Necrostatin-1 attenuates early brain injury after subarachnoid hemorrhage in rats by inhibiting necroptosis

Necrostatin-1: a promising compound for neurological disorders

Necrostatin-1, a small molecular alkaloid, was identified as an inhibitor of necroptosis in 2005. Investigating the fundamental mechanism of Necrostatin-1 and its role in various diseases is of great significance for scientific and clinical research. Accumulating evidence suggests that Necrostatin-1 plays a crucial role in numerous neurological disorders. This review aims to provide a comprehensive overview of the potential functions of Necrostatin-1 in various neurological disorders, offering valuable insights for future research.

NeuroD1 administration ameliorated neuroinflammation and boosted neurogenesis in a mouse model of subarachnoid hemorrhage

BACKGROUND

Subarachnoid hemorrhage (SAH) causes significant long-term neurocognitive dysfunction, which is associated with hippocampal neuroinflammation. Growing evidences have shown that astrocytes played a significant role in mediating neuroinflammation. Recently, in vivo reprogramming of astrocytes to neurons by NeuroD1 or PTBP1 administration has generated a lot of interests and controversies. While the debates centered on the source of neurogenesis, no attention has been paid to the changes of the astrocytes-mediated neuroinflammation and its impact on endogenous neurogenesis after NeuroD1 administration.

METHODS

80 adult male C57BL/6 mice were used in this study. SAH was established by pre-chiasmatic injection of 100 μl blood. AAV-NeuroD1-GFP virus was injected to the hippocampus 3 day post-SAH. Neurocognitive function, brain water content, in vivo electrophysiology, Golgi staining, western blot and immunofluorescent staining were assessed at day 14 post-virus injection.

RESULTS

NeuroD1 administration markedly attenuated reactive astrocytes-mediated neuroinflammation by reversing neurotoxic A1 astrocytes transformation, decreasing the secretion of neuroinflammatory cytokines, and reducing the activation of harmful microglia. NeuroD1 treatment significantly reversed the brain-blood barrier impairment and promoted the release of neurotrophic factors pleiotrophin (PTN), all of which contributed to the improvement of cellular microenvironment and made it more suitable for neurogenesis. Interestingly, besides neurogenesis in the hippocampus from cells transfected with NeuroD1 at the early phase of SAH, NeuroD1 administration significantly boosted the endogenous neurogenesis at the late phase of SAH, which likely benefited from the improvement of the neuroinflammatory microenvironment. Functionally, NeuroD1 treatment significantly alleviated neurocognitive dysfunction impaired by SAH.

CONCLUSIONS

NeuroD1 significantly promoted neurofunctional recovery by attenuating reactive astrocytes-mediated neuroinflammation and boosting neurogenesis decimated by SAH. Specifically, NeuroD1 efficiently converted transfected cells, most likely astrocytes, to neurons at the early phase of SAH, suppressed astrocytes-mediated neuroinflammation and boosted endogenous neurogenesis at the late phase of SAH.

[Dihydromyricetin alleviates pyroptosis and necroptosis in mice with MPTP-induced chronic Parkinson's disease by inducing autophagy]

OBJECTIVE

To investigate the effect of 8-week dihydromyricetin (DHM) treatment on motor ability of mice with MPTP/probenecid-induced Parkinson's disease (PD) and explore the molecular mechanism.

METHODS

Sixty C57BL/6 mice were randomized into the control group, PD model group, PD+DHM group and PD+NEC-1 group (n=15). In the latter 3 groups, the mice were treated with 25 mg·kg-1·d-1 MPTP and 250 mg·kg-1·d-1 probenecid twice a week for 5 weeks to establish PD models; DHM (100 mg·kg-1·d-1) was administered 5 times a week via gavage for 8 weeks and NEC-1 (6.25 mg·kg-1·d-1, twice a week) via intraperitoneal injection for 5 weeks. The changes in motor function of the mice were assessed, and the expressions of TH, GFAP and Iba-1 in the substantia nigra were detected with immunofluorescence assay; serum levels of IL-1β and LDH were detected using ELISA. The mRNA expressions of TNF-α and IL-6 were determined with RT-PCR, and the expressions of TH and proteins associated with pyroptosis, neuroinflammation, necroptosis and autophagy in the striatum were detected using Western blotting. MPP +-activated Bv-2 cells were treated with different concentrations of DHM or 3-MA, and the expressions of proteins associated with autophagy and NLRP3 were detected using Western blotting; PI staining was used to detect cell necroptosis.

RESULTS

The PD mouse models showed significantly reduced TH-positive cells and TH protein expression (P < 0.001). DHM obviously ameliorated motor deficits and TH loss in PD mice, increased TH expression (P=0.0023), decreased α-syn levels (P < 0.001), lowered the protein expressions of GFAP (P=0.045) and Iba-1 (P < 0.001) and the mRNA and protein levels of TNF-α (P=0.0015) and IL-6 (P < 0.001), and increased IL-4 level (P < 0.001). The 8-week DHM treatment significantly suppressed pyroptosis and necroptosis and activated autophagy in the striatum of the PD mice. In MPP +-induced Bv-2 cells, DHM treatment effectively reversed autophagy impairment and inhibited NLRP3 and TNF-α, IL-6 and IL-1β release, and the anti--inflammatory effects of DHM was obviously blunted by 3-MA.

CONCLUSION

DHM can improve motor function of PD mice probably by activating autophagy to inhibit pyroptosis and necroptosis and reduce neuroinflammation.

New Insights of Early Brain Injury after Subarachnoid Hemorrhage: A Focus on the Caspase Family

Spontaneous subarachnoid hemorrhage (SAH), primarily caused by ruptured intracranial aneurysms, remains a prominent clinical challenge with a high rate of mortality and morbidity worldwide. Accumulating clinical trials aiming at the prevention of cerebral vasospasm (CVS) have failed to improve the clinical outcome of patients with SAH. Therefore, a growing number of studies have shifted focus to the pathophysiological changes that occur during the periods of early brain injury (EBI). New pharmacological agents aiming to alleviate EBI have become a promising direction to improve outcomes after SAH. Caspases belong to a family of cysteine proteases with diverse functions involved in maintaining metabolism, autophagy, tissue differentiation, regeneration, and neural development. Increasing evidence shows that caspases play a critical role in brain pathology after SAH. Therefore, caspase regulation could be a potential target for SAH treatment. Herein, we provide an overview pertaining to the current knowledge on the role of caspases in EBI after SAH, and we discuss the promising therapeutic value of caspase-related agents after SAH.

Deletion of Bak1 alleviates microglial necroptosis and neuroinflammation after experimental subarachnoid hemorrhage

Microglial necroptosis exacerbates neurodegenerative diseases, central nervous system (CNS) injury, and demonstrates a proinflammatory process, but its contribution to subarachnoid hemorrhage (SAH) is poorly characterized. BCL-2 homologous antagonist-killer protein (Bak1), a critical regulatory molecule of endogenous apoptosis, can be involved in the pathologic process of necroptosis by regulating mitochondrial permeability. In this study, we revealed microglia undergo necroptosis after SAH in vivo and vitro. Western blot revealed that Bak1 was elevated at 24 h after SAH. Knocked down of Bak1 by adeno-associated virus attenuates microglial necroptosis, alleviates neuroinflammation, and improves neurologic function after SAH in mice. Furthermore, oxyhemoglobin (10 μM) induced necroptosis in BV2 microglia, increasing Bak1 expression and mediating proinflammatory phenotype transformation, exacerbating oxidative stress and neuroinflammation. Abrogating BV2 Bak1 could reduce necroptosis by down-regulating the expression of phosphorylated pseudokinase mixed lineage kinase domain-like protein (p-MLKL), then down-regulating proinflammatory phenotype gene expression. RNA-Seq showed that disrupting BV2 Bak1 down-regulates multiple immune and inflammatory pathways and ameliorates cell injury by elevating thrombospondin 1 (THBS1) expression. In summary, we identified a critical regulatory role for Bak1 in microglial necroptosis and neuroinflammation after SAH. Bak1 is expected to be a potential target for the treatment strategy of SAH.

An Update on Antioxidative Stress Therapy Research for Early Brain Injury After Subarachnoid Hemorrhage

The main reasons for disability and death in aneurysmal subarachnoid hemorrhage (aSAH) may be early brain injury (EBI) and delayed cerebral ischemia (DCI). Despite studies reporting and progressing when DCI is well-treated clinically, the prognosis is not well-improved. According to the present situation, we regard EBI as the main target of future studies, and one of the key phenotype-oxidative stresses may be called for attention in EBI after laboratory subarachnoid hemorrhage (SAH). We summarized the research progress and updated the literature that has been published about the relationship between experimental and clinical SAH-induced EBI and oxidative stress (OS) in PubMed from January 2016 to June 2021. Many signaling pathways are related to the mechanism of OS in EBI after SAH. Several antioxidative stress drugs were studied and showed a protective response against EBI after SAH. The systematical study of antioxidative stress in EBI after laboratory and clinical SAH may supply us with new therapies about SAH.

Preclinical Evidence for the Interplay between Oxidative Stress and RIP1-Dependent Cell Death in Neurodegeneration: State of the Art and Possible Therapeutic Implications

Neurodegenerative diseases are the most frequent chronic, age-associated neurological pathologies having a major impact on the patient’s quality of life. Despite a heavy medical, social and economic burden they pose, no causative treatment is available for these diseases. Among the important pathogenic factors contributing to neuronal loss during neurodegeneration is elevated oxidative stress resulting from a disturbed balance between endogenous prooxidant and antioxidant systems. For many years, it was thought that increased oxidative stress was a cause of neuronal cell death executed via an apoptotic mechanism. However, in recent years it has been postulated that rather programmed necrosis (necroptosis) is the key form of neuronal death in the course of neurodegenerative diseases. Such assumption was supported by biochemical and morphological features of the dying cells as well as by the fact that various necroptosis inhibitors were neuroprotective in cellular and animal models of neurodegenerative diseases. In this review, we discuss the relationship between oxidative stress and RIP1-dependent necroptosis and apoptosis in the context of the pathomechanism of neurodegenerative disorders. Based on the published data mainly from cellular models of neurodegeneration linking oxidative stress and necroptosis, we postulate that administration of multipotential neuroprotectants with antioxidant and antinecroptotic properties may constitute an efficient pharmacotherapeutic strategy for the treatment of neurodegenerative diseases.

Celastrol protects against early brain injury after subarachnoid hemorrhage in rats through alleviating blood-brain barrier disruption and blocking necroptosis

BACKGROUND

Subarachnoid hemorrhage (SAH) is a life-threatening disease worldwide, and effective pharmaceutical treatment is still lacking. Celastrol is a plant-derived triterpene which showed neuroprotective potential in several types of brain insults. This study aimed to investigate the effects of celastrol on early brain injury (EBI) after SAH.

METHODS

A total of sixty-one male Sprague-Dawley rats were used in this study. Rat SAH endovascular perforation model was established to mimic the pathological changes of EBI after SAH. Multiple methods such as 3.0T MRI scanning, immunohistochemistry, western blotting and propidium iodide (PI) labeling were used to explore the therapeutic effects of celastrol on SAH.

RESULTS

Celastrol treatment attenuated SAH-caused brain swelling, reduced T2 lesion volume and ventricular volume in MRI scanning, and improved overall neurological score. Albumin leakage and the degradation of tight junction proteins were also ameliorated after celastrol administration. Celastrol protected blood-brain bairrer integrity through inhibiting MMP-9 expression and anti-neuroinflammatory effects. Additionally, necroptosis-related proteins RIP3 and MLKL were down-regulated and PI-positive cells in the basal cortex were less in the celastrol-treated SAH group than that in untreated SAH group.

CONCLUSIONS

Celastrol exhibits neuroprotective effects on EBI after SAH and deserves to be further investigated as an add-on pharmaceutical therapy.

Apelin attenuates streptozotocin-induced learning and memory impairment by modulating necroptosis signaling pathway

Apelin is a neuropeptide that plays an important role in neuronal protection. In this study, we investigated the effects of apelin intracerebroventricular administration on spatial learning and memory-related behaviors, and necroptosis signaling pathways in the hippocampus of streptozotocin (STZ) -injected rats. Apelin treatment was implemented following STZ-induced dementia for 15 days. After conducting a behavioral test (Morris Water Maze), the cellular and molecular aspects were examined to detect the apelin effect on the necroptosis signaling pathway. We demonstrated that STZ administration significantly slowed down the learning capability. However apelin treatment notably reversed this neuroinflammation induced behavioral impairment. Furthermore, molecular investigations showed that apelin treatment reduced the hippocampal RIP1, RIP3, and TNF-α level. Our results suggest that apelin treatment attenuates STZ-induced dementia. This effect may be mediated by inhibition of the necroptosis signaling pathway which seems to be associated with the ability of apelin to reduce central TNF-α level. This data provides evidence of the neuroprotective effect of apelin on STZ-induced learning and memory impairment and characterize some of the underlying mechanisms.

Necrostatin-1 Ameliorates Neutrophilic Inflammation in Asthma by Suppressing MLKL Phosphorylation to Inhibiting NETs Release

Neutrophilic inflammation occurs during asthma exacerbation, and especially, in patients with steroid-refractory asthma, but the underlying mechanisms are poorly understood. Recently, a significant accumulation of neutrophil extracellular traps (NETs) in the airways of neutrophilic asthma has been documented, suggesting that NETs may play an important role in the pathogenesis. In this study, we firstly demonstrated that NETs could induce human airway epithelial cell damage in vitro. In a mouse asthmatic model of neutrophil-dominated airway inflammation, we found that NETs were markedly increased in bronchoalveolar lavage (BAL), and the formation of NETs exacerbated the airway inflammation. Additionally, a small-molecule drug necrostatin-1 (Nec-1) shown to inhibit NETs formation was found to alleviate the neutrophil-dominated airway inflammation. Nec-1 reduced total protein concentration, myeloperoxidase activity, and the levels of inflammatory cytokines in BAL. Finally, further experiments proved that the inhibition of Nec-1 on NETs formation might be related to its ability to inhibiting mixed lineage kinase domain-like (MLKL) phosphorylation and perforation. Together, these results document that NETs are closely associated with the pathogenesis of neutrophilic asthma and inhibition of the formation of NETs by Nec-1 may be a new therapeutic strategy to ameliorate neutrophil-dominated airway inflammation.

Programmed Cell Deaths and Potential Crosstalk With Blood-Brain Barrier Dysfunction After Hemorrhagic Stroke

Hemorrhagic stroke is a life-threatening neurological disease characterized by high mortality and morbidity. Various pathophysiological responses are initiated after blood enters the interstitial space of the brain, compressing the brain tissue and thus causing cell death. Recently, three new programmed cell deaths (PCDs), necroptosis, pyroptosis, and ferroptosis, were also found to be important contributors in the pathophysiology of hemorrhagic stroke. Additionally, blood-brain barrier (BBB) dysfunction plays a crucial role in the pathophysiology of hemorrhagic stroke. The primary insult following BBB dysfunction may disrupt the tight junctions (TJs), transporters, transcytosis, and leukocyte adhesion molecule expression, which may lead to brain edema, ionic homeostasis disruption, altered signaling, and immune infiltration, consequently causing neuronal cell death. This review article summarizes recent advances in our knowledge of the mechanisms regarding these new PCDs and reviews their contributions in hemorrhagic stroke and potential crosstalk in BBB dysfunction. Numerous studies revealed that necroptosis, pyroptosis, and ferroptosis participate in cell death after subarachnoid hemorrhage (SAH) and intracerebral hemorrhage (ICH). Endothelial dysfunction caused by these three PCDs may be the critical factor during BBB damage. Also, several signaling pathways were involved in PCDs and BBB dysfunction. These new PCDs (necroptosis, pyroptosis, ferroptosis), as well as BBB dysfunction, each play a critical role after hemorrhagic stroke. A better understanding of the interrelationship among them might provide us with better therapeutic targets for the treatment of hemorrhagic stroke.

The Neuroprotective Effects of Necrostatin-1 on Subarachnoid Hemorrhage in Rats Are Possibly Mediated by Preventing Blood-Brain Barrier Disruption and RIP3-Mediated Necroptosis

Despite the substantial efforts to elucidate the role of early brain injury in subarachnoid hemorrhage (SAH), an effective pharmaceutical therapy for patients with SAH continues to be unavailable. This study aims to reveal the role of necroptosis after SAH, and explore whether the disruption of the blood-brain barrier (BBB) and RIP3-mediated necroptosis following SAH in a rat SAH model are altered by necrostatin-1 via its selective inhibition of receptor-interacting protein kinase 1 (RIP1). Sixty-five rats were used in the experiments. The SAH model was established using endovascular perforation. Necrostatin-1 was intracerebroventricularly injected 1 h before SAH induction. The neuroprotective effects of necrostatin-1 were evaluated with multiple methods such as magnetic resonance imaging (MRI) scanning, immunohistochemistry, propidium iodide (PI) labeling, and western blotting. Pretreatment with necrostatin-1 attenuated brain swelling and reduced the lesion volume on T2 sequence and ventricular volume on MRI 72 h after SAH induction. Albumin leakage and the degradation of tight junction proteins were also ameliorated by necrostatin-1 administration. In addition, necrostatin-1 decreased the number of PI-positive cells in the basal cortex, reduced the levels of the RIP3 and MLKL proteins, and inhibited the production of the pro-inflammatory cytokines IL-1β, IL-6, and TNF-α. Based on the findings from the present study, the selective RIP1 inhibitor necrostatin-1 functioned as a neuroprotective agent after SAH by attenuating brain swelling and BBB disruption. Moreover, the necrostatin-1 pretreatment prevented SAH-induced necroptosis by suppressing the activity of the RIP3/MLKL signaling pathway. These results will provide insights into new drugs and pharmacological targets to manage SAH, which are worth further study.

RIP3 participates in early brain injury after experimental subarachnoid hemorrhage in rats by inducing necroptosis

Necroptosis is a regulated form of necrosis that is mediated by a variety of proteins including tumor necrosis factor-α (TNF-α) and receptor-interacting proteins (RIPs). TNF-α, a critical inflammatory molecule, is one of the initiating signals in the necroptosis pathway, and RIP3 acts as a switch that commits the cell to necroptosis. Subarachnoid hemorrhage (SAH) is a common type of hemorrhagic stroke with high mortality and disability rates. RIP3 has been studied in many central nervous system (CNS) diseases, but its role in SAH has not been investigated in depth. Here, we used an autologous-blood injection model to study the role of RIP3 in brain injury induced by SAH in rats. Several indexes such as brain edema, loss of blood-brain barrier (BBB) integrity, and behavioral tests of neurological function were used to evaluate brain damage in SAH-injured rats. We found that the expression of RIP3 was increased in the rat brain after SAH, reaching the highest point 24 h post-injury. We also showed that genetic or pharmacological inhibition of RIP3 or TNF-α reduced the brain damage induced by SAH, whereas overexpression of RIP3 aggravated brain injury and neurological damage. Additionally, we verified the presence of RIP3-mediated necroptosis in an in vitro SAH model of primary cultured neurons treated with conditioned medium from primary microglia activated by oxygen hemoglobin (OxyHb). Collectively, our findings indicated that RIP3 contributed to brain damage after SAH by inducing necroptosis.

Upregulation of miRNA-223-3p ameliorates RIP3-mediated necroptosis and inflammatory responses via targeting RIP3 after spinal cord injury

Spinal cord injury (SCI) has been a major burden on the society because of the high rate of disability. Receptor-interacting protein 3 (RIP3)-mediated necroptosis is a newly discovered pathway of programmed cell death and is involved in multiple pathologies of various human diseases. Micro RNAs (miRNAs) have been shown to be a potential target for therapeutic interventions after SCI. The aim of the present study is to explore the potential role of miR-223-3p and possible mechanism in SCI. We found that miR-223-3p was significantly downregulated in spinal neurons after H₂ O ₂ -induced damage, while RIP3-mediated necroptosis was elevated. Accordingly, RIP3-mediated necroptosis and the inflammatory factor secretion could be significantly inhibited by Nec-1 treatment. In adittion, overexpression of miR-223-3p in spinal neurons protected against H ₂ O ₂ -induced necroptosis, and ablation of miR-223-3p exhibited the opposite effect. We found that miR-223-3p bound to the 3'-untranslated region of RIP3 mRNA to negatively regulate the expression of RIP3. Moreover, the activated RIP3 reversed the inhibition of RIP3 and MLKL expression and the levels of TNF-α, IL-1β, and lactate dehydrogenase, which were induced by transfection with miR-223-3p in a H ₂ O ₂ -induced model. Finally, these results indicate that miR-223-3p negatively regulates the RIP3 necroptotic signaling cascades and inflammatory factor secretion, which significantly relieves injury of spinal neurons. The miR-223-3p/RIP3 pathway offers a novel therapeutic target for the protection of spinal neurons after SCI.

Necrostatin-1 Ameliorates Peripheral Nerve Injury-Induced Neuropathic Pain by Inhibiting the RIP1/RIP3 Pathway

Necrostatin-1 is an inhibitor of necroptosis, a form of programmed cell death that has been reported to be involved in various neurological diseases. Presently, the role of necroptosis in neuropathic pain induced by peripheral nerve injury is still unclear. This study was focused on investigating the potential effects of necroptosis in the development and progression of neuropathic pain in a rat model and the possible neuroprotective effects of necrostatin-1 in neuropathic pain. The results indicated that the necroptosis-related proteins RIP1 and RIP3 significantly increased postoperation in the spinal cord in a neuropathic pain model and peaked 7 days postoperation, which was consistent with the time-dependent changes of hyperalgesia. Additionally, we found that peripheral nerve injury-related behavioral and biochemical changes were significantly reduced by necrostatin-1. In particular, hyperalgesia was attenuated, and the levels of RIP1 and RIP3 were decreased. Furthermore, the ultrastructure of necrotic cell death and neuroinflammation were alleviated by necrostatin-1. Collectively, these results suggest that necroptosis is an important mechanism of cell death in neuropathic pain induced by peripheral nerve injury and that necrostatin-1 may be a promising neuroprotective treatment for neuropathic pain.

Sodium/Hydrogen Exchanger 1 Participates in Early Brain Injury after Subarachnoid Hemorrhage both in vivo and in vitro via Promoting Neuronal Apoptosis

Sodium/hydrogen exchanger 1 (NHE1) plays an essential role in maintaining intracellular pH (pHi) homeostasis in the central nervous system (CNS) under physiological conditions, and it is also associated with neuronal death and intracellular Na⁺ and Ca²⁺ overload induced by cerebral ischemia. However, its roles and underlying mechanisms in early brain injury (EBI) induced by subarachnoid hemorrhage (SAH) have not been fully explored. In this research, a SAH model in adult male rat was established through injecting autologous arterial blood into prechiasmatic cistern. Meanwhile, primary cultured cortical neurons of rat treated with 5 μM oxygen hemoglobin (OxyHb) for 24 h were applied to mimic SAH in vitro. We find that the protein levels of NHE1 are significantly increased in brain tissues of rats after SAH. Downregulation of NHE1 by HOE642 (a specific chemical inhibitor of NHE1) and genetic-knockdown can effectively alleviate behavioral and cognitive dysfunction, brain edema, blood-brain barrier (BBB) injury, inflammatory reactions, oxidative stress, neurondegeneration, and neuronal apoptosis, all of which are involved in EBI following SAH. However, upregulation of NHE1 by genetic-overexpression can produce opposite effects. Additionally, inhibiting NHE1 significantly attenuates OxyHb-induced neuronal apoptosis in vitro and reduces interaction of NHE1 and CHP1 both in vivo and in vitro. Collectively, we can conclude that NHE1 participates in EBI induced by SAH through mediating inflammation, oxidative stress, behavioral and cognitive dysfunction, BBB injury, brain edema, and promoting neuronal degeneration and apoptosis.

Annexin A7 induction of neuronal apoptosis via effect on glutamate release in a rat model of subarachnoid hemorrhage

OBJECTIVE

Glutamate excitotoxicity and neuronal apoptosis are suggested to contribute to early brain injury after subarachnoid hemorrhage (SAH). Annexin A7 (ANXA7) has been shown to regulate glutamate release. However, the role of ANXA7 in early brain injury after SAH has not been illustrated. In this study, we aimed to investigate the effect of ANXA7 knockdown in reducing the severity of early brain injury after SAH, and determine the underlying mechanisms.

METHODS

Endovascular perforation was performed to induce SAH in male Sprague-Dawley rats. ANXA7-siRNA was administered via intraventricular injection 5 days before SAH induction. Neurological test, evaluation of SAH grade, assessment of blood-brain barrier (BBB) permeability, measurement of brain water content, Western blot, double immunofluorescence staining, TUNEL staining, and enzyme-linked immunosorbent assay (ELISA) were performed at 24 hours of SAH induction.

RESULTS

ANXA7 protein expression increased significantly after SAH induction and was seen mainly in neurons. High expression of ANXA7 was associated with poor neurological status. ANXA7 knockdown dramatically ameliorated early brain injury through alleviating BBB disruption and brain edema. Further investigation of the mechanism showed that inhibiting ANXA7 expression can rescue neuronal apoptosis. In addition, ANXA7 knockdown also significantly reduced glutamate release, which was consistent with a significant increase of Bcl-2 expression and decreases of Bax and cleaved caspase-3 expression.

CONCLUSIONS

ANXA7 can induce neuronal apoptosis by affecting glutamate release in rats with SAH. Downregulating the expression of ANXA7 can significantly attenuate early brain injury after SAH. Future therapy targeting ANXA7 may be a promising new choice.

Inhibition of Necroptosis Rescues SAH-Induced Synaptic Impairments in Hippocampus via CREB-BDNF Pathway

Subarachnoid hemorrhage (SAH) is a devastating form of stroke that leads to incurable outcomes. Increasing evidence has proved that early brain injury (EBI) contributes mostly to unfavorable outcomes after SAH. A previously unknown mechanism of regulated cell death known as necroptosis has recently been reported. Necrostatin-1 (nec-1), a specific and potent inhibitor of necroptosis, can attenuate brain impairments after SAH. However, the effect of nec-1 on the hippocampus and its neuroprotective impact on synapses after SAH is not well understood. Our present study was designed to investigate the potential effects of nec-1 administration on synapses and its relevant signal pathway in EBI after SAH. Nec-1 was administrated in a rat model via intracerebroventricular injection after SAH. Neurobehavior scores and brain edema were detected at 24 h after SAH occurred. The expression of the receptor-interacting proteins 1 and 3 (RIP1and3) was examined as a marker of necroptosis. We used hematoxylin and eosin staining, Nissl staining, silver staining and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) to observe the morphological changes in hippocampus. The protective effect of nec-1 on synapses was evaluated using western blotting and electron microscopy and Western blotting was used to detect the cAMP responsive element binding (CREB) protein and brain-derived neurotrophic factor (BDNF), and we used transmission electron microscopy and TUNEL to detect the protective effects of nec-1 when a specific inhibitor of CREB, known as 666-15, was used. Our results showed that in the SAH group, RIP1, and RIP3 significantly increased in the hippocampus. Additionally, injection of nec-1 alleviated brain edema and improved neurobehavior scores, compared with those in the SAH group. The damage to neurons was attenuated, and synaptic structure also improved in the Sham+nec-1 group. Furthermore, nec-1 treatment significantly enhanced the levels of phospho-CREB and BDNF compared with those in the SAH group. The protective effect of nec-1 could hindered by 666-15. Thus, nec-1 mitigated SAH-induced synaptic impairments in the hippocampus through the inhibition of necroptosis in connection with the CREB-BDNF pathway. This study may provide a new strategy for SAH patients in clinical practice.

Crashing the computer: apoptosis vs. necroptosis in neuroinflammation

Programmed cell death (PCD) plays critical roles in development, homeostasis, and both control and progression of a plethora of diseases, including cancer and neurodegenerative pathologies. Besides classical apoptosis, several different forms of PCD have now been recognized, including necroptosis. The way a cell dies determines the reaction of the surrounding environment, and immune activation in response to cell death proceeds in a manner dependent on which death pathways are activated. Apoptosis and necroptosis are major mechanisms of cell death that typically result in opposing immune responses. Apoptotic death usually leads to immunologically silent responses whereas necroptotic death releases molecules that promote inflammation, a process referred to as necroinflammation. Diseases of the nervous system, in particular neurodegenerative diseases, are characterized by neuronal death and progressive neuroinflammation. The mechanisms of neuronal death are not well defined and significant cross-talk between pathways has been suggested. Moreover, it has been proposed that the dying of neurons is a catalyst for activating immune cells in the brain and sustaining inflammatory output. In the current review we discuss the effects of apoptotis and necroptosis on inflammatory immune activation, and evaluate the roles of each cell death pathway in a variety of pathologies with specific focus on neurodegeneration. A putative model is proposed for the regulation of neuronal death and neuroinflammation that features a role for both the apoptotic and necroptotic pathways in disease establishment and progression.

Cell Death Mechanisms in Stroke and Novel Molecular and Cellular Treatment Options

As a result of ischemia or hemorrhage, blood supply to neurons is disrupted which subsequently promotes a cascade of pathophysiological responses resulting in cell loss. Many mechanisms are involved solely or in combination in this disorder including excitotoxicity, mitochondrial death pathways, and the release of free radicals, protein misfolding, apoptosis, necrosis, autophagy and inflammation. Besides neuronal cell loss, damage to and loss of astrocytes as well as injury to white matter contributes also to cerebral injury. The core problem in stroke is the loss of neuronal cells which makes recovery difficult or even not possible in the late states. Acute treatment options that can be applied for stroke are mainly targeting re-establishment of blood flow and hence, their use is limited due to the effective time window of thrombolytic agents. However, if the acute time window is exceeded, neuronal loss starts due to the activation of cell death pathways. This review will explore the most updated cellular death mechanisms leading to neuronal loss in stroke. Ischemic and hemorrhagic stroke as well as subarachnoid hemorrhage will be debated in the light of cell death mechanisms and possible novel molecular and cellular treatment options will be discussed.

RIP1 and RIP3 mediate hemin-induced cell death in HT22 hippocampal neuronal cells

BACKGROUND

Intracerebral hemorrhage (ICH) is a devastating neurological injury associated with significant mortality. Necroptosis is a newly identified type of programmed necrosis initiated by the activation of tumor necrosis factor alpha. Evidences had demonstrated the importance of necroptosis in neuronal cell death. Necrostatin-1 is a specific inhibitor of necroptosis. The present study was carried out to explore whether RIP1/RIP3 pathways participate in hemin induced cell death in HT-22 hippocampal neuronal cells and investigate the potential neuroprotection of necrostatin-1 in hemin induced cell death in HT-22.

METHODS

First, different concentrations of hemin (0, 25, 50, 100 μmol/L) were added to HT-22 cells. Propidium iodide (PI) positive cells and cell viability were measured at 24 hours after hemin treatment. Then, necrostatin-1, pan-caspase inhibitor Benzyloxycarbonyl-Val-Ala-Asp(OMe)-fluoromethylketone (z-VAD-fmk) and reactive oxygen species (ROS) scavenger butylated hydroxyanisole (BHA) were applied to hemin-treated HT-22 cells. PI positive cells and cell viability were measured at 24 hours after hemin treatment. MitoSox Red was used to indicate ROS level. Last, the effect of RIP3 in hemin induced HT-22 cell death was explored through RIP3 knockdown using siRNA. PI positive cells, cell viability and ROS lever were measured at 24 h after hemin treatment.

RESULTS

Hemin could induce a dose dependent cell death in HT22 neural cells. RIP1 specific inhibitor necrostatin-1 significantly inhibited cell death induced by hemin in HT-22 cells, greatly reducing PI positive cells, dramatically improving cell viability and decreasing ROS accumulation. BHA could significantly inhibit PI positive cells induced by hemin in HT-22 cells. Furthermore, silencing of RIP3 using siRNA attenuated hemin induced cell death in HT-22 cells, greatly reducing PI positive cells, dramatically improving cell viability and decreasing ROS accumulation.

CONCLUSION

These data revealed that RIP1/RIP3 might mediate hemin induced cell death in HT-22 cells, and necrostatin-1 played a neuroprotection role in hemin induced cell death in HT-22. RIP1 and RIP3 might represent novel therapeutic targets for ICH.