Reduced metallothionein expression induced by Zinc deficiency results in apoptosis in hepatic stellate cell line LX-2.

The present study is to investigate the molecular mechanism by which Zinc (Zn) deficiency induces apoptosis in hepatic stellate cells. LX-2 cells were incubated with N,N,N',N'-tetrakis(2-pyridylmethyl)ethane-1,2-diamine (TPEN; 5 μM, 10 μM and 25 μM) for 24 h. MTT assay was used to test the proliferation ability of LX-2 cells. Flow cytometry was performed to detect cell apoptosis. Western blotting assay was employed to determine the expression of metallothionein (MT). Atomic absorption spectroscopy was performed to measure intracellular reactive oxygen species content. To test the activity of mitochondria, respiratory control rate was tested. To investigate the activation of apoptotic signaling pathway, cytochrome C oxidase activity was determined. TPEN effectively decreased the content of Zn in LX-2 cells. Zn deficiency led to the inhibition of proliferation and enhancement of apoptosis of LX-2 cells. Zn deficiency induced the inhibition of MT expression in LX-2 cells. Inhibition of MT expression induced by Zn deficiency resulted in enhanced reactive oxygen species content, impaired mitochondrial function and inhibition of cytochrome C oxidase activity. Intracellular MT content in LX-2 cells is reduced by Zn deficiency. Reduction in MT expression further increases intracellular ROS content, enhances oxidative stress, inhibits cytochrome C oxidase activity, impairs mitochondrial function, and finally leads to cell apoptosis.