Biomedical subjects

Clemens Kunz

Publications and source records attributed to Clemens Kunz.

3 recordsLinked to original sources

PubMed2004

Human milk oligosaccharides reduce platelet-neutrophil complex formation leading to a decrease in neutrophil beta 2 integrin expression.

Human milk is thought by many authorities to be preferable to formula as a source of nutrients for infants. Some of the benefits may stem from its high concentration of unbound oligosaccharides (5-10 g/L). These sugars have structural similarities to selectin ligands, known to mediate important cell-cell interactions in the immune system. Platelet-neutrophil complexes (PNC) exist in healthy individuals but have been implicated in disease states. Formation of these complexes requires selectins and as such, could be influenced by human milk oligosaccharides (HMO). Here, we investigate this possibility by examining the effect of HMO on the formation of PNC and activation of associated neutrophils. We collected blood from 10 healthy volunteers, activated platelets with adenosine 5'-diphosphate, and added HMO, oligosaccharide standards, or phosphate-buffered saline as a control. We determined the influence of HMO on PNC formation and adjacent neutrophil activation with fluorescein-activated cell sorter analysis after labeling with antibodies for the platelet marker CD42a and the neutrophil activation marker CD11b. Within physiologically achievable concentrations (6.25-125 microg/mL), an acidic HMO fraction reduced PNC formation up to 20%, which was similar to the effect seen with high concentrations of sialyl-Lewis x. Associated neutrophils showed a dose-dependent decrease in beta 2 integrin expression, up to 30%, at high but physiological concentrations. The neutral HMO fraction had no effect. These results support the hypothesis that acidic HMO serve as anti-inflammatory components of human milk and thus, contribute to the lower incidence of inflammatory diseases such as necrotizing enterocolitis in breast-fed versus formula-fed infants.

Adenosine Diphosphate↗

PubMed2004

Effect of pulmonary surfactant on TNF-alpha-activated endothelial cells and neutrophil adhesion in vitro.

Pulmonary surfactant given to infants and adults with respiratory failure is metabolized and recycled to a large extent. A small proportion also enters the circulation in cases of increased permeability of the alveolar-capillary membrane. We therefore investigated whether exogenous surfactants such as a natural bovine (natSF) or a synthetic (synSF) preparation had an impact on inflammatory conditions involving the adhesion of neutrophils to endothelial cells. Human umbilical cord vein endothelial cells (HUVEC) were plated on coverslips until confluence, activated by tumor necrosis factor-alpha and incubated with or without surfactant in the media. Human neutrophils passed the HUVEC layer in a flow chamber and interactions were visualized using a video microscope. To test if surfactant affected the expression of cell adhesion molecules, RT-PCR analyses were performed for E-selectin, vascular cell adhesion molecule 1 (VCAM-1) and intercellular adhesion molecule 1 (ICAM-1). Using concentrations between 50 and 300 microg/ml of surfactant in the pre-incubation media the number of adherent neutrophils increased by 10-20% at the higher concentration of the natSF (*P < 0.05) whereas the synSF had no effect. Increased neutrophil adhesion was associated with a significant up-regulation of mRNA levels for E-selectin and VCAM-1; mRNA levels for ICAM-1, however, were not affected by the presence of surfactant. These observations indicate that natSF but not synSF might have pro-inflammatory effects when higher amounts of the exogenous dose reach the circulation. This might be explained by different fatty acid profiles, e.g. the presence of arachidonic acid in the natSF or higher concentrations of surfactant-associated protein-C in the synSF.

Cell Adhesion↗

PubMed2002

Detection of ligands for selectins in the oligosaccharide fraction of human milk.

BACKGROUND: Human milk contains a large variety of oligosaccharides which show struc tural similarities with ligands for selectins, a family of cell adhesion molecules which are involved in many cell-cell interactions. AIM OF THE STUDY: Due to their structural similarity with selectin ligands, human milk oligosaccharides were labelled with phosphatidyl ethanolamine to be able to investigate specific effects of antibodies against carbohydrate epitopes. METHODS: Various monoclonal antibodies against physiological selectin ligands were used to determine whether epitopes within human milk oligosaccharides are recognized. Oligosaccharides were isolated from human milk, transferred into neoglycolipids and separated using high performance thin layer chromatography prior to incubation with monoclonal antibodies for the selectin ligands sialyl-Lewis a (sLe a), sialyl-Lewis x (sLe x), Lewis x (Le x) and Lewis y (Le y) after Western blotting. Fast atom bombardment-mass spectrometry was then used to identify antibody-binding compounds. Results In the immunoassays all ligand epitopes except for Le y were detected in the oligosaccharide fraction of human milk. Anti-sLe a showed the most distinct reaction with N-acetylneuraminic acid containing neoglycolipids of which two were identified as neuraminylfucosyl-lacto-N-hexaose and neuraminyl-lacto-N-tetraose. Such oligosaccharides as well as similar structures are present in relatively high concentrations in human milk. CONCLUSIONS: The presence of sialyl-Lewis ligands on milk oligosaccharides together with their abundancy in human milk may suggest that they could be selectin ligands and they may be part of inflammatory processes.

Animals↗