DNA-DAMAGE, GADD153 EXPRESSION, AND CYTOTOXICITY IN PLATEAU-PHASE RENAL PROXIMAL TUBULAR EPITHELIAL-CELLS TREATED WITH A QUINOL THIOETHER

2-Bromo-bis-(glutathion-S-yl)hydroquinone [2-Br-bis-(GSyl)HQ] causes D NA single-strand breaks (SSB), causes growth arrest, induces the expre ssion of gadd153 (a gene inducible by growth arrest and DNA damage), a nd decreases histone H2B mRNA in log-phase renal proximal tubular epit helial cells (LLC-PK1). Renal epithelial cells in vivo normally exhibi t a low mitotic index, therefore experiments in both plateau- and log- phase cells are necessary for a comprehensive understanding of the str ess response to 2-Br-bis-(GSyl)HQ. In the present article we demonstra te that not all features of the stress response in log-phase cells are reproduced in plateau-phase cells. Thus, although 2-Br-bis-(GSyl)HQ c auses concentration and time-dependent increases in DNA SSB, and incre ases the expression of gadd153, histone H2B mRNA levels are unaltered in plateau-phase cells. The relationship between reactive oxygen speci es, DNA damage, gene expression, and cytotoxicity was also investigate d. Our findings suggest that (i) 2-Br-bis-(GSyl)HQ-mediated DNA damage in LLC-PK1 cells is mediated by the generation of H2O2; (ii) DNA dama ge, either directly or indirectly, contributes to cell death; and (iii ) DNA damage, either directly or indirectly, provides the initial sign al for gadd153 expression. In addition, DNA repair is rapid in LLC-PK1 cells, and the DNA-repair inhibitors 1-beta-D-arabinofuranosylcytosin e and hydroxyurea have no effect on the amount of DNA SSB.