YImpact of exogenous TGF-β1 on cell cycle progression and apoptosis in rat liver cell line BRL-3A

AIM: To explore whether exogenous transforming growth factor-beta 1 (TGF-β1) affects rat liver cell line BRL-3A in terms of cell cycle progression and apoptosis. METHODS: (1) BRL-3A cells were divided into six groups and exposed to different concentrations of TGF-β1 (0, 2, 4, 6, 8, 10 μg/L), and cell proliferation was detected by MTT assay at 24, 36 and 48 h after treatment. (2) After BRL-3A cells were treated with TGF-β1 (8 μg/L) for 24, 36 or 48 h, flow cytometry was performed to measure cell cycle progression and apoptosis and real-time quantitative RT-PCR was used to quantify the mRNA expression of Cyclin E, Cdk-2, EGF, HGF, Bcl-2, c-Myc, MMP9, and NF-κB genes. RESULTS: (1) There was no statistical difference in cell proliferation among cells treated with six different concentrations of TGF-β1 for 24, 36 or 48 h (all P > 0.05). (2) Cell cycle progression and apoptosis rate also showed no statistical differ- ence between cells treated with 8 μg/L TGF-β1 and control cells at 24, 36 and 48 h (all P > 0.05). Compared to control cells, the mRNA expres- sion of Cyclin E, Cdk-2, and EGF in cells treated with 8 μg/L TGF-β1 significantly decreased at 24 and 36 h but significantly increased at 48 h (all P < 0.05); that of HGF signif icantly declined at all three time points (all P < 0.05); that of Bcl-2 showed no signif icant changes at 24 and 36 h but increased at 48 h; and that of c-Myc, MMP9 and NF-κB was up-regulated at all three time points (all P < 0.05). CONCLUSION: The insensitivity of BRL-3A cells to TGF-β1-induced apoptosis and cell cycle arrest may be related to activation of non-SMAD pathway and up-regulation of NF-κB, Bcl-2, c-Myc, and MMP9 expression.