Abstract:[Objective]This study aims to investigate the effects and differences of the natural antioxidant (+)-catechin and its isomer (-)-epicatechin on the antioxidant activity of HEK293T cells based on the nuclear factor erythroid 2-related factor 2 (Nrf2)-antioxidant response element (ARE) pathway.[Method]The effects of (+)-catechin and (-)-epicatechin on the viability of HEK293T cells were investigated via the methyl thiazolyl tetrazolium (MTT) assay. Reporter genes were employed to investigate the regulatory effects on the activation of ARE. The effects of (+)-catechin and (-)-epicatechin on the mRNA and proteins levels of the downstream factors [glutamate-cysteine ligase modifier subunit (GCLM), NAD(P)H quinone dehydrogenase 1 (NQO1), and heme oxygenase-1 (HO-1)] of the Nrf2-ARE signaling pathway were explored by RT-PCR and Western blot, respectively.[Result]The expression of reporter genes showed that ARE-mediated transcriptional activation was significantly induced by (+)-catechin and (-)-epicatechin at 20 μmol/L and 10 μmol/L, respectively. RT-PCR and Western blot results showed that (+)-catechin at 40 μmol/L significantly up-regulated the mRNA levels of GCLM, NQO1, and HO-1, and (-)-epicatechin at the same concentration significantly up-regulated the mRNA levels of NQO1 and HO-1. At 10 μmol/L, (+)-catechin up-regulated the protein levels of GCLM, NQO1, and HO-1, and (-)-epicatechin up-regulated the protein levels of GCLM and HO-1.[Conclusion](+)-Catechin and (-)-epicatechin have different minimum effect concentrations on cells. Both of them have the ability to activate the Nrf2-ARE signaling pathway, and the required concentration of (-)-epicatechin to activate the pathway is lower than that of (+)-catechin. In addition, the two compounds have different effects on the expression of genes and proteins downstream of the Nrf2-ARE signaling pathway, with (+)-catechin outperforming (-)-epicatechin at the same concentration.
