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Biomedical subjects

M Bickel

Publications and source records attributed to M Bickel.

At least 37 records · Page 2Linked to original sources
PubMed1999

Soluble IL-6 receptor induces calcium flux and selectively modulates chemokine expression in human dermal fibroblasts.

Truncated forms of cytokine receptors have been regarded as modulators of the activity of their cognate ligands. In addition to inhibiting effects of their respective ligands, soluble receptors can also facilitate ligand-mediated signaling. Several studies have demonstrated that exogenous IL-6 in association with the soluble IL-6 receptor alpha (sIL-6Ralpha) can activate cells expressing the gp130 signal transducer lacking the specific, membrane-bound IL-6Ralpha. Since cell cultures of human dermal fibroblasts express high amounts of IL-6, we examined whether the addition of sIL-6Ralpha in association with endogenous IL-6 would be sufficient to stimulate these cells via gp130. As an early rapid signal we analyzed changes in intracellular free calcium concentrations ([Ca2+]i). Addition of sIL-6Ralpha induced an acute and transient increase in cytosolic free calcium concentrations in a dose-dependent fashion. This Ca2+-signal was abolished when cells were pretreated with anti-IL-6 or anti-gp130 antibodies. Using flow cytometric analysis we could demonstrate membrane-associated IL-6 and gp130, but not IL-6Ralpha on fibroblasts. We also analyzed MCP-1 and IL-8 expression as a response involved in the more recently recognized chemoattractant functions of fibroblasts, and found MCP-1 to be up-regulated, but not IL-8. These data suggest that sIL-6Ralpha binds to cell-associated, endogenous IL-6 produced by fibroblasts and this complex then activates the cells via gp130. This pathway of fibroblast activation by sIL-6Ralpha adds another dimension to the role of fibroblasts in the cytokine network.

Antigens, CD↗
PubMed1998

Soluble IL-1 receptor type I binds to human dermal fibroblasts and induces calcium flux.

Soluble cytokine receptors appear to modify ligand concentrations by stabilizing ligands or by specifically inhibiting interactions of ligands with their membrane-bound receptors. Here we describe a new function of the soluble interleukin-1 receptor type I (IL-1sR I). This receptor induced a transient rise of intracellular free calcium concentration in human dermal fibroblasts in a dose-dependent fashion. Mobilization of calcium by IL-1sR I was abolished in the presence of an equimolar concentration of IL-1 receptor antagonist (IL-1ra). Neutralizing antibodies against IL-1beta also abolished calcium mobilization stimulated with IL-1sR I indicating that IL-1beta is involved. IL-1sR I bound with high affinity (Kd 1-2 nM) to the fibroblasts. In addition, IL-1sR I enhanced expression of IL-6 and IL-8 mRNA. The observation that IL-1sR I can act as a ligand and agonist for membrane IL-1 extends the concept of the ligand-receptor functions of both IL-1 and IL-1sR I and adds a new dimension to the cytokine network.

Calcium↗
PubMed1998

Selective inhibition of hepatic collagen accumulation in experimental liver fibrosis in rats by a new prolyl 4-hydroxylase inhibitor.

Fibrosis and cirrhosis of the liver are often the result of chronic liver damage by a variety of different agents. Pathological accumulation of collagen, disruption of the lobular structure, and impaired hepatocellular function frequently lead to systemic involvement and fatal complications. Drugs inhibiting collagen hydroxylation and accumulation are expected to improve this situation, making prolyl 4-hydroxylase (P4H), the key enzyme of intracellular collagen processing, a rational target for pharmacological intervention. S 4682, a novel inhibitor of purified P4H (Ki = 155 nmol/L), reduced hydroxyproline (Hyp) synthesis in chicken embryo calvaria (IC50 = 8.2 micromol/L) and in cultured hepatic stellate cells (HSC) (IC50 = 39 micromol/L). S 4682 inhibited hepatic collagen hydroxylation in vivo after metabolic labeling with [14C]proline. In the CCl4 model of chronic hepatic injury, characterized by histologically and biochemically evident fibrosis and highly elevated levels of serum procollagen type III N-peptide, S 4682 reduced hepatic collagen accumulation, decreased prevalence of ascites, and lowered serum procollagen type III N-peptide (PIIINP) levels. The hepatic Hyp content of drug-treated animals was closely correlated with serum levels of PIIINP S 4682 had no influence on Hyp content of heart, lung, and kidney.

Animals↗
PubMed1998

Two novel antifibrotics, HOE 077 and Safironil, modulate stellate cell activation in rat liver injury: differential effects in males and females.

The perisinusoidal stellate cells of the liver in an injury milieu undergo activation, acquiring a myofibroblast-like phenotype. In this state, they are the principal source of collagen and related proteins in fibrosis. The present studies evaluate the mechanism of action of two novel antifibrotic compounds, HOE 077 and Safironil, which were designed as competitive inhibitors of collagen protein synthesis. Fibrosis was induced in rats by administration of carbon tetrachloride, and activation was monitored as the level of collagen I mRNA or smooth muscle alpha-actin. Both male and female rats were studied. Stellate cell activation, rather than collagen synthesis, proved to be the target of both HOE 077 and Safironil in the intact liver. In culture, the drugs not only prevented the activation of stellate cells but also accelerated their deactivation. They were no more effective in co-cultures containing hepatocytes than in pure stellate cell cultures, indicating that metabolic conversion of HOE 077 was not required. Interestingly, the response of cells from females was greater than that of male cells, leading to the conclusion that stellate activation is sexually dimorphic. This finding may be relevant to the observation that fibrosis in chronic viral hepatitis progresses less rapidly and that hepatocellular carcinoma is less frequent in females than in males.

Animals↗
PubMed1997

The bradykinin B2 receptor antagonist Icatibant (HOE 140) corrects avid Na+ retention in rats with CCl4-induced liver cirrhosis: possible role of enhanced microvascular leakage.

Avid Na+ retention is a hallmark of liver cirrhosis. The aim of this study was to investigate whether and how bradykinin is involved in Na+ retention in rats with CCl4-induced liver cirrhosis. To this end the bradykinin B2 receptor antagonist Icatibant (HOE 140) was used. On one hand, bradykinin has a renal natriuretic action. On the other hand, bradykinin is a potent mediator of both vasodilation and microvascular leakage. Both vascular mechanisms, which are reported for cirrhosis, could cause vascular underfilling and Na+ retention by activating the renin-angiotensin-aldosterone system. Icatibant normalised Na+ retention and reduced the hyperactivity of the renin-angiotensin-aldosterone system, suggesting a bradykinin-induced vascular disturbance. Icatibant had no significant effect on the mild hypotension which developed with CCl4 treatment. However, there was indirect evidence for enhanced microvascular leakage that was strongly inhibited by Icatibant. Our experimental results demonstrate that bradykinin is a key mediator of Na+ retention in liver cirrhosis and suggest that a bradykinin-induced increase in microvascular leakage is mainly responsible.

Animals↗
PubMed1997

Identification of proteins binding specifically to the 3'-untranslated region of granulocyte/macrophage-colony stimulating factor mRNA.

The 3'-untranslated region of granulocyte/macrophage colony-stimulating factor (GM-CSF) mRNA contributes to the post-transcriptional regulation of gene expression. Degradation is partly mediated by adenosine- uridine-rich sequence elements (ARE), which serve as binding sites for specific proteins. Stabilization of RNA by phytohemagglutinin and concanavalin A treatment is dependent on regulatory sequence elements upstream of ARE. We have performed northwestern blot and filter binding assays using cell extracts and RNA sequences containing or lacking ARE. Murine and human T cell extracts (EL-4 and Jurkat) yielded two specific proteins of 93 and 94 kDa, respectively, that were binding to sequences upstream of ARE. Within this region, the human and murine RNA do not share any obvious sequence identity, yet both are target sites for the binding proteins. The smallest RNA fragments protected by the proteins from RNase A digestion, were 44 in the murine, and 38 ribonucleotides long in the human sequence. The binding activity of the 94 kDa protein derived from human Jurkat cells could be enhanced by phytohemagglutinin. The interaction with regulatory mRNA sequences and the responsiveness to phytohemagglutinin suggests that the proteins are involved in controlling GM-CSF mRNA turnover.

Animals↗
PubMed1997

Autologous versus allogeneic T cell-stimulated IL-6 production by dermal fibroblasts.

T cells adhere to human dermal fibroblasts (HDF). This cellular interaction leads to a pronounced secretion of the proinflammatory cytokines IL-6 and IL-8 via a juxtacrine stimulation induced by HDF-associated IL-1. Upon stimulation, fibroblasts express various surface proteins such as MCH-I molecules, which may interact with corresponding receptors on T cells. The present study was conducted to further investigate the mechanism of this complex interaction with regard to the secretion of IL-6 in cocultures of T cells and HDF. IL-6 was time- and dose-dependently upregulated in such cocultures. Spatial separation of the cells by microporous membranes resulted in a 90% reduction of IL-6 secretion, but when cells had limited cell contact IL-6 secretion was increased again. Allogeneic cocultures of T cells and HDF showed increased capacity of IL-6 stimulation as compared to autologous cultures. Our results suggest that MHC-I/T cell receptor interaction modulates IL-6 secretion in allogeneic and autologous cocultures.

Cell Communication↗
PubMed1997

Comparative detection and quantitation of human CDK inhibitor mRNA expression of p15INK4B, p16INK4A, p16beta, p18INK4C, p19INK4D, p21WAF1, p27KIP1 and p57KIP2 by RT-PCR using a polycompetitive internal standard.

For comparative and quantitative analysis of human cyclin-dependent kinase inhibitor gene expression (CKI; p15INK4B, p16INK4A, p16beta, p18INK4C, p19INK4D, p21WAF1, p27KIP1 and p57KIP2) we set up an RT-PCR assay with a construct termed pCKIquant producing polycompetitive RNA as an internal standard. We demonstrated the reproducibility, accuracy and high sensitivity of the assay in the in vitro model of myeloid leukaemic HL-60 cells. We also showed that the pCKIquant CKI assay is an excellent tool for the assessment of CKI mRNA expression in clinical samples, e.g. single cryostat sections of lymphoma biopsies.

Blotting, Northern↗
PubMed1996

Juxtacrine stimulation of cytokine production in cocultures of human dermal fibroblasts and T cells.

Adhesion of T cells to fibroblasts activates cells to produce cytokines, either by direct cell contact and/or soluble factors. A cell-associated form of IL-1 beta on fibroblasts might act through a cell contact mediated fashion. To test this hypothesis we analysed the activation of T cells and human dermal fibroblasts (HDF) in coculture experiments. Elevated levels of IL-1 beta, secreted by T cells as well as IL-6 and IL-8, mainly produced by HDF, were found in supernatant fluids of cocultured cells. IL-1 beta mRNA expression was induced in T cells as well as in HDF. While in HDF IL-1 beta remained cell-associated, T cells were activated to produce and secrete soluble IL-1 beta and IL-6. IL-1 beta and possibly other soluble factors increased IL-6 production by fibroblasts. These effects could be mainly attributed to CD8+ T cells. Our results suggest, that IL-1 beta, produced as a cell-associated cytokine by human dermal fibroblasts, acts as a juxtacrine molecule to stimulate T cells. Such a cellular cooperation, could be a powerful mediator in inflammatory response and possibly in wound healing.

Coculture Techniques↗
PubMed1996

Expression of matrix proteins during the development of mineralized tissues.

The specific properties of mineralized tissues are defined by the composition of the fraction of the noncollagenous matrix proteins. Because these proteins play a pivotal role in the processes of cell differentiation and activation and of mineralization, their temporal and spatial expression is tightly regulated. Within this study, the expression of the enamel protein amelogenin and of the bone matrix proteins osteopontin, bone sialoprotein, osteocalcin, and osteonectin was investigated by in situ hybridization. Two models that allow observation of the formation of mineralized tissues were chosen. The development of bone and cartilage was observed on murine metatarsals from 15-day-old embryos up to 1-day-old mice. This time covers the periods of initial bone formation as well as onset of resorption of mineralized cartilage and bone. To study gene expression in the mineralized tissues of the dental organ, enamel, dentin, and cementum, developing molars ranging in age from 16-day-old embryos to 14 days after delivery were chosen. Within this time frame, the molars develop from an immature state to the differentiated organ which erupts through the mandibular bone. In the developing metatarsals, osteopontin and bone sialoprotein mRNAs were detected in osteoblasts and hypertrophic chondrocytes at the onset of mineralization. In the tooth organ, only cementoblasts expressed transcripts encoding the two proteins; odontoblasts and ameloblasts did not express these genes. Osteonectin was expressed by osteoblasts and hypertrophic chondrocytes as well, whereas in the molars it was produced exclusively by odontoblasts. Osteocalcin was expressed specifically by osteoblasts in the developing metatarsals. In tooth, osteocalcin transcripts were detected in odontoblasts. Finally, amelogenin was a specific product of ameloblasts. Thus, a sequential and cell type-restricted expression of matrix proteins takes place during the development of the mineralized tissues. The expression patterns of the transcripts encoding the bone matrix proteins suggest different biological roles depending on the time and site of expression.

Amelogenin↗
PubMed1996

Chemokine expression in human oral keratinocyte cell lines and keratinized mucosa.

Chemoattractant cytokines regulate the immune response within the tissue by recruiting neutrophils and macrophages. These so-called chemokines include a large family of peptide molecules encoded by distinct genes. Their expression is controlled by a variety of microbial and host factors. Among host factors, interleukin-1 (IL-1) is thought to be a key regulator of tissue destruction and mediator of the local immune response. To study its influence on chemokine expression, we used a highly sensitive, semi-quantitative method to assess gene expression at the level of mRNA. RNA was extracted from human oral keratinocyte cell lines after treatment with recombinant human IL-1. To test the method further and possibly establish a chemokine mRNA expression pattern, we also extracted RNA from healthy oral keratinized mucosa. Purified RNA was reverse-transcribed and subsequently amplified in a polymerase chain reaction (RT-PCR) by means of specific primer pairs. Amplified sequences were analyzed by agarose gel electrophoresis, visualized by ethidium bromide staining, transferred to nylon membranes, and hybridized to biotinylated oligonucleotide probes. Detection was achieved by streptavidin-conjugated alkaline phosphatase, a chemiluminescent substrate, and autoradiography. Autoradiographs were analyzed by densitometric measurements. IL-1 stimulation resulted in an increase of the chemokine mRNAs encoding interleukin-8 (IL-8), monocyte chemoattractant protein-1 (MCP-1), and GRO gamma. Macrophage inflammatory protein-1 alpha (MIP-1 alpha) mRNA was not detectable in keratinocytes. In healthy oral mucosa, we found considerable variation between the subjects. Detection of chemokine mRNAs by RT-PCR proved to be sensitive, specific, and fast. It allows for the study of not only cell-line-derived RNA, but also of RNA isolated directly from biopsy material. The latter feature makes this method well-suited for diagnostic purposes.

Cell Line↗
PubMed1995

A rapid method for the detection of uranium in surface water.

A method has been optimized to preconcentrate uranium from waters using the ion exchanger Hyphan. The sample (up to 10 1) is agitated thoroughly with a portion of the ion exchanger for between 40 min and 2 h. The exchanger is filtered off and treated with a small volume (< 100 ml) of either nitric acid (for ICP measurement) or hydrochloric acid (for alpha measurement). The acid is filtered off and measured directly by ICP-AES, or it is brought to pH 2 and saturated with ammonium chloride, then directly electrolyzed. Yields lie in the order of 60-90% and the overall analysis time is approximately 3 h (ICP) or approximately 4 h (alpha measurement). Precisions reached are better than 15% relative. Detection limits lie at about 2 ppb (ICP) and 0.4 ppb (alpha measurement).

Fresh Water↗
PubMed1995

A review of masticatory ability and efficiency.

Masticatory function can be assessed by chewing tests and questionnaires or personal interviews. Whereas the chewing tests allow the assessment of masticatory efficiency with some objectivity, questionnaires help evaluate a person's subjective responses about chewing ability. Epidemiologic studies indicate a subjective decrease in chewing ability with increasing degree of tooth loss, a trend that was confirmed in the literature. Of interest was that the subjective measures of masticatory ability are often overrated when compared with the functional tests. Masticatory function is a patient factor rather than a parameter that prosthetic treatment can qualify. It depends on a variety of personal and subjective factors that can hardly be influenced by the practitioner. This article describes and discusses scientific sociophysiologic and biomedical approaches to evaluating masticatory function.

Bite Force↗