Neutrophil chemotactic factor (IL-8) gene expression by cytokine-treated retinal pigment epithelial cells

The neural-derived retinal pigment epithelium (RPE) underlies the sensory retina and is central to both retinal homeostasis and many common retinal diseases. Retinal pigment epithelium cells are actively phagocytic and share several features with macrophages that have recently been shown to produce a neutrophil chemotactic factor (NCF), also known as interleukin-8, after cytokine stimulation. Because RPE cell responses to cytokines are largely unknown, human RPE cell NCF production was monitored after interleukin-1-beta (IL-1 beta), tumor necrosis factor-alpha, or lipopolysaccharide stimulation. RPE NCF mRNA expression and RPE production of biologically active NCF was time and concentration dependent. Maximal NCF mRNA expression occurred at 20 ng/ml for IL-1 beta. Messenger RNA expression in RPE cells and biologically active NCF in RPE cell supernatants were found 1 hour after stimulation and were maintained for 24 hours. These findings demonstrate that cytokine-stimulated RPE cells may evoke or augment neutrophil-mediated inflammation by synthesizing NCF, a cytokine that may be important in ocular disease mechanisms.