Role of mitochondrial damage in cadmium-induced cell apoptosis and DNA damage of hepatocytes

Abstract

To investigate the role of mitochondrial damage mediated by reactive oxidative species(ROS) in cadmium-induced cell apoptosis and DNA damage of L02 hepatocytes, so as to provide experimental basis for the subsequent study and protection of people exposed to Cd. The L02 hepatocytes were cultured in vitro treated with 0-90 μmol/L Cd for 24 h, and the methylthiazolyldiphenyltetrazoliumbromide assay was used to detect the cell viability. The colony formation assay, flow cytometry, comet assay, 2', 7'-dichlorofluorescein diacetate, MitoTracker Red CMXRos and 10-N-nonyl-acridine-orange, mitochondrial membrane potential detection kit(JC-1) and adenosine triphosphate(ATP) assay kits and Western Blot were used to investigate cell growth and proliferation, cell apoptosis, DNA damage, ROS levels, mitochondrial morphology, mitochondrial membrane potential, mitochondrial mass, ATP content and related proteins after the cells exposed to 0, 20, 40 μmol/L Cd for 24 h. The cells were pretreated with vitamin C before adding Cd exposure, and ROS levels, mitochondrial function, cell apoptosis, DNA damage and proteins were measured. The cell viability was significantly inhibited with the increase of Cd concentration and treatment time. The cells were treated with Cd for 24 h for further study according to the result of MTT assay. Compared with control group, the colony formation rate were 8. 23% and 6. 17% respectively in 20 and 40 μmol/L Cd treatment and the apoptosis rate were 15. 85% and 26. 26%, respectively. We also found that the B cell lymphoma/leukemia(Bcl-2) gene protein was significantly reduced, while the levels of Bcl-2 associated X protein(Bax) and cleaved cysteine aspastic acid-specific protease 3(cleaved-caspase-3) were increased in a dose-dependent manner. Cd treatment also induced DNA damage and accumulation of intracellular ROS, accompanied by a mitochondrial morphological change, significant decrease in Δψm, mitochondrial mass, ATP content, mitochondrial cytochrome C(cyt c) and an increase in cytoplasmic cyt c expression(P<0. 05). In addition, pretreatment with antioxidant vitamin C not only significantly increased cyt c, mitochondrial mass, ATP content and mitochondrial cyt c, but also reduced the expression of cytoplasmic cyt c(P<0. 05), cell apoptosis and DNA damage induced by Cd. Cd exposure could induce ROS accumulation in L02 hepatocytes, which can lead to mitochondrial damage, and ultimately lead to cell apoptosis and DNA damage.