Recently, a drug discovery approach has revealed a novel class of TLR4 inhibitors which are being developed for personalized approaches to NEC treatment.
In summary, we show that TLR4 activation in Surfactant protein C-1 (Sftpc1) cells disrupts the Treg/Th17 balance in the lung via CCL25 leading to lung injury after NEC and reveal that inhibition of TLR4 and stabilization of Th17/Treg balance in the neonatal lung may prevent this devastating complication of NEC.
This article discusses the state of the science of the molecular mechanisms involved in TLR4-mediated inflammation during NEC and the development of new therapeutic strategies to prevent NEC.
We have recently shown that NEC development is dependent on the expression of the lipopolysaccharide receptor Toll-like receptor 4 (TLR4) on the intestinal epithelium, whose activation by bacteria in the newborn gut leads to mucosal inflammation.
These were achieved partly through restoration of VDR and suppression of TLR4.ConclusionNEC infants have lower levels of vitamin D. The vitamin D/VDR pathway protects against intestinal injury of NEC partly through suppressing the expression of TLR4.
Moreover, LCA attenuated intestinal proinflammatory responses in the early stages of experimental NEC.ConclusionThese findings provide proactive insights into the regulation of TLR4 in the developing intestine.
In this study, we show a previously unknown mechanism for the development of intestinal injury equivalent to that seen in human NEC and that is not dependent on TLR4 pathways.
These results suggest that eNOS-SSG within the MIMECs inhibited NO production and enhanced TLR4 activity, which were implicated in the pathogenesis of NEC.
The aim of this study was to characterize the role of TLR4-mediated inflammation and apoptosis in the development of NEC and to determine the major apoptotic pathways and regulators in the process.
This study demonstrated B. adolescentis prevents NEC in preterm neonatal rats and that the mechanism for this action might be associated with the alteration of TLR4, TOLLIP, and SIGIRR expression.
In NEC model group, the peak expression of TLR4 mRNA occurred later than that of NF-κB mRNA and IL-6, and the expressions of TLR4 mRNA, NF-κB mRNA and IL-6 were decreased at 72 h after IGF-1 intervention.
These findings identify an important role for proinflammatory lymphocytes in NEC development via intestinal epithelial TLR4 that could be reversed through dietary modification.
These findings identify a novel link between TLR4-induced ER stress and ISC apoptosis in NEC pathogenesis and suggest that increased ER stress within the premature bowel predisposes to NEC development.
Our lead compound, C34, is a 2-acetamidopyranoside (MW 389) with the formula C17H27NO9, which inhibited TLR4 in enterocytes and macrophages in vitro, and reduced systemic inflammation in mouse models of endotoxemia and necrotizing enterocolitis.
These findings depart from current dogma in the field by identifying a unique effect of TLR4-induced autophagy within the intestinal epithelium in the pathogenesis of NEC and identify that the negative consequences of autophagy on enterocyte migration play an essential role in its development.
TLR4(-/-) mice and mice with enterocyte-specific deletion of TLR4 were protected from NEC; epithelial differentiation into goblet cells was increased via suppressed Notch signaling in the small intestinal epithelium.
In severe NEC, low hBD2 expression was accompanied by low TLR4/MD2 expression, suggesting an inadequate response to luminal bacteria, possibly predisposing those infants to the development of NEC.
Enterocyte proliferation was detected in IEC-6 cells or in ileum or colon from wild-type, TLR4-mutant, or TLR4(-/-) mice after induction of NEC or endotoxemia. beta-Catenin signaling was assessed by cell fractionation or immunoconfocal microscopy to detect its nuclear translocation.
We now hypothesize that activation of NOD2 in the newborn intestine inhibits TLR4, and that failure of NOD2 signaling leads to NEC through increased TLR4-mediated enterocyte apoptosis.
We now demonstrate that murine and human NEC are associated with increased intestinal HMGB1 expression, that serum HMGB1 is increased in murine NEC, and that HMGB1 inhibits enterocyte migration in vitro and in vivo in a TLR4-dependent manner.
Our findings provide evidence for a mechanism by which PAF augments inflammation in the intestinal epithelium through abnormal TLR4 upregulation, thereby contributing to the intestinal injury of NEC.