The pathological role of mitochondrial apoptosis pathway and related factors in fluorosis-induced apoptosis of human hepatocellular carcinoma cell strain

Abstract

Objective To investigate the possible pathological role of mitochondrial apoptosis pathways and its factors in fluorosis-induced apoptosis of human hepatocellular carcinoma cell strain (HepG2). Methods Under the stimulation of 1, 3, 6 and 9 mmol/L concentrations of NaF in vitro for 24 h (n= 5), while normal control group was cultured under normal condition, the cytotoxicity was measured with MTT. The mitochondrial apoptosis inducing factor (AIF) was measured at both mRNA (n= 5) and protein levels (n= 6), respectively, by real-time PCR and Western blotting. The mitochondrial apoptosis related factors, such as B-cells lymphoma-2 (Bcl-2), Bcl-as-sociated X protein (Bax), cytochrome C, caspase-9 and caspase-3 were measured at protein levels (n= 6). Results After treated with 0, 1, 3, 6 and 9 mmol/L NaF for 24 h, the cell absorbance of HepG2 cells was 0.307±0.031, 0.333±0.028, 0.230±0.011, 0.178 ± 0.001 and 0.152±0.003, respectively, and the differences were statistically significant among groups (F= 82.224, P < 0.01). After treated with 3 mol/L NaF for 24 h, the mRNA level of AIF was [(153.14 ± 5.41)%] which was increased compared to the control group [(100.00 ± 4.70)%, t= -4.73, P < 0.05]. Under the same condition, the protein levels of AIF, Bcl-2, cytochrome C in cytoplasm, caspase-9 and caspase-3 were (152.16 ± 47.30)%, (171.90 ± 51.52)%, (458.00 ± 19.48)%, (527.17 ± 200.67)% and (432.70 ± 64.27)%, which were increased compared to those of the control groups [(100.00 ± 48.86)%, (100.00 ± 34.44)%, (100.00 ± 116.59)%, (100.00 ± 19.58)% and (100.00 ± 137.16)%, t= -3.80, -3.96, -15.76, -4.64, -5.06, all P < 0.05], while the protein levels of Bax and cytochrome C in mitochondrion were (24.66 ± 26.04)%, (72.99 ± 45.34)%, which were decreased compared to those of the control groups [(100.00 ± 44.01)%, (100.00 ± 34.14)%, t = 6.35, 0.68, all P < 0.05]. Conclusion The mitochondrial apoptosis pathway and related factors may be involved in NaF-induced cell death in HepG2 cells. Key words: Fluorides; Mitochondrion; Apoptosis