Bacillus subtilis Attenuates Hepatic and Intestinal Injuries and Modulates Gut Microbiota and Gene Expression Profiles in Mice Infected with Schistosoma japonicum

Abstract

Parasitic infection can induce pathological injuries and impact the gut microbiota diversity and composition of the host. Bacillus subtilis is a nonpathogenic and noninvasive probiotic bacterium for humans and other animals, playing an important role in improving the host immune system’s ability to respond to intestinal and liver diseases and modulating gut microbiota. However, whether B. subtilis can impact biological functions in Schistosoma japonicum–infected mice is unclear. This study used oral administration (OA) of B. subtilis to treat mice infected with S. japonicum. We evaluated changes in the gut microbiota of infected mice using 16 S rRNA gene sequencing and differentially expressed gene profiles using transcriptome sequencing after OA B. subtilis. We found that OA B. subtilis significantly attenuated hepatic and intestinal pathological injuries in infected mice. The gut microbiota of mice were significantly altered after S. japonicum infection, while OA B. subtilis remodel the diversity and composition of gut microbiomes of infected mice. We found that the S. japonicum–infected mice with OA B. subtilis had an overabundance of the most prevalent bacterial genera, including Bacteroides, Enterococcus, Lactobacillus, Blautia, Lachnoclostridium, Ruminiclostridium, and Enterobacter. Transcriptomic analysis of intestinal tissues revealed that OA B. subtilis shaped the intestinal microenvironment of the host responding to S. japonicum infection. Differentially expressed genes were classified into KEGG pathways between S. japonicum–infected mice and those without included cell adhesion molecules, intestinal immune network for IgA production, hematopoietic cell lineage, Fc epsilon RI signaling pathway, Th1 and Th2 cell differentiation, Th17 cell differentiation, calcium signaling pathway, Fc gamma R-mediated phagocytosis, chemokine signaling pathway, phospholipase D signaling pathway, NF-kappa B signaling pathway, B cell receptor signaling pathway, pancreatic secretion, and phagosome. In conclusion, our findings showed that OA B. subtilis alleviates pathological injuries and regulates gene expression, implying that B. subtilis supplementation may be a potential therapeutic strategy for schistosomiasis. Our study may highlight the value of probiotics as a beneficial supplementary therapy during human schistosomiasis, but further studies are needed.

Potential Gut Microbiota Features for Non-Invasive Detection of Schistosomiasis

“…The previous study has revealed that S. japonicum infection could induce alteration of gut microbiota in mice ( 29 ). In this study, Bacteroidetes and Firmicutes were the dominant phyla in mice ( Figure S1A ).…”

“…To further investigate specific diagnostic biomarkers of schistosomiasis, we compared the difference in the gut microbiota of mice infected with non-pathogenic factors and pathogenic S. japonicum . Previous studies have shown that probiotic Bacillus subtilis could affect the composition of gut microbiota and the level of liver disease in mice ( 29 , 39 , 40 ). Here, we showed that gut microbiota diversity and structure of gut microbiota of mice treated with Bacillus subtilis (non-pathogenic factor) significantly differed from these of mice infected with S. japonicum using Shannon index ( Figure S4A ) and PLS-DA analysis ( Figure S4B ), and the diversity of gut microbiota of mice treated with Bacillus subtilis is significantly higher than that of S. japonicum- infected group.…”

“…Liver injuries and alterations of gut microbiota are associated with the infection of schistosomes and other pathogenic or non-pathogenic factors. These factors, such as S. japonicum ( 20 , 29 , 44 ), S. mansoni ( 19 , 21 , 22 ), Clonorchis sinensis ( 45 ), HBV ( 46 , 47 ), hepatitis C virus (HCV) ( 48 ), Tetrachloromethane (CCl4) ( 49 ) and alcohol ( 50 ), induce the dysbiosis of the gut microbiota of animals and humans and acute or chronic liver injuries such as advanced schistosomiasis, liver cirrhosis and liver cancer. Our study found significant differences in the gut microbiota of mice and humans infected with S. japonicum , and S. japonicum infection showed a decrease in gut microbial diversity of hosts and an increase in the relative abundance of the genera Bacteroides , Blautia and Lactobacillus .…”

“…Luminal content samples were collected from colon intestines at 49 or 56 dpi under sterile conditions and transferred directly into sterile tubes. Left liver lobes and colons were collected and immediately fixed in 4% paraformaldehyde for the histopathological analysis described in the previous study ( 29 ). Liver samples were also collected for the detection of hydroxyproline content according to the protocol of the hydroxyproline assay kit (Nanjing, China).…”

“…We analyzed the area of the whole tissue and the blue positive region using Image-Pro Plus 6.0 software (Media Cybernetics, USA). We calculated the percentage of the granulomatous and fibrotic areas described in the previous study ( 29 ).…”