Increase In HIF-1alpha Research Articles

Chronic intracellular hypoxia as a clustering and stratifying factor for clinical severity grade in nephrotic syndrome in children

Abstract. Nephrotic syndrome is the most common glomerular kidney disease in childhood. It is known that chronic hypoxia is a severe disorder and potent factor of kidney damage. The limited success of existing therapeutic strategies in slowing the progression of chronic kidney disease requires the study of new ways to assess and interpret the levels of chronic intracellular hypoxia concerning basic clinical data, grades of NS activity in children, type of therapeutic response.
 The study aimed to investigate the state of transcription factor and marker of intracellular hypoxia HIF-1alfa in children with different degrees of change in basic clinical and laboratory parameters; to evaluate HIF-1alfa as a possible factor of stratification of activity grade of nephrotic syndrome.
 Methods. This case-control study was carried out in the duration from June 2018 to August 2020. The study was conducted on 35 selected patients with NS collected from the nephrology department, Pediatric Clinical Hospital №7 (Kyiv, Ukraine). Plasma samples were used to measure marker intracellular hypoxia HIF-1alfa. ANOVA followed by the post hoc Kruskal-Wallis test for multiple comparisons was used to test the significance of differences. GraphPad Prism 9.0 Software for Windows and Statistica 10.0 software used. P values <0,05 considered statistically significant.
 Results. Three groups of children with different activity grades were stratified on basis of indicators of proteinuria levels, total blood protein, blood alpha2-globulin levels, serum cholesterol levels, and edema. 1st-grade group found to have a mild increase of HIF-1alfa up to 185-195 a.u. proteinuria 3,5-5,5 g/24 h, total blood protein 47-53 g/L, alfa2-globulins level in blood 20-23 g/L, serum cholesterol level 6-8,5 mMol/L, edema - 1-1.6 points. 2nd grade group found to have moderate increase of HIF-1alfa up to 195,1-205 a.u., proteinuria 5,51-8,5 g/24 h, total blood protein 46,9-40 g/L, alfa2-globulins level in blood 23,1-27 g/L, serum cholesterol level 8.51-10,5 mMol/L, edema 1.61-2.2 points. 3rd-grade group found to have pronounced increase of HIF-1alfa up to 205,1-220 a.u., proteinuria 8,51-14 g/24 h, total blood protein 39,9-32 g/L, alfa2-globulins level in blood 27,1-30 g/L, serum cholesterol level 10.51-13.5 mMol/L, edema 2.21-3 points. Higher HIF-1alfa level appears in children with NS and frequent relapses as compared to the group with rare relapses.
 Conclusion. Thus, the increase of HIF-1 alpha to the level of 185-205 a.u., which corresponds to the I-II degree of activity in children with NS can be used as a starting point and therapeutic window for specific anti-hypoxic and antioxidant interventions. Determination of HIF-1 alpha levels in children with NS can be used as a factor for stratification of the activity grade.

HYPOXIC PRECONDITIONING AMELIORATES ISCHEMIA-INDUCED DAMAGE OF ISOLATED RAT ISLETS

Aim: Islet isolation results in disruption of the native islet vascular network until posttransplant islet revascularisation is completed. Prolonged exposure to a hypoxic and nutrient-depleted environment has detrimental effects on morphological and functional integrity of isolated islets. In solid organ transplantation it was shown that short sublethal periods of anoxia can induce adaptive mechanisms in the affected tissue offering protection against subsequent potentially lethal hypoxic insults. This study was aimed to explore the potential of hypoxic preconditioning for isolated islets. Methods: Rat islets, isolated from 20 non-heartbeating donors, were subjected either to 2 x 2 min-periods of anoxia, intermitted by a 2 min-period of oxygen supply, or to sham-treatment. Hypoxic preconditioning and sham-treatment were followed by 4 hours of recovery in normoxia prior to 24 hr-culture at 1.5% oxygen. Islet characterisation included yield of islet equivalents (IEQ) or islet particle number (IN), viability (FDA-PI), DNA (pico-green) and ATP (luciferase assay) content, intraislet reactive oxygen species (ROS) production (DCFH-DA), gene expression (qRT-PCR), and glucose stimulation index (2 vs 20 vs 2 mM). Data were normalised to islet DNA content and are presented as mean ± SEM. Results: Hypoxic preconditioning had no effect on islet survival when compared with sham-treatment (64 ± 7 vs 61 ± 7%). Compared with preconditioned islets, sham-treated controls were characterised by increased fragmentation when determined as IN/IEQ ratio (1.51 ± 0.18 vs 1.24 ± 0.13, p<0.05). Fragmentation corrrelated inversely with viability of sham-treated and preconditioned islets (61 ± 3 vs 66 ± 3 %, p<0.01). ATP (0.66 ± 0.14 vs 0.73 ± 0.20 pM/ng DNA) and insulin content (51.1 ± 12.5 vs 46.3 ± 11.7 ng/ng) were not altered by hypoxic preconditioning compared with sham-treatment. ROS production was reduced after hypoxic preconditioning compared with sham-treatment (645 ± 73 vs 858 ± 88 AU/ng, p<0.01). Islets of both experimental groups responded with insulin release after glucose challenge, but the stimulation index of preconditioned islets was significantly larger compared with sham-treated islets (2.39 ± 0.37 vs 2.09 ± 0.33, p<0.05). Whilst pro-apoptotic BAX and CHOP gene expression was reduced by 54 ± 15% (p<0.05) and 49 ± 8% (p<0.05), hypoxic preconditioning increased HIF-1 alpha and VEGF-A gene expression by 90 ± 41% (p<0.01) and 184 ± 65% (p<0.05), respectively. Conclusion: Although hypoxic preconditioning could not ameliorate ischaemia-induced loss of islets, islet morphology and function was significantly improved presumably as result of reduced intraislet ROS production. qRT-PCR-determined gene expression suggests that hypoxic preconditioning induces rescue mechanisms islets and mediates a significant anti-apoptotic effect. This study describes a new option for pretransplant treatment of isolated human islets. European Union’s Cooperation Programme FP7 (HEALTH-F2-2012-305746). Oxford NIHR Biomedical Research Centre.

(Z)-ligustilide increases ferroportin1 expression and ferritin content in ischemic SH-SY5Y cells

The mechanisms involved in the antioxidant and anti-apoptotic properties of (Z)-ligustilide (LIG) are not fully elucidated. Based on the accumulated data, we hypothesized that LIG might be able to reduce ischemia/reperfusion-induced increase in brain iron by regulating expression of iron transport proteins. We therefore investigated the effects of LIG on iron uptake protein transferrin receptor 1, iron exporter protein ferroportin 1, iron storage protein ferritin light chain and also hypoxia inducible factor-1 alpha (HIF-1 alpha) in oxygen-glucose deprivation/reoxygenation (OGD/R)-treated SH-SY5Y cells, using Western blot analysis. We demonstrated that LIG completely reversed the OGD/R-induced reduction of ferroportin 1, increased ferritin light chain content, and also suppressed the OGD-induced increase in HIF-1 alpha in SH-SY5Y cells. These findings imply that LIG might reduce the OGD/R-induced increase in brain iron by promoting cell iron release and iron corporation into ferritin, and also by inhibiting the HIF-1 alpha-induced increase in transferrin-bound iron uptake and iron accumulation in the brain, consequently attenuating iron-mediated free radical formation, oxidative stress and apoptosis.

Intranasal Oncolytic Virotherapy with CXCR4-Enhanced Stem Cells Extends Survival in Mouse Model of Glioma.

SummaryThe challenges to effective drug delivery to brain tumors are twofold: (1) there is a lack of non-invasive methods of local delivery and (2) the blood-brain barrier limits systemic delivery. Intranasal delivery of therapeutics to the brain overcomes both challenges. In mouse model of malignant glioma, we observed that a small fraction of intranasally delivered neural stem cells (NSCs) can migrate to the brain tumor site. Here, we demonstrate that hypoxic preconditioning or overexpression of CXCR4 significantly enhances the tumor-targeting ability of NSCs, but without altering their phenotype only in genetically modified NSCs. Modified NSCs deliver oncolytic virus to glioma more efficiently and extend survival of experimental animals in the context of radiotherapy. Our findings indicate that intranasal delivery of stem cell-based therapeutics could be optimized for future clinical applications, and allow for safe and repeated administration of biological therapies to brain tumors and other CNS disorders.

Heat-shock-protein 90 protects from downregulation of HIF-1α in calcineurin-induced myocardial hypertrophy

Aim of the studyCapillary/myocyte mismatch is a hallmark of maladaptive myocardial hypertrophy, but the exact mechanisms of this phenomenon remain unknown. We therefore aimed to evaluate the role of calcineurin A in the regulation of hypoxia-inducible factor-1 alpha (HIF-1 alpha) in a calcineurin overexpressing mouse model of myocardial hypertrophy. Methods and resultsMice overexpressing calcineurin A (CnATg) showed persistent upregulation of HIF-1 alpha protein without evidence of a reduction in capillary density despite progressive myocardial hypertrophy. Likewise, overexpression of calcineurin A in isolated cardiomyocytes induced upregulation of HIF-1 alpha protein. In contrast, NFAT-overexpression had no such effect, implying that NFAT-independent mechanisms were responsible for increased HIF-1 alpha levels. In addition, inhibition of HSP90 via the HSP90-inhibitor 17-AAG or siRNA abolished calcineurin A-induced upregulation of HIF-1 alpha. Consequently, upregulation of HIF-1 alpha target genes like VEGF-A, BNIP-3 or PGK-1 was also inhibited by either 17-AAG or siRNA directed against HSP90. Finally, when CnATg mice were treated with 17-AAG, they demonstrated reduced left ventricular function and capillary density. ConclusionsWe describe here for the first time that overexpression of the phosphatase calcineurin A prevents the development of a capillary/myocyte mismatch despite progressive myocardial hypertrophy. This effect was mediated by HSP-90 induced stabilization of HIF-1 alpha. Further work is needed to understand this unexpected cardioprotective effect of calcineurin A.

The Role of Hypoxia-Inducible Factor 1α in Allergic Rhinitis

Hypoxia-inducible factor (HIF) 1alpha is expressed under hypoxic conditions and plays an important role in immune and inflammatory responses. The role of HIF-1alpha in allergic airways has been investigated mainly in bronchial asthma. This study investigated the role of HIF-1alpha in mouse models and patients with allergic rhinitis (AR). Balb/c mice were sensitized with ovalbumin (OVA) and alum and were challenged intranasally with OVA. The HIF-1alpha inhibitor, 2-methoxyestradiol (2-ME), was administered intraperitoneally and multiple parameters of allergic responses were evaluated. HIF-1alpha and vascular endothelial growth factor (VEGF) mRNA and protein expression were also evaluated in patients with AR and a correlation analysis between mRNA expression and allergic symptoms was performed. In mouse models, the HIF-1alpha inhibitor 2-ME reduced allergic symptoms and eosinophilic infiltration into the nasal mucosa. 2-ME was found to suppress IgE production and inhibit local Th2 cytokine transcription in the nasal mucosa and systemic Th2 cytokine production by splenocytes. 2-ME also decreased HIF-1 and VEGF expression in nasal mucosa. An increase in HIF-1alpha and VEGF expression in the nasal mucosa of patients with AR was also observed. Our data suggest that HIF-1alpha plays an important role in mouse models and patients with AR. HIF-1alpha inhibitors induce antiallergic effects by decreasing both local and systemic Th2 cytokine (IL-4 and IL-5) production, IgE production, and eosinophil infiltration into the nasal mucosa in an AR model. HIF-1alpha and VEGF expression increased in the nasal mucosa of patients with AR, showing the role of HIF-1alpha in disease pathogenesis.

Fertility in a high-altitude environment is compromised by luteal dysfunction: the relative roles of hypoxia and oxidative stress

BackgroundAt high altitudes, hypoxia, oxidative stress or both compromise sheep fertility. In the present work, we tested the relative effect of short- or long-term exposure to high altitude hypobaric hypoxia and oxidative stress on corpora luteal structure and function.MethodsThe growth dynamics of the corpora lutea during the estrous cycle were studied daily by ultrasonography in cycling sheep that were either native or naïve to high-altitude conditions and that were supplemented or not supplemented with antioxidant vitamins. Arterial and venous blood samples were simultaneously drawn for determination of gases and oxidative stress biomarkers and progesterone measurement. On day five after ovulation in the next cycle, the ovaries were removed for immunodetection of luteal HIF-1alpha and VEGF and IGF-I and to detect IGF-II gene expression.ResultsThe results showed that both short- and long-term exposure to high-altitude conditions decreased luteal growth and IGF-I and IGF-II gene expression but increased HIF-1 alpha and VEGF immunoexpression. The level of plasma progesterone was also increased at a high altitude, although an association with increased corpus luteum vascularization was only found in sheep native to a high-altitude location. Administration of antioxidant vitamins resulted in a limited effect, which was restricted to decreased expression of oxidative stress biomarkers and luteal HIF-1alpha and VEGF immunoexpression.ConclusionsExposure of the sheep to high-altitude hypobaric hypoxia for short or long time periods affects the development and function of the corpus luteum. Moreover, the observed association of oxidative stress with hypoxia and the absence of any significant effect of antioxidant vitamins on most anatomical and functional corpus luteum traits suggests that the effects of high altitude on this ovarian structure are mainly mediated by hypoxia. Thus, these findings may help explain the decrease in sheep fertility at a high altitude.

Prevention of Age-Related Macular Degeneration–Like Retinopathy by Rapamycin in Rats

Age-related macular degeneration, a neurodegenerative and vascular retinal disease, is the most common cause of blindness in the Western countries. Evidence accumulates that target of rapamycin is involved in aging and age-related diseases, including neurodegeneration. The target of rapamycin inhibitor, rapamycin, suppresses the senescent cell phenotype and extends life span in diverse species, including mice. Rapamycin decreases senescence-associated phenotypes in retinal pigment epithelial cells in culture. Herein, we investigated the effect of rapamycin on spontaneous retinopathy in senescence-accelerated OXYS rats, an animal model of age-related macular degeneration. Rats were treated with either 0.1 or 0.5 mg/kg rapamycin, which was given orally as a food mixture. In a dose-dependent manner, rapamycin decreased the incidence and severity of retinopathy. Rapamycin improved some (but not all) histological abnormalities associated with retinopathy. Thus, in retinal pigment epithelial cell layers, rapamycin decreased nuclei heterogeneity and normalized intervals between nuclei. In photoreceptor cells, associated neurons, and radial glial cells, rapamycin prevented nuclear and cellular pyknosis. More important, rapamycin prevented destruction of ganglionar neurons in the retina. Rapamycin did not exert any adverse effects on the retina in control disease-free Wistar rats. Taken together, our data suggest the therapeutic potential of rapamycin for treatment and prevention of retinopathy.

Hypoxia inducible factor-1α accumulation in steatotic liver preservation: Role of nitric oxide

To examine the relevance of hypoxia inducible factor (HIF-1) and nitric oxide (NO) on the preservation of fatty liver against cold ischemia-reperfusion injury (IRI). We used an isolated perfused rat liver model and we evaluated HIF-1alpha in steatotic and non-steatotic livers preserved for 24 h at 4 degrees C in University of Wisconsin and IGL-1 solutions, and then subjected to 2 h of normothermic reperfusion. After normoxic reperfusion, liver enzymes, bile production, bromosulfophthalein clearance, as well as HIF-1alpha and NO [endothelial NO synthase (eNOS) activity and nitrites/nitrates] were also measured. Other factors associated with the higher susceptibility of steatotic livers to IRI, such as mitochondrial damage and vascular resistance were evaluated. A significant increase in HIF-1alpha was found in steatotic and non-steatotic livers preserved in IGL-1 after cold storage. Livers preserved in IGL-1 showed a significant attenuation of liver injury and improvement in liver function parameters. These benefits were enhanced by the addition of trimetazidine (an anti-ischemic drug), which induces NO and eNOS activation, to IGL-1 solution. In normoxic reperfusion, the presence of NO favors HIF-1alpha accumulation, promoting also the activation of other cytoprotective genes, such as heme-oxygenase-1. We found evidence for the role of the HIF-1alpha/NO system in fatty liver preservation, especially when IGL-1 solution is used.

Abstract 4930: NADPH Oxidase 2 Regulates Stem/Progenitor Cell Mobilization via Modulating Hypoxic Gradient and Proteolytic Enzymes in Bone Marrow Following Hindlimb Ischemia

Bone marrow (BM) microenvironment, which is regulated by hypoxia and proteolytic enzymes, is crucial for stem/progenitor cells mobilization during postnatal neovascularization. We demonstrated that NADPH oxidase2 (Nox2)-derived reactive oxygen species (ROS) in BM play a role in ischemia-induced stem/progenitor mobilization and revascularization. However, role of Nox2 in regulating BM microenvironment remains unknown. Here we show that hindlimb ischemia of mice increases Nox2 expression (2.2-fold) and ROS production (7.2-fold) in BM cells with peak at day 3, which is cotemporaneous with increase in circulating Sca-1 + /Flk-1 + endothelial progenitor cells (2.0-fold). These increases are inhibited in Nox2-deficient mice. Using hypoxia bioprobe, BM section shows that endosteum region is hypoxic in basal steady-state. After contralateral hindlimb ischemia, hypoxic areas are expanded with an increase in HIF-1alpha and Nox2 expression throughout the BM peaking at day 3 in wild type (WT) mice, which are markedly reduced in Nox2-deficient mice. In parallel, hindlimb ischemia increases the expansion of cKit + Lin − cells (1.6-fold) and angiogenic CXCR4 + VEGFR1 + Lin low progenitor cells (31%) in WT mice, which are inhibited in Nox2-deficient mice. This is due to increase in apoptotic (annexin V+) Lin- cells (2.0-fold) and decrease in proliferative (BrdU+) primitive stem/progenitor cKit + /Sca1 + /Lin − cells (36%). Moreover, hindlimb ischemia increases Akt phosphorylation (2.2-fold), MT1-MMP (4.2-fold) expression, and decreases its membrane-anchored inhibitor, RECK (62%) in BM, which are inhibited in Nox2-deficient mice. In summary, Nox2-derived ROS in BM regulate expansion of stem/progenitors, thereby promoting local hypoxia that increases HIF-1alpha in response to hindlimb ischemia. They also activate proteolytic enzyme activity in BM, which may facilitate mobilizing stem/progenitor cells leading to reparative neovascularization. This research has received full or partial funding support from the American Heart Association, Midwest Affiliate (Illinois, Indiana, Iowa, Kansas, Michigan, Minnesota, Missouri, Nebraska, North Dakota, South Dakota &amp; Wisconsin).

Pharmacological Preconditioning of Mesenchymal Stem Cells with Trimetazidine (1-[2,3,4-Trimethoxybenzyl]piperazine) Protects Hypoxic Cells against Oxidative Stress and Enhances Recovery of Myocardial Function in Infarcted Heart through Bcl-2 Expression

Stem cell transplantation is a possible therapeutic option to repair ischemic damage to the heart. However, it is faced with a number of challenges including the survival of the transplanted cells in the ischemic region. The present study was designed to use stem cells preconditioned with trimetazidine (1-[2,3,4-trimethoxybenzyl]piperazine; TMZ), a widely used anti-ischemic drug for treating angina in cardiac patients, to increase the rate of their survival after transplantation. Bone marrow-derived rat mesenchymal stem cells (MSCs) were subjected to a simulated host tissue environment by culturing them under hypoxia (2% O(2)) and using hydrogen peroxide (H(2)O(2)) to induce oxidative stress. MSCs were preconditioned with 10 microM TMZ for 6 h followed by treatment with 100 microM H(2)O(2) for 1 h and characterized for their cellular viability and metabolic activity. The preconditioned cells showed a significant protection against H(2)O(2)-induced loss of cellular viability, membrane damage, and oxygen metabolism accompanied by a significant increase in HIF-1alpha, survivin, phosphorylated Akt (pAkt), and Bcl-2 protein levels and Bcl-2 gene expression. The therapeutic efficacy of the TMZ-preconditioned MSCs was evaluated in an in vivo rat model of myocardial infarction induced by permanent ligation of left anterior descending coronary artery. A significant increase in the recovery of myocardial function and up-regulation of pAkt and Bcl-2 levels were observed in hearts transplanted with TMZ-preconditioned cells. This study clearly demonstrated the potential benefits of pharmacological preconditioning of MSCs with TMZ for stem cell therapy for repairing myocardial ischemic damage.

Radiation‐induced HIF‐1α cell survival pathway is inhibited by soy isoflavones in prostate cancer cells

We previously showed that treatment of prostate cancer cells with soy isoflavones and radiation resulted in greater cell killing in vitro, and caused downregulation of NF-kappaB and APE1/Ref-1. APE1/Ref-1 functions as a redox activator of transcription factors, including NF-kappaB and HIF-1alpha. These molecules are upregulated by radiation and implicated in radioresistance of cancer cells. We extended our studies to investigate the role of HIF-1alpha survival pathway and its upstream Src and STAT3 molecules in isoflavones and radiation interaction. Radiation induced phosphorylation of Src and STAT3 leading to induction of HIF-1alpha. Genistein, daidzein or a mixture of soy isoflavones did not activate this pathway. These data were observed both in PC-3 (AR-) and C4-2B (AR+) androgen-independent cell lines. Pretreatment with isoflavones inhibited Src/STAT3/HIF-1alpha activation by radiation and nuclear translocation of HIF-1alpha. These findings correlated with decreased expression of APE1/Ref-1 and DNA binding activity of HIF-1alpha and NF-kappaB. In APE1/Ref-1 cDNA transfected cells, radiation caused a greater increase in HIF-1alpha and NF-kappaB activities but this effect was inhibited by pretreatment with soy prior to radiation. Transfection experiments indicate that APE1/Ref-1 inhibition by isoflavones impairs the radiation-induced transcription activity of NF-kappaB and HIF-1alpha. This mechanism could result in the inhibition of genes essential for tumor growth and angiogenesis, as demonstrated by inhibition of VEGF production and HUVECs tube formation. Our novel findings suggest that the increased responsiveness to radiation mediated by soy isoflavones could be due to pleiotropic effects of isoflavones blocking cell survival pathways induced by radiation including Src/STAT3/HIF-1alpha, APE1/Ref-1 and NF-kappaB.

In Vivo Bioluminescence Imaging Monitoring of Hypoxia-Inducible Factor 1α, a Promoter That Protects Cells, in Response to Chemotherapy

Bioluminescence imaging is a powerful technique that has shown that hypoxia-inducible factor 1 (HIF-1), a transcription factor that protects tumor cells from hypoxia, is up-regulated in tumors after radiation therapy. We tested the hypothesis that bioluminescence imaging would successfully and noninvasively depict an increase in HIF-1 in the novel therapeutic environment of chemotherapy and that, as in radiation therapy, the underlying mechanism involves inducible nitric oxide synthase originating in macrophages. Active HIF-1 consists of alpha and beta subunits that bind to promoter sequences in many genes, including those that protect endothelial cells, promote angiogenesis, and alter metastasis and tumor cell metabolism. We grew 4T1 murine breast carcinoma cells with an HIF-1alpha luciferase reporter construct to 7 mm in the right rear flanks of 18 Balb-C mice. The mice were evenly randomized to receive one of the following single intraperitoneal doses: maximum tolerated dose cyclophosphamide (231.5 mg/kg), maximum tolerated dose paclitaxel (10 mg/kg), or control saline solution. Immunohistochemical analysis of tumor sections from the cyclophosphamide and control groups was performed 10 days after treatment to assess the intensity and distribution of HIF-1alpha expression, hypoxia, macrophage infiltration, and expression of macrophage-derived inducible nitric oxide synthase in tumor tissues treated with maximum tolerated dose cyclophosphamide compared with control tumors. Cyclophosphamide, but not paclitaxel, significantly inhibited tumor growth and caused a significant increase in HIF-1alpha protein levels, which peaked at a 10-fold increase from baseline on day 10 after administration. In contrast, paclitaxel did not have an antitumor effect in this model and did not cause a significant increase in HIF-1alpha. Immunohistochemical analysis showed increased and more evenly dispersed levels of HIF-1alpha protein, macrophage infiltration, and expression of inducible nitric oxide synthase originating in macrophages after cyclophosphamide treatment. We successfully monitored increased expression of a tumor protective protein in a noninvasive manner. Such monitoring may be a means of detection of resistance to therapy, and it may be possible to use the monitoring findings to alter treatment strategies in real time. The tumor microenvironment seen at immunohistochemical analysis supports the hypothesized mechanism that the cytotoxic effects of radiation therapy that attract macrophages, causing the release of macrophage-derived inducible nitric oxide synthase and production of HIF-1alpha under aerobic conditions, also underlie chemotherapy. Such noninvasive imaging may be a means to development of therapeutic strategies that prevent HIF-1 up-regulation after chemotherapy treatments.

A HIF‐1α‐dependent autocrine feedback loop promotes survival of serum‐deprived prostate cancer cells

We previously reported that normoxic, serum-deprived prostate cancer (PCa) cells upregulate hypoxia-inducible factor-1alpha (HIF-1alpha) protein, which promotes survival during serum deprivation via insulin-like growth factor-2 (IGF-2) upregulation. This study investigated the molecular mechanism of autocrine regulation of HIF-1alpha, IGF-2 and cell survival in serum-deprived PC-3 and LNCaP PCa cells. Cell viability was assessed by trypan blue assay. PI3K activity was inhibited with LY294002, and PTEN overexpression. mRNA was assessed by RT-PCR, and IGF-2 protein by ELISA. Activated insulin-like growth factor-I receptor (IGF-IR) was detected by probing immunoprecipitated IGF-IR for phospho-tyrosine. IGF-IR activity was inhibited with IGF-2 neutralizing antibody and IGF-IR-specific siRNA. HIF-1alpha, phospho-Akt, total-Akt and IGF-IR protein was assessed by immunoblots. HIF-1alpha was suppressed with siRNA. We detected a time-dependent increase in Akt activation during serum deprivation, and inhibition of Akt activation attenuated the serum deprivation-mediated increase in HIF-1alpha and cell survival. Importantly, IGF-2 secretion significantly increased during serum deprivation, and was accompanied by increased activation of its receptor, IGF-IR. Additionally, inhibition of IGF-2 activity markedly attenuated the serum deprivation-mediated increase in IGF-IR and Akt activation, HIF-1alpha expression, and also its own transcription, suggesting autocrine regulation of HIF-1alpha expression via IGF-2. Cross-talk between IGF-2/ IGF-IR system and PI3K-Akt pathway was further demonstrated by findings wherein IGF-IR suppression inhibited Akt activation, and IGF-IR activation was inhibited following PI3K inhibition. Furthermore, HIF-1alpha suppression attenuated the serum deprivation-mediated increase in Akt and IGF-IR activation. Collectively, our study demonstrates existence of a pro-survival HIF-1alpha-dependent autocrine feedback loop in normoxic, serum-deprived PCa cells.

Hypoxia controls CD4+CD25+ regulatory T‐cell homeostasis via hypoxia‐inducible factor‐1α

Recent data suggest that hypoxia and its principal molecular signature HIF-1 (hypoxia-inducing factor-1) may tune down inflammation by dictating anti-inflammatory programs. We tested the effects of hypoxia and HIF-1alpha on the homeostasis of naturally occurring regulatory T cells (Treg) and their transcriptional activator Foxp3. Hypoxia induced a time-dependent increase in HIF-1alpha in mouse and human T cells. Hypoxia upregulated the expression of Foxp3 in Jurkat T cells, human and murine mononuclear cells. The effects of hypoxia on Foxp3 expression were HIF-1alpha-dependent as they were abolished upon transfection with short-interfering RNAs for HIF-1alpha and promoted by HIF-1alpha overexpression. Hypoxia increased the potency of Treg, as hypoxic CD4(+)CD25(+) lymphocytes were more effective than normoxic cells in suppressing the proliferation of CD4(+)CD25(-) effectors. In vivo expression of HIF-1alpha achieved by hydrodynamic injection of the respective naked DNA similarly induced an increase in Foxp3 expression and an increase in the number of functionally active Foxp3(+)CD4(+)CD25(+) Treg. Thus, hypoxia dictates an anti-inflammatory program by driving expression of HIF-1alpha that acts to increase the number and suppressive properties of naturally occurring CD4(+)CD25(+) Treg.

Prostaglandin F2alpha induces the normoxic activation of the hypoxia-inducible factor-1 transcription factor in differentiating 3T3-L1 preadipocytes: Potential role in the regulation of adipogenesis.

Prostaglandin F2alpha (PGF2alpha) is a potent paracrine inhibitor of adipocyte differentiation. Here we show that treatment of differentiating 3T3-L1 preadipocytes with PGF2alpha induces the expression of DEC1, a transcriptional repressor that has previously been implicated in the inhibition of adipogenesis in response to hypoxia as a downstream effector of the hypoxia-inducible factor-1 (HIF-1) transcription factor. Surprisingly, despite performing our experiments under normal ambient oxygen conditions, we find that treatment of differentiating 3T3-L1 preadipocytes with PGF2alpha also results in the marked activation of HIF-1, as measured by an increase in the accumulation of the HIF-1alpha regulatory subunit. However, unlike the effects of hypoxia, this PGF2alpha-induced normoxic increase in HIF-1alpha is not mediated by an increase in the stability of the HIF-1alpha polypeptide, rather we find that PGF2alpha selectively increases the expression of the alternatively spliced HIF-1alpha I.1 mRNA isoform. Significantly, we demonstrate that the shRNA-mediated knockdown of endogenous HIF-1alpha expression attenuates the PGF2alpha-induced expression of DEC1, overcomes the inhibitory effects of PGF2alpha on the expression of proadipogenic transcription factors C/EBPalpha and PPARgamma and partially rescues the PGF2alpha-induced inhibition of adipogenesis. Taken together, these results indicate that PGF2alpha promotes the activation of the HIF-1 transcription factor pathway under normal oxygen conditions, and highlight a potential role for the normoxic activation of the HIF-1/DEC1-pathway in mediating the inhibitory effects of PGF2alpha on adipocyte differentiation.

Bacterial cell wall products increases stabilization of HIF-1 alpha in an oligodendrocyte cell line preconditioned by cobalt chloride or desferrioxamine

We examined the effect of lipopolysaccharide (LPS) or lipotechoic acid (LTA) on the regulation of hypoxia inducible factor (HIF-1) alpha on the MO3.13 cells, a human oligodendroglial cell line. Our study shows that MO3.13 cells express the toll like receptors (TLR's) but do not increase cellular levels of HIF-1 alpha following exposure to bacterial cell wall products. When MO3.13 cells were preconditioned by desferrioxamine (DFO) or cobalt chloride (CoCl 2) and then treated with either LPS or LTA, HIF-1 alpha levels were higher than that induced by DFO or CoCl 2 alone. The increase in HIF-1 alpha was due to increased protein stability that was mediated by activation of the ERK-MAP kinase pathway.

HIF‐1α: A key survival factor for serum‐deprived prostate cancer cells

Hypoxia-inducible factor-1 alpha (HIF-1 alpha) is commonly overexpressed in prostate cancer (PCa) cells. As PCa cells are known to survive serum deprivation, we investigated the effect of prolonged serum deprivation on HIF-1 alpha expression, and the function of HIF-1 alpha in regulating the survival of normoxic serum-deprived PCa cells. HIF-1 alpha protein was assessed by immunoblots. Cell viability and proliferation were assessed by trypan blue assay and flow cytometric analysis. Transcriptional activity was assessed by luciferase reporter assay and RT-PCR. HIF-1 alpha expression was suppressed with siRNA. Activities of HIF-1 alpha-target genes were inhibited with neutralizing antibody. Prolonged serum deprivation is a potent inducer of HIF-1 alpha in PC-3 and LNCaP PCa cells, despite normal oxygen conditions. In contrast, cells grown in the presence of serum did not show HIF-1 alpha protein accumulation. Moreover, HIF-1 alpha protein increase during serum deprivation correlated with increased cell survival, while suppression of HIF-1 alpha expression significantly decreased PCa cell viability. Our results further demonstrate that HIF-1 alpha protein increase is due to increased HIF-1 alpha protein synthesis. First, there was no significant increase in HIF-1 alpha mRNA. Secondly, cycloheximide, a protein synthesis inhibitor, prevented HIF-1 alpha protein increase in serum-deprived PCa cells. Moreover, the expression of HIF-1 alpha-target genes, VEGF and IGF-2, was concomitantly increased in serum-deprived PCa cells, while suppression of HIF-1 alpha expression significantly inhibited their induction. Furthermore, inhibition of IGF-2 activity resulted in a significant decline in PCa cell survival. PCa cells counteract the stress of prolonged serum deprivation by upregulating HIF-1 alpha protein which increases IGF-2 expression to promote cell survival.

Desferoxamine preconditioning protects against cerebral ischemia in rats by inducing expressions of hypoxia inducible factor 1α and erythropoietin

To investigate whether desferoxamine (DFO) preconditioning can induce tolerance against cerebral ischemia and its effect on the expression of hypoxia inducible factor 1alpha (HIF-1alpha) and erythropoietin (EPO) in vivo and in vitro. Rat model of cerebral ischemia was established by middle cerebral artery occlusion with or without DFO administration. Infarct size was examined by TTC staining, and the neurological severity score was evaluated according to published method. Cortical neurons were cultured under ischemia stress which was mimicked by oxygen-glucose deprivation (OGD), and the neuron damage was assessed by MTT assay. Immunofluorescent staining was employed to detect the expressions of HIF-1alpha and EPO. The protective effect induced by DFO (decreasing the infarction volume and ameliorating the neurological function) appeared at 2 d after administration of DFO (post-DFO), lasted until 7 d and disappeared at 14 d (P < 0.05); the most effective action was observed at 3 d post-DFO. DFO induced tolerance of cultured neurons against OGD: neuronal viability was increased 23%, 34%, 40%, 48% and 56% at 8 h, 12 h, 24 h, 36 h, and 48 h, respectively, post-DFO (P < 0.05). Immunofluorescent staining found that HIF-1alpha and EPO were upregulated in the neurons of rat brain at 3 d and 7 d post-DFO; increase of HIF-1alpha and EPO appeared in cultured cortex neurons at 36 h and 48 h post-DFO. DFO induced tolerance against focal cerebral ischemia in rats, and exerted protective effect on OGD cultured cortical neurons. DFO significant induced the expression of HIF-1alpha and EPO both in vivo and in vitro. DFO preconditioning can protect against cerebral ischemia, which may be associated with the synthesis of HIF-1alpha and EPO.

UVB induces a biphasic response of HIF‐1α in cultured human keratinocytes

Hypoxia in the skin is important in chronic degenerative dermo-epidermal changes, inflammation, photoageing and carcinogenesis. In these processes, vascular endothelial growth factor (VEGF) plays a crucial role and is known to be affected by ultraviolet radiation (UVR). Hypoxia-inducible factor-1 (HIF-1) closely regulates the expression of VEGF in several experimental settings. We set out to study the impact of acute UVB irradiation on the level of HIF-1 as a major regulator of hypoxia-induced genes. Effects of UVB exposure on HIF-1alpha expression were investigated in HaCaT cells after a single irradiation by Western blots. Downstream target gene expression was measured by quantitative real-time polymerace chair reaction (PCR). UVB treatment resulted in an initial decrease of the HIF-1alpha protein level followed by a subsequent prolonged increase. If cells were exposed to additional UVB irradiation, another decrease in HIF-1alpha was provoked, similar to the original effect. The observed changes followed a strict timeline and were dose-dependent. The role of the PI3K/AKT pathway was examined. No change in the total level of AKT after UVB treatment was seen; however, its phosphorylation level was found to be markedly higher. In accordance with these observations, wortmannin, an inhibitor of PI3-kinase effectively blocked the UVB-induced increase in HIF-1alpha. In agreement with previous findings, UVB irradiation increased VEGF and haem oxygenase-1 mRNA levels determined by quantitative real-time PCR. It is concluded that changes in HIF-1alpha expression underlie the alterations in expression of VEGF upon UVB irradiation. Our findings indicate the involvement of PI3K in UVB-mediated HIF-1alpha upregulation.