Syndecan‐1 modulates leukocyte adhesion in the murine parietal peritoneum microcirculation in response to Staphylococcus aureus lipotechoic acid

Syndecan‐1 modulates leukocyte recruitment in several tissues. The objective of this study was to determine the effects of syndecan‐1 blockade on leukocyte‐endothelial cell interactions in venules of the parietal peritoneum. BALB/c mice were stimulated with ip injection of E. coli LPS or S. aureus LTA and the microcirculation was examined by intravital microscopy after 4 hrs. Syndecan‐1 was localized to the basal membrane of venular endothelium using in vivo confocal imaging with a fluorescent anti‐syndecan‐1 antibody. Leukocyte‐endothelial interactions and leukocyte extravasation were not significantly different in response to LPS compared to naive control. After stimulation with LTA, rolling (94.8 ± 15.3 cells/min) and adhesion (15.0 ± 4.0 cells) along the endothelial wall and extravascular leukocytes (8.5 ±1.8 cells) were significantly increased compared to control, (37.0 ± 8.5, 1.26 ± 0.5, 0.7 ± 0.3 respectively, p < 0.05). Syndecan‐1 blockade before stimulation with LTA significantly increased the number of adherent leukocytes (37.8 ± 6.0, p < 0.001) and systemic neutrophil counts. Leukocyte‐endothelial interactions and systemic neutrophil counts were not increased in anti‐syndecan‐1‐injected saline controls. Our data suggest the parietal peritoneum vasculature is more responsive to LTA than LPS and syndecan‐1 is a negative regulator of leukocyte adhesion during LTA‐induced inflammation.