Maternal exposure to endotoxin delays alveolarization during postnatal rat lung development

Antenatal Endotoxin Induces Dysanapsis in Experimental Bronchopulmonary Dysplasia

Bronchopulmonary dysplasia (BPD), the chronic lung disease of prematurity, is characterized by impaired lung development with sustained functional abnormalities due to alterations of airways and the distal lung. Although clinical studies have shown striking associations between antenatal stress and BPD, little is known about the underlying pathogenetic mechanisms. Whether dysanapsis, the concept of discordant growth of the airways and parenchyma, contributes to late respiratory disease as a result of antenatal stress is unknown. We hypothesized that antenatal endotoxin (ETX) impairs juvenile lung function as a result of altered central airway and distal lung structure, suggesting the presence of dysanapsis in this preclinical BPD model. Fetal rats were exposed to intraamniotic ETX (10 μg) or saline solution (control) 2 days before term. We performed extensive structural and functional evaluation of the proximal airways and distal lung in 2-week-old rats. Distal lung structure was quantified by stereology. Conducting airway diameters were measured using micro-computed tomography. Lung function was assessed during invasive ventilation to quantify baseline mechanics, response to methacholine challenge, and spirometry. ETX-exposed pups exhibited distal lung simplification, decreased alveolar surface area, and decreased parenchyma-airway attachments. ETX-exposed pups exhibited decreased tracheal and second- and third-generation airway diameters. ETX increased respiratory system resistance and decreased lung compliance at baseline. Only Newtonian resistance, specific to large airways, exhibited increased methacholine reactivity in ETX-exposed pups compared with controls. ETX-exposed pups had a decreased ratio of FEV in 0.1 second to FVC and a normal FEV in 0.1 second, paralleling the clinical definition of dysanapsis. Antenatal ETX causes abnormalities of the central airways and distal lung growth, suggesting that dysanapsis contributes to abnormal lung function in juvenile rats.

Identification of several inflammation-related genes based on bioinformatics and experiments

BACKGROUND

Osteoarthritis (OA) is a common disease of elderly individuals, with an unclear pathogenesis and limited treatment options to date. Inflammation occurs prominently in osteoarthritis, thereby making anti-inflammatory treatments promising in clinical outcomes. Therefore, it is of diagnostic and therapeutic significance to explore more inflammatory genes.

METHOD

In this study, appropriate datasets were first acquired through gene set enrichment analysis (GSEA), followed by inflammation-related genes through weighted gene coexpression network analysis (WGCNA). Two machine learning algorithms (random forest-RF and support vector machine-recursive feature elimination, SVM-RFE) were used to capture the hub genes. In addition, two genes negatively associated with inflammation and osteoarthritis were identified. Afterwards, these genes were verified through experiments and network pharmacology. Due to the association between inflammation and many diseases, the expression levels of the above genes in various inflammatory diseases were determined through literature and experiments.

RESULT

Two hub genes closely related to osteoarthritis and inflammation were obtained, namely, lysyl oxidase-like 1 (LOXL1) and pituitary tumour-transforming gene (PTTG1), which were shown to be highly expressed in osteoarthritis according to the literature and experiments. However, the expression levels of receptor expression-enhancing protein (REEP5) and cell division cycle protein 14B (CDC14B) remained unchanged in osteoarthritis. This finding was consistent with our verification from the literature and experiments that some genes were highly expressed in numerous inflammation-related diseases, while REEP5 and CDC14B were almost unchanged. Meanwhile, taking PTTG1 as an example, we found that inhibition of PTTG1 expression could suppress the expression of inflammatory factors and protect the extracellular matrix through the microtubule-associated protein kinase (MAPK) signalling pathway.

CONCLUSIONS

LOXL1 and PTTG1 were highly expressed in some inflammation-related diseases, while that of REEP5 and CDC14B were almost unchanged. PTTG1 may be a potential target for the treatment of osteoarthritis.

Combination Therapy of Niacin and Apocynin Attenuates Lung Injury During Sepsis in Rats

INTRODUCTION

Oxidative stress contributes to tissue injury through reactive oxygen species-dependent signaling pathways during sepsis. We studied therapeutic benefits of the combination therapy of niacin, which increased reduced glutathione levels, and apocynin, which suppressed reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (Nox) activity, in septic rats.

MATERIALS AND METHODS

Polymicrobial sepsis was induced through cecal ligation and puncture (CLP) with antibiotics in male Sprague-Dawley rats (n = 189). The rats were randomly divided into sham, CLP, CLP + niacin, CLP + apocynin, and CLP + niacin + apocynin groups. Six hours after CLP, vehicle, niacin (360 mg/kg through the orogastric tube), and/or apocynin (20 mg/kg through intraperitoneal injection) were administered. The occurrence of mortality for 72 h after CLP was observed. Next, a separate set of animals was euthanized at 24 h post-CLP for lung tissue analyses.

RESULTS

Combination therapy with niacin and apocynin significantly improved survival in rats with sepsis (75.0% versus 28.8%, P = 0.006) but monotherapy with niacin or apocynin did not. Monotherapy with niacin and apocynin appeared to increase NADPH levels and decrease Nox levels and activity, respectively, but failed to show statistical significances. However, combination therapy significantly decreased Nox levels and activity, increased NADPH and glutathione levels, decreased intranuclear nuclear factor-κB (NF-κB) p65 levels, reduced inflammatory cytokine expression and malondialdehyde levels, and attenuated histological lung injuries.

CONCLUSIONS

Combination therapy with niacin and apocynin synergistically attenuated lung injuries and improved survival in rats with sepsis through niacin-induced glutathione redox cycle activation and apocynin-induced Nox suppression.

Alteration in branching morphogenesis via YAP/TAZ in fibroblasts of fetal lungs in an LPS-induced inflammation model

BACKGROUND

Chorioamnionitis is a common cause of preterm birth and leads to serious complications in newborns. The objective of this study was to investigate the role of the Hippo signaling pathway in lung branching morphogenesis under a lipopolysaccharide (LPS)-induced inflammation model.

MATERIALS AND METHODS

IMR-90 cells and ex vivo fetal lungs were treated with 0, 10, 30, or 50 μg/ml LPS for 24 and 72 h. Supernatant levels of lactate dehydrogenase (LDH), interleukin (IL)-6, IL-8, Chemokine (C-X-C motif) ligand 1(CXCL1), branching and the surface area ratio, Yes-associated protein (YAP), transcription coactivator with PDZ-binding motif (TAZ), fibroblast growth factor 10 (FGF10), fibroblast growth factor receptor II (FGFR2), SRY-box transcription factor 2 (SOX2), SOX9, and sirtuin 1 (SIRT1) levels were examined. Differentially expressed genes in fetal lungs after LPS treatment were identified by RNA-sequencing.

RESULTS

LPS at 50 μg/ml increased IL-6 and IL-8 in IMR-90 cells and increased IL-6, CXCL1 and LDH in fetal lungs. The branching ratio significantly increased by LPS at 30 μg/ml compared to the control but the increased level had decreased by 50 μg/ml LPS exposure. Exposure to 50 μg/ml LPS increased phosphorylated (p)-YAP, p-YAP/YAP, and p-TAZ/TAZ in IMR-90 cells, whereas 50 μg/ml LPS decreased FGF10 and SOX2. Consistently, p-YAP/YAP and p-TAZ/TAZ were increased in fibronectin⁺ cells of fetal lungs. Moreover, results of RNA-sequencing in fetal lungs showed that SMAD, FGF, IκB phosphorylation, tissue remodeling and homeostasis was involved in branching morphogenesis following exposure to 50 μg/ml LPS. The p-SIRT1/SIRT1 ratio increased in IMR-90 cells by LPS treatment.

CONCLUSIONS

This study showed that regulation of the Hippo pathway in fibroblasts of fetal lungs was involved in branching morphogenesis under an inflammatory disease such as chorioamnionitis.

Lung development and immune status under chronic LPS exposure in rat pups with and without CD26/DPP4 deficiency

Dipeptidyl-peptidase IV (CD26), a multifactorial integral type II protein, is expressed in the lungs during development and is involved in inflammation processes. We tested whether daily LPS administration influences the CD26-dependent retardation in morphological lung development and induces alterations in the immune status. Newborn Fischer rats with and without CD26 deficiency were nebulized with 1 µg LPS/2 ml NaCl for 10 min from days postpartum (dpp) 3 to 9. We used stereological methods and fluorescence activated cell sorting (FACS) to determine morphological lung maturation and alterations in the pulmonary leukocyte content on dpp 7, 10, and 14. Daily LPS application did not change the lung volume but resulted in a significant retardation of alveolarization in both substrains proved by significantly lower values of septal surface and volume as well as higher mean free distances in airspaces. Looking at the immune status after LPS exposure compared to controls, a significantly higher percentage of B lymphocytes and decrease of CD4⁺CD25⁺ T cells were found in both subtypes, on dpp7 a significantly higher percentage of CD4 T⁺ cells in CD26⁺ pups, and a significantly higher percentage of monocytes in CD26⁻ pups. The percentage of T cells was significantly higher in the CD26-deficient group on each dpp. Thus, daily postnatal exposition to low doses of LPS for 1 week resulted in a delay in formation of secondary septa, which remained up to dpp 14 in CD26⁻ pups. The retardation was accompanied by moderate parenchymal inflammation and CD26-dependent changes in the pulmonary immune cell composition.

Effect of the Notch4/Dll4 signaling pathway in early gestational intrauterine infection on lung development

Intrauterine infection is an important risk factor for bronchopulmonary dysplasia (BPD). BPD is characterized by arrested lung alveolarization and impaired pulmonary vascularization. The Notch4 signaling pathway is a key regulator of vascular remodeling and angiogenesis. Therefore, the presents study investigated the expression of Notch4, delta-like canonical Notch ligand 4 (Dll4) and related factors in an in vivo rat model and in rat pulmonary microvascular endothelial cells (PMVECs) in vitro, to study the mechanisms by which intrauterine infection affects rat lung development. A rat model of intrauterine infection was established by endocervical inoculation with Escherichia scoli on embryonic day 15. The date of birth was counted as postnatal day 0 (P0). Then, the lung tissues were collected from pups at days P3-P14. The expression of Notch4, Dll4 and related factors was measured by reverse transcription-quantitative PCR and western blotting. In addition, the γ-secretase inhibitor DAPT was used to examine the effect of Notch4 signaling on PMVECs. Intrauterine E. coli infection impaired normal lung development, as indicated by decreased microvessel density, fewer alveoli, fewer secondary septa, and larger alveoli compared with the control group. Furthermore, Notch4, Dll4 and NF-κB levels were significantly increased in the E. coli-infected group at P3 compared with the control group. Similarly, the mRNA expression levels of fetal liver kinase 1 (Flk-1, a VEGF receptor) were significantly increased in the E. coli-infected group at P3 and P7. In PMVECs, the inhibition of Notch4 signaling contributed to decreases in lipopolysaccharide (LPS)-induced expression of VEGF and its receptors. Furthermore, the inhibition of Notch4/Dll4 signaling accelerated cell proliferation and decreased the apoptosis rate of LPS-induced PMVECs. LPS-induced NF-κB expression in PMVECs was also attenuated by the Notch4/Dll4 inhibitor. In conclusion, intrauterine E. coli infection impaired normal lung development, possibly through Notch4/Dll4 signaling and effects on VEGF and its receptors.

CCR5 signaling promotes lipopolysaccharide-induced macrophage recruitment and alveolar developmental arrest

The pathogenesis of bronchopulmonary dysplasia (BPD), involves inflammatory, mechanisms that are not fully characterized. Here we report that overexpression of C-C chemokine receptor 5 (CCR5) and its ligands is associated with BPD development. Lipopolysaccharide-induced BPD rats have increased CCR5 and interleukin-1β (IL-1β) levels, and decreased alveolarization, while CCR5 or IL-1β receptor antagonist treatments decreased inflammation and increased alveolarization. CCR5 enhances macrophage migration, macrophage infiltration in the lungs, IL-1β levels, lysyl oxidase activity, and alveolar development arrest. CCR5 expression on monocytes, and its ligands in blood samples from BPD infants, are elevated. Furthermore, batyl alcohol supplementation reduced CCR5 expression and IL-1β production in lipopolysaccharide-exposed rat lungs. Moreover, receptor-interacting kinase 3 (RIP3) upstream regulator of CCR5-cultured RIP3^−/− macrophages exhibited partly blocked lipopolysaccharide-induced CCR5 expression. We conclude that increased CCR5 expression is a key mechanism in BPD development and represents a novel therapeutic target for treatment.

Maternal hepatitis B or hepatitis C virus carrier status and long-term infectious morbidity of the offspring: A population-based cohort study

The objective of the study was to investigate the long-term effects of maternal hepatitis B virus (HBV) or hepatitis C virus (HCV) carrier status on the long-term infectious morbidity of their offspring. A population-based cohort study was conducted, including all singleton deliveries between the years 1991 and 2014 at a tertiary medical centre. The mothers were subdivided into three groups: HBV carriers, HCV carriers and non-carriers. Data on demographics, maternal, perinatal and long-term hospitalization for infectious morbidity were compared between the groups. During the study period, 242 905 (99.7%) non-carrier mothers, 591 (0.2%) HBV carriers and 186 (0.1%) HCV carriers were observed. Hospitalizations related to infectious morbidity was significantly higher in the offspring of HBV carriers compared with HCV and non-carriers (15.6% vs 11.3% vs 11.0%; P = .002, respectively; Kaplan-Meier, log-rank P < .001). Specifically, a significantly higher rate of hospitalizations gastrointestinal infectious morbidity was noted among the offspring of HBV carrier mothers (3.6% in the HBV carrier group, 1.6% in the HCV carrier group and 1.6% in the non-carrier group [P = .001]). There was a respiratory infectious morbidity of 8.1% among the offspring of HBV carriers, 8.6% among HCV carriers and 5.5% in non-carriers (P = .005). Using a Cox multivariable model, controlling for confounding variables, maternal HBV carrier status was associated with a significantly increased long-term infectious morbidity of the offspring, with an adjusted HR of 1.7 (95% CI, 1.388-2.077, P < .001). Maternal HBV carrier status is an independent risk factor for long-term infectious morbidity of the offspring, particularly for gastrointestinal and respiratory infections.

Sex difference in bronchopulmonary dysplasia of offspring in response to maternal PM2.5 exposure

The adverse effects of fine particulate matters (PM_2.5) on respiratory diseases start in utero. In order to investigate whether maternal PM_2.5 exposure could lead to bronchopulmonary dysplasia (BPD) in offspring, PM_2.5 was collected in Taiyuan, Shanxi, China during the annual heating period. Mice were mated and gestation day 0 (GD0) was considered the day on which a vaginal plug was observed. The plug-positive mice received 3 mg/kg b.w. PM_2.5 by oropharyngeal aspiration every other day starting on GD0 and throughout the gestation period. Offspring were sacrificed at postnatal days (PNDs) 1, 7, 14 and 21. We assessed some typical BPD-like symptoms in offspring. The results showed that maternal PM_2.5 exposure caused low birth weight, hypoalveolarization, decreased angiogenesis, suppressed production of secretory and surfactant proteins, and increased inflammation in the lungs of male offspring. However, maternal PM_2.5 exposure induced only hypoalveolarization and inflammation in the lungs of female offspring. Furthermore, these alterations were reversed during postnatal development. Our results demonstrated that maternal exposure to PM_2.5 caused reversible BPD-related consequences in offspring, and male offspring were more sensitive than females. However, these alterations were reversed during postnatal development.

14-3-3β Is necessary in the regulation of polarization and directional migration of alveolar myofibroblasts by lipopolysaccharide

Aims:Bronchopulmonary dysplasia (BPD) is characterized by alveolarization arrest. During alveolarization, alveolar myofibroblasts are thought to migrate into the septal tips and elongate secondary septa. Lipopolysaccharide (LPS) exposure has been reported to disrupt directional migration and final location of alveolar myofibroblasts in a rat model of BPD induced by intra-amniotic injection of LPS. However, molecular mechanisms that control directional migration of alveolar myofibroblasts have not so far been investigated clearly. Materials and Methods: We assessed the polarization of myofibroblast using scrape wounding assays combined with Golgi tracking. Transwell migration assay was used to detect the directional migration of myofibroblasts. Pull-down assays were performed to isolate the active GTP-bound form using the RhoA activation assay kits. Western blotting analysis was performed to evaluate the changes in protein expression. Functional analysis was performed via siRNA interference. Results: Here, we showed that LPS might affect the directional migration of myofibroblasts by disturbing the polarization of myofibroblasts. In addition, as a main member of RhoGTPases family which plays a vital role in establishing and maintaining cell polarity, RhoA activity was significantly upregulated in myofibroblasts treated with LPS, while activity of epidermal growth factor receptor (EGFR) was upregulated and overexpression of its ligand, TGF-α, in myofibroblasts by LPS treatment. AG1478, an EGFR inhibitor, could abrogate the upregulated RhoA activity of myofibroblasts by LPS and rhTGF-α. Moreover, if we knock down 14-3-3β, LPS and rhTGF-α could not activate RhoA and disturb myofibroblasts polarization. Conclusions: Taken together, our findings suggest that LPS exposure may increase RhoA activity of myofibroblasts by TGF-α/EGFR/14-3-3β signaling pathway, and then disturb myofibroblasts polarization and directional migration.

Maternal Exposure to PM2.5 Affects Fetal Lung Development at Sensitive Windows

Lung development continues from the embryonic period to adulthood. Previous epidemiological studies have noted that maternal exposure of atmospheric pollutants during the sensitive windows disturbed the lung development and increased the risk of lung diseases after birth, but the experimental evidence was insufficient. In the present study, we exposed plug-positive mice to PM_2.5 (3 mg/kg b.w.) by oropharyngeal aspiration every other day, and intended to test whether maternal PM_2.5 exposure affected prenatal lung development in the offspring. First, maternal PM_2.5 exposure decreased embryo weight and crown-rump length at E18.5 but not in earlier developmental stages (E0-E16.5). Second, maternal PM_2.5 exposure did not prevent lung-bud and tracheal specification, and did not cause abnormalities in branching morphogenesis, distal lung epithelium, and mesenchyme differentiation in earlier stages of lung development (E0-E16.5). However, the exposure significantly disturbed the distal lung epithelium and mesenchyme differentiation of lung, led to reduced intact rings of trachea, and suppressed the expression of lung development-related genes (Nkx2.1, Tbx4, Tbx5, and Sox9) at E18.5. Finally, we found that the exposure not only increased PM_2.5-bound metal content (Pb and Cu) but also caused inflammatory response in the placenta, which transmitted from the mother to the fetus and contributed to the developmental abnormalities.

Intra-tracheal administration of a naked plasmid expressing stromal derived factor-1 improves lung structure in rodents with experimental bronchopulmonary dysplasia

Background

Bronchopulmonary dysplasia (BPD) is characterized by alveolar simplification and disordered angiogenesis. Stromal derived factor-1 (SDF-1) is a chemokine which modulates cell migration, proliferation, and angiogenesis. Here we tested the hypothesis that intra-tracheal (IT) administration of a naked plasmid DNA expressing SDF-1 would attenuate neonatal hyperoxia-induced lung injury in an experimental model of BPD, by promoting angiogenesis.

Design/methods

Newborn Sprague-Dawley rat pups (n = 18–20/group) exposed to room air (RA) or hyperoxia (85% O2) from postnatal day (P) 1 to 14 were randomly assigned to receive IT a naked plasmid expressing SDF-1, JVS-100 (Juventas Therapeutics, Cleveland, Ohio) or placebo (PL) on P3. Lung alveolarization, angiogenesis, inflammation, vascular remodeling and pulmonary hypertension (PH) were assessed on P14. PH was determined by measuring right ventricular systolic pressure (RVSP) and the weight ratio of the right to left ventricle + septum (RV/LV + S). Capillary tube formation in SDF-1 treated hyperoxia-exposed human pulmonary microvascular endothelial cells (HPMEC) was determined by matrigel assay. Data is expressed as mean ± SD and analyzed by two-way ANOVA.

Results

Exposure of neonatal pups to 14 days of hyperoxia decreased lung SDF-1 gene expression. Moreover, whilst hyperoxia exposure inhibited capillary tube formation in HPMEC, SDF-1 treatment increased tube length and branching in HPMEC. PL-treated hyperoxia-exposed pups had decreased alveolarization and lung vascular density. This was accompanied by an increase in RVSP, RV/LV + S, pulmonary vascular remodeling and inflammation. In contrast, IT JVS-100 improved lung structure, reduced inflammation, PH and vascular remodeling.

Conclusions

Intratracheal administration of a naked plasmid expressing SDF-1 improves alveolar and vascular structure in an experimental model of BPD. These findings suggest that therapies which modulate lung SDF-1 expression may have beneficial effects in preterm infants with BPD.

Postnatal morphological lung development of wild type and CD26/DPP4 deficient rat pups in dependency of LPS exposure

BACKGROUND

Rodents are born with morphological immature lungs and an intact surfactant system. CD26/DPP4 is a multifactorial transmembrane integral type II protein, which is involved in physiological and pathophysiological processes and is already expressed during development. CD26/DPP4, called CD26 in the following, is able to enhance or dampen differently triggered inflammation. LPS exposure often used to simulate perinatal infection delays lung development.

OBJECTIVE

A perinatal LPS rat model was used to test the hypothesis that CD26 deficiency modulates LPS-induced retardation in morphological lung development.

METHODS

New born Fischer CD26 positive (CD26⁺) and deficient (CD26^-) rats were exposed to LPS on postnatal day (day post partum, dpp) 3 and 5. Morphological parameters of lung development were determined stereologically. Lung development was analysed in 7, 10 14 and 21day old rats.

RESULTS

Compared to controls LPS application resulted (1) in a mild inflammation independent of the strain, (2) in significantly lower total surface and volume of alveolar septa combined with significantly higher total volume of airspaces and alveolar size on dpp 7 in both substrains. However, compared to controls in LPS treated CD26^- rats significant lower values of total septal surface and volume combined with higher values of total parenchymal airspaces and alveolar size were found until the end of classical alveolarization (dpp14). In LPS treated CD26⁺ rat pups the retardation was abolished already on dpp 10.

CONCLUSION

In absence of CD26, LPS enhances the delay of morphological lung development. Morphological recovery was slower after the end of LPS exposure in CD26 deficient lungs.

Terbutaline alleviates the lung injury in the neonatal rats exposed to endotoxin: Potential roles of epithelial sodium channels

Intrauterine inflammation generates inflammatory mediators that damage the developing bronchoalveolar epithelium, resulting in neonatal lung injury. Lung fluid transport disorders are the main reasons for the development of pulmonary edema, an important pathology of lung injury. Previous studies suggested that epithelial sodium channels (ENaCs) play an important role in lung fluid transport. Here, we investigated whether changes in the expression of ENaCs were observed when neonatal rat lung injury was induced by maternal exposure to endotoxin. We also examined the therapeutic effect of terbutaline nebulizer inhalation on this injury. The results showed that maternal exposure to endotoxin increased the levels of TNF-α and IL-1β in bronchoalveolar lavage fluid, suppressed α-, β-, γ-ENaC in the neonatal rat lung, and resulted in the formation of pulmonary edema on postnatal days 1 and 7. Terbutaline up-regulated the expression of β- and γ-ENaC in the distal lung after 7 days of treatment. The potential signal molecules cAMP, PKA, and CREB expressions were increased after terbutaline treatment. In summary, maternal exposure to endotoxin decreased the expression of ENaCs in neonatal rats which, in turn, may exacerbate pulmonary edema. Inhalation of the β2-adrenergic receptor agonist terbutaline improved lung liquid clearance. By increasing the expression of sodium ion channels, the effective removal of alveolar fluid provides a new way for the prevention and treatment of neonatal lung injury.

Consequences of early postnatal lipopolysaccharide exposure on developing lungs in mice

Bronchopulmonary dysplasia (BPD) is a chronic lung disease of infants that is characterized by interrupted lung development. Postnatal sepsis causes BPD, yet the contributory mechanisms are unclear. To address this gap, studies have used lipopolysaccharide (LPS) during the alveolar phase of lung development. However, the lungs of infants who develop BPD are still in the saccular phase of development, and the effects of LPS during this phase are poorly characterized. We hypothesized that chronic LPS exposure during the saccular phase disrupts lung development by mechanisms that promote inflammation and prevent optimal lung development and repair. Wild-type C57BL6J mice were intraperitoneally administered 3, 6, or 10 mg/kg of LPS or a vehicle once daily on postnatal days (PNDs) 3-5. The lungs were collected for proteomic and genomic analyses and flow cytometric detection on PND6. The impact of LPS on lung development, cell proliferation, and apoptosis was determined on PND7. Finally, we determined differences in the LPS effects between the saccular and alveolar lungs. LPS decreased the survival and growth rate and lung development in a dose-dependent manner. These effects were associated with a decreased expression of proteins regulating cell proliferation and differentiation and increased expression of those mediating inflammation. While the lung macrophage population of LPS-treated mice increased, the T-regulatory cell population decreased. Furthermore, LPS-induced inflammatory and apoptotic response and interruption of cell proliferation and alveolarization was greater in alveolar than in saccular lungs. Collectively, the data support our hypothesis and reveal several potential therapeutic targets for sepsis-mediated BPD in infants.

Oxidative stress and NF-κB signaling are involved in LPS induced pulmonary dysplasia in chick embryos

Inflammation or dysbacteriosis-derived lipopolysaccharides (LPS) adversely influence the embryonic development of respiratory system. However, the precise pathological mechanisms still remain to be elucidated. In this study, we demonstrated that LPS exposure caused lung maldevelopment in chick embryos, including higher embryo mortality, increased thickness of alveolar gas exchange zone, and accumulation of PAS⁺ immature pulmonary cells, accompanied with reduced expression of alveolar epithelial cell markers and lamellar body count. Upon LPS exposure, pulmonary cell proliferation was significantly altered and cell apoptosis was inhibited as well, indicating a delayed progress of pulmonary development. LPS treatment also resulted in reduced CAV-1 expression and up-regulation of Collagen I, suggesting increased lung fibrosis, which was verified by Masson staining. Moreover, LPS induced enhanced Nrf2 expression in E18 lungs, and the increased reactive oxygen species (ROS) production was confirmed in MLE-12 cells in vitro. Antioxidant vitamin C restored the LPS induced down-regulation of ABCA3, SP-C and GATA-6 in MLE-12 cells. Furthermore, LPS induced activation of NF-κB signaling in MLE-12 cells, and the LPS-induced decrease in SP-C expression was partially abrogated by blocking NF-κB signaling with Bay-11-7082. Bay-11-7082 also inhibited LPS-induced increases of ROS and Nrf2 expression. Taken together, we have demonstrated that oxidative stress and NF-κB signaling are involved in LPS induced disruption of pulmonary cell development in chick embryos.

Maternal exposure to particulate matter alters early post-natal lung function and immune cell development

BACKGROUND

In utero exposure to particulate matter (PM) from a range of sources is associated with adverse post-natal health; however, the effect of maternal exposure to community-sampled PM on early post-natal lung and immune development is poorly understood.

OBJECTIVES

Using a mouse model, we aimed to determine whether in utero exposure to PM alters early post-natal lung function and immune cell populations. We used PM collected from ceiling voids in suburban houses as a proxy for community PM exposure.

METHODS

Pregnant C57BL/6 mice were intranasally exposed to ceiling derived PM, or saline alone, at gestational day (E) 13.5, 15.5, and 17.5. When mice were two weeks old, we assessed lung function by the forced oscillation technique, and enumerated T and B cell populations in the spleen and thymus by flow cytometry.

RESULTS

Maternal exposure to PM impaired somatic growth of male offspring resulting in reduced lung volume and deficits in lung function. There was no effect on thymic T cell populations in dams and their male offspring but PM decreased the CD4 +CD25 + T cell population in the female offspring. In contrast, maternal exposure to PM increased splenic CD3 +CD4 + and CD3 +CD8 + T cells in dams, and there was some evidence to suggest inhibition of splenic T cell maturation in male but not female offspring.

CONCLUSIONS

Our findings suggested that maternal exposure to ceiling void PM has the capacity to impair early somatic growth and alter early life immune development in a sex specific manner.

Maternal Exposure of BALB/c Mice to Indoor NO2 and Allergic Asthma Syndrome in Offspring at Adulthood with Evaluation of DNA Methylation Associated Th2 Polarization

BACKGROUND

Fetal stress has been proposed to be associated with diseases in both children and adults. Epidemiological studies suggest that maternal exposure to nitrogen dioxide (NO2) contributes to increased morbidity and mortality of offspring with allergic asthma later in life.

OBJECTIVES

We aimed to test whether maternal NO2 exposure causes allergic asthma-related consequences in offspring absent any subsequent lung provocation and whether this exposure enhances the likelihood of developing allergic asthma or the intensity of developed allergic airway disease following postnatal allergic sensitization and challenge. In addition, if such consequences and enhancements occurred, we sought to determine the mechanism(s) of these responses.

METHODS

Pregnant BALB/c mice were exposed to either NO2 (2.5 ppm, 5 h/day) or air daily throughout the gestation period. Offspring were sacrificed on postnatal days (PNDs) 1, 7, 14, 21, and 42, and remaining offspring were sensitized by ovalbumin (OVA) injection followed by OVA aerosol challenge during postnatal wk 7-9. We analyzed the lung histopathology, inflammatory cell infiltration, airway hyper-responsiveness (AHR), immune responses, and gene methylation under different treatment conditions.

RESULTS

Maternal exposure to NO2 caused a striking increase in inflammatory cell infiltration and the release of type 2 cytokines in the lungs of offspring at PNDs 1 and 7; however, these alterations were reversed during postnatal development. Following OVA sensitization and challenge, the exposure enhanced the levels of allergic asthma-characterized OVA-immunoglobulin (Ig) E, AHR, and airway inflammation in adult offspring. Importantly, differentiation of T-helper (Th) 2 cells and demethylation of the interleukin-4 (IL4) gene occurred during the process.

CONCLUSIONS

Maternal exposure to indoor environmental NO2 causes allergic asthma-related consequences in offspring absent any subsequent lung provocation and potentiates the symptoms of allergic asthma in adult offspring following postnatal allergic sensitization and challenge; this response is associated with the Th2-based immune response and DNA methylation of the IL4 gene. https://doi.org/10.1289/EHP685.

Pre- and Postnatal Lung Development: An Updated Species Comparison

The purpose of this review is to give an outline of respiratory tract morphological and functional development with an emphasis on perinatal and postnatal maturational processes. In view of the rising need for qualitative and quantitative data for the development of pediatric pharmaceuticals, a comparison of the human situation to experimental animal models is made, and functional data as well as suitable models for human airway diseases and functional testing are presented. Birth Defects Research 109:1519-1539, 2017. © 2017 Wiley Periodicals, Inc.

Niacin and Selenium Attenuate Sepsis-Induced Lung Injury by Up-Regulating Nuclear Factor Erythroid 2-Related Factor 2 Signaling

OBJECTIVES

To determine whether the combination therapy of niacin and selenium attenuates lung injury and improves survival during sepsis in rats and whether its benefits are associated with the activation of the glutathione redox cycle and up-regulation of nuclear factor erythroid 2-related factor 2.

DESIGN

Prospective laboratory study.

SETTING

University laboratory.

SUBJECTS

Human lung microvascular endothelial cells and male Sprague-Dawley rats (n = 291).

INTERVENTION

In lipopolysaccharide-exposed cells, the dose-related effects of niacin and selenium were assessed, and the therapeutic effects of the combination therapy of niacin (0.9 mM) and selenium (1.5 μM) were evaluated. The role of nuclear factor erythroid 2-related factor 2 was determined using nuclear factor erythroid 2-related factor 2 knockdown cells. In endotoxemic and cecal ligation and puncture with antibiotics rats, the therapeutic effects of the posttreatments of clinically relevant doses of niacin (360 mg/kg) and selenium (60 μg/kg) were evaluated.

MEASUREMENTS AND MAIN RESULTS

Combination therapy reduced the hydrogen peroxide level via the synergistic activation of the glutathione redox cycle, which involves niacin-induced increases in glutathione reductase activity, and reduced the glutathione level and a selenium-induced increase in glutathione peroxidase activity. Combination therapy contributed to the up-regulation of nuclear factor erythroid 2-related factor 2, enhancement of glutathione synthesis, and down-regulation of nuclear factor κB signaling, but nuclear factor erythroid 2-related factor 2 knockdown inhibited the enhancement of glutathione synthesis and down-regulation of the nuclear factor κB pathway. The therapeutic effects of combination therapy on endotoxemic rats were consistent with those on lipopolysaccharide-exposed cells. In addition, the posttreatment of combination therapy attenuated lung injury and improved survival in endotoxemic and cecal ligation and puncture with antibiotics rats. However, individual therapies of niacin or selenium failed to achieve these benefits.

CONCLUSIONS

The combination therapy of niacin and selenium attenuated lung injury and improved survival during sepsis. Its therapeutic benefits were associated with the synergistic activation of the glutathione redox cycle, reduction of hydrogen peroxide level, and up-regulation of nuclear factor erythroid 2-related factor 2.

Csk/Src/EGFR signaling regulates migration of myofibroblasts and alveolarization

Bronchopulmonary dysplasia (BPD) is characterized by premature alveolar developmental arrest. Antenatal exposure to inflammation inhibits lung morphogenesis, thus increasing the risk of developing BPD. Alveolar myofibroblasts are thought to migrate into the septal tips and elongate secondary septa during alveolarization. Here we found lipopolysaccharide (LPS) disrupted the directional migration of myofibroblasts and increased actin stress fiber expression and focal adhesion formation. In addition, COOH-terminal Src kinase (Csk) activity was downregulated in myofibroblasts treated with LPS, while activation of Src or epidermal growth factor receptor (EGFR) was upregulated by LPS treatment. Specifically, decreased Csk activity and increased activation of Src or EGFR was also observed in primary myofibroblasts isolated from newborn rat lungs with intra-amniotic LPS exposure, a model for BPD. Further investigation revealed that EGFR was involved in cell migration impairment induced by LPS, and Src inhibition blocked LPS-induced activation of EGFR or cell migration impairment. Csk silencing also resulted in EGFR activation and cell migration impairment. Besides, we found the effect of EGFR on myofibroblast migration was mediated through RhoA activation. EGFR inhibition alleviated the abnormal localization of myofibroblasts and improved alveolar development in antenatal LPS-treated rats. Taken together, our data suggest that the Csk/Src/EGFR signaling pathway is critically involved in regulating directional migration of myofibroblasts and may contribute to arrested alveolar development in BPD.

Can maternal DHA supplementation offer long-term protection against neonatal hyperoxic lung injury?

The effect of adverse perinatal environment (like maternal infection) has long-standing effects on many organ systems, including the respiratory system. Use of maternal nutritional supplements is an exciting therapeutic option that could be used to protect the developing fetus. In a recent issue of the journal, Ali and associates (Ali M, Heyob KM, Velten M, Tipple TE, Rogers LK. Am J Physiol Lung Cell Mol Physiol 309: L441-L448, 2015) specifically look at maternal docosahexaenoic acid (DHA) supplementation and its effect on chronic apoptosis in the lung in a mouse model of perinatal inflammation and postnatal hyperoxia. Strikingly, the authors show that pulmonary apoptosis was augmented even 8 wk after the hyperoxia-exposed mice had been returned to room air. This effect was significantly attenuated in mice that were subjected to maternal dietary DHA supplementation. These findings are novel, significantly advance our understanding of chronic effects of adverse perinatal and neonatal events on the developing lung, and thereby offer novel therapeutic options in the form of maternal dietary supplementation with DHA. This editorial reviews the long-term effects of adverse perinatal environment on postnatal lung development and the protective effects of dietary supplements such as DHA.

The effect of prenatal maternal infection on respiratory function in mouse offspring: evidence for enhanced chemosensitivity

Systemic maternal inflammation is implicated in preterm birth and bronchopulmonary dysplasia (BPD) and may induce morbidities including reduced pulmonary function, sleep-disordered breathing, and cardiovascular disorders. Here we test the hypothesis that antenatal maternal inflammation per se causes altered alveolar development and increased chemoreflex sensitivity that persists beyond infancy. Pregnant C57BL/6 mice were administered lipopolysaccharide (LPS) (150 μg/kg ip) to induce maternal inflammation or saline (SHAM) at embryonic day 16 (randomized). Pups were weighed daily. On days 7, 28, and 60 (D07, D28, and D60), unrestrained wholebody plethysmography quantified ventilation and chemoreflex responses to hypoxia (10%), hypercapnia (7%), and asphyxia (hypoxic hypercapnia). Lungs were harvested to quantify alveolar number, size, and septal thickness. LPS pups had reduced baseline ventilation per unit bodyweight (∼40%, P < 0.001) vs. SHAM. LPS increased ventilatory responses to hypoxia (D07: 66% vs. 28% increase in ventilation; P < 0.001) hypercapnia (170% vs. 88%; P < 0.001), and asphyxia (249% vs. 154%; P < 0.001); hypersensitive hypoxic responsiveness persisted until D60 (P < 0.001). LPS also increased apnea frequency (P < 0.01). LPS caused thicker alveolar septae (D07, P < 0.001), diminished alveolar number (D28, P < 0.001) vs. SHAM, but effects were minimal by D60. Pups delivered from mothers exposed to antenatal inflammation exhibit deficits in lung structure and hypersensitive responses to respiratory stimuli that persist beyond the newborn period. Antenatal inflammation may contribute to impaired gas exchange and unstable breathing in newborn infants and adversely affect long-term health.

Maternal molecular hydrogen treatment attenuates lipopolysaccharide-induced rat fetal lung injury

Maternal inflammation is associated with spontaneous preterm birth and respiratory impairment among premature infants. Recently, molecular hydrogen (H2) has been reported to have a suppressive effect on oxidative stress and inflammation. The aim of this study was to evaluate the effects of H2 on fetal lung injury caused by maternal inflammation. Cell viability and the production of interleukin-6 (IL-6) and reactive oxygen species (ROS) were examined by treatment with lipopolysaccharide (LPS) contained in ordinal or H2-rich medium (HM) using a human lung epithelial cell line, A549. Pregnant Sprague Dawley rats were divided into three groups: Control, LPS, and HW + LPS groups. Rats were injected with phosphate-buffered saline (Control) or LPS intraperitoneally (LPS) on gestational day 19 and provided H2 water (HW) ad libitum for 24 h before LPS injection (HW + LPS). Fetal lung samples were collected on day 20, and the levels of apoptosis, oxidative damage, IL-6, and vascular endothelial growth factor (VEGF) were evaluated using immunohistochemistry. The number of apoptotic cells, and levels of ROS and IL-6 were significantly increased by LPS treatment, and repressed following cultured with HM in A549 cells. In the rat models, the population positive for cleaved caspase-3, 8-hydroxy-2'-deoxyguanosine, IL-6, and VEGF was significantly increased in the LPS group compared with that observed in the Control group and significantly decreased in the HW + LPS group. In this study, LPS administration induced apoptosis and oxidative damage in fetal lung cells that was ameliorated by maternal H2 intake. Antenatal H2 administration may decrease the pulmonary mobility associated with inflammation in premature infants.

Effects of intra-amniotic lipopolysaccharide exposure on the fetal lamb lung as gestation advances

BACKGROUND

Intra-amniotic lipopolysaccharide (LPS) exposure may affect neonatal outcome by altering fetal lung and immune system development. We hypothesized that intra-amniotic LPS exposure would cause persistent fetal pulmonary responses as the lungs develop in utero.

METHODS

Fetal lambs were exposed to intra-amniotic LPS at 118 or at 118 and 123 d of gestational age (GA) with delivery at 125, 133, or 140 d (term = 147 d). Immune responses, PU.1 expression, Toll-like receptor (TLR)-1,2,4,6 mRNA levels, mast cell levels, and pulmonary elastin deposition were evaluated.

RESULTS

After a single dose of LPS, pulmonary inflammatory responses were observed with increases of (i) PU.1 and TLR1 at 125 d GA and (ii) monocytes, lymphocytes, TLR2, and TLR6 at 133 d GA. Repetitive LPS exposure resulted in (i) increases of neutrophils, monocytes, PU.1, and TLR1 at 125 d GA; (ii) increases of neutrophils, PU.1, and TLR2 at 133 d GA; and (iii) decreases of mast cells, elastin foci, TLR4, and TLR6 at early gestation. At 140 d GA, only PU.1 was increased after repetitive LPS exposure.

CONCLUSION

The preterm fetal lung can respond to a single exposure or repeated exposures from intra-amniotic LPS in multiple ways, but the absence of inflammatory and structural changes in LPS-exposed fetuses delivered near term suggest that the fetus can resolve an inflammatory stimulus in utero with time.

Lipopolysaccharide induces up-regulation of TGF-α through HDAC2 in a rat model of bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is characterized by alveolar simplification with decreased alveolar number and increased airspace. Previous studies suggested that transforming growth factor-α (TGF-α) may contribute to arrested alveolar development in BPD. Histone deacetylases (HDACs) control cellular signaling and gene expression. HDAC2 is crucial for suppression of inflammatory gene expression. Here we investigated whether HDAC2 was involved in the arrest of alveolarization, as well as the ability of HDAC2 to regulate TGF-α expression in a rat model of BPD induced by intra-amniotic injection of lipopolysaccharide (LPS). Results showed that LPS exposure led to a suppression of both HDAC1 and HDAC2 expression and activity, induced TGF-α expression, and disrupted alveolar morphology. Mechanistic studies showed that overexpression of HDAC2, but not HDAC1, suppressed LPS-induced TGF-α expression. Moreover, the HDAC inhibitor TSA or downregulation of HDAC2 by siRNA both significantly increased TGF-α expression in cultured myofibroblasts. Finally, preservation of HDAC activity by theophylline treatment improved alveolar development and attenuated TGF-α release. Together, these findings indicate that attenuation of TGF-α-mediated effects in the lung by enhancing HDAC2 may have a therapeutic effect on treating BPD.

Combined effects of maternal inflammation and neonatal hyperoxia on lung fibrosis and RAGE expression in newborn rats

BACKGROUND

Receptors for advanced glycation end products (RAGE) have been implicated in fibrotic processes. We hypothesized that lung fibrosis induced by maternal lipopolysaccharide (LPS)-mediated inflammation and neonatal hyperoxia involves RAGE in newborn rats.

METHODS

Pregnant Sprague-Dawley rats received intraperitoneal injections of LPS or normal saline (NS) on 20 and 21 d of gestation. The pups were reared in room air (RA) or an O2-enrich atmosphere (O2), creating the four study groups, NS + RA, NS + O2, LPS + RA, and LPS + O2. The O2 treatment was >95% O2 for 7 d, followed by 60% O2 for 14 d.

RESULTS

Rat pups born to LPS-injected dams exhibited significantly higher lung interferon-γ and interleukin-1β (IL-1β) on postnatal day 7 than the pups born to NS-injected dams. Rat pups reared in hyperoxia expressed higher lung IL-10 on postnatal day 7, compared with the RA-reared pups. The LPS + O2 group had significantly higher total collagen and transforming growth factor-β1 on postnatal days 7 and 21 than the NS+RA group. RAGE mRNA and sRAGE protein expression were significantly lower in the LPS + O2 group on postnatal day 7 than the NS+RA group.

CONCLUSION

RAGE may be involved in the pathogenesis of lung fibrosis induced by maternal systemic inflammation and postnatal hyperoxia in rat neonates.

Anti-inflammatory effect of caffeine is associated with improved lung function after lipopolysaccharide-induced amnionitis

BACKGROUND

Although caffeine enhances respiratory control and decreases the need for mechanical ventilation and resultant bronchopulmonary dysplasia, it may also have anti-inflammatory properties in protecting lung function.

OBJECTIVE

We hypothesized that caffeine improves respiratory function via an anti-inflammatory effect in lungs of a lipopolysaccharide (LPS)-induced pro-inflammatory amnionitis rat pup model.

METHODS

Caffeine was given orally (10 mg/kg/day) from postnatal day (p)1 to p14 to pups exposed to intra-amniotic LPS or normal saline. Expression of IL-1β was assessed in lung homogenates at p8 and p14, and respiratory system resistance (Rrs) and compliance (Crs) as well as CD68 cell counts and radial alveolar counts were assessed at p8.

RESULTS

In LPS-exposed rats, IL-1β and CD68 cell counts both increased at p8 compared to normal saline controls. These increases in pro-inflammatory markers were no longer present in caffeine-treated LPS-exposed pups. Rrs was higher in LPS-exposed pups (4.7 ± 0.9 cm H2O/ml·s) at p8 versus controls (1.6 ± 0.3 cm H2O/ml·s, p < 0.01). LPS-exposed pups no longer exhibited a significant increase in Rrs (2.8 ± 0.5 cm H2O/ml·s) after caffeine. Crs did not differ significantly between groups, although radial alveolar counts were lower in both groups of LPS-exposed pups.

CONCLUSIONS

Caffeine promotes anti-inflammatory effects in the immature lung of prenatal LPS-exposed rat pups associated with improvement of Rrs, suggesting a protective effect of caffeine on respiratory function via an anti-inflammatory mechanism.

Lipopolysaccharide and soluble CD14 in cord blood plasma are associated with prematurity and chorioamnionitis

BACKGROUND

Lipopolysaccharide (LPS), an endotoxin of Gram-negative bacteria, causes preterm birth in animals and has been implicated as a factor triggering preterm labor and systemic complications in humans. Little is known regarding LPS in the cord blood (CB) of term and preterm infants and its association with maternal and fetal characteristics.

METHODS

CB was obtained from term (n = 15) and preterm infants (n = 76) after delivery. Plasma levels of LPS, C-reactive protein (CRP), and soluble CD14 (sCD14) were measured using commercially available kits (limulus amebocyte lysate and enzyme-linked immunosorbent assay). Four linear regression models were created in order to identify independent variables that predict plasma LPS levels.

RESULTS

The analyte levels were significantly higher in preterm vs. term infant CB: LPS (24.48 vs. 1 pg/ml; P = 0.0009), CRP (87.9 vs. 47 ng/ml; P = 0.01), and sCD14 (0.32 vs.0.35 µg/ml; P = 0.013). There was a (significant) positive correlation between CB LPS levels and gestational age, birth weight, CRP levels, sCD14 levels, and association with both clinical and histological chorioamnionitis.

CONCLUSION

Our data suggest that LPS is associated with preterm labor and inflammation (CRP elevation and chorioamnionitis). These findings may be relevant to the understanding of the role of LPS in prematurity and its role in preterm morbidities.

IL-1β expression in the distal lung epithelium disrupts lung morphogenesis and epithelial cell differentiation in fetal mice

Perinatal inflammation and the inflammatory cytokine IL-1 can modify lung morphogenesis. To examine the effects of antenatal expression of IL-1β in the distal airway epithelium on fetal lung morphogenesis, we studied lung development and surfactant expression in fetal mice expressing human IL-1β under the control of the surfactant protein (SP)-C promoter. IL-1β-expressing pups suffered respiratory failure and died shortly after birth. IL-1β caused fetal lung inflammation and enhanced the expression of keratinocyte-derived chemokine (KC/CXCL1) and monocyte chemoattractant protein 3 (MCP-3/CCL7), the calgranulins S100A8 and S100A9, the acute-phase protein serum amyloid A3, the chitinase-like proteins Ym1 and Ym2, and pendrin. IL-1β decreased the percentage of the total distal lung area made up of air saccules and the number of air saccules in the lungs of fetal mice. IL-1β inhibited the expression of VEGF-A and its receptors VEGFR-1 and VEGFR-2. The percentage of the cellular area of the distal lung made up of capillaries was decreased in IL-1β-expressing fetal mice. IL-1β suppressed the production of SP-B and pro-SP-C and decreased the amount of phosphatidylcholine and the percentage of palmitic acid in the phosphatidylcholine fraction of lung phospholipids, indicating that IL-1β prevented the differentiation of type II epithelial cells. The production of Clara cell secretory protein in the nonciliated bronchiolar (Clara) cells was likewise suppressed by IL-1β. In conclusion, expression of IL-1β in the epithelium of the distal airways disrupted the development of the airspaces and capillaries in the fetal lung and caused fatal respiratory failure at birth.

Chorioamnionitis and lung injury in preterm newborns

There is a strong evidence that histologic chorioamnionitis is associated with a reduction of incidence and severity of respiratory distress syndrome (RDS). Short-term maturational effects on the lungs of extremely premature infants seem to be, however, accompanied by a greater susceptibility of the lung, eventually contributing to an increased risk of bronchopulmonary dysplasia (BPD). Genetic susceptibility to BPD is an evolving area of research and several studies have directly related the risk of BPD to genomic variants. There is a substantial heterogeneity across the studies in the magnitude of the association between chorioamnionitis and BPD, and whether or not the association is statistically significant. Considerable variation is largely dependent on differences of inclusion and exclusion criteria, as well as on clinical and histopathological definitions. The presence of significant publication bias may exaggerate the magnitude of the association. Controlling for publication bias may conduct to adjusted results that are no longer significant. Recent studies generally seem to confirm the effect of chorioamnionitis on RDS incidence, while no effect on BPD is seen. Recent data suggest susceptibility for subsequent asthma to be increased on long-term followup. Additional research on this field is needed.

Endotoxin inhalation alters lung development in neonatal mice

BACKGROUND

Childhood asthma is a significant public health problem. Epidemiologic evidence suggests an association between childhood asthma exacerbations and early life exposure to environmental endotoxin. Although the pathogenesis of endotoxin-induced adult asthma is well studied, questions remain about the impact of environmental endotoxin on pulmonary responsiveness in early life.

METHODS

We developed a murine model of neonatal/juvenile endotoxin exposures approximating those in young children and evaluated the lungs inflammatory and remodeling responses.

RESULTS

Persistent lung inflammation induced by the inhalation of endotoxin in early life was demonstrated by the influx of inflammatory cells and pro-inflammatory mediators to the airways and resulted in abnormal alveolarization.

CONCLUSIONS

Results of this study advance the understanding of the impact early life endotoxin inhalation has on the lower airways, and demonstrates the importance of an experimental design that approximates environmental exposures as they occur in young children.

Lipopolysaccharide disrupts the directional persistence of alveolar myofibroblast migration through EGF receptor

Bronchopulmonary dysplasia (BPD) is characterized by alveolar simplification with decreased alveolar number and increased airspace size. Formation of alveoli involves a process known as secondary septation triggered by myofibroblasts. This study investigated the underlying mechanisms of altered lung morphogenesis in a rat model of BPD induced by intra-amniotic injection of lipopolysaccharide (LPS). Results showed that LPS disrupted alveolar morphology and led to abnormal localization of myofibroblasts in the lung of newborn rats, mostly in primary septa with few in secondary septa. To identify potential mechanisms, in vitro experiments were carried out to observe the migration behavior of myofibroblasts. The migration speed of lung myofibroblasts increased with LPS treatment, whereas the directional persistence decreased. We found that LPS induced activation of EGFR and overexpression of its ligand, TGF-α in myofibroblasts. AG1478, an EGFR inhibitor, abrogated the enhanced locomotivity of myofibroblasts by LPS and also increased the directional persistence of myofibroblast migration. Myofibroblasts showed a high asymmetry of phospho-EGFR localization, which was absent after LPS treatment. Application of rhTGF-α to myofibroblasts decreased the directional persistence. Our findings indicated that asymmetry of phospho-EGFR localization in myofibroblasts was important for cell migration and its directional persistence. We speculate that LPS exposure disrupts the asymmetric localization of phospho-EGFR, leading to decreased stability of cell polarity and final abnormal location of myofibroblasts in vivo, which is critical to secondary septation and may contribute to the arrested alveolar development in BPD.

Perinatal inflammation and lung injury

Bronchopulmonary dysplasia (BPD) remains the major morbidity of extreme preterm birth. The incidence of BPD has remained stable despite recent efforts to reduce postnatal exposures to volutrauma and hyperoxia. This review will focus on recent clinical and experimental insights that provide support for the concept that the 'new BPD' is the result of inflammation-mediated injury and altered lung development during a window of vulnerability in genetically susceptible infants that is modified by maternal and postnatal exposures.

NF-κB signaling in fetal lung macrophages disrupts airway morphogenesis

Bronchopulmonary dysplasia is a common pulmonary complication of extreme prematurity. Arrested lung development leads to bronchopulmonary dysplasia, but the molecular pathways that cause this arrest are unclear. Lung injury and inflammation increase disease risk, but the cellular site of the inflammatory response and the potential role of localized inflammatory signaling in inhibiting lung morphogenesis are not known. In this study, we show that tissue macrophages present in the fetal mouse lung mediate the inflammatory response to LPS and that macrophage activation inhibits airway morphogenesis. Macrophage depletion or targeted inactivation of the NF-κB signaling pathway protected airway branching in cultured lung explants from the effects of LPS. Macrophages also appear to be the primary cellular site of IL-1β production following LPS exposure. Conversely, targeted NF-κB activation in transgenic macrophages was sufficient to inhibit airway morphogenesis. Macrophage activation in vivo inhibited expression of multiple genes critical for normal lung development, leading to thickened lung interstitium, reduced airway branching, and perinatal death. We propose that fetal lung macrophage activation contributes to bronchopulmonary dysplasia by generating a localized inflammatory response that disrupts developmental signals critical for lung formation.

Niacin attenuates lung inflammation and improves survival during sepsis by downregulating the nuclear factor-κB pathway

OBJECTIVES

To examine whether niacin attenuates lung inflammation and improves survival during sepsis and to determine whether the beneficial effects of niacin are associated with downregulation of the nuclear factor (NF)-κB pathway.

DESIGN

Prospective laboratory study.

SETTING

University laboratory.

SUBJECTS

Male Sprague-Dawley rats (n = 119).

INTERVENTIONS

To induce endotoxemia in rats, lipopolysaccharide (Escherichia coli, O26:B6) at a dosage of 10 mg/kg was injected into a tail vein and 10 mins later, vehicle, a low dose of niacin (360 mg/kg), or a high dose of niacin (1180 mg/kg) was administered once through an orogastric tube, respectively.

MEASUREMENTS AND MAIN RESULTS

We observed the survival of the subjects for 72 hrs. At 6 hrs postlipopolysaccharide, we euthanized animals and measured cytoplasmic phosphorylated inhibitor κB-α and inhibitor κB-α expressions, nuclear NF-κB p65 expression, NF-κB p65 DNA-binding activity, tumor necrosis factor-α, and interleukin-6 gene expressions and histologic damages in lung tissues. We also measured nicotinamide adenine dinucleotide, reduced nicotinamide adenine dinucleotide phosphate, reduced glutathione, and malondialdehyde levels in lung tissues. High dose of niacin suppressed NF-κB activation and proinflammatory cytokine gene expressions in lung tissues, reduced histologic lung damages, and improved survival in endotoxemic rats. Furthermore, it increased nicotinamide adenine dinucleotide, nicotinamide adenine dinucleotide phosphate, and glutathione levels and decreased malondialdehyde level in lung tissues.

CONCLUSIONS

High dose of niacin attenuated lung inflammation, reduced histologic lung damages, and improved survival during sepsis in rats. These therapeutic benefits were associated with downregulation of the NF-κB pathway.

Mechanisms of inflammatory lung injury in the neonate: lessons from a transgenic mouse model of bronchopulmonary dysplasia

The role of inflammation in the pathogenesis of bronchopulmonary dysplasia (BPD) is not well understood. By using a transgenic mouse expressing the inflammatory cytokine interleukin (IL)-1beta in the lung, we have shown that perinatal expression of IL-1beta causes a BPD-like illness in infant mice. We have used this model to identify mechanisms by which inflammation causes neonatal lung injury. Increased matrix metalloproteinase (MMP)-9 activity is associated with BPD. MMP-9 deficiency worsens alveolar hypoplasia in IL-1beta-expressing newborn mice, suggesting that MMP-9 has a protective role in neonatal inflammatory lung injury. The beta6 integrin subunit, an activator of transforming growth factor-beta, is involved in adult lung disease. Absence of the beta6 integrin subunit improves alveolar development in IL-1beta-expressing mice, suggesting that the beta6 integrin subunit is a pathogenetic factor in inflammatory lung disease in the newborn. The authors of clinical studies who have examined maternal inflammation as a risk factor for BPD have found variable results. We have shown that maternal IL-1beta production preceding fetal IL-1beta production prevents lung inflammation, alveolar hypoplasia, and airway remodeling in newborn IL-1beta-expressing mice. Thus, maternal inflammation may protect the newborn lung against subsequent inflammatory injury. In contrast, when maternal and fetal production of IL-1beta are induced simultaneously, the development of IL-1beta-induced lung disease in the newborn is not prevented.

Early gestational intrauterine infection induces postnatal lung inflammation and arrests lung development in a rat model

OBJECTIVE

In order to investigate the early gestational inflammation effect on the prenatal and postnatal lung development, identification of the proinflammatory cytokines (IL-1β and TNF-α), genes implicated in angiogenesis (Vascular endothelial growth factor [VEGF], fms-like tyrosine kinase-1 [Flt-1], fetal liver kinase-1 [Flk-1]), and surfactant proteins (SPs) were observed.

METHODS

Escherichia coli (E. coli) was inoculated into uterine cervix of pregnant rats at embryonic day 15 (E15) during pseudoglandular period of lung development and the control group was inoculated with normal saline. IL-1β, TNF-α, VEGF, Flt-1, Flk-1, SP-A, and SP-B mRNA in pup's lung at E17, 19, 21 and postnatal day (P) 1, 3, 7, 14 were quantified by real-time RT-PCR. Western blot or immunohistochemistry analysis was also performed for the evaluation of VEGF, Flk-1, Flt-1, and SP-A expression in pup's lung.

RESULTS

Compared with the control group, the fetal lung of the E. coli-treated group was more immature, the postnatal lung development was impaired marked by less alveoli, fewer secondary septa, and thicker alveolar wall. The lung weight and lung/body weight ratio were lower in the E. coli-treated group pups. IL-1β and TNF-α mRNA were increased significantly in E. coli-treated pup's lung after birth, but no significant difference of IL-1β and TNF-α mRNA levels in fetal lung were found between the two groups. SP-A expression was depressed at E17, E19, and E21 after intrauterine E. coli treated, accompanied with lower SP-B mRNA level at E19 and E21. Furthermore, intrauterine E. coli treated reduced the VEGF mRNA and protein levels in the fetal lung at E17 and E19, while the expression of Flt-1 and Flk-1 were higher at P7, P14 and P1, P7, P14, respectively, compared to the controls.

CONCLUSIONS

These results suggested early gestational intrauterine E. coli infection could induce a postnatal pulmonary inflammation and might arrest the alveolarization in developing lung which was involved with the VEGF signaling. However, intrauterine E. coli infection could not induce the increase of proinflammatory cytokines in fetal lung and might fail to accelerate the maturation of fetal lung.

Deficits in lung alveolarization and function after systemic maternal inflammation and neonatal hyperoxia exposure

Systemic maternal inflammation contributes to preterm birth and is associated with development of bronchopulmonary dysplasia (BPD). Infants with BPD exhibit decreased alveolarization, diffuse interstitial fibrosis with thickened alveolar septa, and impaired pulmonary function. We tested the hypothesis that systemic prenatal LPS administration to pregnant mice followed by postnatal hyperoxia exposure is associated with prolonged alterations in pulmonary structure and function after return to room air (RA) that are more severe than hyperoxia exposure alone. Timed-pregnant C3H/HeN mice were dosed with LPS (80 microg/kg) or saline on gestation day 16. Newborn pups were exposed to RA or 85% O2 for 14 days and then to RA for an additional 14 days. Data were collected and analyzed on postnatal days 14 and 28. The combination of prenatal LPS and postnatal hyperoxia exposure generated a phenotype with more inflammation (measured as no. of macrophages per high-power field) than either insult alone at day 28. The combined exposures were associated with a diffuse fibrotic response [measured as hydroxyproline content (microg)] but did not induce a more severe developmental arrest than hyperoxia alone. Pulmonary function tests indicated that hyperoxia, independent of maternal exposure, induced compliance decreases on day 14 that did not persist after RA recovery. Either treatment alone or combined induced an increase in resistance on day 14, but the increase persisted on day 28 only in pups receiving the combined treatment. In conclusion, the combination of systemic maternal inflammation and neonatal hyperoxia induced a prolonged phenotype of arrested alveolarization, diffuse fibrosis, and impaired lung mechanics that mimics human BPD. This new model should be useful in designing studies of specific mechanisms and interventions that could ultimately be utilized to define therapies to prevent BPD in premature infants.

Maternal endotoxin exposure attenuates allergic airway disease in infant rats

Prenatal exposures to immunogenic stimuli, such as bacterial LPS, have shown to influence the neonatal immune system and lung function. However, no detailed analysis of the immunomodulatory effects of LPS on postnatal T helper cell differentiation has been performed. Using a rat model, we investigated the effect of prenatal LPS exposure on postnatal T cell differentiation and experimental allergic airway disease. Pregnant rats were injected with LPS on day 20 and 21 (term = 22 days). Some of the offspring were sensitized and challenged with ovalbumin. Positive control animals were placebo exposed to saline instead of LPS, whereas negative controls were sensitized with saline. Expression of T cell-related transcription factors and cytokines was quantified in the lung, and airway hyperresponsiveness was measured. Prenatal LPS exposure induced a T helper 1 (T(H)1) immune milieu in the offspring of rats [i.e., increased T-bet and T(H)1 cytokine expression while expression of T(H)2-associated transcription factors (GATA3 and STAT6) and cytokines was decreased]. Prenatal LPS exposure did not trigger T(H)17 cell differentiation in the offspring. Furthermore, prenatal LPS exposure reduced ovalbumin-induced (T(H)2-mediated) airway inflammation, eosinophilia, and airway responsiveness. Thus, in utero exposure to endotoxin promotes a T(H)1 immune environment, which suppresses the development of allergic airway disease later in life.