Elucidating novel mechanisms of brain injury following subarachnoid hemorrhage: an emerging role for neuroproteomics

Neuroimmune and neuroinflammation response for traumatic brain injury

Traumatic brain injury (TBI) is one of the major diseases leading to mortality and disability, causing a serious disease burden on individuals' ordinary lives as well as socioeconomics. In primary injury, neuroimmune and neuroinflammation are both responsible for the TBI. Besides, extensive and sustained injury induced by neuroimmune and neuroinflammation also prolongs the course and worsens prognosis of TBI. Therefore, this review aims to explore the role of neuroimmune, neuroinflammation and factors associated them in TBI as well as the therapies for TBI. Thus, we conducted by searching PubMed, Scopus, and Web of Science databases for articles published between 2010 and 2023. Keywords included "traumatic brain injury," "neuroimmune response," "neuroinflammation," "astrocytes," "microglia," and "NLRP3." Articles were selected based on relevance and quality of evidence. On this basis, we provide the cellular and molecular mechanisms of TBI-induced both neuroimmune and neuroinflammation response, as well as the different factors affecting them, are introduced based on physiology of TBI, which supply a clear overview in TBI-induced chain-reacting, for a better understanding of TBI and to offer more thoughts on the future therapies for TBI.

Clinical Potential of Immunotherapies in Subarachnoid Hemorrhage Treatment: Mechanistic Dissection of Innate and Adaptive Immune Responses

Subarachnoid hemorrhage (SAH), classified as a medical emergency, is a devastating and severe subtype of stroke. SAH induces an immune response, which further triggers brain injury; however, the underlying mechanisms need to be further elucidated. The current research is predominantly focused on the production of specific subtypes of immune cells, especially innate immune cells, post-SAH onset. Increasing evidence suggests the critical role of immune responses in SAH pathophysiology; however, studies on the role and clinical significance of adaptive immunity post-SAH are limited. In this present study, we briefly review the mechanistic dissection of innate and adaptive immune responses post-SAH. Additionally, we summarized the experimental studies and clinical trials of immunotherapies for SAH treatment, which may form the basis for the development of improved therapeutic approaches for the clinical management of SAH in the future.

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).

Exosomes in subarachnoid hemorrhage: A scoping review

INTRODUCTION

Vasospasm is a common complication following subarachnoid hemorrhage (SAH), causing increased ischemia and tissue injury, and is implicated as a major risk factor for poor outcomes. The success of current treatments for vasospasm is limited, with limited efficacy and unclear clinical benefits. Exosomes, vesicles that carry small molecules such as miRNA, have been theorized as a potential vasospasm treatment. In this study, we aim to survey the current literature discussing the role of exosomes in the setting of SAH.

METHODS

Following PRISMA guidelines, we performed a scoping review evaluating the role of exosomes in the treatment of SAH. The search was conducted using PubMed and Scopus, and all original research papers studying exosomal profiles of SAH research subjects or SAH therapy were eligible for inclusion.

RESULTS

After screening and full text review, seven papers were selected for final inclusion. Of these, two studies analyzed the expression profile of endogenous exosomes after SAH. Four papers identified and characterized miRNA-based exosomal therapies to attenuate early brain injury (EBI) after SAH. One paper discussed the role of protein overexpression in exosome delivery of miRNA for EBI after SAH. Interestingly, all identified papers studying exosomal therapy demonstrated anti-apoptotic or anti-inflammatory effects of miRNA exosomes acting via the BDNF/TrkB/CREB or HDAC3/NF-κB pathways.

CONCLUSION

Identified studies demonstrate potential neuroprotective benefits of miRNA-based exosomal treatment of EBI and SAH. Findings warrant further research investigating the anti-inflammatory and anti-apoptotic role of exosomal miRNA delivery in SAH models, specifically targeting the common pathway identified by the authors.

Microglia and Post-Subarachnoid Hemorrhage Vasospasm: Review of Emerging Mechanisms and Treatment Modalities

Vasospasm is a potentially severe complication of subarachnoid hemorrhage. It can be attributed to neuroinflammation and the robust recruitment of microglia. Emerging evidence has linked this sustained inflammation to the development of delayed cerebral ischemia following subarachnoid hemorrhage. In this focused review, we provide an overview of the historical understanding of vasospasm. We then delve into the role of neuroinflammation and the activation of microglia. These activated microglia releases a host of inflammatory cytokines contributing to an influx of peripheral macrophages. This thereby opens a new and innovative treatment strategy to prevent vasospasm. Pre-clinical work has been promising, and the transition to clinical trials is warranted. Finally, some of the key mechanistic targets are outlined with emphasis on translation. This review will serve as a catalyst for researchers and clinicians alike in the quest to improve treatment options for vasospasm.

The Cerebrospinal Fluid Proteomic Response to Traumatic and Nontraumatic Acute Brain Injury: A Prospective Study

BACKGROUND

Quantitative analysis of ventricular cerebrospinal fluid (vCSF) proteins following acute brain injury (ABI) may help identify pathophysiological pathways and potential biomarkers that can predict unfavorable outcome.

METHODS

In this prospective proteomic analysis study, consecutive patients with severe ABI expected to require intraventricular catheterization for intracranial pressure (ICP) monitoring for at least 5 days and patients without ABI admitted for elective clipping of an unruptured cerebral aneurysm were included. vCSF samples were collected within the first 24 h after ABI and ventriculostomy insertion and then every 24 h for 5 days. In patients without ABI, a single vCSF sample was collected at the time of elective clipping. Data-independent acquisition and sequential window acquisition of all theoretical spectra (SWATH) mass spectrometry were used to compare differences in protein expression in patients with ABI and patients without ABI and in patients with traumatic and nontraumatic ABI. Differences in protein expression according to different ICP values, intensive care unit outcome, subarachnoid hemorrhage (SAH) versus traumatic brain injury (TBI), and good versus poor 3-month functional status (assessed by using the Glasgow Outcome Scale) were also evaluated. vCSF proteins with significant differences between groups were compared by using linear models and selected for gene ontology analysis using R Language and the Panther database.

RESULTS

We included 50 patients with ABI (SAH n = 23, TBI n = 15, intracranial hemorrhage n = 6, ischemic stroke n = 3, others n = 3) and 12 patients without ABI. There were significant differences in the expression of 255 proteins between patients with and without ABI (p < 0.01). There were intraday and interday differences in expression of seven proteins related to increased inflammation, apoptosis, oxidative stress, and cellular response to hypoxia and injury. Among these, glial fibrillary acidic protein expression was higher in patients with ABI with severe intracranial hypertension (ICH) (ICP ≥ 30 mm Hg) or death compared to those without (log 2 fold change: + 2.4; p < 0.001), suggesting extensive primary astroglial injury or death. There were differences in the expression of 96 proteins between patients with traumatic and nontraumatic ABI (p < 0.05); intraday and interday differences were observed for six proteins related to structural damage, complement activation, and cholesterol metabolism. Thirty-nine vCSF proteins were associated with an increased risk of severe ICH (ICP ≥ 30 mm Hg) in patients with traumatic compared with nontraumatic ABI (p < 0.05). No significant differences were found in protein expression between patients with SAH versus TBI or between those with good versus poor 3-month Glasgow Outcome Scale score.

CONCLUSIONS

Dysregulated vCSF protein expression after ABI may be associated with an increased risk of severe ICH and death.

The effect of clopidogrel and aspirin on the severity of traumatic brain injury in a rat model

Traumatic Brain Injury (TBI) is one of the leading causes of death and disability worldwide. Aspirin (ASA) and clopidogrel (CLOP) are antiplatelet agents that inhibit platelet aggregation. They are implicated in worsening the intracerebral haemorrhage (ICH) risk post-TBI. However, antiplatelet drugs may also exert a neuroprotective effect post-injury. We determined the impact of aspirin and clopidogrel treatment, alone or in combination, on ICH and brain damage in an experimental rat TBI model. We assessed changes in platelet aggregation and measured serum thromboxane by enzyme immune assay. We also explored a panel of brain damage and apoptosis biomarkers by immunoblotting. Rats were treated with aspirin and/or clopidogrel for 48 h prior to TBI and sacrificed 48 h post-injury. In rats treated with antiplatelet agents prior to TBI, platelet aggregation was completely inhibited, and serum thromboxane was significantly decreased, compared to the TBI group without treatment. TBI increases UCHL-1 and GFAP, but decreases hexokinase expression compared to the non-injured controls. All groups treated with antiplatelet drugs prior to TBI had decreased UCH-L1 and GFAP serum levels compared to the TBI untreated group. Furthermore, the ASA and CLOP single treatments increased the hexokinase serum levels. We confirmed that αII-spectrin cleavage increased post-TBI, with the highest cleavage detected in CLOP-treated rats. Aspirin and/or clopidogrel treatment prior to TBI is a double-edged sword that exerts a dual effect post-injury. On one hand, ASA and CLOP single treatments increase the post-TBI ICH risk, with a further detrimental effect from the ASA + CLOP treatment. On the other hand, ASA and/or CLOP treatments are neuroprotective and result in a favourable profile of TBI injury markers. The ICH risk and the neuroprotection benefits from antiplatelet therapy should be weighed against each other to ameliorate the management of TBI patients.

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.

AMPK induces regulatory innate lymphoid cells after traumatic brain injury

The CNS is regarded as an immunoprivileged organ, evading routine immune surveillance; however, the coordinated development of immune responses profoundly influences outcomes after brain injury. Innate lymphoid cells (ILCs) are cytokine-producing cells that are critical for the initiation, modulation, and resolution of inflammation, but the functional relevance and mechanistic regulation of ILCs are unexplored after acute brain injury. We demonstrate increased proliferation of all ILC subtypes within the meninges for up to 1 year after experimental traumatic brain injury (TBI) while ILCs were present within resected dura and elevated within cerebrospinal fluid (CSF) of moderate-to-severe TBI patients. In line with energetic derangements after TBI, inhibition of the metabolic regulator, AMPK, increased meningeal ILC expansion, whereas AMPK activation suppressed proinflammatory ILC1/ILC3 and increased the frequency of IL-10-expressing ILC2 after TBI. Moreover, intracisternal administration of IL-33 activated AMPK, expanded ILC2, and suppressed ILC1 and ILC3 within the meninges of WT and Rag1-/- mice, but not Rag1-/- IL2rg-/- mice. Taken together, we identify AMPK as a brake on the expansion of proinflammatory, CNS-resident ILCs after brain injury. These findings establish a mechanistic framework whereby immunometabolic modulation of ILCs may direct the specificity, timing, and magnitude of cerebral immunity.

Soluble receptor for advanced glycation end products as a biomarker of symptomatic vasospasm in subarachnoid hemorrhage

OBJECTIVE

The receptor for advanced glycation end products (RAGE) is a membrane protein associated with the induction of oxidative stress and inflammation in several pathological conditions. Previous studies have demonstrated that soluble RAGE (sRAGE) acts as a decoy for RAGE and protects cells against RAGE-mediated injury. The authors and other groups have reported that the expression of RAGE increases after brain ischemia and subarachnoid hemorrhage (SAH), and deletion of RAGE or overexpression of sRAGE improves neuronal survival. It has also been demonstrated that the plasma sRAGE level could be a predictor of the outcome after ischemic stroke. This study aimed to evaluate plasma sRAGE as a biomarker for symptomatic vasospasm (SVS) in SAH patients, as well as a rat model.

METHODS

The authors measured and compared plasma sRAGE levels in 27 SAH patients (7 with SVS and 20 without SVS) from day 5 to day 14 post-SAH. They also examined plasma sRAGE levels and expression of RAGE and heme oxygenase-1 (HO-1) in a rat SAH model.

RESULTS

The relative plasma sRAGE levels were significantly lower in the SVS group than in the non-SVS group of patients. A cut-off value of 0.84 for predicting SVS was considered to be appropriate for the relative plasma sRAGE levels on day 7 versus day 5. In the rat SAH model, plasma sRAGE levels were significantly lower than those in sham-treated rats, and the expressions of RAGE and HO-1 were enhanced in the SAH group compared with the non-SAH group.

CONCLUSIONS

Plasma sRAGE levels can be used as a potential biomarker for predicting SVS after SAH.

Revisiting Traumatic Brain Injury: From Molecular Mechanisms to Therapeutic Interventions

Studying the complex molecular mechanisms involved in traumatic brain injury (TBI) is crucial for developing new therapies for TBI. Current treatments for TBI are primarily focused on patient stabilization and symptom mitigation. However, the field lacks defined therapies to prevent cell death, oxidative stress, and inflammatory cascades which lead to chronic pathology. Little can be done to treat the mechanical damage that occurs during the primary insult of a TBI; however, secondary injury mechanisms, such as inflammation, blood-brain barrier (BBB) breakdown, edema formation, excitotoxicity, oxidative stress, and cell death, can be targeted by therapeutic interventions. Elucidating the many mechanisms underlying secondary injury and studying targets of neuroprotective therapeutic agents is critical for developing new treatments. Therefore, we present a review on the molecular events following TBI from inflammation to programmed cell death and discuss current research and the latest therapeutic strategies to help understand TBI-mediated secondary injury.

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.

Neutrophil extracellular traps exacerbate neurological deficits after traumatic brain injury

Traumatic brain injury (TBI) is a major cause of mortality and morbidity. Preventative measures reduce injury incidence and/or severity, yet one-third of hospitalized patients with TBI die from secondary pathological processes that develop during supervised care. Neutrophils, which orchestrate innate immune responses, worsen TBI outcomes via undefined mechanisms. We hypothesized that formation of neutrophil extracellular traps (NETs), a purported mechanism of microbial trapping, exacerbates acute neurological injury after TBI. NET formation coincided with cerebral hypoperfusion and tissue hypoxia after experimental TBI, while elevated circulating NETs correlated with reduced serum deoxyribonuclease-1 (DNase-I) activity in patients with TBI. Functionally, Toll-like receptor 4 (TLR4) and the downstream kinase peptidylarginine deiminase 4 (PAD4) mediated NET formation and cerebrovascular dysfunction after TBI. Last, recombinant human DNase-I degraded NETs and improved neurological function. Thus, therapeutically targeting NETs may provide a mechanistically innovative approach to improve TBI outcomes without the associated risks of global neutrophil depletion.

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.

Inflammatory Responses Induced by the Rupture of Intracranial Aneurysms Are Modulated by miRNAs

Influence of an intracranial aneurysm (IA) rupture on the expression of miRNAs and the potential significance of the resulting changes remains poorly understood. We aimed to characterize the response to the IA rupture through the analysis of miRNAs in peripheral blood cells. Expression of small RNAs was investigated using deep transcriptome sequencing in patients in the acute phase of an IA rupture (first 72 h), in the chronic phase (3–15 months), and controls. A functional analysis and the potential interactions between miRNAs and target genes were investigated. We also measured the levels of proteins that were influenced by regulated miRNAs. We found that 106 mature miRNAs and 90 miRNA precursors were differentially expressed among the groups. The regulated miRNAs were involved in a variety of pathways, and the top pathway involved cytokine-cytokine receptor interactions. The identified miRNAs targeted the inflammatory factors HMGB1 and FASLG. Changes in their expression were detected at the mRNA and protein levels. IA rupture strongly influences the transcription profiles in peripheral blood cells. The regulated miRNAs were involved in the control of immune cell homeostasis. In summary, these results may aid in the elucidation of the molecular mechanisms that orchestrate the inflammatory response to IA rupture.

CSF Proteomics of Patients with Hydrocephalus and Subarachnoid Haemorrhage

Background

The pathophysiology of brain injury following aneurysmal subarachnoid haemorrhage (SAH) is associated with numerous mediators. The aim of the study is to analyse protein changes after SAH in cerebrospinal fluid (CSF) using mass spectrometry (MS).

Methods

CSF samples were obtained from forty-four control subjects, seven good outcome and ten poor outcome SAH patients. CSF samples were collected at specific time intervals after SAH (days 1, 5 and 10). MALDI-TOF (Matrix Assisted Laser Desorption/Ionization Time-of-Flight) and ClinProTools software were utilised for MS, MS/MS (Mass Spectrometry) spectra collection and analysis. Selected masses were identified. The MALDI-TOF profiling experiments allowed for the targeted selection of potential markers in SAH. The study was performed in three steps by comparison of CSF samples: (1) from the control group and SAH patients (both good and poor outcome groups); (2) collected on days 1, 5 and 10 within the groups of poor SAH and good SAH patients, respectively; (3) from poor outcome SAH and good outcome patients at days 1, 5 and 10.

Results

15 new proteins whose CSF level is alternated by SAH presence, SAH treatment outcome and time passed since aneurysm rupture were identified.

Conclusions

We demonstrated new proteins which might play a role in different stages of subarachnoid haemorrhage and could be a new target for further investigation.

Systemic High-Mobility Group Box-1: A Novel Predictive Biomarker for Cerebral Vasospasm in Aneurysmal Subarachnoid Hemorrhage

OBJECTIVES

To investigate the release of proinflammatory damage-associated molecular pattern molecule "high-mobility group box-1" in the serum of patients after aneurysmal subarachnoid hemorrhage and its association with cerebral vasospasm.

DESIGN

Retrospective observational study.

SETTING

University hospital.

PATIENTS

Aneurysmal subarachnoid hemorrhage patients admitted within 24 hours of ictus.

INTERVENTIONS

Standard subarachnoid hemorrhage treatment after clipping or coiling of aneurysm.

MEASUREMENTS AND MAIN RESULTS

We enrolled 53 aneurysmal subarachnoid hemorrhage patients from which peripheral venous blood was withdrawn on days 1, 3, 5, 7, 9, 11, and 13 and once from the controls to obtain the serum. Serum high-mobility group box-1 concentration was quantified by enzyme-linked immunosorbent assay. Serum interleukin-6 and peripheral blood leukocytes were also determined over the first 2 weeks after subarachnoid hemorrhage. Patients' data were recorded prospectively. Serum high-mobility group box-1 was significantly elevated in subarachnoid hemorrhage patients from day 1 to day 13 when compared with nonsubarachnoid hemorrhage patients (p < 0.05). Patients with cerebral vasospasm showed significantly higher high-mobility group box-1 starting from day 1 to day 13 when compared with patients without cerebral vasospasm. Cumulative levels of high-mobility group box-1 showed significant correlation with peripheral blood leukocytes and interleukin-6 levels (p < 0.05). Receiver operating characteristic curve analysis showed that serum high-mobility group box-1 level at admission may be a predictive biomarker for cerebral vasospasm with a sensitivity of 59% and a specificity of 82% at a cutoff value of 5.6 ng/mL.

CONCLUSIONS

Serum high-mobility group box-1 is differentially elevated after subarachnoid hemorrhage. Serum high-mobility group box-1 levels were elevated early after subarachnoid hemorrhage (day 1) and remained significantly high until day 13 in patients who developed cerebral vasospasm. Our data suggest that serum high-mobility group box-1 may be a predictive biomarker for the detection of CVS.

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.

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.

White matter damage after traumatic brain injury: A role for damage associated molecular patterns

Traumatic brain injury (TBI) is a leading cause of mortality and long-term morbidity worldwide. Despite decades of pre-clinical investigation, therapeutic strategies focused on acute neuroprotection failed to improve TBI outcomes. This lack of translational success has necessitated a reassessment of the optimal targets for intervention, including a heightened focus on secondary injury mechanisms. Chronic immune activation correlates with progressive neurodegeneration for decades after TBI; however, significant challenges remain in functionally and mechanistically defining immune activation after TBI. In this review, we explore the burgeoning evidence implicating the acute release of damage associated molecular patterns (DAMPs), such as adenosine 5'-triphosphate (ATP), high mobility group box protein 1 (HMGB1), S100 proteins, and hyaluronic acid in the initiation of progressive neurological injury, including white matter loss after TBI. The role that pattern recognition receptors, including toll-like receptor and purinergic receptors, play in progressive neurological injury after TBI is detailed. Finally, we provide support for the notion that resident and infiltrating macrophages are critical cellular targets linking acute DAMP release with adaptive immune responses and chronic injury after TBI. The therapeutic potential of targeting DAMPs and barriers to clinical translational, in the context of TBI patient management, are discussed.

RNA as a stroke biomarker

A biomarker to aid in the diagnosis of ischemic stroke and its causes would be of value in acute clinical practice. It could have applications to aid in acute stroke treatment decisions for tissue plasminogen activator and/or the triage to endovascular therapy. A stroke biomarker may also be useful to identify stroke etiology and guide stroke prevention treatments. This review provides an overview of RNA as a novel biomarker for the diagnosis and assessment of ischemic stroke. Topics addressed include RNA to identify acute ischemic stroke; RNA to identify transient ischemic attack; RNA to predict large vessel, cardioembolic and small vessel cause of stroke; and RNA to predict risk of tissue plasminogen activator related hemorrhagic transformation. Emerging methods to measure RNA as a point-of-care assay include microfluidics sorting and electrochemical sensors.

Long-Lasting Cerebral Vasospasm, Microthrombosis, Apoptosis and Paravascular Alterations Associated with Neurological Deficits in a Mouse Model of Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH) is a devastating disease with high mortality and morbidity. Long-term cognitive and sensorimotor deficits are serious complications following SAH but still not well explained and described in mouse preclinical models. The aim of our study is to characterize a well-mastered SAH murine model and to establish developing pathological mechanisms leading to cognitive and motor deficits, allowing identification of specific targets involved in these long-term troubles. We hereby demonstrate that the double blood injection model of SAH induced long-lasting large cerebral artery vasospasm (CVS), microthrombosis formation and cerebral brain damage including defect in potential paravascular diffusion. These neurobiological alterations appear to be associated with sensorimotor and cognitive dysfunctions mainly detected 10 days after the bleeding episode. In conclusion, this characterized model of SAH in mice, stressing prolonged neurobiological pathological mechanisms and associated sensitivomotor deficits, will constitute a validated preclinical model to better decipher the link between CVS, long-term cerebral apoptosis and cognitive disorders occurring during SAH and to allow investigating novel therapeutic approaches in transgenic mice.

Activation of Myeloid TLR4 Mediates T Lymphocyte Polarization after Traumatic Brain Injury

Traumatic brain injury (TBI) is a major public health issue, producing significant patient mortality and poor long-term outcomes. Increasing evidence suggests an important, yet poorly defined, role for the immune system in the development of secondary neurologic injury over the days and weeks following a TBI. In this study, we tested the hypothesis that peripheral macrophage infiltration initiates long-lasting adaptive immune responses after TBI. Using a murine controlled cortical impact model, we used adoptive transfer, transgenic, and bone marrow chimera approaches to show increased infiltration and proinflammatory (classically activated [M1]) polarization of macrophages for up to 3 wk post-TBI. Monocytes purified from the injured brain stimulated the proliferation of naive T lymphocytes, enhanced the polarization of T effector cells (T_H1/T_H17), and decreased the production of regulatory T cells in an MLR. Similarly, elevated T effector cell polarization within blood and brain tissue was attenuated by myeloid cell depletion after TBI. Functionally, C3H/HeJ (TLR4 mutant) mice reversed M1 macrophage and T_H1/T_H17 polarization after TBI compared with C3H/OuJ (wild-type) mice. Moreover, brain monocytes isolated from C3H/HeJ mice were less potent stimulators of T lymphocyte proliferation and T_H1/T_H17 polarization compared with C3H/OuJ monocytes. Taken together, our data implicate TLR4-dependent, M1 macrophage trafficking/polarization into the CNS as a key mechanistic link between acute TBI and long-term, adaptive immune responses.

Impact of High-Mobility Group Box 1 Polymorphism on Delayed Cerebral Ischemia After Aneurysmal Subarachnoid Hemorrhage

BACKGROUND AND OBJECTIVE

The high-mobility group box 1 (HMGB1) protein is a eukaryotic, ubiquitously expressed protein that serves as a biomarker for various diseases and is involved in the promotion of a proinflammatory response to cell injury. In aneurysmal subarachnoid hemorrhage (aSAH), increased HMGB1 levels have been linked to poor outcome and an increased risk for cerebral vasospasm. The role of HMGB1 polymorphisms in aSAH has not been previously investigated.

METHODS

Patients with aSAH and controls enrolled in the prospective, 2-center CARAS (Cerebral Aneurysm Renin Angiotensin System) study were evaluated. The 3814 C/G HMGB1 single nucleotide polymorphism (SNP) rs2249825 was detected using 5'exonuclease (Taqman) genotyping assays from blood samples from patients with aSAH and controls. Associations between aSAH and its clinical sequelae with the HMGB1 SNP were assessed.

RESULTS

Samples from 149 patients with aSAH and 50 controls were available for analysis. No increased risk for aSAH associated with the SNP was found compared with the control group. Delayed cerebral ischemia (DCI) was defined as a cerebral infarction at the time of discharge from the intensive care unit and identified in 21.2% of patients with aSAH. In multivariable logistic regression analysis, the G allele of rs2249825 was independently associated with DCI (odds ratio, 5.695; 95% confidence interval, 1.804-17.975; P = 0.003).

CONCLUSIONS

The minor allele G of rs2249825 was associated with an increased risk for DCI, or cerebral infarction, after aSAH. This finding may be attributable to an increased HMGB1 protein expression in these patients.

The effect of subarachnoid erythrocyte lysate on brain injury: a preliminary study

We found that more severe brain injury was caused by subarachnoid erythrocyte lysate, and inflammation associated with Prx2 might be involved in mechanism of brain injury.

Abundant erythrocytes remain and lyse partially in the subarachnoid space after severe subarachnoid haemorrhage (SAH). But the effect of subarachnoid erythrocyte lysate on brain injury is still not completely clear. In this study, autologous erythrocytes (the non-lysate group) and their lysate (the lysate group) were injected separately into the cistern magna of rabbits to induce a model of experimental SAH, although the control group received isotonic sodium chloride solution instead of erythrocyte solution. Results showed that vasospasm of the basilar artery was observed at 72 h after experimental SAH, but there was no significant difference between the non-lysate group and the lysate group. Brain injury was more severe in the lysate group than in the non-lysate group. Meanwhile, the levels of peroxiredoxin 2 (Prx2), IL-6 and TNF-α in brain cortex and in CSF were significantly higher in the lysate group than those in the non-lysate group. These results demonstrated that brain injury was more likely to be caused by erythrocyte lysate than by intact erythrocytes in subarachnoid space, and inflammation response positively correlated with Prx2 expression might be involved in mechanism of brain injury after SAH.

Deciphering glycomics and neuroproteomic alterations in experimental traumatic brain injury: Comparative analysis of aspirin and clopidogrel treatment

As populations age, the number of patients sustaining traumatic brain injury (TBI) and concomitantly receiving preinjury antiplatelet therapy such as aspirin (ASA) and clopidogrel (CLOP) is rising. These drugs have been linked with unfavorable clinical outcomes following TBI, where the exact mechanism(s) involved are still unknown. In this novel work, we aimed to identify and compare the altered proteome profile imposed by ASA and CLOP when administered alone or in combination, prior to experimental TBI. Furthermore, we assessed differential glycosylation PTM patterns following experimental controlled cortical impact model of TBI, ASA, CLOP, and ASA + CLOP. Ipsilateral cortical brain tissues were harvested 48 h postinjury and were analyzed using an advanced neuroproteomics LC-MS/MS platform to assess proteomic and glycoproteins alterations. Of interest, differential proteins pertaining to each group (22 in TBI, 41 in TBI + ASA, 44 in TBI + CLOP, and 34 in TBI + ASA + CLOP) were revealed. Advanced bioinformatics/systems biology and clustering analyses were performed to evaluate biological networks and protein interaction maps illustrating molecular pathways involved in the experimental conditions. Results have indicated that proteins involved in neuroprotective cellular pathways were upregulated in the ASA and CLOP groups when given separately. However, ASA + CLOP administration revealed enrichment in biological pathways relevant to inflammation and proinjury mechanisms. Moreover, results showed differential upregulation of glycoproteins levels in the sialylated N-glycans PTMs that can be implicated in pathological changes. Omics data obtained have provided molecular insights of the underlying mechanisms that can be translated into clinical bedside settings.

Antiseptic effect of vicenin-2 and scolymoside from Cyclopia subternata (honeybush) in response to HMGB1 as a late sepsis mediator in vitro and in vivo

Cyclopia subternata is a medicinal plant commonly used in traditional medicine to relieve pain. In this study, we investigated the antiseptic effects and underlying mechanisms of vicenin-2 and scolymoside, which are 2 active compounds from C. subternata that act against high mobility group box 1 (HMGB1)-mediated septic responses in human umbilical vein endothelial cells (HUVECs) and mice. The antiseptic activities of vicenin-2 and scolymoside were determined by measuring permeability, neutrophil adhesion and migration, and activation of proinflammatory proteins in HMGB1-activated HUVECs and mice. According to the results, vicenin-2 and scolymoside effectively inhibited lipopolysaccharide-induced release of HMGB1, and suppressed HMGB1-mediated septic responses such as hyperpermeability, the adhesion and migration of leukocytes, and the expression of cell adhesion molecules. In addition, vicenin-2 and scolymoside suppressed the production of tumor necrosis factor-α and interleukin 6, and activation of nuclear factor-κB and extracellular regulated kinases 1/2 by HMGB1. Collectively, these results indicate that vicenin-2 and scolymoside could be a potential therapeutic agents for the treatment of various severe vascular inflammatory diseases via inhibition of the HMGB1 signaling pathway.

Cerebral vasospasm

Cerebral vasospasm causes delayed ischemic neurologic deficits after aneurysmal subarachnoid hemorrhage. This is a well-established clinical entity with significant associated morbidity and mortality. The underlying patholphysiology is highly complex and poorly understood. Large-vessel vasospasm, autoregulatory dysfunction, inflammation, genetic predispositions, microcirculatory failure, and spreading cortical depolarization are aspects of delayed neurologic deterioration that have been described in the literature. This article presents a perspective on cerebral vasospasm, as guided by the literature to date, specifically examining the mechanism, diagnosis, and treatment of cerebral vasospasm.

The Role of Circulating Tight Junction Proteins in Evaluating Blood Brain Barrier Disruption following Intracranial Hemorrhage

Brain injury after intracranial hemorrhage (ICH) results in significant morbidity and mortality. Blood brain barrier (BBB) disruption is a hallmark of ICH-induced brain injury; however, data mirroring BBB disruption in human ICH are scarce. The aim of this study was to assess the significance of circulating biomarkers in evaluating BBB disruption after ICH. Twenty-two patients with ICH were recruited in this study. Concentrations of the tight junction proteins (TJs) Claudin-5 (CLDN5), Occludin (OCLN), and zonula occludens 1 (ZO-1) and vascular endothelial growth factor (VEGF) and matrix metalloproteinase-9 (MMP-9) were measured by using enzyme-linked immunosorbent assay in serum and cerebrospinal fluid (CSF) samples obtained from patients with ICH. The white blood cell (WBC) count in blood and CSF, albumin (ALB) levels in the CSF (ALBCSF), and the BBB ratio were significantly higher in the ICH than in controls (p < 0.05). Significantly higher levels of CLDN5, OCLN, ZO-1, MMP-9, and VEGF in CSF were observed in the ICH group; these biomarkers were also positively associated with BBB ratio (p < 0.05). Our data revealed that circulating TJs could be considered the potential biomarkers reflecting the integrity of the BBB in ICH.

Subarachnoid Hemorrhage Induces Gliosis and Increased Expression of the Pro-inflammatory Cytokine High Mobility Group Box 1 Protein

Subarachnoid hemorrhage (SAH) following cerebral aneurysm rupture is associated with high rates of morbidity and mortality. Surviving SAH patients often suffer from neurological impairment, yet little is currently known regarding the influence of subarachnoid blood on brain parenchyma. The objective of the present study was to examine the impact of subarachnoid blood on glial cells using a rabbit SAH model. The astrocyte-specific proteins, glial fibrillary acidic protein (GFAP) and S100B, were up-regulated in brainstem from SAH model rabbits, consistent with the development of reactive astrogliosis. In addition to reactive astrogliosis, cytosolic expression of the pro-inflammatory cytokine, high-mobility group box 1 protein (HMGB1) was increased in brain from SAH animals. We found that greater than 90% of cells expressing cytosolic HMGB1 immunostained positively for Iba1, a specific marker for microglia and macrophages. Further, the number of Iba1-positive cells was similar in brain from control and SAH animals, suggesting the majority of these cells were likely resident microglial cells rather than infiltrating macrophages. These observations demonstrate SAH impacts brain parenchyma by activating astrocytes and microglia, triggering up-regulation of the pro-inflammatory cytokine HMGB1.

All's well that transcribes well: non-coding RNAs and post-stroke brain damage

The mammalian genome is replete with various classes of non-coding (nc) RNA genes. Many of them actively transcribe, and their relevance to CNS diseases is just beginning to be understood. CNS is one of the organs in the body that shows very high ncRNAs activity. Recent studies demonstrated that cerebral ischemia rapidly changes the expression profiles of different classes of ncRNAs: including microRNA, long noncoding RNA and piwi-interacting RNA. Several studies further showed that post-ischemic neuronal death and/or plasticity/regeneration can be altered by modulating specific microRNAs. These studies are of interest for therapeutic development as they may contribute to identifying new ncRNA targets that can be modulated to prevent secondary brain damage after stroke.

Fatal hemorrhagic stroke in a Caucasian girl with moyamoya disease

INTRODUCTION

Moyamoya disease (MMD) is an extremely rare neurovascular disorder in Caucasian children. To the best of our knowledge, the aggressive variant including hemorrhagic malignant stroke and consecutive global ischemia has not been reported for this population before.

CASE REPORT

We present the case of an 11-year-old girl with sudden neurological deterioration due to intracerebral hemorrhage with early irruption into the ventricular system. MMD with extensive neovascularization was diagnosed by means of computed tomography and magnetic resonance imaging. Despite immediate ventricular drainage, intracranial pressure increased above the mean arterial pressure resulting in malignant bi-hemispheric ischemia. The girl died within 53 h after admission to hospital.

DISCUSSION

Intracerebral hemorrhage in young patients is often attributed to vascular malformation. This case shows that MMD may constitute a potential diagnosis in the case of sudden neurological deterioration and loss of consciousness, even in previously healthy children.

Trends in treatment and outcomes of pediatric craniopharyngioma, 1975-2011

BACKGROUND

Craniopharyngioma tumors and their treatment can lead to significant long-term morbidity due to their proximity to vital structures. The optimal treatment has been debated for many years. We aimed to review the long-term outcomes of children treated for craniopharyngioma in our institution over the past decade and describe trends in treatment and outcomes over the past 3 decades.

METHODS

Charts of children with craniopharyngioma treated and followed at The Hospital for Sick Children between 2001 and 2011 were reviewed. Data regarding findings at diagnosis, treatment, and long-term outcomes were analyzed. Comparison was made with previously published data from our institution.

RESULTS

Data from 33 patients are included; mean age at treatment, 10.7 ± 4.8 years. In 18 children (55%), the initial surgical approach was tumor cyst decompression with or without adjuvant therapy, compared with only 0-2% in the preceding decades (P < .01). Diabetes insipidus occurred in 55% of children and panhypopituitarism in 58% compared with 88% (P < .01) and 86% (P < .01), respectively, in the previous 10 years. Overall, there was a 36% reduction in the number of children who developed severe obesity compared with the preceding decade. Body mass index at follow-up was associated with body mass index at diagnosis (P = .004) and tumor resection as an initial treatment approach (P = .028).

CONCLUSIONS

A shift in surgical treatment approach away from gross total resection has led to improved endocrine outcomes. This may have beneficial implications for quality of life in survivors.

Relationship between plasma high-mobility group box-1 levels and clinical outcomes of ischemic stroke

PURPOSE

High-mobility group box-1 (HMGB1) is regarded as a central mediator of inflammation and involved in many inflammatory diseases. This study aimed to investigate impact of plasma HMGB1 level on 1-year clinical outcomes of ischemic stroke.

METHODS

Plasma HMGB1 levels of 338 patients were quantified by enzyme-linked immunosorbent assay. The end points were mortality and unfavorable outcome (modified Rankin Scale score>2) after 1 year.

RESULTS

Plasma HMGB1 level emerged as an independent predictor of 1-year clinical outcomes. Its prognostic value was similar to National Institutes of Health Stroke Scale score's. It improved prognostic value of National Institutes of Health Stroke Scale score.

CONCLUSION

Plasma HMGB1 level represents a novel biomarker for predicting 1-year clinical outcomes of ischemic stroke.

Relationship between plasma high mobility group box-1 protein levels and clinical outcomes of aneurysmal subarachnoid hemorrhage

Background

High-mobility group box 1 (HMGB1), originally described as a nuclear protein that binds to and modifies DNA, is now regarded as a central mediator of inflammation by acting as a cytokine. However, the association of HMGB1 in the peripheral blood with disease outcome and cerebrovasospasm has not been examined in patients with aneurysmal subarachnoid hemorrhage.

Methods

In this study, 303 consecutive patients were included. Upon admission, plasma HMGB1 levels were measured by ELISA. The end points were mortality after 1 year, in-hospital mortality, cerebrovasospasm and poor functional outcome (Glasgow Outcome Scale score of 1 to 3) after 1 year.

Results

Upon admission, the plasma HMGB1 level in patients was statistically significantly higher than that in healthy controls. A multivariate analysis showed that the plasma HMGB1 level was an independent predictor of poor functional outcome and mortality after 1 year, in-hospital mortality and cerebrovasospasm. A receiver operating characteristic curve showed that plasma HMGB1 level on admission statistically significantly predicted poor functional outcome and mortality after 1 year, in-hospital mortality and cerebrovasospasm of patients. The area under the curve of the HMGB1 concentration was similar to those of World Federation of Neurological Surgeons (WFNS) score and modified Fisher score for the prediction of poor functional outcome and mortality after 1 year, and in-hospital mortality, but not for the prediction of cerebrovasospasm. In a combined logistic-regression model, HMGB1 improved the area under the curve of WFNS score and modified Fisher score for the prediction of poor functional outcome after 1 year, but not for the prediction of mortality after 1 year, in-hospital mortality, or cerebrovasospasm.

Conclusions

HMGB1 level is a useful, complementary tool to predict functional outcome and mortality after aneurysmal subarachnoid hemorrhage. However, HMGB1 determination does not add to the accuracy of prediction of the clinical outcomes.

Molecular markers and mechanisms of stroke: RNA studies of blood in animals and humans

Whole genome expression microarrays can be used to study gene expression in blood, which comes in part from leukocytes, immature platelets, and red blood cells. Since these cells are important in the pathogenesis of stroke, RNA provides an index of these cellular responses to stroke. Our studies in rats have shown specific gene expression changes 24  hours after ischemic stroke, hemorrhage, status epilepticus, hypoxia, hypoglycemia, global ischemia, and following brief focal ischemia that simulated transient ischemic attacks in humans. Human studies show gene expression changes following ischemic stroke. These gene profiles predict a second cohort with >90% sensitivity and specificity. Gene profiles for ischemic stroke caused by large-vessel atherosclerosis and cardioembolism have been described that predict a second cohort with >85% sensitivity and specificity. Atherosclerotic genes were associated with clotting, platelets, and monocytes, and cardioembolic genes were associated with inflammation, infection, and neutrophils. These gene profiles predicted the cause of stroke in 58% of cryptogenic patients. These studies will provide diagnostic, prognostic, and therapeutic markers, and will advance our understanding of stroke in humans. New techniques to measure all coding and noncoding RNAs along with alternatively spliced transcripts will markedly advance molecular studies of human stroke.

Anacardic acid induces caspase-independent apoptosis and radiosensitizes pituitary adenoma cells

OBJECT

Pituitary adenomas, which are common intracranial tumors, are associated with significant patient morbidity due to hormone secretion or mass effect or as a complication of therapy. Epigenetic regulation has emerged as an important component of malignant tumor pathogenesis, although the contribution in the progression of benign pituitary tumors remains largely unexplored. The present study evaluates the effect of anacardic acid (6-pentadecyl salicylic acid), a natural histone acetyltransferase inhibitor, on pituitary adenoma cells.

METHODS

The concentration- and time-dependent effects of anacardic acid on the viability of GH3 and MMQ pituitary adenoma cells were determined by 3-(4,5-dimethylthiazoyl-2-yl)-2,5-diphenyltetrazolium bromide assay. Cell cycle phase distribution, protein expression, and percentage of apoptotic cells were assessed by flow cytometry and Western blotting. Colony forming assays were used to study the radiosensitizing effect of anacardic acid.

RESULTS

The present study identifies a novel antiproliferative and cytotoxic effect of anacardic acid on pituitary adenoma cells. These effects were associated with an increase in poly([adenosine diphosphate]-ribose) polymerase cleavage, sub-G1 arrest, and annexin V staining, consistent with apoptotic cell death; however, the pancaspase inhibitor carbobenzoxy-valyl-alanyl-aspartyl-(O-methyl)-fluoromethylketone failed to reverse anacardic acid-induced cell death, suggesting a possible nonclassical apoptotic mechanism. Anacardic acid also reduced the expression of survivin and X-linked inhibitor of apoptosis protein, antiapoptotic proteins associated with cellular survival and radioresistance, and radiosensitized pituitary adenoma cells.

CONCLUSIONS

These findings warrant further exploration of anacardic acid as a single agent or as an adjunct to radiation therapy for the treatment of pituitary tumors.