Alpha Subunit Of Hypoxia-inducible Factor Research Articles

Rynchopeterine inhibits the formation of hypertrophic scars by regulating the miR-21/HIF1AN axis

Hypertrophic scar (HS) is a fibroproliferative skin disease characterized by abnormal wound healing and pathological excessive fibrosis of the skin. Currently, the molecular mechanism of the disease is still largely unknown, and there is no effective drug treatment. In this study, we explored the effect of Rynchopeterine on the formation of HS. HS fibroblasts (HSFs) were isolated from the HS tissues of patients recovering from severe burns. After treating HSFs with different concentrations of Rynchopeterine, CCK-8, EdU, and Annexin V-FITC/PI assays were used to detect the proliferation, apoptosis, and contractile ability of HSFs. RT-qPCR and Western blotting were performed to evaluate the effect of Rynchopeterine on the expression of miR-21 and hypoxia-inducible factor 1-alpha subunit suppressor (HIF1AN). The dual-luciferase reporter gene was used to verify the targeting relationship between miR-21 and HIF1AN. Rynchopeterine reduced the expression of Col1a2, Col3a1, and α-SMA, inhibited proliferation and contraction of HSFs, and increased apoptosis in a dose-dependent manner. miR-21 was highly expressed in HS tissues and HSFs, and Rynchopeterine could inhibit miR-21 expression. Overexpression of miR-21 and knockdown of HIF1AN increased proliferation, activation, contraction, and collagen synthesis of HSFs, and inhibited their apoptosis. In vivo, Rynchopeterine could reduce the collagen content of the dermis and the positive ratio of PCNA and α-SMA. Rynchopeterine is a good therapeutic agent for HS, which up-regulates the expression of HIF1AN by inhibiting miR-21, thereby inhibiting the formation of HS.

Germline variants in the Von Hippel-Lindau tumor suppressor gene in Cuban patients

Abstract Background Von Hippel-Lindau (VHL) syndrome is an autosomal dominantly inherited disorder that predisposes to multiple neoplasms. Patients may develop hemangioblastomas of the central nervous system and retina, multiple cysts in the pancreas and kidneys, renal carcinoma, and pheochromocytomas, among other lesions. This disease is caused by germline genetic variants in the VHL gene. The regulation of the alpha subunit of hypoxia-inducible factor-1 is the key tumor suppressor function of the VHL protein. To date, more than seven hundred variants have been reported in VHL gene. This study aimed to investigate the molecular etiology of VHL syndrome in Cuban patients. Results DNA samples from twenty-two individuals were analyzed by Sanger sequencing or enzymatic restriction. The analysis identified four novel pathogenic variants for the Cuban population: c.463 + 2T > C, C162W, R167W, and S183X, in addition to D121G and R161X, previously described in another work. The diagnosis was confirmed in seven patients with clinical manifestations and family history. Two at-risk family members without clinical signs were positive for presymptomatic diagnosis. Conclusions The spectrum of germinal point mutations of VHL gene in Cuban patients was updated. The presence of genetic variants was ruled out in eight asymptomatic relatives, which is a psychological relief for these individuals. The results allow for offering other at-risk relatives the presymptomatic diagnosis and the possibility of receiving genetic counseling.

High glucose promotes osteogenic differentiation of human lens epithelial cells through hypoxia-inducible factor (HIF) activation.

Cataract, a leading cause of blindness, is characterised by lens opacification. Type 2 diabetes is associated with a two- tofivefold higher prevalence of cataracts. The risk of cataract formation increases with the duration of diabetes and the severity of hyperglycaemia. Hydroxyapatite deposition is present in cataractous lenses that could be the consequence of osteogenic differentiation and calcification of lens epithelial cells (LECs). We hypothesised that hyperglycaemia might promote the osteogenic differentiation of human LECs (HuLECs). Osteogenic medium (OM) containing excess phosphate and calcium with normal (1 g/L) or high (4.5 g/L) glucose was used to induce HuLEC calcification. High glucose accelerated and intensified OM-induced calcification of HuLECs, which was accompanied by hyperglycaemia-induced upregulation of the osteogenic markers Runx2, Sox9, alkaline phosphataseand osteocalcin, as well as nuclear translocation of Runx2. High glucose-induced calcification was abolished in Runx2-deficient HuLECs. Additionally, high glucose stabilised the regulatory alpha subunits of hypoxia-inducible factor 1 (HIF-1), triggered nuclear translocation of HIF-1αand increased the expression of HIF-1 target genes. Gene silencing of HIF-1α or HIF-2α attenuated hyperglycaemia-induced calcification of HuLECs, while hypoxia mimetics (desferrioxamine, CoCl2) enhanced calcification of HuLECs under normal glucose conditions. Overall, this study suggests that high glucose promotes HuLEC calcification via Runx2 and the activation of the HIF-1 signalling pathway. These findings may provide new insights into the pathogenesis of diabetic cataracts, shedding light on potential factors for intervention to treat this sight-threatening condition.

Network pharmacology integrated with molecular docking technology to reveal the potential mechanism of Shuganfang against drug-induced liver injury.

This study aimed to investigate the active composition and mechanism of the Shuganfang (SGF) in treating drug-induced liver injury (DILI) using network pharmacology and molecular docking. The potential active ingredients and targets of SGF were obtained from the Traditional Chinese Medicine Systems Pharmacology Database (TCMSP) database. DILI-related targets were queried from various databases including GEO, GeneCards, OMIM, NCBI, and DisGeNET. The STRING database was used to establish a protein-protein interaction (PPI) network. DAVID was utilized for conducting gene ontology (GO) function enrichment and Kyoto encyclopedia of genes and genomes (KEGG) pathway enrichment analyses. The data visualization and analysis of herb-ingredient-target and disease-pathway-target-ingredient networks were conducted using Cytoscape software (version 3.7.2). PyMoL and AutoDock software was used to select the best binding target for molecular docking. A total of 177 active ingredients,126 targets and 10112 disease targets were obtained, including 122 intersection targets. The identified potential active ingredients consisted of quercetin, kaempferol, luteolin, tanshinone IIa, nobiletin, isorhamnetin, beta-sitosterol and naringenin. The core targets implicated in the study were IL6, estrogen receptor 1 (ESR1), hypoxia-inducible factor alpha subunit 1 (HIF1A), MYC and vascular endothelial growth factor A (VEGFA). KEGG analysis revealed that the treatment of DILI with SGF mainly acted through apoptosis, the PI3K-Akt signaling pathway, and the tumor necrosis factor (TNF) signaling pathway. Furthermore, the binding affinities between the potential ingredients and the core targets were subsequently confirmed through molecular docking experiments. The findings indicated that the docking outcomes remained consistent and demonstrated a favorable capacity for binding. SGF exerts a therapeutic effect on DILI through multiple active ingredients, multiple targets and multiple pathways. Our findings contribute to a positive investigation and establish a theoretical basis for further extensive exploration of SGF as a potential treatment for DILI in future research.

A simplified protocol to induce hypoxia in a standard incubator: A focus on retinal cells

Hypoxia chambers have traditionally been used to induce hypoxia in cell cultures. Cellular responses to hypoxia can also be mimicked with the use of chemicals such as cobalt chloride (CoCl2), which stabilizes hypoxia-inducible factor alpha-subunit proteins. In studies of ocular cells using primary cells and cell lines, such as Müller glial cell (MGC) lines, photoreceptor cell lines, retinal pigment epithelial (RPE) cell lines and retinoblastoma cell lines oxygen levels employed in hypoxia chambers range typically between 0.2% and 5% oxygen. For chemical induction of hypoxic response in these cells, the CoCl2 concentrations used typically range from 100 to 600 μM. Here, we describe simplified protocols for stabilizing cellular hypoxia-inducible factor-1α (HIF-1α) in cell culture using either a hypoxia chamber or CoCl2. In addition, we also provide a detailed methodology to confirm hypoxia induction by the assessment of protein levels of HIF-1α, which accumulates in response to hypoxic conditions. Furthermore, we provide a summary of conditions applied in previous studies of ocular cells.

ARC-20: A phase 1 dose-escalation and dose-expansion study to investigate the safety, tolerability, and pharmacology of HIF-2α inhibitor AB521 monotherapy in patients with clear cell renal cell carcinoma and other solid tumors.

TPS4602 Background: Renal cell carcinoma (RCC) is one of the 10 most common neoplasms in the United States. Patients with clear cell RCC (ccRCC) commonly have inactivation of the von Hippel-Lindau tumor suppressor protein, resulting in accumulation of hypoxia-inducible factor alpha (HIFα) subunits (especially HIF-2α) and leading to tumor growth. AB521, an orally bioavailable small molecule inhibitor of HIF-2α, potently inhibits transcription of HIF-2α-dependent genes in cell lines and preclinical species. Single doses of AB521 (3 mg, 10 mg, 30 mg, and 100 mg) and multiple ascending doses of AB521 (15 mg, 30 mg, and 50 mg) have been previously studied in healthy volunteers. ARC-20 is a first-in-patient study to investigate the safety, tolerability, and pharmacology of AB521 monotherapy in patients with solid tumors and evaluate the clinical activity of AB521 in previously treated patients with ccRCC. Methods: ARC-20 (NCT05536141) is a phase 1, multicenter, open-label study. Eligible patients are adults with solid tumors with ≥1 measurable lesion(s) per Response Evaluation Criteria in Solid Tumors (RECIST) v1.1 and an Eastern Cooperative Oncology Group performance status of 0 or 1. ARC-20 has 2 stages, dose escalation and dose expansion. The dose escalation stage uses a standard 3+3 design and includes patients with pathologically confirmed solid tumors and no other available treatment options. Patients will be sequentially assigned to 1 of 4 cohorts evaluating doses of AB521 ranging from 20 to 200 mg/day. Intermediate dose cohorts may be evaluated based on emergent safety or pharmacologic data. The dose expansion stage will evaluate approximately 30 patients with histologically confirmed ccRCC who have received previous treatment for metastasis with an anti-programmed cell death protein 1 (anti-PD-1) therapy and a vascular endothelial growth factor (VEGF)-targeting tyrosine kinase inhibitor (TKI). Patients previously treated with a HIF-2α-targeting therapy are not eligible for dose expansion. Results from the dose-escalation stage will inform the dose and schedule used during dose expansion. Primary endpoints are the incidence of dose-limiting toxicity and adverse events. Secondary endpoints include objective response rate, AB521 plasma concentration, and AB521 pharmacokinetics. Exploratory endpoints include changes in expression of erythropoietin and other HIF-2α driven biomarkers in blood and tumor tissues, along with progression-free survival for ccRCC patients during dose expansion. Clinical trial information: NCT05536141 .

Determination of possible microRNA-markers of cobalt abuse by real-time qPCR using hypoxia signaling pathway panels

Objectives. Cobalt mimics the state of hypoxia to prevent degradation of the alpha subunit of hypoxia-inducible factor, resulting in an increase in blood oxygen capacity and endurance. Athletes can use this property to gain competitive advantage. Nowadays, direct methods of inductively coupled plasma mass spectrometry and liquid chromatography-tandem mass spectrometry are used to determine total cobalt levels in the body. However, the World Anti-Doping Agency is yet to establish a maximum allowable threshold concentration of this element in biofluids. The lack of clear identification criteria complicates the interpretation of the obtained results for the purposes of doping control. In this regard, the present work proposes a new approach for the indirect determination of possible cobalt abuse based on changes in the expression levels of miRNAs involved in the regulation of hypoxia signaling pathways. Here, the aim is to identify possible microRNA markers whose expression does not depend on exercise-induced hypoxia, but changes markedly when taking cobalt preparations.Methods. MicroRNA isolation was performed from blood plasma samples using the PAXgene Blood miRNA Kit. Quantitative real-time polymerase chain reaction (PCR) was performed on CFX96 Bio-Rad (USA) analyzer using miScript® SYBR® Green PCR Kits and panels for studying the expression profiles of mature microRNAs of the hypoxia signaling pathway miScript® miRNA PCR Array.Results. Based on the statistical analysis of the data, it was found that the expression of hsa-miR-15b-5p in the blood plasma of the subjects does not depend on physical activity, but increases when taking cobalt preparations.Conclusions. The difference in expression levels during anaerobic exercise-induced hypoxia and cobalt-induced hypoxia makes hsa-miR-15b-5p a potential candidate to be a marker of erythropoiesis-stimulating agent abuse.

Downstream Targets of VHL/HIF-α Signaling in Renal Clear Cell Carcinoma Progression: Mechanisms and Therapeutic Relevance.

The clear cell variant of renal cell carcinoma (ccRCC) is the most common renal epithelial malignancy and responsible for most of the deaths from kidney cancer. Patients carrying inactivating mutations in the Von Hippel-Lindau (VHL) gene have an increased proclivity to develop several types of tumors including ccRCC. Normally, the Hypoxia Inducible Factor alpha (HIF-α) subunits of the HIF heterodimeric transcription factor complex are regulated by oxygen-dependent prolyl-hydroxylation, VHL-mediated ubiquitination and proteasomal degradation. Loss of pVHL function results in elevated levels of HIF-α due to increased stability, leading to RCC progression. While HIF-1α acts as a tumor suppressor, HIF-2α promotes oncogenic potential by driving tumor progression and metastasis through activation of hypoxia-sensitive signaling pathways and overexpression of HIF-2α target genes. One strategy to suppress ccRCC aggressiveness is directed at inhibition of HIF-2α and the associated molecular pathways leading to cell proliferation, angiogenesis, and metastasis. Indeed, clinical and pre-clinical data demonstrated the effectiveness of HIF-2α targeted therapy in attenuating ccRCC progression. This review focuses on the signaling pathways and the involved genes (cyclin D, c-Myc, VEGF-a, EGFR, TGF-α, GLUT-1) that confer oncogenic potential downstream of the VHL-HIF-2α signaling axis in ccRCC. Discussed as well are current treatment options (including receptor tyrosine kinase inhibitors such as sunitinib), the medical challenges (high prevalence of metastasis at the time of diagnosis, refractory nature of advanced disease to current treatment options), scientific challenges and future directions.

Low expression of HIF1AN accompanied by less immune infiltration is associated with poor prognosis in breast cancer.

Hypoxia-inducible factor 1-alpha (HIF-1α) stability and transcriptional action are reduced by the hypoxia-inducible factor 1-alpha subunit suppressor (HIF1AN). Its inappropriate expression is associated with the development of cancer and immune control. It is yet unknown how HIF1AN, clinical outcomes, and immune involvement in breast cancer (BC) are related. Using the GEPIA, UALCAN, TIMER, Kaplan-Meier plotter, and TISIDB datasets, a thorough analysis of HIF1AN differential expression, medical prognosis, and the relationship between HIF1AN and tumor-infiltrating immune cells in BC was conducted. Quantitative real-time PCR (qRT-PCR) analysis of BC cells were used for external validation. The findings revealed that, as compared to standard specimens, BC cells had significantly lower levels of HIF1AN expression. Good overall survival (OS) for BC was associated with higher HIF1AN expression. Additionally, in BC, the expression of HIF1AN was closely associated with the chemokines and immune cell infiltration, including neutrophils, macrophages, T helper cells, B cells, Tregs, monocytes, dendritic cells, and NK cells. A high correlation between HIF1AN expression and several immunological indicators of T-cell exhaustion was particularly revealed by the bioinformatic study. HIF1AN is a predictive indicator for breast tumors, and it is useful for predicting survival rates.

Hypoxia-inducible factor underlies von Hippel-Lindau disease stigmata.

von Hippel-Lindau (VHL) disease is a rare hereditary cancer syndrome that causes a predisposition to renal clear-cell carcinoma, hemangioblastoma, pheochromocytoma, and autosomal-recessive familial polycythemia. pVHL is the substrate conferring subunit of an E3 ubiquitin ligase complex that binds to the three hypoxia-inducible factor alpha subunits (HIF1-3α) for polyubiquitylation under conditions of normoxia, targeting them for immediate degradation by the proteasome. Certain mutations in pVHL have been determined to be causative of VHL disease through the disruption of HIFα degradation. However, it remains a focus of investigation and debate whether the disruption of HIFα degradation alone is sufficient to explain the complex genotype-phenotype relationship of VHL disease or whether the other lesser or yet characterized substrates and functions of pVHL impact the development of the VHL disease stigmata; the elucidation of which would have a significant ramification to the direction of research efforts and future management and care of VHL patients and for those manifesting sporadic counterparts of VHL disease. Here, we examine the current literature including the other emergent pseudohypoxic diseases and propose that the VHL disease-phenotypic spectrum could be explained solely by the varied disruption of HIFα signaling upon the loss or mutation in pVHL.

Molecular Characterization and Response of Prolyl Hydroxylase Domain (PHD) Genes to Hypoxia Stress in Hypophthalmichthys molitrix

Simple SummaryHypoxia is a common challenge for aquatic organisms, and prolyl hydroxylase domain (PHD) proteins play important roles in hypoxic adaptation by regulating the stability of the hypoxia-inducible factor 1 alpha subunit (HIF-1α). In this study, the full-length cDNAs of three PHD genes were obtained from Hypophthalmichthys molitrix, which is an important freshwater fish and sensitive to low oxygen tension. The amino acid sequence analysis and phylogenetic analysis of PHDs were performed among various species. Furthermore, the expression patterns and the transcriptional responses of H. molitrix PHD genes to acute hypoxia, continued hypoxia, and reoxygenation were explored in different tissues. Our study preliminarily explored the physiological regulation functions of PHD genes at the transcriptional level when addressing the hypoxic challenge and provided a foundation for future systematic explorations of the molecular mechanisms underlying hypoxia adaptation in silver carp.As an economically and ecologically important freshwater fish, silver carp (Hypophthalmichthys molitrix) is sensitive to low oxygen tension. Prolyl hydroxylase domain (PHD) proteins are critical regulators of adaptive responses to hypoxia for their function of regulating the hypoxia inducible factor-1 alpha subunit (HIF-1α) stability via hydroxylation reaction. In the present study, three PHD genes were cloned from H. molitrix by rapid amplification of cDNA ends (RACE). The total length of HmPHD1, HmPHD2, and HmPHD3 were 2981, 1954, and 1847 base pair (bp), and contained 1449, 1080, and 738 bp open reading frames (ORFs) that encoded 482, 359, and 245 amino acids (aa), respectively. Amino acid sequence analysis showed that HmPHD1, HmPHD2, and HmPHD3 had the conserved prolyl 4-hydroxylase alpha subunit homolog domains at their C-termini. Meanwhile, the evaluation of phylogeny revealed PHD2 and PHD3 of H. molitrix were more closely related as they belonged to sister clades, whereas the clade of PHD1 was relatively distant from these two. The transcripts of PHD genes are ubiquitously distributed in H. molitrix tissues, with the highest expressional level of HmPHD1 and HmPHD3 in liver, and HmPHD2 in muscle. After acute hypoxic treatment for 0.5 h, PHD genes of H. molitrix were induced mainly in liver and brain, and different from HmPHD1 and HmPHD2, the expression of HmPHD3 showed no overt tissue specificity. Furthermore, under continued hypoxic condition, PHD genes exhibited an obviously rapid but gradually attenuated response from 3 h to 24 h, and upon reoxygenation, the transcriptional expression of PHD genes showed a decreasing trend in most of the tissues. These results indicate that the PHD genes of H. molitrix are involved in the early response to hypoxic stress, and they show tissue-specific transcript expression when performing physiological regulation functions. This study is of great relevance for advancing our understanding of how PHD genes are regulated when addressing the hypoxic challenge and provides a reference for the subsequent research of the molecular mechanisms underlying hypoxia adaptation in silver carp.

Integration and Visualization of Regulatory Elements and Variations of the EPAS1 Gene in Human.

Endothelial PAS domain-containing protein 1 (EPAS1), also HIF2α, is an alpha subunit of hypoxia-inducible transcription factor (HIF), which mediates cellular and systemic response to hypoxia. EPAS1 has an important role in the transcription of many hypoxia-responsive genes, however, it has been less researched than HIF1α. The aim of this study was to integrate an increasing number of data on EPAS1 into a map of diverse OMICs elements. Publications, databases, and bioinformatics tools were examined, including Ensembl, MethPrimer, STRING, miRTarBase, COSMIC, and LOVD. The EPAS1 expression, stability, and activity are tightly regulated on several OMICs levels to maintain complex oxygen homeostasis. In the integrative EPAS1 map we included: 31 promoter-binding proteins, 13 interacting miRNAs and one lncRNA, and 16 post-translational modifications regulating EPAS1 protein abundance. EPAS1 has been associated with various cancer types and other diseases. The development of neuroendocrine tumors and erythrocytosis was shown to be associated with 11 somatic and 20 germline variants. The integrative map also includes 12 EPAS1 target genes and 27 interacting proteins. The study introduced the first integrative map of diverse genomics, transcriptomics, proteomics, regulomics, and interactomics data associated with EPAS1, to enable a better understanding of EPAS1 activity and regulation and support future research.

Von Hippel–Lindau (VHL) small-molecule inhibitor binding increases stability and intracellular levels of VHL protein

Von Hippel–Lindau (VHL) disease is characterized by frequent mutation of VHL protein, a tumor suppressor that functions as the substrate recognition subunit of a Cullin2 RING E3 ligase complex (CRL2VHL). CRL2VHL plays important roles in oxygen sensing by targeting hypoxia-inducible factor-alpha (HIF-α) subunits for ubiquitination and degradation. VHL is also commonly hijacked by bifunctional molecules such as proteolysis-targeting chimeras to induce degradation of target molecules. We previously reported the design and characterization of VHL inhibitors VH032 and VH298 that block the VHL:HIF-α interaction, activate the HIF transcription factor, and induce a hypoxic response, which can be beneficial to treat anemia and mitochondrial diseases. How these compounds affect the global cellular proteome remains unknown. Here, we use unbiased quantitative MS to identify the proteomic changes elicited by the VHL inhibitor compared with hypoxia or the broad-spectrum prolyl-hydroxylase domain enzyme inhibitor IOX2. Our results demonstrate that VHL inhibitors selectively activate the HIF response similar to the changes induced in hypoxia and IOX2 treatment. Interestingly, VHL inhibitors were found to specifically upregulate VHL itself. Our analysis revealed that this occurs via protein stabilization of VHL isoforms and not via changes in transcript levels. Increased VHL levels upon VH298 treatment resulted in turn in reduced levels of HIF-1α protein. This work demonstrates the specificity of VHL inhibitors and reveals different antagonistic effects upon their acute versus prolonged treatment in cells. These findings suggest that therapeutic use of VHL inhibitors may not produce overt side effects from HIF stabilization as previously thought.

The Content and Activity of Hypoxia-Inducible Factor HIF1α Increased in the Hippocampus of Newborn Rats That Were Subjected to Prenatal Hypoxia on Days 14–16 of Embryogenesis

Abstract—Western blot and quantitative real-time PCR were used to study the content of the regulatory alpha subunit of hypoxia-inducible factor-1 (HIF1α), and the mRNA content of the HIF1-regulated genes lactate dehydrogenase A (ldha) and glucose-6-phosphate dehydrogenase (g6pd) in the hippocampus of 1-day old rat pups whose mothers were subjected to three sessions of severe damaging hypoxia on days 14–16 of pregnancy. Prenatal hypoxia caused a stable increase in HIF1α content, and also led to an increase in the ldha mRNA content and a decrease in the g6pd mRNA content. The results indicate that changes in hippocampal metabolism after prenatal hypoxia are stable and can cause disturbances in the energy metabolism of the brain in further ontogeny.

Role of Microtubule-Associated Factors in HIF1α Nuclear Translocation.

Adaptation to hypoxia is essential for regulating the survival and functions of hypoxic cells; it is mainly mediated by the hypoxia-inducible factor 1 (HIF1). The alpha subunit of HIF1 (HIF1α) is a well-known regulatory component of HIF1, which is tightly controlled by various types of HIF1α-regulating processes. Previous research has shown that microtubule-regulated HIF1α nuclear translocation is a key factor for HIF1 activation under hypoxia. In this review, we summarize experimental reports on the role of microtubule-associated factors, such as microtubule, dynein, and dynein adaptor protein, in nuclear translocation of HIF1α. Based upon scientific evidence, we propose a bicaudal D homolog (BICD) as a novel HIF1α translocation regulating factor. A deeper understanding of the mechanism of the action of regulatory factors in controlling HIF1α nuclear translocation will provide novel insights into cell biology under hypoxia.

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

The pentose phosphate pathway (PPP) of glucose metabolism in the brain serves as a primary source of NADPH which in turn plays a crucial role in multiple cellular processes, including maintenance of redox homeostasis and antioxidant defense. In our model of protective mild hypobaric hypoxia in rats (3MHH), an inverse correlation between hypoxia-inducible factor-1 (HIF1) activity and mRNA levels of glucose-6-phosphate dehydrogenase (G6PD), the key enzyme of PPP, was observed. In the present study, it was demonstrated that severe hypobaric hypoxia (SH) induced short-term upregulation of HIF1 alpha-subunit (HIF1α) in the hippocampal CA1 subfield and decreased the activity of G6PD. The levels of NADPH were also reduced, promoting oxidative stress, triggering apoptosis, and neuronal loss. Injection of a HIF1 inhibitor (HIF1i), topotecan hydrochloride (5mg/kg, i.p.), before SH prevented the upregulation of HIF1α and normalized G6PD activity. In addition, HIF1i injection caused an increase in NADPH levels, normalization of total glutathione levels and of the cellular redox status as well as suppression of free-radical and apoptotic processes. These results demonstrate a new molecular mechanism of post-hypoxic cerebral pathology development which involves HIF1-dependent PPP depletion and support a recently suggested injurious role of HIF1 activation in the acute phase of cerebral hypoxia/ischemia. Application of PPP stimulators in early post-hypoxic/ischemic period might represent a promising neuroprotective strategy. Graphical abstract HIF1-dependent down-regulation of the pentose phosphate pathway contributes to the hypoxia-induced oxidative stress and neuronal apoptosis in the rat hippocampus.

Study on the mechanism of low-frequency electromagnetic field promoting the healing of ischemic foot ulcer in experimental rabbits

Objective By modeling ischemic foot ulcers in experimental rabbits, the mechanism of healing in animal models was investigated. Methods Sixty healthy male clean grade New Zealand rabbits were 3 months. The weight range was 2.1-2.5 kg. Randomly draw auording to the number, the experimental rabbits were randomly divided into 4 groups, namely, no ischemia-no ulcer-no intervention group (group A), no ischemia-no ulcer-no intervention group (group B), no ischemia-no ulcer-no intervention group (group C) and no ischemia-ulcer-intervention group (group D), with 15 rabbits in each group. Ischemic foot ulcers experimental rabbit building complete after 24 h, will naturally exposed ischemic foot ulcers in the low frequency electromagnetic field on experimental rabbit 7 d feeding experiment, the experimental rabbits ischemia crus muscle and the ulcer base were collected, and plasma by enzyme-linked immunosorbent assay (ELISA) verification tests in experimental rabbit plasma hypoxia-inducible factor 1 alpha subunit (HIF-1α), matrix metalloproteinases 9 (MMP-9) and soluble leukocyte differentiation antigen 40 ligand 1 (sCD40L1) expression level, while detecting ulcer healing area change, hematoxylin-eosin staining was used to detect and analyzed the pathological changes of ulcerated skin. Measurement data were expressed as mean±standard deviation (Mean±SD), one-way analysis of variance was used for comparison between groups, and LSD method was used for pairwise comparison. Results The concentration of MMP-9 and sCD40L1 in group D were (40.510±10.155) ng/ml and (44.580±19.138) ng/ml, respectively. Concentrations in group C were (93.210±17.838) ng/ml and (318.500±52.680) ng/ml, respectively. Group D was significantly lower than group C, and the difference was statistically significant (P< 0.000 1). The concentrations of HIF-1α in group D was (249.700±71.824) ng/ml, and that in group C was (124.830±20.110) ng/ml. The concentration in group D was significantly higher than that in group C, and the difference was statistically significant (P< 0.000 1). The concentrations of HIF-1α, MMP-9 and sCD40L1 in group B were (181.590±31.927), (78.950±16.652) and (173.670±43.048) ng/ml, respectively. The concentrations of group A were (35.420±9.916), (32.700±6.449) and (47.440±11.831) ng/ml, respectively. The concentration in group B was significantly higher than that in group A, the difference was statistically significant(P<0.000 1). The concentration of HIF-1α in group D was (249.700±71.824) ng/ml, and the concentration of group A was (35.420±9.916) ng/ml. The concentration of group D was significantly higher than that of group A, and the difference was statistically significant (P=0.000 1). The concentration of the MMP-9 in the group D was compared with the concentration of group A, and the difference was not statistically significant (P=0.207). The concentration of sCD40L1 in group D was (44.580±19.138) ng/ml, and that in group A was (47.440±11.831) ng/ml. The difference between group D and group A was not statistically significant(P=0.858). The healing area of ulcer was (1.855±0.394) cm2 in group D and (0.653±0.269) cm2 in group C. Group D was significantly higher than group C, and the difference was statistically significant (P<0.000 1). Hematoxylin-eosin staining results of ulcer skin showed that the epithelial of ischemic foot ulcer was significantly atrophied, hyperkeratinized, and the acinous cell layer was atrophied with a small amount of obvious inflammatory cell infiltration and hyperplasia of small vessels. After intervention, the symptoms were relieved. Conclusion Low frequency electromagnetic fields can promote the expression of HIF-1α in experimental rabbits, inhibit the expression of MMP-9 and sCD40L1, and promote the healing of ischemic foot ulcer. Key words: Foot ulcer; Matrix metalloproteinase 9; Electromagnetic fields; Hypoxia-inducible factor 1, alpha subunit; Rabbits

Genetic variability of hypoxia-inducible factor alpha (HIFA) genes in familial erythrocytosis: Analysis of the literature and genome databases.

Familial erythrocytosis (FE) is a congenital disorder, defined by elevated red blood cell number, hemoglobin, and hematocrit. Among eight types of FE, type 4 is caused by variants in the EPAS1 gene. Two other hypoxia-inducible factor alpha (HIFA) subunits, HIF1A and HIF3A, have not yet been associated with medical history of FE, but have potential role in the development of erythrocytosis. To improve diagnosis, it is crucial to identify new variants in genes involved in erythrocyte production. Published literature and data from genome browsers were used to obtain HIFA sequence variants associated with erythrocytosis and to locate them on protein sequence and regulatory sites. We retrieved 24 variants from the literature: 2 in HIF1A, 20 in EPAS1 and 2 in HIF3A gene. Sixteen out of 20 variants in the EPAS1 gene are positioned in a conserved region of 13 amino acids within exon 12, next to regulatory post-translational modification and binding sites, suggesting that EPAS1 has an important role in erythropoiesis. The role of HIF1A and HIF3A in the development of erythrocytosis should be further investigated.

Absolute expressions of hypoxia-inducible factor-1 alpha (HIF1A) transcript and the associated genes in chicken skeletal muscle with white striping and wooden breast myopathies

Development of white striping (WS) and wooden breast (WB) in broiler breast meat have been linked to hypoxia, but their etiologies are not fully understood. This study aimed at investigating absolute expression of hypoxia-inducible factor-1 alpha subunit (HIF1A) and genes involved in stress responses and muscle repair using a droplet digital polymerase chain reaction. Total RNA was isolated from pectoralis major collected from male 6-week-old medium (carcass weight ≤ 2.5 kg) and heavy (carcass weight > 2.5 kg) broilers. Samples were classified as “non-defective” (n = 4), “medium-WS” (n = 6), “heavy-WS” (n = 7) and “heavy-WS+WB” (n = 3) based on abnormality scores. The HIF1A transcript was up-regulated in all of the abnormal groups. Transcript abundances of genes encoding 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 4 (PFKFB4), lactate dehydrogenase-A (LDHA), and phosphorylase kinase beta subunit (PHKB) were increased in heavy-WS but decreased in heavy-WS+WB. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was up-regulated in non-defective samples. The muscle-specific mu-2 isoform of glutathione S-transferases (GSTM2) was up-regulated in the abnormal samples, particularly in the heavy groups. The genes encoding myogenic differentiation (MYOD1) and myosin light chain kinase (MYLK) exhibited similar expression pattern, of which medium-WS and heavy-WS significantly increased compared to non-defective whereas expression in heavy-WS+WB was not different from either non-defective or WS-affected group. The greatest and the lowest levels of calpain-3 (CAPN3) and delta-sarcoglycan (SCGD) were observed in heavy-WS and heavy-WS+WB, respectively. Based on micrographs, the abnormal muscles primarily comprised fibers with cross-sectional areas ranging from 2,000 to 3,000 μm2. Despite induced glycolysis at the transcriptional level, lower stored glycogen in the abnormal muscles corresponded with the reduced lactate and higher pH within their meats. The findings support hypoxia within the abnormal breasts, potentially associated with oversized muscle fibers. Between WS and WB, divergent glucose metabolism, cellular detoxification and myoregeneration at the transcriptional level could be anticipated.

Role of HIF1α Regulatory Factors in Stem Cells.

Hypoxia-inducible factor 1 (HIF1) is a master transcription factor that induces the transcription of genes involved in the metabolism and behavior of stem cells. HIF1-mediated adaptation to hypoxia is required to maintain the pluripotency and survival of stem cells under hypoxic conditions. HIF1 activity is well known to be tightly controlled by the alpha subunit of HIF1 (HIF1α). Understanding the regulatory mechanisms that control HIF1 activity in stem cells will provide novel insights into stem cell biology under hypoxia. Recent research has unraveled the mechanistic details of HIF1α regulating processes, suggesting new strategies for regulating stem cells. This review summarizes recent experimental studies on the role of several regulatory factors (including calcium, 2-oxoglutarate-dependent dioxygenase, microtubule network, importin, and coactivators) in regulating HIF1α activity in stem cells.