科研之友
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摘要
Cataractogenic stresses are associated with the induction of endoplasmic reticulum (ER) stress. However, little is known about oxygen (O-2)-induced ER stress in the lens. Cataract research has focused on elevated levels of O-2 in lens epithelial cells (LECs). Excessive levels or a lack of O-2 are known to induce ER stress whereas chronic ER stress activates the unfolded protein response (UPR). The present study investigated the hypothesis that the fluctuation of O-2 levels induces a UPR, and may be controlled by maintaining human LECs (hLECs) in a specific concentration of O-2. Human LECs were cultured in different atmospheric levels of O-2. Hypoxic conditions were determined by the level of hypoxia-inducible factor (HIF)-1 alpha. 2',7'-Dichlorodihydrofluorescein diacetate and ethidium homodimer-1 staining were conducted to detect reactive oxygen species (ROS) and cell death, respectively. Protein blot analyses were performed with antibodies specific to antioxidant and UPR-specific proteins. Reverse transcription-quantitatative polymerase chain reaction assays were performed to quantify the mRNA levels of activated NF-E2-related factor 2 (Nrf2) and kelch-like ECH-associated protein 1 (Keap1). The treatment of human LECs with 0 and 20% atmospheric O-2 activated Nrf2/Keap1. The LECs shifted to 1% atmospheric O-2 from 0, 4 or 20% for 24 h showed decreased levels of Keap1. By contrast, hLECs cultured in 1% atmospheric O-2 for 24 h and then shifted to 0, 4 or 20% O-2 exhibited a significant upregulation of Nrf2. These results suggest that oxidative stress proteins were not expressed in a 1% O-2 environment. The O-2 levels in the culture medium were equilibrated within 2 h in the cell culture plates. These results showed that an appropriate oxygen environment for the culture of LECs is 1 % atmospheric O-2. Either 0 or 20% of atmospheric O-2 activated the UPR and the Nrf2/Keap1-mediated antioxidant system in LECs and chronic exposure to O-2 fluctuation led to ROS production and cell death. This study revealed that O-2 fluctuation-induced UPR/ER stress could be prevented by maintaining the cells in a 1% 02 environment.
- 出版日期2015-11
- 单位浙江大学
