LncRNA AC136007.2 alleviates cerebral ischemic-reperfusion injury by suppressing autophagy

Morphine Induced Neuroprotection in Ischemic Stroke by Activating Autophagy Via mTOR-Independent Activation of the JNK1/2 Pathway

Morphine (Mor) has exhibited efficacy in safeguarding neurons against ischemic injuries by simulating ischemic/hypoxic preconditioning (I/HPC). Concurrently, autophagy plays a pivotal role in neuronal survival during IPC against ischemic stroke. However, the involvement of autophagy in Mor-induced neuroprotection and the potential mechanisms remain elusive. Our experiments further confirmed the effect of Mor in cellular and animal models of ischemic stroke and explored its potential mechanism. The findings revealed that Mor enhanced cell viability in a dose-dependent manner by augmenting autophagy levels and autophagic flux in neurons subjected to oxygen-glucose deprivation/reoxygenation (OGD/R). Pretreatment of Mor improved neurological outcome and reduced infarct size in mice with middle cerebral artery occlusion/reperfusion (MCAO/R) at 1, 7 and 14 days. Moreover, the use of autophagy inhibitors nullified the protective effects of Mor, leading to reactive oxygen species (ROS) accumulation, increased loss of mitochondrial membrane potential (MMP) and neuronal apoptosis in OGD/R neurons. Results further demonstrated that Mor-induced autophagy activation was regulated by mTOR-independent activation of the c-Jun NH2- terminal kinase (JNK)1/2 Pathway, both in vitro and in vivo. Overall, these findings suggested Mor-induced neuroprotection by activating autophagy, which were regulated by JNK1/2 pathway in ischemic stroke.

Mailuoning oral liquid attenuates convalescent cerebral ischemia by inhibiting AMPK/mTOR-associated apoptosis and promoting CREB/BDNF-mediated neuroprotection

ETHNOPHARMACOLOGICAL RELEVANCE

Ischemic stroke is divided into acute, subacute and convalescent phases according to the time of onset. Clinically, Mailuoning oral liquid (MLN O) is a traditional Chinese patent medicine for treating ischemic stroke. Previous studies have shown that MLN O could prevent acute cerebral ischemia-reperfusion. However, its underlying mechanism remains unclear.

AIM OF THE STUDY

To investigate the relationship between neuroprotection and apoptosis for clarifying MLN O mechanism in the recovery phase of ischemic stroke.

MATERIALS AND METHODS

We imitated stroke using middle cerebral artery occlusion/reperfusion (MCAO/R) in vivo and oxygen-glucose deprivation/reoxygenation (OGD/R) in vitro models. The infarct volume, neurological deficit scores, HE staining, Nissl staining, TUNEL staining, immunohistochemistry, and Western blot were correspondingly performed to find pathological changes and detect neuronal apoptosis in rat cerebral cortex. The contents of LDH, Cyt-c, c-AMP and BDNF in rat plasma and cerebral cortex were detected by ELISA. Cell viability was measured by CCK8 assay. Cell morphology, Hoechst 33342 staining and Annexin-V-Alexa Fluor 647/PI staining were performed to assess neuronal apoptosis. The expression levels of proteins were evaluated by western blotting.

RESULTS

MLN O obviously reduced brain infarct volume and neurological deficit scores in MCAO rats. MLN O inhibited inflammatory cell infiltration and neuronal apoptosis, but promoted gliosis, neuronal survival, and neuroprotection in the cortical region of MCAO rats. Additionally, MLN O decreased the amount of LDH and cytochrome c, while increasing the expression of c-AMP in the plasma and ischemic cerebral cortex of MCAO rats, and promoting the expression of BDNF in the cortical tissue of MCAO rats. Besides, MLN O improved cell viability, restored cell morphology, while attenuating cell damage, inhibiting neuronal apoptosis following OGD/R in PC-12 cells. Moreover, MLN O inhibited apoptosis by suppressing the expression of pro-apoptotic-associated proteins, including Bax, cytochrome c, Cleaved caspase 3 and HIF-1α, whereas accelerating the expression of Bcl-2 in vivo and in vitro. Furthermore, MLN O inhibited the activity of AMP-activated protein kinase (AMPK)/mechanistic target of rapamycin (mTOR), but activated the signaling pathway of cAMP-response element binding protein (CREB)/brain-derived neurotrophic factor (BDNF) in MCAO rats and OGD/R-stimulated PC-12 cells.

CONCLUSIONS

These results demonstrated that MLN O inhibited AMPK/mTOR to affect apoptosis associated with mitochondria, leading to improve CREB/BDNF-mediated neuroprotection in the recovery period of ischemic stroke in vivo and in vitro.

USP22 knockdown protects against cerebral ischemia/reperfusion injury via destabilizing PTEN protein and activating the mTOR/TFEB pathway

Ubiquitin-specific protease 22 (USP22) expression was reported to be increased in response to ischemic brain damage, but the biological role and underlying mechanism remain little understood. USP22 shRNA was intravenously injected into the mouse brain, and then a middle cerebral artery occlusion/reperfusion (MCAO/R) mouse model was constructed, and the infarct volume, neurobehavioral deficit score, cell apoptosis, oxidative stress, and autophagy in vivo were evaluated. Oxygen-glucose deprivation/reperfusion (OGD/R) treated pheochromocytoma-12 (PC12) cells were used as an in vitro model of ischemia/reperfusion. The effects of USP22 on proliferation, apoptosis, oxidative stress, and autophagy were explored by CCK-8, flow cytometry, ELISA, and Western blot assays. The relationship between USP22 and the phosphatase and tensin homolog (PTEN) was measured by Co-IP and Western blot assays. Both USP22 and PTEN were highly expressed in MCAO/R mouse brain tissues and OGD/R-induced PC12 cells. In vitro, USP22 knockdown strongly improved OGD/R-mediated changes in cell viability, apoptosis, oxidative stress, and lactate dehydrogenase (LDH) production in PC12 cells. USP22 bound to PTEN and stabilized PTEN expression by decreasing its ubiquitination. PTEN overexpression reversed the promoting effect of USP22 knockdown on cell viability and the inhibitory effects of USP22 knockdown on apoptosis, oxidative stress, and LDH release rate in PC12 cells subjected to OGD/R. PTEN silencing elevated the protein levels of p62, p-mTOR, TFEB, and LAMP1 and reduced the protein levels of LC3-II/LC3-I. USP22 expression levels were negatively correlated with mTOR expression levels, and USP22-shRNA-mediated expression of p62, p-mTOR, TFEB, and LAMP1 was reversed by rapamycin, an inhibitor of mTOR. In vivo, USP22 silencing significantly alleviated infarct volume, neurobehavioral impairments, cell apoptosis, oxidative stress, and autophagy in MCAO/R mice. USP22 knockdown exerts neuroprotective effects in cerebral ischemia/reperfusion injury by downregulating PTEN and activating the mTOR/TFEB pathway.

ALDH2 activation attenuates oxygen-glucose deprivation/reoxygenation-induced cell apoptosis, pyroptosis, ferroptosis and autophagy

PURPOSE

It is previously reported that aldehyde dehydrogenase 2 family member (ALDH2) shows neuroprotective effects in cerebral ischemia/reperfusion injury. However, whether the protective effects are through mediating the programmed cell death is yet to be fully elucidated.

METHODS

In vitro oxygen-glucose deprivation/reoxygenation (OGD/R) model was established in HT22 cells and mouse cortical neurons. Subsequently, ALDH2 expression were assessed by qRT-PCR and western blot. The methylation status was examined by methylation-specific PCR (MS-PCR). Then, ALDH2 expression was promoted and suppressed to explore the role of ALDH2 in OGD/R-treated cells. CCK-8 assay was applied to detect cell viability, and flow cytometry was applied to evaluate cell apoptosis. Western blot was applied to detect the apoptosis-related proteins (Caspase 3, Bcl-2 and Bax), necroptosis-related proteins (RIP3 and MLKL), pyroptosis-related proteins (NLRP3 and GSDMD), ferroptosis-related protein (ACSL4 and GPX4), and autophagy-related proteins (LC3B, and p62). IL-1β and IL-18 production was evaluated by ELISA assay. Reactive oxygen species production and Fe2+ content were evaluated by the corresponding detection kit.

RESULTS

In OGD/R-treated cells, ALDH2 expression was decreased, which was due to the hypermethylation of ALDH2 in the promoter region. ALDH2 overexpression improved cell viability and ALDH2 knockdown suppressed cell viability in OGD/R-treated cells. We also found that ALDH2 overexpression attenuated OGD/R-induced cell apoptosis, pyroptosis, ferroptosis and autophagy, while ALDH2 knockdown facilitated the OGD/R-induced cell apoptosis, pyroptosis, ferroptosis and autophagy.

CONCLUSIONS

Collectively, our results implied that ALDH2 attenuated OGD/R-induced cell apoptosis, pyroptosis, ferroptosis and autophagy to promote cell viability in HT22 cells and mouse cortical neurons.

Neuronal Responses to Ischemia: Scoping Review of Insights from Human-Derived In Vitro Models

Translation of neuroprotective treatment effects from experimental animal models to patients with cerebral ischemia has been challenging. Since pathophysiological processes may vary across species, an experimental model to clarify human-specific neuronal pathomechanisms may help. We conducted a scoping review of the literature on human neuronal in vitro models that have been used to study neuronal responses to ischemia or hypoxia, the parts of the pathophysiological cascade that have been investigated in those models, and evidence on effects of interventions. We included 147 studies on four different human neuronal models. The majority of the studies (132/147) was conducted in SH-SY5Y cells, which is a cancerous cell line derived from a single neuroblastoma patient. Of these, 119/132 used undifferentiated SH-SY5Y cells, that lack many neuronal characteristics. Two studies used healthy human induced pluripotent stem cell derived neuronal networks. Most studies used microscopic measures and established hypoxia induced cell death, oxidative stress, or inflammation. Only one study investigated the effect of hypoxia on neuronal network functionality using micro-electrode arrays. Treatment targets included oxidative stress, inflammation, cell death, and neuronal network stimulation. We discuss (dis)advantages of the various model systems and propose future perspectives for research into human neuronal responses to ischemia or hypoxia.

The Dual Role of Autophagy in Postischemic Brain Neurodegeneration of Alzheimer's Disease Proteinopathy

Autophagy is a self-defense and self-degrading intracellular system involved in the recycling and elimination of the payload of cytoplasmic redundant components, aggregated or misfolded proteins and intracellular pathogens to maintain cell homeostasis and physiological function. Autophagy is activated in response to metabolic stress or starvation to maintain homeostasis in cells by updating organelles and dysfunctional proteins. In neurodegenerative diseases, such as cerebral ischemia, autophagy is disturbed, e.g., as a result of the pathological accumulation of proteins associated with Alzheimer's disease and their structural changes. Postischemic brain neurodegeneration, such as Alzheimer's disease, is characterized by the accumulation of amyloid and tau protein. After cerebral ischemia, autophagy was found to be activated in neuronal, glial and vascular cells. Some studies have shown the protective properties of autophagy in postischemic brain, while other studies have shown completely opposite properties. Thus, autophagy is now presented as a double-edged sword with possible therapeutic potential in brain ischemia. The exact role and regulatory pathways of autophagy that are involved in cerebral ischemia have not been conclusively elucidated. This review aims to provide a comprehensive look at the advances in the study of autophagy behavior in neuronal, glial and vascular cells for ischemic brain injury. In addition, the importance of autophagy in neurodegeneration after cerebral ischemia has been highlighted. The review also presents the possibility of modulating the autophagy machinery through various compounds on the development of neurodegeneration after cerebral ischemia.

The autophagy in ischemic stroke: A regulatory role of non-coding-RNAs

Ischemic stroke (IS) is a central nervous system neurological disorder ascribed to an acute focal trauma, with high mortality and disability, leading to a heavy burden on family and society. Autophagy is a self-digesting process by which damaged organelles and useless proteins are recycled to maintain cellular homeostasis, and plays a pivotal role in the process of IS. Non-coding RNAs (ncRNAs), mainly contains microRNA, long non-coding RNA and circular RNA, have been extensively investigated on regulation of autophagy in human diseases. Recent studies have implied that ncRNAs-regulating autophagy participates in pathophysiological process of IS, including cell apoptosis, inflammation, oxidative stress, blood-brain barrier damage and glial activation, which indicates that regulating autophagy by ncRNAs may be beneficial for IS treatment. This review summarizes the role of autophagy in IS, as well as focuses on the role of ncRNAs-mediated autophagy in IS, for the development of potential therapeutic strategies in this disease.

An update on the molecular mechanism and pharmacological interventions for Ischemia-reperfusion injury by regulating AMPK/mTOR signaling pathway in autophagy

AMP-activated protein kinase (5'-adenosine monophosphate-activated protein kinase, AMPK)/mammalian target of rapamycin (mTOR) is an important signaling pathway maintaining normal cell function and homeostasis in vivo. The AMPK/mTOR pathway regulates cellular proliferation, autophagy, and apoptosis. Ischemia-reperfusion injury (IRI) is secondary damage that frequently occurs clinically in various disease processes and treatments, and the exacerbated injury during tissue reperfusion increases disease-associated morbidity and mortality. IRI arises from multiple complex pathological mechanisms, among which cell autophagy is a focus of recent research and a new therapeutic target. The activation of AMPK/mTOR signaling in IRI can modulate cellular metabolism and regulate cell proliferation and immune cell differentiation by adjusting gene transcription and protein synthesis. Thus, the AMPK/mTOR signaling pathway has been intensively investigated in studies focused on IRI prevention and treatment. In recent years, AMPK/mTOR pathway-mediated autophagy has been found to play a crucial role in IRI treatment. This article aims to elaborate the action mechanisms of AMPK/mTOR signaling pathway activation in IRI and summarize the progress of AMPK/mTOR-mediated autophagy research in the field of IRI therapy.

LncRNA PEG11as aggravates cerebral ischemia/reperfusion injury after ischemic stroke through miR-342-5p/PFN1 axis

AIM

LncRNAs are highly expressed in the CNS and regulate pathophysiological processes. However, the potential role of lncRNAs inischemic stroke (IS) remains unknown. In this study, we investigated the functions and possible molecular mechanism of lncRNA paternal expressed gene 11 antisense (PEG11as) in this process.

METHODS

Middle cerebral artery occlusion/reperfusion (MCAO/R) mice model and N2a cells model from oxygen-glucose deprivation/reoxygenation (OGD/R) were used to simulate cerebral I/R in vivo and in vitro. High-throughput sequencing (RNA-Seq) was used todetect differential expression of lncRNAs in cerebral I/R. QRT-PCR was used to detect the expression of PEG11as and miR-342-5p. Bioinformatics analysis, FISH, luciferase reporter assay, RIP, Western blot, and immunofluorescence were used to detect the interaction between PEG11as, miR-342-5p and PFN1. The effect on neuronal apoptosis was analyzed using loss-of-function combined with TUNEL, Hoechst, and caspase3 activity assays.

KEY FINDINGS

254 lncRNAs were differentially expressed in MCAO1h/R6h mice. Among them, PEG11as was significantly up-regulated. PEG11as down-regulated could markedly attenuate the brain infarct volume, alleviate neurological deficit in vivo, and effectively promote neuron survival, attenuate neuronal apoptosis both in vivo and in vitro. FISH assay discovered that PEG11as was mainly located in the cytoplasm. Furthermore, we demonstrated that PEG11as was able to bind miR-342-5p to inhibit miR-342-5p activity, whereas the down-regulated of miR-342-5p resulted in profilin 1 (PFN1) overexpression and thus promoting apoptosis.

SIGNIFICANCE

This study suggests that PEG11as regulates neuronal apoptosis by miR-342-5p/PFN1 axis, which may contribute to our understanding of pathogenesis and provide a potential therapeutic option for cerebral I/R.

Activation of the Akt/FoxO3 signaling pathway enhances oxidative stress-induced autophagy and alleviates brain damage in a rat model of ischemic stroke

Autophagy has been implicated in stroke. Our previous study showed that the FoxO3 transcription factor promotes autophagy after transient cerebral ischemia/reperfusion (I/R). However, whether the Akt/FoxO3 signaling pathway plays a regulatory role in autophagy in cerebral I/R-induced oxidative stress injury is still unclear. The present study aims to investigate the effects of the Akt/FoxO3 signaling pathway on autophagy activation and neuronal injury in vitro and in vivo. By employing LY294002 or insulin to regulate the Akt/FoxO3 signaling pathway, we found that insulin pretreatment increased cell viability, decreased reactive oxygen species production, and enhanced the expression of antiapoptotic and autophagy-related proteins following H₂O₂ injury in HT22 cells. In addition, insulin significantly decreased neurological deficit scores and infarct volume and increased the expression of antiapoptotic and autophagy-related proteins following I/R injury in rats. However, LY294002 showed the opposite effects under these conditions. Altogether, these results indicate that Akt/FoxO3 signaling pathway activation inhibited oxidative stress-mediated cell death through activation of autophagy. Our study supports a critical role for the Akt/FoxO3 signaling pathway in autophagy activation in stroke.

EGCG protects the mouse brain against cerebral ischemia/reperfusion injury by suppressing autophagy via the AKT/AMPK/mTOR phosphorylation pathway

Stroke remains one of the leading reasons of mortality and physical disability worldwide. The treatment of cerebral ischemic stroke faces challenges, partly due to a lack of effective treatments. In this study, we demonstrated that autophagy was stimulated by transient middle cerebral artery occlusion/reperfusion (MCAO/R) and oxygen-glucose deprivation/reoxygenation (OGD/R). Treatment with (−)-epigallocatechin-3-gallate (EGCG), a bioactive ingredient in green tea, was able to mitigate cerebral ischemia/reperfusion injury (CIRI), given the evidence that EGCG administration could reduce the infarct volume and protect poststroke neuronal loss in MCAO/R mice in vivo and attenuate cell loss in OGD/R-challenged HT22 cells in vitro through suppressing autophagy activity. Mechanistically, EGCG inhibited autophagy via modulating the AKT/AMPK/mTOR phosphorylation pathway both in vivo and in vitro models of stroke, which was further confirmed by the results that the administration of GSK690693, an AKT/AMPK inhibitor, and rapamycin, an inhibitor of mTOR, reversed aforementioned changes in autophagy and AKT/AMPK/mTOR signaling pathway. Overall, the application of EGCG relieved CIRI by suppressing autophagy via the AKT/AMPK/mTOR phosphorylation pathway.

Research progress on astrocyte autophagy in ischemic stroke

Ischemic stroke is a highly disabling and potentially fatal disease. After ischemic stroke, autophagy plays a key regulatory role as an intracellular catabolic pathway for misfolded proteins and damaged organelles. Mounting evidence indicates that astrocytes are strongly linked to the occurrence and development of cerebral ischemia. In recent years, great progress has been made in the investigation of astrocyte autophagy during ischemic stroke. This article summarizes the roles and potential mechanisms of astrocyte autophagy in ischemic stroke, briefly expounds on the crosstalk of astrocyte autophagy with pathological mechanisms and its potential protective effect on neurons, and reviews astrocytic autophagy-targeted therapeutic methods for cerebral ischemia. The broader aim of the report is to provide new perspectives and strategies for the treatment of cerebral ischemia and a reference for future research on cerebral ischemia.

Novel Therapeutic Strategies for Ischemic Stroke: Recent Insights into Autophagy

Stroke is one of the leading causes of death and disability worldwide. Autophagy is a conserved cellular catabolic pathway that maintains cellular homeostasis by removal of damaged proteins and organelles, which is critical for the maintenance of energy and function homeostasis of cells. Accumulating evidence demonstrates that autophagy plays important roles in pathophysiological mechanisms under ischemic stroke. Previous investigations show that autophagy serves as a “double-edged sword” in ischemic stroke as it can either promote the survival of neuronal cells or induce cell death in special conditions. Following ischemic stroke, autophagy is activated or inhibited in several cell types in brain, including neurons, astrocytes, and microglia, as well as microvascular endothelial cells, which involves in inflammatory activation, modulation of microglial phenotypes, and blood-brain barrier permeability. However, the exact mechanisms of underlying the role of autophagy in ischemic stroke are not fully understood. This review focuses on the recent advances regarding potential molecular mechanisms of autophagy in different cell types. The focus is also on discussing the “double-edged sword” effect of autophagy in ischemic stroke and its possible underlying mechanisms. In addition, potential therapeutic strategies for ischemic stroke targeting autophagy are also reviewed.

Role of autophagy and transcriptome regulation in acute brain injury

Autophagy is an evolutionarily conserved intracellular system that routes distinct cytoplasmic cargo to lysosomes for degradation and recycling. Accumulating evidence highlight the mechanisms of autophagy, such as clearance of proteins, carbohydrates, lipids and damaged organelles. The critical role of autophagy in selective degradation of the transcriptome is still emerging and could shape the total proteome of the cell, and thus can regulate the homeostasis under stressful conditions. Unregulated autophagy that potentiates secondary brain damage is a key pathological features of acute CNS injuries such as stroke and traumatic brain injury. This review discussed the mutual modulation of autophagy and RNA and its significance in mediating the functional consequences of acute CNS injuries.

Dysregulation of mTOR Signaling after Brain Ischemia

In this review, we provide recent data on the role of mTOR kinase in the brain under physiological conditions and after damage, with a particular focus on cerebral ischemia. We cover the upstream and downstream pathways that regulate the activation state of mTOR complexes. Furthermore, we summarize recent advances in our understanding of mTORC1 and mTORC2 status in ischemia–hypoxia at tissue and cellular levels and analyze the existing evidence related to two types of neural cells, namely glia and neurons. Finally, we discuss the potential use of mTORC1 and mTORC2 as therapeutic targets after stroke.

Interleukin-35 from Interleukin-4-Stimulated Macrophages Alleviates Oxygen Glucose Deprivation/Re-oxygenation-Induced Neuronal Cell Death via the Wnt/β-Catenin Signaling Pathway

Currently, brain stroke is one of the leading causes of death and disabilities. It results in depletion of oxygen and glucose in certain areas of the brain, leading to neuronal death. Re-oxygenation has been proven to attenuate neuronal damage; however, sudden oxygen supply may also cause oxidative stress and subsequent inflammation. Hence, therapies to suppress re-oxygenation-induced oxidative damage are urgently needed. Interleukin (IL)-35, an immunomodulator secreted by regulatory T cells and regulatory B cells, is proven to be a strong immune-repressive cytokine. Here, we investigated the potential role of IL-35 in a disease model of oxygen glucose deprivation/re-oxygenation (OGD/R) and found that M2 macrophage-derived IL-35 significantly alleviated inflammatory response induced by oxidative stress. Our results also showed that IL-35 treatment decreased OGD/R-induced neuronal cell death and inflammatory response. Additionally, we demonstrated that IL-35 suppresses inflammatory response via the Wnt/β-catenin signaling pathway. Hence, our findings indicate that IL-35 therapy has great potential in the treatment of OGD/R-induced oxidative damage and related inflammatory diseases.

Deoxyhypusine hydroxylase as a novel pharmacological target for ischemic stroke via inducing a unique post-translational hypusination modification

Ischemic stroke remains one of the leading causes of death worldwide, thereby highlighting the urgent necessary to identify new therapeutic targets. Deoxyhypusine hydroxylase (DOHH) is a fundamental enzyme catalyzing a unique posttranslational hypusination modification of eukaryotic translation initiation factor 5A (eIF5A) and is highly involved in the progression of several human diseases, including HIV-1 infection, cancer, malaria, and diabetes. However, the potential therapeutic role of pharmacological regulation of DOHH in ischemic stroke is still poorly understood. Our study first discovered a natural small-molecule brazilin (BZ) with an obvious neuroprotective effect against oxygen-glucose deprivation/reperfusion insult. Then, DOHH was identified as a crucial cellular target of BZ using HuProt™ human proteome microarray. By selectively binding to the Cys232 residue, BZ induced a previously undisclosed allosteric effect to significantly increase DOHH catalytic activity. Furthermore, BZ-mediated DOHH activation amplified mitophagy for mitochondrial function and morphology maintenance via DOHH/eIF5A hypusination signaling pathway, thereby protecting against ischemic neuronal injury in vitro and in vivo. Collectively, our study first identified DOHH as a previously unreported therapeutic target for ischemic stroke, and provided a future drug design direction for DOHH allosteric activators using BZ as a novel molecular template.