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Normoxic Conditions (normoxic + condition)

Distribution by Scientific Domains

Medical Sciences	59%
Life Sciences	22%
Chemistry	9%

Selected Abstracts

Oestrogen Promotes Coronary Angiogenesis even under Normoxic Conditions

BASIC AND CLINICAL PHARMACOLOGY & TOXICOLOGY, Issue 3 2008
Mehdi Nematbakhsh
Oestrogen has angiogenic properties under hypoxic condition, and if oestrogen also induces angiogenesis under normoxic condition, it could be used in combination with other angiogenic therapies in the treatment of ischaemic heart disease. In this study, we evaluated the angiogenic effect of high-dose oestrogen treatment in normoxic rat heart tissue. Fifty-two ovariectomized rats were randomized in oestrogen-treated and control groups. 17,-Oestradiol (1 mg/week) and normal saline (1 mg/week) were administered intramuscularly in the treatment and control groups for 2 months. After that, coronary capillary density and coronary vessel permeability were measured. The serum vascular endothelial growth factor (VEGF) level was also measured before and after the treatment. The results indicate that coronary capillary density (number of capillary per square millimetre) and coronary vessel permeability (fluorescence intensity) were significantly higher in the oestrogen-treated group than in the control group (628 ± 26 per mm2 versus 540 ± 26 per mm2; P < 0.05 and 207 ± 10 versus 147 ± 19 per gram tissue; P < 0.05). Oestrogen treatment increased serum VEGF level in the oestrogen-treated group compared to the control group (52 ± 3 versus 33 ± 6 pg/ml; P < 0.05), but interestingly VEGF was also increased in the control group after placebo treatment. It seems that high-dose oestrogen administration has angiogenic properties even in normoxic conditions. These angiogenic properties may result from oestrogen's direct effect on VEGF or other mechanisms, such as endothelial progenitor cell mobilization. Because of the broad effect of oestrogen on angiogenic growth factors and endothelial cells, more studies are required to clarify angiogenic properties of high-dose oestrogen. [source]

Cardiac and coronary function in the Langendorff-perfused mouse heart model

EXPERIMENTAL PHYSIOLOGY, Issue 1 2009
Melissa E. Reichelt
The Langendorff mouse heart model is widely employed in studies of myocardial function and responses to injury (e.g. ischaemia). Nonetheless, marked variability exists in its preparation and functional properties. We examined the impact of early growth (8, 16, 20 and 24 weeks), sex, perfusion fluid [Ca2+] and pacing rate on contractile function and responses to 20 min ischaemia followed by 45 min reperfusion. We also assessed the impact of strain, and tested the utility of the model in studying coronary function. Under normoxic conditions, hearts from 8-week-old male C57BL/6 mice (2 mm free perfusate [Ca2+], 420 beats min,1) exhibited 145 ± 2 mmHg left ventricular developed pressure (LVDP). Force development declined by ,15% (126 ± 5 mmHg) with a reduction in free [Ca2+] to 1.35 mm, and by 25% (108 ± 3 mmHg) with increased pacing to 600 beats min,1. While elevated heart rate failed to modify ischaemic outcome, the lower [Ca2+] significantly improved contractile recovery (by >30%). We detected minimal sex-dependent differences in normoxic function between 8 and 24 weeks, although age modified contractile function in males (increased LVDP at 24 versus 8 weeks) but not females. Both male and female hearts exhibited age-related reductions in ischaemic tolerance, with a significant decline in recovery evident at 16 weeks in males and later, at 20,24 weeks, in females (versus recoveries in hearts at 8 weeks). Strain also modified tolerance to ischaemia, with similar responses in hearts from C57BL/6, 129/sv, Quackenbush Swiss and FVBN mice, but substantially greater tolerance in BALB/c hearts. In terms of vascular function, baseline coronary flow (20,25 ml min,1 g,1) was 50,60% of maximally dilated flows, and coronary reactive and functional hyperaemic responses were pronounced (up to 4-fold elevations in flow in hearts lacking ventricular balloons). These data indicate that attention to age (and sex) of mice will reduce variability in contractile function and ischaemic responses. Even small differences in perfusion fluid [Ca2+] also significantly modify tolerance to ischaemia (whereas modest shifts in heart rate do not impact). Ischaemic responses are additionally strain dependent, with BALB/c hearts displaying greatest intrinsic tolerance. Finally, the model is applicable to the study of vascular reactivity, providing large responses and excellent reproducibility. [source]

Dual effect of echinomycin on hypoxia-inducible factor-1 activity under normoxic and hypoxic conditions

FEBS JOURNAL, Issue 21 2007
Benoit Vlaminck
Hypoxia-inducible factor-1 (HIF-1) is now recognized as a possible target for cancer treatment. This transcription factor is responsible for the overexpression of several genes favouring cancer cell survival and inducing neo-angiogenesis. Echinomycin has recently been described to inhibit HIF-1 DNA binding and transcriptional activity. In this work, it is shown that echinomycin strongly inhibits the activity of HIF-1 under hypoxic conditions, and also interferes with the activity of other transcription factors. These results demonstrate the lack of specificity of this molecule. Moreover, it is demonstrated that echinomycin induces an increase in HIF-1 activity under normoxic conditions, parallel to an increase in the expression of HIF-1 target genes. This effect is caused by an increase in HIF-1, protein level, resulting from an increase in the transcription of the HIF-1A gene in the presence of a low concentration of echinomycin. Transfection experiments with HIF-1, promoter constructs revealed the presence of an Sp1 binding element responsive to echinomycin. Furthermore, echinomycin enhanced Sp1 activity, as measured by the use of a specific reporter system. These findings show, for the first time, that echinomycin has a dual effect on HIF-1 activity under normoxic and hypoxic conditions, demonstrating that this molecule cannot be used in cancer treatment. [source]

Hypoxia is an inducer of vasodilator agents in peritoneal macrophages of cirrhotic patients

HEPATOLOGY, Issue 5 2002
Pilar Cejudo-Martín
The aim of the investigation was to assess whether hypoxia induces the production of endogenous vasoactive peptides in macrophages of cirrhotic patients with ascites because low tissue oxygenation is a relatively frequent event in these patients. Peritoneal macrophages were isolated from ascites, seeded on well plates, and cultured at different times under hypoxic (5% O2) or normoxic conditions (21% O2). Then, accumulation of vasoactive peptides sensitive to hypoxia including endothelin-1 (ET-1), vascular endothelial growth factor (VEGF), and adrenomedullin (ADM) was measured. Only VEGF and ADM were constitutively secreted, and hypoxia further stimulated the release of these vasodilator peptides. In concordance, increased messenger RNA (mRNA) levels of VEGF and ADM were found at culturing macrophages in hypoxia. This characteristic response was not observed in circulating monocytes of either cirrhotic patients or healthy subjects. Next the expression of the transcription factor, hypoxia inducible factor 1 (HIF-1), was analyzed. Expression of HIF-1, and HIF-1, messengers and HIF-1, protein subunit remained unchanged regardless of O2 tension, whereas HIF-1, protein subunit was overexpressed under hypoxic conditions. Moreover, conditioned medium from macrophages cultured under hypoxic conditions promoted a larger nitric oxide (NO) release in endothelial cells than that of normoxic macrophages. In conclusion, these data indicate that hypoxia induces the synthesis of VEGF and ADM in macrophages of cirrhotic patients, likely through HIF-1,enhanced transcriptional activity. These data suggest that a local reduction in O2 tension could enhance the synthesis of macrophage-derived vasodilators, thus aggravating the circulatory disturbance of these patients. [source]

Selective induction of mucin-3 by hypoxia in intestinal epithelia

JOURNAL OF CELLULAR BIOCHEMISTRY, Issue 6 2006
Nancy A. Louis
Abstract Epithelial cells line mucosal surfaces (e.g., lung, intestine) and critically function as a semipermeable barrier to the outside world. Mucosal organs are highly vascular with extensive metabolic demands, and for this reason, are particularly susceptible to diminished blood flow and resultant tissue hypoxia. Here, we pursue the hypothesis that intestinal barrier function is regulated in a protective manner by hypoxia responsive genes. We demonstrate by PCR confirmation of microarray data and by avidin blotting of immunoprecipitated human Mucin 3 (MUC3), that surface MUC3 expression is induced in T84 intestinal epithelial cells following exposure to hypoxia. MUC3 RNA is minimally detectable while surface protein expression is absent under baseline normoxic conditions. There is a robust induction in both the mRNA (first evident by 8 h) and protein expression, first observed and maximally expressed following 24 h hypoxia. This is followed by a subsequent decline in protein expression, which remains well above baseline at 48 h of hypoxia. Further, we demonstrate that this induction of MUC3 protein is associated with a transient increase in the barrier restorative peptide, intestinal trefoil factor (ITF). ITF not only colocalizes with MUC3, by confocal microscopy, to the apical surface of T84 cells following exposure to hypoxia, but is also found, by co-immunoprecipitation, to be physically associated with MUC3, following 24 h of hypoxia. In exploration of the mechanism of hypoxic regulation of mucin 3 expression, we demonstrated by luciferase assay that the full-length promoter for mouse Mucin 3 (Muc3) is hypoxia-responsive with a 5.08,±,1.76-fold induction following 24 h of hypoxia. Furthermore, analysis of both the human (MUC3A) and mouse (Muc3) promoters revealed potential HIF-1 binding sites which were shown by chromatin immunoprecipitation to bind the pivotal hypoxia-regulating transcription factor HIF-1,. Taken together, these studies implicate the HIF-1, mediated hypoxic induced expression of mucin 3 and associated ITF in the maintenance of intestinal barrier function under hypoxic conditions. J. Cell. Biochem. 99: 1616,1627, 2006. © 2006 Wiley-Liss, Inc. [source]

Effect of Sublethal Hypoxia on the Immune Response and Susceptibility of Channel Catfish, Ictalurus punctatus, to Enteric Septicemia

JOURNAL OF THE WORLD AQUACULTURE SOCIETY, Issue 1 2007
Thomas L. Welker
The effect of sublethal hypoxia exposure on stress and immune responses and susceptibility to Edwardsiella ictaluri infection in juvenile channel catfish, Ictalurus punctatus, was investigated. Fish were monitored for temporal changes in glucose and cortisol concentrations before, during, and after 2 h exposure to sublethal hypoxia (<2 mg/L dissolved oxygen [DO]) and when maintained under normoxic conditions (6.0 ± 0.3 mg/L DO). Both blood glucose and plasma cortisol increased significantly in response to hypoxic conditions. Fish exposed to hypoxic or normoxic conditions were challenged with a high dose (1.3 × 107 colony-forming units [CFU]/mL) or a low dose (1.3 × 105 CFU/mL) of E. ictaluri or sterile culture broth by 30-min immersion bath. Approximately 1% of fish in both the normoxic and the hypoxic groups died when challenged with the low dose of E. ictaluri. However, when challenged with the high dose of E. ictaluri, catfish exposed to hypoxic conditions had significantly higher cumulative mortality (36 ± 12.1%) than those maintained under normoxic conditions (12 ± 1.1%). Total hemolytic complement and bactericidal activities and antibody response were lower in hypoxia-exposed channel catfish, indicating that increased susceptibility of channel catfish to E. ictaluri may be the result of the immunosuppressive effects of the stress response to hypoxia. [source]

Effect of Oxygen Saturation in Water on Reproductive Performances of Pacu Piaractus brachypomus

JOURNAL OF THE WORLD AQUACULTURE SOCIETY, Issue 4 2003
Konrad Dabrowski
Broodstock pacu Piaractus brachypomus as well as their eggs during their embryonic development were exposed to either normoxia (5.5,7.5 mg O2/L) or hypoxia (2.0,4.5 mg O2/L) conditions. The plasma concentrations of 11-ketotestosterone in males and estradiol-17, in females, as well as that of their precursor testosterone (T) were significantly (P < 0.01) higher in fish maintained under normoxic conditions than in fish exposed to hypoxia. After ovulation and spermiation induced by hormonal treatments, the plasma concentrations of T and 17,20,-dihydroxy-4-pregnen-3-one (17,20,P) significantly (P 0.05) increased in both sexes under both normoxic and hypoxic conditions. The plasma levels of T and 17,20,P achieved under normoxic conditions were higher than the ones recorded under hypoxia, except for those of 17,20,P in males. Males responded positively to the hormonal treatments, and the concentration of spermatozoa was 10.5 ± 0.8 109/mL under both oxygen conditions. Hypoxia resulted in significantly lower survival of embryos (17.3 ± 28%) in comparison to normoxic conditions (68.5 ± 25%). Moreover, larval deformities were found when exposed to hypoxia (91.6 ± 6%). During embryonic development of this species 4 mg/L of oxygen is tolerated at 26,27 C without negative impact. We conclude that despite the highly adaptable nature of adult pacu to environmental hypoxia, oxygen concentrations below 4 mg/L severely impacted survival of embryos. [source]

Simultaneous separation of intracellular and extracellular lactate NMR signals of human erythrocytes

MAGNETIC RESONANCE IN MEDICINE, Issue 2 2007
Götz Kohler
Abstract Intracellular/extracellular lactate (Lac) distribution has been determined before in human and animal erythrocytes (red blood cells [RBCs]) with various methods. However, all previous methods determine intra- and extracellular Lac separately or indirectly. Now, 13C-NMR spectroscopy has been used to monitor intra- and extracellular Lac simultaneously in intact RBCs. Isolated human RBCs were incubated with [3- 13C]-Lac, [3- 13C]-pyruvate (Pyr), and [1- 13C]-glucose (Gluc). A distortionless enhancement by polarization transfer (DEPT) sequence was used (TR = 3.3 s, N = 128) to monitor the 13C-NMR resonances in both compartments. The intra- and extracellular methyl group resonances of Lac and Pyr were clearly separated by 9.6 Hz and 7.0 Hz, respectively, under normoxic conditions due to the RBC chemical-shift effect. The results show that the chemical-shift effect of RBCs is convenient to monitor intra- and extracellular Lac simultaneously in intact RBCs under normoxic conditions. Magn Reson Med 58:213,217, 2007. © 2007 Wiley-Liss, Inc. [source]

Retinal Endothelial Angiogenic Activity: Effects of Hypoxia and Glial (Müller) Cells

MICROCIRCULATION, Issue 7 2004
YOUSEF YAFAI
ABSTRACT Objective: To explore the impact of retinal glial (Müller) cells on survival and neovascularization-related activities of cultured retinal endothelial cells under normoxic and hypoxic conditions. Methods: Bovine retinal endothelial cells (BRECs) were cultured under normoxia or hypoxia (0.5% O2) either alone, together with the human Müller cell line MIO-M1, or in normoxia- or hypoxia-conditioned media of MIO-M1 cells. Cell number, proliferation, apoptotic cell death, and migration of BRECs were determined. Results: Exposure of BRECs to hypoxia for 24 h decreased the number of adherent cells and the proliferation rate, but increased apoptosis and cell migration. Increased apoptosis and decreased proliferation of the BRECs occurred also in the presence of conditioned media of MIO-M1 cells. Under normoxic conditions, co-culture with MIO-M1 cells resulted in increased proliferation, but decreased apoptosis and migration rates of BRECs. Under hypoxic conditions, the Müller cells released elevated amounts of VEGF but their presence decreased proliferation, apoptosis and the migration rates of BRECs. Conclusions: Hypoxia inhibits the proliferation of retinal endothelial cells. Müller cells release soluble mediators that enhance this hypoxia-mediated effect but, under certain conditions (i.e., in co-culture), may protect retinal endothelial cells from apoptosis, thus supporting their survival. Altogether the findings indicate that the key signal necessary to trigger retinal endothelial proliferation under hypoxia remains to be determined. [source]

A Rox1-independent hypoxic pathway in yeast.

MOLECULAR MICROBIOLOGY, Issue 4 2000
Antagonistic action of the repressor Ord, activator Yap1 for hypoxic expression of the SRP1/TIR1 gene
Hypoxic SRP1/TIR1 gene expression depends on the absence of haem but is independent of Rox1-mediated repression. We have found a new hypoxic pathway involving an antagonistic interaction between the Ixr1/Ord1 repressor and the Yap1 factor, a transcriptional activator involved in oxidative stress response. Here, we show that Ord1 repressed SRP1 gene expression under normoxia and hypoxia, whereas Yap1 activated it. Ord1 and Yap1 have been shown to bind the SRP1 promoter in a region extending from ,299 to ,156 bp upstream of the start codon. A typical AP-1 responsive element lying from ,247 to ,240 bp allows Yap1 binding. Internal deletion of sequences within the SRP1 promoter were introduced. Two regions were characterized at positions ,299/,251 and ,218/,156 that, once removed, resulted in a constitutive expression of SRP1 in a wild-type strain under normoxic conditions. Deletion of both these two sequences allowed the bypass of YAP1 requirement in a ,yap1 strain, whereas these two internal deletions did not yield increased expression in a ,ord1 strain compared with the full-length promoter. Both a single ,ord1 mutant and a doubly disrupted ,yap1 ,ord1 strain yielded normoxic constitutive SRP1 expression and increased hypoxic SRP1 induction, thereby demonstrating that ord1 is epistatic to yap1. Thus, Yap1 is not directly involved in SRP1 induction by hypoxia, but is necessary to counteract the Ord1 effect. [source]

Proteomic analysis of Aspergillus nidulans cultured under hypoxic conditions

PROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 1 2009
Motoyuki Shimizu
Abstract The fungus Aspergillus nidulans reduces nitrate to ammonium and simultaneously oxidizes ethanol to acetate to generate ATP under hypoxic conditions in a mechanism called ammonia fermentation (Takasaki, K. et al.. J. Biol. Chem. 2004, 279, 12414,12420). To elucidate the mechanism, the fungus was cultured under normoxic and hypoxic (ammonia fermenting) conditions, intracellular proteins were resolved by 2-DE, and 332 protein spots were identified using MALDI MS after tryptic digestion. Alcohol and aldehyde dehydrogenases that play key roles in oxidizing ethanol were produced at the basal level under hypoxic conditions but were obviously provoked by ethanol under normoxic conditions. Enzymes involved in gluconeogenesis, as well as the tricarboxylic and glyoxylate cycles, were downregulated. These results indicate that the mechanism of fungal energy conservation is altered under hypoxic conditions. The results also showed that proteins in the pentose phosphate pathway as well as the metabolism of both nucleotide and thiamine were upregulated under hypoxic conditions. Levels of xanthine and hypoxanthine, deamination products of guanine and adenine were increased in DNA from hypoxic cells, indicating an association between hypoxia and intracellular DNA base damage. This study is the first proteomic comparison of the hypoxic responses of A. nidulans. [source]

Oestrogen Promotes Coronary Angiogenesis even under Normoxic Conditions

Hypoxia enhances proliferation of mouse embryonic stem cell-derived neural stem cells

BIOTECHNOLOGY & BIOENGINEERING, Issue 2 2010
Carlos A.V. Rodrigues
Abstract Neural stem (NS) cells can provide a source of material with potential applications for neural drug testing, developmental studies, or novel treatments for neurodegenerative diseases. Herein, the ex vivo expansion of a model system of mouse embryonic stem (mES) cell-derived NS cells was characterized and optimized, cells being cultivated under adherent conditions. Culture was first optimized in terms of initial cell plating density and oxygen concentration, known to strongly influence brain-derived NS cells. To this end, the growth of cells cultured under hypoxic (2%, 5%, and 10% O2) and normoxic (20% O2) conditions was compared. The results showed that 2,5% oxygen, without affecting multipotency, led to fold increase values in total cell number about twice higher than observed under 20% oxygen (20-fold vs. 10-fold, respectively) this effect being more pronounced when cells were plated at low density. With an optimal cell density of 104,cells/cm2, the maximum growth rates were 1.9,day,1 under hypoxia versus 1.7,day,1 under normoxia. Cell division kinetics analysis by flow cytometry based on PKH67 tracking showed that when cultured in hypoxia, cells are at least one divisional generation ahead compared to normoxia. In terms of cell cycle, a larger population in a quiescent G0 phase was observed in normoxic conditions. The optimization of NS cell culture performed here represents an important step toward the generation of a large number of neural cells from a reduced initial population, envisaging the potential application of these cells in multiple settings. Biotechnol. Bioeng. 2010;106: 260,270. © 2009 Wiley Periodicals, Inc. [source]

Brief, repeated, oxygen-glucose deprivation episodes protect neurotransmission from a longer ischemic episode in the in vitro hippocampus: role of adenosine receptors

BRITISH JOURNAL OF PHARMACOLOGY, Issue 2 2003
Anna Maria Pugliese
Ischemic preconditioning in the brain consists of reducing the sensitivity of neuronal tissue to further, more severe, ischemic insults. We recorded field epsps (fepsps) extracellularly from hippocampal slices to develop a model of in vitro ischemic preconditioning and to evaluate the role of A1, A2A and A3 adenosine receptors in this phenomenon. The application of an ischemic insult, obtained by glucose and oxygen deprivation for 7 min, produced an irreversible depression of synaptic transmission. Ischemic preconditioning was induced by four ischemic insults (2 min each) separated by 13 min of normoxic conditions. After 30 min, an ischemic insult of 7 min was applied. This protocol substantially protected the tissue from the irreversible depression of synaptic activity. The selective adenosine A1 receptor antagonist, 8-cyclopentyl-1,3-dipropylxanthine (DPCPX, 100 nM), completely prevented the protective effect of preconditioning. The selective adenosine A2A receptor antagonist 4-(2-[7-amino-2-(2-furyl)[1,2,4]triazolo[2,3- a][1,3,5]triazin-5-ylamino]ethyl)phenol (ZM 241385, 100 nM) did not modify the magnitude of fepsp recovery compared to control slices. The selective A3 adenosine receptor antagonists, 3-propyl-6-ethyl-5[ethyl(thio)carbonyl]-2-phenyl-4-propyl-3-pyridinecarboxylate (MRS 1523, 100 nM) significantly improved the recovery of fepsps after 7 min of ischemia. Our results show that in vitro ischemic preconditioning allows CA1 hippocampal neurons to become resistant to prolonged exposure to ischemia. Adenosine, by stimulating A1 receptors, plays a crucial role in eliciting the cell mechanisms underlying preconditioning; A2A receptors are not involved in this phenomenon, whereas A3 receptor activation is harmful to ischemic preconditioning. British Journal of Pharmacology (2003) 140, 305,314. doi:10.1038/sj.bjp.0705442 [source]

Activation and potentiation of the NO/cGMP pathway by NG -hydroxyl- L -arginine in rabbit corpus cavernosum under normoxic and hypoxic conditions and ageing

BRITISH JOURNAL OF PHARMACOLOGY, Issue 1 2003
Javier Angulo
When nitric oxide synthase (NOS) produces NO from NG -hydroxy- L -arginine (OH-arginine) instead of L -arginine, the total requirement of molecular oxygen and NADPH to form NO is reduced. The aim of this work was to evaluate the effects of OH-arginine on the contractility of rabbit corpus cavernosum (RCC) and to compare the capacities of L -arginine and OH-arginine to enhance NO-mediated responses under normoxic and hypoxic conditions and in ageing, as models of defective NO production. OH-arginine, but not L -arginine, was able to relax phenylephrine-contracted rabbit trabecular smooth muscle. OH-arginine-induced relaxation was inhibited by the NOS-inhibitor, L -NNA (300 ,M), and by the guanylyl cyclase inhibitor, ODQ (20 ,M), while it was not affected by the cytochrome P450 oxygenase inhibitor, miconazole (0.1 mM). Administration of OH-arginine, but not L -arginine, produced a significant increment of cGMP accumulation in RCC tissue. Relaxation elicited by OH-arginine (300 ,M) was still observed at low oxygen tension. The increase of cGMP levels induced by ACh (30 ,M) in RCC was significantly enhanced by addition of OH-arginine (300 ,M) in normoxic conditions, as well as under hypoxia, while L -arginine did not alter the effects of ACh on cGMP accumulation. Endothelium-dependent and nitrergic nerve-mediated relaxations were both significantly reduced in RCC from aged animals (>20-months-old) when compared with young adult rabbits (5-months-old). Treatment with OH-arginine (300 ,M) significantly potentiated endothelium-dependent and neurogenic relaxation in corpus cavernosum from aged rabbits, while L -arginine (300 ,M) did not have significant effects. Results show that OH-arginine promotes NO-mediated relaxation of RCC and potentiates the NO-mediated responses induced by stimulation of endogenous NO generation in hypoxic and aged tissues. We propose that the use of OH-arginine could be of interest in the treatment of erectile dysfunction, at least in those secondary to defective NO production. British Journal of Pharmacology (2003) 138, 63,70. doi:10.1038/sj.bjp.0705027 [source]

Subcellular distribution of S100A4 and its transcriptional regulation under hypoxic conditions in gastric cancer cell line BGC823

CANCER SCIENCE, Issue 5 2010
Ruixiu Zhang
It is well known that S100A4 is overexpressed in many tumors and involved in tumor invasion and metastasis. But the regualtion of it is ill understood. We previously found that hypoxia mimicking cobalt chloride (CoCl2) enhanced the mRNA and protein expressions of the S100A4 gene in the gastric cancer cell line BGC823. In this study we found that S100A4 also displayed increased expression in BGC823 cells after exposure to real hypoxia (2.5% O2) as that by CoCl2 treatment. Moreover, S100A4 protein showed different subcellular distribution under real hypoxia compared with that by CoCl2 treatment or in normoxic conditions. To investigate the underlying molecular mechanism by which hypoxia regulates the expression of S100A4, we analyzed the regulatory sequences of the genes by bioinformatics and found a putative hypoxia responsive element (HRE) motif in the first intron of S1004. Furthermore, luciferase reporter assay showed that it is responsive to hypoxia. Electrophoretic mobility shift assay and chromatin immunoprecipitation assays demonstrated that hypoxia-inducible factor 1 (HIF-1) binds to the functional HRE in vitro and in vivo. The results provide evidence that S100A4 is a hypoxia-inducible gene, whose transcription is stimulated at least partly through the interaction of HIF-1 and HRE located at +329 to +334 of S100A4. (Cancer Sci 2010; 101: 1141,1146) [source]

Hypoxia-inducible factor-1, contributes to hypoxia-induced chemoresistance in gastric cancer

CANCER SCIENCE, Issue 1 2008
Lili Liu
Hypoxia induced drug resistance is a major obstacle in the development of effective cancer therapy. Our previous study revealed that hypoxia-inducible factor-1 (HIF-1), the major transcriptional factor significantly activated by hypoxia, was overexpressed in gastric vincristine-resistant cells SGC7901/vincristine (VCR) under normoxic conditions, which suggested that it was associated with drug resistance in gastric cancer cells. In the present study, a colony-forming assay revealed that hypoxia and forced HIF-1, expression increased maximal ,8.9-fold or ,14.8-fold of IC50 toward vincristine in gastric cancer cell lines SGC7901 and SGC7901/VCR, respectively (P < 0.01). Annexin-V/propidium iodide staining analysis revealed hypoxia or forced HIF-1, expression reduced apoptosis by 24% or 18% in SGC7901 cells (P < 0.05). Flow cytometry analysis of intracellular adriamycin revealed that hypoxia and forced expression of HIF-1, increased ,1.79-fold or ,2.36-fold of the adriamycin releasing index, respectively (P < 0.05). However, resistance acquisition subject to hypoxia in vitro and in vivo was suppressed by blocking HIF-1, expression with siRNA. We further demonstrated that HIF-1 , overexpression showed a 1.85-fold increased expression of Bcl-2 and a 2.16-fold decreased expression of Bax, and also showed significantly induced expression of p-gp and MRP1, which indicated that HIF-1, may confer hypoxia-induced drug resistance via inhibition of drug-induced apoptosis and decreases in intracellular drug accumulation. (Cancer Sci 2008; 99: 121,128) [source]

Short-period hypoxia increases mouse embryonic stem cell proliferation through cooperation of arachidonic acid and PI3K/Akt signalling pathways

CELL PROLIFERATION, Issue 2 2008
S. H. Lee
Hypoxia plays important roles in some early stages of mammalian embryonic development and in various physiological functions. This study examined the effect of arachidonic acid on short-period hypoxia-induced regulation of G1 phase cell-cycle progression and inter-relationships among possible signalling molecules in mouse embryonic stem cells. Hypoxia increased the level of hypoxia-inducible factor-1, (HIF-1,) expression and H2O2 generation in a time-dependent manner. In addition, hypoxia increased the levels of cell-cycle regulatory proteins (cyclin D1, cyclin E, cyclin-dependent kinase 2 (CDK2) and CDK4). Maximum increases in the level of these proteins and retinoblastoma phosphorylation were observed after 12,24 h of exposure to hypoxic conditions, and then decreased. Alternatively, the level of the CDK inhibitors, p21Cip1 and p27Kip1 were decreased. These results were consistent with the results of [3H]-thymidine incorporation and cell counting. Hypoxia also increased the level of [3H]-arachidonic acid release and inhibition of cPLA2 reduced hypoxia-induced increase in levels of the cell-cycle regulatory proteins and [3H]-thymidine incorporation. The level of cyclooxygenase-2 (COX-2) was also increased by hypoxia and inhibition of COX-2 decreased the levels of cell-cycle regulatory proteins and [3H]-thymidine incorporation. Indeed, the percentage of cells in S phase, levels of cell cycle regulatory proteins, and [3H]-thymidine incorporation were further increased in hypoxic conditions with arachidonic acid treatment compared to normoxic conditions. Hypoxia-induced Akt and mitogen-activated protein kinase (MAPK) phosphorylation was inhibited by vitamin C (antioxidant, 10,3 M). In addition, hypoxia-induced increase of cell-cycle regulatory protein expression and [3H]-thymidine incorporation were attenuated by LY294002 (PI3K inhibitor, 10,6 M), Akt inhibitor (10,6 M), rapamycin (mTOR inhibitor, 10,9 M), PD98059 (p44/42 inhibitor, 10,5 M), and SB203580 (p38 MAPK inhibitor, 10,6 M). Furthermore, hypoxia-induced increase of [3H]-arachidonic acid release was blocked by PD98059 or SB203580, but not by LY294002 or Akt inhibitor. In conclusion, arachidonic acid up-regulates short time-period hypoxia-induced G1 phase cyclins D1 and E, and CDK 2 and 4, in mouse embryonic stem cells through the cooperation of PI3K/Akt/mTOR, MAPK and cPLA2 -mediated signal pathways. [source]

Protective effects of triamcinolone acetonide upon the upregulation and phosphorylation of GAP 43 in an animal model of retinopathy of prematurity

ACTA OPHTHALMOLOGICA, Issue 6 2010
In Y. Chung
Acta Ophthalmol. 2010: 88: e217,e221 Abstract. Purpose:, The aim of the current study was to investigate the effects of triamcinolone acetonide (TA) upon the expression and phosphorylation of growth-associated protein 43 (GAP 43) in the retinas of oxygen-induced retinopathy (OIR) rats. Methods:, Oxygen-induced retinopathy was induced by exposing Sprague-Dawley rats to hyperoxia (80% oxygen) from postnatal (P) days 2,14 and then returning the rats to normoxic conditions. Triamcinolone acetonide or a conditioned saline (control) was injected intravitreally into the right or left eye, respectively, of OIR rats at P15. We then assessed the molecular and histological changes in the expression of GAP 43 and phospho-GAP 43 in OIR and control rat retinas, and also after treatment with TA by RT-PCR, Western blotting and immunohistochemistry. Results:, Growth-associated protein 43 mRNA levels were found to be increased by 1.6-fold (p = 0.001, n = 5) in the retinas of P18 OIR rats compared with the control rats. The protein levels of GAP 43 and phospho-GAP43 were found to be elevated in the retina of P18 OIR rats (2.40- and 2.39-fold greater than each control, p<0.001, n = 5, respectively). Immunoreactivities of GAP 43 and phospho-GAP 43 were stronger in the inner plexiform layer in OIR rat retinas compared with the control. However, treatment with TA attenuated GAP 43 and phospho-GAP 43 upregulation in the OIR retinas. Conclusion:, Our results indicate that GAP 43 and phospho-GAP 43 participate in retinal (potentially pathologic) changes following oxygen-induced damage. Triamcinolone acetonide protects the retinal damage in relatively hypoxic retinas of OIR rats. Therefore, TA treatment does not induce the expression and phosphorylation of GAP 43 in OIR rat retinas. [source]

Oxygen-sensing pathway for SK channels in the ovine adrenal medulla

CLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 10 2005
Damien J Keating
SUMMARY 1.,The intracellular pathways that modulate the opening of oxygen-sensitive ion channels during periods of hypoxia are poorly understood. Different tissues appear to use either NADPH oxidase or a rotenone-sensitive mechanism as an oxygen sensor. The aim of the present study was to identify the oxygen-sensing pathway in the oxygen-sensitive sheep adrenal medullary chromaffin cell (AMCC). 2.,The whole-cell patch-clamp technique was used to measure K+ currents in dissociated adult ovine chromaffin cells as well as SK channel currents expressed in the H4IIE cell line. 3.,Diphenyliodonium, an inhibitor of NADPH oxidase, had no effect on the hypoxia-evoked closure of K+ channels in primary AMCC, whereas the mitochondrial inhibitor rotenone abolished the hypoxia-evoked response. Both these compounds significantly reduced K+ current amplitude under normoxic conditions. 4.,One possible mechanism through which the oxygen sensor may modulate K+ channel activity is by altering the redox state of the cell. In sheep AMCC, altering the redox state by the addition of H2O2 to the extracellular solution increased K+ conductance. 5.,The oxygen-sensitive K+ (Ko2) channels in sheep chromaffin cells are from the SK family and the whole-cell conductance of cells expressing mouse SK2 or SK3, but not human SK1, was increased by H2O2 and decreased by the reducing agent dithiothreitol. 6.,These studies show that, in sheep AMCC, Ko2 channels are modulated via a rotenone-sensitive mechanism and that alteration of the cellular redox state mimics the change produced by alterations in Po2. In a heterologous expression system, SK2 and SK3 channels, the channels that initiate hypoxia-evoked changes in AMCC function, are modulated appropriately by changes in cellular redox state. [source]

Cardiac baroreflex control in humans during and immediately after brief exposure to simulated high altitude

CLINICAL PHYSIOLOGY AND FUNCTIONAL IMAGING, Issue 5 2002
Frédéric Roche
Summary To examine the baroreflex response in humans during and immediately after acute hypoxia exposure, the cardiac baroreflex sensitivity (BRS) was studied using adaptation of RR intervals in response to spontaneous systolic blood pressure fluctuations (sequences methodology) in 11 unacclimatized subjects. All measurements were made under fixed breathing rate, and realized consecutively at baseline level (20 min), at an inspired oxygen concentration of 11% (15 min) and again under normoxic conditions (20 min; recovery period). The spontaneous baroreflex response decreases progressively during hypoxic exposure, causing a tachycardic response at this FiO2 without any significant alteration of the systolic or diastolic blood pressure. The magnitude of decrease for this variable at the end of exposure averaged 42·9 ± 15·6%. The simultaneous spectral analysis of heart rate (HR) variability in hypoxic condition confirmed an alteration in the parasympathetic activity (HFnu: ,17·8 ± 30·9% versus basal conditions, P<0·01) counterbalanced by an exaggerated sympathetic activity (LFnu: +33 ± 42·4%, P<0·05) at the sinus node. Interestingly, we could observe an enhanced cardiac baroreflex response during the period following the inhalation of the hypoxic mixture (+130·6 ± 15·6% of basal conditions, P<0·001). There is a relationship with a significant and abrupt increase in the parasympathetic control of HR (mean HR reached 111 ± 8·1% of the mean basal HR, P<0·01). These results suggest that brief exposure to hypoxia under rate-controlled ventilation is associated with a significant alteration in the spontaneous cardiac baroreflex. This important cardiac autonomic imbalance is followed by a significant increase in the cardiac parasympathetic drive even after the disappearance of the hypoxic stimulus. [source]