Post-translational inhibition of IP-10 secretion in IEC by probiotic bacteria: impact on chronic inflammation

PLoS One. 2009;4(2):e4365. doi: 10.1371/journal.pone.0004365. Epub 2009 Feb 6.

Abstract

Background: Clinical and experimental studies suggest that the probiotic mixture VSL#3 has protective activities in the context of inflammatory bowel disease (IBD). The aim of the study was to reveal bacterial strain-specific molecular mechanisms underlying the anti-inflammatory potential of VSL#3 in intestinal epithelial cells (IEC).

Methodology/principal findings: VSL#3 inhibited TNF-induced secretion of the T-cell chemokine interferon-inducible protein (IP-10) in Mode-K cells. Lactobacillus casei (L. casei) cell surface proteins were identified as active anti-inflammatory components of VSL#3. Interestingly, L. casei failed to block TNF-induced IP-10 promoter activity or IP-10 gene transcription at the mRNA expression level but completely inhibited IP-10 protein secretion as well as IP-10-mediated T-cell transmigration. Kinetic studies, pulse-chase experiments and the use of a pharmacological inhibitor for the export machinery (brefeldin A) showed that L. casei did not impair initial IP-10 production but decreased intracellular IP-10 protein stability as a result of blocked IP-10 secretion. Although L. casei induced IP-10 ubiquitination, the inhibition of proteasomal or lysosomal degradation did not prevent the loss of intracellular IP-10. Most important for the mechanistic understanding, the inhibition of vesicular trafficking by 3-methyladenine (3-MA) inhibited IP-10 but not IL-6 expression, mimicking the inhibitory effects of L. casei. These findings suggest that L. casei impairs vesicular pathways important for the secretion of IP-10, followed by subsequent degradation of the proinflammatory chemokine. Feeding studies in TNF(DeltaARE) and IL-10(-/-) mice revealed a compartimentalized protection of VSL#3 on the development of cecal but not on ileal or colonic inflammation. Consistent with reduced tissue pathology in IL-10(-/-) mice, IP-10 protein expression was reduced in primary epithelial cells.

Conclusions/significance: We demonstrate segment specific effects of probiotic intervention that correlate with reduced IP-10 protein expression in the native epithelium. Furthermore, we revealed post-translational degradation of IP-10 protein in IEC to be the molecular mechanism underlying the anti-inflammatory effect.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Autophagy / drug effects
  • Bacterial Proteins / metabolism
  • Chemokine CXCL10 / metabolism*
  • Chemotaxis / drug effects
  • Chronic Disease
  • Colitis / microbiology
  • Colitis / pathology
  • Epithelial Cells / cytology
  • Epithelial Cells / drug effects
  • Epithelial Cells / metabolism*
  • Epithelial Cells / microbiology*
  • Humans
  • Inflammation / microbiology*
  • Intestines / cytology*
  • Intracellular Space / drug effects
  • Intracellular Space / metabolism
  • Lactobacillus casei / drug effects
  • Lactobacillus casei / metabolism*
  • Lysosomes / drug effects
  • Lysosomes / metabolism
  • Mice
  • Organ Specificity / drug effects
  • Probiotics / pharmacology
  • Protein Processing, Post-Translational* / drug effects
  • Signal Transduction / drug effects
  • Transcription, Genetic / drug effects
  • Tumor Necrosis Factor-alpha / pharmacology

Substances

  • Bacterial Proteins
  • Chemokine CXCL10
  • Tumor Necrosis Factor-alpha