Investigation on the role of endoplasmie reticulum stress in the fatty acids-induced hepatocyte injury

Abstract

Objective To explore the role of fatty acid on endoplasmic reticulum (ER) stress and to detect the influence of tauroursodeoxycholic acid (TUDCA) on the expression of ER related genes in steatosis hepatocytes by establishing different models of hepatic steatosis.Methods Healthy adult hepatocyte cell line HL-7702 was taken as research object.The model of hepatic steatosis was established with palmitic acid alone or mixed fatty acids.The cell viability was measured and calculated through CCK-8 positive cell proliferation assay.The cell morphology and steatosis was observed.The intracellular triglyceride content was tested with the triglyceride determination kit.With TUDCA intervention,the relative expression of Glucose-regulated protein 78 (GRP78) and CCAAT/Enhancer binding protein homologous protein (CHOP) at mRNA level was determined by real-time PCR.Results The viability of hepatocyte was influenced once the concentration of mixed fatty acid reached 0.5 mmol/L or palmitic acid was 0.125 mmol/L.The effect of palmitic acid alone was stronger than that of mixed fatty acid on hepatocyte injury.The content of intra-hepatocyte triglyceride gradually increased in mixed fatty acid group,which only significantly increased after treated for 12 hours in palmitic acid alone group and then there was no significant change.There was no significant difference in relative expression of GRP78 and CHOP at mRNA level in various concentrations and treated time of mixed fatty acid group.After treated with palmitic acid at 0.5 mmol/L,intra-hepatocyte relative expression of CHOP at mRNA level increased obviously,however there was no effect on GRP78mRNA expression.After treated with palmitic acid at 1.0 mmol/L,both intra-hepatocyte GRP78 and CHOP mRNA relative expression increased.There was no significant difference in GRP78 and CHOP mRNA relative expression before and after ER stress in TUDCA intervented low dose palmitic acid group.There was significant difference in CHOP mRNA relative expression before and after ER stress in TUDCA intervented high dose palmitic acid group (at 12hrs:8.6400 to 5.1032; at 24hrs:13.7948to 6.4928,P=0.042 and 0.017),while no significant difference in GRP78 mRNA expression.Conclusion At same fatty acid concentration,the larger propotion palmitic acid has,the more severe injury hepatocyte has.The regulation of palmitic acid on intra-hepatic ER stress is a time and dose dependent manner.TUDCA may improve palmitic acid induced ER stress to some degree. Key words: Fatty liver; Endoplasmic reticulum; Palmitic acids; Taurodeoxycholic acid; Cells,culturel