Effects of nonpathogenic bacteria on cytokine secretion by human intestinal mucosa.
OBJECTIVE
The human intestine harbors a complex microbial ecosystem, and the mucosa is the interface between the immune system and the luminal environment. The aim of this study was to elucidate whether host-bacteria interactions influence mucosal cytokine production.


METHODS
Macroscopically normal colonic specimens were obtained at surgery from eight patients with neoplasm, and inflamed ileal specimens were obtained from two patients with Crohn's disease. Mucosal explants were cultured for 24 h with either nonpathogenic Escherichia coli ECOR-26, Lactobacillus casei DN-114 001, L. casei DN-114 056, L. casei ATCC-334, or Lactobacillus bulgaricus LB-10. Each study included blank wells with no bacteria. Tissue and bacteria viability were confirmed by LDH release and culture. Concentration of tumor necrosis factor (TNF)alpha, transforming growth factor beta1, interleukin (IL)-8, and IL-10 was measured in supernatants. In parallel experiments, neutralizing anti-TNFalpha antibody was added to the culture.


RESULTS
Co-culture of mucosa with bacteria did not modify LDH release. Co-culture with L. casei strains significantly reduced TNFalpha release, whereas E. coli increased it. These effects were observed both in normal and inflamed mucosa. In combination studies, L. casei DN-114 001 prevented TNFalpha stimulation by E. coli. L. casei DN-114 001 also reduced IL-8 release via a TNFalpha-independent pathway. L. casei DN-114 056 or E. coli increased IL-10 release in the presence of neutralizing anti-TNFalpha.


CONCLUSIONS
Nonpathogenic bacteria interact with human intestinal mucosa and can induce changes in cytokine production that are strain specific.
Digestive System Research Unit, Hospitals Vall d'Hebron, Universidad Autónoma de Barcelona, Barcelona, Spain.
Natalia
N
Borruel
Francesc
F
Casellas
María
M
Antolín
Marta
M
Llopis
Monica
M
Carol
Eloy
E
Espíin
Javier
J
Naval
Francisco
F
Guarner
Juan R
JR
Malagelada
D000368:Aged; D000369:Aged, 80 and over; D018920:Coculture Techniques; D016207:Cytokines / Q000378:metabolism* / Q000502:physiology; D004926:Escherichia coli / Q000472:pathogenicity* / Q000502:physiology*; D005260:Female; D006801:Humans; D016753:Interleukin-10 / Q000032:analysis; D016209:Interleukin-8 / Q000032:analysis; D007410:Intestinal Diseases / Q000209:etiology* / Q000382:microbiology* / Q000503:physiopathology; D007413:Intestinal Mucosa / Q000378:metabolism* / Q000382:microbiology* / Q000503:physiopathology; D007778:Lactobacillus / Q000472:pathogenicity* / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D016212:Transforming Growth Factor beta / Q000032:analysis; D053773:Transforming Growth Factor beta1; D014409:Tumor Necrosis Factor-alpha / Q000032:analysis
D016207:Cytokines; D016209:Interleukin-8; C508960:TGFB1 protein, human; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D014409:Tumor Necrosis Factor-alpha; D016753:Interleukin-10