Superoxide and nitric oxide--participation in cell communication.
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Animals↗
Biomedical subjects
A Görlach
Publications and source records attributed to A Görlach.
Thrombin activates the hypoxia-inducible factor-1 signaling pathway in vascular smooth muscle cells: Role of the p22(phox)-containing NADPH oxidase.
The heterodimeric transcription factor hypoxia-inducible factor-1 (HIF-1) is activated under hypoxic conditions, resulting in the upregulation of its target genes plasminogen activator inhibitor-1 (PAI-1) and vascular endothelial growth factor (VEGF). PAI-1 and VEGF are also induced in response to vascular injury, which is characterized by the activation of platelets and the coagulation cascade as well as the generation of reactive oxygen species (ROS). However, it is not known whether HIF-1 is also stimulated by thrombotic factors. We investigated the role of thrombin, platelet-associated growth factors, and ROS derived from the p22(phox)-containing NADPH oxidase in the activation of HIF-1 and the induction of its target genes PAI-1 and VEGF in human vascular smooth muscle cells (VSMCs). Thrombin, platelet-derived growth factor-AB (PDGF-AB), and transforming growth factor-beta(1) (TGF-beta(1)) upregulated HIF-1alpha protein in cultured and native VSMCs. This response was accompanied by nuclear accumulation of HIF-1alpha as well as by increased HIF-1 DNA-binding and reporter gene activity. The thrombin-induced expression of HIF-1alpha, PAI-1, and VEGF was attenuated by antioxidant treatment as well as by transfection of p22(phox) antisense oligonucleotides. Inhibition of p38 mitogen-activated protein kinase and phosphatidylinositol-3-kinase significantly decreased thrombin-induced HIF-1alpha, PAI-1, and VEGF expression. These findings demonstrate that the HIF-1 signaling pathway can be stimulated by thrombin and platelet-associated growth factors and that a redox-sensitive cascade activated by ROS derived from the p22(phox)-containing NADPH oxidase is crucially involved in this response.
Antioxidants↗
Thrombin causes vascular endothelial growth factor expression in vascular smooth muscle cells: role of reactive oxygen species.
Vascular endothelial growth factor (VEGF) has been implicated in the reendothelialization of the vascular wall after balloon injury. This study investigated whether thrombin, which is formed during activation of the coagulation cascade at sites of vascular injury, upregulates VEGF expression in vascular smooth muscle cells (VSMCs). VEGF expression was assessed in native and cultured VSMCs by Northern blot analysis and reverse transcription-polymerase chain reaction and the release of VEGF protein by immunoassay. alpha-Thrombin time- and concentration-dependently increased VEGF mRNA levels, mainly that mRNA coding for the soluble splice variant VEGF(164/165), and stimulated the release of VEGF protein. These effects required the proteolytic activity of thrombin and were mimicked by a thrombin receptor activating-peptide. Upregulation of VEGF expression was also induced by conditioned medium from alpha-thrombin-stimulated VSMCs. Both the early and the delayed alpha-thrombin-induced VEGF expressions were attenuated by antioxidants and by diphenyleneiodonium. alpha-Thrombin-induced VEGF release was significantly reduced by a platelet-derived growth factor (PDGF)-, a transforming growth factor (TGF)-beta-, and a basic fibroblast growth factor (bFGF)-neutralizing antibody. Thrombin caused a redox-sensitive upregulation of expression of VEGF in VSMCs through a direct and an indirect effect, which was dependent on the endogenous formation of PDGF, TGF-beta, and bFGF. Upregulation of VEGF expression may represent an important mechanism by which the coagulation cascade contributes to the regeneration of the endothelial lining at sites of balloon injury.
Acetylcysteine↗
Thrombin-induced MCP-1 expression involves activation of the p22phox-containing NADPH oxidase in human vascular smooth muscle cells.
UNLABELLED: Activation of vascular smooth muscle cells (VMSC) by thrombin induces the expression of the chemokine, monocyte chemoattractant protein-1 (MCP-1). We investigated in cultured human and rat VSMC whether reactive oxygen species (ROS) derived from the vascular NADPH oxidase contribute to this effect. Exposure of cultured VSMC to thrombin rapidly increased ROS formation, phosphorylation of p38 MAP kinase as well as the expression of MCP-1. Specific inhibition of the p22phox subunit of the vascular NADPH oxidase using either p22phox neutralizing antibody or p22phox antisense oligonucleotides attenuated thrombin-induced ROS generation. Furthermore, thrombin-induced p38 MAP kinase activation as well as MCP-1 expression were impaired by antioxidants as well as by p22phox antisense oligonucleotides. Inhibition of p38 MAP kinase diminished the thrombin-induced expression of MCP-1. CONCLUSION: Thrombin, by activating a p22phox-containing NADPH oxidase, elicits ROS generation and activation of p38 MAP kinase in VSMC. The subsequent induction of MCP-1 expression highligts the crucial role of the p22phox-containing NADPH oxidase in thrombin-induced signal transduction in VSMC.
Animals↗
Efficient translation of mouse hypoxia-inducible factor-1alpha under normoxic and hypoxic conditions.
The heterodimeric hypoxia-inducible factor-1 (HIF-1), consisting of the subunits HIF-1alpha and HIF-1beta/ARNT, is a master transcriptional regulator of oxygen homeostasis. Under hypoxic conditions, HIF-1alpha levels very rapidly increase, mostly due to protein stabilization. However, translational regulation of HIF-1alpha has not been directly analyzed so far. Mouse HIF-1alpha exists as two mRNA isoforms (termed mHIF-1alphaI.1 and mHIF-1alphaI. 2) containing structurally different 5'-termini which might modulate translation initiation. Whereas the in vitro translation efficiency of these two mRNA isoforms was about equal, the mHIF-1alphaI.2 5'-untranslated region (5'-UTR) conferred significantly higher in vivo luciferase reporter gene activity than the mHIF-1alphaI.1 5'-UTR. Similar corresponding luciferase mRNA levels indicate translational rather than transcriptional alterations. Reporter gene expression was not affected upon exposure of transiently transfected cells to hypoxia (1% oxygen). Direct assessment of translational regulation by polysomal profile analysis of HeLaS3 cells showed that HIF-1alpha (and to a lower extent ARNT) mRNA was found mainly in the translationally active polyribosomal fractions under both normoxic and hypoxic conditions. In contrast, the association of mRNAs for beta-actin and ribosomal protein L28 with the polyribosomal fractions was substantially reduced under hypoxic conditions, suggesting decreased overall protein synthesis. Thus, efficient translation of mouse HIF-1alpha in a situation where the general translation efficiency is reduced represents a prerequisite for the very rapid accumulation of HIF-1alpha protein upon exposure to hypoxia.
Animals↗
A gp91phox containing NADPH oxidase selectively expressed in endothelial cells is a major source of oxygen radical generation in the arterial wall.
Reactive oxygen species (ROS) play an important role in regulating vascular tone and intracellular signaling; the enzymes producing ROS in the vascular wall are, however, poorly characterized. We investigated whether a functionally active NADPH oxidase similar to the leukocyte enzyme, ie, containing the subunits p22phox and gp91phox, is expressed in endothelial cells (ECs) and smooth muscle cells (SMCs). Phorbol 12-myristate 13-acetate (PMA), a stimulus for leukocyte NADPH oxidase, increased ROS generation in cultured ECs and endothelium-intact rat aortic segments, but not in SMCs or endothelium-denuded arteries. NADPH enhanced chemiluminescence in all preparations. p22phox mRNA and protein was detected in ECs and SMCs, whereas the expression of gp91phox was confined to ECs. Endothelial gp91phox was identical to the leukocyte form as determined by sequence analysis. In contrast, mitogenic oxidase-1 (mox1) was expressed in SMCs, but not in ECs. To determine the functional relevance of gp91phox expression, experiments were performed in aortic segments from wild-type, gp91phox(-/-), and endothelial NO synthase (eNOS)(-/-) mice. PMA-induced ROS generation was comparable in aortae from wild-type and eNOS(-/-) mice, but was attenuated in segments from gp91phox(-/-) mice. Endothelium-dependent relaxation was greater in aortae from gp91phox(-/-) than from wild-type mice. The ROS scavenger tiron increased endothelium-dependent relaxation in segments from wild-type, but not from gp91phox(-/-) mice. These data demonstrate that ECs, in contrast to SMCs, express a gp91phox-containing leukocyte-type NADPH oxidase. This enzyme is a major source for arterial ROS generation and affects the bioavailability of endothelium-derived NO.
Acetylcholine↗
Genomic structure of the human p47-phox (NCF1) gene.
The cytosolic factor p47-phox, encoded by the NCF1 gene, is an essential component of the phagocyte NADPH-oxidase system. Upon activation of this multicomponent system, p47-phox translocates to the membrane and participates in the electron transfer from NADPH to molecular oxygen. A deficiency or absence of p47-phox is the most common autosomal form of chronic granulomatous disease (CGD). We have cloned and characterized the NCF1 gene from four bacteriophage clones, a P1 clone and genomic DNA from normal individuals. The gene is 15,236 base pairs long and includes 11 exons. It is 98.6% homologous in sequence to at least one pseudogene that maps to the same region of chromosome 7q11.23. Slightly more than half (50.37%) of the wild-type NCF1 gene consists of repetitive elements. In particular, the density of Alu sequences is high (1.4 Alu/kb); there are 21 Alu repeats interspersed through 10 introns. These findings are consistent with the observation that recombination events between the wild-type gene and its highly homologous pseudogenes account for the majority of potentially lethal mutations in p47-phox-deficient chronic granulomatous disease. Analysis of 1.96 kb of sequence 5' of the start of translation revealed a high homology (99.6%) between wild-type and pseudogene clones. Characterization of NCF1 establishes a foundation for detailed molecular analysis of p47-phox-deficient CGD patients as well as for the study of the regulation of the NCF1 gene and pseudogenes, both of which are present as full-length transcripts in normal individuals.
5' Untranslated Regions↗
Molecular characterization of the mouse p47-phox (Ncf1) gene and comparative analysis of the mouse p47-phox (Ncf1) gene to the human NCF1 gene.
The cytosolic factor p47-phox (NCF1) is a key component of the phagocyte NADPH-oxidase system, critical for microbicidal activity. The human p47-phox gene has been well characterized and resides on chromosome 7q11. Here we describe the molecular characterization of the mouse ortholog (Ncf1), which maps to distal chromosome 5, and compare the structure of the genes, commenting on the degree of homology. The mouse and human genes contain the same number of exons and introns, but the mouse gene is more compact (7.8 kb versus 15.2 kb). A percentage identity plot analysis comparing the human and mouse genes indicates that sequence homology is generally restricted to exons and does not include any large segment of introns or the 5' flanking sequence. The mouse gene also contains notably fewer repetitive elements than its human counterpart (34% versus 50%). The start of transcription of the mouse gene has been localized to within 12 nucleotides of the translation start site, similar to the human ortholog. Our findings provide an important foundation for investigating the evolutionary history of the p47-phox gene, particularly as it relates to understanding the molecular basis of the p47-phox-deficient autosomal recessive form of chronic granulomatous disease.
5' Untranslated Regions↗
Visual perception and stimulus orientation in cattle.
The pupil in the eye of adult cattle is oval under contraction with the long axis nearly horizontal. Based on simple optophysical facts it is hypothesised that visual perception in such eyes is different for stimuli with vertically-separated details rather than stimuli with horizontally-separated details. This hypothesis was tested with three adult dairy bulls using an operant conditioning technique. The bulls had to discriminate a solid white line from broken white lines with decreasing interspaces. They solved this task better when the stimuli were presented vertically rather than horizontally. This result is discussed in terms of visual acuity and related to the topographical anatomy of the eye, particularly the pupil.
Animals↗
Oxidative stress and expression of p22phox are involved in the up-regulation of tissue factor in vascular smooth muscle cells in response to activated platelets.
Vascular injury after balloon angioplasty results in the rapid activation of platelets leading to the release of growth factors and vasoactive substances. In addition, up-regulation of tissue factor (TF) and an increased production of reactive oxygen species (ROS) have been detected at sites of vascular injury. We investigated whether platelet-derived products (PDP) released from activated human platelets increase ROS production, resulting in the induction of TF expression in vascular smooth muscle cells (SMC). PDP induced a time- and concentration-dependent increase in ROS generation in cultured SMC that was mediated mainly by PDGF-AB and TGF-beta1 and impaired by the flavin inhibitor diphenylene iodonium. Increased ROS formation was associated with enhanced mRNA levels of the small NAD(P)H oxidase subunit p22phox or its smooth muscle isoform. Transient transfection with a p22phox antisense vector decreased PDP-induced ROS generation. PDP up-regulated TF mRNA expression, which was redox sensitive and reduced by transfection of the p22phox antisense vector. In addition, PDP-stimulated reporter gene activity of two TF promoter constructs was decreased by coexpression of the p22phox antisense vector. These results indicate that activated platelets up-regulate TF expression and that this response involves ROS generation and a p22phox-containing NAD(P)H oxidase in SMC.
Animals↗
Visual identification of small sizes by adult dairy bulls.
The objective of these trials was to measure the visual acuity of adult dairy bulls using a psychophysical approach. Three adult dairy bulls (2 Holstein Friesian and 1 Red Holstein) were trained to recognize a black disk and then to differentiate between that disk and a black annulus that had a white center. The diameter of the center of the annulus varied from 30 to 0.5 cm. Bulls could identify a white center as small as 1 cm. Because bulls had to discriminate between the black disk and the black annulus at a distance of at least 1.5 m, we calculated a visual angle of 23' (arc minutes) to describe the visual acuity of the bull. This acuity is much poorer than that of other ungulates, such as sheep, and even poorer than the acuity of younger cattle.
Animals↗
A p47-phox pseudogene carries the most common mutation causing p47-phox- deficient chronic granulomatous disease.
The predominant genetic defect causing p47-phox-deficient chronic granulomatous disease (A47 degrees CGD) is a GT deletion (DeltaGT) at the beginning of exon 2. No explanation exists to account for the high incidence of this single mutation causing a rare disease in an unrelated, racially diverse population. In each of 34 consecutive unrelated normal individuals, both the normal and mutant DeltaGT sequences were present in genomic DNA, suggesting that a p47-phox related sequence carrying DeltaGT exists in the normal population. Screening of genomic bacteriophage and YAC libraries identified 13 p47-phox bacteriophage and 19 YAC clones. The GT deletion was found in 11 bacteriophage and 15 YAC clones. Only 5 exonic and 33 intronic differences distinguished all DeltaGT clones from all wild-type clones. The most striking differences were a 30-bp deletion in intron 1 and a 20-bp duplication in intron 2. These results provide good evidence for the existence of at least one highly homologous p47-phox pseudogene containing the DeltaGT mutation. The p47-phox gene and pseudogene(s) colocalize to chromosome 7q11.23. This close linkage, together with the presence within each gene of multiple recombination hot spots, suggests that the predominance of the DeltaGT mutation in A47 degrees CGD is caused by recombination events between the wild-type gene and the pseudogene(s).
Bacteriophages↗
Visual discrimination in adult dairy bulls.
Adult Holstein-Friesian dairy bulls were trained to recognize a black disk and then to discriminate between that disk and smaller ones. The bulls learned these tasks, but much more slowly than did dairy calves. Achievement of a consistently high percentage of correct choices varied among bulls because of daily variation in the disposition of the bull, which seemed to affect willingness to concentrate on the experimental task. Nevertheless, all bulls demonstrated learning, and each bull remembered very well what he once had learned. A 36-cm disk was easily detected and discriminated from smaller disks. However, bulls were not able to discriminate between two disks that differed in area by less than a factor of 4. The ability to use visual cues, such as shapes and size of shapes, suggested that the visual system is important in the biology of bulls. The slow learning rate and the variability in the percentages of correct responses were not considered to be an indication of cognitive disabilities in general but rather a reflection of the daily disposition of the bull, which affected his willingness to cooperate.
Animals↗
pO2- and pH-gradients in multicellular spheroids and their relationship to cellular metabolism and radiation sensitivity of malignant human tumor cells.
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Humans↗
Effects of cobalt on haem proteins of erythropoietin-producing HepG2 cells in multicellular spheroid culture.
The hypoxia-induced increase of spectrophotometrically measured light absorption at 560 nm, considered as reduced cytochrome b, in HepG2 cells is diminished after exposure to cobalt chloride (50 or 100 microM) for 18-36 h. The redox state of cytochrome c and cytochrome aa3, however, remains stable, indicating a particular affinity of cytochrome b for cobalt. Erythropoietin production of HepG2 cells increases after application of cobalt chloride, whereas H2O2 production, as measured by the dihydrorhodamine technique, decreases. It is concluded that cobalt stimulates a signal cascade with cytochrome b as receptor and H2O2 as second messenger for regulating erythropoietin production.
Cells, Cultured↗
Effects of nIFN beta and rIFN gamma on growth and morphology of two human melanoma cell lines: comparison between two- and three-dimensional culture.
We compared the anti-proliferative effects of natural interferon beta (nIFN beta) and recombinant interferon gamma (rIFN gamma) on 2 human melanoma cell lines, IGRI and SK-Mel28, grown in 2-dimensional monolayer and in 3-dimensional spheroid culture. In monolayer culture, growth of both lines was inhibited in a dose-dependent manner by 5-day treatments with IFN in concentrations ranging between 1 and 5,000 IU/ml. Incubations with 120 IU/ml nIFN beta or 25 IU/ml rIFN gamma led to a 50% growth inhibition of IGRI cells. A 50% growth inhibition of SK-Me128 cells was obtained with 60 IU/ml nIFN beta, whereas even 5,000 IU/ml rIFN gamma inhibited the growth of this line by only 30%. Growing these melanoma cell lines in 3-dimensional spheroid culture for 5 days reduced their sensitivity to interferon. Growth inhibition values of 50% were achieved with 3,000 IU/ml rIFN gamma or 9,000 IU/ml nIFN beta for IGRI spheroids and 10,000 IU/ml nIFN beta for SK-Me128 spheroids, while 10,000 IU/ml rIFN gamma reduced the growth of SK-Me128 spheroids by only 25%. Outgrowth tests showed that the proliferative capacity after 5-day incubations with IFN was only reduced in IGRI spheroids treated with high doses of nIFN beta. The macroscopically observed increased density of interferon-treated spheroids could be confirmed by light microscopy as corresponding to reduced intercellular space in these spheroids. Scanning electron microscopy furthermore showed variations on the surface of IFN-treated spheroids as well as in cellular organization and structures between cells, hinting at a possible involvement of extracellular matrix substances in the reaction to interferons.(ABSTRACT TRUNCATED AT 250 WORDS)
Cell Division↗
The relationship of radiation sensitivity and microenvironment of human tumor cells in multicellular spheroid tissue culture.
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Adenocarcinoma↗
Photometric characteristics of haem proteins in erythropoietin-producing hepatoma cells (HepG2).
Erythropoietin (Epo)-producing hepatoma cells (HepG2) reveal, in addition to the cytochromes of the respiratory chain, a photometrically measurable haem signal with absorbance maxima at 559 nm and 427 nm, suggesting the presence of a b-type cytochrome. This activity exhibited a low midpoint potential, CO-binding spectra and reduction which was insensitive to both cyanide and antimycin. This haem possessed a 22 kDa subunit and might be part of an electron transfer chain similar to the NADPH oxidase, since the NADPH oxidase cytosolic activating factor (p47) could be identified by Western blot analysis. H2O2, which was detected inside the cells by confocal microscopy, might therefore be produced by the suggested electron transfer chain. This cyanide- and antimycin-insensitive but hypoxia-sensitive cytochrome b would be an attractive candidate for controlled Epo production in response to pO2.
Blotting, Western↗