DIFFERENT MECHANISMS OF TERT-BUTYL HYDROPEROXIDE-INDUCED LETHAL INJURY IN NORMAL AND TUMOR THYMOCYTES

Normal thymocytes and thymoma cells have been exposed to the toxic act ion of tert-butyl hydroperoxide (t-BOOH) to study the mechanisms of ox idative lethal cell injury and the sensitivity of normal and tumor cel ls to an oxidative stress. From our data, we can suggest that: (a) In thymoma cells two mechanisms can operate in determining t-BOOH toxicit y: the first one, involving glutathione peroxidase and nicotinamide nu cleotides, leads to cell death by alteration of calcium homoeostasis, and the second one, involving potent oxygen reactive species, affects cell viability by ATP depletion. The first mechanism is demonstrated b y the decrease of nicotinamide nucleotides, the partial protection fro m lactate dehydrogenase (LDH) release by ethylene glycol bis(beta-amin oethyl ether)-N,N'-tetraacetic acid (EGTA) (40%) and by dithiothreitol (DTT) (52%). The second mechanism is based on the partial protection of LDH release by deferoxamine (42%) and glucose (50%) and by total pr otection of ATP depletion by glucose. In agreement with these observat ions, DTT and deferoxamine in combination totally prevent cell death a s well as EGTA and glucose do. (b) In normal thymocytes only the mecha nism involving oxygen radical species is implicated. t-BOOH-induced de ath is not related to modifications of nicotinamide nucleotide pool. N o changes are observed in LDH release by the addition of EGTA and DTT. In contrast, deferoxamine totally prevents cell death. Mechanisms dep ending on cellular ATP are involved in t-BOOH-induced oxidative damage . Glucose completely prevents t-BOOH-mediated ATP depletion and comple tely protects from LDH release. Our data indicate that tumor transform ation deeply affects cell properties and metabolism, changing cell res ponsiveness to an oxidative stress. (C) 1994 Academic Press,Inc.