[Neutralization of interleukin-6 alleviates acute liver injury in mice].

Objective

To study the role of interleukin 6 (IL-6) in the occurrence and development of acute liver injury.

Methods

Twelve C57BL/6 male mice without specific pathogens were randomly divided into a control group and an acute liver injury model group, with six mice in each group. Control and model group were injected with an equal volume (dosage of 10 mg/kg) of phosphate-buffered saline (PBS) and concanavalin A (ConA) into the tail vein, respectively. Samples were collected at 6 h for liver HE staining. Transaminase assay was used to determine the success of the induction model. The expression of IL-6, IL-17, IL-1β, interferon (IFN) γ and tumor necrosis factor α were screened by quantitative fluorescence PCR (qPCR). The expressional condition of IL-6 and IFNγ were measured by enzyme-linked immunosorbent assay (ELISA). Subsequently, three control groups and three IL-6 neutralizing antibody groups were established for acute liver injury, respectively. Equal volumes of PBS or IL-6 neutralizing antibody (100 μg/body) were injected prior 30 minutes, followed by injection of ConA (10 mg/kg) into the tail vein. Blood sampled from eye and liver tissue were fetched at 6 h. Liver tissues were stained with HE and serum alanine aminotransferase (ALT) was determined. An independent sample T-test was used for data comparison.

Results

Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) of the model group was significantly higher than control group [ALT: (2 618.99 ± 188.08) U/L and (43.34 ± 5.02) U/L, t = -13.69, P = 0.001; AST: (942.48 ± 150.44) U/L and (57.80 ± 4.84) U/L, t = -5.878, P = 0.01]. Liver HE staining showed that the structure of hepatocyte cord was disordered, the cytoplasm of hepatocyte was lightly stained, and large necrotic foci were gradually formed, accompanied by lymphocyte infiltration, and then a mouse model of acute liver injury was successfully established. Protein levels of IL-6 and IFN, and mRNA of the model group were significantly up-regulated, as compared to control group. IL-6 mRNA expression of the model group was increased 73.7 times that of the control group (t =-6.218, P < 0.001), and the serum IL-6 expression level was also higher than that of the control group (18 537.02 ± 92.57) pg/ml (t = -199.782, P < 0.001). IFNγ mRNA was 108.4 times higher than that of the control the group (t = -4.413, P = 0.003), and serum IFNγ concentration of the model group was also higher than the control group (12 068.30 ± 288.43) pg/ml (t = -41.748, P < 0.001). Among them, IL-6 level was obviously increased, suggesting that it could participate in the occurrence and development of liver injury. IL-6 neutralizing antibody was injected into the tail vein. ALT level of IL-6 neutralizing antibody was significantly lower than acute liver injury control group [(167.41 ± 47.80) U/L and (1 520.34 ± 190.21) U/L, t = 6.899, P = 0.015]. Liver tissue HE staining showed that hepatocyte necrosis and the number of necrotic foci was significantly alleviated after blocking serum IL-6.Immunohistochemical results showed that the expression of activated caspase3 and hepatocyte apoptosis in the IL-6 neutralizing antibody group was decreased.

Conclusion

Neutralizing IL-6 can significantly reduce acute liver injury caused by concanavalin A.