Background Long-term exposure to sodium arsenite leads to its accumulation in the liver and liver injury as a result. Previous studies showed that mesenchymal cells play an important role in hepatic fibrosis, and epithelial-mesenchymal transformation (EMT) is considered to be a main source of mesenchymal cells.

Objective To investigate the effects of sodium arsenite at different doses on liver fibrosis and EMT-related protein expressions in SD rats.

Methods Twenty-four healthy weaned SD rats, half male and half female, were randomly divided into four groups according to body weight, with 6 rats in each group. The four groups were control group (gavage with 10.0 mL·kg⁻¹ physiological saline), 2.5 mg·kg⁻¹ sodium arsenite group, 5.0 mg·kg⁻¹ sodium arsenite group, and 10.0 mg·kg⁻¹ sodium arsenite group. All rats were gavaged 6 d per week for 36 weeks and weighed once a week, the serum and liver tissues of rats were collected and weighed, then the organ coefficient was calculated. Hematoxylin-eosin staining and Masson's trichrome staining were used to determine the pathological changes of hepatic fibrosis in rats. The serum secretion levels of hyaluronic acid (HA), laminin (LN), procollagen Ⅲ N-terminal propeptide (PⅢNP), and collagen Ⅳ (COL-Ⅳ) in rats were detected by enzyme-linked immunosorbent assay (ELISA). The protein expressions of HSCs activation-related proteins, such as α-smooth muscle actin (α-SMA) and transforming growth factor-β1 (TGF-β1), as well as EMT-related markers, such as E-cadherin, N-cadherin, Vimentin, and Snail, were detected by Western blotting.

Results Compared with the control group, the 10.0 mg·kg⁻¹ sodium arsenite group showed decreased body weight (P<0.05) and increased liver coefficient (P<0.05) of female and male rats. The pathological staining showed that, compared with the control group, a large number of inflammatory cells were observed in liver tissue of rats exposed to sodium arsenite, liver parenchymal cells were also liquefied, necrotic, and denatured, and the collagen positive staining area of liver tissue showed an upward trend along with the increase of arsenic exposure dose (P<0.05). The results of ELISA and Western blotting showed that the serum secretion levels of HA, LN, PⅢNP, and COL-Ⅳ in the 5.0 and 10.0 mg·kg⁻¹ sodium arsenite groups were higher than those in the control group and the 2.5 mg·kg⁻¹ sodium arsenite group (P<0.05). Compared with the control group, the expressions of α-SMA and TGF-β1 proteins in liver tissue were increased in each sodium arsenite exposure group (P<0.05), the expression levels of E-cadherin protein were decreased (P<0.05), and the expression levels of N-cadherin, Vimentin, and Snail were increased (P<0.05).

Conclusion Sodium arsenite exposure can induce HSCs activation and liver fibrosis injury in SD rats, resulting in increased extracellular matrix secretion levels, accompanied by EMT in liver tissue, suggesting that EMT is closely related to the process of liver fibrosis caused by arsenic.