Changes in PUFA Levels and Inflammation in a Cell Model of Hepatic Endoplasmic Reticulum Stress

Abstract

Background The presence of endoplasmic reticulum (ER) stress is as an important contributing factor in various liver diseases, including alcoholic liver disease, nonalcoholic steatohepatitis, drug-induced liver injury, acute-on-chronic liver failure and hepatocellular carcinoma. Thus, investigating the ER stress response in cell cultures can help to understand the pathology of these diseases. This study aimed to determine hepatic polyunsaturated fatty acids (PUFAs) and inflammatory response in a cell model of ER stress. Materials and Methods Liver THLE-3 cells were treated with tunicamycin (TM) to induce ER stress and tauroursodeoxycholic acid (TUDCA) was administered in advance to decrease cytotoxic effects. Cell viability was determined via MTT assay. ER stress was confirmed by immunofluorescence and western blot analysis of C/EBP-homologous protein (CHOP) and 78-kDa glucose-regulated protein (GRP78). Arachidonic acid (AA, C20:4n-6), dihomo-gamma-linolenic acid (DGLA, C20:3n-6), eicosapentaenoic acid (EPA, C20:5n-3) and docosahexaenoic acid (DHA, C22:6n-3) in THLE-3 cells were determined by LC-MS/MS. Phospholipase A2 (PLA2), cyclooxygenase (COX) and prostaglandin E2 (PGE2) were measured in cells via ELISA. Results Hepatic ER stress was accomplished by TM and was alleviated by TUDCA. Tunicamycin treatment significantly decreased PUFAs in THLE-3 cells compared to controls. Activity of PLA2, COX and PGE2 levels were significantly increased in TM treated THLE-3 cells compared to controls. Tauroursodeoxycholic acid lead to a partial restoration of PUFA levels and decreased PLA2, COX and PGE2. Discussion In summary, we report that TM treatment results in significantly decreased PUFA levels and leads to significantly increased activity of cPLA2, COX and PGE2 levels in human hepatocytes. We also show that TUDCA increases PUFA levels and alleviates cPLA2, COX and PGE2 levels in TM treated liver cells. Conclusion To our best knowledge, this is the first study reporting decreased PUFA levels in ER stress and supports the use of omega-3 fatty acids in liver diseases demonstrating ER stress.