Induction of cytotoxicity, aldehydic DNA lesions, and poly(ADP-ribose) polymerase-1 activation by catechol derivatives of pentachlorophenol in calf thymus DNA and in human breast cancer cells.

The purpose of this study was to investigate the degree of chlorination of catechol (CAT) derivatives of pentachlorophenol (PCP) on the induction of cytotoxicity and DNA damaging effects in calf thymus DNA (ct-DNA) and in two human breast carcinoma cell lines. Results indicated that with the addition of the transition metal copper(II), increases in the amount of aldehydic DNA lesions (ADL) were detected in ct-DNA exposed to PCP-derived CATs over the corresponding control. The DNA lesions induced by various degrees of chlorination of PCP-derived CATs decrease in the rank order CAT congruent with 4-chlorocatechol (4-ClCAT) > 4,5-dichlorocatechol (4,5-Cl2CAT) > 3,4,5-trichlorocatechol (3,4,5-Cl3CAT) > tetrachlorocatechol (Cl4CAT). In contrast, Cl4CAT was the only congeneric form of PCP-derived catechols that induced a significant increase in the number of ADL in human MCF-7 cells, and this only occurred when glutathione was depleted. Pretreatment with copper(I) and iron(II) chelators significantly reduced the formation of ADL in cells exposed to Cl4CAT. The data also indicated that the ADL induced by Cl4CAT in MCF-7 cells contain approximately 70% putrescine excisable ADL. This evidence confirmed that the ADL induced by Cl4CAT in MCF-7 cells were derived from oxidative events. In addition, we demonstrated that the depletion of NAD(P)H in human T47D cells exposed to chlorinated CATs decreased in the rank order Cl4CAT >> 4-ClCAT congruent with CAT. The depletion of NAD(P)H induced by Cl4CAT in T47D cells was partially blocked by catalase, superoxide dismutase, dimethyl sulfoxide, and copper(I) and iron(II) specific chelators. Additionally, the depletion of NAD(P)H in T47D cells exposed to Cl4CAT (1-10 microM) was completely blocked by three types of poly(ADP-ribose) polymerase-1 inhibitors. This evidence suggests that Cl4CAT induces an imbalance in DNA repair and the subsequent accumulation of DNA strand breaks in human cultured cells. Overall, these findings indicate that dechlorination may decrease the potentials of chlorinated catechols to induce oxidative DNA lesions and cytotoxic effects in living cells.