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 werestudied in Syrian hamster embryo (SHE) cells by measuring the cellularconcentrations of the polymer poly(ADP-ribose) (pADPr) and of NAD+, thesubstrate of poly(ADP-ribose) polymerase (PARP). As biotransformationpathways of ethylene glycol ethers involve NAD+-dehydrogenases, it washypothesized that 2-BE could reduce poly(ADP-ribosyl)ation by consumingNAD+. As a result DNA repair could be altered, which would explain that2-BE had been shown to potentiate the effects of clastogenic substancessuch as methyl-methanesulfonate (MMS). In this study, the effects of 2- BEon MMS-induced pADPr metabolism were analyzed. The results indicated that:(i) 2-BE (5 mM) by itself did not influence significantly pADPr or NAD+levels. (ii) 2-BE inhibited pADPr synthesis in MMS (0.2 mM)- pretreatedcells, without any change in NAD+ concentrations. (iii) MMS treatment,which rapidly increased pADPr levels, also affected thepoly(ADP-ribosyl)ation system as a secondary effect by damaging cellstructures. Membrane permeabilization, which occurred at concentrations>1 mM MMS, led to a dramatic leakage of cellular NAD+ resulting in astrong reduction in pADPr levels. (iv) A bleomycin pulse (100 microM)applied after MMS and/or 2-BE treatment confirmed that 2-BE reducedpoly(ADP-ribosyl)ation capacities of MMS-treated cells, though the glycolether had no effect alone. This study confirmed that the inhibition ofpADPr synthesis could be responsible for the synergistic effects of 2-BEwith genotoxic substances. The mechanism of this inhibition cannot beexplained by a lack of NAD+ at the concentrations of 2-BE tested.