Pharmacological HIF1 Inhibition Eliminates Downregulation of the Pentose Phosphate Pathway and Prevents Neuronal Apoptosis in Rat Hippocampus Caused by Severe Hypoxia

Low oxygen in inspired air causes severe cerebrocortical hypoxia and cell death in the cerebral cortex of awake rats

Type 1 respiratory failure (T1RF) is associated with secondary acute brain injury (sABI). The underlying mechanisms of sABI could include injury to brain cells mediated either by hypoxia or by lung injury-triggered inflammation. To elucidate to what extent T1RF causes hypoxia and a consequent hypoxic injury in the brain in the absence of lung injury, we exposed healthy, conscious Sprague-Dawley rats to 48 h long low partial pressure of O2 in inspired air (PiO2) (7.5-8 % O2 in N2, CO2 < 0.5 %, normal barometric pressure) and measured the partial pressure of oxygen in the premotor cortex (PtO2), cerebral blood flow (CBF), lactate concentrations, and cell death. Low PiO2 significantly affected PtO2, which was 52.3 (SD 2.1) mmHg when PiO2 was normal but declined to 6.4 (SD 3.8) mmHg when PiO2 was low for 1 h. This was accompanied by increased lactate concentrations in plasma, CSF, and premotor cortex. Low PiO2 elevated the number of dead cells in the cerebral cortex from 5.6 (SD 4.8) % (when PiO2 was normal) to 20.5 (SD 4.1) % and 32.37 (SD 6.5) % after 24 h and 48 h exposure to low PiO2, respectively. The Mann-Kendall test could not detect any monotonic increase or decrease in pial blood flow during the 48 h exposure to low PiO2. In summary, our findings suggest that exposure to low PiO2 caused a severe hypoxia in the cerebral cortex, which triggers a massive cell death. Since these conditions mimic T1RF, hypoxic injury could be an important underlying cause of T1RF-induced sABI.

Neuroadaptive Biochemical Mechanisms of Remote Ischemic Conditioning

This review summarizes the currently known biochemical neuroadaptive mechanisms of remote ischemic conditioning. In particular, it focuses on the significance of the pro-adaptive effects of remote ischemic conditioning which allow for the prevention of the neurological and cognitive impairments associated with hippocampal dysregulation after brain damage. The neuroimmunohumoral pathway transmitting a conditioning stimulus, as well as the molecular basis of the early and delayed phases of neuroprotection, including anti-apoptotic, anti-oxidant, and anti-inflammatory components, are also outlined. Based on the close interplay between the effects of ischemia, especially those mediated by interaction of hypoxia-inducible factors (HIFs) and steroid hormones, the involvement of the hypothalamic-pituitary-adrenocortical system in remote ischemic conditioning is also discussed.

HIF-1α promotes astrocytic production of macrophage migration inhibitory factor following spinal cord injury

BACKGROUND

Macrophage migration inhibitory factor (MIF) is an important mediator of neuropathology in various central nervous system (CNS) diseases. However, little is known about its inducers for production from the nerve cells, as well as the underlying regulatory mechanism. Injury-induced HIF-1α has been shown to exacerbate neuroinflammation by activating multiple downstream target molecules. It is postulated that HIF-1α is involved in the regulation of MIF following spinal cord injury (SCI).

METHODS

SCI model of Sprague-Dawley rats was established by cord contusion at T8-T10. The dynamic changes of HIF-1α and MIF protein levels at lesion site of rat spinal cord were determined by Western blot. The specific cell types of HIF-1α and MIF expression were examined by immunostaining. Primary astrocytes were isolated from the spinal cord, cultured and stimulated with various agonist or inhibitor of HIF-1α for analysis of HIF-1α-mediated expression of MIF. Luciferase report assay was used to determine the relationship between HIF-1α and MIF. The Basso, Beattie, and Bresnahan (BBB) locomotor scale was used to assess the locomotor function following SCI.

RESULTS

The protein levels of HIF-1α and MIF at lesion site were significantly elevated by SCI. Immunofluorescence demonstrated that both HIF-1α and MIF were abundantly expressed in the astrocytes of the spinal cord. By using various agonists or inhibitors of HIF-1α, it was shown that HIF-1α sufficiently induced astrocytic production of MIF. Mechanistically, HIF-1α promoted MIF expression through interaction with MIF promoter. Inhibition of HIF-1α activity using specific inhibitor markedly reduced the protein levels of MIF at lesion site following SCI, which in turn favored for the functional recovery.

CONCLUSION

SCI-induced activation of HIF-1α is able to promote MIF production from astrocytes. Our results have provided new clues for SCI-induced production of DAMPs, which may be helpful for clinical treatment of neuroinflammation.

The Brain at High Altitude: From Molecular Signaling to Cognitive Performance

The brain requires over one-fifth of the total body oxygen demand for normal functioning. At high altitude (HA), the lower atmospheric oxygen pressure inevitably challenges the brain, affecting voluntary spatial attention, cognitive processing, and attention speed after short-term, long-term, or lifespan exposure. Molecular responses to HA are controlled mainly by hypoxia-inducible factors. This review aims to summarize the cellular, metabolic, and functional alterations in the brain at HA with a focus on the role of hypoxia-inducible factors in controlling the hypoxic ventilatory response, neuronal survival, metabolism, neurogenesis, synaptogenesis, and plasticity.

Protective effects on acute hypoxic-ischemic brain damage in mfat-1 transgenic mice by alleviating neuroinflammation

Acute hypoxic-ischemic brain damage (HIBD) mainly occurs in adults as a result of perioperative cardiac arrest and asphyxia. The benefits of n-3 polyunsaturated fatty acids (n-3 PUFAs) in maintaining brain growth and development are well documented. However, possible protective targets and underlying mechanisms of mfat-1 mice on HIBD require further investigation. The mfat-1 transgenic mice exhibited protective effects on HIBD, as indicated by reduced infarct range and improved neurobehavioral defects. RNA-seq analysis showed that multiple pathways and targets were involved in this process, with the anti-inflammatory pathway as the most significant. This study has shown for the first time that mfat-1 has protective effects on HIBD in mice. Activation of a G protein-coupled receptor 120 (GPR120)-related anti-inflammatory pathway may be associated with perioperative and postoperative complications, thus innovating clinical intervention strategy may potentially benefit patients with HIBD.

Yap-Hippo Signaling Activates Mitochondrial Protection and Sustains Breast Cancer Viability under Hypoxic Stress

Yes-associated protein (Yap) is a transcriptional regulator that upregulates oncogenes and downregulates tumor repressor genes. In this study, we analyzed protein expression, RNA transcription, and signaling pathways to determine the function and mechanism of Yap in breast cancer survival during hypoxic stress. Yap transcription was drastically upregulated by hypoxia in a time-dependent manner. siRNA-mediated Yap knockdown attenuated breast cancer viability and impaired cell proliferation under hypoxic conditions. Yap knockdown induced mitochondrial stress, including mitochondrial membrane potential reduction, mitochondrial oxidative stress, and ATP exhaustion after exposure to hypoxia. It also repressed mitochondrial protective systems, including mitophagy and mitochondrial fusion upon exposure to hypoxia. Finally, our data showed that Yap knockdown suppresses MCF-7 cell migration by inhibiting F-actin transcription and promoting lamellipodium degradation under hypoxic stress. Taken together, Yap maintenance of mitochondrial function and activation of F-actin/lamellipodium signaling is required for breast cancer survival, migration, and proliferation under hypoxic stress.

Hypoxia-inducible transcription factor-1α inhibition by topotecan protects against lipopolysaccharide-induced inflammation and apoptosis of cardiomyocytes

Background

Myocarditis, an inflammatory disease of the myocardium, is a serious hazard to human life due to the expansion of inflammatory lesions in the myocardium. The aim of this study was to investigate the role of hypoxia-inducible transcription factor (HIF)-1α and its inhibitor topotecan in the pathogenesis of myocarditis.

Methods

H9c2 cardiomyoblasts was stimulated with lipopolysaccharide (LPS) to simulate myocarditis model in vitro. The levels of myocardial damage markers were determined using commercially available kits. Western blotting was used to evaluate HIF-1α expression after LPS challenge. Then, after HIF-1α silencing, the contents of inflammatory factors were determined with enzyme-linked immunosorbent assay (ELISA). Cell viability was tested by means of a cell counting kit-8 (CCK-8) assay. Cell apoptosis was assessed by flow cytometry, and the expression of apoptotic proteins was examined using western blot analysis. Subsequently, HIF-1α was overexpressed and topotecan was employed to treat H9c2 cells under LPS exposure condition. The biological functions were detected again.

Results

LPS significantly elevated the levels of lactate dehydrogenase (LDH), creatine kinase-MB (CK-MB) and cardiac troponin-I (cTn-I) in supernatant of H9c2 cell lysates. Additionally, LPS led to the notably upregulated expression of HIF-1α. HIF-1α-knockdown markedly decreased the concentrations of tumor necrosis factor (TNF)-α, interleukin (IL)-6 and IL-8 compared with the LPS-induced group. Moreover, the cell viability was conspicuously enhanced and cell apoptotic ratio was remarkably reduced, accompanied by downregulated expression of Bax, Bim, caspase 3 and caspase 9 after HIF-1α silencing. Consistently, HIF-1α gain-of-function significantly promoted the production of inflammatory cytokines and cell apoptosis, which was partially counteracted by topotecan administration.

Conclusion

To conclude, these findings demonstrated that HIF-1α inhibition by topotecan ameliorates LPS-induced myocarditis in vitro, providing a new approach in the treatment of myocarditis.

Pulmonary arterial hypertension induces the release of circulating extracellular vesicles with oxidative content and alters redox and mitochondrial homeostasis in the brains of rats

Pulmonary arterial hypertension (PAH) is characterized by increased resistance of the pulmonary vasculature and afterload imposed on the right ventricle (RV). Two major contributors to the worsening of this disease are oxidative stress and mitochondrial impairment. This study aimed to explore the effects of monocrotaline (MCT)-induced PAH on redox and mitochondrial homeostasis in the RV and brain and how circulating extracellular vesicle (EV) signaling is related to these phenomena. Wistar rats were divided into control and MCT groups (60 mg/kg, intraperitoneal), and EVs were isolated from blood on the day of euthanasia (21 days after MCT injections). There was an oxidative imbalance in the RV, brain, and EVs of MCT rats. PAH impaired mitochondrial function in the RV, as seen by a decrease in the activities of mitochondrial complex II and citrate synthase and manganese superoxide dismutase (MnSOD) protein expression, but this function was preserved in the brain. The key regulators of mitochondrial biogenesis, namely, proliferator-activated receptor gamma coactivator 1-alpha and sirtuin 1, were poorly expressed in the EVs of MCT rats, and this result was positively correlated with MnSOD expression in the RV and negatively correlated with MnSOD expression in the brain. Based on these findings, we can conclude that the RV is severely impacted by the development of PAH, but this pathological injury may signal the release of circulating EVs that communicate with different organs, such as the brain, helping to prevent further damage through the upregulation of proteins involved in redox and mitochondrial function.

Hypoxia-Inducible Factor (HIF) in Ischemic Stroke and Neurodegenerative Disease

Hypoxia is one of the most common pathological conditions, which can be induced by multiple events, including ischemic injury, trauma, inflammation, tumors, etc. The body's adaptation to hypoxia is a highly important phenomenon in both health and disease. Most cellular responses to hypoxia are associated with a family of transcription factors called hypoxia-inducible factors (HIFs), which induce the expression of a wide range of genes that help cells adapt to a hypoxic environment. Basic mechanisms of adaptation to hypoxia, and particularly HIF functions, have being extensively studied over recent decades, leading to the 2019 Nobel Prize in Physiology or Medicine. Based on their pivotal physiological importance, HIFs are attracting increasing attention as a new potential target for treating a large number of hypoxia-associated diseases. Most of the experimental work related to HIFs has focused on roles in the liver and kidney. However, increasing evidence clearly demonstrates that HIF-based responses represent an universal adaptation mechanism in all tissue types, including the central nervous system (CNS). In the CNS, HIFs are critically involved in the regulation of neurogenesis, nerve cell differentiation, and neuronal apoptosis. In this mini-review, we provide an overview of the complex role of HIF-1 in the adaptation of neurons and glia cells to hypoxia, with a focus on its potential involvement into various neuronal pathologies and on its possible role as a novel therapeutic target.

Glucocorticoid-Dependent Mechanisms of Brain Tolerance to Hypoxia

Adaptation of organisms to stressors is coordinated by the hypothalamic-pituitary-adrenal axis (HPA), which involves glucocorticoids (GCs) and glucocorticoid receptors (GRs). Although the effects of GCs are well characterized, their impact on brain adaptation to hypoxia/ischemia is still understudied. The brain is not only the most susceptible to hypoxic injury, but also vulnerable to GC-induced damage, which makes studying the mechanisms of brain hypoxic tolerance and resistance to stress-related elevation of GCs of great importance. Cross-talk between the molecular mechanisms activated in neuronal cells by hypoxia and GCs provides a platform for developing the most effective and safe means for prevention and treatment of hypoxia-induced brain damage, including hypoxic pre- and post-conditioning. Taking into account that hypoxia- and GC-induced reprogramming significantly affects the development of organisms during embryogenesis, studies of the effects of prenatal and neonatal hypoxia on health in later life are of particular interest. This mini review discusses the accumulated data on the dynamics of the HPA activation in injurious and non-injurious hypoxia, the role of the brain GRs in these processes, interaction of GCs and hypoxia-inducible factor HIF-1, as well as cross-talk between GC and hypoxic signaling. It also identifies underdeveloped areas and suggests directions for further prospective studies.

17β-oestradiol alleviates endoplasmic reticulum stress injury induced by chronic cerebral hypoperfusion through the Haemoglobin/HIF 1α signalling pathway in ovariectomized rats

Endoplasmic reticulum stress (ERS) is known to be an essential target in protecting against ischaemic brain injury. In this study, using a vascular dementia (VaD) animal model induced by bilateral common carotid artery occlusion (BCCAO), we evaluated the effect and mechanism of 17β-oestradiol (E2) against VaD by inhibiting ERS at the early stage (14 d, 21 d, 28 d) and late stage (3 m) after BCCAO in the hippocampal CA1 region of ovariectomized rats. The results showed that the activation of the PERK-eIF2α-ATF4-CHOP axis, a typical ERS pathway, was significantly increased at the early and late stages after BCCAO. JNK (c-Jun N-terminal kinase)-cJun, a pro-death pathway, also displayed the same pattern as the ERS axis. E2 treatment profoundly suppressed the impairments caused by BCCAO. Further mechanistic studies revealed that cerebral blood flow (CBF) was sharply decreased at 14 d and returned to the normal level at 21 d after BCCAO. E2 could not change CBF, while it unexpectedly enhanced the ability to carry oxygen. This is evidenced by the fact that the protein expression of haemoglobin α/β (Hα/β), an oxygen carrier, robustly increased at BCCAO 21 d and 3 m after E2 treatment. The oxygen carrier increased strongly after 21 d and 3 m of BCCAO treated with E2. Moreover, E2 correspondingly enhanced the protein expression of hypoxia-inducible factor 1α (HIF 1α) in both the early and late stage after BCCAO in the hippocampal CA1 region. Finally, E2 administration markedly decreased the activities of caspase-8, caspase-3, and caspase-12 and increased the number of NeuN-positive cells. These findings suggest that E2 serves as a neuroprotectant to alleviate VaD by suppressing ERS injury involving the haemoglobin/HIF 1α signalling pathway.

Brain Energy Deficit as a Source of Oxidative Stress in Migraine: A Molecular Basis for Migraine Susceptibility

People with migraine are prone to a brain energy deficit between attacks, through increased energy demand (hyperexcitable brain) or decreased supply (mitochondrial impairment). However, it is uncertain how this precipitates an acute attack. Here, the central role of oxidative stress is adduced. Specifically, neurons' antioxidant defenses rest ultimately on internally generated NADPH (reduced nicotinamide adenine dinucleotide phosphate), whose levels are tightly coupled to energy production. Mitochondrial NADPH is produced primarily by enzymes involved in energy generation, including isocitrate dehydrogenase of the Krebs (tricarboxylic acid) cycle; and an enzyme, nicotinamide nucleotide transhydrogenase (NNT), that depends on the Krebs cycle and oxidative phosphorylation to function, and that works in reverse, consuming antioxidants, when energy generation fails. In migraine aura, cortical spreading depression (CSD) causes an initial severe drop in level of NADH (reduced nicotinamide adenine dinucleotide), causing NNT to impair antioxidant defense. This is followed by functional hypoxia and a rebound in NADH, in which the electron transport chain overproduces oxidants. In migraine without aura, a similar biphasic fluctuation in NADH very likely generates oxidants in cortical regions farthest from capillaries and penetrating arterioles. Thus, the perturbations in brain energy demand and/or production seen in migraine are likely sufficient to cause oxidative stress, triggering an attack through oxidant-sensing nociceptive ion channels. Implications are discussed for the development of new classes of migraine preventives, for the current use of C57BL/6J mice (which lack NNT) in preclinical studies of migraine, for how a microembolism initiates CSD, and for how CSD can trigger a migraine.

Exploration of the potential mechanism of the Tao Hong Si Wu Decoction for the treatment of postpartum blood stasis based on network pharmacology and in vivo experimental verification

ETHNOPHARMACOLOGICAL RELEVANCE

Tao Hong Si Wu Decoction (THSWD) is a traditional prescription for blood management in traditional Chinese medicine, THSWD consists of Paeoniae Radix Alba (Paeonia lactiflora Pall.), Rehmanniae Radix Praeparata (Rehmannia glutinosa (Gaertn.) DC.), Angelicae Sinensis Radix (Angelica sinensis (Oliv.) Diels), Chuanxiong Rhizoma (Conioselinum anthriscoides 'Chuanxiong'), Persicae Seman (Prunus persica (L.) Batsch) and Carthami Flos (Carthamus tinctorius L.) at a weight ratio of 3: 4: 3: 2: 3: 2. THSWD is a commonly used prescription in the treatment of postpartum blood stasis disease.

AIM OF THE STUDY

To explore the potential mechanism of THSWD for the treatment of postpartum blood stasis using network pharmacology and experimental research.

MATERIALS AND METHODS

We extracted the active ingredients and targets in THSWD from the Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform (TCMSP), and constructed a herbs-ingredients-targets-disease-network, devised a protein-protein interaction (PPI) network, performed GO enrichment analysis, and performed Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis to discover potential treatment mechanisms. A postpartum blood stasis model was established in rats, and the results of network pharmacology were verified by in vivo experiments.

RESULTS

The results showed that 69 potential active ingredients and 207 THSWD target genes for the treatment of postpartum blood stasis disease were obtained after ADME filtering analysis. The targets were enriched in multiple gene functions and different signaling pathways. By exploring various different signaling pathways, it was found that mitochondrial regulation of oxidative stress plays a potentially important role in the treatment of postpartum blood stasis with THSWD. Compared to model group, THSWD alleviated mitochondrial damage, decreased levels of oxidative stress in the rat model of postpartum blood stasis and reduced apoptosis in uterine cells.

CONCLUSION

The therapeutic effect of THSWD on postpartum blood stasis is likely related to mitochondrial regulation of oxidative stress, which paves the way for further research investigating its mechanisms.

MicroRNA-489-3p plays a significant role in congenital hypothyroidism through regulating neuronal cell apoptosis via targeting translationally controlled tumor protein 1

Accumulating reports have indicated that congenital hypothyroidism (CH) is an endocrine disorder caused by underdeveloped thyroid gland or thyroid dyshormonogenesis. It has been also reported that certain microRNAs (miRNAs) may exert protective effects against the development of CH. However, whether miR-489-3p regulates CH progression remains unclear. The aim of the present study was to investigate the effects of miR-489-3p on CH and elucidate the underlying mechanisms. Therefore, Sprague Dawley rats were injected with propylthiouracil (50 mg/day) to establish a CH model. Reverse transcription-quantitative PCR (RT-qPCR) assay demonstrated that miR-489-3p was upregulated in the hippocampal tissues of CH rats. Furthermore, the TargetScan software was employed to predict the target gene of miR-489-3p, and a dual luciferase reporter assay revealed that translationally controlled tumor protein 1 (TPT1) was directly targeted by miR-489-3p. Additionally, RT-qPCR and western blot assays suggested that TPT1 was markedly downregulated in the hippocampal tissues of CH rats compared with control rats. In addition, inhibitor control, miR-489-3p inhibitor, control-shRNA or TPT1-shRNA were injected into CH rats. The results of the open-field and forced swimming tests revealed that miR-489-3p inhibitor notably improved the behavior of CH rats. Flow cytometry was applied to explore the effects of miR-489-3p inhibitor on neuronal cell apoptosis, and the findings indicated that miR-489-3p inhibitor attenuated CH-induced neuronal cell apoptosis, whereas these effects were reversed by treatment with miR-489-3p inhibitor and TPT1-shRNA. Finally, the function of miR-489-3p in neuronal cells was investigated in vitro. Neuronal cell viability, apoptosis and the expression of apoptosis-related proteins were determined using MTT assay, flow cytometry and western blot analysis, respectively. The results demonstrated that miR-489-3p inhibitor enhanced cell viability, suppressed apoptosis and upregulated Pim-3, phosphorylated (p)-Bad (Ser112) and Bcl-xL expression. Rescue experiments indicated that these effects were reversed following silencing of TPT1. Taken together, the findings of the present study demonstrated that miR-489-3p inhibitor could relieve CH-induced neurological damage through regulating TPT1 expression.

The New CIC Mutation Associates with Mental Retardation and Severity of Seizure in Turkish Child with a Rare Class I Glucose-6-Phosphate Dehydrogenase Deficiency

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is an X-linked recessive disease that causes acute or chronic hemolytic anemia and potentially leads to severe jaundice in response to oxidative agents. Capicua transcriptional repressor (CIC) is an important gene associated with mental retardation, autosomal dominant 45. Affiliated tissues including skin, brain, bone, and related phenotypes are intellectual disability and seizures. Clinical, biochemical, and whole exome analysis are carried out in a Turkish family. Mutation analysis of G6PD and CIC genes by Sanger sequencing in the whole family was carried out to reveal the effect of these mutations on the patient's clinical outcome. Here, we present the case of epilepsy in an 8-year-old child with a hemizygous variation in G6PD gene and heterozygous mutation in CIC gene, resulting in focal epileptiform activity and hypsarrhythmia in electroencephalography (EEG), seizures, psychomotor retardation, speech impairment, intellectual disability, developmental regression, and learning difficulties. Whole exome sequencing confirmed the diagnosis of X-linked increased susceptibility for hemolytic anemia due to G6PD deficiency and mental retardation type 45 due to CIC variant, which explained the development of epileptic seizures. Considering CIC variant and relevant relation with the severity and course of the disease, G6PD mutations sustained through the family are defined as hereditary. Our findings could represent the importance of variants found in G6PD as well as CIC genes linked to the severity of epilepsy, which was presumed based on the significant changes in protein configuration.