FolC2‐mediated folate metabolism contributes to suppression of inflammation by probiotic Lactobacillus reuteri

Abstract

Bacterial‐derived compounds from the intestinal microbiome modulate host mucosal immunity. Identification and mechanistic studies of these compounds provide insights into host–microbial mutualism. Specific Lactobacillus reuteri strains suppress production of the proinflammatory cytokine, tumor necrosis factor (TNF), and are protective in a mouse model of colitis. Human‐derived L. reuteri strain ATCC PTA 6475 suppresses intestinal inflammation and produces 5,10‐methenyltetrahydrofolic acid polyglutamates. Insertional mutagenesis identified the bifunctional dihydrofolate synthase/folylpolyglutamate synthase type 2 (folC2) gene as essential for 5,10‐methenyltetrahydrofolic acid polyglutamate biosynthesis, as well as for suppression of TNF production by activated human monocytes, and for the anti‐inflammatory effect of L. reuteri 6475 in a trinitrobenzene sulfonic acid‐induced mouse model of acute colitis. In contrast, folC encodes the enzyme responsible for folate polyglutamylation but does not impact TNF suppression by L. reuteri. Comparative transcriptomics between wild‐type and mutant L. reuteri strains revealed additional genes involved in immunomodulation, including previously identified hdc genes involved in histidine to histamine conversion. The folC2 mutant yielded diminished hdc gene cluster expression and diminished histamine production, suggesting a link between folate and histadine/histamine metabolism. The identification of genes and gene networks regulating production of bacterial‐derived immunoregulatory molecules may lead to improved anti‐inflammatory strategies for digestive diseases.

Microbial lysate upregulates host oxytocin

“…Along the same lines, bacterial DNA, exopolysaccharides, bacteriocins, lipoteichoic acids and other microbial cell wall components possess promising postbiotic attributes (Adams, 2010; Caselli et al, 2011; Kataria et al, 2009; Ruiz et al, 2014; Sanchez et al, 2010; Surana and Kasper, 2012). Thus far postbiotic compounds identified for L. reuteri include histamine and the bifunctional dihydrofolate synthase/ folylpolyglutamate synthase type 2 (folC2)-mediated folate metabolism products essential for anti-inflammatory properties (Gao et al, 2015; Thomas et al, 2016). Taken together, this suggests that L. reuteri possesses powerful bioactive postbiotic molecules that are worthy of further exploration and testing for pharmaceutical applications.…”

Biochemical Features of Beneficial Microbes: Foundations for Therapeutic Microbiology

“…Although folate is primarily absorbed in the duodenum and jejunum, folate compounds generated by the mammalian microbiome in the colon represent a major source of host folate. Bacteria generate mono- and poly-glutamylated folate, a form of foliate which is easily absorbed by mammalian cells (230, 231). Multiple LAB strains such as Lactobacillus reuteri, L. acidophilus , L. plantarum, L. bulgaricus, Lact.…”

“…Multiple LAB strains such as Lactobacillus reuteri, L. acidophilus , L. plantarum, L. bulgaricus, Lact. lactis , Bifidobacobacterium adolescentis , Bifidobacterium animalis and Bifidobacterium longum synthesize folate (228, 232–238). However not all LAB strains are capable of generating folate.…”

“…Bacteria produce folate using the precursor 6-hydroxymethyl-7,8-dihydropterin pyrophosphate (DHPPP) and para-aminobenzoic acid (pABA, vitamin B10) (25, 242). All bacteria capable of producing folate contain the folC or homologous genes (235, 238). Additional genes involved in folate production include folKE genes which encode 6-hydroxymethyl-dihydropterinpyrophosphokinase (folK) and GTP cyclohydrolase (folE) or pABA (243).…”

“…In vivo addition of L. lactic overexpressing the folC, folKE or folC-folKE genes improved folate status in a rat folate deficiency model (228). Moreover, production of a 5,10-methenyltetrahydrofolic acid polyglutamates via the folC2 gene by L. reuteri ATCC PTA 6475 was found to suppress TNF production by activated human monocytes and partake in the anti-inflammatory effect of L. reuteri in a TNBS-induced mouse model of acute colitis (231). These studies demonstrate that select folate producing microbes can be utilized to improve folate status and modulate the immune system in animal models.…”