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


RESULTS
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
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.
Hoermannsperger
Gabriele
G
Chair for Biofunctionality, ZIEL-Research Center for Nutrition and Food Science, Technische Universität München, Freising-Weihenstephan, Germany.
Hörmannsperger
Gabriele
G
Clavel
Thomas
T
Hoffmann
Micha
M
Reiff
Caroline
C
Kelly
Denise
D
Loh
Gunnar
G
Blaut
Michael
M
Hölzlwimmer
Gabriele
G
Laschinger
Melanie
M
Haller
Dirk
D
D000818:Animals; D001343:Autophagy / Q000187:drug effects; D001426:Bacterial Proteins / Q000378:metabolism; D054357:Chemokine CXCL10 / Q000378:metabolism*; D002633:Chemotaxis / Q000187:drug effects; D002908:Chronic Disease; D003092:Colitis / Q000382:microbiology / Q000473:pathology; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism* / Q000382:microbiology*; D006801:Humans; D007249:Inflammation / Q000382:microbiology*; D007422:Intestines / Q000166:cytology*; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism; D007780:Lacticaseibacillus casei / Q000187:drug effects / Q000378:metabolism*; D008247:Lysosomes / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D009928:Organ Specificity / Q000187:drug effects; D019936:Probiotics / Q000494:pharmacology; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects; D014158:Transcription, Genetic / Q000187:drug effects; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D001426:Bacterial Proteins; D054357:Chemokine CXCL10; D014409:Tumor Necrosis Factor-alpha