The MicroRNA Landscapes Profiling Reveals Potential Signatures of Necrotizing Enterocolitis in Infants

Chromatin as alarmins in necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a severe gastrointestinal disease primarily affecting premature neonates, marked by poorly understood pro-inflammatory signaling cascades. Recent advancements have shed light on a subset of endogenous molecular patterns, termed chromatin-associated molecular patterns (CAMPs), which belong to the broader category of damage-associated molecular patterns (DAMPs). CAMPs play a crucial role in recognizing pattern recognition receptors and orchestrating inflammatory responses. This review focuses into the realm of CAMPs, highlighting key players such as extracellular cold-inducible RNA-binding protein (eCIRP), high mobility group box 1 (HMGB1), cell-free DNA, neutrophil extracellular traps (NETs), histones, and extracellular RNA. These intrinsic molecules, often perceived as foreign, have the potential to trigger immune signaling pathways, thus contributing to NEC pathogenesis. In this review, we unravel the current understanding of the involvement of CAMPs in both preclinical and clinical NEC scenarios. We also focus on elucidating the downstream signaling pathways activated by these molecular patterns, providing insights into the mechanisms that drive inflammation in NEC. Moreover, we scrutinize the landscape of targeted therapeutic approaches, aiming to mitigate the impact of tissue damage in NEC. This in-depth exploration offers a comprehensive overview of the role of CAMPs in NEC, bridging the gap between preclinical and clinical insights.

miR-375-3p targets YWHAB to attenuate intestine injury in neonatal necrotizing enterocolitis

PURPOSE

Necrotizing enterocolitis (NEC) is a significant contributor to neonatal mortality. This study aimed to investigate the role of high levels of miR-375-3p in breast milk in the development of NEC and elucidate its mechanism.

METHODS

Differential expression of miR-375-3p in the intestines of breast-fed and formula-fed mice was confirmed using real-time polymerase chain reaction (RT-PCR). NEC mice models were established, and intestinal injury was assessed using HE staining. RT-PCR and Western blot were conducted to examine the expression of miR-375-3p, tyrosine 3-monooxygenase/tryptophan 5-monooxygenase activation protein β (YWHAB), as well as the inflammatory in IEC-6 cells, and intestinal tissues obtained from NEC mice and patients. Flow cytometry and cell counting kit-8 (CCK-8) were employed to elucidate the impact of miR-375-3p and YWHAB on cell apoptosis and proliferation.

RESULTS

Breastfeeding increases miR-375-3p expression in the intestines. The expression of miR-375-3p in NEC intestinal tissues exhibited a significant decrease compared to the healthy group. Additionally, the expression of interleukin-6 (IL-6), interleukin-10 (IL-10), and tumor necrosis factor-α (TNF-α) was higher in the NEC group compared to the control group. Down-regulation of miR-375-3p inhibited IEC-6 cell proliferation, increased apoptosis, and elevated secretion of inflammatory factors. Bioinformatics revealed that YWHAB may be a target of miR-375-3p. RT-PCR and Western blot indicated a down-regulation of YWHAB expression in intestines of NEC patients and mice. Furthermore, YWHAB was found to be positively connected with miR-375-3p. Knockdown miR-375-3p down-regulated YWHAB expression in cells. Inhibition of YWHAB exhibited similar effects to miR-375-3p in IEC-6 cells. YWHAB plasmid partially reverse cellular functional impairment induced by miR-375-3p knockdown.

CONCLUSIONS

Breastfeeding elevated miR-375-3p expression in intestines in neonatal mice. MiR-375-3p leads to a decrease in apoptosis of intestinal epithelial cells, an increase in cell proliferation, and a concomitant reduction in the expression of inflammatory factors partly through targeting YWHAB.

The Impact of MicroRNAs in Neonatal Necrotizing Enterocolitis and other Inflammatory Conditions of Intestine: A Review

The understanding of necrotizing enterocolitis (NEC) etiopathogenesis is incomplete, contributing to the lack of early biomarkers and therapeutic options. Micro RNAs (miRNAs) are a class of RNAs that can alter gene expression and modulate various physiological and pathological processes. Several studies have been performed to evaluate the role of miRNA in the pathogenesis of NEC. In this article, we review the information on miRNAs that have been specifically identified in NEC or have been noted in other inflammatory bowel disorders that share some of the histopathological abnormalities seen frequently in NEC. This review highlights miRNAs that could be useful as early biomarkers of NEC and suggests possible approaches for future translational studies focused on these analytes. It is a novel field with potential for immense translational and clinical relevance in preventing, detecting, or treating NEC in very premature infants. Impact • Current information categorizes necrotizing enterocolitis (NEC) as a multifactorial disease, but microRNAs (miRNAs) may influence the risk of occurrence of NEC. • MiRNAs may alter the severity of the intestinal injury and the clinical outcome of NEC. • The literature on intestinal diseases of adults suggests additional miRNAs that have not been studied in NEC yet but share some features and deserve further exploration in human NEC, especially if affecting gut dysbiosis, intestinal perfusion, and coagulation disorders.

Fecal microbiota transplantation by enema reduces intestinal injury in experimental necrotizing enterocolitis

PURPOSE

Necrotizing Enterocolitis (NEC) is a devastating neonatal disease with a high mortality rate. Fecal Microbiota Transplantation (FMT) has been used to treat a variety of gastrointestinal diseases. We aimed to investigate the role of FMT in NEC.

METHODS

NEC was induced by hypoxia, LPS, and hyperosmolar gavage feeding between postnatal days P5 and P9 (n = 8). Breastfed mice were used as control (n = 7). FMT (30 μl/g) was administered by gavage or enema at P6 during NEC induction. Distal ileum was harvested on P9. Disease severity was evaluated by H&E staining. Gene expression of inflammatory markers IL6 and TNFa was measured. Expression of intestinal barrier function was investigated by measuring Claudin-7. Microbiota composition in ileum and colon was analyzed by quantitative PCR.

RESULTS

FMT by gavage further increased terminal ileum inflammation and did not improve the histological damage owing to experimental NEC. Conversely, FMT by enema decreased intestinal inflammation and improved histology of the NEC-like injury in the ileum. In addition, compared with NEC alone, FMT by enema increased Claudin-7 expression indicating an improvement in barrier function. These beneficial effects occurred despite no change in microbiota.

CONCLUSION

Our results show that FMT by enema may be an effective strategy to reduce NEC progression as it attenuates intestinal inflammation and enhances intestinal barrier function. FMT by enema is a potential novel treatment for NEC.

LEVEL OF EVIDENCE

Level IV, Evidence from well-designed case-control or cohort studies.

Beneficial effects of butyrate in intestinal injury

PURPOSE

Butyrate is a short-chain fatty acid produced in the intestine. It is controversial whether butyrate is protective or destructive for the intestinal epithelium in the development of diseases like necrotizing enterocolitis (NEC), and its mechanism of action remains unclear. We aimed to determine the effect of butyrate on the intestinal epithelium by studying its effects on intestinal epithelial cells (IEC-18) exposed to injury and in vivo by investigating the effects on the intestine in an experimental model of NEC.

METHODS

A) In vitro study: Butyrate was given to normal IEC-18 to determine the dose triggering injury. Based on above results, low dose butyrate (1 mM) was given to H₂O₂-injured cells to determine its effect against inflammation. B) In vivo study: NEC was induced by hypoxia and gavage feeding between postnatal day P5 and P9 (n = 8). Breastfed mice were used as control (n = 7). Butyrate (150 mM) was administered by enema on P6 in NEC (n = 6). Distal ileum was harvested on P9.

RESULTS

High dose (16 mM) butyrate upregulated inflammatory marker IL-6, while low dose butyrate protected cells from injury by reducing IL-6 expression. Similarly, compared with NEC alone, NEC mice who received butyrate had reduced intestinal damage, reduced IL-6 and NF-ĸB expression, and increased intestinal tight junction marker Claudin-7.

CONCLUSION

Butyrate has opposite effects depending on the dose administered. Butyrate can protect cells from H₂O₂-induced injury and can in vivo protect the intestine from NEC. This beneficial effect is because of downregulation of inflammation and enhancement of intestinal barrier.