[Protective effect of active vitamin D on liver fibrosis induced by sodium arsenite in SD rats].

Objective: To explore the protective effect of active vitamin D(VD) on liver fibrosis injury induced by sodium arsenite(NaAsO_2) in SD rats.

Methods: Eighteen healthy newly weaned SD rats, half male and half female, were randomly divided into Control group(gavaged with 10 mL/kg normal saline), NaAsO_2-treated group(gavaged with 10 mg/kg NaAsO_2), Active VD(calcitriol) intervention group(gavaged with 10 mg/kg NaAsO_2 and 1.0 μg/kg calcitriol was given by gavage along with NaAsO_2 administration after 12 weeks), all rats were administered 6 days a week for 36 weeks and weighed every week. Enzyme-linked immunosorbent(ELISA) was used to detect the secretion levels of 25(OH)D_3 and hyaluronic acid(HA), laminin(LN), type Ⅲ pre-collagen amino-terminal peptide(PⅢNP), type Ⅳ collagen(COL-Ⅳ) in the serum of rats in each group; HE staining was used to observe the basic pathological changes of liver tissues in each group, Masson and Sirius Red staining were used to observe the fibrosis and collagen deposition of liver tissues in each group; Western Blot was used to detected the protein levels of fibrosis-related markers α-smooth actin(α-SMA), transforming growth factor-β1(TGF-β1) and Vimentin in each group.

Results: After 36 weeks of NaAsO_2 exposure, the weight of rats was significantly decreased compared with the control group, and the weight of female rats after calcitriol intervention was significantly increased compared with NaAsO_2-treated group(P<0.05). The result of liver coefficient showed increasing in NaAsO_2-treated group compared with the control group, while decreasing in calcitriol intervention group compared with NaAsO_2-treated group, and the difference was statistically significant in female rats. ELISA assay showed that compared with the control group((550.21±29.16) ng/L), the serum level of 25(OH)D_3 in NaAsO_2-treated group((436.82±74.37) ng/L) was significantly decreased(P<0.05), while the serum level of 25(OH)D_3 was significantly higher in calcitriol intervention group than that of NaAsO_2-treated group(P<0.05). HE staining found that, compared with the control group, the liver tissue of rats in NaAsO_2-treated group showed abnormal morphology, the liver tissue was structurally disordered, false lobules and fat vacuoles were also increased. Masson and Sirius Red staining also revealed abnormal hepatic lobule structure, enlarged and deformed portal area and abundant collagen fiber deposition in NaAsO_2-treated group. Further analysis showed that the positive staining area of collagen deposition in liver tissue of rats exposed to NaAsO_2 increased significantly compared with the control group(P<0.05). Those above changes in calcitriol intervention group were significantly alleviated compared with NaAsO_2-treated group(P<0.05). Western Blot analysis showed that the protein levels of α-SMA, TGF-β1 and Vimentin were obviously higher in NaAsO_2-treated group(1.12±0.21, 1.12±0.26, 1.31±0.15) than that in the control group(0.57±0.10, 0.64±0.13, 0.72±0.16)(P<0.05). In addition, the serum levels of HA, LN, PⅢNP and COL-Ⅳ in rats exposed to NaAsO_(2 )((87.92±9.67), (89.04±11.91), (12.09±2.97) and(19.86±3.40)ng/mL) were also higher than those in control group. After calcitriol intervention, the protein levels of α-SMA, TGF-β1 and Vimentin(0.68±0.16, 0.85±0.21, 0.84±0.09) in liver tissue and the serum levels of HA, LN, PⅢNP and COL-Ⅳ((54.29±7.23), (55.56±9.43), (6.49±1.08), (10.15±1.99) ng/mL) were significantly lower than those of NaAsO_2-treated group(P<0.05).

Conclusion: Calcitriol can effectively alleviate liver fibrosis injury caused by long-term NaAsO_2 exposure in SD rats.