The role of Toll-like receptor 4-mediated immune inflammation in inorganic arsenic-induced liver fibrosis in rats / 中华地方病学杂志

ABSTRACT

Objective:To observe the expression levels of Toll-like receptor 4 (TLR4) signaling pathway-related proteins and their phosphorylation in the liver tissues of rats with inorganic arsenic poisoning, and to explore the role of TLR4-mediated inflammatory signaling pathway in arsenic-induced liver fibrosis injury.Methods:Eighteen healthy weanling SD rats were divided into 3 groups according to their body weight (80 - 100 g) using a random number table (6 rats in each group, half males and half females). The control group was given 10 ml/kg of normal saline by gavage. The sodium arsenite (NaAsO 2) exposure group was given 10 mg/kg of NaAsO 2 by gavage. The TAK-242 intervention group was given 10 mg/kg of NaAsO 2 by gavage, and 0.5 mg/kg of TAK-242 was also administered intraperitoneally to inhibit TLR4 after 12 weeks. All rats were administered 6 days a week for 36 weeks. At the end of the treatment, the liver tissues and serum of the rats in each group were collected. HE and Masson staining were used to observe the pathological and fibrotic changes of the liver tissues. Automatic biochemical analyzer was used to detect serum liver function indexes of alanine aminotransferase (ALT), aspartate aminotransferase (AST) and alkaline phosphatase (ALP). Western blot was used to detect the expression changes of rat liver fibrosis protein α-smooth muscle actin (α-SMA), transforming growth factor-β1 (TGF-β1), Vimentin and TLR4 signaling pathway-related proteins TLR4, nuclear factor κB (NF-κB)-p65 subunit (p65), NF-κB-p50 subunit (p50) and their phosphorylation p-p65 and p-p50 expression levels. Enzyme-linked immunosorbent assay (ELISA) was used to detect the secretion levels of inflammatory related factors interleukin (IL)-6, tumor necrosis factor-α (TNF-α) and IL-10. Results:HE and Masson staining results showed that compared with the control group, the NaAsO 2 exposure group showed significant inflammatory cell infiltration, hepatocyte necrosis and collagen fibrous deposition, while the TAK-242 intervention group showed improvement of the inflammatory cell infiltration and reduction of collagen fibrous deposition compared with the NaAsO 2 exposure group. The results of serum liver function indexes showed that ALT, AST and ALP in NaAsO 2 exposure group were increased compared with the control group, but the TAK-242 intervention group was significantly decreased compared with the NaAsO 2 exposure group ( P < 0.05). Western bolt results showed that in NaAsO 2 exposure group, the expression levels of fibrosis protein α-SMA, TGF-β1 and Vimentin (1.04 ± 0.19, 0.92 ± 0.14, 1.20 ± 0.21) and TLR4 signaling pathway-related proteins and their phosphorylation TLR4, p50, p-p50 and p-p65 (1.16 ± 0.21, 0.95 ± 0.16, 1.24 ± 0.23, 1.56 ± 0.25) were higher than the control group (0.44 ± 0.08, 0.42 ± 0.08, 0.72 ± 0.07, 0.69 ± 0.15, 0.71 ± 0.11, 0.46 ± 0.07, 0.54 ± 0.11, P < 0.05), and the TAK-242 intervention group (0.60 ± 0.13, 0.59 ± 0.16, 0.49 ± 0.11, 0.47 ± 0.08, 0.86 ± 0.09, 0.79 ± 0.14, 1.02 ± 0.17) were lower than the NaAsO 2 exposure group ( P < 0.05). There was no significant difference in the expression level of TLR4 signal pathway-related protein p65 among the three groups ( F = 14.29, P = 0.053). ELISA results showed that the secretion levels of IL-6 and TNF-α [(98.89 ± 4.58), (83.25 ± 4.57) ng/g] in rats liver tissues of the NaAsO 2 exposure group were higher than the control group [(27.30 ± 3.92), (27.77 ± 1.83) ng/g, P < 0.05], while the secretion level of IL-10 [(36.88 ± 3.86) ng/g] was lower than the control group [(77.96 ± 7.87) ng/g, P < 0.05]. In TAK-242 intervention group, IL-6 and TNF-α secretion levels [(44.32 ± 3.60), (36.51 ± 2.93) ng/g] were lower and IL-10 secretion level [(60.40 ± 4.94) ng/g] was higher compared with the NaAsO 2 exposure group ( P < 0.05). Conclusion:TLR4-mediated inflammatory signaling pathway-related proteins and their phosphorylation are highly expressed in the liver tissues of rats with inorganic arsenic poisoning, and inhibition of TLR4 signaling pathway could significantly reduce the degree of liver fibrosis injury caused by inorganic arsenic in rats.