Transforming Growth Factor-β Inhibits the Cytokine-Mediated Expression of the Inducible Nitric Oxide Synthase mRNA in Human Retinal Pigment Epithelial Cells

Human retinal pigment epithelial (RPE) cells in culture respond to a mixture of cytokines (IFN-gamma, IL-1 beta, TNF-alpha) by producing large amounts of nitric oxide. Transforming growth factor-beta, unlike other growth factors, was found to inhibit this response by more than 75%. The expression of mRNA for the inducible form of nitric oxide synthase in RPE cells treated with cytokines was demonstrated by reverse transcription-polymerase chain reaction, sequencing of the PCR product and northern blotting. Transforming growth factor-beta was highly effective in inhibiting (by 75%) the cytokine-induced nitric oxide synthase mRNA expression. This response by RPE may play an important role in the etiology of infectious and inflammatory diseases affecting retina. (C) 1995 Academic Press, Inc.