The Studies on the Effect and Mechanisms of Endoplasmic Reticulum Stress Preconditioning on Proximal Renal Tubule against Oxidative Stress

• Main Authors: Cheng-Chieh Hung, 洪振傑
• Other Authors: Chih-Wei Yang
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/17107501586804656804

博士 === 長庚大學 === 臨床醫學研究所 === 92 === English Abstract We investigated the role of the endoplasmic reticulum (ER) stress response in intracellular Ca2+ regulation, MAPK activation, and cytoprotection in LLC-PK1 renal epithelial cells in an attempt to identify the mechanisms of protection afforded by ER stress. Cells preconditioned with trans-4,5-dihydroxy-1,2-dithiane, tunicamycin, thapsigargin, or A23187 expressed ER stress proteins and were resistant to subsequent H2O2-induced cell injury. In addition, ER stress preconditioning prevented the increase in intracellular Ca2+ concentration that normally follows exposure. Stable transfection of cells with antisense RNA targeted against GRP78 (pkASgrp78 cells) prevented GRP78 induction, disabled the ER stress response, sensitized cells to H2O2-induced injury, and prevented the development of tolerance to H2O2 that normally occurs with preconditioning. ERK and JNK were transiently (30-60 min) phosphorylated in LLC-PK1 cells in response to H2O2. ER stress-preconditioned cells had more ERK and less JNK phosphorylation than control cells in response to H2O2 exposure. Preincubation with a specific inhibitor of JNK activation or adenoviral infection with construct that encodes constitutively active MEK1, the upstream activation of ERK, also protected cells against H2O2 toxicity. In contrast, the pkASgrp78 cells had less ERK and more JNK phosphorylation upon H2O2 toxicity. Expression of constitutively active ERK also conferred protection on native as well as pkASgrp78 cells. These results indicate that GRP78 plays an important role in the ER stress response and cytoprotection. ER stress preconditioning attenuates H2O2-induced cell injury in LLC-PK1 cells by preventing an increase in intracellular Ca2+ concentration, potentiating ERK activation and decreasing JNK activation. Thus, the ER stress response modulates the balance between ERK and JNK signaling pathways to prevent cell death after oxidative injury. Furthermore, ERK activation is an important downstream effector mechanism for cellular protection by ER stress.