Opsonization of Staphylococcus aureus protects endothelial cells from damage by phagocytosing polymorphonuclear leukocytes

Abstract

When phagocytosis of Staphylococcus aureus by human polymorphonuclear leukocytes (PMN) takes place on the surface of cultured human endothelial cells, the endothelial monolayers are damaged by lysosomal enzymes that are released by the PMN. Because PMN can phagocytose opsonized as well as unopsonized staphylococci on an endothelial surface, we studied the role of bacterial opsonization in the damage caused to the endothelium. Phagocytosis of unopsonized S. aureus was accompanied by greater damage (expressed as the percentage of the endothelial cells detached from the culture plates) of the monolayers than was phagocytosis of opsonized S. aureus: 52 +/- 10% and 24 +/- 7%, respectively, after 30 min of phagocytosis and 73 +/- 5% and 50 +/- 6%, respectively, after 60 min of phagocytosis. When correlated to the amount of phagocytosis, this difference was even greater (uptake was 35 +/- 4% for unopsonized S. aureus and 56 +/- 5% for opsonized S. aureus after 30 min and 42 +/- 3% and 60 +/- 5%, respectively, after 60 min). Total release of lysozyme and myeloperoxidase and generation of superoxide anion were the same during phagocytosis of opsonized or unopsonized staphylococci. Adherence of PMN to the endothelial cells was greater during phagocytosis of unopsonized S. aureus: 42 +/- 4% verus 27 +/- 3% during phagocytosis of opsonized staphylococci. Possibly, increased adherence of the PMN resulted in a locally higher concentration of enzymes which induced more damage. We conclude that opsonization of bacteria not only improves bacterial uptake, but also protects bystander cells from damage by the phagocytosing PMN.

Adherence of Alpha‐Hemolytic Streptococci to Human Endocardial, Endothelial and Buccal Cells

“…In recent years, considerable evidence has accumulated showing that human pathogenic bacteria of different species attach themselves efficiently to mucosal epithelial cells, usually taken from the genito-urinary tract or from the oral cavity (12, 13, 14). There are, however, few such studies with alpha-hemolytic streptococci, especially concerning the attachment of these and other bacteria to endothelial cells (15,16). In the present study we were able to show that alpha-hemolytic streptococci, isolated from blood of patients with endocarditis, adhered more efficiently in vitro than carrier strains to endocardial and endothelial cells.…”

Bovine pulmonary endothelial cell damage mediated by Pasteurella haemolytica pathogenic factors

“…Cellular detachment assay. As a more sensitive indicator of endothelial cell damage, a previously described detachment assay (19) was also used to quantify the degree of endothelial cell membrane damage and decreased adhesion to the culture well plastic surface. The experimental culture wells described above for the 51Cr release assay were used.…”