Lactobacillus probiotic protects intestinal epithelium from radiation injury in a TLR-2/cyclo-oxygenase-2-dependent manner.
BACKGROUND
The small intestinal epithelium is highly sensitive to radiation and is a major site of injury during radiation therapy and environmental overexposure.


OBJECTIVE
To examine probiotic bacteria as potential radioprotective agents in the intestine.


METHODS
8-week-old C57BL/6 wild-type or knockout mice were administered probiotic by gavage for 3 days before 12 Gy whole body radiation. The intestine was evaluated for cell-positional apoptosis (6 h) and crypt survival (84 h).


RESULTS
Gavage of 5×10⁷ Lactobacillus rhamnosus GG (LGG) improved crypt survival about twofold (p<0.01); the effect was observed when administered before, but not after, radiation. Conditioned medium (CM) from LGG improved crypt survival (1.95-fold, p<0.01), and both LGG and LGG-CM reduced epithelial apoptosis particularly at the crypt base (33% to 18%, p<0.01). LGG was detected in the distal ileal contents after the gavage cycle, but did not lead to a detectable shift in bacterial family composition. The reduction in epithelial apoptosis and improved crypt survival offered by LGG was lost in MyD88⁻/⁻, TLR-2⁻/⁻ and cyclo-oxygenase-2⁻/⁻ (COX-2) mice but not TLR-4⁻/⁻ mice. LGG administration did not lead to increased jejunal COX-2 mRNA or prostaglandin E2 levels or a change in number of COX-2-expressing cells. However, a location shift was observed in constitutively COX-2-expressing cells of the lamina propria from the villi to a position near the crypt base (villi to crypt ratio 80:20 for control and 62:38 for LGG; p<0.001). Co-staining revealed these COX-2-expressing small intestinal lamina propria cells to be mesenchymal stem cells.


CONCLUSIONS
LGG or its CM reduce radiation-induced epithelial injury and improve crypt survival. A TLR-2/MyD88 signalling mechanism leading to repositioning of constitutive COX-2-expressing mesenchymal stem cells to the crypt base is invoked.
Division of Gastroenterology, Washington University Saint Louis, 660 South Euclid Avenue, Box 8124, Saint Louis, MO 63110, USA. MCiorba@dom.wustl.edu
Matthew A
MA
Ciorba
Terrence E
TE
Riehl
M Suprada
MS
Rao
Clara
C
Moon
Xueping
X
Ee
Gerardo M
GM
Nava
Monica R
MR
Walker
Jeffrey M
JM
Marinshaw
Thaddeus S
TS
Stappenbeck
William F
WF
Stenson
D000818:Animals; D017209:Apoptosis / Q000528:radiation effects; D051546:Cyclooxygenase 2 / Q000502:physiology*; D005260:Female; D007413:Intestinal Mucosa / Q000382:microbiology / Q000528:radiation effects*; D052201:Lacticaseibacillus rhamnosus / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D053594:Myeloid Differentiation Factor 88 / Q000502:physiology; D019936:Probiotics / Q000627:therapeutic use*; D011833:Radiation Injuries, Experimental / Q000517:prevention & control*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051195:Toll-Like Receptor 2 / Q000502:physiology*; D014916:Whole-Body Irradiation / Q000009:adverse effects*
C507780:Myd88 protein, mouse; D053594:Myeloid Differentiation Factor 88; C493486:Tlr2 protein, mouse; D051195:Toll-Like Receptor 2; C077623:Ptgs2 protein, mouse; D051546:Cyclooxygenase 2