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 (alpha-tocopherol) on DNA in human VH10 cells and hamster V79 cells exposed to H2O2 and N-methyl-N'-nitro-N-nitrosoguanidine (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, endonuclease 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.

Dna damage in human mononuclear cells induced by bacterial endotoxin

“…This enzyme catalyzes reduction of molecular oxygen with the formation of superoxide anion radicals (O 2 -) [11]. For evaluation of the role of exogenous ROS (e.g., O 2 -) in DNA damage, MNC were incubated with LPS in the presence of a specific NADPH oxidase inhibitor DPI [10], SOD (enzyme antioxidant catalyzing O 2 -dismutation with the formation of H 2 O 2 and molecular oxygen), and natural polyphenol antioxidant (water-soluble highly polymeric compound obtained by partial degradation and carboxylation of lignin) [13]. SOD and polyphenols cannot permeate cell membrane because of high molecular weight and charge.…”

Lignin as Renewable Raw Material

“…[44] Lignin-based biopolymers have antioxidant capacity. [45] These properties have been applied to reduce the genotoxicity in drugs and side effects on patients. [46] Natural lignin, together with carbohydrates, is considered to be part of dietary fiber resistant to digestion.…”

Lignin-Stimulated Reduction of Oxidative DNA Lesions in Testicular Cells and Lymphocytes of Sprague-Dawley Rats In Vitro and Ex Vivo

“…We confirmed this dual effect of lignin in our previous in vitro experiments. Lignin reduced genotoxic effects of N-methyl-N′-nitro-N-nitrosoguanidine (MNNG) as well as H 2 O 2 in stabilized cell lines VH10, Caco-2, and V79 cultured in vitro (11), genotoxic effects of visible light-excited MB in V79 cells (12), the level of 6TG r mutations in MNNG-treated V79 cells (13) as well as the frequency of mutations and SOS response induced by 4-nitroquinoline-N-oxide in Escherichia coli PQ37 cells (14). Because DNA damage and its repair have important implications in cancer, in this study we extended our interest to a possible DNA-protecting effect of lignin in the proliferately active testicular cells and in peripheral blood lymphocytes.…”

“…Values of DNA lesions measured at each concentration of H 2 O 2 in lymphocytes isolated from rats fed 2%, 4%, or 8% lignin and their controls were statistically compared. Statistical significance (by t-test): *P < 0.01; **P < 0.001. lignin as an agent that reduces the DNA-damaging effects of hydrogen peroxide (11). In further experiments we tried to find a protective effect of lignin against oxidative DNA lesions induced by visible light-excited MB.…”