The importance of early brain injury after subarachnoid hemorrhage

Blockage of mitochondrial calcium uniporter prevents iron accumulation in a model of experimental subarachnoid hemorrhage

Previous studies have shown that iron accumulation is involved in the pathogenesis of brain injury following subarachnoid hemorrhage (SAH) and chelation of iron reduced mortality and oxidative DNA damage. We previously reported that blockage of mitochondrial calcium uniporter (MCU) provided benefit in the early brain injury after experimental SAH. This study was undertaken to identify whether blockage of MCU could ameliorate iron accumulation-associated brain injury following SAH. Therefore, we used two reagents ruthenium red (RR) and spermine (Sper) to inhibit MCU. Sprague-Dawley (SD) rats were randomly divided into four groups including sham, SAH, SAH+RR, and SAH+Sper. Biochemical analysis and histological assays were performed. The results confirmed the iron accumulation in temporal lobe after SAH. Interestingly, blockage of MCU dramatically reduced the iron accumulation in this area. The mechanism was revealed that inhibition of MCU reversed the down-regulation of iron regulatory protein (IRP) 1/2 and increase of ferritin. Iron-sulfur cluster dependent-aconitase activity was partially conserved when MCU was blocked. In consistence with this and previous report, ROS levels were notably reduced and ATP supply was rescued; levels of cleaved caspase-3 dropped; and integrity of neurons in temporal lobe was protected. Taken together, our results indicated that blockage of MCU could alleviate iron accumulation and the associated injury following SAH. These findings suggest that the alteration of calcium and iron homeostasis be coupled and MCU be considered to be a therapeutic target for patients suffering from SAH.

Ursolic acid alleviates early brain injury after experimental subarachnoid hemorrhage by suppressing TLR4-mediated inflammatory pathway

Our previous studies proved that ursolic acid (UA) protected against early brain injury (EBI) by modulating oxidative stress after experimental subarachnoid hemorrhage (SAH), but it has not been evaluated yet about its effects on an inflammatory pathway in a SAH model. This study was undertaken to evaluate the influence of UA on the toll-like receptor 4 (TLR4) signaling pathway after SAH. Adult male SD rats were divided into vehicle-treated sham, vehicle-treated SAH, and UA-treated SAH groups. The endovascular puncture model was used to induce SAH and all the rats were subsequently sacrificed at 48 h after SAH. UA administration markedly decreased the expressions of TLR4 pathway-related agents, such as intercellular adhesion molecule-1 (ICAM-1), TLR4, nuclear factor-κB (NF-κB) P65, interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), inducible nitric oxide synthase (iNOS) and matrix metalloproteinase (MMP)-9. Apoptosis detected by TUNEL indicated that fewer positive cells appeared in UA administration SAH groups than the control group. In conclusion, UA may attenuate EBI after SAH in rats by suppressing the TLR4-mediated inflammatory pathway.

Early brain injury linearly correlates with reduction in cerebral perfusion pressure during the hyperacute phase of subarachnoid hemorrhage

Background

It is unclear how complex pathophysiological mechanisms that result in early brain injury (EBI) after subarachnoid hemorrhage (SAH) are triggered. We investigate how peak intracranial pressure (ICP), amount of subarachnoid blood, and hyperacute depletion of cerebral perfusion pressure (CPP) correlate to the onset of EBI following experimental SAH.

Methods

An entire spectrum of various degrees of SAH severities measured as peak ICP was generated and controlled using the blood shunt SAH model in rabbits. Standard cardiovascular monitoring, ICP, CPP, and bilateral regional cerebral blood flow (rCBF) were continuously measured. Cells with DNA damage and neurodegeneration were detected using terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) and Fluoro-jade B (FJB).

Results

rCBF was significantly correlated to reduction in CPP during the initial 15 min after SAH in a linear regression pattern (r² = 0.68, p < 0.001). FJB- and TUNEL-labeled cells were linearly correlated to reduction in CPP during the first 3 min of hemorrhage in the hippocampal regions (FJB: r² = 0.50, p < 0.01; TUNEL: r² = 0.35, p < 0.05), as well as in the basal cortex (TUNEL: r² = 0.58, p < 0.01). EBI occurred in animals with severe (relative CPP depletion >0.4) and moderate (relative CPP depletion >0.25 but <0.4) SAH. Neuronal cell death was equally detected in vulnerable and more resistant brain regions.

Conclusions

The degree of EBI in terms of neuronal cell degeneration in both the hippocampal regions and the basal cortex linearly correlates with reduced CPP during hyperacute SAH. Temporary CPP reduction, however, is not solely responsible for EBI but potentially triggers processes that eventually result in early brain damage.

Electronic supplementary material

The online version of this article (doi:10.1186/s40635-014-0030-1) contains supplementary material, which is available to authorized users.

Enhancement of Autophagy by Histone Deacetylase Inhibitor Trichostatin A Ameliorates Neuronal Apoptosis After Subarachnoid Hemorrhage in Rats

Trichostatin A (TSA), a pan-histone deacetylase inhibitor, exerts multiple neuroprotective properties. This study aims to examine whether TSA could enhance autophagy, thereby reduce neuronal apoptosis and ultimately attenuate early brain injury (EBI) following subarachnoid hemorrhage (SAH). SAH was performed through endovascular perforation method, and mortality, neurological score, and brain water content were evaluated at 24 h after surgery. Western blot were used for quantification of acetylated histone H3, LC3-II, LC3-I, Beclin-1, cytochrome c, Bax, and cleaved caspase-3 expression. Immunofluorescence was performed for colocalization of Beclin-1 and neuronal nuclei (NeuN). Apoptotic cell death of neurons was quantified with double staining of terminal deoxynucleotidyl transferase-mediated uridine 5'-triphosphate-biotin nick end-labeling (TUNEL) and NeuN. The autophagy inhibitor 3-methyladenine (3-MA) was used to manipulate the proposed pathway. Our results demonstrated that TSA reduced brain edema and alleviated neurological deficits at 24 h after SAH. TSA significantly increased acetylated histone H3, the LC3-II/LC3-I ratio, and Beclin-1 while decreased Bax and cleaved caspase-3 in the cortex. Beclin-1 and NeuN, TUNEL, and NeuN, respectively, were colocalized in cortical cells. Neuronal apoptosis in the ipsilateral basal cortex was significantly inhibited after TSA treatment. Conversely, 3-MA reversed the beneficial effects of TSA. These results proposed that TSA administration enhanced autophagy, which contributes to alleviation of neuronal apoptosis, improvement of neurological function, and attenuation of EBI following SAH.

Rat endovascular perforation model

Experimental animal models of aneurysmal subarachnoid hemorrhage (SAH) have provided a wealth of information on the mechanisms of brain injury. The rat endovascular perforation (EVP) model replicates the early pathophysiology of SAH and hence is frequently used to study early brain injury following SAH. This paper presents a brief review of historical development of the EVP model and details the technique used to create SAH and considerations necessary to overcome technical challenges.

Nimodipine activates TrkB neurotrophin receptors and induces neuroplastic and neuroprotective signaling events in the mouse hippocampus and prefrontal cortex

The L-type calcium channel blocker nimodipine improves clinical outcome produced by delayed cortical ischemia or vasospasm associated with subarachnoid hemorrhage. While vasoactive mechanisms are strongly implicated in these therapeutic actions of nimodipine, we sought to test whether nimodipine might also regulate neurotrophic and neuroplastic signaling events associated with TrkB neurotrophin receptor activation. Adult male mice were acutely treated with vehicle or nimodipine (10 mg/kg, s.c., 1.5 h) after which the phosphorylation states of TrkB, cyclic-AMP response element binding protein (CREB), protein kinase B (Akt), extracellular regulated kinase (ERK), mammalian target of rapamycin (mTor) and p70S6 kinase (p70S6k) from prefrontal cortex and hippocampus were assessed. Nimodipine increased the phosphorylation of the TrkB catalytic domain and the phosphoslipase-Cγ1 (PLCγ1) domain, whereas phosphorylation of the TrkB Shc binding site remained unaltered. Nimodipine-induced TrkB phosphorylation was associated with increased phosphorylation levels of Akt and CREB in the prefrontal cortex and the hippocampus whereas phosphorylation of ERK, mTor and p70S6k remained unaltered. Nimodipine-induced TrkB signaling was not associated with changes in BDNF mRNA or protein levels. These nimodipine-induced changes on TrkB signaling mimic those produced by antidepressant drugs and thus propose common mechanisms and long-term functional consequences for the effects of these medications. This work provides a strong basis for investigating the role of TrkB-associated signaling underlying the neuroprotective and neuroplastic effects of nimodipine in translationally relevant animal models of brain trauma or compromised synaptic plasticity.

Effects of intravenous infusion of hydrogen-rich fluid combined with intra-cisternal infusion of magnesium sulfate in severe aneurysmal subarachnoid hemorrhage: study protocol for a randomized controlled trial

Background

The failures of recent studies intended to prevent cerebral vasospasm have moved the focus of research into delayed cerebral ischemia away from cerebral artery constriction towards other mechanisms. Recent accumulating evidence has suggested that early brain injury is also involved in the development of delayed cerebral ischemia, and that hydrogen can prevent early brain injury. Therefore, we have established a combination therapy of intravenous hydrogen infusion and intra-cisternal magnesium sulfate infusion for the treatment of both early brain injury and cerebral vasospasm. The present randomized controlled clinical trial is designed to investigate the effects of this novel therapeutic strategy on the occurrence of cerebral vasospasm, delayed cerebral ischemia, and clinical outcomes after high-grade subarachnoid hemorrhage.

Methods

This study is a randomized, double-blind, placebo-controlled design to be conducted in two hospitals. A total of 450 patients with high-grade subarachnoid hemorrhage will be randomized to one of three arms: (i) Mg + H₂ group, (ii) Mg group, and (iii) control group. Patients who are assigned to the Mg + H₂ group will receive intra-cisternal magnesium sulfate infusion (2.5 mmol/L) at 20 mL/h for 14 days and intravenous hydrogen-rich fluid infusion (200 mL) twice a day for 14 days. Patients who are assigned to the Mg group will receive intra-cisternal magnesium sulfate infusion (2.5 mmol/L) at 20 mL/h for 14 days and intravenous normal glucose-electrolyte solution (200 mL) without added hydrogen twice a day for 14 days. Patients who are assigned to the control group will receive intra-cisternal Ringer solution without magnesium sulfate at 20 mL/h for 14 days and intravenous normal glucose-electrolyte solution (200 mL) without added hydrogen twice a day for 14 days. Primary outcome measures will be occurrence of delayed cerebral ischemia and cerebral vasospasm. Secondary outcome measures will be modified Rankin scale score at 3, 6, and 12 months and biochemical markers.

Discussion

The present protocol for a randomized, placebo-controlled study of intravenous hydrogen therapy with intra-cisternal magnesium infusion is expected to establish the efficacy and safety of this therapeutic strategy.

Trial registration

UMIN-CTR: UMIN000014696

Ghrelin alleviates early brain injury after subarachnoid hemorrhage via the PI3K/Akt signaling pathway

Early brain injury (EBI) plays a key role in the pathogenesis of subarachnoid hemorrhage (SAH). Although the neuroprotective effects of ghrelin have been demonstrated in several studies, whether ghrelin reduces EBI after SAH remains unknown. In this study, we hypothesized that treatment with ghrelin would attenuate EBI after SAH, and that this protection would be mediated, at least in part, by activation of the PI3K/Akt signaling pathway. Adult male Sprague-Dawley rats (n=100) were randomly divided into the following groups: control group (n=20), SAH group (n=20), SAH+vehicle group (n=20), SAH+ghrelin group (n=20) and SAH+ghrelin+LY294002 group (n=20). The rats were injected with autologous blood (0.3mL) into the prechiasmatic cistern to induce SAH. Ghrelin (80μg/kg, IP), or an equal volume of vehicle, was administered immediately after surgery. The PI3K inhibitor, LY294002, was applied to manipulate the proposed pathway. Mortality, neurological scores, brain edema, cell apoptosis, and the expression of p-Akt, and cleaved caspase-3 proteins were assayed after 24h SAH. Ghrelin significantly improved neurological function and reduced neuronal apoptosis and brain edema at 24h after SAH. The level of p-Akt, expressed mainly in neurons, was markedly up-regulated. Additionally, the level of cleaved caspase-3 was decreased by ghrelin treatment. The beneficial effects of ghrelin in SAH rats were partially suppressed by LY294002. These results demonstrate that ghrelin may reduce EBI after SAH, via a mechanism involving the PI3K/Akt signaling pathway.

Ursolic acid reduces oxidative stress to alleviate early brain injury following experimental subarachnoid hemorrhage

Ursolic acid (UA), a well-known anti-oxidative reagent, has been reported to protect the brain against ischemic stoke. However, the potential role of UA in protecting against early brain injury (EBI) after subarachnoid hemorrhage (SAH) remains unclear. The present study aimed to examine the effect of UA against EBI following SAH, and to demonstrate whether the effect is associated with its powerful antioxidant property. Male SD rats were divided into vehicle-treated sham, vehicle-treated SAH, and UA-treated SAH groups. The endovascular puncture model was used to induce SAH and all the rats were subsequently sacrificed at 48h after SAH. The results show that UA administration could significantly attenuate EBI (including brain edema, blood-brain barrier disruption, neural cell apoptosis, and neurological deficient) after SAH in rats and up-regulate the antioxidative levels in the rat cerebral cortex, suggesting that administration of UA in experimental SAH rats could alleviate brain injury symptom, potentially through its powerful antioxidant property. Hence, we concluded that UA might be a novel therapeutic agent for EBI following SAH.

Carnosine attenuates early brain injury through its antioxidative and anti-apoptotic effects in a rat experimental subarachnoid hemorrhage model

Carnosine (β-alanyl-L-histidine) has been demonstrated to provide antioxidative and anti-apoptotic roles in the animal of ischemic brain injuries and neurodegenerative diseases. The aim of this study was to examine whether carnosine prevents subarachnoid hemorrhage (SAH)-induced early brain injury (EBI) in rats. We found that intraperitoneal administration of carnosine improved neurobehavioral deficits, attenuated brain edema and blood-brain barrier permeability, and decreased reactive oxygen species level at 48 h following SAH in rat models. Carnosine treatment increased tissue copper/zinc superoxide dismutase (CuZn-SOD) and glutathione peroxidase (GSH-Px) enzymatic activities, and reduced post-SAH elevated lactate dehydrogenase (LDH) activity, the concentration of malondialdehyde (MDA), 3-nitrotyrosine (3-NT), 8-hydroxydeoxyguanosine (8-OHDG), interleukin (IL)-1β, IL-6, and tumor necrosis factor-α (TNF-α) in rats. Furthermore, carnosine treatment attenuated SAH-induced microglia activation and cortical neuron apoptosis. These results indicated that administration of carnosine may provide neuroprotection in EBI following SAH in rat models.

Astaxanthin alleviates early brain injury following subarachnoid hemorrhage in rats: possible involvement of Akt/bad signaling

Apoptosis has been proven to play a crucial role in early brain injury pathogenesis and to represent a target for the treatment of subarachnoid hemorrhage (SAH). Previously, we demonstrated that astaxanthin (ATX) administration markedly reduced neuronal apoptosis in the early period after SAH. However, the underlying molecular mechanisms remain obscure. In the present study, we tried to investigate whether ATX administration is associated with the phosphatidylinositol 3-kinase-Akt (PI3K/Akt) pathway, which can play an important role in the signaling of apoptosis. Our results showed that post-SAH treatment with ATX could cause a significant increase of phosphorylated Akt and Bad levels, along with a significant decrease of cleaved caspase-3 levels in the cortex after SAH. In addition to the reduced neuronal apoptosis, treatment with ATX could also significantly reduce secondary brain injury characterized by neurological dysfunction, cerebral edema and blood-brain barrier disruption. In contrast, the PI3K/Akt inhibitor, LY294002, could partially reverse the neuroprotection of ATX in the early period after SAH by downregulating ATX-induced activation of Akt/Bad and upregulating cleaved caspase-3 levels. These results provided the evidence that ATX could attenuate apoptosis in a rat SAH model, potentially, in part, through modulating the Akt/Bad pathway.

The role of microclot formation in an acute subarachnoid hemorrhage model in the rabbit

Background. Microvascular dysfunction and microthrombi formation are believed to contribute to development of early brain injury (EBI) after aneurysmal subarachnoid hemorrhage (SAH). Objective. This study aimed to determine (i) extent of microthrombus formation and neuronal apoptosis in the brain parenchyma using a blood shunt SAH model in rabbits; (ii) correlation of structural changes in microvessels with EBI characteristics. Methods. Acute SAH was induced using a rabbit shunt cisterna magna model. Extent of microthrombosis was detected 24 h post-SAH (n = 8) by fibrinogen immunostaining, compared to controls (n = 4). We assessed apoptosis by terminal deoxynucleotidyl transferase nick end labeling (TUNEL) in cortex and hippocampus. Results. Our results showed significantly more TUNEL-positive cells (SAH: 115 ± 13; controls: 58 ± 10; P = 0.016) and fibrinogen-positive microthromboemboli (SAH: 9 ± 2; controls: 2 ± 1; P = 0.03) in the hippocampus after aneurysmal SAH. Conclusions. We found clear evidence of early microclot formation in a rabbit model of acute SAH. The extent of microthrombosis did not correlate with early apoptosis or CPP depletion after SAH; however, the total number of TUNEL positive cells in the cortex and the hippocampus significantly correlated with mean CPP reduction during the phase of maximum depletion after SAH induction. Both microthrombosis and neuronal apoptosis may contribute to EBI and subsequent DCI.

Astaxanthin offers neuroprotection and reduces neuroinflammation in experimental subarachnoid hemorrhage

BACKGROUND

Neuroinflammation has been proven to play a crucial role in early brain injury pathogenesis and represents a target for treatment of subarachnoid hemorrhage (SAH). Astaxanthin (ATX), a dietary carotenoid, has been shown to have powerful anti-inflammation property in various models of tissue injury. However, the potential effects of ATX on neuroinflammation in SAH remain uninvestigated. The goal of this study was to investigate the protective effects of ATX on neuroinflammation in a rat prechiasmatic cistern SAH model.

METHODS

Rats were randomly distributed into multiple groups undergoing the sham surgery or SAH procedures, and ATX (25 mg/kg or 75 mg/kg) or equal volume of vehicle was given by oral gavage at 30 min after SAH. All rats were sacrificed at 24 h after SAH. Neurologic scores, brain water content, blood-brain barrier permeability, and neuronal cell death were examined. Brain inflammation was evaluated by means of expression changes in myeloperoxidase, cytokines (interleukin-1β, tumor necrosis factor-α), adhesion molecules (intercellular adhesion molecule-1), and nuclear factor kappa B DNA-binding activity.

RESULTS

Our data indicated that post-SAH treatment with high dose of ATX could significantly downregulate the increased nuclear factor kappa B activity and the expression of inflammatory cytokines and intercellular adhesion molecule-1 in both messenger RNA transcription and protein synthesis. Moreover, these beneficial effects lead to the amelioration of the secondary brain injury cascades including cerebral edema, blood-brain barrier disruption, neurological dysfunction, and neuronal degeneration.

CONCLUSIONS

These results indicate that ATX treatment is neuroprotective against SAH, possibly through suppression of cerebral inflammation.

Tert-butylhydroquinone alleviates early brain injury and cognitive dysfunction after experimental subarachnoid hemorrhage: role of Keap1/Nrf2/ARE pathway

Tert-butylhydroquinone (tBHQ), an Nrf2 activator, has demonstrated neuroprotection against brain trauma and ischemic stroke in vivo. However, little work has been done with respect to its effect on early brain injury (EBI) after subarachnoid hemorrhage (SAH). At the same time, as an oral medication, it may have extensive clinical applications for the treatment of SAH-induced cognitive dysfunction. This study was undertaken to evaluate the influence of tBHQ on EBI, secondary deficits of learning and memory, and the Keap1/Nrf2/ARE pathway in a rat SAH model. SD rats were divided into four groups: (1) Control group (n=40); (2) SAH group (n=40); (3) SAH+vehicle group (n=40); and (4) SAH+tBHQ group (n=40). All SAH animals were subjected to injection of autologous blood into the prechiasmatic cistern once in 20 s. In SAH+tBHQ group, tBHQ was administered via oral gavage at a dose of 12.5 mg/kg at 2 h, 12 h, 24 h, and 36 h after SAH. In the first set of experiments, brain samples were extracted and evaluated 48 h after SAH. In the second set of experiments, changes in cognition and memory were investigated in a Morris water maze. Results shows that administration of tBHQ after SAH significantly ameliorated EBI-related problems, such as brain edema, blood-brain barrier (BBB) impairment, clinical behavior deficits, cortical apoptosis, and neurodegeneration. Learning deficits induced by SAH was markedly alleviated after tBHQ therapy. Treatment with tBHQ markedly up-regulated the expression of Keap1, Nrf2, HO-1, NQO1, and GSTα1 after SAH. In conclusion, the administration of tBHQ abated the development of EBI and cognitive dysfunction in this SAH model. Its action was probably mediated by activation of the Keap1/Nrf2/ARE pathway.

Amelioration of oxidative stress and protection against early brain injury by astaxanthin after experimental subarachnoid hemorrhage

OBJECT.: Aneurysmal subarachnoid hemorrhage (SAH) causes devastating rates of mortality and morbidity. Accumulating studies indicate that early brain injury (EBI) greatly contributes to poor outcomes after SAH and that oxidative stress plays an important role in the development of EBI following SAH. Astaxanthin (ATX), one of the most common carotenoids, has a powerful antioxidative property. However, the potential role of ATX in protecting against EBI after SAH remains obscure. The goal of this study was to assess whether ATX can attenuate SAH-induced brain edema, blood-brain barrier permeability, neural cell death, and neurological deficits, and to elucidate whether the mechanisms of ATX against EBI are related to its powerful antioxidant property.

METHODS

Two experimental SAH models were established, including a prechiasmatic cistern SAH model in rats and a one-hemorrhage SAH model in rabbits. Both intracerebroventricular injection and oral administration of ATX were evaluated in this experiment. Posttreatment assessments included neurological scores, body weight loss, brain edema, Evans blue extravasation, Western blot analysis, histopathological study, and biochemical estimation.

RESULTS

It was observed that an ATX intracerebroventricular injection 30 minutes post-SAH could significantly attenuate EBI (including brain edema, blood-brain barrier disruption, neural cell apoptosis, and neurological dysfunction) after SAH in rats. Meanwhile, delayed treatment with ATX 3 hours post-SAH by oral administration was also neuroprotective in both rats and rabbits. In addition, the authors found that ATX treatment could prevent oxidative damage and upregulate the endogenous antioxidant levels in the rat cerebral cortex following SAH.

CONCLUSIONS

These results suggest that ATX administration could alleviate EBI after SAH, potentially through its powerful antioxidant property. The authors conclude that ATX might be a promising therapeutic agent for EBI following SAH.

Controversies and evolving new mechanisms in subarachnoid hemorrhage

Despite decades of study, subarachnoid hemorrhage (SAH) continues to be a serious and significant health problem in the United States and worldwide. The mechanisms contributing to brain injury after SAH remain unclear. Traditionally, most in vivo research has heavily emphasized the basic mechanisms of SAH over the pathophysiological or morphological changes of delayed cerebral vasospasm after SAH. Unfortunately, the results of clinical trials based on this premise have mostly been disappointing, implicating some other pathophysiological factors, independent of vasospasm, as contributors to poor clinical outcomes. Delayed cerebral vasospasm is no longer the only culprit. In this review, we summarize recent data from both experimental and clinical studies of SAH and discuss the vast array of physiological dysfunctions following SAH that ultimately lead to cell death. Based on the progress in neurobiological understanding of SAH, the terms "early brain injury" and "delayed brain injury" are used according to the temporal progression of SAH-induced brain injury. Additionally, a new concept of the vasculo-neuronal-glia triad model for SAH study is highlighted and presents the challenges and opportunities of this model for future SAH applications.

Genetic elimination of Nrf2 aggravates secondary complications except for vasospasm after experimental subarachnoid hemorrhage in mice

Nuclear factor erythroid 2-related factor 2 (Nrf2) is a key endogenous protective regulator in the body. This study aimed to explore the role of Nrf2 in subarachnoid hemorrhage (SAH)-induced secondary complications. Wild type (WT) and Nrf2 knockout (KO) mice were subjected to experimental SAH by injecting fresh autologous blood into pre-chiasmatic cistern. The absence of Nrf2 function in mice resulted in exacerbated brain injury with increased brain edema, blood-brain barrier (BBB) disruption, neural apoptosis, and severe neurological deficits at 24h after SAH. Moreover, cerebral vasospasm was severe at 24h after SAH, but not significantly different between WT and Nrf2 KO mice after SAH. Meanwhile, Molondialdehyde (MDA) was increased and GSH/GSSG ratio was decreased in Nrf2 KO mice after SAH. Furthermore, higher expression of TNF-α and IL-1β was also found after SAH in Nrf2 KO mice. In conclusion, our results revealed that Nrf2 plays an important role in attenuating SAH-induced secondary complications by regulating excessive oxidative stress and inflammatory response.

Rosuvastatin ameliorates early brain injury after subarachnoid hemorrhage via suppression of superoxide formation and nuclear factor-kappa B activation in rats

BACKGROUND

Statins, or 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors, have been suggested to possess pleiotropic effects, including antioxidant and anti-inflammatory properties. We investigated the protective effects of pretreatment with rosuvastatin, a relatively hydrophilic statin, on early brain injury (EBI) after a subarachnoid hemorrhage (SAH), using the endovascular perforation SAH model.

METHODS

Eighty-six male Sprague-Dawley rats were randomly divided into 3 groups: (1) sham operation, (2) SAH+vehicle, and (3) SAH+10 mg/kg rosuvastatin. Rosuvastatin or vehicle was orally administered to rats once daily from 7 days before to 1 day after the SAH operation. After SAH, we examined the effects of rosuvastatin on the neurologic score, brain water content, neuronal cell death estimated by terminal deoxynucleotidyl transferase-mediated uridine 5'-triphosphate nick end labeling staining, blood-brain barrier disruption by immunoglobulin G (IgG) extravasation, oxidative stress, and proinflammatory molecules.

RESULTS

Compared with the vehicle group, rosuvastatin significantly improved the neurologic score and reduced the brain water content, neuronal cell death, and IgG extravasation. Rosuvastatin inhibited brain superoxide production, nuclear factor-kappa B (NF-κB) activation, and the increase in activated microglial cells after SAH. The increased expressions of tumor necrosis factor-alpha, endothelial matrix metalloproteinase-9, and neuronal cyclooxygenase-2 induced by SAH were prevented by rosuvastatin pretreatment.

CONCLUSIONS

The present study demonstrates that rosuvastatin pretreatment ameliorates EBI after SAH through the attenuation of oxidative stress and NF-κB-mediated inflammation.

Resveratrol prevents neuronal apoptosis in an early brain injury model

BACKGROUND

Resveratrol has been shown to attenuate cerebral vasospasm after subarachnoid hemorrhage (SAH); however, no study has explored its neuroprotective effect in early brain injury (EBI) after experimental SAH. The aim of this study was to evaluate the antiapoptotic function of resveratrol in EBI and its relationship with the PI3K/Akt survival pathway.

METHODS

Experimental SAH was induced in adult male rats by prechiasmatic cistern injection. Control and SAH rats were divided into six groups and treated with low (20 mg/kg) or high (60 mg/kg) concentrations of resveratrol with or without LY294002 cotreatment. Brain samples of the rats were analyzed by immunohistochemistry, immunofluorescence staining, Western blotting, and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) apoptosis assays.

RESULTS

High-concentration but not low-concentration resveratrol treatment in SAH rats led to a significant increase in phosphorylated Akt (p-Akt) protein levels compared with SAH rats without treatment. In addition, p-Akt-positive cells mainly colocalized with NeuN-positive cells. Neuronal apoptosis in SAH rat brain was attenuated by high-concentration resveratrol treatment. The antiapoptotic effect of resveratrol in SAH rats could be partially abrogated by the PI3K/Akt signaling inhibitor LY294002.

CONCLUSIONS

Our results show that resveratrol has an antiapoptotic effect in EBI and that resveratrol might act through the PI3K/Akt signaling pathway.

SIRT1 inhibition by sirtinol aggravates brain edema after experimental subarachnoid hemorrhage

Secondary brain injury following subarachnoid hemorrhage (SAH) is poorly understood. We utilized a rat model of SAH to investigate whether SIRT1 has a protective role against brain edema via the tumor suppressor protein p53 pathway. Experimental SAH was induced in adult male Sprague-Dawley rats by prechiasmatic cistern injection. Brain SIRT1 protein levels were examined in the sham controls and in rats 6, 12, 24, 48, and 72 hr after SAH induction. The SIRT1 inhibitor sirtinol was administered by intracerebroventricular infusion. Neurological functions, blood-brain barrier (BBB) disruption, and brain water content were assessed. Endothelial cell apoptosis, caspase 3 protein expression, p53 acetylation, and matrix metalloproteinase-9 (MMP-9) activity were examined. Compared with the control, SIRT1 protein expression increased remarkably, reaching a maximum at 24 hr after SAH. Sirtinol treatment significantly lowered SIRT1 expression, accompanied by deteriorated neurologic function, BBB disruption, brain edema, increased endothelial cell apoptosis, and increased MMP-9 gelatinase activity compared with the rats treated with vehicle only. Our results suggest that increased expression of endogenous SIRT1 may play a neuroprotective role against brain edema after SAH.

Protective effect of quercetin against oxidative stress and brain edema in an experimental rat model of subarachnoid hemorrhage

Quercetin has been demonstrated to play an important role in altering the progression of ischemic brain injuries and neurodegenerative diseases by protecting against oxidative stress. The effects of quercetin on brain damage after subarachnoid hemorrhage (SAH), however, have not been investigated. This study was designed to explore the effects of quercetin on oxidative stress and brain edema after experimental SAH using four equal groups (n = 16) of adult male Sprague-Dawley (SD) rats, including a sham group, an SAH + vehicle group, an SAH + quercetin10 group, and an SAH + quercetin50 group. The rat SAH model was induced by injection of 0.3 ml of non-heparinised arterial blood into the prechiasmatic cistern. In the SAH + quercetin10 and SAH + quercetin50 groups, doses of 10 mg/kg and 50 mg/kg quercetin, respectively, were directly administered by intraperitoneal injection at 30 min, 12 h, and 24 h after SAH induction. Cerebral tissue samples were extracted for enzymatic antioxidant determination, lipid peroxidation assay, caspase-3 activity and water content testing 48 h after SAH. Treatment with a high dose (50 mg/kg) of quercetin markedly enhanced the activities of copper/zinc superoxide dismutase (CuZn-SOD) and glutathione peroxidase (GSH-Px), and treatment with this dose significantly reduced the level of malondialdehyde (MDA). Caspase-3 and brain edema was ameliorated and neurobehavioral deficits improved in rats that received the high dose of quercetin. The findings suggest that the early administration of optimal dose of quercetin may ameliorate brain damage and provide neuroprotection in the SAH model, potentially by enhancing the activity of endogenous antioxidant enzymes and inhibiting free radical generation.

Melatonin-enhanced autophagy protects against neural apoptosis via a mitochondrial pathway in early brain injury following a subarachnoid hemorrhage

Melatonin is a strong antioxidant that has beneficial effects against early brain injury (EBI) following a subarachnoid hemorrhage (SAH) in rats; protection includes reduced mortality and brain water content. The molecular mechanisms underlying these clinical effects in the SAH model, however, have not been clearly identified. This study was undertaken to determine the influence of melatonin on neural apoptosis and the potential mechanism of these effects in EBI following SAH using the filament perforation model of SAH in male Sprague Dawley rats. Melatonin (150 mg/kg) or vehicle was given via an intraperitoneal injection 2 hr after SAH induction. Brain samples were extracted 24 hr after SAH. The results show that melatonin treatment markedly reduced caspase-3 activity and the number of TUNEL-positive cells, while the treatment increased the LC3-II/LC3-I, an autophagy marker, which indicated that melatonin-enhanced autophagy ameliorated apoptotic cell death in rats subjected to SAH. To further identify the mechanism of autophagy protection, we demonstrated that melatonin administration reduced Bax translocation to the mitochondria and the release of cytochrome c into the cytosol. Taken together, this report demonstrates that melatonin improved the neurological outcome in rats by protecting against neural apoptosis after the induction of filament perforation SAH; moreover, the mechanism of these antiapoptosis effects was related to the enhancement of autophagy, which ameliorated cell apoptosis via a mitochondrial pathway.

Astragaloside IV alleviates early brain injury following experimental subarachnoid hemorrhage in rats

Astragaloside IV, one of the main effective components isolated from Astragalus membranaceus, has multiple neuroprotective properties, while the effects of astragaloside IV on the attenuation of subarachnoid hemorrhage (SAH)-induced early brain injury (EBI) and its possible mechanisms are unknown. In the present study, we aimed to determine whether astragaloside IV could inhibit oxidative stress, reduce neuronal apoptosis, and improve neurological deficits after experimental SAH in rats. Rats (n=68) were randomly divided into the following groups: Sham group, SAH group, SAH+vehicle group, and SAH+astragaloside IV group. Astragaloside IV or an equal volume of vehicle was administered at 1 h and 6 h after SAH, all the rats were subsequently sacrificed at 24 h after SAH. Mortality, neurological scores, and brain edema were assessed, biochemical tests and histological studies were also performed at that point. SAH induced an increase in the malondialdehyde (MDA) level, neuronal apoptosis, cleaved caspase 3, brain edema and decreased activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px). Astragaloside IV treatment reversed these changes and improved neurobehavioral outcomes of SAH rats. Our findings suggested that astragaloside IV may alleviate EBI after SAH through antioxidative and anti-apoptotic effects.

Tamoxifen as an effective neuroprotectant against early brain injury and learning deficits induced by subarachnoid hemorrhage: possible involvement of inflammatory signaling

Background

Tamoxifen, a selective estrogen receptor modulator, has successfully been used to treat several animal models of brain injury, but the underlying mechanisms remain unclear. This study was undertaken to evaluate the effect of tamoxifen on the toll-like receptor 4 (TLR4)- and nuclear factor-κB (NF-κB)-related inflammatory signaling pathway and secondary brain injury in rats after subarachnoid hemorrhage (SAH).

Methods

Adult male Sprague-Dawley rats were divided into four groups: (1) control group (n = 28); (2) SAH group (n = 28); (3) SAH + vehicle group (n = 28); and (4) SAH + tamoxifen group (n = 28). All SAH animals were subjected to injection of autologous blood into the prechiasmatic cistern once on day 0. In SAH + tamoxifen group, tamoxifen was administered intraperitoneally at a dose of 5 mg/kg at 2 h, 12 h, and 36 h after SAH. In the first set of experiments, brain samples were extracted and evaluated at 48 h after SAH. In the second set of experiments, the Morris water maze was used to investigate cognitive and memory changes.

Results

We found that treatment with tamoxifen markedly inhibited the protein expressions of TLR4, NF-κB and the downstream inflammatory agents, such as interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and intercellular adhesion molecule-1 (ICAM-1). Administration of tamoxifen following SAH significantly ameliorated the early brain injury (EBI), such as brain edema, blood-brain barrier (BBB) impairment, and clinical behavior scale. Learning deficits induced by SAH were markedly alleviated after tamoxifen treatment.

Conclusions

Post-SAH tamoxifen administration may attenuate TLR4/NF-kappaB-mediated inflammatory response in the rat brain and result in abatement of the development of EBI and cognitive dysfunction after SAH.

Delayed neurological deterioration after subarachnoid haemorrhage

Subarachnoid haemorrhage (SAH) causes early brain injury (EBI) that is mediated by effects of transient cerebral ischaemia during bleeding plus effects of the subarachnoid blood. Secondary effects of SAH include increased intracranial pressure, destruction of brain tissue by intracerebral haemorrhage, brain shift, and herniation, all of which contribute to pathology. Many patients survive these phenomena, but deteriorate days later from delayed cerebral ischaemia (DCI), which causes poor outcome or death in up to 30% of patients with SAH. DCI is thought to be caused by the combined effects of angiographic vasospasm, arteriolar constriction and thrombosis, cortical spreading ischaemia, and processes triggered by EBI. Treatment for DCI includes prophylactic administration of nimodipine, and current neurointensive care. Prompt recognition of DCI and immediate treatment by means of induced hypertension and balloon or pharmacological angioplasty are considered important by many physicians, although the evidence to support such approaches is limited. This Review summarizes the pathophysiology of DCI after SAH and discusses established treatments for this condition. Novel strategies--including drugs such as statins, sodium nitrite, albumin, dantrolene, cilostazol, and intracranial delivery of nimodipine or magnesium--are also discussed.

Attenuation of early brain injury and learning deficits following experimental subarachnoid hemorrhage secondary to Cystatin C: possible involvement of the autophagy pathway

Cystatin C (CysC) is a cysteine protease inhibitor and previous studies have demonstrated that increasing endogenous CysC expression has therapeutic implications on brain ischemia, Alzheimer's disease, and other neurodegenerative disorders. Our previous reports have demonstrated that the autophagy pathway was activated in the brain after experimental subarachnoid hemorrhage (SAH), and it may play a beneficial role in early brain injury (EBI). This study investigated the effects of exogenous CysC on EBI, cognitive dysfunction, and the autophagy pathway following experimental SAH. All SAH animals were subjected to injections of 0.3 ml fresh arterial, nonheparinized blood into the prechiasmatic cistern in 20 s. As a result, treatment with CysC with low and medial concentrations significantly ameliorated the degree of EBI when compared with vehicle-treated SAH rats. Microtubule-associated protein light chain-3 (LC3), a biomarker of autophagosomes, and beclin-1, a Bcl-2-interacting protein required for autophagy, were significantly increased in the cortex 48 h after SAH and were further up-regulated after CysC therapy. By ultrastructural observation, there was a marked increase in autophagosomes and autolysosomes in neurons of CysC-treated rats. Learning deficits induced by SAH were markedly alleviated after CysC treatment with medial doses. In conclusion, pre-SAH CysC administration may attenuate EBI and neurobehavioral dysfunction in this SAH model, possibly through activating autophagy pathway.

Gender influences the initial impact of subarachnoid hemorrhage: an experimental investigation

Aneurysmal subarachnoid hemorrhage (SAH) carries high early patient mortality. More women than men suffer from SAH and the average age of female SAH survivors is greater than that of male survivors; however, the overall mortality and neurological outcomes are not better in males despite their younger age. This pattern suggests the possibility of gender differences in the severity of initial impact and/or in subsequent pathophysiology. We explored gender differences in survival and pathophysiology following subarachnoid hemorrhage induced in age-matched male and female rats by endovascular puncture. Intracranial pressure (ICP), cerebral blood flow (CBF), blood pressure (BP) and cerebral perfusion pressure (CPP) were recorded at and after induction of SAH. Animals were sacrificed 3 hours after lesion and studied for subarachnoid hematoma size, vascular pathology (collagen and endothelium immunostaining), inflammation (platelet and neutrophil immunostaining), and cell death (TUNEL assay). In a second cohort, 24-hour survival was determined. Subarachnoid hematoma, post-hemorrhage ICP peak, BP elevation, reduction in CPP, intraluminal platelet aggregation and neutrophil accumulation, loss of vascular collagen, and neuronal and non-neuronal cell death were greater in male than in female rats. Hematoma size did not correlate with the number of apoptotic cells, platelet aggregates or neutrophil. The ICP peak correlated with hematoma size and with number of apoptotic cells but not with platelet aggregates and neutrophil number. This suggests that the intensity of ICP rise at SAH influences the severity of apoptosis but not of inflammation. Mortality was markedly greater in males than females. Our data demonstrate that in rats gender influences the initial impact of SAH causing greater bleed and early injury in males as compared to females.

Chronic hydrocephalus after experimental subarachnoid hemorrhage

Chronic communicating hydrocephalus is a significant health problem affecting up to 20% of survivors of spontaneous subarachnoid hemorrhage (SAH). The development of new treatment strategies is hampered by the lack of well characterized disease models. This study investigated the incidence of chronic hydrocephalus by evaluating the temporal profile of intracranial pressure (ICP) elevation after SAH, induced by endovascular perforation in rats. Twenty-five adult male Sprague-Dawley rats (260-320 g) were subjected to either endovascular perforation or sham surgery. Five animals died after SAH induction. At 7, 14 and 21 days after surgery ICP was measured by stereotaxic puncture of the cisterna magna in SAH (n=10) and SHAM (n=10) animals. On day 21 T-maze test was performed and the number of alterations and latency to decision was recorded. On day 23, samples were processed for histological analyses. The relative ventricle area was evaluated in coronal Nissl stained sections. On day 7 after surgery all animals showed normal ICP. The absolute ICP values were significantly higher in SAH compared to SHAM animals on day 21 (8.26±4.53 mmHg versus 4.38±0.95 mmHg) but not on day 14. Observing an ICP of 10 mmHg as cut-off, 3 animals showed elevated ICP on day 14 and another animal on day 21. The overall incidence of ICP elevation was 40% in SAH animals. On day 21, results of T-maze testing were significantly correlated with ICP values, i.e. animals with elevated ICP showed a lower number of alterations and a delayed decision. Histology yielded a significantly higher (3.59 fold increased) relative ventricle area in SAH animals with ICP elevation compared to SAH animals without ICP elevation. In conclusion, the current study shows that experimental SAH leads to chronic hydrocephalus, which is associated with ICP elevation, behavioral alterations and ventricular dilation in about 40% of SAH animals.

P2X7R/cryopyrin inflammasome axis inhibition reduces neuroinflammation after SAH

Neuroinflammation contributes to the pathogenesis of early brain injury (EBI) after subarachnoid hemorrhage (SAH). Cytotoxic events following SAH, such as extracellular accumulation of adenosine triphosphate (ATP), may activate the P2X purinoceptor 7 (P2X7R)/cryopyrin inflammasome axis, thus inducing the proinflammatory cytokine IL-1β/IL-18 secretion. We therefore hypothesized that inhibition of P2X7R/cryopyrin inflammasome axis would ameliorate neuroinflammation after SAH. In the present study, SAH was induced by the endovascular perforation in rats. Small interfering RNAs (siRNAs) of P2X7R or cryopyrin were administered intracerebroventricularly 24h before SAH. Brilliant blue G (BBG), a non-competitive antagonist of P2X7R, was administered intraperitoneally 30min following SAH. Post-assessments including SAH severity score, neurobehavioral test, brain water content, Western blot and immunofluorescence, were performed. Administration of P2X7R and cryopyrin siRNA as well as pharmacologic blockade of P2X7R by BBG ameliorated neurological deficits and brain edema at 24h following SAH. Inhibition of P2X7R/cryopyrin inflammasome axis suppressed caspase-1 activation, which subsequently decreased maturation of IL-1β/IL-18. To investigate the link between P2X7R and cryopyrin inflammasome in vivo, Benzoylbenzoyl-ATP (BzATP), a P2X7R agonist, was given to lipopolysaccharide (LPS) primed naive rats with scramble or cryopyrin siRNAs. In LPS-primed naive rats, BzATP induced caspase-1 activation and mature IL-1β release were neutralized by cryopyrin siRNA. Thus, the P2X7R/cryopyrin inflammasome axis may contribute to neuroinflammation via activation of caspase-1 and thereafter mature IL-1β/IL-18 production following SAH. Therapeutic interventions targeting P2X7R/cryopyrin pathway may be a novel approach to ameliorate EBI following SAH.

Aneurysmal subarachnoid hemorrhage models: do they need a fix?

The discovery of tissue plasminogen activator to treat acute stroke is a success story of research on preventing brain injury following transient cerebral ischemia (TGI). That this discovery depended upon development of embolic animal model reiterates that proper stroke modeling is the key to develop new treatments. In contrast to TGI, despite extensive research, prevention or treatment of brain injury following aneurysmal subarachnoid hemorrhage (aSAH) has not been achieved. A lack of adequate aSAH disease model may have contributed to this failure. TGI is an important component of aSAH and shares mechanism of injury with it. We hypothesized that modifying aSAH model using experience acquired from TGI modeling may facilitate development of treatment for aSAH and its complications. This review focuses on similarities and dissimilarities between TGI and aSAH, discusses the existing TGI and aSAH animal models, and presents a modified aSAH model which effectively mimics the disease and has a potential of becoming a better resource for studying the brain injury mechanisms and developing a treatment.

Pathophysiological Role of Global Cerebral Ischemia following Subarachnoid Hemorrhage: The Current Experimental Evidence

Subarachnoid hemorrhage (SAH) is the subtype of stroke with one of the highest mortality rates and the least well-understood pathophysiologies. One of the very early events which may occur after SAH is a significant decrease of cerebral perfusion pressure (CPP) caused by the excessive increase of intracranial pressure during the initial bleeding. A severely decreased CPP results in global cerebral ischemia, an event also occurring after cardiac arrest. The aim of the current paper is to review the pathophysiological events occurring in experimental models of SAH and global cerebral ischemia and to evaluate the contribution and the importance of global cerebral ischemia for the pathophysiology of SAH.

Acute microvascular changes after subarachnoid hemorrhage and transient global cerebral ischemia

Subarachnoid hemorrhage and transient global cerebral ischemia result in similar pathophysiological changes in the cerebral microcirculation. These changes include microvascular constriction, increased leukocyte-endothelial interactions, blood brain barrier disruption, and microthrombus formation. This paper will look at various animal and preclinical studies that investigate these various microvascular changes, perhaps providing insight in how these microvessels can be a therapeutic target in both subarachnoid hemorrhage and transient global cerebral ischemia.

Subarachnoid hemorrhage, spreading depolarizations and impaired neurovascular coupling

Aneurysmal subarachnoid hemorrhage (SAH) has devastating consequences on brain function including profound effects on communication between neurons and the vasculature leading to cerebral ischemia. Physiologically, neurovascular coupling represents a focal increase in cerebral blood flow to meet increased metabolic demand of neurons within active regions of the brain. Neurovascular coupling is an ongoing process involving coordinated activity of the neurovascular unit-neurons, astrocytes, and parenchymal arterioles. Neuronal activity can also influence cerebral blood flow on a larger scale. Spreading depolarizations (SD) are self-propagating waves of neuronal depolarization and are observed during migraine, traumatic brain injury, and stroke. Typically, SD is associated with increased cerebral blood flow. Emerging evidence indicates that SAH causes inversion of neurovascular communication on both the local and global level. In contrast to other events causing SD, SAH-induced SD decreases rather than increases cerebral blood flow. Further, at the level of the neurovascular unit, SAH causes an inversion of neurovascular coupling from vasodilation to vasoconstriction. Global ischemia can also adversely affect the neurovascular response. Here, we summarize current knowledge regarding the impact of SAH and global ischemia on neurovascular communication. A mechanistic understanding of these events should provide novel strategies to treat these neurovascular disorders.

Early brain injury: a common mechanism in subarachnoid hemorrhage and global cerebral ischemia

Early brain injury (EBI) has become an area of extreme interest in the recent years and seems to be a common denominator in the pathophysiology of global transient ischemia and subarachnoid hemorrhage (SAH). In this paper, we highlight the importance of cerebral hypoperfusion and other mechanisms that occur in tandem in both pathologies and underline their possible roles in triggering brain injury after hemorrhagic or ischemic strokes.