Bifidobacterium breve MCC-117 is able to significantly reduce the
expression of inflammatory cytokines in porcine intestinal epithelial (PIE) cells and to
improve IL-10 levels in CD4+CD25high Foxp3+ lymphocytes
in response to heat-stable enterotoxigenic Escherichia coli (ETEC)
pathogen-associated molecular patterns (PAMPs), while the immunoregulatory effect of
B. adolescentis ATCC15705 was significantly lower than that observed
for the MCC-117 strain. Considering the different capacities of the two bifidobacterium
strains to activate toll-like receptor (TLR)-2 and their differential immunoregulatory
activities in PIE and immune cells, we hypothesized that comparative studies with both
strains could provide important information regarding the molecular mechanism(s) involved
in the anti-inflammatory activity of bifidobacteria. In this work, we demonstrated that
the anti-inflammatory effect of B. breve MCC-117 was achieved by a
complex interaction of multiple negative regulators of TLRs as well as inhibition of
multiple signaling pathways. We showed that B. breve MCC-117 reduced
heat-stable ETEC PAMP-induced NF-κB, p38 MAPK and PI3 K activation and expression of
pro-inflammatory cytokines in PIE cells. In addition, we demonstrated that B.
breve MCC-117 may activate TLR2 synergistically and cooperatively with one or
more other pattern recognition receptors (PRRs), and that interactions may result in a
coordinated sum of signals that induce the upregulation of A20, Bcl-3, Tollip and SIGIRR.
Upregulation of these negative regulators could have an important physiological impact on
maintaining or reestablishing homeostatic TLR signals in PIE cells. Therefore, in the
present study, we gained insight into the molecular mechanisms involved in the
immunoregulatory effect of B. breve MCC-117.