RESUMO
Reversal of activated hepatic stellate cells (HSCs) to a quiescent state and apoptosis of activated HSCs are key elements in the reversion of hepatic fibrosis. CCAAT/enhancer binding protein α (C/EBP-α) has been shown to inhibit HSC activation and promote its apoptosis. This study aims to investigate how C/EBP-α acetylation affects the fate of activated HSCs. Effects of a histone deacetylation inhibitor trichostatin A (TSA) on HSC activation were evaluated in a mouse model of liver fibrosis caused by carbon tetrachloride (CCl4) intoxication. TSA was found to ameliorate CCl4-induced hepatic fibrosis and improve liver function through increasing the protein level and enhancing C/EBP-α acetylation in the mouse liver. C/EBP-α acetylation was determined in HSC lines in the presence or absence of TSA, and the lysine residue K276 was identified as a main acetylation site in C/EBP-α protein. C/EBP-α acetylation increased its stability and protein level, and inhibited HSC activation. The present study demonstrated that C/EBP-α acetylation increases the protein level by inhibiting its ubiquitination-mediated degradation, and may be involved in the fate of activated HSCs. Use of TSA may confer an option in minimizing hepatic fibrosis by suppressing HSC activation, a key process in the initiation and progression of hepatic fibrosis.
Assuntos
Proteína alfa Estimuladora de Ligação a CCAAT/metabolismo , Células Estreladas do Fígado/efeitos dos fármacos , Células Estreladas do Fígado/metabolismo , Ácidos Hidroxâmicos/farmacologia , Acetilação , Animais , Apoptose/efeitos dos fármacos , Apoptose/genética , Sítios de Ligação , Biomarcadores , Proteína alfa Estimuladora de Ligação a CCAAT/genética , Tetracloreto de Carbono/efeitos adversos , Linhagem Celular , Expressão Gênica , Células Estreladas do Fígado/patologia , Humanos , Imuno-Histoquímica , Cirrose Hepática/etiologia , Cirrose Hepática/metabolismo , Cirrose Hepática/patologia , Masculino , Camundongos , Mutação , Ligação Proteica , Estabilidade Proteica , Ratos , UbiquitinaçãoRESUMO
CCAAT enhancer binding proteinα (C/EBPα) is a transcription factor expressed only in certain tissues, including the liver. It has been previously demonstrated that C/EBPα may induce apoptosis in hepatic stellate cells (HSCs), raising the question of whether acetylation of C/EBPα is associated with HSCs, and the potential associated mechanism. A total of three histone deacetylase inhibitors (HDACIs), including trichostatin A (TSA), suberoylanilide hydroxamic acid and nicotinamide, were selected to determine whether acetylation affects C/EBPα expression. A Cell Counting Kit8 assay was used to determine the rate of proliferation inhibition following treatment with varying doses of the three HDACIs in HSCT6 and BRL3A cells. Western blot analysis was used to examine Caspase3, 8, 9, and 12 levels in HSCT6 cells treated with adenoviralC/EBPα and/or TSA. Following treatment with TSA, a combination of reverse transcriptionquantitative polymerase chain reaction and western blot analyses was used to determine the inherent C/EBPα mRNA and protein levels in HSCT6 cells at 0, 1, 2, 4, 8, 12, 24, 36 and 48 h. Nuclear and cytoplasmic proteins were extracted to examine C/EBPα distribution. Coimmunoprecipitation analysis was used to examine the lysine acetylation of C/EBPα. It was observed that TSA inhibited the proliferation of HSCT6 cells to a greater extent compared with BRL3A cells, following treatment with the three HDACIs. TSA induced apoptosis in HSCT6 cells and enhanced the expression of C/EBPα. Following treatment of HSCT6 cells with TSA, inherent C/EBPα expression increased in a timedependent manner, and its lysine acetylation simultaneously increased. Therefore, the results of the present study suggested that TSA may increase C/EBPα expression by increasing its lysine acetylation in HSCs.