Salmonella-induced changes in the level of key immunoregulatory bacteria affect the transcriptional activity of the <i>Foxp3</i> and <i>RORgt</i> genes in the gut-associated lymphoid tissue of rats

Abstract

Intestinal microbes involved in many physiological processes owner, contributes to the formation and maintenance of immune homeostasis by regulating immune responses to protect against colonization by pathogens. A special role in the differentiation of various subpopulations of T-lymphocytes play the segmental filamentous bacteria (Segmented filamentous bacteria, SFB), capable of inducing a gut-associated lymphoid tissue (GALT) differentiation proinflammatory Th17-cells and members of the genus Clostridium (cluster IV and XIVa) and Bacteroides fragilis (polysaccharide A [PSA]), stimulating the formation of regulatory T-cells (Treg) and production of suppressor of cytokine IL-10. Important metabolites of B. fragilis are short-chain fatty acids (SCFA), which are able to activate GALT cells through the FFAR2 receptor. Lowering of the SCFA concentration leads to the reduction of the number of Treg in the intestine and breaks Th17/Treg balance. These changes lead to direct reducing of mRNA FFAR2, Foxp3 expression and increasing in RORyt GALT. Therefore, the goal was to determine the level of the key in the edge immunoregulatory bacteria intestinal microflora rats and their effects on the transcriptional activity of the genes Foxp3 and RORyt in GALT with Salmonella-induced inflammation and during administration of vancomycin and B. fragilis. To determine the genus and species of bacteria, as well as their number in the microflora of rats, was used the method of polymerase chain reaction (PCR-RV) with their identification by 16S rDNA genes. To study the transcriptional activity of genes using polymerase chain reaction reverse transcription real-time (RT-PCR). During the experiment with the introduction of animals vancomycin and Salmonella there was an increase in the level of SFB and a decrease in A. muciniphila, F. prausnitzii. Also, during infecting rats with S. Enteritidis and S. Typhimurium on the background of pre-treatment with vancomycin, there was an increase in the number of SFBs against the background of a pronounced decrease in Bacteroides—Prevotela group, A. muciniphila, Clostridium spp. clusters XIV, IV, and F. prausnitzii, which led to a decrease in the expression level of Foxp3+ mRNA and an increase in RORyt+, respectively. However, administration of B. fragilis to animals receiving S. Enteritidis or S. Typhimurium against pretreatment with vancomycin caused a decrease in the level of SFB and mRNA RORyt+, and, conversely, increased the number of Bacteroides—Prevotela group, A. muciniphila, Clostridium spp. clusters XIV, IV, F. prausnitzii and expression of Foxp3+ genes, which indicates the restoration of the homeostasis of the intestinal microbiome. The obtained results showed that B. fragilis can be successfully used in the treatment of inflammatory bowel diseases or diseases with impaired intestinal barrier function.

Keywords

• microbiome
• gut-associated lymphoid tissue
• salmonella
• vancomycin
• bacteroides
• expression
• rt-pcr