ALTERATION IN METHYL-METHANESULFONATE-INDUCED POLY(ADP-RIBOSYL)ATION BY 2-BUTOXYETHANOL IN SYRIAN-HAMSTER EMBRYO CELLS

The effects of 2-butoxyethanol (2-BE) on poly(ADP-ribosyl)ation mere s tudied in Syrian hamster embryo (SHE) cells by measuring the cellular concentrations of the polymer poly(ADP-ribose) (pADPr) and of NAD(+), the substrate of poly(ADP-ribose) polymerase (PARP), As biotransformat ion pathways of ethylene glycol ethers involve NAD(+)-dehydrogenases, it was hypothesized that 2-BE could reduce poly(ADP-ribosyl)ation by c onsuming NAD(+), As a result DNA repair could be altered, which would explain that 2-BE had been shown to potentiate the effects of clastoge nic substances such as methyl-methanesulfonate (MMS). In this study, t he effects of 2-BE on MMS-induced pADPr metabolism were analyzed, The results indicated that: (i) 2-BE (5 mM) by itself did not influence si gnificantly pADPr or NAD(+) levels, (ii) 2-BE inhibited pADPr synthesi s in MMS (0.2 mM)-pretreated cells, without any change in NAD(+) conce ntrations. (iii) MMS treatment, which rapidly increased pADPr levels, also affected the poly(ADP-ribosyl)ation system as a secondary effect by damaging cell structures, Membrane permeabilization, which occurred at concentrations >1 mM MMS, led to a dramatic leakage of cellular NA D(+) resulting in a strong reduction in pADPr levels, (iv) A bleomycin pulse (100 mu M) applied after MMS and/or 2-BE treatment confirmed th at 2-BE reduced poly(ADP-ribosyl)ation capacities of MMS-treated cells , though the glycol ether had no effect alone, This study confirmed th at the inhibition of pADPr synthesis could be responsible for the syne rgistic effects of 2-BE with genotoxic substances, The mechanism of th is inhibition cannot be explained by a lack of NAD(+) at the concentra tions of 2-BE tested.