Profile analysis reveals endogenous RNAs regulate necrotizing enterocolitis progression

Macrophage α7nAChR alleviates the inflammation of neonatal necrotizing enterocolitis through mTOR/NLRP3/IL-1β pathway

BACKGROUND

Neonatal necrotizing enterocolitis (NEC) is one of the most prevalent and severe intestinal emergencies in newborns. The inflammatory activation of macrophages is associated with the intestinal injury of NEC. The neuroimmune regulation mediated by α7 nicotinic acetylcholine receptor (α7nAChR) plays an important role in regulating macrophage activation and inflammation progression, but in NEC remains unclear. This study aims to explore the effect of macrophage α7nAChR on NEC.

METHODS

Mice NEC model were conducted with high-osmolarity formula feeding, hypoxia, and cold stimulation. The α7nAChR agonist PNU-282987 and mTOR inhibitor rapamycin were treated by intraperitoneal injections in mice. The expression and distribution of macrophages, α7nAChR, and phospho-mammalian target of rapamycin (p-mTOR) in the intestines of NEC patients and mice was assessed using immunohistochemistry, immunofluorescence, and flow cytometry. The expression of NLRP3, activated caspase-1 and IL-1β in mice intestines was detected by flow cytometry, western blot or ELISA. In vitro, the mouse RAW264.7 macrophage cell line was also cultured followed by various treatments. Expression of p-mTOR, NLRP3, activated caspase-1, and IL-1β in macrophages was determined.

RESULTS

Macrophages accumulated in the intestines and the expression of α7nAChR in the mucosal and submucosal layers of the intestines was increased in both the NEC patients and mice. The p-mTOR and CD68 were increased and co-localized in intestines of NEC patients. In vitro, α7nAChR agonist PNU-282987 significantly reduced the increase of NLRP3, activated caspase-1, and IL-1β in macrophages. PNU-282987 also significantly reduced the increase of p-mTOR. The effect was blocked by AMPK inhibitor compound C. The expression of NLRP3, activated caspase-1, and IL-1β was inhibited after mTOR inhibitor rapamycin treatment. In NEC model mice, PNU-282987 reduced the expression of p-mTOR, NLRP3, activated caspase-1, and IL-1β in the intestine. Meanwhile, rapamycin significantly attenuated NLRP3 activation and the release of IL-1β. Moreover, the proportion of intestinal macrophages and intestinal injury decreased after PNU-282987 treatment.

CONCLUSION

Macrophage α7nAChR activation mitigates NLRP3 inflammasome activation by modulating mTOR phosphorylation, and subsequently alleviates intestinal inflammation and injury in NEC.

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.

Noninvasive Fecal Cytokine and Microbiota Profiles Predict Commencement of Necrotizing Enterocolitis in a Proof-of-Concept Study

Background and Aims

Necrotizing enterocolitis (NEC) is a life-threatening disease and the most common gastrointestinal emergency in premature infants. Accurate early diagnosis is challenging. Modified Bell's staging is routinely used to guide diagnosis, but early diagnostic signs are nonspecific, potentially leading to unobserved disease progression, which is problematic given the often rapid deterioration observed. We investigated fecal cytokine levels, coupled with gut microbiota profiles, as a noninvasive method to discover specific NEC-associated signatures that can be applied as potential diagnostic markers.

Methods

Premature babies born below 32 weeks of gestation were admitted to the 2-site neonatal intensive care unit (NICU) of Imperial College hospitals (St. Mary's or Queen Charlotte's & Chelsea) between January 2011 and December 2012. During the NICU stay, expert neonatologists grouped individuals by modified Bell's staging (healthy, NEC1, NEC2/3) and fecal samples from diapers were collected consecutively. Microbiota profiles were assessed by 16S rRNA gene amplicon sequencing and cytokine concentrations were measured by V-Plex multiplex assays.

Results

Early evaluation of microbiota profiles revealed only minor differences. However, at later time points, significant changes in microbiota composition were observed for Bacillota (adj. P = .0396), with Enterococcus being the least abundant in Bell stage 2/3 NEC. Evaluation of fecal cytokine levels revealed significantly higher concentrations of IL-1α (P = .045), IL-5 (P = .0074), and IL-10 (P = .032) in Bell stage 1 NEC compared to healthy individuals.

Conclusion

Differences in certain fecal cytokine profiles in patients with NEC indicate their potential use as diagnostic biomarkers to facilitate earlier diagnosis. Additionally, associations between microbial and cytokine profiles contribute to improving knowledge about NEC pathogenesis.

miRNA Profiling of Major Testicular Germ Cells Identifies Stage-Specific Regulators of Spermatogenesis

Spermatogenesis is tightly controlled at transcriptional, post-transcriptional, and epigenetic levels by various regulators, including miRNAs. This study deals with the identification of miRNAs critical to the three important stages of germ cell development (spermatocytes, round spermatids, and mature sperm) during spermatogenesis. We used high-throughput transcriptome sequencing to identify the differentially expressed miRNAs in the pachytene spermatocytes, round spermatids, and mature sperm of rat. We identified 1843 miRNAs that were differentially expressed across the three stages of germ cell development. These miRNAs were further categorized into three classes according to their pattern of expression during spermatogenesis: class 1 - miRNAs found exclusively in one stage and absent in the other two stages; class 2 - miRNAs found in any two stages but absent in the third stage; class 3 - miRNAs expressed in all the three stages. Six hundred forty-six miRNAs were found to be specific to one developmental stage, 443 miRNAs were found to be common across any two stages, and 754 miRNAs were common to all the three stages. Target prediction for ten most abundant miRNAs specific to each category identified miRNA regulators of mitosis, meiosis, and cell differentiation. The expression of each miRNA is specific to a particular developmental stage, which is required to maintain a significant repertoire of target mRNAs in the respective stage. Thus, this study provided valuable data that can be used in the future to identify the miRNAs involved in spermatogenic arrest at a particular stage of the germ cell development.

Advances in our understanding of the molecular pathogenesis of necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a multifactorial and complex disease. Our knowledge of the cellular and genetic basis of NEC have expanded considerably as new molecular mechanisms have been identified. This article will focus on the current understanding of the molecular pathogenesis of NEC with a focus on the inflammatory, immune, infectious, and genetic mechanisms that drive disease development.

Biomarkers of gut injury in neonates - where are we in predicting necrotising enterocolitis?

Despite advances in neonatal care Necrotising Enterocolitis (NEC) continues to have a significant mortality and morbidity rate, and with increasing survival of those more immature infants the population at risk of NEC is increasing. Ischaemia, reperfusion, and inflammation underpin diseases affecting intestinal blood flow causing gut injury including Necrotising Enterocolitis. There is increasing interest in tissue biomarkers of gut injury in neonates, particularly those representing changes in intestinal wall barrier and permeability, to determine whether these could be useful biomarkers of gut injury. This article reviews current and newly proposed markers of gut injury, the available literature evidence, recent advances and considers how effective they are in clinical practice. We discuss each biomarker in terms of its effectiveness in predicting NEC onset and diagnosis or predicting NEC severity and then those that will aid in surveillance and identifying those infants are greatest risk of developing NEC.

Non-coding RNAs in Necrotizing Enterocolitis- A New Frontier?

With the recognition that only 2% of the human genome encodes for a protein, a large part of the "non-coding" portion is now being evaluated for a regulatory role in cellular processes. These non-coding RNAs (ncRNAs) are subdivided based on the size of the nucleotide transcript into microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), but most of our attention has been focused on the role of microRNAs (miRNAs) in human health and disease. Necrotizing enterocolitis (NEC), an inflammatory bowel necrosis affecting preterm infants, has a multifactorial, unclear etiopathogenesis, and we have no specific biomarkers for diagnosis or the impact of directed therapies. The information on ncRNAs, in general, and particularly in NEC, is limited. Increasing information from other inflammatory bowel disorders suggests that these transcripts may play an important role in intestinal inflammation. Here, we review ncRNAs for definitions, classifications, and possible roles in prematurity and NEC using some preliminary information from our studies and from an extensive literature search in multiple databases including PubMed, EMBASE, and Science Direct. miRNAs will be described in another manuscript in this series, hence in this manuscript we mainly focus on lncRNAs.

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.

miR‑34a increases inflammation and oxidative stress levels in patients with necrotizing enterocolitis by downregulating SIRT1 expression

The miR‑34a/SIRT1 signaling axis is an important signaling axis in tumors and diseases. Notably, low SIRT1 expression in the intestinal tissues of patients with necrotizing enterocolitis (NEC) has been reported. However, whether miR‑34a/SIRT1 signaling as a target to protect the intestines during the NEC process is unclear and remains to be elucidated. Blood samples were collected from 30 patients with NEC, and an NEC rat model was used. The miR‑34a and SIRT1 gene and protein expression levels were assayed by qPCR and Western blotting method. The inflammatory cytokine levels and oxidative stress levels were detected using the ELISA method. The results demonstrated that birth weight, albumin and glucose concentrations were significantly decreased in the NEC patient group compared with the control group, but the C‑reactive protein (CRP) and procalcitonin (PCT) concentrations were significantly increased. The miR‑34a expression level was notably increased in the NEC group, but the SIRT1 expression level was markedly decreased. Notably, the miR‑34a was significantly correlated with NEC severity and the concentrations of CRP, PCT, IL‑6, TNF‑α, IL‑1β, IL‑8, MCP‑1, VCAM1 and malondialdehyde (MDA), but was significantly negatively correlated with SIRT1 gene expression and the concentration of IL‑10. Intestinal villi damage in NEC rats was decreased with miR‑34a inhibition and SIRT1 activation treatment by decreasing the levels of inflammatory cytokines, including IL‑6, TNF‑α, IL‑1β and IL‑8, and oxidative stress proteins, including MCP‑1, VCAM1, and MDA, as well as increasing the level of the anti‑inflammatory cytokine IL‑10. In addition, the results indicated that miR‑34a inhibition and SIRT1 activation strongly protected the intestine and decreased the damage caused by NEC, not only by decreasing the protein levels of SIRT1, TNF‑α, IL‑1β, IL‑6 and IL‑8, but also by increasing the IL‑10 protein levels. The miR‑34a inhibition and SIRT1 activation may decrease the damage caused by NEC by decreasing proinflammatory cytokines and oxidative stress proteins and by increasing the anti‑inflammatory cytokine pathway. Based on the aforementioned analysis, the miR‑34a and SIRT1 proteins may be potential novel therapeutic targets in NEC.

MiR-141-3p ameliorates RIPK1-mediated necroptosis of intestinal epithelial cells in necrotizing enterocolitis

AIM

To explore the effects of miR-141-3p on intestinal epithelial cells in necrotizing enterocolitis and the underlying mechanism.

RESULTS

The expression of miR-141-3p was significantly downregulated in serum samples of patients with NEC and LPS-treated Caco-2 cells. The in vitro assays showed that miR-141-3p mimics inhibited expression of IL-6 and TNF-α and reduced PI positive rate of the LPS-treated Caco-2 cells. Next, receptor interacting protein kinase 1 (RIPK1) was identified as the downstream molecule of miR-141-3p, and RIPK1 overexpression aggravated LPS-induced Caco-2 cell injury, which was ameliorated by miR-141-3p mimics. Finally, we found miR-141-3p mimics inhibited upregulation of necroptosis-related molecules and interaction of RIPK1 and RIPK3 in LPS-treated Caco-2 cells.

CONCLUSION

Our research indicated that miR-141-3p protected intestinal epithelial cells from LPS damage by suppressing RIPK1-mediated inflammation and necroptosis, providing an alternative perspective to explore the pathogenesis of NEC.

METHODS

Quantitative real time-polymerase chain reaction (qRT-PCR) was used to detect the expression of miR-141-3p in serum samples of participants and lipopolysaccharide (LPS)-treated Caco-2 cells. Cell Counting Kit-8 (CCK-8) assay, Propidium Iodide (PI) staining and detection of inflammatory cytokines were performed to evaluate the role of miR-141-3p in LPS-treated Caco-2 cells. TargetScanHuman database and luciferase reporter gene assay were utilized to confirm the direct downstream molecule of miR-141-3p. Western blot analysis was used to explore the mechanism.

Emerging Biomarkers for Prediction and Early Diagnosis of Necrotizing Enterocolitis in the Era of Metabolomics and Proteomics

Necrotizing Enterocolitis (NEC) is a catastrophic disease affecting predominantly premature infants and is characterized by high mortality and serious long-term consequences. Traditionally, diagnosis of NEC is based on clinical and radiological findings, which, however, are non-specific for NEC, thus confusing differential diagnosis of other conditions such as neonatal sepsis and spontaneous intestinal perforation. In addition, by the time clinical and radiological findings become apparent, NEC has already progressed to an advanced stage. During the last three decades, a lot of research has focused on the discovery of biomarkers, which could accurately predict and make an early diagnosis of NEC. Biomarkers used thus far in clinical practice include acute phase proteins, inflammation mediators, and molecules involved in the immune response. However, none has been proven accurate enough to predict and make an early diagnosis of NEC or discriminate clinical from surgical NEC or other non-NEC gastrointestinal diseases. Complexity of mechanisms involved in NEC pathogenesis, which remains largely poorly elucidated, could partly explain the unsatisfactory diagnostic performance of the existing NEC biomarkers. More recently applied technics can provide important insight into the pathophysiological mechanisms underlying NEC but can also aid the detection of potentially predictive, early diagnostic, and prognostic biomarkers. Progress in omics technology has allowed for the simultaneous measurement of a large number of proteins, metabolic products, lipids, and genes, using serum/plasma, urine, feces, tissues, and other biological specimens. This review is an update of current data on emerging NEC biomarkers detected using proteomics and metabolomics, further discussing limitations and future perspectives in prediction and early diagnosis of NEC.