Tumor necrosis factor-stimulated gene-6 ameliorates early brain injury after subarachnoid hemorrhage by suppressing NLRC4 inflammasome-mediated astrocyte pyroptosis

Subarachnoid hemorrhage is associated with high morbidity and mortality and lacks effective treatment.Pyroptosis is a crucial mechanism underlying early brain injury after subarachnoid hemorrhage.Previous studies have confirmed that tumor necrosis factor-stimulated gene-6(TSG-6)can exert a neuroprotective effect by suppressing oxidative stress and apoptosis.However,no study to date has explored whether TSG-6 can alleviate pyroptosis in early brain injury after subarachnoid hemorrhage.In this study,a C57BL/6J mouse model of subarachnoid hemorrhage was established using the endovascular perforation method.Our results indicated that TSG-6 expression was predominantly detected in astrocytes,along with NLRC4 and gasdermin-D(GSDMD).The expression of NLRC4,GSDMD and its N-terminal domain(GSDMD-N),and cleaved caspase-1 was significantly enhanced after subarachnoid hemorrhage and accompanied by brain edema and neurological impairment.To explore how TSG-6 affects pyroptosis during early brain injury after subarachnoid hemorrhage,recombinant human TSG-6 or a siRNA targeting TSG-6 was injected into the cerebral ventricles.Exogenous TSG-6 administration downregulated the expression of NLRC4 and pyroptosis-associated proteins and alleviated brain edema and neurological deficits.Moreover,TSG-6 knockdown further increased the expression of NLRC4,which was accompanied by more severe astrocyte pyroptosis.In summary,our study revealed that TSG-6 provides neuroprotection against early brain injury after subarachnoid hemorrhage by suppressing NLRC4 inflammasome activation-induced astrocyte pyroptosis.

Obstructive sleep apnea aggravates neuroinflammation and pyroptosis in early brain injury following subarachnoid hemorrhage via ASC/HIF-1α pathway

Obstructive sleep apnea can worsen the prognosis of subarachnoid hemorrhage.Howeve r,the underlying mechanism remains unclear.In this study,we established a mouse model of subarachnoid hemorrhage using the endovascular perforation method and exposed the mice to intermittent hypoxia for 8 hours daily for 2 consecutive days to simulate sleep apnea.We found that sleep apnea aggravated brain edema,increased hippocampal neuron apoptosis,and worsened neurological function in this mouse model of subarachnoid hemorrhage.Then,we established an in vitro HT-22 cell model of hemin-induced subarachnoid hemorrhage/intermittent hypoxia and found that the cells died,and lactate dehydrogenase release increased,after 48 hours.We further investigated the underlying mechanism and found that sleep apnea increased the expression of hippocampal neuroinflammatory factors interleukin-1β,interleukin-18,inte rleukin-6,nuclear factorκB,pyro ptosis-related protein caspase-1,pro-caspase-1,and NLRP3,promoted the prolife ration of astrocytes,and increased the expression of hypoxia-inducible factor 1αand apoptosis-associated speck-like protein containing a CARD,which are the key proteins in the hypoxia-inducible factor 1α/apoptosis-associated speck-like protein containing a CARD signaling pathway.We also found that knockdown of hypoxia-inducible factor 1αexpression in vitro greatly reduced the damage to HY22 cells.These findings suggest that sleep apnea aggravates early brain injury after subarachnoid hemorrhage by aggravating neuroinflammation and pyroptosis,at least in part through the hypoxia-inducible factor 1α/apoptosis-associated speck-like protein containing a CARD signaling pathway.

Matricellular proteins as possible biomarkers for early brain injury after aneurysmal subarachnoid hemorrhage

Aneurysmal subarachnoid hemorrhage remains devastating,and the most important determinant of poor outcome is early brain injury（EBI）.In clinical settings,as a surrogate marker of EBI,loss of consciousness at ictus,poor initial clinical grades,and some radiographic findings are used,but these markers are somewhat subjective.Thus,it is imperative to find biomarkers of EBI that have beneficial prognostic and therapeutic implications.In our opinion,an ideal biomarker is a molecule that is implicated in the pathogenesis of both EBI and subsequently developing delayed cerebral ischemia（DCI）,being a therapeutic target,and can be measured easily in the peripheral blood in an acute stage.A good candidate of such a biomarker is a matricellular protein,which is a secreted,inducible and multifunctional extracellular matrix protein.There are many kinds of matricellular proteins reported,but only tenascin-C,osteopontin,galectin-3 and periostin are reported relevant to EBI and DCI.Reliable biomarkers of EBI may stratify aneurysmal subarachnoid hemorrhage patients into categories of risk to develop DCI,and allow objective monitoring of the response to treatment for EBI and earlier diagnosis of DCI.This review emphasizes that further investigation of matricellular proteins as an avenue for biomarker discovery is warranted.

Role of Glucose-regulated Protein 78 in Early Brain Injury after Experimental Subarachnoid Hemorrhage in Rats

Early brain injury（EBI） plays a key role in the pathogenesis of subarachnoid hemorrhage（SAH）. This study investigated the role of glucose-regulated protein 78（GRP78） in EBI after SAH. Male Sprague-Dawley rats（n=108） weighing 260±40 g were divided into control, sham-operated, and operated groups. Blood was injected into the prechiasmatic cistern of rats in the operated group. Neurological scores, ultrastructures of neurons, apoptosis, and GRP78 expression in the hippocampus were examined using Garcia scoring system, transmission electron microscopy, terminal deoxynucleotidyl transferase-mediated d UTP nick-end labelling, and Western blotting at 1, 6, 12, 24, 48, and 72 h after SAH, respectively. The results showed that neurological scores were significantly decreased in the operated group as compared with those in control and sham-operated groups at 12, 24, 48, and 72 h. Metachromatin, chromatin pyknosis at the edge, endoplasmic reticulum swelling, and invagination of nuclear membrane were observed at 24 h in the operated group, indicating the early morphological changes of apoptosis. The number of apoptotic cells was significantly increased in the operated group as compared with that in control and sham-operated groups at 6, 12, 24, 48, and 72 h. The GRP78 protein expression levels in the operated group were significantly elevated at all time points and reached the peak at 12 h. GRP78 expression was positively associated with apoptosis cells and negatively with neurological scores. In conclusion, EBI was demonstrated to occur after SAH and GRP78 was involved in the development of EBI after SAH.

Study on the Effect of Ginaton on Reducing Cerebral Vasospasm and Early Brain Injury after Hemorrhagic Stroke by Inhibiting Inflammatory Response

Objective:The objective of this study was to investigate the effects and possible mechanisms of action of ginseng on cerebral vasospasm and early brain injury(EBI)following hemorrhagic stroke.Materials and Methods:Sprague-Dawley(SD)rats(n=48)were randomly divided into sham operation(sham group),subarachnoid hemorrhage(SAH)model(SAH group),normal saline(NS group),and Ginaton(Extract of Ginkgo Biloba Leaves Drops)intervention(gin group)groups.MCP-1 m RNA and tumor necrosis factor levels were detected using reverse transcription-polymerase chain reaction.The relative expression of m RNA was detected by Western blotting.Results:(1)Compared with the sham group,the SAH,NS,and gin groups had different degrees of neurological dysfunction.Compared with the SAH and NS groups,the neurological deficits in the gin group were significantly improved(P<0.05).(2)Compared with the sham group,the relative expression levels of MCP-1 m RNA in the SAH,NS,and gin groups were 5.1±0.9,3.4±0.6,and 2.5±0.4,respectively;the relative expression levels of m RNA were 13.3±2.4,11.2±1.8,and 3.8±0.6,respectively.(3)The apoptosis rates of brain tissue in the sham,SAH,NS,and gin groups were 4.8±0.7,54.2±10.3,50.1±7.4,and 28.4±4.5,respectively.(4)Western blot showed that the relative expression levels of toll-like receptor-4(TLR-4)protein in the sham,SAH,NS,and gin groups were 0.29±0.03,0.87±0.15,0.65±0.13,and 0.41±0.17,respectively;the relative expression levels of B protein were 0.21±0.04,0.96±0.14,0.73±0.18,and 0.30±0.05,respectively.Gin treatment could inhibit TLR-4 and nuclear factor-κB(NF-κB)protein expression.Conclusions:Dona tablets may inhibit activation of the NF-κB signaling pathway,and SAH-induced inflammatory response,so as to reduce cerebral vasospasm and EBI.

Baicalin Reduces Early Brain Injury after Subarachnoid Hemorrhage in Rats

Objective: To evaluate the effect of baicalin on subarachnoid hemorrhage(SAH) in rats and explore the potential mechanisms. Methods: Sprague-Dawley rats underwent experimental SAH and received treatment with baicalin at 10 or 50 mg/kg after 2 and 12 h of SAH. Neurological scores, brain water content, Evans-blue extravasation, and levels of glutathione peroxidase(GSH-Px), superoxide dismutase(SOD), myeloperoxidase(MPO), and malondialdehyde(MDA) were measured 24 h after SAH. Expression of nuclear factor erythroid-related factor 2(Nrf2), NAD(P)H: quinone oxidoreductase 1(NQO1), matrix metalloproteinase-9(MMP-9), aquaporin 4(AQP4), occludin, and zonulaoccludens-1(ZO-1) were detected in the brain by Western blot. Heme oxygenase-1(HO-1) was detected by quantitative polymerase chain reaction, and tumor necrosis factor-α(TNF-α) and interleukin-1β(IL-1β) were assessed by enzyme-linked immunosorbent assay. Results: Baicalin attenuated EBI 24 h after SAH in rats(P<0.05). Baicalin elevated neurological scores, GSH-Px, SOD, and increased the expression of Nrf2, NQO1, HO-1, occludin, and ZO-1 in SAH rats(P<0.05 or P<0.01). Baicalin reduced MPO, MDA, and the expression of MMP-9, AQP4, TNF-α, and IL-1β(P<0.05 or P<0.01). Conclusion: Baicalin reduced SAH-induced EBI, partially via activation of the Nrf2/HO-1 pathway and inhibition of MMP-9 and AQP4.

PTEN and AKT/GSK-3β/CRMP-2 signaling pathway are involved in neuronal apoptosis and axonal injury in early brain injury after SAH in rats

In early brain injury(EBI)after subarachnoid hemorrhage(SAH),white matter(WM)axonal injury plays a key role in the prognosis of the disease.The purpose of this study was to investigate the effects of phosphatase and tensin homolog deleted on chromosome ten(PTEN)on axonal injury and neuronal apoptosis post-SAH in rats and to find its underlying mechanism.Adeno-associated virus was injected into the lateral ventricle to suppress or promote PTEN.Neural function post-SAH in animals was determined by the modified Garcia score,beam balance,and Rotarod test,and the blood–brain barrier disruption was assessed by the brain water content.Axonal injury post-SAH was observed by TEM and determined by IF,and neuron apoptosis was measured by TUNEL staining.The mechanism was analyzed by Western blot to detect p-PTEN/PTEN,p-AKT/AKT,p-GSK-3β/GSK-3β,p-CRMP-2/CRMP-2,axonal injury markerβ-APP and pro-and anti-apoptosis proteins,including Bax and Bcl-2,expression.We found 1.After knocking down PTEN,neuronal apoptosis and axonal injury were alleviated,and nerve function and blood–brain barrier were protected;accordingly,after overexpression of PTEN,neuronal apoptosis and axon damage were aggravated,and nerve function damage and blood–brain barrier damage were increased.2.PTEN and AKT/GSK-3β/CRMP-2 pathway were jointly involved in regulating neuronal apoptosis and WM axon injury after SAH.According to our research,PTEN was a negative factor of EBI,and together with the AKT/GSK-3β/CRMP-2 signaling pathway aggravates neuronal apoptosis and WM axon damage after SAH.Inhibition of PTEN expression may become a new target for SAH treatment.

Schisandrin B Inhibits NLRP3 Inflammasome Pathway and Attenuates Early Brain Injury in Rats of Subarachnoid Hemorrhage

Objective: To determine whether Schisandrin B(Sch B) attenuates early brain injury(EBI) in rats with subarachnoid hemorrhage(SAH). Methods: Sprague-Dawley rats were divided into sham(sham operation), SAH, SAH+vehicle, and SAH+Sch B groups using a random number table. Rats underwent SAH by endovascular perforation and received Sch B(100 mg/kg) or normal saline after 2 and 12 h of SAH. SAH grading, neurological scores, brain water content, Evan’s blue extravasation, and terminal transferase-mediated dUTP nick end-labeling(TUNEL) staining were carried out 24 h after SAH. Immunofluorescent staining was performed to detect the expressions of ionized calcium binding adapter molecule 1(Iba-1) and myeloperoxidase(MPO) in the rat brain, while the expressions of B-cell lymphoma 2(Bcl-2), Bax, Caspase-3, nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing 3(NLRP3), apoptosis-associated specklike protein containing the caspase-1 activator domain(ASC), Caspase-1, interleukin(IL)-1β, and IL-18 in the rat brains were detected by Western blot. Results: Compared with the SAH group, Sch B significantly improved the neurological function, reduced brain water content, Evan’s blue content, and apoptotic cells number in the brain of rats(P<0.05 or P<0.01). Moreover, Sch B decreased SAH-induced expressions of Iba-1 and MPO(P<0.01). SAH caused the elevated expressions of Bax, Caspase-3, NLRP3, ASC, Caspase-1, IL-1β, and IL-18 in the rat brain(P<0.01), all of which were inhibited by Sch B(P<0.01). In addition, Sch B increased the Bcl-2 expression(P<0.01). Conclusion: Sch B attenuated SAH-induced EBI, which might be associated with the inhibition of neuroinflammation, neuronal apoptosis, and the NLRP3 inflammatory signaling pathway.

Elevated NKCC1 transporter expression facilitates early post-traumatic brain injury seizures

As a leading cause for morbidity and mortality in young adults,traumatic brain injury（TBI）,along with the poorly understood TBI-related seizures inducing their predispositions,pose a major health and socioeconomic problem in the world（Huang,2013）.

Sarcopenia diagnosed using masseter muscle area predictive of early mortality following severe traumatic brain injury

Traumatic brain injury（TBI）represents a global pandemic and is currently a leading cause of injury related death worldwide.Unfortunately,those who survive initial injury often suffer devastating functional,social,and economic consequences.

Therapeutic potential of stem cells in subarachnoid hemorrhage

Aneurysm rupture can result in subarachnoid hemorrhage,a condition with potentially severe consequences,such as disability and death.In the acute stage,early brain injury manifests as intracranial pressure elevation,global cerebral ischemia,acute hydrocephalus,and direct blood–brain contact due to aneurysm rupture.This may subsequently cause delayed cerebral infarction,often with cerebral vasospasm,significantly affecting patient outcomes.Chronic complications such as brain volume loss and chronic hydrocephalus can further impact outcomes.Investigating the mechanisms of subarachnoid hemorrhage-induced brain injury is paramount for identifying effective treatments.Stem cell therapy,with its multipotent differentiation capacity and anti-inflammatory effects,has emerged as a promising approach for treating previously deemed incurable conditions.This review focuses on the potential application of stem cells in subarachnoid hemorrhage pathology and explores their role in neurogenesis and as a therapeutic intervention in preclinical and clinical subarachnoid hemorrhage studies.

An early neuroprotective effect of atorvastatin against subarachnoid hemorrhage

Atorvastatin has been shown to reduce early brain edema and neuronal death after subarachnoid hemorrhage,but its mechanism is not clear.In this study,rat models of subarachnoid hemorrhage were established by autologous blood injection in the cisterna magna.Rat models were intragastrically administered 20 mg/kg atorvastatin 24 hours before subarachnoid hemorrhage,12 and 36 hours after subarachnoid hemorrhage.Compared with the controls,atorvastatin treatment demonstrated that at 72 hours after subarachnoid hemorrhage,neurological function had clearly improved;brain edema was remarkably relieved;cell apoptosis was markedly reduced in the cerebral cortex of rats;the number of autophagy-related protein Beclin-1-positive cells and the expression levels of Beclin-1 and LC3 were increased compared with subarachnoid hemorrhage only.The ultrastructural damage of neurons in the temporal lobe was also noticeably alleviated.The similarities between the effects of atorvastatin and rapamycin were seen in all the measured outcomes of subarachnoid hemorrhage.However,these were contrary to the results of 3-methyladenine injection,which inhibits the signaling pathway of autophagy.These findings indicate that atorvastatin plays an early neuroprotective role in subarachnoid hemorrhage by activating autophagy.The experimental protocol was approved by the Animal Ethics Committee of Anhui Medical University,China(904 Hospital of Joint Logistic Support Force of PLA;approval No.YXLL-2017-09)on February 22,2017.

Toll-like receptor 4 as a possible therapeutic target for delayed brain injuries after aneurysmal subarachnoid hemorrhage

Neuroinflammation is a well-recognized consequence of subarachnoid hemorrhage（SAH）, and Toll-like receptor（TLR） 4 may be an important therapeutic target for post-SAH neuroinflammation. Of the TLR family members, TLR4 is expressed in various cell types in the central nervous system, and is unique in that it can signal through both the myeloid differentiation primary-response protein 88-dependent and the toll receptor associated activator of interferon-dependent cascades to coordinate the maximal inflammatory response. TLR4 can be activated by many endogenous ligands having damage-associated molecular patterns including heme and fibrinogen at the rupture of an intracranial aneurysm, and the resultant inflammatory reaction and thereby tissue damages may furthermore activate TLR4. It is widely accepted that the excreted products of TLR4 signaling alter neuronal functions. Previous studies have focused on the pathway through nuclear factor（NF）-κΒ signaling among TLR4 signaling pathways as to the development of early brain injury（EBI） such as neuronal apoptosis and blood-brain barrier disruption, and cerebral vasospasm. However, many findings suggest that both pathways via NF-κΒ and mitogen-activated protein kinases may be involved in EBI and cerebral vasospasm development. To overcome EBI and cerebral vasospasm is important to improve outcomes after SAH, because both EBI and vasopasm are responsible for delayed brain injuries or delayed cerebral ischemia, the most important preventable cause of poor outcomes after SAH. Increasing evidence has shown that TLR4 signaling plays an important role in SAH-induced brain injuries. Better understanding of the roles of TLR4 signaling in SAH will facilitate development of new treatments.

In vivo observation of cerebral microcirculation after experimental subarachnoid hemorrhage in mice

Acute brain injury caused by subarachnoid hemorrhage is the major cause of poor prognosis. The pathology of subarachnoid hemorrhage likely involves major morphological changes in the microcirculation. However, previous studies primarily used fixed tissue or delayed injury models. Therefore, in the present study, we used in vivo imaging to observe the dynamic changes in cerebral microcirculation after subarachnoid hemorrhage. Subarachnoid hemorrhage was induced by perforation of the bifurcation of the middle cerebral and anterior cerebral arteries in male C57/BL6 mice. The diameter of pial arterioles and venules was measured by in vivo fluorescence microscopy at different time points within 180 minutes after subarachnoid hemorrhage. Cerebral blood flow was examined and leukocyte adhesion/albumin extravasation was determined at different time points before and after subarachnoid hemorrhage. Cerebral pial microcirculation was abnormal and cerebral blood flow was reduced after subarachnoid hemorrhage. Acute vasoconstriction occurred predominantly in the arterioles instead of the venules. A progressive increase in the number of adherent leukocytes in venules and substantial albumin extravasation were observed between 10 and 180 minutes after subarachnoid hemorrhage. These results show that major changes in microcirculation occur in the early stage of subarachnoid hemorrhage. Our findings may promote the development of novel therapeutic strategies for the early treatment of subarachnoid hemorrhage.

Neuroprotective mechanism of L-cysteine after subarachnoid hemorrhage

Hydrogen sulfide,which can be generated in the central nervous system from the sulfhydryl-containing amino acid,L-cysteine,by cystathionine-β-synthase,may exert protective effects in experimental subarachnoid hemorrhage;however,the mechanism underlying this effect is unknown.This study explored the mechanism using a subarachnoid hemorrhage rat model induced by an endovascular perforation technique.Rats were treated with an intraperitoneal injection of 100 mM L-cysteine(30μL)30 minutes after subarachnoid hemorrhage.At 48 hours after subarachnoid hemorrhage,hematoxylin-eosin staining was used to detect changes in prefrontal cortex cells.L-cysteine significantly reduced cell edema.Neurological function was assessed using a modified Garcia score.Brain water content was measured by the wet-dry method.L-cysteine significantly reduced neurological deficits and cerebral edema after subarachnoid hemorrhage.Immunofluorescence was used to detect the number of activated microglia.Reverse transcription-polymerase chain reaction(RT-PCR)was used to detect the levels of interleukin 1β and CD86 mRNA in the prefrontal cortex.L-cysteine inhibited microglial activation in the prefrontal cortex and reduced the mRNA levels of interleukin 1βand CD86.RT-PCR and western blot analysis of the complement system showed that L-cysteine reduced expression of the complement factors,C1q,C3αand its receptor C3aR1,and the deposition of C1q in the prefrontal cortex.Dihydroethidium staining was applied to detect changes in reactive oxygen species,and immunohistochemistry was used to detect the number of NRF2-and HO-1-positive cells.L-cysteine reduced the level of reactive oxygen species in the prefrontal cortex and the number of NRF2-and HO-1-positive cells.Western blot assays and immunohistochemistry were used to detect the protein levels of CHOP and GRP78 in the prefrontal cortex and the number of CHOP-and GRP78-positive cells.L-cysteine reduced CHOP and GRP78 levels and the number of CHOP-and GRP78-positive cells.The cystathionine-β-synthase inhibitor,aminooxyacetic acid,significantly reversed the above neuroprotective effects of L-cysteine.Taken together,L-cysteine can play a neuroprotective role by regulating neuroinflammation,complement deposition,oxidative stress and endoplasmic reticulum stress.The study was approved by the Animals Ethics Committee of Shandong University,China on February 22,2016(approval No.LL-201602022).