Influence of flavonoids in ROS production and oxidative DNA damage in Caenorhabditis elegans submitted to thermal stress

Abstract

Polyphenols exhibit a range of biological activities that have been associated to their ability to detoxify radicals and to repair oxidative damage [1]. The aim of the present work was to evaluate ROS production and levels of DNA damage in Caenorhabditis elegans submitted to thermally-induced oxidative stress when it was grown in the presence of different flavonoids, i.e., epicatechin (EC), quercetin (Q) and their methylated metabolites: 3'-O-methylEC (3'MetEC) and 4'-O-methylQ (tamarixetin, TMX). Levels of intracellular ROS were significantly reduced in the thermally-stressed worms when they were treated with EC and Q. However, increased ROS production was found in the worms treated with the methylated metabolites indicating that they did not protect against oxidative insult. The observed effects might be explained by the presence of the catechol group in Q and EC, which is absent in their methylated derivatives. Catechol-containing flavonoids are known to act as pro-oxidants in cell systems; however, by imposing a mild degree of oxidative stress they might contribute to activate endogenous antioxidant defences and lead to overall cytoprotection [2, 3]. No clear results were, however, observed regarding DNA damage, which was not increased in the worms submitted thermal stress neither affected by exposure to the assayed flavonoids, but in the case of EC that surprisingly increased the levels of 8-hydroxydeoxyguanosine (8-OHdG). Further studies are required to confirm and explain this unexpected observation. Acknowledgement: Financial support was obtained from the Spanish MINECO (project ref. BFU2012 – 35228). Keywords: Flavonoids, C. elegans, thermal stress, methylated metabolites, ROS, 8-hydroxydeoxyguanosine, oxidative stress