Tumour necrosis factor‐α‐induced loss of intestinal barrier function requires TNFR1 and TNFR2 signalling in a mouse model of total parenteral nutrition
Authors: Feng Yongjia , Teitelbaum Daniel H. 
Published: June 2013

Key points
Total parenteral nutrition (TPN) is critical for patients who cannot tolerate enteral nutrition. However, TPN‐associated loss of barrier function leads to an increase in enterically derived pathogens that may harm the patient.
Tumour necrosis factor‐α (TNF‐α) is involved in the dysregulation of intestinal barrier function in many animal models.
The mouse model of TPN provides an excellent, non‐destructive approach to examine epithelial barrier dysfunction.
Tumour necrosis factor‐α is shown to be a major mediator of epithelial barrier dysfunction using this TPN model.
Tumour necrosis factor‐α signalling is reliant on both the TNFR1 and TNFR2 pathways to effect epithelial barrier dysfunction.
Anti‐TNF treatment protected against TPN‐associated epithelial barrier dysfunction and might prove to be a viable future clinical approach.
Abstract  Tumour necrosis factor‐α (TNF‐α) has been reported to play a central role in intestinal barrier dysfunction in many diseases; however, the precise role of the TNF‐α receptors (TNFRs) has not been well defined using in vivo models. Our previous data showed that enteral nutrient deprivation or total parenteral nutrition (TPN) led to a loss of intestinal epithelial barrier function (EBF), with an associated upregulation of TNF‐α and TNFR1. In this study, we hypothesized that TNF‐α plays an important role in TPN‐associated EBF dysfunction. Using a mouse TPN model, we explored the relative roles of TNFR1 vs. TNFR2 in mediating this barrier loss. C57/BL6 mice underwent intravenous cannulation and were given enteral nutrition or TPN for 7 days. Tumour necrosis factor‐α receptor knockout (KO) mice, including TNFR1KO, TNFR2KO or TNFR1R2 double KO (DKO), were used. Outcomes included small intestine transepithelial resistance (TER) and tracer permeability, junctional protein zonula occludens‐1, occludin, claudins and E‐cadherin expression. In order to address the dependence of EBF on TNF‐α further, exogenous TNF‐α and pharmacological blockade of TNF‐α (Etanercept) were also performed. Total parenteral nutrition led to a loss of EBF, and this was almost completely prevented in TNFR1R2DKO mice and partly prevented in TNFR1KO mice but not in TNFR2KO mice. The TPN‐associated downregulation of junctional protein expression and junctional assembly was almost completely prevented in the TNFR1R2DKO group. Blockade of TNF‐α also prevented dysfunction of the EBF and junctional protein losses in mice undergoing TPN. Administration of TPN upregulated the downstream nuclear factor‐κB and myosin light‐chain kinase (MLCK) signalling, and these changes were almost completely prevented in TNFR1R2DKO mice, as well as with TNF‐α blockade, but not in TNFR1KO or TNFR2KO TPN groups. Tumour necrosis factor‐α is a critical factor for TPN‐associated epithelial barrier dysfunction, and both TNFR1 and TNFR2 are involved in EBF loss. Nuclear factor‐κB and MLCK signalling appear to be important downstream mediators involved in this TNF‐α signalling process.