Hypoxic preconditioning reduces propofol-induced neuroapoptosis via regulation of Bcl-2 and Bax and downregulation of activated caspase-3 in the hippocampus of neonatal rats

The impact of chronic intermittent hypoxia on enzymatic activity in memory-associated brain regions of male and female rats

BACKGROUND

Obstructive sleep apnea (OSA) is an intermittent hypoxia disorder associated with cognitive dysfunction, including learning and memory impairments. There is evidence that alterations in protease activity and neuronal activation are associated with cognitive dysfunction, are dependent on sex, and may be brain region-specific. However, the mechanisms mediating OSA-induced cognitive impairments are unclear. Therefore, we used a rat model of OSA, chronic intermittent hypoxia (CIH) to investigate protease activity (e.g., calpain and caspase-3) on spectrin, a cytoskeletal protein associated with neurotransmitter release, and neuronal activation (early growth response protein 1, EGR-1) in brain regions associated with learning and memory.

METHODS

Male and female Sprague Dawley rats were exposed to CIH or room air (normoxic) for 14 days. We quantified protease activity and cleaved spectrin products, along with EGR-1 protein expression in hippocampal subregions (CA1, CA3), cortical regions [entorhinal cortex (ETC), retrosplenial cortex (RSC), cerebellar cortex (CC)], and subcortical regions [raphe nucleus (RN), locus coeruleus (LC)] associated with learning and memory. Within each group, Pearson correlations of calpain activity, caspase-3 activity, and EGR-1 expression were performed between brain regions. Sex differences within normoxic and CIH correlations were examined.

RESULTS

CIH dysregulated calpain activity in male ETC, and female CA1 and RSC. CIH dysregulated caspase-3 activity in male RN, and female CA1 and RSC. CIH decreased calpain and caspase-3 cleavage products in male ETC. CIH decreased calpain-cleaved spectrin in male RSC but increased these products in female RSC. EGR-1 expression was decreased in male and female RN. Correlational analysis revealed CIH increased excitatory connections in males and increased inhibitory connections in females. EGR-1 expression in males shifted from negative to positive correlations.

CONCLUSIONS

Overall, these data indicate CIH dysregulates protease activity and impairs neuronal function in a brain region- and sex-dependent manner. This indicates that males and females exhibit sex-specific vulnerabilities to mild OSA. These findings concur with our previous behavioral studies that demonstrated memory impairment in CIH-exposed rats.

The impact of chronic intermittent hypoxia on enzymatic activity in memory-associated brain regions of male and female rats

Background

Obstructive sleep apnea (OSA) is an intermittent hypoxia disorder associated with cognitive dysfunction, including learning and memory impairments. There is evidence that alterations in protease activity and neuronal activation as associated with cognitive dysfunction, are dependent on sex, and may be brain region-specific. However, the mechanisms mediating OSA-induced cognitive impairments are unclear. Therefore, we used a rat model of OSA, chronic intermittent hypoxia (CIH), to investigate protease activity (e.g., calpain and caspase-3) and neuronal activation (early growth response protein 1, EGR-1) in brain regions associated with learning and memory. We used a rat model of OSA known as chronic intermittent hypoxia (CIH) to investigate protease activity (calpain and caspase-3) and neuronal activation (early growth response protein 1, EGR-1) in brain regions associated with learning and memory.

Methods

Male and female Sprague Dawley rats were exposed to CIH or room air (normoxic) for 14 days. We quantified protease activity and cleaved spectrin products, along with EGR-1 protein expression in hippocampal subregions (CA1, CA3), cortical regions [entorhinal cortex (ETC), retrosplenial cortex (RSC), cerebellar cortex (CC)], and subcortical regions [raphe nucleus (RN), locus coeruleus (LC)] associated with learning and memory. Within each group, Pearson correlations of calpain activity, caspase-3 activity, and EGR-1 expression were performed between brain regions. Sex differences within normoxic and CIH correlations were examined.

Results

CIH dysregulated calpain activity in male ETC and female CA1 and RSC. CIH dysregulated caspase-3 activity in male RN and female CA1 and RSC. CIH decreased calpain and caspase-3 cleavage products in male ETC. CIH decreased calpain-cleaved spectrin in male RSC but increased these products in female RSC. EGR-1 expression was decreased in male and female RN. Correlational analysis revealed CIH increased excitatory connections in males and increased inhibitory connections in females. EGR-1 expression in males shifted from negative to positive correlations.

Conclusions

Overall, these data show that CIH dysregulates protease activity and impairs neuronal function in a brain region- and sex-dependent manner. This indicates that males and females exhibit sex-specific vulnerabilities to mild OSA. These findings concur with our previous behavioral studies that demonstrated memory impairment in CIH-exposed rats.

Propofol-induced hippocampal Neurotoxicity: A mitochondrial perspective

Propofol is a frequently used anesthetic. It can induce neurodegeneration and inhibit neurogenesis in the hippocampus. This effect may be temporary. It can, however, become permanent in vulnerable populations, such as the elderly, who are more susceptible to Alzheimer's disease, and neonates and children, whose brains are still developing and require neurogenesis. Current clinical practice strategies have failed to provide an effective solution to this problem. In addition, the molecular mechanism of this toxicity is not fully understood. Recent advances in molecular research have revealed that apoptosis, in close association with mitochondria, is a crucial mechanism through which propofol contributes to hippocampal toxicity. Preventing the toxicity of propofol on the hippocampus has shown promise in in-vivo, in-vitro, and to a lesser extent human studies. This study seeks to provide a comprehensive literature review of the effects of propofol toxicity on the hippocampus via mitochondria and to suggest translational suggestions based on these molecular results.

MiR-34a targets SIRT1 to reduce p53 deacetylation and promote sevoflurane inhalation anesthesia-induced neuronal autophagy and apoptosis in neonatal mice

This study is to investigate the function of miR-34a and interactions between miR-34a, SIRT1, and p53 in sevoflurane-induced neuronal apoptosis and autophagy in neonatal mice. A mouse model was established by inhalation anesthesia with sevoflurane and injected with genetic reagents, followed by tests of learning and memory abilities and histological staining of the hippocampus. CCK-8 and AnnexinV/PI staining respectively measured the survival and apoptosis rates of primary hippocampal neurons cultured with sevoflurane. The expression levels of miR-34a, SIRT1, p53, Ac-p53, and autophagy- or apoptosis-related proteins were measured. Sevoflurane impaired the learning and memory abilities of mice, increased TUNEL-positive cells in their hippocampus, and hindered the survival of hippocampal neurons. Sevoflurane increased miR-34a, Bax, cleaved caspase-3, and the ratio of LC3-II/LC3-I and reduced SIRT1 and p62. MiR-34a overexpression promoted sevoflurane-induced neural damage, whereas SIRT1 inhibition or p53 upregulation counteracted the neuroprotection of miR-34a knockdown. SIRT1 was a target of miR-34a and promoted p53 deacetylation. MiR-34a promotes sevoflurane-stimulated neuronal apoptosis and autophagy in neonatal mice by inhibiting SIRT1 expression and subsequent p53 deacetylation.

RUNX1 Upregulation Causes Mitochondrial Dysfunction via Regulating the PI3K-Akt Pathway in iPSC from Patients with Down Syndrome

Down syndrome (DS) is the most common autosomal aneuploidy caused by trisomy of chromosome 21. Previous studies demonstrated that DS affected mitochondrial functions, which may be associated with the abnormal development of the nervous system in patients with DS. Runt-related transcription factor 1 (RUNX1) is an encoding gene located on chromosome 21. It has been reported that RUNX1 may affect cell apoptosis via the mitochondrial pathway. The present study investigated whether RUNX1 plays a critical role in mitochondrial dysfunction in DS and explored the mechanism by which RUNX1 affects mitochondrial functions. Expression of RUNX1 was detected in induced pluripotent stem cells of patients with DS (DS-iPSCs) and normal iPSCs (N-iPSCs), and the mitochondrial functions were investigated in the current study. Subsequently, RUNX1 was overexpressed in N-iPSCs and inhibited in DS-iPSCs. The mitochondrial functions were investigated thoroughly, including reactive oxygen species levels, mitochondrial membrane potential, ATP content and lysosomal activity. Finally, RNA-sequencing was used to explore the global expression pattern. It was observed that the expression levels of RUNX1 in DS-iPSCs were significantly higher than those in normal controls. Impaired mitochondrial functions were observed in DS-iPSCs. Of note, overexpression of RUNX1 in N-iPSCs resulted in mitochondrial dysfunction, while inhibition of RUNX1 expression could improve the mitochondrial function in DS-iPSCs. Global gene expression analysis indicated that overexpression of RUNX1 may promote the induction of apoptosis in DS-iPSCs by activating the PI3K/Akt signaling pathway. The present findings indicate that abnormal expression of RUNX1 may play a critical role in mitochondrial dysfunction in DS-iPSCs.

Continuous Glucose Monitoring in Hypoxic Environments Based on Water Splitting-Assisted Electrocatalysis

Conventional enzyme-based continuous glucose sensors in interstitial fluid usually rely on dissolved oxygen as the electron-transfer mediator to bring electrons from oxidase to electrode while generating hydrogen peroxide. This may lead to several problems. First, the sensor may provide biased detection results owing to fluctuation of oxygen in interstitial fluid. Second, the polymer coatings that regulate the glucose/oxygen ratio can affect the dynamic response of the sensor. Third, the glucose oxidation reaction continuously produces corrosive hydrogen peroxide, which may compromise the long-term stability of the sensor. Here, we introduce an oxygen-independent nonenzymatic glucose sensor based on water splitting-assisted electrocatalysis for continuous glucose monitoring. For the water splitting reaction (i.e., hydrogen evolution reaction), a negative pretreatment potential is applied to produce a localized alkaline condition at the surface of the working electrode for subsequent nonenzymatic electrocatalytic oxidation of glucose. The reaction process does not require the participation of oxygen; therefore, the problems caused by oxygen can be avoided. The nonenzymatic sensor exhibits acceptable sensitivity, reliability, and biocompatibility for continuous glucose monitoring in hypoxic environments, as shown by the in vitro and in vivo measurements. Therefore, we believe that it is a promising technique for continuous glucose monitoring, especially for clinically hypoxic patients.

Role of ferroptosis in hypoxic preconditioning to reduce propofol neurotoxicity

Background: An increasing number of studies have reported that neurotoxicity of propofol may cause long-term learning and cognitive dysfunction. Hypoxic preconditioning has been shown to have neuroprotective effects, reducing the neurotoxicity of propofol. Ferroptosis is a new form of death that is different from apoptosis, necrosis, autophagy and pyroptosis. However, it is unclear whether hypoxic preconditioning reduces propofol neurotoxicity associated with ferroptosis. Thus, we aimed to evaluate the effect of propofol on primary hippocampal neurons in vitro to investigate the neuroprotective mechanism of hypoxic preconditioning and the role of ferroptosis in the reduction of propofol neurotoxicity by hypoxic preconditioning. Methods: Primary hippocampal neurons were cultured for 8 days in vitro and pretreated with or without propofol, hypoxic preconditioning, agonists or inhibitors of ferroptosis. Cell counting kit-8, Calcein AM, Reactive oxygen species (ROS), Superoxide dismutase (SOD), Ferrous iron (Fe²⁺), Malondialdehyde (MDA) and Mitochondrial membrane potential assay kit with JC-1 (JC-1) assays were used to measure cell viability, Reactive oxygen species level, Superoxide dismutase content, Fe²⁺ level, MDA content, and mitochondrial membrane potential. Cell apoptosis was evaluated using flow cytometry analyses, and ferroptosis-related proteins were determined by Western blot analysis. Results: Propofol had neurotoxic effects that led to decreased hippocampal neuronal viability, reduced mitochondrial membrane potential, decreased SOD content, increased ROS level, increased Fe²⁺ level, increased MDA content, increased neuronal apoptosis, altered expression of ferroptosis-related proteins and activation of ferroptosis. However, hypoxic preconditioning reversed these effects, inhibited ferroptosis caused by propofol and reduced the neurotoxicity of propofol. Conclusion: The neurotoxicity of propofol in developing rats may be related to ferroptosis. Propofol may induce neurotoxicity by activating ferroptosis, while hypoxic preconditioning may reduce the neurotoxicity of propofol by inhibiting ferroptosis.

The propofol-induced mitochondrial damage in fetal rat hippocampal neurons via the AMPK/P53 signaling pathway

BACKGROUND

Propofol is a commonly used general anesthetic that may cause neuronal damage, especially in infants and young children. Mitochondria play an essential role in cellular metabolism and signal transduction. Propofol may cause neurotoxicity by inhibiting mitochondrial function, but the mechanism by this which occurs remains unclear.

METHODS

First, the primary rat hippocampal neurons were cultured for 7 days in vitro. The neurons were incubated with propofol at different times or different concentrations, and then the adenosine triphosphate (ATP), reactive oxygen species (ROS), mitochondrial membrane potential, and apoptosis-related proteins were analyzed. Based on the results of the 1st phase, the neurons were then incubated with propofol (100 µM) or corresponding reagents, including 5-aminoimidazole-4-carboxamide ribonucleotide, tenovin-1, and pifithrin-α. Subsequently, the ATP, ROS, mitochondrial membrane potential, phospho-adenosine 5'-monophosphate-activated protein kinase (p-AMPK), protein 53 (p53), and related apoptosis proteins were analyzed.

RESULTS

Higher propofol concentrations or longer incubation times were associated with more pronounced decreases in ATP, B-cell lymphoma 2 (Bcl-2), and mitochondrial membrane potential, and more pronounced increases in ROS, BCL2-associated X (Bax), Cytochrome C (CytC), and cleaved caspase-9. Additionally, after incubation with propofol (100 µM), neuronal Bcl-2, p-AMPK, ATP, and mitochondrial membrane potential were downregulated, and ROS, p53, CytC, Bax, cleaved caspase-3, and cleaved caspase-9 were upregulated. AMPK activators or p53 inhibitors reversed the above-mentioned changes.

CONCLUSIONS

Propofol (100 µM)-induced mitochondrial damage in fetal rat hippocampal neurons may be mediated by the AMPK/p53 signaling pathway. Propofol (100 µM) was shown to inhibit the activity of AMPK in neurons, upregulate the expression of p53, and then activate the mitochondrial-dependent apoptosis pathway, which may lead to neuronal apoptosis.

Superoxide anion radical induced phototoxicity of 2,4,5,6-Tetraminopyrimidine sulfate via mitochondrial-mediated apoptosis in human skin keratinocytes at ambient UVR exposure

2,4,5,6-Tetraaminopyrimidine sulfate (TAPS) is worldwide the most commonly used developer in hair dyes. As skin is the major organ, which is directly exposed to these permanent hair dyes, a comprehensive dermal safety assessment is needed. Hereto, we studied the photosensitization potential and mechanism involved in dermal phototoxicity of TAPS exposed to the dark and UVA/UVB/Sunlight by using different in-chemico and mammalian (HaCaT) cells, as test systems. Our experimental outcomes illustrate that TAPS get photodegraded (LC-MS/MS) and specifically generated superoxide anion radical (O₂^•-) under UVA and UVB via type-I photodynamic reaction. The phototoxic potential of TAPS is measured through MTT, NRU, and LDH assays that depicted a significant reduction in cell viability at the concentration of 25 μg/ml and higher. Different cellular stainings (PI uptake, AO/EB, JC-1, NR uptake) suggested the role of mitochondrial-mediated apoptosis. Further, the transcriptomics study revealed upregulation of Apaf-1, Bax, Caspase 3, Caspase 9, Cytochrome c and downregulation of Bcl-2 and Catalase by TAPS treated cells that strengthen our findings. Thus, the above findings suggest that chronic application of TAPS may be hazardous for human skin and promote various skin diseases.

Attenuation of the cytoprotection induced by hypoxic preconditioning upon transfection with BNIP3-siRNA in human neuroblastoma SH-SY5Y cells

PURPOSE

The aim of this study was to investigate the functional role of hypoxic preconditioning (HPC) in human neuroblastoma cells.

METHODS

BNIP3 small-interfering RNA (BNIP3-siRNA) sequence was synthesized and used to transfect human neuroblastoma SH-SY5Y cell lines. Thereafter, BNIP3 expression at mRNA and protein levels and its effects on the cell proliferation were analyzed. The most effective pair of siRNA was selected to knockdown the expression level of BNIP3. Moreover, the effects of HPC on oxygen-glucose deprivation/reperfusion (OGD/R)-induced apoptosis and autophagy in SH-SY5Y cells were explored to further reveal the possible mechanisms underlying HPC.

RESULTS

BNIP3-siRNA attenuated the protective effects of HPC by decreasing the cell viability, increasing the enzymatic activity of caspase-3 and 9, increasing the rate of apoptosis, and increasing the protein expression level of activated caspase-3. Additionally, BNIP3-siRNA had no significant influence on the expression level of HIF-1α induced by HPC, while it substantially inhibited HPC-induced BNIP3/Beclin1 and autophagy.

CONCLUSIONS

HPC promoted autophagy through regulating BNIP3 to reduce OGD/R.

Protective Effect of Chitosan Oligosaccharide against Hydrogen Peroxide-Mediated Oxidative Damage and Cell Apoptosis via Activating Nrf2/ARE Signaling Pathway

Chitosan oligosaccharide (COS), hydrolyzed and deacetylated from chitosan, has been reported to possess varieties of biological activities. Alzheimer's disease (AD) is a multifactorial progressive neurodegenerative disorder characterized by cognitive decline and memory loss, where oxidative stress was reported to be an overwhelming cause of the occurrence of AD. We have previously reported that COS could significantly decrease cell death, ROS generation, and lipid peroxidation, though the potential mechanism was yet to be determined. This study was designed to investigate the neuroprotective effect of COS against hydrogen peroxide (H2O2)-induced oxidative stress and apoptosis in neuronal SH-SY5Y cells. Our results indicated that COS could dose-dependently scavenge H2O2 in the cell-free systems. Accordingly, COS markedly decreased H2O2-induced cell apoptosis and intracellular ROS generation, while increased antioxidant capacity in SH-SY5Y cells. Further, COS significantly reduced the expression of Bax and upregulated Bcl-2. The mRNA and protein expression levels of nuclear Nrf2, heme oxygenase 1 (HO-1), and NAD(P)H: quinone oxidoreductase 1 (NQO1) were significantly increased upon COS treatment. Moreover, Nrf2-siRNA evidently reversed the promotive effect of COS on expression levels of HO-1 and NQO1, and ARE-driven transcriptional activity as determined by double-luciferase reporter gene assay. Besides, COS reversed H2O2-mediated increased phosphorylation of ERK1/2 and p38 MAPK. In conclusion, our findings indicate that COS could protect SH-SY5Y cells from oxidative damage and apoptosis via regulating Nrf2/ARE signaling pathway, which may provide new applications for the prevention and treatment of AD.

Propofol Downregulates lncRNA MALAT1 to Alleviate Cerebral Ischemia-Reperfusion Injury

Propofol (PPF) is reported to play a protective role in ischemia/reperfusion (I/R) injury, including cerebral ischemia-reperfusion injury (CIRI). This study aims to investigate the mechanism by which PPF ameliorates CIRI. Kunming mice were used to establish the middle cerebral artery occlusion (MCAO)/reperfusion mouse model in vivo. PPF pre-treatment was performed before CIRI. Lactate dehydrogenase (LDH) and creatine phosphokinase (CPK) levels were detected to evaluate the tissue injury. PC12 cells were exposed to hypoxia/reoxygenation (H/R) to construct the in vitro CIRI model, and PC12 cells were pre-treated with PPF before H/R. Quantitative real-time polymerase chain reaction (qRT-PCR) was employed to detect the expression of lncRNA MALAT1 and miR-182-5p. Flow cytometry was used to detect the apoptosis of PC12 cells. Bioinformatics analysis, qRT-PCR, dual-luciferase reporter gene experiments, and RNA immunoprecipitation (RIP) experiments were performed to predict and validate the targeting relationship between MALAT1 and miR-182-5p. Western blot was used to detect Toll-like receptor 4 (TLR4) expression at protein level. PPF pre-treatment remarkably inhibited LDH and CPK levels in the serum of the mice with CIRI, and reduced the apoptosis of PC12 cells exposed to H/R. Besides, PPF pre-treatment markedly suppressed MALAT1 expression in both in vivo and in vitro models and upregulated miR-182-5p expression. MiR-182-5p was validated to be a downstream target gene of MALAT1, and MALAT1 could increase the expression of TLR4 by suppressing miR-182-5p. The effects of PPF on the injury of the mice brain and PC12 cells were partly counteracted by the restoration of MALAT1. PPF protects the brain against I/R-induced injury by regulating MALAT1/miR-182-5p/TLR4 axis.

MicroRNA-29b reduces myocardial ischemia-reperfusion injury in rats via down-regulating PTEN and activating the Akt/eNOS signaling pathway

Reperfusion may cause injuries to the myocardium in ischemia situation, which is called ischemia/reperfusion (I/R) injury. The study aimed to explore the roles of microRNA-29b (miR-29b) in myocardial I/R injury. Myocardial I/R injury rat model was established. Differentially expressed miRNAs between the model rats and the sham-operated rats were analyzed. miR-29b expression in myocardial tissues was measured. Gain-of-function of miR-29b was performed, and then the morphological changes, infarct size, myocardial function, oxidative stress, and the cell apoptosis in myocardial tissues were detected. The target relation between miR-29b and PTEN was detected through bio-information prediction and dual luciferase reporter gene assay. Activation of Akt/eNOS signaling was detected. H9C2 cells were subjected to hypoxia/reoxygenation treatment to perform in vitro experiments. I/R rats presented severe inflammatory infiltration, increased infarct size and cell apoptosis, increased oxidative stress and decreased myocardial function. miR-29b was downregulated in I/R rats, and up-regulation of miR-29b reversed the above changes. miR-29b directly bound to PTEN, and overexpression of miR-29b reduced PTEN expression level and increased the protein levels of p-Akt/Akt and p-eNOS/eNOS. In vivo results were confirmed in in vitro experiments. This study provided evidence that miR-29b could alleviate the myocardial I/R injury in vivo and in vitro by inhibiting PTEN expression and activating the Akt/eNOS signaling pathway.

Neuroprotective effects and mechanisms of ischemic/hypoxic preconditioning on neurological diseases

As the organ with the highest demand for oxygen, the brain has a poor tolerance to ischemia and hypoxia. Despite severe ischemia/hypoxia induces the occurrence and development of various central nervous system (CNS) diseases, sublethal insult may induce strong protection against subsequent fatal injuries by improving tolerance. Searching for potential measures to improve brain ischemic/hypoxic is of great significance for treatment of ischemia/hypoxia related CNS diseases. Ischemic/hypoxic preconditioning (I/HPC) refers to the approach to give the body a short period of mild ischemic/hypoxic stimulus which can significantly improve the body's tolerance to subsequent more severe ischemia/hypoxia event. It has been extensively studied and been considered as an effective therapeutic strategy in CNS diseases. Its protective mechanisms involved multiple processes, such as activation of hypoxia signaling pathways, anti-inflammation, antioxidant stress, and autophagy induction, etc. As a strategy to induce endogenous neuroprotection, I/HPC has attracted extensive attention and become one of the research frontiers and hotspots in the field of neurotherapy. In this review, we discuss the basic and clinical research progress of I/HPC on CNS diseases, and summarize its mechanisms. Furthermore, we highlight the limitations and challenges of their translation from basic research to clinical application.

Dexmedetomidine upregulates microRNA-185 to suppress ovarian cancer growth via inhibiting the SOX9/Wnt/β-catenin signaling pathway

Dexmedetomidine (DEX) could serve as an adjuvant analgesic during cancer therapies. Abnormal expression of microRNAs (miRNAs) could lead to cancer development. This study was aimed to explore the roles of DEX in ovarian cancer (OC) development. OC cell lines SKOV3 and HO-8910 were treated with DEX, after which OC development and the miR-185, SOX9, and Wnt/β-catenin pathway were measured. DEX-treated HO-8910 cells were transfected with miR-185 mimic, miR-185 antisense or miR-185 antisense + silenced SOX9 to further measure the OC cell growth. The target relation between miR-185 and SOX9 was identified, and SOX9 and Wnt/β-catenin pathway were protein levels detected after miR-185 transfection. The role of miR-185 in OC in vivo was also measured. Our study found DEX had a dose-dependent inhibition on OC growth, and DEX promoted miR-185 but suppressed SOX9 expression in OC cells. miR-185 targeted SOX9. After interfering with miR-185 expression, HO-8910 cell proliferation, invasion, migration, and apoptosis were affected. SOX9 knockdown repressed OC development and Wnt/β-catenin pathway. The volume, weight, positive rate of Ki67, CyclinD1, p53 and the degree of tumor necrosis were affected by miR-185 expression. This study demonstrated that DEX could inhibit OC development via upregulating miR-185 expression and inactivating the SOX9/Wnt/β-catenin signaling pathway.

Astrocyte-derived exosomes carry microRNA-17-5p to protect neonatal rats from hypoxic-ischemic brain damage via inhibiting BNIP-2 expression

Exosomes play critical roles in neurogenesis. This study aims to explore the mechanism of astrocyte-derived exosomes in neonatal rats with hypoxic-ischemic brain damage (HIBD). Astrocytes were collected and astrocyte-derived exosomes were isolated and identified. Neonatal rats were pre-treated with exosomes and then subjected to HIBD induction. Then the neurobehaviors, neuronal apoptosis, inflammation and oxidative stress in rat brain were measured. Differentially expressed microRNAs (miRNAs) in rat brain before and after HI procedure were analyzed. H19-7 cells were subjected to oxygen and glucose deprivation (OGD) for in vitro studies. Target relation between miR-17-5p and BNIP2 was identified. Gain- and loss-of functions of miR-17-5p and BNIP2 were conducted to identify their roles in viability, apoptosis, oxidative stress and inflammation of OGD-treated cells. Collectively, astrocyte-derived exosomes improved neurobehaviors, and reduced cerebral infarction, neuronal apoptosis, oxidative and inflammation in vivo and in vitro. The exosomes carried miR-17-5p bound to BNIP2 and negatively regulated BNIP2 expression in OGD-treated cells. Over-expression of miR-17-5p increased viability, and decreased OGD-induced apoptosis, oxidative stress and inflammation of H19-7 cells, which were reversed by over-expression of BNIP2. Taken together, the study suggested that astrocyte-derived exosomes could carry miR-17-5p to protect neonatal rats from HIBD via inhibiting BNIP-2 expression.

Exploring the beneficial effects and possible mechanisms of repeated episodes of whole-body hypoxic perconditioning in rat model of preeclampsia

AIM

The study explored the beneficial effects of repeated episodes of whole body hypoxic perconditioning (WHPC) on preeclampsia (PE)-like symptoms in rats.

MATERIAL AND METHODS

PE was induced by administration of L-NAME (75 mg/kg) and WHPC was performed by exposing rats to low O₂ (8%) and normal O₂ of 10 min each in four alternate cycles.

RESULTS

L-NAME induced PE like symptoms in rats along with a decrease in the cystathionine-β-synthase (CBS) activity in the placental tissue, plasma levels of H₂S and NO metabolites in pregnant rats. Two (GD9, GD14) and three episodes (GD9, GD14 and GD18) of WHPC improved PE-like symptoms with an increase in CBS activity and H₂S levels. CBS inhibitor, amino-oxyacetic acid abolished the beneficial effects of three episodes of WHPC; while H₂S donor, 4-methylbenzenecarbothioamide, 4-MBC attenuated PE-like symptoms.

CONCLUSION

WHPC attenuates L-NAME-induced PE-like symptoms due to increase in CBS activity and H₂S-production.

Long non-coding RNA NCK1-AS1 promotes the tumorigenesis of glioma through sponging microRNA-138-2-3p and activating the TRIM24/Wnt/β-catenin axis

BACKGROUND

Glioma is a common brain malignancy with high mortality. The competing endogenous RNA (ceRNA) networks may play key roles in cancer progression. This study was conducted to probe the role of long noncoding RNA (lncRNA) NCK1-AS1 in glioma progression and the involved mechanisms.

METHODS

Microarray analyses were performed to explore the lncRNAs/miRNAs/genes with differential expression in glioma. NCK1-AS1 levels in glioma tissues and normal brain tissues, and in glioma cell lines and normal human glial cells were identified. The interactions among NCK1-AS1, miR-138-2-3p and TRIM24 were validated through luciferase reporter, RNA immunoprecipitation and RNA pull-down assays. Gain- and loss-of functions of NCK1-AS1, miR-138-2-3p and TRIM24 were performed to identify their roles in the behaviors of glioma cells. The activity of the Wnt/β-catenin pathway was measured. In vivo experiments were performed as well.

RESULTS

High expression of NCK1-AS1 was found in glioma tissues and cells, especially in U251 cells. Online predictions and the integrated experiments identified that NCK1-AS1 elevated the TRIM24 expression through sponging miR-138-2-3p, and further activated the Wnt/β-catenin pathway. Artificial silencing of NCK1-AS1 or up-regulation of miR-138-2-3p led to inhibited proliferation, invasion and migration but promoted cell apoptosis of U251 cells, while up-regulation of TRIM24 reversed these changes, and it activated the Wnt/β-catenin pathway. The in vitro results were reproduced in in vivo experiments.

CONCLUSIONS

Our study suggested that NCK1-AS1 might elevate TRIM24 expression and further activate the Wnt/β-catenin pathway via acting as a ceRNA for miR-138-2-3p. Silencing of NCK1-AS1 might inhibit the progression of glioma.

Role of p75 neurotrophin receptor in neuronal autophagy in intracerebral hemorrhage in rats through the mTOR signaling pathway

Rupture of weakened blood vessels could lead to severe intracerebral hemorrhage (ICH) and brain injuries. This study was designed to explore the roles of p75 neurotrophin receptor (p75^NTR) in neuronal autophagy in ICH rats. An ICH rat model was established, and then gain and loss of functions of p75^NTR in rat tissues were performed. Then, the pathologic morphology, water content, and inflammation in brain tissues were assessed. Western blot analysis was applied to detect the levels of inflammatory proteins, apoptosis- and autophagy-related proteins, and the mammalian target of rapamycin (mTOR) pathway-related proteins. Neuronal autophagy was further measured with mTOR activated. In vitro experiments were also performed on brain microvascular endothelial cells (BMECs) and astrocytes. Consequently, we found p75^NTR knockdown improved the pathologic morphology with reduced neuron damage, water content, permeability of blood-brain barrier and inflammation in ICH rat brain tissues. Besides, Knockdown of p75^NTR decreased neuronal apoptosis and inactivated mTOR signaling pathway, but it elevated the levels of autophagy-related proteins. In vivo results were reproduced in in vitro experiments. This study demonstrated that knockdown of p75^NTR could promote neuronal autophagy and reduce neuronal apoptosis via inactivating the mTOR pathway. We hope these findings could provide new therapeutic options for ICH treatment.

The expression of glucose transporters and mitochondrial division and fusion proteins in rats exposed to hypoxic preconditioning to attenuate propofol neurotoxicity

Purpose: Evidence has shown that propofol may cause widespread apoptotic neurodegeneration. Hypoxic preconditioning has been demonstrated to provide neuroprotection and brain recovery from both acute and chronic neurodegeneration in several cellular and animal models. However, the mechanism has not been well elucidated. Therefore, the present study was designed to investigate the expression of glucose transporters (GLUT1 and GLUT3) and mitochondrial division and fusion (Drp1 and Mfn2) proteins in rats exposed to hypoxic preconditioning to attenuate propofol neurotoxicity.Methods: Propofol (100 mg/kg) was given to 7-day-old Sprague-Dawley rats; in some rats, hypoxic preconditioning was administered before intraperitoneal propofol injection by subjecting rats to five cycles of 10 min of hypoxia (8% O₂₎ and 10 min of normoxia (21% O₂). Then, the rats were allowed to breathe room air for 2 h. Neuronal mitochondrial morphology was observed by transmission electron microscopy. ATP content was detected using an ATP assay kit. The expression levels of GLUT1, GLUT3, pDrp1, Drp1 and Mfn2 were detected by Western blot, and the expression levels of GLUT1 and GLUT3 were further examined by immunohistochemistry.Results: Propofol damaged mitochondria, and decreased ATP content and GLUT3 and pDrp1 protein expression. However, our results suggested that hypoxic preconditioning could attenuate propofol neurotoxicity by reducing mitochondrial damage and increasing ATP content and pDrp1, GLUT1 and GLUT3 protein expression.Conclusion: Hypoxic preconditioning reduced propofol-induced damage in the hippocampus of neonatal rats by attenuating the increase in mitochondrial division and decrease in GLUT3 expression.

Potential role of the cAMP/PKA/CREB signalling pathway in hypoxic preconditioning and effect on propofol‑induced neurotoxicity in the hippocampus of neonatal rats

Hypoxic preconditioning (HPC) is neuroprotective against ischaemic brain injury; however, the roles of potential anti‑apoptotic signals in this process have not been assessed. To elucidate the molecular mechanisms involved in HPC‑induced neuroprotection, the effects of HPC on the cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA)/cAMP response element‑binding protein (CREB) signalling pathway and apoptosis in Sprague‑Dawley pups (postnatal day 7) treated with propofol were investigated. Western blot and histological analyses demonstrated that HPC exerts multiple effects on the hippocampus, including the upregulation of cAMP and phosphorylation of CREB. These effects were partially blocked by intracerebroventricular injection of the protein kinase antagonist H89 (5 µmol/5 µl). Notably, the level of cleaved caspase‑3 was significantly downregulated by treatment with the cAMP agonist Sp‑cAMP (20 nmol/5 µl). The results indicate that propofol increased the level of cleaved caspase‑3 and Bax by suppressing the activity of cAMP‑dependent proteins and Bcl‑2; thus, HPC prevents propofol from triggering apoptosis via the cAMP/PKA/CREB signalling pathway.