Oral Administration of Transforming Growth Factor-β1 (TGF-β1) Protects the Immature Gut from Injury via Smad Protein-dependent Suppression of Epithelial Nuclear Factor κB (NF-κB) Signaling and Proinflammatory Cytokine Production

Background: Intestinal production of TGF- is decreased in neonatal necrotizing enterocolitis (NEC). Results: Oral administration of TGF- (TGF-1) inhibited inflammation in intestinal epithelium and systemic production of IL-6 and IFN- as well as NEC incidence in an animal model. Conclusion: Oral administration of TGF-1 can compensate for TGF-1 deficiency in gut diseases. Significance: TGF-1 can potentially be used to prevent and treat gut diseases. Inflammatory immune responses play an important role in mucosal homeostasis and gut diseases. Nuclear factor B (NF-B), central to the proinflammatory cascade, is activated in necrotizing enterocolitis (NEC), a devastating condition of intestinal injury with extensive inflammation in premature infants. TGF- is a strong immune suppressor and a factor in breast milk, which has been shown to be protective against NEC. In an NEC animal model, oral administration of the isoform TGF-1 activated the downstream effector Smad2 in intestine and significantly reduced NEC incidence. In addition, TGF-1 suppressed NF-B activation, maintained levels of the NF-B inhibitor IB in the intestinal epithelium, and systemically decreased serum levels of IL-6 and IFN-. The immature human fetal intestinal epithelial cell line H4 was used as a reductionistic model of the immature enterocyte to investigate mechanism. TGF-1 pretreatment inhibited the TNF--induced IB phosphorylation that targets the IB protein for degradation and inhibited NF-B activation. Chromatin immunoprecipitation (ChIP) assays demonstrated decreased NF-B binding to the promoters of IL-6, IL-8, and IB in response to TNF- with TGF-1 pretreatment. These TGF-1 effects appear to be mediated through the canonical Smad pathway as silencing of the TGF- central mediator Smad4 resulted in loss of the TGF-1 effects. Thus, TGF-1 is capable of eliciting anti-inflammatory effects by inhibiting NF-B specifically in the intestinal epithelium as well as by decreasing systemic IL-6 and IFN- levels. Oral administration of TGF-1 therefore can potentially be used to protect against gastrointestinal diseases.