Roles of HIF1α- and HIF2α-regulated BNIP3 in hypoxia-induced injury of neurons

Mechanisms and therapeutic targets of mitophagy after intracerebral hemorrhage

Mitochondria are dynamic organelles responsible for cellular energy production. In addition to regulating energy homeostasis, mitochondria are responsible for calcium homeostasis, clearance of damaged organelles, signaling, and cell survival in the context of injury and pathology. In stroke, the mechanisms underlying brain injury secondary to intracerebral hemorrhage are complex and involve cellular hypoxia, oxidative stress, inflammatory responses, and apoptosis. Recent studies have shown that mitochondrial damage and autophagy are essential for neuronal metabolism and functional recovery after intracerebral hemorrhage, and are closely related to inflammatory responses, oxidative stress, apoptosis, and other pathological processes. Because hypoxia and inflammatory responses can cause secondary damage after intracerebral hemorrhage, the restoration of mitochondrial function and timely clearance of damaged mitochondria have neuroprotective effects. Based on studies on mitochondrial autophagy (mitophagy), cellular inflammation, apoptosis, ferroptosis, the BNIP3 autophagy gene, pharmacological and other regulatory approaches, and normobaric oxygen (NBO) therapy, this article further explores the neuroprotective role of mitophagy after intracerebral hemorrhage.

Role of the HIF-1α/BNIP3 Signaling Pathway in Recurrent Hepatocellular Carcinoma and the Mechanism of Traditional Chinese Medicine

Recurrence of hepatocellular carcinoma (HCC) negatively affects the quality of life of patients and leads to death. Studies have shown that recurrent hepatocellular carcinoma (RHCC) is closely related to tissue hypoxia and autophagy. It has been shown that hypoxia-inducible factor-1α (HIF-1α) and its downstream factor BCL-2 19 kDa-interacting protein 3 (BNIP3) promote cellular autophagy under hypoxic conditions, resulting in metastasis and RHCC. In this article, the molecular structures of HIF-1α and BNIP3 are described, and the significance of the HIF-1α/BNIP3 signaling pathway in RHCC is explained. Moreover, the role and mechanism of traditional Chinese medicine (TCM) in treating RHCC by modulating the HIF-1α/BNIP3 signaling pathway is discussed. Studies have shown that the HIF-1α/BNIP3 signaling pathway is a potential target of TCM in the treatment of RHCC. The mechanism of the HIF-1α/BNIP3 signaling pathway in RHCC and the progress achieved in TCM research on targeting and regulating this pathway are also reviewed in this article. The objective was to provide a theoretical basis for the prevention and treatment of RHCC, as well as further drug development.

The evolutionarily conserved hif-1/bnip3 pathway promotes mitophagy and mitochondrial fission in crustacean testes during hypoxia

The hypoxia-inducible factor 1 (HIF-1) cascade is an ancient and strongly evolutionarily conserved signaling pathway that is involved in the hypoxic responses of most metazoans. Despite immense advances in the understanding of the HIF-1-mediated regulation of hypoxic responses in mammals, the contribution of the hif-1 cascade in the hypoxic adaptation of nonmodel invertebrates remains unclear. In this study, we used the oriental river prawn Macrobrachium nipponense for investigating the roles of hif-1-regulated mitophagy in crustacean testes under hypoxic conditions. We identified that the Bcl-2/adenovirus E1B 19-kDa interacting protein (bnip3) functions as a regulator of mitophagy in M. nipponense and demonstrated that hif-1α activates bnip3 by binding to the bnip3 promoter. Hif-1α knockdown suppressed the expression of multiple mitophagy-related genes, and prawns with hif-1α knockdown exhibited higher mortality under hypoxic conditions. We observed that the levels of BNIP3 were induced under hypoxic conditions and detected that bnip3 knockdown inhibited the mitochondrial translocation of dynamin-related protein 1 (drp1), which is associated with mitochondrial fission. Notably, bnip3 knockdown inhibited hypoxia-induced mitophagy and aggravated the deleterious effects of hypoxia-induced reactive oxygen species (ROS) production and apoptosis. The experimental studies demonstrated that hypoxia induced mitochondrial fission in M. nipponense via drp1. Altogether, the study elucidated the mechanism underlying hif-1/bnip3-mediated mitochondrial fission and mitophagy and demonstrated that this pathway protects crustaceans against ROS production and apoptosis induced by acute hypoxia.

Improvement of obesity-induced fatty liver disease by intermittent hypoxia exposure in a murine model

Background: The high prevalence of non-alcoholic fatty liver disease (NAFLD) in the world raises an important concern for human health. The western diet containing high fat and fructose is the risk factor for NAFLD development. Intermittent hypoxia (IH), known as the basis of obstructive sleep apnea (OSA), normally is correlated with impaired liver function. However, the role of IH in liver injury prevention has been revealed by many other studies based on the different IH paradigms. The current study, therefore, tests the impact of IH on the liver of high-fat and high-fructose diet (HFHFD) fed mice. Material and Method: Mice were exposed to IH (2 min cycle, FiO₂ 8% for 20 s, FiO₂ 20.9% for 100 s; 12 h/day) or intermittent air (FiO₂ 20.9%) for 15 weeks, with normal diet (ND) or high-fat and high-fructose diet (HFHFD). Indices of liver injury and metabolism were measured. Results: IH causes no overt liver injury in mice fed an ND. However, HFHFD-induced lipid accumulation, lipid peroxidation, neutrophil infiltration, and apoptotic process were significantly attenuated by IH exposure. Importantly, IH exposure altered bile acids composition and shifted the hepatic bile acids towards FXR agonism, which was involved in the protection of IH against HFHFD. Conclusion: These results support that the IH pattern in our model prevents liver injury from HFHFD in experimental NAFLD.

Acute Hypoxia Stress-Induced Apoptosis in Gill of Japanese Flounder (Paralichthys olivaceus) by Modulating the Epas1/Bad Pathway

The physiological responses and molecular mechanisms of apoptosis in Japanese flounder under hypoxic stress remain unclear. In the present study, we performed acute hypoxia stress on Japanese flounder (2.39 ± 0.84 mg/L) and detected gills responses in histomorphology and molecular mechanisms. The results showed that the volume of the interlamellar cell mass decreased and the gill lamellae prolonged, indicating the expansion of the respiratory surface area. Additionally, the fluorescence signal of apoptosis increased under hypoxic stress. In addition, the expression of two genes (EPAS1 and Bad) related to apoptosis increased about four-fold and two-fold, respectively, at 6 h of hypoxia. Meanwhile, the result of the dual-luciferase reporter assay showed that EPAS1 is a transcription factor, which could regulate (p < 0.05) the expression of the Bad gene, and we identified the binding site of EPAS1 was the AATGGAAAC sequence located near −766. DNA methylation assay showed that hypoxia affected the methylation status of CpG islands of EPAS1 and Bad genes. All results indicated that hypoxia could activate the EPAS1/Bad signal pathway to induce gill apoptosis of Japanese flounder. Our study provides new light on understanding the molecular mechanism of hypoxia-induced apoptosis in Japanese flounder.

Hypoxic preconditioning neural stem cell transplantation promotes spinal cord injury in rats by affecting transmembrane immunoglobulin domain-containing

OBJECTIVE

To explore the effects of hypoxic preconditioning neural stem cell (P-NSC) transplantation on rats with spinal cord injury (SCI).

METHODS

After identification, the NSCs were treated with hypoxic preconditioning. The NSCs migration was detected by Transwell method. RT-qPCR was used to detect the mRNA levels of HIF-1α, CXCR4 in NSC. The secretion of representative neurotrophic factors (VEGF, HGF, and BDNF) was checked by Western blot. Forty-six SCI rats were randomly divided into three experimental groups: SCI group (PBS injection, n = 10); N-NSC group (NSC atmospheric normoxic pretreatment injection, n = 18); and P-NSC group (NSC 's hypoxic preconditioning injection, n = 18). The sham operation group was also included (rats underwent laminectomy but not SCI, n = 10). The recovery of hindlimb motor function was evaluated by BBB score. The level of spinal cord inflammation (IL-1β, TNF-α, and IL-6) was determined by ELISA. Western blot was used to detect the content of TMIGD1 and TMIGD3 in spinal cord.

RESULTS

Compared with the N-NSC group, the number of NSC-passing membranes in the P-NSC group increased with the increase of the culture time (p < 0.05). Compared with N-NSC, P-NSC had higher levels of VEGF, HGF, and BDNF after 1 week of culture (p < 0.05). The BBB score of the P-NSC group was significantly higher than that of the N-NSC group at 7 and 28 days (p < 0.05). Compared with the SCI group, the levels of TNF-α, IL-1β, and IL-6 were significantly reduced after NSC treatment, and the P-NSC group was lower than the N-NSC group (p < 0.05). Compared with the SCI group, the levels of TMIGD1 and TMIGD3 increased. Compared with the N-NSC group, and the levels of TMIGD1 and TMIGD3 increased in the P-NSC group (p < 0.05).

CONCLUSION

P-NSC administration could improve SCI injury, and the levels of TMIGD1 and TMIGD3.

Sodium-Glucose Cotransporter 2 Inhibitors Work as a "Regulator" of Autophagic Activity in Overnutrition Diseases

Several large clinical trials have shown renal and cardioprotective effects of sodium–glucose cotransporter 2 (SGLT2) inhibitors in diabetes patients, and the protective mechanisms need to be elucidated. There have been accumulating studies which report that SGLT2 inhibitors ameliorate autophagy deficiency of multiple organs. In overnutrition diseases, SGLT2 inhibitors affect the autophagy via various signaling pathways, including mammalian target of rapamycin (mTOR), sirtuin 1 (SIRT1), and hypoxia-inducible factor (HIF) pathways. Recently, it turned out that not only stagnation but also overactivation of autophagy causes cellular damages, indicating that therapeutic interventions which simply enhance or stagnate autophagy activity might be a “double-edged sword” in some situations. A small number of studies suggest that SGLT2 inhibitors not only activate but also suppress the autophagy flux depending on the situation, indicating that SGLT2 inhibitors can “regulate” autophagic activity and help achieve the appropriate autophagy flux in each organ. Considering the complicated control and bilateral characteristics of autophagy, the potential of SGLT2 inhibitors as the regulator of autophagic activity would be beneficial in the treatment of autophagy deficiency.

The Potential Relationship Between HIF-1α and Amino Acid Metabolism After Hypoxic Ischemia and Dual Effects on Neurons

Hypoxia inducible factor (HIF) is one of the major transcription factors through which cells and tissues adapt to hypoxic-ischemic injury. However, the specific mechanism by which HIF regulates amino acid metabolism and its effect on neurons during hypoxic ischemia (HI) have remained unclear. This study analyzed the changes in cerebral metabolism of amino acids after HI by using ¹H-MRS and investigated the relationship between the changes in cerebral metabolism of amino acids and HIF-1α as well as the potential effects on neurons. Newborn pigs were used as an HI model in this study. Twenty-eight newborn Yorkshire pigs (male, 1.0-1.5 kg) aged 3-5 days were selected and randomly divided into experimental groups tested at 0-2 h (n = 4), 2-6 h (n = 4), 6-12 h (n = 4), 12-24 h (n = 4), 24-48 h (n = 4), and 48-72 h (n = 4) after HI, and a control group (n = 4). After the modeling was completed, ¹H-MRS imaging was conducted, followed by immunohistochemical staining of HIF-1α, NeuN, and doublecortin (DCX), and immunofluorescence of glutamic oxaloacetic transaminase (GOT)-1, GOT2, glutathione synthase (GS), glutamate-cysteine ligase catalytic subunit (GCLC), and glutamate-cysteine ligase modifier subunit (GCLM) in brain tissues. The expression of HIF-1α exhibited two increases after HI injury. The first time was opposite to the trends of change of GOT2, aspartic acid, and the number of neurons, while the second was consistent with these trends, suggesting that HIF-1α may have a two-way induction effect on neurons by regulating GOT2 after HI. HIF-1α was closely related to GCLM expression, and GSH level was correlated with the number of hippocampal neurons, indicating that HIF-1α may regulate GCLM to promote GSH synthesis and additionally play a neuroprotective role.

Mitophagy: A Novel Therapeutic Target for Treating DN

Diabetic nephropathy (DN) is a common microvascular complication of diabetes and one of the leading causes of end-stage renal disease. Tubular damage is an early change and characteristic of DN, and mitochondrial dysfunction plays an important role in the development of DN. Therefore, the timely removal of damaged mitochondria in tubular cells is an effective treatment strategy for DN. Mitophagy is a type of selective autophagy that ensures the timely elimination of damaged mitochondria to protect cells from oxidative stress. In this review, we summarize our understanding of mitochondrial dysfunction and dynamic disorders in tubular cells in DN and the molecular mechanism of mitophagy. Finally, the role of mitophagy in DN and its feasibility as a therapeutic target for DN are discussed.

Early onset senescence and cognitive impairment in a murine model of repeated mTBI

Mild traumatic brain injury (mTBI) results in broad neurological symptoms and an increased risk of being diagnosed with a neurodegenerative disease later in life. While the immediate oxidative stress response and post-mortem pathology of the injured brain has been well studied, it remains unclear how early pathogenic changes may drive persistent symptoms and confer susceptibility to neurodegeneration. In this study we have used a mouse model of repeated mTBI (rmTBI) to identify early gene expression changes at 24 h or 7 days post-injury (7 dpi). At 24 h post-injury, gene expression of rmTBI mice shows activation of the DNA damage response (DDR) towards double strand DNA breaks, altered calcium and cell–cell signalling, and inhibition of cell death pathways. By 7 dpi, rmTBI mice had a gene expression signature consistent with induction of cellular senescence, activation of neurodegenerative processes, and inhibition of the DDR. At both timepoints gliosis, microgliosis, and axonal damage were evident in the absence of any gross lesion, and by 7 dpi rmTBI also mice had elevated levels of IL1β, p21, 53BP1, DNA2, and p53, supportive of DNA damage-induced cellular senescence. These gene expression changes reflect establishment of processes usually linked to brain aging and suggests that cellular senescence occurs early and most likely prior to the accumulation of toxic proteins. These molecular changes were accompanied by spatial learning and memory deficits in the Morris water maze. To conclude, we have identified DNA damage-induced cellular senescence as a repercussion of repeated mild traumatic brain injury which correlates with cognitive impairment. Pathways involved in senescence may represent viable treatment targets of post-concussive syndrome. Senescence has been proposed to promote neurodegeneration and appears as an effective target to prevent long-term complications of mTBI, such as chronic traumatic encephalopathy and other related neurodegenerative pathologies.

Pramipexole attenuates neuronal injury in Parkinson's disease by targeting miR-96 to activate BNIP3-mediated mitophagy

BACKGROUND

Parkinson's disease is a common neurodegenerative problem. Pramipexole (PPX) plays protective role in Parkinson's disease. Nevertheless, the mechanism of PPX in Parkinson's disease-like neuronal injury is largely uncertain.

METHODS

1-methyl-4-phenylpyridinium (MPP⁺)-stimulated neuronal cells and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced mice were used as the model of Parkinson's disease. MPP⁺-induced neuronal injury was assessed via cell viability, lactic dehydrogenase (LDH) release and apoptosis. microRNA-96 (miR-96) and BCL2/adenovirus E1B 19 kDa interacting protein 3 (BNIP3) abundances were examined by quantitative reverse transcription polymerase chain reaction (qRT-PCR) or Western blotting. Mitophagy was tested by Western blotting and immunofluorescence staining. MPTP-induced neuronal injury in mice was investigated via behavioral tests and TUNEL.

RESULTS

PPX alleviated MPP⁺-induced neuronal injury via increasing cell viability and decreasing LDH release and apoptosis. PPX reversed MPP⁺-induced miR-96 expression and inhibition of mitophagy. miR-96 overexpression or BNIP3 interference weakened the suppressive role of PPX in MPP⁺-induced neuronal injury. miR-96 targeted BNIP3 to inhibit PTEN-induced putative kinase 1 (PINK1)/Parkin signals-mediated mitophagy. miR-96 overexpression promoted MPP⁺-induced neuronal injury via decreasing BNIP3. PPX weakened MPTP-induced neuronal injury in mice via regulating miR-96/BNIP3-mediated mitophagy.

CONCLUSION

PPX mitigated neuronal injury in MPP⁺-induced cells and MPTP-induced mice by activating BNIP3-mediated mitophagy via directly decreasing miR-96.

Role of the neurovascular unit in the process of cerebral ischemic injury

Cerebral ischemic injury exhibits both high morbidity and mortality worldwide. Traditional research of the pathogenesis of cerebral ischemic injury has focused on separate analyses of the involved cell types. In recent years, the neurovascular unit (NVU) mechanism of cerebral ischemic injury has been proposed in modern medicine. Hence, more effective strategies for the treatment of cerebral ischemic injury may be provided through comprehensive analysis of brain cells and the extracellular matrix. However, recent studies that have investigated the function of the NVU in cerebral ischemic injury have been insufficient. In addition, the metabolism and energy conversion of the NVU depend on interactions among multiple cell types, which make it difficult to identify the unique contribution of each cell type. Therefore, in the present review, we comprehensively summarize the regulatory effects and recovery mechanisms of four major cell types (i.e., astrocytes, microglia, brain-microvascular endothelial cells, and neurons) in the NVU under cerebral ischemic injury, as well as discuss the interactions among these cell types in the NVU. Furthermore, we discuss the common signaling pathways and signaling factors that mediate cerebral ischemic injury in the NVU, which may help to provide a theoretical basis for the comprehensive elucidation of cerebral ischemic injury.

Acheron/Larp6 Is a Survival Protein That Protects Skeletal Muscle From Programmed Cell Death During Development

The term programmed cell death (PCD) was coined in 1965 to describe the loss of the intersegmental muscles (ISMs) of moths at the end of metamorphosis. While it was subsequently demonstrated that this hormonally controlled death requires de novo gene expression, the signal transduction pathway that couples hormone action to cell death is largely unknown. Using the ISMs from the tobacco hawkmoth Manduca sexta, we have found that Acheron/LARP6 mRNA is induced ∼1,000-fold on the day the muscles become committed to die. Acheron functions as a survival protein that protects cells until cell death is initiated at eclosion (emergence), at which point it becomes phosphorylated and degraded in response to the peptide Eclosion Hormone (EH). Acheron binds to a novel BH3-only protein that we have named BBH1 (BAD/BNIP3 homology 1). BBH1 accumulates on the day the ISMs become committed to die and is presumably liberated when Acheron is degraded. This is correlated with the release and rapid degradation of cytochrome c and the subsequent demise of the cell. RNAi experiments in the fruit fly Drosophila confirmed that loss of Acheron results in precocious ecdysial muscle death while targeting BBH1 prevents death altogether. Acheron is highly expressed in neurons and muscles in humans and drives metastatic processes in some cancers, suggesting that it may represent a novel survival protein that protects terminally differentiated cells and some cancers from death.

Expression profile of circular RNAs in the peripheral blood of neonates with hypoxic‑ischemic encephalopathy

Circular RNAs (circRNAs) are a class of non-coding RNAs that participate in various biological processes. However, the function of circRNAs in neonatal hypoxic‑ischemic encephalopathy (HIE) is not fully understood. In the present study, the differentially expressed circRNAs in the peripheral blood of neonates with HIE and control samples were characterized by a microarray assay. A total of 456 circRNAs were significantly differentially expressed in the peripheral blood of neonates with HIE, with 250 upregulated and 206 downregulated circRNAs in HIE compared with the control samples. Reverse transcription‑quantitative PCR was used to investigate specific circRNAs. Gene Ontology, and Kyoto Encyclopedia of Genes and Genomes pathway analyses were used to determine the function of the parent genes of the dysregulated circRNAs. In addition, microRNAs that may be associated with specific circRNAs were predicted using miRanda. Collectively, the present results indicated the potential importance of circRNAs in the peripheral blood of neonates with HIE.