Publications

Editorial overview: Hypoxia

Correction: HIF-1-dependent expression of angiopoietin-like 4 and L1CAM mediates vascular metastasis of hypoxic breast cancer cells to the lungs

Oxygen-regulated transcription factors and their role in pulmonary disease

The transcription factors nuclear factor interleukin-6 (NF-IL6), early growth response-1 (EGR-1) and hypoxia-inducible factor-1 (HIF-1) have important roles in the molecular pathophysiology of hypoxia-associated pulmonary disease. NF-IL6 controls the production of interleukin (IL)-6 in vascular endothelial cells, which may have anti-inflammatory activity by counteracting effects of IL-1 and IL-8. EGR-1 controls the production of tissue factor by macrophages, which triggers fibrin deposition in the pulmonary vasculature. HIF-1 activates the expression of the vasoconstrictor endothelin-1 in vascular endothelial cells. Angiotensin II induces HIF-1 expression and hypertrophy of pulmonary arterial smooth muscle cells. HIF-1 might therefore have multiple roles in the pathogenesis of pulmonary vascular remodeling.

Hypoxia-Inducible Factor 1 Regulates Vascular Endothelial Growth Factor Expression in Human Pancreatic Cancer

We conclude that HIF-1 is the regulatory link between tumor hypoxia and VEGF production in pancreatic cancer, thus establishing a biochemical pathway between tumor hypoxia and neoangiogenesis in this highly aggressive neoplasm.

<scp>ZBTB2</scp> links p53 deficiency to <scp>HIF</scp>‐1‐mediated hypoxia signaling to promote cancer aggressiveness

Abstract Aberrant activation of the hypoxia‐inducible transcription factor HIF‐1 and dysfunction of the tumor suppressor p53 have been reported to induce malignant phenotypes and therapy resistance of cancers. However, their mechanistic and functional relationship remains largely unknown. Here, we reveal a mechanism by which p53 deficiency triggers the activation of HIF‐1‐dependent hypoxia signaling and identify zinc finger and BTB domain‐containing protein 2 (ZBTB2) as an important mediator. ZBTB2 forms homodimers via its N‐terminus region and increases the transactivation activity of HIF‐1 only when functional p53 is absent. The ZBTB2 homodimer facilitates invasion, distant metastasis, and growth of p53‐deficient, but not p53‐proficient, cancers. The intratumoral expression levels of ZBTB2 are associated with poor prognosis in lung cancer patients. ZBTB2 N‐terminus‐mimetic polypeptides competitively inhibit ZBTB2 homodimerization and significantly suppress the ZBTB2–HIF‐1 axis, leading to antitumor effects. Our data reveal an important link between aberrant activation of hypoxia signaling and loss of a tumor suppressor and provide a rationale for targeting a key mediator, ZBTB2, to suppress cancer aggressiveness.

Is 15-min Ischemia too Lethal to Be an Ischemic Preconditioning Stimulus?

Inhibitors of hypoxia-inducible factor 1 block breast cancer metastatic niche formation and lung metastasis

Regulation Of Histone 3 Acetylation By Intermittent Hypoxia

Acetylation of nucleosome core histone proteins determines the structure of chromatin, which regulates the accessibility of DNA sequences to the transcriptional machinery. In general, histone hyperacetylation activates gene transcription and histone hypoacetylation leads to gene silencing. Intermittent hypoxia (IH), a hallmark feature of sleep apnea, induces transcriptional activation of several genes. Whether histone acetylation contributes to IH‐induced gene transcription is not known. The goal of the present study was to determine the effects of IH on histone acetylation and assess the underlying mechanisms. Experiments were performed on rat pheochromocytoma (PC12) cells exposed to alternating cycles of 1.5% O 2 for 30 sec followed by 20% O 2 for 5 min. Exposure of cells to 60 cycles of IH increased global acetylation of histone 3 (H3) but not histone 4 (H4) in a stimulus‐dependent and reversible manner compared to cell exposed to normoxia (20% O 2 ). Specific lysine residues K9, K14, K18 and K27 contributed to increased H3 acetylation by IH. Histone deacetylase (HDAC) inhibitors mimicked IH‐increased H3 acetylation under normoxic conditions. IH reduced HDAC3 and HDAC5 protein expression. Pharmacological blockade of NADPH oxidase with triazolo pyrimidine (VAS‐2870), a specific Nox inhibitor inhibited the increased H3 acetylation and decreased HDAC expression that were induced by IH. These results suggest that ROS generated by NADPH oxidase triggers IH‐induced HDAC downregulation, leading to increased H3 acetylation. Support or Funding Information Supported by NIH‐PO1‐HL90554.

Hypoxia and cancer

Endothelin‐1 (ET‐1) induces hypoxia‐inducible factor 1 (HIF‐1) in Pulmonary Arterial Smooth Muscle Cells (PASMCs).

Numerous cellular responses to hypoxia are mediated by the transcription factor, HIF‐1. Recent data suggest that, under certain conditions, HIF‐1 may require feed forward for full expression (Peng, et al. J Physiol, 2006). Recently, ET‐1 was found to increase HIF‐1 levels in tumor cells (Spinella, et al. Cancer Res 2007). Since hypoxia increases ET‐1 levels in the lung, we hypothesized that during moderate prolonged hypoxia ET‐1 might feed forward and amplify activation of HIF‐1 in PASMCs. Primary cultures of rat PASMCs were treated with ET‐1 (10 −8 M; 48 hr) or exposed to hypoxia (4% O 2 ; 60 hrs). Protein levels of the oxygen‐sensitive α subunit of HIF‐1 (HIF‐1α) were markedly increased in nuclear extracts from both hypoxic cells and cells treated with ET‐1 under non‐hypoxic conditions. Time course studies revealed that accumulation of HIF‐1α in response to ET‐1 required greater than 4 hr of exposure. Real‐time PCR revealed that ET‐1 (10 −10 ‐10 −8 M; 48 hr) increased Hif1a mRNA expression. ET‐1 also decreased mRNA and protein expression of prolyl hydroxylase 2 (PHD2), the protein responsible for targeting HIF‐1α for degradation. The induction of HIF‐1α by moderate prolonged hypoxia (4% O 2 ; 60 hr) was blocked by BQ‐123, an ET‐1 receptor subtype A antagonist, whereas BQ‐123 had no effect on the induction of HIF‐1α by severe acute hypoxia (1% O 2 ; 4 hr). These results suggest that ET‐1 induces HIF‐1α by upregulation of HIF‐1α synthesis and downregulation of PHD2‐mediated degradation. Furthermore, the sustained induction of HIF‐1α in PASMCs during moderate prolonged hypoxia may require amplification by ET‐1. Funded by: HL67191

ANGPTL4 influences the therapeutic response of patients with neovascular age-related macular degeneration by promoting choroidal neovascularization

Most patients with neovascular age-related macular degeneration (nvAMD), the leading cause of severe vision loss in elderly US citizens, respond inadequately to current therapies targeting a single angiogenic mediator, vascular endothelial growth factor (VEGF). Here, we report that aqueous fluid levels of a second vasoactive mediator, angiopoietin-like 4 (ANGPTL4), can help predict the response of patients with nvAMD to anti-VEGF therapies. ANGPTL4 expression was higher in patients who required monthly treatment with anti-VEGF therapies compared with patients who could be effectively treated with less-frequent injections. We further demonstrate that ANGPTL4 acts synergistically with VEGF to promote the growth and leakage of choroidal neovascular (CNV) lesions in mice. Targeting ANGPTL4 expression was as effective as targeting VEGF expression for treating CNV in mice, while simultaneously targeting both was more effective than targeting either factor alone. To help translate these findings to patients, we used a soluble receptor that binds to both VEGF and ANGPTL4 and effectively inhibited the development of CNV lesions in mice. Our findings provide an assay that can help predict the response of patients with nvAMD to anti-VEGF monotherapy and suggest that therapies targeting both ANGPTL4 and VEGF will be a more effective approach for the treatment of this blinding disease.

EC does it with HIF

Comment on Licht et al, page [584][1] Expression of a dominant-negative form of hypoxia-inducible factor 2α (HIF-2α) in endothelial cells (ECs) disrupts cardiovascular development in mouse embryos, providing further evidence that HIFs exert both non–cell-autonomous and cell-autonomous control

Fig. S5 from Reciprocal Regulation of DUSP9 and DUSP16 Expression by HIF1 Controls ERK and p38 MAP Kinase Activity and Mediates Chemotherapy-Induced Breast Cancer Stem Cell Enrichment

&lt;p&gt;p38 MAPK regulates stability of pluripotency factor mRNAs.&lt;/p&gt;

Activation of hypoxia-inducible factor 1 during macrophage differentiation

Monocytes/macrophages of the myeloid lineage are the main cellular effectors of innate immunity. Hypoxia-inducible factor 1 (HIF-1) is essential for myeloid cell activation in response to inflammatory stimuli. However, it has not been established whether HIF-1 activity is induced during differentiation from monocyte to macrophage. We demonstrate that macrophage differentiation of THP-1 cells or monocytes from peripheral blood induces increased expression of both HIF-1α and HIF-1β as well as increased HIF-1 transcriptional activity leading to increased expression of HIF-1 target genes. The increased HIF-1 activity in differentiated THP-1 cells resulted from the combined effect of increased HIF-1α mRNA levels and increased HIF-1α protein synthesis. Differentiation-induced HIF-1α protein and mRNA and HIF-1-dependent gene expression was blocked by treating cells with an inhibitor of the protein kinase C or MAP kinase signaling pathway. THP-1 cell differentiation was also associated with increased phosphorylation of the translational regulatory proteins p70 S6 kinase, S6 ribosomal protein, eukaryotic initiation factor 4E, and 4E binding protein 1, thus providing a possible mechanism for the modulation of HIF-1α protein synthesis. RNA interference studies demonstrated that HIF-1α is dispensable for macrophage differentiation but is required for functional maturation.

Hypoxia-Inducible Factor 1 and Dysregulated c-Myc Cooperatively Induce Vascular Endothelial Growth Factor and Metabolic Switches Hexokinase 2 and Pyruvate Dehydrogenase Kinase 1

Hypoxia is a pervasive microenvironmental factor that affects normal development as well as tumor progression. In most normal cells, hypoxia stabilizes hypoxia-inducible transcription factors (HIFs), particularly HIF-1, which activates genes involved in anaerobic metabolism and angiogenesis. As hypoxia signals a cellular deprivation state, HIF-1 has also been reported to counter the activity of MYC, which encodes a transcription factor that drives cell growth and proliferation. Since many human cancers express dysregulated MYC, we sought to determine whether HIF-1 would in fact collaborate with dysregulated MYC rather countering its function. Here, using the P493-6 Burkitt's lymphoma model with an inducible MYC, we demonstrate that HIF-1 cooperates with dysregulated c-Myc to promote glycolysis by induction of hexokinase 2, which catalyzes the first step of glycolysis, and pyruvate dehydrogenase kinase 1, which inactivates pyruvate dehydrogenase and diminishes mitochondrial respiration. We also found the collaborative induction of vascular endothelial growth factor (VEGF) by HIF-1 and dysregulated c-Myc. This study reports the previously unsuspected collaboration between HIF-1 and dysregulated MYC and thereby provides additional insights into the regulation of VEGF and the Warburg effect, which describes the propensity for cancer cells to convert glucose to lactate.

Hypoxia-Inducible Factor 1α Is a Critical Downstream Mediator for Hypoxia-Induced Mitogenic Factor (FIZZ1/RELMα)–Induced Pulmonary Hypertension

Objective— Pulmonary hypertension (PH) is characterized by progressive elevation of pulmonary vascular resistance, right ventricular failure, and ultimately death. We have shown that in rodents, hypoxia-induced mitogenic factor (HIMF; also known as FIZZ1 or resistin-like molecule-β) causes PH by initiating lung vascular inflammation. We hypothesized that hypoxia-inducible factor-1 (HIF-1) is a critical downstream signal mediator of HIMF during PH development. Approach and Results— In this study, we compared the degree of HIMF-induced pulmonary vascular remodeling and PH development in wild-type (HIF-1α +/+ ) and HIF-1α heterozygous null (HIF-1α +/− ) mice. HIMF-induced PH was significantly diminished in HIF-1α +/− mice and was accompanied by a dysregulated vascular endothelial growth factor-A–vascular endothelial growth factor receptor 2 pathway. HIF-1α was critical for bone marrow–derived cell migration and vascular tube formation in response to HIMF. Furthermore, HIMF and its human homolog, resistin-like molecule-β, significantly increased interleukin (IL)-6 in macrophages and lung resident cells through a mechanism dependent on HIF-1α and, at least to some extent, on nuclear factor κB. Conclusions— Our results suggest that HIF-1α is a critical downstream transcription factor for HIMF-induced pulmonary vascular remodeling and PH development. Importantly, both HIMF and human resistin-like molecule-β significantly increased IL-6 in lung resident cells and increased perivascular accumulation of IL-6–expressing macrophages in the lungs of mice. These data suggest that HIMF can induce HIF-1, vascular endothelial growth factor-A, and interleukin-6, which are critical mediators of both hypoxic inflammation and PH pathophysiology.

H ₂ S production by reactive oxygen species in the carotid body triggers hypertension in a rodent model of sleep apnea

Suppressing hydrogen sulfide production in the carotid body may prevent the hypertension associated with sleep apnea.

Supplemental Table 1 from Hypoxia Selectively Enhances Integrin α&lt;sub&gt;5&lt;/sub&gt;β&lt;sub&gt;1&lt;/sub&gt; Receptor Expression in Breast Cancer to Promote Metastasis

&lt;p&gt;Supplemental Table 1 - Primer Sequences used for Real-Time qPCR&lt;/p&gt;