TNF-alpha sensitizes HT-29 colonic epithelial cells to intestinal lactobacilli.
The ability of the proinflammatory cytokine tumor necrosis factor-alpha (TNF-alpha) to influence epithelial interleukin (IL)-8 responses to the intestinal bacterium Lactobacillus plantarum 299v was analyzed in the human HT-29 colonic epithelial cell line. In the absence of TNF-alpha, IL-8 mRNA expression was not detectable by Northern blot analysis in HT-29 cells alone or in HT-29 cells co-cultured with L. plantarum 299v. However, TNF-alpha induced IL-8 mRNA expression, and co-culture of TNF-alpha-treated HT-29 cells with L. plantarum 299v significantly increased IL-8 mRNA expression above levels induced by TNF-alpha alone in an adhesion-dependent manner. The increase in IL-8 mRNA expression was not observed in TNF-alpha-treated HT-29/L. plantarum 299v co-cultures using heat-killed lactobacilli or when L. plantarum adhesion was prevented using mannoside or a trans-well membrane. Paradoxically, IL-8 secretion was decreased in TNF-alpha-treated HT-29 cells with L. plantarum 299v relative to cells treated with TNF-alpha alone. TNF-alpha-mediated responsiveness to L. plantarum 299v was further investigated by analyzing expression of a coreceptor for bacterial cell wall products CD14. HT-29 cells expressed CD14 mRNA and cell-surface CD14; however, TNF-alpha did not alter CD14 mRNA or cell-surface expression, and blockade of CD14 with monoclonal antibody MY4 did not alter the IL-8 response to L. plantarum 299v in TNF-alpha-treated HT-29 cells. These results indicate that although TNF-alpha sensitizes HT-29 epithelial cells to intestinal lactobacilli, the bacteria exert a protective effect by downregulating IL-8 secretion.
Department of Animal Sciences, University of Illinois, Urbana, Illinois 61801, USA.
Vance J
VJ
McCracken
Taehoon
T
Chun
Manuel E
ME
Baldeón
Siv
S
Ahrné
Göran
G
Molin
Roderick I
RI
Mackie
H Rex
HR
Gaskins
D000911:Antibodies, Monoclonal / Q000494:pharmacology; D001422:Bacterial Adhesion / Q000187:drug effects; D002460:Cell Line / Q000187:drug effects / Q000382:microbiology; D003106:Colon / Q000166:cytology* / Q000187:drug effects / Q000382:microbiology; D004847:Epithelial Cells / Q000187:drug effects / Q000382:microbiology; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D016209:Interleukin-8 / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D007413:Intestinal Mucosa / Q000166:cytology* / Q000187:drug effects / Q000382:microbiology; D007778:Lactobacillus / Q000502:physiology*; D018950:Lipopolysaccharide Receptors / Q000096:biosynthesis / Q000235:genetics / Q000276:immunology; D008362:Mannosides / Q000494:pharmacology; D008766:Methylmannosides; D012333:RNA, Messenger / Q000096:biosynthesis; D011993:Recombinant Fusion Proteins / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D000911:Antibodies, Monoclonal; D016209:Interleukin-8; D018950:Lipopolysaccharide Receptors; D008362:Mannosides; D008766:Methylmannosides; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D014409:Tumor Necrosis Factor-alpha; C008466:methylmannoside