INDUCTION OF OXIDATIVE DNA-DAMAGE AND ENHANCEMENT OF CELL-PROLIFERATION IN HUMAN-LYMPHOCYTES IN-VITRO BY BUTYLATED HYDROXYANISOLE

The food additive butylated hydroxyanisole (BHA) has been shown to ind uce gastrointestinal hyperplasia in rodents by an unknown mechanism. T he relevance of this observation for human risk assessment is not clea r. We therefore analysed the effect of BHA and its primary metabolites tert-butylhydroquinone (TBHQ) and tert-butylquinone (TBQ) on 8-oxo-de oxyguanosine formation and labelling indices in human lymphocytes in v itro. Analysis of culture medium and cell lysate fractions after admin istration of BHA or metabolites of BHA revealed that BHA and TBHQ unde rgo biotransformation in whole blood cultures, Moreover, TBQ can be re duced to TBHQ. While in cultures treated with BHA 50-60% of the dose a dministered was recovered, a much lower dose recovery was found in cul tures treated with either TBHQ or TBQ, This indicates a considerable b inding of these compounds to macromolecules, BHA and TBHQ, as well as TBQ, induced a dose-dependent increase in cell proliferation of phytoh aemagglutinin-stimulated lymphocytes, 50 mu M being the optimal dose, Since BHA is metabolized to TBHQ, it is not clear which compound is re sponsible for the proliferation enhancing effects observed in culture, Inhibition of TBHQ metabolism to its semiquinone radical by acetylsal icylic acid (ASA) reduced the increase in labelling indices induced by TBHQ. This indicates that this metabolic pathway is involved in the e nhancement of cell proliferation induced by the hydroquinone, HPLC-ECD analysis of oxidative DNA damage in lymphocytes exposed to 10, 50 and 100 mu M BHA, TBHQ or TBQ respectively showed that BHA was not capabl e of inducing oxidative DNA damage to a significant degree, TBQ and, i n particular, TBHQ at a dose of 50 mu M (the optimal dose for inductio n of cell proliferation), however, increased lymphocyte 7-hydroxy-8-ox o-2'-deoxyguanosine formation by 320 and 680% respectively, Inhibition of prostaglandin H synthase by ASA in cultures treated with TBHQ decr eased the oxidation ratio significantly, confirming the significance o f this enzyme system in the mechanism of toxicity of BHA.