IFN-gamma-induced TNFR2 expression is required for TNF-dependent intestinal epithelial barrier dysfunction.
OBJECTIVE
Tumor necrosis factor (TNF) plays a critical role in intestinal disease. In intestinal epithelia, TNF causes tight junction disruption and epithelial barrier loss by up-regulating myosin light chain kinase (MLCK) activity and expression. The aim of this study was to determine the signaling pathways by which TNF causes intestinal epithelial barrier loss.


METHODS
Caco-2 cells that were either nontransfected or stably transfected with human TNF receptor 1 (TNFR1) or TNFR2 and mouse colonocytes were used for physiologic, morphologic, and biochemical analyses.


RESULTS
Colitis induced in vivo by adoptive transfer of CD4(+)CD45RB(hi) T cells was associated with increased epithelial MLCK expression and myosin II regulatory light chain (MLC) phosphorylation as well as morphologic tight junction disruption. In vitro studies showed that TNF caused similar increases in MLCK expression and MLC phosphorylation, as well as barrier dysfunction, in Caco-2 monolayers only after interferon (IFN)-gamma pretreatment. This reductionist model was therefore used to determine the molecular mechanism by which IFN-gamma and TNF synergize to cause intestinal epithelial barrier loss. IFN-gamma priming increased TNFR1 and TNFR2 expression, and blocking antibody studies showed that TNFR2, but not TNFR1, was required for TNF-induced barrier dysfunction. Transgenic TNFR2, but not TNFR1, expression allowed IFN-gamma-independent TNF responses.


CONCLUSIONS
IFN-gamma primes intestinal epithelia to respond to TNF by inducing TNFR2 expression, which in turn mediates TNF-induced MLCK-dependent barrier dysfunction. The data further suggest that epithelial TNFR2 blockade may be a novel approach to restore barrier function in intestinal disease.
Wang
Fengjun
F
State Key Laboratory of Trauma, Burns, and Combined Injury, Institute of Burn Research, Southwest Hospital, Third Military Medical University, Chongqing, China.
Schwarz
Brad T
BT
Graham
W Vallen
WV
Wang
Yingmin
Y
Su
Liping
L
Clayburgh
Daniel R
DR
Abraham
Clara
C
Turner
Jerrold R
JR
D000818:Animals; D018938:Caco-2 Cells; D018398:Homeodomain Proteins / Q000235:genetics; D006801:Humans; D007371:Interferon-gamma / Q000378:metabolism* / Q000494:pharmacology; D007410:Intestinal Diseases / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology*; D007413:Intestinal Mucosa / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D018994:Myosin Light Chains / Q000378:metabolism; D009219:Myosin-Light-Chain Kinase / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D018124:Receptors, Tumor Necrosis Factor / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D019108:Tight Junctions / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*; D015854:Up-Regulation / Q000502:physiology
D018398:Homeodomain Proteins; D018994:Myosin Light Chains; D018124:Receptors, Tumor Necrosis Factor; C469948:Tnfrh2 protein, mouse; C469947:Tnfrsf23 protein, mouse; D014409:Tumor Necrosis Factor-alpha; C064658:RAG-1 protein; D007371:Interferon-gamma; D009219:Myosin-Light-Chain Kinase