Mechanism of bis(2-ethylhexyl)phthalate in inducing cholestasis and liver injury in mice
Objective To investigate the mechanism of bis(2-ethylhexyl)phthalate(DEHP)in inducing cholestasis and liver injury in mice.Methods In the in vivo experiment,adult female ICR mice were randomly divided into control group(corn oil)and DEHP group(200 mg/kg/d),and a model of cholestasis was established by intragastric administration for 4 weeks.After blood and liver tissue samples were collected from all mice,a biochemical analyzer was used to measure the level of total bile acid(TBA)in serum and the liver,and a microplate reader was used to measure alkaline phosphatase(ALP)and gamma-glutamyl transpeptidase(GGT);HE staining was used to observe the pathological changes of the liver;RT-PCR was used to measure the mRNA expression levels of the inflammatory factors interleukin-1β(IL-1β),interleukin-6(IL-6),and tumor necrosis factor-α(TNF-α)in the liver;liquid chromatography/triple quadrupole mass spectrometry was used to measure the bile acid profile in the liver of mice.In the in vitro experiment,AML-12 mouse hepatocytes were cultured and treated with DEHP(250 μmol/L),DCA(125 μmol/L),and CDCA(125 μmol/L)for 24 hours,and RT-PCR was used to measure the mRNA expression levels of the inflammatory cytokines IL-1β,IL-6,and TNF-α.The independent-samples t test was used for comparison of continuous data between two groups;a one-way analysis of variance was used for comparison between multiple groups,and the LSD-t test was used for further comparison between two groups.Results The in vivo experiment showed that compared with the control group,the DEHP group had significant increases in the serum levels of TBA,ALP,and GGT and the level of TBA in the liver(the t values are respectively-4.396,-5.109,-8.504,-3.792 and-7.974,all P<0.05,).Compared with the control group,the DEHP group had significant increases in cholic acid,chenodeoxycholic acid,taurocholic acid,deoxycholic acid,and ursodeoxycholic acid(the t values are respectively-2.802,-3.177,-2.633,-2.874 and-2.311,all P<0.05).HE staining of the liver showed that the mice in the DEHP group had enlargement of the portal area,bile duct deformation,inflammatory cell infiltration around the bile duct,and significant increases in the mRNA expression levels of the inflammatory factors IL-1β,IL-6,and TNF-α in the liver(the t values are respectively-2.539,-2.823 and-4.636,all P<0.05).The in vitro experiment showed that the actual difference in hepatocyte viability after 0-1 000 μmol/L DEHP treatment does not exceed 15%,but there were significant increases in the mRNA expression levels of the inflammatory cytokines IL-1β,IL-6,and TNF-α after treatment with DEHP at different concentrations of 125 μmol/L,250 μmol/L,and 500 μmol/L(all P<0.05).Compared with DEHP stimulation alone,the combined stimulation of CDCA and DEHP upregulates the cytokine in hepatocyte IL-1β mRNA levels(P<0.01);the combined stimulation of DCA and DEHP can significantly increase the cytokine in hepatocyte IL-1β and IL-6 mRNA levels(all P<0.01).Conclusion DEHP exposure can cause cholestasis and induce liver inflammation in mice,possibly by promoting the production of toxic bile acids and the secretion of inflammatory factors.
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