INCREASED EXPRESSION OF HEME OXYGENASE-1 IN HUMAN RETINAL-PIGMENT EPITHELIAL-CELLS BY TRANSFORMING GROWTH-FACTOR-BETA

Antibodies specific for heme oxygenase-1 (HO-1) were produced in rabbi ts, using the multiple antigen peptide (MAP) technique, and were emplo yed to investigate the ability of transforming growth factor-beta 1 (T GF-beta 1) to induce the HO-1 protein in cultured human retinal pigmen t epithelial (RPE) cells. Western blot analyses showed that the cytoki ne induced HO-1 in these cells in a time- and dose-dependent manner. T GF-beta 1 also increased the mRNA for HO-1 in treated cells prior to t he increase in HO-1 protein. The induction was effectively blocked by a neutralizing antibody preparation against TGF-beta 1. When tested un der similar conditions, other growth factors such as basic fibroblast growth factor-I, platelet-derived growth factor, insulin-like growth f actor, transforming growth factor-beta, and epidermal growth factor di d not show appreciable induction of HO-1. Lipopolysaccharide, tumor ne crosis factor-alpha, and interferon-gamma were also not inducers, alth ough TGF-beta 2 effectively induced HO-1. Heavy metal ions and thiol r eagents were also highly potent inducers of HO-1 in human RPE cells. T he induction of HO-1 by TGF-beta 1 was also observed in bovine choroid fibroblasts, but not in HELA, HEL or bovine corneal fibroblasts. Our results demonstrate for the first time that HO-1 can be induced by an important cytokine, TGF-beta 1, causing an increase in the expression of both HO-1 message and protein in specific neuroepithelial and fibro blast cells. (C) 1994 Wiley-Liss, Inc.*