Effect Of Endoplasmic Reticulum Stress And Oxidative Stress On Hepatocyte Steatosis In Mice Induced By Vinyl Chloride

Objective:To establish an animal model of hepatocyte steatosis in mice subchronic exposure to vinyl chloride,and to explore the effect of endoplasmic reticulum stress and oxidative stress on hepatic steatosis induced by vinyl chloride by examining indicators related to oxidative stress and endoplasmic reticulum stress,in order to provide scientific basis for the study of the etiology and mechanism of hepatocyte steatosis.Methods:Forty C57BL/6J mice were randomly classified into three exposed groups[4000mg/m~3(high),800mg/m~3(medium)and 160mg/m~3(low)]and control group(exposed to clean air).All mice exposure was via static inhalation for sixteen weeks(5 times per week,2 hours each time).Mice were sacrificed at the 16th week of exposure,and serum and liver tissues were collected.Liver histopathological examination was performed by HE staining and oil red O staining.Serum alanine aminotransferase(ALT)and aspartate aminotransferase(AST)levels to assess liver injury,serum and liver triglyceride(TG)and cholesterol(TC)levels to reflect liver lipid metabolic disorders were measured.Hepatic CYP2E1 and indicators of oxidative stress-related including malondialdehyde(MDA),glutathione(GSH)and superoxide dismutase(SOD)were measured.The mRNA expression of glycoregulatory protein-78(GRP-78),sterol regulatory element binding protein-1(SREBP-1),acetyl-CoA carboxylase(ACC)and fatty acid synthase(FAS)were detected by real-time PCR(RT-PCR),and proteins of these indexes were examined by western-blot.SPSS22.0 was used for statistical analysis of experimental data.Data with normal distribution or approximately normal distribution was observed.One-way ANOVA with LSD method was performed with a test level of 0.05.Results:1.Vinyl chloride can induce hepatic steatosis,cell edema,hepatocyte necrosis,and other pathological changes.Oil Red O(ORO)staining showed that parts of steatosis of the liver were red stained,and the degree of hepatocyte damage increased with the increase of dose.2.Effect of vinyl chloride on serum and liver biochemical indexes in mice:The levels of serum ALT and AST in mouse were all increased.Serum TC and TG levels were not statistical y different among groups(P>0.05),but serum TG levels increased with increasing doses,and serum TG first decreased and then increased.The contents of hepatic TC and TG increased with the increase of doses.TC content in the liver was significantly different between the treated groups and control group(P<0.05),and high group in liver TC differed significantly from low group and medium group(P<0.05).There was a statistical y significant difference in TG content between the high and medium groups,and high and medium groups of that differed from control group(P<0.05).3.Changes of CYP2E1 and oxidative stress indicators:There was an increase in CYP2E1level with no significant difference among groups(P>0.05).The MDA content in liver increased,and SOD and GSH levels decreased.MDA content in high group was significantly different from that in other groups(P<0.05).GSH content in high group differed from control and low groups(P<0.05).Compared with low group,level of SOD in high group was significantly different(P<0.05).4.Endoplasmic reticulum stress and the downstream indicators:The relative expressions of mRNA and protein of GRP-78,SREBP-1,ACC,and FAS all increased.The mRNA expression of GRP-78 in high and medium groups was significantly different from control group(P<0.05),but there was no significant difference in the protein expression among groups(P>0.05);There was no difference in mRNA and protein expressions of SREBP-1among groups(P>0.05).Compared with the control group,the mRNA expression of ACC was increased in accordance with increase of doses(P<0.05),and the protein expression was different between high group and control group(P<0.05).The mRNA and protein expressions of FAS in exposed groups were higher than those in control group(P<0.05).Conclusion:1.Vinyl chloride can induce hepatic steatosis and elevated lipids of blood and hepatic in mice,and the degree of hepatocyte steatosis increased with the increase of the doses.The levels of serum ALT and AST increased,and the degree of hepatocyte damage increased with the increase of doses.2.Oxidative stress and endoplasmic reticulum stress could be induced by vinyl chloride,which then upregulated SREBP-1,increased mRNA and protein expression of genes related to de novo lipogenesis.All may lead to increased fatty synthesis in the liver,further aggravate hepatic steatosis.