The early intracellular production of a reactive oxygen intermediate mediates apoptosis in dexamethasone-treated thymocytes.

Many conditions that induce an oxidative stress are capable of evoking apoptosis. This has lead to the proposal of oxidative stress as a mediator of apoptosis. We show that, in murine thymocytes, oxidative stress and apoptosis occur in the same cell. We identified four distinct apoptotic subpopulations that appeared sequentially in time. Catalase protected from dex-amethasone-induced death in the initial stages of apoptosis, while iron chelators and Vitamin E did not. Further studies provided evidence supporting the early production of an intracellular oxidative intermediate as an obligatory step for the efficient induction of apoptosis. We propose that at least one of the molecules capable of filling this role is hydrogen peroxide.