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J Pfeilschifter

Publications and source records attributed to J Pfeilschifter.

At least 163 records · Page 9Linked to original sources
PubMed1996

Smoking and endocrine ophthalmopathy: impact of smoking severity and current vs lifetime cigarette consumption.

OBJECTIVE: Smoking has been associated with an increased incidence of endocrine ophthalmopathy (EO). In this study we examined the relation between smoking severity and the incidence of EO symptoms in patients with Graves' hyperthyroidism. DESIGN: Patients were prospectively followed for at least one year after the onset of hyperthyroidism. Smoking and EO status were evaluated at 3-6- months intervals. PATIENTS: Two hundred and fifty-three ambulatory patients with recent onset of Graves' hyperthyroidism were studied. MEASUREMENTS: The incidence of total EO symptoms, proptosis, and diplopia at any time point before and after the occurrence of Graves' hyperthyroidism was assessed by interview and physical examination. RESULTS: Smoking was associated with a 1.3-fold increase in the overall incidence of symptomatic EO, and a 2.6 and 3.1-fold increase in the incidence of proptosis and diplopia, respectively. The relative risk increased in parallel with the current number of cigarettes smoked per day. In contrast, lifetime tobacco use was not an independent risk factor for the development of EO symptoms. Former smokers had a significantly lower risk for the occurrence of proptosis and diplopia than active smokers with a comparable lifetime cigarette consumption. CONCLUSIONS: Our data suggest that current, but not lifetime, tobacco consumption constitutes a risk for the incidence of proptosis and diplopia in patients with Graves' hyperthyroidism, and that this risk increases with smoking severity.

Adult↗
PubMed1996

Regulatory functions of protein kinase C isoenzymes in purinoceptor signalling in mesangial cells.

1. The expression and functional roles of protein kinase C (PKC) isoenzymes in purinoceptor signalling have been examined in rat renal mesangial cells. 2. It is observed that rat mesangial cells express four PKC isoenzymes, PKC-alpha, -delta, -epsilon and zeta, as determined by Western blot analysis. No PKC-beta, -gamma, -eta, -theta, or -mu isoforms were detected. 3. By using specific PKC inhibitors and down-regulation experiments we provide evidence that PKC alpha acts as a negative feedback regulator of ATP- and UTP-stimulated phosphoinositide turnover, whereas PKC epsilon triggers arachidonic acid release and subsequent prostaglandin synthesis and stimulates a phosphatidylcholine-hydrolysing phospholipase D. Moreover, PKC delta may activate the mitogen-activated protein kinase cascade and thus promote mesangial cell proliferation in response to extracellular ATP and UTP. 4. In summary our data identify mesangial cells in culture as an excellently characterized cell culture system with well-defined functions of PKC isoenzymes. Functional identification of PKC isoenzymes involved in specific cell responses is one of the most promising steps towards understanding of molecular mechanisms of cell regulation and identifies new targets for drug development.

Adenosine Triphosphate↗
PubMed1996

Inhibition by tetranactin of interleukin 1 beta- and cyclic AMP-induced nitric oxide synthase expression in rat renal mesangial cells.

1. We have investigated whether tetranactin, a cyclic antibiotic produced by Streptomyces aureus with a molecular structure related to cyclosporin A, influences inducible nitric oxide synthase (iNOS; EC 1.14.13.39) induction in rat glomerular mesangial cells. 2. Previously we have shown that iNOS is expressed in renal mesangial cells in response to two principal classes of activating signals comprising inflammatory cytokines such as interleukin 1 (IL-1) or tumour necrosis factor alpha and agents that elevate cellular levels of cyclic AMP. Treatment of mesangial cells with IL-1 beta or the membrane-permeable cyclic AMP analogue, N6, 0-2'-dibutyryladenosine 3',5'-phosphate (Bt2 cyclic AMP) for 24 h induces iNOS activity measured as nitrite levels in cell culture supernatants by 44 fold or 33 fold, respectively. Incubation of mesangial cells with tetranactin inhibits IL-1 beta- and cyclic AMP-dependent production of nitrite in a dose-dependent fashion with IC50 values of 50 nM and 10 nM, respectively. 3. Western-blot analyses of mesangial cell extracts reveal that the inhibition of nitrite synthesis by tetranactin is due to a suppression of iNOS protein levels. This effect is preceded by a reduction of iNOS mRNA steady state levels as demonstrated by Northern blot analyses of total cellular RNA isolated from stimulated mesangial cells. 4. Thus, tetranactin is a potent inhibitor of iNOS expression in cytokine- and cyclic AMP-stimulated mesangial cells and represents a new class of iNOS inhibitors with IC50s in the low nanomolar range. This compound may be useful in the therapy of diseases associated with pathological NO overproduction due to iNOS expression.

Animals↗
PubMed1996

Relationship between circulating insulin-like growth factor components and sex hormones in a population-based sample of 50- to 80-year-old men and women.

There is a large body of evidence that points to a systemic link between the somatotropic axis and sex hormones, but epidemiologic data on the interactions between the two hormonal systems are still missing. We examined here the associations between the plasma levels of insulin-like growth factor (IGF) I, IGF-II, IGF-binding protein 3 (IGFBP-3), and sex hormones in a population-based sample of 486 men and women, aged 50-80 yr. The strongest association was an age-independent inverse correlation between all three circulating IGF components and sex hormone-binding globulin (SHBG), the major testosterone-binding protein in plasma. Consistent with this, bio-available (non-SHBG-bound) but not total testosterone levels were positively associated with the IGF system in men, and 3 alpha-androstanediol glucuronide was positively correlated with circulating IGFs in women. Moreover, part of the correlation between the circulating IGF system and bone mineral density at the femur and the calcaneus could be accounted for by SHBG. Our data suggest that sex hormones and the GH/IGF system are significantly interrelated in the elderly population. These hormonal interactions may play an important role in human aging and the pathogenesis of age-related diseases.

Aged↗
PubMed1995

Modulatory role of platelet-derived growth factor on cytokine-induced nerve growth factor synthesis in rat glomerular mesangial cells.

Recent evidence indicates that cytokines are potent inducers of nerve growth factor (NGF) expression in peripheral tissues and in brain. Cultured rat glomerular mesangial cells respond to interleukin-1 beta (IL-1 beta) and tumour necrosis factor-alpha (TNF-alpha) by increased NGF synthesis. We found that co-stimulation of rat glomerular mesangial cells with platelet-derived growth factor (PGDF-BB) and IL-1 beta/TNF-alpha significantly augments the IL-1 beta/TNF-alpha-induced NGF mRNA levels and NGF synthesis. In contrast, preincubation with PDGF-BB drastically reduces NGF gene expression and NGF protein synthesis in response to IL-1 beta/TNF-alpha stimulation. Thus our results indicate that PDGF-BB is a potent modulator of cytokine-induced NGF expression; its precise action is critically depending on the time at which the PDGF receptor is activated.

Animals↗
PubMed1995

Interleukin 1 beta-induced expression of nitric oxide synthase in rat renal mesangial cells is suppressed by cyclosporin A.

The expression of inducible nitric oxide synthase (iNOS) is triggered in rat renal mesangial cells by exposure to the inflammatory cytokine interleukin 1 beta (IL-1 beta). Here we report that cyclosporin A (CsA) a potent immunosuppressive drug, inhibits IL-1 beta dependent iNOS expression in renal mesangial cells. Addition of CsA dose dependently suppresses IL-1 beta-induced nitrite formation (IC50 = 0.9 microM). Western- and Northern blot analyses of mesangial cell extracts reveal that the inhibition of IL-1 beta-induced nitrite formation by CsA is due to decreased iNOS protein and iNOS mRNA steady state levels. Using nuclear run on experiments we show that the transcription rate of the IL-1 beta-induced iNOS gene is reduced. Furthermore, by electrophoretic mobility shift analysis we demonstrate reduced DNA-binding of the nuclear factor NF kappa B, an essential component of the IL-1 beta-dependent upregulation of iNOS gene transcription. The data presented in this report suggest that the cellular machinery involved in the IL-1 beta dependent transcriptional upregulation of the iNOS gene in mesangial cells is a target for the action of CsA.

Animals↗
PubMed1995

Pyrrolidine dithiocarbamate differentially affects cytokine- and cAMP-induced expression of group II phospholipase A2 in rat renal mesangial cells.

Renal mesangial cells express group II phospholipase A2 in response to two principal classes of activating signals that may interact in a synergistic fashion. These two groups of activators comprise inflammatory cytokines such as interleukin-1 beta (IL-1 beta) and tumor necrosis factor-alpha (TNF alpha) and agents that elevate cellular levels of cAMP such as forskolin, an activator of adenylate cyclase. Using pyrrolidine dithiocarbamate (PDTC), a potent inhibitor of nuclear factor NF kappa B, we determined its role in cytokine--and cAMP--triggered group II PLA2 expression. Micromolar amounts of PDTC suppress the IL-1 beta- and TNF alpha-dependent, but not the forskolin-stimulated group II PLA2 activity in mesangial cells. Furthermore, PDTC inhibited the increase of group II PLA2 mRNA steady state levels in response to IL-1 beta and TNF alpha, while only marginally affecting forskolin-induced PLA2 mRNA levels. Our data suggest that NF kappa B activation is an essential component of the cytokine signalling pathway responsible for group II PLA2 gene regulation and that cAMP triggers a separate signalling cascade not involving NF kappa B. These observations may provide a basis to study the underlying mechanisms involved in the regulation of group II PLA2 gene expression.

Animals↗
PubMed1995

Platelet-derived growth factor and angiotensin II stimulate the mitogen-activated protein kinase cascade in renal mesangial cells: comparison of hypertrophic and hyperplastic agonists.

Exposure of mesangial cells to platelet-derived growth factor (PDGF) BB caused a significant stimulation of cell proliferation and protein synthesis, as measured by [3H]thymidine incorporation and [3H]leucine incorporation respectively. In contrast, cells treated with angiotensin II had no significant increase in [3H]thymidine incorporation, but demonstrated a marked increase in [3H]leucine incorporation. Furthermore, angiotensin II significantly increased total protein content per cell. These data show that, whereas PDGF-BB is a mitogen and stimulates mesangial-cell hyperplasia, angiotensin II causes hypertrophy of the cells without hyperplasia. Treatment of mesangial cells with PDGF and angiotensin II rapidly and dose-dependently stimulated mitogen-activated protein (MAP) kinase activity, as shown by an assay for activity in vitro using myelin basic protein as a substrate, and by immunoprecipitation of 32P-labelled cells with specific antibodies against the 42 kDa and 44 kDa mitogen-activated protein kinases p42mapk and p44mapk, respectively. Whereas stimulation with PDGF-BB caused a potent and sustained (for more than 30 min) phosphorylation and activation of p42mapk and p44mapk, as well as of the upstream activators MAP kinase kinase and c-Raf, the effect of angiotensin II was less potent, reaching a peak at 5-10 min and thereafter declining rapidly. In summary, these results suggest that PDGF-BB and angiotensin II differ in their potency and duration of activation of the MAP kinase cascade, which may explain why PDGF-BB is a potent mitogen for mesangial cells, whereas angiotensin II only triggers mesangial-cell hypertrophy.

Amino Acid Sequence↗
PubMed1995

Platelet-derived growth factor stimulates de-novo synthesis of mitogen-activated protein kinase in renal mesangial cells.

Platelet-derived growth factor (PDGF) BB is a potent mitogen for renal mesangial cells and stimulates a biphasic mitogen-activated protein kinase (MAP kinase) activation. A rapid increase in activity (maximal at 10 min) is followed by a lower persistent level of activity which is maximal at 4-6 h. The second peak of MAP kinase activity is markedly attenuated by the protein synthesis inhibitor cycloheximide and, consequently, is paralleled by a marked de-novo synthesis of p42 and p44 MAP kinases, as measured by immunoprecipitation of [35S]methionine-labeled mesangial cells and by a 700% increase in total MAP kinase protein, as detected by Western-blot analysis. A 30-min treatment with PDGF-BB is sufficient to induce pronounced de-novo synthesis of MAP kinase. However, for maximal induction of MAP kinase synthesis, PDGF is required to be present for at least 4 h. In addition, an increased de-novo synthesis of MAP kinase kinase, the upstream activator of MAP kinase, is observed in response to PDGF stimulation. We propose that PDGF-induced de-novo synthesis of MAP kinase and MAP kinase kinase is important for the potent mitogenic activity of this growth factor.

Amino Acid Sequence↗
PubMed1995

5-Hydroxytryptamine 5-HT1B receptors inhibiting cyclic AMP accumulation in rat renal mesangial cells.

A clonal cell line derived from rat renal mesangial cells was shown to express endogenous 5-hydroxytryptamine (serotonin, 5-HT) receptors that mediate inhibition of cyclic AMP accumulation. These receptors were characterized as being of the 5-HT1B receptor subtype. 5-HT1 receptor agonists inhibited forskolin-stimulated cyclic AMP accumulation in rat renal mesangial cells (60-70% maximal inhibition) with the following rank order of potency (mean pEC50 values +/- SEM, n > or = 3): ergotamine (9.58 +/- 0.51) > RU 24969 (8.67 +/- 0.23) > or = 5-CT (8.42 +/- 0.06) > or = CP 93129 (8.15 +/- 0.27) > 5-HT (7.75 +/- 0.11) > sumatriptan (6.29 +/- 0.30) > 8-OH-DPAT (4.32 +/- 0.15). 5-HT2 and 5-HT4 receptor agonists were without effect. 5-HT-induced inhibition of cyclic AMP accumulation was abolished by a pre-treatment of the cells with pertussis toxin. (-)Propranolol was a partial agonist (27% maximal inhibition, pEC50 7.19 +/- 0.24, n = 3); when used as an antagonist at 1 microM, it shifted the concentration-response curve of 5-HT to the right (pKB 7.22 +/- 0.35, n = 3). Methiothepin was a competitive antagonist of 5-HT (pA2 8.04 +/- 0.10, Schild slope 0.87 +/- 0.21, n = 3). Rauwolscine (10 microM) had no antagonist activity. There was a significant correlation (r = 0.98, P = 0.0001) between the cyclic AMP data obtained in rat mesangial cells and 5-HT1B binding data reported in rat brain cortex. The same pattern of responses was observed in early passages of primary cultures of rat mesangial cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Translocation of protein kinase C isoenzymes by elevated extracellular Ca2+ concentration in cells from a human giant cell tumor of bone.

In this study we investigated the protein kinase C isoenzymes expressed by human osteoclast-like cells harvested from a giant cell tumor of bone (GCT23 cells), and by freshly isolated rat osteoclasts. Immunoblotting analysis revealed that the -alpha, -delta, and -epsilon, PKC isoforms, but not the -beta isoenzyme, are expressed by GCT23 cells. Immunofluorescence studies demonstrated that PKC-alpha, -delta, and -epsilon are homogeneously expressed by both mononuclear and multinucleated GCT23 cells, as well as by rat osteoclasts. Similar to authentic osteoclasts, GCT23 cells responded to an increase of extracellular Ca2+ concentration ([Ca2+]o) with a dose-dependent elevation of the cytosolic free Ca2+ concentration ([Ca2+]i). An increase of [Ca2+]o stimulated the translocation of PKC-alpha from the cytosolic to the particulate fraction, suggesting the involvement of this isoenzyme in the signal transduction mechanism prompted by stimulation of the [Ca2+]o sensing. By contrast, PKC-delta was not altered by exposure to elevated [Ca2+]o, whereas PKC-epsilon underwent reciprocal translocation, disappearing from the insoluble fraction and increasing in the cytosol. The effects of PKC on GCT23 cell functions were investigated by treatment with phorbol 12-myristate, 13-acetate (PMA). We observed that activation of PKC by PMA failed to affect adhesion onto the substrate, but down-regulated the [Ca2+]o-induced [Ca2+]i increases. The latter effect was specific, since it was reversed by treatment with the PKC inhibitors staurosporine and chelerythrine.

Animals↗
PubMed1995

Proliferative mechanisms in kidney cells.

The activation of the mitogen-activated protein kinase cascade is one of the major signalling pathways by which growth factors transmit their mitogenic messages from the cell membrane to the nucleus. Two major breakthroughs reported in the past months are the cross-communication between the mitogen-activated protein kinase cascade and the cAMP-protein kinase A signal pathway, and the role of alpha- and beta gamma-complexes of heterotrimeric G proteins in activating the mitogen-activated protein kinase pathway. These signalling strategies have now also been demonstrated in renal mesangial cells. Another important step has been the identification of a candidate gene for polycystic kidney disease. Knowledge of the molecular mechanisms of action of growth factors in the kidney will promote greatly our understanding of the aetiology of renal disease.

Animals↗
PubMed1995

Amplification of nitric oxide synthase expression by nitric oxide in interleukin 1 beta-stimulated rat mesangial cells.

Nitric oxide (NO) plays an important role in immunological reactions as a host defense mechanism against tumor cells and invasive microorganisms, but it may also damage healthy tissue. The excessive formation of NO in IL-1 beta-stimulated renal mesangial cells not only alters glomerular filtration, but it may also cause tissue injury and thus contribute to the pathogenesis of certain forms of glomerulonephritis. We report here that, although NO alone has no evident effect on NO synthase expression, it potently augments IL-1 beta-stimulated NO synthase expression in mesangial cells. NO donors such as sodium nitroprusside and S-nitroso-N-acetyl-D,L-penicillamine markedly increase IL-1 beta-induced NO synthase mRNA and protein levels as well as enzyme activity. Nuclear run-on experiments suggest that NO acts to increase IL-1 beta-induced NO synthase gene expression at the transcriptional level. Furthermore, inhibition of NO synthesis by different pharmacological approaches reduces IL-1 beta-induced NO synthase expression, thus suggesting that NO functions in a positive feedback loop that speeds up and strengthens its own biosynthesis. We suggest that this potent amplification mechanism forms the basis for the excessive formation of NO in acute and chronic inflammatory diseases.

Amino Acid Oxidoreductases↗
PubMed1995

Parathyroid hormone increases the concentration of insulin-like growth factor-I and transforming growth factor beta 1 in rat bone.

Intermittent treatment with parathyroid hormone (PTH) increases bone mass in experimental animals and humans. In vitro studies have suggested that the anabolic effect of PTH may be mediated by local growth factors. However, the relevance of these findings to in vivo situations remains unclear. In this study, we examined a time course of daily s.c. injections of hPTH (1-34) on the skeletal concentration of insulin-like growth factor (IGF)-I, IGF-II, and transforming growth factor beta (TGF-beta) in the proximal tail vertebrae of male rats. PTH caused a time and dose-dependent increase in the bone mineral density of the lumbar spine. This anabolic effect on bone mass was accompanied by progressive increases in bone matrix-associated IGF-I and TGF-beta 1. Increases in IGF-I and TGF-beta 1 became apparent after four and eight weeks of PTH treatment respectively and persisted through week 12. PTH had no effect on circulating IGF-I, suggesting that the increase of bone matrix IGF-I was due to the local effect of PTH on bone tissue directly rather than to an increase of circulating IGF-I. These data are consistent with the hypothesis that IGF-I and TGF-beta 1 may play a role as local mediators of the anabolic effects of PTH on bone metabolism.

Age Factors↗
PubMed1995

Increased cytokine secretion by human bone marrow cells after menopause or discontinuation of estrogen replacement.

Studies on circulating human mononuclear cells and rodents have suggested that cytokines such as interleukin-1 (IL-1) and IL-6 may be paracrine mediators of postmenopausal bone loss. However, the assumption that the concentration of these cytokines is increased in the local bone microenvironment of postmenopausal women is still unproved. To address this question, we aspirated bone marrow from the iliac crest of 40 women during surgery for localized breast cancer and analyzed cytokine release in short term cultures. Cytokine levels in the cell supernatants from premenopausal (n = 12) and late postmenopausal (n = 18) subjects were not significantly different. Bone marrow cells from women who had discontinued estrogen replacement within 1 month before aspiration (n = 5) secreted significantly more IL-1 alpha, tumor necrosis factor-alpha, IL-6, prostaglandin E2, and granulocyte-macrophage colony-stimulating factor than bone marrow cells from either premenopausal or late postmenopausal subjects. Increased levels of IL-6, prostaglandin E2, and granulocyte-macrophage colony-stimulating factor were also observed in cultures from women who were within 5 yr of natural menopause (n = 5). Our data show that estrogen withdrawal is associated with an increased potential of human bone marrow cells to release bone-resorbing cytokines and strengthen the hypothesis that these cytokines may play a role in the accelerated bone resorption after menopause.

Adult↗
PubMed1994

Dexamethasone differentially affects interleukin 1 beta- and cyclic AMP-induced nitric oxide synthase mRNA expression in renal mesangial cells.

Inducible nitric oxide synthase (iNOS) is expressed in renal mesangial cells in response to two principal classes of activating signals that interact in a synergistic fashion. These two groups of activators comprise inflammatory cytokines such as interleukin (IL)-1 beta or tumour necrosis factor alpha and agents that elevate cellular levels of cyclic AMP (cAMP). We examined whether dexamethasone differentially affects iNOS induction in response to IL-1 beta and a membrane-permeable cAMP analogue, N6,O-2'-dibutyryladenosine 3',5'-phosphate (Bt2cAMP). Nanomolar concentrations of dexamethasone suppress IL-1 beta- as well as Bt2cAMP-induced iNOS protein expression and production of nitrite, the stable end product of nitric oxide (NO) formation. In contrast, dexamethasone prevents induction of iNOS mRNA in response to Bt2cAMP without affecting IL-1 beta-triggered increase in iNOS mRNA levels. These data suggest that dexamethasone acts at different levels, depending on the stimulus used to suppress iNOS induction in mesangial cells.

Amino Acid Oxidoreductases↗
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↗