Abstract

Introduction Cellular redox homeostasis corresponds to a complex set of antioxidant enzymes to maintain the reducing environment. Cells at the intestinal epithelium face dietary compounds with antioxidant potential, however, it is not clear if these compounds interact by altering the equilibrium of disulfide bond formation of cytoplasmic proteins. Material and Methods Caco-2 cells expressing a fluorescent redox biosensor (HyPer), combined with pulses of 50M H2O2, were useful to record three phases of the biosensor response: steady-state, under exogenous oxidation and during spontaneous disulfide bond reduction. These responses were compared in cells treated by 24h with caffeic acid (CAPE, 10M) and quercetin (5M). The mRNA for enzymes that participate in cytoplasmic redox tone were evaluated by qPCR. Results CAPE provoked higher steady-state ratio values of HyPer and minor responses upon H2O2 addition, whereas that quercetin decreased steady-state values but did not affect the biosensor response in the presences of exogenous H2O2, [Steady-state: control 0.85±0.01, CAPE 0.92±0.01, Quer 0.75±0.01; responses upon H2O2 addition: control 38±2, CAPE 25±3, Quer 32±3%]. CAPE and quercetin increased the mRNAs of SOD1 and peroxiredoxin-1, but only quercetin elevated thiorredoxin-1 transcripts for along with an acceleration of disulfide bond reduction in the biosensor. Discussion Elevations in SOD1 and peroxiredoxin-1 by CAPE exposure might result in more efficient handling of intracellular H2O2, it means an increased capacity for disulfide bond transmission between proteins. Now, if the antioxidant machinery gains thiorredoxin activity, as quercetin did, a major disulfide reduction efficiency should be observed at cytoplasm, as the biosensor reported it.