Neuronal Differentiation of RPE Cells, but Not Y-79 or PC-12 Cells, Is Induced by Fenretinide and Results in a Time-Dependent Increase in Hsp70 Expression

Abstract

Abstract: : Purpose: We have reported that fenretinide (4-HPR), a chemopreventive synthetic retinoid, induced the differentiation of ARPE-19 cells to a neuronal phenotype (Chen et al., J. Neurochem., in press). 2D gel electrophoresis followed by mass spectrometric analysis identified increased expression of Hsp70 in 5-day treated cells. The purpose of this study was to determine whether fenretinide can induce the differentiation of other types of cells into neuronal phenotypes and to investigate the involvement of Hsp70 in this process. Methods: Human RPE cells, ARPE-19 and D-407 (a gift from Dr. R. C. Hunt, University of South Carolina School of Medicine), Y-79 human retinoblastoma cells and PC-12 rat pheochromocytoma cells were treated with 0-5 µM fenretinide for 1 week and examined daily under a microscope. Cells were also analyzed by immunocytochemistry using an anti-Hsp70 antibody. Western blot and ELISA were performed using cell extracts prepared from control and treated ARPE-19 cells. Results: ARPE-19 and D-407 cells, but not Y-79 or PC-12 cells, differentiated into a neuronal phenotype following fenretinide treatment. Western blot and immunocytochemical analyses showed a large increase in Hsp70 protein expression in ARPE-19 cells treated with fenretinide. ELISA demonstrated that Hsp70 expression reached a maximum of ~4 fold above control levels within 24 hours and remained at this level for 10 days during treatment. Conclusions: Fenretinide does not induce neuronal differentiation of Y-79 or PC-12 cells. Fenretinide-induced differentiation of RPE cells is associated with an increase in the expression of Hsp70, a protein involved in stress response as well as cell differentiation. CR: None

Keywords: retinal pigment epithelium • retina: neurochemistry • retinoids/retinoid binding proteins