Different patterns of cyclin D1/CDK4-E2F-1/4 pathways in human embryo lung fibroblasts treated by benzo[a]pyrene at different doses

Activation of MAPK and Cyclin D1/CDK4 in Malignant Transformation of Human Embryonic Lung Fibroblasts Induced by Silica and Benzopyrene

Objective:

Silica and Benzo(a)pyrene are listed as carcinogens. This study aims to explore Cyclin D1, CDK4 and difference of cell cycle adjusted by MAPK signal transduction pathway in silica and B(a)P-induced malignant transformation of human embryonic lung fibroblasts.

Methods:

Activity of the subfamily (ERK, p38 and JNK) of mitogen-activated protein kinase (MAPK), cyclin D1 and CDK4 (cyclin dependent kinase) were evaluated using Human embryonic lung fibroblast (HELF) purchased from the cell room, basic research institute, Chinese Academy of Medical Sciences. The expression of cyclin D1 and CDK4 (cyclin dependent kinase) were measured in silica and B(a)P induced malignant using Western blot (WB) assay.

Results:

P-ERK and P-JNK expression increased significantly (P<0.01), while CDK4 and P-p38 expression decreased (P<0.01, P<0.05) in silica-induced malignant transformation cells compared with the control group. P-ERK, P-JNK and Cyclin D1 expression increased (P<0.01, P<0.01, P<0.05) in B(a)P-induced group compared with the control group. P-ERK and P-JNK expression decreased (P<0.01), while P-p38, Cyclin D1 and CDK4 expression increased (P<0.05, P<0.05, P<0.01) in B(a)P-induced group compared with the silica-induced group.

Conclusion:

MAPK and cyclin D1/CDK4 activation expressed differently in human embryo lung fibroblasts malignant transformation induced by silica and benzopyrene.

Mitochondrial dysfunction and transactivation of p53-dependent apoptotic genes in BaP-treated human fetal lung fibroblasts

Benzo(a)pyrene (BaP) has been shown to be an inducer of apoptosis. However, mechanisms involved in BaP-induced mitochondrial dysfunction are not well-known. In this study, human fetal lung fibroblasts cells were treated with BaP (8, 16, 32, 64 and 128 μM) for 4 and 12 h. Cell viability, intracellular level of reactive oxygen species (ROS), total antioxidant capacity (T-AOC), mitochondrial membrane potential (Δ Ψm) and cytochrome c release were determined. Changes in transcriptional levels of p53-dependent apoptotic genes ( p53, APAF1, CASPASE3, CASPASE9, NOXA and PUMA) were measured. At time point of 4 h, BaP induced the intracellular ROS generation in 64 ( p < .05) and 128 μM BaP groups ( p < .01) but decreased the T-AOC activities in 32, 64 ( p < .05 for both) and 128 μM BaP groups ( p < .01). At time point of 12 h, Δ Ψm significantly decreased in ≥32 μM BaP groups ( p < .05 for all). Amount of mitochondrial cytochrome c significantly increased in 128 μM BaP group ( p < .01). Transcriptional levels of CASPASE3, CASPASE9, APAF1 and PUMA were up-regulated in all BaP groups ( p < .05 for all) and in ≥32 μM groups for NOXA ( p < .05). But only in 16 μM BaP group a relatively little expression of p53 mRNA was observed ( p < .05). The results indicate that in the earlier period BaP promoted the generation of excessive ROS and subsequently the mitochondrial depolarization, whereas transactivations of the p53-dependent apoptotic genes were significantly induced at the later period.