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Here, we investigate the impact of hypoxia on the hepatic response of glucocorticoid receptor (GR) to dexamethasone (DEX) in mice via RNA‐sequencing. Hypoxia causes three types of reprogramming of GR: (i) much weaker induction of classical GR‐responsive genes by DEX in hypoxia, (ii) a number of genes is induced by DEX specifically in hypoxia, and (iii) hypoxia induces a group of genes via activation of the hypothalamic–pituitary–adrenal (HPA) axis. Transcriptional profiles are reflected by changed GR DNA‐binding as measured by ChIP sequencing. The HPA axis is induced by hypothalamic HIF1α and HIF2α activation and leads to GR‐dependent lipolysis and ketogenesis. Acute inflammation, induced by lipopolysaccharide, is prevented by DEX in normoxia but not during hypoxia, and this is attributed to HPA axis activation by hypoxia. We unfold new physiological pathways that have consequences for patients suffering from GC resistance. Synopsis: This study investigates the impact of hypoxia on hepatic GR function and unfolds new physiological pathways that might have implications for patients suffering from GC resistance. Hypoxia stabilizes HIF1α and HIF2α at the hypothalamus and activates the HPA axis which leads to increased GR‐dependent lipolysis and ketogenesis.Hypoxia induces transcriptional reprogramming of the GR.In hypoxic conditions, DEX is no longer able to protect against acute inflammation. [ABSTRACT FROM AUTHOR]

Prolyl hydroxylase domain-containing proteins (PHDs) regulate the adaptation of cells to hypoxia. Pan-hydroxylase inhibition is protective in experimental colitis, in which PHD1 plays a prominent role. However, it is currently unknown how PHD1 targeting regulates this protection and which cell type(s) are involved. Here, we demonstrated that Phd1 deletion in endothelial and haematopoietic cells (Phd1f/fTie2:cre) protected mice from dextran sulphate sodium (DSS)-induced colitis, with reduced epithelial erosions, immune cell infiltration, and colonic microvascular dysfunction, whereas the response of Phd2f/+Tie2:cre and Phd3f/fTie2:cre mice to DSS was similar to that of their littermate controls. Using bone marrow chimeras and cell-specific cre mice, we demonstrated that ablation of Phd1 in haematopoietic cells but not in endothelial cells was both necessary and sufficient to inhibit experimental colitis. This effect relied, at least in part, on skewing of Phd1-deficient bone marrow-derived macrophages towards an anti-inflammatory M2 phenotype. These cells showed an attenuated nuclear factor-κB-dependent response to lipopolysaccharide (LPS), which in turn diminished endothelial chemokine expression. In addition, Phd1 deficiency in dendritic cells significantly reduced interleukin-1β production in response to LPS. Taken together, our results further support the development of selective PHD1 inhibitors for ulcerative colitis, and identify haematopoietic cells as their primary target. [ABSTRACT FROM AUTHOR]

ABSTRACT The main oxygen sensor hypoxia inducible factor (HIF) prolyl hydroxylase 2 (PHD2) is a critical regulator of tissue homeostasis during erythropoiesis, hematopoietic stem cell maintenance, and wound healing. Recent studies point toward a role for the PHD2-erythropoietin (EPO) axis in the modulation of bone remodeling, even though the studies produced conflicting results. Here, we used a number of mouse strains deficient of PHD2 in different cell types to address the role of PHD2 and its downstream targets HIF-1α and HIF-2α in bone remodeling. Mice deficient for PHD2 in several cell lineages, including EPO-producing cells, osteoblasts, and hematopoietic cells (CD68:cre-PHD2f/f) displayed a severe reduction of bone density at the distal femur as well as the vertebral body due to impaired bone formation but not bone resorption. Importantly, using osteoblast-specific (Osx:cre-PHD2f/f) and osteoclast-specific PHD2 knock-out mice (Vav:cre- PHD2f/f), we show that this effect is independent of the loss of PHD2 in osteoblast and osteoclasts. Using different in vivo and in vitro approaches, we show here that this bone phenotype, including the suppression of bone formation, is directly linked to the stabilization of the α-subunit of HIF-2, and possibly to the subsequent moderate induction of serum EPO, which directly influenced the differentiation and mineralization of osteoblast progenitors resulting in lower bone density. Taken together, our data identify the PHD2:HIF-2α:EPO axis as a so far unknown regulator of osteohematology by controlling bone homeostasis. Further, these data suggest that patients treated with PHD inhibitors or EPO should be monitored with respect to their bone status. © 2016 American Society for Bone and Mineral Research. [ABSTRACT FROM AUTHOR]

Erythropoietin (EPO) primarily regulates red blood cell formation, and EPO serum levels are increased on hypoxic stress (e.g., anemia and altitude). In addition to anemia, recent discoveries suggest new therapeutic indications for EPO, unrelated to erythropoiesis. We investigated the skeletal role of EPO using several models of overexpression (Tg6 mice) and EPO administration (intermittent/continuous, high/low doses) in adult C57Bl6 female mice. Using microcomputed tomography, histology, and serum markers, we found that EPO induced a 32%-61% trabecular bone loss caused by increased bone resorption (+60%-88% osteoclast number) and reduced bone formation rate (-19 to -74%; P < 0.05 throughout). EPO targeted the monocytic lineage by increasing the number of bonemonocytes/macrophages, preosteoclasts, and mature osteoclasts. In contrast to the attenuated bone formation in vivo, EPO treatment in vitro did not inhibit osteoblast differentiation and activity, suggesting an indirect effect of EPO on osteoblasts. However, EPO had a direct effect on preosteoclasts by stimulating osteoclastogenesis in isolated cultures (+60%) via the Jak2 and PI3K pathways. In summary, our findings demonstrate that EPO negatively regulates bone mass and thus bears significant clinical implications for the potential management of patients with endogenously or therapeutically elevated EPO levels. [ABSTRACT FROM AUTHOR]

The tumor microenvironment plays a pivotal role during cancer development and progression. The balance between suppressive and cytotoxic responses of the tumor immune microenvironment has been shown to have a direct effect on the final outcome in various human and experimental tumors. Recently, we demonstrated that the oxygen sensor HIF-prolyl hydroxylase-2 (PHD2) plays a detrimental role in tumor cells, stimulating systemic growth and metastasis in mice. In our current study, we show that the conditional ablation of PHD2 in the hematopoietic system also leads to reduced tumor volume, intriguingly generated by an imbalance between enhanced cell death and improved proliferation of tumor cells. This effect seems to rely on the overall downregulation of protumoral as well as antitumoral cytokines. Using different genetic approaches, we were able to confine this complex phenotype to the crosstalk of PHD2-deficient myeloid cells and T-lymphocytes. Taken together, our findings reveal a multifaceted role for PHD2 in several hematopoietic lineages during tumor development and might have important implications for the development of tumor therapies in the future. [ABSTRACT FROM AUTHOR]

Low levels of oxygen or hypoxia is often an obstacle in health, particularly in pathological disorders like cancer. The main family of transcription factors responsible for cell survival and adaptation under strenuous conditions of hypoxia are the 'hypoxia-inducible factors' (HIFs). Together with prolyl hydroxylase domain enzymes (PHDs), HIFs regulates tumor angiogenesis, proliferation, invasion, metastasis, in addition to resistance to radiation and chemotherapy. Additionally, the entire HIF transcription cascade is involved in the 'seventh' hallmark of cancer; inflammation. Studies have shown that hypoxia can influence tumor associated immune cells toward assisting in tumor proliferation, differentiation, vessel growth, distant metastasis and suppression of the immune response via cytokine expression alterations. These changes are not necessarily analogous to HIF's role in non-cancer immune responses, where hypoxia often encourages a strong inflammatory response. [ABSTRACT FROM AUTHOR]

Recent studies have revealed that the maturation state of vessels in tumors, in addition to vascularity, is a critical determinant of tumor growth. The role of oxygen-dependent signaling pathways in hypoxia-stimulated angiogenesis is well established, however, little is known about their impact on vessel maturation in tumors. Here, we have studied the function of the cellular oxygen sensor, factor inhibiting HIF-1 (FIH), which controls the activity of hypoxia-inducible factor-1. FIH silencing in mouse LM8 osteosarcoma stimulated angiogenesis but did not influence tumor growth. In contrast, FIH overexpression led to increased pericyte coverage of the tumor vasculature, reduced vessel leakiness and enhanced tumor growth. Vessel maturation was paralleled by up-regulation of platelet-derived growth factor (PDGF)-C in tumors and expression of PDGF receptor-α on pericytes. Ablation of PDGF-C in FIH-overexpressing tumor cells reduced pericyte coverage and tumor growth. Our data suggest that FIH-mediated PDGF-C induction in LM8 osteosarcoma stimulates the recruitment of PDGFR-α positive pericytes to the tumor vasculature, leading to vessel maturation and enhanced tumor growth. [ABSTRACT FROM AUTHOR]

Deals with a study which assessed the impact of matrix metalloproteinases (MMP) deficiencies in in vivo and in vitro models of angiogenesis. In vivo activation of the MMP-9 promoter of host cells in tumor transplants; Effect of MMP-9 and MMP-3 deficiency on tumor invasion and vascularization; Effect of the combined deficiency of MMP-2 and MMP-9 on tumor invasion and vascularization.

Investigates the expression and activities of matrix metalloproteinase (MMP) 2 and MMP-9 gelatinase in the course of laser-induced murine choroidal neovascularization. Gelatin zymography analysis of ocular posterior segments; Fluorescein angiography performed before death; Role of MMP during the early phases of choroidal neovascularization.