Abstract
Colon is exposed to a number of prooxidant conditions and several colon diseases are associated with increased levels of reactive species. Polyphenols are the most abundant antioxidants in the diet, but to date no information is available about their absorption and potential intracellular antioxidant activity on colon epithelial cells. The work was addressed to study the intracellular antioxidant activity of red grape polyphenolic extracts on rat colon epithelium experimentally exposed to prooxidant conditions. The experimental model chosen was represented by freshly isolated colon explants, which closely resemble the functional, and morphological characteristics of the epithelium in vivo. The study was carried out by in situ confocal microscopy observation on CM-H2DCFDA charged explants exposed to H2O2 (5, 10, and 15 min). The qualitative and quantitative polyphenolic composition of the extracts as well as their in vitro oxygen radical absorbing capacity (ORAC) was determined. The incubation of the explants with the polyphenolic extracts for 1 h produced a significant decrease of the H2O2 induced fluorescence. This effect was more pronounced following 15 min H2O2 exposure with respect to 5 min and it was also more evident for extracts obtained from mature grapes, which showed an increased ORAC value and qualitative peculiarities in the polyphenolic composition. The results demonstrated the ability of red grape polyphenols to cross the plasma membrane and exert a direct intracellular antioxidant activity in surface colonocytes, inducing a protection against pro-oxidant conditions. The changes in the polyphenol composition due to ripening process was reflected in a more effective antioxidant protection.
Highlights
Oxidative stress condition is defined as a disturbance in the balance between antioxidant defenses and the production of reactive oxygen species (ROS), such as superoxide anions (O−2 ), hydrogen peroxide (H2O2), hydroxyl radical (−OH), as well as reactive nitrogen species (RNS) such as nitric oxide (NO) and peroxynitrite (OONO−)
The appearance of rat colon surface of control and H2O2 exposed explants charged with the CM-H2DCFDA probe is reported in Figures 1A,B as observed by confocal microscopy
We investigated the antioxidant effects of polyphenols mainly represented in the grape skin extracts GSPE1 and GSPE2, such as flavonoids, namely flavonols, as well as non-flavonoids such as soluble acids stilbenes and anthocyanins
Summary
Oxidative stress condition is defined as a disturbance in the balance between antioxidant defenses and the production of reactive oxygen species (ROS), such as superoxide anions (O−2 ), hydrogen peroxide (H2O2), hydroxyl radical (−OH), as well as reactive nitrogen species (RNS) such as nitric oxide (NO) and peroxynitrite (OONO−). The gastrointestinal tract is exposed to reactive species via exogenous and endogenous routes. Examples of endogenous route are represented by the nitrosation of precursors of nitrosamines and increased production of reactive oxygen and nitrogen species by Helicobacter pylori infection at the gastric level (Handa et al, 2011), or increased production of H2O2 by numerous stimulated phagocytes and from some bacteria species in chronic gastrointestinal inflammatory conditions (Nathan, 2002; Strus et al, 2009)
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