Detection of lignin biopolymer‐ and vitamin e‐stimulated reduction of DNA strand breaks in H₂O₂‐ and MNNG‐treated mammalian cells by the comet assay

Abstract

In this study the possible protective effects of water‐soluble sulfur‐free lignin biopolymer and vitamin E (α‐tocopherol) on DNA in human VH10 cells and hamster V79 cells exposed to H₂O₂ and N‐methyl‐N'‐nitro‐N‐ni‐trosoguanidine (MNNG) were investigated. The level of DNA damage (DNA strand breaks) was measured using single‐cell gel electrophoresis, i.e., comet assay. Lignin biopolymer and vitamin E exhibited a protective effect against the overall DNA damage induced after H₂O₂ treatment. If H₂O₂‐treated human cells were incubated for 90 minutes to ligate frank breaks of DNA, two lesion‐specific enzymes, endonu‐clease III and formamidopyrimidine DNA glycosylase (FPG), significantly increased the level of DNA strand breaks originating from oxidized pyrimidines and purines. Preincubation of cells with lignin or vitamin E reduced mainly the level of oxidized pyrimidines. Reduction of oxidized purines was less evident. In addition, lignin biopolymer exhibited a protective effect against MNNG‐induced DNA damage, whereas vitamin E exhibited a protective effect only against H₂O₂‐induced DNA damage. These findings suggest that the antioxidant nature of lignin biopolymer enables a reduction of the level of frank breaks and of oxidized DNA bases in H₂O₂‐treated cells, and its adsorptive capacity enables binding of nitroso compounds and reduction of alkylation in MNNG‐treated cells.