Oxidized Low Density Lipoprotein Induces Endoplasmic Reticulum Stress In3T3-L1Adipocytes

Objective: Obesity is closed associated with diabetes andcardiovascular diseases. The adipose tissue show chronic inflammatory statein obesity. Endoplasmic reticulum stress (ER stress, ERS) play an importantrole in the development of chronic inflammatory state in adipose tissue.Most obese subjects have high level of oxidized low density lipoprotein(ox-LDL).The purpose of the study is to observe the expression of ERSrelated molecules glucose-regulated protein78kDa (GRP78), C/EBPhomologous protein (CHOP) and phosphorylation of eukaryotictranslational initiation factor2a (p-eIF2a) in3T3-L1adipocytes treated withoxidized low density lipoprotein (ox-LDL), and to investigate the effect ofox-LDL on the induction of ERS in3T3-L1adipocytes.Methods:3T3-L1adipocytes were cultured and treated with ox-LDL(50ug/ml,100ug/ml,200ug/ml)and ERS positive control tunicamycin(Tun,5ug/ml) respectively. RT-PCR was used to detect the mRNAexpression of GRP78, CHOP, and the most appropriate concentration wasselected to treat adipocytes for6hours,12hours and24hours. RT-PCR was used to detect the mRNA expression of GRP78, CHOP and Western blot wasused to detect the protein levels of GRP78, CHOP and p-eIF2a.Results: The ox-LDL up-regulated the expression of GRP78, CHOPand p-eIF2a. The expression of GRP78and CHOP was increased with timeincreasing, peaked at24hours, while the expression of p-eIF2a was inducedin early stage of ox-LDL stimulation (6hours,12hours), decreasedgradually after24hours.Conclusion: ox-LDL may induce ERS and activate the unfoldedprotein response in3T3-L1adipocytes. The expression of GRP78andCHOP was induced in time-depended manner, while the expression ofp-eIF2a was induced in early stage of ox-LDL stimulation.