Protective Effect on LPS-induced Intercellular Hyperpermeability in Intestinal Caco-2 Cells of Total Flavonoid Extracts from Pomelo Levels

To investigate the protective effect of total flavonoid extracts from pomelo levels (PLTFE) on lipopolysaccharide (LPS, 2 g/mL) induced hypepermeability in Caco-2 cells. The model cells were treated with different concentrations (0、10、50、100、150 μg/mL) of PLTFE for 24 h. Following this treatment, cell survival rate was measured by MTT assay. The cellular level of lactate dehydrogenase (LDH) was determined by kit. Enzyme linked immunosorbent assay (ELISA) was used to determine the level of Interlukin-1β (IL-1β), IL-8, and tumor necrosis factor-α (TNF-α). The transepithelial cell resistance (TEER) and fluorescein dextran (FD40) permeability were used to evaluate the permeability of cells. Quantitative real-time PCR (qRT-PCR) was used to detect the expression of IL-1β, IL-8, TNF-α, Occludin, claudin-1, ZO-1, and myosin light chain kinase (MLCK). PLTFE treatment significantly increased the cell survival rate (to 86.1%) and inhibited the spillover of LDH in LPS treated Caco-2 cells (p<0.05). PLTFE treatment effectively inhibited the secretion of inflammatory cytokines (IL-1β, IL-8, TNF-α) and reduced their mRNA transcription in LPS treated Caco-2 cells (p<0.05). At the same time, it could effectively inhibit the secretion of inflammatory cytokines (IL-1β, IL-8, TNF-α) and mRNA transcription in damaged cells. In addition, PLTFE also significantly increased the mRNA levels of Occludin, claudin-1, ZO-1, and inhibited the MLCK mRNA transcription to improve the intercellular permeability in LPS treated Caco-2 cells (p<0.05). These results suggest that the PLTFE showed a strong anti-inflammatory activity, and could improve the LPS induced high permeability of Caco-2 cells associated with regulating the mRNA transcription of tight junction related factors.