IFN-γ-Induced TNFR2 Expression Is Required for TNF-Dependent Intestinal Epithelial Barrier Dysfunction

State Key Laboratory of Trauma, Burns, and Combined Injury, Institute of Burn Research, Southwest Hospital, Third Military Medical University, Chongqing, China.
Gastroenterology (Impact Factor: 16.72). 10/2006; 131(4):1153-63. DOI: 10.1053/j.gastro.2006.08.022
Source: PubMed


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.
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.
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.
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.

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Available from: Liping Su
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    • "Therefore, in our study, MOC1 cells were transfected with the TNRF2 siRNA to determine MLCK activities in the presence of rTNF. This resulted in the abrogation of TNF-induced TJ disruption associated with suppressed MLCK up-regulation (Fig. 3B and C), and these results are consistent with previous reports [11], [29]. Moreover, we also observed that the TJ remained intact with anti-TNF treatment as well as inhibiting MLCK activity (Fig. 4B and C). "
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    ABSTRACT: It has been suggested that prolonged inflammatory bowel diseases (IBD) may lead to colitis-associated carcinogenesis (CAC). We previously observed that the NF-κB activation in colonic epithelial cells is associated with increased tumor necrosis factor receptor 2 (TNFR2) expression in CAC development. However, the mechanism by which epithelial NF-κB activation leading to CAC is still unclear. Myosin light chain kinase (MLCK) has been reported to be responsible for the epithelial permeability associated with TNF signaling. Therefore we focused on the role of MLCK expression via TNFR2 signaling on CAC development. Pro-tumorigenic cytokines such as IL-1β, IL-6 and MIP-2 production as well as INF-γ and TNF production at the lamina propria were increased in the setting of colitis, and further in tumor tissues in associations with up-regulated TNFR2 and MLCK expressions in the epithelial cells of a CAC model. The up-regulated MLCK expression was observed in TNF-stimulated colonic epithelial cells in a dose-dependent fashion in association with up-regulation of TNFR2. Silencing TNFR2, but not TNFR1, resulted in restoration of epithelial tight junction (TJ) associated with decreased MLCK expression. Antibody-mediated blockade of TNF signaling also resulted in restoration of TJ in association with suppressed MLCK expression, and interestingly, similar results were observed with suppressing TNFR2 and MLCK expressions by inhibiting MLCK in the epithelial cells. Silencing of MLCK also resulted in suppressed TNFR2, but not TNFR1, expression, suggesting that the restored TJ leads to reduced TNFR2 signaling. Such suppression of MLCK as well as blockade of TNFR2 signaling resulted in restored TJ, decreased pro-tumorigenic cytokines and reduced CAC development. These results suggest that MLCK may be a potential target for the prevention of IBD-associated tumor development.
    Full-text · Article · Feb 2014 · PLoS ONE
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    • "MLCK is known to be the predominant determinant of MLC phosphorylation. Previous studies including ours have demonstrated that MLCK protein up-regulation is involved in barrier function disruption and paracellular hyperpermeability [9], [10], [15], [33], [34], [37]–[39]. Thus, we next investigated the effect of berberine on MLCK protein expression in Caco-2 monolayers challenged with or without IFN-γ and TNF-α. "
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    ABSTRACT: Intestinal barrier dysfunction occurs in many intestinal diseases, in which proinflammatory cytokines play critical roles. However, researchers are still on the way to defining the underlying mechanisms and to evaluate therapeutic strategies for restoring intestinal barrier function. Berberine, a drug that has clinically been used to treat gastroenteritis and diarrhea for thousands of years, has been shown to protect barrier function in both endothelial and epithelial cells, but the mechanisms are completely unknown. In this study, we investigate the protective actions of berberine on barrier function and the underlying mechanisms in Caco-2 monolayers challenged with IFN-γ and TNF-α. Caco-2 monolayers were treated without or with simultaneous IFN-γ and TNF-α in the absence or presence of berberine. Both transepithelial electrical resistance (TER) and paracellular permeability were measured to evaluate barrier function. The expression and distribution of tight junction proteins ZO-1, occluding, and claudin-1 were respectively analyzed by immunoblot or immunofluorescence. The expressions of phosphorylated myosin light chain (pMLC), MLC kinase (MLCK) and hypoxia-inducible factor-1α (HIF-1α) were determined by immunoblot. The translocation of NF-κB p65 to nuclei was analyzed by immunofluorescence and immunoblot, respectively. The results showed that berberine significantly attenuated TER decrease and paracellular permeability increase in Caco-2 monolayers treated with IFN-γ and TNF-α. Berberine also dramatically alleviated IFN-γ and TNF-α-induced morphological alteration of tight junction proteins ZO-1, occluding, and claudin-1. The increase of both MLC phosphorylation and MLCK protein expression induced by IFN-γ and TNF-α was significantly inhibited by berberine treatment. Additionally, berberine suppressed the activation of HIF-1α, but not NF-κB. Taken together, it is suggested that berberine attenuates IFN-γ and TNF-α-induced intestinal epithelial barrier dysfunction by inhibiting the signaling pathway of MLCK-dependent MLC phosphorylation mediated by HIF-1α.
    Preview · Article · May 2013 · PLoS ONE
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    • "Increased epithelial permeability in Caco-2 cells treated with relatively high concentrations of TNFα was first shown to require activation of NF-κB [40], resulting in transcriptional activation of myosin light chain kinase and phosphorylation of myosin light chain [41], with reduced expression and delocalization of tight junction proteins such as ZO1 and occludin, occurring at a later stage. Moreover, priming by interferon gamma was shown to enhance the effects of TNFα on epithelial permeability through increased expression of TNFα receptor (TNFR) [42]. In a more recent report, up-regulation of a specific microRNA (miR-122) induced by TNFα was shown to be responsible for occludin mRNA degradation, another mechanism whereby tight junction permeability can be regulated [43] [44]. "
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