Activation Of Hypoxia-inducible Factor Research Articles

HIF-1α increases the osteogenic capacity of ADSCs by coupling angiogenesis and osteogenesis via the HIF-1α/VEGF/AKT/mTOR signaling pathway

BackgroundStabilization and increased activity of hypoxia-inducible factor 1-α (HIF-1α) can directly increase cancellous bone formation and play an essential role in bone modeling and remodeling. However, whether an increased HIF-1α expression in adipose-derived stem cells (ADSCs) increases osteogenic capacity and promotes bone regeneration is not known.ResultsIn this study, ADSCs transfected with small interfering RNA and HIF-1α overexpression plasmid were established to investigate the proliferation, migration, adhesion, and osteogenic capacity of ADSCs and the angiogenic ability of human umbilical vein endothelial cells (HUVECs). Overexpression of HIF-1α could promote the biological functions of ADSCs, and the angiogenic ability of HUVECs. Western blotting showed that the protein levels of osteogenesis-related factors were increased when HIF-1α was overexpressed. Furthermore, the influence of upregulation of HIF-1α in ADSC sheets on osseointegration was evaluated using a Sprague–Dawley (SD) rats implant model, in which the bone mass and osteoid mineralization speed were evaluated by radiological and histological analysis. The overexpression of HIF-1α in ADSCs enhanced bone remodeling and osseointegration around titanium implants. However, transfecting the small interfering RNA (siRNA) of HIF-1α in ADSCs attenuated their osteogenic and angiogenic capacity. Finally, it was confirmed in vitro that HIF-1α promotes osteogenic differentiation and the biological functions in ADSCs via the VEGF/AKT/mTOR pathway.ConclusionsThis study demonstrates that HIF-1α has a critical ability to promote osteogenic differentiation in ADSCs by coupling osteogenesis and angiogenesis via the VEGF/AKT/mTOR signaling pathway, which in turn increases osteointegration and bone formation around titanium implants.Graphical

Crosstalk between hypoxic cellular micro-environment and the immune system: a potential therapeutic target for infectious diseases.

There are overwhelming reports on the promotional effect of hypoxia on the malignant behavior of various forms of cancer cells. This has been proposed and tested exhaustively in the light of cancer immunotherapy. However, there could be more interesting functions of a hypoxic cellular micro-environment than malignancy. There is a highly intricate crosstalk between hypoxia inducible factor (HIF), a transcriptional factor produced during hypoxia, and nuclear factor kappa B (NF-κB) which has been well characterized in various immune cell types. This important crosstalk shares common activating and inhibitory stimuli, regulators, and molecular targets. Impaired hydroxylase activity contributes to the activation of HIFs. Inflammatory ligands activate NF-κB activity, which leads to the expression of inflammatory and anti-apoptotic genes. The eventual sequelae of the interaction between these two molecular players in immune cells, either bolstering or abrogating functions, is largely cell-type dependent. Importantly, this holds promise for interesting therapeutic interventions against several infectious diseases, as some HIF agonists have helped prevent immune-related diseases. Hypoxia and inflammation are common features of infectious diseases. Here, we highlighted the role of this crosstalk in the light of functional immunity against infection and inflammation, with special focus on various innate and adaptive immune cells. Particularly, we discussed the bidirectional effects of this crosstalk in the regulation of immune responses by monocytes/macrophages, dendritic cells, neutrophils, B cells, and T cells. We believe an advanced understanding of the interplay between HIFs and NF-kB could reveal novel therapeutic targets for various infectious diseases with limited treatment options.

In vivo optical imaging of tumor stromal cells with hypoxia-inducible factor activity.

Tumors contain various stromal cells, such as immune cells, endothelial cells, and fibroblasts, which contribute to the development of a tumor-specific microenvironment characterized by hypoxia and inflammation, and are associated with malignant progression. In this study, we investigated the activity of intratumoral hypoxia-inducible factor (HIF), which functions as a master regulator of the cellular response to hypoxia and inflammation. We constructed the HIF activity-monitoring reporter gene hypoxia-response element-Venus-Akaluc (HVA) that expresses the green fluorescent protein Venus and modified firefly luciferase Akaluc in a HIF activity-dependent manner, and created transgenic mice harboring HVA transgene (HVA-Tg). In HVA-Tg, HIF-active cells can be visualized using AkaBLI, an ultra-sensitive in vivo bioluminescence imaging technology that produces an intense near-infrared light upon reaction of Akaluc with the D-luciferin analog AkaLumine-HCl. By orthotopic transplantation of E0771, a mouse triple negative breast cancer cell line without a reporter gene, into HVA-Tg, we succeeded in noninvasively monitoring bioluminescence signals from HIF-active stromal cells as early as 8 days after transplantation. The HIF-active stromal cells initially clustered locally and then spread throughout the tumors with growth. Immunohistochemistry and flow cytometry analyses revealed that CD11b+ F4/80+ macrophages were the predominant HIF-active stromal cells in E0771 tumors. These results indicate that HVA-Tg is a useful tool for spatiotemporal analysis of HIF-active tumor stromal cells, facilitating investigation of the roles of HIF-active tumor stromal cells in tumor growth and malignant progression.

Disruption of sirtuin 7 in zebrafish facilitates hypoxia tolerance

SIRT7 is a member of the sirtuin family proteins with nicotinamide adenine dinucleotide (NAD+)-dependent histone deacetylase activity, which can inhibit the activity of hypoxia-inducible factors independently of its enzymatic activity. However, the role of SIRT7 in affecting hypoxia signaling invivo is still elusive. Here, we find that sirt7-null zebrafish are more resistant to hypoxic conditions, along with an increase of hypoxia-responsive gene expression and erythrocyte numbers, compared with their wildtype siblings. Overexpression of sirt7 suppresses the expression of hypoxia-responsive genes. Further assays indicate that sirt7 interacts with zebrafish hif-1αa, hif-1αb, hif-2αa, and hif-2αb to inhibit their transcriptional activity and mediate their protein degradation. In addition, sirt7 not only binds to the hypoxia responsive element of hypoxia-inducible gene promoters but also causes a reduction of H3K18Ac on these promoters. Sirt7 may regulate hypoxia-responsive gene expression through its enzymatic and nonenzymatic activities. This study provides novel insights into sirt7 function and sheds new light on the regulation of hypoxia signaling by sirt7.

Hypoxia-inducible factor affects hepatitis B virus transcripts and genome levels as well as the expression and subcellular location of the hepatitis B virus core protein

Globally, a chronic-hepatitis B virus (HBV) infection is the leading cause of hepatocellular carcinoma (HCC). The transcription factor hypoxia-inducible factor 1 (HIF1) is often elevated in HCC, including HBV-associated HCC. Previous studies have suggested that the expression of the HIF1 subunit, HIF1α, is elevated in HBV-infected hepatocytes; however, whether HIF1 activity affects the HBV lifecycle has not been fully explored. We used a liver-derived cell line and ex vivo cultured primary hepatocytes as models to determine how HIF1 affects the HBV lifecycle. We observed that HIF1 elevates HBV RNA transcript levels, core protein levels, core protein localization to the cytoplasm, and HBV genome replication. Attenuating the transcription activity of HIF1 blocked HIF1-mediated effects on the HBV lifecycle. Our studies show that HIF1 regulates various stages of the HBV lifecycle in hepatocytes and could be a therapeutic target for blocking HBV replication and the development of HBV-associated diseases.

Regulatory Functions of Hypoxia in Host-Parasite Interactions: A Focus on Enteric, Tissue, and Blood Protozoa.

Body tissues are subjected to various oxygenic gradients and fluctuations and hence can become transiently hypoxic. Hypoxia-inducible factor (HIF) is the master transcriptional regulator of the cellular hypoxic response and is capable of modulating cellular metabolism, immune responses, epithelial barrier integrity, and local microbiota. Recent reports have characterized the hypoxic response to various infections. However, little is known about the role of HIF activation in the context of protozoan parasitic infections. Growing evidence suggests that tissue and blood protozoa can activate HIF and subsequent HIF target genes in the host, helping or hindering their pathogenicity. In the gut, enteric protozoa are adapted to steep longitudinal and radial oxygen gradients to complete their life cycle, yet the role of HIF during these protozoan infections remains unclear. This review focuses on the hypoxic response to protozoa and its role in the pathophysiology of parasitic infections. We also discuss how hypoxia modulates host immune responses in the context of protozoan infections.

The impact of hypoxia-inducible factors in the pathogenesis of kidney diseases: a link through cell metabolism.

Kidneys are sensitive to disturbances in oxygen homeostasis. Hypoxia and activation of the hypoxia-inducible factor (HIF) pathway alter the expression of genes involved in the metabolism of renal and immune cells, interfering with their functioning. Whether the transcriptional activity of HIF protects the kidneys or participates in the pathogenesis of renal diseases is unclear. Several studies have indicated that HIF signaling promotes fibrosis in experimental models of kidney disease. Other reports showed a protective effect of HIF activation on kidney inflammation and injury. In addition to the direct effect of HIF on the kidneys, experimental evidence indicates that HIF-mediated metabolic shift activates inflammatory cells, supporting the HIF cascade as a link between lung or gut damage and worsening of renal disease. Although hypoxia and HIF activation are present in several scenarios of renal diseases, further investigations are needed to clarify whether interfering with the HIF pathway is beneficial in different pathological contexts.

The role of microRNA in the regulation of cellular responses to hypoxia

The impact of hypoxia causes changes in the transcription of genes that contribute to the adaptation of cells to a lack of oxygen. The main mechanism regulating the cellular response to hypoxia is the activation of a group of transcription factors of the HIF (Hypoxia-Inducible Factor) family, which include several isoforms and control the expression of more than a thousand genes. HIF activity is regulated at various levels, including by small non-coding RNA molecules called microRNAs (miRNAs). miRNAs regulate the cellular response to hypoxia by influencing the activation of HIF, its degradation, and the translation of proteins dependent on it. At the same time, HIF also affects miRNA biogenesis. Data on the relationship of a particular HIF isoform with miRNA are contradictory, since studies are performed using different cell lines, different types of experimental animals and clinical material, as well as at different oxygen concentrations and different durations of hypoxic exposure. In addition, HIF expression may be affected by the initial resistance of organisms to lack of oxygen, which is not taken into account in studies. This review analyzes data on the effect of hypoxia on the biogenesis and functioning of miRNAs, as well as the effect of microRNAs on mRNAs of genes involved in adaptation to oxygen deficiency. Understanding the mechanisms of the relationship between HIF, hypoxia, and miRNA is necessary to develop new approaches to personalized therapy for diseases accompanied by oxygen deficiency.

#2768 DIFFERENT EFFECTS OF HYPOXIA-INDUCIBLE FACTOR PROLYL HYDROXYLASE INHIBITORS ON SERUM LIPIDS LEVELS IN HEMODIALYSIS PATIENTS

Abstract Background The activity of hypoxia-inducible factor (HIF), an oxygen-sensitive transcription factor involved in erythropoiesis, is regulated by HIF-prolyl hydroxylases. With reduced oxygen tension, the activity of these enzymes is suppressed, resulting in increased erythropoiesis. Chen et al. reported that the decrease in that total cholesterol (TC) was greater with roxadustat than with epoetin alfa, as was the decrease in low density lipoprotein-cholesterol (LDL-C) in patients undergoing dialysis [1]. Csiky et al. reported roxadustat was superior to erythropoiesis-stimulating agent (ESA) in decreasing LDL-C levels from baseline in patients on dialysis [2]. Roxadustat is an oral HIF-prolyl hydroxylase inhibitor (HIF-PHI) developed for dialysis-dependent chronic kidney disease (CKD) anemia. While the impact of HIF-PHI on mean hemoglobin (Hb) change in patients on hemodialysis (HD) has been investigated [1], its effects on serum lipid levels have yet to be explored. Clarifying such effects is particularly important because HD patients usually have lower plasma high-density lipoprotein-cholesterol (HDL-C) levels than healthy individuals. Low HDL-C levels are associated with an increased risk of death in HD patients. The effects of HIF-PHIs on dyslipidemia in patients on HD are unclear. This study aimed to investigate the effects of HIF-PHIs on serum lipid levels in HD patients. Methods We investigated the effect of HIF-PHIs in three groups by measuring the levels Hb, serum TC, LDL-C, HDL-C, triglycerides (TG), iron, total iron-binding capacity (TIBC), transferrin saturation (TSAT), ferritin. Study 1: We evaluated the efficacy of roxadustat in 13 patients (1 female and 12 males) with HD-dependent CKD anemia and dyslipidemia over 24 weeks. Study 2: We evaluated the efficacy of daprodustat in 9 patients (2 females and 7 males) with HD-dependent CKD anemia and dyslipidemia over 24 weeks. Study 3: We evaluated the efficacy of enarodustat in 15 patients (3 females and 12 males) with HD-dependent CKD anemia and dyslipidemia over 12 weeks. Results Study 1: The mean age and mean HD vintage were 77.7 and 6.6 years, respectively. After roxadustat treatment, the mean Hb values (from 10.4 to 10.7 g/dL) did not significantly change. There were no significant changes in mean serum iron, TG, ferritin. However, the following parameters showed a significant decrease: mean TC (from 138.4 to 106.6 mg/dL, p = 0.0002), LDL-C (77.7 to 53.8 mg/dL, p = 0.0002), HDL-C (from 43.3 to 35.9 mg/dL, p = 0.0005), and TSAT (from 32.6 to 31.2%, p = 0.0479). There was a significant increases in the mean TIBC (from 220.5 to 265.1 μg/dL, p = 0.0002). Study 2: The mean age and mean HD vintage were 74.6 and 3.2 years, respectively. After daprodustat treatment, the mean Hb values did not significantly change. There were no significant changes in the mean TC, LDL-C, TG, TSAT, ferritin. However, the mean HDL-C levels showed a statistically significant decrease (from 50.4 to 45.3 mg/dL, p = 0.0117). Furthermore, there were significant increases in the serum iron level (from 72.5 to 89.1 μg/dL, p = 0.0078) and the mean TIBC level (from 229.7 to 272.8 μg/dL, p = 0.0039). Study 3: The mean age and mean HD vintage were 69.3 and 8.9 years, respectively. After enarodustat treatment, the mean Hb values did not significantly change. There were no significant changes in the mean TC, LDL-C, HDL-C, TG, TSAT, ferritin, iron. There was a significant increase in the mean TIBC (from 230.0 to 259.4 μg/dL, p = 0.0151). Conclusions We found that HIF-PHIs had different effects on serum lipids levels in HD patients. Roxadustat treatment improved iron metabolism stabilized Hb levels, and significantly decreased LDL-C levels. Daprodustat and enarodustat treatment improved iron metabolism, maintained stable Hb levels.

Interplay of hypoxia-inducible factors and oxygen therapy in cardiovascular medicine.

Mammals have evolved to adapt to differences in oxygen availability. Although systemic oxygen homeostasis relies on respiratory and circulatory responses, cellular adaptation to hypoxia involves the transcription factor hypoxia-inducible factor (HIF). Given that many cardiovascular diseases involve some degree of systemic or local tissue hypoxia, oxygen therapy has been used liberally over many decades for the treatment of cardiovascular disorders. However, preclinical research has revealed the detrimental effects of excessive use of oxygen therapy, including the generation of toxic oxygen radicals or attenuation of endogenous protection by HIFs. In addition, investigators in clinical trials conducted in the past decade have questioned the excessive use of oxygen therapy and have identified specific cardiovascular diseases in which a more conservative approach to oxygen therapy could be beneficial compared with a more liberal approach. In this Review, we providenumerous perspectives on systemic and molecular oxygen homeostasis and the pathophysiological consequences of excessive oxygen use. In addition, we provide an overview of findings from clinical studies on oxygen therapy for myocardial ischaemia, cardiac arrest, heart failure and cardiac surgery. These clinical studies have prompted a shift from liberal oxygen supplementation to a more conservative and vigilant approach to oxygen therapy. Furthermore, we discuss the alternative therapeutic strategies that target oxygen-sensing pathways, including various preconditioning approaches and pharmacological HIF activators, that can be used regardless of the level of oxygen therapy that a patient is already receiving.

Hypoxia-inducible factor activation promotes osteogenic transition of valve interstitial cells and accelerates aortic valve calcification in a mice model of chronic kidney disease.

Valve calcification (VC) is a widespread complication in chronic kidney disease (CKD) patients. VC is an active process with the involvement of in situ osteogenic transition of valve interstitial cells (VICs). VC is accompanied by the activation of hypoxia inducible factor (HIF) pathway, but the role of HIF activation in the calcification process remains undiscovered. Using in vitro and in vivo approaches we addressed the role of HIF activation in osteogenic transition of VICs and CKD-associated VC. Elevation of osteogenic (Runx2, Sox9) and HIF activation markers (HIF-1α and HIF-2α) and VC occurred in adenine-induced CKD mice. High phosphate (Pi) induced upregulation of osteogenic (Runx2, alkaline-phosphatase, Sox9, osteocalcin) and hypoxia markers (HIF-1α, HIF-2α, Glut-1), and calcification in VICs. Down-regulation of HIF-1α and HIF-2α inhibited, whereas further activation of HIF pathway by hypoxic exposure (1% O2) or hypoxia mimetics [desferrioxamine, CoCl2, Daprodustat (DPD)] promoted Pi-induced calcification of VICs. Pi augmented the formation of reactive oxygen species (ROS) and decreased viability of VICs, whose effects were further exacerbated by hypoxia. N-acetyl cysteine inhibited Pi-induced ROS production, cell death and calcification under both normoxic and hypoxic conditions. DPD treatment corrected anemia but promoted aortic VC in the CKD mice model. HIF activation plays a fundamental role in Pi-induced osteogenic transition of VICs and CKD-induced VC. The cellular mechanism involves stabilization of HIF-1α and HIF-2α, increased ROS production and cell death. Targeting the HIF pathways may thus be investigated as a therapeutic approach to attenuate aortic VC.

Role of MicroRNAs in Regulation of Cellular Response to Hypoxia.

Hypoxia causes changes in transcription of the genes that contribute to adaptation of the cells to low levels of oxygen. The main mechanism regulating cellular response to hypoxia is activation of hypoxia-inducible transcription factors (HIF), which include several isoforms and control expression of more than a thousand genes. HIF activity is regulated at various levels, including by small non-coding RNA molecules called microRNAs (miRNAs). miRNAs regulate cellular response to hypoxia by influencing activation of HIF, its degradation, and translation of HIF-dependent proteins. At the same time, HIFs also affect miRNAs biogenesis. Data on the relationship of a particular HIF isoform with miRNAs are contradictory, since studies have been performed using different cell lines, various types of experimental animals and clinical material, as well as at different oxygen concentrations and durations of hypoxic exposure. In addition, HIF expression may be affected by the initial resistance of organisms to lack of oxygen, which has not been taken into account in the studies. This review analyzes the data on the effect of hypoxia on biogenesis and functioning of miRNAs, as well as on the effect of miRNAs on mRNAs of the genes involved in adaptation to oxygen deficiency. Understanding the mechanisms of relationship between HIF, hypoxia, and miRNA is necessary to develop new approaches to personalized therapy for diseases accompanied by oxygen deficiency.

VBP1 negatively regulates CHIP and selectively inhibits the activity of hypoxia-inducible factor (HIF)-1α but not HIF-2α

Hypoxia-inducible factor-1 (HIF-1) is a critical transcription factor that regulates the expression of genes involved in cellular adaptation to low oxygen levels. Aberrant regulation of the HIF-1 signaling pathway is linked to various human diseases. Previous studies have established that HIF-1α is rapidly degraded in a von Hippel-Lindau protein (pVHL)-dependent manner under normoxic conditions. In this study, we find that pVHL binding protein 1 (VBP1) is a negative regulator of HIF-1α but not HIF-2α using zebrafish as an invivo model and invitro cell culture models. Deletion of vbp1 in zebrafish caused Hif-1α accumulation and upregulation of Hif target genes. Moreover, vbp1 was involved in the induction of hematopoietic stem cells (HSCs) under hypoxic conditions. However, VBP1 interacted with and promoted the degradation of HIF-1α in a pVHL-independent manner. Mechanistically, we identify the ubiquitin ligase CHIP and HSP70 as new VBP1 binding partners and demonstrate that VBP1 negatively regulated CHIP and facilitated CHIP-mediated degradation of HIF-1α. In patients with clear cell renal cell carcinoma (ccRCC), lower VBP1 expression was associated with worse survival outcomes. In conclusion, our results link VBP1 with CHIP stability and provide insights into underlying molecular mechanisms of HIF-1α-driven pathological processes.

The Intriguing Role of Hypoxia-Inducible Factor in Myocardial Ischemia and Reperfusion: A Comprehensive Review

Hypoxia-inducible factors (HIFs) play a crucial role in cellular responses to low oxygen levels during myocardial ischemia and reperfusion injury. HIF stabilizers, originally developed for treating renal anemia, may offer cardiac protection in this context. This narrative review examines the molecular mechanisms governing HIF activation and function, as well as the pathways involved in cell protection. Furthermore, we analyze the distinct cellular roles of HIFs in myocardial ischemia and reperfusion. We also explore potential therapies targeting HIFs, emphasizing their possible benefits and limitations. Finally, we discuss the challenges and opportunities in this research area, underscoring the need for continued investigation to fully realize the therapeutic potential of HIF modulation in managing this complex condition.

Enhancement of Collagen-I Levels in Human Gingival Fibroblasts by Small Molecule Activation of HIF-1α.

Collagen is the most abundant protein in various mammalian tissues and has an essential role in various cellular processes. Collagen is necessary for food-related biotechnological applications such as cultivated meat, medical engineering, and cosmetics. High-yield expression of natural collagen from mammalian cells is challenging and not cost-effective. Thus, external collagen is obtained primarily from animal tissues. Under cellular hypoxia, overactivation of the transcription factor hypoxia-inducible factor (HIF) was shown to correlate with enhanced accumulation of collagen. Herein, we showed that the small molecule ML228, a known molecular activator of HIF, enhances the accumulation of collagen type-I in human fibroblast cells. We report an increase in collagen levels by 2.33 ± 0.33 when fibroblasts were incubated with 5 μM of ML228. Our experimental results demonstrated, for the first time, that external modulation of the hypoxia biological pathway can boost collagen levels in mammalian cells. Our findings pave the way for enhancing natural collagen production in mammals by altering cellular signaling pathways.

Hypoxia-inducible factor prolyl hydroxylase inhibitors suppressed thymic stromal lymphopoietin production and allergic responses in a mouse air-pouch-type ovalbumin sensitization model.

Atopic dermatitis (AD) is an allergic skin disease, triggered by excessive type 2 immune reactions. Thymic stromal lymphopoietin (TSLP) is an epithelial-derived cytokine that induces type 2 immune response through dendritic cell activation. Therefore, TSLP inhibitors may serve as novel antiallergic drugs. Hypoxia-inducible factor (HIF) activation in the epithelia contributes to several homeostatic phenomena, such as re-epithelialization. However, the effects of HIF activation on TSLP production and immune activation in the skin remain unclear. In this study, we found that selective HIF prolyl hydroxylase inhibitors (PHD inhibitors), which induce HIF activation, suppressed TSLP production in a mouse ovalbumin (OVA) sensitization model. PHD inhibitors also suppressed the production of tumor necrosis factor-alpha (TNF-α), which is a major inducer of TSLP production, in this mouse model and in a macrophage cell line. Consistent with these findings, PHD inhibitors suppressed OVA-specific IgE levels in the serum and OVA-induced allergic responses. Furthermore, we found a direct suppressive effect on TSLP expression in a human keratinocyte cell line mediated by HIF activation. Taken together, our findings suggest that PHD inhibitors exert antiallergic effects by suppressing TSLP production. Controlling the HIF activation system has therapeutic potential in AD.

In Vitro and In Silico Analysis of Epithelial-Mesenchymal Transition and Cancer Stemness as Prognostic Markers of Clear Cell Renal Cell Carcinoma.

The process of epithelial-mesenchymal transition (EMT) involves the phenotypic transformation of cells from epithelial to mesenchymal status. The cells exhibiting EMT contain features of cancer stem cells (CSC), and the dual processes are responsible for progressive cancers. Activation of hypoxia-inducible factors (HIF) is fundamental to the pathogenesis of clear cell renal cell carcinoma (ccRCC), and their role in promoting EMT and CSCs is crucial for ccRCC tumour cell survival, disease progression, and metastatic spread. In this study, we explored the status of HIF genes and their downstream targets, EMT and CSC markers, by immunohistochemistry on in-house accrued ccRCC biopsies and adjacent non-tumorous tissues from patients undergoing partial or radical nephrectomy. In combination, we comprehensively analysed the expression of HIF genes and its downstream EMT and CSC-associated targets relevant to ccRCC by using publicly available datasets, the cancer genome atlas (TCGA) and the clinical proteome tumour analysis consortium (CPTAC). The aim was to search for novel biological prognostic markers that can stratify high-risk patients likely to experience metastatic disease. Using the above two approaches, we report the development of novel gene signatures that may help to identify patients at a high risk of developing metastatic and progressive disease.

Hypoxia-Inducible Factors-Based Single Nucleotide Polymorphism in Breast Cancer with More Cancer Susceptibility.

Hypoxia-inducible factors (HIFs) are a collection of transcriptional factors that engage in the regulation of oxygen homeostasis. They are hypoxia-responsive stress factors whose expression is linked to tumor growth and angiogenesis. HIF is a crucial player in the progression of breast cancer. Patients with high levels of hypoxia-inducible HIFs in their primary tumor biopsies had a higher chance of metastasis, the leading cause of breast cancer-related death. HIF polymorphisms have been shown in several epidemiological studies to influence breast cancer susceptibility. In the oxygendependent degradation domain, several short nucleotide polymorphisms (SNPs) of the HIF gene have been connected with higher HIF activity. To find SNP that make up the genetic diversity that underpins the phenotypic difference found between individuals in their susceptibility to cancer and the course of their disease, researchers used a variety of potential pathway-based approaches.

Hypoxic Stress-Dependent Regulation of Na,K-ATPase in Ischemic Heart Disease.

In cardiomyocytes, regular activity of the Na,K-ATPase (NKA) and its Na/K pump activity is essential for maintaining ion gradients, excitability, propagation of action potentials, electro-mechanical coupling, trans-membrane Na+ and Ca2+ gradients and, thus, contractility. The activity of NKA is impaired in ischemic heart disease and heart failure, which has been attributed to decreased expression of the NKA subunits. Decreased NKA activity leads to intracellular Na+ and Ca2+ overload, diastolic dysfunction and arrhythmias. One signal likely related to these events is hypoxia, where hypoxia-inducible factors (HIF) play a critical role in the adaptation of cells to low oxygen tension. HIF activity increases in ischemic heart, hypertension, heart failure and cardiac fibrosis; thus, it might contribute to the impaired function of NKA. This review will mainly focus on the regulation of NKA in ischemic heart disease in the context of stressed myocardium and the hypoxia-HIF axis and argue on possible consequences of treatment.

Evolution of hypoxia and hypoxia-inducible factor asparaginyl hydroxylase regulation in chronic kidney disease.

The roles of hypoxia and hypoxia inducible factor (HIF) during chronic kidney disease (CKD) are much debated. Interventional studies with HIF-α activation in rodents have yielded contradictory results. The HIF pathway is regulated by prolyl and asparaginyl hydroxylases. While prolyl hydroxylase inhibition is a well-known method to stabilize HIF-α, little is known about the effect asparaginyl hydroxylase factor inhibiting HIF (FIH). We used a model of progressive proteinuric CKD and a model of obstructive nephropathy with unilateral fibrosis. In these models we assessed hypoxia with pimonidazole and vascularization with three-dimensional micro-computed tomography imaging. We analysed a database of 217 CKD biopsies from stage 1 to 5 and we randomly collected 15 CKD biopsies of various severity degrees to assess FIH expression. Finally, we modulated FIH activity in vitro and in vivo using a pharmacologic approach to assess its relevance in CKD. In our model of proteinuric CKD, we show that early CKD stages are not characterized by hypoxia or HIF activation. At late CKD stages, some areas of hypoxia are observed, but these are not colocalizing with fibrosis. In mice and in humans, we observed a downregulation of the HIF pathway, together with an increased FIH expression in CKD, according to its severity. Modulating FIH in vitro affects cellular metabolism, as described previously. In vivo, pharmacologic FIH inhibition increases the glomerular filtration rate of control and CKD animals and is associated with decreased development of fibrosis. The causative role of hypoxia and HIF activation in CKD progression is questioned. A pharmacological approach of FIH downregulation seems promising in proteinuric kidney disease.