INHIBITION OF POLY(ADP-RIBOSE) POLYMERASE INCREASES (+ -)-ANTI-BENZO[A]PYRENE DIOLEPOXIDE-INDUCED MICRONUCLEI FORMATION AND P53 ACCUMULATION IN ISOLATED HUMAN PERIPHERAL-BLOOD LYMPHOCYTES/

In response to DNA damage, in particular DNA strand breaks, the propos ed roles for normal tumour suppressor protein p53 are to increase the period of time available for DNA repair prior to replication, or to di rect damaged cells into programmed cell-death, Since treatment of mamm alian cells with (+/-)-anti-benzo[a]pyrene diolepoxide [(+/-)-anti-BPD E]-a mixture of metabolites comprising the most reactive (+)-anti-enan tiomer of the full environmental carcinogen benzo[a]pyrene-has been sh own to result in induction of DNA repair processes and consequently in DNA strand break formation, the aim of the present study was to inves tigate whether p53 accumulation is induced in (+/-)-anti-BPDE-treated phytohaemagglutinin-stimulated human peripheral blood lymphocytes (PBL s), Both immunocytochemical and immunoblot analysis indicated that tre atment of PBLs with (+/-)-anti-BPDE results in p53 accumulation, Optim al accumulation was observed at 2.5 mu M, while no increase of p53 lev els was observed at concentrations <2.5 mu M and >10 mu M. Further, (/-)-anti-BPDE-induced p53 accumulation in PBLs was found to be time-de pendent with accumulation up to 24 h after the onset of treatment. Tre atment of PBLs with 2.5 mu M of (+/-)-anti-BPDE and 1 mM of 3-aminoben zamide, an inhibitor of the DNA strand break-dependent enzyme poly(ADP -ribose) polymerase, resulted in increased p53 levels, in comparison t o cells treated with (+/-)-anti-BPDE alone, This combination also pote ntiated the frequency of (+/-)-anti-BPDE-induced micronuclei, These fi ndings suggest that (+/-)-anti-BPDE-induced DNA strand break formation is responsible for the observed p53 accumulation, It is unlikely that poly(ADP-ribose) polymer formation is a prerequisite in the process o f p53 accumulation, as triggered by DNA strand-break inducing agents l ike (+/-)-anti-BPDE, It is hypothesized that p53-dependent pathways ma y be activated in phytohaemagglutinin-stimulated human peripheral bloo d lymphocytes exposed ex vivo to (+/-)-anti-BPDE.