Biomedical subjects

Maria Cristina Plotkowski

Publications and source records attributed to Maria Cristina Plotkowski.

4 recordsLinked to original sources

PubMed2005

Nod1 participates in the innate immune response to Pseudomonas aeruginosa.

The mammalian innate immune system recognizes pathogen-associated molecular patterns through pathogen recognition receptors. Nod1 has been described recently as a cytosolic receptor that detects specifically diaminopimelate-containing muropeptides from Gram-negative bacteria peptidoglycan. In the present study we investigated the potential role of Nod1 in the innate immune response against the opportunistic pathogen Pseudomonas aeruginosa. We demonstrate that Nod1 detects the P. aeruginosa peptidoglycan leading to NF-kappaB activation and that this activity is diminished in epithelial cells expressing a dominant-negative Nod1 construct or in mouse embryonic fibroblasts from Nod1 knock-out mice infected with P. aeruginosa. Finally, we demonstrate that the cytokine secretion kinetics and bacterial killing are altered in Nod1-deficient cells infected with P. aeruginosa in the early stages of infection.

Adaptor Proteins, Signal Transducing↗

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

Binding of plasminogen to Pseudomonas aeruginosa results in formation of surface-associated plasmin and enhanced bacterial invasiveness.

The interaction of Pseudomonas aeruginosa with plasminogen (Plg) is herein reported. Plg bound similarly to laboratory and clinical P. aeruginosa isolates from blood of septicemic patients and stools of asymptomatic carriers. No difference in Plg capture was detected between the piliated PAK strain and its isogenic nonpiliated mutant. Western immunoblotting results suggested that low molecular weight nonpilus adhesins from the bacterial outer membranes accounted for the Plg capture. Bacteria-bound Plg was converted to bioactive plasmin in the presence of exogenous urokinase-type Plg activator. The presence of surface-bound plasmin enhanced significantly the P. aeruginosa capability to invade fibrin gels and a reconstituted basement membrane matrix. These findings support the concept that Plg capture by P. aeruginosa may represent a mechanism which offers advantages to bacterial invasiveness through tissue barriers.

Adhesins, Bacterial↗

PubMed2002

Expression of inducible nitric oxide synthase in human umbilical vein endothelial cells during primary culture.

The adaptive response of endothelial cells to stress may lead to the upregulation of nitric oxide (NO) production. Herein, we report inducible nitric oxide synthase (iNOS) induction in primary cultures of human umbilical vein endothelial cells (HUVEC). The enzyme expression was earlier observed in 12-h cultures, reaching maximal levels after 3 days and decreasing when cells become confluent. The time course of NO production by HUVEC paralleled iNOS expression during the whole culture period, indicating that enzyme was functionally active. Conversely, iNOS induction could not be further detected in HUVEC subcultures passed once from cells presenting maximal levels of iNOS expression in the primary culture. Induction of iNOS in HUVEC was not related to lipopolysaccharide contamination, since the enzyme expression was not affected in the presence of polymyxin B added to primary cultures. Further analysis showed that aminoguanidine, a specific iNOS inhibitor, did not affect cell proliferation, suggesting that the NO produced by HUVEC may not be directly related to cell growth. Platelet endothelial cell adhesion molecule-1 expression was upregulated during cell confluence, in contrast to the decrease of iNOS expression and activity. The data suggest that iNOS expression may be a molecular mechanism mediating the adaptive response of endothelial cells to culture environment.

Blotting, Western↗