Germ-free and Antibiotic-treated Mice are Highly Susceptible to Epithelial Injury in DSS Colitis.
OBJECTIVE
Intestinal microbiota is required to maintain immune homeostasis and intestinal barrier function. At the same time, intraluminal bacteria are considered to be involved in inflammatory bowel disease and are required for colitis induction in animal models, with the possible exception of dextran sulphate sodium [DSS] colitis. This study was carried out to ascertain the mechanism underlying the induction of colitis by DSS in the absence of bacteria.


METHODS
Conventional and germ-free [GF] Naval Medical Research Institute [NMRI] mice were used, plus conventional mice treated with an antibiotic cocktail to deplete the intestinal microbiota ['pseudo-GF' or PGF mice]. The differential response to DSS was assessed.


RESULTS
Conventional mice developed DSS-induced colitis normally, whereas GF mice showed only minimal inflammation [no colonic thickening, lower myeloperoxidase activity, IL-6, IL-17, TNF-α, and IFN-γ secretion by splenocytes and mesenteric cell cultures, etc.]. However, these mice suffered enhanced haemorrhage, epithelial injury and mortality as a consequence of a weakened intestinal barrier, as shown by lower occludin, claudin 4, TFF3, MUC3, and IL-22. In contrast, PGF mice had a relatively normal, albeit attenuated, inflammatory response, but were less prone to haemorrhage and epithelial injury than GF mice. This was correlated with an increased expression of IL-10 and Foxp3 and preservation barrier-related markers.


CONCLUSIONS
We conclude that enteric bacteria are essential for the development of normal DSS-induced colitis. The absence of microbiota reduces DSS colonic inflammation dramatically but it also impairs barrier function, whereas subtotal microbiota depletion has intermediate effects at both levels.
Department of Biochemistry and Molecular Biology II, Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas [CIBERehd], University of Granada, Granada, Spain.
Cristina
C
Hernández-Chirlaque
Department of Biochemistry and Molecular Biology II, Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas [CIBERehd], University of Granada, Granada, Spain.
Carlos J
CJ
Aranda
Department of Pharmacology, Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas [CIBERehd], University of Granada, Granada, Spain.
Borja
B
Ocón
Department of Biochemistry and Molecular Biology II, Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas [CIBERehd], University of Granada, Granada, Spain.
Fermín
F
Capitán-Cañadas
Department of Biochemistry and Molecular Biology II, Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas [CIBERehd], University of Granada, Granada, Spain.
Mercedes
M
Ortega-González
Center for Molecular Medicine, Karolinska Institutet, Stockholm, Sweden.
Juan Jesús
JJ
Carrero
Department of Biochemistry and Molecular Biology II, Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas [CIBERehd], University of Granada, Granada, Spain.
María Dolores
MD
Suárez
Department of Pharmacology, Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas [CIBERehd], University of Granada, Granada, Spain.
Antonio
A
Zarzuelo
Department of Pharmacology, Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas [CIBERehd], University of Granada, Granada, Spain.
Fermín
F
Sánchez de Medina
Department of Biochemistry and Molecular Biology II, Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas [CIBERehd], University of Granada, Granada, Spain omartine@ugr.es.
Olga
O
Martínez-Augustin
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002470:Cell Survival; D003092:Colitis / Q000139:chemically induced* / Q000473:pathology; D016207:Cytokines / Q000378:metabolism; D016264:Dextran Sulfate / Q000494:pharmacology*; D004195:Disease Models, Animal; D005260:Female; D000069196:Gastrointestinal Microbiome; D005856:Germ-Free Life; D007413:Intestinal Mucosa / Q000473:pathology*; D008297:Male; D051379:Mice
D000900:Anti-Bacterial Agents; D016207:Cytokines; D016264:Dextran Sulfate
Germ-free; barrier function; microbiota; mucosal