The purpose of this study was to characterize the early molecular responses to quantified levels of oxidative stress (OS) in the human retinal pigment epithelium (RPE). Confluent ARPE-19 cells were cultured for 3 days in defined medium to stabilize gene expression. The cells were exposed to varying levels of OS (0-500 microM H(2)O(2)) for 1-8 h and gene expression was followed for up to 24-h after OS. Using real-time qPCR, we quantified the expression of immediate early genes from the AP-1 transcription factor family and other genes involved in regulating the redox status of the cells. Significant and quantitative changes were seen in the expression of six AP-1 transcription factor genes, FosB, c-Fos, Fra-1, c-Jun, JunB, and ATF3 from 1-8 h following OS. The peak level of induced transcription from OS varied from 2- to 128-fold over the first 4 h, depending on the gene and magnitude of OS. Increased transcription at higher levels of OS was also seen for up to 8-h for some of these genes. Protein translation was examined for 24-h following OS using Western blotting methods, and compared to the qPCR responses. We identified six AP-1 family genes that demonstrate quantitative upregulation of expression in response to OS. Two distinct types of quantifiable OS-specific responses were observed; dose-dependent responses, and threshold responses. Our studies show that different levels of OS can regulate the expression of AP-1 transcription factors quantitatively in the human RPE in vitro.
(c) 2009 Wiley-Liss, Inc.