Premium
Crosstalk between Lactobacillus reuteri and mammalian intestinal epithelium
Author(s) -
Gsnesh Bhanu Priya,
Hall Anne,
Ayyaswamy Sriram,
Fultz Robert,
Versalovic James
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.652.14
Subject(s) - lactobacillus reuteri , histamine , chemistry , diacylglycerol kinase , phosphorylation , receptor , microbiology and biotechnology , biochemistry , biology , protein kinase c , endocrinology , lactobacillus , fermentation
Lactobacillus reuteri ATCC PTA 6475, probiotic bacterium, with an intact hdc gene cluster is known to synthesize and secrete histamine, and can suppress inflammation in mammalian systems via specific activation of the type 2 histamine receptor (H2R). However, it is unclear how L. reuteri‐ derived histamine avoids activation of inflammatory H1 receptors in the intestinal epithelium. In this work, we identified a soluble secreted isoform of diacylglycerol kinase (Dgk) from L. reuteri 6475. DGKs belong to a distinct, conserved family of intracellular lipid kinases that phosphorylate diacylglycerol (DAG), catalyzing its conversion into phosphatidic acid (PA). This reaction attenuates DAG levels in the cell membrane, modifying host intracellular signaling proteins that have evolved the ability to bind this lipid for activation. Histamine binding to H1R can cause phosphorylation of PKC via lipid DAG activation. We found that L. reuteri 6475 suppressed basal levels of the pro‐inflammatory cytokines IL‐6, IL‐1, Eotaxin (eosinophilic chemoattractant proteins) and G‐CSF in the luminal mucosa and in blood plasma. L. reuteri lacking dgkA expression could not suppress the aforementioned pro‐inflammatory biomarkers. In addition, we demonstrate for the first time that histamine synthesized by L. reuteri 6475 activates both H1 and H2 receptors, but Dgk synthesized by the bacterium terminates H1R downstream signaling. Inhibition of signaling downstream of H1R was shown by decreased levels of PKC phosphorylation of intestinal epithelium in wild‐type (WT) L. reuteri treated but not in ΔdgkA mutant treated germ‐free (GF) mice. In addition, we also recorded suppression of CD11b + Gr1 + Ly6G hi immature myeloid cells (IMCs) after WT L. reuteri treatment. In line with mouse experiment PKC phosphorylation was reduced in human epithelial cells after treating the cells with L. reuteri derived conditioned media in vitro . L. reuteri suppress immune response by direct effects of the metabolite histamine and an enzyme diacylglycerol kinase that removes a pro‐inflammatory signal. As a next step we started looking at the effect of L. reuteri and the corresponding mutants in a DSS induced colitis mouse model with conventional microbiome. Support or Funding Information This work was supported by the National Institutes of Health (R01 AT004326, UH3 DK083990, and U01 CA170930), the NIH (National Institute for Diabetes and Digestive and Kidney Diseases)‐funded Texas Medical Center Digestive Diseases Center (DK56338), and unrestricted research support from BioGaia AB (Stockholm, Sweden) (J.V.).