Autophagy activation involved in hypoxic-ischemic brain injury induces cognitive and memory impairment in neonatal rats

Traumatic brain injury heterogeneity affects cell death and autophagy

Traumatic brain injury (TBI) mechanism and severity are heterogenous clinically, resulting in a multitude of physical, cognitive, and behavioral deficits. Impact variability influences the origin, spread, and classification of molecular dysfunction which limits strategies for comprehensive clinical intervention. Indeed, there are currently no clinically approved therapeutics for treating the secondary consequences associated with TBI. Thus, examining pathophysiological changes from heterogeneous impacts is imperative for improving clinical translation and evaluating the efficacy of potential therapeutic strategies. Here we utilized TBI models that varied in both injury mechanism and severity including severe traditional controlled cortical impact (CCI), modified mild CCI (MTBI), and multiple severities of closed-head diffuse TBI (DTBI), and assessed pathophysiological changes. Severe CCI induced cortical lesions and necrosis, while both MTBI and DTBI lacked lesions or significant necrotic damage. Autophagy was activated in the ipsilateral cortex following CCI, but acutely impaired in the ipsilateral hippocampus. Additionally, autophagy was activated in the cortex following DTBI, and autophagic impairment was observed in either the cortex or hippocampus following impact from each DTBI severity. Thus, we provide evidence that autophagy is a therapeutic target for both mild and severe TBI. However, dramatic increases in necrosis following CCI may negatively impact the clinical translatability of therapeutics designed to treat acute dysfunction in TBI. Overall, these results provide evidence that injury sequalae affiliated with TBI heterogeneity is linked through autophagy activation and/or impaired autophagic flux. Thus, therapeutic strategies designed to intervene in autophagy may alleviate pathophysiological consequences, in addition to the cognitive and behavioral deficits observed in TBI.

Sevoflurane postconditioning alleviates hypoxic-ischemic brain damage in rats by inhibiting the endoplasmic reticulum stress PERK/ATF4/CHOP pathway

Hypoxic-ischemic brain damage (HIBD) frequently induces cognitive impairments. Investigating the role of sevoflurane postconditioning (SPC) in HIBD, we conducted experiments involving HIBD modeling, SPC treatment, and interventions with the PERK inhibitor GSK2656157 or the PERK activator CCT020312, administered 30 min before modeling, followed by SPC treatment. Behavioral testing using the Morris water maze test and Neurological Deficiency Scale (NDS) was conducted. Additionally, Nissl staining assessed hippocampal CA1 area neuronal density, TUNEL staining evaluated hippocampal CA1 area neuronal apoptosis, and Western blot determined hippocampal CA1 area protein levels, including Bax, Bcl-2, p-PERK/PERK, p-eIF2/eIF2, ATF4, CHOP, GRP78, Bax, and Bcl-2 protein levels. Following SPC treatment, HIBD rats exhibited improved spatial learning and memory abilities, reduced neuronal apoptosis, increased neuronal density in the hippocampal CA1 area, elevated Bcl-2 protein level, decreased Bax protein levels, and decreased levels of endoplasmic reticulum stress pathway related proteins (p-PERK/PERK, p-eIF2/eIF2, ATF4, CHOP and GRP78). Pre-modeling treatment with the PERK inhibitor treatment improved outcomes in HIBD rats. However, pre-modeling treatment with the PERK activator CCT020312 counteracted the protective effects of SPC against HIBD in rats. In conclusion, SPC alleviates neuronal apoptosis in the hippocampus CA1 area of HIBD rats by inhibiting the endoplasmic reticulum stress pathway PERK/ATF4/CHOP, thereby mitigating HIBD in rats.

β-asarone improves cognitive impairment and alleviates autophagy in mice with vascular dementia via the cAMP/PKA/CREB pathway

BACKGROUND

Vascular dementia (VD) is the second most common type of dementia after Alzheimer's disease. β-asarone, a major component of Acorus tatarinowii Schott, is important in neurodegenerative and neurovascular diseases. Studies have confirmed that β-asarone can mitigate autophagy and reduce damage in hypoxic cells. We also reported that β-asarone improves learning and memory. This study further clarifies whether β-asarone attenuates cerebral ischaemic injury by acting through the cAMP/PKA/CREB pathway in VD model mice.

METHODS

Here, genes and potential pathways that may be targeted by β-asarone for the treatment of transient cerebral ischaemia (TCI) and cognitive impairment (CI) were obtained using network pharmacology. The two-vessel occlusion method was used to establish the VD model. The Morris water maze test was used to evaluate the effects on memory. Then, the protein levels of mitofusin-2 (Mfn2), brain-derived neurotrophic factor (BDNF), optic atrophy 1 (OPA1), cyclic adenosine monophosphate (cAMP), myelin basic protein (MBP), matrix metalloproteinase-9 (MMP9) and neuron specific enolase (NSE) were determined by ELISA. The levels of superoxide dismutase (SOD) and malonaldehyde (MDA) were measured using commercial kits. Then, qRT-PCR was employed to investigate the expression of the candidate genes screened from the protein-protein interaction (PPI) network. Furthermore, the expression of the autophagy-related proteins Beclin-1, (microtubule-associated protein light chain 3) LC3, p62, postsynaptic density protein 95 (PSD95), protein kinase A (PKA), pPKA, cyclic-AMP response binding protein (CREB), and pCREB was determined by western blotting. The expression of autophagy-related proteins, PSD95 and translocase of outer mitochondrial membrane 20 (TOM20) was determined by immunofluorescence analyses.

RESULTS

The network pharmacological analysis showed 234 targets related to β-asarone, 1,118 genes related to TCI and 2,039 genes associated with CI. Our results confirm that β-asarone treatment not only alleviated brain damage in the VD model by improving mitochondrial and synaptic function, reducing neuronal injury and upregulating the expression of antioxidants but also effectively improved the cognitive behaviour of VD model mice. Moreover, β-asarone downregulated VD-induced RELA and CCND1 mRNA expression. In addition, we validated that β-asarone increased the phosphorylation of PKA and CREB and upregulated cAMP protein expression. The results showed that the cAMP/PKA/CREB signalling pathway was upregulated. Moreover, β-asarone administration decreased the protein expression levels of Beclin-1 and LC3 and increased the expression levels of p62 in VD model mice.

CONCLUSIONS

β-asarone inhibits Beclin-1-dependent autophagy and upregulates the cAMP/PKA/CREB signalling pathway to attenuate mitochondrial and synaptic damage from cerebral ischaemia and improve learning and cognitive abilities in VD model mice.

N6-methyladenosine demethylase FTO regulates synaptic and cognitive impairment by destabilizing PTEN mRNA in hypoxic-ischemic neonatal rats

Hypoxic-ischemic brain damage (HIBD) can result in significant global rates of neonatal death or permanent neurological disability. N6-methyladenosine (m6A) modification of RNA influences fundamental aspects of RNA metabolism, and m6A dysregulation is implicated in various neurological diseases. However, the biological roles and clinical significance of m6A in HIBD remain unclear. We currently evaluated the effect of HIBD on cerebral m6A methylation in RNAs in neonatal rats. The m6A dot blot assay showed a global augmentation in RNA m6A methylation post-HI. Herein, we also report on demethylase FTO, which is markedly downregulated in the hippocampus and is the main factor involved with aberrant m6A modification following HI. By conducting a comprehensive analysis of RNA-seq data and m6A microarray results, we found that transcripts with m6A modifications were more highly expressed overall than transcripts without m6A modifications. The overexpression of FTO resulted in the promotion of Akt/mTOR pathway hyperactivation, while simultaneously inhibiting autophagic function. This is carried out by the demethylation activity of FTO, which selectively demethylates transcripts of phosphatase and tensin homolog (PTEN), thus promoting its degradation and reduced protein expression after HI. Moreover, the synaptic and neurocognitive disorders induced by HI were effectively reversed through the overexpression of FTO in the hippocampus. Cumulatively, these findings demonstrate the functional importance of FTO-dependent hippocampal m6A methylome in cognitive function and provides novel mechanistic insights into the therapeutic potentials of FTO in neonatal HIBD.

Protein modification regulated autophagy in Bombyx mori and Drosophila melanogaster

Post-translational modifications refer to the chemical alterations of proteins following their biosynthesis, leading to changes in protein properties. These modifications, which encompass acetylation, phosphorylation, methylation, SUMOylation, ubiquitination, and others, are pivotal in a myriad of cellular functions. Macroautophagy, also known as autophagy, is a major degradation of intracellular components to cope with stress conditions and strictly regulated by nutrient depletion, insulin signaling, and energy production in mammals. Intriguingly, in insects, 20-hydroxyecdysone signaling predominantly stimulates the expression of most autophagy-related genes while concurrently inhibiting mTOR activity, thereby initiating autophagy. In this review, we will outline post-translational modification-regulated autophagy in insects, including Bombyx mori and Drosophila melanogaster, in brief. A more profound understanding of the biological significance of post-translational modifications in autophagy machinery not only unveils novel opportunities for autophagy intervention strategies but also illuminates their potential roles in development, cell differentiation, and the process of learning and memory processes in both insects and mammals.

A PSD-95 peptidomimetic mitigates neurological deficits in a mouse model of Angelman syndrome

Angelman Syndrome (AS) is a severe cognitive disorder caused by loss of neuronal expression of the E3 ubiquitin ligase UBE3A. In an AS mouse model, we previously reported a deficit in brain-derived neurotrophic factor (BDNF) signaling, and set out to develop a therapeutic that would restore normal signaling. We demonstrate that CN2097, a peptidomimetic compound that binds postsynaptic density protein-95 (PSD-95), a TrkB associated scaffolding protein, mitigates deficits in PLC-CaMKII and PI3K/mTOR pathways to restore synaptic plasticity and learning. Administration of CN2097 facilitated long-term potentiation (LTP) and corrected paired-pulse ratio. As the BDNF-mTORC1 pathway is critical for inhibition of autophagy, we investigated whether autophagy was disrupted in AS mice. We found aberrantly high autophagic activity attributable to a concomitant decrease in mTORC1 signaling, resulting in decreased levels of synaptic proteins, including Synapsin-1 and Shank3. CN2097 increased mTORC1 activity to normalize autophagy and restore hippocampal synaptic protein levels. Importantly, treatment mitigated cognitive and motor dysfunction. These findings support the use of neurotrophic therapeutics as a valuable approach for treating AS pathology.

The Notch pathway regulates autophagy after hypoxic-ischemic injury and affects synaptic plasticity

Following neonatal hypoxic-ischemia (HI) injury, it is crucial factor to reconstruct neural circuit and maintain neural network homeostasis for neurological recovery. A dynamic balance between the synthesis and degradation of synaptic protein is required for maintaining synaptic plasticity. Protein degradation is facilitated by autophagy. This study aimed to investigate the regulation of synaptic structural plasticity by the Notch pathway, by assessing changes in Notch pathway activation and their effects on synaptic proteins and autophagy after HI injury. The study involved 48 male newborn Yorkshire piglets, each weighing 1.0-1.5 kg and 3 days old. They were randomly assigned to two groups: the HI group and the Notch pathway inhibitor + HI group (n = 24 per group). Each group was further divided into six subgroups according to HI duration (n = 4 per group): a control subgroup, and 0-6, 6-12, 12-24, 24-48, and 48-72 h subgroups. The expression of Notch pathway-related proteins, including Notch1, Hes1, and Notch intracellular domains, increased following HI injury. The expression of autophagy proteins increased at 0-6 h and 6-12 h post-HI. The expression of synaptic proteins, such as postsynaptic density protein 95 (PSD95) and synaptophysin, increased 6-12 h and 12-24 h after HI, respectively. Notably, the increased expression of these proteins was reversed by a Notch pathway inhibitor. Transmission electron microscopy revealed the presence of autophagosome structures in synapses. These findings shed light on the underlying mechanisms of neurological recovery after HI injury and may provide insights into potential therapeutic targets for promoting neural circuit reconstruction and maintaining neural network homeostasis.

Diabetes influences the fusion of autophagosomes with lysosomes in SH-SY5Y cells and induces Aβ deposition and cognitive dysfunction in STZ-induced diabetic rats

Diabetes has been regarded as an independent risk factor for Alzheimer's disease (AD). Our previous study found that diabetes activated autophagy, but lysosome function was impaired. Autophagy-lysosome dysfunction may be involved in Aβ deposition in diabetic cognitive impairment. In the present study, we used STZ-induced diabetic rats and SH-SY5Y cells to investigate whether diabetes inhibits autophagosome fusion with lysosomes. We found that in the in vivo study, STZ-induced diabetic rats exhibited cognitive dysfunction, and the lysosome function-related factors CTSL, CTSD, and Rab7 were decreased (P < 0.05). In an in vitro study, the mRFP-GFP-LC3 assay showed that the fusion of autophagosomes with lysosomes was partly blocked in SH-SY5Y cells. High glucose treatment downregulated the number of autophagolysosomes, downregulated CTSD, CTSL, and Rab7 expression (P < 0.05), and then influenced the function of ACP2 to partly block the fusion of autophagosomes and lysosomes to inhibit Aβ clearance. These findings indicate that high glucose treatment affected lysosome function, interfered with the fusion of autophagosomes with lysosomes, and partly blocked autophagic flux to influence Aβ clearance.

Maternal sevoflurane exposure induces neurotoxicity in offspring rats via the CB1R/CDK5/p-tau pathway

Sevoflurane is widely used for maternal anesthesia during pregnancy. Sevoflurane exposure of rats at mid-gestation can cause abnormal development of the central nervous system in their offspring. Sevoflurane is known to increase the expression of cannabinoid 1 receptor (CB1R) in the hippocampus. However, the effect of cannabinoid 1 receptor on fetal and offspring rats after maternal anesthesia is still unclear. At gestational day 14, pregnant rats were subjected to 2-h exposure to 3.5% sevoflurane or air. Rats underwent intraperitoneal injection with saline or rimonabant (1 mg/kg) 30 min prior to sevoflurane or air exposure. cannabinoid 1 receptor, cyclin-dependent kinase 5 (CDK5), p35, p25, tau, and p-tau expression in fetal brains was measured at 6, 12, and 24 h post-sevoflurane/air exposure. Neurobehavioral and Morris water maze tests were performed postnatal days 3-33. The expression of cannabinoid 1 receptor/cyclin-dependent kinase 5/p-tau and histopathological staining of brain tissues in offspring rats was observed. We found that a single exposure to sevoflurane upregulated the activity of cyclin-dependent kinase 5 and the level of p-tau via cannabinoid 1 receptor. This was accompanied by the diminished number of neurons and dendritic spines in hippocampal CA1 regions. Finally, these effects induced lower scores and platform crossing times in behavioral tests. The present study suggests that a single exposure to 3.5% sevoflurane of rats at mid-gestation impairs neurobehavioral abilities and cognitive memory in offspring. cannabinoid 1 receptor is a possible target for the amelioration of postnatal neurobehavioral ability and cognitive memory impairments induced by maternal anesthesia.

Nrf2 and Parkin-Hsc70 regulate the expression and protein stability of p62/SQSTM1 under hypoxia

Solid tumors often contain regions with very low oxygen concentrations or hypoxia resulting from altered metabolism, uncontrolled proliferation, and abnormal tumor blood vessels. Hypoxia leads to resistance to both radio- and chemotherapy and a predisposition to tumor metastases. Under hypoxia, sequestosome 1 (SQSTM1/p62), a multifunctional stress-inducible protein involved in various cellular processes, such as autophagy, is down-regulated. The hypoxic depletion of p62 is mediated by autophagic degradation. We herein demonstrated that hypoxia down-regulated p62 in the hepatoma cell line Hep3B at the transcriptional and post-translational levels. At the transcriptional level, hypoxia down-regulated p62 mRNA by inhibiting nuclear factor erythroid 2-related factor 2 (Nrf2). The overexpression of Nrf2 and knockdown of Siah2, a negative regulator of Nrf2 under hypoxia, diminished the effects of hypoxia on p62 mRNA. At the post-translational level, the proteasome inhibitor MG132, but not the lysosomal inhibitors ammonium chloride and bafilomycin, prevented the hypoxic depletion of p62, suggesting the involvement of the proteasome pathway. Under hypoxia, the expression of the E3 ubiquitin ligase Parkin was up-regulated in a hypoxia-inducible factor 1α-dependent manner. Parkin ubiquitinated p62 and led to its proteasomal degradation, ensuring low levels of p62 under hypoxia. We demonstrated that the effects of Parkin on p62 required heat shock cognate 71 kDa protein (Hsc70). We also showed that the overexpression of Nrf2 and knockdown of Parkin or Hsc70 induced the accumulation of p62 and reduced the viability of cells under hypoxia. We concluded that a decrease in p62, which involves regulation at the transcriptional and post-translational levels, is critical for cell survival under hypoxia. The present results show the potential of targeting Nrf2/Parkin-Hsc70-p62 as a novel strategy to eradicate hypoxic solid tumors.

Sevoflurane up-regulates miR-7a to protect against ischemic brain injury in rats by down-regulating ATG7 and reducing neuronal autophagy

The current study aimed to elucidate the effects of Sevoflurane on neuronal autophagy and ischemic brain injury by regulating miR-7a/ATG7 axis. The rat model of middle cerebral artery occlusion (MCAO) was established by thread embolization. The expression pattern of microRNA-7a (miR-7a) and autophagy-related gene 7 (ATG7) was subsequently determined in Sevoflurane-treated MCAO rats with their relation and effects on neuronal autophagy and ischemic brain injury further analyzed. Bioinformatics analysis confirmed that miR-7a could target to inhibit ATG7 in ischemic brain injury samples. Sevoflurane could alleviate ischemic brain injury in rats by reducing the level of neuronal autophagy-related factors. The expression of miR-7a was up-regulated and ATG7 was down-regulated in the brain tissues of MCAO rats after Sevoflurane treatment. ATG7 was found to induce neuronal autophagy during autophagy in the brain tissues of MCAO rats. In summary, Sevoflurane exerts protective effects on ischemic brain injury via inhibiting autophagy of neurons and microglia through the miR-7a-mediated downregulation of ATG7.

Mechanisms Underlying Abnormal Expression of lncRNA H19 in Neonatal Hypoxic-Ischemic Encephalopathy

OBJECTIVE

Hypoxic-ischemic (HI)-related brain injury, especially HI encephalopathy (HIE) is a leading cause of morbidity and disability in newborns. Long noncoding RNAs (lncRNAs) are implicated in the progress of HI brain damage. However, the mechanisms underlying the regulatory effects of lncRNA H19 on autophagy in HIE remain unknown. This study was designed to identify the potential mechanisms involving lncRNA H19 in HIE.

STUDY DESIGN

We selected three HIE newborns and three healthy newborns for neonatal behavioral neurological assessment and screened the differentially expressed lncRNAs by microarray analysis and detected H19 expression in serum. After that, neonatal HIE rats were established and injected with H19 overexpression lentivirus vector or autophagy activator Rapa. The structure and apoptotic levels of brain tissue were observed, and righting reflex and geotaxis reflex were utilized to evaluate the short-term neurological function of HIE rats. The Morris water maze was performed to measure the long-term neurological functions of HIE rats. The binding relationships among H19/miR-19b/protein kinase B3 (Akt3) were verified. Levels of Akt3- and autophagy-related proteins were measured.

RESULTS

H19 was upregulated in HIE newborns and rat models. The areas of cerebral infarction and apoptosis in neonatal HIE rats were increased, and the nerve functions were compromised. The overexpression of H19 alleviated nerve damage of neonatal HIE rats, and reduced autophagy of brain tissue. H19 upregulated Akt3 as a miR-29b sponge. The protective effects of overexpression of H19 on brain tissue and nerve functions of neonatal HIE rats were partially reversed by autophagy activator.

CONCLUSION

H19 improved the brain tissue and alleviated nerve damage of neonatal HIE rats by upregulating the Akt3/mTOR pathway as a miR-29b sponge.

KEY POINTS

· H19 overexpression reduces the nerve damage in neonatal HIE rats.. · H19 reduces autophagy in neonatal HIE rats by the miR-29b/Akt3/mTOR axis.. · Autophagy activator reverses the protection of H19 in neonatal HIE..

Mitophagy in neurological disorders

Selective autophagy is an evolutionarily conserved mechanism that removes excess protein aggregates and damaged intracellular components. Most eukaryotic cells, including neurons, rely on proficient mitophagy responses to fine-tune the mitochondrial number and preserve energy metabolism. In some circumstances (such as the presence of pathogenic protein oligopolymers and protein mutations), dysfunctional mitophagy leads to nerve degeneration, with age-dependent intracellular accumulation of protein aggregates and dysfunctional organelles, leading to neurodegenerative disease. However, when pathogenic protein oligopolymers, protein mutations, stress, or injury are present, mitophagy prevents the accumulation of damaged mitochondria. Accordingly, mitophagy mediates neuroprotective effects in some forms of neurodegenerative disease (e.g., Alzheimer's disease, Parkinson’s disease, Huntington's disease, and Amyotrophic lateral sclerosis) and acute brain damage (e.g., stroke, hypoxic–ischemic brain injury, epilepsy, and traumatic brain injury). The complex interplay between mitophagy and neurological disorders suggests that targeting mitophagy might be applicable for the treatment of neurodegenerative diseases and acute brain injury. However, due to the complexity of the mitophagy mechanism, mitophagy can be both harmful and beneficial, and future efforts should focus on maximizing its benefits. Here, we discuss the impact of mitophagy on neurological disorders, emphasizing the contrast between the positive and negative effects of mitophagy.

Overexpression of Long Noncoding RNA H19 Inhibits Cardiomyocyte Apoptosis in Neonatal Rats with Hypoxic-Ischemic Brain Damage Through the miR-149-5p/LIF/PI3K/Akt Axis

Hypoxic-ischemic brain damage (HIBD) is a leading cause of fatality and neural system injury in neonates. This study aims to explore the effect of long noncoding RNA H19 on cardiomyocyte apoptosis in neonatal rats with HIBD. The neonatal rat model of HIBD was established. The cerebral infarction volume and apoptosis index of cardiomyocyte increased, while H19 expression decreased in neonatal rats with HIBD. After the lentivirus vector of overexpressed H19 was injected into neonatal rats with HIBD, the cardiomyocyte apoptosis was suppressed; levels of inflammatory factors and oxidative stress injury of myocardial tissues were reduced. The binding relationships between H19 and miR-149-5p, and miR-149-5p and leukemia inhibitory factor (LIF) were predicted by a bioinformatics website and verified using the dual-luciferase reporter gene assay. H19 competitively bound to miR-149-5p to upregulate LIF expression and activate the PI3K/Akt pathway. Moreover, a functional rescue experiment was carried out. Injection of Wortmannin reversed the inhibitory effect of H19 overexpression on cardiomyocyte apoptosis in neonatal rats with HIBD. It could be concluded that H19 competitively bound to miR-149-5p to upregulate LIF expression and activate the PI3K/Akt pathway, thus reducing cardiomyocyte apoptosis in neonatal rats with HIBD. This study may offer new insights for HIBD treatment.

Sevoflurane post-conditioning alleviated hypoxic-ischemic brain injury in neonatal rats by inhibiting endoplasmic reticulum stress-mediated autophagy via IRE1 signalings

Post-conditioning with sevoflurane, a volatile anesthetic, has been proved to be neuroprotective against hypoxic-ischemic brain injury (HIBI). Our previous research showed that autophagy is over-activated in a neonatal HIBI rat model, and inhibition of autophagy confers neuroprotection. There is increasing recognition that autophagy can be stimulated by activating endoplasmic reticulum (ER) stress. Herein, we purposed to explore: i) the association of ER stress with autophagy in the setting of neonatal HIBI; and ii) the possible roles of ER stress-triggered autophagy, as well as IRE1 signaling in the neuroprotection of sevoflurane post-conditioning against neonatal HIBI. Seven-day-old rats underwent ligation of the left common artery, and a subsequent 2 h hypoxia (8% O2/92% N2). The association of ER stress with autophagy was examined by ER stress inducer (tunicamycin), 4-PBA (ER stress inhibitor), or 3-MA (autophagy inhibitor). Rats in the sevoflurane post-conditioning groups were treated with 2.4% sevoflurane for 30 min after HIBI stimulation. The roles of ER stress-mediated autophagy, as well as the IRE1-JNK-beclin1 signaling cascade in the neuroprotection afforded by sevoflurane were explored by ER stress inducer (tunicamycin) and the IRE1 inhibitor (STF-083010). HIBI over-activated ER stress and autophagy in neonatal rats. HIBI-induced autophagy was significantly aggravated by tunicamycin but blocked by 4-PBA; however, HIBI-induced ER stress was not affected by 3-MA. Sevoflurane post-conditioning significantly alleviated ER stress, autophagy, cell apoptosis, and cognitive impairments, which were remarkably abolished by tunicamycin. Also, tunicamycin blocked sevoflurane-induced downregulation of IRE1-JNK-beclin1 signaling pathway. Whereas, IRE1 inhibitor could reverse the effects of tunicamycin. ER stress contributes to autophagy induced by HIBI. Furthermore, sevoflurane post-conditioning significantly protects against HIBI in neonatal rats by inhibiting ER stress-mediated autophagy via IRE1-JNK-beclin1 signaling cascade.

Update on mechanisms of the pathophysiology of neonatal encephalopathy

Therapeutic hypothermia is now well established to significantly improve survival without disability after neonatal encephalopathy (NE). To further improve outcomes, we need to better understand the mechanisms of brain injury. The central finding, which offers the potential for neuroprotective and neurorestorative interventions, is that brain damage after perinatal hypoxia-ischemia evolves slowly over time. Although brain cells may die during profound hypoxia-ischemia, even after surprisingly severe insults many cells show transient recovery of oxidative metabolism during a "latent" phase characterized by actively suppressed neural metabolism and activity. Critically, after moderate to severe hypoxia-ischemia, this transient recovery is followed after ~6 h by a phase of secondary deterioration, with delayed seizures, failure of mitochondrial function, cytotoxic edema, and cell death over ~72 h. This is followed by a tertiary phase of remodeling and recovery. This review discusses the mechanisms of injury that occur during the primary, latent, secondary and tertiary phases of injury and potential treatments that target one or more of these phases. By analogy with therapeutic hypothermia, treatment as early as possible in the latent phase is likely to have the greatest potential to prevent injury ("neuroprotection"). In the secondary phase of injury, anticonvulsants can attenuate seizures, but show limited neuroprotection. Encouragingly, there is now increasing preclinical evidence that late, neurorestorative interventions have potential to improve long-term outcomes.

LncRNA TCONS_00041002 improves neurological outcomes in neonatal rats with hypoxic-ischemic encephalopathy by inhibiting apoptosis and promoting neuron survival

It has been reported that Neonatal hypoxic-ischemic encephalopathy (HIE) could induce apoptosis in neonates and result in cognitive and sensory impairments, which are associated with poor developmental outcomes. Despite the improvement in neonatology, there is still no clinically effective treatment for HIE presently. Long non-coding RNAs (lncRNAs) play important roles in cellular homeostasis. Nevertheless, their effects in developing rat brains with HI is little known. Here, we established HIE model in neonate rats and explored the expression and function of lncRNAs in HI, and found the expression of 19 lncRNAs was remarkably changed in the brains of HI rats, compared to the sham group. Among them, three lncRNAs (TCONS_00041002, TCONS_00070547, TCONS_00045572) were enriched in the apoptotic process via gene ontology (GO) and pathway analysis, which were selected for the further qRT-PCR verification. Through lentivirus-mediated overexpression of these three lncRNAs, we found that overexpression of TCONS_00041002 attenuated the cell apoptosis, and increased the vitality of neurons after oxygen-glucose deprivation (OGD), therefore reduced the brain infarction and further promoted the neuron survival as well as improved the neurological disorders in the rats subjected to HIE. What's more, ceRNA network prediction and co-expression verification showed that the expression of TCONS_00041002 was positively associated with Foxe1, Pawr and Nfkbiz. Altogether, this study has exhibited that lncRNA TCONS_00041002 participates in the cell apoptosis and neuronal survival of HIE and represents a potential new target for the treatment of HIE.

H2S Attenuates Sleep Deprivation-Induced Cognitive Impairment by Reducing Excessive Autophagy via Hippocampal Sirt-1 in WISTAR RATS

Sleep deprivation (SD) is widespread in society causing serious damage to cognitive function. Hydrogen sulfide (H2S), the third gas signal molecule, plays important regulatory role in learning and memory functions. Inhibition of excessive autophagy and upregulation of silent information regulator 1 (Sirt-1) have been reported to prevent cognitive dysfunction. Therefore, this present work was to address whether H2S attenuates the cognitive impairment induced by SD in Wistar rats and whether the underlying mechanisms involve in inhibition of excessive autophagy and upregulation of Sirt-1. After treatment with SD for 72 h, the cognitive function of Wistar rats was evaluated by Y-maze, new object recognition, object location, and Morris water maze tests. The results shown that SD-caused cognitive impairment was reversed by treatment with NaHS (a donor of H2S). NaHS also prevented SD-induced hippocampal excessive autophagy, as evidenced by the decrease in autophagosomes, the down-regulation of Beclin1, and the up-regulation of p62 in the hippocampus of SD-exposed Wistar rats. Furthermore, Sirtinol, an inhibitor of Sirt-1, reversed the inhibitory roles of NaHS in SD-induced cognitive impairment and excessive hippocampal autophagy in Wistar rats. Taken together, our results suggested that H2S improves the cognitive function of SD-exposed rats by inhibiting excessive hippocampal autophagy in a hippocampal Sirt-1-dependent way.

Sevoflurane Postconditioning Ameliorates Neuronal Migration Disorder Through Reelin/Dab1 and Improves Long-term Cognition in Neonatal Rats After Hypoxic-Ischemic Injury

Sevoflurane postconditioning (SPC) has been widely reported to attenuate brain injury after hypoxia-ischemia encephalopathy (HIE) by inhibiting neural necrosis and autophagy. Moreover, recent reports revealed that sevoflurane facilitated hippocampal reconstruction via regulating migration. Yet, it remains unclear whether the promotion of neural migration by SPC repairs the hippocampal injury after HIE. Here, we hypothesize that SPC exerts a neuroprotective effect by ameliorating neuronal migration disorder after HIE and regulating Reelin expression. Furthermore, the downstream Reelin/Dab1 pathway may be involved. The classical Rice-Vannucci model of hypoxia-ischemia was performed on postnatal day 7 rat pups, which was followed by SPC at 1 minimum alveolar concentration (MAC 2.5%) for 30 min. Piceatannol, causing Reelin aggregation in vivo, was used to detect whether Reelin/Dab1 was involved in the neuroprotection effect of SPC. Hippocampal-dependent learning ability tests were conducted to assess the long-term effects on locomotor activity and spatial learning ability. Our findings suggest that hypoxia-ischemia injury inhibited neurons migrated outward from the basal zone of dentate gyrus, disrupted cytoarchitecture of the dentate gyrus (DG), and led to long-term cognition deficits. However, SPC could relieve the restricted hippocampal neurons and repair the hippocampal-dependent memory function damaged after HIE by attenuating the overactivation of the Reelin/Dab1 pathway. These results demonstrate that SPC plays a pivotal role in ameliorating neuronal migration disorder and maintaining normal cytoarchitecture of the DG via inhibiting overactivated Reelin expression. This process may involve overactivated Reelin/Dab1 signaling pathway and spatial learning ability by regulating the Reelin expression which may associate with its neuroprotection.

Lycopene prevents oxygen-glucose deprivation-induced autophagic death in SH-SY5Y cells via inhibition of the oxidative stress-activated AMPK/mTOR pathway

Lycopene has been reported to exert a protective effect on the brain against transient ischemia‑induced damage; however, whether it could regulate autophagic neuronal death remains elusive. The present study aimed to investigate the role of autophagy in the protective effects of lycopene against neuronal damage and its underlying mechanism. Oxygen‑glucose deprivation (OGD) was used to simulate neuronal ischemic injury in human SH‑SY5Y cells. Lactate dehydrogenase (LDH) release assay revealed that OGD induced SH‑SY5Y cell death. Western blotting demonstrated that OGD upregulated the expression levels of the autophagy marker proteins autophagy protein 5 (ATG5) and LC3II, but downregulated the autophagy substrate p62 in a time‑dependent manner. By contrast, OGD‑induced cell death was significantly inhibited by the autophagy inhibitors 3‑methyladenine or bafilomycin A1 or by knockdown of ATG5, indicating that OGD may induce autophagic death in SH‑SY5Y cells. Notably, lycopene was shown not only to prevent OGD‑induced SH‑SY5Y cell death, but was also able to effectively inhibit OGD‑induced upregulation of ATG5 and LC3II, and downregulation of p62 in a dose‑dependent manner. Mechanistically, it was suggested that lycopene inhibited OGD‑induced activation of the AMPK/mTOR pathway via attenuation of oxidative stress by maintaining the intracellular antioxidant glutathione (GSH). Furthermore, the inhibitory role of lycopene in GSH depletion was found to be associated with the prevention of OGD‑induced depletion of intracellular cysteine and downregulation of xCT. Collectively, the present study demonstrated that lycopene protected SH‑SY5Y cells against OGD‑induced autophagic death by inhibiting oxidative stress‑dependent activation of the AMPK/mTOR pathway.

Post-Treatment Sevoflurane Protects Against Hypoxic-Ischemic Brain Injury in Neonatal Rats by Downregulating Histone Methyltransferase G9a and Upregulating Nuclear Factor Erythroid 2-Related Factor 2 (NRF2)

BACKGROUND Perinatal hypoxia and subsequent reduction of cerebral blood flow leads to neonatal hypoxic-ischemic brain injury (HIBI), resulting in severe disability and even death. Preconditioning or post-conditioning with sevoflurane protects against cerebral injury. This study investigated the mechanism of sevoflurane in HIBI. MATERIAL AND METHODS The HIBI model of neonatal rats was established and the model rats were post-treated with sevoflurane. The oxygen-glucose deprivation (OGD) cell model was established, and the OGD cells were transfected with NRF2-siRNA plasmid and post-treated with sevoflurane. The Morris water maze test was used to detect the motor activity, spatial learning, and memory ability of HIBI rats. Histological stainings were performed to observe the area of cerebral infarction, record the number of neurons in the hippocampus, and assess neuron apoptosis. The levels of inflammatory factors were detected by ELISA. The protein levels of histone methyltransferase G9a and histone H3 lysine 9 (H3K9me2) were detected by western blot assay. The apoptosis was detected by flow cytometry. RESULTS Sevoflurane post-treatment significantly shortened the escape latency of HIBI neonatal rats, increased the density of neurons, reduced the area of cerebral infarction, and decreased the levels of inflammatory factors and neuronal apoptosis. Sevoflurane post-treatment decreased G9a and H3K9me2 levels, and G9a level was negatively correlated with NRF2 level. NRF2 silencing reversed the alleviation of sevoflurane post-treatment on OGD-induced cell injury. CONCLUSIONS Sevoflurane post-treatment promotes NRF2 expression by inhibiting G9a and H3K9me2, thus alleviating HIBI in neonatal rats.

The Role of Autophagy in Hypoxia-Induced Neuroinflammation

Autophagy is a critical cytoprotective mechanism that takes a hand in innate or adaptive immune responses. Hypoxia is a common pathophysiological mechanism that can lead to systemic pathological reactions. In recent years, the impact of hypoxia on the central nervous system has attracted more attention. In the past, autophagy was thought to be directly involved in the apoptosis of nerve cells under hypoxia. An increasing amount of evidence shows that the neuroinflammatory response plays an indispensable role in the neural damage caused by hypoxia. There are many mechanisms related to the neuroinflammatory response induced by hypoxia, among which autophagy is an important aspect, but the role of autophagy is still unclear. This article focuses on how autophagy flux of central immune cells is modified under hypoxic conditions, and how this autophagy affects neuroinflammatory response.

Reduction of Autophagosome Overload Attenuates Neuronal Cell Death After Traumatic Brain Injury

Previous studies have shown that alterations in autophagy-related proteins exist extensively after traumatic brain injury (TBI). However, whether autophagy is enhanced or suppressed by TBI remains controversial. In our study, a controlled cortical impact was used to establish a model of moderate TBI in rats. We found that a significant increase in protein levels of LC3-II and SQSTM1 in the injured cortex group. However, there were no significant differences in protein levels of VPS34, Beclin-1, and phosphor-ULK1, which are the promoters of autophagy. Lysosome dysfunction after TBI might lead to autophagosome accumulation. In addition, the highly specific autophagy inhibitor SAR405 administration reduced TBI-induced apoptosis-related protein cleaved caspase-3 and cleaved caspase-9 levels in the ipsilateral cortex, as well as brain edema and neurological defects accessed by mNSS. Furthermore, chloroquine treatment reversed the beneficial effects of SAR405 by increasing the accumulation of autophagosomes. Finally, our data showed that autophagy inhibition by VPS34 gene knockout method attenuated cell death after TBI. Our findings indicate that impaired autophagosome degradation is involved in the pathological reaction after TBI, and the inhibition of autophagy contributes to attenuate neuronal cell death and functional defects.

Dexmedetomidine post-conditioning ameliorates long-term neurological outcomes after neonatal hypoxic ischemia: The role of autophagy

BACKGROUND

Hypoxic-ischemic brain injury (HIBI) is a major cause of mortality in neonates and can cause long-term neurological sequelae. Excessive autophagy caused by HI may cause neuronal death. Dexmedetomidine was reported neuroprotective against HIBI. Therefore, in the present study, the autophagy-related mechanisms underlying the protective effects of dexmedetomidine against cerebral HI in neonatal rats were investigated.

METHODS

In the present study, the expression of autophagy-related proteins microtubule-associated protein 1 light chain 3 (LC3) B-II and Beclin1, neuronal and microglia autophagy levels, the myelin basic protein (MBP) expression, long-term neuronal density ratio, and long-term behavioral prognosis in HIBI model were investigated by ligating the left common carotid artery in neonatal rats, followed by 2-h hypoxia.

RESULTS

Dexmedetomidine inhibited the overactivated autophagy of hippocampal neurons and microglia after HI. In addition, dexmedetomidine inhibited neuronal density decrease and axon demyelination after HI-induced overactivated autophagy. Lastly, dexmedetomidine improved the long-term neurological prognosis and was reversed by the autophagy agonist rapamycin.

CONCLUSION

The protective effects of dexmedetomidine on HI neonatal rats were evidenced by inhibition of excessive autophagy of neurons and microglia, thereby reducing the decline of long-term neuronal density and axon demyelination as well as improving long-term learning cognitive function.

(2R,6R)-Hydroxynorketamine Alleviates Electroconvulsive Shock-Induced Learning Impairment by Inhibiting Autophagy

PURPOSE

Learning impairment after electroconvulsive therapy (ECT) is common. Ketamine, an anesthetic used for ECT, has been demonstrated to attenuate cognitive impairment after ECT. However, the mechanism by which ketamine occurs in this case is still unknown. We aimed to explore the role of ketamine metabolite (2R,6R)-hydroxynorketamine [(2R,6R)-HNK] in the protection against learning impairment and investigate whether autophagy is involved in the protective effect.

MATERIALS AND METHODS

A rat depression model received electroconvulsive shock (ECS; simulated ECT in animal models) daily for 3 days. The Morris water maze was used to assess the spatial learning function of the rats. Western blotting was used to detect the expression of Beclin-1, light chain (LC)3-II/LC3-I, p62, mammalian target of rapamycin (mTOR), and p-mTOR in the hippocampus.

RESULTS

The escape latency for the maze in the ECS group was significantly longer than that in the sham ECS group (P=0.042). Meanwhile, the escape latency in the (2R,6R)-HNK+ECS group was significantly shorter than that in the ECS group (P=0.005). The LC3-II/LC3-I ratio and Beclin-1 expression level significantly increased, and the p62 expression level significantly decreased in the ECS group, compared with those in the sham ECS group (all P<0.001). The (2R,6R)-HNK+ECS group showed lower LC3-II/LC3-I ratio (P<0.001) and Beclin-1 expression level (P<0.001) and higher p62 (P<0.001) and p-mTOR expression levels (P=0.048) than did the ECS group. After small-molecule enhancer of rapamycin 28 (SMER28) administration, the role of (2R,6R)-HNK in protecting against learning impairment and inhibiting autophagy was abrogated, showing no difference in the escape latency; the difference in the LC3-II/LC3-I ratio and p62 expression level between the SMER28+(2R,6R)-HNK+ECS and ECS groups was not as significant as that between the (2R,6R)-HNK+ECS and ECS groups (P<0.05-0.01 vs P<0.001).

CONCLUSION

(2R,6R)-HNK yields cognitive protection by suppressing autophagy through the mTOR signaling pathway in the ECS-treated rat hippocampus.

Inhibition of NOD1 Attenuates Neonatal Hypoxia-Ischemia Induced Long-Term Cognitive Impairments in Mice Through Modulation of Autophagy-Related Proteins

BACKGROUND

Autophagy is implicated in neonatal hypoxia-ischemia (HI) induced cognitive impairment. The nucleotide-oligomerizing domain-1 (NOD1), a protein involved in inflammatory responses, has been shown to activate autophagy to promote progression of other diseases. We aimed to investigate whether and how NOD1 is involved in HI-induced brain injury using an HI mouse model.

METHODS

We induced HI in neonatal mice and examined levels of NOD1 and genes associated with autophagy. We then inhibited NOD1 by intracerebroventricular injection of si-NOD1 following HI induction and tested the effects on autophagy, inflammatory responses and long-term behavioral outcomes through Morris water maze and open field tests.

RESULTS

We found that HI induction significantly elevated mRNA levels of NOD1 (3.54 folds change) and autophagy-related genes including Atg5 (3.89 folds change) and Beclin-1 (3.34 folds change). NOD1 inhibition following HI induction suppressed autophagy signaling as well as HI induced proinflammatory cytokine production. Importantly, NOD1 inhibition after HI improved long-term cognitive function, without impacting exploratory and locomotor activities.

CONCLUSION

We show here that NOD1 is involved in the pathogenesis of HI-induced brain injury through modulation of autophagy-related proteins and inflammatory responses. Our findings suggest that NOD1 may be a potent target for developing therapeutic strategies for treating HI-induced brain injury.

Galuteolin Inhibited Autophagy for Neuroprotection Against Transient Focal Cerebral Ischemia in Rats

Galuteolin, a Chinese herbal medicine, purified from Lonicera Japonica. In this study, we aimed to investigate the neuroprotective effect of galuteolin against cerebral ischemia/reperfusion (I/R) injury. We administered galuteolin or galuteolin and rapamycin to rats which had middle cerebral artery occlusion/reperfusion (MCAO/R). A series of characterizations were carried out to monitor the outcomes of galuteolin in I/R rats regarding the infarct volumes, neurological deficits, and brain water, as well as its effect on neuroprotection and autophagy. It was found that galuteolin significantly reduced the infarct volume, brain water content, and the neurological deficits in a dose-dependent manner. Neuron damages were decreased in the hippocampal carotid artery 1 pyramidal layer by galuteolin. The expression levels of neuron-specific enolase (NSE) increased after galuteolin treatment. Galuteolin significantly decreased the expression levels of autophagy-related proteins. In addition, galuteolin decreased rapamycin-related neuron damages and activations of autophagy in I/R rats. Our data suggested that galuteolin can inhibit ischemic brain injuries through the regulation of autophagy-related indicators in I/R.

Sevoflurane Post-Conditioning Ameliorates Neuronal Deficits and Axon Demyelination After Neonatal Hypoxic Ischemic Brain Injury: Role of Microglia/Macrophage

Microglia/macrophages have been identified to be highly polarized after ischemia. Interestingly, the polarization of these microglia/macrophages varies immensely under differing disease conditions. Post-conditioning using sevoflurane, a volatile anesthetic, could provide long-term neuroprotection to neonatal rats after hypoxic-ischemic brain injury (HIBI). Thus, the current study aimed at investigating the effects of sevoflurane post-conditioning (SPC) on microglia/macrophage polarization after HIBI induction in neonatal rats. Additionally, we aimed at identifying the underpinning mechanisms specifically related to autophagy and lysosomal protease enzyme, cathepsin B. To develop a HIBI model, 7-day-old Sprague-Dawley rats underwent left common carotid artery ligation followed by 2 h of hypoxia. The role of microglia/macrophages in the neuroprotection conferred by SPC was examined by left-side intra-cerebroventricular injection with adenovirus vector carrying catB-GFP or rapamycin. The number of interleukin (IL)-1β⁺ cells, cathepsin B⁺ cells, light chain 3B positive (LC3B⁺) cells among ionized calcium binding adaptor molecule 1(Iba1⁺)cells to investigate microglia polarization, neuronal apoptosis to assess neuronal death in the acute phase were tested at 24 h after HIBI. Behavioral tests including suspension test, Morris water maze tests were performed to investigate the long-term effects of SPC, at 21 to 34 days post HIBI. Nissl staining and myelin basic protein (MBP) immunostaining to assess the long-term neuronal and myelin damage were performed at 34 days after HIBI. Based on the obtained results post HIBI, we observed the cells that were positive for IL-1β, cathepsin B, and LC3B among Iba1 positive cell population in the hippocampus were significantly decreased after SPC treatment. SPC significantly attenuated the HIBI-induced increase in neuronal apoptosis, improved long-term cognitive function, and attenuated HI-induced decrease of Nissl-positive cells and MBP expression. However, these trends were reversed by injection of adenovirus vector carrying catB-GFP and rapamycin. SPC attenuated microglia polarization towards neurotoxic phenotypes, alleviates neuronal death and axon demyelination after HIBI in neonatal rats by regulating microglia autophagy and cathepsin B expression, and therefore provided long-term cognitive, learning and memory protection.

Silencing of long non-coding RNA CRNDE promotes autophagy and alleviates neonatal hypoxic-ischemic brain damage in rats

Hypoxic-ischemic (HI) brain damage (HIBD) leads to high neonatal mortality and severe neurologic morbidity. Autophagy is involved in the pathogenesis of HIBD. This study aims to investigate the effect of long non-coding RNA colorectal neoplasia differentially expressed (CRNDE) on HIBD and to validate whether autophagy is involved in this process. A HIBD model in rat pups and a HI model in rat primary cerebrocortical neurons were established. Autophagy was evaluated by western blot. The HIBD in rats was evaluated by hematoxylin and eosin staining, TUNEL staining, triphenyl tetrazolium chloride staining, and morris water maze test. The HI injury in vitro was evaluated by determining cell viability and apoptosis. The results showed that CRNDE expression was time-dependently increased in the brain after HIBD. Administration with CRNDE shRNA-expressing lentiviruses alleviated pathological injury and apoptosis in rat hippocampus, decreased infarct volume, and improved behavior performance of rats subjected to HIBD. Furthermore, CRNDE silencing promoted cell viability and inhibited cell apoptosis in neurons exposed to HI. Moreover, CRNDE silencing promoted autophagy and the autophagy inhibitor 3-methyladenine counteracted the neuroprotective effect of CRNDE silencing on HI-induced neuronal injury both in vivo and in vitro. Collectively, CRNDE silencing alleviates HIBD, at least partially, through promoting autophagy.

Melatonin activates autophagy via the NF-κB signaling pathway to prevent extracellular matrix degeneration in intervertebral disc

OBJECTIVE

This study investigated whether melatonin alleviates intervertebral disc degeneration (IVDD) by promoting autophagy through inhibiting the NF-κB signaling pathway.

METHODS

Magnetic resonance imaging (MRI), hematoxylin and eosin (H&E) staining and Safranin-O staining were used to measure disc degeneration in rat needle puncture IVDD models, and melatonin was injected intraperitoneally in the treated group to test its function. The expression of autophagy and extracellular matrix (ECM) degeneration related-markers were measured in the discs using immunohistochemistry. Transmission electron microscopy was used to evaluate the activation of autophagy in human nucleus pulposus (NP) tissues with different degenerated statuses. The expression of autophagy and disc degeneration related-markers were detected in NP cells by Western blot, RT-qPCR, and immunofluorescence analyses. NF-κB signaling pathway involvement was studied by lentivirus-mediated knockdown, Western blotting, and immunohistochemistry and immunofluorescence staining.

RESULTS

Melatonin prevented IVDD development in vivo and in vitro. Compared to non-degenerated disc tissues, degenerated human NP tissues showed a decrease in the autophagy-specific marker LC3B and the numbers of autophagosomes and autolysosomes, whereas the p62 level was increased; similar results were observed in rat IVDD models, indicating a negative correlation between autophagy and IVDD. Furthermore, both in vivo and in vitro studies found that melatonin application induced autophagy and reduced ECM disc degradation. Melatonin was also shown to regulate autophagy by inhibiting the NF-κB signaling pathway in vivo and vitro.

CONCLUSION

This study indicates that melatonin prevents IVDD by promoting autophagy, indicating its possible therapeutic potential for controlling the progression of IVDD.

Oligodendrocyte Response to Pathophysiological Conditions Triggered by Episode of Perinatal Hypoxia-Ischemia: Role of IGF-1 Secretion by Glial Cells

Differentiation of oligodendrocyte progenitors towards myelinating cells is influenced by a plethora of exogenous instructive signals. Insulin-like growth factor 1 (IGF-1) is one of the major factors regulating cell survival, proliferation, and maturation. Recently, there is an ever growing recognition concerning the role of autocrine/paracrine IGF-1 signaling in brain development and metabolism. Since oligodendrocyte functioning is altered after the neonatal hypoxic-ischemic (HI) insult, a question arises if the injury exerts any influence on the IGF-1 secreted by neural cells and how possibly the change in IGF-1 concentration affects oligodendrocyte growth. To quantify the secretory activity of neonatal glial cells, the step-wise approach by sequentially using the in vivo, ex vivo, and in vitro models of perinatal asphyxia was applied. A comparison of the results of in vivo and ex vivo studies allowed evaluating the role of autocrine/paracrine IGF-1 signaling. Accordingly, astroglia were indicated to be the main local source of IGF-1 in the developing brain, and the factor secretion was shown to be significantly upregulated during the first 24 h after the hypoxic-ischemic insult. And conversely, the IGF-1 amounts released by oligodendrocytes and microglia significantly decreased. A morphometric examination of oligodendrocyte differentiation by means of the Sholl analysis showed that the treatment with low IGF-1 doses markedly improved the branching of oligodendroglial cell processes and, in this way, promoted their differentiation. The changes in the IGF-1 amounts in the nervous tissue after HI might contribute to the resulting white matter disorders, observed in newborn children who experienced perinatal asphyxia. Pharmacological modulation of IGF-1 secretion by neural cells could be reasonable solution in studies aimed at searching for therapies alleviating the consequences of perinatal asphyxia.

Pathophysiology of hypoxic-ischemic encephalopathy: a review of the past and a view on the future

Hypoxic-ischemic encephalopathy, also referred as HIE, is a type of brain injury or damage that is caused by a lack of oxygen to the brain during neonatal period. The incidence is approximately 1.5 cases per 1000 live births in developed countries. In low and middle-income countries, the incidence is much higher (10‒20 per 1000 live births). The treatment for neonatal HIE is hypothermia that is only partially effective (not more than 50% of the neonates treated achieve an improved outcome). HIE pathophysiology involves oxidative stress, mitochondrial energy production failure, glutaminergic excitotoxicity, and apoptosis. So, in the last years, many studies have focused on peptides that act somewhere in the pathway activated by severe anoxic injury leading to HIE. This review describes the pathophysiology of perinatal HIE and the mechanisms that could be the target of innovative HIE treatments.

Mitochondrial Degeneration and Autophagy Associated With Delayed Effects of Radiation in the Mouse Brain

Mitochondria are linked with various radiation responses, including mitophagy, genomic instability, apoptosis, and the bystander effect. Mitochondria play an important role in preserving cellular homeostasis during stress responses, and dysfunction in mitochondrial contributes to aging, carcinogenesis and neurologic diseases. In this study, we have investigated the mitochondrial degeneration and autophagy in the hippocampal region of brains from mice administered with BBT-059, a long-acting interleukin-11 analog, or its formulation buffer 24 h prior to irradiation at different radiation doses collected at 6 and 12 months post-irradiation. The results demonstrated a higher number of degenerating mitochondria in 12 Gy BBT-059 treated mice after 6 months and 11.5 Gy BBT-059 treated mice after 12 months as compared to the age-matched naïve (non-irradiated control animals). Apg5l, Lc3b and Sqstm1 markers were used to analyze the autophagy in the brain, however only the Sqstm1 marker exhibited significantly reduced expression after 12 months in 11.5 Gy BBT-059 treated mice as compared to naïve. Immunohistochemistry (IHC) results of Bcl2 also demonstrated a decrease in expression after 12 months in 11.5 Gy BBT-059 treated mice as compared to other groups. In conclusion, our results demonstrated that higher doses of ionizing radiation (IR) can cause persistent upregulation of mitochondrial degeneration. Reduced levels of Sqstm1 and Bcl2 can lead to intensive autophagy which can lead to degradation of cellular structure.

Dexmedetomidine Promotes Hippocampal Neurogenesis and Improves Spatial Learning and Memory in Neonatal Rats

Background

Dexmedetomidine (Dex) is a highly selective α2-adrenoceptor agonist used as an off-label medication for pediatric sedation and analgesia. Recently, Dex was reported to exhibit neuroprotective efficacy in several brain injury models. Here we investigate whether neonatal Dex administration promotes hippocampal neurogenesis and enhances hippocampus-dependent spatial learning and memory under physiological conditions.

Methods

Postnatal day 7 (P7) pups were administered saline (vehicle control) or Dex (10, 20, or 40 µg/kg) by intraperitoneal injection. Neurogenesis and astrogenesis were examined in brain slices by BrdU immunostaining on P8 and changes in the expression levels of GDNF, NCAM, CREB, PSD95, and GAP43 were assessed by Western blotting on P35, respectively. Open field and Morris water maze (MWM) tests were conducted from P28 to P36 in order to assess effects on general motor activity and spatial learning, respectively.

Results

Dexmedetomidine at 20 µg/kg significantly enhanced neurogenesis and astrogenesis in hippocampus and upregulated GDNF, NCAM, CREB, PSD95, and GAP43 compared to vehicle and other Dex doses. Moreover, 20 µg/kg Dex-injected rats showed no changes in motor or anxiety-like behavior but performed better in the MWM test compared to all other groups.

Conclusion

Neonatal injection of Dex (20 µg/kg) enhances spatial learning and memory in rat pups, potentially by promoting hippocampal neurogenesis and synaptic plasticity via activation of GDNF/NCAM/CREB signaling.

Activation of G-Protein-Coupled Receptor 30 Protects Neurons against Excitotoxicity through Inhibiting Excessive Autophagy Induced by Glutamate

Autophagy is a protecting intracellular pathway to transmit unnecessary or dysfunctional components to the lysosome for degeneration. Autophagic imbalance is connected with neurodegeneration. Neurodegenerative diseases including Parkinson's disease, Alzheimer's disease, and Huntington's disease are closely related to excitotoxicity and neuronal loss. Activation of G-protein-coupled receptor 30 (GPR30), an estrogen membrane receptor, protects neurons from excitotoxicity-induced cell death. However, whether autophagy is involved in the neuroprotective effect of GPR30 activation is not well-known. In this study, methyl thiazolyl tetrazolium (MTT), Western blot, monodansylcadaverine (MDC) staining, and immunofluorescent staining were employed to detect the role of autophagy in cultured primary cortical neurons after glutamate exposure and G1 treatment. Pretreatment of G1 (GPR30 specific agonist) reduced neuronal loss through inhibiting excessive autophagy induced by glutamate exposure, which was blocked by GPR30 antagonist G15, phosphatidylinositol-3-kinase (PI3K), and the mammalian target of rapamycin (mTOR) inhibitors. These data suggest that GPR30 protects neurons from cell loss primarily by modulating PI3K-AKT-mTOR signaling pathway. In addition, G1 alone did not affect the basal autophagy and cell viability. We conclude that GPR30 activation reduces glutamate-induced excessive autophagy in neurons and protects neurons against excitotoxicity.

Oridonin prevents insulin resistance-mediated cognitive disorder through PTEN/Akt pathway and autophagy in minimal hepatic encephalopathy

Minimal hepatic encephalopathy (MHE) was characterized for cognitive dysfunction. Insulin resistance (IR) has been identified to be correlated with the pathogenesis of MHE. Oridonin (Ori) is an active terpenoid, which has been reported to rescue synaptic loss and restore insulin sensitivity. In this study, we found that intraperitoneal injection of Ori rescued IR, reduced the autophagosome formation and synaptic loss and improved cognitive dysfunction in MHE rats. Moreover, in insulin‐resistant PC12 cells and N2a cells, we found that Ori blocked IR‐induced synaptic deficits via the down‐regulation of PTEN, the phosphorylation of Akt and the inhibition of autophagy. Taken together, these results suggested that Ori displays therapeutic efficacy towards memory deficits via improvement of IR in MHE and represents a novel bioactive therapeutic agent for treating MHE.

Mild hypothermia improves neurological outcome in mice after cardiopulmonary resuscitation through Silent Information Regulator 1-actviated autophagy

Mild hypothermia treatment (MHT) improves the neurological function of cardiac arrest (CA) patients, but the exact mechanisms of recovery remain unclear. Herein, we generated a CA and cardiopulmonary resuscitation (CPR) mouse model to elucidate such function. Naïve mice were randomly divided into two groups, a normothemia (NT) group, in which animals had normal body temperature, and a MHT group, in which animals had a body temperature of 33 °C (range: 32–34 °C), after the return of spontaneous circulation (ROSC), followed by CA/CPR. MHT significantly improved the survival rate of CA/CPR mice compared with NT. Mechanistically, MHT increased the expression of Silent Information Regulator 1 (Sirt1) and decreased P53 phosphorylation (p-P53) in the cortex of CA/CPR mice, which coincided with the elevated autophagic flux. However, Sirt1 deletion compromised the neuroprotection offered by MHT, indicating that Sirt1 plays an important role. Consistent with the observations obtained from in vivo work, our in vitro study utilizing cultured neurons subjected to oxygen/glucose deprivation and reperfusion (OGD/R) also indicated that Sirt1 knockdown increased OGD/R-induced neuron necrosis and apoptosis, which was accompanied by decreased autophagic flux and increased p-P53. However, the depletion of P53 did not suppress neuron death, suggesting that P53 was not critically involved in MHT-induced neuroprotection. In contrast, the application of autophagic inhibitor 3-methyladenine attenuated MHT-improved neuron survival after OGD/R, further demonstrating that increased autophagic flux significantly contributes to MHT-linked neuroprotection of CA/CRP mice. Our findings indicate that MHT improves neurological outcome of mice after CA/CPR through Sirt1-mediated activation of autophagic flux.

Upregulation of aryl hydrocarbon receptor nuclear translocator 2 in the hippocampi of post-stroke depression rats

Aryl hydrocarbon receptor nuclear translocator protein 2 (ARNT2), a member of the basic helix-loop-helix superfamily of transcription factors, may serve a vital role in neuronal survival and cell proliferation via formation of heterodimers with hypoxia-inducible factor-1α. Previous studies indicated that ARNT2 levels were elevated in the brains of ischemic rats; however, the involvement of ARNT2 in post-stroke depression (PSD) rats is not well understood. Therefore, the present study aimed to investigate the levels of ARNT2 in the hippocampi of PSD rats, and to clarify the potential association between ARNT2 and behavioral performance. A PSD rat model was established by middle cerebral artery occlusion (MCAO) followed by a 4-week chronic unpredictable mild stress (CUMS) regimen. A sucrose preference test and open field test (OFT) were conducted, and body weight was measured. In addition, reverse transcription-polymerase chain reaction and immunohistochemistry were performed to measure ARNT expression. Results indicated that MCAO+CUMS rats had lower weight gain, consumed less sucrose and moved less compared with controls. Furthermore, the mRNA and protein levels of ARNT in MCAO+CUMS rats were increased compared with in controls. The sucrose preference index and horizontal movement distance in the OFT were positively correlated with ARNT mRNA level. Thus, from these findings it was suggested that ARNT2 may be positively associated with improvement of cognitive impairment, and therefore may be a potential target in PSD treatment.

5-Aza-2'-deoxycytidine increases hypoxia tolerance-dependent autophagy in mouse neuronal cells by initiating the TSC1/mTOR pathway

BACKGROUND

Our previous study found that 5-Aza-2'-deoxycytidine (5-Aza-CdR) can repress the expression and activity of protein serine/threonine phosphatase-1γ (PP1γ) in mouse hippocampus. It is well known that PP1γ regulates cell metabolism, which is related to hypoxia/ischaemia tolerance. It has been reported that it can also induce autophagy in cancer cells. Autophagy is important for maintaining cellular homeostasis associated with metabolism. In this study, we examined whether 5-Aza-CdR increases hypoxia tolerance-dependent autophagy by initiating the TSC1/mTOR/autophagy signalling pathway in neuronal cells.

METHODS

5-Aza-CdR was either administered to mice via intracerebroventricular injection (i.c.v) or added to cultured hippocampal-derived neuronal cell line (HT22 cell) in the medium for cell culture. The hypoxia tolerance of mice was measured by hypoxia tolerance time and Perl's iron stain. The mRNA and protein expression levels of tuberous sclerosis complex 1 (TSC1), mammalian target of rapamycin (mTOR) and autophagy marker light chain 3 (LC3) were measured by real-time PCR and western blot. The p-mTOR and p-p70S6k proteins were used as markers for mTOR activity. In addition, the role of autophagy was determined by correlating its intensity with hypoxia tolerance in a time-dependent manner. At the same time, the involvement of the TSC1/mTOR pathway in autophagy was also examined through transfection with TSC1 (hamartin) plasmid.

RESULTS

5-Aza-CdR was revealed to increase hypoxia tolerance and induce autophagy, accompanied by an increase in mRNA and protein expression levels of TSC1, reduction in p-mTOR (Ser2448) and p-p70S6k (Thr389) protein levels, and an increase in the ratio of LC3-II/LC3-I in both mouse hippocampus and hippocampal-derived neuronal cell line (HT22). The fluorescence intensity of hamartin was enhanced in the hippocampus of mice exposed to 5-Aza-CdR. Moreover, HT22 cells that over-expressed TSC1 showed more autophagy.

CONCLUSIONS

5-Aza-CdR can increase hypoxia tolerance by inducing autophagy by initiating the TSC1/mTOR pathway.

Sevoflurane post-conditioning alleviates neonatal rat hypoxic-ischemic cerebral injury via Ezh2-regulated autophagy

Background: When neonatal rats suffer hypoxic-ischemic brain injury (HIBI), autophagy is over-activated in the hippocampus, and inhibition of autophagy provides neuroprotection. The aim of this study was to investigate the possible roles of autophagy and Ezh2-regulated Pten/Akt/mTOR pathway in sevoflurane post-conditioning (SPC)-mediated neuroprotection against HIBI in neonatal rats.

Methods: Seven-day-old Sprague–Dawley rats underwent left common artery ligation followed by 2 h hypoxia as described in the Rice–Vannucci model. The roles of autophagy and the Ezh2-regulated Pten/Akt/mTOR signaling pathway in the neuroprotection conferred by SPC were examined by left-side intracerebroventricular injection with the autophagy activator rapamycin and the Ezh2 inhibitor GSK126.

Results: SPC was neuroprotective against HIBI through the inhibition of over-activated autophagy in the hippocampus as characterized by the rapamycin-induced reversal of neuronal density, neuronal morphology, cerebral morphology, and the expression of the autophagy markers, LC3B-II and Beclin1. SPC significantly increased the expression of Ezh2, H3K27me3, pAkt, and mTOR and decreased the expression of Pten induced by HI. The Ezh2 inhibitor, GSK126, significantly reversed the SPC-induced changes in expression of H3K27me3, Pten, pAkt, mTOR, LC3B-II, and Beclin1. Ezh2 inhibition also reversed SPC-mediated attenuation of neuronal loss and behavioral improvement in the Morris water maze.

Conclusion: These results indicate that SPC inhibits excessive autophagy via the regulation of Pten/Akt/mTOR signaling by Ezh2 to confer neuroprotection against HIBI in neonatal rats.

Phosphorylated mTORC1 represses autophagic-related mRNA translation in neurons exposed to ischemia-reperfusion injury

OBJECTIVES

The sequential reactivation of mechanistic target of rapamycin (mTOR) inhibited autophagic flux in neurons exposed to oxygen-glucose deprivation/reperfusion (OGD/R), which was characterized by reduction of autophagosome formation and restriction of autolysosome degradation. However, its detailed molecular mechanism was still unknown. In this study, we further explore the existing form of mTOR and its suppression on the transcriptional levels of related mRNA from neurons exposed to ischemia-reperfusion injury.

METHODS

The OGD/R or middle cerebral artery occlusion/reperfusion (MCAO/R)-treated neurons was used to simulate ischemia/reperfusion injury . Autophagy flux was monitored by means of microtubule-associated protein 1 light chain 3 (LC3) and p62. The reactivation of mTOR was determined by phosphorylation of ribosomal protein S6 kinase 1 (S6K1). Then the inhibitors of mTOR were used to confirm its existence form. Finally, the mRNA transcription levels were analyzed to observe the negative regulation of mTOR.

RESULTS

The sequential phosphorylation of mTOR contributed to the neuronal autophagy flux blocking. mTOR was re-phosphorylated and existed as mTOR complex 1 (mTORC1), which was supported by phosphorylation of S6K1 at Thr 389 in neurons. In addition, the phosphorylation of S6K1 was decreased roughly by applying mTORC1 inhibitors, rapamycin and torin 1. However, the administration of mTORC1/2 inhibitor PP242 could recover the phosphorylation of S6K1, which suggested that mTORC2 was involved in the regulation of mTORC1 activity. In paralleling with reactivation of mTORC1, related mRNA transcription was repressed in neurons under ischemia-reperfusion exposure in vivo and in vitro. The mRNA expression levels of LC3, Stx17, Vamp8, Snap29, Lamp2a, and Lamp2b were decreased in neurons after reperfusion, comparing with ischemia-treated neurons.

CONCLUSIONS

The reactivated mTORC1 could suppress the transcription levels of related mRNA, such as LC3, Stx17, Vamp8, Snap29, Lamp2a, and Lamp2b. The research will expand the horizons that mTOR would negatively regulate autophagy at transcription and post-translation levels in neurons suffering ischemia-reperfusion injury.

Retracted: microRNA-129-5p involved in the neuroprotective effect of dexmedetomidine on hypoxic-ischemic brain injury by targeting COL3A1 through the Wnt/β-catenin signaling pathway in neonatal rats

Our study aims to elucidate the mechanisms how microRNA-129-5p (miR-129-5p) involved in the neuroprotective effect of dexmedetomidine (DEX) on hypoxic-ischemic brain injury (HIBI) by targeting the type III procollagen gene (COL3A1) through the Wnt/β-catenin signaling pathway in neonatal rats. A total of 120 rats were obtained, among which 15 rats were selected as sham group and rest rats as model, DEX, DEX + negative control (DEX + NC), DEX + miR-129-5p mimics, DEX + miR-129-5p inhibitors, DEX + XAV-939, and DEX + miR-129-5p inhibitors + XAV-939 groups. A dual-luciferase reporter assay was performed for the target relationship between miR-129-5p and COL3A1. Weight rate and water content of cerebral hemisphere were detected. Quantitative real-time polymerase chain reaction and Western blot analysis were conducted to detect miR-129-5p expression and expressions of COL3A1, E-cadherin, T-cell factor (TCF)- 4, and β-catenin. The DEX, DEX + miR-129-5p mimics, DEX + XAV-939 groups had increased weight rate of the cerebral hemisphere, but decreased water content of left cerebral hemisphere, levels of COL3A1, β-catenin, TCF-4, and E-cadherin in the hippocampus compared with the model and DEX + miR-129-5p inhibitors groups. COL3A1 was verified as the target gene of the miR-129-5p. Compared with the DEX + NC and DEX + miR-129-5p inhibitors + XAV-939 groups, the DEX + XAV-939 and DEX + miR-129-5p mimics groups had elevated weight rate of the cerebral hemisphere, but reduced water content of left cerebral hemisphere, levels of COL3A1, β-catenin, TCF-4, and E-cadherin in the hippocampus. Our findings demonstrate that miR-129-5p improves the neuroprotective role of DEX in HIBI by targeting COL3A1 through the Wnt/β-catenin signaling pathway in neonatal rats.

SAR405, a Highly Specific VPS34 Inhibitor, Disrupts Auditory Fear Memory Consolidation of Mice via Facilitation of Inhibitory Neurotransmission in Basolateral Amygdala

BACKGROUND

Autophagy has been demonstrated to play an important role in memory deficits as well as the degradation of neurotransmitter receptors. SAR405 is a newly discovered inhibitor that can specifically inhibit vacuolar sorting protein 34 and prevent autophagosome biogenesis. However, the effects of SAR405 on memory processes remain largely unknown.

METHODS

Western blotting, immunofluorescence, and transmission electron microscopy were used to assess the level of autophagy after fear conditioning and SAR405 treatment. Behavioral tests, biotinylation assay, electrophysiology, and co-immunoprecipitation were used to unravel the mechanisms of SAR405 in memory consolidation.

RESULTS

SAR405 infusion into the basolateral amygdala impaired long-term memory through autophagy inhibition. Furthermore, the trafficking of gamma-aminobutyric acid type A receptors (GABA_ARs) following fear conditioning was disrupted by SAR405, and the decreased frequency and amplitude of miniature inhibitory postsynaptic currents induced by fear conditioning were also reversed by SAR405, suggesting that SAR405 disrupted memory consolidation through blockade of the downregulated inhibitory neurotransmission in basolateral amygdala. GABA_AR-associated protein (GABARAP) and its interaction with GABA_AR γ2 subunit were found to be upregulated after fear conditioning, and SAR405 could suppress this increased interaction. Moreover, disruption of the GABARAP-GABA_AR binding by a trans-activating transcriptional activator-GABARAP inhibitory peptide blocked the decrease in surface expression of GABA_ARs and attenuated long-term memory.

CONCLUSIONS

The present study suggests that SAR405 can prevent the memory consolidation via intervening autophagy and GABA_AR trafficking and has a potential therapeutic value for disorders characterized by exaggerated fear memories, such as posttraumatic stress disorder.

Inhibited Endogenous H2S Generation and Excessive Autophagy in Hippocampus Contribute to Sleep Deprivation-Induced Cognitive Impairment

Background and Aim: Sleep deprivation (SD) causes deficit of cognition, but the mechanisms remain to be fully established. Hydrogen sulfide (H₂S) plays an important role in the formation of cognition, while excessive and prolonged autophagy in hippocampus triggers cognitive disorder. In this work, we proposed that disturbances in hippocampal endogenous H₂S generation and autophagy might be involved in SD-induced cognitive impairment.

Methods: After treatment of adult male wistar rats with 72-h SD, the Y-maze test, object location test (OLT), novel object recognition test (NORT) and the Morris water maze (MWM) test were performed to determine the cognitive function. The autophagosome formation was observed with electron microscope. Generation of endogenous H₂S in the hippocampus of rats was detected using unisense H₂S microsensor method. The expressions of cystathionine-β-synthase (CBS), 3-mercaptopyruvate sulfurtransferase (3-MST), beclin-1, light chain LC3 II/LC3 I, and p62 in the hippocampus were assessed by western blotting.

Results: The Y-maze, OLT, NORT, and MWM test demonstrated that SD-exposed rats exhibited cognitive dysfunction. SD triggered the elevation of hippocampal autophagy as evidenced by enhancement of autophagosome, up-regulations of beclin-1 and LC3 II/LC3 I, and down-regulation of p62. Meanwhile, the generation of endogenous H₂S and the expressions of CBS and 3-MST (H₂S producing enzyme) in the hippocampus of SD-treated rats were reduced.

Conclusion: These results suggested that inhibition of endogenous H₂S generation and excessiveness of autophagy in hippocampus are involved in SD-induced cognitive impairment.

Sevoflurane Postconditioning Inhibits Autophagy Through Activation of the Extracellular Signal-Regulated Kinase Cascade, Alleviating Hypoxic-Ischemic Brain Injury in Neonatal Rats

Hypoxic-ischemic brain injury (HIBI) in neonates is one of the major contributors of newborn death and cognitive impairment. Numerous animal studies have demonstrated that autophagy is substantially increased in HIBI and that sevoflurane postconditioning (SPC) can attenuate HIBI. However, if SPC-induced neuroprotection inhibits autophagy in HIBI remains unknown. To investigate if cerebral protection induced by SPC is related to decreased autophagy in the setting of HIBI. Postnatal rats at day 7 (P7) were randomly assigned to 7 different groups: Sham, HIBI, SPC-HIBI, HIBI + rapamycin, SPC-HIBI + rapamycin, HIBI + p-extracellular signal-regulated kinase (p-ERK) inhibitor, and SPC-HIBI + p-ERK inhibitor. To induce HIBI, neonatal rats underwent left common carotid artery ligation, followed by 2 h of hypoxia (8% O₂). Rats in the SPC groups were treated with 1 minimum alveolar concentration ([MAC], 2.4%) SPC for 30 min after HIBI induction. Markers of autophagy and expression of ERK cascade components were measured in the rat brains after 24 h. Spatial learning and memory function were examined 29-34 days after administration of an autophagy agonist or a p-ERK inhibitor. The expression of microtubule-associated proteins 1A/1B, light chain 3B II (LC3-II) and tuberous sclerosis complex 2 (TSC2) were decreased in the SPC-HIBI group compared to the HIBI group. Expression of the p62 sequestosome 1 (P62/SQSTM1) protein, p-ERK/ERK, phospho-mammalian target of rapamycin (p-mTOR) and phospho-p70S6 were increased in SPC-HIBI group. Rats within the SPC-HIBI groups that also received the p-ERK inhibitor or autophagy inhibitor demonstrated reduced cross platform times and increased escape latency. Approximately 30 min of 2.4% SPC treatment in the P7 rat HIBI model attenuated excessive autophagy in the brain by elevating the ERK cascade. This finding provides additional insight into HIBI and identifies new targets for therapeutic approaches to treat HIBI.

Fibroblast growth factor 21 facilitates peripheral nerve regeneration through suppressing oxidative damage and autophagic cell death

Seeking for effective drugs which are beneficial to facilitating axonal regrowth and elongation after peripheral nerve injury (PNI) has gained extensive attention. Fibroblast growth factor 21 (FGF21) is a metabolic factor that regulates blood glucose and lipid homeostasis. However, there is little concern for the potential protective effect of FGF21 on nerve regeneration after PNI and revealing related molecular mechanisms. Here, we firstly found that exogenous FGF21 administration remarkably promoted functional and morphologic recovery in a rat model of sciatic crush injury, manifesting as persistently improved motor and sensory function, enhanced axonal remyelination and regrowth and accelerated Schwann cells (SCs) proliferation. Furthermore, local FGF21 application attenuated the excessive activation of oxidative stress, which was accompanied with the activation of nuclear factor erythroid‐2‐related factor 2 (Nrf‐2) transcription and extracellular regulated protein kinases (ERK) phosphorylation. We detected FGF21 also suppressed autophagic cell death in SCs. Additionally, treatment with the ERK inhibitor U0126 or autophagy inhibitor 3‐MA partially abolishes anti‐oxidant effect and reduces SCs death. Taken together, these results indicated that the role of FGF21 in remyelination and nerve regeneration after PNI was probably related to inhibit the excessive activation of ERK/Nrf‐2 signalling‐regulated oxidative stress and autophagy‐induced cell death. Overall, our work suggests that FGF21 administration may provide a new therapy for PNI.

Enhanced autophagy contributes to excitotoxic lesions in a rat model of preterm brain injury

Cystic periventricular leukomalacia is commonly diagnosed in premature infants, resulting from severe hypoxic-ischemic white matter injury, and also involving some grey matter damage. Very few is known concerning the cell death pathways involved in these types of premature cerebral lesions. Excitotoxicity is a predominant mechanism of hypoxic-ischemic injury in the developing brain. Concomitantly, it has been recently shown that autophagy could be enhanced in excitotoxic conditions switching this physiological intracellular degradation system to a deleterious process. We here investigated the role of autophagy in a validated rodent model of preterm excitotoxic brain damage mimicking in some aspects cystic periventricular leukomalacia. An excitotoxic lesion affecting periventricular white and grey matter was induced by injecting ibotenate, a glutamate analogue, in the subcortical white matter (subcingulum area) of five-day old rat pups. Ibotenate enhanced autophagy in rat brain dying neurons at 24 h as shown by increased presence of autophagosomes (increased LC3-II and LC3-positive dots) and enhanced autophagic degradation (SQSTM1 reduction and increased number and size of lysosomes (LAMP1- and CATHEPSIN B-positive vesicles)). Co-injection of the pharmacological autophagy inhibitor 3-methyladenine prevented not only autophagy induction but also CASPASE-3 activation and calpain-dependent cleavage of SPECTRIN 24 h after the insult, thus providing a strong reduction of the long term brain injury (16 days after ibotenate injection) including lateral ventricle dilatation, decreases in cerebral tissue volume and in subcortical white matter thickness. The autophagy-dependent neuroprotective effect of 3-methyladenine was confirmed in primary cortical neuronal cultures using not only pharmacological but also genetic autophagy inhibition of the ibotenate-induced autophagy. Strategies inhibiting autophagy could then represent a promising neuroprotective approach in the context of severe preterm brain injuries.

Expression of Autophagy Signaling Molecules in the Outer Membranes of Chronic Subdural Hematomas

Chronic subdural hematoma (CSDH) is fundamentally treatable, although it sometimes recurs. We observed, however, several cases of spontaneous resolution of CSDH outer membranes, even in a trabecular type of CSDH, after a trepanation surgical procedure. In this study, we examined the expression of molecules of the autophagy signaling pathway in CSDH outer membranes. Eight patients whose outer membranes were obtained successfully during trepanation were included in this study. By Western blot analysis, we examined the expression of mammalian target of rapamycin (mTOR); GβL; UNC-51-like kinase-1 (ULK1); Beclin-1; autophagy-related genes (Atg) 3, 5, 7, 12, 13, and 16L1β,α; the autophagy marker Light Chain3A/B (LC3A/B); and β-actin, which constitute the autophagy signaling pathway. The expression levels of Beclin-1, Atg12, and LC3A/B were also examined by immunohistochemistry. Almost all of these molecules could be detected in all samples. Beclin-1, Atg12, and LC3A/B were found to be localized in the endothelial cells of vessels and fibroblasts in CSDH. We detected molecules of the autophagy signaling pathway in CSDH outer membranes. Autophagy contributes to the tissue homeostatic process, maintaining cellular integrity by clearing debris. Our data suggest that autophagy might play an important role in the spontaneous resolution of CSDH. Therefore, these molecules may be novel therapeutic targets for the treatment of those with CSDH.

Trehalose inhibits H2O2-induced autophagic death in dopaminergic SH-SY5Y cells via mitigation of ROS-dependent endoplasmic reticulum stress and AMPK activation

Autophagy is a catabolic process to maintain intracellular homeostasis via removal of cytoplasmic macromolecules and damaged cellular organelles through lysosome-mediated degradation. Trehalose is often regarded as an autophagy inducer, but we reported previously that it could prevent ischemic insults-induced autophagic death in neurons. Thus, we further investigated in this study whether trehalose could protect human dopaminergic SH-SY5Y cells against H2O2-induced lethal autophagy. We found pretreatment with trehalose not only prevented H2O2-induced death in SH-SY5Y cells, but also reversed H2O2-induced upregulation of LC3II, Beclin1 and ATG5 and downregulation of p62. Then, we proved that either autophagy inhibitor 3MA or genetic knockdown of ATG5 prevented H2O2-triggered death in SH-SY5Y cells. These indicated that trehalose could inhibit H2O2-induced autophagic death in SH-SY5Y cells. Further, we found that trehalose inhibited H2O2-induced AMPK activation and endoplasmic reticulum (ER) stress. Moreover, inhibition of AMPK activation with compound C or alleviation of ER stress with chemical chaperone 4-PBA obviously attenuated H2O2-induced changes in autophagy-related proteins. Notably, we found that trehalose inhibited H2O2-induced increase of intracellular ROS and reduction in the activities of CAT and SOD. Consistently, our data revealed as well that mitigation of intracellular ROS levels with antioxidant NAC markedly attenuated H2O2-induced AMPK activation and ER stress. Therefore, we demonstrated in this study that trehalose prevented H2O2-induced autophagic death in SH-SY5Y cells via mitigation of ROS-dependent endoplasmic reticulum stress and AMPK activation.