title: DNA damage and cytotoxicity induced by beta-lapachone: relation to poly(ADP-ribose) polymerase inhibition.
abstract: beta-Lapachone (3,4-dihydro-2,2-dimethyl-2H-naphtho[1,2-b]pyran-5, 6-dione) was previously shown to enhance the lethality of X-rays and radiomimetic agents and its radiosensitizing role in mammalian cells was attributed to a possible interference with topoisomerase I activity. Furthermore, beta-lapachone alone was found to induce chromosomal damage in Chinese hamster ovary (CHO) cells. The aim of the present study was to further elucidate the possible mechanisms by which beta-lapachone exerts its genotoxic action in cultured mammalian cells. Flow cytometry analysis of beta-lapachone-treated CHO cells indicated a selective cytotoxic effect upon S phase of the cell cycle. beta-lapachone produced DNA strand breaks as determined by alkaline elution assay; alkaline elution profiles from treated cells showed a bimodal dose-response pattern, with a threshold dose above which a massive dose-independent DNA degradation was observed. Furthermore, beta-lapachone increased the capacity of crude CHO cellular extracts to unwind supercoiled plasmid DNA, while significantly inhibiting in vitro poly(ADP-ribose) polymerase (PARP). These results suggest that damage induction is probably mediated by the interaction between beta-lapachone and cellular enzymatic function(s), rather than reflecting a direct action on the DNA. We suggest that the inhibition of PARP plays a central role in the complex biological effects induced by beta-lapachone in CHO cells.
authors.affiliation: Centro di Genetica Evoluzionistica, CNR, via degli Apuli no. 4, Roma 00185, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Vanni
authors.forename: M
authors.initials: M
authors.lastname: Fiore
authors.forename: R
authors.initials: R
authors.lastname: De Salvia
authors.forename: E
authors.initials: E
authors.lastname: Cundari
authors.forename: R
authors.initials: R
authors.lastname: Ricordy
authors.forename: R
authors.initials: R
authors.lastname: Ceccarelli
authors.forename: F
authors.initials: F
authors.lastname: Degrassi
mesh_terms: D000818:Animals; D016466:CHO Cells; D002453:Cell Cycle / Q000187:drug effects*; D002470:Cell Survival / Q000187:drug effects; D006224:Cricetinae; D004249:DNA Damage; D007700:Kinetics; D009153:Mutagens; D009285:Naphthoquinones / Q000633:toxicity*; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D011838:Radiation-Sensitizing Agents / Q000633:toxicity*; D016196:S Phase
chemical_list: D009153:Mutagens; D009285:Naphthoquinones; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D011838:Radiation-Sensitizing Agents; C014638:beta-lapachone