Chitooligosaccharide prevents vascular endothelial cell apoptosis by attenuation of endoplasmic reticulum stress via suppression of oxidative stress through Nrf2-SOD1 up-regulation

Abstract

Context Endoplasmic reticulum (ER) stress contributes to endothelium pathological conditions. Chitooligosaccharides (COS) have health benefits, but their effect on endothelial cells is unknown. We demonstrate for the first time a protective effect of COS against ER-induced endothelial cell damage. Objective To evaluate the protective effect of COS on ER stress-induced apoptosis in endothelial cells. Material and methods Endothelial (EA.hy926) cells were pre-treated with COS (250 or 500 mu g/mL) for 24 h, and then treated with 0.16 mu g/mL of Tg for 24 h and compared to the untreated control. Apoptosis and necrosis were detected by Annexin V-FITC/propidium iodide co-staining. Reactive oxygen species (ROS) were measured with the DCFH2-DA and DHE probes. The protective pathway and ER stress markers were evaluated by reverse transcription-polymerase chain reaction, western blot, and immunofluorescence analyses. Results COS attenuated ER stress-induced cell death. The viability of EA.hy926 cells treated with Tg alone was 44.97 +/- 1% but the COS pre-treatment increased cells viability to 74.74 +/- 3.95% in the 250 mu g/mL COS and 75.34 +/- 2.4% in the 500 mu g/mL COS treatments. Tg induced ER stress and ROS, which were associated with ER stress-mediated death. Interestingly, COS reduced ROS by upregulating nuclear factor-E2-related factor 2 (Nrf2), and the oxidative enzymes, superoxide dismutase1 (SOD1) and catalase. COS also suppressed up-regulation of the ER-related apoptosis protein, CHOP induced by Tg. Conclusions COS protected against ER stress-induced apoptosis in endothelial cells by suppressing ROS and up-regulation Nrf2 and SOD1. These findings support the use of COS to protect endothelial cells.