Activation of hypoxia-inducible factor 1alpha: posttranscriptional regulation and conformational change by recruitment of the Arnt transcription factor

Achaete-scute family bHLH transcription factor 2 activation promotes hepatoblastoma progression

Achaete-scute family bHLH transcription factor 2 (ASCL2) is highly expressed in hepatoblastoma (HB) tissues, but its role remains unclear. Thus, biological changes in the HB cell line HepG2 in response to induced ASCL2 expression were assessed. ASCL2 expression was induced in HepG2 cells using the Tet-On 3G system, which includes doxycycline. Cell viability, proliferation activity, mobility, and stemness were evaluated using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, colony-formation, migration, invasion, and sphere-formation assays. Quantitative reverse-transcription polymerase chain reaction was used to assess the expression of markers for proliferation (CCND1 and MYC), epithelial-mesenchymal transition (EMT; SNAI1, TWIST1, and ZEB1), mesenchymal-epithelial transition (CDH1), and stemness (KLF4, POU5F1, and SOX9). Compared with the non-induced HepG2 cells, cells with induced ASCL2 expression showed significant increases in viability, colony number, migration area (%), and sphere number on days 7, 14, 8, and 7, respectively, and invasion area (%) after 90 h. Furthermore, induction of ASCL2 expression significantly upregulated CCND1, MYC, POU5F1, SOX9, and KLF4 expression on days 2, 2, 3, 3, and 5, respectively, and increased the ratios of SNAI1, TWIST1, and ZEB1 to CDH1 on day 5. ASCL2 promoted the formation of malignant phenotypes in HepG2 cells, which may be correlated with the upregulation of the Wnt signaling pathway-, EMT-, and stemness-related genes. ASCL2 activation may therefore be involved in the progression of HB.

Surviving winter on the Qinghai-Xizang Plateau: Extensive reversible protein phosphorylation plays a dominant role in regulating hypometabolism in hibernating Nanorana parkeri

Changes in protein abundance and reversible protein phosphorylation (RPP) play important roles in regulating hypometabolism but have never been documented in overwintering frogs at high altitudes. To test the hypothesis that protein abundance and phosphorylation change in response to winter hibernation, we conducted a comprehensive and quantitative proteomic and phosphoproteomic analysis of the liver of the Xizang plateau frog, Nanorana parkeri, living on the Qinghai-Xizang (Tibet) Plateau (QTP). In total, 5 170 proteins and 5 695 phosphorylation sites in 1 938 proteins were quantified. Based on proteomic analysis, 674 differentially expressed proteins (438 up-regulated, 236 down-regulated) were screened in hibernating N. parkeri versus summer individuals. Functional enrichment analysis revealed that higher expressed proteins in winter were significantly enriched in immune-related signaling pathways, whereas lower expressed proteins were mainly involved in metabolic processes. A total of 4 251 modified sites (4 147 up-regulated, 104 down-regulated) belonging to 1 638 phosphoproteins (1 555 up-regulated, 83 down-regulated) were significantly changed in the liver. During hibernation, RPP regulated a diverse array of proteins involved in multiple functions, including metabolic enzymatic activity, ion transport, protein turnover, signal transduction, and alternative splicing. These changes contribute to enhancing protection, suppressing energy-consuming processes, and inducing metabolic depression. Moreover, the activities of phosphofructokinase, glutamate dehydrogenase, and ATPase were all significantly lower in winter compared to summer. In conclusion, our results support the hypothesis and demonstrate the importance of RPP as a regulatory mechanism when animals transition into a hypometabolic state.

Glucose Deprivation Promotes Pseudohypoxia and Dedifferentiation in Lung Adenocarcinoma

Increased utilization of glucose is a hallmark of cancer. Sodium-glucose transporter 2 (SGLT2) is a critical player in glucose uptake in early-stage and well-differentiated lung adenocarcinoma (LUAD). SGLT2 inhibitors, which are FDA approved for diabetes, heart failure, and kidney disease, have been shown to significantly delay LUAD development and prolong survival in murine models and in retrospective studies in diabetic patients, suggesting that they may be repurposed for lung cancer. Despite the antitumor effects of SGLT2 inhibition, tumors eventually escape treatment. Here, we studied the mechanisms of resistance to glucose metabolism-targeting treatments. Glucose restriction in LUAD and other tumors induced cancer cell dedifferentiation, leading to a more aggressive phenotype. Glucose deprivation caused a reduction in alpha-ketoglutarate (αKG), leading to attenuated activity of αKG-dependent histone demethylases and histone hypermethylation. The dedifferentiated phenotype depended on unbalanced EZH2 activity that suppressed prolyl-hydroxylase PHD3 and increased expression of hypoxia-inducible factor 1α (HIF1α), triggering epithelial-to-mesenchymal transition. Finally, a HIF1α-dependent transcriptional signature of genes upregulated by low glucose correlated with prognosis in human LUAD. Overall, this study furthers current knowledge of the relationship between glucose metabolism and cell differentiation in cancer, characterizing the epigenetic adaptation of cancer cells to glucose deprivation and identifying targets to prevent the development of resistance to therapies targeting glucose metabolism.

SIGNIFICANCE

Epigenetic adaptation allows cancer cells to overcome the tumor-suppressive effects of glucose restriction by inducing dedifferentiation and an aggressive phenotype, which could help design better metabolic treatments.

ABCE1 selectively promotes HIF-1α transactivation of angiogenic gene expression

BACKGROUND

Copper (Cu), by inhibiting the factor inhibiting HIF-1 (FIH-1), promotes the transcriptional activity of hypoxia-inducible factor-1 (HIF-1).

OBJECTIVE

The present study was undertaken to understand the molecular mechanism by which Cu inhibits FIH-1.

METHODS

Human umbilical vein endothelial cells (HUVECs) were treated with dimethyloxalylglycine (DMOG) resulting in HIF-1α accumulation and the FIH-1 protein complexes were pulled down for candidate protein analysis. The metal binding sites were predicted by both MetalDetector V2.0 and Metal Ion-Binding Site Prediction Server, and then the actual ability to bind to Cu in vitro was tested by both Copper-Immobilized metal affinity chromatography (Cu-IMAC) and Isothermal Titration Calorimetry (ITC). Subsequently, subcellular localization was monitored by immunocytochemistry, GFP-fusion protein expression plasmid and Western blotting in the nuclear extract. The interaction of candidate protein with HIF-1α and FIH-1 was validated by Co-Immunoprecipitation (Co-IP). Finally, the effect of candidate protein on the FIH-1 structure and HIF-1α transcriptional activity was analyzed by the InterEvDock3 web server and real-time quantitative RT-PCR.

RESULTS

ATP-binding cassette E1 (ABCE1) was present in the FIH-1 complexes and identified as a leading Cu-binding protein as indicated by a number of possible Cu binding sites. The ability of ABCE1 to bind Cu was demonstrated in vitro. ABCE1 entered the nucleus along with FIH-1 under hypoxic conditions. Protein interaction analysis revealed that ABCE1 prevented FIH-1 to bind iron ions, inhibiting FIH-1 enzymatic activity. ABCE1 silencing suppressed the expression of Cu-dependent HIF-1 target gene BNIP3, not that of Cu-independent IGF-2.

CONCLUSION

The results demonstrate that ABCE1, as a Cu-binding protein, enters the nucleus under hypoxic conditions and inhibits FIH-1degradation of HIF-1α, thus promoting HIF-1 transactivation of angiogenic gene expression.

Nanotoxicity of multifunctional stoichiometric cobalt oxide nanoparticles (SCoONPs) with repercussions toward apoptosis, necrosis, and cancer necrosis factor (TNF-α) at nano-biointerfaces

Introduction

Apoptosis, necrosis, and cancer necrosis factor (TNF-a) are all impacted by the nanotoxicity of multifunctional stoichiometric cobalt oxide nanoparticles (SCoONPs) at nano-biointerfaces. The creation of multi-functional nanoparticles has had a considerable impact on the transport of drugs and genes, nanotheranostics (in-vivo imaging, concurrent diagnostics), interventions for external healing, the creation of nano-bio interfaces, and the instigation of desired changes in nanotherapeutics.

Objectives

The quantitative structure-activity relationships, chemical transformations, biological interactions as well as toxicological analyses are considered as main objectives. Discrete dimensions of SCoNPs-cell interaction interfaces, their characteristic physical features (size, shape, shell structure, and surface chemistry), impact on cell proliferation and differentiation are the key factors responsible for nanotoxicity.

Methods

The development of multi-functional nanoparticles has been significant in drug/gene delivery, nanotheranostics (in-vivo imaging, coinciding diagnostics), and external healing interventions, designing a nano-bio interface, as well as inciting desired alterations in nanotherapeutics. Every so often, the cellular uptake of multi-functional cobalt [Co, CoO, Co2(CO)8 and Co3O4] nanoparticles (SCoONPs) influences cellular mechanics and initiates numerous repercussions (oxidative stress, DNA damage, cytogenotoxicity, and chromosomal damage) in pathways, including the generation of dysregulating factors involved in biochemical transformations.

Results

The concerns and influences of multifunctional SCoNPs on different cell mechanisms (mitochondria impermeability, hydrolysis of ATP, the concentration of Ca2+, impaired calcium clearance, defective autophagy, apoptosis, and necrosis), and interlinked properties (adhesion, motility, and internalization dynamics, role in toxicity, surface hydrophilic and hydrophobicity, biokinetics and biomimetic behaviors of biochemical reactions) have also been summarized. SCoONPs have received a lot of interest among the nanocarriers family because of its advantageous qualities such as biodegradability, biocompatibility, nontoxicity, and nonimmunogenicity.

Conclusion

Various applications, such as bio-imaging, cell labeling, gene delivery, enhanced chemical stability, and increased biocompatibility, concerning apoptosis, necrosis, and nano-bio interfaces, along with suitable examples. In this analysis, the multi-functional cobalt [Co, CoO, Co2(CO)8 and Co3O4] nanoparticles (SCoNPs) intricacies (cytogenotoxicity, clastogenicity, and immunomodulatory), nanotoxicity, and associated repercussions have been highlighted and explained.

Hypoxia in aquatic invertebrates: Occurrence and phenotypic and molecular responses

Global deoxygenation in aquatic systems is an increasing environmental problem, and substantial oxygen loss has been reported. Aquatic animals have been continuously exposed to hypoxic environments, so-called "dead zones," in which severe die-offs among organisms are driven by low-oxygen events. Multiple studies of hypoxia exposure have focused on in vivo endpoints, metabolism, oxidative stress, and immune responses in aquatic invertebrates such as molluscs, crustaceans, echinoderms, and cnidarians. They have shown that acute and chronic exposure to hypoxia induces significant decreases in locomotion, respiration, feeding, growth, and reproduction rates. Also, several studies have examined the molecular responses of aquatic invertebrates, such as anaerobic metabolism, reactive oxygen species induction, increased antioxidant enzymes, immune response mechanisms, regulation of hypoxia-inducible factor 1-alpha (HIF-1α) genes, and differently expressed hemoglobin/hemocyanin. The genetic basis of those molecular responses involves HIF-1α pathway genes, which are highly expressed in hypoxic conditions. However, the identification of HIF-1α-related genes and understanding of their applications in some aquatic invertebrates remain inadequate. Also, some species of crustaceans, rotifers, sponges, and ctenophores that lack HIF-1α are thought to have alternative defense mechanisms to cope with hypoxia, but those factors are still unclear. This review covers the formation of hypoxia in aquatic environments and the various adverse effects of hypoxia on aquatic invertebrates. The limitations of current hypoxia research and genetic information about the HIF-1α pathway are also discussed. Finally, this paper explains the underlying processes of the hypoxia response and presents an integrated program for research about the molecular mechanisms of hypoxic stresses in aquatic invertebrates.

Thrombotic Alterations under Perinatal Hypoxic Conditions: HIF and Other Hypoxic Markers

Hypoxia is considered to be a stressful physiological condition, which may occur during labor and the later stages of pregnancy as a result of, among other reasons, an aged placenta. Therefore, when gestation or labor is prolonged, low oxygen supply to the tissues may last for minutes, and newborns may present breathing problems and may require resuscitation maneuvers. As a result, poor oxygen supply to tissues and to circulating cells may last for longer periods of time, leading to life-threatening conditions. In contrast to the well-known platelet activation that occurs after reperfusion of the tissues due to an ischemia/reperfusion episode, platelet alterations in response to reduced oxygen exposition following labor have been less frequently investigated. Newborns overcome temporal hypoxic conditions by changing their organ functions or by adaptation of the intracellular molecular pathways. In the present review, we aim to analyze the main platelet modifications that appear at the protein level during hypoxia in order to highlight new platelet markers linked to complications arising from temporal hypoxic conditions during labor. Thus, we demonstrate that hypoxia modifies the expression and activity of hypoxic-response proteins (HRPs), including hypoxia-induced factor (HIF-1), endoplasmic reticulum oxidase 1 (Ero1), and carbonic anhydrase (CIX). Finally, we provide updates on research related to the regulation of platelet function due to HRP activation, as well as the role of HRPs in intracellular Ca2+ homeostasis.

Angiogenesis and Hepatocellular Carcinoma: From Molecular Mechanisms to Systemic Therapies

Hepatocellular carcinoma (HCC) is the most common primary liver malignancy. The hypervascular nature of the majority of HCCs and the peculiar vascular derangement occurring during liver carcinogenesis underscore the importance of angiogenesis in the development and progression of these tumors. Indeed, several angiogenic molecular pathways have been identified as deregulated in HCC. The hypervascular nature and the peculiar vascularization of HCC, as well as deregulated angiogenic pathways, represent major therapeutic targets. To a large extent, intra-arterial locoregional treatments (transarterial-(chemo)embolization) rely on tumor ischemia caused by embolization of tumor feeding arteries, even though this may represent the "primum movens" of tumor recurrence through the activation of neoangiogenesis. Considering systemic therapies, the currently available tyrosine kinase inhibitors (sorafenib, regorafenib, cabozantinib and lenvatinib) and monoclonal antibodies (ramucirumab and bevacizumab, in combination with the anti-PD-L1, atezolizumab) primarily target, among others, angiogenic pathways. Considering the importance of angiogenesis in the pathogenesis and treatment of liver cancer, in this paper, we aim to review the role of angiogenesis in HCC, addressing the molecular mechanisms, available antiangiogenic therapies and prognostic biomarkers in patients receiving these treatments.

Adipose-Derived Stem Cells Improve Angiogenesis and Lymphangiogenesis in a Hypoxic Dermal Regeneration Model In Vitro

Background and Objectives: Impaired wound healing represents an unsolved medical issue with a high impact on patients’ quality of life and global health care. Even though hypoxia is a significant limiting factor for wound healing, it reveals stimulating effects in gene and protein expression at cellular levels. In particular, hypoxically treated human adipose tissue-derived stem cells (ASCs) have previously been used to stimulate tissue regeneration. Therefore, we hypothesized that they could promote lymphangiogenesis or angiogenesis. Materials and Methods: Dermal regeneration matrices were seeded with human umbilical vein endothelial cells (HUVECs) or human dermal lymphatic endothelial cells (LECs) that were merged with ASCs. Cultures were maintained for 24 h and 7 days under normoxic or hypoxic conditions. Finally, gene and protein expression were measured regarding subtypes of VEGF, corresponding receptors, and intracellular signaling pathways, especially hypoxia-inducible factor-mediated pathways using multiplex-RT-qPCR and ELISA assays. Results: All cell types reacted to hypoxia with an alteration of gene expression. In particular, vascular endothelial growth factor A (VEGFA), vascular endothelial growth factor B (VEGFB), vascular endothelial growth factor C (VEGFC), vascular endothelial growth factor receptor 1 (VEGFR1/FLT1), vascular endothelial growth factor receptor 2 (VEGFR2/KDR), vascular endothelial growth factor receptor 3 (VEGFR3/FLT4), and prospero homeobox 1 (PROX1) were overexpressed significantly depending on upregulation of hypoxia-inducible factor 1 alpha (HIF-1a). Moreover, co-cultures with ASCs showed a more intense change in gene and protein expression profiles and gained enhanced angiogenic and lymphangiogenic potential. In particular, long-term hypoxia led to continuous stimulation of HUVECs by ASCs. Conclusions: Our findings demonstrated the benefit of hypoxic conditioned ASCs in dermal regeneration concerning angiogenesis and lymphangiogenesis. Even a short hypoxic treatment of 24 h led to the stimulation of LECs and HUVECs in an ASC-co-culture. Long-term hypoxia showed a continuous influence on gene expressions. Therefore, this work emphasizes the supporting effects of hypoxia-conditioned-ASC-loaded collagen scaffolds on wound healing in dermal regeneration.

Glucose deprivation promotes pseudo-hypoxia and de-differentiation in lung adenocarcinoma

Increased utilization of glucose is a hallmark of cancer. Several studies are investigating the efficacy of glucose restriction by glucose transporter blockade or glycolysis inhibition. However, the adaptations of cancer cells to glucose restriction are unknown. Here, we report the discovery that glucose restriction in lung adenocarcinoma (LUAD) induces cancer cell de-differentiation, leading to a more aggressive phenotype. Glucose deprivation causes a reduction in alpha-ketoglutarate (αKG), leading to attenuated activity of αKG-dependent histone demethylases and histone hypermethylation. We further show that this de-differentiated phenotype depends on unbalanced EZH2 activity, causing inhibition of prolyl-hydroxylase PHD3 and increased expression of hypoxia inducible factor 1α (HIF1α), triggering epithelial to mesenchymal transition. Finally, we identified an HIF1α-dependent transcriptional signature with prognostic significance in human LUAD. Our studies further current knowledge of the relationship between glucose metabolism and cell differentiation in cancer, characterizing the epigenetic adaptation of cancer cells to glucose deprivation and identifying novel targets to prevent the development of resistance to therapies targeting glucose metabolism.

Hypoxia-mediated activation of hypoxia-inducible factor-1α in head and neck squamous cell carcinoma: A review

Since the 1950s, hypoxia has been recognized as a crucial characteristic of cancer cells and their microenvironment. Indeed, hypoxia promotes the growth, survival, and metastasis of cancer cells. In the early 1990s, we found that as many phenomena in hypoxia can occur through hypoxia-inducible factor-1α (HIF1α). HIF1α is known as an angiogenesis converter in hypoxia, which promotes tumorigenesis, development, immune escape, recurrence, etc; This page goes into great detail on how HIF1α is activated during hypoxia and how the 2 signaling channels interact. It specifically emphasizes the significance of reactive oxygen species, the function of the PI3K/the serine/threonine kinase Akt/mammalian target of rapamycin cascade, and outlines the similarities between the 2 important factors (reactive oxygen species and PI3K/the serine/threonine kinase Akt/mammalian target of rapamycin cascade), nuclear factor κB, for HIF1α Important implications, in an effort to offer fresh views for the treatment of head and neck squamous cell carcinoma and HIF1α research.

The Role of Hypoxia in Brain Tumor Immune Responses

Oxygen is a vital component of living cells. Low levels of oxygen in body tissues, known as hypoxia, can affect multiple cellular functions across a variety of cell types and are a hallmark of brain tumors. In the tumor microenvironment, abnormal vasculature and enhanced oxygen consumption by tumor cells induce broad hypoxia that affects not only tumor cell characteristics but also the antitumor immune system. Although some immune reactions require hypoxia, hypoxia generally negatively affects immunity. Hypoxia induces tumor cell invasion, cellular adaptations to hypoxia, and tumor cell radioresistance. In addition, hypoxia limits the efficacy of immunotherapy and hinders antitumor responses. Therefore, understanding the role of hypoxia in the brain tumor, which usually does not respond to immunotherapy alone is important for the development of effective anti-tumor therapies. In this review, we discuss recent evidence supporting the role of hypoxia in the context of brain tumors.

Non-canonical approaches to targeting hypoxic tumors

Hypoxia is a common characteristic in solid cancers. Hypoxia-inducible factors (HIFs) are involved in various aspects of cancer, such as angiogenesis, metastasis and therapy resistance. Targeting the HIF pathway has been regarded as a challenging but promising strategy in cancer treatment with recent FDA approval of a HIF2α-inhibitor. During the past several decades, numerous efforts have been made to understand how HIFs participate in cancer development and progression along with how HIF signaling can be modulated to achieve anti-cancer effect. In this chapter, we will provide an overview of the role of hypoxia and HIFs in cancer, summarize the oxygen-dependent and independent mechanisms of HIF-1α regulation, and discuss emerging approaches targeting hypoxia and HIF signaling which possess therapeutic potential in cancer. We will emphasize on two signaling pathways, involving cyclin-dependent kinases (CDKs) and heat shock protein 90 (HSP90), which contribute to HIF-1α (and HIF-2α) stabilization in an oxygen-independent manner. Through reviewing their participation in malignant progression and the potential targeting strategies, we discuss the non-canonical approaches to target HIF signaling in cancer therapy.

Hypoxia-Inducible Factor-1: A Novel Therapeutic Target for the Management of Cancer, Drug Resistance, and Cancer-Related Pain

Hypoxia-inducible factor-1 (HIF-1) is a key transcription factor that regulates the transcription of many genes that are responsible for the adaptation and survival of tumor cells in hypoxic environments. Over the past few decades, tremendous efforts have been made to comprehensively understand the role of HIF-1 in tumor progression. Based on the pivotal roles of HIF-1 in tumor biology, many HIF-1 inhibitors interrupting expression, stabilization, DNA binding properties, or transcriptional activity have been identified as potential therapeutic agents for various cancers, yet none of these inhibitors have yet been successfully translated into clinically available cancer treatments. In this review, we briefly introduce the regulation of the HIF-1 pathway and summarize its roles in tumor cell proliferation, angiogenesis, and metastasis. In addition, we explore the implications of HIF-1 in the development of drug resistance and cancer-related pain: the most commonly encountered obstacles during conventional anticancer therapies. Finally, the current status of HIF-1 inhibitors in clinical trials and their perspectives are highlighted, along with their modes of action. This review provides new insights into novel anticancer drug development targeting HIF-1. HIF-1 inhibitors may be promising combinational therapeutic interventions to improve the efficacy of current cancer treatments and reduce drug resistance and cancer-related pain.

Hypoxia-Inducible Expression of Annexin A6 Enhances the Resistance of Triple-Negative Breast Cancer Cells to EGFR and AR Antagonists

Physiological changes such as hypoxia in the tumor microenvironment (TME) endow cancer cells with malignant properties, leading to tumor recurrence and rapid progression. Here, we assessed the effect of hypoxia (1% Oxygen) on the tumor suppressor Annexin A6 (AnxA6) and the response of triple-negative breast cancer (TNBC) cells to epidermal growth factor receptor (EGFR) and androgen receptor (AR) targeted therapies. We demonstrate that brief exposure of TNBC cells to hypoxia (within 24 h) is associated with down regulation of AnxA6 while > 24 h exposure cell type dependently stimulated the expression of AnxA6. Hypoxia depicted by the expression and stability of HIF-1/2α led to up regulation of the HIF target genes SLC2A1, PGK1 as well as AR and the AR target genes FABP-4 and PPAR-γ, but the cellular levels of AnxA6 protein decreased under prolonged hypoxia. Down regulation of AnxA6 in TNBC cells inhibited, while AnxA6 over expression enhanced the expression and cellular levels of HIF-1/2α, SLC2A1 and PGK1. RNAi mediated inhibition of hypoxia induced AnxA6 expression also strongly inhibited glucose uptake and ROS production in AnxA6 expressing TNBC cells. Using a luciferase reporter assay, we confirm that short-term exposure of cells to hypoxia inhibits while prolonged exposure of cells to hypoxia enhances AnxA6 promoter activity in HEK293T cells. Compared to cells cultured under normoxia, TNBC cells were more resistant to lapatinib under hypoxic conditions, and the downregulation of AnxA6 sensitized the cells to EGFR as well as AR antagonists. These data suggest that AnxA6 is a hypoxia inducible gene and that targeting AnxA6 upregulation may be beneficial in overcoming TNBC resistance to EGFR and/or AR targeted therapies.

Mutual antagonism between aryl hydrocarbon receptor and hypoxia-inducible factor-1α (AhR/HIF-1α) signaling: Impact on the aging process

The ambient oxygen level, many environmental toxins, and the rays of ultraviolet light (UV) provide a significant risk for the maintenance of organismal homeostasis. The aryl hydrocarbon receptors (AhR) represent a complex sensor system not only for environmental toxins and UV radiation but also for many endogenous ligands, e.g., L-tryptophan metabolites. The AhR signaling system is evolutionarily conserved and AhR homologs existed as many as 600 million years ago. The ancient atmosphere demanded the evolution of an oxygen-sensing system, i.e., hypoxia-inducible transcription factors (HIF) and their prolyl hydroxylase regulators (PHD). Given that both signaling systems have important roles in embryogenesis, it seems that they have been involved in the evolution of multicellular organisms. The evolutionary origin of the aging process is unknown although it is most likely associated with the evolution of multicellularity. Intriguingly, there is compelling evidence that while HIF-1α signaling extends the lifespan, that of AhR promotes many age-related degenerative processes, e.g., it increases oxidative stress, inhibits autophagy, promotes cellular senescence, and aggravates extracellular matrix degeneration. In contrast, HIF-1α signaling stimulates autophagy, inhibits cellular senescence, and enhances cell proliferation. Interestingly, there is a clear antagonism between the AhR and HIF-1α signaling pathways. For instance, (i) AhR and HIF-1α factors heterodimerize with the same factor, ARNT/HIF-1β, leading to their competition for DNA-binding, (ii) AhR and HIF-1α signaling exert antagonistic effects on autophagy, and (iii) co-chaperone p23 exhibits specific functions in the signaling of AhR and HIF-1α factors. One might speculate that it is the competition between the AhR and HIF-1α signaling pathways that is a driving force in the aging process.

LncRNA USP2-AS1 Promotes Hepatocellular Carcinoma Growth by Enhancing YBX1-Mediated HIF1α Protein Translation Under Hypoxia

Recently, the role of lncRNAs in tumorigenesis and development has received increasing attention, but the mechanism underlying lncRNAs-mediated tumor growth in the hypoxic microenvironment of solid tumors remains obscure. Using RNA sequencing, 25 hypoxia-related lncRNAs were found to be upregulated in HCC, of which lncRNA USP2-AS1 were significantly increased under hypoxia. We further confirmed that USP2-AS1 was significantly upregulated in liver cancer using FISH assay and that USP2-AS1 was associated with advanced liver cancer and increased tumor size. Furthermore, overexpression of USP2-AS1 under hypoxia dramatically increased HCC proliferation and clone formation, whereas the opposite results were observed after USP2-AS1 knockdown. We also found that overexpression of USP2-AS1 increased migration and invasion of HCC cells, while USP2-AS1 knockdown led to the opposite effect. In addition, USP2-AS1 knockdown can increase the efficacy of lenvatinib in our mice tumor xenograft model. Our findings also suggest that USP2-AS1 could increase the protein level of HIF1α by enhancing YBX1 protein binding to HIF1α mRNA under hypoxia and the therapeutic effect of lenvatinib can be enhanced by combination with HIF1α inhibitors in liver cancer.

Role of abnormal energy metabolism in the progression of chronic kidney disease and drug intervention

Chronic kidney disease (CKD) is a severe clinical syndrome with significant socioeconomic impact worldwide. Orderly energy metabolism is essential for normal kidney function and energy metabolism disorders are increasingly recognized as an important player in CKD. Energy metabolism disorders are characterized by ATP deficits and reactive oxygen species increase. Oxygen and mitochondria are essential for ATP production, hypoxia and mitochondrial dysfunction both affect the energy production process. Renin-angiotensin and adenine signaling pathway also play important regulatory roles in energy metabolism. In addition, disturbance of energy metabolism is a key factor in the development of hereditary nephropathy such as autosomal dominant polycystic kidney disease. Currently, drugs with clinically clear renal function protection, such as Angiotensin II Type 1 receptor blockers and fenofibrate, have been proven to improve energy metabolism disorders. The sodium-glucose co-transporter inhibitors 2 that can mediate glucose metabolism disorders not only delay the progress of diabetic nephropathy, but also have significant protective effects in non-diabetic nephropathy. Hypoxia-inducible factor enhances ATP production to the kidney by improving renal oxygen supply and increasing glycolysis, and the mitochondria targeted peptides (SS-31) plays a protective role by stabilizing the mitochondrial inner membrane. Moreover, several drugs are being studied and are predicted to have potential renal protective properties. We propose that the regulation of energy metabolism represents a promising strategy to delay the progression of CKD.

The Metabolic Basis of ILC Plasticity

Innate Lymphoid Cells (ILCs) are the innate counterpart of adaptive lymphoid T cells. They are key players in the regulation of tissues homeostasis and early inflammatory host responses. ILCs are divided into three groups, and further subdivided into five subsets, that are characterised by distinct transcription factors, surface markers and their cytokine expression profiles. Group 1 ILCs, including natural killer (NK) cells and non-NK cell ILC1s, express T-bet and produce IFN-γ. Group 2 ILCs depend on GATA3 and produce IL-4, IL-5 and IL-13. Group 3 ILCs, composed of ILC3s and Lymphoid Tissue Inducer (LTi) cells, express RORγt and produce IL-17 and IL-22. Even though, the phenotype of each subset is well defined, environmental signals can trigger the interconversion of phenotypes and the plasticity of ILCs, in both mice and humans. Several extrinsic and intrinsic drivers of ILC plasticity have been described. However, the changes in cellular metabolism that underlie ILC plasticity remain largely unexplored. Given that metabolic changes critically affect fate and effector function of several immune cell types, we, here, review recent findings on ILC metabolism and discuss the implications for ILC plasticity.

Current Understanding of Hypoxia in Glioblastoma Multiforme and Its Response to Immunotherapy

Simple Summary

Glioblastoma multiforme (GBM) is the most aggressive tumor type in the central nervous system. Hypoxia, defined as a lack of sufficient oxygen in tissues, is the most detrimental factor for the survival of GBM patients, promoting drug resistance, and invasion and inhibition of immune responses. Traditionally, tumor hypoxia has been studied from a narrow viewpoint, excluding the immune system and focusing primarily on the effect of hypoxia on blood vessels and tumor cells. More recently, however, evidence highlighting the important role of immunosurveillance has been uncovered for multiple tumors, including GBM. Thus, connecting the knowledge gained from traditional hypoxia studies with findings from recent immunological studies is urgently needed to better understand the role of hypoxia in cancer.

Abstract

Hypoxia is a hallmark of glioblastoma multiforme (GBM), the most aggressive cancer of the central nervous system, and is associated with multiple aspects of tumor pathogenesis. For example, hypoxia induces resistance to conventional cancer therapies and inhibits antitumor immune responses. Thus, targeting hypoxia is an attractive strategy for GBM therapy. However, traditional studies on hypoxia have largely excluded the immune system. Recently, the critical role of the immune system in the defense against multiple tumors has become apparent, leading to the development of effective immunotherapies targeting numerous cancer types. Critically, however, GBM is classified as a “cold tumor” due to poor immune responses. Thus, to improve GBM responsiveness against immunotherapies, an improved understanding of both immune function in GBM and the role of hypoxia in mediating immune responses within the GBM microenvironment is needed. In this review, we discuss the role of hypoxia in GBM from a clinical, pathological, and immunological perspective.

Inhibition of the HIF-1 Survival Pathway as a Strategy to Augment Photodynamic Therapy Efficacy

Photodynamic therapy (PDT) is a non-to-minimally invasive treatment modality that utilizes photoactivatable drugs called photosensitizers to disrupt tumors with locally photoproduced reactive oxygen species (ROS). Photosensitizer activation by light results in hyperoxidative stress and subsequent tumor cell death, vascular shutdown and hypoxia, and an antitumor immune response. However, sublethally afflicted tumor cells initiate several survival mechanisms that account for decreased PDT efficacy. The hypoxia inducible factor 1 (HIF-1) pathway is one of the most effective cell survival pathways that contributes to cell recovery from PDT-induced damage. Several hundred target genes of the HIF-1 heterodimeric complex collectively mediate processes that are involved in tumor cell survival directly and indirectly (e.g., vascularization, glucose metabolism, proliferation, and metastasis). The broad spectrum of biological ramifications culminating from the activation of HIF-1 target genes reflects the importance of HIF-1 in the context of therapeutic recalcitrance. This chapter elaborates on the involvement of HIF-1 in cancer biology, the hypoxic response mechanisms, and the role of HIF-1 in PDT. An overview of inhibitors that either directly or indirectly impede HIF-1-mediated survival signaling is provided. The inhibitors may be used as pharmacological adjuvants in combination with PDT to augment therapeutic efficacy.

FDA approved L-type channel blocker Nifedipine reduces cell death in hypoxic A549 cells through modulation of mitochondrial calcium and superoxide generation

As hypoxia is a major driver for the pathophysiology of COVID-19, it is crucial to characterize the hypoxic response at the cellular and molecular levels. In order to augment drug repurposing with the identification of appropriate molecular targets, investigations on therapeutics preventing hypoxic cell damage is required. In this work, we propose a hypoxia model based on alveolar lung epithelial cells line using chemical inducer, CoCl₂ that can be used for testing calcium channel blockers (CCBs). Since recent studies suggested that CCBs may reduce the infectivity of SARS-Cov-2, we specifically select FDA approved calcium channel blocker, nifedipine for the study. First, we examined hypoxia-induced cell morphology and found a significant increase in cytosolic calcium levels, mitochondrial calcium overload as well as ROS production in hypoxic A549 cells. Secondly, we demonstrate the protective behaviour of nifedipine for cells that are already subjected to hypoxia through measurement of cell viability as well as 4D imaging of cellular morphology and nuclear condensation. Thirdly, we show that the protective effect of nifedipine is achieved through the reduction of cytosolic calcium, mitochondrial calcium, and ROS generation. Overall, we outline a framework for quantitative analysis of mitochondrial calcium and ROS using 3D imaging in laser scanning confocal microscopy and the open-source image analysis platform ImageJ. The proposed pipeline was used to visualize mitochondrial calcium and ROS level in individual cells that provide an understanding of molecular targets. Our findings suggest that the therapeutic value of nifedipine may potentially be evaluated in the context of COVID-19 therapeutic trials.

The Role of Cyclophilins in Inflammatory Bowel Disease and Colorectal Cancer

Cyclophilins (Cyps) is a kind of ubiquitous protein family in organisms, which has biological functions such as promoting intracellular protein folding and participating in the pathological processes of inflammation and tumor. Inflammatory bowel disease (IBD) and colorectal cancer (CRC) are two common intestinal diseases, but the etiology and pathogenesis of these two diseases are still unclear. IBD and CRC are closely associated, IBD has always been considered as one of the main risks of CRC. However, the role of Cyps in these two related intestinal diseases is rarely studied and reported. In this review, the expression of CypA, CypB and CypD in IBD, especially ulcerative colitis (UC), and CRC, their relationship with the development of these two intestinal diseases, as well as the possible pathogenesis, were briefly summarized, so as to provide modest reference for clinical researches and treatments in future.

The Regulatory Role of Oxygen Metabolism in Exercise-Induced Cardiomyocyte Regeneration

During heart failure, the heart is unable to regenerate lost or damaged cardiomyocytes and is therefore unable to generate adequate cardiac output. Previous research has demonstrated that cardiac regeneration can be promoted by a hypoxia-related oxygen metabolic mechanism. Numerous studies have indicated that exercise plays a regulatory role in the activation of regeneration capacity in both healthy and injured adult cardiomyocytes. However, the role of oxygen metabolism in regulating exercise-induced cardiomyocyte regeneration is unclear. This review focuses on the alteration of the oxygen environment and metabolism in the myocardium induced by exercise, including the effects of mild hypoxia, changes in energy metabolism, enhanced elimination of reactive oxygen species, augmentation of antioxidative capacity, and regulation of the oxygen-related metabolic and molecular pathway in the heart. Deciphering the regulatory role of oxygen metabolism and related factors during and after exercise in cardiomyocyte regeneration will provide biological insight into endogenous cardiac repair mechanisms. Furthermore, this work provides strong evidence for exercise as a cost-effective intervention to improve cardiomyocyte regeneration and restore cardiac function in this patient population.

Sanguinarine combats hypoxia-induced activation of EphB4 and HIF-1α pathways in breast cancer

BACKGROUND

Breast cancer is the most common female cancer worldwide. Large hypoxic area is one of the features of tumor microenvironment. Highly activated hypoxia-induced pathways positively correlate with poor clinical response to chemo- and radiotherapy and high mortality in breast cancer patients.

PURPOSE

We explore the effect of sanguinarine on hypoxia-induced activation of Ephrin type-B receptor 4 (EphB4) and hypoxia inducible factor-1α (HIF-1α) pathways in breast cancer.

RESULTS

Hypoxia-induced expression of a receptor tyrosine kinase EphB4 was observed in hypoxic breast cancer cell models. Sanguinarine, a natural alkaloid, could effectively combat hypoxia-induced EphB4 and HIF-1α expression. Sanguinarine inhibited the activation of downstream protein signal transducer and activator of transcription-3 (STAT3), thereby blocking hypoxia-induced HIF-1α/STAT3 interaction and downregulating the mRNA levels of their target genes. Mechanically, sanguinarine attenuated HIF-1α protein levels via inhibition of MAPK/ERK pathways and promotion of HIF-1α proteasome degradation. Sanguinarine inhibited STAT3 activation through targeting its upstream EphB4 and accelerating STAT3 dephosphorylation. Correspondingly, xenograft models confirmed that sanguinarine treatment disrupted hypoxia-induced pathways and inhibited tumor growth in vivo.

CONCLUSIONS

Our results may bring insights to the hypoxia-induced pathways in breast cancers, and suggest sanguinarine as a promising candidate for EphB4 and HIF-1α-targeted inhibition.

The Role of Hypoxia in Glioblastoma Radiotherapy Resistance

Glioblastoma (GB) (grade IV astrocytoma) is the most malignant type of primary brain tumor with a 16 months median survival time following diagnosis. Despite increasing attention regarding the development of targeted therapies for GB that resulted in around 450 clinical trials currently undergoing, radiotherapy still remains the most clinically effective treatment for these patients. Nevertheless, radiotherapy resistance (radioresistance) is commonly observed in GB patients leading to tumor recurrence and eventually patient death. It is therefore essential to unravel the molecular mechanisms underpinning GB cell radioresistance in order to develop novel strategies and combinational therapies focused on enhancing tumor cell sensitivity to radiotherapy. In this review, we present a comprehensive examination of the current literature regarding the role of hypoxia (O2 partial pressure less than 10 mmHg), a main GB microenvironmental factor, in radioresistance with the ultimate goal of identifying potential molecular markers and therapeutic targets to overcome this issue in the future.

Hypoxia as a modulator of cytochromes P450: Overexpression of the cytochromes CYP2S1 and CYP24A1 in human liver cancer cells in hypoxia

Low levels of oxygen (hypoxia) have been reported in solid tumours. This hypoxic microenvironment modulates the expression of genes linked to a more aggressive disease. However, it is unclear if the expression of drug-metabolizing enzymes as cytochromes P450 (CYPs) is affected by hypoxia in cancer. We aimed to define which cytochromes are affected by hypoxia using a liver cancer model in vitro. For this purpose, we assessed whole-genome expression microarrays of HepG2 liver cancer cell line from free repository databases, looking for gene expression hypoxia-associated profiles and selected those cytochromes with significant differences. Then, we corroborated their mRNA expression and protein levels by RT-qPCR and western blot, respectively, as well as immunofluorescence. Based on microarray analysis, we found that the expression of CYP2S1 and CYP24A1 were up-regulated with at least twice fold change compared with normoxia. The levels of mRNA and protein of CYP2S1 and CYP24A1 were increased significantly in hypoxic conditions (P < .05), and this tendency was also observed by immunofluorescence assays. Our data show that the expression of cytochromes CYP2S1 and CYP24A1 are induced in hypoxia, being the first time that CYP24A1 expression is associated with tumour hypoxia; which might have consequences in cancer progression and drug resistance. SIGNIFICANCE OF THE STUDY: Hypoxia is among the most important factors for cellular adaptation to stress. Especially in cancer, a major public health issue, hypoxia plays a substantial role in angiogenesis, metastasis and resistance to therapy. Tumoral hypoxia has been described at least in the brain, breast, cervical, liver, renal, lung, pancreatic and renal cancer. However, the understanding of how hypoxia drives cancer progression is still a major challenge. One emerging question is the role of hypoxia over the expression of drug-metabolizing enzymes, with a significant impact on drug treatment. In this context, our paper focus on the effect of hypoxia on CYPs, which is an essential group of drug-metabolizing enzymes. We show that hypoxia induces the expression of two members of the CYPs family: CYP2S1 and CYP24A1. Importantly, CYP2S1 is a major metabolizer of carcinogenic substances being relevant that hypoxia could promote this function. Interestingly, CYP24A1 limits the action of the active form of vitamin D, which is an anti-proliferative factor in cancer. Our evidence shows for the first time that hypoxia can induce CYP24A1 expression, with a potential effect on cancer progression. Our contribution clarifies a particular effect of tumoral hypoxia and the implications will be useful in the understanding of the progression of cancer, the resistance to treatment and the development of alternative therapies.

Comparative gene expression profiling reveals the mechanisms of axon regeneration

Axons are vulnerable to injury, potentially leading to degeneration or neuronal death. While neurons in the central nervous system fail to regenerate, neurons in the peripheral nervous system are known to regenerate. Since it has been shown that injury-response signal transduction is mediated by gene expression changes, expression profiling is a useful tool to understand the molecular mechanisms of regeneration. Axon regeneration is regulated by injury-responsive genes induced in both neurons and their surrounding non-neuronal cells. Thus, an experimental setup for the comparative analysis between regenerative and nonregenerative conditions is essential to identify ideal targets for the promotion of regeneration-associated genes and to understand the mechanisms of axon regeneration. Here, we review the original research that shows the key factors regulating axon regeneration, in particular by using comparative gene expression profiling in diverse systems.

Squalene deters drivers of RCC disease progression beyond VHL status

Identifying drug candidates to target cellular events/signaling that evades von Hippel-Lindau tumor suppressor (VHL) gene interaction is critical for the cure of renal cell carcinoma (RCC). Recently, we characterized a triterpene-squalene derived from marine brown alga. Herein, we investigated the potential of squalene in targeting HIF-signaling and other drivers of RCC progression. Squalene inhibited cell proliferation, induced cell dealth and reverted the cells' metastatic state (migration, clonal expansion) independent of their VHL status. Near-identical inhibition of HIF-1α and HIF-2α and the regulation of downstream targets in VHL wild type and mutant cell lines demonstrated squalene efficacy beyond VHL-HIF interaction. In a rat model of chemically induced RCC, squalene displayed chemopreventive capabilities by substantial reversal of lipid peroxidation, mitochondrial redox regulation, maintaining ∆ψ_m, inflammation [Akt, nuclear factor κB (NF-κB)], angiogenesis (VEGFα), metastasis [matrix metalloproteinase 2 (MMP-2)], and survival (Bax/Bcl2, cytochrome-c, Casp3). Squalene restored glutathione, glutathione reductase, glutathione-s-transferase, catalase, and superoxide dismutase and stabilized alkaline phosphatase, alkaline transaminase, and aspartate transaminase. The correlation of thiobarbituric acid reactive substance with VEGF/NF-κB and negative association of GSH with Casp3 show that squalene employs reduction in ROS regulation. Cytokinesis-block micronuclei (CBMN) assay in VHL^wt/mut cells revealed both direct and bystander effects of squalene with increased micronucleus (MN) frequency. Clastogenicity analysis of rat bone marrow cells demonstrated an anti-clastogenic effect of squalene, with increased polychromatic erythrocytes (PCEs), decreased MNPCE,s and MN normochromatic erythrocytes. Squalene could effectively target HIF signaling that orchestrate RCC evolution. The efficacy of squalene is similar in VHL^wt and VHL^mut RCC cells, and hence, squalene could serve as a promising drug candidate for an RCC cure beyond VHL status and VHL-HIF interaction dependency. Summary: Squalene derived from marine brown algae displays strong anti-cancer (RCC) activity, functionally targeting HIF-signaling pathway, and affects various cellular process. The significance of squalene effect for RCC is highlighted by its efficiency beyond VHL status, designating itself a promising drug candidate. Graphical abstract.

Contribution of hypoxia inducible factor-1 during viral infections

Hypoxia-inducible factor 1 (HIF-1) is a transcription factor that plays critical roles during the cellular response to hypoxia. Under normoxic conditions, its function is tightly regulated by the degradation of its alpha subunit (HIF-1α), which impairs the formation of an active heterodimer in the nucleus that otherwise regulates the expression of numerous genes. Importantly, HIF-1 participates in both cancer and infectious diseases unveiling new therapeutic targets for those ailments. Here, we discuss aspects related to the activation of HIF-1, the effects of this transcription factor over immune system components, as well as the involvement of HIF-1 activity in response to viral infections in humans. Although HIF-1 is currently being assessed in numerous clinical settings as a potential therapy for different diseases, up to date, there are no clinical studies evaluating the pharmacological modulation of this transcription factor as a possible new antiviral treatment. However, based on the available evidence, clinical trials targeting this molecule are likely to occur soon. In this review we discuss the role of HIF-1 in viral immunity, the modulation of HIF-1 by different types of viruses, as well as the effects of HIF-1 over their life cycle and the potential use of HIF-1 as a new target for the treatment of viral infections.

Hypoxia-inducible factors not only regulate but also are myeloid-cell treatment targets

Hypoxia describes limited oxygen availability at the cellular level. Myeloid cells are exposed to hypoxia at various bodily sites and even contribute to hypoxia by consuming large amounts of oxygen during respiratory burst. Hypoxia-inducible factors (HIFs) are ubiquitously expressed heterodimeric transcription factors, composed of an oxygen-dependent α and a constitutive β subunit. The stability of HIF-1α and HIF-2α is regulated by oxygen-sensing prolyl-hydroxylases (PHD). HIF-1α and HIF-2α modify the innate immune response and are context dependent. We provide a historic perspective of HIF discovery, discuss the molecular components of the HIF pathway, and how HIF-dependent mechanisms modify myeloid cell functions. HIFs enable myeloid-cell adaptation to hypoxia by up-regulating anaerobic glycolysis. In addition to effects on metabolism, HIFs control chemotaxis, phagocytosis, degranulation, oxidative burst, and apoptosis. HIF-1α enables efficient infection defense by myeloid cells. HIF-2α delays inflammation resolution and decreases antitumor effects by promoting tumor-associated myeloid-cell hibernation. PHDs not only control HIF degradation, but also regulate the crosstalk between innate and adaptive immune cells thereby suppressing autoimmunity. HIF-modifying pharmacologic compounds are entering clinical practice. Current indications include renal anemia and certain cancers. Beneficial and adverse effects on myeloid cells should be considered and could possibly lead to drug repurposing for inflammatory disorders.

Low oxygen tension differentially regulates the expression of placental solute carriers and ABC transporters

Low oxygen concentration, or hypoxia, is an important physiological regulator of placental function including chemical disposition. Here, we compared the ability of low oxygen tension to alter the expression of solute carriers (SLC) and ABC transporters in two human placental models, namely BeWo cells and term placental explants. We found that exposure to low oxygen concentration differentially regulates transporter expression in BeWo cells, including downregulation of ENT1, OATP4A1, OCTN2, BCRP, and MRP2/3/5, and upregulation of CNT1, OAT4, OATP2B1, SERT, SOAT, and MRP1. Similar upregulation of MRP1 and downregulation of MRP5 and BCRP were observed in explants, whereas uptake transporters were decreased or unchanged. Furthermore, a screening of transcriptional regulators of transporters revealed that hypoxia leads to a decrease in the mRNA levels of aryl hydrocarbon receptor, nuclear factor erythroid 2-related factor 2, and retinoid x receptor alpha in both human placental models. These data suggest that transporter expression is differentially regulated by oxygen concentration across experimental human placental models.

HIF-1α and RKIP: a computational approach for pancreatic cancer therapy

Protein-protein interactions (PPIs) are important biochemical processes that represent a major challenge in modern biology. Current approaches, which include high-throughput screening and computer aided ligand design, have limitations regarding the identification of hit matter. This current investigation focuses on computational study for protein-protein docking of hypoxia inducible factor-1α (HIF-1α), a tumor inducible factor, and Raf-1 kinase inhibitory protein (RKIP), a tumor metastasis suppressor. These are individually crystallized structures of interacting proteins, which interact to generate a conformational space. HIF activity in pancreatic tumors is determined by hypoxia and HIF-1α subunit availability. RKIP can be used as a prognostic indicator in a number of tumors. The interaction of RKIP with HIF-1α protects against pancreatic cancer (PC) metastasis by inhibiting its hypoxia function. We have explored the binding affinity between both the proteins with the HADDOCK (high ambiguity driven protein-protein docking) server, which determined that 158 structures in 11 clusters represent 79.0% of water-refined models. Of the best 10 clusters, the structures of cluster 2 were found to be better, as they had the lowest Z-score. Further supporting HIF-1α-RKIP interaction, pulldown assay has shown dissociation of RKIP from HIF-1α after CoCl2 treatment in both PC cell lines.

Transcriptional Profiling of Normal, Stenotic, and Regurgitant Human Aortic Valves

The genetic mechanisms underlying aortic stenosis (AS) and aortic insufficiency (AI) disease progression remain unclear. We hypothesized that normal aortic valves and those with AS or AI all exhibit unique transcriptional profiles. Normal control (NC) aortic valves were collected from non-matched donor hearts that were otherwise acceptable for transplantation (n = 5). Valves with AS or AI (n = 5, each) were collected from patients undergoing surgical aortic valve replacement. High-throughput sequencing of total RNA revealed 6438 differentially expressed genes (DEGs) for AS vs. NC, 4994 DEGs for AI vs. NC, and 2771 DEGs for AS vs. AI. Among 21 DEGs of interest, APCDD1L, CDH6, COL10A1, HBB, IBSP, KRT14, PLEKHS1, PRSS35, and TDO2 were upregulated in both AS and AI compared to NC, whereas ALDH1L1, EPHB1, GPX3, HIF3A, and KCNT1 were downregulated in both AS and AI (p < 0.05). COL11A1, H19, HIF1A, KCNJ6, PRND, and SPP1 were upregulated only in AS, and NPY was downregulated only in AS (p < 0.05). The functional network for AS clustered around ion regulation, immune regulation, and lipid homeostasis, and that for AI clustered around ERK1/2 regulation. Overall, we report transcriptional profiling data for normal human aortic valves from non-matched donor hearts that were acceptable for transplantation and demonstrated that valves with AS and AI possess unique genetic signatures. These data create a roadmap for the development of novel therapeutics to treat AS and AI.

Bone marrow-derived humoral factors suppress oxidative phosphorylation, upregulate TSG-6, and improve therapeutic effects on liver injury of mesenchymal stem cells

Mesenchymal stem cells, which have the potential to be used in regenerative medicine, require improvements in quality for patient use. To maintain stemness of cultured bone marrow-derived mesenchymal stem cells, we focused on the bone marrow microenvironment, generated a conditioned medium of whole bone marrow cells (BMC-CM), and assessed its effects on bone marrow-derived mesenchymal stem cells. BMC-CM suppressed morphological deterioration and proliferative decline in cultured bone marrow-derived mesenchymal stem cells, suppressed mitochondrial oxidative phosphorylation activity, a stemness indicator, and upregulated suppressors of oxidative phosphorylation such as hypoxia-inducible factor-1 alpha, Sirtuin 3, 4, and 5. Furthermore, BMC-CM upregulated TNF-stimulated gene 6 and ameliorated the therapeutic effects of cells on liver injury in carbon tetrachloride-administered rats. Since the elimination of 20-220-nm particles attenuated the effects of BMC-CM, we further analyzed exosomal microRNAs produced by whole bone marrow cells. Among the 49 microRNAs observed to be upregulated during the preparation of BMC-CM, several were identified that were associated with suppression of oxidative phosphorylation, upregulation of TNF-stimulated gene 6, and the pathogenesis of liver diseases. Thus, bone marrow-derived humoral factors including exosomal microRNAs may help to improve the therapeutic quality of bone marrow-derived mesenchymal stem cells for liver regenerative therapy.

Bclaf1 is a direct target of HIF-1 and critically regulates the stability of HIF-1α under hypoxia

Hypoxic stress is intimately connected with tumor progression, with hypoxia-inducible factor-1α (HIF-1α) being a critical regulator in this process. HIF-1α is stabilized in response to hypoxia, which is required for the induction of gene transcriptions important for hypoxic adaptation. Bclaf1 is a multifunctional protein involved in tumorigenesis, however, its role in this process is not well characterized. Here we report Bclaf1 is a direct transcriptional target of HIF-1 and upregulated in multiple cell lines during hypoxia. Importantly, we found Bclaf1 is involved in the stabilization of HIF-1α during long-term hypoxic treatments. Compared with the control cells, the protein level and stability of HIF-1α in Bclaf1 knockdown or knockout cells is greatly compromised after long-term hypoxic treatments, concomitant with the impaired inductions of HIF-1 target gene transcription. Bclaf1 knockout HeLa cells exhibit a reduced tumor growth in mice xenografts, in which the expressions of HIF-1α and its target genes are also decreased. Bclaf1 binds to HIF-1α in the nucleus, and this interaction is required for Bclaf1 to stabilize HIF-1α in hypoxic condition. These results uncover a positive feedback loop, HIF-1-Bclaf1, that sustains HIF-1 activity during long-term hypoxic conditions by binding to and protecting HIF-1α from degradation, and suggest that Bclaf1 may promote tumor progression by enhancing HIF-1α stability.

Hypoxia inducible factors in the tumor microenvironment as therapeutic targets of cancer stem cells

Cancer stem cells (CSC) constitute a small area of the tumor mass and are characterized by self-renewal, differentiation and the ability to promote the development of secondary chemo-resistant tumors. Self-renewal of CSCs is regulated through various signaling pathways including Hedgehog, Notch, and Wnt/β-catenin pathways. A few surface markers have been identified, which provide a means of targeting CSCs according to tumor type. Depending on the proximity of CSCs to the tumor hypoxic niche, hypoxia-inducible factors (HIFs) can play a critical role in modulating several CSC-related characteristics. For instance, the upregulation of HIF-1 and HIF-2 at tumor sites, which correlates with the expansion of CSCs and poor cancer prognosis, has been demonstrated. In this review, we will discuss the mechanisms by which hypoxia enhances the development of CSCs in the tumor microenvironment. Targeting HIFs in combination with other common therapeutics is pre-requisite for effective eradication of CSCs.

Metabolic Maturation of Human Pluripotent Stem Cell-Derived Cardiomyocytes by Inhibition of HIF1α and LDHA

RATIONALE

Human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) are a readily available, robustly reproducible, and physiologically appropriate human cell source for cardiac disease modeling, drug discovery, and toxicity screenings in vitro. However, unlike adult myocardial cells in vivo, hPSC-CMs cultured in vitro maintain an immature metabolic phenotype, where majority of ATP is produced through aerobic glycolysis instead of oxidative phosphorylation in the mitochondria. Little is known about the underlying signaling pathways controlling hPSC-CMs' metabolic and functional maturation.

OBJECTIVE

To define the molecular pathways controlling cardiomyocytes' metabolic pathway selections and improve cardiomyocyte metabolic and functional maturation.

METHODS AND RESULTS

We cultured hPSC-CMs in different media compositions including glucose-containing media, glucose-containing media supplemented with fatty acids, and glucose-free media with fatty acids as the primary carbon source. We found that cardiomyocytes cultured in the presence of glucose used primarily aerobic glycolysis and aberrantly upregulated HIF1α (hypoxia-inducible factor 1α) and its downstream target lactate dehydrogenase A. Conversely, glucose deprivation promoted oxidative phosphorylation and repressed HIF1α. Small molecule inhibition of HIF1α or lactate dehydrogenase A resulted in a switch from aerobic glycolysis to oxidative phosphorylation. Likewise, siRNA inhibition of HIF1α stimulated oxidative phosphorylation while inhibiting aerobic glycolysis. This metabolic shift was accompanied by an increase in mitochondrial content and cellular ATP levels. Furthermore, functional gene expressions, sarcomere length, and contractility were improved by HIF1α/lactate dehydrogenase A inhibition.

CONCLUSIONS

We show that under standard culture conditions, the HIF1α-lactate dehydrogenase A axis is aberrantly upregulated in hPSC-CMs, preventing their metabolic maturation. Chemical or siRNA inhibition of this pathway results in an appropriate metabolic shift from aerobic glycolysis to oxidative phosphorylation. This in turn improves metabolic and functional maturation of hPSC-CMs. These findings provide key insight into molecular control of hPSC-CMs' metabolism and may be used to generate more physiologically mature cardiomyocytes for drug screening, disease modeling, and therapeutic purposes.

Protective effect of nobiletin on isolated human islets survival and function against hypoxia and oxidative stress-induced apoptosis

Islets transplantation, as a treatment of type 1 diabetes, faces challenges, including the loss of islets in the process of isolation and pre-transplantation due to cellular stresses-induced apoptosis. Accordingly, the optimization of culture plays a decisive role in the transplantation success. In this study, we evaluated the effect of nobiletin on the cultured human islets. Isolated human islets were treated by different concentrations of nobiletin and cultured for 24 and 72 hours. Then, the islets viability, apoptosis, insulin and C-peptide secretion, and apoptosis markers were evaluated. Also, the production of reactive oxygen species (ROS), hypoxia inducible factor 1 alpha (HIF-1α), and its target genes in the islets were examined. Our findings showed that the islets were encountered with hypoxia and oxidative stress after isolation and during culture. These insults induced apoptosis and reduced viability during culture period. Moreover, the secretion of insulin and C-peptide decreased. Nobiletin treatments significantly improved the islets survival through reduction of HIF-1α and ROS production and suppression of apoptosis, along with increased islets function. Islet protective effect of nobiletin might be related to its anti-oxidant, anti-apoptotic and insulinotropic properties. Hence, in order to achieve viable and functional islets for clinical transplantation, the application of nobiletin during pre-transplantation period is useful.

Exploring the molecular interface between hypoxia-inducible factor signalling and mitochondria

Oxygen is required for the survival of the majority of eukaryotic organisms, as it is important for many cellular processes. Eukaryotic cells utilize oxygen for the production of biochemical energy in the form of adenosine triphosphate (ATP) generated from the catabolism of carbon-rich fuels such as glucose, lipids and glutamine. The intracellular sites of oxygen consumption-coupled ATP production are the mitochondria, double-membraned organelles that provide a dynamic and multifaceted role in cell signalling and metabolism. Highly evolutionarily conserved molecular mechanisms exist to sense and respond to changes in cellular oxygen levels. The primary transcriptional regulators of the response to decreased oxygen levels (hypoxia) are the hypoxia-inducible factors (HIFs), which play important roles in both physiological and pathophysiological contexts. In this review we explore the relationship between HIF-regulated signalling pathways and the mitochondria, including the regulation of mitochondrial metabolism, biogenesis and distribution.

Hypomethylation at non-CpG/CpG sites in the promoter of HIF-1α gene combined with enhanced H3K9Ac modification contribute to maintain higher HIF-1α expression in breast cancer

HIF-1α has a broad impact on tumors, including enhanced utilization of glucose, tumor cell stemness, migration, metastasis and so on. In pilot study, we found that the expression of HIF-1α significantly increased in breast cancer cell lines and tissue samples with higher malignant behaviors and decreased in luminal subtype breast cancer cells and tissue samples. We analyzed and found there is one large CpG island in HIF-1α promoter around transcription start site, and the hypermethylation occurred at these CpGs and their surrounding non-CpGs sites. Epigenetic events driving tumorigenesis has been characterized. However, knowledge is lacking on the non-CpGs methylation of HIF-1α promoter in breast cancer cells. We validated that non-CpGs methylation can directly regulate HIF-1α expression by luciferase activity assay. We also found DNMT3a and Mecp2 play vital role in methylation at non-CpGs and CpGs sites. In addition, we noticed that H3K9ac modification could promote the transcription of HIF-1α in MDA-MB-231 cells by binding to the region contained hypomethylated non-CpG and CpG sites. Taken together, the hypomethylation status at non-CpG and CpG loci in HIF-1α promoter and H3K9ac modification together contribute to maintain higher HIF-1αactivity in invasive breast cancer cells when compared with the non-invasive breast cancer cells, which may establish a tissue-specific epigenetic modification pattern and point to the new directions for future understanding breast cancer therapy.

Endometrial injury increases expression of hypoxia-inducible factor and angiogenesis in the endometrium of women with recurrent implantation failure

RESEARCH QUESTION

The aim of this study was to compare expression of hypoxia-inducible factor 1-alpha (HIF-1α), angiogenesis and apoptosis in endometrial tissue near the implantation window of women with recurrent implantation failure (RIF) and in fertile control women, and to describe possible mechanisms of endometrial injury.

DESIGN

A controlled clinical study was conducted. Endometrial tissue specimens were obtained from 20 women undergoing IVF who had had at least three previous failed treatment cycles; normal endometrial specimens were obtained from 10 fertile control women.

RESULTS

HIF-1α expression was down-regulated in the endometrium of women with RIF compared with that of control women. In addition, micro-vessel density (MVD) was much lower in the endometrium of women with RIF than in that of the control women. Apoptosis was significantly reduced in the endometrium of the RIF group compared with the control group. Endometrial injury increased HIF-1α expression and MVD in endometrial samples of the RIF group, but apoptosis was not significantly altered.

CONCLUSIONS

HIF-1α expression, MVD and endometrial apoptosis were reduced in the peri-implantation endometrium of women with RIF. This suggests that altered endometrial HIF-1α expression and angiogenesis may contribute to implantation failure.

Immune regulation by protein ubiquitination: roles of the E3 ligases VHL and Itch

Protein ubiquitination is an important means of post-translational modification which plays an essential role in the regulation of various aspects of leukocyte development and function. The specificity of ubiquitin tagging to a protein substrate is determined by E3 ubiquitin ligases via defined E3-substrate interactions. In this review, we will focus on two E3 ligases, VHL and Itch, to discuss the latest progress in understanding their roles in the differentiation and function of CD4⁺ T helper cell subsets, the stability of regulatory T cells, effector function of CD8⁺ T cells, as well as the development and maturation of innate lymphoid cells. The biological implications of these E3 ubiquitin ligases will be highlighted in the context of normal and dysregulated immune responses including the control of homeostasis, inflammation, auto-immune responses and anti-tumor immunity. Further elucidation of the ubiquitin system in immune cells will help in the design of new therapeutic interventions for human immunological diseases and cancer.

Cellular Phenotype Plasticity in Cancer Dormancy and Metastasis

Cancer dormancy is a period of cancer progression in which residual tumor cells exist, but clinically remain asymptomatic for a long time, as well as resistant to conventional chemo- and radiotherapies. Cellular phenotype plasticity represents that cellular phenotype could convert between epithelial cells and cells with mesenchymal traits. Recently, this process has been shown to closely associate with tumor cell proliferation, cancer dormancy and metastasis. In this review, we have described different scenarios of how the transition from epithelial to mesenchymal morphology (EMT) and backwards (MET) are connected with the initiation of dormancy and reactivation of proliferation. These processes are fundamental for cancer cells to invade tissues and metastasize. Recognizing the mechanisms underlying the cellular phenotype plasticity as well as dormancy and targeting them is likely to increase the efficiency of traditional tumor treatment inhibiting tumor metastasis.

Vasculogenesis and angiogenesis initiation under normoxic conditions through Wnt/β-catenin pathway in gliomas

The canonical Wnt/β-catenin pathway is up-regulated in gliomas and involved in proliferation, invasion, apoptosis, vasculogenesis and angiogenesis. Nuclear β-catenin accumulation correlates with malignancy. Hypoxia activates hypoxia-inducible factor (HIF)-1α by inhibiting HIF-1α prolyl hydroxylation, which promotes glycolytic energy metabolism, vasculogenesis and angiogenesis, whereas HIF-1α is degraded by the HIF prolyl hydroxylase under normoxic conditions. We focus this review on the links between the activated Wnt/β-catenin pathway and the mechanisms underlying vasculogenesis and angiogenesis through HIF-1α under normoxic conditions in gliomas. Wnt-induced epidermal growth factor receptor/phosphatidylinositol 3-kinase (PI3K)/Akt signaling, Wnt-induced signal transducers and activators of transcription 3 (STAT3) signaling, and Wnt/β-catenin target gene transduction (c-Myc) can activate HIF-1α in a hypoxia-independent manner. The PI3K/Akt/mammalian target of rapamycin pathway activates HIF-1α through eukaryotic translation initiation factor 4E-binding protein 1 and STAT3. The β-catenin/T-cell factor 4 complex directly binds to STAT3 and activates HIF-1α, which up-regulates the Wnt/β-catenin target genes cyclin D1 and c-Myc in a positive feedback loop. Phosphorylated STAT3 by interleukin-6 or leukemia inhibitory factor activates HIF-1α even under normoxic conditions. The activation of the Wnt/β-catenin pathway induces, via the Wnt target genes c-Myc and cyclin D1 or via HIF-1α, gene transactivation encoding aerobic glycolysis enzymes, such as glucose transporter, hexokinase 2, pyruvate kinase M2, pyruvate dehydrogenase kinase 1 and lactate dehydrogenase-A, leading to lactate production, as the primary alternative of ATP, at all oxygen levels, even in normoxic conditions. Lactate released by glioma cells via the monocarboxylate lactate transporter-1 up-regulated by HIF-1α and lactate anion activates HIF-1α in normoxic endothelial cells by inhibiting HIF-1α prolyl hydroxylation and preventing HIF labeling by the von Hippel-Lindau protein. Increased lactate with acid environment and HIF-1α overexpression induce the vascular endothelial growth factor (VEGF) pathway of vasculogenesis and angiogenesis under normoxic conditions. Hypoxia and acidic pH have no synergistic effect on VEGF transcription.

Regulation of the iron regulatory proteins by reactive nitrogen and oxygen species

Iron regulatory proteins 1 and 2 (IRP1 and IRP2) are RNA binding proteins that posttranscriptionally regulate the expression of mRNAs coding for proteins involved in the maintenance of iron and energy homeostasis. The RNA binding activities of the IRPs are regulated by changes in cellular iron. Thus, the IRPs are considered iron sensors and the principle regulators of cellular iron homeostasis. The mechanisms governing iron regulation of the IRPs are well described. Recently, however, much attention has focused on the regulation of IRPs by reactive nitrogen and oxygen species (RNS, ROS). Here we focus on summarizing the iron-regulated RNA binding activities of the IRPs, as well as the recent findings of IRP regulation by RNS and ROS. The recent observations that changes in oxygen tension regulate both IRP1 and IRP2 RNA binding activities will be addressed in light of ROS regulation of the IRPs.