Reactivity of corneal and conjunctival epithelial cells to lipopolysaccharide (LPS) and/or irradiation with visible light in vitro

Abstract

introduCtion. Visible light and inflammation caused by bacterial endotoxins strongly influence direct cell interactions and modulate the expression of selected factors, such as nitric oxide (NO) and cyclooxygenase-2 (COX-2). The aim of the study is to establish whether exposition of corneal or conjunctival epithelial cells to visible light and/ or LPS may change their viability, direct cellular interactions and expression of NO and COX-2. MateriaLs and Methods. In vitro cultured human corneal and conjunctival epithelial cells were used in the study. The following assays were performed: Neutral Red (NR) uptake, nitric oxide (NO) quantification by the Griess method, cytoskeletal F-actin organization by fluorescent staining, and COX-2 expression by immunofluorescence. resuLts. LPS reduced the viability of the cells, especially conjunctival epithelial cells. All cell stimulation variants tested (visible light and/or LPS treatment) led to decreased nitric oxide (NO) production both by corneal and conjunctival epithelial cells. No changes in cytoskeletal F-actin filaments were observed after the cells had been treated with light or the endotoxin. LPS slightly increased COX-2 expression, but light had no, or a slightly reducing, effect on the level of this enzyme. ConCLusions. Visible light and/or bacterial endotoxin (LPS) may, depending on the local microenvironmental conditions, cooperate or interfere with each other's activity in inducing ocular surface inflammation.