Toll-like receptor 9 signaling mediates the anti-inflammatory effects of probiotics in murine experimental colitis.
OBJECTIVE
We tested whether the attenuation of experimental colitis by live probiotic bacteria is due to their immunostimulatory DNA, whether toll-like receptor (TLR) signaling is required, and whether nonviable probiotics are effective.


METHODS
Methylated and unmethylated genomic DNA isolated from probiotics (VSL-3), DNAse-treated probiotics and Escherichia coli (DH5 alpha) genomic DNA were administered intragastrically (i.g.) or subcutaneously (s.c.) to mice prior to the induction of colitis. Viable or gamma-irradiated probiotics were administered i.g. to wild-type mice and mice deficient in different TLR or in the adaptor protein MyD88, 10 days prior to administration of dextran sodium sulfate (DSS) to their drinking water and for 7 days thereafter.


RESULTS
Intragastric and s.c. administration of probiotic and E. coli DNA ameliorated the severity of DSS-induced colitis, whereas methylated probiotic DNA, calf thymus DNA, and DNase-treated probiotics had no effect. The colitis severity was attenuated to the same extent by i.g. delivery of nonviable gamma-irradiated or viable probiotics. Mice deficient in MyD88 did not respond to gamma-irradiated probiotics. The severity of DSS-induced colitis in TLR2 and TLR4 deficient mice was significantly decreased by i.g. administration of gamma-irradiated probiotics, whereas, in TLR9-deficient mice, gamma-irradiated probiotics had no effect.


CONCLUSIONS
The protective effects of probiotics are mediated by their own DNA rather than by their metabolites or ability to colonize the colon. TLR9 signaling is essential in mediating the anti-inflammatory effect of probiotics, and live microorganisms are not required to attenuate experimental colitis because nonviable probiotics are equally effective.
Rachmilewitz
Daniel
D
Division of Medicine, Shaare Zedak Medical Center, Jerusalem, Israel.
Katakura
Kyoko
K
Karmeli
Fanny
F
Hayashi
Tomoko
T
Reinus
Constantin
C
Rudensky
Bernard
B
Akira
Shizuo
S
Takeda
Kiyoshi
K
Lee
Jongdae
J
Takabayashi
Kenji
K
Raz
Eyal
E
D000042:Absorption; D000276:Adjuvants, Immunologic / Q000494:pharmacology; D000818:Animals; D000893:Anti-Inflammatory Agents / Q000737:chemistry / Q000494:pharmacology* / Q000528:radiation effects; D003092:Colitis / Q000139:chemically induced / Q000473:pathology* / Q000503:physiopathology*; D004247:DNA / Q000302:isolation & purification / Q000494:pharmacology; D004269:DNA, Bacterial / Q000493:pharmacokinetics; D004268:DNA-Binding Proteins / Q000378:metabolism*; D016264:Dextran Sulfate; D004926:Escherichia coli / Q000235:genetics; D005720:Gamma Rays; D051379:Mice; D008815:Mice, Inbred Strains; D019936:Probiotics / Q000737:chemistry / Q000494:pharmacology* / Q000528:radiation effects; D011956:Receptors, Cell Surface / Q000378:metabolism*; D012720:Severity of Illness Index; D015398:Signal Transduction; D051217:Toll-Like Receptor 9
D000276:Adjuvants, Immunologic; D000893:Anti-Inflammatory Agents; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D011956:Receptors, Cell Surface; C495370:Tlr9 protein, mouse; D051217:Toll-Like Receptor 9; D004247:DNA; D016264:Dextran Sulfate