Bacterial adherence to human endothelial cells

Abstract

The adult respiratory distress syndrome (ARDS) is frequently caused by exposure of the lung endothelium to circulating endotoxin (lipopolysaccharide, LPS) and pulmonary infections frequently develop during the course of ARDS. The present studies demonstrate that LPS and interleukin 1 (IL-1, a mediator released by endothelial cells after exposure to LPS) enhance the adherence of Staphylococcus aureus to human umbilical vein endothelial cells. gamma-Interferon, another mediator that induces expression of some cell surface antigens on endothelial cells, had no effect on bacterial adherence. The adherence of bacteria to endothelium was increased by prior opsonization of the bacteria with fresh human serum and was reduced by prior absorption of the serum with bacteria before the use of the serum for opsonization. The capacity of LPS to increase bacterial adherence was time dependent and was maximally expressed after 6 h of exposure; it was blocked by exposure of endothelial cells to LPS in the presence of reduced temperature or dactinomycin (Actinomycin D). These observations suggest that circulating LPS not only can trigger the development of ARDS but also may predispose the lung to the development of pulmonary infections by increasing adherence of bacteria to endothelium.