Objective To study the role and mechanism of endoplasmic reticulum stress in subacute N, N-dimethylformamide (DMF) exposure induced liver injury in mice.
Methods Twenty male C57BL/6 mice (8 weeks old) were randomly divided into control group (n=5), low-dose group (n=5), middle-dose group (n=5), and high-dose group (n=5). The mice in the exposure groups were administrated by gavage with DMF at 150 mg/kg·bw (low), 450 mg/kg·bw (middle), 1 350 mg/kg·bw (high), respectively, once a day for 28 days; the control group was administrated by gavage with normal saline at the same volume. All the animals were sacrificed the next day after last exposure. The levels of serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were measured with automatic biochemistry analyzer. Histopathological changes of liver were observed after HE staining. Expression levels of endoplasmic reticulum stress markers (GRP94 and GRP78) and DMF metabolic enzyme (CYP2E1) were detected by Western blot.
Results The body weight gain was significantly suppressed after repeated DMF administrations at various doses compared with the control group (P < 0.05), and the suppression was aggravated with the increase of exposure dose. Compared with the control group, the liver coefficients of mice in the middle-and high-dose groups were significantly increased (P < 0.05). The levels of serum ALT in the middle-and high-dose groups were significantly higher than that in the control group (P < 0.05), and the level of ALT in the high-dose group was higher than that in the middle-dose group (P < 0.05). The level of AST in the high-dose DMF exposure group was also increased compared with the control group (P < 0.05), but there were no significant differences between the low-or middle-dose groups and the control group (P > 0.05). The pathological examination results of liver showed hepatocellular edema and vacuolization in the low-dose group; a large area of vacuolar degeneration of cells, nucleus contraction, and sinus dilatation were observed in the middle-dose group; amounts of eosinophilic cells with cytoplasm concentration, nucleus contraction, and eosinophilic bodies appeared in centrilobular hepatocytes in the high-dose group; the mice in the control group did not show any abnormal change. The Western blot results showed that the expression levels of GRP94 and CYP2E1 in the low-, middle-, and high-dose groups were significantly higher than those in the control group (P < 0.05), and the expression level of GRP94 was increased in a dose-dependent manner. In addition, the expression levels of GRP78 in the middle-and high-dose groups were different from that in the control group (P < 0.05).
Conclusion Subacute exposure to DMF could induce liver injury in mice, and the mechanism may be associated with endoplasmic reticulum stress.
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