Methylprednisolone Decreases Mitochondria-Mediated Apoptosis and Autophagy Dysfunction in Hepatocytes of Experimental Autoimmune Hepatitis Model via the Akt/mTOR Signaling.

Xiaoli Fan,Tingting Wang,Xuefeng Luo,Haoran Wang,Mengyi Shen,Li Yang,Tinghong Ye,Ruoting Men

doi:10.3389/fphar.2019.01189

Xiaoli Fan, Tingting Wang + Show 6 more

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https://doi.org/10.3389/fphar.2019.01189

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Abstract

Autoimmune hepatitis (AIH) is characterized by massive immune cell-mediated hepatocyte destruction. Glucocorticoids, particularly methylprednisolone (MP), are the most effective treatment for AIH; however, the mechanism underlying the effects of glucocorticoid treatment has not been fully elucidated. The present study explored the effects of MP on damaged hepatocytes in mice with concanavalin A (ConA)−induced experimental autoimmune hepatitis (EAH). C57BL/6 mice were divided into three groups: a normal control group (injected with normal saline), a ConA (20 mg/kg) group, and a ConA + MP (3.12 mg/kg) group. The serum levels of liver enzymes, cytokines, activated T cells, and apoptosis− and autophagy−associated marker proteins were determined 12 h after ConA injection. Human hepatocyte cell line LO2 was used to verify the effects of ConA and MP in vitro. MP treatment significantly decreased inflammatory reactions in the serum and liver tissues and activated the Akt/mTOR signaling pathway to inhibit apoptosis and autophagy in hepatocytes in vivo. Transmission electron microscopy (TEM) revealed fewer autophagosomes in the MP-treated group than in the ConA-treated group. MP treatment obviously suppressed apoptosis and mitochondrial membrane potential (ΔΨm) loss in hepatocytes in vitro. Furthermore, ConA treatment increased the levels of LC3-II, p62/SQSTM1, and Beclin-1, while bafilomycin A1 did not augment the levels of LC3-II. MP treatment decreased the levels of LC3-II, p62/SQSTM1, and Beclin-1 and upregulated the levels of phosphorylated (p)-Akt and p-mTOR. In conclusion, MP ameliorated mitochondria-mediated apoptosis and autophagy dysfunction in ConA-induced hepatocyte injury in vivo and in vitro via the Akt/mTOR signaling pathway.

Highlights

Autoimmune hepatitis (AIH) is a self-perpetuating inflammatory liver disease, and the misdiagnosis or delayed treatment of AIH can lead to liver cirrhosis, liver cancer, transplantation, and rapid deathMethylprednisolone Mediated Hepatocytes Improvement in AIH (European Association for the Study of the Liver, 2015; Manns et al, 2015; Montano-Loza and Czaja, 2015).Methylprednisolone (MP) is a physiological inhibitor of inflammatory responses that is widely used as an antiinflammatory and immunosuppressive agent in the treatment of numerous autoimmune and allergic diseases, mainly through suppressing CD4+ T cell activation indirectly by modulating dendritic cell function and directly by regulating T cell receptor signaling (Cain and Cidlowski, 2017)
Glucocorticoids have been reported to prevent the progression of various liver diseases by the following mechanisms: (i) protection of normal human liver cells from apoptosis induced by tumor necrosis factor (Zhao et al, 2015), (ii) suppression of calpain μ activation and talin degradation in ischemia-induced liver injury in rats (Wang et al, 2008), (iii) increased ability of hepatocytes to accumulate cAMP due to protein synthesis-dependent processes (Thoresen et al, 1989)
The alanine transaminase (ALT) and aspartate transaminase (AST) levels were reduced by MP treatment, demonstrating the protective effect of MP in the experimental autoimmune hepatitis (EAH) liver

Summary

Introduction

Methylprednisolone (MP) is a physiological inhibitor of inflammatory responses that is widely used as an antiinflammatory and immunosuppressive agent in the treatment of numerous autoimmune and allergic diseases, mainly through suppressing CD4+ T cell activation indirectly by modulating dendritic cell function and directly by regulating T cell receptor signaling (Cain and Cidlowski, 2017). Glucocorticoids have been reported to prevent the progression of various liver diseases by the following mechanisms: (i) protection of normal human liver cells from apoptosis induced by tumor necrosis factor (Zhao et al, 2015), (ii) suppression of calpain μ activation and talin degradation in ischemia-induced liver injury in rats (Wang et al, 2008), (iii) increased ability of hepatocytes to accumulate cAMP due to protein synthesis-dependent processes (Thoresen et al, 1989). The mechanisms by which glucocorticoids alleviate AIH remain to be elucidated

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