Oxygen sensing, homeostasis, and disease

Molecular mechanism of infectious spleen and kidney necrosis virus in manipulating the hypoxia-inducible factor pathway to augment virus replication

Infectious spleen and kidney necrosis virus (ISKNV), a member of the genus Megalocytivirus in the family Iridoviridae, can infect over 50 fish species and cause significant economic losses in Asia. Our previous study showed that hypoxia triggers the hypoxia-inducible factor pathway (HIF-pathway), leading to increased replication of ISKNV through promoting the upregulation of viral hypoxic response genes like orf077r. This study delved into the molecular mechanism of how ISKNV manipulates the HIF-pathway to enhance its replication. In vitro and in vivo experiments confirmed that ISKNV infection activated the HIF-pathway, which in turn promoted ISKNV replication. These findings suggest that ISKNV actively manipulates the HIF-pathway. Co-immunoprecipitation experiments revealed that the ISKNV-encoded protein VP077R interacts with the Von Hippel-Lindau (VHL) protein at the HIF-binding region, competitively inhibiting the interaction of HIF-1α with VHL. This prevents HIF degradation and activates the HIF-pathway. Furthermore, VP077R interacts with factor-inhibiting HIF (FIH), recruiting FIH and S-phase kinase-associated protein 1 (Skp1) to form an FIH - VP077R - Skp1 complex. This complex promotes FIH protein degradation via ubiquitination, further activating the HIF-pathway. These findings indicated that ISKNV takes over the HIF-pathway by releasing two "brakes" on this pathway (VHL and FIH) via VP077R, facilitating virus replication. We speculate that hypoxia initiates a positive feedback loop between ISKNV VP077R and the HIF pathway, leading to the outbreak of ISKNV disease. This work offers valuable insights into the complex interactions between the environment, host, and virus.

Ameliorative potential of eriocitrin against cadmium instigated hepatotoxicity in rats via regulating Nrf2/keap1 pathway

BACKGROUND

Cadmium (Cd) is a hazardous heavy metal that adversely affects the vital body organs particularly liver. Eriocitrin (ERCN) is a plant-based flavonoid that is well-known for its wide range of pharmacological potential. This research trial was aimed to determine the ameliorative potential of ERCN against Cd provoked hepatotoxicity in rats.

METHODOLOGY

Twenty-four rats (Rattus norvegicus) were apportioned into control, Cd treated (5 mg/kg), Cd (5 mg/kg) + ERCN (25 mg/kg) and only ERCN (25 mg/kg) administrated group. Expressions of Nrf2/Keap1 pathway and apoptotic markers were assessed through qRT-PCR. The levels of inflammatory and liver function markers were evaluated by using standard ELISA kits.

KEY FINDINGS

Cd exposure reduced the expression of Nrf2 and anti-oxidant genes as well as the activity of catalase (CAT), glutathione reductase (GSR), superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione S-transferase (GST) and glutathione (GSH) contents while escalating the expression of Keap1. Furthermore, Cd intoxication augmented malondialdehyde (MDA) and reactive oxygen species (ROS) levels in hepatic tissues. Exposure to Cd resulted in a notable elevation in the levels of alanine transaminase (ALT), alkaline phosphatase (ALP) and aspartate aminotransferase (AST). Cd administration upregulated nuclear factor-kappa B (NF-κB), interleukin-1 beta (IL-1β), tumor necrosis factor-alpha (TNF-α), and interleukin-6 (IL-6) levels as well as cyclooxygenase-2 (COX-2) activity. Furthermore, Cd administration upsurged Bax and Caspase-3 expression while reducing the expression of Bcl-2. Moreover, Cd intoxication disrupted the normal architecture of hepatic tissues. However, supplementation of ERCN significantly (p < 0.05) ameliorated the aforementioned disruptions induced by Cd intoxication.

CONCLUSION

ERCN treatment remarkably ameliorated the hepatic tissues owing to its antioxidant, anti-inflammatory, and anti-apoptotic potentials. These findings underscore the therapeutic potential of ERCN to counteract the adverse effects of environmental pollutants on hepatic tissues.

HSPA12A maintains aerobic glycolytic homeostasis and Histone3 lactylation in cardiomyocytes to attenuate myocardial ischemia/reperfusion injury

Myocardial ischemia/reperfusion (MI/R) injury is a major cause of adverse outcomes of revascularization following myocardial infarction. Anaerobic glycolysis during myocardial ischemia is well studied, but the role of aerobic glycolysis during the early phase of reperfusion is incompletely understood. Lactylation of Histone H3 (H3) is an epigenetic indicator of the glycolytic switch. Heat shock protein A12A (HSPA12A) is an atypic member of the HSP70 family. In the present study, we report that, during reperfusion following myocardial ischemia, HSPA12A was downregulated and aerobic glycolytic flux was decreased in cardiomyocytes. Notably, HSPA12A KO in mice exacerbated MI/R-induced aerobic glycolysis decrease, cardiomyocyte death, and cardiac dysfunction. Gain- and loss-of-function studies demonstrated that HSPA12A was required to support cardiomyocyte survival upon hypoxia/reoxygenation (H/R) challenge and that its protective effects were mediated by maintaining aerobic glycolytic homeostasis for H3 lactylation. Further analyses revealed that HSPA12A increased Smurf1-mediated Hif1α protein stability, thus increasing glycolytic gene expression to maintain appropriate aerobic glycolytic activity to sustain H3 lactylation during reperfusion and, ultimately, improving cardiomyocyte survival to attenuate MI/R injury.

Protein neddylation and its role in health and diseases

NEDD8 (Neural precursor cell expressed developmentally downregulated protein 8) is an ubiquitin-like protein that is covalently attached to a lysine residue of a protein substrate through a process known as neddylation, catalyzed by the enzyme cascade, namely NEDD8 activating enzyme (E1), NEDD8 conjugating enzyme (E2), and NEDD8 ligase (E3). The substrates of neddylation are categorized into cullins and non-cullin proteins. Neddylation of cullins activates CRLs (cullin RING ligases), the largest family of E3 ligases, whereas neddylation of non-cullin substrates alters their stability and activity, as well as subcellular localization. Significantly, the neddylation pathway and/or many neddylation substrates are abnormally activated or over-expressed in various human diseases, such as metabolic disorders, liver dysfunction, neurodegenerative disorders, and cancers, among others. Thus, targeting neddylation becomes an attractive strategy for the treatment of these diseases. In this review, we first provide a general introduction on the neddylation cascade, its biochemical process and regulation, and the crystal structures of neddylation enzymes in complex with cullin substrates; then discuss how neddylation governs various key biological processes via the modification of cullins and non-cullin substrates. We further review the literature data on dysregulated neddylation in several human diseases, particularly cancer, followed by an outline of current efforts in the discovery of small molecule inhibitors of neddylation as a promising therapeutic approach. Finally, few perspectives were proposed for extensive future investigations.

Rapid evaluation of PHD2 inhibitory activity of natural products based on capillary electrophoresis online stacking strategy

Prolyl hydroxylase domain 2 (PHD2) is an important enzyme in the human body that perceives changes in oxygen concentration and regulates response in hypoxic environments. Evaluation of PHD2 inhibitory activity of natural products is crucial for drug development of hypoxia related diseases. At present, the detection of low concentration of α-ketoglutaric acid (the substrate of PHD2 enzymatic reaction) requires derivatization reactions or sample pretreatment, which undoubtedly increases the workload of PHD2 inhibitory activity evaluation. In this paper, a direct detection approach of α-ketoglutaric acid was established by using the online stacking strategy of capillary electrophoresis to evaluate the PHD2 inhibitory activity of natural products. Under optimized conditions, detection of a single sample can be achieved within 2 min. By calculation, the intraday precision RSD of the apparent electrophoretic mobility and peak areas of α-ketoglutaric acid are 0.92 % and 0.79 %, respectively, and the interday RSD were 1.27 % and 0.96 % respectively. The recoveries of the present approach were 97.9-105.2 %, and the LOQ and LOD were 2.0 μM and 5.0 μM, respectively. Furthermore, this approach was applied for the evaluation of inhibitory activity of PHD2 for 13 natural products, and PHD2 inhibitory activity of salvianolic acid A was firstly reported. The present work not only realizes evaluation of PHD2 inhibitory activity through direct detection of α-ketoglutaric acid, but also provides technical support for the discovery of potential drug molecules in hypoxia related diseases.

Hypoxia delays steroid-induced developmental maturation in Drosophila by suppressing EGF signaling

Animals often grow and develop in unpredictable environments where factors like food availability, temperature, and oxygen levels can fluctuate dramatically. To ensure proper sexual maturation into adulthood, juvenile animals need to adapt their growth and developmental rates to these fluctuating environmental conditions. Failure to do so can result in impaired maturation and incorrect body size. Here we describe a mechanism by which Drosophila larvae adapt their development in low oxygen (hypoxia). During normal development, larvae grow and increase in mass until they reach critical weight (CW), after which point a neuroendocrine circuit triggers the production of the steroid hormone ecdysone from the prothoracic gland (PG), which promotes maturation to the pupal stage. However, when raised in hypoxia (5% oxygen), larvae slow their growth and delay their maturation to the pupal stage. We find that, although hypoxia delays the attainment of CW, the maturation delay occurs mainly because of hypoxia acting late in development to suppress ecdysone production. This suppression operates through a distinct mechanism from nutrient deprivation, occurs independently of HIF-1 alpha and does not involve dilp8 or modulation of Ptth, the main neuropeptide that initiates ecdysone production in the PG. Instead, we find that hypoxia lowers the expression of the EGF ligand, spitz, and that the delay in maturation occurs due to reduced EGFR/ERK signaling in the PG. Our study sheds light on how animals can adjust their development rate in response to changing oxygen levels in their environment. Given that hypoxia is a feature of both normal physiology and many diseases, our findings have important implications for understanding how low oxygen levels may impact animal development in both normal and pathological situations.

Downregulation of miR-337-3p in hypoxia/reoxygenation neuroblastoma cells increases KCTD11 expression

Neurodegeneration is linked to the progressive loss of neural function and is associated with several diseases. Hypoxia is a hallmark in many of these diseases, and several therapies have been developed to treat this disease, including gene expression therapies that should be tightly controlled to avoid side effects. Cells experiencing hypoxia undergo a series of physiological responses that are induced by the activation of various transcription factors. Modulation of microRNA (miRNA) expression to alter transcriptional regulation has been demonstrated to be beneficial in treating multiple diseases, and in this study, we therefore explored potential miRNA candidates that could influence hypoxia-induced nerve cell death. Our data suggest that in mouse neuroblasts Neuro-2a cells with hypoxia/reoxygenation (H/R), miR-337-3p is downregulated to increase the expression of Potassium channel tetramerization domain containing 11 (KCTD11) and subsequently promote apoptosis. Here, we demonstrate for the first time that KCTD11 plays a role in the cellular response to hypoxia, and we also provide a possible regulatory mechanism by identifying the axis of miR-337-3p/KCTD11 as a promising candidate modulator of nerve cell survival after H/R exposure.

Oxy-Inflammation in Humans during Underwater Activities

Underwater activities are characterized by an imbalance between reactive oxygen/nitrogen species (RONS) and antioxidant mechanisms, which can be associated with an inflammatory response, depending on O2 availability. This review explores the oxidative stress mechanisms and related inflammation status (Oxy-Inflammation) in underwater activities such as breath-hold (BH) diving, Self-Contained Underwater Breathing Apparatus (SCUBA) and Closed-Circuit Rebreather (CCR) diving, and saturation diving. Divers are exposed to hypoxic and hyperoxic conditions, amplified by environmental conditions, hyperbaric pressure, cold water, different types of breathing gases, and air/non-air mixtures. The "diving response", including physiological adaptation, cardiovascular stress, increased arterial blood pressure, peripheral vasoconstriction, altered blood gas values, and risk of bubble formation during decompression, are reported.

Reprogramming of the developing heart by Hif1a-deficient sympathetic system and maternal diabetes exposure

Introduction

Maternal diabetes is a recognized risk factor for both short-term and long-term complications in offspring. Beyond the direct teratogenicity of maternal diabetes, the intrauterine environment can influence the offspring's cardiovascular health. Abnormalities in the cardiac sympathetic system are implicated in conditions such as sudden infant death syndrome, cardiac arrhythmic death, heart failure, and certain congenital heart defects in children from diabetic pregnancies. However, the mechanisms by which maternal diabetes affects the development of the cardiac sympathetic system and, consequently, heightens health risks and predisposes to cardiovascular disease remain poorly understood.

Methods and results

In the mouse model, we performed a comprehensive analysis of the combined impact of a Hif1a-deficient sympathetic system and the maternal diabetes environment on both heart development and the formation of the cardiac sympathetic system. The synergic negative effect of exposure to maternal diabetes and Hif1a deficiency resulted in the most pronounced deficit in cardiac sympathetic innervation and the development of the adrenal medulla. Abnormalities in the cardiac sympathetic system were accompanied by a smaller heart, reduced ventricular wall thickness, and dilated subepicardial veins and coronary arteries in the myocardium, along with anomalies in the branching and connections of the main coronary arteries. Transcriptional profiling by RNA sequencing (RNA-seq) revealed significant transcriptome changes in Hif1a-deficient sympathetic neurons, primarily associated with cell cycle regulation, proliferation, and mitosis, explaining the shrinkage of the sympathetic neuron population.

Discussion

Our data demonstrate that a failure to adequately activate the HIF-1α regulatory pathway, particularly in the context of maternal diabetes, may contribute to abnormalities in the cardiac sympathetic system. In conclusion, our findings indicate that the interplay between deficiencies in the cardiac sympathetic system and subtle structural alternations in the vasculature, microvasculature, and myocardium during heart development not only increases the risk of cardiovascular disease but also diminishes the adaptability to the stress associated with the transition to extrauterine life, thus increasing the risk of neonatal death.

Hypoxia suppresses glucose-induced increases in collective cell migration in vascular endothelial cell monolayers

Blood glucose levels fluctuate during daily life, and the oxygen concentration is low compared to the atmosphere. Vascular endothelial cells (ECs) maintain vascular homeostasis by sensing changes in glucose and oxygen concentrations, resulting in collective migration. However, the behaviors of ECs in response to high-glucose and hypoxic environments and the underlying mechanisms remain unclear. In this study, we investigated the collective migration of ECs simultaneously stimulated by changes in glucose and oxygen concentrations. Cell migration in EC monolayer formed inside the media channels of microfluidic devices was observed while varying the glucose and oxygen concentrations. The cell migration increased with increasing glucose concentration under normoxic condition but decreased under hypoxic condition, even in the presence of high glucose levels. In addition, inhibition of mitochondrial function reduced the cell migration regardless of glucose and oxygen concentrations. Thus, oxygen had a greater impact on cell migration than glucose, and aerobic energy production in mitochondria plays an important mechanistic role. These results provide new insights regarding vascular homeostasis relative to glucose and oxygen concentration changes.

Targeting hypoxia-inducible factors: therapeutic opportunities and challenges

Hypoxia-inducible factors (HIFs) are highly conserved transcription factors that are crucial for adaptation of metazoans to limited oxygen availability. Recently, HIF activation and inhibition have emerged as therapeutic targets in various human diseases. Pharmacologically desirable effects of HIF activation include erythropoiesis stimulation, cellular metabolism optimization during hypoxia and adaptive responses during ischaemia and inflammation. By contrast, HIF inhibition has been explored as a therapy for various cancers, retinal neovascularization and pulmonary hypertension. This Review discusses the biochemical mechanisms that control HIF stabilization and the molecular strategies that can be exploited pharmacologically to activate or inhibit HIFs. In addition, we examine medical conditions that benefit from targeting HIFs, the potential side effects of HIF activation or inhibition and future challenges in this field.

Targeting the Warburg effect: A revisited perspective from molecular mechanisms to traditional and innovative therapeutic strategies in cancer

Cancer reprogramming is an important facilitator of cancer development and survival, with tumor cells exhibiting a preference for aerobic glycolysis beyond oxidative phosphorylation, even under sufficient oxygen supply condition. This metabolic alteration, known as the Warburg effect, serves as a significant indicator of malignant tumor transformation. The Warburg effect primarily impacts cancer occurrence by influencing the aerobic glycolysis pathway in cancer cells. Key enzymes involved in this process include glucose transporters (GLUTs), HKs, PFKs, LDHs, and PKM2. Moreover, the expression of transcriptional regulatory factors and proteins, such as FOXM1, p53, NF-κB, HIF1α, and c-Myc, can also influence cancer progression. Furthermore, lncRNAs, miRNAs, and circular RNAs play a vital role in directly regulating the Warburg effect. Additionally, gene mutations, tumor microenvironment remodeling, and immune system interactions are closely associated with the Warburg effect. Notably, the development of drugs targeting the Warburg effect has exhibited promising potential in tumor treatment. This comprehensive review presents novel directions and approaches for the early diagnosis and treatment of cancer patients by conducting in-depth research and summarizing the bright prospects of targeting the Warburg effect in cancer.

Metabolic characteristics of transmembrane prolyl 4-hydroxylase (P4H-TM) deficient mice

Transmembrane prolyl 4-hydroxylase (P4H-TM) is an enigmatic enzyme whose cellular function and primary substrate remain to be identified. Its loss-of-function mutations cause a severe neurological HIDEA syndrome with hypotonia, intellectual disability, dysautonomia and hypoventilation. Previously, P4H-TM deficiency in mice was associated with reduced atherogenesis and lower serum triglyceride levels. Here, we characterized the glucose and lipid metabolism of P4h-tm-/- mice in physiological and tissue analyses. P4h-tm-/- mice showed variations in 24-h oscillations of energy expenditure, VO2 and VCO2 and locomotor activity compared to wild-type (WT) mice. Their rearing activity was reduced, and they showed significant muscle weakness and compromised coordination. Sedated P4h-tm-/- mice had better glucose tolerance, lower fasting insulin levels, higher fasting lactate levels and lower fasting free fatty acid levels compared to WT. These alterations were not present in conscious P4h-tm-/- mice. Fasted P4h-tm-/- mice presented with faster hepatic glycogenolysis. The respiratory rate of conscious P4h-tm-/- mice was significantly lower compared to the WT, the decrease being further exacerbated by sedation and associated with acidosis and a reduced ventilatory response to both hypoxia and hypercapnia. P4H-TM deficiency in mice is associated with alterations in whole-body energy metabolism, day-night rhythm of activity, glucose homeostasis and neuromuscular and respiratory functions. Although the underlying mechanism(s) are not yet fully understood, the phenotype appears to have neurological origins, controlled by brain and central nervous system circuits. The phenotype of P4h-tm-/- mice recapitulates some of the symptoms of HIDEA patients, making this mouse model a valuable tool to study and develop tailored therapies.

Prolyl hydroxylase domain inhibitor is an effective pre-hospital pharmaceutical intervention for trauma and hemorrhagic shock

Pre-hospital potentially preventable trauma related deaths are mainly due to hypoperfusion-induced tissue hypoxia leading to irreversible organ dysfunction at or near the point of injury or during transportation prior to receiving definitive therapy. The prolyl hydroxylase domain (PHD) is an oxygen sensor that regulates tissue adaptation to hypoxia by stabilizing hypoxia inducible factor (HIF). The benefit of PHD inhibitors (PHDi) in the treatment of anemia and lactatemia arises from HIF stabilization, which stimulates endogenous production of erythropoietin and activates lactate recycling through gluconeogenesis. The results of this study provide insight into the therapeutic roles of MK-8617, a pan-inhibitor of PHD-1, 2, and 3, in the mitigation of lactatemia in anesthetized rats with polytrauma and hemorrhagic shock. Additionally, in an anesthetized rat model of lethal decompensated hemorrhagic shock, acute administration of MK-8617 significantly improves one-hour survival and maintains survival at least until 4 h following limited resuscitation with whole blood (20% EBV) at one hour after hemorrhage. This study suggests that pharmaceutical interventions to inhibit prolyl hydroxylase activity can be used as a potential pre-hospital countermeasure for trauma and hemorrhage at or near the point of injury.

Downregulation of Hypoxia Inducible Factor-1α in Primary Human Natural Killer Cells Using Small Interfering RNA Delivery with ExPERT ATx by MaxCyte

Natural killer (NK) cells are innate cytokine-producing and cytolytic effector lymphocytes. Their function is responsive to environmental factors, e.g., hypoxia, a frequent feature of inflamed tissues. Such responses require that the NK cells up-regulate HIF-1α (hypoxia inducible factor-1α), the major mediator of cellular responses to hypoxia that affects cell survival as well as immune responses. Thus, a major approach to the study of NK cell effector function under hypoxic conditions involves the ability to regulate HIF-1α levels in primary human NK cells. One difficulty with this approach, however, is that NK cells are difficult-to-transfect cells and common transfection methods, including electroporation or lipofection, suffer from variable transfection efficiency and cell viability. Moreover, the detection of HIF-1α is technically challenging because of the rapid degradation of the protein under normoxic conditions. Here, using the commercially available ExPERT ATx by MaxCyte, we report a workflow for the reliable delivery of small interfering RNA (siRNA) for targeting HIF-1α expression in primary human NK cells. We further provide a protocol for the detection of HIF-1α by immunoblot analysis demonstrating its efficient downregulation by siRNA. © 2024 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: Isolation of natural killer cells from human peripheral blood mononuclear cells Basic Protocol 2: Delivery of non-coding small interfering RNA and HIF-1α targeting siRNA into natural killer cells using ExPERT ATx Basic Protocol 3: Assessing the downregulation of HIF-1α protein using immunoblot analysis Support Protocol 1: Exemplary assessment of transfection efficiency using fluorescently labeled non-targeting siRNA Support Protocol 2: Exemplary assessment of NK cell viability 20 hr post-transfection Support Protocol 3: Exemplary assessment of HIF-1α knockdown using immunoblot analysis.

Identification of Hypoxia Prognostic Signature in Glioblastoma Multiforme Based on Bulk and Single-Cell RNA-Seq

Glioblastoma (GBM) represents a profoundly aggressive and heterogeneous brain neoplasm linked to a bleak prognosis. Hypoxia, a common feature in GBM, has been linked to tumor progression and therapy resistance. In this study, we aimed to identify hypoxia-related differentially expressed genes (DEGs) and construct a prognostic signature for GBM patients using multi-omics analysis. Patient cohorts were collected from publicly available databases, including the Gene Expression Omnibus (GEO), the Chinese Glioma Genome Atlas (CGGA), and The Cancer Genome Atlas-Glioblastoma Multiforme (TCGA-GBM), to facilitate a comprehensive analysis. Hypoxia-related genes (HRGs) were obtained from the Molecular Signatures Database (MSigDB). Differential expression analysis revealed 41 hypoxia-related DEGs in GBM patients. A consensus clustering approach, utilizing these DEGs' expression patterns, identified four distinct clusters, with cluster 1 showing significantly better overall survival. Machine learning techniques, including univariate Cox regression and LASSO regression, delineated a prognostic signature comprising six genes (ANXA1, CALD1, CP, IGFBP2, IGFBP5, and LOX). Multivariate Cox regression analysis substantiated the prognostic significance of a set of three optimal signature genes (CP, IGFBP2, and LOX). Using the hypoxia-related prognostic signature, patients were classified into high- and low-risk categories. Survival analysis demonstrated that the high-risk group exhibited inferior overall survival rates in comparison to the low-risk group. The prognostic signature showed good predictive performance, as indicated by the area under the curve (AUC) values for one-, three-, and five-year overall survival. Furthermore, functional enrichment analysis of the DEGs identified biological processes and pathways associated with hypoxia, providing insights into the underlying mechanisms of GBM. Delving into the tumor immune microenvironment, our analysis revealed correlations relating the hypoxia-related prognostic signature to the infiltration of immune cells in GBM. Overall, our study highlights the potential of a hypoxia-related prognostic signature as a valuable resource for forecasting the survival outcome of GBM patients. The multi-omics approach integrating bulk sequencing, single-cell analysis, and immune microenvironment assessment enhances our understanding of the intricate biology characterizing GBM, thereby potentially informing the tailored design of therapeutic interventions.

The Role of Hypoxia-Inducible Factor 1 Alpha in Acute-on-Chronic Liver Failure

Acute-on-chronic liver failure (ACLF) is associated with increased mortality. Specific therapy options are limited. Hypoxia-inducible factor 1 alpha (HIF-1α) has been linked to the pathogenesis of chronic liver disease (CLD), but the role of HIF-1α in ACLF is poorly understood. In the current study, different etiologies of CLD and precipitating events triggering ACLF were used in four rodent models. HIF-1α expression and the intracellular pathway of HIF-1α induction were investigated using real-time quantitative PCR. The results were verified by Western blotting and immunohistochemistry for extrahepatic HIF-1α expression using transcriptome analysis. Exploratory immunohistochemical staining was performed to assess HIF-1α in human liver tissue. Intrahepatic HIF-1α expression was significantly increased in all animals with ACLF, regardless of the underlying etiology of CLD or the precipitating event. The induction of HIF-1α was accompanied by the increased mRNA expression of NFkB1 and STAT3 and resulted in a marked elevation of mRNA levels of its downstream genes. Extrahepatic HIF-1α expression was not elevated. In human liver tissue samples, HIF-1α expression was elevated in CLD and ACLF. Increased intrahepatic HIF-1α expression seems to play an important role in the pathogenesis of ACLF, and future studies are pending to investigate the role of therapeutic HIF inhibitors in ACLF.

Kidney Fibrosis and Oxidative Stress: From Molecular Pathways to New Pharmacological Opportunities

Kidney fibrosis, diffused into the interstitium, vessels, and glomerulus, is the main pathologic feature associated with loss of renal function and chronic kidney disease (CKD). Fibrosis may be triggered in kidney diseases by different genetic and molecular insults. However, several studies have shown that fibrosis can be linked to oxidative stress and mitochondrial dysfunction in CKD. In this review, we will focus on three pathways that link oxidative stress and kidney fibrosis, namely: (i) hyperglycemia and mitochondrial energy imbalance, (ii) the mineralocorticoid signaling pathway, and (iii) the hypoxia-inducible factor (HIF) pathway. We selected these pathways because they are targeted by available medications capable of reducing kidney fibrosis, such as sodium-glucose cotransporter-2 (SGLT2) inhibitors, non-steroidal mineralocorticoid receptor antagonists (MRAs), and HIF-1alpha-prolyl hydroxylase inhibitors. These drugs have shown a reduction in oxidative stress in the kidney and a reduced collagen deposition across different CKD subtypes. However, there is still a long and winding road to a clear understanding of the anti-fibrotic effects of these compounds in humans, due to the inherent practical and ethical difficulties in obtaining sequential kidney biopsies and the lack of specific fibrosis biomarkers measurable in easily accessible matrices like urine. In this narrative review, we will describe these three pathways, their interconnections, and their link to and activity in oxidative stress and kidney fibrosis.

HPV16 E6 Oncogene Contributes to Cancer Immune Evasion by Regulating PD-L1 Expression through a miR-143/HIF-1a Pathway

Human Papillomaviruses have been associated with the occurrence of cervical cancer, the fourth most common cancer that affects women globally, while 70% of cases are caused by infection with the high-risk types HPV16 and HPV18. The integration of these viruses' oncogenes E6 and E7 into the host's genome affects a multitude of cellular functions and alters the expression of molecules. The aim of this study was to investigate how these oncogenes contribute to the expression of immune system control molecules, using cell lines with integrated HPV16 genome, before and after knocking out E6 viral gene using the CRISPR/Cas9 system, delivered with a lentiviral vector. The molecules studied are the T-cell inactivating protein PD-L1, its transcription factor HIF-1a and the latter's negative regulator, miR-143. According to our results, in the E6 knock out (E6KO) cell lines an increased expression of miR-143 was recorded, while a decrease in the expression of HIF-1a and PD-L1 was exhibited. These findings indicate that E6 protein probably plays a significant role in enabling cervical cancer cells to evade the immune system, while we propose a molecular pathway in cervical cancer, where PD-L1's expression is regulated by E6 protein through a miR-143/HIF-1a axis.

Hypoxia represses FOXF1 in lung endothelial cells through HIF-1α

Introduction: Forkhead Box F1 (FOXF1) transcription factor plays a critical role in lung angiogenesis during embryonic development and lung repair after injury. FOXF1 expression is decreased in endothelial cells after lung injury; however, molecular mechanisms responsible for the FOXF1 transcript changes in injured lung endothelium remain unknown. Methods: We used immunostaining of injured mouse lung tissues, FACS-sorted lung endothelial cells from hypoxia-treated mice, and data from patients diagnosed with hypoxemic respiratory failure to demonstrate that hypoxia is associated with decreased FOXF1 expression. Endothelial cell cultures were used to induce hypoxia in vitro and identify the upstream molecular mechanism through which hypoxia inhibits FOXF1 gene expression. Results: Bleomycin-induced lung injury induced hypoxia in the mouse lung tissue which was associated with decreased Foxf1 expression. Human FOXF1 mRNA was decreased in the lungs of patients diagnosed with hypoxemic respiratory failure. Mice exposed to hypoxia exhibited reduced Foxf1 expression in the lung tissue and FACS-sorted lung endothelial cells. In vitro, hypoxia (1% of O2) or treatment with cobalt (II) chloride increased HIF-1α protein levels but inhibited FOXF1 expression in three endothelial cell lines. Overexpression of HIF-1α in cultured endothelial cells was sufficient to inhibit Foxf1 expression. siRNA-mediated depletion of HIF-1α prevented the downregulation of Foxf1 gene expression after hypoxia or cobalt (II) chloride treatment. Conclusion: Hypoxia inhibits FOXF1 expression in endothelial cells in a HIF-1α dependent manner. Our data suggest that endothelial cell-specific inhibition of HIF-1α via gene therapy can be considered to restore FOXF1 and improve lung repair in patients with severe lung injury.

Glycosylation: A new signaling paradigm for the neurovascular diseases

A wide range of life-threatening conditions with complicated pathogenesis involves neurovascular disorders encompassing Neurovascular unit (NVU) damage. The pathophysiology of NVU is characterized by several features including tissue hypoxia, stimulation of inflammatory and angiogenic processes, and the initiation of intricate molecular interactions, collectively leading to an elevation in blood-brain barrier permeability, atherosclerosis and ultimately, neurovascular diseases. The presence of compelling data about the significant involvement of the glycosylation in the development of diseases has sparked a discussion on whether the abnormal glycosylation may serve as a causal factor for neurovascular disorders, rather than being just recruited as a secondary player in regulating the critical events during the development processes like embryo growth and angiogenesis. An essential tool for both developing new anti-ischemic therapies and understanding the processes of ischemic brain damage is undertaking pre-clinical studies of neurovascular disorders. Together with the post-translational modification of proteins, the modulation of glycosylation and its enzymes implicates itself in several abnormal activities which are known to accelerate neuronal vasculopathy. Despite the failure of the majority of glycosylation-based preclinical and clinical studies over the past years, there is a significant probability to provide neuroprotection utilizing modern and advanced approaches to target abnormal glycosylation activity at embryonic stages as well. This article focuses on a variety of experimental evidence to postulate the interconnection between glycosylation and vascular disorders along with possible treatment options.

[The development of innovative therapeutic drugs targeting hypoxia responses]

The 2019 Nobel Prize in Physiology or Medicine was awarded to Dr. William G. Kaelin Jr, Dr. Peter J. Ratcliffe, and Dr. Gregg L. Semenza for their elucidation of new physiological mechanisms "How cells sense and adapt to oxygen availability". Moreover, two different drugs, HIF-PH inhibitors and HIF-2 inhibitors were also developed based on the discovery. Interestingly, those three doctors have different backgrounds as a medical oncologist, a nephrologist, and a pediatrician, respectively. They have started the research based on their own unique perspectives and eventually merged as "the elucidation of the response mechanism of living organisms to hypoxic environments". In this review, we will explain how the translational research that has begun to solve unmet clinical needs successfully contributed to the development of innovative therapeutic drugs.

Genetically Encoded Reporters to Monitor Hypoxia

Hypoxia resulting from an imbalance of oxygen availability and consumption defines a metabolic cellular state with a profound impact on developmental processes, tissue maintenance, and the development of pathologies. Fluorescence imaging using genetically encoded reporters enables hypoxia and oxygen imaging with cellular resolution. Thereby unrestricted visualization of hypoxic cells and regions essentially relies on the availability of oxygen-independent fluorescent proteins like UnaG, isolated from the Japanese freshwater eel. Here, we describe the application of recently developed members of a UnaG-based hypoxia reporter family to visualize oxygenation patterns by in vitro live-cell imaging and during the ex vivo analysis of intracranial xenografted tumors. Thus, the generation of stably transfected transgenic tumor cell lines, the in vitro calibration of the genetically encoded sensors, the surgical procedures for orthotopic xenografting of tumors in mice, and workflows for the respective sample preparation and microscopy are outlined.

Loss of prolyl hydroxylase 1 and 2 in SM22α-expressing cells prevents Hypoxia-Induced pulmonary hypertension

Pulmonary arterial hypertension (PAH) is a disease characterized by increased vasoconstriction and vascular remodeling. Pulmonary artery smooth muscle cells (PASMCs) highly express the transcription factor hypoxia-inducible factor-1α (HIF-1α), yet the role of PASMC HIF-1α in the development of PAH remains controversial. To study the role of SMC HIF-1α in the pulmonary vascular response to acute and chronic hypoxia, we used a gain-of-function strategy to stabilize HIF-1α in PASMC by generating mice lacking prolyl hydroxylase domain (PHD) 1 and 2 in SM22α-expressing cells. This strategy increased HIF-1α expression and transcriptional activity under conditions of normoxia and hypoxia. Acute hypoxia increased right ventricular systolic pressure (RVSP) in control, but not in SM22α-PHD1/2-/- mice. Chronic hypoxia increased RVSP and vascular remodeling more in control SM22α-PHD1/2+/+ than in SM22α-PHD1/2-/- mice. In vitro studies demonstrated increased contractility and myosin light chain phosphorylation in isolated PHD1/2+/+ compared with PHD1/2-/- PASMC under both normoxic and hypoxic conditions. After chronic hypoxia, there was more p27 and less vascular remodeling in SM22α-PHD1/2-/- compared with SM22α-PHD1/2+/+ mice. Hypoxia increased p27 in PASMC isolated from control patients, but not in cells from patients with idiopathic pulmonary arterial hypertension (IPAH). These findings highlight an SM22α-expressing cell-specific role for HIF-1α in the inhibition of pulmonary vasoconstriction and vascular remodeling. Modulating HIF-1α expression in PASMC may represent a promising preventative and therapeutic strategy for patients with PAH.NEW & NOTEWORTHY In a mouse model wherein hypoxia-inducible factor 1 alpha (HIF-1α) is stabilized in vascular smooth muscle cells, we found that HIF-1α regulates vasoconstriction by limiting phosphorylation of myosin light chain and regulates vascular remodeling through p27 induction. These findings highlight a cell-specific role for HIF-1α in the inhibition of pulmonary vasoconstriction and vascular remodeling.

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.

Somatic EPAS1 Variants in Pheochromocytoma and Paraganglioma in Patients With Sickle Cell Disease

CONTEXT

Somatic EPAS1 variants account for 5% to 8% of all pheochromocytoma and paragangliomas (PPGL) but are detected in over 90% of PPGL in patients with congenital cyanotic heart disease, where hypoxemia may select for EPAS1 gain-of-function variants. Sickle cell disease (SCD) is an inherited hemoglobinopathy associated with chronic hypoxia and there are isolated reports of PPGL in patients with SCD, but a genetic link between the conditions has yet to be established.

OBJECTIVE

To determine the phenotype and EPAS1 variant status of patients with PPGL and SCD.

METHODS

Records of 128 patients with PPGL under follow-up at our center from January 2017 to December 2022 were screened for SCD diagnosis. For identified patients, clinical data and biological specimens were obtained, including tumor, adjacent non-tumor tissue and peripheral blood. Sanger sequencing of exons 9 and 12 of EPAS1, followed by amplicon next-generation sequencing of identified variants was performed on all samples.

RESULTS

Four patients with both PPGL and SCD were identified. Median age at PPGL diagnosis was 28 years. Three tumors were abdominal paragangliomas and 1 was a pheochromocytoma. No germline pathogenic variants in PPGL-susceptibility genes were identified in the cohort. Genetic testing of tumor tissue detected unique EPAS1 variants in all 4 patients. Variants were not detected in the germline, and 1 variant was detected in lymph node tissue of a patient with metastatic disease.

CONCLUSION

We propose that somatic EPAS1 variants may be acquired through exposure to chronic hypoxia in SCD and drive PPGL development. Future work is needed to further characterize this association.

T-cell dysfunction by pseudohypoxia and autocrine purinergic signaling in chronic lymphocytic leukemia

Acquired T-cell dysfunction is common in chronic B-cell malignancies. Given the strong connection between T-cell metabolism and function, we investigated metabolic alterations as the basis of T-cell dysfunction induced by malignant cells. Using B-cell malignant cell lines and human peripheral blood mononuclear cells, we first established a model that recapitulates major aspects of cancer-induced T-cell dysfunction. Cell lines derived from chronic lymphocytic leukemia (CLL) (PGA-1, CII, and Mec-1), but not from other B-cell malignancies, altered the T-cell metabolome by generating a pseudohypoxic state. T cells were retained in aerobic glycolysis and were not able to switch to oxidative phosphorylation (OXPHOS). Moreover, T cells produced immunosuppressive adenosine that negatively affected function by dampening the activation, which could be restored by the blocking of adenosine receptors. Subsequently, we uncovered a similar hypoxic-like signature in autologous T cells from primary CLL samples. Pseudohypoxia was reversible upon depletion of CLL cells ex vivo and, importantly, after the in vivo reduction of the leukemic burden with combination therapy (venetoclax and obinutuzumab), restoring T-cell function. In conclusion, we uncovered a pseudohypoxic program connected with T-cell dysfunction in CLL. Modulation of hypoxia and the purinergic pathway might contribute to therapeutic restoration of T-cell function.

Macrophage-Derived Extracellular Vesicles-Coated Palladium Nanoformulations Modulate Inflammatory and Immune Homeostasis for Targeting Therapy of Ulcerative Colitis

Ulcerative colitis (UC) is a chronic inflammatory bowel disease mainly involving the colon and rectum, which features recurrent mucosal inflammation. The excessive production of reactive oxygen species (ROS) is a trigger for pathological changes such as cell apoptosis and disordered immune microenvironments, which are crucial for the progression of UC and can be a promising therapeutic target. Nowadays, the development of targeted therapeutic strategies for UC is still in its infancy. Thus, developing effective therapies based on ROS scavenging and elucidating their molecular pathways are urgently needed. Herein, a biomimetic nanoformulation (Pd@M) with cubic palladium (Pd) as the core and macrophage-derived extracellular vesicles (MEVs) as the shell is synthesized for the treatment of UC. These Pd@M nanoformulations exhibit multienzyme-like activities for effective ROS scavenging, excellent targeting ability as well as good biocompatibility. It is verified that Pd@M can regulate the polarization state of macrophages by inhibiting glycolysis, and decrease neutrophil infiltration and recruitment. In this way, the colonic inflammatory and immune microenvironment is remodeled, and apoptosis is prevented, ultimately improving colonic mucosal barrier function and alleviating colitis in the mouse model. This finding provides a promising alternative option for the treatment of UC patients.

Evolution, characterization, and expression profile of Egl-9 family hypoxia-inducible factor (egln) in rainbow trout (Oncorhynchus mykiss) under hypoxia stress

Egl-9 family hypoxia-inducible factor (egln), an oxygen-sensing enzyme family, has been thoroughly characterized in mammals and certain fishes, but there is few research on its involvement in reproductive development and hypoxic stress in rainbow trout. In this study, we investigated the gene structure, physicochemical properties, and evolutionary connection of the egln gene family. The expression profile of egln gene family and their regulatory mechanism were explored using bioinformatics analysis and hypoxia treatment experiments. Five egln genes were discovered in the rainbow trout genome in this investigation (egln1, egln2a, egln2b, egln3a, and egln3b). Domain prediction revealed that all egln proteins have p4hc conserved domains, and phylogenetic analysis revealed that rainbow trout egln2 and egln3 were closely related to Atlantic salmon. The results of real-time quantitative PCR (RT-qPCR) showed that egln genes were generally expressed in all detected tissues, and higher in the ovary, testis, and brain in normoxia. Under hypoxia, the expression level of eglns was significantly down-regulated in most tissues except the liver. Our research contributes to future research on the functional properties of egln genes, as well as the evolution of teleosts and the impact of hypoxia on biological immunity.

Effects of a physical exercise program on HIF-1α in people with Chronic Obstructive Pulmonary Disease living at high altitude: study protocol for a clinical trial

BACKGROUND

Chronic Obstructive Pulmonary Disease (COPD) is a chronic, noncommunicable disease characterized by hypoxemia, with altered lung function, dyspnea on mild exertion, limited tolerance to physical exertion, and functional impairment. Physical exercise has been recommended worldwide as an efficient strategy to improve the autonomy and quality of life of patients affected by COPD. However, the adaptive molecular mechanisms occurring in these patients after the exposure to the hypoxic stimulus triggered by physical exercise have currently not been described in populations living at high altitude.

METHODS

The clinical trial we are presenting here consists of a quasi-experimental design with longitudinal analysis of repeated measures, with intra- and inter-group comparisons, measuring primary and secondary variables in 4 temporal points. Participants will be people with a diagnosis of COPD residing at high altitudes (> 2600 m), without oncological, renal, cardiac, or musculoskeletal comorbidities with a low level of physical activity. The intervention will be an 8-week program of physical exercise of resistance and muscular strength (8-WVP) which will be carried out at home. Primary outcome variables will be the expression of HIF-1α, VEGF, and EPO. As secondary outcome variables, we will consider lung function (measured by spirometry), physical performance (measured by ergospirometry and dynamometry), and hematological parameters.

DISCUSSION

The results obtained after the clinical trial proposed here will promote knowledge on the expression of signaling proteins as an adaptive response to hypoxia in people with COPD living at high altitude, which will be relevant because there are not data on this population group. The knowledge generated from the application of this protocol will increase the pathophysiological understanding of the disease and future medical and therapeutic decision-making based on physical exercise prescription. TRIAL REGISTRATION {2A}: NCT04955977 [ClinicalTrials.gov]-NCT04955977 [WHO ICRTP]. First Posted: July 9, 2021.

The use of hyperbaric oxygen for veterans with PTSD: basic physiology and current available clinical data

Post-traumatic stress disorder (PTSD) affects up to 30% of veterans returning from the combat zone. Unfortunately, a substantial proportion of them do not remit with the current available treatments and thus continue to experience long-term social, behavioral, and occupational dysfunction. Accumulating data implies that the long-standing unremitting symptoms are related to changes in brain activity and structure, mainly disruption in the frontolimbic circuit. Hence, repair of brain structure and restoration of function could be a potential aim of effective treatment. Hyperbaric oxygen therapy (HBOT) has been effective in treating disruptions of brain structure and functions such as stroke, traumatic brain injury, and fibromyalgia even years after the acute insult. These favorable HBOT brain effects may be related to recent protocols that emphasize frequent fluctuations in oxygen concentrations, which in turn contribute to gene expression alterations and metabolic changes that induce neuronal stem cell proliferation, mitochondrial multiplication, angiogenesis, and regulation of the inflammatory cascade. Recently, clinical findings have also demonstrated the beneficial effect of HBOT on veterans with treatment-resistant PTSD. Moderation of intrusive symptoms, avoidance, mood and cognitive symptoms, and hyperarousal were correlated with improved brain function and with diffusion tensor imaging-defined structural changes. This article reviews the current data on the regenerative biological effects of HBOT, and the ongoing research of its use for veterans with PTSD.

Unlocking antitumor immunity with adenosine receptor blockers

Tumors survive by creating a tumor microenvironment (TME) that suppresses antitumor immunity. The TME suppresses the immune system by limiting antigen presentation, inhibiting lymphocyte and natural killer (NK) cell activation, and facilitating T cell exhaustion. Checkpoint inhibitors like anti-PD-1 and anti-CTLA4 are immunostimulatory antibodies, and their blockade extends the survival of some but not all cancer patients. Extracellular adenosine triphosphate (ATP) is abundant in inflamed tumors, and its metabolite, adenosine (ADO), is a driver of immunosuppression mediated by adenosine A2A receptors (A2AR) and adenosine A2B receptors (A2BR) found on tumor-associated lymphoid and myeloid cells. This review will focus on adenosine as a key checkpoint inhibitor-like immunosuppressive player in the TME and how reducing adenosine production or blocking A2AR and A2BR enhances antitumor immunity.

Factor-inhibiting HIF (FIH) promotes lung cancer progression

Factor-inhibiting HIF (FIH) is an asparagine hydroxylase that acts on hypoxia-inducible factors (HIFs) to control cellular adaptation to hypoxia. FIH is expressed in several tumor types, but its impact in tumor progression remains largely unexplored. We observed that FIH was expressed on human lung cancer tissue. Deletion of FIH in mouse and human lung cancer cells resulted in an increased glycolytic metabolism, consistent with increased HIF activity. FIH-deficient lung cancer cells exhibited decreased proliferation. Analysis of RNA-Seq data confirmed changes in the cell cycle and survival and revealed molecular pathways that were dysregulated in the absence of FIH, including the upregulation of angiomotin (Amot), a key component of the Hippo tumor suppressor pathway. We show that FIH-deficient tumors were characterized by higher immune infiltration of NK and T cells compared with FIH competent tumor cells. In vivo studies demonstrate that FIH deletion resulted in reduced tumor growth and metastatic capacity. Moreover, high FIH expression correlated with poor overall survival in non-small cell lung cancer (NSCLC). Our data unravel FIH as a therapeutic target for the treatment of lung cancer.

von-Hippel Lindau and Hypoxia-Inducible Factor at the Center of Renal Cell Carcinoma Biology

The most common form of kidney cancer is clear cell renal cell carcinoma (ccRCC). Biallelic VHL tumor suppressor gene inactivation is the usual initiating event in both hereditary (VHL Disease) and sporadic ccRCCs. The VHL protein, pVHL, earmarks the alpha subunits of the HIF transcription factor for destruction in an oxygen-dependent manner. Deregulation of HIF2 drives ccRCC pathogenesis. Drugs inhibiting the HIF2-responsive growth factor VEGF are now mainstays of ccRCC treatment. A first-in-class allosteric HIF2 inhibitor was recently approved for treating VHL Disease-associated neoplasms and appears active against sporadic ccRCC in early clinical trials.

A series of ligustrazine platinum(IV) complexes with potent anti-proliferative and anti-metastatic properties that exert chemotherapeutic and immunotherapeutic effects

The development of novel anticancer drugs with antiproliferative and antimetastatic activities is of great importance in the pharmaceutical field. Herein, a series of ligustrazine (LSZ) platinum(IV) complexes with chemotherapeutic and immunotherapeutic effects were designed, prepared and evaluated as antitumor agents for the first time. Complex 4 with potent antitumor activities both in vitro and in vivo was screened out as a candidate. Notably, it displays significantly more effective anti-metastatic activities than the platinum(II) drugs cisplatin and oxaliplatin. Mechanism detection discloses that it causes serious DNA damage and increases the expression of γ-H2AX and P53. Then, the apoptosis of tumor cells is promoted by activating the mitochondrial apoptotic pathway Bcl-2/Bax/caspase-3 and causing autophagy via modulating LC3-I/II and P62 expression. Furthermore, the immune therapeutic responses are significantly elevated by blocking HIF-1α, ERK 1/2 and COX-2 pathways to reduce PD-L1 expression, and further increasing CD3+ and CD8+ T cells to elevate T cell immunity in tumors. Tumor metastasis is blocked by the synergistic functions of DNA damage, hypoxia modulation and immune activation.

Efficient targeting of HIF-1α mediated by YC-1 and PX-12 encapsulated niosomes: potential application in colon cancer therapy

A number of molecular biofactors have been documented in pathogenesis and poor prognosis of colorectal cancer (CRC). Among them, the Hypoxia-Inducible Factor (HIF-1a) is frequently reported to become over-expressed, and its targeting could restrict and control a variety of essential hallmarks of CRC. Niosomes are innovative drug delivery vehicles with the encapsulating capacity for co-loading both hydrophilic and hydrophobic drugs at the same time. Also, they can enhance the local accumulation while minimizing the dose and side effects of drugs. YC-1 and PX-12 are two inhibitors of HIF-1a. The purpose of this work was to synthesize dual-loaded YC-1 and PX-12 niosomes to efficiently target HIF-1α in CRC, HT-29 cells. The niosomes were prepared by the thin-film hydration method, then the niosomal formulation of YC-1 and PX-12 (NIO/PX-YC) was developed and optimized by the central composition method (CCD) using the Box-Behnken design in terms of size, polydispersity index (PDI), entrapment efficiency (EE). Also, they are characterized by DLS, FESEM, and TEM microscopy, as well as FTIR spectroscopy. Additionally, entrapment efficiency, in vitro drug release kinetics, and stability were assessed. Cytotoxicity, apoptosis, and cell cycle studies were performed after the treatment of HT-29 cells with NIO/PX-YC. The expression of HIF-1αat both mRNA and protein levels were studied after NIO/PX-YC treatment. The prepared NIO/PX-YC showed a mean particle size of 185 nm with a zeta potential of about-7.10 mv and a spherical morphology. Also, PX-12 and YC-1 represented the entrapment efficiency of about %78 and %91, respectively, with a sustainable and controllable release. The greater effect of NIO/PX-YC than the free state of PX-YC on the cell survival rate, cell apoptosis, and HIF-1α gene/protein expression were detected (p < 0.05). In conclusion, dual loading of niosomes with YC-1 and PX-12 enhanced the effect of drugs on HIF-1α inhibition, thus boosting their anticancer effects.

Intracellular energy production and distribution in hypoxia

The hydrolysis of ATP is the primary source of metabolic energy for eukaryotic cells. Under physiological conditions, cells generally produce more than sufficient levels of ATP to fuel the active biological processes necessary to maintain homeostasis. However, mechanisms underpinning the distribution of ATP to subcellular microenvironments with high local demand remain poorly understood. Intracellular distribution of ATP in normal physiological conditions has been proposed to rely on passive diffusion across concentration gradients generated by ATP producing systems such as the mitochondria and the glycolytic pathway. However, subcellular microenvironments can develop with ATP deficiency due to increases in local ATP consumption. Alternatively, ATP production can be reduced during bioenergetic stress during hypoxia. Mammalian cells therefore need to have the capacity to alter their metabolism and energy distribution strategies to compensate for local ATP deficits while also controlling ATP production. It is highly likely that satisfying the bioenergetic requirements of the cell involves the regulated distribution of ATP producing systems to areas of high ATP demand within the cell. Recently, the distribution (both spatially and temporally) of ATP-producing systems has become an area of intense investigation. Here, we review what is known (and unknown) about intracellular energy production and distribution and explore potential mechanisms through which this targeted distribution can be altered in hypoxia, with the aim of stimulating investigation in this important, yet poorly understood field of research.

Unveiling the angiogenic effects of cannabinoids: Enhancers or inhibitors?

Cannabinoids are compounds found in the cannabis sativa plant. Cannabinoids, such as delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD), have potential therapeutic benefits in various medical conditions. Some can activate the cannabinoid receptors type-1 and -2 (CB1 and CB2), that are part of the endocannabinoid system (ECS), alongside the endocannabinoids and their metabolic enzymes. The ECS regulates physiological and cognitive processes and is a potential therapeutic target for a wide range of health conditions like chronic pain, anxiety, and neurodegenerative diseases. Synthetic cannabinoids, are associated with serious health risks, including addiction, psychosis, and death. Nonetheless, some of these molecules are also being explored for pharmacological applications. Angiogenesis is the process of forming new blood vessels from existing ones, crucial for growth, repair, and tissue maintenance. Dysregulation of this process is associated with several diseases, including cancer, diabetic retinopathy and reproductive pathologies, such as preeclampsia. Recent data suggests that cannabinoids may affect angiogenesis. Here, we reviewed their impact on pro-angiogenic factors, extracellular matrix enzymes and inhibitors, immune-inflammatory responses, angiogenic pathways and functional assays, focusing on the main compounds for each cannabinoid class: THC and CBD for phytocannabinoids, anandamide (AEA) and 2-arachidonoylglycerol (2-AG) for endocannabinoids and WIN-55, JWH-133, XLR-11, LYR-7 and LYR-8, for the synthetic cannabinoids. Despite conflicting reports about the actions of phytocannabinoids and endocannabinoids on angiogenesis, the ability to modulate the angiogenic process is undoubtedly confirmed. This may open a new therapeutical route for angiogenesis-related pathologies. In addition, synthetic cannabinoids present anti-angiogenic actions in several cell models, hinting their potential as anti-angiogenic drugs.

Effects of hyperbaric oxygen therapy on human psychomotor performance: A review

Psychomotor performance is the coordination of a sensory or ideational (cognitive) process and a motor activity. All sensorimotor processes involved in planning and execution of voluntary movements need oxygen supply and seem to be significantly disrupted in states of hypoxia. Hyperbaric oxygen therapy has become a widely used treatment in routine medicine and sport medicine due to its beneficial effects on different aspects of human physiology and performance. This paper presents state-of-the-art data on the effects of hyperbaric oxygen therapy on different aspects of human psychomotor function. The therapy's influence on musculoskeletal properties and motor abilities as well as the effects of hyperbaric oxygenation on cognitive, myocardial and pulmonary functions are presented. In this review the molecular and physiological processes related to human psychomotor performance in response to hyperbaric oxygen are discussed to contribute to this fast-growing field of research in integrative medicine. Please cite this article as: Olex-Zarychta D. Effects of hyperbaric oxygen therapy on human psychomotor performance: A review. J Integr Med. 2023; 21(5): 430-440.

Endothelial FIS1 DeSUMOylation Protects Against Hypoxic Pulmonary Hypertension

BACKGROUND

Hypoxia is a major cause and promoter of pulmonary hypertension (PH), a representative vascular remodeling disease with poor prognosis and high mortality. However, the mechanism underlying how pulmonary arterial system responds to hypoxic stress during PH remains unclear. Endothelial mitochondria are considered signaling organelles on oxygen tension. Results from previous clinical research and our studies suggested a potential role of posttranslational SUMOylation (small ubiquitin-like modifier modification) in endothelial mitochondria in hypoxia-related vasculopathy.

METHODS

Chronic hypoxia mouse model and Sugen/hypoxia rat model were employed as PH animal models. Mitochondrial morphology and subcellular structure were determined by transmission electron and immunofluorescent microscopies. Mitochondrial metabolism was determined by mitochondrial oxygen consumption rate and extracellular acidification rate. SUMOylation and protein interaction were determined by immunoprecipitation.

RESULTS

The involvement of SENP1 (sentrin-specific protease 1)-mediated SUMOylation in mitochondrial remodeling in the pulmonary endothelium was identified in clinical specimens of hypoxia-related PH and was verified in human pulmonary artery endothelial cells under hypoxia. Further analyses in clinical specimens, hypoxic rat and mouse PH models, and human pulmonary artery endothelial cells and human embryonic stem cell-derived endothelial cells revealed that short-term hypoxia-induced SENP1 translocation to endothelial mitochondria to regulate deSUMOylation (the reversible process of SUMOylation) of mitochondrial fission protein FIS1 (mitochondrial fission 1), which facilitated FIS1 assembling with fusion protein MFN2 (mitofusin 2) and mitochondrial gatekeeper VDAC1 (voltage-dependent anion channel 1), and the membrane tethering activity of MFN2 by enhancing its oligomerization. Consequently, FIS1 deSUMOylation maintained the mitochondrial integrity and endoplasmic reticulum-mitochondria calcium communication across mitochondrial-associated membranes, subsequently preserving pulmonary endothelial function and vascular homeostasis. In contrast, prolonged hypoxia disabled the FIS1 deSUMOylation by diminishing the availability of SENP1 in mitochondria via inducing miR (micro RNA)-138 and consequently resulted in mitochondrial dysfunction and metabolic reprogramming in pulmonary endothelium. Functionally, introduction of viral-packaged deSUMOylated FIS1 within pulmonary endothelium in mice improved pulmonary endothelial dysfunction and hypoxic PH development, while knock-in of SUMO (small ubiquitin-like modifier)-conjugated FIS1 in mice exaggerated the diseased cellular and tissue phenotypes.

CONCLUSIONS

By maintaining endothelial mitochondrial homeostasis, deSUMOylation of FIS1 adaptively preserves pulmonary endothelial function against hypoxic stress and consequently protects against PH. The FIS1 deSUMOylation-SUMOylation transition in pulmonary endothelium is an intrinsic pathogenesis of hypoxic PH.

Changes in Metabolomic Profiles Induced by Switching from an Erythropoiesis-Stimulating Agent to a Hypoxia-Inducible Factor Prolyl Hydroxylase Inhibitor in Hemodialysis Patients: A Pilot Study

Hypoxia-inducible factor prolyl hydroxylase inhibitors (HIF-PHIs) are a new class of medications for managing renal anemia in patients with chronic kidney disease (CKD). In addition to their erythropoietic activity, HIF-PHIs exhibit multifaceted effects on iron and glucose metabolism, mitochondrial metabolism, and angiogenesis through the regulation of a wide range of HIF-responsive gene expressions. However, the systemic biological effects of HIF-PHIs in CKD patients have not been fully explored. In this prospective, single-center study, we comprehensively investigated changes in plasma metabolomic profiles following the switch from an erythropoiesis-stimulating agent (ESA) to an HIF-PHI, daprodustat, in 10 maintenance hemodialysis patients. Plasma metabolites were measured before and three months after the switch from an ESA to an HIF-PHI. Among 106 individual markers detected in plasma, significant changes were found in four compounds (erythrulose, n-butyrylglycine, threonine, and leucine), and notable but non-significant changes were found in another five compounds (inositol, phosphoric acid, lyxose, arabinose, and hydroxylamine). Pathway analysis indicated decreased levels of plasma metabolites, particularly those involved in phosphatidylinositol signaling, ascorbate and aldarate metabolism, and inositol phosphate metabolism. Our results provide detailed insights into the systemic biological effects of HIF-PHIs in hemodialysis patients and are expected to contribute to an evaluation of the potential side effects that may result from long-term use of this class of drugs.

Nuclear localization of NRF2 in stroma of HER2 positive and triple-negative breast cancer

Breast cancer is one of the leading causes of cancer-related mortality in women. During tumor growth, periods of hypoxia are followed by reoxygenation due to neovascularisation leading to disturbed redox homeostasis. ROS (Reactive Oxygen Species) produced under hypoxia activate HIF1α. ROS can also activate the major antioxidant transcription factor NRF2, but also cause damage to biomolecules. Lipids are susceptible to peroxidation, as evidenced by the formation of reactive aldehydes, among which, HNE (4-hydroxynonenal) is the most studied one. Knowing that HIF1α (Hypoxia Inducing Factor 1α) is associated with breast cancer malignancy, we aimed to investigate its correlation with HNE and NRF2 (Nuclear factor erythroid 2-related factor 2). Our results show that HIF1α is activated in breast cancer, indicating an increase in ROS but not followed by HNE production. On the other hand, NRF2 was increased in all types of breast cancer suggesting that oxidative stress is present in these pathologies, but also supporting HIF1α. Interestingly, NRF2 was activated in HER2 positive and TNBC, indicating the role of stromal NRF2 in breast cancer malignancy.

Gliflozins, Erythropoietin, and Erythrocytosis: Is It Renal Normoxia- or Hypoxia-Driven?

The introduction of gliflozins in the management of type 2 diabetes mellitus leads to a better control of hyperglycemia, obesity, hypertension, dyslipidemia, and fluid retention. Most importantly, it also improves renal survival and reduces major cardiovascular events and mortality. Gliflozins were also found to induce erythropoietin (EPO) synthesis, leading to reticulocytosis and erythropoiesis. The mechanism(s) by which gliflozins induce erythropoiesis is a matter of debate. Although the canonical pathway of triggering EPO synthesis is through renal tissue hypoxia, it has been suggested that improved renal oxygenation may facilitate EPO synthesis via non-canonical routes. The latter proposes that the recovery of peritubular interstitial fibroblasts producing erythropoietin (EPO) is responsible for enhanced erythropoiesis. According to this hypothesis, enhanced glucose/sodium re-uptake by proximal tubules in uncontrolled diabetes generates cortical hypoxia, with injury to these cells. Once transport workload declines with the use of SGLT2i, they recover and regain their capacity to produce EPO. In this short communication, we argue that this hypothesis may be wrong and propose that gliflozins likely induce EPO through the documented intensification of renal hypoxia at the corticomedullary junction, related to the translocation of tubular transport from cortical segments to medullary thick ascending limbs. We propose that gliflozins, through intensified hypoxia in this region, trigger local EPO synthesis in peritubular interstitial cells via the canonical pathway of blocking HIF-prolyl hydroxylases (that initiate HIF alpha degradation), with the consequent stabilization of HIF-2 signal and an apocrinic induction of EPO in these same cells.

Comparative effectiveness and acceptability of HIF prolyl-hydroxylase inhibitors versus for anemia patients with chronic kidney disease undergoing dialysis: a systematic review and network meta-analysis

Background: The comparative benefits and acceptability of HIF-PHIs for treating anemia have not been well researched to date. We sought to compare the effectiveness of 6 HIF-PHIs and 3 ESAs for the treatment of renal anemia patients undergoing dialysis. Data sources: Cochrane Central Register of Controlled Trials, PubMed, Embase, Cochrane Library, MEDLINE, Web of Science, and clinicaltrials.gov databases. Results: Twenty-five RCTs (involving 17,204 participants) were included, all of which were designed to achieve target Hb levels by adjusting thee dose of HIF-PHIs. Regarding the efficacy in achieving target Hb levels, no significant differences were found between HIF-PHIs and ESAs in Hb response at the dose-adjusted designed RCTs selected for comparison. Intervention with roxadustat showed a significantly lower risk of RBC transfusion than rhEPO, with an OR and 95% CI of 0.76 (0.56-0.93). Roxadustat and vadadustat had higher risks of increasing the discontinuation rate than ESAs; the former had ORs and 95% CIs of 1.58 (95% CI: 1.21-2.06) for rhEPO, 1.66 (1.16-2.38) for DPO (darbepoetin alfa), and 1.76 (1.70-4.49) for MPG-EPO, and the latter had ORs and 95% CIs of 1.71 (1.09-2.67) for rhEPO, 1.79 (1.29-2.49) for DPO, and 2.97 (1.62-5.46) for MPG-EPO. No differences were observed in the AEs and SAEs among patients who received the studied drugs. Results of a meta-analysis of gastrointestinal disorders among AEs revealed that vadadustat was less effect on causing diarrea than DPO, with an OR of 0.97 (95% CI, 0.9-0.99). Included HIF-PHIs, were proven to be more effective than ESAs in reducing hepcidin levels and increasing TIBC and serum iron level with OR of -0.17 (95% CI, -0.21 to -0.12), OR of 0.79 (95% CI, 0.63-0.95), and OR of 0.39 (95% CI, 0.33-0.45), respectively. Conclusion: HIF-PHIs and ESAs have their characteristics and advantages in treating anemia undergoing dialysis. With the selected dose-adjusted mode, some HIF-PHIs appeared to be a potential treatment for DD-CKD patients when ompared with rhEPO, due to its effectiveness in decreasing the risk of RBC transfusion rate or regulating iron or lipid metabolism while achieving target Hb levels. Systematic Review Registration: https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=306511; Identifier: CRD42022306511.

Managing Anemia: Point of Convergence for Heart Failure and Chronic Kidney Disease?

The pathologic triangle formed by chronic heart failure (HF), chronic kidney disease (CKD), and anemia carries high morbidity and mortality rates and decreases quality of life. Anemia represents a common condition in patients with advanced HF and CKD, with a total prevalence in cardiorenal syndrome (CRS) ranging from 5% to 55%. Searching for a pragmatic approach for these patients with guided and disease-specific recommendations beyond just targeted hemoglobin therapeutic behavior represents the core of research for ongoing clinical trials. It is well known that the prevalence of anemia increases with the advancement of CKD and HF. The physiopathological mechanisms of anemia, such as the reduction of endogenous erythropoietin and the decrease in oxygen transport, are leading to tissue hypoxia, peripheral vasodilation, stimulating neurohormonal activity, and maintenance of the progressive renal and cardiac dysfunction. Given the challenges with the treatment options for patients with cardiorenal anemia syndrome (CRSA), new therapeutic agents such as hypoxia-inducible factor-prolyl hydroxylase domain inhibitors (HIF-PH) or hepcidin antagonists are emerging in the light of recent research. This review summarizes the potential therapeutic tools for anemia therapy in the cardiorenal population.

Oxygenation target in acute respiratory distress syndrome

Determining oxygenation targets in acute respiratory distress syndrome (ARDS) remains a challenge. Although oxygenation targets have been used since ARDS was first described, they have not been investigated in detail. However, recent retrospective and prospective trials have evaluated the optimal oxygenation threshold in patients admitted to the general intensive care unit. In view of the lack of prospective data, clinicians continue to rely on data from the few available trials to identify the optimal oxygenation strategy. Assessment of the cost-benefit ratio of the fraction of inspired oxygen (FiO₂) to the partial pressure of oxygen in the arterial blood (PaO₂) is an additional challenge. A high FiO₂ has been found to be responsible for respiratory failure and deaths in numerous animal models. Low and high PaO₂ values have also been demonstrated to be potential risk factors in experimental and clinical situations. The findings from this literature review suggest that PaO₂ values ranging between 80 mmHg and 90 mmHg are acceptable in patients with ARDS. The costs of rescue maneuvers needed to reach these targets have been discussed. Several recent papers have highlighted the risk of disagreement between arterial oxygen saturation (SaO₂) and peripheral oxygen saturation (SpO₂) values. In order to avoid discrepancies and hidden hypoxemia, SpO₂ readings need to be compared with those of SaO₂. Higher SpO₂ values may be needed to achieve the recommended PaO₂ and SaO₂ values.

Hypoxia-inducible factor-1α regulates the interleukin-6 production by B cells in rheumatoid arthritis

Objectives

Rheumatoid arthritis (RA) is a disease characterised by bone destruction and systemic inflammation, and interleukin-6 (IL-6) is a therapeutic target for treating it. The study aimed at investigating the sources of IL-6 and the influence of hypoxia-inducible factor-1α (HIF-1α) on IL-6 production by B cells in RA patients.

Methods

The phenotype of IL-6-producing cells in the peripheral blood of RA patients was analysed using flow cytometry. Bioinformatics, real-time polymerase chain reaction, Western blot and immunofluorescence staining were used to determine the IL-6 production and HIF-1α levels in B cells. A dual-luciferase reporter assay and chromatin immunoprecipitation were used to investigate the regulatory role of HIF-1α on IL-6 production in human and mouse B cells.

Results

Our findings revealed that B cells are major sources of IL-6 in the peripheral blood of RA patients, with the proportion of IL-6-producing B cells significantly correlated with RA disease activity. The CD27-IgD+ naïve B cell subset was identified as the typical IL-6-producing subset in RA patients. Both HIF-1α and IL-6 were co-expressed by B cells in the peripheral blood and synovium of RA patients, and HIF-1α was found to directly bind to the IL6 promoter and enhance its transcription.

Conclusion

This study highlights the role of B cells in producing IL-6 and the regulation of this production by HIF-1α in patients with RA. Targeting HIF-1α might provide a new therapeutic strategy for treating RA.

Molecular Characterization and Functional Analysis of Hypoxia-Responsive Factor Prolyl Hydroxylase Domain 2 in Mandarin Fish (Siniperca chuatsi)

With increased breeding density, the phenomenon of hypoxia gradually increases in aquaculture. Hypoxia is primarily mediated by the hypoxia-inducible factor 1 (HIF-1) signaling pathway. Prolyl hydroxylase domain proteins (PHD) are cellular oxygen-sensing molecules that regulate the stability of HIF-1α through hydroxylation. In this study, the characterization of the PHD2 from mandarin fish Siniperca chuatsi (scPHD2) and its roles in the HIF-1 signaling pathway were investigated. Bioinformation analysis showed that scPHD2 had the conserved prolyl 4-hydroxylase alpha subunit homolog domains at its C-terminal and was more closely related to other Perciformes PHD2 than other PHD2. Tissue-distribution results revealed that scphd2 gene was expressed in all tissues tested and more highly expressed in blood and liver than in other tested tissues. Dual-luciferase reporter gene and RT-qPCR assays showed that scPHD2 overexpression could significantly inhibit the HIF-1 signaling pathway. Co-immunoprecipitation analysis showed that scPHD2 could interact with scHIF-1α. Protein degradation experiment results suggested that scPHD2 could promote scHIF-1α degradation through the proteasome degradation pathway. This study advances our understanding of how the HIF-1 signaling pathway is regulated by scPHD2 and will help in understanding the molecular mechanisms underlying hypoxia adaptation in teleost fish.

Bacterial Lysate from the Multi-Strain Probiotic SLAB51 Triggers Adaptative Responses to Hypoxia in Human Caco-2 Intestinal Epithelial Cells under Normoxic Conditions and Attenuates LPS-Induced Inflammatory Response

Hypoxia-inducible factor-1α (HIF-1α), a central player in maintaining gut-microbiota homeostasis, plays a pivotal role in inducing adaptive mechanisms to hypoxia and is negatively regulated by prolyl hydroxylase 2 (PHD2). HIF-1α is stabilized through PI3K/AKT signaling regardless of oxygen levels. Considering the crucial role of the HIF pathway in intestinal mucosal physiology and its relationships with gut microbiota, this study aimed to evaluate the ability of the lysate from the multi-strain probiotic formulation SLAB51 to affect the HIF pathway in a model of in vitro human intestinal epithelium (intestinal epithelial cells, IECs) and to protect from lipopolysaccharide (LPS) challenge. The exposure of IECs to SLAB51 lysate under normoxic conditions led to a dose-dependent increase in HIF-1α protein levels, which was associated with higher glycolytic metabolism and L-lactate production. Probiotic lysate significantly reduced PHD2 levels and HIF-1α hydroxylation, thus leading to HIF-1α stabilization. The ability of SLAB51 lysate to increase HIF-1α levels was also associated with the activation of the PI3K/AKT pathway and with the inhibition of NF-κB, nitric oxide synthase 2 (NOS2), and IL-1β increase elicited by LPS treatment. Our results suggest that the probiotic treatment, by stabilizing HIF-1α, can protect from an LPS-induced inflammatory response through a mechanism involving PI3K/AKT signaling.

Hypoxia induces polycystin-1 expression in the renal epithelium

Mutations in polycystin-1 which is encoded by the PKD1 gene are the main causes for the development of autosomal dominant polycystic kidney disease. However, only little is known about the physiological function of polycystin-1 and even less about the regulation of its expression. Here, we show that expression of PKD1 is induced by hypoxia and compounds that stabilize the hypoxia-inducible transcription factor (HIF) 1α in primary human tubular epithelial cells. Knockdown of HIF subunits confirms HIF-1α-dependent regulation of polycystin-1 expression. Furthermore, HIF ChIP-seq reveals that HIF interacts with a regulatory DNA element within the PKD1 gene in renal tubule-derived cells. HIF-dependent expression of polycystin-1 can also be demonstrated in vivo in kidneys of mice treated with substances that stabilize HIF. Polycystin-1 and HIF-1α have been shown to promote epithelial branching during kidney development. In line with these findings, we show that expression of polycystin-1 within mouse embryonic ureteric bud branches is regulated by HIF. Our finding links expression of one of the main regulators of accurate renal development with the hypoxia signalling pathway and provides additional insight into the pathophysiology of polycystic kidney disease.