Abstract: OBJECTIVE:To investigate whether sodium sulfite (Na₂SO₃) induces lipid accumulation by inhibition of very low density lipoprotein (VLDL) assembly and activation of endoplasmic reticulum stress. METHODS:Human diploid liver cells (HL-7702) were cultured in DMEM medium containing 10% fetal bovine serum. Cells were exposed to different concentrations (0.1, 0.5, 2.5, 10 mmol/L) of Na₂SO₃ for 24 h and 48 h, and positive controls were used. VLDL secretion was detected by ELISA and Western blot, mRNA levels of VLDL assembly related factors were detected by quantitative real-time PCR (qPCR) and protein expressions of endoplasmic reticulum stress were detected by Western blot. RESULTS:ELISA and Western blot results showed that after exposure to Na₂SO₃ for 24 h, VLDL contents were significantly increased compared to the controls (P<0.05). After 48 hours, the difference became non-significant (P>0.05). QPCR test results showed that, compared with the negative control group, exposure to 10 mmol/L Na₂SO₃ for 24 h increased the expression of apoB100 mRNA significantly (P<0.05). In addition, the mRNA level of TGH in 10 mmol/L Na₂SO₃ and 2.5 mmol/L Na₂SO₃ groups were significantly increased (P<0.05). After exposure for 48 h, the mRNA levels of TGH in 2.5 mmol/L Na₂SO₃ and 0.5 mmol/L Na₂SO₃ groups were increased significantly (P<0.05). Protein expression of Calnexin was significantly increased (P<0.05) after Na₂SO₃ exposure. CONCLUSION:Na₂SO₃ may increase VLDL assembly and interfere with the correct folding of glycoprotein in hepatocytes.

Key words: sodium sulfite, very low density lipoprotein assembly, endoplasmic reticulum stress, hepatocytes