GLUCOCORTICOIDS AND ITS RECEPTORS IN RETINAL PIGMENT EPITHELIAL CELLS

MARQUIONI-RAMELLA MD; TATE P; MARAZITA MC; CIDLOWSKI J; SUBURO AM

Congreso; Reunión Conjunta de Sociedades de Biociencias; 2017

Glucocorticoids are required for photoreceptor survival and retinal protection, but little is known about their signaling pathways in the retinal pigment epithelium (RPE). Several glucocorticoid receptors (GRs) are known, including GRα and GRβ. Therefore, we studied the presence of these receptors in mice and ARPE-19 cells, a human RPE cell line. In addition we studied their modifications after treatment with dexamethasone (DEX, a GRα agonist) and mifepris- tone (MFP, an inhibitor of GRα and a possible agonist of GRβ). Balb-c mice eye sections were immunostained with GRα and GRβ antisera. ARPE-19 cells were treated with DEX and/or MFP. Controls with or without ethanol were used. After 24 h, apoptosis was measured with acridine orange and ethidium bromide (AO/EB) stai- ning, and viability with MTT. Immunofluorescence, Western blots or qPCR were used for GRα and GRβ assays.Immunochemistry showed that GRα and GRβ appeared in retinal cell nuclei, whereas in the RPE, GRβ showed a strong cytoplasmic localization. Control ARPE-19 cells exhibited GRβ in a perinuclear localization. In these cultures, DEX induced a concentration-depen- dent increase of necrotic/apoptotic cells and a decrease of cell viability. MFP did not induce significant alterations in these parameters. Co-treatment with MFP did not avoid the cytotoxic effects of DEX. GRα mRNA was not significantly modified by 0.32 mM DEX, but it was significantly increased by 10 μM MFP. DEX did not affect GRβ mRNA. 50 μM MFP only induced a slight increase of GRβ mRNA, but the combination of 50 μM MFP with 0.08 or 0.32 mM DEX indu- ced a ten-fold increase.DEX cytotoxicity was not antagonized by MFP, indicating that the effects would not be mediated by GRα. The strong expression of GRβ in RPE cells, together with its localization and upregulation under DEX and MFP exposure suggests that this receptor might play an important role in retinal cell survival. However, further studies are required to understand the involved mechanisms.