Lipopolysaccharide-induced expression of intercellular adhesion molecule-1 and chemokines in cultured human corneal fibroblasts

PURPOSE. Invasion of bacteria into the corneal stroma induces the infiltration of leukocytes and subsequent corneal ulceration. The role of corneal fibroblasts in the detection of bacterial invasion into the stroma was investigated by examining the in vitro expression of the receptor complex for lipopolysaccharide (LPS), a common component of Gram-negative bacteria, as well as the possible effects of LPS on both the expression of adhesion molecules and the release of chemokines in cultured human corneal fibroblasts. METHODS. Expression of the LPS receptor complex, intercellular adhesion molecule (ICAM)-1, and the chemokines interleukin (IL)-8 and monocyte chemotactic protein (MCP)-1 was examined by reverse transcription - polymerase chain reaction, enzyme-linked immunosorbent assay, or immunofluorescence analysis. RESULTS. Corneal fibroblasts were found to contain transcripts encoding toll-like receptor-4, CD14, and MD-2, all of which are components of the LPS receptor complex. The expression of ICAM-1 at the surface of corneal fibroblasts and the amount of ICAM-1 mRNA in the cells were both increased by LPS. Similarly, LPS increased both the release of IL-8 and MCP-1 by corneal fibroblasts as well as the amounts of the corresponding mRNAs in these cells. These various effects of LPS were potentiated by the presence of a low concentration of human serum. CONCLUSIONS. Corneal fibroblasts may play an important role in the defense system of the cornea by recognizing the presence of LPS and subsequently expressing adhesion molecules and chemokines that promote leukocyte infiltration.