Exendin-4 protects HUVECs from tunicamycin-induced apoptosis via inhibiting the IRE1a/JNK/caspase-3 pathway.

PURPOSE: The abnormal increase of apoptosis of endothelial cells induced by endoplasmic reticulum stress is a significant factor for vascular disease, especially for atherosclerosis. Protecting endothelial cells from endoplasmic reticulum stress is a crucial strategies to combate these diseases. The goal of this study was to explore the effect of Exendin-4, a glucagon-like peptide-1 receptor agonist, on tunicamycin-induced apoptosis in human umbilical vein endothelial cells. METHODS: All studies were performed in primary human umbilical vein endothelial cells treated with tunicamycin with or without Exendin-4 pretreatment. Markers of cell viability and apoptosis were assessed in all cells, as well as the protein expression levels of IRE1α (inositol requiring enzyme-1а), p-IRE1α, JNK (c-Jun N-terminal kinase), p-JNK, and caspase-3. RESULTS: Following tunicamycin administration, human umbilical vein endothelial cells viability was gradually reduced in a dose-dependent manner, and fluorescence microscopy confirmed that tunicamycin was inducing human umbilical vein endothelial cells apoptosis. This apoptotic effect was attenuated by Exendin-4 pretreatment. Similarly, the ratio of p-IRE1α/IRE1α, p-JNK/JNK and active caspase-3/procaspase-3 were increased by tunicamycin (10 μg/ml); an effect that was counteracted by Exendin-4. The effect of exendin-4 was similar to that of the anti-endoplasmic reticulum stress agent, tauroursodeoxycholic acid (TUDCA). CONCLUSIONS: This study demonstrates that Exendin-4 can protect human umbilical vein endothelial cells from tunicamycin-induced apoptosis. Furthermore, our data suggests that the mechanism for this effect is mediated by inhibiting the IRE1α/JNK/caspase-3 pathway.