Intestinal barrier dysfunction in human necrotizing enterocolitis

Abstract

Background Intestinal barrier dysfunction has been implicated in necrotizing enterocolitis (NEC), but has not been directly measured in human NEC. Methods Small intestines removed during surgery were immediately mounted in an Ussing chamber. mRNA expression of tight junction (TJ) proteins was measured with RT-PCR. Results Fifteen infants were included, 5 with NEC and 10 with other diagnoses. Average transepithelial resistance (TER) was 11.61 ± 1.65 Ω/cm2 in NEC specimens, 23.36 ± 1.48 Ω/cm2 at resection margin, and 46.48 ± 5.65 Ω/cm2 in controls. Average flux of permeability marker mannitol was 0.23 ± 0.06 μMol/cm2 per h in NEC, 0.04 ± 0.01 μMol/cm2 per h at resection margin, and 0.017 ± 0.004 μMol/cm2 per h in control tissue (p < 0.05). RT-PCR analysis showed marked decrease in mRNA expression of a TJ protein occludin in NEC affected tissue (p < 0.03 vs. control). Additionally, mRNA expression of myosin light chain kinase (MLCK), an important regulator of TJ permeability, was increased in NEC specimens. Conclusion These studies show for the first time that NEC intestinal tissue have increased intestinal permeability, even at grossly healthy-appearing resection areas. The increase in intestinal permeability in NEC appeared to be related in part to a decrease in occludin and an increase in MLCK expression. Level of evidence Level 2.

Anemia induces gut inflammation and injury in an animal model of preterm infants

“…In this manner, macrophage cytokine secretion likely outweighs the potentially beneficial increase in epithelial HIF1α expression, leading to an overall decrease in tight junction protein expression and increased barrier permeability, both key factors that can predispose neonates to NEC. 58 Given prior epidemiologic data demonstrating an increased risk of NEC in anemic neonates and our present findings implicating anemia as a causal factor in intestinal inflammation, severe anemia may increase the risk of intestinal injury that may predispose VLBW infants to subsequent development of NEC. As anemia is also associated with chronic inflammatory conditions within the intestines, such as IBD and graft versus host disease, 33,38 the use of lower hemoglobin thresholds in these populations may likewise unintentionally contribute to intestinal inflammation and injury.…”

“…55 An additional critical component associated with the development of intestinal inflammatory conditions is increased gut permeability. 58 Consistent with this, inflammation can directly impair gut barrier function. 41,59 As a result, we next investigated the potential impact of neonatal anemia on the expression of epithelial tight junctions, key features of the intestinal epithelium responsible for normal barrier function.…”

“…An additional critical component associated with the development of intestinal inflammatory conditions is increased gut permeability . Consistent with this, inflammation can directly impair gut barrier function .…”

“…Our data demonstrate that anemia alone appears to alter immune function and intestinal injury, both of which have previously been shown to potentially increase the risk for developing of NEC. [15][16][17][27][28][29][30][31][32]58,68 In doing so, these data provide a novel mechanistic link between anemia and intestinal alterations that may increase an infant's susceptibility to developing NEC.…”

“…Moreover, the ability of clodronate to not only deplete intestinal macrophages, but also reverse anemia‐induced intestinal injury, suggests that in this model macrophages may serve as a key population responsible for detecting and subsequently responding to anemic insults; prolonged pro‐inflammatory programming in macrophages may therefore tip the balance between tolerance and inflammation in additional immune populations within the gut upon secondary stress events. In this manner, macrophage cytokine secretion likely outweighs the potentially beneficial increase in epithelial HIF1α expression, leading to an overall decrease in tight junction protein expression and increased barrier permeability, both key factors that can predispose neonates to NEC …”