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Biomedical subjects

M Lantz

Publications and source records attributed to M Lantz.

51 records · Page 3Linked to original sources
PubMed1991

On the binding of tumor necrosis factor (TNF) to heparin and the release in vivo of the TNF-binding protein I by heparin.

Tumor necrosis factor (TNF), a protein released by activated macrophages, is a central mediator of the host response to infection and inflammation. The TNF-binding protein I (TNF-BP-I) is a soluble fragment of the p60 transmembrane TNF receptor and an antagonist to TNF. The level of serum TNF-BP-I was found to be increased in patients with renal insufficiency as a result of a decrease in the glomerular filtration rate. During hemodialysis of patients with renal failure there was a rapid but transient increase in serum TNF-BP-I. This increase was found to be caused by heparin given before dialysis and a similar dose-dependent response to heparin was observed also in healthy individuals. The finding of a repeated release of TNF-BP-I into the circulation with intermittent injections of heparin indicates that TNF-BP-I is present both in a storage pool and in a circulating pool. The mechanism for the heparin-mediated release of TNF-BP-I was not explained; TNF-BP did not show affinity for heparin. On the other hand, TNF was found to have affinity for heparin and it could also be dissociated from heparin by TNF-BP-I. It is suggested that heparin-like molecules of the extracellular matrix can retain TNF in physical proximity with target cells and restrict the actions of TNF and protect against systemic harmful manifestations.

Carrier Proteins↗
PubMed1990

Modulation of the constitutive gene expression of the 55 kD tumor necrosis factor receptor in hematopoietic cells.

The expression of the 55 kD human tumor necrosis factor (TNF) receptor gene was investigated. By use of a 1.2 kb cDNA we demonstrated a constitutive expression of a single 2.3 kb transcript in cell lines and fresh blood cells. The TNF receptor gene expression was not affected by phorbol esters, dibutyryl cAMP (dbcAMP), interleukin-1 (IL-1), interferon-gamma (IFN-gamma) or by TNF, agents known to modulate functional TNF receptors. The phosphodiesterase inhibitor 3-isobutyl-1-methyl-xanthine (IBMX) showed a dose dependent inhibition of the TNF receptor gene expression. This inhibition is not mediated by cAMP, since neither dbcAMP nor forskolin had any effects on the expression of the 55 kD receptor gene. The results suggest that the effects of phorbol diesters, IL-1, IFN-gamma, TNF and dbcAMP previously observed on binding of TNF to cells are limited to posttranscriptional regulation of the 55 kD TNF receptor.

1-Methyl-3-isobutylxanthine↗
PubMed1990

Cytokine and non-cytokine differentiating agents for myeloid leukemic cells.

Existing data suggest that normal maturation can sometimes be re-established in leukemia. A number of differentiation-inducing substances have been reported; these include retinoic acid, vitamin D3 and cytokines such as differentiation-inducing factor, tumor necrosis factor and lymphotoxin. Different agents obviously act by separate mechanisms to provide terminal maturation.

Binding Sites↗
PubMed1990

Infusion of tumor necrosis factor (TNF) causes an increase in circulating TNF-binding protein in humans.

Serum samples from cancer patients receiving intravenous infusions of recombinant tumor necrosis factor (rTNF) and recombinant interferon-gamma (rIFN-gamma) were analyzed for TNF and the TNF-binding protein (TNF-BP). TNF-BP is a soluble fragment of the transmembrane TNF receptor with antagonistic effects to TNF and is released by proteolytic cleavage of the receptor. During a 60-min infusion of rTNF, peak serum levels of rTNF were observed after 30 to 60 min and a transient increase of circulating TNF-BP was observed with peak levels between 30 and 120 min. Injection of IFN-gamma alone did not affect the levels of TNF and TNF-BP. Thus administration of rTNF leads to release into the circulation of TNF-BP, which may modulate both systemic and local effects of TNF and influence its therapeutic efficacy.

Carrier Proteins↗
PubMed1990

Molecular cloning and expression of human and rat tumor necrosis factor receptor chain (p60) and its soluble derivative, tumor necrosis factor-binding protein.

Tumor necrosis factor-alpha (TNF-alpha), a protein released by activated macrophages, is involved in a wide variety of human diseases including septic shock, cachexia, and chronic inflammation. TNF binding protein (TNF-BP), a glycoprotein with high affinity to TNF-alpha isolated from urine, acts as an inhibitor of TNF-alpha by competing with the cell-surface TNF receptor. We report here the partial amino acid sequencing of human TNF-BP as well as the isolation, sequence, and expression of cDNA clones encoding a human and rat TNF receptor. The calculated Mr of the mature human and rat TNF receptor chains is 47,526 and 48,072, respectively. The extracellular ligand binding domain represents the soluble TNF-BP which is released by proteolytic cleavage. TNF-BP contains 24 cysteine residues and three potential N-glycosylation sites and shows sequence homology to the extracellular portions of TNF-R p80 chain and nerve growth factor receptor. Transfection of the human TNF receptor cDNA into mammalian cells resulted in increased binding capacity for TNF-alpha and increased reactivity with a monoclonal antibody directed against the human TNF receptor chain p60. When a stop codon was introduced into the cDNA at the site corresponding to the carboxyl terminus of TNF-BP, transfected cells secreted a protein that reacted with antibodies raised against natural TNF-BP.

Amino Acid Sequence↗
PubMed1990

Characterization in vitro of a human tumor necrosis factor-binding protein. A soluble form of a tumor necrosis factor receptor.

Tumor necrosis factor (TNF) is a pleiotropic mediator of inflammatory responses. A cysteine-rich, highly glycosylated 30-kD TNF-binding protein (TNF-BP) purified from urine may have a role in regulation because it protects in vitro against the biological effects of TNF. The cytotoxic effect of TNF on the fibrosarcoma cell line WEHI 164 was inhibited by 50% at a 10-fold excess of TNF-BP. The binding of TNF to the receptor was partially reversed after the addition of TNF-BP. Results from biosynthetic labeling of cells with 35S-cysteine followed by immunoprecipitation with anti-TNF-BP indicated that TNF-BP is formed and released at the cell surface by cleavage because no corresponding cellular polypeptide was observed. A cellular 60-kD polypeptide, which was immunoprecipitated with anti-TNF-BP, may correspond to the transmembrane TNF-receptor molecule and be the precursor of TNF-BP. Thus, TNF-BP appears to be a soluble form of a transmembrane TNF-receptor. Moreover our results demonstrate that the production of TNF-BP is increased when the TNF receptor is downregulated in cells by treatment with TNF or by activation of protein kinase C with phorbol esters. TNF-BP may be an important agent that blocks harmful effects of TNF, and, therefore, useful in clinical applications.

Cell Survival↗
PubMed1989

Isolation and characterization of a tumor necrosis factor binding protein from urine.

Tumor necrosis factor (TNF)/cachectin can produce both beneficial and harmful manifestations. Mechanisms may operate to counteract potentially harmful effects such as shock and cachexia. The TNF binding protein (TNF-BP), which is found at increased levels in serum and urine of patients with chronic renal failure, may play such a role. TNF-BP was purified 1,000,000-fold to homogeneity from urine of patients with chronic renal failure by use of ion exchange chromatography, affinity chromatography on TNF-Sepharose and reverse phase chromatography. The purified protein contained only one chain with an apparent Mr on sodium dodecyl sulfate-polyacrylamide gel electrophoresis of 30,000. The aminoterminal amino acid sequence D-S-V-X-P-Q-G-K-Y-I-H-P-Q-V-N-S-I-X-K-T revealed no significant homologies with previously described protein sequences. TNF-BP may act as a regulator of the bioactivities of TNF/cachectin.

Amino Acid Sequence↗
PubMed1989

Characterization of the receptor for lymphotoxin; a spontaneous internalization without recycling and ligand-induced downregulation in HL-60 cells.

The receptor system for lymphotoxin (LT) was investigated by use of the human promyelocytic HL-60 cell line. Utilizing subcellular fractionation, internalization of cell surface bound recombinant LT (rLT) and transfer to lysosomes followed by degradation was demonstrated. Binding of rLT to its cell surface receptor induced a downregulation of the receptor which was persistent for at least 6 h. Downregulation of the receptors from the cell surface by activation of protein kinase C with the diacylglycerol OAG was completely reversible but the recovery of the binding capacity was dependent on protein synthesis as it was inhibited by cycloheximide. Treatment with cycloheximide alone resulted in a loss of binding capacity with a half life of approximately 2 h, suggesting a spontaneous consumption of receptors. Affinity cross-linking revealed three ligand-receptor complexes with Mr of 85, 105 and 125 kDa. Because of a strong tendency for ligand polymerization these results suggest oligomer binding of the ligand to a single receptor molecule with an apparent Mr of 70 kDa. N-linked glycosylation constituted 4 to 5 kDa of the total molecular weight. In conclusion, we demonstrated a spontaneous internalization of the receptor for LT without recycling, and that ligand binding resulted in an irreversible downregulation of the receptor.

Asparagine↗
PubMed1988

Biosynthesis and processing of lactoferrin in bone marrow cells, a comparison with processing of myeloperoxidase.

The processing and intracellular transport of lactoferrin of the neutrophil specific granules was investigated by biosynthetic labeling with (14C)leucine of bone marrow cells from healthy individuals and patients with chronic myeloid leukemia. Lactoferrin was precipitated with antilactoferrin serum and the immunoprecipitates were analyzed by sodium dodecyl sulfate (SDS), polyacrylamide gel electrophoresis (PAGE) followed by fluorography. In contrast to myeloperoxidase of azurophil granules, lactoferrin was not synthesized as a larger precursor, and it was not found to be phosphorylated. The transfer to granules of newly synthesized lactoferrin was demonstrated in pulse-chase labeling experiments followed by centrifugation of cell homogenate in a Percoll gradient. Monensin, which exchanges protons for Na+ and NH4+ cation, blocked the transfer completely, indicating a need for acidification mechanisms. Unlike myeloperoxidase, newly synthesized lactoferrin rapidly became resistant to endoglycosidase H, indicating a transport through the medial and transcisternae of the Golgi apparatus with conversion of "high mannose" to "complex" oligosaccharide side chains. Intracellular transfer of some major neutrophil azurophil and specific granule constituents is obviously regulated differently. Lactoferrin seems to be processed like proteins destined for secretion, while myeloperoxidase is processed more or less like lysosomal enzymes.

Ammonium Chloride↗
PubMed1988

Myeloid cell differentiation: the differentiation inducing factors of myeloid leukemia cells.

Mitogen-stimulated lymphocytes and some T-lymphocyte lines released a polypeptide called differentiation-inducing factor (DIF), which restored maturation of promyelocytic HL-60 cells and inhibited growth of leukemic and normal progenitor cells. Tumor Necrosis Factor (TNF), which has been found to be not identical with DIF, displayed similar effects. On the other hand, an antigenic relationship was shown between DIF and lymphotoxin (LT) by use of neutralizing antibodies. An activity, which cochromatographed with DIF during all purification steps, competed with binding of both rLT and rTNF to HL-60 cells. Approximately 2,000 binding sites for rLT were detected per cell, with a Kd of 330 pmol/l. Our observations are indications of a functional and an antigenic connection between DIF and LT, and indicate that TNF, LT and DIF share cell surface-binding sites. These binding sites are down regulated by activation of protein kinase-C. Results from modulation of the response indicated that the signal for differentiation might be transduced through activation of phospholipase A2. In order to understand myeloid differentiation and the effects of differentiation factors, we have pursued investigations of the biosynthesis and processing of one marker of myeloid differentiation, namely myeloperoxidase (MPO). Our results disclosed that MPO was synthesized as a larger precursor of Mr 90,000 to which a heme group was added, followed by proteolytic cleavage in pregranular structures to generate mature heavy Mr 60,000 and light Mr 12,000 subunits. Processing of MPO was independent of acidification. cDNA probes are now available for MPO, so that investigation of gene expression in relation to differentiation and induction of differentiation is facilitated.

Cell Differentiation↗
PubMed1987

Characterization of a relationship between the T-lymphocyte derived differentiation inducing factor (DIF) and lymphotoxin: a common receptor system for DIF, lymphotoxin and tumor necrosis factor downregulated by phorbol diesters.

Here we describe results which show that recombinant lymphotoxin (rLT), like the T-lymphocyte derived differentiation inducing factor (DIF), inhibited the clonogenic growth of some myeloid leukemia cell lines by concentrations of 1 to 30 pmol/l. Wild type HL-60 cells were resistant at these concentrations but responded with differentiation into monocyte-like cells at higher concentrations. An antigenic relationship between DIF and LT was indicated because a neutralizing monoclonal anti-LT antibody bound to and neutralized both differentiation and growth inhibitory effects of DIF. An activity, which cochromatographed with DIF during all purification steps, competed with binding of both rLT and recombinant tumor necrosis factor (rTNF) to HL-60 cells. By use of radioiodinated ligand, 2100 binding sites for rLT were detected on HL-60 cells with a Kd of 330 pmol/l. At 37 degrees C bound ligand was transferred to lysosomes, followed by degradation. rTNF and rLT were shown to compete for binding sites on HL-60 cells. Receptors for both rLT and rTNF were downregulated by activators of protein kinase C such as phorbol diester or diacylglycerol; the number of cell surface receptors decreased while the Kd remained unchanged. Our observations demonstrate a functional and antigenic relationship between DIF and LT and indicate that TNF, LT and DIF share binding sites on myeloid leukemia cells that are downregulated by activation of protein kinase-C.

Binding Sites↗
PubMed1986

The biosynthesis of neutrophil and eosinophil granule proteins.

Composition of azurophil and specific granules from human polymorphonuclear neutrophils and granules from eosinophils is presented. Biosynthesis of the granule proteins is discussed in detail with particular emphasis on neutrophil myeloperoxidase (MPO) and eosinophil cationic protein (ECP).

Blood Proteins↗
PubMedDate not supplied

Lymphotoxin produced by human B- and T-cell lines appears in two distinct forms.

Production and release of lymphotoxin (LT) was studied by metabolic labeling of human B- and T-cell lines with 14C-leucine and 35S-methionine. LT was immunoprecipitated with antiserum to LT and separated by sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis (PAGE) followed by fluorography. Two molecular weight forms of LT with different rates of release were found both in cell supernatants and cell extracts. Monensin, a sodium ionophore, inhibited the release of LT. LT still appeared in two molecular weight forms after deglycosylation with N-glycanase. Treatment of cells with swainsonine followed by digestion of released LT with endoglycosidase H (endo H) demonstrated that the oligosaccharides were of the complex type. Subcellular fractionation of cells on Percoll density gradients demonstrated that intracellular LT is located to intermediate density fractions. No LT was found in the high density fractions corresponding to lysosomes. Phorbol 12-myristate 13-acetate induced production of tumor necrosis factor (TNF) in the B-lymphoblastoid cell line RPMI-1788. In conclusion, we have demonstrated the presence of two distinct molecular weight forms of LT, which contain N-linked oligosaccharides of the complex type.

B-Lymphocytes↗
PubMedDate not supplied

Tumour necrosis factor (TNF) binding proteins (soluble TNF receptor forms) with possible roles in inflammation and malignancy.

Inhibitors of Tumour Necrosis Factor (TNF) may be necessary for protection of the host against harmful systemic manifestations of this cytokine such as in the septic syndrome and inflammatory conditions. TNF-binding proteins (TNF-BP) have been identified and shown to be the soluble extracellular domains of two transmembrane TNF receptors produced by proteolytic cleavage. TNF-BP inactivates TNF by formation of high affinity complexes thereby reducing the binding of TNF to target cell membrane receptors. In addition, TNF is stabilized in complex with TNF-BP, and under certain conditions the complex may act as a slow releaser of biologically active TNF. TNF can induce the release of TNF-BP in vivo which might neutralize the bioactivity of TNF. Cytokine control by natural and recombinant cytokine inhibitors such as TNF-BP could be a promising therapeutic approach in chronic inflammatory disorders to shift the balance between a cytokine-induced response and counteracting "anticytokines". A local production of TNF-BP in some tumour tissues may inactivate TNF for the benefit of the tumour. In some leukemias e.g. B-cell chronic lymphocytic leukemia, where TNF can act as a growth factor for the malignant cells, TNF-BP may be growth inhibitory.

Cloning, Molecular↗