[Preventive and therapeutic effects of rapamycin against autoimmune hepatitis and liver fibrosis and possible mechanisms]

OBJECTIVE

To investigate the preventive and therapeutic effects of rapamycin (RAPA) on autoimmune hepatitis and liver fibrosis induced by concanavalin A (ConA) and possible mechanisms.

METHODS

Female C57BL/6 mice aged 8 weeks were randomly divided into normal control group, ConA model group, and ConA+RAPA treatment group. The serum levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were measured; hematoxylin-eosin and Masson staining and Knodell HAI and Ishak scoring systems were used to evaluate the degrees of liver inflammation and fibrosis. Gradient centrifugation was used to separate mononuclear cells, flow cytometry was used to measure CD4(+)/CD8(+) ratio, and intracellular cytokine staining was performed to measure the levels of interferon-γ (IFN-γ), interleukin-4 (IL-4), interleukin-10 (IL-10), and transforming growth factor β (TGF-β) in immune cells. The t-test was used for data comparison between groups.

RESULTS

The RAPA treatment group showed a significant reduction in serum ALT level compared with the ConA model group (P < 0.05). Liver inflammatory injury was reduced significantly, and there was no obvious fibrous tissue proliferation. The level of TGF-β in mononuclear cells was reduced significantly, and the treatment group had a significantly lower level of TGF-β than the model group (8.91%±1.25% vs 16.65%±2.05%, P < 0.05). The proportions of CD4(+) and CD8(+)T cells in the liver were reduced, and the treatment group had significantly lower proportions of CD4(+) and CD8(+)T cells than the model group (proportion of CD4(+)T cells: 4.09%±1.20% vs 8.91%±0.69%, P < 0.05; proportion of CD8(+)T cells: 3.28%±0.66% vs 9.68%±1.46%, P < 0.05). The proportion of Th1 cells was reduced, and the treatment group had a significantly lower proportion of Th1 cells than the model group (1.02%±0.06% vs 2.83%±0.21%, P < 0.05); the proportions of Th3 and Tr1 regulatory T cells were increased, and the treatment group had significantly higher proportions of Th3 and Tr1 regulatory T cells than the model group (proportion of Th3 regulatory T cells: 59.53%±9.82% vs 47.13%±4.79%, P < 0.05; proportion of Tr1 regulatory T cells: 10.63%±2.27% vs 7.09%±1.66%, P < 0.05), but the proportion of Th2 cells showed no significant difference between the two groups (P > 0.05).

CONCLUSION

RAPA can promote the differentiation of Th3/Tr1 cells, reduce the expression of TGF-β in mononuclear cells, slow down the progression of chronic hepatitis induced by ConA into liver fibrosis, and thus prevent liver fibrosis.