Neurovascular Protection Reduces Early Brain Injury After Subarachnoid Hemorrhage

Protection of the brain following cerebral ischemia through the attenuation of PARP-1-induced neurovascular unit damage in rats

Cerebral ischemia is a major health crisis throughout the world, and the currently available thrombolytic therapy is unsatisfactory. Cell death following cerebral ischemia is mediated by a complex pathophysiological interaction of various mechanisms. During an ischemic insult, not only neurons but all of the components of the neurovascular unit, such as glia, endothelia, pericytes and basal membranes, are destroyed. Previous studies have shown that excessive stimulation of poly (ADP-ribose) polymerase (PARP-1) is crucial for cerebral injury after ischemic insult, which is an important cause of cell death in all cell types within the neurovascular unit. To investigate whether PARP-1 plays an important role in protecting the neurovascular unit following cerebral ischemia, we evaluated neurobehavioral deficits, PARP-1 activity, blood brain barrier (BBB) disruption and neurovascular unit deficits using Western blot analysis, TTC staining and electron microscopy in an MCAO rat model. The results revealed that PARP-1 enzymatic activity was dramatically increased after ischemia. Inhibition of PARP-1 significantly reduced the extent of both cerebral infarction and edema, improved neurological scores, and attenuated the damage to the neurovascular unit in cerebral ischemia. Collectively, these findings demonstrate that the down-regulation of PARP-1 activity contributes to reducing post-ischemic brain damage via protection of the neurovascular unit.

Rosiglitazone attenuates early brain injury after experimental subarachnoid hemorrhage in rats

Early brain injury (EBI) plays a crucial role in the pathological progress of subarachnoid hemorrhage (SAH). This study was designed to determine whether rosiglitazone protects the brain against EBI in rats, and discuss the role of the anti-apoptotic mechanism mediated by Bcl-2 family proteins in this neuroprotection. 86 male Sprague-Dawley rats were divided into the sham group, the SAH+ vehicle group and the SAH+ rosiglitazone group. SAH was induced via an endovascular perforation technique and rosiglitazone (3mg/kg) or vehicle was administered. Mortality, neurological scores, brain water content, Evans blue dye assay, TUNEL stain assay, Gelatin zymography, and western blot analysis were performed. Rosiglitazone significantly improved mortality, neurological scores, brain water content, blood brain barrier (BBB) and apoptosis compared with the vehicle group within 24h after SAH. The TUNEL staining assay demonstrated that apoptosis was ameliorated. Cleaved Caspase-3 and MMP-9 expression was reduced, whereas Bcl-2 and p-Bad was markedly preserved by rosiglitazone. A significant elevation of p-Akt was detected after rosiglitazone treatment. Our study demonstrated that rosiglitazone plays a neuroprotective role in EBI after SAH via attenuation of BBB disruption, brain edema and apoptosis.

Inhibition of SENP3 by lentivirus induces suppression of apoptosis in experimental subarachnoid hemorrhage in rats

BACKGROUND

Subarachnoid hemorrhage (SAH) is one of the life-threatening diseases with high morbidity and mortality rates. SUMO-specific proteases 3 (SENP3), a member of the small ubiquitin-like modifier specific protease family, was identified as an isopeptidase that deconjugates SUMOylation (The covalent modification by SUMO) of modified protein substrates. It is reported that SUMO-2/3 conjugation, a member of SUMOylation, presented neuroprotection. The study aimed to evaluate the expression of SENP3 and to explore its potential role in SAH.

MATERIALS AND METHODS

A total of 108 Sprague Dawley (SD) rats were randomly divided into 2 parts experiment and 9 subgroups (part 1:Sham group, SAH group, SAH+NAC group, SAH+vehicle group; part 2: Sham group, SAH group, SAH+lv-SENP3 group, SAH+lv-null group, SAH+NS group). 7 days before SAH, lentivirus was administrated into rats׳ left lateral ventricle to down-regulate SENP3. Experimental SAH was imitated by injection with 0.3ml nonheparinized autoblood into the prechiasmatic cistern. MDA levels, SOD activities, and GSH contents were detected to evaluate oxidative stress level. SENP3 and cleaved caspase 3 were detected by western blot, apoptosis was observed by TUNEL staining.

RESULTS

High oxidative stress level following SAH induced rising of SENP3. And inhibition of SENP3 by lentivirus induces suppression of apoptosis in experimental subarachnoid hemorrhage in rats.

CONCLUSION

When SENP3 accumulated by high oxidative stress, caspase 3 activated subsequently. And it leads to more severe apoptosis than physiological.

Memantine Attenuates Delayed Vasospasm after Experimental Subarachnoid Hemorrhage via Modulating Endothelial Nitric Oxide Synthase

Delayed cerebral vasospasm is an important pathological feature of subarachnoid hemorrhage (SAH). The cause of vasospasm is multifactorial. Impairs nitric oxide availability and endothelial nitric oxide synthase (eNOS) dysfunction has been reported to underlie vasospasm. Memantine, a low-affinity uncompetitive N-methyl-d-aspartate (NMDA) blocker has been proven to reduce early brain injury after SAH. This study investigated the effect of memantine on attenuation of vasospasm and restoring eNOS functionality. Male Sprague-Dawley rats weighing 350–450 g were randomly divided into three weight-matched groups, sham surgery, SAH + vehicle, and SAH + memantine groups. The effects of memantine on SAH were evaluated by assessing the severity of vasospasm and the expression of eNOS. Memantine effectively ameliorated cerebral vasospasm by restoring eNOS functionality. Memantine can prevent vasospasm in experimental SAH. Treatment strategies may help combat SAH-induced vasospasm in the future.

Neuroprotective Effect of Radix Trichosanthis Saponins on Subarachnoid Hemorrhage

Redox homeostasis has been implicated in subarachnoid hemorrhage (SAH). As a result, antioxidants and/or free radical scavengers have become an important therapeutic modality. Considering that radix trichosanthis (RT) saponins exhibited strong antioxidant ability both in vivo and in vitro, the present study aimed to reveal whether the neuroprotective activities of RT saponins were mediated by p38/p53 signal pathway after SAH. An established SAH model was used and superoxide dismutase (SOD), malondialdehyde (MDA), induced nitric oxide synthase (iNOS), nitric oxide (NO), lactate dehydrogenase (LDH), p-p38, and p53 activation were detected after 48 h of SAH. The results showed that RT saponins inhibited iNOS expression to restore NO to basal level. Moreover, compared with Cu/Zn-SOD, RT saponins (2 mg/kg/d dosage) significantly increased Mn-SOD activity after SAH. Accompanied with lowered NO and elevated SOD, decreased p38 phosphorylation and p53 activities were observed, especially for RT saponins at 2 mg/kg/d dosage. In this setting, the neurological outcome was also improved with less neuronal cells damage after RT saponins pretreatment. Our findings demonstrated the beneficial effects of RT saponins in enhancing neuroprotective effects by deducing iNOS activity, normalizing SOD level, and inhibiting p-p38 and p53 expression, hence offering significant therapeutic implications for SAH.

Topiramate attenuates early brain injury following subarachnoid haemorrhage in rats via duplex protection against inflammation and neuronal cell death

Early brain injury (EBI) following aneurysmal subarachnoid haemorrhage (SAH) insults contributes to the poor prognosis and high mortality observed in SAH patients. Topiramate (TPM) is a novel, broad-spectrum, antiepileptic drug with a reported protective effect against several brain injuries. The current study aimed to investigate the potential of TPM for neuroprotection against EBI after SAH and the possible dose-dependency of this effect. An endovascular perforation SAH model was established in rats, and TPM was administered by intraperitoneal injection after surgery at three different doses (20mg/kg, 40mg/kg, and 80mg/kg). The animals' neurological scores and brain water content were evaluated, and ELISA, Western blotting and immunostaining assays were conducted to assess the effect of TPM. The results revealed that TPM lowers the elevated levels of myeloperoxidase and proinflammatory mediators observed after SAH in a dose-related fashion, and the nuclear factor-kappa B (NF-κB) signalling pathway is the target of neuroinflammation regulation. In addition, TPM ameliorated SAH-induced cortical neuronal apoptosis by influencing Bax, Bcl-2 and cleaved caspase-3 protein expression, and the effect of TPM was enhanced in a dose-dependent manner. Various dosages of TPM also upregulated the protein expression of the γ-aminobutyric acid (GABA)-ergic signalling molecules, GABAA receptor (GABAAR) α1, GABAAR γ2, and K(+)-Cl(-) co-transporter 2 (KCC2) together and downregulated Na(+)-K(+)-Cl(-) co-transporter 1 (NKCC1) expression. Thus, TPM may be an effective neuroprotectant in EBI after SAH by regulating neuroinflammation and neuronal cell death.

Rosiglitazone attenuates cerebral vasospasm and provides neuroprotection in an experimental rat model of subarachnoid hemorrhage

BACKGROUND

Glutamate and oxidative stress play important roles after subarachnoid hemorrhage (SAH). The ability to modulate glutamate transporter 1 (GLT-1) and the antioxidative effect of rosiglitazone have been demonstrated. We investigated the neuroprotective effect of rosiglitazone after SAH.

METHODS

SAH was induced by double blood injection. The rats were randomly divided into sham, SAH + vehicle, and SAH + rosiglitazone groups and treated with dimethyl sulfoxide, dimethyl sulfoxide, and 6 mg/kg of rosiglitazone, respectively, at 2 and 12 h after SAH induction and then daily for 6 days. Cerebrospinal fluid dialysates were collected 30 min before SAH induction and then daily for 7 days for glutamate measurement. Mortality, body weight, and neurological scores were also measured daily. On day 7 after SAH, the wall thickness and the perimeter of the basilar artery (BA), neuron variability, GLT-1 levels, glial fibrillary acidic protein (GFAP) expression and activity, and malondialdehyde, superoxide dismutase, and catalase activities were also evaluated.

RESULTS

Rosiglitazone improved survival (relative risk = 0.325) and neurological functions and reduced neuronal degeneration (5.7 ± 0.8 vs. 10.0 ± 0.9; P < 0.001) compared with the SAH + vehicle group. Rosiglitazone also lowered glutamate levels by 43.5-fold and upregulated GLT-1 expression by 1.5-fold and astrocyte activity by 1.8-fold compared with the SAH + vehicle group. The increase in BA wall thickness was significantly attenuated by rosiglitazone, whereas the perimeter of the BA was increased. In addition, rosiglitazone abated the 1.9-fold increase in malondialdehyde levels and the 1.6-fold increase in catalase activity after SAH.

CONCLUSION

Rosiglitazone reduced SAH mortality, neurological deficits, body weight loss, GFAP loss, and cerebral vasospasm by preventing the neurotoxicity induced by glutamate and oxidative stress.

Increased ICP promotes CaMKII-mediated phosphorylation of neuronal NOS at Ser⁸⁴⁷ in the hippocampus immediately after subarachnoid hemorrhage

Early brain injury has recently been identified as an indicator of poor prognosis after subarachnoid hemorrhage (SAH). Calmodulin-dependent protein kinase IIα (CaMKIIα) has been shown to phosphorylate neuronal NOS (nNOS) at Ser(847), resulting in a reduction in nNOS activity. In this study, we revealed chronological changes in the phosphorylation of nNOS at Ser(847) in the hippocampus and cortex immediately after SAH. In a rat single-hemorrhage model of SAH, the hippocampus and adjacent cortex were collected up to 24h after SAH. Samples from rats that were not injected with blood were used as controls. NOS was partially purified from the crude samples using ADP-agarose affinity chromatography. Western blot analysis revealed that nNOS phosphorylated (p-nNOS) at Ser(847) was significantly increased in the hippocampus, but not in the cortex, at 1h after SAH compared with that resulting from the control treatment. Immunoreactivity of p-nNOS at Ser(847) was observed in interneurons of the hippocampus at 1h after SAH. Injection of saline instead of blood also significantly induced p-nNOS at Ser(847) levels in the hippocampus at 1h after injection. The colocalization of CaMKIIα and nNOS was transiently increased in the hippocampus at 0.5h after SAH. Our data suggest that immediately after SAH, an increase in intracranial pressure might induce transient cerebral ischemia, potentially promoting the phosphorylation of nNOS at Ser(847) by CaMKIIα in the hippocampus. The activation of p-nNOS at Ser(847) in the hippocampus may alleviate ischemic insults immediately after SAH to exert a neuroprotective effect against early brain injury.

Protective effects of thrombomodulin on microvascular permeability after subarachnoid hemorrhage in mouse model

The enhanced vascular permeability is a major early brain injury following subarachnoid hemorrhage (SAH). However, its mechanism is not clear yet. In this work, we explored its potential mechanism and investigated the roles of thrombomodulin (TM) in maintaining microvascular integrity after SAH. SAH models were established in adult male ICR mice (28-32 g) by endovascular perforation. TM was immediately administered by femoral vein injection following SAH. The brain water content, Evans Blue content and neurological functions were evaluated. Brain edema was also detected by magnetic resonance imaging (MRI) (T2 map). The siRNA technique, enzyme-linked immunosorbent assay (ELISA), immunofluorescence staining and western blotting were performed to explore the potential mechanism of TM treatment. The number of microthrombi in the hippocampus microvessels was also recorded. TM significantly decreased brain water content and Evans Blue content, alleviated brain edema and neurological deficits after SAH. The plasma concentration of activated protein C was increased after TM treatment. In addition, the levels of phospho-p38MAPK, phospho-p53, cleaved caspase-3, phospho-NF-κB (p65) were markedly decreased. Additionally, the loss of VE-cadherin and Occludin (markers of vascular integrity) and the number of microthrombi in the hippocampus were also reduced. Our results indicated that TM has protective effects on preserving microvascular integrity following SAH partly through preserving endothelial junction proteins and quenching apoptosis/inflammation in endothelial cells via blocking p38MAPK-p53/NF-κB (p65) pathway.

Expression and cell distribution of SENP3 in the cerebral cortex after experimental subarachnoid hemorrhage in rats: a pilot study

Subarachnoid hemorrhage (SAH) is one of the life-threatening diseases with high morbidity and mortality rates. Small ubiquitin-like modifier (SUMO)-specific proteases 3 (SENP3), a member of the SUMO-specific protease family, was identified as an isopeptidase that deconjugates SUMOylation (The covalent modification by SUMO) of modified protein substrates. It is reported that SUMO-2/3 conjugation, a member of SUMOylation, presented neuroprotection. The study aimed to evaluate the expression of SENP3 and to explore its role potential role in SAH. A total of 95 Sprague-Dawley rats were randomly divided into sham group and SAH groups at 6, 12, 24, 48 h, day 3, day 5, and day 7. SAH groups suffered experimental SAH by injection with 0.3 ml nonheparinized autoblood into the prechiasmatic cistern. SENP3 expression is surveyed by western blot analysis, real-time polymerase chain reaction, immunohistochemistry, and immunofluorescence. The levels of cleavage caspase-3 were determined by western blot and immunohistochemistry. SENP3 protein expression was significantly up-regulated after SAH which peaked at 24 h; however, the mRNA expression of SENP3 remained unchanged. Meanwhile, the level of cleaved caspase-3 was also increased after SAH. There is a highly positive correlation between cleavage caspase-3 and SENP3 in protein level. Immunofluorescent results showed that the expression of SENP3 was increased in neurons, rather than astrocytes nor microglia. Our findings indicated a possible role of SENP3 in the pathogenesis of early brain injury mediated by apoptosis following SAH.

Aneurysmal subarachnoid hemorrhage: pathobiology, current treatment and future directions

Aneurysmal subarachnoid hemorrhage is the most devastating form of stroke. Many pathological mechanisms ensue after cerebral aneurysm rupture, including hydrocephalus, apoptosis of endothelial cells and neurons, cerebral edema, loss of blood-brain barrier, abnormal cerebral autoregulation, microthrombosis, cortical spreading depolarization and macrovascular vasospasm. Although studied extensively through experimental and clinical trials, current treatment guidelines to prevent delayed cerebral ischemia is limited to oral nimodipine, maintenance of euvolemia, induction of hypertension if ischemic signs occur and endovascular therapy for patients with continued ischemia after induced hypertension. Future investigations will involve agents targeting vasodilation, anticoagulation, inhibition of apoptosis pathways, free radical neutralization, suppression of cortical spreading depolarization and attenuation of inflammation.

A magnetic resonance imaging grading system for subarachnoid hemorrhage severity in a rat model

BACKGROUND

The endovascular perforation model of subarachnoid hemorrhage (SAH) has a large variation in outcomes. This may reflect differences in the SAH size.

NEW METHOD

Magnetic resonance imaging (MRI) was performed 24h after endovascular perforation in adult male (n=58) and female (n=58) rats. Rats were divided into five grades according to MRI characteristics: grade 0: no SAH or intraventricular hemorrhage (IVH); grade 1: minimal or thin SAH without IVH; grade 2: minimal or thin SAH with IVH; grade 3: thick SAH without IVH; grade 4: thick SAH with IVH. We investigated whether MRI grading scale reflected severity of SAH (determined post mortem) and neurological score.

RESULTS

There was a strong correlation between MRI grading scale and current SAH grading scale (P<0.01) and neurological score (P<0.01) in male rats. In female rats, there was also a strong correlation between MRI grading scale and SAH grading scale (P<0.01) but not with neurological score (P=0.24).

COMPARISON WITH EXISTING METHODS

The current grading system is based on the amount of SAH and needs animal euthanasia to evaluate SAH severity. There is no useful grading system to classify severity of SAH without decapitating animals.

CONCLUSIONS

We demonstrated a correlation between the MRI grading scale and the current SAH grading scale in an endovascular perforation rat model. The MRI grading scale allows evaluation of SAH severity without euthanizing animals.

DDR1 may play a key role in destruction of the blood-brain barrier after cerebral ischemia-reperfusion

Discoidin domain receptor 1 (DDR1) has been shown to mediate matrix metalloproteinase-9 (MMP-9) secretions and degrade all extracellular matrix compounds in mammalian tumor cells. We hypothesized that DDR1 expression will be elevated and the blood-brain barrier (BBB) will be damaged after focal cerebral ischemia in rats. Inhibiting DDR1 expression can alleviate BBB disruption and cerebral ischemic damage via down-regulation of MMP-9 expression and activity. To test our hypothesis, we injected specific DDR1 siRNA into ipsilateral ischemic lateral ventricles in a focal ischemic model. Our results showed that phospho-DDR1 expression increased after ischemia/reperfusion (I/R) injury (p < 0.01). Inactivation of DDR1 by specific siRNA caused a decrease in phospho-DDR1 and MMP-9 expression in the ischemic cortex, reduced stroke-induced infarct volume, and alleviated BBB disruption in rat brain following I/R injury (p < 0.01). Our results suggested that DDR1-siRNA attenuates phospho-DDR1 and MMP-9 upregulation, which was followed by a reduction in infarction and BBB disruption in the ischemic brain after I/R injury. DDR1 may represent a molecular target for the prevention of BBB disruption after cerebral I/R injury.

Mouse cerebral magnetic resonance imaging fails to visualize brain volume changes after experimental subarachnoid hemorrhage

BACKGROUND

Brain atrophy after subarachnoid hemorrhage (SAH) has been detected in humans and might serve as a functional read-out parameter for neuropsychological deficits. To determine whether serial magnetic resonance imaging (MRI) can provide information on brain atrophy in animals as well, mice that had undergone experimental SAH were scanned repeatedly after the bleeding.

METHODS

Using a 7-T rodent MRI, six mice were evaluated for total hemispheric, cerebrospinal fluid (CSF) and hippocampal volumes on days 1, 2, 4, 21, 28, 42 and 60 after experimental SAH or sham operation, respectively.

RESULTS

Repeated MRI scanning demonstrated a very high reproducibility with minimum standard deviation. Nevertheless, no significant differences were found between the two groups concerning hemispherical volumes or hippocampal volumes. A transient but significant increase in CSF volume was detected on days 2 and 60 after SAH. Compared with the existing method, no MRI data on brain atrophy in mice after experimental SAH have been published.

CONCLUSION

Repeated brain MRI in mice after experimental SAH did not provide additional information on brain atrophy. Our data suggest that this is not due to a lack of sensitivity of the method. Despite all promising details about MRI, our results should initiate careful consideration (additional sequences/other questions) before its further use in this certain area, especially since it is expensive and associated with demanding logistics.

The pathophysiology and treatment of delayed cerebral ischaemia following subarachnoid haemorrhage

Cerebral vasospasm has traditionally been regarded as an important cause of delayed cerebral ischaemia (DCI) which occurs after aneurysmal subarachnoid haemorrhage, and often leads to cerebral infarction and poor neurological outcome. However, data from recent studies argue against a pure focus on vasospasm as the cause of delayed ischaemic complications. Findings that marked reduction in the incidence of vasospasm does not translate to a reduction in DCI, or better outcomes has intensified research into other possible mechanisms which may promote ischaemic complications. Early brain injury and cell death, blood-brain barrier disruption and initiation of an inflammatory cascade, microvascular spasm, microthrombosis, cortical spreading depolarisations and failure of cerebral autoregulation, have all been implicated in the pathophysiology of DCI. This review summarises the current knowledge about the mechanisms underlying the development of DCI. Furthermore, it aims to describe and categorise the known pharmacological treatment options with respect to the presumed mechanism of action and its role in DCI.

Melatonin attenuates inflammatory response-induced brain edema in early brain injury following a subarachnoid hemorrhage: a possible role for the regulation of pro-inflammatory cytokines

Melatonin is a strong anti-oxidant that has beneficial effects against early brain injury (EBI) following a subarachnoid hemorrhage (SAH) in rats; protection includes the reduction of both mortality and neurological deficits. The molecular mechanisms underlying these clinical effects in the SAH model have not been clearly identified. This study examined the influence of melatonin on brain edema secondary to disruption of the blood-brain barrier (BBB) and the relationship between these effects and pro-inflammatory cytokines 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. Melatonin treatment markedly attenuated brain edema secondary to BBB dysfunctions by preventing the disruption of tight junction protein expression (ZO-1, occludin, and claudin-5). Melatonin treatment also repressed cortical levels of pro-inflammatory cytokines (IL-1β, IL-6, and TNF-α), which were increased in EBI 24 hr after SAH. To further identify the mechanism of this protection, we demonstrated that administration of melatonin attenuated matrix metallopeptidase 9 expression/activity and vascular endothelial growth factor expression, which are related to the inflammatory response and BBB disruption in EBI after SAH. Taken together, this report shows that melatonin prevents disruption of tight junction proteins which might play a role in attenuating brain edema secondary to BBB dysfunctions by repressing the inflammatory response in EBI after SAH, possibly associated with regulation of pro-inflammatory cytokines.

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.

Apoptosis and necrosis in the circumventricular organs after experimental subarachnoid hemorrhage as detected with annexin V and caspase 3 immunostaining

OBJECTIVES

The circumventricular organs (CVOs) are essential for most autonomic and endocrine functions. Trauma and bleeding can affect their function. The aim of this study was to investigate apoptosis and necrosis in CVOs in the early period after experimental subarachnoid hemorrhage (SAH) in rats, using annexin V affinity and caspase 3 immunostaining.

METHODS

Three experimental groups were used: Days 1 and 2 after SAH, and a control group, seven Wistar albino rats each. Subarachnoid hemorrhage was accomplished by transclival basilar artery puncture. Rats were perfused with 0.9% NaCl and 0·1M phosphate buffer pH 7.4 until heart stoppage. Apoptosis and necrosis in CVOs were measured by flow cytometry with annexin V staining, and by caspase 3 immunostaining.

RESULTS

Apoptosis in the organum vasculosum lamina terminalis (OVLT), median eminence (ME), and area postrema (AP) was significantly higher in the Day 1 group than in the control group. Apoptosis in the subfornicial organ (SFO), OVLT, ME, and AP was significantly higher in the Day 2 group than in the control group. There were significant differences between the Day 1 and Day 2 groups, except for AP. Necrosis in SFO and OVLT was significantly higher in the Day 2 group than in the Day 1 or control groups, whereas necrosis in the ME and AP did not differ between the three groups. Caspase 3-positive cell density was more intense in the Day 2 group than in the Day 1 and control groups.

DISCUSSION

Prevention of apoptosis may potentially improve impaired functions of CVOs after SAH.

Early brain injury, an evolving frontier in subarachnoid hemorrhage research

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

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.

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

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

Memantine alleviates brain injury and neurobehavioral deficits after experimental subarachnoid hemorrhage

Subarachnoid hemorrhage (SAH) causes brain injury via glutamate excitotoxicity, which leads to an excessive Ca(2+) influx and this starts an apoptotic cascade. Memantine has been proven to reduce brain injury in several types of brain insults. This study investigated the neuro-protective potential of memantine after SAH and explored the underlying mechanisms. An endovascular perforation rat model of SAH was used and Sprague-Dawley rats were randomized into sham surgery, SAH + vehicle, and SAH + memantine groups. The effects of memantine on SAH were evaluated by assessing the neuro-behavioral functions, blood-brain barrier (BBB) permeability and neuronal cell preservation. The mechanisms of action of memantine, with its N-methyl-D-aspartate (NMDA) antagonistic characteristics on nitric oxide synthase (NOS) expression and peroxynitrite formation, were also investigated. The apoptotic cascade after SAH was suppressed by memantine. Neuronal NOS (nNOS) expression, peroxynitrite formation, and subsequent oxidative/nitrosative stress were also reduced. Memantine effectively preserved BBB integrity, rescued neuronal injury, and improved neurological outcome in experimental SAH. Memantine has neuro-protective potential in experimental SAH and may help combat SAH-induced brain damage in the future.

Role of oxidized LDL and lectin-like oxidized LDL receptor-1 in cerebral vasospasm after subarachnoid hemorrhage

OBJECT

Cerebral vasospasm after subarachnoid hemorrhage (SAH) is a serious complication. Free radicals derived from subarachnoid clotting are recognized to play an important role. Oxidized low-density lipoprotein (ox-LDL) and lectin-like oxidized LDL receptor-1 (LOX-1) have been shown to be related to the pathogenesis of atherosclerosis and may increase in cerebral arteries after SAH, due to the action of free radicals derived from a subarachnoid clot. These molecules may also affect the pathogenesis of vasospasm, generating intracellular reactive oxygen species and downregulating the expression of endothelial NO synthase (eNOS). If so, apple polyphenol might be effective in the prevention of vasospasm due to an abundant content of procyanidins, which exhibit strong radical scavenging effects, and the ability to suppress ox-LDL and LOX-1. The purposes of this study were to investigate changes in levels of ox-LDL and LOX-1 after SAH and whether administering apple polyphenol can modify cerebral vasospasm.

METHODS

Forty Japanese white rabbits were assigned randomly to 4 groups: an SAH group (n = 10); a shamoperation group (n = 10), which underwent intracisternal saline injection; a low-dose polyphenol group (n = 10) with SAH and oral administration of apple polyphenol at 10 mg/kg per day from Day 0 to Day 3; and a high-dose polyphenol group (n = 10) with SAH and oral administration of apple polyphenol at 50 mg/kg per day. At Day 4, the basilar artery and brain was excised from each rabbit. The degree of cerebral vasospasm was evaluated by measuring the cross-sectional area of each basilar artery, and the expression of ox-LDL, LOX-1, and eNOS was examined for each basilar artery by immunohistochemical staining and reverse transcriptase polymerase chain reaction. In addition, neuronal apoptosis in the cerebral cortex was evaluated by TUNEL.

RESULTS

Compared with the sham group, the expression of ox-LDL and LOX-1 in the basilar arterial wall was significantly increased in the SAH group, the expression of eNOS was significantly decreased, and the cross-sectional area of basilar artery was significantly decreased. Compared with the SAH group, the cross-sectional area of basilar artery was increased in the polyphenol groups, together with the decreased expression of ox-LDL and LOX-1 and the increased expression of eNOS. In the high-dose polyphenol group, those changes were statistically significant compared with the SAH group. In the low-dose polyphenol group, those changes were smaller than in the high-dose polyphenol group. No apoptosis and no changes were seen in the cerebral cortex in all groups.

CONCLUSIONS

This is the first study suggesting that ox-LDL and LOX-1 increase due to SAH and that they may play a role in the pathogenesis of vasospasm. It is assumed that procyanidins in apple polyphenol may inhibit a vicious cycle of ox-LDL, LOX-1, and ROS in a dose-dependent manner. Apple polyphenol is a candidate for preventive treatment of cerebral vasospasm.

Voltage-dependent anion channels (VDACs) promote mitophagy to protect neuron from death in an early brain injury following a subarachnoid hemorrhage in rats

The term mitophagy is coined to describe the selective removal of mitochondria by autophagy but the process itself is still contentious, especially in the early period following subarachnoid hemorrhage (SAH). In the present study, we investigated the role of mitophagy following 48h after SAH injury in rats. Specifically evaluating whether mitophagy, through voltage dependant anion channels (VDACs) interacting with microtubule-associated protein 1 light chain 3, could orchestrate the induction of apoptotic and necrotic cell death in neurons, a VDAC1siRNA and an activitor Rapamycian (RAPA), were engaged. One hundred and twelve male Sprague-Dawley rats were randomly divided into 4 groups: Sham, SAH, SAH+VDAC1siRNA, and SAH+RAPA. Outcomes measured included mortality rate, brain edema, BBB disruption, and neurobehavioral testing. We also used western blotting techniques to analyze the expressions of key mitophagic/autophagic proteins and pro-apoptotic protein such as ROS, VDAC1, LC-3II and Caspase-3. Rapamycin treatment significantly improved the mortality rate, cerebral edema, and neurobehavioral deficits; apoptotic and necrotic cell death in neurons were reduced by Rapamycin following SAH injury. However, VDAC1siRNA worsened the brain injury following SAH. Immunohistochemical staining and western blot analysis demonstrated a decreased expression of VDAC1, LC3II, and an increase of ROS and Caspase-3 followed by VDAC1siRNA administration. In conclusion, mitophagy induced by VDAC1 following SAH injury may in fact play a significant role in neuroprotection, the mechanism which may be through the attenuation of the apoptosic and necrosic molecular pathways. This translates a preservation of functional integrity and an improvement in mortality.

Arachidonic acid induces brain endothelial cell apoptosis via p38-MAPK and intracellular calcium signaling

Arachidonic acid (AA), a bioactive fatty acid whose levels increase during neuroinflammation, contributes to cerebral vascular damage and dysfunction. However, the mode of injury and underlying signaling mechanisms remain unknown. Challenge of primary human brain endothelial cells (HBECs) with AA activated a stress response resulting in caspase-3 activation, poly(ADP-ribose) polymerase cleavage, and disruption of monolayer integrity. AA also induced loss of mitochondrial membrane potential and cytochrome c release consistent with activation of intrinsic apoptosis. HBEC stimulation with AA resulted in sustained p38-MAPK activation and subsequent phosphorylation of mitogen-activated protein kinase activated protein-2 (MAPKAP-2) kinase and heat shock protein-27 (Hsp27). Conversely, other unsaturated and saturated fatty acids had no effect. Pharmacological and RNA interference-mediated p38α or p38β suppression abrogated AA signaling to caspase-3 and Hsp27, suggesting involvement of both p38 isoforms in AA-induced HBEC apoptosis. Hsp27 silencing also blocked caspase-3 activation. AA stimulated intracellular calcium release, which was attenuated by inositol 1,4,5-trisphosphate (IP3) receptor antagonists. Blockade of intracellular calcium release decreased caspase-3 activation, but had no effect on AA-induced p38-MAPK activation. However, inhibition of p38-MAPK or blockade of intracellular calcium mobilization abrogated AA-induced cytochrome c release. AA-induced caspase-3 activation was abrogated by pharmacological inhibition of lipooxygenases. These findings support a previously unrecognized signaling cooperation between p38-MAPK/MAPKAP-2/Hsp27 and intracellular calcium release in AA-induced HBEC apoptosis and suggest its relevance to neurological disorders associated with vascular inflammation.

The ferric iron chelator 2,2'-dipyridyl attenuates basilar artery vasospasm and improves neurological function after subarachnoid hemorrhage in rabbits

We investigated the efficacy of the ferrous iron (Fe(2+)) chelator 2,2'-dipyridyl (DP) to attenuate cerebral vasospasm after subarachnoid hemorrhage (SAH). Thirty-six New Zealand white rabbits were randomly assigned to four groups: untreated control, SAH, SAH + dimethyl sulfoxide (DMSO) vehicle, and SAH + DP. SAH was induced by injection of autologous blood into the cisterna magna and then DP or vehicle was infused into the cistern magna for 5 days (20 mg/kg/day or an equal volume of DMSO). Neurological deficit score (NDS) was used to assess neurological function and cerebral angiography to measure basilar artery (BA) diameter following SAH. TUNEL staining was used to detect BA endothelial cell apoptosis, and immunohistochemistry and Western blotting to assess changes in caspase-3 protein levels 5 days post-SAH. The SAH + DP group had a significantly larger mean BA diameter and lower mean NDS post-SAH compared to the SAH + DMSO and SAH groups (p < 0.05). TUNEL-positive cell numbers and caspase-3 levels were significantly reduced in BA endothelial cells of the SAH + DP group as compared to the SAH and SAH + DMSO groups (p < 0.05). The iron chelator DP reduced vasospasm and neurological sequelae in rabbits, likely by chelating the Fe(2+) in oxyhemoglobin and reducing oxidative stress-induced endothelial cell apoptosis.

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.

The endothelium, a protagonist in the pathophysiology of critical illness: focus on cellular markers

The endotheliumis key in the pathophysiology of numerous diseases as a result of its precarious function in the regulation of tissue homeostasis. Therefore, its clinical evaluation providing diagnostic and prognostic markers, as well as its role as a therapeutic target, is the focus of intense research in patientswith severe illnesses. In the critically ill with sepsis and acute brain injury, the endothelium has a cardinal function in the development of organ failure and secondary ischemia, respectively. Cellular markers of endothelial function such as endothelial progenitor cells (EPC) and endothelialmicroparticles (EMP) are gaining interest as biomarkers due to their accessibility, although the lack of standardization of EPC and EMP detection remains a drawback for their routine clinical use. In this paper we will review data available on EPC, as a general marker of endothelial repair, and EMP as an equivalent of damage in critical illnesses, in particular sepsis and acute brain injury. Their determination has resulted in new insights into endothelial dysfunction in the critically ill. It remains speculative whether their determination might guide therapy in these devastating acute disorders in the near future.

Necrostatin-1 reduces neurovascular injury after intracerebral hemorrhage

Intracerebral hemorrhage (ICH) is the most common form of hemorrhagic stroke, accounting for 15% of all strokes. ICH has the highest acute mortality and the worst long-term prognosis of all stroke subtypes. Unfortunately, the dearth of clinically effective treatment options makes ICH the least treatable form of stroke, emphasizing the need for novel therapeutic targets. Recent work by our laboratory identified a novel role for the necroptosis inhibitor, necrostatin-1, in limiting neurovascular injury in tissue culture models of hemorrhagic injury. In the present study, we tested the hypothesis that necrostatin-1 reduces neurovascular injury after collagenase-induced ICH in mice. Necrostatin-1 significantly reduced hematoma volume by 54% at 72 h after-ICH, as compared to either sham-injured mice or mice administered an inactive, structural analogue of necrostatin-1. Necrostatin-1 also limited cell death by 48%, reduced blood-brain barrier opening by 51%, attenuated edema development to sham levels, and improved neurobehavioral outcomes after ICH. These data suggest a potential clinical utility for necrostatin-1 and/or novel necroptosis inhibitors as an adjunct therapy to reduce neurological injury and improve patient outcomes after ICH.

Therapeutic implications of estrogen for cerebral vasospasm and delayed cerebral ischemia induced by aneurysmal subarachnoid hemorrhage

Cerebral vasospasm (CV) remains the leading cause of delayed morbidity and mortality following aneurysmal subarachnoid hemorrhage (SAH). However, increasing evidence supports etiologies of delayed cerebral ischemia (DCI) other than CV. Estrogen, specifically 17 β -estradiol (E2), has potential therapeutic implications for ameliorating the delayed neurological deterioration which follows aneurysmal SAH. We review the causes of CV and DCI and examine the evidence for E2-mediated vasodilation and neuroprotection. E2 potentiates vasodilation by activating endothelial nitric oxide synthase (eNOS), preventing increased inducible NOS (iNOS) activity caused by SAH, and decreasing endothelin-1 production. E2 provides neuroprotection by increasing thioredoxin expression, decreasing c-Jun N-terminal kinase activity, increasing neuroglobin levels, preventing SAH-induced suppression of the Akt signaling pathway, and upregulating the expression of adenosine A2a receptor. The net effect of E2 modulation of these various effectors is the promotion of neuronal survival, inhibition of apoptosis, and decreased oxidative damage and inflammation. E2 is a potentially potent therapeutic tool for improving outcomes related to post-SAH CV and DCI. However, clinical evidence supporting its benefits remains lacking. Given the promising preclinical data available, further studies utilizing E2 for the treatment of patients with ruptured intracranial aneurysms appear warranted.

CT perfusion-derived mean transit time of cortical brain has a negative correlation with the plasma level of Nitric Oxide after subarachnoid hemorrhage

BACKGROUND

Vasospasm of both large and small parenchymal arteries may contribute to the occurrence of delayed ischemic neurological deficits, and nitric oxide(NO) is an important mediators in the development of cerebral vasospasm after subarachnoid hemorrhage (SAH). We used a rabbit two-hemorrhage model to investigate changes in plasma NO after SAH, and the relationship between NO and brain microcirculation.

METHODS

SAH was induced in rabbits and a control group was sham operated. There were 32 rabbits in each group that survived the second operation, and they were randomly assigned to four groups of eight rabbits each for follow-up assessments on Days 1, 4, 7, or 14, respectively. Cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT) were calculated at six regions of interest (ROIs): symmetrical areas of the frontal, parietal-occipital, and temporal lobes. Before the contrast CT scan, blood was drawn from the central artery of the ear for measurement of plasma NO.

RESULTS

In the control group, there was no difference in CBV, CBF, and MTT in the six ROIs, and plasma NO was unchanged. Compared to controls, in the SAH group, CBV decreased slightly in the six ROIs (P > 0.05), frontal lobe CBF decreased, MTT increased (P < 0.05, for both), and NO plasma levels were significantly lower (P < 0.01).

CONCLUSIONS

There was a significant correlation between the increase in MTT and the decrease in plasma NO (P < 0.05), We hypothesized that normalization of NO might have a positive influence on brain microcirculation following SAH.

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.

Endoplasmic reticulum stress is associated with neuroprotection against apoptosis via autophagy activation in a rat model of subarachnoid hemorrhage

Endoplasmic reticulum (ER) stress might play an important role in a range of neurological diseases; however, this phenomenon's role in subarachnoid hemorrhage (SAH) remains unclear. In this study, we explored the potential role of endoplasmic reticulum stress in early brain injury following SAH.84 rats were used for an endovascular perforation-induced subarachnoid hemorrhage model. The rats were intraperitoneally pretreated with the ER stress inducer tunicamycin (Tm) or with the inhibitor tauroursodeoxycholic acid (TUDCA) before SAH onset. An intracerebral ventricular infusion of autophagy inhibitor 3-methyladenine (3-MA) was also used to determine the relation between autophagy and ER stress in early brain injury following SAH. At 24h, rats were neurologically evaluated, and their brains were extracted for molecular biological and histological studies. ER stress was activated in rats after 24h of SAH. Enhanced ER stress via Tm pretreatment significantly improved neurological deficits, attenuated the expression of pro-apoptotic molecules of caspase-3 and reduced the number of TUNEL-positive cells. In contrast, the ER stress inhibitor TUDCA aggravated neurological deficits and apoptotic cell death. Western blot analysis revealed that levels of the autophagic protein Beclin 1 and the ratio of LC3-II to LC3-I were both increased by Tm infusion and reduced by TUDCA administration. The suppression of autophagic activity with 3-MA attenuated Tm-induced anti-apoptotic effects. Our study indicates that ER stress alleviates early brain injury following SAH via inhibiting apoptosis. This neuroprotective effect is most likely exerted by autophagy activation.

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.

The rodent endovascular puncture model of subarachnoid hemorrhage: mechanisms of brain damage and therapeutic strategies

Subarachnoid hemorrhage (SAH) represents a considerable health problem. To date, limited therapeutic options are available. In order to develop effective therapeutic strategies for SAH, the mechanisms involved in SAH brain damage should be fully explored. Here we review the mechanisms of SAH brain damage induced by the experimental endovascular puncture model. We have included a description of similarities and distinctions between experimental SAH in animals and human SAH pathology. Moreover, several novel treatment options to diminish SAH brain damage are discussed.SAH is accompanied by cerebral inflammation as demonstrated by an influx of inflammatory cells into the cerebral parenchyma, upregulation of inflammatory transcriptional pathways and increased expression of cytokines and chemokines. Additionally, various cell death pathways including cerebral apoptosis, necrosis, necroptosis and autophagy are involved in neuronal damage caused by SAH.Treatment strategies aiming at inhibition of inflammatory or cell death pathways demonstrate the importance of these mechanisms for survival after experimental SAH. Moreover, neuroregenerative therapies using stem cells are discussed as a possible strategy to repair the brain after SAH since this therapy may extend the window of treatment considerably. We propose the endovascular puncture model as a suitable animal model which resembles the human pathology of SAH and which could be applied to investigate novel therapeutic therapies to combat this debilitating insult.

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.

Novel siRNA delivery strategy: a new "strand" in CNS translational medicine?

RNA interference has been envisaged as a powerful tool for molecular and clinical investigation with a great potential for clinical applications. In recent years, increased understanding of cancer biology and stem cell biology has dramatically accelerated the development of technology for cell and gene therapy in these areas. This paper is a review of the most recent report of innovative use of siRNA to benefit several central nervous system diseases. Furthermore, a description is made of innovative strategies of delivery into the brain by means of viral and non-viral vectors with high potential for translation into clinical use. Problems are also highlighted that might hamper the transition from bench to bed, analyzing the lack of reliable preclinical models with predictive validity and the lack of effective delivery systems, which are able to overcome biological barriers and specifically reach the brain site of action.

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.

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.