scholarly journals Hypoxic induction of an HIF-1α–dependent bFGF autocrine loop drives angiogenesis in human endothelial cells

Blood ◽  
2006 ◽  
Vol 107 (7) ◽  
pp. 2705-2712 ◽  
Author(s):  
Maura Calvani ◽  
Annamaria Rapisarda ◽  
Badarch Uranchimeg ◽  
Robert H. Shoemaker ◽  
Giovanni Melillo
Keyword(s):  
Endothelial Cells ◽  
Mammalian Cells ◽  
Neutralizing Antibodies ◽  
Umbilical Vein ◽  
Hypoxia Inducible Factor ◽  
Transcriptional Response ◽  
Low Oxygen ◽  
Autocrine Loop ◽  
Hypoxic Induction ◽  
Hypoxic Conditions

AbstractHypoxia is a major pathophysiological condition for the induction of angiogenesis, which is a crucial aspect of growth in solid tumors. In mammalian cells, the transcriptional response to oxygen deprivation is largely mediated by hypoxia-inducible factor 1 (HIF-1), a heterodimer composed of HIF-1α and HIF-1β subunits. However, the response of endothelial cells to hypoxia and the specific involvement of HIF-α subunits in this process are still poorly understood. We show that human umbilical vein endothelial cells (HUVECs) cultured in the absence of growth factors survive and form tubelike structures when cultured under hypoxic, but not normoxic, conditions. HUVECs expressed both HIF-1α and HIF-2α when cultured under hypoxic conditions. Transfection of HIF-1α, but not HIF-2α, siRNA to HUVECs completely abrogated hypoxic induction of cords. Neutralizing antibodies to bFGF, but not IGF-1, VEGF, or PDGF-BB, blocked survival and sprouting of HUVECs under hypoxic conditions, suggesting the existence of an autocrine loop induced by low oxygen levels. Notably, bFGF-dependent induction of cord formation under normoxic conditions required HIF-1α activity, which was also essential for hypoxic induction of bFGF mRNA and protein expression. These results uncover the existence of an HIF-1α–bFGF amplification pathway that mediates survival and sprouting of endothelial cells under hypoxic conditions.

scholarly journals Cell-Free Hemoglobin Does Not Attenuate the Effects of SARS-CoV-2 Spike Protein S1 Subunit in Pulmonary Endothelial Cells

2021 ◽  
Vol 22 (16) ◽  
pp. 9041
Author(s):  
Sirsendu Jana ◽  
Michael R. Heaven ◽  
Abdu I. Alayash
Keyword(s):  
Endothelial Cells ◽  
Hypoxia Inducible Factor ◽  
Spike Protein ◽  
Receptor Interaction ◽  
Low Oxygen ◽  
Viral Receptor ◽  
Hypoxic Conditions ◽  
Viral Components ◽  
Induced Changes ◽  
The Impact

SARS-CoV-2 primarily infects epithelial airway cells that express the host entry receptor angiotensin-converting enzyme 2 (ACE2), which binds to the S1 spike protein on the surface of the virus. To delineate the impact of S1 spike protein interaction with the ACE2 receptor, we incubated the S1 spike protein with human pulmonary arterial endothelial cells (HPAEC). HPAEC treatment with the S1 spike protein caused disruption of endothelial barrier function, increased levels of numerous inflammatory molecules (VCAM-1, ICAM-1, IL-1β, CCL5, CXCL10), elevated mitochondrial reactive oxygen species (ROS), and a mild rise in glycolytic reserve capacity. Because low oxygen tension (hypoxia) is associated with severe cases of COVID-19, we also evaluated treatment with hemoglobin (HbA) as a potential countermeasure in hypoxic and normal oxygen environments in analyses with the S1 spike protein. We found hypoxia downregulated the expression of the ACE2 receptor and increased the critical oxygen homeostatic signaling protein, hypoxia-inducible factor (HIF-1α); however, treatment of the cells with HbA yielded no apparent change in the levels of ACE2 or HIF-1α. Use of quantitative proteomics revealed that S1 spike protein-treated cells have few differentially regulated proteins in hypoxic conditions, consistent with the finding that ACE2 serves as the host viral receptor and is reduced in hypoxia. However, in normoxic conditions, we found perturbed abundance of proteins in signaling pathways related to lysosomes, extracellular matrix receptor interaction, focal adhesion, and pyrimidine metabolism. We conclude that the spike protein alone without the rest of the viral components is sufficient to elicit cell signaling in HPAEC, and that treatment with HbA failed to reverse the vast majority of these spike protein-induced changes.

scholarly journals Comprehensive transcriptomic profiling reveals SOX7 as an early regulator of angiogenesis in hypoxic human endothelial cells

2020 ◽  
Vol 295 (15) ◽  
pp. 4796-4808 ◽  
Author(s):  
Jeff Klomp ◽  
James Hyun ◽  
Jennifer E. Klomp ◽  
Kostandin Pajcini ◽  
Jalees Rehman ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Transcription Factor ◽  
Umbilical Vein ◽  
Critical Role ◽  
Hypoxia Inducible Factor ◽  
Temporal Analysis ◽  
Low Oxygen ◽  
Gene Encoding ◽  
Transcriptomic Response ◽  
Functional Analyses

Endothelial cells (ECs) lining the vasculature of vertebrates respond to low oxygen (hypoxia) by maintaining vascular homeostasis and initiating adaptive growth of new vasculature through angiogenesis. Previous studies have uncovered the molecular underpinnings of the hypoxic response in ECs; however, there is a need for comprehensive temporal analysis of the transcriptome during hypoxia. Here, we sought to investigate the early transcriptional programs of hypoxic ECs by using RNA-Seq of primary cultured human umbilical vein ECs exposed to progressively increasing severity and duration of hypoxia. We observed that hypoxia modulates the expression levels of approximately one-third of the EC transcriptome. Intriguingly, expression of the gene encoding the developmental transcription factor SOX7 (SRY-box transcription factor 7) rapidly and transiently increased during hypoxia. Transcriptomic and functional analyses of ECs following SOX7 depletion established its critical role in regulating hypoxia-induced angiogenesis. We also observed that depletion of the hypoxia-inducible factor (HIF) genes, HIF1A (encoding HIF-1α) and endothelial PAS domain protein 1 (EPAS1 encoding HIF-2α), inhibited both distinct and overlapping transcriptional programs. Our results indicated a role for HIF-1α in down-regulating mitochondrial metabolism while concomitantly up-regulating glycolytic genes, whereas HIF-2α primarily up-regulated the angiogenesis transcriptional program. These results identify the concentration and time dependence of the endothelial transcriptomic response to hypoxia and an early key role for SOX7 in mediating angiogenesis.

Oxygen-dependent gene expression in fishes

2005 ◽  
Vol 288 (5) ◽  
pp. R1079-R1090 ◽  
Author(s):  
Mikko Nikinmaa ◽  
Bernard B. Rees
Keyword(s):  
Gene Expression ◽  
Mammalian Cells ◽  
Hypoxia Inducible Factor ◽  
Transcriptional Response ◽  
Hypoxia Tolerance ◽  
Hypoxic Exposure ◽  
Low Oxygen ◽  
Mammalian Development ◽  
Molecular Responses ◽  
And Function

The role of oxygen in regulating patterns of gene expression in mammalian development, physiology, and pathology has received increasing attention, especially after the discovery of the hypoxia-inducible factor (HIF), a transcription factor that has been likened to a “master switch” in the transcriptional response of mammalian cells and tissues to low oxygen. At present, considerably less is known about the molecular responses of nonmammalian vertebrates and invertebrates to hypoxic exposure. Because many animals live in aquatic habitats that are variable in oxygen tension, it is relevant to study oxygen-dependent gene expression in these animals. The purpose of this review is to discuss hypoxia-induced gene expression in fishes from an evolutionary and ecological context. Recent studies have described homologs of HIF in fish and have begun to evaluate their function. A number of physiological processes are known to be altered by hypoxic exposure of fish, although the evidence linking them to HIF is less well developed. The diversity of fish presents many opportunities to evaluate if inter- and intraspecific variation in HIF structure and function correlate with hypoxia tolerance. Furthermore, as an aquatic group, fish offer the opportunity to examine the interactions between hypoxia and other stressors, including pollutants, common in aquatic environments. It is possible, if not likely, that results obtained by studying the molecular responses of fish to hypoxia will find parallels in the oxygen-dependent responses of mammals, including humans. Moreover, novel responses to hypoxia could be discovered through studies of this diverse and species-rich group.

scholarly journals IOP1, a novel hydrogenase-like protein that modulates hypoxia-inducible factor-1α activity

2006 ◽  
Vol 401 (1) ◽  
pp. 341-352 ◽  
Author(s):  
Jianhe Huang ◽  
Daisheng Song ◽  
Adrian Flores ◽  
Quan Zhao ◽  
Sharon M. Mooney ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Hypoxia Inducible Factor ◽  
Cell Types ◽  
Mrna Levels ◽  
Low Oxygen ◽  
Gene Expressions ◽  
Iron Sulfur Cluster ◽  
Α Subunit ◽  
Protein Levels ◽  
Hypoxic Conditions

A central means by which mammalian cells respond to low oxygen tension is through the activation of the transcription factor HIF-1 (hypoxia-inducible factor-1). Under normoxic conditions, HIF-1α (the α subunit of HIF-1) is targeted for rapid degradation by the ubiquitin–proteasome pathway. Under hypoxic conditions, this degradation is inhibited, thereby leading to the stabilization and activation of HIF-1α. Here, we report the identification of IOP1 (iron-only hydrogenase-like protein 1), a protein homologous with enzymes present in anaerobic organisms that contain a distinctive iron–sulfur cluster. IOP1 is present in a broad range of cell types. Knockdown of IOP1 using siRNA (small interfering RNA) in mammalian cells increases protein levels of HIF-1α under both normoxic and hypoxic conditions, and augments hypoxia-induced HRE (hypoxia response element) reporter gene and endogenous HIF-1α target gene expressions. We find that IOP1 knockdown up-regulates HIF-1α mRNA levels, thereby providing a mechanism by which knockdown induces the observed effects. The results collectively provide evidence that IOP1 is a component of the protein network that regulates HIF-1α in mammalian cells.

PGE1analog alprostadil induces VEGF and eNOS expression in endothelial cells

2005 ◽  
Vol 289 (5) ◽  
pp. H2066-H2072 ◽  
Author(s):  
Dominik G. Haider ◽  
Robert A. Bucek ◽  
Aura G. Giurgea ◽  
Gerald Maurer ◽  
Helmut Glogar ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Umbilical Vein ◽  
Hypoxia Inducible Factor ◽  
Disease Process ◽  
Hypoxia Inducible Factor 1 ◽  
Hypoxic Conditions ◽  
Umbilical Vein Endothelial Cells ◽  
End Stage ◽  
Oxide Synthase ◽  
Endothelial Nitric Oxide

Endothelial nitric oxide synthase (eNOS), VEGF, and hypoxia-inducible factor 1-α (HIF-1α) are important regulators of endothelial function, which plays a role in the pathophysiology of heart failure (HF). PGE1analog treatment in patients with HF elicits beneficial hemodynamic effects, but the precise mechanisms have not been investigated. We have investigated the effects of the PGE1analog alprostadil on eNOS, VEGF, and HIF-1α expression in human umbilical vein endothelial cells (HUVEC) using RT-PCR and immunoblotting under normoxic and hypoxic conditions. In addition, we studied protein expression by immunohistochemical staining in explanted hearts from patients with end-stage HF, treated or untreated with systemic alprostadil. Alprostadil causes an upregulation of eNOS and VEGF protein and mRNA expression in HUVEC and decreases HIF-1α. Hypoxia potently increased eNOS, VEGF, and HIF-1α synthesis. The alprostadil-induced upregulation of eNOS and VEGF was prevented by inhibition of MAPKs with PD-98056 or U-0126. Consistently, the expression of eNOS and VEGF was increased, and HIF-1α was reduced in failing hearts treated with alprostadil. The potent effects of alprostadil on endothelial VEGF and eNOS synthesis may be useful for patients with HF where endothelial dysfunction is involved in the disease process.

Hypoxia-induced pulmonary endothelin-1 expression is unaltered by nitric oxide

2002 ◽  
Vol 92 (3) ◽  
pp. 1152-1158 ◽  
Author(s):  
Scott Earley ◽  
Leif D. Nelin ◽  
Louis G. Chicoine ◽  
Benjimen R. Walker
Keyword(s):  
Nitric Oxide ◽  
Endothelial Cells ◽  
Promoter Activity ◽  
Umbilical Vein ◽  
Hypoxia Inducible Factor ◽  
Hypoxic Exposure ◽  
Mrna Levels ◽  
Protective Effects ◽  
No Donor ◽  
Umbilical Vein Endothelial Cells

Nitric oxide (NO) attenuates hypoxia-induced endothelin (ET)-1 expression in cultured umbilical vein endothelial cells. We hypothesized that NO similarly attenuates hypoxia-induced increases in ET-1 expression in the lungs of intact animals and reasoned that potentially reduced ET-1 levels may contribute to the protective effects of NO against the development of pulmonary hypertension during chronic hypoxia. As expected, hypoxic exposure (24 h, 10% O2) increased rat lung ET-1 peptide and prepro-ET-1 mRNA levels. Contrary to our hypothesis, inhaled NO (iNO) did not attenuate hypoxia-induced increases in pulmonary ET-1 peptide or prepro-ET-1 mRNA levels. Because of this surprising finding, we also examined the effects of NO on hypoxia-induced increases in ET peptide levels in cultured cell experiments. Consistent with the results of iNO experiments, administration of the NO donor S-nitroso- N-acetyl-penicillamine to cultured bovine pulmonary endothelial cells did not attenuate increases in ET peptide levels resulting from hypoxic (24 h, 3% O2) exposure. In additional experiments, we examined the effects of NO on the activity of a cloned ET-1 promoter fragment containing a functional hypoxia inducible factor-1 binding site in reporter gene experiments. Whereas moderate hypoxia (24 h, 3% O2) had no effect on ET-1 promoter activity, activity was increased by severe hypoxic (24 h, 0.5% O2) exposure. ET-1 promoter activity after S-nitroso- N-acetyl-penicillamine administration during severe hypoxia was greater than that in normoxic controls, although activity was reduced compared with that in hypoxic controls. These findings suggest that hypoxia-induced pulmonary ET-1 expression is unaffected by NO.

scholarly journals Endothelial Cells Are Main Producers of Interleukin 8 through Toll-Like Receptor 2 and 4 Signaling during Bacterial Infection in Leukopenic Cancer Patients

2003 ◽  
Vol 10 (4) ◽  
pp. 558-563 ◽  
Author(s):  
C. S. M. Oude Nijhuis ◽  
E. Vellenga ◽  
S. M. G. J. Daenen ◽  
W. A. Kamps ◽  
E. S. J. M. de Bont
Keyword(s):  
Endothelial Cells ◽  
Cancer Patients ◽  
Whole Blood ◽  
Neutralizing Antibodies ◽  
Bacterial Infections ◽  
Umbilical Vein ◽  
Interleukin 8 ◽  
Toll Like Receptor ◽  
Necrosis Factor Alpha ◽  
Umbilical Vein Endothelial Cells

ABSTRACT Cancer patients who are leukopenic due to chemotherapy are susceptible to bacterial infections. Normally, clinical conditions during bacterial infections are caused by pathogen-associated molecular patterns, which are components that bind to Toll-like receptor (TLR) 2 (TLR-2) and TLR-4 on leukocytes, resulting in the production of inflammatory cytokines. The mechanism of this inflammatory response in cancer patients with diminished numbers of leukocytes is not completely clear. The levels of interleukin 1β (IL-1β) and tumor necrosis factor alpha measured in the circulation of leukopenic cancer patients are lower than those measured in that of nonleukopenic patients during bacterial infections, whereas plasma interleukin 8 (IL-8) levels show distinct identical increases during bacterial infections in both leukopenic and nonleukopenic patients. Normally, these cytokines are mainly secreted by leukocytes. In cancer patients with bacterial infections and a diminished number of leukocytes, other sources of IL-8 production, such as endothelial cells, might be expected. Endothelial cells instead of leukocytes become the most important producers of IL-8 during bacterial infections in patients with chemotherapy-induced leukopenia through TLR-2 and TLR-4 signaling. Whole blood samples from six cancer patients were stimulated with lipopolysaccharide (LPS), and then IL-8 concentrations in supernatants were measured. Further, human umbilical vein endothelial cells (HUVECs) were incubated with sera from leukopenic cancer patients with or without bacterial infections, and then IL-8 concentrations in supernatants were measured (n = 6). In addition, the same HUVEC experiment was performed with the addition of neutralizing antibodies against TLR-2 and TLR-4. During leukopenia (<109 cells/liter), LPS stimulation of whole blood did not result in an increase in IL-8 levels. However, when endothelial cells were incubated with sera from leukopenic cancer patients during bacterial infections, a three- to eightfold increase in IL-8 production was found, compared to the IL-8 production found after incubation with sera from patients without signs of infections. This increase did not reflect a higher level of IL-8 already present in the sera. Further, we demonstrated that IL-8 production induced in endothelial cells by sera from patients with documented gram-negative infections could be reduced significantly by up to 40% when the cells were incubated with neutralizing antibodies against TLR-4 (P = 0.028). The addition of TLR-2 antibodies slightly enhanced the reduction of IL-8 production. These results suggest that during bacterial infections in cancer patients with markedly diminished numbers of leukocytes, endothelial cells become important producers of IL-8 through TLR-4 signaling and, to a lesser extent, TLR-2 signaling.

scholarly journals Hypoxia-Induced Gene Expression Occurs Solely through the Action of Hypoxia-Inducible Factor 1α (HIF-1α): Role of Cytoplasmic Trapping of HIF-2α

2003 ◽  
Vol 23 (14) ◽  
pp. 4959-4971 ◽  
Author(s):  
Sang-ki Park ◽  
Agnes M. Dadak ◽  
Volker H. Haase ◽  
Lucrezia Fontana ◽  
Amato J. Giaccia ◽  
...  
Keyword(s):  
Gene Expression ◽  
Transcriptional Activity ◽  
Hypoxia Inducible Factor ◽  
Low Oxygen ◽  
Hypoxic Conditions ◽  
Show Evidence ◽  
Dependent Protein ◽  
A Cell ◽  
Cell Type Specific ◽  
Inducible Genes

ABSTRACT The hypoxia-inducible factors 1α (HIF-1α) and 2α (HIF-2α) have extensive structural homology and have been identified as key transcription factors responsible for gene expression in response to hypoxia. They play critical roles not only in normal development, but also in tumor progression. Here we report on the differential regulation of protein expression and transcriptional activity of HIF-1α and -2α by hypoxia in immortalized mouse embryo fibroblasts (MEFs). We show that oxygen-dependent protein degradation is restricted to HIF-1α, as HIF-2α protein is detected in MEFs regardless of oxygenation and is localized primarily to the cytoplasm. Endogenous HIF-2α remained transcriptionally inactive under hypoxic conditions; however, ectopically overexpressed HIF-2α translocated into the nucleus and could stimulate expression of hypoxia-inducible genes. We show that the factor inhibiting HIF-1 can selectively inhibit the transcriptional activity of HIF-1α but has no effect on HIF-2α-mediated transcription in MEFs. We propose that HIF-2α is not a redundant transcription factor of HIF-1α for hypoxia-induced gene expression and show evidence that there is a cell type-specific modulator(s) that enables selective activation of HIF-1α but not HIF-2α in response to low-oxygen stress.

scholarly journals The Response of Macrophages and Neutrophils to Hypoxia in the Context of Cancer and Other Inflammatory Diseases

2016 ◽  
Vol 2016 ◽  
pp. 1-10 ◽  
Author(s):  
Antje Egners ◽  
Merve Erdem ◽  
Thorsten Cramer
Keyword(s):  
Endothelial Cells ◽  
Inflammatory Diseases ◽  
Neutrophil Function ◽  
Proper Function ◽  
Low Oxygen ◽  
Bacterial Killing ◽  
Molecular Responses ◽  
Chronic Inflammatory Diseases ◽  
Hypoxic Conditions ◽  
Cellular Components

Lack of oxygen (hypoxia) is a hallmark of a multitude of acute and chronic diseases and can be either beneficial or detrimental for organ restitution and recovery. In the context of inflammation, hypoxia is particularly important and can significantly influence the course of inflammatory diseases. Macrophages and neutrophils, the chief cellular components of innate immunity, display distinct properties when exposed to hypoxic conditions. Virtually every aspect of macrophage and neutrophil function is affected by hypoxia, amongst others, morphology, migration, chemotaxis, adherence to endothelial cells, bacterial killing, differentiation/polarization, and protumorigenic activity. Prominent arenas of macrophage and neutrophil function, for example, acute/chronic inflammation and the microenvironment of solid tumors, are characterized by low oxygen levels, demonstrating the paramount importance of the hypoxic response for proper function of these cells. Members of the hypoxia-inducible transcription factor (HIF) family emerged as pivotal molecular regulators of macrophages and neutrophils. In this review, we will summarize the molecular responses of macrophages and neutrophils to hypoxia in the context of cancer and other chronic inflammatory diseases and discuss the potential avenues for therapeutic intervention that arise from this knowledge.

scholarly journals Different Adaptive Responses to Hypoxia in Normal and Multiple Myeloma Endothelial Cells

2018 ◽  
Vol 46 (1) ◽  
pp. 203-212 ◽  
Author(s):  
Irene Filippi ◽  
Ilaria Saltarella ◽  
Carlo Aldinucci ◽  
Fabio Carraro ◽  
Roberto Ria ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Endothelial Cells ◽  
Cell Survival ◽  
Glucose Transporter ◽  
Umbilical Vein ◽  
Hypoxia Inducible Factor ◽  
Monocarboxylate Transporter ◽  
Hypoxic Exposure ◽  
Adaptive Responses ◽  
Pathological Conditions

Background/Aims: Hypoxia is a powerful stimulator of angiogenesis under physiological as well as pathological conditions. Normal endothelial cells (EC), such as human umbilical vein EC (HUVEC), are relatively affected by hypoxic insult in terms of cell survival. In contrast, EC from tumors are particularly resistant to hypoxia-induced cell death. Previous reports have shown that EC in bone marrow from multiple myeloma (MM) patients had a hypoxic phenotype, even under normoxic conditions. The aim of this study was to evaluate whether HUVEC and MMEC adapt differently to hypoxia. Methods: Cell proliferation was assessed by the CyQUANT assay. Cdc25A, p21, Bax, Bcl-xl, BNIP3, glucose transporter (GLUT)-1, monocarboxylate transporter (MCT)-4 and carbonic anhydrase (CA)IX mRNA expression was determined by qRT-PCR. HIF-1α, BNIP3, Beclin-1, LC3B, livin, Bax, Bcl-xl, p21, p62 and β-actin protein expression was analyzed by western blot. Apoptosis was determined by TUNEL assay. Silencing of BNIP3 was achieved by stealth RNA system technology. Results: While HUVEC survival was reduced after prolonged hypoxic exposure, MMEC were completely unaffected. This difference was also significant in terms of livin, cdc25A and p21 expression. Hypoxia induced apoptosis and inhibited autophagy in HUVEC, but not in MMEC, where hypoxic treatment resulted in a more sustained adaptive response. In fact, MMEC showed a more significant increase in the expression of genes regulated transcriptionally by hypoxia-inducible factor (HIF)-1α. Interestingly, they showed higher expression of BNIP3 than did HUVEC, indicating a more pronounced autophagic (and pro-survival) phenotype. The potential role of BNIP3 in EC survival was confirmed by BNIP3 siRNA experiments in HUVEC, where BNIP3 inhibition resulted in reduced cell survival and increased apoptosis. Conclusion: These findings provide further information on how hypoxia may affect EC survival and could be important for a better understanding of EC physiology under normal and pathological conditions, such as in multiple myeloma.

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