Toll-like receptor 9 signaling mediates the anti-inflammatory effects of probiotics in murine experimental colitis

Gastroenterology. 2004 Feb;126(2):520-8. doi: 10.1053/j.gastro.2003.11.019.


Background & aims: 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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Absorption
  • Adjuvants, Immunologic / pharmacology
  • Animals
  • Anti-Inflammatory Agents / chemistry
  • Anti-Inflammatory Agents / pharmacology*
  • Anti-Inflammatory Agents / radiation effects
  • Colitis / chemically induced
  • Colitis / pathology*
  • Colitis / physiopathology*
  • DNA / isolation & purification
  • DNA / pharmacology
  • DNA, Bacterial / pharmacokinetics
  • DNA-Binding Proteins / metabolism*
  • Dextran Sulfate
  • Escherichia coli / genetics
  • Gamma Rays
  • Mice
  • Mice, Inbred Strains
  • Probiotics / chemistry
  • Probiotics / pharmacology*
  • Probiotics / radiation effects
  • Receptors, Cell Surface / metabolism*
  • Severity of Illness Index
  • Signal Transduction*
  • Toll-Like Receptor 9


  • Adjuvants, Immunologic
  • Anti-Inflammatory Agents
  • DNA, Bacterial
  • DNA-Binding Proteins
  • Receptors, Cell Surface
  • Tlr9 protein, mouse
  • Toll-Like Receptor 9
  • DNA
  • Dextran Sulfate