Biomedical subjects

Marc Merten

Publications and source records attributed to Marc Merten.

4 recordsLinked to original sources

PubMed2004

Live Staphylococcus aureus and bacterial soluble factors induce different transcriptional responses in human airway cells.

To characterize the response of respiratory epithelium to infection by Staphylococcus aureus (S. aureus), human airway cells were incubated for 1 to 24 h with a supernatant of a S. aureus culture (bacterial supernatant), then profiled with a pangenomic DNA microarray. Because an upregulation of many genes was noticed around 3 h, three independent approaches were then used to characterize the host response to a 3-h contact either with bacterial supernatant or with live bacteria: 1) a DNA microarray containing 4,200 sequence-verified probes, 2) a semiquantitative RT-PCR with a set of 537 pairs of validated primers, or 3) ELISA assay of IL-8, IL-6, TNFalpha, and PGE(2). Among others, Fos, Jun, and EGR-1 were upregulated by the bacterial supernatant and by live bacteria. Increased expression of bhlhb2 and Mig-6, promoter regions which harbor HIF responding elements, was explained by an increased expression of the HIF-1alpha protein. Activation of the inducible form of cyclooxygenase, COX-2, and of the interleukins IL-1, IL-6, and IL-8, as well as of the NF-kappaB pathway, was observed preferentially in cells in contact with bacterial supernatant. Early infection was characterized by an upregulation of anti-apoptotic genes and a downregulation of pro-apoptotic genes. This correlated with a necrotic, rather than apoptotic cell death. Overall, this first global description of an airway epithelial infection by S. aureus demonstrates a larger global response to bacterial supernatant (in term of altered genes and variation factors) than to exponentially growing live bacteria.

Cell Culture Techniques↗

PubMed2004

Dynamic interaction between airway epithelial cells and Staphylococcus aureus.

Staphylococcus aureus is a major cause of pulmonary infection, particularly in cystic fibrosis (CF) patients. However, few aspects of the interplay between S. aureus and host airway epithelial cells have been investigated thus far. We investigated by videomicroscopy the time- and bacterial concentration-dependent (10(4), 10(6), and 10(8) CFU/ml) effect of S. aureus on adherence, internalization, and the associated damage of the airway epithelial cells. The balance between the secretion by S. aureus of the alpha-toxin virulence factor and by the airway cells of the antibacterial secretory leukoproteinase inhibitor (SLPI) was also analyzed. After 1 h of interaction, whatever the initial bacterial concentration, a low percentage of S. aureus (<8%) adhered to airway cells, and no airway epithelial cell damage was observed. In contrast, after 24 h of incubation, more bacteria adhered to airway epithelial cells, internalized bacteria were observed, and a bacterial concentration-dependent effect on airway cell damage was observed. At 24 h, most airway cells incubated with bacteria at 10(8) CFU/ml exhibited a necrotic phenotype. The necrosis was preceded by a transient apoptotic process. In parallel, we observed a time- and bacterial concentration-dependent decrease in SLPI and increase in alpha-toxin expression. These results suggest that airway cells can defend against S. aureus in the early stages of infection. However, in later phases, there is a marked imbalance between the bactericidal capacity of host cells and bacterial virulence. These findings reinforce the potential importance of S. aureus in the pathogenicity of airway infections, including those observed early in CF patients.

Apoptosis↗

PubMed2004

Homocysteine increases methionine synthase mRNA level in Caco-2 cells.

BACKGROUND: Methionine synthase (MTR) synthesizes methionine from homocysteine, using cobalamin as a cofactor and 5-methyltetrahydrofolate as a cosubstrate. AIM: To determine the influence of homocystine (Hcy, dimer of homocysteine) in the presence of either cobalamin or methionine on the transcription and the activity of methionine synthase in Caco-2, a human adenocarcinoma cell line. METHODS: Methionine synthase activity and quantification of its mRNA by real-time RT-PCR were determined in cells cultivated under four differents conditions: Hcy with cobalamin (Hcy+ Cbl+), Hcy with methionine (Hcy+Met+), methionine with Cbl (Met+ Cbl+) and methionine only (Met+). RESULTS: Activity (nmol/h/mg protein) was maximal in cells cultivated in Hcy+Cbl+ (2.45 +/- 0.35), compared to cells cultivated in Hcy+Met+ (0.18 +/- 0.01, p<0.001), in Met+ Cbl+ (1.60 +/- 0.06, p<0.05), and in Met+ (0.40 +/- 0.05, p<0.001), suggesting an adaptation of the cells to requirement in synthesized methionine. The mRNA level of MTR in Hcy+ Cbl+ and Hcy+Met+ (2.82 +/-0.49 and 3.33 +/- 0.48 AU, respectively ) was about 2.5 / 3.0-fold higher than that in Met+ Cbl+ and in Met+ (1.00 +/-0.13 and 1.20 +/-0.20 AU, respectively, p<0.001). CONCLUSION: Methionine synthase expression of Caco-2 cell is under a transcriptional control influenced by Hcy.

5-Methyltetrahydrofolate-Homocysteine S-Methyltran↗

PubMed2003

Uptake of plasmid/glycosylated polymer complexes and gene transfer efficiency in differentiated airway epithelial cells.

BACKGROUND: We have studied gene transfer efficiency of glycosylated polylysines and glycosylated polyethylenimines as vectors in immortalized differentiated airway gland serous cells and primary cultures of human airway surface epithelial cells. METHODS AND RESULTS: In both cell types, lactosylated PEI was more efficient for gene transfer than unsubstituted PEI and lactosylated polylysine which requires the presence of endosomolytic agents. However, for all the vectors tested, gene transfer efficiency was lower in differentiated cells as compared with poorly differentiated cells. The presence of membrane lectins, i.e. cell surface sugar-specific receptors, was evaluated using fluorescein-conjugated neoglycoproteins and microscopy or flow cytometry. In differentiated airway surface epithelial cells, membrane lectins were not expressed and plasmid DNA/fluorescein-conjugated glycosylated polymer complexes were not incorporated. This accounted in part for the lack of gene transfer efficiency in these cells. In contrast, in differentiated airway gland serous cells, expression of lectins and their endocytotic properties appeared to be similar to that observed in undifferentiated cells, and plasmid DNA/fluorescein-conjugated glycosylated polymer complexes were incorporated in similar amounts by cells in both differentiated states CONCLUSIONS: Glycosylated PEI appears to be a promising gene delivery system since it is more efficient than the sugar-free polymer and does not require endosomolytic agents. However, in differentiated airway gland serous cells, a low gene transfer efficiency was observed that could not be attributed to low expression of membrane lectins or low uptake of glycosylated complexes. An impaired intracellular trafficking of glycosylated complexes in differentiated airway gland serous cells is suggested.

Cell Line↗