Pulmonary Epithelial TLR4 Activation Leads to Lung Injury in Neonatal Necrotizing Enterocolitis

The Novel MFG-E8-derived Oligopeptide, MOP3, Improves Outcomes in a Preclinical Murine Model of Neonatal Sepsis

INTRODUCTION

Neonatal sepsis is a devastating inflammatory condition that remains a leading cause of morbidity and mortality. Milk fat globule-EGF-factor VIII (MFG-E8) is a glycoprotein that reduces inflammation, whereas extracellular cold-inducible RNA binding protein (eCIRP) worsens inflammation. This study aimed to determine the therapeutic potential of a novel MFG-E8-derived oligopeptide 3 (MOP3) designed to clear eCIRP and protect against inflammation, organ injury, and mortality in neonatal sepsis.

METHODS

C57BL6 mouse pups were injected intraperitoneally with cecal slurry (CS) and treated with MOP3 (20 μg/g) or vehicle. 10 h after injection, blood, lungs, and intestines were collected for analyses, and in a 7-day experiment, pups were monitored for differences in mortality.

RESULTS

MOP3 treatment protected septic pups from inflammation by reducing eCIRP, IL-6, TNFα, and LDH. MOP3 reduced lung and intestinal inflammation and injury as assessed by reductions in tissue mRNA levels of inflammatory markers, histopathologic injury, and apoptosis in lung and intestines. MOP3 also significantly improved 7-day overall survival for CS-septic mouse pups compared to vehicle (75% vs. 46%, respectively).

CONCLUSION

Deriving from MFG-E8 and designed to clear eCIRP, MOP3 protects against sepsis-induced inflammation, organ injury, and mortality in a preclinical model of neonatal sepsis, implicating it as an exciting potential new therapeutic.

LEVEL OF EVIDENCE

Level 1.

Clinical Correlates of Moderate-to-Severe Bronchopulmonary Dysplasia in Preterm Infants following Surgical Necrotizing Enterocolitis

OBJECTIVE

 The aim of the study is to determine clinical correlates of moderate to severe bronchopulmonary dysplasia (BPD) in preterm infants following surgical necrotizing enterocolitis (NEC).

STUDY DESIGN

 This is a retrospective, single-center cohort study comparing patients with moderate to severe BPD to patients with non/mild BPD among surgical NEC infants. BPD was defined by NIH 2001 consensus definition.

RESULTS

 Of 92 consecutive neonates with surgical NEC, 77% (71/92) had moderate/severe BPD and 22% (21/92) had non/mild BPD. The patent ductus arteriosus (PDA) was significantly higher in those developing moderate/severe BPD (67.6% [48/71]) than non/mild BPD (28.6% [6/21]; p = 0.001). Postoperatively, infants with moderate/severe BPD had more severe acute kidney injury (AKI; 67.6 [48/71] vs. 28.6% [6/21]; p = 0.001), were intubated longer (40.5 [interquartile (IQR): 12, 59] vs. 6 days [IQR: 2, 13]; p <0.001), received more parenteral nutrition (109 [IQR: 77, 147] vs. 55 days [IQR: 19, 70]; p <0.001), developed higher surgical morbidity (46.5 [33/71] vs. 14.3% [3/21]; p = 0.008), had more intestinal failure (62.5 vs. 13.3%; p <0.001), required a longer hospital stay (161 [IQR: 112, 186] vs. 64 days [IQR: 20, 91]; p <0.001), and were more likely to need home oxygen. In a multivariable analysis, lower birth weight (OR = 0.3, [95% confidence interval (CI): 0.1-0.5]; p = 0.001), PDA (OR = 10.3, [95% CI: 1.6-65.4]; p = 0.014), and longer parenteral nutritional days (OR = 8.8; [95% CI: 2.0-43.0]; p = 0.005) were significantly and independently associated with higher odds of moderate/severe versus non-/mild BPD.

CONCLUSION

 Development of moderate/severe BPD occurred in the majority of preterm infants with surgical NEC in this consecutive series. Preterm infants with moderate/severe BPD were more likely to have a PDA before NEC. Development of moderate/severe BPD was associated with significantly greater burden and duration of postoperative morbidity following surgical NEC. Identifying surgical NEC infants at increased risk of moderate/severe BPD and developing lung protection strategies may improve surgical NEC outcomes.

KEY POINTS

· Three-fourths of preterm infants experienced severe lung injury following surgical NEC.. · The infants with severe moderate/severe BPD were most likely associated with greater duration of postoperative morbidity.. · There is need to understand and develop lung protective strategies in infants with surgical 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.

Necrotizing enterocolitis: current understanding of the prevention and management

Necrotizing enterocolitis (NEC) is one of the diseases in neonates, with a high morbidity and mortality rate, especially in preterm infants. This review aimed to briefly introduce the latest epidemiology, susceptibility factors, and clinical diagnosis and presentation of NEC. We also organized new prevention strategies by risk factors according to different pathogeneses and then discussed new treatment methods based on Bell's staging and complications, and the classification of mild to high severity based on clinical and imaging manifestations. Such a generalization will help clinicians and researchers to gain a deeper understanding of the disease and to conduct more targeted classification, grading prevention, and exploration. We focused on prevention and treatment of the early and suspected stages of NEC, including the discovery of novel biomarkers and drugs to control disease progression. At the same time, we discussed its clinical application, future development, and shortcomings.

Changes in inflammatory proteins following platelet transfusion in a neonatal population

BACKGROUND

Studies have demonstrated increased morbidity and mortality with platelet transfusions in the neonatal period. Platelets are as important for host immunity and inflammation as for hemostasis. Increased inflammation may explain the dose-associated increase in mortality, bleeding, and lung disease.

OBJECTIVE

This study aims to assess if there are any changes in inflammatory cytokines post-platelet transfusion in babies in NICU.

METHODS

This prospective observational study recruited babies due to receive a non-emergency platelet transfusion. Dried whole blood samples were collected prior to and 2 h post-transfusion. Samples were processed using multiplex immunoassay to enable analysis of tiny blood volumes. Statistical analysis was performed using R.

RESULTS

Seventeen babies underwent 26 platelet transfusions across two centers. Median birthweight was 1545 g (535-3960 g) and median birth gestation was 31 weeks and 1 day (23 + 1 to 40 + 5). Median pre-transfusion platelet count was 19.5 × 109/l. There was a significant increase in levels of CXCL5 (p < 0.001), CD40 (p = 0.001), and TGF-β (p = 0.001) in neonatal blood samples post-platelet transfusion in the study group.

CONCLUSION

The increase in the cytokines CXCL5, CD40 and TGF-β after platelet transfusion in babies in NICU could potentiate existing inflammation, NEC, lung, or white matter injury. This could potentially explain long-term harm from platelet transfusion in babies.

IMPACT

There is a change in levels of immunomodulatory proteins CXCL5, CD40, and TGF-β after platelet transfusion in babies in NICU. Murine neonatal models have demonstrated an increase in cytokine levels after platelet transfusions. This is the first time that this has been demonstrated in human neonates. The increase in proinflammatory cytokines could potentially explain the long-term harm from platelet transfusion in babies, as they could potentiate existing inflammation, NEC, lung injury, or white matter injury.

Pneumonia, lymphocytes and C-reactive protein are valuable tests for predicting surgical intervention in necrotizing enterocolitis

Background

Necrotizing enterocolitis (NEC) is one of the important causes of neonatal death, and proper timing of operation is of critical significance. This study aimed to explore the high-risk factors for NEC requiring surgical intervention and to provide a reference for its clinical diagnosis and treatment.

Methods

Clinical and radiological evidence of NEC neonates admitted to Zhujiang Hospital of Southern Medical University and Zhongshan Boai Hospital from January 2010 to October 2022 were retrospectively analyzed. Patients were divided into surgical group and conservative group according to whether they underwent surgery or not. Univariate analysis of the clinical data of the two groups was conducted, and multivariate logistic regression analysis was then performed for statistically significant results in the univariate analysis.

Results

267 infants were included in this study, of which 90 patients underwent surgical intervention for NEC and 177 conservation treatment. The univariate analysis showed that the gestational age, pneumonia, leukocytes, lymphocytes, erythrocytes, platelets, C-reactive protein, and blood glucose were statistically significant in the surgical group compared to the conservative group (All P < 0.05). Furthermore, the results of multivariate logistic regression analysis showed that compared to the conservative group, patients in the surgical group had a higher proportion of pneumonia (OR = 2.098; 95% CI: 1.030-4.272; P = 0.041), lower lymphocyte values (OR = 0.749; 95% CI: 0.588-0.954; P = 0.019), and higher C-reactive protein values (OR = 1.009; 95% CI: 1.003-1.016; P = 0.004).

Conclusions

Pneumonia, decreased lymphocytes, and elevated C-reactive protein are potential high-risk factors for neonates with NEC requiring surgical intervention and may have potential clinical implications for predicting surgical risk.

Bovine milk-derived exosomes attenuate NLRP3 inflammasome and NF-κB signaling in the lung during neonatal necrotizing enterocolitis

PURPOSE

Necrotizing enterocolitis (NEC), an inflammatory intestinal disease common in premature infants, has been associated with the development of lung damage. Toll-like receptor 4 has been shown to regulate inflammation in the NEC lungs, however, other important inflammatory mechanisms have not been thoroughly investigated. In addition, we reported that milk-derived exosomes were able to attenuate intestinal injury and inflammation in experimental NEC. This study aims to (i) investigate the role of the NLRP3 inflammasome and NF-κB pathway in regulating lung damage during experimental NEC; and (ii) evaluate the therapeutic potential of bovine milk exosomes in reducing lung inflammation and injury during NEC.

METHODS

NEC was induced by gavage feeding of hyperosmolar formula, hypoxia, and lipopolysaccharide administration in neonatal mice from postnatal days 5-9. Exosomes were obtained by ultracentrifugation of bovine milk and administered during each formula feed.

RESULTS

The lung of NEC pups showed increased inflammation, tissue damage, NLRP3 inflammasome expression, and NF-κB pathway activation, which were attenuated upon exosome administration.

CONCLUSION

Our findings suggest that the lung undergoes significant inflammation and injury following experimental NEC which are attenuated by bovine milk-derived exosomes. This emphasizes the therapeutic potential of exosomes not just on the intestine but also on the lung.

A Paternal Fish Oil Diet Preconception Reduces Lung Inflammation in a Toxicant-Driven Murine Model of New Bronchopulmonary Dysplasia

New bronchopulmonary dysplasia (BPD) is a neonatal disease that is theorized to begin in utero and manifests as reduced alveolarization due to inflammation of the lung. Risk factors for new BPD in human infants include intrauterine growth restriction (IUGR), premature birth (PTB) and formula feeding. Using a mouse model, our group recently reported that a paternal history of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) exposure increased his offspring's risk of IUGR, PTB, and new BPD. Additionally, formula supplementation of these neonates worsened the severity of pulmonary disease. In a separate study, we reported that a paternal preconception fish oil diet prevented TCDD-driven IUGR and PTB. Not surprisingly, eliminating these two major risk factors for new BPD also significantly reduced development of neonatal lung disease. However, this prior study did not examine the potential mechanism for fish oil's protective effect. Herein, we sought to determine whether a paternal preconception fish oil diet attenuated toxicant-associated lung inflammation, which is an important contributor to the pathogenesis of new BPD. Compared to offspring of standard diet TCDD-exposed males, offspring of TCDD-exposed males provided a fish oil diet prior to conception exhibited a significant reduction in pulmonary expression of multiple pro-inflammatory mediators (Tlr4, Cxcr2, Il-1 alpha). Additionally, neonatal lungs of pups born to fish oil treated fathers exhibited minimal hemorrhaging or edema. Currently, prevention of BPD is largely focused on maternal strategies to improve health (e.g., smoking cessation) or reduce risk of PTB (e.g., progesterone supplementation). Our studies in mice support a role for also targeting paternal factors to improve pregnancy outcomes and child health.

β-glucan protects against necrotizing enterocolitis in mice by inhibiting intestinal inflammation, improving the gut barrier, and modulating gut microbiota

BACKGROUND

Necrotizing enterocolitis (NEC) is a devastating gastrointestinal disease with high morbidity and mortality, affecting preterm infants especially those with very low and extremely low birth weight. β-glucan has manifested multiple biological effects including anti-inflammatory, regulation of gut microbiota, and immunomodulatory activities. This study aimed to investigate the effects of β-glucan on NEC.

METHODS

Neonatal C57BL/6 mice were randomly divided into three groups: Control group, NEC group and β-glucan group. Newborn 3-day-old mice were gavaged with either 1 mg/ml β-glucan or phosphate buffer saline at 0.03 ml/g for 7 consecutive days before NEC induction and a NEC model was established with hypoxia combined with cold exposure and formula feeding. All the pups were killed after 72-h modeling. Hematoxylin-eosin staining was performed to assess the pathological injury to the intestines. The mRNA expression levels of inflammatory factors in intestinal tissues were determined using quantitative real-time PCR. The protein levels of TLR4, NF-κB and tight junction proteins in intestinal tissues were evaluated using western blotting and immunohistochemistry. 16S rRNA sequencing was performed to determine the structure of the gut microbiota.

RESULTS

β-glucan administration ameliorated intestinal injury of NEC mice; reduced the intestinal expression of TLR4, NF-κB, IL-1β, IL-6, and TNF-α; increased the intestinal expression of IL-10; and improved the expression of ZO-1, Occludin and Claudin-1 within the intestinal barrier. Pre-treatment with β-glucan also increased the proportion of Actinobacteria, Clostridium butyricum, Lactobacillus johnsonii, Lactobacillus murinus, and Lachnospiraceae bacterium mt14 and reduced the proportion of Klebsiella oxytoca g Klebsiella in the NEC model.

CONCLUSION

β-glucan intervention prevents against NEC in neonatal mice, possibly by suppressing the TLR4-NF-κB signaling pathway, improving intestinal barrier function, and partially regulating intestinal microbiota.

Tumor-intrinsic NLRP3-HSP70-TLR4 axis drives premetastatic niche development and hyperprogression during anti-PD-1 immunotherapy

The tumor-intrinsic NOD-, LRR- and pyrin domain-containing protein-3 (NLRP3) inflammasome-heat shock protein 70 (HSP70) signaling axis is triggered by CD8⁺ T cell cytotoxicity and contributes to the development of adaptive resistance to anti-programmed cell death protein 1 (PD-1) immunotherapy by recruiting granulocytic polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) into the tumor microenvironment. Here, we demonstrate that the tumor NLRP3-HSP70 axis also drives the accumulation of PMN-MDSCs into distant lung tissues in a manner that depends on lung epithelial cell Toll-like receptor 4 (TLR4) signaling, establishing a premetastatic niche that supports disease hyperprogression in response to anti-PD-1 immunotherapy. Lung epithelial HSP70-TLR4 signaling induces the downstream Wnt5a-dependent release of granulocyte colony-stimulating factor (G-CSF) and C-X-C motif chemokine ligand 5 (CXCL5), thus promoting myeloid granulopoiesis and recruitment of PMN-MDSCs into pulmonary tissues. Treatment with anti-PD-1 immunotherapy enhanced the activation of this pathway through immunologic pressure and drove disease progression in the setting of Nlrp3 amplification. Genetic and pharmacologic inhibition of NLRP3 and HSP70 blocked PMN-MDSC accumulation in the lung in response to anti-PD-1 therapy and suppressed metastatic progression in preclinical models of melanoma and breast cancer. Elevated baseline concentrations of plasma HSP70 and evidence of NLRP3 signaling activity in tumor tissue specimens correlated with the development of disease hyperprogression and inferior survival in patients with stage IV melanoma undergoing anti-PD-1 immunotherapy. Together, this work describes a pathogenic mechanism underlying the phenomenon of disease hyperprogression in melanoma and offers candidate targets and markers capable of improving the management of patients with melanoma.

A hydrogen-sulfide derivative of mesalamine reduces the severity of intestinal and lung injury in necrotizing enterocolitis through endothelial nitric oxide synthase

Necrotizing enterocolitis (NEC) remains a devastating disease that affects preterm infants. Hydrogen sulfide (H2S) donors have been shown to reduce the severity of NEC, but the optimal compound has yet to be identified. We hypothesized that oral H2S-Mesalamine (ATB-429) would improve outcomes in experimental NEC, and its benefits would be dependent on endothelial nitric oxide synthase (eNOS) pathways. NEC was induced in 5-day-old wild-type (WT) and eNOS knockout (eNOSKO) pups by formula feeding and stress. Four groups were studied in both WT and eNOSKO mice: 1) breastfed controls, 2) NEC, 3) NEC + 50 mg/kg mesalamine, and 4) NEC + 130 mg/kg ATB-429. Mesalamine and ATB-429 doses were equimolar. Pups were monitored for sickness scores and perfusion to the gut was measured by Laser Doppler Imaging (LDI). After euthanasia of the pups, intestine and lung were hematoxylin and eosin-stained and scored for injury in a blind fashion. TLR4 expression was quantified by Western blot and IL-6 expression by ELISA. P < 0.05 was significant. Both WT and eNOSKO breastfed controls underwent normal development and demonstrated milder intestinal and pulmonary injury compared with NEC groups. For the WT groups, ATB-429 significantly improved weight gain, reduced clinical sickness score, and improved perfusion compared with the NEC group. In addition, WT ATB-429 pups had a significantly milder intestinal and pulmonary histologic injury when compared with NEC. ATB-429 attenuated the increase in TLR4 and IL-6 expression in the intestine. When the experiment was repeated in eNOSKO pups, ATB-429 offered no benefit in weight gain, sickness scores, perfusion, intestinal injury, pulmonary injury, or decreasing intestinal inflammatory markers. An H2S derivative of mesalamine improves outcomes in experimental NEC. Protective effects appear to be mediated through eNOS. Further research is warranted to explore whether ATB-429 may be an effective oral therapy to combat NEC.

LncRNA H19 alleviates sepsis-induced acute lung injury by regulating the miR-107/TGFBR3 axis

Objective

Acute lung injury (ALI) increases sepsis morbidity and mortality. LncRNA H19 plays a critical role in sepsis. miR-107 is highly-expressed and TGFβ type III receptor (TGFBR3) is poorly-expressed in sepsis, yet their roles in sepsis development require further investigation. This study aimed to investigate the mechanism of H19 in alleviating sepsis-induced ALI through the miR-107/TGFBR3 axis.

Methods

Mice were intravenously injected with Ad-H19 adenovirus vector or control vector one week before establishing the mouse model of cecal ligation and puncture (CLP). Pulmonary microvascular endothelial cells (PMVECs) were transfected with oe-H19 or oe-NC plasmids and then stimulated by lipopolysaccharide (LPS). Lung injury was assessed via hematoxylin–eosin staining, measurement of wet-to-dry (W/D) ratio, and TUNEL staining. Levels of H19, miR-107, and TGFBR3 were determined by RT-qPCR. Apoptosis of PMVECs was evaluated by flow cytometry. Levels of Bax and Bcl-2 in lung tissues and PMVECs were measured using Western blot. Total protein concentration and the number of total cells, neutrophils, and macrophages in bronchoalveolar lavage fluid (BALF) were quantified. Levels of TNF-α, IL-1β, IL-6, and IL-10 in BALF, lung tissues, and PMVECs were measured by ELISA. Cross-linking relationships among H19, miR-107 and TGFBR3 were verified by dual-luciferase and RIP assays.

Results

H19 was poorly-expressed in CLP-operated mice. H19 overexpression attenuated sepsis-induced ALI, which was manifested with complete alveolar structure, decreased lung injury score and lung W/D ratio, and inhibited apoptosis in CLP-operated mice, which was manifested with decreased number of TUNEL-positive cells and Bax level and increased Bcl-2 level. CLP-operated mice had increased concentration of total protein and number of total cells, neutrophils, and macrophages in BALF, which was nullified by H19 overexpression. H19 overexpression declined levels of TNF-α, IL-1β, and IL-6 and elevated IL-10 levels. H19 inhibited LPS-induced PMVEC apoptosis and pro-inflammatory cytokine production. H19 targeted TGFBR3 as the ceRNA of miR-107. miR-107 overexpression or silencing TGFBR3 partially averted the inhibition of H19 overexpression on LPS-induced PMVEC apoptosis and pro-inflammatory cytokine production.

Conclusion

LncRNA H19 inhibited LPS-induced PMVEC apoptosis and pro-inflammatory cytokine production and attenuated sepsis-induced ALI by targeting TGFBR3 as the ceRNA of miR-107.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12890-022-02091-y.

The administration of a pre-digested fat-enriched formula prevents necrotising enterocolitis-induced lung injury in mice

Necrotising enterocolitis (NEC) is a devastating gastrointestinal disease of prematurity that typically develops after the administration of infant formula, suggesting a link between nutritional components and disease development. One of the most significant complications that develops in patients with NEC is severe lung injury. We have previously shown that the administration of a nutritional formula that is enriched in pre-digested Triacylglyceride that do not require lipase action can significantly reduce the severity of NEC in a mouse model. We now hypothesise that this 'pre-digested fat (PDF) system' may reduce NEC-associated lung injury. In support of this hypothesis, we now show that rearing newborn mice on a nutritional formula based on the 'PDF system' promotes lung development, as evidenced by increased tight junctions and surfactant protein expression. Mice that were administered this 'PDF system' were significantly less vulnerable to the development of NEC-induced lung inflammation, and the administration of the 'PDF system' conferred lung protection. In seeking to define the mechanisms involved, the administration of the 'PDF system' significantly enhanced lung maturation and reduced the production of reactive oxygen species (ROS). These findings suggest that the PDF system protects the development of NEC-induced lung injury through effects on lung maturation and reduced ROS in the lung and also increases lung maturation in non-NEC mice.

Bench to bedside - new insights into the pathogenesis of necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is the leading cause of death and disability from gastrointestinal disease in premature infants. Recent discoveries have shed light on a unifying theorem to explain the pathogenesis of NEC, suggesting that specific treatments might finally be forthcoming. A variety of experiments have highlighted how the interaction between bacterial signalling receptors on the premature intestine and an abnormal gut microbiota incites a pro-inflammatory response in the intestinal mucosa and its underlying endothelium that leads to NEC. Central amongst the bacterial signalling receptors implicated in NEC development is the lipopolysaccharide receptor Toll-like receptor 4 (TLR4), which is expressed at higher levels in the premature gut than in the full-term gut. The high prenatal intestinal expression of TLR4 reflects the role of TLR4 in the regulation of normal gut development, and supports additional studies indicating that NEC develops in response to signalling events that occur in utero. This Review provides new evidence explaining the pathogenesis of NEC, explores new findings indicating that NEC development has origins before birth, and discusses future questions and opportunities for discovery in this field.

Placental dysfunction influences fetal monocyte subpopulation gene expression in preterm birth

The placenta is the primary organ for immune regulation, nutrient delivery, gas exchange, protection against environmental toxins, and physiologic perturbations during pregnancy. Placental inflammation and vascular dysfunction during pregnancy are associated with a growing list of prematurity-related complications. The goal of this study was to identify differences in gene expression profiles in fetal monocytes - cells that persist and differentiate postnatally - according to distinct placental histologic domains. Here, by using bulk RNA-Seq, we report that placental lesions are associated with gene expression changes in fetal monocyte subsets. Specifically, we found that fetal monocytes exposed to acute placental inflammation upregulate biological processes related to monocyte activation, monocyte chemotaxis, and platelet function, while monocytes exposed to maternal vascular malperfusion lesions downregulate these processes. Additionally, we show that intermediate monocytes might be a source of mitogens, such as HBEGF, NRG1, and VEGFA, implicated in different outcomes related to prematurity. This is the first study to our knowledge to show that placental lesions are associated with unique changes in fetal monocytes and monocyte subsets. As fetal monocytes persist and differentiate into various phagocytic cells following birth, our study may provide insight into morbidity related to prematurity and ultimately potential therapeutic targets.

Postnatal Sepsis and Bronchopulmonary Dysplasia in Premature Infants: Mechanistic Insights into "New BPD"

Bronchopulmonary dysplasia (BPD) is a debilitating disease in premature infants resulting from lung injury that disrupts alveolar and pulmonary vascular development. Despite the use of lung-protective ventilation and targeted oxygen therapy, BPD rates have not significantly changed over the last decade. Recent evidence suggests that sepsis and conditions initiating the systemic inflammatory response syndrome in preterm infants are key risk factors for BPD. However, the mechanisms by which sepsis-associated systemic inflammation and microbial dissemination program aberrant lung development are not fully understood. Progress has been made within the last 5 years with the inception of animal models allowing mechanistic investigations into neonatal acute lung injury and alveolar remodeling due to endotoxemia and NEC. These recent studies begin to unravel the pathophysiology of early endothelial immune activation via pattern recognition receptors such as Toll Like Receptor 4 and disruption of critical lung developmental processes such as angiogenesis, extracellular matrix deposition, and ultimately alveologenesis. Here we review scientific evidence from preclinical models of neonatal sepsis-induced lung injury to new data emerging from clinical literature.

Necrotizing enterocolitis and the gut-lung axis

The recently recognized connection between the gut microbiota and pulmonary disease has been termed the gut-lung axis. However, broader connections link the gut and the lungs and these organ systems are tightly interrelated in both homeostasis and disease. This concept is often ignored in the compartmentalized treatment of pulmonary or gastrointestinal disease. In newborns, the most severe gastrointestinal complication of prematurity, necrotizing enterocolitis, and the most severe pulmonary complication, bronchopulmonary dysplasia, both produce significant systemic morbidity. In this review, we highlight the often neglected pathophysiology of the gut-lung axis contributes to increased risk of bronchopulmonary dysplasia in premature infants with necrotizing enterocolitis.

Nitric Oxide System and Bronchial Epithelium: More Than a Barrier

Airway epithelium forms a physical barrier that protects the lung from the entrance of inhaled allergens, irritants, or microorganisms. This epithelial structure is maintained by tight junctions, adherens junctions and desmosomes that prevent the diffusion of soluble mediators or proteins between apical and basolateral cell surfaces. This apical junctional complex also participates in several signaling pathways involved in gene expression, cell proliferation and cell differentiation. In addition, the airway epithelium can produce chemokines and cytokines that trigger the activation of the immune response. Disruption of this complex by some inflammatory, profibrotic, and carcinogens agents can provoke epithelial barrier dysfunction that not only contributes to an increase of viral and bacterial infection, but also alters the normal function of epithelial cells provoking several lung diseases such as asthma, chronic obstructive pulmonary disease (COPD), cystic fibrosis (CF) or lung cancer, among others. While nitric oxide (NO) molecular pathway has been linked with endothelial function, less is known about the role of the NO system on the bronchial epithelium and airway epithelial cells function in physiological and different pathologic scenarios. Several data indicate that the fraction of exhaled nitric oxide (F_ENO) is altered in lung diseases such as asthma, COPD, lung fibrosis, and cancer among others, and that reactive oxygen species mediate uncoupling NO to promote the increase of peroxynitrite levels, thus inducing bronchial epithelial barrier dysfunction. Furthermore, iNOS and the intracellular pathway sGC-cGMP-PKG are dysregulated in bronchial epithelial cells from patients with lung inflammation, fibrosis, and malignancies which represents an attractive drug molecular target. In this review we describe in detail current knowledge of the effect of NOS-NO-GC-cGMP-PKG pathway activation and disruption in bronchial epithelial cells barrier integrity and its contribution in different lung diseases, focusing on bronchial epithelial cell permeability, inflammation, transformation, migration, apoptosis/necrosis, and proliferation, as well as the specific NO molecular pathways involved.

Dissect the immunity using cytokine profiling and NF-kB target gene analysis in systemic inflammatory minipig model

Minipigs have remarkably similar physiology to humans, therefore, they it can be a good animal model for inflammation study. Thus, the conventional (serum chemistry, histopathology) and novel analytic tools [immune cell identification in tissue, cytokine level in peripheral blood mononuclear cells (PBMC) and serum, NF-kB target gene analysis in tissue] were applied to determine inflammation in Chicago Miniature Swine (CMS) minipig. Lipopolysaccharide (LPS)-induced acute systemic inflammation caused liver and kidney damage in serum chemistry and histopathology. Immunohistochemistry (IHC) also showed an increase of immune cell distribution in spleen and lung during inflammation. Moreover, NF-kB-target gene expression was upregulated in lung and kidney in acute inflammation and in heart, liver, and intestine in chronic inflammation. Cytokine mRNA was elevated in PBMC under acute inflammation along with elevated absolute cytokine levels in serum. Overall, LPS-mediated systemic inflammation affects the various organs, and can be detected by IHC of immune cells, gene analysis in PBMC, and measuring the absolute cytokine in serum along with conventional inflammation analytic tools.

Narciclasine attenuates LPS-induced acute lung injury in neonatal rats through suppressing inflammation and oxidative stress

Acute lung injury (ALI) is a life-threatening disorder related to serious pulmonary inflammation. Narciclasine exhibits strong anti-inflammation activity and attenuates the reactive oxygen species (ROS) production. The present study aims to investigate the underlying mechanism related to the effect of narciclasine on the pathogenesis of neonatal acute lung injury (ALI). Narciclasine attenuated LPS-induced pathological injury and pulmonary edema. In addition, narciclasine suppressed the secretion of inflammatory cytokines, including necrosis factor-α (TNF-α), Interleukin (IL-6), IL-1β, monocyte chemotactic protein-1 (MCP-1) in serum, and inhibited the expressions of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) in lung tissues of neonatal ALI rats. Furthermore, narciclasine alleviated oxidative stress and apoptosis in lung tissues. Importantly, narciclasine exerted an inhibition effect on NF-κB nuclear translocation and activation of Toll-like Receptor 4 (TLR4)/Nuclear factor (NF)-κB/Cyclooxygenase 2 (Cox2) signaling pathway. Taken together, narciclasine protected against lung injury via inhibition effect on excessive inflammation, oxidative stress and apoptosis, hence, narciclasine may be considered as an effective and novel agent for clinical therapeutic strategy of ALI Treatment.

Prenatal Immunity and Influences on Necrotizing Enterocolitis and Associated Neonatal Disorders

Prior to birth, the neonate has limited exposure to pathogens. The transition from the intra-uterine to the postnatal environment initiates a series of complex interactions between the newborn host and a variety of potential pathogens that persist over the first few weeks of life. This transition is particularly complex in the case of the premature and very low birth weight infant, who may be susceptible to many disorders as a result of an immature and underdeveloped immune system. Chief amongst these disorders is necrotizing enterocolitis (NEC), an acute inflammatory disorder that leads to necrosis of the intestine, and which can affect multiple systems and have the potential to result in long term effects if the infant is to survive. Here, we examine what is known about the interplay of the immune system with the maternal uterine environment, microbes, nutritional and other factors in the pathogenesis of neonatal pathologies such as NEC, while also taking into consideration the effects on the long-term health of affected children.

Targeting SARS-CoV-2 receptors as a means for reducing infectivity and improving antiviral and immune response: an algorithm-based method for overcoming resistance to antiviral agents

The ongoing severe acute respiratory syndrome pandemic caused by the novel coronavirus 2 (SARS-CoV-2) is associated with high morbidity and mortality rates, and it has created a pressing global need for effective antiviral therapies against it. COVID-19 disease pathogenesis is characterized by an initial virus-mediated phase, followed by inappropriate hyperactivation of the immune system leading to organ damage. Targeting of the SARS-CoV-2 viral receptors is being explored as a therapeutic option for these patients. In this paper, we summarize several potential receptors associated with the infectivity of SARS-CoV-2 and discuss their association with the immune-mediated inflammatory response. The potential for the development of resistance towards antiviral drugs is also presented. An algorithm-based platform to improve the efficacy of and overcome resistance to viral receptor blockers through the introduction of personalized variability is described. This method is designed to ensure sustained antiviral effectiveness when using SARS-CoV-2 receptor blockers.

The performance of the alarmin HMGB1 in pediatric diseases: From lab to clinic

INTRODUCTION

The ubiquitously expressed nonhistone nuclear protein high-mobility group box protein 1 (HMGB1) has different functions related to posttranslational modifications and cellular localization. In the nucleus, HMGB1 modulates gene transcription, replication and DNA repair as well as determines chromosomal architecture. When the post-transcriptional modified HMGB1 is released into the extracellular space, it triggers several physiological and pathological responses and initiates innate immunity through interacting with its reciprocal receptors (i.e., TLR4/2 and RAGE). The effect of HMGB1-mediated inflammatory activation on different systems has received increasing attention. HMGB1 is now considered to be an alarmin and participates in multiple inflammation-related diseases. In addition, HMGB1 also affects the occurrence and progression of tumors. However, most studies involving HMGB1 have been focused on adults or mature animals. Due to differences in disease characteristics between children and adults, it is necessary to clarify the role of HMGB1 in pediatric diseases.

METHODS AND RESULTS

Through systematic database retrieval, this review aimed to first elaborate the characteristics of HMGB1 under physiological and pathological conditions and then discuss the clinical significance of HMGB1 in the pediatric diseases according to different systems.

CONCLUSIONS

HMGB1 plays an important role in a variety of pediatric diseases and may be used as a diagnostic biomarker and therapeutic target for new strategies for the prevention and treatment of pediatric diseases.

Toll Like Receptor 4 Mediated Lymphocyte Imbalance Induces Nec-Induced Lung Injury

Necrotizing enterocolitis (NEC) is the leading cause of death from gastrointestinal disease in premature infants, and is associated with the development of severe lung inflammation. The pathogenesis of NEC-induced lung injury remains unknown, yet infiltrating immune cells may play a role. In support of this possibility, we now show that NEC in mice and humans was associated with the development of profound lung injury that was characterized by an influx of Th17 cells and a reduction in T regulatory lymphocytes (Tregs). Importantly, the adoptive transfer of CD4 T cells isolated from lungs of mice with NEC into the lungs of immune incompetent mice (Rag1 mice) induced profound inflammation in the lung, while the depletion of Tregs exacerbated NEC induced lung injury, demonstrating that imbalance of Th17/Treg in the lung is required for the induction of injury. In seeking to define the mechanisms involved, the selective deletion of toll-like receptor 4 (TLR4) from the Sftpc1 pulmonary epithelial cells reversed lung injury, while TLR4 activation induced the Th17 recruiting chemokine (C-C motif) ligand 25 (CCL25) in the lungs of mice with NEC. Strikingly, the aerosolized inhibition of both CCL25 and TLR4 and the administration of all trans retinoic acid restored Tregs attenuated NEC-induced lung injury. 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.

Precision-based modeling approaches for necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is the leading cause of death from gastrointestinal disease in premature infants and remains stubbornly difficult to treat in many cases. Much of our understanding of NEC pathogenesis has been gained through the study of highly translational animal models. However, most models of NEC are limited by their overall complexity and by the fact that they do not incorporate human tissue. To address these limitations, investigators have recently developed precision-based ex vivo models of NEC, also termed ‘NEC-in-a-dish’ models, which provide the opportunity to increase our understanding of this disease and for drug discovery. These approaches involve exposing intestinal cells from either humans or animals with or without NEC to a combination of environmental and microbial factors associated with NEC pathogenesis. This Review highlights the current progress in the field of NEC model development, introduces NEC-in-a-dish models as a means to understand NEC pathogenesis and examines the fundamental questions that remain unanswered in NEC research. By answering these questions, and through a renewed focus on precision model development, the research community may finally achieve enduring success in improving the outcome of patients with this devastating disease.

Summary: Much of our understanding of necrotizing enterocolitis (NEC) pathogenesis has been achieved through animal models. Here, we discuss the development of advanced precision-based models to improve outcomes for patients with NEC.

Dysregulated Mucosal Immunity and Associated Pathogeneses in Preterm Neonates

Many functions of the immune system are impaired in neonates, allowing vulnerability to serious bacterial, viral and fungal infections which would otherwise not be pathogenic to mature individuals. This vulnerability is exacerbated in compromised newborns such as premature neonates and those who have undergone surgery or who require care in an intensive care unit. Higher susceptibility of preterm neonates to infections is associated with delayed immune system maturation, with deficiencies present in both the innate and adaptive immune components. Here, we review recent insights into early life immunity, and highlight features associated with compromised newborns, given the challenges of studying neonatal immunity in compromised neonates due to the transient nature of this period of life, and logistical and ethical obstacles posed by undertaking studies newborns and infants. Finally, we highlight how the unique immunological characteristics of the premature host play key roles in the pathogenesis of diseases that are unique to this population, including necrotizing enterocolitis and the associated sequalae of lung and brain injury.

Intestinal Dysbiosis and the Developing Lung: The Role of Toll-Like Receptor 4 in the Gut-Lung Axis

Background

In extremely premature infants, postnatal growth restriction (PNGR) is common and increases the risk of developing bronchopulmonary dysplasia (BPD) and pulmonary hypertension (PH). Mechanisms by which poor nutrition impacts lung development are unknown, but alterations in the gut microbiota appear to play a role. In a rodent model, PNGR plus hyperoxia causes BPD and PH and increases intestinal Enterobacteriaceae, Gram-negative organisms that stimulate Toll-like receptor 4 (TLR4). We hypothesized that intestinal dysbiosis activates intestinal TLR4 triggering systemic inflammation which impacts lung development.

Methods

Rat pups were assigned to litters of 17 (PNGR) or 10 (normal growth) at birth and exposed to room air or 75% oxygen for 14 days. Half of the pups were treated with the TLR4 inhibitor TAK-242 from birth or beginning at day 3. After 14 days, pulmonary arterial pressure was evaluated by echocardiography and hearts were examined for right ventricular hypertrophy (RVH). Lungs and serum samples were analyzed by western blotting and immunohistochemistry.

Results

Postnatal growth restriction + hyperoxia increased pulmonary arterial pressure and RVH with trends toward increased plasma IL1β and decreased IκBα, the inhibitor of NFκB, in lung tissue. Treatment with the TLR4 inhibitor attenuated PH and inflammation.

Conclusion

Postnatal growth restriction induces an increase in intestinal Enterobacteriaceae leading to PH. Activation of the TLR4 pathway is a promising mechanism by which intestinal dysbiosis impacts the developing lung.

A Novel Role for Necroptosis in the Pathogenesis of Necrotizing Enterocolitis

BACKGROUND & AIMS

Necrotizing enterocolitis (NEC) is a devastating disease of premature infants characterized by Toll-like receptor 4 (TLR4)-dependent intestinal inflammation and enterocyte death. Given that necroptosis is a proinflammatory cell death process that is linked to bacterial signaling, we investigated its potential role in NEC, and the mechanisms involved.

METHODS

Human and mouse NEC intestine were analyzed for necroptosis gene expression (ie, RIPK1, RIPK3, and MLKL), and protein activation (phosphorylated RIPK3). To evaluate a potential role for necroptosis in NEC, the effects of genetic (ie, Ripk3 knockout or Mlkl knockout) or pharmacologic (ie, Nec1s) inhibition of intestinal inflammation were assessed in a mouse NEC model, and a possible upstream role of TLR4 was assessed in Tlr4-deficient mice. The NEC-protective effects of human breast milk and its constituent milk oligosaccharides on necroptosis were assessed in a NEC-in-a-dish model, in which mouse intestinal organoids were cultured as either undifferentiated or differentiated epithelium in the presence of NEC bacteria and hypoxia.

RESULTS

Necroptosis was activated in the intestines of human and mouse NEC in a TLR4-dependent manner, and was up-regulated specifically in differentiated epithelium of the immature ileum. Inhibition of necroptosis genetically and pharmacologically reduced intestinal-epithelial cell death and mucosal inflammation in experimental NEC, and ex vivo in the NEC-in-a-dish system. Strikingly, the addition of human breast milk, or the human milk oligosaccharide 2 fucosyllactose in the ex vivo system, reduced necroptosis and inflammation.

CONCLUSIONS

Necroptosis is activated in the intestinal epithelium upon TLR4 signaling and is required for NEC development, and explains in part the protective effects of breast milk.

Cognitive impairments induced by necrotizing enterocolitis can be prevented by inhibiting microglial activation in mouse brain

Necrotizing enterocolitis (NEC) is a severe gastrointestinal disease of the premature infant. One of the most important long-term complications observed in children who survive NEC early in life is the development of profound neurological impairments. However, the pathways leading to NEC-associated neurological impairments remain unknown, thus limiting the development of prevention strategies. 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. Here, we hypothesized that damage-induced production of TLR4 endogenous ligands in the intestine might lead to activation of microglial cells in the brain and promote cognitive impairments. We identified a gut-brain signaling axis in an NEC mouse model in which activation of intestinal TLR4 signaling led to release of high-mobility group box 1 in the intestine that, in turn, promoted microglial activation in the brain and neurological dysfunction. We further demonstrated that an orally administered dendrimer-based nanotherapeutic approach to targeting activated microglia could prevent NEC-associated neurological dysfunction in neonatal mice. These findings shed light on the molecular pathways leading to the development of NEC-associated brain injury, provide a rationale for early removal of diseased intestine in NEC, and indicate the potential of targeted therapies that protect the developing brain in the treatment of NEC in early childhood.

C23, an oligopeptide derived from cold-inducible RNA-binding protein, suppresses inflammation and reduces lung injury in neonatal sepsis

INTRODUCTION

Neonatal sepsis remains a leading cause of infant mortality. Cold-inducible RNA binding protein (CIRP) is an inflammatory mediator that induces TNF-α production in macrophages. C23 is a CIRP-derived peptide that blocks CIRP from binding its receptor. We therefore hypothesized that treatment with C23 reduces systemic inflammation and protects the lungs in neonatal sepsis.

METHODS

Sepsis was induced in C56BL/6 mouse pups (5-7 days) by intraperitoneal injection of adult cecal slurry (0.525 mg/g body weight, LD₁₀₀). One hour later pups received retroorbital injection of C23 (8 mg/kg) or vehicle (normal saline). Ten hours after sepsis induction, blood and tissues were collected for analysis.

RESULTS

C23 treatment resulted in a 58% and 69% reduction in serum levels of proinflammatory cytokines IL-6 and IL-1β, respectively, and a 40% and 45% reduction of AST and LDH, as compared to vehicle-treated septic pups. In the lungs, C23 treatment reduced expression of cytokines IL-6 and IL-1β by 78% and 74%. In addition, the mRNA level of neutrophil chemoattractants KC and MIP-2 was reduced by 84% and 74%, respectively. These results corresponded to a reduction in histologic lung injury score. Vehicle-treated pups scored 0.49 ± 0.19, while C23 treatment reduced scores to 0.29 ± 0.12 (p < 0.05; Max = 1). Apoptosis in the lungs, measured by TUNEL assay, was also decreased by 53% with C23 treatment (p < 0.05).

CONCLUSIONS

Inhibition of CIRP with C23 treatment is protective in septic neonatal mice as demonstrated by reduced inflammatory markers systemically and in the lung. Therefore, C23 has promising therapeutic potential in treatment of neonatal sepsis.

LEVEL OF EVIDENCE

Level I.

Sex-differences in LPS-induced neonatal lung injury

Being of the male sex has been identified as a risk factor for multiple morbidities associated with preterm birth, including bronchopulmonary dysplasia (BPD). Exposure to inflammatory stress is a well-recognized risk factor for developing BPD. Whether there is a sex difference in pulmonary innate immune TLR4 signaling, lung injury and subsequent abnormal lung development is unknown. Neonatal (P0) male and female mice (ICR) were exposed to systemic LPS (5 mg/kg, IP) and innate immune signaling, and the transcriptional response were assessed (1 and 5 hours), along with lung development (P7). Male and female mice demonstrated a similar degree of impaired lung development with decreased radial alveolar counts, increased surface area, increased airspace area and increased mean linear intercept. We found no differences between male and female mice in the baseline pulmonary expression of key components of TLR4-NFκB signaling, or in the LPS-induced pulmonary expression of key mediators of neonatal lung injury. Finally, we found no difference in the kinetics of LPS-induced pulmonary NFκB activation between male and female mice. Together, these data support the conclusion that the innate immune response to early postnatal LPS exposure and resulting pulmonary sequelae is similar in male and female mice.

Inhibiting hydrogen sulfide production in umbilical stem cells reduces their protective effects during experimental necrotizing enterocolitis

INTRODUCTION

Umbilical mesenchymal stem cells (USC) have been shown to reduce illness in animal models of necrotizing enterocolitis (NEC), possibly through the paracrine release of hydrogen sulfide (H₂S). We hypothesized that animals treated with USCs with inhibited H₂S synthesis would exhibit more severe disease.

METHODS

NEC was induced in five-day-old mouse pups by formula feeding and hypoxic and hypothermic stress. Experimental groups received intraperitoneal injection of either saline vehicle or 80,000cells/gram of one of the following cell types: USC, USCs with negative-control siRNA, or USCs with targeted siRNA inhibition of the H₂S-producing enzymes. Pups were monitored by clinical assessment and after euthanasia, intestine and lung histologic injury were scored. Tissue was homogenized, and concentrations of IL-6, IL-10, and VEGF were determined by ELISA. For statistical analysis, p<0.05 was considered significant.

RESULTS

Animals treated with negative-control siRNA USCs were significantly improved compared to vehicle. Clinical sickness scores as well as intestinal and lung histologic injury scores in the targeted siRNA groups were significantly worse when compared to the negative-control siRNA group. IL-6, IL-10, and VEGF had varying patterns of expression in the different groups.

CONCLUSION

Inhibition of H₂S production in USCs reduces the beneficial effects of these cells during therapy in experimental NEC.

LEVEL OF EVIDENCE

Animal studies are typically described as "foundational evidence" without a true level assigned.

TYPE OF STUDY

Animal Study.

Treg-Cell Control of a CXCL5-IL-17 Inflammatory Axis Promotes Hair-Follicle-Stem-Cell Differentiation During Skin-Barrier Repair

Restoration of barrier-tissue integrity after injury is dependent on the function of immune cells and stem cells (SCs) residing in the tissue. In response to skin injury, hair-follicle stem cells (HFSCs), normally poised for hair generation, are recruited to the site of injury and differentiate into cells that repair damaged epithelium. We used a SC fate-mapping approach to examine the contribution of regulatory T (Treg) cells to epidermal-barrier repair after injury. Depletion of Treg cells impaired skin-barrier regeneration and was associated with a Th17 inflammatory response and failed HFSC differentiation. In this setting, damaged epithelial cells preferentially expressed the neutrophil chemoattractant CXCL5, and blockade of CXCL5 or neutrophil depletion restored barrier function and SC differentiation after epidermal injury. Thus, Treg-cell regulation of localized inflammation enables HFSC differentiation and, thereby, skin-barrier regeneration, with implications for the maintenance and repair of other barrier tissues.

Loss of endothelial nitric oxide synthase exacerbates intestinal and lung injury in experimental necrotizing enterocolitis

BACKGROUND

Necrotizing enterocolitis (NEC) continues to be a devastating condition among preterm infants. Nitric oxide, which is synthesized in the intestine by endothelial nitric oxide synthase (eNOS), acts as a potent vasodilator and antioxidant within the mesentery and may play a role in prevention of NEC. We hypothesized that loss of endothelial nitric oxide would worsen both intestinal and associated lung injury and increase local and systemic inflammation during experimental NEC.

METHODS

NEC was induced in five-day-old wild type (WT) and eNOS-knockout (eNOSKO) mouse pups. Experimental groups (n=10) were formula fed and subjected to intermittent hypoxic and hypothermic stress, while control groups (n=10) remained with their mother to breastfeed. Pups were monitored by daily clinical assessment. After sacrifice on day nine, intestine and lung were assessed for injury, and cytokines were measured in tissue homogenates by ELISA. Data were compared with Mann-Whitney, and p<0.05 was significant.

RESULTS

Each NEC group was compared to its respective strain's breastfed control to facilitate comparisons between the groups. Both NEC groups were significantly sicker than their breastfed controls. eNOSKO NEC animals had a median clinical assessment score of 3 (IQR=1-5), and the WT NEC animal's median score was 3 (IQR=2-5). Despite similar clinical scores, intestinal injury was significantly worse in the eNOSKO NEC groups compared to WT NEC groups (median injury scores of 3.25 (IQR=2.25-3.625) and 2 (IQR=1-3), respectively (p=0.0474). Associated lung injury was significantly worse in the eNOSKO NEC group as compared to the WT NEC group (median scores of 8.5 (IQR=6.75-11.25) and 6.5 (IQR=5-7.5), respectively, p=0.0391). Interestingly, cytokines in both tissues were very different between the two groups, with varying effects noted for each cytokine (IL-6, IL-1β, VEGF, and IL-12) in both tissues.

CONCLUSION

Nitric oxide from eNOS plays a key role in preventing the development of NEC. Without eNOS function, both intestinal and lung injuries are more severe, and the inflammatory cascade is significantly altered. Further studies are needed to determine how eNOS-derived nitric oxide facilitates these beneficial effects.

Vitamin D attenuates hyperoxia-induced lung injury through downregulation of Toll-like receptor 4

With considerable morbidity and mortality, bron-chopulmonary dysplasia (BPD) is a focus of attention in neonatology. Hyperoxia-induced lung injury has long been used as a model of BPD. Among all the signaling pathways involved, Toll-like receptor 4 (TLR4) has been demonstrated to play an important role, and is known to be regulated by vitamin D. This study aimed at elucidating the effect of vitamin D on hyperoxia-induced lung injury and the role of TLR4 in the process. Vitamin D was administered to hyperoxia-treated neonatal rats to investigate changes in the morphology of lungs and expression of pro-inflammatory cytokines, apoptotic proteins and TLR4. Vitamin D attenuated hyperoxia-induced lung injury by protecting the integrity of the lung structure, decreasing extracellular matrix deposition and inhibiting inflammation. The upregulation of TLR4 by hyperoxia was ameliorated by vitamin D and apoptosis was reduced. Vitamin D administration antagonized the activation of TLR4 and therefore alleviated inflammation, reduced apoptosis and preserved lung structure.