Enhancement of cell attachment to a substrate coated with oral bacterial endotoxin by plasma fibronectin

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Abstract
Normal human fibroblasts were inhibited from attaching to a culture surface that was coated with endotoxic lipopolysaccharide (LPS) isolated from oral strains of Bacteroides or Fusobacterlum. The LPS from Fusobacterium inhibited cell attachment to a greater degree (p < 0.001) than that of the LPS from Bacteroides, and at a concentration as low as 12.5 ng/cm2 (p < 0.001), When LPS‐coated culture dishes (12.5 ng/cm2) were incubated with concentrations of plasma fibronectin as low as 50 μg/ml for at least 15 min, the fibronectin significantly enhanced cell attachment, returning it to control levels (p < 0.001). Futhermore, when plasma fibronectin (50 μg/ml) was compared to other agents such as bile acids, citrated serum, and human plasma fraction IV1 (Cohn), which have been shown to affect the toxicity of LPS, fibronectin led to significantly more cell attachment in the presence of LPS than any other treatment (p < 0.001). Evidence is presented by means of transmission electron microscopy (TEM) that LPS may bind to fibronectin. Subsequently, the cell surface interacts with the fibronectin‐LPS and internalizes it via phagocytosis. This mechanism provides for the clearance of LPS from the culture surface.