Biomedical subjects

H Lindmark

Publications and source records attributed to H Lindmark.

8 recordsLinked to original sources

PubMed1999

Pulsed-field gel electrophoresis and distribution of the genes zag and fnz in isolates of Streptococcus equi.

Streptococcus equi subsp. equi and subsp. zooepidemicus are important pathogens of the equine respiratory tract. Isolates of both subspecies were examined by pulsed-field gel electrophoresis (PFGE). With the exception of eight isolates, a unique band pattern was displayed for each of the 48 subsp. zooepidemicus isolates tested. A method to distinguish isolates of the genetically very homogeneous subsp. equi has hitherto not been available, although several methods have been tested. By the use of PFGE, 50 isolates of subsp. equi could be divided into eleven groups, each with a unique pulsotype. In addition, the recently characterised genes encoding the cell-wall proteins ZAG and FNZ of S. equi subsp. zooepidemicus strain ZV were shown by Southern blots to be present in all 98 tested isolates, including the type strains of the two subspecies. Binding assays showed that the expression of the two genes clearly differentiate between the two subspecies.

Adhesins, Bacterial↗

PubMed1999

SFS, a novel fibronectin-binding protein from Streptococcus equi, inhibits the binding between fibronectin and collagen.

The obligate parasitic bacterium Streptococcus equi subsp. equi is the causative agent of strangles, a serious disease of the upper respiratory tract in horses. In this study we have, using shotgun phage display, cloned from S. equi subsp. equi and characterized a gene, called sfs, encoding a protein termed SFS, representing a new type of fibronectin (Fn)-binding protein. The sfs gene was found to be present in all 50 isolates of S. equi subsp. equi tested and in 41 of 48 S. equi subsp. zooepidemicus isolates tested. The sfs gene is down-regulated during growth in vitro compared to fnz, a previously characterized gene encoding an Fn-binding protein from S. equi subsp. zooepidemicus. Sequence comparisons revealed no similarities to previously characterized Fn-binding proteins, but high scores were obtained against collagen. Besides similarity due to the high content of glycine, serine, and proline residues present in both proteins, there was a nine-residue motif present both in collagen and in the Fn-binding domain of SFS. By searching the Oklahoma S. pyogenes database, we found that this motif is also present in a potential cell surface protein from S. pyogenes. Protein SFS was found to inhibit the binding between Fn and collagen in a concentration-dependent way.

Adhesins, Bacterial↗

PubMed1998

Butylated hydroxytoluene and N-acetylcysteine attenuates tumor necrosis factor-alpha (TNF-alpha) secretion and TNF-alpha mRNA expression in alveolar macrophages from human lung transplant recipients in vitro.

BACKGROUND: Tumor necrosis factor-alpha (TNF-alpha) is a polypeptide cytokine principally produced by macrophages/monocytes and commonly associated with inflammatory conditions. The present study was designed to investigate whether the antioxidants butylated hydroxytoluene (BHT) and N-acetylcysteine (NAC) modified TNF-alpha production in stimulated and unstimulated alveolar macrophages from lung transplant recipients in vitro. METHODS: The effects of BHT and NAC on TNF-alpha production were studied both with and without lipopolysaccharide (LPS) activation of alveolar macrophages from bronchoalveolar lavage fluid. TNF-alpha was quantitated in cell culture medium using an enzyme-linked immunosorbent assay. TNF-alpha mRNA expression was analyzed by quantitative reverse transcription-polymerase chain reaction on total RNA extracted from the incubated alveolar macrophages. RESULTS: In unstimulated alveolar macrophages, TNF-alpha levels were significantly reduced by incubation with BHT or NAC. When alveolar macrophages from patients with cytomegalovirus infection were incubated with BHT, TNF-alpha secretion was significantly lowered. A significant reduction of TNF-alpha levels in LPS-stimulated alveolar macrophages was obtained in the presence of BHT or NAC. Our data from quantitative reverse transcription-polymerase chain reaction showed that the observed decrease in protein levels of TNF-alpha was associated with a decrease in TNF-alpha mRNA expression. CONCLUSIONS: Our results indicate that antioxidant treatment may be an effective step to lower the inflammatory process caused by cytomegalovirus infection or in endotoxin (LPS)-activated macrophages. The therapeutic use of antioxidant compounds could, therefore, be of interest in conditions such as lung transplantation, in which oxidative stress and inflammation can contribute significantly to the loss of allograft function.

Acetylcysteine↗

PubMed1997

Shot-gun phage display mapping of two streptococcal cell-surface proteins.

We have used a phage display shot-gun cloning technique to map the binding domains in two cell surface proteins from animal group C streptococci. The proteins, MAG and ZAG, have affinity for alpha (2)-macroglobulin (alpha (2)M), serum albumin and IgG. In this work, parts of cloned i mag and zag genes were randomly cloned into a phagemid vector, and recombinant phages expressing alpha (2)-M- or albumin-binding activity were isolated through panning against immobilized alpha (2)M or albumin. Analysis of the clones revealed two distinct alpha (2)M-binding sites in protein MAG and two slightly overlapping binding sites in protein ZAG. The minimal albumin-binding domain in protein ZAG, as deduced from the affinity selected clones, consisted of 42 amino acids. These results show that the phage display shot-gun cloning is a rapid and convenient way to characterize the binding site(s) in receptor proteins without any prior knowledge of their number, size, and localization.

Albumins↗

PubMed1997

Effect of phenotype on the transcription of the genes for platelet-derived growth factor (PDGF) isoforms in human smooth muscle cells, monocyte-derived macrophages, and endothelial cells in vitro.

Proliferation of arterial smooth muscle cells (ASMCs) contributes considerably to enlargement of the arterial wall during atherosclerosis. The platelet-derived growth factor (PDGF) is a well-known mitogen and chemoattractant for ASMCs. Quantitative reverse transcription-polymerase chain reaction showed that cells appearing in atherosclerotic lesions, such as ASMCs, endothelial cells, and monocytes/macrophages, expressed mRNAs for both PDGF A and B chains in vitro, with the highest expression in endothelial cells. On proliferation, ASMCs and endothelial cells upregulated PDGF A mRNA. Differentiation of macrophages increased the amount of both mRNAs. Thus, the regulation of PDGF A- and B-chain expression depends on cell types and phenotypic states of the cells, which have also been found in vivo in human atherosclerotic lesions. PDGF A can be produced as short and long isoforms. The latter binds with high affinity to glycosaminoglycans. Irrespective of phenotype, only the minor part of total PDGF A mRNA consisted of the long variant in ASMCs, while endothelial cells produced 40% of total PDGF A as the long form. The differentiation of macrophages increased the production of the long PDGF A mRNA from 10% to 40%. Thus, increasing numbers of stimulated cells in the atherosclerotic lesion may increase the transcription of PDGF isoforms, and particularly of the long PDGF A isoform. Together with increasing amounts of ASMC-derived proteoglycans in developing lesions, this may contribute to accumulation of PDGF in the arterial wall matrix, resulting in prolonged stimulation of ASMCs.

Adult↗

PubMed1996

Oxysterols present in atherosclerotic tissue decrease the expression of lipoprotein lipase messenger RNA in human monocyte-derived macrophages.

The presence of oxysterols in macrophages isolated from atherosclerotic tissue and the effect of oxysterols on the regulation of lipoprotein lipase (LPL) mRNA were studied. Both rabbit and human macrophages, freshly isolated from atherosclerotic aorta, show about the same distribution of oxysterols, analyzed by isotope dilution mass spectrometry, except that all three preparations of human arterial-derived macrophages contained high levels of 27-hydroxycholesterol, which was not found in rabbit macrophages. To determine if oxysterols regulate LPL expression, human monocyte-derived macrophages were incubated with different oxysterols. Incubation with 7 beta-hydroxycholesterol and 25-hydroxycholesterol resulted in a 70-75% reduction of LPL mRNA, analyzed by quantitative RT-PCR. Cholesterol and other tested oxysterols showed no effect on macrophage LPL mRNA expression compared with control. LPL activity in the medium was also reduced after exposure of the macrophages to 7 beta-hydroxycholesterol and 25-hydroxycholesterol. In conclusion, we have demonstrated accumulation of oxysterols in macrophage-derived foam cells isolated from atherosclerotic aorta. There was suppression of LPL mRNA in human monocyte-derived macrophages after incubation with 7 beta-hydroxycholesterol and 25-hydroxycholesterol. It is tempting to suggest that an exposure to oxysterols may explain our earlier observation of a low level of LPL mRNA in arterial foam cells.

Animals↗

PubMed1996

Fibronectin-binding protein of Streptococcus equi subsp. zooepidemicus.

By screening a genomic lambda library of Streptococcus equi subsp. zooepidemicus, we have cloned and sequenced a gene, termed fnz, encoding a fibronectin (Fn)-binding protein called FNZ. On the basis of the deduced amino acid sequence of FNZ, the mature protein has a molecular mass of approximately 61 kDa. Analysis of FNZ reveals a structural organization similar to that of other cell surface proteins from streptococci and staphylococci. The Fn-binding activity is localized to two domains in the C-terminal part of FNZ. One domain is composed of five repeats, which contain a motif similar to what has earlier been found in other Fn-binding proteins in streptococci and staphylococci. The first and second repeats are separated by a short stretch of amino acids, including the motif LAGESGET, which is an important part of the second Fn-binding domain. This motif is also present in an Fn-binding domain (UR) in protein F of Streptococcus pyogenes. A fusion protein covering the Fn-binding domain of FNZ inhibits the binding of the 29-kDa N-terminal fragment of Fn to cells of various streptococcal species as well as to Staphylococcus aureus.

Adhesins, Bacterial↗

PubMed1995

A protein G-related cell surface protein in Streptococcus zooepidemicus.

This work describes the cloning and sequencing of a gene encoding a plasma protein receptor from Streptococcus zooepidemicus. This receptor, termed protein ZAG, is a 45-kDa protein that binds alpha 2-macroglobulin (alpha 2M), serum albumin, and immunoglobulin G (IgG). The IgG-binding activity is located in the C-terminal part of the molecule and is mediated by two repeated domains highly homologous to each other as well as to the corresponding domains in streptococcal type III Fc receptors. The IgG-binding profile of protein ZAG is similar to that previously reported for S. zooepidemicus. Binding to serum albumin is mediated by a short amino acid sequence in the middle of the molecule. This domain shows homology to previously described albumin-binding proteins from streptococci, and the albumin-binding profile of protein ZAG is similar to that of streptococcal protein G. The N-terminal part of protein ZAG, which mediates binding to the plasma proteinase inhibitor alpha 2M, is composed of a unique stretch of amino acids. Protein ZAG competes for the same, or nearby, binding site(s) in alpha 2M as do two recently described Streptococcus dysgalactiae receptors, although the sequences of the alpha 2M-binding domains in these three receptors show only minor sequence similarities.

Amino Acid Sequence↗