Syntaxin 17 inhibits ischemic neuronal injury by resuming autophagy flux and ameliorating endoplasmic reticulum stress

Inhibition of the cGAS-STING pathway: contributing to the treatment of cerebral ischemia-reperfusion injury

The cGAS-STING pathway plays an important role in ischemia-reperfusion injury in the heart, liver, brain, and kidney, but its role and mechanisms in cerebral ischemia-reperfusion injury have not been systematically reviewed. Here, we outline the components of the cGAS-STING pathway and then analyze its role in autophagy, ferroptosis, cellular pyroptosis, disequilibrium of calcium homeostasis, inflammatory responses, disruption of the blood-brain barrier, microglia transformation, and complement system activation following cerebral ischemia-reperfusion injury. We further analyze the value of cGAS-STING pathway inhibitors in the treatment of cerebral ischemia-reperfusion injury and conclude that the pathway can regulate cerebral ischemia-reperfusion injury through multiple mechanisms. Inhibition of the cGAS-STING pathway may be helpful in the treatment of cerebral ischemia-reperfusion injury.

An emerging role of SNAREs in ischemic stroke: From pre-to post-diseases

Ischemic stroke is a debilitating condition characterized by high morbidity, disability, recurrence, and mortality rates on a global scale, posing a significant threat to public health and economic stability. Extensive research has thoroughly explored the molecular mechanisms underlying ischemic stroke, elucidating a strong association between soluble N-ethylmaleimide-sensitive factor (NSF) attachment protein receptor proteins (SNAREs) and the pathogenesis of this condition. SNAREs, a class of highly conserved proteins involved in membrane fusion, play a crucial role in modulating neuronal information transmission and promoting myelin formation in the central nervous system (CNS). Preventing the SNARE complex formation, malfunctions in SNARE-dependent exocytosis, and altered regulation of SNARE-mediated vesicle fusion are linked to excitotoxicity, endoplasmic reticulum (ER) stress, and programmed cell death (PCD) in ischemic stroke. However, its underlying mechanisms remain unclear. This study conducts a comprehensive review of the existing literature on SNARE proteins, encompassing the structure, classification, and expression of the SNARE protein family, as well as the assembly - disassembly cycle of SNARE complexes and their physiological roles in the CNS. We thoroughly examine the mechanisms by which SNAREs contribute to the pathological progression and associated risk factors of ischemic stroke (hypertension, hyperglycemia, dyslipidemia, and atherosclerosis). Furthermore, our findings highlight the promise of SNAREs as a viable target for pharmacological interventions in the treatment of ischemic stroke.

TIGAR Suppresses ER Stress-Induced Neuronal Injury through Targeting ATF4 Signaling in Cerebral Ischemia/Reperfusion

Endoplasmic reticulum (ER) stress is crucial in cerebral ischemia/reperfusion injury by triggering cellular apoptosis and exacerbating neuronal damage. This study elucidates the dynamics of TP53-induced glycolysis and apoptosis regulator (TIGAR) translocation and its role in regulating neural fate during cerebral ischemia-induced ER stress, specifically in male mice. We found enhanced nuclear localization of TIGAR in neurons after transient middle cerebral artery occlusion/reperfusion (tMCAO/R) in male mice, as well as oxygen glucose deprivation/reperfusion (OGD/R) and treatment with ER stress inducer (tunicamycin and thapsigargin) in neuronal cells. Conditional neuronal knockdown of Tigar aggravated the injury following ischemia-reperfusion, whereas overexpression of Tigar attenuated cerebral ischemic injury and ameliorated intraneuronal ER stress. Additionally, TIGAR overexpression reduced the elevation of ATF4 target genes and attenuated ER stress-induced cell death. Notably, TIGAR colocalized and interacted with ATF4 in the nucleus, inhibiting its downstream proapoptotic gene transcription, consequently protecting against ischemic injury. In vitro and in vivo experiments revealed that ATF4 overexpression reversed the protective effects of TIGAR against cerebral ischemic injury. Intriguingly, our study identified the Q141/K145 residues of TIGAR, crucial for its nuclear translocation and interaction with ATF4, highlighting a novel aspect of TIGAR's function distinct from its known phosphatase activity or mitochondrial localization domains. These findings reveal a novel neuroprotective mechanism of TIGAR in regulating ER stress through ATF4-mediated signaling pathways. These insights may guide targeted therapeutic strategies to protect neuronal function and alleviate the deleterious effects of cerebral ischemic injury.

Artemisinin alleviates astrocyte overactivation and neuroinflammation by modulating the IRE1/NF-κB signaling pathway in in vitro and in vivo Alzheimer's disease models

Recent studies have shown that neuroinflammation and heightened glial activity, particularly astrocyte overactivation, are associated with Alzheimer's disease (AD). Abnormal accumulation of amyloid-beta (Aβ) induces endoplasmic reticulum (ER) stress and activates astrocytes. Artemisinin (ART), a frontline anti-malarial drug, has been found to have neuroprotective properties. However, its impact on astrocytes remains unclear. In this study, we used Aβ1-42 induced astrocyte cultures and 3 × Tg-AD mice as in vitro and in vivo models, respectively, to investigate the effects of ART on AD related astrocyte overactivation and its underlying mechanisms. ART attenuated Aβ1-42-induced astrocyte activation, ER stress, and inflammatory responses in astrocyte cultures by inhibiting IRE1 phosphorylation and the NF-κB pathway, as evidenced by the overexpression of IRE1 WT and IRE1-K599A (kinase activity invalidated), along with application of activators and inhibitors related to ER stress. Furthermore, ART alleviated the detrimental effects and restored neurotrophic function of astrocytes on co-cultured neurons, preventing neuronal apoptosis during Aβ1-42 treatment. In 3 × Tg-AD mice, ART treatment improved cognitive function and reduced astrocyte overactivation, neuroinflammation, ER stress, and neuronal apoptosis. Moreover, ART attenuated the upregulation of IRE1/NF-κB pathway activity in AD mice. Astrocyte-specific overexpression of IRE1 via adeno-associated virus in AD mice reversed the ameliorating effects of ART. Our findings suggest that ART inhibits astrocyte overactivation and neuroinflammation in both in vitro and in vivo AD models by modulating the IRE1/NF-κB signaling pathway, thereby enhancing neuronal functions. This study underscores the therapeutic potential of ART in AD and highlights the significance of modulating the ER stress-inflammatory cycle and normalizing astrocyte-neuron communication.

The correlation between mitochondria-associated endoplasmic reticulum membranes (MAMs) and Ca2+ transport in the pathogenesis of diseases

Mitochondria and the endoplasmic reticulum (ER) are vital organelles that influence various cellular physiological and pathological processes. Recent evidence shows that about 5%-20% of the mitochondrial outer membrane is capable of forming a highly dynamic physical connection with the ER, maintained at a distance of 10-30 nm. These interconnections, known as MAMs, represent a relatively conserved structure in eukaryotic cells, acting as a critical platform for material exchange between mitochondria and the ER to maintain various aspects of cellular homeostasis. Particularly, ER-mediated Ca2+ release and recycling are intricately associated with the structure and functionality of MAMs. Thus, MAMs are integral in intracellular Ca2+ transport and the maintenance of Ca2+ homeostasis, playing an essential role in various cellular activities including metabolic regulation, signal transduction, autophagy, and apoptosis. The disruption of MAMs observed in certain pathologies such as cardiovascular and neurodegenerative diseases as well as cancers leads to a disturbance in Ca2+ homeostasis. This imbalance potentially aggravates pathological alterations and disease progression. Consequently, a thorough understanding of the link between MAM-mediated Ca2+ transport and these diseases could unveil new perspectives and therapeutic strategies. This review focuses on the changes in MAMs function during disease progression and their implications in relation to MAM-associated Ca2+ transport.

N-ethylmaleimide-sensitive factor elicits a neuroprotection against ischemic neuronal injury by restoring autophagic/lysosomal dysfunction

Autophagosome-lysosome fusion defects play a critical role in driving autolysosomal dysfunction, leading to autophagic/lysosomal impairment in neurons following ischemic stroke. However, the mechanisms hindering autophagosome-lysosome fusion remain unclear. Soluble N-ethylmaleimide-sensitive factor (NSF) is an essential ATPase to reactivate STX17 and VAMP8, which are the paired molecules to mediate fusion between autophagosomes and lysosomes. However, NSF is frequently inactivated to inhibit the reactivation of STX17 and VAMP8 in ischemic neurons. Herein, we investigated whether autophagosome-lysosome fusion could be facilitated to alleviate autophagic/lysosomal impairment in ischemic neurons by over-expressing NSF. Rat model of middle cerebral artery occlusion (MCAO) and HT22 neuron ischemia model of oxygen-glucose deprivation (OGD) were prepared, respectively. The results demonstrated that NSF activity was significantly suppressed, accompanied by reduced expressions of STX17 and VAMP8 in penumbral neurons 48 h post-MCAO and in HT22 neurons 2 h post-OGD. Moreover, the attenuated autolysosome formation accompanied by autophagic/lysosomal dysfunction was observed. Thereafter, NSF activity in HT22 neurons was altered by over-expression and siRNA knockdown, respectively. After transfection with recombinant NSF-overexpressing lentiviruses, both STX17 and VAMP8 expressions were concurrently elevated to boost autophagosome-lysosome fusion, as shown by enhanced immunofluorescence intensity co-staining with LC3 and LAMP-1. Consequently, the OGD-created autophagic/lysosomal dysfunction was prominently ameliorated, as reflected by augmented autolysosomal functions and decreased autophagic substrates. By contrast, NSF knockdown conversely aggravated the autophagic/lysosomal impairment, and thereby exacerbated neurological damage. Our study indicates that NSF over-expression induces neuroprotection against ischemic neuronal injury by restoring autophagic/lysosomal dysfunction via the facilitation of autophagosome-lysosome fusion. Over-expression of NSF promotes fusion by reactivating STX17 and VAMP8. Black arrows represent the pathological process after cerebral ischemia, green arrows represent the mechanism of remission after NSF over-expression, and red arrows represent the effect on the pathological process after NSF knockdown.

Activation of SIRT1/Nrf2/HO-1 and Beclin-1/AMPK/mTOR autophagy pathways by eprosartan ameliorates testicular dysfunction induced by testicular torsion in rats

Testicular torsion carries the ominous prospect of inducing acute scrotal distress and the perilous consequence of testicular atrophy, necessitating immediate surgical intervention to reinstate vital testicular perfusion, notwithstanding the paradoxical detrimental impact of reperfusion. Although no drugs have secured approval for this urgent circumstance, antioxidants emerge as promising candidates. This study aspires to illustrate the influence of eprosartan, an AT1R antagonist, on testicular torsion in rats. Wistar albino rats were meticulously separated into five groups, (n = 6): sham group, eprosartan group, testicular torsion-detorsion (T/D) group, and two groups of T/D treated with two oral doses of eprosartan (30 or 60 mg/kg). Serum testosterone, sperm analysis and histopathological examination were done to evaluate spermatogenesis. Oxidative stress markers were assessed. Bax, BCL-2, SIRT1, Nrf2, HO-1 besides cleaved caspase-3 testicular contents were estimated using ELISA or qRT-PCR. As autophagy markers, SQSTM-1/p62, Beclin-1, mTOR and AMPK were investigated. Our findings highlight that eprosartan effectively improved serum testosterone levels, testicular weight, and sperm count/motility/viability, while mitigating histological irregularities and sperm abnormalities induced by T/D. This recovery in testicular function was underpinned by the activation of the cytoprotective SIRT1/Nrf2/HO-1 axis, which curtailed testicular oxidative stress, indicated by lowering the MDA content and increasing GSH content. In terms of apoptosis, eprosartan effectively countered apoptotic processes by decreasing cleaved caspase-3 content, suppressing Bax and stimulating Bcl-2 gene expression. Simultaneously, it reactivated impaired autophagy by increasing Beclin-1 expression, decreasing the expression of SQSTM-1/p62 and modulate the phosphorylation of AMPK and mTOR proteins. Eprosartan hold promise for managing testicular dysfunction arising from testicular torsion exerting antioxidant, pro-autophagic and anti-apoptotic effect via the activation of SIRT1/Nrf2/HO-1 as well as Beclin-1/AMPK/mTOR pathways.

Exacerbation of atherosclerosis by STX17 knockdown: Unravelling the role of autophagy and inflammation

Syntaxin 17 (STX17) has been identified as a crucial factor in mediating the fusion of autophagosomes and lysosomes. However, its specific involvement in the context of atherosclerosis (AS) remains unclear. This study sought to elucidate the role and mechanistic contributions of STX17 in the initiation and progression of AS. Utilizing both in vivo and in vitro AS model systems, we employed ApoE knockout (KO) mice subjected to a high-fat diet and human umbilical vein endothelial cells (HUVECs) treated with oxidized low-density lipoprotein (ox-LDL) to assess STX17 expression. To investigate underlying mechanisms, we employed shRNA-STX17 lentivirus to knock down STX17 expression, followed by evaluating autophagy and inflammation in HUVECs. In both in vivo and in vitro AS models, STX17 expression was significantly upregulated. Knockdown of STX17 exacerbated HUVEC damage, both with and without ox-LDL treatment. Additionally, we observed that STX17 knockdown impaired autophagosome degradation, impeded autophagy flux and also resulted in the accumulation of dysfunctional lysosomes in HUVECs. Moreover, STX17 knockdown intensified the inflammatory response following ox-LDL treatment in HUVECs. Further mechanistic exploration revealed an association between STX17 and STING; reducing STX17 expression increased STING levels. Further knockdown of STING enhanced autophagy flux. In summary, our findings suggest that STX17 knockdown worsens AS by impeding autophagy flux and amplifying the inflammatory response. Additionally, the interaction between STX17 and STING may play a crucial role in STX17-mediated autophagy.

Syntaxin17 Restores Lysosomal Function and Inhibits Pyroptosis Caused by Acinetobacter baumannii

Acinetobacter baumannii (A. baumannii) causes autophagy flux disorder by degrading STX17, resulting in a serious inflammatory response. It remains unclear whether STX17 can alter the inflammatory response process by controlling autolysosome function. This study aimed to explore the role of STX17 in the regulation of pyroptosis induced by A. baumannii. Our findings indicate that overexpression of STX17 enhances autophagosome degradation, increases LAMP1 expression, reduces Cathepsin B release, and improves lysosomal function. Conversely, knockdown of STX17 suppresses autophagosome degradation, reduces LAMP1 expression, augments Cathepsin B release, and accelerates lysosomal dysfunction. In instances of A. baumannii infection, overexpression of STX17 was found to improve lysosomal function and reduce the expression of mature of GSDMD and IL-1β, along with the release of LDH, thus inhibiting pyroptosis caused by A. baumannii. Conversely, knockdown of STX17 led to increased lysosomal dysfunction and further enhanced the expression of mature of GSDMD and IL-1β, and increased the release of LDH, exacerbating pyroptosis induced by A. baumannii. These findings suggest that STX17 regulates pyroptosis induced by A. baumannii by modulating lysosomal function.

Identification of 7 mitochondria-related genes as diagnostic biomarkers of MDD and their correlation with immune infiltration: New insights from bioinformatics analysis

BACKGROUND

Major depressive disorder (MDD) is one of the most prevalent and debilitating psychiatric disorders. It becomes more recognized that mitochondrial dysfunction contributes to the pathophysiology of depression. However, little research has systematically investigated the mitochondria-related biomarkers for MDD diagnosis. This study aimed to develop a novel diagnostic gene signature in MDD based on mitochondria-related genes.

METHOD

We identified the differentially expressed mitochondrial-related genes (DeMRGs) by combing the gene expression data of the GEO database with mitochondria-related gene lists obtained from the MitoCarta3.0 database. Next, three kinds of machine-learning algorithms were used to screen characteristic DeMRGs. Then, we constructed a multivariable diagnostic model based on these characteristic genes and evaluated the diagnostic ability of this model. Subsequently, the immune landscape of infiltrated immune cells between MDD patients and controls was evaluated by CIBERSORT. Using consensus clustering analysis, we divided MDD patients into different clusters based on the characteristic DeMRGs expression patterns. Finally, the variations in immune cell infiltration between different clusters, and the correlation between characteristic DeMRGs and immune cell infiltration were analyzed.

RESULTS

Seven characteristic genes, including PMPCB, MRPS28, LYRM2, MGST1, COX20, PTPMT1, and STX17, were identified from the 31 DeMRGs. Based on the seven characteristic genes, we successfully constructed a diagnostic model which had relatively good diagnostic performance and potential application in the clinical diagnosis of MDD. In addition, our results also imply an intimate and comprehensive association between the characteristic DeMRGs and immune infiltrating cells.

CONCLUSION

A novel mitochondria-related gene signature with a good diagnostic performance and a relationship with immune microenvironment were identified in major depressive disorder.

The Multiple Roles of Autophagy in Neural Function and Diseases

Autophagy involves the sequestration and delivery of cytoplasmic materials to lysosomes, where proteins, lipids, and organelles are degraded and recycled. According to the way the cytoplasmic components are engulfed, autophagy can be divided into macroautophagy, microautophagy, and chaperone-mediated autophagy. Recently, many studies have found that autophagy plays an important role in neurological diseases, including Alzheimer's disease, Parkinson's disease, Huntington's disease, neuronal excitotoxicity, and cerebral ischemia. Autophagy maintains cell homeostasis in the nervous system via degradation of misfolded proteins, elimination of damaged organelles, and regulation of apoptosis and inflammation. AMPK-mTOR, Beclin 1, TP53, endoplasmic reticulum stress, and other signal pathways are involved in the regulation of autophagy and can be used as potential therapeutic targets for neurological diseases. Here, we discuss the role, functions, and signal pathways of autophagy in neurological diseases, which will shed light on the pathogenic mechanisms of neurological diseases and suggest novel targets for therapies.

Lipid peroxidation products' role in autophagy regulation

Autophagy, which is responsible for removing damaged molecules, prevents their accumulation in cells, thus maintaining intracellular homeostasis. It is also responsible for removing the effects of oxidative stress, so its activation takes place during increased reactive oxygen species (ROS) generation and lipid peroxidation. Therefore, the aim of this review was to summarize all the available knowledge about the effect of protein modifications by lipid peroxidation products on autophagy activation and the impact of this interaction on the functioning of cells. This review shows that reactive aldehydes (including 4-hydroxynonenal and malondialdehyde), either directly or by the formation of adducts with autophagic proteins, can activate or prevent autophagy, depending on their concentration. This effect relates not only to the initial stages of autophagy, when 4-hydroxynonenal and malondialdehyde affect the levels of proteins involved in autophagy initiation and phagophore formation, but also to the final stage, degradation, when reactive aldehydes, by binding to the active center of cathepsins, inactivate their proteolytic functions. Moreover, this review also shows how little research exists on analyzing the impact of lipid peroxidation products and their protein adducts on autophagy. Such knowledge could be used in the therapy of diseases related to autophagy disorders.

Berberine Alleviates Ischemic Brain Injury by Enhancing Autophagic Flux via Facilitation of TFEB Nuclear Translocation

Berberine has been demonstrated to alleviate cerebral ischemia/reperfusion injury, but its neuroprotective mechanism has yet to be understood. Studies have indicated that ischemic neuronal damage was frequently driven by autophagic/lysosomal dysfunction, which could be restored by boosting transcription factor EB (TFEB) nuclear translocation. Therefore, this study investigated the pharmacological effects of berberine on TFEB-regulated autophagic/lysosomal signaling in neurons after cerebral stroke. A rat model of ischemic stroke and a neuronal ischemia model in HT22 cells were prepared using middle cerebral artery occlusion (MCAO) and oxygen-glucose deprivation (OGD), respectively. Berberine was pre-administered at a dose of 100[Formula: see text]mg/kg/d for three days in rats and 90[Formula: see text][Formula: see text]M in HT22 neurons for 12[Formula: see text]h. 24[Formula: see text]h after MCAO and 2[Formula: see text]h after OGD, the penumbral tissues and OGD neurons were obtained to detect nuclear and cytoplasmic TFEB, and the key proteins in the autophagic/lysosomal pathway were examined using western blot and immunofluorescence, respectively. Meanwhile, neuron survival, infarct volume, and neurological deficits were assessed to evaluate the therapeutic efficacy. The results showed that berberine prominently facilitated TFEB nuclear translocation, as indicated by increased nuclear expression in penumbral neurons as well as in OGD HT22 cells. Consequently, both autophagic activity and lysosomal capacity were simultaneously augmented to alleviate the ischemic injury. However, berberine-conferred neuroprotection could be greatly counteracted by lysosomal inhibitor Bafilomycin A1 (Baf-A1). Meanwhile, autophagy inhibitor 3-Methyladenine (3-MA) also slightly neutralized the pharmacological effect of berberine on ameliorating autophagic/lysosomal dysfunction. Our study suggests that berberine-induced neuroprotection against ischemic stroke is elicited by enhancing autophagic flux via facilitation of TFEB nuclear translocation in neurons.

Zanthoxylum armatum DC fruit ethyl acetate extract site induced hepatotoxicity by activating endoplasmic reticulum stress and inhibiting autophagy in BRL-3A models

ETHNOPHARMACOLOGICAL RELEVANCE

Zanthoxylum armatum DC (Z. armatum) is renowned not only as a culinary spice but also as a staple in traditional ethnic medicine, predominantly in Southeast Asia and various other regions. Recent research has unveiled its multifaceted pharmacological properties, including anti-inflammatory, antibacterial, and toothache relief effects. Nonetheless, some studies have reported the potential toxicity of Z. armatum, emphasizing the need to further explore its toxicity mechanisms for safer application.

AIM OF THE STUDY

This study investigated the effect and mechanism of hepatotoxicity in BRL-3A cells induced by Z. armatum.

MATERIALS AND METHODS

The compounds of the ethyl acetate extract of Z. armatum (ZADC-EA) were identified by ultrahigh performance liquid chromatography coupled with quadrupole-orbitrap high resolution mass spectrometry (UPLC-Q-Orbitrap HRMS). The hepatotoxicity of the extract was evaluated by detecting cell viability, aspartate aminotransferase (AST), alanine aminotransferase (ALT), and lactate dehydrogenase (LDH) activity, and apoptosis. Endoplasmic reticulum stress, autophagy, and apoptosis were detected by Ad-mCherry-GFP-LC3B, flow cytometry, and Western blot to explore the mechanism of hepatotoxicity induced by ZADC-EA.

RESULTS

UPLC-Q-Orbitrap HRMS analysis revealed the presence of compounds belonging to flavonoids, terpenoids, and alkaloids. The IC50 value of ZADC-EA was 62.43 μg/mL, the cell viability of BRL-3A decreased in a time-dose dependent manner, and the levels of AST, ALT, and LDH were upregulated. In addition, ZADC-EA-induced increased expression of eIF2α-ATF4-CHOP pathway proteins, inhibited autophagy, and promoted apoptosis.

CONCLUSIONS

This study provides insights into the hepatotoxicity mechanisms of ZADC-EA on BRL-3A cells. It was found that ZADC-EA could induce endoplasmic reticulum stress and inhibit autophagy, then intensify apoptosis, and endoplasmic reticulum stress could exacerbate autophagy inhibition.

Growth differentiation factor 7 pretreatment enhances the therapeutic capacity of bone marrow-derived mesenchymal stromal cells against cerebral ischemia-reperfusion injury

Bone marrow-derived mesenchymal stem cells (BMSCs) transplantation is a promising therapeutic strategy for cerebral ischemia/reperfusion (I/R) injury; however, the clinical outcome is barely satisfactory and demands further improvement. The present study aimed to investigate whether preconditioning of BMSCs by recombinant human growth differentiation factor 7 (rhGDF7) could enhance its therapeutic capacity against cerebral I/R injury. Mouse BMSCs and primary neurons were co-cultured and exposed to oxygen glucose deprivation/reperfusion (OGD/R) stimulation. To investigate the role of exosomal microRNA-369-3p (miR-369-3p), inhibitors, RNAi and the miR-369-3p antagomir were used. Meanwhile, mice were intravenously injected with rhGDF7-preconditioned BMSCs and then received cerebral I/R surgery. Markers of inflammation, oxidative stress and neural damage were evaluated. To inhibit AMP-activated protein kinase (AMPK), compound C was used in vivo and in vitro. Compared with cell-free transwell or vehicle-preconditioned BMSCs, rhGDF7-preconditioned BMSCs significantly prevented OGD/R-induced inflammation, oxidative stress and neural damage in vitro. Meanwhile, rhGDF7-preconditioned BMSCs could prevent I/R-induced cerebral inflammation and oxidative stress in vivo. Mechanistically, rhGDF7 preconditioning significantly increased exosomal miR-369-3p expression in BMSCs and then transferred exosomal miR-369-3p to primary neurons, where it bound to phosphodiesterase 4 D (Pde4d) 3'-UTR and downregulated PDE4D expression, thereby preventing I/R-induced inflammation, oxidative stress and neural damage through activating AMPK pathway. Our study identify GDF7 pretreatment as a promising adjuvant reagent to improve the therapeutic potency of BMSCs for cerebral I/R injury and ischemic stroke.

Ginkgo biloba extract (EGb-761) confers neuroprotection against ischemic stroke by augmenting autophagic/lysosomal signaling pathway

Ginkgo biloba extract (EGb-761) is well-recognized to have neuroprotective properties. Meanwhile, autophagy machinery is extensively involved in the pathophysiological processes of ischemic stroke. The EGb-761 is widely used in the clinical treatment of stroke patients. However, its neuroprotective mechanisms against ischemic stroke are still not fully understood. The present study was conducted to uncover whether the pharmacological effects of EGb-761 can be executed by modulation of the autophagic/lysosomal signaling axis. A Sprague-Dawley rat model of ischemic stroke was established by middle cerebral artery occlusion (MCAO) for 90 min, followed by reperfusion. The EGb-761 was then administered to the MCAO rats once daily for a total of 7 days. Thereafter, the penumbral tissues were acquired to detect proteins involved in the autophagic/lysosomal pathway including Beclin1, LC-3, SQSTM1/p62, ubiquitin, cathepsin B, and cathepsin D by western blot and immunofluorescence, respectively. Subsequently, the therapeutic outcomes were evaluated by measuring the infarct volume, neurological deficits, and neuron survival. The results showed that the autophagic activities of Beclin1 and LC3-II in neurons were markedly promoted by 7 days of EGb-761 therapy. Meanwhile, the autophagic cargoes of insoluble p62 and ubiquitinated proteins were effectively degraded by EGb-761-augmented lysosomal activity of cathepsin B and cathepsin D. Moreover, the infarction size, neurological deficiencies, and neuron death were also substantially attenuated by EGb-761 therapy. Taken together, our study suggests that EGb-761 exerts a neuroprotective effect against ischemic stroke by promoting autophagic/lysosomal signaling in neurons at the penumbra. Thus, it might be a new therapeutic target for treating ischemic stroke.

Mitochondria associated ER membranes and cerebral ischemia: Molecular mechanisms and therapeutic strategies

Endoplasmic reticulum (ER) and mitochondria are two important organelles that are highly dynamic in mammalian cells. The physical connection between them is mitochondria associated ER membranes (MAM). In recent years, studies on endoplasmic reticulum and mitochondria have shifted from independent division to association and comparison, especially MAM has gradually become a research hotspot. MAM connects the two organelles, not only to maintain their independent structure and function, but also to promote metabolism and signal transduction between them. This paper reviews the morphological structure and protein localization of MAM, and briefly analyzes the functions of MAM in regulating Ca2+ transport, lipid synthesis, mitochondrial fusion and fission, endoplasmic reticulum stress and oxidative stress, autophagy and inflammation. Since ER stress and mitochondrial dysfunction are important pathological events in neurological diseases including ischemic stroke, MAM is likely to play an important role in cerebral ischemia by regulating the signaling of the two organelles and the crosstalk of the two pathological events.

Free radical biology in neurological manifestations: mechanisms to therapeutics interventions

Recent advancements and growing attention about free radicals (ROS) and redox signaling enable the scientific fraternity to consider their involvement in the pathophysiology of inflammatory diseases, metabolic disorders, and neurological defects. Free radicals increase the concentration of reactive oxygen and nitrogen species in the biological system through different endogenous sources and thus increased the overall oxidative stress. An increase in oxidative stress causes cell death through different signaling mechanisms such as mitochondrial impairment, cell-cycle arrest, DNA damage response, inflammation, negative regulation of protein, and lipid peroxidation. Thus, an appropriate balance between free radicals and antioxidants becomes crucial to maintain physiological function. Since the 1brain requires high oxygen for its functioning, it is highly vulnerable to free radical generation and enhanced ROS in the brain adversely affects axonal regeneration and synaptic plasticity, which results in neuronal cell death. In addition, increased ROS in the brain alters various signaling pathways such as apoptosis, autophagy, inflammation and microglial activation, DNA damage response, and cell-cycle arrest, leading to memory and learning defects. Mounting evidence suggests the potential involvement of micro-RNAs, circular-RNAs, natural and dietary compounds, synthetic inhibitors, and heat-shock proteins as therapeutic agents to combat neurological diseases. Herein, we explain the mechanism of free radical generation and its role in mitochondrial, protein, and lipid peroxidation biology. Further, we discuss the negative role of free radicals in synaptic plasticity and axonal regeneration through the modulation of various signaling molecules and also in the involvement of free radicals in various neurological diseases and their potential therapeutic approaches. The primary cause of free radical generation is drug overdosing, industrial air pollution, toxic heavy metals, ionizing radiation, smoking, alcohol, pesticides, and ultraviolet radiation. Excessive generation of free radicals inside the cell R1Q1 increases reactive oxygen and nitrogen species, which causes oxidative damage. An increase in oxidative damage alters different cellular pathways and processes such as mitochondrial impairment, DNA damage response, cell cycle arrest, and inflammatory response, leading to pathogenesis and progression of neurodegenerative disease other neurological defects.

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.

Development and Evaluation of Novel Metformin Derivative Metformin Threonate for Brain Ischemia Treatment

Epidemiologic data reveal that diabetes patients taking metformin exhibit lower incidence of stroke and better functional outcomes during post-stroke neurologic recovery. We previously demonstrated that chronic post-ischemic administration of metformin improved functional recovery in experimental cerebral ischemia. However, few beneficial effects of metformin on the acute phase of cerebral ischemia were reported either in experimental animals or in stroke patients, which limits the application of metformin in stroke. We hypothesized that slow cellular uptake of metformin hydrochloride may contribute to the lack of efficacy in acute stroke. We recently developed and patented a novel metformin derivative, metformin threonate (SHY-01). Pharmacokinetic profile in vivo and in cultured cells revealed that metformin is more rapidly uptaken and accumulated from SHY-01 than metformin hydrochloride. Accordingly, SHY-01 treatment exhibited more potent and rapid activation of AMP-activated protein kinase (AMPK). Furthermore, SHY-01 elicited a stronger inhibition of microglia activation and more potent neuroprotection when compared to metformin hydrochloride. SHY-01 administration also had superior beneficial effects on neurologic functional recovery in experimental stroke and offered strong protection against acute cerebral ischemia with reduced infarct volume and mortality, as well as the improved sensorimotor and cognitive functions in rats. Collectively, these results indicated that SHY-01 had an improved pharmacokinetic and pharmacological profile and produced more potent protective effects on acute stroke and long-term neurological damage. We propose that SHY-01 is a very promising therapeutic candidate for cerebral ischemic stroke.

Pitavastatin Induces Cancer Cell Apoptosis by Blocking Autophagy Flux

Statins, a class of lipid-lowering drugs, are used in drug repositioning for treatment of human cancer. However, the molecular mechanisms underlying statin-induced cancer cell death and autophagy are not clearly defined. In the present study, we showed that pitavastatin could increase apoptosis in a FOXO3a-dependent manner in the oral cancer cell line, SCC15, and the colon cancer cell line, SW480, along with the blockade of autophagy flux. The inhibition of autophagy by silencing the LC3B gene reduced apoptosis, while blockade of autophagy flux using its inhibitor, Bafilomycin A1, further induced apoptosis upon pitavastatin treatment, which suggested that autophagy flux blockage was the cause of apoptosis by pitavastatin. Further, the FOXO3a protein accumulated due to the blockade of autophagy flux which in turn was associated with the induction of ER stress by transcriptional upregulation of PERK-CHOP pathway, subsequently causing apoptosis due to pitavastatin treatment. Taken together, pitavastatin-mediated blockade of autophagy flux caused an accumulation of FOXO3a protein, thereby leading to the induction of PERK, ultimately causing CHOP-mediated apoptosis in cancer cells. Thus, the present study highlighted the additional molecular mechanism underlying the role of autophagy flux blockade in inducing ER stress, eventually leading to apoptosis by pitavastatin.

Reverse relationship between autophagy and apoptosis in an in vitro model of cortical neuronal injury

Autophagy and apoptosis are intertwined, and their relationship involves complex cross-talk. Whether the activation and inhibition of autophagy protect or damage neurons in the central nervous system has been a matter of longstanding controversy. We investigated the effect of autophagy on the apoptosis of cortical neurons after oxygen- and glucose-deprivation/reoxygenation (OGD/R) injury in vitro and found that protective mechanism activation was the predominant response to enhanced autophagy activation and increased autophagic flux. After successful establishment of an OGD/R model with cortical neurons, the autophagy activator rapamycin (Rap) or the late-autophagy inhibitor bafilomycin A1 (BafA1) was added to cell groups according to the experimental design. Cell viability was determined by Cell Counting Kit-8 (CCK-8) and lactate dehydrogenase (LDH) assays, and the apoptosis rate was measured by analysing Annexin V-FITC/PI-stained cells. The protein and mRNA expression levels of the apoptosis factors Caspase8 and Caspase3 and autophagy-associated proteins LC3 and p62 were measured by Western blotting and RT-qPCR. The extent of autophagic flux was determined by measuring the intensity of double immunofluorescence labelled protein after cells were transfected with RFP-GFP-LC3-expressing virus, and the ultrastructures of autophagosomes were observed by transmission electron microscopy (TEM). The results showed that cell viability decreased and that cells underwent autophagy and apoptosis after OGD/R. After the addition of Rap, cell viability was increased, and the apoptosis rate was decreased significantly. In addition, the level of the autophagic flux protein LC3II was increased, and the level of p62 was decreased. The number of autophagosomes and the ratio of autophagosomes to lysosomes were increased significantly. After BafA1 intervention, however, these results were reversed, with decreased cell viability, a significantly increased apoptosis rate, and disrupted autophagic flux. In conclusion, enhanced autophagy activation or autophagic flux exerted a significant protective effect on neurons after OGD/R injury in vitro.

Ubiquitin-Specific Protease 29 Exacerbates Cerebral Ischemia-Reperfusion Injury in Mice

Oxidative stress and apoptosis contribute to the progression of cerebral ischemia/reperfusion (I/R) injury. Ubiquitin-specific protease 29 (USP29) is abundantly expressed in the brain and plays critical roles in regulating oxidative stress and cell apoptosis. The purpose of the present study is to investigate the role and underlying mechanisms of USP29 in cerebral I/R injury. Neuron-specific USP29 knockout mice were generated and subjected to cerebral I/R surgery. For USP29 overexpression, mice were stereotactically injected with the adenoassociated virus serotype 9 vectors carrying USP29 for 4 weeks before cerebral I/R. And primary cortical neurons were isolated and exposed to oxygen glucose deprivation/reperfusion (OGD/R) stimulation to imitate cerebral I/R injury in vitro. USP29 expression was elevated in the brain and primary cortical neurons upon I/R injury. Neuron-specific USP29 knockout significantly diminished, whereas USP29 overexpression aggravated cerebral I/R-induced oxidative stress, apoptosis, and neurological dysfunction in mice. In addition, OGD/R-induced oxidative stress and neuronal apoptosis were also attenuated by USP29 silence but exacerbated by USP29 overexpression in vitro. Mechanistically, neuronal USP29 enhanced p53/miR-34a-mediated silent information regulator 1 downregulation and then promoted the acetylation and suppression of brain and muscle ARNT-like protein, thereby aggravating oxidative stress and apoptosis upon cerebral I/R injury. Our findings for the first time identify that USP29 upregulation during cerebral I/R may contribute to oxidative stress, neuronal apoptosis, and the progression of cerebral I/R injury and that inhibition of USP29 may help to develop novel therapeutic strategies to treat cerebral I/R injury.

Neuritin attenuates oxygen-glucose deprivation/reoxygenation (OGD/R)-induced neuronal injury by promoting autophagic flux

The autophagy/apoptosis interaction has always been a focus of study in pathogenicity models. Neuritin is a neurotrophic factor that is highly expressed primarily in the central nervous system. Our previous study revealed that it protects against apoptosis in cortical neurons subjected to oxygen-glucose deprivation (OGD)/reoxygenation (OGD/R), and later animal experiments revealed that it can increase the expression of the autophagy-related protein LC3. Whether this neuroprotective effect is closely related to autophagy is still unclear. In this study, we hypothesized that neuritin can promote autophagic flux to protect nerve cells after OGD/R. To verify this hypothesis, we induced OGD/R in primary cortical neurons and assessed cell viability by the CCK8 and LDH assays. Cell apoptosis was assessed by Annexin V-FITC/PI, staining, and the contents and mRNA abundances of the autophagy-related proteins LC3 and p62, the apoptotic protein Caspase3 were quantified by Western blotting and RT-PCR. Autophagic flux was assessed by immunofluorescence after RFP-GFP-LC3 virus transfection, and ultrastructural changes in autophagosomes were observed by transmission electron microscopy (TEM). The results showed that cell viability was decreased, apoptosis was increased and autophagy was enhanced after OGD/R. Neuritin significantly increased cell viability, decreased apoptosis, further increased the expression of the autophagic flux-related protein LC3, further decreased p62 expression, and significantly increased the autophagosome number and autophagosome to lysosome ratio. Bafilomycin A1 (BafA1) is a late autophagy inhibitor, aggravated cell damage and apoptosis and counteracted the enhancement of autophagy activation and protective effects of neuritin. In conclusion, neuritin may promote the completion of autophagic flux by ameliorating neuronal damage after OGD/R.

Targeting autophagy in ischemic stroke: From molecular mechanisms to clinical therapeutics

Stroke constitutes the second leading cause of death and a major cause of disability worldwide. Stroke is normally classified as either ischemic or hemorrhagic stroke (HS) although 87% of cases belong to ischemic nature. Approximately 700,000 individuals suffer an ischemic stroke (IS) in the US each year. Recent evidence has denoted a rather pivotal role for defective macroautophagy/autophagy in the pathogenesis of IS. Cellular response to stroke includes autophagy as an adaptive mechanism that alleviates cellular stresses by removing long-lived or damaged organelles, protein aggregates, and surplus cellular components via the autophagosome-lysosomal degradation process. In this context, autophagy functions as an essential cellular process to maintain cellular homeostasis and organismal survival. However, unchecked or excessive induction of autophagy has been perceived to be detrimental and its contribution to neuronal cell death remains largely unknown. In this review, we will summarize the role of autophagy in IS, and discuss potential strategies, particularly, employment of natural compounds for IS treatment through manipulation of autophagy.

Roflumilast prevents ischemic stroke-induced neuronal damage by restricting GSK3β-mediated oxidative stress and IRE1α/TRAF2/JNK pathway

Inhibition of phosphodiesterase 4 (PDE4) protects against neuronal apoptosis induced by cerebral ischemia. However, the exact mechanisms responsible for the protection of PDE4 inhibition have not been completely clarified. Roflumilast (Roflu) is an FDA-approved PDE4 inhibitor for the treatment of chronic obstructive pulmonary disease. The potential protective role of Roflu against ischemic stroke-associated neuronal injury remains unexplored. In this study, we investigated the effect and mechanism of Roflu against ischemic stroke using in vitro oxygen-glucose deprivation reperfusion (OGD/R) and in vivo rat middle cerebral artery occlusion (MCAO) models. We demonstrated that Roflu significantly reduced the apoptosis of HT-22 cells exposed to OGD/R, enhanced the nuclear translocation of nuclear factor erythroid 2-related factor 2 (Nrf-2), and reduced oxidative stress. Treatment with Roflu increased the phosphorylation of protein kinase B (Akt) and glycogen synthase kinase 3β (GSK3β) but decreased the level of phosphorylated inositol requiring enzyme 1α (IRE1α). Interestingly, constitutively active GSK3β (S9A) mutation abolished the effects of Roflu on oxidative stress and IRE1α phosphorylation. Moreover, Roflu decreased the binding of IRE1α to tumor necrosis factor receptor-associated factor 2 (TRAF2) and attenuated the phosphorylation of c-Jun N-terminal kinase (JNK). We also found that PDE4B knockdown reduced the phosphorylation of both IRE1α and JNK, while overexpression of PDE4B antagonized the role of PDE4B knockdown on the activation of IRE1α and JNK. Besides, the inhibition of PDE4 by Roflu produced similar effects in primary cultured neurons. Finally, Roflu ameliorated MCAO-induced cerebral injury by decreasing infarct volume, restoring neurological score, and reducing the phosphorylation of IRE1α and JNK. Collectively, these data suggest that Roflu protects neurons from cerebral ischemia reperfusion-mediated injury via the activation of GSK3β/Nrf-2 signaling and suppression of the IRE1α/TRAF2/JNK pathway. Roflu has the potential as a protective drug for the treatment of cerebral ischemia.

Pcgf1 Regulates Early Neural Tube Development Through Histone Methylation in Zebrafish

The neural induction constitutes the initial step in the generation of the neural tube. Pcgf1, as one of six Pcgf paralogs, is a maternally expressed gene, but its role and mechanism in early neural induction during neural tube development have not yet been explored. In this study, we found that zebrafish embryos exhibited a small head and reduced or even absence of telencephalon after inhibiting the expression of Pcgf1. Moreover, the neural induction process of zebrafish embryos was abnormally activated, and the subsequent NSC self-renewal was inhibited after injecting the Pcgf1 MO. The results of in vitro also showed that knockdown of Pcgf1 increased the expression levels of the neural markers Pax6, Pou3f1, and Zfp521, but decreased the expression levels of the pluripotent markers Oct4, Hes1, and Nanog, which further confirmed that Pcgf1 was indispensable for maintaining the pluripotency of P19 cells. To gain a better understanding of the role of Pcgf1 in early development, we analyzed mRNA profiles from Pcgf1-deficient P19 cells using RNA-seq. We found that the differentially expressed genes were enriched in many functional categories, which related to the development phenotype, and knockdown of Pcgf1 increased the expression of histone demethylases. Finally, our results showed that Pcgf1 loss-of-function decreased the levels of transcriptional repression mark H3K27me3 at the promoters of Ngn1 and Otx2, and the levels of transcriptional activation mark H3K4me3 at the promoters of Pou5f3 and Nanog. Together, our findings reveal that Pcgf1 might function as both a facilitator for pluripotent maintenance and a repressor for neural induction.