Effects of Kiwifruit Peel Polyphenols on Antioxidant Capacity of Lipopolysaccharide-Stressed Caco-2 Cells

Abstract

Purpose: To explore the effects of kiwifruit peel polyphenols (KPP) on the antioxidant capacity of lipopolysaccharide (LPS)-stressed Caco-2 cells. Methods: The viability of Caco-2 cells in different treatment groups was determined by the cell counting kit-8 (CCK-8) assay, reactive oxygen species (ROS) and mitochondrial membrane potential by fluorescence spectrophotometry, the activity of superoxide dismutase (SOD), and the contents of glutathione (GSH) and malonaldehyde (MDA) by spectrophotometry, the gene expression of nuclear factor erythroid 2-related factor 2 (Nrf2), Kelch-like ECH-associated protein 1 (Keap1), NAD(P)H:quinone oxidoreductase 1 (NQO1), superoxide dismutase 1 (SOD1) and SOD2 by real-time quantitative polymerase chain reaction, and the protein expression levels of Nrf2, Keap1, and NQO1 by Western blot. Results: Compared with the LPS group, cell viability was elevated after 50 µg/mL KPP intervention (P < 0.05); the levels of ROS and MDA were decreased to 1.82 ± 0.28 and 5.08 nmol/mg (P < 0.05), respectively; mitochondrial membrane potential, SOD activity and GSH content were increased to 1.84 ± 0.10, 52.57 U/mg and 69.46 µmol/g (P < 0.05), respectively. Meanwhile, KPP intervention increased the gene and protein expression of Nrf2 and NQO1 (P < 0.05) and decreased Keap1 gene and protein expression (P < 0.05). Conclusion: KPP can enhance the antioxidant capacity of Caco-2 cells through the Keap1/Nrf2/NQO1 signaling pathway, thereby alleviating the cellular damage caused by LPS stress.

Keywords

• kiwifruit peel polyphenols; lipopolysaccharide; caco-2 cells; antioxidant capacity; nrf2 pathway