The relationship between standard reduction potentials of catechins and biological activities involved in redox control

Abstract

Redox homeostasis involves factors that ensure proper function of cells. The excess reactive oxygen species (ROS) leads to oxidative stress and increased risk of oxidative damage to cellular components. In contrast, upon reductive stress, insufficient ROS abundance may result in faulty cell signalling. It may be expected that dietary antioxidants, depending on their standard reduction potentials (E°), will affect both scenarios. In our study, for the first time, we systematically tested the relationship among E°, chemical properties, and biological effects in HT29 cells for a series of structurally different catechins and a major endogenous antioxidant – glutathione (GSH), at both physiological and dietary concentrations. Among chemical antioxidant activity tests, the strongest correlation with E° was seen using a DPPH assay. The values of E° were also highly correlated with cellular antioxidant activity (CAA) values determined in HT29 cells. Our results indicated that physiological concentrations (1–10 µM) of tested catechins stabilized the redox status of cells, which was not exhibited at higher concentrations. This stabilization of redox homeostasis was mirrored by constant, dose and E° independent CAA values, uninhibited growth of HT29 cells, modulation of hydrogen peroxide-induced DNA damage, as well as effects at the genomic level, where either up-regulation of three redox-related genes (ALB, CCL5, and HSPA1A) out of 84 in the array (1 µM) or no effect (10 µM) was observed for catechins. Higher catechin concentrations (over 10 µM) increased CAA values in a dose- and E°-dependent manner, caused cell growth inhibition, but surprisingly did not protect HT29 cells against reactive oxygen species (ROS)-induced DNA fragmentation. In conclusion, dose-dependent effects of dietary antioxidants and biological functions potentially modulated by them may become deregulated upon exposure to excessive doses.

DNA Methylation Changes Induced by Redox-Active Compounds—Choosing the Right PCR-Based Method

“…Based on the results of microarray analysis from the previous study [2], we expected that DNA of cells treated with EGC at 10 µM concentration would be more methylated within the examined CpG island of SRXN1 promoter, since such a treatment caused down-regulation of this gene. These initial assumptions were confirmed only in the experiments carried out by MS-HRM approach.…”

“…In a previous study, we reported that exposure of HT29 cell line to physiological concentration of catechins up-regulates the expression of genes related to oxidative stress defense [2]. On the other hand, the higher-10 µM-concentration, relevant only for the intestinal cells which are in a direct contact with consumed food, seems to preserve cellular redox state.…”

“…Human colon adenocarcinoma cell line (HT29) was cultured in supplemented McCoy's medium in a humidified atmosphere with 5% CO2 at 37 °C as described previously [2]. Cells for DNA methylation analysis were seeded in 6-well tissue culture plates and treated with (+)-catechin (C), (-)-epigallocatechin (EGC) (Extrasynthese) or glutathione (GSH) (Sigma-Aldrich, St. Louis, MO, USA) for 24 h at 37 °C.…”

Determination of Antioxidant Activity of Vitamin C by Voltammetric Methods

“…Voltammetric techniques are based on the measurement of the current arising from oxidation or reduction on the electrode surface, following the application of variable potential. CV and DPV are characterized by good sensitivity, thus they are very suitable methods for a wide range of applications and the most effective electro-analytical technique for the study of electroactive species [3]. The objective of the work is to present electrochemical parameters that can be obtained by carrying out CV and DPV measurements of AA in aqueous solution (pH = 7.4).…”

Kinetics of the reactions of catechins with hypochlorite, peroxynitrite, and amino acid–derived peroxyl‐ radicals

“…Many beneficial health effects of flavonoids are connected with their powerful antioxidant activity. It is also suggested that flavonoids and/or their metabolites can affect endogenous antioxidant defense systems of cells . Catechins, present in high amount in green tea, cocoa, and red wine, are among the most often consumed flavonoids.…”