The present study was designed to investigate how tert-butylhydroquinone (tBHQ) prevents hydrogen peroxide-induced apoptosis in IMR-32 cells. tBHQ pretreatment (10 microm) attenuated hydrogen peroxide-induced cell death and reduced the number of TUNEL (terminal deoxynucleotidyltransferase-mediated, dUTP-incorporated nick end labeling)-positive cells. We hypothesize that tBHQ-mediated activation of the antioxidant responsive element is critical for generating this protective response. Addition of LY294002, a selective inhibitor of phosphatidylinositol 3-kinase (PI3K), 30 min prior to tBHQ treatment completely reversed the protective effect of tBHQ. Oligonucleotide microarrays were used to analyze the gene expression profile associated with tBHQ treatment in the absence and presence of LY294002. Ranking analysis using Affymetrix's difference call indicated that the expression of 137 genes changed with tBHQ treatment. Further analysis using the coefficient of variation for -fold change or average difference change reduced the list to 63 increased and 0 decreased genes. Reverse transcription-PCR for selected genes also confirmed the gene expression pattern. Many of these genes function to combat oxidative stress and increase the detoxification potential of the cells. Inhibition of PI3K significantly blocked the enhanced expression of 49 of the 63 genes induced by tBHQ. These data are the first to show a set of programmed cell life genes involved in conferring protection from an oxidative stress-induced apoptosis.