Arsenite exposure induces premature senescence and senescence-associated secretory phenotype (SASP) in human hepatocyte-derived cell line Huh-7.

BACKGROUND

Chronic arsenite exposure has been known to induce cancer in various organs; however, the underlying mechanisms remain elusive. The characteristic feature of carcinogenesis due to arsenic exposure is that the disease develops after a prolonged latent period, even after cessation of exposure. Our previous study revealed that arsenite exposure induces premature senescence in hepatic stellate cells and suggests that the senescence-associated secretory phenotype (SASP) factors from the senescent cells promote hepatic carcinogenesis. However, arsenite exposure in the liver occurs not only in hepatic stellate cells, but also in hepatocytes. Therefore, we examined whether arsenite exposure in hepatocytes also causes premature senescence and the enhancement of SASP factors. We also assessed whether those effects remained after cessation of arsenite exposure.

METHODS

Human hepatocyte-derived cell line Huh-7 was exposed to sodium arsenite for 72 hours to determine the concentration at which cell proliferation was inhibited. In the 5 µM of exposure, various cellular senescence markers and SASP factors were analyzed and compared with unexposed cells. We also examined whether those senescence markers and SASP factors were maintained after cessation of arsenite exposure. Finally, we explored whether the increased expression of SASP factor, which was upregulated in hepatocytes by arsenic exposure in this study, is related to the prognosis of human hepatocellular carcinoma.

RESULTS

After exposure to 5 µM of sodium arsenite for 72 hours, various senescent features, such as the induction of P21 mRNA, the reduction of LAMINB1 mRNA, morphological changes, phosphorylation of P53, and the presence of SA-β-gal positive cells were observed. Those changes were maintained after cessation of arsenite exposure. In addition, mRNA levels of SASP factors (MMP1, MMP3, MMP10, GDF15, PAI-1, and IL-6) were increased after arsenite exposure, and their high expression levels were maintained after cessation of arsenite exposure. Furthermore, by analyzing the TCGA database, we found that the increased expression levels of many SASP factors negatively correlated with prognosis.

CONCLUSIONS

Arsenite exposure induces premature senescence in hepatocyte-derived cells and increases SASP factors that are related to hepatic tumorigenesis. Once arsenite exposure induces premature senescence, the senescent cells remain even after cessation of exposure.