Effects of interleukin-9 blockage on immunopathological injury and gut microbiota during Schistosoma japonicum infection in mice
Objective To evaluate the effects of interleukin-9(IL-9)blockage on liver tissue immune damage and gut microbiota in mice infected with Schistosoma japonicum(Sj),and explore the mechanism of IL-9 blockage improving immunopathological injury in schistosomiasis.Methods Fifteen mice were randomly divide into control group,Sj group,and IL-9 blockage group.Each mouse in the Sj group and the IL-9 blockage group was infected with(15±1)S.japonicum cercariae.Each mouse in the IL-9 blockage group was intraperitoneally injected with anti-IL-9 antibody twice a week.Mice in the Sj group were injected with IgG antibody twice a week as an isotype control.At week 9 post-infection,mice were sacrificed and their liver tissues were examined by hematoxylin-eosin(HE)staining,Masson staining and immunohistochemistry.Colon contents were collected from mice and perform metagenomic sequencing on gut microbiota.Results HE and Masson staining showed that the percentage of individual granuloma area,Sj group(58.6±4.9)%>IL-9 blockage group(37.0±2.1)%;the difference was statistically significant(F=678.4,P<0.001).Percentage of collagen deposition area,Sj group(35.5±2.0)%>IL-9 blockage group(16.2±0.3)%>normal control group(0.4±0.1)%;the difference was statistically significant(F=1 314.0,P<0.001).Immunohistochemistry showed that IL-9 blockage markedly declined the expression levels of α-smooth muscle actin(α-SMA),collagen Ⅰ,and collagen Ⅲ proteins in liver tissue of mice.Percent of α-SMA protein expression,the Sj group(29.9±4.0)%>IL-9 blockage group(14.9±1.4)%>normal control group(1.4±0.4)%;the differences was statistically significant(F=267.9,P<0.001).Percent of collagen Ⅰ protein expression,Sj group(33.9±1.2)%>IL-9 blockage group(16.2±0.7)%>normal control group(1.3±0.2)%;the difference was statistically significant(F=3 112.0,P<0.001).Percentage of collagen Ⅲ expression,Sj group(14.5±3.0)%>IL-9 blockage group(5.3±0.6)%>normal control group(1.4±0.2)%;the difference was statistically significant(F=131.1,P<0.001).Metagenomic sequencing of mouse gut microorganisms revealed mouse intestines in the Sj and IL-9 block groups compared with normal controls,the diversity and species richness of the flora were reduced,among them,the difference between IL-9 blocking group and normal control group was statistically significant(P=0.002),and the abundance of Candidatus homeothermus,Barnesiella,unclassified_f_Enterobacteriaceae and Escherichia changed significantly.Conclusion IL-9 blockage could alter the species structure and diversity of gut microbiota in mice infected with S.japonicum,and this change might be closely related to the occurrence and development of immunopathological injury caused by S.japonicum.
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