Abstract:

Objective To investigate the occurrence and development of renal inflammation in mice with acute infection of Schistosoma japonicum and evaluate the therapeutic effect of praziquantel on the impairment of renal function in the infected mice. Methods Fifty-five female C57BL/6J mice were randomly divided into 5 groups including the health control group (20), health control with praziquantel-treatment group (5), infection group (20), infection with praziquantel-treatment group(5) and praziquantel treatment group (5). Mice in the latter 3 groups were infected with 14 ± 2 cercariae of S. japonicum. Praziquantel treatment was given from the 6th week after infection. In the health control with praziquantel-treatment group and the infection with praziquantel-treatment group, praziquantel was given at a dosage of 300 mg/kg every 12 h for two consecutive weeks, and the praziquantel dosage in the praziquantel treatment group was 250 mg/kg for 3 consecutive days. Five mice in each of the health control group and the infection group were dissected at weeks 1, 3, 6 and 8 after infection. Five mice in each of the health control with praziquantel-treatment group, the infection with praziquantel-treatment group and the praziquantel treatment group were dissected at week 8 after infection. Urine and blood samples were collected to detect the levels of urinary protein and serum creatinine to evaluate renal function of the mice. The histopathological changes of kidney in each group were observed by HE staining. The infiltration of macrophages in the kidneys of mice was assessed by F4/80 immunohistochemical staining. Quantitative real-time PCR (qRT-PCR) and Western blotting were used to detect the relative transcription and protein expression level of mRNA of inflammatory cytokines (TNF-α, TGF-β, IL-1β and IL-6) and macrophage chemokine CCL2. Results At weeks 1, 3, 6 and 8 after infection, the urine protein contents in the infection group were (1.67 ± 0.52) g/L, (2.17 ± 0.41) g/L, (3.00 ± 0.89) g/L and (4.00 ± 0. 63) g/L, respectively, all higher than those in the health control group (P < 0.01). The serum creatinine levels in the infection group were (10.01 ± 1.45)μmol/, (13.00 ± 2.12)μmol/, (14.33 ± 1.21) and (19.00 ± 2.54) μmol/L, which were higher than those in the health control group (P > 0.05 or P < 0.01). qRT-PCR results showed that in the infection group the relative transcription level of inflammatory factor TNF-α mRNA were 2.47 ± 0.51, 3.14 ± 1.43, 1.83 ± 0.31 and 7.48 ± 5.54, the relative transcription level of TGF-β mRNA were 0.94 ± 0.24, 2.80 ± 1.07, 2.72 ± 0.88 and 3.03 ± 0.36, the relative transcription level of IL-1β mRNA were 1.49 ± 0.28, 4.32 ± 1.85, 2.08 ± 0.69 and 2.81 ± 0.73, the relative transcription level of IL-6 mRNA were 1.96 ± 0.31, 1.48 ± 0.35, 2.38 ± 1.17 and 2.85 ± 1.32, respectively, which were all higher in the health control group (P < 0.05 or P < 0.01). Western blotting analysis showed that the expression of TNF-α and IL-1β in the infection group were higher than those in the health control group. The relative transcription level of macrophage chemokine CCL2 mRNA in the infection group were 1.84 ± 0.17, 3.42 ± 0.85, 3.03 ± 1.00 and 2.63 ± 0.43, respectively, which were also higher than that in the health control group (P < 0.01). HE staining of renal pathological sections showed massive inflammatory cell infiltration, glomerular enlargement, and mesangial cell proliferation. Immunohistochemical results showed that the F4/80-positive areas in the kidneys of the infection group were (1.99 ± 0.49)%, (4.27 ± 0.90)%, (6.71 ± 1.38)% and (9.83 ± 1.91)%, which were higher than those in the health control group (P < 0.01). After treatment with praziquantel for two weeks, the renal tissue impairment and glomerular mesangial cell proliferation were alleviated. Compared with the infection group, the urinary protein content [(2.67 ± 0.52) g/L], serum creatinine level [(14.17 ± 2.88) μmol/L], F4/80-positive area [(5.92 ± 1.81)%], mRNA relative transcription of TGF-β and IL-6 (0.99 ± 0.23, 1.24 ± 0.53), and the protein levels of TNF-α and IL-1β were decreased in the infection with praziquantel-treatment group (P < 0.05 or P < 0.01), but did not change significantly in the praziquantel treatment group (P > 0.05). Compared with the infection group (5.29 ± 2.98, 2.81 ± 0.73, 2.63 ± 0.43), the mRNA relative transcription of TNF-α, IL-1β and CCL2 were decreased (P < 0.05 or P < 0.01) in the infection with praziquantel-treatment group (0.98 ± 0.36, 0.95 ± 0.33, 0.80 ± 0.27) and the praziquantel treatment group (1.56 ± 0.66, 1.76 ± 0.76, 1.41 ± 0.48). Conclusion In mice infected with S. japonicum, renal inflammation may occur in the early and acute stages of infection, accompanied by infiltration of macrophages in renal tissues, and impairment in glomerular and renal functions. Treatment with praziquantel for two weeks can significantly ameliorate renal inflammation and renal function in mice infected with S. japonicum.

Key words: Schistosoma japonicum, Kidney injury, Inflammation, Praziquantel, Macrophages