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]

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.

Suppressing APOE4-induced neural pathologies by targeting the VHL-HIF axis

The ε4 variant of human apolipoprotein E (APOE4) is a key genetic risk factor for neurodegeneration in Alzheimer's disease and elevated all-cause mortality in humans. Understanding the factors and mechanisms that can mitigate the harmful effects of APOE4 has significant implications. In this study, we find that inactivating the VHL-1 (Von Hippel-Lindau) protein can suppress mortality, neural and behavioral pathologies caused by transgenic human APOE4 in Caenorhabditis elegans. The protective effects of VHL-1 deletion are recapitulated by stabilized HIF-1 (hypoxia-inducible factor), a transcription factor degraded by VHL-1. HIF-1 activates a genetic program that safeguards against mitochondrial dysfunction, oxidative stress, proteostasis imbalance, and endolysosomal rupture-critical cellular events linked to neural pathologies and mortality. Furthermore, genetic inhibition of Vhl reduces cerebral vascular injury and synaptic lesions in APOE4 mice, suggesting an evolutionarily conserved mechanism. Thus, we identify the VHL-HIF axis as a potent modulator of APOE4-induced neural pathologies and propose that targeting this pathway in nonproliferative tissues may curb cellular damage, protect against neurodegeneration, and reduce tissue injuries and mortality.

Physiological and cellular mechanisms of ischemic preconditioning microRNAs-mediated in underlying of ischemia/reperfusion injury in different organs

Ischemia-reperfusion (I/R) injury, as a pathological phenomenon, takes place when blood supply to an organ is disrupted and then aggravated during restoration of blood flow. Ischemic preconditioning (IPC) is a potent method for attenuating subsequent events of IR damage in numerous organs. IPC protocol is determined by a brief and sequential time periods of I/R before the main ischemia. MicroRNAs are endogenous non-coding RNAs that regulate post-transcriptionally target mRNA translation via degrading it and/or suppressing protein synthesis. This review introduces the physiological and cellular mechanisms of ischemic preconditioning microRNAs-mediated after I/R insult in different organs such as the liver, kidney, heart, brain, and intestine. Data of this review have been collected from the scientific articles published in databases such as Science Direct, Scopus, PubMed, Web of Science, and Scientific Information Database from 2000 to 2023. Based on these literature studies, IPC/IR intervention can affect cellular mechanisms including oxidative stress, apoptosis, angiogenesis, and inflammation through up-regulation or down-regulation of multiple microRNAs and their target genes.

The interplay of NAD and hypoxic stress and its relevance for ageing

Nicotinamide adenine dinucleotide (NAD) is an essential regulator of cellular metabolism and redox processes. NAD levels and the dynamics of NAD metabolism change with increasing age but can be modulated via the diet or medication. Because NAD metabolism is complex and its regulation still insufficiently understood, achieving specific outcomes without perturbing delicate balances through targeted pharmacological interventions remains challenging. NAD metabolism is also highly sensitive to environmental conditions and can be influenced behaviorally, e.g., by exercise. Changes in oxygen availability directly and indirectly affect NAD levels and may result from exposure to ambient hypoxia, increased oxygen demand during exercise, ageing or disease. Cellular responses to hypoxic stress involve rapid alterations in NAD metabolism and depend on many factors, including age, glucose status, the dose of the hypoxic stress and occurrence of reoxygenation phases, and exhibit complex time-courses. Here we summarize the known determinants of NAD-regulation by hypoxia and evaluate the role of NAD in hypoxic stress. We define the specific NAD responses to hypoxia and identify a great potential of the modulation of NAD metabolism regarding hypoxic injuries. In conclusion, NAD metabolism and cellular hypoxia responses are strongly intertwined and together mediate protective processes against hypoxic insults. Their interactions likely contribute to age-related changes and vulnerabilities. Targeting NAD homeostasis presents a promising avenue to prevent/treat hypoxic insults and - conversely - controlled hypoxia is a potential tool to regulate NAD homeostasis.

Physiological, biochemical, and genome-wide expression patterns during graded normobaric hypoxia in healthy individuals

The regulation of oxygen homeostasis is critical in physiology and disease pathogenesis. High-altitude environment or hypoxia (lack of oxygen) can lead to adverse health conditions such as high-altitude pulmonary edema (HAPE) despite initial adaptive physiological responses. Studying genetic, hematological and biochemical, and the physiological outcomes of hypoxia together could yield a comprehensive understanding and potentially uncover valuable biomarkers for predicting responses. To this end, healthy individuals (n = 51) were recruited and exposed to graded normobaric hypoxia. Physiological parameters such as heart rate (HR), heart rate variability (HRV), oxygen saturation (Spo2), and blood pressure (BP) were constantly monitored, and a blood sample was collected before and after the hypoxia exposure for the hematological and gene-expression profiles. HR was elevated, and Spo2 and HRV were significantly reduced in a fraction of inspired oxygen ([Formula: see text])-dependent manner. After exposure to hypoxia, there was a minimal decrease in HCT, red blood cell distribution width (RDW)-coefficient of variation (CV), mean platelet volume (MPV), platelet distribution width, plateletcrit, eosinophils, lymphocytes, and HDL cholesterol. Additionally, there was a marginal increase observed in neutrophils. The effect of hypoxia was further assessed at the genome-wide expression level in a subset of individuals. Eighty-two genes significantly differed after hypoxia exposure, with 46 upregulated genes and 36 downregulated genes (P ≤ 0.05 and log2-fold change greater than ±0.5). We also conducted an integrative analysis of global gene expression profiles linked with physiological parameters, and we uncovered numerous reliable gene signatures associated with BP, Spo2, HR, and HRV in response to graded normobaric hypoxia.NEW & NOTEWORTHY Our study delves into the multifaceted response to hypoxia, integrating gene expression and hematological, biochemical, and physiological assessments. Hypoxia, crucial in both physiology and pathology, prompts varied responses, necessitating a thorough systemic understanding. Examining healthy subjects exposed to graded normobaric hypoxia, we observed significant shifts in heart rate, oxygen saturation, and heart rate variability. Moreover, genomic analysis unveiled distinct gene signatures associated with physiological parameters, offering insights into molecular perturbations and adaptations to oxygen deprivation.

Hypoxic Responses in Periodontal Tissues: Influence of Smoking and Periodontitis

AIM

This study aimed to investigate the hypoxic changes in periodontal tissues resulting from smoking and periodontitis by assessing levels of hypoxia-inducible factors (HIF-1α, HIF-2α, HIF-3α) and vascular endothelial growth factor (VEGF) in gingival crevicular fluid (GCF).

MATERIALS AND METHODS

The study comprised 22 periodontally healthy non-smokers (Group H), 22 periodontally healthy smokers (Group HS), 22 non-smokers with periodontitis (Group P) and 22 smokers with periodontitis (Group PS). Clinical periodontal parameters were documented, and GCF samples were collected and analysed using enzyme-linked immunosorbent assay (ELISA).

RESULTS

Significantly elevated levels of HIF-1α, HIF-3α and VEGF were observed in Groups HS, P and PS compared to Group H (p < 0.05). Moreover, higher HIF-2α levels were detected in the Groups HS and P compared to Group H (p < 0.05). Significant correlations were detected between all evaluated hypoxia biomarkers in the Group P (p < 0.05) except HIF-2α and HIF-3α. However, in the PS group, significant correlation appeared only between HIF-1α and HIF-2α (p < 0.05).

CONCLUSION

Our findings indicate that smoking and periodontitis induce comparable hypoxic effects in periodontal tissues, as evidenced by the evaluated biomarkers. Further research is warranted to gain a deeper understanding of the mechanisms underlying hypoxia in periodontal tissues.

Hypoxia as a critical player in extracellular vesicles-mediated intercellular communication between tumor cells and their surrounding microenvironment

In the past years, increasing attention has been paid to the role of extracellular vesicles (EVs) as mediators of intercellular communication in cancer. These small size particles mediate the intercellular transfer of important bioactive molecules involved in malignant initiation and progression. Hypoxia, or low partial pressure of oxygen, is recognized as a remarkable feature of solid tumors and has been demonstrated to exert a profound impact on tumor prognosis and therapeutic efficacy. Indeed, the high-pitched growth rate and chaotic neovascular architecture that embodies solid tumors results in a profound reduction in oxygen pressure within the tumor microenvironment (TME). In response to oxygen-deprived conditions, tumor cells and their surrounding milieu develop homeostatic adaptation mechanisms that contribute to the establishment of a pro-tumoral phenotype. Latest evidence suggests that the hypoxic microenvironment that surrounds the tumor bulk may be a clincher for the observed elevated levels of circulating EVs in cancer patients. Thus, it is proposed that EVs may play a role in mediating intercellular communication in response to hypoxic conditions. This review focuses on the EVs-mediated crosstalk that is established between tumor cells and their surrounding immune, endothelial, and stromal cell populations, within the hypoxic TME.

Spring viremia of carp virus infection induces hypoxia response in zebrafish by stabilizing hif1α

The hypoxia signaling pathway controls hypoxia adaptation and tolerance of organisms, which is regulated by multiple mechanisms. Viral infection elicits various pathophysiological responses in the host. However, whether viral infection can affect the hypoxia response is not yet fully understood. In this study, we found that Spring viremia of carp virus (SVCV) infection in zebrafish caused symptoms similar to those in zebrafish under hypoxic conditions. Further assays indicated that SVCV infection activated the hypoxia signaling pathway in zebrafish. In addition, SVCV infection caused increased glycolysis and reactive oxygen species (ROS) levels in cells. Mechanistically, SVCV-G protein interacted with hif1α-a/b and attenuated their K48-linked polyubiquitination, leading to their stabilization and subsequent enhancement of target gene expression. Moreover, treatment with the HIF1α-specific inhibitor PX478 enhanced the antiviral ability against SVCV infection in zebrafish and zebrafish cells. This study reveals a relationship between SVCV infection and the hypoxia signaling pathway in fish and provides a strategy for reducing the damage of viral disease in the aquaculture industry.

IMPORTANCE

Viral infection triggers various pathophysiological responses in the host. The hypoxia signaling pathway controls hypoxia adaptation and tolerance of organisms. However, whether viral infection can affect the hypoxia response is not yet fully understood. This study showed that Spring viremia of carp virus (SVCV) infection activated the hypoxia signaling pathway and induced a hypoxia response. The SVCV-G protein interacted with hif1α-a/b and reduced their K48-linked polyubiquitination, leading to their stabilization and subsequent enhancement of target gene expression. Additionally, treatment with the HIF1α-specific inhibitor PX478 enhanced the antiviral ability against SVCV infection in zebrafish and zebrafish cells. Our findings not only reveal a relationship between SVCV infection and the hypoxia signaling pathway in fish but also provide a strategy for reducing the damage of viral disease in the aquaculture industry.

Landscape of Noncoding RNA in the Hypoxic Tumor Microenvironment

Amidst the prevalent and notable characteristic of a hypoxic microenvironment present in the majority of solid tumors, a burgeoning number of studies have revealed the significance of noncoding RNAs (ncRNAs) in hypoxic tumor regions. The transcriptome of cancers is highly heterogeneous, with noncoding transcripts playing crucial roles. Long noncoding RNAs (lncRNAs) and circular RNAs (circRNAs) are two distinctive classes of ncRNA that are garnering increasing attention. Biologically, they possess intriguing properties and possess significant regulatory functions. Clinically, they present as promising biomarkers and therapeutic targets. Additionally, recent research has evaluated the clinical applications of these ncRNAs in RNA-based treatments and noninvasive liquid biopsies. This review provides a comprehensive summary of recent studies on lncRNAs and circRNAs within the hypoxic tumor microenvironment. Furthermore, the clinical significance of lncRNAs and circRNAs in cancer diagnosis and treatment is emphasized, which could pave the way for the development of effective targeted therapies.

Hypoxia as a medicine

Oxygen is essential for human life, yet a growing body of preclinical research is demonstrating that chronic continuous hypoxia can be beneficial in models of mitochondrial disease, autoimmunity, ischemia, and aging. This research is revealing exciting new and unexpected facets of oxygen biology, but translating these findings to patients poses major challenges, because hypoxia can be dangerous. Overcoming these barriers will require integrating insights from basic science, high-altitude physiology, clinical medicine, and sports technology. Here, we explore the foundations of this nascent field and outline a path to determine how chronic continuous hypoxia can be safely, effectively, and practically delivered to patients.

HIF-1 and HIF-2 in cancer: structure, regulation, and therapeutic prospects

Hypoxia, or a state of low tissue oxygenation, has been characterized as an important feature of solid tumors that is related to aggressive phenotypes. The cellular response to hypoxia is controlled by Hypoxia-inducible factors (HIFs), a family of transcription factors. HIFs promote the transcription of gene products that play a role in tumor progression including proliferation, angiogenesis, metastasis, and drug resistance. HIF-1 and HIF-2 are well known and widely described. Although these proteins share a high degree of homology, HIF-1 and HIF-2 have non-redundant roles in cancer. In this review, we summarize the similarities and differences between HIF-1α and HIF-2α in their structure, expression, and DNA binding. We also discuss the canonical and non-canonical regulation of HIF-1α and HIF-2α under hypoxic and normal conditions. Finally, we outline recent strategies aimed at targeting HIF-1α and/or HIF-2α.

Regulation of PHD2 by HIF-1α in Erythroid Cells: Insights into Erythropoiesis Under Hypoxia

The hypoxia-inducible factor (HIF) pathway has been demonstrated to play a pivotal role in the process of high-altitude adaptation. PHD2, a key regulator of the HIF pathway, has been found to be associated with erythropoiesis. However, the relationship between changes in Phd2 abundance and erythroid differentiation under hypoxic conditions remains to be elucidated. A hemin-induced K562 erythroid differentiation model was used to explore the effects of PHD2 knockdown under hypoxia. Erythroid differentiation was assessed by flow cytometry and immunofluorescence. HIF-1α's regulation of PHD2 was examined using luciferase assays and ChIP-seq. CRISPR/Cas9 was applied to knock out EGLN1 and HIF1A, and a fluorescent reporter system was developed to track PHD2 expression. PHD2 knockdown enhanced erythroid differentiation, evident by increased CD71 and CD235a expression. Reporter assays and ChIP-seq identified an HIF-1α binding site in the EGLN1 5' UTR, confirming HIF-1α as a regulator of PHD2 expression. The fluorescent reporter system provided real-time monitoring of endogenous PHD2 expression, showing that HIF-1α significantly modulates PHD2 levels under hypoxic conditions. PHD2 influences erythropoiesis under hypoxia, with HIF-1α regulating its expression. This feedback loop between HIF-1α and PHD2 sheds light on mechanisms driving erythroid differentiation under low-oxygen conditions.

Whole genome re-sequencing reveals high altitude adaptation signatures and admixture in Ladakhi cattle

Ladakhi cattle, native to the high-altitude region of Ladakh in northern India (ranging from 3,000 to 5,000 m above sea level), have evolved unique genetic adaptations to thrive in harsh environmental conditions, such as hypoxia, extreme cold, and low humidity. This study explored the genome of Ladakhi cattle to investigate genetic structure, selection signatures, and adaptive mechanisms. Whole genome sequencing reads, generated on Illumina NovaSeq 6000 platform, were aligned to the Bos taurus reference genome with BWA-MEM. SNPs were identified and filtered using GATK and bcftools, and functionally annotated with SnpEff. For population genomic analysis, PCA and admixture modeling assessed genetic structure, while Neighbor-Joining trees, LD decay, nucleotide diversity (π), and FST evaluated phylogenetic relationships and genetic variation. Selective sweeps were detected using RAiSD, and gene-set enrichment and protein-protein interaction analyses were conducted to explore functional pathways related to adaptation. The study revealed 3,759,279 unique SNPs and demonstrated that Ladakhi cattle form a distinct genetic cluster with an estimated admixture of 68 % Bos indicus and 32 % Bos taurus ancestry. Key findings include rapid linkage disequilibrium decay, low inbreeding level, and the identification of selection signatures and genes associated with hypoxia response, energy metabolism, and cold adaptation. Mean nucleotide diversity (π, 0.0037) and FST values indicated moderate genetic differentiation from other breeds. The analysis highlighted selection signatures for genes like HIF1A, ENO4, ANGPT1, EPO, NOS3, MAPK3, HMOX1, BCL2,CAMK2D, MTOR, AKT2,PIK3CB, and MAP2K1, among others, including various keratin and heat shock proteins. The interaction between genes associated with hypoxia signaling (HIF-1) and other enriched pathways such as PI3K, mTOR, NFκB, ERK, and ER stress, reveals a complex mechanism for managing hypoxic stress in Ladakhi cattle. These findings offer valuable insights for breeding programs aimed at enhancing livestock resilience in extreme environments and enhance understanding of mammalian adaptation to high-altitude conditions.

[Familial erythrocytosis type 2 due to VHL germline mutations: a case report and literature review]

To enhance the understanding of familial erythrocytosis type 2 (ECYT2) resulting from compound heterozygous mutations in the VHL gene. Methods: We conducted a retrospective analysis of the case data from a patient with ECYT2 to investigate its pathogenesis, clinical features, diagnosis and treatment options, as well as prognosis, while also reviewing the relevant literature. Results: A 31-year-old man was admitted to the hospital due to facial and hand flushing that had persisted for 29 years. Whole exome sequencing revealed compound heterozygous mutations in VHL p.P81L and p.N90T. Both of his parents were found to carry only one of these heterozygous mutations, yet they exhibited normal phenotypes. Based on the patient's hematological tests, a clear diagnosis of ECYT2 was established. Following treatment with erythrocytapheresis and daily administration of aspirin at a dosage of 100 mg, the patient experienced relief from dizziness and headaches associated with blood hyperviscosity, without any thrombotic or bleeding complications during this period. Conclusions: ECYT2 is a rare group of autosomal recessive genetic disorders. This case of ECYT2, resulting from compound heterozygous mutations in the VHL gene, represents the first report in China. Clinically, it is characterized by elevated red cell mass, normal or increased serum erythropoietin levels, and normal hemoglobin oxygen affinity levels. These factors contribute to thrombotic and bleeding complications that can lead to early mortality.

Discovery of ZG-2305, an Orally Bioavailable Factor Inhibiting HIF Inhibitor for the Treatment of Obesity and Fatty Liver Disease

Genetic loss of the 2-oxoglutarate oxygenase factor inhibiting hypoxia-inducible factor (FIH) enhances both glycolysis and aerobic metabolism. FIH is thus a potential target for adiposity control and improving hepatic steatosis. We describe development of a series of novel, potent, and selective FIH inhibitors that occupy both the FIH catalytic site and a recently defined tyrosine conformational-flip pocket. ZG-2305, with a Ki of 79.6 nM for FIH, manifests 38-fold selectivity over the hypoxia-inducible factor (HIF) prolyl hydroxylase PHD2. Oral administration of ZG-2305 in the western-diet induced obesity mouse model results in improved lipid accumulation and recovery from abnormal body weight/hepatic steatosis. Amelioration of nonalcoholic steatohepatitis (NASH) related pathological phenotypes in the HF-CDAA-diet induced NASH mouse model was observed. Preliminary preclinical studies indicate ZG-2305 has good pharmacokinetic properties and an acceptable safety profile. The results imply ZG-2305 is a promising candidate for treatment of obesity and fatty liver disease.

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

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 discover that Sima, the Drosophila ortholog of Hif1α, is also essential for establishing the larval glycolytic program. Using a multi-omics approach, we demonstrate that sima mutants fail to properly activate aerobic glycolysis and die during larval development with metabolic defects that phenocopy 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. Considering that the mammalian homologs of ERR and Hif1α also cooperatively regulate aerobic glycolysis in cancer cells, our findings establish the fly as a powerful genetic model for studying the interaction between these two key metabolic regulators.

Intestinal E. coli-produced yersiniabactin promotes profibrotic macrophages in Crohn's disease

Inflammatory bowel disease (IBD)-associated fibrosis causes significant morbidity. Mechanisms are poorly understood but implicate the microbiota, especially adherent-invasive Escherichia coli (AIEC). We previously demonstrated that AIEC producing the metallophore yersiniabactin (Ybt) promotes intestinal fibrosis in an IBD mouse model. Since macrophages interpret microbial signals and influence inflammation/tissue remodeling, we hypothesized that Ybt metal sequestration disrupts this process. Here, we show that macrophages are abundant in human IBD-fibrosis tissue and mouse fibrotic lesions, where they co-localize with AIEC. Ybt induces profibrotic gene expression in macrophages via stabilization and nuclear translocation of hypoxia-inducible factor 1-alpha (HIF-1α), a metal-dependent immune regulator. Importantly, Ybt-producing AIEC deplete macrophage intracellular zinc and stabilize HIF-1α through inhibition of zinc-dependent HIF-1α hydroxylation. HIF-1α+ macrophages localize to sites of disease activity in human IBD-fibrosis strictures and mouse fibrotic lesions, highlighting their physiological relevance. Our findings reveal microbiota-mediated metal sequestration as a profibrotic trigger targeting macrophages in the inflamed intestine.

Systematic and comprehensive insights into HIF-1 stabilization under normoxic conditions: implications for cellular adaptation and therapeutic strategies in cancer

Hypoxia-inducible factors (HIFs) are essential transcription factors that orchestrate cellular responses to oxygen deprivation. HIF-1α, as an unstable subunit of HIF-1, is usually hydroxylated by prolyl hydroxylase domain enzymes under normoxic conditions, leading to ubiquitination and proteasomal degradation, thereby keeping low levels. Instead of hypoxia, sometimes even in normoxia, HIF-1α translocates into the nucleus, dimerizes with HIF-1β to generate HIF-1, and then activates genes involved in adaptive responses such as angiogenesis, metabolic reprogramming, and cellular survival, which presents new challenges and insights into its role in cellular processes. Thus, the review delves into the mechanisms by which HIF-1 maintains its stability under normoxia including but not limited to giving insights into transcriptional, translational, as well as posttranslational regulation to underscore the pivotal role of HIF-1 in cellular adaptation and malignancy. Moreover, HIF-1 is extensively involved in cancer and cardiovascular diseases and potentially serves as a bridge between them. An overview of HIF-1-related drugs that are approved or in clinical trials is summarized, highlighting their potential capacity for targeting HIF-1 in cancer and cardiovascular toxicity related to cancer treatment. The review provides a comprehensive insight into HIF-1's regulatory mechanism and paves the way for future research and therapeutic development.

Head and neck paraganglioma in Pacak-Zhuang syndrome

BACKGROUND

Head and neck paragangliomas (HNPGLs) are typically slow-growing, hormonally inactive tumors of parasympathetic paraganglia. Inactivation of prolyl-hydroxylase domain-containing 2 protein causing indirect gain-of-function of hypoxia-inducible factor-2α (HIF-2α), encoded by EPAS1, was recently shown to cause carotid body hyperplasia. We previously described a syndrome with multiple sympathetic paragangliomas caused by direct gain-of-function variants in EPAS1 (Pacak-Zhuang syndrome, PZS) and developed a corresponding mouse model.

METHODS

We evaluated a cohort of patients with PZS (n = 9) for HNPGL by positron emission tomography, magnetic resonance imaging, and computed tomography and measured carotid body size compared to literature reference values. Resected tumors were evaluated by histologic sectioning and staining. We evaluated the corresponding mouse model at multiple developmental stages (P8 and adult) for lesions of the head and neck by high resolution ex vivo imaging and performed immunohistochemical staining on histologic sections of the identified lesions.

RESULTS

hree patients had imaging consistent with HNPGL, one of which warranted resection and was confirmed on histology. Three additional patients had carotid body enlargement (Z-score > 2.0), and 3 had carotid artery malformations. We found that 9 of 10 adult variant mice had carotid body tumors and 6 of 8 had a paraganglioma on the cranio-caval vein, the murine homologue of the superior vena cava; these were also found in 4 of 5 variant mice at post-natal day 8. These tumors and the one resected from a patient were positive for tyrosine hydroxylase, synaptophysin, and chromogranin A. Brown fat in a resected patient tumor carried the EPAS1 pathogenic variant.

CONCLUSIONS

These findings (1) suggest HNPGL as a feature of PZS and (2) show that these pathogenic variants are sufficient to cause the development of these tumors, which we believe represents a continuous spectrum of disease starting from hyperplasia.

Molecular mechanisms of ubiquitination in wound healing

Wound healing is a complex biological process involving multiple cellular and molecular mechanisms. Ubiquitination, a crucial post-translational modification, plays a vital role in regulating various aspects of wound healing through protein modification and degradation. This review comprehensively examines the molecular mechanisms of ubiquitination in wound healing, focusing on its regulation of inflammatory responses, macrophage polarization, angiogenesis, and the activities of fibroblasts and keratinocytes. We discuss how ubiquitination modifies key signaling pathways, including TGF-β/Smad3, NF-κB, and HIF-α, which are essential for proper wound healing. Understanding these mechanisms provides insights into potential therapeutic strategies for treating impaired wound healing, particularly in conditions such as diabetes. The review highlights recent advances in understanding ubiquitination's role in wound healing and discusses future research directions for developing targeted therapeutic approaches.

Hif-1α ablation reduces the efficiency of NeuroD1 gene-based therapy and aggravates the brain damage following ischemic stroke

INTRODUCTION

Hypoxia-inducible factor 1α [HIF1α] regulates gene expression, allowing the organism to respond to low oxygen levels. Meanwhile, astrocytes participate in inflammatory processes and are associated with neurotoxic chemicals that can increase stroke volume, contributing considerably to the devastating effects of a stroke.

OBJECTIVE

To evaluate whether Hif-1α ablation from the central nervous system is implicated in motor dysfunction and ischemic brain damage following stroke. Furthermore, to explore if Hif-1α ablation affects the therapeutic impact of NeuroD1 gene-based therapy.

METHODS

Endothelin-1 [ET-1] was injected to induce ischemic stroke in mice. Both wild-type and Hypoxia-inducible factor 1α conditional knockout [Hif-1α CKO] mice were used. The effect of Hif-1α ablation was assessed by the neuron numbers, astrocyte activity, vascular endothelial growth factor [VEGF] expression, and behavioral tests. Moreover, western blot, ELISA, and RNA sequencing were used. Then, we used pAAV2/9-GfaABC1D-NeuroD1-P2A-EGFP-WPRE injection to examine the impact of NeuroD1 in Hif-1α CKO mice following ischemic stroke.

RESULTS

We found that following stroke, motor dysfunction significantly increased in Hif-1α CKO mice. Furthermore, elevation of apoptosis and activation in both microglia and astrocytes were observed, consequently up-regulating neuroinflammation. Meanwhile, Hif-1α ablation significantly decreased the efficiency of NeuroD1 gene-based therapy.

CONCLUSION

Our findings demonstrate that Hif-1α ablation from the nervous system is implicated in ischemic stroke pathogenesis mainly by increasing neuron cell death and inducing astrocytes as well as decreasing the efficiency of NeuroD1. These data support the idea that manipulating HIF-1α is a viable therapeutic for ischemic stroke.

Intestinal oxygen utilisation and cellular adaptation during intestinal ischaemia-reperfusion injury

The gastrointestinal tract can be deranged by ailments including sepsis, trauma and haemorrhage. Ischaemic injury provokes a common constellation of microscopic and macroscopic changes that, together with the paradoxical exacerbation of cellular dysfunction and death following restoration of blood flow, are collectively known as ischaemia-reperfusion injury (IRI). Although much of the gastrointestinal tract is normally hypoxemic, intestinal IRI results when there is inadequate oxygen availability due to poor supply (pathological hypoxia) or abnormal tissue oxygen use and metabolism (dysoxia). Intestinal oxygen uptake usually remains constant over a wide range of blood flows and pressures, with cellular function being substantively compromised when ischaemia leads to a >50% decline in intestinal oxygen consumption. Restoration of perfusion and oxygenation provokes additional injury, resulting in mucosal damage and disruption of intestinal barrier function. The primary cellular mechanism for sensing hypoxia and for activating a cascade of cellular responses to mitigate the injury is a family of heterodimer proteins called hypoxia-inducible factors (HIFs). The HIF system is connected to numerous biochemical and immunologic pathways induced by IRI and the concentration of those proteins increases during hypoxia and dysoxia. Activation of the HIF system leads to augmented transcription of specific genes in various types of affected cells, but may also augment apoptotic and inflammatory processes, thus aggravating gut injury. KEY POINTS: During intestinal ischaemia, mitochondrial oxygen uptake is reduced when cellular oxygen partial pressure decreases to below the threshold required to maintain normal oxidative metabolism. Upon reperfusion, intestinal hypoxia may persist because microcirculatory flow remains impaired and/or because available oxygen is consumed by enzymes, intestinal cells and neutrophils.

HIF1α Plays a Crucial Role in the Development of TFE3-Rearranged Renal Cell Carcinoma by Orchestrating a Metabolic Shift Toward Fatty Acid Synthesis

Tumor development often requires cellular adaptation to a unique, high metabolic state; however, the molecular mechanisms that drive such metabolic changes in TFE3-rearranged renal cell carcinoma (TFE3-RCC) remain poorly understood. TFE3-RCC, a rare subtype of RCC, is defined by the formation of chimeric proteins involving the transcription factor TFE3. In this study, we analyzed cell lines and genetically engineered mice, demonstrating that the expression of the chimeric protein PRCC-TFE3 induced a hypoxia-related signature by transcriptionally upregulating HIF1α and HIF2α. The upregulation of HIF1α by PRCC-TFE3 led to increased cellular ATP production by enhancing glycolysis, which also supplied substrates for the TCA cycle while maintaining mitochondrial oxidative phosphorylation. We crossed TFE3-RCC mouse models with Hif1α and/or Hif2α knockout mice and found that Hif1α, rather than Hif2α, is essential for tumor development in vivo. RNA-seq and metabolomic analyses of the kidney tissues from these mice revealed that ketone body production is inversely correlated with tumor development, whereas de novo lipid synthesis is upregulated through the HIF1α/SREBP1-dependent mechanism in TFE3-RCC. Our data suggest that the coordinated metabolic shift via the PRCC-TFE3/HIF1α/SREBP1 axis is a key mechanism by which PRCC-TFE3 enhances cancer cell metabolism, promoting tumor development in TFE3-RCC.

C/EBPβ Regulates HIF-1α-Driven Invasion of Non-Small-Cell Lung Cancer Cells

Metastatic cancer accounts for most cancer-related deaths, and identifying specific molecular targets that contribute to metastatic progression is crucial for the development of effective treatments. Hypoxia, a feature of solid tumors, plays a role in cancer progression by inducing resistance to therapy and accelerating metastasis. Here, we report that CCAAT/enhancer-binding protein beta (C/EBPβ) transcriptionally regulates hypoxia-inducible factor 1 subunit alpha (HIF1A) and thus promotes migration and invasion of non-small-cell lung cancer (NSCLC) cells under hypoxic conditions. Our results show that knockdown or forced expression of C/EBPβ was correlated with HIF-1α expression and that C/EBPβ directly bound to the promoter region of HIF1A. Silencing HIF1A inhibited the enhanced migration and invasion induced by C/EBPβ overexpression in NSCLC cells under hypoxia. Expression of the HIF-1α target gene, SLC2A1, was also altered in a C/EBPβ-dependent manner, and knockdown of SLC2A1 reduced migration and invasion enhanced by C/EBPβ overexpression. These results indicate that C/EBPβ is a critical regulator for the invasion of NSCLC cells in the hypoxic tumor microenvironment. Collectively, the C/EBPβ-HIF-1α-GLUT1 axis represents a potential therapeutic target for preventing metastatic progression of NSCLC and improving patient outcomes.

Hypoxia Regulates Brown Adipocyte Differentiation and Stimulates miR-210 by HIF-1α

MicroRNAs (miRNAs) are short sequences of single-stranded non-coding RNAs that target messenger RNAs, leading to their repression or decay. Interestingly, miRNAs play a role in the cellular response to low oxygen levels, known as hypoxia, which is associated with reactive oxygen species and oxidative stress. However, the physiological implications of hypoxia-induced miRNAs ("hypoxamiRs") remain largely unclear. Here, we investigate the role of miR-210 in brown adipocyte differentiation and thermogenesis. We treated the cells under sympathetic stimulation with hypoxia, CoCl2, or IOX2. To manipulate miR-210, we performed reverse transfection with antagomiRs. Adipocyte markers expression, lipid accumulation, lipolysis, and oxygen consumption were measured. Hypoxia hindered BAT differentiation and suppressed sympathetic stimulation. Hypoxia-induced HIF-1α stabilization increased miR-210 in brown adipocytes. Interestingly, miR-210-5p enhanced differentiation under normoxic conditions but was insufficient to rescue the inhibition of brown adipocyte differentiation under hypoxic conditions. Although adrenergic stimulation activated HIF-1α signaling and upregulated miR-210 expression, inhibition of miR-210-5p did not significantly influence UCP1 expression or oxygen consumption. In summary, hypoxia and adrenergic stimulation upregulated miR-210, which impacted brown adipocyte differentiation and thermogenesis. These findings offer new insights for the physiological role of hypoxamiRs in brown adipose tissue, which could aid in understanding oxidative stress and treatment of metabolic disorders.

Designed to breathe: synthetic biology applications in plant hypoxia

Over the past years, plant hypoxia research has produced a considerable number of new resources to monitor low oxygen responses in model species, mainly Arabidopsis thaliana. Climate change urges the development of effective genetic strategies aimed at improving plant resilience during flooding events. This need pushes forward the search for optimized tools that can reveal the actual oxygen available to plant cells, in different organs or under various conditions, and elucidate the mechanisms underlying plant hypoxic responses, complementing the existing transcriptomics, proteomics, and metabolic analysis methods. Oxygen-responsive reporters, dyes, and nanoprobes are under continuous development, as well as novel synthetic strategies that make precision control of plant hypoxic responses realistic. In this review, we summarize the recent progress made in the definition of tools for oxygen response monitoring in plants, either adapted from bacterial and animal research or peculiar to plants. Moreover, we highlight how adoption of a synthetic biology perspective has enabled the design of novel genetic circuits for the control of oxygen-dependent responses in plants. Finally, we discuss the current limitations and challenges toward the implementation of synbio solutions in the plant low-oxygen biology field.

Nanoscale Systems for Local Activation of Hypoxia-Inducible Factor-1 Alpha: A New Approach in Diabetic Wound Management

Chronic wounds in diabetic patients experience significant clinical challenges due to compromised healing processes. Hypoxia-inducible factor-1 alpha (HIF-1α) is a critical regulator in the cellular response to hypoxia, enhancing angiogenesis and tissue restoration. Nevertheless, the cellular response to the developed chronic hypoxia within diabetes is impaired, likely due to the destabilization of HIF-1α via degradation by prolyl hydroxylase domain (PHD) enzymes. Researchers have extensively explored HIF-1α activation as a potential pathway for diabetic wound management, focusing mainly on deferoxamine (DFO) as a potent agent to stabilize HIF-1α. This review provides an update of the other recent pharmacological agents managing HIF-1α activation, including novel PHD inhibitors (roxadustat and daprodustat) and Von Hippel-Lindau protein (VHL) antagonists, which could be potential alternatives for the local treatment of diabetic wounds. Furthermore, it highlights how localized delivery via advanced nanostructures can enhance the efficacy of these novel therapies. Importantly, by addressing these points, the current review can offer a promising area for research. Given that, these novel drugs have minimal applications in diabetic wound healing, particularly in the context of local application through nanomaterials. This gap presents an exciting opportunity for further investigation, as combining these drugs with localized nanotechnology could avoid undesired systemic side effects and sustain drug release within wound site, offering a transformative platform for diabetes wound treatment.

A closer look at the role of deubiquitinating enzymes in the Hypoxia Inducible Factor pathway

Hypoxia Inducible transcription Factors (HIFs) are central to the metazoan oxygen-sensing response. Under low oxygen conditions (hypoxia), HIFs are stabilised and govern an adaptive transcriptional programme to cope with prolonged oxygen starvation. However, when oxygen is present, HIFs are continuously degraded by the proteasome in a process involving prolyl hydroxylation and subsequent ubiquitination by the Von Hippel Lindau (VHL) E3 ligase. The essential nature of VHL in the HIF response is well established but the role of other enzymes involved in ubiquitination is less clear. Deubiquitinating enzymes (DUBs) counteract ubiquitination and provide an important regulatory aspect to many signalling pathways involving ubiquitination. In this review, we look at the complex network of ubiquitination and deubiquitination in controlling HIF signalling in normal and low oxygen tensions. We discuss the relative importance of DUBs in opposing VHL, and explore roles of DUBs more broadly in hypoxia, in both VHL and HIF independent contexts. We also consider the catalytic and non-catalytic roles of DUBs, and elaborate on the potential benefits and challenges of inhibiting these enzymes for therapeutic use.

Evaluation of Anti-Angiogenic Therapy Combined with Immunotherapy and Chemotherapy as a Strategy to Treat Locally Advanced and Metastatic Non-Small-Cell Lung Cancer

Immunotherapy has made recent improvements in disease-free survival (DFS) and/or overall survival (OS) in all stages of non-small-cell lung cancer (NSCLC). Here, we review the tumor microenvironment and its immunosuppressive effects and discuss how anti-angiogenic therapies may potentiate the anti-carcinogenic effects of immunotherapy. We also review all the past literature and discuss strategies of combining anti-angiogenic therapy and immunotherapy +/- chemotherapy and hypothesize how we can use this strategy for non-small-cell lung cancer in metastatic previously untreated/previously treated settings in previously treated EGFR-mutated NSCLC for the upfront treatment of brain metastases prior to radiation therapy and for the incorporation of this strategy into stage III unresectable disease. We assert the use of anti-angiogenic therapy and immunotherapy when combined appropriately with chemotherapy and radiotherapy has the potential to increase the long-term survivals in both the stage III and metastatic setting so that we can now consider more patients to experience curative treatment.

miR-210 loss leads to widespread phenotypic and gene expression changes in human 293T cells

Introduction

Hypoxia responses are critical for myriad physiological and pathological processes, such as development, tissue repair, would healing, and tumorigenesis. microRNAs (miRNAs) are a class of small non-coding RNAs that exert their functions by inhibiting the expression of their target genes, and miR-210 is the miRNA universally and most conspicuously upregulated by hypoxia in mammalian systems. For its relationship to hypoxia, miR-210 has been studied extensively, yet no consensus exists on the roles and mechanisms of miR-210 in human physiological processes or diseases, and we know little about genuine miR-210 target genes in humans.

Methods

To better investigate the functions and mechanisms of human miR-210, therefore, we derived the human miR-210 gene knockout (KO) 293T cell lines using the CRISPR/Cas9 technology. We then examined the cellular phenotypes and gene expression profiles of 293T cells under normoxia and hypoxia conditions.

Results and Discussion

We found that the loss of miR-210 altered a variety of cellular phenotypes including proliferation and apoptosis. Subsequent global gene expression analyses identified plausible mechanisms underlying these phenotypic changes in 293T cells. In particular, we showed that miR-210 might target the expression of BNIP3L as a potential mechanism to suppress apoptosis. Surprisingly, the mRNA levels of most previously reported miR-210 target genes were not induced upon miR-210 KO, suggesting a need to reexamining and studying human miR-210 functions directly and comprehensively. Thus, our work established a human cellular system and opportunity to unravel the complexity of the regulatory networks by miR-210.

Unlocking lung regeneration: insights into progenitor cell dynamics and metabolic control

Regenerative responses are particularly important in the lungs, which are critical for gas exchange and frequently challenged by environmental insults. The lung progenitor cells play a central role in the lung regeneration response, and their dysfunction is associated with various lung diseases. Understanding the mechanisms regulating lung progenitor cell function is essential for developing new therapeutic approaches to promote lung regeneration. This review summarizes recent advancements in the field of lung regeneration, focusing on the metabolic control of lung progenitor cell function. We discuss cell lineage plasticity and cell-cell signaling under different physiological conditions. Additionally, we highlight the connection between progenitor cell dysfunction and lung diseases, emphasizing the need to develop new therapeutic strategies in regenerative medicine to improve lung regenerative capacity.

Minocycline inhibits microglial activation in the CA1 hippocampal region and prevents long-term cognitive sequel after experimental cerebral malaria

Cerebral malaria is the worst complication of malaria infection, has a high mortality rate, and may cause different neurodysfunctions, including cognitive decline. Neuroinflammation is an important cause of cognitive damage in neurodegenerative diseases, and microglial cells can be activated in a disease-associated profile leading to tissue damage and neuronal death. Here, we demonstrated that treatment with minocycline reduced blood-brain barrier breakdown and modulated ICAM1 mRNA expression; reduced proinflammatory cytokines, such as TNF-α, IL-1β, IFN-γ, and IL-6; and prevented long-term cognitive decline in contextual and aversive memory tasks. Taken together, our data suggest that microglial cells are activated during experimental cerebral malaria, leading to neuroinflammatory events that end up in cognitive damage. In addition, pharmacological modulation of microglial activation, by drugs such as minocycline may be an important therapeutic strategy in the prevention of long-term memory impairment.

The Physiological Functions and Therapeutic Potential of Hypoxia-Inducible Factor-1α in Vascular Calcification

HIF-1α plays a crucial regulatory role in vascular calcification (VC), primarily influencing the osteogenic differentiation of VSMCs through oxygen-sensing mechanisms. Under hypoxic conditions, the stability of HIF-1α increases, avoiding PHD and VHL protein-mediated degradation, which promotes its accumulation in cells and then activates gene expressions related to calcification. Additionally, HIF-1α modulates the metabolic state of VSMCs by regulating the pathways that govern the switch between glycolysis and oxidative phosphorylation, thereby further advancing the calcification process. The interaction between HIF-1α and other signaling pathways, such as nuclear factor-κB, Notch, and Wnt/β-catenin, creates a complex regulatory network that serves as a critical driving force in VC. Therefore, a deeper understanding of the role and regulatory mechanism of the HIF-1α signaling during the development and progression of VC is of great significance, as it is not only a key molecular marker for understanding the pathological mechanisms of VC but also represents a promising target for future anti-calcification therapies.

Bypassing Ca2+ Influx for Antimetastasis Photodynamic Therapy via Robust Nucleus-Targeted Near-Infrared Cyanines

Hypoxia-induced tumor metastasis severely hinders the efficacy of photodynamic therapy (PDT) in cancer treatment. Current strategies predominantly offer palliative suppression of the HIF-1α pathway, emphasizing the urgent need for innovative PDT approaches to prevent metastasis from the outset. Our study revealed that typical PDT triggers an increase in cytoplasmic Ca2+ levels, activating HIF-1α, and that reducing Ca2+ levels can, in turn, mitigate metastasis. Considering cytoplasm's role in Ca2+ storage and regulation, we propose that PDT-induced metastasis can be addressed at its source by precise intracellular localization of photosensitizers (PSs). We developed near-infrared (NIR) cyanine PSs with inherent nucleus targeting capabilities. These PSs effectively inhibit cytoplasmic Ca2+ elevation and reduce HIF-1α activity upon irradiation, achieving remarkable antimetastatic effects in 4T1 tumors. Consequently, our findings highlight the pivotal role of Ca2+ in PDT-induced metastasis and provide a robust approach for circumventing metastasis from the outset using new nucleus-targeting organic PSs.

Decoding ferroptosis: transforming orthopedic disease management

As a mechanism of cell death, ferroptosis has gained popularity since 2012. The process is distinguished by iron toxicity and phospholipid accumulation, in contrast to autophagy, apoptosis, and other cell death mechanisms. It is implicated in the advancement of multiple diseases across the body. Researchers currently know that osteosarcoma, osteoporosis, and other orthopedic disorders are caused by NRF2, GPX4, and other ferroptosis star proteins. The effective relief of osteoarthritis symptoms from deterioration has been confirmed by clinical treatment with multiple ferroptosis inhibitors. At the same time, it should be reminded that the mechanisms involved in ferroptosis that regulate orthopedic diseases are not currently understood. In this manuscript, we present the discovery process of ferroptosis, the mechanisms involved in ferroptosis, and the role of ferroptosis in a variety of orthopedic diseases. We expect that this manuscript can provide a new perspective on clinical diagnosis and treatment of related diseases.

Mouse embryonic kidney transplantation identifies maturation defects in the medulla

Kidney organoids are connected to the host circulation and mature after transplantation. However, they are still immature compared to the adult kidneys, and their precise maturation stages remain unclear. By transplanting the mouse embryonic kidney as a model system for organoid transplantation, we report here the maturation defects of the graft, especially in the medulla. Single cell profiling of the developing kidneys in vivo identified gene sets associated with the maturation of the collecting duct epithelium and medullary stroma. These data revealed an upregulation of genes associated with channel/transporter functions and immune defense, as well as a downregulation of neuronal genes. Using these marker genes, we found that the maturation of the collecting duct and medullary stroma in the grafts barely corresponds to the perinatal stage, which was confirmed histologically by using representative genes. Thus, the gene sets obtained serve as maturation coordinates for the renal medulla and will be helpful in analyzing its maturation defects after transplantation. They will also provide a useful basis for further maturation of transplanted kidney organoids.

Cytochrome c and cancer cell metabolism: A new perspective

Cytochrome c is a vital electron carrier in the mitochondrial respiratory chain. When the outer membrane of mitochondria becomes permeable, cytochrome c is discharged into the cytoplasm, where it initiates the intrinsic apoptosis pathway. The complex interaction between cytochrome c and apoptosis protease-activating factor-1 (Apaf-1) leads to the formation of the apoptosome and activation of a cascade of caspases, highlighting the critical role of cytochrome c in controlling cell death mechanisms. Additionally, cytochrome c undergoes post-translational modifications, especially phosphorylation, which intricately regulate its roles in both respiration and apoptosis. These modifications add layers of complexity to how cytochrome c effectively controls cellular functions. cytochrome c becomes a lighthouse in the intricate web of cancer, its expression patterns providing hints about prognosis and paths toward treatment. Reduced levels of cytochrome c have been observed in cancer tissues, indicating a potential inhibition of apoptosis. For instance, in glioma tissues, cytochrome c levels were lower compared to healthy tissues, and this reduction became more pronounced in advanced stages of the disease. However, the role of cytochrome c in cancer becomes more intricate as it becomes intertwined with the metabolic reprogramming of cancer cells. This suggests that cytochrome c plays a crucial role in tumor progression and resistance to treatment. Viewing cytochrome c as a molecular mosaic reveals that it is not merely a protein, but also a central player in determining cellular fate. This realization opens up exciting avenues for potential advancements in cancer diagnosis and treatment strategies. Despite the advancements made, the narrative surrounding cytochrome c remains incomplete, urging further exploration into its complexities and the biological implications linked to cancer. cytochrome c stands as a beacon of hope and a promising target for therapy in the battle against cancer, particularly due to its significant involvement in tumor metabolism. It holds the potential for a future where innovative solutions can be developed to address the intricate challenges of cellular fate. In this review, we have endeavored to illuminate the multifaceted domain of cytochrome c drawing connections among apoptosis, metabolic reprogramming, and the Warburg effect in the context of cancer.

Roxadustat has risks of reversible central hypothyroidism in patients undergoing hemodialysis: a single-center retrospective cohort study

Roxadustat, a hypoxia-inducible factor-prolyl hydroxylase inhibitor, has proven efficacy in the treatment of renal anemia; however, evidence indicates that it may cause central hypothyroidism. The prevalence and reversibility of roxadustat-induced central hypothyroidism in patients undergoing hemodialysis remain unclear. Here, we retrospectively analyzed thyroid-stimulating hormone (TSH), free thyroxine (FT4), and free triiodothyronine (FT3) levels in 51 patients (mean age: 72.3 ± 10.7 years; 58.8% male) undergoing hemodialysis before, during, and after halting roxadustat treatment. TSH levels were significantly decreased from a median of 2.46 (interquartile range:1.60-4.51) mU/L before roxadustat treatment to 1.36 (0.72-2.41) mU/L during treatment (p < 0.001), and improved to 2.56 (1.78-4.63) mU/L after halting roxadustat (p < 0.001). Similarly, FT4 levels decreased from 1.11 (0.97-1.24) ng/dL before roxadustat treatment to 0.92 (0.71-1.03) ng/dL during treatment (p < 0.001) and improved to 1.05 (0.93-1.17) ng/dL after halting roxadustat (p < 0.001). FT3 levels were 2.04 (1.78-2.31) pg/mL before starting roxadustat, 1.97 (1.69-2.27) pg/mL during treatment, and 1.90 (1.63-2.18) pg/mL after halting roxadustat, with no significant difference between each group. Moreover, 2.0% of patients exhibited extremely low TSH levels (≤0.1 mU/L) and low TSH levels (>0.1 mU/L to <0.4 mU/L) before starting roxadustat and that percentage increased to 5.9% and 7.8%, respectively, during treatment. After roxadustat cessation, extremely low or low TSH levels recovered in all patients. Taken together, the results indicate that roxadustat can cause reversible central hypothyroidism in patients undergoing hemodialysis.

AAV-mediated combination gene therapy of inducible Caspase 9 and miR-199a-5p is therapeutic in hepatocellular carcinoma

Advanced-stage hepatocellular carcinoma (HCC) remains an untreatable disease with an overall survival of less than one year. One of the critical molecular mediators contributing to increased resistance to therapy and relapse, is increased hypoxia-inducible factor 1α (HIF-1α) levels, leading to metastasis of tumor cells. Several microRNAs are known to be dysregulated and impact HIF-1α expression in HCC. An in silico analysis demonstrated that hsa-miR-199a-5p is downregulated at various stages of HCC and is known to repress HIF-1α expression. Based on this analysis, we developed a combinatorial suicide gene therapy by employing hepatotropic Adeno-associated virus-based vectors encoding an inducible caspase 9 (iCasp9) and miR-199a. The overexpression of miR-199a-5p alone significantly decreased ( ~ 2-fold vs. Mock treated cells, p < 0.05) HIF-1α mRNA levels, with a concomitant increase in cancer cell cytotoxicity in Huh7 cells in vitro and in xenograft models in vivo. To further enhance the efficacy of gene therapy, we evaluated the synergistic therapeutic effect of AAV8-miR-199a and AAV6-iCasp9 in a xenograft model of HCC. Our data revealed that mice receiving combination suicide gene therapy exhibited reduced expression of HIF-1α ( ~ 4-fold vs. Mock, p < 0.001), with a significant reduction in tumor growth when compared to mock-treated animals. These findings underscore the therapeutic potential of downregulating HIF-1α during suicide gene therapy for HCC.

Triggering immunogenic death of cancer cells by nanoparticles overcomes immunotherapy resistance

Immunotherapy resistance poses a significant challenge in oncology, necessitating novel strategies to enhance the therapeutic efficacy. Immunogenic cell death (ICD), including necroptosis, pyroptosis and ferroptosis, triggers the release of tumor-associated antigens and numerous bioactive molecules. This release can potentiate a host immune response, thereby overcoming resistance to immunotherapy. Nanoparticles (NPs) with their biocompatible and immunomodulatory properties, are emerging as promising vehicles for the delivery of ICD-inducing agents and immune-stimulatory adjuvants to enhance immune cells tumoral infiltration and augment immunotherapy efficacy. This review explores the mechanisms underlying immunotherapy resistance, and offers an in-depth examination of ICD, including its principles and diverse modalities of cell death that contribute to it. We also provide a thorough overview of how NPs are being utilized to trigger ICD and bolster antitumor immunity. Lastly, we highlight the potential of NPs in combination with immunotherapy to revolutionize cancer treatment.

The dimer of human SVCT1 is key for transport function

Humans and other primates lack the ability to synthesize the essential nutrient, Vitamin C, which is derived exclusively from the diet. Crucial for effective vitamin C uptake are the Na+ dependent Vitamin C transporters, SVCT1 and SVCT2, members of the nucleobase ascorbate transporter (NAT) family. SVCT1 and 2 actively transport the reduced form of Vitamin C, ascorbic acid, into key tissues. The recent structure of the mouse SVCT1 revealed the molecular basis of substrate binding and that, like the other structurally characterised members of the NAT family, it exists as a closely associated dimer. SVCT1 is likely to function via the elevator mechanism with the core domain of each protomer able to bind substrate and move through the membrane carrying the substrate across the membrane. Here we explored the function of a range of variants of the human SVCT1, revealing a range of residues involved in substrate selection and binding, and confirming the importance of the C-terminus in membrane localisation. Furthermore, using a dominant negative mutant we show that the dimer is essential for transport function, as previously seen in the fungal homologue, UapA. In addition, we show that a localisation deficient C-terminal truncation of SVCT1 blocks correct localisation of co-expressed, associated wildtype SVCT1. These results clearly show the importance of the dimer in both correct SVCT1 trafficking and transport activity.

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.

Tivozanib Monotherapy in the Frontline Setting for Patients with Metastatic Renal Cell Carcinoma and Favorable Prognosis

PURPOSE OF REVIEW

In this review, we discuss which patients with metastatic clear cell renal cell carcinoma (mRCC) may be most suitable for frontline tyrosine kinase inhibitor (TKI) monotherapy, a treatment option supported by emerging long-term efficacy data including overall survival and quality of life. We specifically focus on tivozanib, a potent and selective inhibitor of vascular endothelial growth factor receptor, which has comparable efficacy to other single-agent TKIs in frontline treatment for mRCC while exhibiting fewer off-target side effects.

RECENT FINDINGS

Combination therapy with TKIs and checkpoint inhibitors (CPIs) and CPI/CPI combination therapies, as well as TKI monotherapy are recommended frontline treatment options for mRCC. Treatment decisions are complex and based on several factors, including the patient's International Metastatic RCC Database Consortium risk status, age, comorbidities, and personal preferences related to response, tolerability, and quality of life. TKIs not only serve as backbone of most combination therapies for mRCC, but also remain a viable monotherapy option in the first-line setting for patients in favorable risk groups and those with contraindications to CPI combination therapies. Given that overall survival benefits have not yet been confirmed for CPI-containing combination regimens in favorable risk patients, we argue that frontline single-agent TKI treatment remains a standard of care option for these patients. This is supported by treatment guidelines, even in the era of TKI/CPI combination therapies.

Current views on the role of HIF-2α in the pathogenesis and syndromic presentation of pheochromocytoma and paraganglioma

Pathogenic variants (PVs) in EPAS1, which encodes hypoxia-inducible factor-2α (HIF-2α), could be the underlying genetic cause of about 3%-6% of pheochromocytoma and paragangliomas (PPGLs). EPAS1-related PPGLs may occur as isolated tumors or as part of Pacak-Zhuang Syndrome (PZS) with two or more of a triad of PPGL, polycythemia, and somatostatinoma. HIF-2α plays a critical role in the regulation of the cellular hypoxia pathway. When a gain-of-function PV is acquired, HIF-2α evades steady-state hydroxylation by the prolyl hydroxylase type 2 (PHD2), which accelerates von Hippel-Lindau (VHL)-mediated proteasomal degradation. In this situation, HIF-2α is stabilized and can translocate to the nucleus, inducing the expression of several genes involved in tumorigenesis. This leads to the development of PPGL and other manifestations of PZS. EPAS1-related PPGLs usually occur in the second or third decade of life, more frequently in females, and are usually multiple, adrenal and extra-adrenal, and norepinephrine-secreting. In addition, these tumors carry an increased metastatic potential and have been reported with metastatic disease in up to 30% of cases. While polycythemia is fairly common in PZS, somatostatinomas are rare. It has been suggested that the character of the acquired PV in EPAS1, which affects its binding to PHD2, correlates with certain phenotypes in PZS. PVs in EPAS1 that have been found in related sporadic PPGLs have also been associated with hypoxic conditions including cyanotic congenital heart disease, hemoglobinopathies and high altitude. Understanding the hypoxia pathway and its role in the pathogenesis of PPGL may open a new avenue for developing effective therapies for these tumors. Indeed, one of these therapies is Belzutifan, a HIF-2α inhibitor that is being tested in the treatment of metastatic PPGLs.

Insoluble HIFa protein aggregates by cadmium disrupt hypoxia-prolyl hydroxylase (PHD)-hypoxia inducible factor (HIFa) signaling in renal epithelial (NRK-52E) and interstitial (FAIK3-5) cells

The kidney is the main organ that senses changes in systemic O2 pressure by hypoxia-PHD-HIFa (HPH) signaling, resulting in adaptive target gene activation, including erythropoietin (EPO). The non-essential transition metal cadmium (Cd) is nephrotoxic and disrupts the renal HPH pathway, which may promote Cd-associated chronic renal disease (CKD). A deeper molecular understanding of Cd interference with renal HPH signaling is missing, and no data with renal cell lines are available. In rat kidney NRK-52E cells, which model the proximal tubule, and murine fibroblastoid atypical interstitial kidney (FAIK3-5) cells, which mimic renal EPO-producing cells, the chemical hypoxia mimetic dimethyloxalylglycine (DMOG; 1 mmol/l) or hypoxia (1% O2) activated HPH signaling. Cd2+ (2.5-20 µmol/l for ≤ 24 h) preferentially induced necrosis (trypan blue uptake) of FAIK3-5 cells at high Cd whereas NRK-52E cells specially developed apoptosis (PARP-1 cleavage) at all Cd concentrations. Cd (12.5 µmol/l) abolished HIFa stabilization and prevented upregulation of target genes (quantitative real-time polymerase chain reaction and immunoblotting) induced by DMOG or hypoxia in both cell lines, which was caused by the formation of insoluble HIFa aggregates. Strikingly, hypoxic preconditioning (1% O2 for 18 h) reduced apoptosis of FAIK3-5 and NRK-52E cells at low Cd concentrations and decreased insoluble HIFa proteins. Hence, drugs mimicking hypoxic preconditioning could reduce CKD induced by chronic low Cd exposure.

Anemia and Mineral Bone Disorder in Kidney Disease Patients: The Role of FGF-23 and Other Related Factors

Anemia and mineral and bone disorder (MBD) are significant complications of chronic kidney disease (CKD). The erythropoietin (Epo) pathway plays a key role in both of these processes in CKD. Another molecule that plays an important role in CKD-MBD is fibroblast growth factor (FGF)-23, whose main role is to maintain serum phosphate levels in the normal range, acting via its co-receptor Klotho; however, its activity may also be related to anemia and inflammation. In this review, the regulation of Epo and FGF-23 and the molecular mechanisms of their action are outlined. Furthermore, the complex interaction between EPO and FGF-23 is discussed, as well as their association with other anemia-related factors and processes such as Klotho, vitamin D, and iron deficiency. Together, these may be part of a "kidney-bone marrow-bone axis" that promotes CKD-MBD.

Nanomaterial-based regulation of redox metabolism for enhancing cancer therapy

Altered redox metabolism is one of the hallmarks of tumor cells, which not only contributes to tumor proliferation, metastasis, and immune evasion, but also has great relevance to therapeutic resistance. Therefore, regulation of redox metabolism of tumor cells has been proposed as an attractive therapeutic strategy to inhibit tumor growth and reverse therapeutic resistance. In this respect, nanomedicines have exhibited significant therapeutic advantages as intensively reported in recent studies. In this review, we would like to summarize the latest advances in nanomaterial-assisted strategies for redox metabolic regulation therapy, with a focus on the regulation of redox metabolism-related metabolite levels, enzyme activity, and signaling pathways. In the end, future expectations and challenges of such emerging strategies have been discussed, hoping to enlighten and promote their further development for meeting the various demands of advanced cancer therapies. It is highly expected that these therapeutic strategies based on redox metabolism regulation will play a more important role in the field of nanomedicine.

Global surveillance of circulating microRNA for diagnostic and prognostic assessment of acute myocardial infarction based on the plasma small RNA sequencing

BACKGROUND

Circulating microRNAs (miRNAs) are recently a rapidly increasing of interest as non-invasive biomarkers for diagnosis and prognosis of acute myocardial infarction (AMI). Previous studies revealed that several miRNAs exhibited the capacity for diagnosis and prognosis of AMI, the reasons why these circulating miRNAs are concerned as targets for investigation are quite cryptogenic, presumably due to the lack of clues provided by global surveillance at the transcriptome level, and the current data for some miRNAs are controversial and inconsistent among independent studies.

METHODS

To comprehensively profiling the potential miRNAs for diagnosis and prognosis of AMI, we reported transcriptomes of circulating miRNAs in the plasma of 27 healthy controls, 64 AMI patients (37 STEMI and 27 NSTEMI) and 20 AMI patients who were subjected to reperfusion therapy. Meanwhile, the cTnI of AMI patients was parallel determined. Differentially-circulated miRNAs were analyzed between each group. All detected circulating miRNAs were examined by ROC analysis and then LASSO dimension reduction to obtain an optimal panel for diagnosis of AMI. A five-year period follow-up towards the AMI and reperfusion patients was performed, and the prognostic value of circulating miRNAs in these patients was estimated by using the Cox regression model, ROC and Kaplan-Meier curves.

RESULTS

Comprehensive global differences of miRNAs transcriptome among AMI, reperfusion patients and healthy controls were identified. A total of 40 miRNAs, called high diagnostic performance miRNAs, including several previous well-studied miRNAs with AUC greater than 0.85 were shown to discriminate AMI with healthy controls. In addition, 29 miRNAs were analyzed to be strongly correlated with the plasma cTnI level, of which 20 overlapped with high diagnostic performance miRNAs. These overlapped miRNAs are over-represented in the pathways which actually reflect the pathological cause of myocardial infarction, as well as the regulation of gene expression and energetic pathway of cellular response to hypoxia. Finally, two miRNAs were analyzed to be significantly correlated to all-cause mortality.

CONCLUSION

This is the first time to survey plasma miRNAs for the development of AMI diagnostic and prognostic biomarkers at the transcriptome level. A subset of miRNAs exhibited potential diagnostic and prognostic merits for AMI.

A Hypoxia-Inflammation Cycle and Multiple Sclerosis: Mechanisms and Therapeutic Implications

Purpose of Review

Multiple sclerosis (MS) is a complex neurodegenerative disease characterized by inflammation, demyelination, and neurodegeneration. Significant hypoxia exists in brain of people with MS (pwMS), likely contributing to inflammatory, neurodegenerative, and vascular impairments. In this review, we explore the concept of a negative feedback loop between hypoxia and inflammation, discussing its potential role in disease progression based on evidence of hypoxia, and its implications for therapeutic targets.

Recent Findings

In the experimental autoimmune encephalomyelitis (EAE) model, hypoxia has been detected in gray matter (GM) using histological stains, susceptibility MRI and implanted oxygen sensitive probes. In pwMS, hypoxia has been quantified using near-infrared spectroscopy (NIRS) to measure cortical tissue oxygen saturation (StO2), as well as through blood-based biomarkers such as Glucose Transporter-1 (GLUT-1). We outline the potential for the hypoxia-inflammation cycle to drive tissue damage even in the absence of plaques. Inflammation can drive hypoxia through blood-brain barrier (BBB) disruption and edema, mitochondrial dysfunction, oxidative stress, vessel blockage and vascular abnormalities. The hypoxia can, in turn, drive more inflammation.

Summary

The hypoxia-inflammation cycle could exacerbate neuroinflammation and disease progression. We explore therapeutic approaches that target this cycle, providing information about potential treatments in MS. There are many therapeutic approaches that could block this cycle, including inhibiting hypoxia-inducible factor 1-α (HIF-1α), blocking cell adhesion or using vasodilators or oxygen, which could reduce either inflammation or hypoxia. This review highlights the potential significance of the hypoxia-inflammation pathway in MS and suggests strategies to break the cycle. Such treatments could improve quality of life or reduce rates of progression.

The role of hypoxic microenvironment in autoimmune diseases

The hypoxic microenvironment, characterized by significantly reduced oxygen levels within tissues, has emerged as a critical factor in the pathogenesis and progression of various autoimmune diseases (AIDs). Central to this process is the hypoxia-inducible factor-1 (HIF-1), which orchestrates a wide array of cellular responses under low oxygen conditions. This review delves into the multifaceted roles of the hypoxic microenvironment in modulating immune cell function, particularly highlighting its impact on immune activation, metabolic reprogramming, and angiogenesis. Specific focus is given to the mechanisms by which hypoxia contributes to the development and exacerbation of diseases such as rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), multiple sclerosis (MS), and dermatomyositis (DM). In these conditions, the hypoxic microenvironment not only disrupts immune tolerance but also enhances inflammatory responses and promotes tissue damage. The review also discusses emerging therapeutic strategies aimed at targeting the hypoxic pathways, including the application of HIF-1α inhibitors, mTOR inhibitors, and other modulators of the hypoxic response. By providing a comprehensive overview of the interplay between hypoxia and immune dysfunction in AIDs, this review offers new perspectives on the underlying mechanisms of these diseases and highlights potential avenues for therapeutic intervention.