Adrenomedullin in cultured human retinal pigment epithelial cells

PURPOSE. To determine whether adrenomedullin (ADM), a vasorelaxant peptide is produced and secreted by human retinal pigment epithelial (RPE) cells, w hether ADM expression is regulated by inflammatory cytokines and a growth f actor, and whether ADM has proliferative effects on these cells. METHODS. Production and secretion of ADM by cultured human RPE cells were e xamined by Northern blot analysis and radioimmunoassay. Regulation of the A DM expression by basic fibroblast growth factor, interferon (IFN)-gamma, tu mor necrosis factor-alpha, interleukin (IL)-1 beta, or all-trans-retinoic a cid was studied. In addition, proliferative effects of ADM on human RPE cel ls were examined by modified 3-(4,5-dimetylthiazol-2-yl)-2,5-diphenyltetraz olium bromide (MTT) assay. RESULTS. ADM mRNA was expressed constitutively in all three human RPE cell lines (F-0202, D407, and ARPE-19) examined. Immunoreactive ADM was detected in the cultured media by radioimmunoassay. Sephadex G-50 column chromatogr aphy of the cultured medium showed a single peak eluting in the position of ADM-(1-52). Treatment with IFN-gamma or IL-1 beta increased ADM mRNA level s and immunoreactive-ADM levels in the medium in dose- and time-dependent m anners in ARPE-19 cells. Exogenously added ADM increased the number of F-02 02 cells and ARPE-19 cells, and the treatment with ADM antibody or ADM-(22- 52) (an ADM antagonist) decreased it. CONCLUSIONS. Human RPE cells produced and secreted ADM. IFN-gamma and IL-1 beta induced ADM expression in ARPE-19 cells. Furthermore, ADM stimulated p roliferation of RPE cells. These results raise the possibility that ADM is related to the pathophysiology of some inflammatory and proliferative ocula r diseases.