Acute-Phase Plasma Pigment Epithelium-Derived Factor Predicting Outcomes after Aneurysmal Subarachnoid Hemorrhage in the Elderly.

Aneurysmal subarachnoid hemorrhage (SAH) has increased with the aging of the population, but the outcome for elderly SAH patients is very poor. Therefore, predicting the outcome is important for determining whether to pursue aggressive treatment. Pigment epithelium-derived factor (PEDF) is a matricellular protein that is induced in the brain, and the plasma levels could be used as a biomarker for the severity of metabolic diseases. This study investigated whether acute-phase plasma PEDF levels could predict outcomes after aneurysmal SAH in the elderly. Plasma samples and clinical variables were collected over 1-3 days, post-SAH, from 56 consecutive elderly SAH patients ≥75 years of age registered in nine regional stroke centers in Japan between September 2013 and December 2016. The samples and variables were analyzed in terms of 3-month outcomes. Acute-phase plasma PEDF levels were significantly elevated in patients with ultimately poor outcomes, and the cutoff value of 12.6 µg/mL differentiated 3-month outcomes with high sensitivity (75.6%) and specificity (80.0%). Acute-phase plasma PEDF levels of ≥12.6 µg/mL were an independent and possibly better predictor of poor outcome than previously reported clinical variables. Acute-phase plasma PEDF levels may serve as the first biomarker to predict 3-month outcomes and to select elderly SAH patients who should be actively treated.

Anti-Apoptotic Effects of AMPA Receptor Antagonist Perampanel in Early Brain Injury After Subarachnoid Hemorrhage in Mice.

This study was aimed to investigate if acute neuronal apoptosis is induced by activation of AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazole propionate) receptors (AMPARs) and inhibited by a clinically available selective AMPAR antagonist and antiepileptic drug perampanel (PER) in subarachnoid hemorrhage (SAH), and if the mechanisms include upregulation of an inflammation-related matricellular protein periostin. Sham-operated and endovascular perforation SAH mice randomly received an administration of 3 mg/kg PER or the vehicle intraperitoneally. Post-SAH neurological impairments and increased caspase-dependent neuronal apoptosis were associated with activation of AMPAR subunits GluA1 and GluA2, and upregulation of periostin and proinflammatory cytokines interleukins-1ß and -6, all of which were suppressed by PER. PER also inhibited post-SAH convulsion-unrelated increases in the total spectral power on video electroencephalogram (EEG) monitoring. Intracerebroventricularly injected recombinant periostin blocked PER's anti-apoptotic effects on neurons. An intracerebroventricular injection of a selective agonist for GluA1 and GluA2 aggravated neurological impairment, neuronal apoptosis as well as periostin upregulation, but did not increase the EEG total spectral power after SAH. A higher dosage (10 mg/kg) of PER had even more anti-apoptotic effects compared with 3 mg/kg PER. Thus, this study first showed that AMPAR activation causes post-SAH neuronal apoptosis at least partly via periostin upregulation. A clinically available AMPAR antagonist PER appears to be neuroprotective against post-SAH early brain injury through the anti-inflammatory and anti-apoptotic effects, independent of the antiepileptic action, and deserves further study.

Cilostazol May Improve Outcomes Even in Patients with Aneurysmal Subarachnoid Hemorrhage Aged 75 Years and Older: Multicenter Cohort Study and Propensity Score-Matched Analyses.

BACKGROUND: The opportunities to treat elderly patients with aneurysmal subarachnoid hemorrhage (aSAH) are increasing globally, but the outcome remains poor. This study seeks to investigate treatment-related factors that can modify functional outcomes in patients with aSAH aged ≥75 years. METHODS: A total of 202 patients with aSAH aged ≥75 years prospectively enrolled in 9 primary stroke centers from 2013 to 2021 were retrospectively analyzed. Clinical variables including treatments for hydrocephalus, angiographic vasospasm, and delayed cerebral ischemia were compared between patients with good (modified Rankin Scale [mRS] score 0-2) and poor (mRS score 3-6) outcomes at 90 days from onset, followed by multivariate analyses to find independent outcome determinants. A modifiable treatment-related variable was evaluated after propensity score matching with adjustments for age, sex, pre-onset mRS score, aSAH severity, and treatment modality. RESULTS: More than half of patients showed World Federation of Neurological Societies grades IV-V on admission. Univariate analyses showed that advanced age, worse pre-onset mRS score, more severe neurologic status on admission, higher modified Fisher grade on admission computed tomography scans, and acute and chronic hydrocephalus were associated with poor outcomes. In contrast, administration of a phosphodiesterase type III inhibitor, cilostazol, was associated with good outcomes in both univariate (P = 0.036) and multivariate analyses (adjusted odds ratio, 0.305; 95% confidence interval, 0.097-0.955; P = 0.042). Propensity score matching analyses showed that patients treated with cilostazol had better outcomes (P = 0.016) with fewer incidences of delayed cerebral infarction (P = 0.008). CONCLUSIONS: Even in patients with aSAH aged ≥75 years, cilostazol administration may lead to better outcomes by suppressing the development of delayed cerebral infarction.

Epidermal Growth Factor Receptor Mediates Neuronal Apoptosis After Subarachnoid Hemorrhage in Mice.

BACKGROUND: Early brain injury including neuronal apoptosis is a main contributor to neurological deterioration after subarachnoid hemorrhage (SAH). This study was aimed to investigate whether EGFR (epidermal growth factor receptor)/NFκB (nuclear factor-kappa B) inducing kinase (NIK)/NFκB (p65 and p50) pathway is involved in the neuronal apoptosis after SAH in mice. METHODS: C57BL/6 adult male mice underwent endovascular perforation SAH modeling or sham-operation (n=286), and 86 mild SAH mice were excluded. In experiment 1, vehicle or an EGFR inhibitor (632.0 ng AG1478) was administered intraventricularly at 30 minutes postmodeling. At 24 or 72 hours, after neurological score was tested, brain water content, double immunolabeling with terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) and a neuronal marker antimicrotubule-associated protein-2 antibody, Western blotting using whole tissue lysate or nuclear protein extraction of the left cortex, and immunohistochemistry for cleaved caspase-3, phosphorylated (p-) EGFR, NIK, p-NFκB p65, and NFκB p105/50 were evaluated. In experiment 2, after sham or SAH modeling, AG1478+vehicle or AG1478+4.0 ng EGF was administered intraventricularly. The brain was used for TUNEL staining and immunohistochemistry after 24-hour observation. RESULTS: SAH group showed deteriorated neurological score (P<0.01, Mann-Whitney U test), more TUNEL- and cleaved caspase-3-positive neurons (P<0.01, ANOVA), and higher brain water content (P<0.01, Mann-Whitney U test), and these observations were improved in SAH-AG1478 group. Western blotting showed that expression levels of p-EGFR, p-p65, p50, and nuclear-NIK were increased after SAH (P<0.05, ANOVA), and decreased by AG1478 administration. Immunohistochemistry revealed these molecules localized in degenerating neurons. EGF administration resulted in neurological deterioration, increased TUNEL-positive neurons, and activation of EGFR, NIK, and NFκB. CONCLUSIONS: Activated EGFR, nuclear-NIK, and NFκB expressions were observed in cortical degenerating neurons after SAH, and were decreased by administration of AG1478, associated with suppression of TUNEL- and cleaved caspase-3-positive neurons. EGFR/NIK/NFκB pathway is suggested to be involved in neuronal apoptosis after SAH in mice.

Inflammatory Skin Disease Causes Anxiety Symptoms Leading to an Irreversible Course.

Intense itching significantly reduces the quality of life, and atopic dermatitis is associated with psychiatric conditions, such as anxiety and depression. Psoriasis, another inflammatory skin disease, is often complicated by psychiatric symptoms, including depression; however, the pathogenesis of these mediating factors is poorly understood. This study used a spontaneous dermatitis mouse model (KCASP1Tg) and evaluated the psychiatric symptoms. We also used Janus kinase (JAK) inhibitors to manage the behaviors. Gene expression analysis and RT-PCR of the cerebral cortex of KCASP1Tg and wild-type (WT) mice were performed to examine differences in mRNA expression. KCASP1Tg mice had lower activity, higher anxiety-like behavior, and abnormal behavior. The mRNA expression of S100a8 and Lipocalin 2 (Lcn2) in the brain regions was higher in KCASP1Tg mice. Furthermore, IL-1ß stimulation increased Lcn2 mRNA expression in astrocyte cultures. KCASP1Tg mice had predominantly elevated plasma Lcn2 compared to WT mice, which improved with JAK inhibition, but behavioral abnormalities in KCASP1Tg mice did not improve, despite JAK inhibition. In summary, our data revealed that Lcn2 is closely associated with anxiety symptoms, but the anxiety and depression symptoms caused by chronic skin inflammation may be irreversible. This study demonstrated that active control of skin inflammation is essential for preventing anxiety.

Plasma SPARC Elevation in Delayed Cerebral Ischemia After Aneurysmal Subarachnoid Hemorrhage.

Matricellular proteins have been implicated in pathologies after subarachnoid hemorrhage (SAH). To find a new therapeutic molecular target, the present study aimed to clarify the relationships between serially measured plasma levels of a matricellular protein, secreted protein acidic and rich in cysteine (SPARC), and delayed cerebral ischemia (DCI) in 117 consecutive aneurysmal SAH patients with admission World Federation of Neurological Surgeons (WFNS) grades I-III. DCI developed in 25 patients with higher incidences of past history of hypertension and dyslipidemia, preoperative WFNS grade III, modified Fisher grade 4, spinal drainage, and angiographic vasospasm. Plasma SPARC levels were increased after SAH, and significantly higher in patients with than without DCI at days 7-9, and in patients with VASOGRADE-Yellow compared with VASOGRADE-Green at days 1-3 and 7-9. However, there were no relationships between plasma SPARC levels and angiographic vasospasm. Receiver-operating characteristic curves differentiating DCI from no DCI determined the cut-off value of plasma SPARC ≥ 82.1 ng/ml at days 7 - 9 (sensitivity, 0.800; specificity, 0.533; and area under the curve, 0.708), which was found to be an independent determinant of DCI development in multivariate analyses. This is the first study to show that SPARC is upregulated in peripheral blood after SAH, and that SPARC may be involved in the development of DCI without angiographic vasospasm in a clinical setting.

Effects of New-Generation Antiepileptic Drug Prophylaxis on Delayed Neurovascular Events After Aneurysmal Subarachnoid Hemorrhage.

Neuroelectric disruptions such as seizures and cortical spreading depolarization may contribute to the development of delayed cerebral ischemia (DCI) after aneurysmal subarachnoid hemorrhage (SAH). However, effects of antiepileptic drug prophylaxis on outcomes remain controversial in SAH. The authors investigated if prophylactic administration of new-generation antiepileptic drugs levetiracetam and perampanel was beneficial against delayed neurovascular events after SAH. This was a retrospective single-center cohort study of 121 consecutive SAH patients including 56 patients of admission World Federation of Neurological Surgeons grades IV - V who underwent aneurysmal obliteration within 72 h post-SAH from 2013 to 2021. Prophylactic antiepileptic drugs differed depending on the study terms: none (2013 - 2015), levetiracetam for patients at high risks of seizures (2016 - 2019), and perampanel for all patients (2020 - 2021). The 3rd term had the lowest occurrence of delayed cerebral microinfarction on diffusion-weighted magnetic resonance imaging, which was related to less development of DCI. Other outcome measures were similar among the 3 terms including incidences of angiographic vasospasm, computed tomography-detectable delayed cerebral infarction, seizures, and 3-month good outcomes (modified Rankin Scale 0 - 2). The present study suggests that prophylactic administration of levetiracetam and perampanel was not associated with worse outcomes and that perampanel may have the potential to reduce DCI by preventing microcirculatory disturbances after SAH. Further studies are warranted to investigate anti-DCI effects of a selective α-amino-3-hydroxy-5-methyl-4-isoxazole propionate receptor antagonist perampanel in SAH patients in a large-scale prospective study.

Plasma Fibulin-5 Levels as an Independent Predictor of a Poor Outcome after an Aneurysmal Subarachnoid Hemorrhage.

Aneurysmal subarachnoid hemorrhage (SAH) is a poor-outcome disease with a delayed neurological exacerbation. Fibulin-5 (FBLN5) is one of matricellular proteins, some of which have been involved in SAH pathologies. However, no study has investigated FBLN5's roles in SAH. This study was aimed at examining the relationships between serially measured plasma FBLN5 levels and neurovascular events or outcomes in 204 consecutive aneurysmal SAH patients, including 77 patients (37.7%) with poor outcomes (90-day modified Rankin Scale 3-6). Plasma FBLN5 levels were not related to angiographic vasospasm, delayed cerebral ischemia, and delayed cerebral infarction, but elevated levels were associated with severe admission clinical grades, any neurological exacerbation and poor outcomes. Receiver-operating characteristic curves indicated that the most reasonable cut-off values of plasma FBLN5, in order to differentiate 90-day poor from good outcomes, were obtained from analyses at days 4-6 for all patients (487.2 ng/mL; specificity, 61.4%; and sensitivity, 62.3%) and from analyses at days 7-9 for only non-severe patient (476.8 ng/mL; specificity, 66.0%; and sensitivity, 77.8%). Multivariate analyses revealed that the plasma FBLN5 levels were independent determinants of the 90-day poor outcomes in both all patients' and non-severe patients' analyses. These findings suggest that the delayed elevation of plasma FBLN5 is related to poor outcomes, and that FBLN5 may be a new molecular target to reveal a post-SAH pathophysiology.

Roles of glutamate in brain injuries after subarachnoid hemorrhage.

Aneurysmal subarachnoid hemorrhage (SAH) is a stroke type with a high rate of mortality and morbidity. Post-SAH brain injury as a determinant of poor outcome is classified into the following two types: early brain injury (EBI) and delayed cerebral ischemia (DCI). EBI consists of various acute brain pathophysiologies that occur within the first 72 hours of SAH in a clinical setting. The underlying mechanisms of DCI are considered to be cerebral vasospasm or microcirculatory disturbance, which develops mostly 4 to 14 days after clinical SAH. Glutamate is the principal neurotransmitter in the central nervous system, but excessive glutamate is known to induce neurotoxicity. Experimental and clinical studies have revealed that excessive glutamates are released after SAH. In addition, many studies have reported the relationships between excessive glutamate release or overactivation of glutamate receptors and excitotoxicity, cortical spreading depolarization, seizure, increased blood-brain barrier permeability, neuroinflammation, microthrombosis formation, microvasospasm, cerebral vasospasm, impairments of brain metabolic supply and demand, impaired neurovascular coupling, and so on, all of which potentially contribute to the development of EBI or DCI. As glutamates always exert their functions through one or more of 4 major receptors of glutamates, it would be valuable to know the mechanisms as to how glutamates cause these pathologies, and the possibility that a glutamate receptor antagonist may block the pathologies. To prevent the mechanistic steps leading to glutamate-mediated neurotoxicity may ameliorate SAH-induced brain injuries and improve the outcomes. This review addresses the current knowledge of glutamate-mediated neurotoxicity, focusing on EBI and DCI after SAH.

Neuroelectric Mechanisms of Delayed Cerebral Ischemia after Aneurysmal Subarachnoid Hemorrhage.

Delayed cerebral ischemia (DCI) remains a challenging but very important condition, because DCI is preventable and treatable for improving functional outcomes after aneurysmal subarachnoid hemorrhage (SAH). The pathologies underlying DCI are multifactorial. Classical approaches to DCI focus exclusively on preventing and treating the reduction of blood flow supply. However, recently, glutamate-mediated neuroelectric disruptions, such as excitotoxicity, cortical spreading depolarization and seizures, and epileptiform discharges, have been reported to occur in high frequencies in association with DCI development after SAH. Each of the neuroelectric disruptions can trigger the other, which augments metabolic demand. If increased metabolic demand exceeds the impaired blood supply, the mismatch leads to relative ischemia, resulting in DCI. The neuroelectric disruption also induces inverted vasoconstrictive neurovascular coupling in compromised brain tissues after SAH, causing DCI. Although glutamates and the receptors may play central roles in the development of excitotoxicity, cortical spreading ischemia and epileptic activity-related events, more studies are needed to clarify the pathophysiology and to develop novel therapeutic strategies for preventing or treating neuroelectric disruption-related DCI after SAH. This article reviews the recent advancement in research on neuroelectric disruption after SAH.

Inhibition of AMPA (α-Amino-3-Hydroxy-5-Methyl-4-Isoxazole Propionate) Receptor Reduces Acute Blood-Brain Barrier Disruption After Subarachnoid Hemorrhage in Mice.

Activation of α-amino-3-hydroxy-5-methyl-4-isoxazole propionate receptor (AMPAR) is thought to cause acute brain injury, but the role remains poorly understood in subarachnoid hemorrhage (SAH). This study was conducted to evaluate if AMPAR activation induces acute blood-brain barrier (BBB) disruption after SAH. C57BL/6 male adult mice (n = 117) underwent sham or filament perforation SAH modeling, followed by a random intraperitoneal injection of vehicle or two dosages (1 mg/kg or 3 mg/kg) of a selective noncompetitive AMPAR antagonist perampanel (PER) at 30 min post-modeling. The effects were evaluated by mortality, neurological scores, and brain water content at 24-48 h and video electroencephalogram monitoring, immunostaining, and Western blotting at 24 h post-SAH. PER significantly suppressed post-SAH neurological impairments, brain edema, and BBB disruption. SAH developed epileptiform spikes without obvious convulsion, which were also inhibited by PER. Western blotting showed that the expression of AMPAR subunits GluA1 and GluA2 was unchanged after SAH, but they were significantly activated after SAH. PER prevented post-SAH activation of GluA1/2, associated with the suppression of post-SAH induction of tenascin-C, a causative mediator of post-SAH BBB disruption. Meanwhile, an intracerebroventricular injection of a subtype-selective GluA1/2 agonist augmented the activation of GluA1/2 and the induction of tenascin-C in brain capillary endothelial cells and aggravated post-SAH BBB disruption without increases in epileptiform spikes. Neurological impairments and brain edema were not correlated with the occurrence of epileptiform spikes. This study first showed that AMPAR plays an important role in the development of post-SAH BBB disruption and can be a novel therapeutic target against it.

Clarithromycin Ameliorates Early Brain Injury After Subarachnoid Hemorrhage via Suppressing Periostin-Related Pathways in Mice.

Subarachnoid hemorrhage (SAH) remains a life-threatening disease, and early brain injury (EBI) is an important cause of poor outcomes. The authors have reported that periostin, a matricellular protein, is one of key factors of post-SAH EBI. Clarithromycin (CAM) is a worldwide antibiotic that can inhibit periostin expression. This study aimed to investigate whether CAM suppressed EBI after experimental SAH, focusing on blood-brain barrier (BBB) disruption, an important pathology of EBI. C57BL/6 male adult mice underwent endovascular perforation SAH modeling (n = 139) or sham operation (n = 30). Different dosages (25, 50, or 100 mg/kg) of CAM or the vehicle (n = 16, 52, 13, and 58, respectively) were randomly administered by an intramuscular injection 5 min after SAH induction. Post-SAH 50 mg/kg CAM treatment most effectively improved neurological scores and brain water content at 24 and 48 h and reduced immunoglobulin G extravasation at 24 h compared with vehicle-treated SAH mice (p < 0.01). Western blotting showed that post-SAH BBB disruption was associated with increased expressions of periostin, phosphorylated signal transducer and activator of transcription 1 and 3, matrix metalloproteinase-9, and the consequent degradation of zonula occludens-1, which were suppressed by 50 mg/kg CAM treatment (p < 0.05, respectively, versus vehicle-treated SAH mice). Periostin and its related molecules were upregulated in capillary endothelial cells and neurons after SAH. An intracerebroventricular injection of recombinant periostin blocked the neuroprotective effects of CAM in SAH mice (n = 6, respectively; p < 0.05). In conclusion, this study first demonstrated that CAM improved post-SAH EBI in terms of BBB disruption at least partly via the suppression of periostin-related pathways.

Higher Plasma Osteopontin Concentrations Associated with Subsequent Development of Chronic Shunt-Dependent Hydrocephalus After Aneurysmal Subarachnoid Hemorrhage.

A matricellular protein osteopontin (OPN) is considered to exert neuroprotective and healing effects on neurovascular injuries in an acute phase of aneurysmal subarachnoid hemorrhage (SAH). However, the relationships between OPN expression and chronic shunt-dependent hydrocephalus (SDHC) have never been investigated. In 166 SAH patients (derivation and validation cohorts, 110 and 56, respectively), plasma OPN levels were serially measured at days1-3, 4-6, 7-9, and 10-12 after aneurysmal obliteration. The OPN levels and clinical factors were compared between patients with and without subsequent development of chronic SDHC. Plasma OPN levels in the SDHC patients increased from days 1-3 to days 4-6 and remained high thereafter, while those in the non-SDHC patients peaked at days 4-6 and then decreased over time. Plasma OPN levels had no correlation with serum levels of C-reactive protein (CRP), a systemic inflammatory marker. Univariate analyses showed that age, modified Fisher grade, acute hydrocephalus, cerebrospinal fluid drainage, and OPN and CRP levels at days 10-12 were significantly different between patients with and without SDHC. Multivariate analyses revealed that higher plasma OPN levels at days 10-12 were an independent factor associated with the development of SDHC, in addition to a more frequent use of cerebrospinal fluid drainage and higher modified Fisher grade at admission. Plasma OPN levels at days 10-12 maintained similar discrimination power in the validation cohort and had good calibration on the Hosmer-Lemeshow goodness-of-fit test. Prolonged higher expression of OPN may contribute to the development of post-SAH SDHC, possibly by excessive repairing effects promoting fibrosis in the subarachnoid space.

Cerebrovascular pathophysiology of delayed cerebral ischemia after aneurysmal subarachnoid hemorrhage.

Aneurysmal subarachnoid hemorrhage (SAH) remains a serious cerebrovascular disease. Even if SAH patients survive the initial insults, delayed cerebral ischemia (DCI) may occur at 4 days or later post-SAH. DCI is characteristics of SAH, and is considered to develop by blood breakdown products and inflammatory reactions, or secondary to early brain injury, acute pathophysiological events that occur in the brain within the first 72 hours of aneurysmal SAH. The pathology underlying DCI may involve large artery vasospasm and/or microcirculatory disturbances by microvasospasm, microthrombosis, dysfunction of venous outflow and compression of microvasculature by vasogenic or cytotoxic tissue edema. Recent clinical evidence has shown that large artery vasospasm is not the only cause of DCI, and that both large artery vasospasm-dependent and -independent cerebral infarction causes poor outcome. Animal studies suggest that mechanisms of vasospasm may differ between large artery and arterioles or capillaries, and that many kinds of cells in the vascular wall and brain parenchyma may be involved in the pathogenesis of microcirculatory disturbances. The impairment of the paravascular and glymphatic systems also may play important roles in the development of DCI. As pathological mediators for DCI, glutamate and several matricellular proteins have been investigated in addition to inflammatory molecules. Glutamate is involved in excitotoxicity contributing to cortical spreading ischemia and epileptic activity-related events. Microvascular dysfunction is an attractive mechanism to explain the cause of poor outcomes independently of large cerebral artery vasospasm, but needs more studies to clarify the pathophysiologies or mechanisms and to develop a novel therapeutic strategy.

Prognostic factors varying with age in patients with aneurysmal subarachnoid hemorrhage.

With the advent of an aging society, more elderly patients with aneurysmal subarachnoid hemorrhage (aSAH) have been treated. We investigated if prognostic factors differ with age in aSAH patients. In a prospectively maintained aSAH database at multiple institutions from 2013 to 2016, 238 patients who underwent clipping or coiling for a ruptured aneurysm within 48 h of onset were divided into elderly (≥75 years; 57 patients) and non-elderly groups, or categorized into 4-age groups (<54, 55-64, 65-74, and ≥75 years). Prognostic factors and clinical characteristics were retrospectively analyzed. The elderly group had a higher incidence of pre-morbidities, co-morbidities, poor admission World Federation of Neurological Surgeons (WFNS) grades, modified Fisher grade 4, and resultantly 90-day poor outcomes (modified Rankin scale [mRS] 3-6). Multivariate logistic regression analyses revealed that independent determinants for poor outcomes were hypertension and modified Fisher grade 4 in the elderly group, and admission WFNS grades IV-V, systemic complications, non-procedural cerebral infarction and shunt-dependent chronic hydrocephalus in the non-elderly group. The 4-age group analyses showed that higher age group was more frequently associated with the prognostic factors. As higher age itself causes poor outcomes and more association of prognostic factors, prognostic factors in elderly patients may be rather limited.

Tenascin-C in brain injuries and edema after subarachnoid hemorrhage: Findings from basic and clinical studies.

Subarachnoid hemorrhage (SAH) by a rupture of cerebral aneurysms remains the most devastating cerebrovascular disease. Early brain injury (EBI) is increasingly recognized to be the primary determinant for poor outcomes, and also considered to cause delayed cerebral ischemia (DCI) after SAH. Both clinical and experimental literatures emphasize the impact of global cerebral edema in EBI as negative prognostic and direct pathological factors. The nature of the global cerebral edema is a mixture of cytotoxic and vasogenic edema, both of which may be caused by post-SAH induction of tenascin-C (TNC) that is an inducible, non-structural, secreted and multifunctional matricellular protein. Experimental SAH induces TNC in brain parenchyma in rats and mice. TNC knockout suppressed EBI in terms of brain edema, blood-brain barrier disruption, neuronal apoptosis and neuroinflammation, associated with the inhibition of post-SAH activation of mitogen-activated protein kinases and nuclear factor-kappa B in mice. In a clinical setting, more severe SAH increases more TNC in cerebrospinal fluid and peripheral blood, which could be a surrogate marker of EBI and predict DCI development and outcomes. In addition, cilostazol, a selective inhibitor of phosphodiesterase type III that is a clinically available anti-platelet agent and is known to suppress TNC induction, dose-dependently inhibited delayed cerebral infarction and improved outcomes in a pilot clinical study. Thus, further studies may facilitate application of TNC as biomarkers for non-invasive diagnosis or assessment of EBI and DCI, and lead to development of a molecular target drug against TNC, contributing to the improvement of post-SAH outcomes.

Possible Involvement of Caspase-Independent Pathway in Neuronal Death After Subarachnoid Hemorrhage in Mice.

Early brain injury is now considered as an important cause of delayed neurological deterioration after aneurysmal subarachnoid hemorrhage (SAH), and neuronal apoptosis is one of the constituents of early brain injury. Caspase family is popular proteases in apoptotic pathways, but there also exist caspase-independent cell death pathways in many pathologic states. In this study, we investigated the ratio of caspase-related and caspase-unrelated neuronal deaths in a mice endovascular perforation SAH model. At 24 h after SAH, about half of neurons in the perforation-side cortex showed increased cleaved caspase-3 immunoreactivity. On the other hand, about half of cleaved caspase-3-immunonegative neurons showed abnormal morphology, suggesting that they were in the process of some sort of cell death in the absence of caspase-3 activity. These findings suggest that both caspase-dependent and caspase-independent signaling pathways may cause neuronal death after SAH.

Link Between Receptors That Engage in Developing Vasospasm After Subarachnoid Hemorrhage in Mice.

Vasospasm after subarachnoid hemorrhage (SAH) has been studied, but the mechanisms remain to be unveiled. Tenascin-C (TNC), which is a matricellular protein and reported to increase in spastic cerebral artery wall after SAH, is a ligand for both Toll-like receptor 4 (TLR4) and epidermal growth factor receptor (EGFR). Our previous studies suggested the involvement of TNC and these receptors in vasoconstriction or vasospasm after SAH. In this study, we investigated whether upregulation of TNC and TLR4 is observed and if an EGFR inhibitor has suppressive effects against them in a mice endovascular perforation SAH model. At 24 h after SAH, TNC and TLR4 expressions were widely observed in spastic cerebral arteries, and these expressions were suppressed by the administration of an EGFR inhibitor. From these results, EGFR inhibitors possibly suppress the expression of not only EGFR but also TLR4 at least partly through regulating TNC upregulation. More studies are needed to clarify the precise mechanisms linking these receptors.