PubMed Health⌕ Search

Biomedical subjects

J Fandrey

Publications and source records attributed to J Fandrey.

At least 55 records · Page 3Linked to original sources
PubMed1996

Neopterin activates transcription factor nuclear factor-kappa B in vascular smooth muscle cells.

We have previously shown that the pteridine compound neopterin stimulates inducible nitric oxide synthase (iNOS) gene expression in vascular smooth muscle cells in vitro. The mechanisms whereby neopterin exhibits these effects remained unclear. The present study demonstrates that neopterin induces the translocation of the transcription factor nuclear factor-kappa B (NF-kappa B) to the nucleus. Pretreatment of cells with the antioxidant pyrrolidine dithiocarbamate completely suppressed the effects of neopterin on NF-kappa B activation, iNOS gene expression, and nitric oxide release. From these data we conclude that neopterin activates the translocation of NF-kappa B subunits to the nucleus by modulating the intracellular redox state. This is one possible explanation for the impact of neopterin on iNOS gene expression.

Animals↗
PubMed1996

Oxygen supply and oxygen-dependent gene expression in differentiating embryonic stem cells.

Blastocyst-derived pluripotent mouse embryonic stem cells can differentiate in vitro to form so-called embryoid bodies (EBs), which recapitulate several aspects of murine embryogenesis. We used this in vitro model to study oxygen supply and consumption as well as the response to reduced oxygenation during the earliest stages of development. EBs were found to grow equally well when cultured at 20% (normoxia) or 1% (hypoxia) oxygen during the first 5 days of differentiation. Microelectrode measurements of pericellular oxygen tension within 13- to 14-day-old EBs (diameter 510-890 micron) done at 20% oxygen revealed efficient oxygenation of the EBs' core region. Confocal laser scanning microscopy analysis of EBs incubated with fluorescent dyes that specifically stain living cells confirmed that the cells within an EB were viable. To determine the EBs' capability to sense low oxygen tension and to specifically respond to low ambient oxygen by modulating gene expression we quantified aldolase A and vascular endothelial growth factor (VEGF) mRNAs, since expression of these genes is upregulated by hypoxia in a variety of cells. Compared with the normoxic controls, we found increased aldolase A and VEGF mRNA levels after exposing 8- to 9-day-old EBs to 1% oxygen. We propose that EBs represent a powerful tool to study oxygen-regulated gene expression during the early steps of embryogenesis, where the preimplantation conceptus resides in a fluid environment with low oxygen tension until implantation and vascularization allow efficient oxygenation.

Aerobiosis↗
PubMed1996

Interleukin 1 beta and phorbol ester induce tumour necrosis factor alpha production in a hepatic cell line (HepG2).

Tumour necrosis factor "alpha" (TNF "alpha") is a pleiotropic cytokine that is produced mainly by monocytes and macrophages. TNF "alpha" appears to be responsible for many of the inflammatory and necrotic changes seen in malignant or infectious liver diseases. In addition, blood levels of TNF "alpha" have been reported to be elevated in those with hepatic diseases. Although TNF "alpha" is synthesized mainly by monocytes and macrophages, its production has recently been found in nonhaemopoietic cells as well. Therefore we have used the human liver cell line HepG2 to test for the inducible production of TNF "alpha" in hepatic parenchymal cells. No constitutive TNF "alpha" gene expression was detected by quantitative reverse transcriptase-polymerase chain reaction (RT-PCR). However, treatment with the proinflammatory cytokine interleukin 1 "beta" (IL-1 "beta") or phorbol 12-myristate-acetate (PMA) led to a marked increase in TNF "alpha" mRNA levels. Maximal TNF "alpha" mRNA levels were observed after 3-h incubation periods, decreased thereafter and became undetectable after 12 h. The culture supernatant from cells treated with IL-1 "beta" or PMA contained significant amounts of TNF "alpha" protein which was immunologically detectable and biologically active. We believe that our report of inducible TNF "alpha" production in this widely available hepatic cell line adds a valuable tool for understanding TNF "alpha" gene expression in nonhaematopoietic cells.

Cell Line↗
PubMed1996

Nitric oxide donors suppress erythropoietin production in vitro.

Many inflammatory diseases are associated with a hypoproliferative anaemia. Patients with this anaemia often present with serum erythropoietin (EPO) concentrations that are too low for the degree of their anaemia. Proinflammatory cytokines, in addition to their inhibitory effects on proliferation of erythroid progenitors, could contribute to the pathogenesis of this anaemia by reducing EPO production. Because several cytokines stimulate nitric oxide (NO) synthase we propose that nitric oxide might mediate the suppression of EPO production during inflammation. In order to test this hypothesis we investigated the effects of NO donors on 24-h hypoxia-induced EPO production in the hepatocellular carcinoma cell line HepG2. Following application of the NO donors sodium nitroprusside (SNP), 3-morpholinosydnonimine (SIN-1), and S-nitroso-N-acetyl-D,L-penicillamine (SNAP), EPO production was dose-dependently reduced: compared to the untreated control EPO production was lowered by 89% with SNP (1000 microM), by 66% with SIN-1 (1000 microM), and by 72% with SNAP (500 microM). In contrast, 8-bromo-cGMP did not inhibit EPO formation. Since pyrogallol (300 microM) and H2O2 (250 microM) showed a comparable suppression of EPO synthesis, we propose that NO might affect EPO production either by a similar direct influence on the cellular redox state or via increasing the cellular content of reactive oxygen species.

Carcinoma, Hepatocellular↗
PubMed1996

Serum erythropoietin levels in patients with sepsis and septic shock.

The role of the immune system in the control of the production of erythropoietin is still poorly understood. Herein, the levels of circulating immunoreactive erythropoietin, tumour necrosis factor alpha, interleukin-1 beta and interleukin-6 were determined in 10 septic patients for up to 4 d following the admission to an internal intensive care unit. The data show that the production of erythropoietin was not suppressed despite an increase in the levels of proinflammatory cytokines. Circulating erythropoietin and interleukin-6 greatly increased in the 6 nonsurviving patients. The pattern of the serum erythropoietin level in the nonsurvivors resembled that of acute phase proteins and was independent of the blood haemoglobin concentration. Similar to interleukin 6, abnormally high serum erythropoietin levels appear to be a negative prognostic indicator in patients suffering from septic shock.

Adult↗
PubMed1996

Erythropoietin induces Ca2+ mobilization and contraction in rat mesangial and aortic smooth muscle cultures.

Reportedly, recombinant human erythropoietin (rhEpo) can induce constriction of isolated resistance vessels. We have studied whether rhEpo affects cytosolic calcium concentration, [Ca2+]i, and contraction of cultured smooth-muscle cells grown from rat renal corpuscles and aortae. rhEpo at high dose (> or = 20 U/mL) induced a transient increase in [Ca2+]i as detected by fura-2 fluorescence analysis. The number of cells responding with an increase in [Ca2+]i was dose-dependent. No significant changes of [Ca2+]i occurred when lower doses of rhEpo (< 20 U/mL) were applied. The effect of Epo on contraction was studied by phase-contrast microscopy. The number of cells responding with contraction was dose-dependent, too (76% mesangial cells contracting at 200 U rhEpo per mL). The receptor mechanism of this unusual action of Epo still needs to be clarified.

Animals↗
PubMed1996

[Use of recombinant erythropoietin in surgery--are the costs justified?].

The combination of autologous blood donation and rHuEPO therapy is rarely justified for medical and economic reasons. Adequate alternative indications for the use of rHuEPO perioperatively have yet to be studied. Therefore, in addition to the increasing costs of safe homologous blood products and the decreasing costs of recombinant proteins, a reevaluation of the cost-effectivity relationship will be mandatory for rHuEPO in surgery.

Blood Transfusion, Autologous↗
PubMed1995

Pericellular PO2 and O2 consumption in monolayer cell cultures.

The current study was based on the uncertainty as to how well monolayer cell cultures growing in customary polystyrene dishes are supplied with O2. For dishes maintained in an air-5% CO2 atmosphere at 37 degrees C, microelectrode measurements revealed that the pericellular steady-state PO2 was 78 mm Hg in confluent bovine endothelial, 110 mm Hg in rat renal mesangial, and 0 (< 0.2) mm Hg in renal (LLC-PK1 and LLC-MK2) or hepatic (HepG2, Hep3B) epithelial cell cultures. These measured PO2 values were in good agreement with those calculated from Fick's law of gas diffusion, applied for the present culture conditions (one-dimensional O2 diffusion, 0.52 cm medium height), the individual cell layer density and the tissue-specific rate of O2 utilization. Our results provide reasons to speculate that conventional monolayer cultures are often hypoxic when incubated in an air-5% CO2 atmosphere. Diffusion-limitations of cellular O2 availability are to be taken into consideration when tissue cultures are used to study PO2-dependent processes.

Animals↗
PubMed1995

Hypoxia-inducible gene expression.

When oxygen is lacking the cellular production of some hormones, cytokines and glycolytic enzymes can be dramatically increased by a hypoxia-induced increase in the expression of the respective genes that encode for these proteins. The most progress in understanding how the transcription of genes is increased under hypoxic conditions has been made by studying the hypoxia-inducible expression of the erythropoietin gene. Elucidating the oxygen sensitive enhancer elements of the erythropoietin gene has prompted studies on other oxygen-regulated genes. The transcription-regulating proteins that are induced with hypoxia bind to closely related regulatory DNA sequences that control the expression of the genes for erythropoietin, the vascular endothelial growth factor and a number of glycolytic enzymes. It became evident that the hypoxia-inducible enhancer may be part of a widespread oxygen-sensing mechanism acting in a wide variety of mammalian cells. Comparison with the oxygen sensor system in the bacterium Rhizobium meliloti revealed some similarities with the putative oxygen sensor in mammalian cells. This sensor is thought to respond to hypoxia by inducing the signalling cascade that results in binding of the transcription factors to their respective enhancer elements to induce transcription of the respective gene.

Animals↗
PubMed1994

Distinct signaling pathways mediate phorbol-ester-induced and cytokine-induced inhibition of erythropoietin gene expression.

Hypoxia-induced erythropoietin (Epo) production in vitro is suppressed by interleukin 1 beta (IL-1 beta), tumor necrosis factor alpha (TNF) and phorbol esters. Herein, the Epo-synthesizing human hepatoma cell line HepG2 was used to investigate whether protein kinase C (PKC) is involved in the inhibitory action of the cytokines. Within 1 h after the onset of hypoxia, Epo mRNA levels were markedly increased in untreated HepG2 cells as quantitated by competitive reverse transcription PCR. The cytokines IL-1 beta and TNF prevented this hypoxia-induced increase in Epo mRNA levels. In phorbol-ester-treated cells first inhibitory effects on Epo mRNA levels were observed only after 3 h. Western blot analyses revealed the presence of four isoenzymes of PKC in HepG2 cells. None of these isoenzymes was translocated in response to TNF or IL-1 beta, suggesting that the cytokines do not activate PKC in HepG2 cells. In contrast, phorbol esters translocated and, upon prolonged exposure, down-regulated PKC isoenzymes alpha and epsilon. Activation of protein kinase A by dibutyryl-cAMP partially antagonized the cytokine-dependent inhibition of Epo production but did not influence the inhibitory effect of phorbol esters. Endogenous cAMP levels in HepG2 cells were unchanged by cytokine treatment. Obviously, at least two signaling pathways exist that can confer inhibition of Epo production in HepG2 cells. One of these may be mediated by down-regulation of the PKC alpha or epsilon isoenzyme. The other pathway, however, which is triggered by IL-1 beta and TNF, is independent of PKC.

1-Methyl-3-isobutylxanthine↗
PubMed1994

Role of hydrogen peroxide in hypoxia-induced erythropoietin production.

The addition of exogenous H2O2 inhibited hypoxia-induced erythropoietin (Epo) production in the human hepatoma cell line HepG2. Likewise, elevation of endogenous H2O2 levels by the addition of menadione or the catalase inhibitor, aminotriazole, dose-dependently lowered Epo production. The inhibitory effect of exogenous H2O2 on Epo formation could be completely overcome by co-incubation with catalase. When GSH levels in HepG2 cells were lowered, Epo production was more susceptible to H2O2-induced inhibition, indicating that H2O2 might affect thiol groups in regulatory proteins. Endogenous production of H2O2 in HepG2 cells was dependent on the pericellular O2 tension, being lowest under conditions of hypoxia. Our results support the hypothesis that an H2O2-generating haem protein might be part of the O2 sensor that controls Epo production. High H2O2 levels under conditions of normoxia suppress, whereas lower levels in hypoxic cells allow epo gene expression.

Amitrole↗
PubMed1994

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↗
PubMed1994

[Polycythemia in the late metastasis of an erythropoietin-producing renal-cell carcinoma].

An 85-year-old woman had a right-sided renal cell carcinoma removed 20 years ago. At haemoglobin concentration. Two years ago she had a syncope, at which time the haemoglobin concentration was 16.9 g/dl. Ultrasound and computed tomography (CT) revealed an extensive retroperitoneal space-occupying lesion, which however was not investigated further, and no therapeutic consequences were drawn. An erythrocytosis (7.5 x 10(6)/microliters) and elevated haemoglobin concentration (> 20 g/dl) were found when she was examined after a fall in which she had sustained only minimal injury. The retroperitoneal mass had slightly increased in size. Histological examination of a CT-guided fine-needle biopsy revealed metastases of the hypernephroid carcinoma. The serum erythropoietin concentration was increased (42.4 U/l) and failed to increase even after repeated venesections, indicating erythropoietin production by the late metastases of the renal cell carcinoma. There was no evidence for any systemic haematological disease. Six months after the diagnosis of metastases the patient died at home, presumably of a cerebrovascular accident.

Aged↗
PubMed1994

Inhibition of erythropoietin production by cytokines. Implications for the anemia involved in inflammatory states.

In patients with the anemia of chronic diseases, the plasma level of EPO is often low in relation to the blood hemoglobin concentration. Because infectious and inflammatory processes cause activation of cytokine-producing macrophages and lymphocytes, we investigated whether isolated inflammatory cytokines influence the synthesis of EPO in vitro. IL-1 and TNF-alpha were shown to inhibit EPO mRNA levels and EPO formation in the human hepatoma cell cultures HepG2 and Hep3B, and to lower EPO formation in isolated perfused rat kidneys. IFN-alpha and IFN-beta also induced some inhibition of EPO production in HepG2 cultures. IL-3, TGF-beta 2, and IFN-gamma did not inhibit. IL-6 stimulated the production of EPO in Hep3B cells but was ineffective in HepG2 cells and lowered EPO production in isolated perfused rat kidneys. IL-1, TNF-alpha, and possibly other cytokines could contribute to defective EPO production in renal and nonrenal immune responses.

Anemia↗