Protective effect and pathways of the selenylation-modified nondigestive longan (Dimocarpus longan Lour.) polysaccharides in IEC-6 cells with indomethacin injury

Covalent combination of Se with natural polysaccharides provides bioactive organic Se strategically. Thus, nondigestive longan ( Dimocarpus longan Lour.) polysaccharides (LP) were selenylation-modified to obtain SeLP1 and SeLP2 with Se contents of 1.46 and 4.79 g/kg. SeLP1, SeLP2, and LP (as control) were assessed for their activities in IEC-6 cells exposed to indomethacin. Compared with LP, SeLP1 and especially SeLP2 were more active in ameliorating the indomethacin-induced cytotoxicity and oxidative stress, via increasing cell viability, decreasing lactate dehydrogenase release and ROS production, and reducing mitochondrial membrane potential loss. Both SeLP1 and SeLP2 were more potent than LP in alleviating the induced barrier disruption, causing rescued barrier integrity and up-regulated three tight junction-related genes and proteins. Additionally, both SeLP1 and SeLP2 ameliorated barrier dysfunction by suppressing MAPK- and mitochondrial apoptosis-mediated signaling pathways. Collectively, this selenylation and higher selenylation extent endowed SeLP2 with higher activity in ameliorating the indomethacin-caused cytotoxicity and barrier disruption. • Selenylated longan polysaccharides have higher Se content and activity in IEC-6 cells. • The polysaccharides actively reduce the indomethacin-induced injury in IEC-6 cells. • The polysaccharides also can protect the cells from indomethacin-caused barrier loss. • Barrier protection involve in both MAPK- & mitochondrial apoptosis-mediated pathways.