Overexpression of apolipoprotein A-I alleviates endoplasmic reticulum stress in hepatocytes

• Main Authors: Qing Guo, Can Zhang, Yutong Wang
• Format: Article
• Language: English
• Published: BMC 2017-06-01
• Series: Lipids in Health and Disease
• Subjects: Apolipoprotein A-I; Endoplasmic reticulum stress; Sterol regulatory element binding protein; Non-alcoholic fatty liver disease
• Online Access: http://link.springer.com/article/10.1186/s12944-017-0497-3

Abstract Background Abnormal lipid metabolism may contribute to an increase in endoplasmic reticulum (ER) stress, resulting in the pathogenesis of non-alcoholic steatohepatitis. Apolipoprotein A-I (apoA-I) accepts cellular free cholesterol and phospholipids transported by ATP-binding cassette transporter A1 to generate nascent high density lipoprotein particles. Previous studies have revealed that the overexpression of apoA-I alleviated hepatic lipid levels by modifying lipid transport. Here, we examined the effects of apoA-I overexpression on ER stress and genes involved in lipogenesis in both HepG2 cells and mouse hepatocytes. Methods Human apoA-I was overexpressed in HepG2 hepatocytes, which were then treated with 2 μg/mL tunicamycin or 500 μM palmitic acid. Eight-week-old male apoA-I transgenic or C57BL/6 wild-type mice were intraperitoneally injected with 1 mg/kg body weight tunicamycin or with saline. At 48 h after injecting, blood and liver samples were collected. Results The overexpression of apoA-I in the models above resulted in decreased protein levels of ER stress makers and lipogenic gene products, including sterol regulatory element binding protein 1, fatty acid synthase, and acetyl-CoA carboxylase 1. In addition, the cellular levels of triglycerides and free cholesterol also decreased. Some of gene products which are related to ER stress-associated apoptosis were also affected by apoA-I overexpression. These results suggested that apoA-I overexpression could reduce steatosis by decreasing lipid levels and by suppressing ER stress and lipogenesis in hepatocytes. Conclusion ApoA-I expression could significantly reduce hepatic ER stress and lipogenesis in hepatocytes.