Effect of inducible costmulator/inducible costmulator ligand signaling pathway on hepatic fibrosis in mice infected with Schistosoma japonicum / 中华传染病杂志

ABSTRACT

Objective To analyze the effect of inducible costmulator (ICOS)/inducible costmulator ligand (ICOSL) signaling pathway on hepatic fibrosis in mice infected with Schistosoma japonicum.Methods Seventy-eight ICOSL knockout (ICOSL-KO) mice and 77 wild type C57BL/6J mice were used as experimental schistosomiasis model infected with Schistosoma japonicum.The sera of mice were collected on the day before infection (0 week),and at 4,7,12,16 and 20 weeks post infection.Then,the concentrations of hyaluronic acid (HA) and hydroxyproline (HYP) in mice sera were measured by sandwich enzyme linked immunosorbent assay (ELISA) kits.The expressions of transforming growth factor β1 (TGF-β1),α-smooth muscle actin (a-SMA) and Collagen-Ⅰ in livers from ICOSL-KO/wild type mice were assessed by immunohistochemical staining.The granulomatous pathology and fibrosis level in mice liver were dynamically observed by hematoxylin and eosin (HE) staining and Masson's staining,respectively.The difference between groups was detected by t test or x2 test when appropriate.Results After infection with Schistosoma japonicum,the levels of HA and HYP were gradually increased.In ICOSL-KO mice,the levels of HA at 7,12,16 and 20 weeks post infection were all significantly lower than those in wild type mice [(161.32±15.44) vs (186.01±21.24) ng/mL,t=2.528 2,P＜0.05; (166.73±18.18) vs (231.39±20.12) ng/mL,t=4.342 4,P＜0.05; (193.58±21.06) vs (252.51±25.29) ng/mL,t=4.003 9,P＜0.05; (253.98±24.53) vs (310.88±23.86) ng/mL,t=3.718 0,P＜0.05].Similarly,HYP levels in ICOSL-KO mice at 12,16 and 20 weeks post infection were all significantly lower than those in wild type mice (all P＜0.05).Immunohistochemical staining showed that TGF-β1,α-SMA and Collagen-Ⅰ expressions in liver of ICOSL-KO mice from 7 to 20 weeks post infection were all significantly lower than those of wild type mice (all P＜0.05).HE staining showed,the volume of liver egg granulomas of ICOSL-KO mice was significantly smaller than that of wild type C57BL/6J mice (P＜0.01).Furthermore,Masson's staining showed that the level of hepatic fibrosis in ICOSL-KO mice was lower than that in wild type mice and the fibrosis scores were statistically different between two groups (all P＜0.05).The mortality rate of the wilde type C57BL/6J mice was higher than that of ICOSL-KO mice.After 20 weeks of infection,the difference was statistically significant (55.84 ％ vs 37.18 ％,x2 =5.427,P＜0.05).Conclusions The degree of hepatic fibrosis and related indicators are obviously down-regulated in ICOSL-KO mice infected with Schistosoma japonicum.These findings suggest that ICOS/ICOSL signaling pathway has an important impact on the process of hepatic fibrosis caused by Schistosoma japonicum.