Effects of sodium arsenite on mitochondrial function and expression of SIRT1/PGC-1α pathway-related proteins in human normal liver cell

Background Long-term exposure to arsenic can cause liver injury of varying degrees. Mitochondrial damage may be an early key event of arsenic-induced liver injury. Silent mating type information regulation 2 homolog 1 (SIRT1)/ recombinant peroxisome proliferators-activated receptor gamma coactivator 1 alpha (PGC-1α) is an important pathway regulating mitochondrial mass and function. However, whether arsenic-induced liver injury is related to mitochondrial dysfunction mediated by SIRT1/PGC-1α pathway remains unclear.

Objective To investigate potential effects of sodium arsenite (NaAsO₂) on mitochondrial function and expressions of SIRT1/PGC-1α pathway-related proteins in human normal liver cell.

Methods Human normal liver cells (MIHA cells) were used as the research object. MIHA cells were treated with different concentrations of NaAsO₂ (0, 5, 10 and 20 μmol·L⁻¹) for 24 h, and the cells were collected for study. The ultrastructure of mitochondria was observed by transmission electron microscopy, adenosine triphosphate (ATP) concentration by fluorescence method, mitochondrial membrane potential (MMP) level by flow cytometry, and SIRT1, PGC-1α and their downstream nuclear respiratory factor 1 (NRF1) and mitochondrial transcription factor A (TFAM) protein expression levels by Western blotting. One-way analysis of variance and trend test were used for data statistical analysis.

Results The viability of MIHA cells decreased gradually with the increase of NaAsO₂ concentration (F=6495.47, P<0.001). The transmission electron microscope observation showed that the size of mitochondria in the 10 μmol·L⁻¹ NaAsO₂ treatment group was different, and the mitochondria were swollen or elongated in a rod-like shape. The mitochondria in the 20 μmol·L⁻¹ NaAsO₂ treatment group swelled like air spheres or vacuoles. The ATP concentration and MMP level of MIHA cells gradually decreased with the increase of NaAsO₂ concentration (F_{trend of ATP}=172.28, F_{trend of MMP}=59.91, both Ps<0.001). Compared with the control group, the protein expression levels of SIRT1, PGC-1α, NRF1, and TFAM were not significantly changed in the 5 μmol·L⁻¹ NaAsO₂ treatment group, while the protein expression levels of SIRT1, PGC-1α, and TFAM were decreased in the 10 μmol·L⁻¹ NaAsO₂ treatment group, and the protein expression levels of SIRT1, PGC-1α, and NRF1 were decreased in the 20 μmol·L⁻¹ NaAsO₂ treatment group. The results of trend test showed that the protein expression levels of SIRT1, PGC-1α, NRF1, and TFAM decreased gradually with the increase of NaAsO₂ concentration (F_{trend of SIRT1}=47.07, P<0.001; F_{trend of PGC-1α}=15.17, P<0.01; F_{trend of NRF1}=13.54, P<0.01; F _{trend of TFAM}=4.20, P<0.05).

Conclusion The down-regulation of SIRT1/PGC-1α and its downstream NRF1 and TFAM may be involved in NaAsO₂-induced mitochondrial dysfunction in liver cells.