The Impact of Heat Treatment of Quercetin and Myricetin on their Activities to Alleviate the Acrylamide-Induced Cytotoxicity and Barrier Loss in IEC-6 Cells

Two flavonols quercetin and myricetin were assessed for their in vitro activities to attenuate the acrylamide-induced cytotoxicity and barrier loss in rat intestinal epithelial (IEC-6) cells and to identify whether heat treatment of the flavonols might cause activity changes. The results showed that the flavonols could alleviate the acrylamide-caused cell injury, resulting in higher cell viability, lower lactate dehydrogenase release, and less formation of reactive oxygen species. Meanwhile, the flavonols could antagonize the acrylamide-induced barrier dysfunction via decreasing the paracellular permeability, increasing the transepithelial resistance of cell monolayer, and enhancing the expression of three tight junction proteins namely occludin, claudin-1, and zonula occludens-1. The flavonols also could down-regulate the expression of JNK/Src proteins and thus cause lower relative protein ratios of p-JNK/JNK and p-Src/Src, resulting in a suppressed JNK/Src activation. Totally, quercetin was more potent than myricetin to exert these assessed activities, while the heated flavonols obtained lower activity than the unheated ones. It is thus concluded that the flavonols had beneficial activities towards the intestinal epithelial cells with acrylamide exposure by alleviating the acrylamide-induced cytotoxicity and barrier disruption, while heat treatment of the flavonols was unfavorable because it led to a reduced flavonol activity to the cells.