Oxygen sensing by metazoans: the central role of the HIF hydroxylase pathway. Mol Cell. 2008;30:393-402. [PMID: 18498744 DOI: 10.1016/j.molcel.2008.04.009]

Hypoxia-inducible factor-1α involves in regulating anti-lipopolysaccharide factors expression via NF-κB under hypoxia stress in Chinese mitten crab (Eriocheir sinensis)

Oxygen is essential for the survival of organisms. Hypoxia profoundly affects the immune response in aquatic crustaceans, nevertheless, the precise mechanisms of immunological regulation under hypoxic conditions remain unclear. Hypoxia-inducible factor 1-alpha (HIF-1α), a key regulator of oxygen homeostasis, also plays a vital role in the immunological responses of mammals. Nonetheless, it remains uncertain whether HIF-1α regulates the immune response of crustaceans under hypoxia stress. This study investigated the expression patterns of EsHIF-1α and anti-lipopolysaccharide factors (ALFs) in response to Aeromonas hydrophila stimulation under hypoxia stress in Eriocheir sinensis. The mRNA expression levels of EsHIF-1α in haemocytes were significantly increased after hypoxia treatment, while were markedly reduced following A. hydrophila stimulation under hypoxic condition. Similarly, the EsALFs mRNA expression levels were also significantly decreased post A. hydrophila injection under hypoxic condition. Subsequently, the effect of EsHIF-1α on EsALFs mRNA expression was detected. The mRNA transcripts of EsALFs significantly diminished in HIF-1α inhibitor (KC7F2) injected crabs, however, a significant increase was observed in HIF-1α activator (IOX4) injected crabs. Furthermore, the mRNA expression and phosphorylation levels of NF-κB exhibited a similar trend following the inhibition or activation of EsHIF-1α, indicating that EsHIF-1α has a positive effect on the expression and activity of NF-κB. In addition, the bacterial clearance of haemolymph in the HIF-1α activated group was significantly higher, whereas in the HIF-1α inhibited group it was significantly lower, compared to the control group. Our findings collectively suggested that EsHIF-1α regulated ALFs expression through NF-κB activation in E. sinensis in response to A. hydrophila stimulation under hypoxic conditions. This research improves the understanding of the immunological regulation mechanisms in crustaceans under hypoxia stress.

Iron metabolism in rheumatic diseases

Iron is a crucial element for living organism in terms of oxygen transport, hematopoiesis, enzymatic activity, mitochondrial respiratory chain function and also immune system function. The human being has evolved a mechanism to regulate body iron. In some rheumatic diseases such as rheumatoid arthritis (RA), systemic lupus erythematous (SLE), systemic sclerosis (SSc), ankylosing spondylitis (AS), and gout, this balanced iron regulation is impaired. Altered iron homeostasis can contribute to disease progression through ROS production, fibrosis, inflammation, abnormal bone homeostasis, NETosis and cell senescence. In this review, we have focused on the iron metabolism in rheumatic disease and its role in disease progression.

Hypoxia in multiple sclerosis

Low oxygen availability (hypoxia) is a prominent but poorly understood feature in multiple sclerosis (MS). Whether hypoxia causes or drives MS pathology and symptoms or whether it is a consequence of other pathological events, such as inflammation and vascular dysfunction, is unknown. Here, we summarize the available literature on the interplay between hypoxia and both pathological and symptomatic features of MS. Severe environmental hypoxia (i.e., altitude) may trigger or facilitate MS-related events, possibly by exacerbating tissue hypoxia in the central nervous system. Accordingly, increasing oxygen supply can mitigate pathological and clinical parameters in MS models. In contrast, stimulating the endogenous hypoxia response and adaptation systems by controlled exposure to hypoxia (hypoxia conditioning) renders the central nervous system more resistant to hypoxic insults, thereby attenuating pathology and symptomatology in MS models. Overlapping mechanisms likely play a role in the benefits conferred by physical activity in MS. We provide an integrative model to explain the paradoxically beneficial outcomes of both increased and decreased ambient oxygen conditions. In conclusion, controlled exposure to hypoxia, perhaps in combination with exercise, is a promising, possibly disease-course modifying therapeutic approach for MS. However, many open questions remain.

Light-Induced, Lysine-Targeting Irreversible Covalent Inhibition of the Human Oxygen Sensing Hydroxylase Factor Inhibiting HIF (FIH)

Factor inhibiting hypoxia-inducible factor (FIH) is a JmjC domain 2-oxoglutarate (2OG) and Fe(II)-dependent oxygenase that catalyzes protein hydroxylations, including of specific asparagines in the C-terminal transcriptional activation domains of hypoxia-inducible factor alpha (HIF-α) isoforms. FIH is of medicinal interest due to its ability to alter metabolism and modulate the course of the HIF-mediated hypoxic response. We report the development of a light-induced, lysine (Lys106)-targeting irreversible covalent inhibitor of FIH. The approach is complementary to optogenetic methods for regulation of transcription. The covalently reacting inhibitor NBA-ZG-2291 was the result of structure-guided modification of the reported active site binding FIH inhibitor ZG-2291 with an appropriately positioned o-nitrobenzyl alcohol (o-NBA) group. The results demonstrate that NBA-ZG-2291 forms a stable covalent bond in a light-dependent process with Lys106 of FIH, inactivating its hydroxylation activity and resulting in sustained upregulation of FIH-dependent HIF target genes. The light-controlled inhibitors targeting a lysine residue enable light and spatiotemporal control of FIH activity in a manner useful for dissecting the context-dependent physiological roles of FIH.

An mRNA-display derived cyclic peptide scaffold reveals the substrate binding interactions of an N-terminal cysteine oxidase

N-terminal cysteine oxidases (NCOs) act as enzymatic oxygen (O2) sensors, coordinating cellular changes to hypoxia in animals and plants. They regulate the O2-dependent stability of proteins bearing an N-terminal cysteine residue through the N-degron pathway. Despite their important role in hypoxic adaptation, which renders them potential therapeutic and agrichemical targets, structural information on NCO substrate binding remains elusive. To overcome this challenge, we employed a unique strategy by which a cyclic peptide inhibitor of the mammalian NCO, 2-aminoethanethiol dioxygenase (ADO), was identified by mRNA display and used as a scaffold to graft substrate moieties. This allowed the determination of two substrate analogue-bound crystal structures of ADO. Key binding interactions were revealed, including bidentate coordination of the N-terminal residue at the metal cofactor. Subsequent structure guided mutagenesis identified aspartate-206 as an essential catalytic residue, playing a role in reactive oxygen intermediate orientation or stabilisation. These findings provide fundamental information on ADO substrate interactions, which can elucidate enzyme mechanism and act as a platform for chemical discovery.

MYLIP attenuates hypoxia tolerance by inducing K27-linked polyubiquitination and subsequent proteasomal degradation of HIF-α

Hypoxia tolerance is mainly controlled by the hypoxia signaling pathway and HIF-1α/2α serve as master regulators in this pathway. Here we identify MYLIP, an E3 ubiquitin ligase thought to specifically target lipoprotein receptors, as a downstream target of HIF-2α and a negative regulator of both HIF-1α and HIF-2α. MYLIP interacts with HIF-1α/2α and catalyzes K27-linked polyubiquitination at lysine 118/442 (HIF-1α) or lysine 117 (HIF-2α). This modification induces proteasomal degradation of HIF-1α, resulting in inhibition of hypoxia signaling. Furthermore, Mylip-deficient bluntsnout bream, zebrafish and mice are more tolerant to hypoxia. These findings reveal a role for MYLIP in regulating hypoxia signaling and identify a target for the development of fish strains with high hypoxia tolerance for the benefit of the aquaculture industry.

Small-molecule RNA therapeutics to target prostate cancer

Tuning protein expression by targeting RNA structure using small molecules is an unexplored avenue for cancer treatment. To understand whether this vulnerability could be therapeutically targeted in the most lethal form of prostate cancer, castration-resistant prostate cancer (CRPC), we use a clinical small molecule, zotatifin, that targets the RNA helicase and translation factor eukaryotic initiation factor 4A (eIF4A). Zotatifin represses tumorigenesis in patient-derived and xenograft models and prolonged survival in vivo alongside hormone therapy. Genome-wide transcriptome, translatome, and proteomic analysis reveals two important translational targets: androgen receptor (AR), a key oncogene in CRPC, and hypoxia-inducible factor 1A (HIF1A), an essential cancer modulator in hypoxia. We solve the structure of the 5' UTRs of these oncogenic mRNAs and strikingly observe complex structural remodeling of these select mRNAs by this small molecule. Remarkably, tumors treated with zotatifin become more sensitive to anti-androgen therapy and radiotherapy. Therefore, "translatome therapy" provides additional strategies to treat the deadliest cancers.

Electroacupuncture ameliorates cognitive impairment and white matter injury in vascular dementia rats via activating HIF-1α/VEGF/VEGFR2 pathway

Vascular dementia (VaD) significantly impairs patients' quality of life and imposes a major social and economic burden. Electroacupuncture (EA), a contemporary modification of traditional acupuncture, has demonstrated potential in improving cognitive function in VaD, particularly when applied at the Shenting and Baihui. However, the underlying mechanisms remain inadequately understood. Elucidating how EA ameliorates cognitive deficits is critical for validating its clinical application and advancing non-pharmacological interventions for neurodegenerative disorders. This study aimed to investigate the neuroprotective mechanisms of electroacupuncture at these acupoints on cognitive function in VaD rats. VaD was induced in male Sprague-Dawley rats through bilateral common carotid artery occlusion (BCAO), with sham rats serving as controls. Rats were subsequently divided into three groups: BCAO, BCAO + EA and BCAO + EA + YC-1 (a HIF-1α inhibitor). Electroacupuncture was applied to the Shenting and Baihui. Cerebral blood flow (CBF) was measured using dynamic susceptibility contrast functional MRI, and cognitive recovery was evaluated through the Morris water maze. Immunohistochemical analysis quantified myelin repair and angiogenesis, while expression of HIF-1α, VEGF and VEGFR2 in white matter was quantified using PCR and Western blot. The results indicated that electroacupuncture improved learning and memory, increased CBF, enhanced myelin recovery and promoted angiogenesis in VaD rats. The expression of HIF-1α, VEGF and VEGFR2 in the white matter was significantly elevated in VaD rats. Electroacupuncture at Shenting and Baihui activates the HIF-1α/VEGF/VEGFR2 pathway, enhances angiogenesis, white matter perfusion and myelin repair, thereby restoring cognitive function in VaD rats.

The context-dependent epigenetic and organogenesis programs determine 3D vs. 2D cellular fitness of MYC-driven murine liver cancer cells

3D cellular-specific epigenetic and transcriptomic reprogramming is critical to organogenesis and tumorigenesis. Here, we dissect the distinct cell fitness in 2D (normoxia vs. chronic hypoxia) vs 3D (normoxia) culture conditions for an MYC-driven murine liver cancer model. We identify over 600 shared essential genes and additional context-specific fitness genes and pathways. Knockout of the VHL-HIF1 pathway results in incompatible fitness defects under normoxia vs. 1% oxygen or 3D culture conditions. Moreover, deletion of each of the mitochondrial respiratory electron transport chain complex has distinct fitness outcomes. Notably, multicellular organogenesis signaling pathways including TGFβ-SMAD, which is upregulated in 3D culture, specifically constrict the uncontrolled cell proliferation in 3D while inactivation of epigenetic modifiers (Bcor, Kmt2d, Mettl3, and Mettl14) has opposite outcomes in 2D vs. 3D. We further identify a 3D-dependent synthetic lethality with partial loss of Prmt5 due to a reduction of Mtap expression resulting from 3D-specific epigenetic reprogramming. Our study highlights unique epigenetic, metabolic, and organogenesis signaling dependencies under different cellular settings.

EPO Enhances Adaptation to Hypoxic Environment in the Freshwater Teleost (Micropterus salmoides) through the PI3K/AKT Pathway

Hypoxia has become one of the most common environmental stress events in the life history of aquatic organisms due to accelerated global warming. Exploring the adaptation mechanisms of aquatic organisms in hypoxic environments is important to deepen our understanding of environmental toxicology and to design breeding programs. In this study, the largemouth bass Micropterus salmoides exhibited greater hypoxic adaptability after 4 weeks of intermittent hypoxic exposure (IHE), with the O2 tension for loss of equilibrium decreased from 1.17 ± 0.20 to 0.66 ± 0.10 mg/L. Combined transcriptomics, biochemical detection, and immunostaining results revealed that the hypoxia-tolerant phenotype driven by IHE was strongly correlated with the activation of erythropoietin (EPO). EPO promoted phosphoinositide-3-kinase (PI3K)/protein kinase B (AKT) signaling to alleviate hepatic damage under acute hypoxic exposure (AHE) by selectively regulating the expression of genes related to antioxidant defense, antiapoptosis, and cell proliferation, which plays an important role in regulating hypoxic adaptation. The inhibition of EPO impaired cell survival in hypoxic environments, but intervention with the PI3K agonist 740 Y-P reversed this process. This novel finding provides insights into exploring how aquatic organisms cope with the challenges of hypoxia under increasing environmental risks.

The Distinct Role of HIF-1α and HIF-2α in Hypoxia and Angiogenesis

Hypoxia results in a wide range of adaptive physiological responses, including metabolic reprogramming, erythropoiesis, and angiogenesis. The response to hypoxia at the cellular level is mainly regulated by hypoxia-inducible factors (HIFs): HIF1α and HIF2α isoforms. Although structurally similar and overlapping gene targets, both isoforms can exhibit distinct expression patterns and functions in some conditions of hypoxia. The interaction between these isoforms, known as the "HIF switch", determines their coordinated function under varying oxygen levels and exposure time. In angiogenesis, HIF-1α is rapidly stabilized under acute hypoxia, prompting a metabolic shift from oxidative phosphorylation to glycolysis and initiating angiogenesis by activating endothelial cells and extracellular matrix remodeling. Conversely, HIF-2α regulates cell responses to chronic hypoxia by sustaining genes critical for vascular remodeling and maturation. The current review highlights the different roles and regulatory mechanisms of HIF-1α and HIF-2α isoforms, focusing on their involvement in cell metabolism and the multi-step process of angiogenesis. Tuning the specific targeting of HIF isoforms and finding the right therapeutic window is essential to obtaining the best therapeutic effect in diseases such as cancer and vascular ischemic diseases.

Under (Genetic Selection) Pressure: Human Tumors and Human Populations in Hypoxia

Arenillas and colleagues report that pheochromocytomas and paragangliomas in the setting of chronic hypoxia due to cyanotic congenital heart disease harbor, at high frequency, somatic gain-of-function mutations in the EPAS1 gene, which encodes for one of the oxygen-labile subunits of the hypoxia-inducible factor complex. Interestingly, germline loss-of-function EPAS1 alleles are under natural selection in human populations subjected to a different chronic hypoxia condition, namely, high altitude. See related article by Arenillas et al., p. 1037.

Cr (VI) induces lactate utilization through HIF-1α/MCT1 dependent on p53 protein level

Hexavalent chromium [Cr (VI)] is a known environmental pollutant, which promotes tumorigenesis. Hypoxia-inducible factor-1α (HIF-1α) is crucial for cancer development. Here, we found that Cr (VI) treatment promoted lactate utilization by increasing monocarboxylate transporter 1 (MCT1) and monocarboxylate transporter 4 (MCT4) expression, while increasing the expression of HIF-1α in A549 cells but reducing HIF-1α and MCT1 in HELF cells. CoCl2, an HIF-1α inducer, increased MCT1, while the HIF-1α inhibitor YC-1 and MCT1 inhibitor AZD3965 suppressed Cr (VI)-induced lactate utilization and cell growth. Chromatin immunoprecipitation (ChIP) assay revealed HIF-1α bound to the MCT1 promoter to enhance its transcription. Using Reactivating p53 and Inducing Tumor Apoptosis (RITA), which can increase the protein level of p53, we discovered that the low level of p53 protein in A549 cells determined the effect of Cr (VI)-induced HIF-1α. These findings highlighted the role of p53 protein level in the effects of Cr (VI) on HIF-1α/MCT1 to induce lactate utilization and cell growth. Targeting the p53/HIF-1α/MCT1 pathway could inhibit Cr (VI)-mediated tumorigenesis.

Geographic Variation in Epigenetic Responses to Hypoxia in Deer Mice (Peromyscus maniculatus) Distributed Along an Elevational Gradient

Lowland and highland Peromyscus maniculatus populations display divergent, locally adapted physiological phenotypes shaped by altitudinal differences in oxygen availability. Many physiological responses to hypoxia seem to have evolved in lowland ancestors to offset episodic and localised bouts of low internal oxygen availability. However, upon chronic hypoxia exposure at high elevation, these responses can lead to physiological complications. Therefore, highland ancestry is often associated with evolved hypoxia responses, particularly traits promoting tolerance of constant hypoxia. Environmentally induced DNA methylation can dynamically alter gene expression patterns, providing a proximate basis for phenotypic plasticity. Given each population's differential reliance on plasticity for hypoxia tolerance, we hypothesised that lowland mice have a more robust epigenetic response to hypoxia exposure, driving trait plasticity, than highland mice. Using DNA methylation data of tissues from the heart's left ventricle, we show that upon hypoxia exposure, lowland mice chemically modulate the epigenetic landscape to a greater extent than highland mice, especially at key hypoxia-relevant genes such as Egln3. This gene is a regulator of the gene Epas1 that is frequently targeted for positive selection at high elevation. We find higher methylation among wild highland mice at gene Egln3 compared to wild lowland mice, suggesting a shared epigenetic ancestral response to episodic and chronic hypoxia. These findings highlight each population's distinct reliance on molecular plasticity driven by their unique evolutionary histories.

Cd stabilizes HIF-1α under normoxic conditions via lysine-63-linked ubiquitination and induces ER stress and cell proliferation

Cadmium, a carcinogenic and toxic substance released into the environment, has emerged as a potent activator of lysine-63 ubiquitination, and lysine-63 is a crucial regulator of signal transduction pathways. Although critical, very little information is currently available about how the activation of lysine 63 ubiquitination by Cd might contribute to cancers and inflammatory diseases. The present study provides the first evidence that Cd stabilizes hypoxia-inducible factor-1-alpha, a transcription factor, under normoxic conditions via lysine 63 ubiquitination. Cd induces the accumulation of lysine 63 polyubiquitinated proteins. Importantly, Cd-induced ubiquitination does not prevent oxidative damage or proteasome impairment. Instead, we demonstrated that Cd activates lysine 63 ubiquitination and amplifies its accumulation by overloading the capacity of the autophagy pathway, thus promoting endoplasmic reticulum stress and cell death. At the molecular level, Cd-induced lysine 63 polyubiquitination is correlated with the stabilization of hypoxia-inducible factor-1-alpha, which translocates into the nucleus and promotes the expression of oncogenes such as interleukin 8 and vascular endothelial growth factor. Strikingly, prolonged cell exposure to high Cd concentrations induces increased lysine-63 polyubiquitination, which promotes aggresome formation, thus preventing this protein from interacting with its downstream nuclear targets. Our results showed that Cd is an activator of K63-linked ubiquitination that stabilizes and promotes the accumulation of HIF-1α, which blocks autophagy, thus resulting in endoplasmic reticulum stress. In addition, a small amount of HIF-1α was observed in the nucleus. We therefore propose that the aberrant activation of lysine 63 polyubiquitination by the carcinogen Cd could promote cell proliferation and inflammation at low levels, while high levels lead to cell death.

Supplementary Information

The online version contains supplementary material available at 10.1007/s43188-024-00266-9.

Distinct Stress Regulators in the CRL Family: Emerging Roles of F-Box Proteins: Cullin-RING Ligases and Stress-Sensing

Cullin-RING ligases (CRLs) are central regulators of environmental and cellular stress responses, orchestrating diverse processes through the ubiquitination of substrate proteins. As modular complexes, CRLs employ substrate-specific adaptors to target proteins for degradation and other ubiquitin-mediated processes, enabling dynamic adaptation to environmental cues. Recent advances have highlighted the largest CRL subfamily SCF (Skp1-cullin-F-box) in environmental sensing, a role historically underappreciated for SCF ubiquitin ligases. Notably, emerging evidence suggests that the F-box domain, a 50-amino acid motif traditionally recognized for mediating protein-protein interactions, can act as a direct environmental sensor due to its ability to bind heavy metals. Despite these advances, the roles of many CRL components in environmental sensing remain poorly understood. This review provides an overview of CRLs in stress response regulation and emphasizes the emerging functions of F-box proteins in environmental adaptation.

2-Methoxyestradiol Inhibits the Oxygen-Sensing Pathway in Keloid Fibroblasts by Targeting HIF-1α/PHD

Maintaining oxygen homeostasis is a basic cellular process for adapting to physiological oxygen variations in which the oxygen-sensing pathway plays a critical role, especially in tumour progression. Little is known about the activity of the oxygen-sensing pathway in keloid tissue. In this study, key features of the oxygen-sensing pathway and its downstream effects were evaluated and compared between normal skin tissue and keloid tissue. Keloid tissue showed increased oxygen-sensing pathway activation and a higher expression of key downstream factors such as tumour necrosis factor-1α (TNF-α) and vascular endothelial growth factor (VEGF). In addition, the effects of 2-methoxyestradiol on the oxygen-sensing pathway in both hypoxic and normoxic keloid fibroblasts were evaluated. Our results suggest that 2-methoxyestradiol could be used to inhibit keloid fibroblast activity by inhibiting the oxygen-sensing pathway and its downstream effectors.

Advances in plant oxygen sensing: endogenous and exogenous mechanisms

Oxygen is essential for the biochemical processes that sustain life in eukaryotic organisms. Although plants produce oxygen through photosynthesis, they often struggle to survive in low-oxygen environments, such as during flooding or submergence. To endure these conditions, they must reprogram their developmental and metabolic networks, and the adaptation process involves the continuous detection of both exogenous hypoxic signals and endogenous oxygen gradients. Recent research has significantly advanced our understanding of how plants respond to both endogenous and exogenous hypoxia signals. In this review, we explore advancements in both areas, comparing them to responses in animals, with a primary focus on how plants perceive and respond to exogenous hypoxic conditions, particularly those caused by flooding or submergence, as well as the hypoxia signaling pathways in different crops. Additionally, we discuss the interplay between endogenous and exogenous hypoxia signals in plants. Finally, we discuss future research directions aimed at improving crop resilience to flooding by integrating the perception and responses to both endogenous and exogenous signals. Through these efforts, we aspire to contribute to the development of crop varieties that are not only highly resistant but also experience minimal growth and yield penalties, thereby making substantial contributions to agricultural science.

BMAL1-HIF2A heterodimer modulates circadian variations of myocardial injury

Acute myocardial infarction is a leading cause of morbidity and mortality worldwide1. Clinical studies have shown that the severity of cardiac injury after myocardial infarction exhibits a circadian pattern, with larger infarcts and poorer outcomes in patients experiencing morning-onset events2-7. However, the molecular mechanisms underlying these diurnal variations remain unclear. Here we show that the core circadian transcription factor BMAL17-11 regulates circadian-dependent myocardial injury by forming a transcriptionally active heterodimer with a non-canonical partner-hypoxia-inducible factor 2 alpha (HIF2A)12-16-in a diurnal manner. To substantiate this finding, we determined the cryo-EM structure of the BMAL1-HIF2A-DNA complex, revealing structural rearrangements within BMAL1 that enable cross-talk between circadian rhythms and hypoxia signalling. BMAL1 modulates the circadian hypoxic response by enhancing the transcriptional activity of HIF2A and stabilizing the HIF2A protein. We further identified amphiregulin (AREG)16,17 as a rhythmic target of the BMAL1-HIF2A complex, critical for regulating daytime variations of myocardial injury. Pharmacologically targeting the BMAL1-HIF2A-AREG pathway provides cardioprotection, with maximum efficacy when aligned with the pathway's circadian phase. These findings identify a mechanism governing circadian variations of myocardial injury and highlight the therapeutic potential of clock-based pharmacological interventions for treating ischaemic heart disease.

HIF-1α Pathway in COVID-19: A Scoping Review of Its Modulation and Related Treatments

The COVID-19 pandemic, driven by SARS-CoV-2, has led to a global health crisis, highlighting the virus's unique molecular mechanisms that distinguish it from other respiratory pathogens. It is known that the Hypoxia-Inducible Factor 1α (HIF-1α) activates a complex network of intracellular signaling pathways regulating cellular energy metabolism, angiogenesis, and cell survival, contributing to the wide range of clinical manifestations of COVID-19, including Post-Acute COVID-19 Syndrome (PACS). Emerging evidence suggests that dysregulation of HIF-1α is a key driver of systemic inflammation, silent hypoxia, and pathological tissue remodeling in both the acute and post-acute phases of the disease. This scoping review was conducted following PRISMA-ScR guidelines and registered in INPLASY. It involved a literature search in Scopus and PubMed, supplemented by manual reference screening, with study selection facilitated by Rayyan software. Our analysis clarifies the dual role of HIF-1α, which may either worsen inflammatory responses and viral persistence or support adaptive mechanisms that reduce cellular damage. The potential for targeting HIF-1α therapeutically in COVID-19 is complex, requiring further investigation to clarify its precise role and translational applications. This review deepens the molecular understanding of SARS-CoV-2-induced cellular and tissue dysfunction in hypoxia, offering insights for improving clinical management strategies and addressing long-term sequelae.

The hypoxic microenvironment of Candida albicans biofilms shapes neutrophil responses

Introduction

The microenvironment of Candida albicans biofilms create a hypoxic microenvironment, which exerts a profound influence on host immune responses during infection. Neutrophils are key defenders against C. albicans; however, the impact of biofilm-induced hypoxia on neutrophil function remains unclear.

Methods

We co-cultured human neutrophils in vitro with C. albicans biofilms at various stages of maturation, using both wild-type strains and extracellular matrix (ECM)-deficient mutants. Intracellular hypoxia was assessed using a fluorescent oxygen-sensitive probe. Neutrophil effector functions were evaluated by measuring caspase-3/7 activity, stabilization of hypoxia-inducible factor 1-alpha (HIF-1α), and accumulation of the anti-apoptotic Mcl-1 protein. Analyses included also quantification of reactive oxygen species (ROS) production, neutrophil extracellular trap (NET) formation, chemokine secretion (IL-8 and MIP-1β), and neutrophil elastase release. To assess the role of hypoxia signaling in neutrophil responses, cells were treated with the selective HIF-1α inhibitors LW6 and PX478.

Results

Neutrophils infiltrating C. albicans wild-type biofilms experience progressive hypoxia, which intensifies with biofilm maturation. This hypoxia results from high fungal metabolic activity and extracellular matrix (ECM) production. Within the biofilm microenvironment, neutrophils exhibit increased stabilization of HIF-1α and Mcl-1, elevated secretion of MIP-1β, IL-8, and reduced caspase 3/7 activity, collectively suggesting a biofilm-induced pro-survival phenotype. Simultaneously, mature biofilms markedly suppress NET formation and ROS production while enhancing degranulation. Comparative analyses using mannan-deficient C. albicans mutants highlight the critical role of ECM composition in modulating hypoxia-driven immune responses. Pharmacological inhibition of HIF-1α with LW6 and PX478 partially restores NETosis and ROS production, underscoring the pivotal role of this protein in regulation of neutrophil function.

Discussion

These findings provide novel insights into the impact of biofilm-induced hypoxia on neutrophil responses, identifying HIF-1α as a key regulator of immune adaptation in fungal biofilms. Targeting hypoxia pathways may offer new therapeutic strategies to modulate neutrophil responses and enhance host defenses against fungal infections.

Exploration potential sepsis-ferroptosis mechanisms through the use of CETSA technology and network pharmacology

As an important self-protection response mechanism of the body, inflammation can not only remove the necrotic or even malignant cells in the body, but also take a series of targeted measures to eliminate the pathogen of foreign invasion and block the foreign substances that may affect the life and health of the body. Flavonoids have known anti-inflammatory, anti-oxidation, anti-cancer and other effects, including glycyrrhizin molecules is one of the representatives. Licochalcone D has known anti-inflammatory and antioxidant properties and is effective in the treatment of a variety of inflammatory diseases. However, the underlying mechanism for the treatment of sepsis remains unclear. In this study, the therapeutic potential of Licochalcone D for sepsis was studied by analyzing network pharmacology and molecular dynamics simulation methods. Sepsis-related genes were collected from the database to construct PPI network maps and drug-targeting network profiles. The potential mechanism of Licochalcone D in sepsis was predicted by gene ontology, KEGG and molecular dynamics simulation. Sixty drug-disease genes were subsequently validated. Go analysis showed that monomeric small molecule Licochalcone D could regulate the process of intracellular enzyme system. The KEGG pathway analysis showed that the signal pathway of the main effect was related to the calcium pathway. The results of intersections with iron death-related target genes showed that ALOX5, ALOX15B and other nine targets all had the effect of possibly improving sepsis, while GSE 54,514, GSE 95,233 and GSE 69,528 were used to analyze the survival rate and ROC curve. Five genes were screened, including ALOX5, ALOX15B, NFE2L2 and NR4A1, HIF1A. The results of molecular docking showed that ALOX5 and Licochalcone D had strong binding activity. Finally, the results of molecular dynamics simulation showed that there was good binding power between drug and target. In the present study, we utilized molecular dynamics simulation techniques to assess the binding affinity between the small-molecule ligand and the protein receptor. The simulation outcomes demonstrate that the binding interface between the ligand and receptor remains stable, with a calculated binding free energy (ΔG) of -32.47 kJ/mol. This signifies a high-affinity interaction between the ligand and receptor, suggesting the long-term stability of the small molecule under physiological conditions. These findings provide critical insights for drug development efforts. This study elucidates the therapeutic potential of Licochalcone D, a traditional Chinese medicine monomer, in improving sepsis through the regulation of ferroptosis, thereby providing a new direction and option for subsequent clinical drug development in the treatment of sepsis.

Discovery of niclosamide as a p300/transcription factor protein-protein interaction inhibitor

Protein-protein interactions (PPIs) are crucial in various biological processes and are attractive targets for drug discovery. In this study, we identified niclosamide (9) as a novel inhibitor of the hypoxia-inducible factor 1α (HIF-1α)/p300 PPI from the RIKEN NPDepo compound library using a fluorescence anisotropy-based screening method. We synthesized niclosamide azide (10) as a photoaffinity labelling probe to identify the p300 binding site of compound 9 and elucidated the binding mode using photoaffinity labelling experiments and molecular docking simulations. Furthermore, we demonstrated that compound 9 inhibited not only HIF-1α/p300 PPI but also p300-transcription factor PPIs, including interaction with p53 and STAT3, thereby suppressing the expression of BAX and c-MYC, respectively.

Functional cobalt-doped hydrogel scaffold enhances concurrent vascularization and neurogenesis

Achieving functional tissue regeneration hinges on the coordinated growth of intricate blood vessels and nerves within the defect area. However, current strategies do not offer a reliable and effective way to fulfill this critical need. To address this challenge, a three-dimensional (3D) gelatin methacryloyl-multi-walled carbon nanotube/cobalt (GelMA-MWCNTs/Co) hydrogel with controlled release of cobalt (Co) ions was developed for hypoxia-mimicking and dual beneficial effects on promoting vasculogenesis and neurogenesis. GelMA-MWCNTs/Co hydrogel exhibited sustained release of Co ions, promoting laden cell viability and long-term cell survival. GelMA-MWCNTs/Co hydrogel effectively enhanced human umbilical vein endothelial cells (HUVECs) vasculogenesis when cocultured with stem cells from apical papilla (SCAP). Moreover, this hydrogel facilitated the interaction between the pre-formed vascular and neural-like structures generated by electrical stimulation-induced SCAP (iSCAP). Furthermore, our in vivo study revealed that the GelMA-MWCNTs/Co hydrogel remarkably enhanced neovascularization and accelerated anastomosis with the host vasculature. The pre-vascularized scaffolds boosted the presence of neural differentiated SCAP in the regenerated tissue. This study provided proof of integrating functional Co ions release materials and dental-derived stem cells within a hydrogel scaffold as a promising potential for achieving simultaneous vascularization and neurogenesis.

Unlocking the Potential of Curcumae Rhizoma Aqueous Extract in Stress Resistance and Extending Lifespan in Caenorhabditis elegans

The enhancement of stress resistance is crucial for delaying aging and extending a healthy lifespan. Traditional Chinese medicine (TCM), a cherished treasure of Chinese heritage, has shown potential in mitigating stress and promoting longevity. This study integrates network pharmacology and in vivo analysis to investigate the mechanisms and effects of Curcumae Rhizoma (C. Rhizoma), known as "E Zhu" in Chinese. Ultra-Performance Liquid Chromatography-Tandem Mass Spectrometry (UPLC-MS/MS) identified 10 active compounds in its aqueous extract, interacting with 128 stress-related targets. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses revealed pathways such as stress response, FoxO signaling, and insulin resistance. In Caenorhabditis elegans, 10 mg/mL of C. Rhizoma aqueous extract improved resistance to UV, thermal, oxidative, and pathogen-induced stress, extending lifespan in a dose-dependent manner. Mechanistically, it reduced reactive oxygen species (ROS), increased superoxide dismutase (SOD) activity, and enhanced UV resistance via the insulin/IGF-1 pathway and DAF-16 translocation. Molecular docking highlighted hexahydrocurcumin (HHC) and related compounds as key bioactives. Furthermore, we also observed that C. Rhizoma aqueous extract significantly extended both the lifespan and healthspan of nematodes. These findings highlight the potential of C. Rhizoma in stress mitigation and longevity promotion, offering valuable insights into the therapeutic applications of TCM.

Molecular gatekeepers of endogenous adult mammalian cardiomyocyte proliferation

Irreversible cardiac fibrosis, cardiomyocyte death and chronic cardiac dysfunction after myocardial infarction pose a substantial global health-care challenge, with no curative treatments available. To regenerate the injured heart, cardiomyocytes must proliferate to replace lost myocardial tissue - a capability that adult mammals have largely forfeited to adapt to the demanding conditions of life. Using various preclinical models, our understanding of cardiomyocyte proliferation has progressed remarkably, leading to the successful reactivation of cell cycle induction in adult animals, with functional recovery after cardiac injury. Central to this success is the targeting of key pathways and structures that drive cardiomyocyte maturation after birth - nucleation and ploidy, sarcomere structure, developmental signalling, chromatin and epigenetic regulation, the microenvironment and metabolic maturation - forming a complex regulatory framework that allows efficient cellular contraction but restricts cardiomyocyte proliferation. In this Review, we explore the molecular pathways underlying these core mechanisms and how their manipulation can reactivate the cell cycle in cardiomyocytes, potentially contributing to cardiac repair.

Metabolic Adaptations and Therapies in Cardiac Hypoxia: Mechanisms and Clinical Implications/ Potential Strategies

Cardiac hypoxia triggers a cascade of responses and functional changes in myocardial and non-myocardial cells, profoundly affecting cellular metabolism, oxygen-sensing mechanisms, and immune responses. Myocardial cells, being the primary cell type in cardiac tissue, undergo significant alterations in energy metabolism, including glycolysis, fatty acid metabolism, ketone body utilization, and branched-chain amino acid metabolism, to maintain cardiac function under hypoxic conditions. Non-myocardial cells, such as fibroblasts, endothelial cells, and immune cells, although fewer in number, play crucial roles in regulating cardiac homeostasis, maintaining structural integrity, and responding to injury. This review discusses the metabolic reprogramming of immune cells, particularly macrophages, during ischemia-reperfusion injury and explores various therapeutic strategies that modulate these metabolic pathways to protect the heart during hypoxia. Understanding these interactions provides valuable insights and potential therapeutic targets for heart disease treatment.

Biochemical investigations using mass spectrometry to monitor JMJD6-catalysed hydroxylation of multi-lysine containing bromodomain-derived substrates

Jumonji-C domain-containing protein 6 (JMJD6) is a human 2-oxoglutarate (2OG)/Fe(ii)-dependent oxygenase catalysing post-translational C5 hydroxylation of multiple lysine residues, including in the bromodomain-containing proteins BRD2, BRD3 and BRD4. The role(s) of JMJD6-catalysed substrate hydroxylation are unclear. JMJD6 is important in development and JMJD6 catalysis may promote cancer. We report solid-phase extraction coupled to mass spectrometry assays monitoring JMJD6-catalysed hydroxylation of BRD2-4 derived oligopeptides containing multiple lysyl residues. The assays enabled determination of apparent steady-state kinetic parameters for 2OG, Fe(ii), l-ascorbate, O2 and BRD substrates. The JMJD6 K app m for O2 was comparable to that reported for the structurally related 2OG oxygenase factor inhibiting hypoxia-inducible factor-α (FIH), suggesting potential for limitation of JMJD6 activity by O2 availability in cells, as proposed for FIH and some other 2OG oxygenases. The new assays will help development of small-molecule JMJD6 inhibitors for functional assignment studies and as potential cancer therapeutics.

Interactions Between Non-Coding RNAs and HIF-1alpha in the Context of Colorectal Cancer

Hypoxia-inducible factor-1α (HIF-1α), a master regulator of cellular adaptation to hypoxia, drives colorectal cancer (CRC) progression by fueling angiogenesis, metastasis, and therapy resistance. Emerging evidence delineates intricate crosstalk between non-coding RNAs (ncRNAs)-including microRNAs, long non-coding RNAs, and circular RNAs-and HIF-1α, forming bidirectional regulatory networks that orchestrate CRC pathogenesis. By interacting with HIF-1α, these non-coding RNAs contribute to the orchestration of the aggressive hypoxic tumor microenvironment. Recent studies have evaluated the clinical potential of lncRNAs and miRNAs in the realms of non-invasive liquid biopsies and RNA-targeted therapies. This review offers a comprehensive synthesis of recent investigations into the mechanisms by which lncRNAs and miRNAs interact with HIF-1α to modulate CRC progression. Additionally, we further explore the clinical implications of ncRNA/HIF-1α crosstalk, emphasizing their potential as diagnostic biomarkers and therapeutic targets, while also spotlighting intriguing and promising areas of ncRNA research. Methods: In this study, our search strategy employed in databases such as PubMed, Web of Science, and EMBASE is as follows: we will specify search terms, including combinations of "non-coding RNA", "HIF-1α", and "colorectal cancer", along with a date range for the literature search (for example, from 2000 to 2025) to capture the most relevant and up-to-date research.

Succinate predisposes mice to atrial fibrillation by impairing mitochondrial function via SUCNR1/AMPK axis

Atrial fibrillation (AF), a major public health concern, is associated with high rates of death and disability. Mitochondrial dysfunction has emerged as a key contributor to the pathophysiology of AF. Succinate, an essential Krebs cycle metabolite, is often elevated in the circulation of patients at risk for AF. However, its exact role in AF pathogenesis is still not well understood. To explore the association linking succinate overload and AF, we first established AF-susceptible mouse models of obesity and diabetes, confirming that circulating succinate levels were significantly elevated in these AF-prone mice. Next, we assessed AF vulnerability and atrial remodeling in succinate-treated mice (2 %/5 % for 7 weeks) or isolated primary atrial cells (0.5 mM for 24 h). Our results demonstrated that succinate overload increased AF susceptibility in mice and triggered adverse atrial remodeling, characterized by left atrial dilation, connexins lateralization, ion channel disturbances, and fibrosis. Moreover, succinate compromised atrial mitochondrial structure, leading to increased oxidative stress. Mechanistically, succinate overload upregulated the expression of its cognate receptor SUCNR1 (succinate receptor 1) and decreased AMPK (AMP-activated protein kinase) phosphorylation both in vitro and in vivo. AICAR (AMPK activator) maintained mitochondrial health to mitigate remodeling in succinate-exposed cells and prevented succinate-induced AF in obese and diabetic mice. In conclusion, succinate overload enhances AF vulnerability and atrial remodeling by impairing AMPK signaling and mitochondrial function. Succinate, therefore, represents an underappreciated contributor to AF pathogenesis and a potential biomarker.

Mitochondrial fission produces a Warburg effect via the oxidative inhibition of prolyl hydroxylase domain-2

Excessive mitochondrial fission and a shift to a Warburg phenotype are hallmarks of pulmonary hypertension (PH), although the mechanistic link between these processes remains unclear. We show that in pulmonary arterial endothelial cells (PAEC), Drp1 overexpression induces mitochondrial fission and increases glycolytic ATP production and glycolysis. This is due to mitochondrial reactive oxygen species (mito-ROS)-mediated activation of hypoxia-inducible factor-1α (HIF-1α) signaling, and this is linked to hydrogen peroxide (H2O2)-mediated inhibition of prolyl hydroxylase domain-2 (PHD2) due to its cysteine 326 oxidation and dimerization. Furthermore, these findings are validated in PAEC isolated from a lamb model of PH, which are glycolytic (Shunt PAEC), exhibit increases in both H2O2 and PHD2 dimer levels. The overexpression of catalase reversed the PHD2 dimerization, decreased HIF-1α levels, and attenuated glycolysis in Shunt PAEC. Our data suggest that reducing PHD2 dimerization could be a potential therapeutic target for PH.

Control of circadian muscle glucose metabolism through the BMAL1-HIF axis in obesity

Disruptions of circadian rhythms are widespread in modern society and lead to accelerated and worsened symptoms of metabolic syndrome. In healthy mice, the circadian clock factor BMAL1 is required for skeletal muscle function and metabolism. However, the importance of muscle BMAL1 in the development of metabolic diseases, such as diet-induced obesity (DIO), remains unclear. Here, we demonstrate that skeletal muscle-specific BMAL1-deficient mice exhibit worsened glucose tolerance upon high-fat diet feeding, despite no evidence of increased weight gain. Metabolite profiling from Bmal1-deficient muscles revealed impaired glucose utilization specifically at early steps in glycolysis that dictate the switch between anabolic and catabolic glucose fate. We provide evidence that this is due to abnormal control of the nutrient stress-responsive hypoxia-inducible factor (HIF) pathway. Genetic HIF1α stabilization in muscle Bmal1-deficient mice restores glucose tolerance and expression of 217/736 dysregulated genes during DIO, including glycolytic enzymes. Together, these data indicate that during DIO, skeletal muscle BMAL1 is an important regulator of HIF-driven glycolysis and metabolic flexibility, which influences the development of high-fat-diet-induced glucose intolerance.

Discovery of Novel, Potent, Orally Bioavailable and Efficacious, Hypoxia-Inducible Factor Prolyl Hydroxylase Inhibitors for Hematopoietic Stem Cell Mobilization

Hematopoietic stem cell (HSC) mobilization is often difficult to achieve in patients suffering from multiple myeloma and non-Hodgkin's lymphoma. Granulocyte-colony stimulating factor (G-CSF) therapy alone has often not led to the desired outcomes. Herein, we describe the discovery of 7-cyclohexyl-4-hydroxy-8-oxo-N-(pyridazin-4-ylmethyl)-7,8-dihydro-2,7-naphthyridine-3-carboxamide 13, a hypoxia-inducible factor prolyl hydroxylase (HIF-PH) inhibitor, which was discovered by focusing on drug-like properties. Building on a previous discovery that HIF-PH inhibitors can enhance HSC mobilization in combination with G-CSF, we optimized 13 to exhibit high PHD2 potency, improved solubility, and an optimized PK profile. 13 was effective at enhancing G-CSF-induced HSC mobilization in mice at a dose of 2 mg/kg.

The pro-inflammatory cytokine IL6 suppresses mitochondrial function via the gp130-JAK1/STAT1/3-HIF1α/ERRα axis

Chronic inflammation and a decline in mitochondrial function are hallmarks of aging. Here, we show that the two mechanisms may be linked. We found that interleukin-6 (IL6) suppresses mitochondrial function in settings where PGC1 (both PGC1α and PGC1β) expression is low. This suppression is mediated by the JAK1/STAT1/3 axis, which activates HIF1α through non-canonical mechanisms involving upregulation of HIF1A and ERRα transcription, and subsequent stabilization of the HIF1A protein by ERRα. HIF1α, in turn, inhibits ERRα, which is a master regulator of mitochondrial biogenesis, thus contributing to the inhibition of mitochondrial function. When expressed at higher levels, PGC1 rescues ERRα to boost baseline mitochondrial respiration, including under IL6-treated conditions. Our study suggests that inhibition of the IL6 signaling axis could be a potential treatment for those inflammatory settings where mitochondrial function is compromised.

Cardiotoxicity of tris(2-chloroethyl) phosphate exposure: Insights into the role of oxygen sensor mediated energy metabolism remodeling

Tris(2-chloroethyl) phosphate, an extensively used organophosphorus flame retardant in consumer products, has caused pervasive environmental contamination and increased human exposure, raising concerns about its cardiotoxic potential. However, the detailed toxicological profile, particularly concerning the crucial cardiac energy metabolism, and the precise mechanisms remain poorly understood. This study in C57BL/6 J mice exposed to TCEP for 36 days at varying doses revealed cardiac dysfunction, structural abnormalities, and hypoxia. Analysis of energy metabolism indicated a shift from aerobic processes (tricarboxylic acid cycle, β-oxidation, and oxidative phosphorylation) to anaerobic metabolism (glycolysis). Further restoration of energy metabolism remodeling, which was achieved by activating oxidative phosphorylation and inhibiting glycolysis, mitigated TCEP-induced cardiotoxicity, highlighting the critical role of energy metabolism remodeling in TCEP-induced cardiac injury. Mechanistically, this metabolic remodeling was primarily driven by TCEP-enhanced hyperubiquitination and degradation of prolyl hydroxylase domain 2 (PHD2), leading to the accumulation and nuclear translocation of hypoxia-inducible factor-1α (HIF-1α). This study yields key insights into the cardiotoxicity of TCEP-like OPFRs exposure, and emphasizes the role of altered cardiac energy metabolism and the oxygen-sensing pathway, thereby proposing potential intervention strategies for OPFR-induced cardiac toxicity.

Effect of FLT3 ligand on the gene expression of TIM-3, HIF1-α, and TNF-α in an acute myeloid leukemia cell line

BACKGROUND

Acute Myeloid Leukemia (AML) pathogenesis is driven by the dysregulation of various cell signaling pathways, including the FMS-Like Tyrosine Kinase 3 (FLT3) pathway and its ligand (FLT3L). These pathways play a critical role in promoting cell survival, proliferation, and resistance to apoptosis, contributing to leukemogenesis. In this study, we investigated the effects of FLT3L on the expression of key genes associated with immune regulation, hypoxia, and inflammation-TIM-3, HIF-1α, and TNF-α-in the THP-1 cell line, a well-established model for AML research.

METHODS

THP-1 cells were cultured under standard conditions and treated with varying concentrations of FLT3L, alongside PMA as a positive control. Quantitative RT-PCR was employed to measure the expression levels of TIM-3, HIF-1α, and TNF-α genes after 48 h of treatment.

RESULTS

Our findings demonstrated that specific concentrations of FLT3L significantly upregulated the expression of TIM-3, HIF-1α, and TNF-α in THP-1 cells. This suggests that FLT3L not only influences cell proliferation and survival but also modulates pathways related to immune evasion, hypoxia adaptation, and inflammatory responses, which are hallmarks of leukemia progression.

CONCLUSION

These results highlight the pivotal role of FLT3L in regulating the expression of genes associated with AML pathogenesis, particularly those involved in hypoxia (HIF-1α), immune checkpoint regulation (TIM-3), and inflammation (TNF-α). The findings underscore the potential of targeting the FLT3 pathway as a therapeutic strategy in AML. Further studies are warranted to elucidate the underlying molecular mechanisms and explore their clinical implications for improving patient outcomes.

PHD-2/HIF-1α axis mediates doxorubicin-induced angiogenesis in SH-SY5Y neuroblastoma microenvironment: a potential survival mechanism

The response of neuroblastoma (NB) cells to chemotherapeutics and their influence on NB microenvironment remain incompletely understood. Herein, we examined the underlying molecular mechanism via which Doxorubicin, a chemotherapeutic agent used for NB treatment, promotes proangiogenic response in the SH-SY5Y microenvironment. Doxorubicin treatment at 1 µg/ml reduced SH-SY5Y cell proliferation and primed the apoptosis pathway. Unexpectedly, SH-SY5Y cells treated with doxorubicin upregulated their expression of the pro-angiogenic factors, including vascular endothelial growth factor (VEGF), platelets-derived growth factor (PDGF), and matrix metalloprotease-2 (MMP-2) and secretion of nitric oxide. To assess the functional angiogenesis of SH-SY5Y cells pre-treated with doxorubicin, an indirect co-culture system with human umbilical vein endothelial cells (HUVEC) was established. These HUVECs acquired enhanced proliferation, migration capacity, and tube formation capability and exhibited increased nitric oxide (NO) production, in addition to upregulated α-smooth muscle actin expression, suggesting enhanced contractility. In-ovo studies of the neo-angiogenic response of SH-SY5Y pre-treated with doxorubicin further show their promoted neo-angiogenesis as indicated by the generated blood vessels and histological analysis of CD31 expression. Inhibition of PHD-2 could be a potential target for doxorubicin, as indicated by molecular docking, molecular dynamics (MD) simulation, and MM-GBSA calculations, leading to hypoxia-inducible factor-1 alpha (HIF-1α) stabilization. Bioinformatics analyses and enrichment analyses of RNA-seq data revealed activation of Pi3K pathway which is further validated in-vitro. These results provide evidence of the unexpected pro-angiogenic response of SH-SY5Y cells to doxorubicin treatment and suggest the potential use of multi-modal therapeutic regimens for a more comprehensive approach to NB treatment.

Vascular HIF2 Signaling Prevents Cardiomegaly, Alveolar Congestion, and Capillary Remodeling During Chronic Hypoxia

BACKGROUND

Hypoxia is associated with the onset of cardiovascular diseases including cardiac hypertrophy and pulmonary hypertension. HIF2 (hypoxia inducible factor 2) signaling in the endothelium mediates pulmonary arterial remodeling and subsequent elevation of the right ventricular systolic pressure during chronic hypoxia. Thus, novel therapeutic opportunities for pulmonary hypertension based on specific HIF2 inhibitors have been proposed. Nevertheless, HIF2 relevance beyond the pulmonary endothelium or in the cardiac adaptation to hypoxia remains elusive. Wt1 (Wilms tumor 1) lineage contributes to the heart and lung vascular compartments, including pericytes, endothelial cells, and smooth muscle cells.

METHODS

Here, we describe the response to chronic hypoxia of a novel HIF2 mutant mouse model in the Wt1 lineage (Hif2/Wt1 cKO [conditional knockout]), characterizing structural and functional aspects of the heart and lungs by means of classical histology, immunohistochemistry, flow cytometry, echocardiography, and lung ultrasound analysis.

RESULTS

Hif2/Wt1 cKO is protected against pulmonary remodeling and increased right ventricular systolic pressure induced by hypoxia, but displays alveolar congestion, inflammation, and hemorrhages associated with microvascular instability. Furthermore, lack of HIF2 in the Wt1 lineage leads to cardiomegaly, capillary remodeling, right and left ventricular hypertrophy, systolic dysfunction, and left ventricular dilation, suggesting pulmonary-independent cardiac direct roles of HIF2 in hypoxia. These structural defects are partially restored upon reoxygenation, while cardiac functional parameters remain altered.

CONCLUSIONS

Our results indicate that cardiopulmonary HIF2 signaling prevents excessive vascular proliferation during chronic hypoxia and define novel protective roles of HIF2 to warrant stable microvasculature and organ function.

Hypoxia-inducible factor 1α is required to establish the larval glycolytic program in Drosophila melanogaster

OBJECTIVES

The rapid growth that occurs during Drosophila larval development requires a dramatic rewiring of central carbon metabolism to support biosynthesis. Larvae achieve this metabolic state, in part, by coordinately up-regulating the expression of genes involved in carbohydrate metabolism. The resulting metabolic program exhibits hallmark characteristics of aerobic glycolysis and establishes a physiological state that supports growth. To date, the only factor known to activate the larval glycolytic program is the Drosophila Estrogen-Related Receptor (dERR). However, dERR is dynamically regulated during the onset of this metabolic switch, indicating that other factors must be involved. Here we examine the possibility that the Drosophila ortholog of Hypoxia inducible factor 1α (Hif1α) is also required to activate the larval glycolytic program.

METHODS

CRISPR/Cas9 was used to generate new loss-of-function alleles in the Drosophila gene similar (sima), which encodes the sole fly ortholog of Hif1α. The resulting mutant strains were analyzed using a combination of metabolomics and RNAseq for defects in carbohydrate metabolism.

RESULTS

Our studies reveal that sima mutants fail to activate aerobic glycolysis and die during larval development with metabolic phenotypes that mimic those displayed by dERR mutants. Moreover, we demonstrate that dERR and Sima/Hif1α protein accumulation is mutually dependent, as loss of either transcription factor results in decreased abundance of the other protein.

CONCLUSIONS

These findings demonstrate that Sima/HIF1α is required during embryogenesis to coordinately up-regulate carbohydrate metabolism in preparation for larval growth. Notably, our study also reveals that the Sima/HIF1α-dependent gene expression program shares considerable overlap with that observed in dERR mutant, suggesting that Sima/HIF1α and dERR cooperatively regulate embryonic and larval glycolytic gene expression.

A conditionally replicative adenovirus vector containing the synNotch receptor gene for the treatment of muscle-invasive bladder cancer

Muscle-invasive bladder cancer (MIBC), a highly heterogeneous disease, shows genomic instability and a high mutation rate, making it difficult to treat. Recent studies revealed that cancer stem cells (CSCs) play a critical role in MIBC frequent recurrence and high morbidity. Previous research has shown that Cyclooxygenases-2 (COX-2) is particularly highly expressed in bladder cancer cells. In recent years, the development of oncolytic adenoviruses and their use in clinical trials have gained increased attention. In this study, we composed a conditionally replicative adenovirus vector (CRAd-synNotch) that carries the COX-2 promotor driving adenoviral E1 gene, the synNotch receptor therapeutic gene, and the Ad5/35 fiber gene. Activation of the COX-2 promoter gene causes replication only within COX-2 expressing cancer cells, thereby leading to tumor oncolysis. Also, CD44 and HIF signals contribute to cancer stemness and maintaining CSCs in bladder cancer, and the transduced synNotch receptor inhibits both CD44 and HIF signals simultaneously. We performed an in vivo study using a mouse xenograft model of T24 human MIBC cells and confirmed the significant antitumor activity of CRAd-synNotch. Our findings in this study warrant the further development of CRAd-synNotch for treating patients with MIBC.

Crosstalk between glomeruli and tubules

Models of kidney injury have classically concentrated on glomeruli as the primary site of injury leading to glomerulosclerosis or on tubules as the primary site of injury leading to tubulointerstitial fibrosis. However, current evidence on the mechanisms of progression of chronic kidney disease indicates that a complex interplay between glomeruli and tubules underlies progressive kidney injury. Primary glomerular injury can clearly lead to subsequent tubule injury. For example, damage to the glomerular filtration barrier can expose tubular cells to serum proteins, including complement and cytokines, that would not be present in physiological conditions and can promote the development of tubulointerstitial fibrosis and progressive decline in kidney function. In addition, although less well-studied, increasing evidence suggests that tubule injury, whether primary or secondary, can also promote glomerular damage. This feedback from the tubule to the glomerulus might be mediated by changes in the reabsorptive capacity of the tubule, which can affect the glomerular filtration rate, or by mediators released by injured proximal tubular cells that can induce damage in both podocytes and parietal epithelial cells. Examining the crosstalk between the various compartments of the kidney is important for understanding the mechanisms underlying kidney pathology and identifying potential therapeutic interventions.

How oxygenation shapes immune responses: emerging roles for physioxia and pathological hypoxia

Most eukaryotes require oxygen for their survival and, with increasing multicellular complexity, oxygen availability and delivery rates vary across the tissues of complex organisms. In humans, healthy tissues have markedly different oxygen gradients, ranging from the hypoxic environment of the bone marrow (where our haematopoietic stem cells reside) to the lungs and their alveoli, which are among the most oxygenated areas of the body. Immune cells are therefore required to adapt to varying oxygen availability as they move from the bone marrow to peripheral organs to mediate their effector functions. These changing oxygen gradients are exaggerated during inflammation, where oxygenation is often depleted owing to alterations in tissue perfusion and increased cellular activity. As such, it is important to consider the effects of oxygenation on shaping the immune response during tissue homeostasis and disease conditions. In this Review, we address the relevance of both physiological oxygenation (physioxia) and disease-associated hypoxia (where cellular oxygen demand outstrips supply) for immune cell functions, discussing the relevance of hypoxia for immune responses in the settings of tissue homeostasis, inflammation, infection, cancer and disease immunotherapy.

Osteocytic oxygen sensing: Distinct impacts of VHL and HIF-2alpha on bone integrity

Skeletal fracture resistance emerges from multiple components of bone structure like microarchitecture, matrix mineralization, and organization. These characteristics are engendered via mechanisms like the hypoxia-inducible factors (HIF) pathway, involving two paralogs, HIF-1α and HIF-2α. Under normoxia, HIF-α is targeted for degradation via von-Hippel Lindau (VHL); hypoxia enables HIF-α stabilization and induction of target genes. We previously showed that osteocytic Vhl deletion or expression of degradation-resistant HIF-2α cDR female mice each produced high bone mass, whereas degradation-resistant osteocytic HIF-1α produced no overt phenotype. We report within that Vhl cKO increased bone strength, while HIF-2α cDR displayed markedly reduced bone strength below Cre-negative controls. This suggests that VHL and HIF-2α drive distinct responses that promote disparate effects on bone strength. Both Vhl deletion or HIF-2α accumulation generated two discrete bone morphologies: an outer lamellar cortex and a woven, poorly mineralized endocortex that imparted dramatically different functional outcomes. Our studies reveal novel influence of osteocytic HIF-2α signaling on collagen matrix organization, mineralization, and bone strength.

Hypoxia regulates small extracellular vesicle biogenesis and cargo sorting through HIF-1α/HRS signaling pathway in head and neck squamous cell carcinoma

Small extracellular vesicles (sEVs) act as crucial messengers that transmit biological signals in hypoxic tumor microenvironment (TME), significantly impacting cancer progression. However, the precise mechanism by which hypoxia influences sEV biogenesis remains poorly understood. In this study, we observed increased sEV secretion and alterations in cargo composition in head and neck squamous cell carcinoma (HNSCC) cells under hypoxic conditions. We found that hepatocyte growth factor-regulated tyrosine kinase substrate (HRS), a key component of the endosomal sorting complexes required for transport (ESCRT), was upregulated during hypoxia. This upregulation activated the endosomal system and reduced degradation of multivesicular bodies (MVBs). HRS depletion altered the packaging of protein cargoes such as mitochondria-related proteins into sEVs under hypoxia, and these cargoes promoted a pro-tumorigenic phenotype of macrophages. Importantly, we demonstrated that HRS is transcriptionally activated by hypoxia inducible factor-1α (HIF-1α). Spatial transcriptomics and immunohistochemistry revealed a positive correlation between HRS and HIF-1α. These findings establish a link between the hypoxic response, sEV biogenesis, and cargo packaging, enhancing our understanding of how the hypoxic TME influences sEV biogenesis in HNSCC cells.

Oxygen sensing in the kidney

The kidneys fulfil several essential homeostatic functions for the body. One of them is the maintenance of sufficient oxygen supply to the organs. For this purpose, the kidneys control the formation of red blood cells by the production of the hormone erythropoietin. This control of red cell formation is not only relevant to prevent states of oxygen deficiency but also to prevent an unwanted increase of red cell numbers causing thromboembolic risks. The adequate production of erythropoietin requires a sensing of the arterial oxygen content and transduction to hormone production. This oxygen sensing is a two-step process which includes a translation of the arterial oxygen content to respective oxygen tension in the tubulointerstitium and a perception of the resulting local interstitial oxygen tension to translate them into specific cellular responses such as the production of erythropoietin. This contribution will describe these steps of oxygen sensing for the healthy kidney and for the changes occurring during states of chronic renal disease, which are commonly associated with anemia. In this context a special focus will also be set on intrarenal hypoxia and oxygen sensing in the diabetic kidney including the treatment with tubular glucose transport (sodium-glucose cotransporter 2) inhibitors which might influence the oxygen sensing in the kidney. Finally, we will consider the effects of prolyl-hydroxylase inhibitors (HIF-PHIs), which fundamentally interfere with the cellular oxygen sensing and which are meanwhile treatment options in renal anemia.

Total saponins from Panax japonicus reduced lipid deposition and inflammation in hepatocyte via PHD2 and hepatic macrophage-derived exosomal miR-463-5p

ETHNOPHARMACOLOGICAL RELEVANCE

Panax japonicus (T. Nees) C.A. Mey. (PJ) is a traditional Chinese herbal medicine revered as the "King of Herbs" in Tujia and Hmong medical practices. Clinically, it is primarily used to treat weakness and fatigue, wound bleeding, arthritis, hyperlipidemia, and fatty liver. It is rich in saponins, and the total saponins from PJ (TSPJ), possess immunomodulatory, antioxidant, and lipid-lowering effects. These properties hold significant potential in managing liver-related metabolic diseases such as non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH).

AIM OF STUDY

Evaluate the therapeutic effects of TSPJ on lipid metabolism disorders in a NASH model and explore the possible underlying mechanisms.

MATERIALS AND METHODS

To model NASH, C57BL/6J mice were fed a high-fat diet (HFD) and RAW264.7 cells were stimulated with lipopolysaccharide (LPS) and palmitic acid (PA). The animal and cell models were also treated with TSPJ, and the changes in inflammation and lipid metabolism were measured. Additional models were created by transfecting lentiviral vectors to cause miR-463-5p knockdown in the C57BL/6J mouse and the RAW264.7 cells.

RESULTS

In the HFD-induced mice, TSPJ reduced the body weight and liver weight, lowered the serum levels of TG, T-CHO, ALT, and AST, and reduced the hepatic lipid droplet formation and vacuolization. In the RAW264.7 cells, TSPJ upregulated the M2 markers and downregulated the M1 markers. TSPJ also significantly increased the expression of miR-463-5p in the exosomes derived from the RAW264.7 cells or the primary mouse hepatic macrophages, and miR-463-5p suppressed the expression of PHD2 in hepatocytes to improve lipid metabolism. However, when the exosome secretion inhibitor GW4869 was applied, TSPJ became less effective in alleviating the lipid deposition and inflammation in hepatocytes.

CONCLUSIONS

TSPJ significantly upregulated the expression of miR-463-5p in the exosomes of hepatic macrophages to thus downregulate PHD2 expression in hepatocytes and improve hepatic lipid metabolism.

O2-dependent incapacitation of the Salmonella pathogenicity island 1 repressor HilE

For successful colonization, pathogenic bacteria need to adapt their metabolism and virulence functions to challenging environments within their mammalian hosts that are frequently characterized by low oxygen (O2) tensions. Upon oral ingestion, the human pathogen Salmonella enterica serovar Typhimurium (S. Typhimurium) is exposed to changing O2 and pH levels. Low concentrations of O2, which can enhance the virulence of enteroinvasive pathogens, facilitate the expression of the type three secretion system (T3SS-1) encoded by the Salmonella pathogenicity island 1 (SPI-1) that is critical for enteroinvasion and pathogenicity of S. Typhimurium. To study the impact of key environmental cues of the intestine when Salmonella encounter enterocytes, we established an in vitro growth model, which allows shifting the concentration of O2 from 0.5% to 11% and the pH from 5.9 to 7.4 in the presence of acetate and the alternative electron acceptor nitrate. Compared to normoxia, hypoxia elevated the expression of SPI-1 genes encoding T3SS-1 translocators and effectors, which resulted in higher invasion and effector translocation in epithelial cells. While hypoxia and pH shift only marginally altered the gene expression of SPI-1 regulators, including the SPI-1 repressor hilE, hypoxia and pH shift completely incapacitated HilE in a post-translational manner, ultimately promoting SPI-1 activity. From these findings, we conclude that O2-dependent HilE function allows for ultrasensitive adaptation of SPI-1 activity in environments with varying O2 availability such as the intestinal tract.

Mint3 as a Molecular Target Activated in the Early Stage of Hepatocarcinogenesis

Mint3 enhances aerobic ATP production with subsequent nuclear translocation of hypoxia-inducible factor-1 (HIF-1) and activation of angiogenesis-related genes. It remains unclear if and when Mint3 is activated and whether it is involved in hepatocarcinogenesis. We explored the expression of Mint3 in surgically resected hepatocellular carcinoma (HCC) tissues. We evaluated the effects of Mint3 knockdown on spheroid formation capacity and subcutaneous tumor growth in immune-deficient mice. We used Mint3 knockout mice to evaluate the effects of chemically induced HCC development. Mint3 was overexpressed in well-differentiated HCC with the activation of HIF-1 target genes irrespective of the absence of hypervascularization. Mint3 knockdown ameliorated the expression of HIF-1 target genes in patient-derived HCC cell lines and suppressed spheroid formation. Mint3 knockdown further inhibited subcutaneous tumor formation in vivo in immune-deficient mice. Chemical HCC development induced by N-nitrosodiethylamine (DEN) or DEN/CCl4 was dramatically suppressed in Mint3 knockout mice compared to control mice. Mint3 plays a crucial role in early-stage HCC development before hypervascularization by activating HIF-1 target genes before the tumor becomes hypoxic. Mint3 is a molecular target that prevents HCC development in the early stages.

2-Oxoglutarate-dependent dioxygenases as oxygen sensors: their importance in health and disease

Since low oxygen conditions below physiological levels, hypoxia, are associated with various diseases, it is crucial to understand the molecular basis behind cellular response to hypoxia. Hypoxia-inducible factors (HIFs) have been revealed to primarily orchestrate the hypoxic response at the transcription level and have continuously attracted great attention over the past three decades. In addition to these hypoxia-responsive effector proteins, 2-oxoglutarate-dependent dioxygenase (2-OGDD) superfamily including prolyl-4-hydroxylase domain-containing proteins (PHDs) and factor inhibiting HIF-1 (FIH-1) has attracted even greater attention in recent years as factors that act as direct oxygen sensors due to their necessity of oxygen for the regulation of the expression and activity of the regulatory subunit of HIFs. Herein, we present a detailed classification of 2-OGDD superfamily proteins, such as Jumonji C-domain-containing histone demethylases, ten-eleven translocation enzymes, AlkB family of DNA/RNA demethylases and lysyl hydroxylases, and discuss their specific functions and associations with various diseases. By introducing the multifaceted roles of 2-OGDD superfamily proteins in the hypoxic response, this review aims to summarize the accumulated knowledge about the complex mechanisms governing cellular adaptation to hypoxia in various physiological and pathophysiological contexts.