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Biomedical subjects

T Geiger

Publications and source records attributed to T Geiger.

54 records · Page 3Linked to original sources
PubMed1988

Regulation of synthesis and secretion of major rat acute-phase proteins by recombinant human interleukin-6 (BSF-2/IL-6) in hepatocyte primary cultures.

The regulation of the three major acute-phase proteins alpha 2-macroglobulin, cysteine proteinase inhibitor and alpha 1-antitrypsin by recombinant human interleukin-1 beta, recombinant human interleukin-6 and recombinant human tumor necrosis factor alpha was studied in rat hepatocyte primary cultures. Synthesis and secretion of the acute-phase proteins was measured after labeling with [35S]methionine and immunoprecipitation. Incubation of hepatocytes with interleukin-6 led to dose-dependent and time-dependent changes in the synthesis of the three major acute-phase proteins and albumin, similar to those occurring in vivo during experimental inflammation. alpha 2-Macroglobulin and cysteine proteinase inhibitor synthesis was induced 54-fold and 8-fold, respectively, 24 h after the addition of 100 units/ml interleukin-6. At the same time synthesis of the negative acute-phase protein albumin was reduced to 30% of controls. Half-maximal effects were achieved with 4 units interleukin-6/ml. Interleukin-1 beta had only a partial effect on the regulation of the four patients studied: only a twofold stimulation of alpha 2-macroglobulin and a 60% reduction of albumin synthesis were observed. Tumor necrosis factor alpha did not alter the synthesis of acute-phase proteins. The stimulation of alpha 2-macroglobulin and cysteine proteinase inhibitor synthesis by interleukin-6 was inhibited by interleukin-1 beta in a dose-dependent manner. In pulse-chase experiments the effect of interleukin-1 beta, interleukin-6 and tumor necrosis factor alpha on the secretion of acute-phase proteins was examined. Interleukin-6 markedly accelerated the secretion of total proteins and alpha 2-macroglobulin, whereas the secretion of cysteine proteinase inhibitor, alpha 1-antitrypsin and albumin was not affected. The inhibition of N-glycosylation by tunicamycin abolished the effect of interleukin-6 on the secretion of alpha 2-macroglobulin, indicating a possible role of interleukin-6 on N-glycosylation.

Acute-Phase Proteins↗
PubMed1988

Induction of rat acute-phase proteins by interleukin 6 in vivo.

Recombinant human interleukin 6 (rhIL 6) was injected i.p. into male Wistar rats to investigate its role as a mediator of the acute-phase response. Hepatic mRNA levels of beta-fibrinogen, alpha 2-macroglobulin, cysteine proteinase inhibitor, alpha 1-acid glycoprotein and albumin were measured at different times after the administration of rhIL 6. Maximal increases of mRNA concentrations were observed already 4 h after the injection of rhIL 6 leading to 4.8-, 19.7-, 10- and 16-fold stimulations in mRNA levels of beta-fibrinogen, alpha 2-macroglobulin, cysteine proteinase inhibitor or alpha 1-acid glycoprotein, respectively. The rhIL 6-induced stimulation of acute-phase protein mRNA was much more rapid than the acute-phase induction after turpentine, where maximal mRNA levels were found between 16 and 24 h. For all acute-phase proteins studied, the stimulation of mRNA synthesis was found to be dependent on the dose of rhIL 6 injected. In the case of alpha 2-macroglobulin mRNA a sex-specific induction by rhIL 6 was found. Only male rats showed an acute-phase response, whereas in female rats an acute-phase reaction of alpha 2-macroglobulin mRNA was not inducible by IL 6. The increases in mRNA levels of the acute-phase proteins studied were followed by corresponding changes of the proteins in the serum determined by rocket immunoelectrophoresis. It is concluded that IL 6 represents a potent mediator of the acute-phase response in the rat.

Acute-Phase Proteins↗
PubMed1988

Action of recombinant human interleukin 6, interleukin 1 beta and tumor necrosis factor alpha on the mRNA induction of acute-phase proteins.

The rat hepatoma cell line Fao was used to study the role of three inflammatory mediators on the mRNA regulation of several acute-phase proteins. In the presence of 10(-6) M dexamethasone beta-fibrinogen mRNA levels increased 6-fold after addition of recombinant human IL 6 (rhIL 6). rhIL 1 beta or recombinant human tumor necrosis factor alpha (rhTNF alpha) had essentially no effect on beta-fibrinogen mRNA induction but led to a 20-fold increase in alpha 1-acid glycoprotein mRNA in the presence of dexamethasone. On the other hand, rhIL 6 was a much weaker stimulator of alpha 1-acid glycoprotein mRNA synthesis. All three mediators reduced albumin mRNA concentrations to about 30% of controls. Whereas the induction of beta-fibrinogen mRNA was potentiated by dexamethasone, the synthetic glucocorticoid analog was an absolute requirement for the stimulation of alpha 1-acid glycoprotein mRNA. The mRNA levels of the negative acute-phase protein albumin were induced 5-fold by dexamethasone alone. The beta-fibrinogen mRNA induction started immediately after addition of rhIL 6 and reached a maximum between 12 and 18 h. In contrast, the time-course for alpha 1-acid glycoprotein mRNA synthesis showed a lag phase of 8 h followed by an increase up to 20 h after rhIL 1 beta. rhTNF alpha led to an even more delayed increase in alpha 1-acid glycoprotein mRNA. Whereas in the case of beta-fibrinogen mRNA induction no synergistic effect was observed between various concentrations of the three mediators, the combination of rhIL 6/rhIL 1 beta as well as rhIL 6/rhTNF alpha or rhIL 1 beta/rhTNF alpha regulated synergistically alpha 1-acid glycoprotein and albumin mRNA. It is concluded that discrete acute-phase proteins are regulated differently by the inflammatory mediators IL 6, IL 1 beta and TNF alpha, indicating that the acute-phase response is more complex than previously assumed. The Fao cell line used in this study turned out to be an ideal model for acute-phase protein regulation, suitable for the discrimination between the inflammatory mediators IL 6 and IL 1/TNF alpha.

Acute-Phase Proteins↗
PubMed1988

Regulation of alpha 2-macroglobulin gene expression by interleukin-6 (BSF-2/HSF).

In rat hepatocyte primary cultures recombinant human interleukin-6 (rhIL-6) induced alpha 2-macroglobulin (alpha 2M) synthesis 54-fold. Half-maximal induction was achieved at a rhIL-6 concentration of 30 pM. RhIL-1 beta led only to a 2-fold increase in alpha 2M synthesis, but strongly impaired the action of IL-6. Intraperitoneal injection of rhIL-6 into male rats resulted in a 19.7-fold increase of alpha 2M mRNA already after 4h. In contrast, alpha 2M mRNA levels (50-fold increase) were reached between 16 and 24 h after intramuscular injection of turpentine. Whereas turpentine-induced inflammation resulted in an increased alpha 2M synthesis in male and female rats, rhIL-6 injection had no effect in female rats. The increases after rhIL-6 administration in mRNA concentrations were followed by corresponding changes in alpha 2M levels in serum. By Northern analysis it was demonstrated that LPS-stimulated human monocytes synthesize IL-6 mRNA. The 5'-end of the rat alpha 2M gene has been isolated and the first 3 exons and 166 base pairs of the 5'-flanking region were identified by a combination of oligonucleotide hybridization and DNA sequencing. The transcriptional start site was determined by RNase protection as well as by primer extension experiments. 5'-CATAAAG-3' and 5'-TCAAAA-3' were found as TATA- and CAAT-box equivalent sequences, respectively. Furthermore, a potential glucocorticoid binding site (5'-TGTTCT-3') was localized on the antisense strand of the alpha 2M gene.

Animals↗
PubMed1988

Regulation of interleukin-6 expression in cultured human blood monocytes and monocyte-derived macrophages.

A culture system that allows human blood monocytes to differentiate into macrophages in vitro was used to study B-cell stimulatory factor-2/interleukin-6 (interferon-beta 2/26 kd protein) expression in mononuclear phagocytes. Using B-cell stimulatory factor-2 (BSF-2) cDNA and a polyclonal, monospecific antibody directed against human BSF-2, we find that strong interleukin-6 (IL-6) expression is initiated in cultured monocytes on stimulation with endotoxin. Maximally induced monocytic BSF-2/IL-6 synthesis (1% to 2% of total proteins secreted by monocytes) is more than ten times stronger than in terminally differentiated macrophages (approximately 0.1% of total secretory proteins). BSF-2/IL-6 mRNA was detectable as early as one hour after stimulation with endotoxin, reaching maximum levels three hours after stimulus. Interleukin-1 (IL-1) was able to stimulate IL-6 synthesis in monocytes, but not in macrophages. Tumor necrosis factor, interferon-gamma and interleukin-2 (IL-2) had no effect on IL-6 synthesis in monocytes or macrophages. We found five molecular weight forms of BSF-2/IL-6 to be secreted by monocytes of 21.5 kd, 23.5 kd, 24 kd, 26 kd, and 28 kd apparent molecular weight. The 26 kd and 28 kd forms were found to represent N-glycosylated molecules, which were not detectable on treatment of the cells with the N-glycosylation inhibitor tunicamycin. The 21.5 kd, 23.5 kd, and 24 kd BSF-2/IL-6 forms were unaffected by tunicamycin treatment. We conclude from our data that cells of the mononuclear phagocyte lineage are one of the main sites of BSF-2/IL-6 (interferon-beta 2/26 kd protein/HSF) synthesis.

Cell Differentiation↗
PubMed1987

Recombinant human B cell stimulatory factor 2 (BSF-2/IFN-beta 2) regulates beta-fibrinogen and albumin mRNA levels in Fao-9 cells.

Conditioned medium from human monocytes contains a partially characterized hepatocyte-stimulating factor that simultaneously elevates the mRNA levels of the acute-phase protein beta-fibrinogen and decreases albumin mRNA in rat hepatoma cells. We demonstrate that recombinant human B-cell stimulatory factor 2, which is identical to interferon-beta 2/26 kDa protein and interleukin-HP1, exhibits the same activity as hepatocyte-stimulating factor. Furthermore, a specific antibody against B-cell stimulatory factor 2 was able to inhibit hepatocyte-stimulating factor in conditioned medium from human monocytes. Our data show that hepatocyte-stimulating factor and B-cell stimulatory factor 2 are functionally and immunologically related proteins.

Albumins↗
PubMed1987

Biosynthesis and regulation of rat alpha 1-inhibitor3, a negative acute-phase reactant of the macroglobulin family.

The biosynthesis of rat alpha 1-inhibitor3, a negative acute-phase reactant specifically found in rodents, was studied in vitro in a cell-free translation system from rabbit reticulocytes, in rat hepatocyte primary cultures and in vivo by immunocytochemistry using normal and turpentine-injected rats. By sucrose-gradient centrifugation and subsequent translation of the fractionated RNA in vitro it was found that the mRNA coding for alpha 1-inhibitor3 exhibited a size of about 28S. For the alpha 1-inhibitor3 translated in vitro an apparent Mr of 155,000 was determined. A continuous decrease in the level of alpha 1-inhibitor3 in serum during experimental inflammation induced by turpentine injection was demonstrated by means of quantitative 'rocket' immunoelectrophoresis. This result agrees with the observation by immunocytochemistry of a drastic decrease in alpha 1-inhibitor3 levels in hepatocytes 24 h after turpentine injection. At that time alpha 1-inhibitor3 is mainly located in the Golgi apparatus, whereas it is also present in the membranes of the rough and smooth endoplasmic reticulum when normal liver is used. All hepatocytes, but no other hepatic cells, contain alpha 1-inhibitor3. When hepatocyte primary cultures were labelled with [35S]methionine and alpha 1-inhibitor3 was immunoprecipitated from the hepatocyte medium and the supernatant of homogenized cells, two different forms of alpha 1-inhibitor3 were found. The intracellular form of alpha 1-inhibitor3, with an apparent Mr of 173,000, is characterized by oligosaccharide side chains of the high-mannose type. The form of alpha 1-inhibitor3 in the medium exhibited an Mr of 186,000 and carried carbohydrate side chains of the complex type. After labelling hepatocytes with radioactive sugars, [3H]mannose was found in both forms of alpha 1-inhibitor3, whereas [3H]fucose and [3H]galactose were incorporated only into the form found in the medium. In the presence of tunicamycin an unglycosylated alpha 1-inhibitor3 with an apparent Mr of 154,000 was found in cells and in the medium. In a pulse-chase experiment it was shown that inhibition of glycosylation by tunicamycin resulted in a marked delay of secretion of alpha 1-inhibitor3. Thus the oligosaccharide side chains of alpha 1-inhibitor3 play an important role during its transport into the medium.

Acute-Phase Proteins↗
PubMed1987

Identification and sequencing of cDNA clones for the rodent negative acute-phase protein alpha 1-inhibitor 3.

Rat alpha 1-inhibitor 3 clones were isolated by immunological screening of a lambda gt11 cDNA library prepared from rat liver poly(A)-rich RNA. The recombinant cDNA clones were identified by the absence of their immunoprecipitable products following hybrid-arrested in vitro translation. The size of the cognate poly(A)-rich RNA was estimated to be roughly 5000 residues. Approximately 16 h after induction of inflammation the amount of alpha 1-inhibitor 3 poly(A)-rich RNA decreases as shown by dot-blot hybridization and Northern analyses. The response of this negative acute-phase plasma protein to inflammation may therefore be considered to be at the pretranslational level. The characterized DNA constitutes an open reading frame of 225 amino acids followed by a canonical eucaryotic polyadenylation signal and a poly(A) tail. Sequence microheterogeneity, particularly in the 3'-flanking region was observed. An amino acid homology of 70% for alpha 1-inhibitor 3 with human and rodent alpha 2-macroglobulin emphasizes the evolutionary relationship of the macroglobulins.

Acute-Phase Proteins↗
PubMed1987

Biosynthesis of rat alpha 1-macroglobulin. Identification of an intracellular precursor.

Alpha 1-macroglobulin was purified from rat plasma by gel filtration (Sephacryl S-300) and ion exchange chromatography (DE52). Analysis of the purified alpha 1-macroglobulin by sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed two polypeptides: a light chain which could be resolved into a double band (36/38 kDa) and a heavy chain (160 kDa). Under non-reducing conditions complexes of 200 and 400 kDa could be demonstrated. Antibodies were raised against both chains of alpha 1-macroglobulin which did not cross-react with either rat alpha 2-macroglobulin or rat alpha 1-inhibitor 3. It was shown that in the medium of [35S]methionine-labeled hepatocytes the two subunits of alpha 1-macroglobulin are linked by disulfide bridges. Intracellularly, however, a high molecular mass polypeptide (185 kDa) could be immunoprecipitated with either the antiserum to the heavy or the light chain of alpha 1-macroglobulin, indicating the existence of a polyprotein precursor. Also in a cell-free translation system alpha 1-macroglobulin was synthesized as a polyprotein consisting of heavy and light chains (162 kDa). In a pulse-chase experiment using tunicamycin to block N-glycosylation, alpha 1-macroglobulin secretion was totally inhibited. This finding reflects the importance of the oligosaccharide side chains for the proteolytic processing to the two subunits and/or secretion of alpha 1-macroglobulin.

Animals↗
PubMed1987

Deamidation, isomerization, and racemization at asparaginyl and aspartyl residues in peptides. Succinimide-linked reactions that contribute to protein degradation.

Aspartyl and asparaginyl deamidation, isomerization, and racemization reactions have been studied in synthetic peptides to model these spontaneous processes that alter protein structure and function. We show here that the peptide L-Val-L-Tyr-L-Pro-L-Asn-Gly-L-Ala undergoes a rapid deamidation reaction with a half-life of only 1.4 days at 37 degrees C, pH 7.4, to give an aspartyl succinimide product. Under these conditions, the succinimide product can further react by hydrolysis (half-time, 2.3h) and by racemization (half-time, 19.5 h). The net product of the deamidation reaction is a mixture of L- and D-normal aspartyl and beta-transpeptidation (isoaspartyl) hexapeptides. Replacement of the asparagine residue by an aspartic acid residue results in a 34-fold decrease in the rate of succinimide formation. Significant racemization was found to accompany the deamidation and isomerization reactions, and most of this could be accounted for by the rapid racemization of the succinimide intermediate. Replacement of the glycyl residue in the asparagine-containing peptide with a bulky leucyl or prolyl residue results in a 33-50-fold decrease in the rate of degradation. Peptide cleavage products are observed when these Asn-Leu and Asn-Pro-containing peptides are incubated. Our studies indicate that both aspartic acid and asparagine residues may be hot spots for the nonenzymatic degradation of proteins, especially in cells such as erythrocytes and eye lens, where these macromolecules must function for periods of about 120 days and 80 years, respectively.

Amino Acid Sequence↗
PubMed1982

Biosynthesis and secretion of alpha 1-antitrypsin in primary cultures of rat hepatocytes. Characterization of differently glycosylated intracellular and extracellular forms.

The biosynthesis and secretion of alpha 1-antitrypsin was studied in rat hepatocyte primary cultures. After labeling with [35S]methionine an alpha 1-antitrypsin with an apparent molecular weight of 49000 estimated by sodium dodecyl sulfate/polyacrylamide slab gel electrophoresis was immunoprecipitated from the cell homogenate. This intracellular form of alpha 1-antitrypsin could be deglycosylated by endoglycosidase H treatment indicating that its oligosaccharide chains were of the high-mannose type. Pulse-chase experiments showed that about 30 min after its synthesis the transformation of the 49000-Mr alpha 1-antitrypsin to a protein with an apparent molecular weight of 54000 began. Only this 54000-Mr protein was secreted by the hepatocytes. The 54000-Mr alpha 1-antitrypsin was not sensitive to endoglycosidase H, but sensitive to neuraminidase, and it incorporated [3H]galactose and [3H]fucose indicating that its oligosaccharide chains were of the complex type. In the presence of tunicamycin, which blocks the formation of N-asparagine-linked oligosaccharide chains, an unglycosylated alpha 1-antitrypsin with an apparent molecular weight of 41000 was found in the cells as well as in the medium. However, tunicamycin decreased the secretion of alpha 1-antitrypsin by 60-70%, whereas the secretion of albumin remained unaffected. In the presence of colchicine the secretion of both alpha 1-antitrypsin and albumin was impaired. The results demonstrate the importance of glycosylation for the secretion of alpha 1-antitrypsin.

Animals↗
PubMedDate not supplied

Changes in hepatic mRNA levels of acute phase proteins during rat adjuvant arthritis.

Using specific cDNA probes, we have investigated changes in hepatic mRNA concentrations of the major acute phase proteins fibrinogen, alpha 2-macroglobulin (alpha 2-MG), albumin and alpha 1-acid glycoprotein (alpha 1-AGP) during developing adjuvant arthritis in Lewis rats. Continuously increasing levels in the mRNA of the positive reactants beta-fibrinogen, alpha 2-MG and alpha 1-AGP were found during developing disease with peak levels from day 15 to 21, whereas mRNA concentrations of the negative reactant albumin decreased, reaching their lowest levels on day 11 to 15. As early as 4 days after arthritis induction, the hepatic mRNA levels of beta-fibrinogen, alpha 1-AGP and albumin were distinctly different from control values. The most dramatic changes in the hepatic mRNA levels and plasma concentrations of acute phase reactants were seen between days 11 and 21. These results indicate that overproduction of the major inflammatory cytokines IL-1, TNF-alpha and IL-6, which are now felt to be largely responsible for the acute phase response in the rat, is an early event during adjuvant arthritis and that the highest amounts are produced during the inflammatory phase of the disease. mRNA changes in the acute phase proteins alpha 1-AGP and albumin, which are mainly regulated by IL-1/TNF alpha, were more pronounced than those of alpha 2-MG and beta-fibrinogen, which are predominantly controlled by IL-6.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute-Phase Proteins↗
PubMedDate not supplied

Neutralization of interleukin-1 beta activity in vivo with a monoclonal antibody alleviates collagen-induced arthritis in DBA/1 mice and prevents the associated acute-phase response.

Interleukin-1 (IL-1) has been implicated in the development and progression of a variety of acute and chronic inflammatory diseases. Due to its pro-inflammatory and tissue-degrading activities, IL-1 is regarded as a major mediator of chronic inflammatory joint diseases, including rheumatoid arthritis in man, adjuvant arthritis in rats and collagen-induced arthritis in mice. However, conclusive experimental evidence for the crucial role of IL-1 in the development of joint destruction has not been presented as yet. In the present study, we investigated the effect of a neutralizing monoclonal mouse antibody against mouse IL-1 beta (IgG1 isotype) on the development and progression of collagen-induced arthritis in DBA/1 mice. The antibody was injected intraperitoneally 3 times a week, either from day 3 or from day 21 after primary immunization, to day 60. In the positive control group an arthritis incidence of 80% was observed after 60 days. The injection of a control antibody of the same isotype did not influence the incidence of arthritis, whereas injection of anti-IL-1 beta from day 21 reduced the arthritis incidence to about 30%. Injection of anti-IL-1 beta starting at day 3 totally prevented both the development of arthritis and the associated increase of the acute phase protein serum amyloid P (SAP). Anti-collagen antibody titers, which increased significantly after immunization, were not influenced by the injection of anti-IL-1 beta antibodies, in spite of the suppressive effect on arthritis development.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute-Phase Reaction↗