Endoplasmic reticulum stress plays a role in the advanced glycation end product-induced inflammatory response in endothelial cells

Aims: Both advanced glycation end products (AGEs) and endoplasmic reticulum(ER) stress play important roles in the development of various diseases. This study aimed to clarify the consequence of AGE-induced ER stress and its underlying mechanisms in human umbilical venous endothelial cells (HUVECs). Main methods: AGE-induced ER stress was assessed by the increased expression and activation of the ER stress marker proteins GRP78, IRE1 alpha and JNK, which were detected using Western blot. NF-kappa B translocation was revealed using Western blot and immunofluorescent staining in IRE1 alpha-knockdown HUVECs. The mechanism of AGE-induced ER stress was also explored by inhibiting the effect of reactive oxygen species (ROS) using NADPH oxidase 4 (Nox4) siRNA and the antioxidant reduced glutathione (GSH). The cellular ROS level was measured using flow cytometry. Key findings: AGEs time- and dose-dependently enhanced the expression of GRP78 and increased the phosphorylation of IRE1 alpha and its downstream signal JNK in HUVECs. siRNA-induced IRE1 alpha down-regulation suppressed AGE-induced NF-kappa B p65 nuclear translocation. Inhibiting the ROS production using Nox4 siRNA or antagonizing ROS using GSH reduced cellular ROS level and attenuated AGE-induced GRP78 expression and IRE1 alpha and JNK activation. Significance: This study confirms that AGE-induced ER stress in HUVECs focuses on the ER stress-enhanced inflammatory response through JNK and NF-kappa B activation. It further reveals the involvement of ROS in the AGE-induced ER stress mechanism. (C) 2014 Elsevier Inc. All rights reserved.