their signaling pathways may represent targets for pharmacological management of hydrocephalus.

High Mobility Group Box-1 and Blood-Brain Barrier Disruption

Increasing evidence suggests that inflammatory responses are involved in the progression of brain injuries induced by a diverse range of insults, including ischemia, hemorrhage, trauma, epilepsy, and degenerative diseases. During the processes of inflammation, disruption of the blood–brain barrier (BBB) may play a critical role in the enhancement of inflammatory responses and may initiate brain damage because the BBB constitutes an interface between the brain parenchyma and the bloodstream containing blood cells and plasma. The BBB has a distinct structure compared with those in peripheral tissues: it is composed of vascular endothelial cells with tight junctions, numerous pericytes surrounding endothelial cells, astrocytic endfeet, and a basement membrane structure. Under physiological conditions, the BBB should function as an important element in the neurovascular unit (NVU). High mobility group box-1 (HMGB1), a nonhistone nuclear protein, is ubiquitously expressed in almost all kinds of cells. HMGB1 plays important roles in the maintenance of chromatin structure, the regulation of transcription activity, and DNA repair in nuclei. On the other hand, HMGB1 is considered to be a representative damage-associated molecular pattern (DAMP) because it is translocated and released extracellularly from different types of brain cells, including neurons and glia, contributing to the pathophysiology of many diseases in the central nervous system (CNS). The regulation of HMGB1 release or the neutralization of extracellular HMGB1 produces beneficial effects on brain injuries induced by ischemia, hemorrhage, trauma, epilepsy, and Alzheimer’s amyloidpathy in animal models and is associated with improvement of the neurological symptoms. In the present review, we focus on the dynamics of HMGB1 translocation in different disease conditions in the CNS and discuss the functional roles of extracellular HMGB1 in BBB disruption and brain inflammation. There might be common as well as distinct inflammatory processes for each CNS disease. This review will provide novel insights toward an improved understanding of a common pathophysiological process of CNS diseases, namely, BBB disruption mediated by HMGB1. It is proposed that HMGB1 might be an excellent target for the treatment of CNS diseases with BBB disruption.

Tim-3 deteriorates neuroinflammatory and neurocyte apoptosis after subarachnoid hemorrhage through the Nrf2/HMGB1 signaling pathway in rats

Inflammation is known to play an important role in early brain injury (EBI) after subarachnoid hemorrhage (SAH). T cell immunoglobulin and mucin domain-3 (Tim-3) has emerged as a critical regulator of adaptive and innate immune responses, and has been identified to play a vital role in certain inflammatory diseases; The present study explored the effect of Tim-3 on inflammatory responses and detailed mechanism in EBI following SAH. We investigated the effects of Tim-3 on SAH models established by endovascular puncture method in Sprague–Dawley rats. The present studies revealed that SAH induced a significant inflammatory response and significantly increased Tim-3 expression. Tim-3-AAV administration aggravated neurocyte apoptosis, brain edema, blood-brain barrier permeability, and neurological dysfunction; significantly inhibited Nrf2 expression; and increased HMGB1 expression and secretion of pro-inflammatory cytokines, such as tumor necrosis factor alpha, interleukin (IL)-1 beta, IL-17, and IL-18. However, Tim-3 siRNA or NK252 administration abolished the pro-inflammatory effects of Tim-3. Our results indicate a function for Tim-3 as a molecular player that links neuroinflammation and brain damage after SAH. We reveal that Tim-3 overexpression deteriorates neuroinflammatory and neurocyte apoptosis after subarachnoid hemorrhage through the Nrf2/HMGB1 signaling pathway in rats.

HMGB1-Mediated Neuroinflammatory Responses in Brain Injuries: Potential Mechanisms and Therapeutic Opportunities

Brain injuries are devastating conditions, representing a global cause of mortality and morbidity, with no effective treatment to date. Increased evidence supports the role of neuroinflammation in driving several forms of brain injuries. High mobility group box 1 (HMGB1) protein is a pro-inflammatory-like cytokine with an initiator role in neuroinflammation that has been implicated in Traumatic brain injury (TBI) as well as in early brain injury (EBI) after subarachnoid hemorrhage (SAH). Herein, we discuss the implication of HMGB1-induced neuroinflammatory responses in these brain injuries, mediated through binding to the receptor for advanced glycation end products (RAGE), toll-like receptor4 (TLR4) and other inflammatory mediators. Moreover, we provide evidence on the biomarker potential of HMGB1 and the significance of its nucleocytoplasmic translocation during brain injuries along with the promising neuroprotective effects observed upon HMGB1 inhibition/neutralization in TBI and EBI induced by SAH. Overall, this review addresses the current advances on neuroinflammation driven by HMGB1 in brain injuries indicating a future treatment opportunity that may overcome current therapeutic gaps.

Targeting High Mobility Group Box 1 in Subarachnoid Hemorrhage: A Systematic Review

Aneurysmal subarachnoid hemorrhage (aSAH) is a complex and potentially deadly disease. Neurosurgical clipping or endovascular coiling can successfully obliterate ruptured aneurysms in almost every case. However, despite successful interventions, the clinical outcomes of aSAH patients are often poor. The reasons for poor outcomes are numerous, including cerebral vasospasm (CVS), post-hemorrhagic hydrocephalus, systemic infections and delayed cerebral ischemia. Although CVS with subsequent cerebral ischemia is one of the main contributors to brain damage after aSAH, little is known about the underlying molecular mechanisms of brain damage. This review emphasizes the importance of pharmacological interventions targeting high mobility group box 1 (HMGB1)-mediated brain damage after subarachnoid hemorrhage (SAH) and CVS. We searched Pubmed, Ovid medline and Scopus for "subarachnoid hemorrhage" in combination with "HMGB1". Based on these criteria, a total of 31 articles were retrieved. After excluding duplicates and selecting the relevant references from the retrieved articles, eight publications were selected for the review of the pharmacological interventions targeting HMGB1 in SAH. Damaged central nervous system cells release damage-associated molecular pattern molecules (DAMPs) that are important for initiating, driving and sustaining the inflammatory response following an aSAH. The discussed evidence suggested that HMGB1, an important DAMP, contributes to brain damage during early brain injury and also to the development of CVS during the late phase. Different pharmacological interventions employing natural compounds with HMGB1-antagonizing activity, antibody targeting of HMGB1 or scavenging HMGB1 by soluble receptors for advanced glycation end products (sRAGE), have been shown to dampen the inflammation mediated brain damage and protect against CVS. The experimental data suggest that HMGB1 inhibition is a promising strategy to reduce aSAH-related brain damage and CVS. Clinical studies are needed to validate these findings that may lead to the development of potential treatment options that are much needed in aSAH.

Elucidating the novel biomarker and therapeutic potentials of High-mobility group box 1 in Subarachnoid hemorrhage: A review

Subarachnoid hemorrhage (SAH) frequently arises after an aneurysm in a cerebral artery ruptures, resulting into bleeding as well as clot formation. High-mobility group box 1 (HMGB1) is an extremely preserved, universal protein secreted in the nuclei of all cell varieties. This review explores the biomarker as well as therapeutic potentials of HMBG1 in SAH especially during the occurrence of cerebral vasospasms. Plasma HMGB1 levels have proven to be very useful prognosticators of effective outcome as well as death after SAH. Correspondingly, higher HMGB1 levels in the cerebrospinal fluid (CSF) of SAH patients correlated well with poor outcome; signifying that, CSF level of HMGB1 is a novel predictor of outcome following SAH. Nonetheless, the degree of angiographic vasospasm does not always correlate with the degree of neurological deficits in SAH patients. HMGB1 stimulated cerebral vasospasm, augmented gene as well as protein secretory levels of receptor for advance glycation end product (RAGE) in neurons following SAH; which means that, silencing HMGB1 during SAH could be of therapeutic value. Compounds like resveratrol, glycyrrhizin, rhinacanthin, purpurogallin, 4′-O-β-D-Glucosyl-5-O-Methylvisamminol (4OGOMV) as well as receptor-interacting serine/threonine-protein kinase 3 (RIPK3) gene are capable of interacting with HMGB1 resulting in therapeutic benefits following SAH.

Danger Signals in the ICU

OBJECTIVES

Sterile and infectious critical illnesses often result in vasoplegic shock and a robust systemic inflammatory response that are similar in presentation. The innate immune system is at the center of the response to both infectious and traumatic insults. Damage-associated molecular patterns are small molecules that are released from stressed or dying cells. Damage-associated molecular patterns activate pattern recognition receptors and coordinate the leading edge of the innate immune response. This review introduces the concept of damage-associated molecular patterns and how they activate a systemic inflammatory response, specifically in trauma, neurologic injury, and infection. It also explores how, when carried to extremes, damage-associated molecular patterns may even perpetuate multisystem organ failure.

DATA SOURCES

Basic and clinical studies were obtained from a PubMed search through August 2017.

STUDY SELECTION

Articles considered include original articles, review articles, and conference proceedings.

DATA EXTRACTION

An analysis of scientific, peer-reviewed data was performed. High quality preclinical and clinical studies adjudicated by the authors were included and summarized.

DATA SYNTHESIS

Pattern recognition receptors respond to damage-associated molecular patterns and then activate inflammatory pathways. Damage-associated molecular patterns have been linked to the recruitment of sentinel leukocytes and the initiation of the inflammatory cascade. Damage-associated molecular patterns have been linked to many conditions in critical care illnesses. Preclinical models have added insight into how they may mediate distant organ dysfunction.

CONCLUSIONS

Damage-associated molecular pattern activation and release is an important research for intensive care practitioners. It will add to our understanding of the phase and state of the innate immune response to an insult. Early work is encouraging. However, only with improved understanding of damage-associated molecular pattern activation and function, we can perhaps hope to target damage-associated molecular patterns as diagnostic and/or therapeutic modalities in the future.

Anti-HMGB1 monoclonal antibody therapy for a wide range of CNS and PNS diseases

High mobility group box-1 (HMGB1), a representative damage associated-molecular pattern (DAMP), has been reported to be involved in many inflammatory diseases. Several drugs are thought to have potential to control the translocation and secretion of HMGB1, or to neutralize extracellular HMGB1 by binding to it. One of these drugs, anti-HMGB1 monoclonal antibody (mAb), is highly specific for HMGB1 and has been shown to be effective for the treatment of a wide range of CNS diseases when modeled in animals, including stroke, traumatic brain injury, Parkinson's disease, epilepsy and Alzheimer's disease. Thus, anti-HMGB1 mAb not only is useful for target validation but also has extensive potential for the treatment of the above-mentioned diseases. In this review, we summarize existing knowledge on the effects of anti-HMGB1 mAb on CNS and PNS diseases, the common features of translocation and secretion of HMGB1 and the functional roles of HMGB1 in these diseases. The existing literature suggests that anti-HMGB1 mAb therapy would be effective for a wide range of CNS and PNS diseases.

Nonanesthetic Effects of Ketamine: A Review Article

Ketamine is considered a dissociative anesthetic medication, and it is commonly administered by a parenteral route. It works mainly by blocking the N-methyl-D-aspartate receptor. It inhibits the voltage-gated Na and K channels and serotonin and dopamine reuptake; also, it affects specific receptors, such as α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid, kainate, and aminobutyric acid A receptors. Ketamine appears to have particular mechanisms that are potentially involved during analgesic induction, including enhancing of descending inhibition and antiinflammatory effects. More recently, it has been shown that ketamine has potential in clinical practice for the management of chronic pain, cognitive function, depression, acute brain injury, and disorders of the immune system.

Role of Damage Associated Molecular Pattern Molecules (DAMPs) in Aneurysmal Subarachnoid Hemorrhage (aSAH)

Aneurysmal subarachnoid hemorrhage (aSAH) represents only a small portion of all strokes, but accounts for almost half of the deaths caused by stroke worldwide. Neurosurgical clipping and endovascular coiling can successfully obliterate the bleeding aneurysms, but ensuing complications such as cerebral vasospasm, acute and chronic hydrocephalus, seizures, cortical spreading depression, delayed ischemic neurological deficits, and delayed cerebral ischemia lead to poor clinical outcomes. The mechanisms leading to these complications are complex and poorly understood. Early brain injury resulting from transient global ischemia can release molecules that may be critical to initiate and sustain inflammatory response. Hence, the events during early brain injury can influence the occurrence of delayed brain injury. Since the damage associated molecular pattern molecules (DAMPs) might be the initiators of inflammation in the pathophysiology of aSAH, so the aim of this review is to highlight their role in the context of aSAH from diagnostic, prognostic, therapeutic, and drug therapy monitoring perspectives. DAMPs represent a diverse and a heterogenous group of molecules derived from different compartments of cells upon injury. Here, we have reviewed the most important DAMPs molecules including high mobility group box-1 (HMGB1), S100B, hemoglobin and its derivatives, extracellular matrix components, IL-1α, IL-33, and mitochondrial DNA in the context of aSAH and their role in post-aSAH complications and clinical outcome after aSAH.

Hypothesis on the Role of Cryptochromes in Inflammation and Subarachnoid Hemorrhage Outcome

We have recently found that the temperature variability (TV) in the day-night cycle may predict the mean intracranial pressure in the following 24 h (ICP₂₄) in subarachnoid hemorrhage (SAH) patients under multimodality monitoring, sedation, and hypothermia (<35°C). Specifically, we found that ICP₂₄ = 6 (4 - TV) mmHg. TV is the ratio between the coefficient of variation of temperature during the nocturnal and the preceding diurnal periods. This result suggests that the circadian clock reflects brain plasticity mechanisms and its malfunctioning leads to deterioration of the neurologic status. The sleep-wake cycle is absent in these patients and their circadian clock can function properly only by environment light-independent mechanisms. One mechanism involves the circadian clock proteins named cryptochromes (CRYs). CRYs are highly preserved and widespread in the evolutionary tree, are expressed in different cell types in humans [type II CRYs, in two forms: human cryptochrome 1 and 2 (hCRY1 and hCRY2)], and in certain species, respond to blue light and play role in magnetoreception. Interestingly, SAH outcome seems to correlate with inflammation, and CRYs decrease inflammatory activity. Our hypothesis derived from these observations is that CRYs modulate the circadian oscillation of temperature even during therapeutic hypothermia and improve outcome in SAH through decrease in inflammation. A strategy to test this hypothesis is to measure periodically during the acute phase of high-grade SAH the level of CRYs in cerebrospinal fluid (CSF) and circulating white blood cells, and to correlate these levels with outcome, TV, ICP₂₄, and pro- and anti-inflammatory markers in CSF and blood. If this hypothesis is true, the development of therapies targeting inflammation in SAH could take advantage of cryptochrome properties. It has been shown that blue light phototherapy increases the expression of CRYs in blood mononuclear cells in jaundiced neonates. Likewise, visual stimulus with flashing light improves Alzheimer's disease features in experimental model and there is a prominent expression of CRYs in the retina. Remarkably, recent evidence showed that hCRY2 responds to electromagnetic fields, which could be one elusive mechanism of action of transcranial magnetic stimulation and a reason for its use in SAH.

Amino Acids in Cerebrospinal Fluid of Patients with Aneurysmal Subarachnoid Haemorrhage: An Observational Study

Background

The authors are aware of only one article investigating amino acid concentrations in cerebrospinal fluid (CSF) in patients with ruptured intracranial aneurysms, and this was published 31 years ago. Since then, both management of subarachnoid haemorrhage (SAH) and amino acid assay techniques have seen radical alterations, yet the pathophysiology of SAH remains unclear.

Objective

To analyse the pattern of concentrations of amino acids and related compounds in patients with different outcomes following aneurysmal SAH.

Methods

49 CSF samples were collected from 23 patients on days 0–3, 5, and 10 post-SAH. Concentrations of 33 amino acids and related compounds were assayed by liquid chromatography tandem mass spectrometry in patients with good [Glasgow Outcome Scale (GOS) 1–3] and poor (GOS 4–5) outcome.

Results

Of the 33 compounds assayed, only hydroxyproline and 3-aminoisobutyric acid appeared not to increase significantly following SAH. In poor outcome patients, we found significantly higher concentrations of aspartic acid (p = 0.038), glutamic acid (p = 0.038), and seven other compounds on days 0–3 post-SAH; glutamic acid (p = 0.041) on day 5 post-SAH, and 2-aminoadipic acid (p = 0.033) on day 10 post-SAH. The most significant correlation with GOS at 3 months was found for aminoadipic acid on day 10 post-SAH (cc = −0.81).

Conclusion

Aneurysmal rupture leads to a generalised increase of amino acids and related compounds in CSF. The patterns differ between good and poor outcome cases. Increased excitatory amino acids are strongly indicative of poor outcome.

Cerebrospinal Fluid and Microdialysis Cytokines in Aneurysmal Subarachnoid Hemorrhage: A Scoping Systematic Review

Objective

To perform two scoping systematic reviews of the literature on cytokine measurement in cerebral microdialysis (CMD) and cerebrospinal fluid (CSF) in aneurysmal subarachnoid hemorrhage (SAH) patients, aiming to summarize the evidence relating cytokine levels to pathophysiology, disease progression, and outcome.

Methods

Two separate systematic reviews were conducted: one for CMD cytokines and the second for CSF cytokines.

Data sources

Articles from MEDLINE, BIOSIS, EMBASE, Global Health, Scopus, Cochrane Library (inception to October 2016), reference lists of relevant articles, and gray literature were searched.

Study selection

Two reviewers independently identified all manuscripts utilizing predefined inclusion/exclusion criteria. A two-tier filter of references was conducted.

Data extraction

Patient demographic and study data were extracted to tables.

Results

There were 9 studies identified describing the analysis of cytokines via CMD in 246 aneurysmal SAH patients. Similarly, 20 studies were identified describing the analysis of CSF cytokines in 630 patients. The two scoping systematic reviews demonstrated the following: (1) limited literature available on CMD cytokine measurement in aneurysmal SAH with some preliminary data supporting feasibility of measurement and potential association between interleukin (IL)-6 and patient outcome. (2) Various CSF measured cytokines may be associated with patient outcome at 3–6 months, including IL-1ra, IL-6, IL-8, and tumor necrosis factor-alpha. (3) There is a small literature body supporting an association between acute/subacute CSF transforming growth factor levels and the development of chronic hydrocephalus at 2–3 months.

Conclusion

The evaluation of CMD and CSF cytokines is an emerging area of the literature in aneurysmal SAH. Further large prospective multicenter studies on cytokines in CMD and CSF need to be conducted.

In Vogue: Ketamine for Neuroprotection in Acute Neurologic Injury

Neurologic deterioration following acute injury to the central nervous system may be amenable to pharmacologic intervention, although, to date, no such therapy exists. Ketamine is an anesthetic and analgesic emerging as a novel therapy for a number of clinical entities in recent years, including refractory pain, depression, and drug-induced hyperalgesia due to newly discovered mechanisms of action and new application of its known pharmacodynamics. In this focused review, the evidence for ketamine as a neuroprotective agent in stroke, neurotrauma, subarachnoid hemorrhage, and status epilepticus is highlighted, with a focus on its applications for excitotoxicity, neuroinflammation, and neuronal hyperexcitability. Preclinical modeling and clinical applications are discussed.

Increase of Soluble RAGE in Cerebrospinal Fluid following Subarachnoid Haemorrhage

Receptors for advanced glycation end-products (RAGE) mediate the inflammatory reaction that follows aneurysmal subarachnoid haemorrhage. Soluble RAGE (sRAGE) may function as a decoy receptor. The significance of this endogenous anti-inflammatory mechanism in subarachnoid haemorrhage (SAH) remains unknown. The present study aims to analyse sRAGE levels in the cerebrospinal fluid (CSF) of SAH patients. sRAGE levels were assayed by ELISA kit in 47 CSF samples collected on post-SAH days 0–3, 5–7, and 10–14 from 27 SAH patients with acute hydrocephalus. CSF levels of sRAGE were compared with a control group and correlated with other monitored parameters. In the control group, the CSF contained only a trace amount of sRAGE. By contrast, the CSF of 20 SAH patients collected on post-SAH days 0–3 was found to contain statistically significant higher levels of sRAGE (mean concentration 3.91 pg/mL, p < 0.001). The most pronounced difference in CSF sRAGE levels between good and poor outcome patients was found on days 0–3 post-SAH but did not reach the significance threshold (p = 0.234). CSF sRAGE levels did not change significantly during hospitalisation (p = 0.868) and correlated poorly with treatment outcome, systemic inflammatory markers, and other monitored parameters. Our study revealed an early and constant increase of sRAGE level in the CSF of SAH patients.

Radiodensity of intraventricular hemorrhage associated with aneurysmal subarachnoid hemorrhage may be a negative predictor of outcome

OBJECTIVE The presence, extent, and distribution of intraventricular hemorrhage (IVH) have been associated with negative outcomes in aneurysmal subarachnoid hemorrhage (SAH). Several qualitative scores (Fisher grade, LeRoux score, and Graeb score) have been established for evaluating SAH and IVH. However, no study has assessed the radiodensity within the ventricular system in aneurysmal SAH patients with IVH. Prior studies have suggested that hemorrhage with a higher radiodensity, as measured by CT Hounsfield units, can cause more irritation to brain parenchyma. Therefore, the authors set out to investigate the relationship between the overall radiodensity of the ventricular system in aneurysmal SAH patients with IVH and their clinical outcome scores. METHODS The authors reviewed the records of 101 patients who were admitted to their institution with aneurysmal SAH and IVH between January 2011 and July 2015. The following data were collected: age, sex, Glasgow Coma Scale (GCS) score, Hunt and Hess grade, extent of SAH (none, thin, or thick/localized), aneurysm location, and Glasgow Outcome Scale (GOS) score. To evaluate the ventricular radiodensity, the initial head CT scan was loaded into OsiriX MD. The ventricular system was manually selected as the region of interest (ROI) through all pertinent axial slices. After this, an averaged ventricular radiodensity was calculated from the ROI by the software. GOS scores were dichotomized as 1-3 and 4-5 subgroups for analysis. RESULTS On univariate analysis, younger age, higher GCS score, lower Hunt and Hess grade, and lower ventricular radiodensity significantly correlated with better GOS scores (all p < 0.05). Subsequent multivariate analysis yielded age (OR 0.936, 95% CI 0.895-0.979), GCS score (OR 3.422, 95% CI 1.9-6.164), and ventricular density (OR 0.937, 95% CI 0.878-0.999) as significant independent predictors (p < 0.05). A receiver operating characteristic curve yielded 12.7 HU (area under the curve 0.625, p = 0.032, sensitivity = 0.591, specificity = 0.596) as threshold between GOS scores of 1-3 and 4-5. CONCLUSIONS This study suggests that the ventricular radiodensity in aneurysmal SAH patients with IVH, along with GCS score and age, may serve as a predictor of clinical outcome.

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.

The Role of HMGB1 in Pial Arteriole Dilating Reactivity following Subarachnoid Hemorrhage in Rats

High-mobility group box 1 protein (HMGB1) has been implicated in inflammatory responses, and is also associated with cerebral vasospasm after subarachnoid hemorrhage (SAH). However, there are no direct evident links between HMGB1 and cerebral vasospasm. We therefore investigated the effects of HMGB1 on pial arteriole reactivity following SAH in rats. We initially found that SAH induced a significant decrease in pial arteriole dilating responses to sciatic nerve stimulation (SNS), hypercapnia (CO2), and the topical suffusion of acetylcholine (ACh), adenosine (ADO), and s-nitroso-N-acetylpenicillamine (SNAP) over a 7-day period after SAH. The percent change of arteriolar diameter was decreased to the lowest point at 48 h after SAH, in response to dilating stimuli (i.e., it decreased from 41.0 ± 19.0% in the sham group to 11.00 ± 0.70% after SNS) (n = 5, p < 0.01). HMGB1 infusion in the lateral ventricle in normal rats for 48 h did not change the pial arteriole dilating response. In addition, inhibitors of HMGB1-receptor for advanced glycation end-product or HMGB1-toll-like receptor 2/4 interaction, or the HMBG1 antagonist did not improve pial arteriole reactivity 48 h after SAH. These findings suggest that HMGB1 may not be a major player in cerebral vascular dilating dysfunction after SAH.

High-Mobility Group Box 1 (HMGB1) Is Elevated Systemically in Persons with Acute or Chronic Traumatic Spinal Cord Injury

Inflammation in traumatic spinal cord injury (SCI) has been proposed to promote damage acutely and oppose functional recovery chronically. However, we do not yet understand the signals that initiate or prolong inflammation in persons with SCI. High-Mobility Group Box 1 (HMGB1) is a potent systemic inflammatory cytokine-or damage-associated molecular pattern molecule (DAMP)-studied in a variety of clinical settings. It is elevated in pre-clinical models of traumatic spinal cord injury (SCI), where it promotes secondary injury, and strategies that block HMGB1 improve functional recovery. To investigate the potential translational relevance of these observations, we measured HMGB1 in plasma from adults with acute (≤ 1 week post-SCI, n = 16) or chronic (≥ 1 year post-SCI, n = 47) SCI. Plasma from uninjured persons (n = 51) served as controls for comparison. In persons with acute SCI, average HMGB1 levels were significantly elevated within 0-3 days post-injury (6.00 ± 1.8 ng/mL, mean ± standard error of the mean [SEM]) or 4-7 (6.26 ± 1.3 ng/mL, mean ± SEM), compared with controls (1.26 ± 0.24 ng/mL, mean ± SEM; p ≤ 0.001 and p ≤ 0.01, respectively). In persons with chronic SCI who were injured for 15 ± 1.5 years (mean ± SEM), HMGB1 also was significantly elevated, compared with uninjured persons (3.7 ± 0.69 vs. 1.26 ± 0.24 ng/mL, mean ± SEM; p ≤ 0.0001). Together, these data suggest that HMGB1 may be a common, early, and persistent danger signal promoting inflammation in individuals with SCI.

Blood/Brain Biomarkers of Inflammation After Stroke and Their Association With Outcome: From C-Reactive Protein to Damage-Associated Molecular Patterns

Stroke represents one of the most important causes of disability and death in developed countries. However, there is a lack of prognostic tools in clinical practice to monitor the neurological condition and predict the final outcome. Blood biomarkers have been proposed and studied in this indication; however, no biomarker is currently used in clinical practice. The stroke-related neuroinflammatory processes have been associated with a poor outcome in stroke, as well as with poststroke complications. In this review, we focus on the most studied blood biomarkers of this inflammatory processes, cytokines, and C-reactive protein, evaluating its association with outcome and complications in stroke through the literature, and performing a systematic review on the association of C-reactive protein and functional outcome after stroke. Globally, we identified uncertainty with regard to the association of the evaluated biomarkers with stroke outcome, with little added value on top of clinical predictors such as age or stroke severity, which makes its implementation unlikely in clinical practice for global outcome prediction. Regarding poststroke complications, despite being more practical scenarios in which to make medical decisions following a biomarker prediction, not many studies have been performed, although there are now some candidates for prediction of poststroke infections. Finally, as potential new candidates, we reviewed the pathophysiological actions of damage-associated molecular patterns as triggers of the neuroinflammatory cascade of stroke, and their possible use as biomarkers.

Inflammasome Proteins in Cerebrospinal Fluid of Patients with Subarachnoid Hemorrhage are Biomarkers of Early Brain Injury and Functional Outcome

BACKGROUND

Aneurysmal subarachnoid hemorrhage (SAH) remains a devastating disease with significant morbidity and mortality. To date, clinical variables are still used to evaluate injury severity and prognosis. This study was designed to investigate the role of cerebrospinal fluid (CSF) inflammasome proteins as laboratory-based biomarkers of brain injury severity and outcome in SAH patients.

METHODS

Ten control patients and 24 SAH patients were prospectively enrolled in this study. CSF samples were collected within 72 hours after SAH. Levels of inflammasome proteins in the CSF, including NLRP1, ASC, and caspase-1 were analyzed.

RESULTS

Immunoblot analysis exhibited that levels of NLRP1, ASC and caspase-1 were elevated in the CSF of SAH patients (P < 0.0001, P = 0.0178, and P < 0.0001, respectively). In the group of SAH patients, these inflammasome proteins were significantly higher in the patients with cerebral edema on computed tomographic scans (P = 0.0002, P = 0.0005, and P = 0.0004, respectively), and in the patients with acute hydrocephalus (P = 0.0009, P = 0.00017, and P = 0.0016, respectively). Higher levels of inflammasome proteins were associated with severe SAH and poor outcome 3 months after the SAH. High level of NLRP1 was the independent risk factor of poor outcome after SAH (P = 0.049, odds ratio = 1.730).

CONCLUSIONS

Inflammasome proteins are potential biomarkers to assess early brain injury and to predict functional outcome after SAH.