IL-1 alpha causes lung inflammation and maturation by direct effects on preterm fetal lamb lungs

IL-1 promotes α-epithelial Sodium Channel (α-ENaC) expression in murine lung epithelial cells: involvement of NF-κB

Intra-amniotic exposure to proinflammatory cytokines such as interleukin-1 (IL-1) correlates with a decreased incidence of respiratory distress syndrome (RDS) in infants following premature birth. At birth, inadequate absorption of fluid from the fetal lung contributes to the onset RDS. Lung fluid clearance is coupled to Na⁺ transport via epithelial sodium channels (ENaC). In this study, we assessed the effects of IL-1 on the expression of ENaC, particularly the α-subunit which is critical for fetal lung fluid clearance at birth. Cultured mouse lung epithelial (MLE-12) cells were treated with either IL-1α or IL-1β to determine their effects on α-ENaC expression. Changes in IL-1-induced α-ENaC levels in the presence of IL-1 receptor antagonist (IL-1ra), cycloheximide, NF-κB inhibitor, and MAP kinase inhibitors were investigated. IL-1α and IL-1β independently induced a significant increase of α-ENaC mRNA and protein after 24 h compared to untreated cells. IL-1-dependent increases in α-ENaC protein were mitigated by IL-1ra and cycloheximide. IL-1 exposure induced NF-κB binding activity. Attenuation of IL-1-induced NF-κB activation by its inhibitor SN50 decreased α-ENaC protein abundance. Inhibition of ERK 1,2 MAPK significantly decreased both IL-1α and β-induced α-ENaC protein expression whereas inhibition of p38 MAPK only blocked IL-1β-induced α-ENaC protein levels. In contrast, IL-1-induced α-ENaC protein levels were unaffected by a c-Jun N-terminal kinase (JNK) inhibitor. Our results suggest that in MLE-12 cells, IL-1-induced elevation of α-ENaC is mediated via NF-κB activation and in part involves stimulation of the ERK 1,2 and p38 MAPK signaling pathways.

Inflammatory Th17 responses to infection with Mycobacterium avium subspecies paratuberculosis (MAP) in cattle and their potential role in development of Johne's disease

Chronic intestinal inflammation typically associated with late stage Johne's disease (JD) in cattle occurs despite a lack of significant expression of the typical proinflammatory cytokines IFNγ and TNFα derived from Th1- like T cells. In contrast, these cytokines appear to be relatively abundant during early infections with Mycobacterium avium subspecies paratuberculosis (MAP), the causative agent of JD in cattle. The roles of non-classical immune responses, such as those associated with Th17 cells, in response to MAP infection and development of clinical JD are less clear. In this review, we examine literature suggesting that Mycobacterial infections, including Mycobacterium tuberculosis, Mycobacterium bovis, and MAP, are all associated with expression of Th17 promoting cytokines (IL-23, IL-22, IL-17a). We discuss the possibility that Th17 associated cytokines, particularly IL-23, may act as contributing factors in development and maintenance of inflammation characteristic of clinical JD. An as yet relatively unexplored source of chronic inflammation due to over expression of IL-1α and IL-1β is also presented. We further discuss the fact that, as with the typical Th1-like cytokines IFNγ and TNFα , IL-17a is not significantly expressed in CD4+ T cells from cows with clinical JD, possibly due to T cell exhaustion. Finally, we present the notion that the Th17 driving cytokine IL-23 expressed by infected macrophages and associated epithelial cells may contribute to chronic inflammation during later stages of JD.

Developmentally Regulated Innate Immune NFκB Signaling Mediates IL-1α Expression in the Perinatal Murine Lung

Bronchopulmonary dysplasia (BPD) is the most common morbidity complicating premature birth. Importantly, preclinical models have demonstrated that IL-1 receptor antagonism prevents the lung injury and subsequent abnormal development that typically results following perinatal exposure to inflammatory stresses. This receptor is activated by two pro-inflammatory cytokines, IL-1α and IL-1β. While many studies have linked IL-1β to BPD development, IL-1α is relatively under-studied. The objective of our study was to determine whether systemic inflammatory stress induces IL-1α expression in the neonatal lung, and if so, whether this expression is mediated by innate immune NFκB signaling. We found that endotoxemia induced IL-1α expression during the saccular stage of neonatal lung development and was not present in the other neonatal organs or the adult lung. This IL-1α expression was dependent upon sustained pulmonary NFκB activation, which was specific to the neonatal lung. Using in vivo and in vitro approaches, we found that pharmacologic and genetic inhibition of NFκB signaling attenuated IL-1α expression. These findings demonstrate that innate immune regulation of IL-1α expression is developmentally regulated and occurs via an NFκB dependent mechanism. Importantly, the specific role of developmentally regulated pulmonary IL-1α expression remains unknown. Future studies must determine the effect of attenuating innate immune IL-1α expression in the developing lung before adopting broad IL-1 receptor antagonism as an approach to prevent neonatal lung injury.

Suggested Mechanisms of Tracheal Occlusion Mediated Accelerated Fetal Lung Growth: A Case for Heterogeneous Topological Zones

In this article, we report an up-to-date summary on tracheal occlusion (TO) as an approach to drive accelerated lung growth and strive to review the different maternal- and fetal-derived local and systemic signals and mechanisms that may play a significant biological role in lung growth and formation of heterogeneous topological zones following TO. Pulmonary hypoplasia is a condition whereby branching morphogenesis and embryonic pulmonary vascular development are globally affected and is classically seen in congenital diaphragmatic hernia. TO is an innovative approach aimed at driving accelerated lung growth in the most severe forms of diaphragmatic hernia and has been shown to result in improved neonatal outcomes. Currently, most research on mechanisms of TO-induced lung growth is focused on mechanical forces and is viewed from the perspective of homogeneous changes within the lung. We suggest that the key principle in understanding changes in fetal lungs after TO is taking into account formation of unique variable topological zones. Following TO, fetal lungs might temporarily look like a dynamically changing topologic mosaic with varying proliferation rates, dissimilar scale of vasculogenesis, diverse patterns of lung tissue damage, variable metabolic landscape, and different structures. The reasons for this dynamic topological mosaic pattern may include distinct degree of increased hydrostatic pressure in different parts of the lung, dissimilar degree of tissue stress/damage and responses to this damage, and incomparable patterns of altered lung zones with variable response to systemic maternal and fetal factors, among others. The local interaction between these factors and their accompanying processes in addition to the potential role of other systemic factors might lead to formation of a common vector of biological response unique to each zone. The study of the interaction between various networks formed after TO (action of mechanical forces, activation of mucosal mast cells, production and secretion of damage-associated molecular pattern substances, low-grade local pulmonary inflammation, and cardiac contraction-induced periodic agitation of lung tissue, among others) will bring us closer to an appreciation of the biological phenomenon of topological heterogeneity within the fetal lungs.

Clinical chorioamnionitis at term VI: acute chorioamnionitis and funisitis according to the presence or absence of microorganisms and inflammation in the amniotic cavity

OBJECTIVE

Neonates born to mothers with clinical chorioamnionitis at term are at an increased risk of infection. Acute subchorionitis, chorioamnionitis, and funisitis are considered placental histologic features consistent with acute inflammation according to the Society for Pediatric Pathology. The objectives of this study were to examine the performance of placental histologic features in the identification of: 1) microbial-associated intra-amniotic inflammation (intra-amniotic infection); and 2) fetal inflammatory response syndrome (FIRS).

METHODS

This retrospective cohort study included women with the diagnosis of clinical chorioamnionitis at term (n=45), who underwent an amniocentesis to determine: 1) the presence of microorganisms using both cultivation and molecular biologic techniques [polymerase chain reaction (PCR) with broad range primers]; and 2) interleukin (IL)-6 concentrations by enzyme-linked immunosorbent assay (ELISA). The diagnostic performance (sensitivity, specificity, accuracy, and likelihood ratios) of placental histologic features consistent with acute inflammation was determined for the identification of microbial-associated intra-amniotic inflammation and FIRS.

RESULTS

1) The presence of acute histologic chorioamnionitis and funisitis was associated with the presence of proven intra-amniotic infection assessed by amniotic fluid analysis; 2) funisitis was also associated with the presence of FIRS; 3) the negative predictive value of acute funisitis ≥stage 2 for the identification of neonates born to mothers with intra-amniotic infection was <50%, and therefore, suboptimal to exclude fetal exposure to bacteria in the amniotic cavity; and 4) acute funisitis ≥stage 2 had a negative predictive value of 86.8% for the identification of FIRS in a population with a prevalence of 20%.

CONCLUSION

Acute histologic chorioamnionitis and funisitis are associated with intra-amniotic infection and the presence of FIRS. However, current pathologic methods have limitations in the identification of the fetus exposed to microorganisms present in the amniotic cavity. Further studies are thus required to determine whether molecular markers can enhance the performance of placental pathology in the identification of neonates at risk for neonatal sepsis.

Selective IL-1α exposure to the fetal gut, lung, and chorioamnion/skin causes intestinal inflammatory and developmental changes in fetal sheep

Chorioamnionitis, caused by intra-amniotic exposure to bacteria and their toxic components, is associated with fetal gut inflammation and mucosal injury. In a translational ovine model, we have shown that these adverse intestinal outcomes to chorioamnionitis were the combined result of local gut and pulmonary-driven systemic immune responses. Chorioamnionitis-induced gut inflammation and injury was largely prevented by inhibiting interleukin-1 (IL-1) signaling. Therefore, we investigated whether local (gut-derived) IL-1α signaling or systemic IL-1α-driven immune responses (lung or chorioamnion/skin-derived) were sufficient for intestinal inflammation and mucosal injury in the course of chorioamnionitis. Fetal surgery was performed in sheep to isolate the lung, gastrointestinal tract, and chorioamnion/skin, and IL-1α or saline was given into the trachea, stomach, or amniotic cavity 1 or 6 days before preterm delivery. Selective IL-1α exposure to the lung, gut, or chorioamnion/skin increased the CD3+ cell numbers in the fetal gut. Direct IL-1α exposure to the gut impaired intestinal zonula occludens protein-1 expression, induced villus atrophy, changed the expression pattern of intestinal fatty acid-binding protein along the villus, and increased the CD68, IL-1, and TNF-α mRNA levels in the fetal ileum. With lung or chorioamnion/skin exposure to IL-1α, intestinal inflammation was associated with increased numbers of blood leukocytes without induction of intestinal injury or immaturity. We concluded that local IL-1α signaling was required for intestinal inflammation, disturbed gut maturation, and mucosal injury in the context of chorioamnionitis.

Preterm birth, intrauterine infection, and fetal inflammation

Preterm birth (PTB) (delivery before 37 weeks’ gestation) is a leading cause of neonatal death and disease in industrialized and developing countries alike. Infection (most notably in high-risk deliveries occurring before 28 weeks’ gestation) is hypothesized to initiate an intrauterine inflammatory response that plays a key role in the premature initiation of labor as well as a host of the pathologies associated with prematurity. As such, a better understanding of intrauterine inflammation in pregnancy is critical to our understanding of preterm labor and fetal injury, as well as on-going efforts to prevent PTB. Focusing on the fetal innate immune system responses to intrauterine infection, the present paper will review clinical and experimental studies to discuss the capacity for a fetal contribution to the intrauterine inflammation associated with PTB. Evidence from experimental studies to suggest that the fetus has the capacity to elicit a pro-inflammatory response to intrauterine infection is highlighted, with reference to the contribution of the lung, skin, and gastrointestinal tract. The paper will conclude that pathological intrauterine inflammation is a complex process that is modified by multiple factors including time, type of agonist, host genetics, and tissue.

Fetal immune response to chorioamnionitis

Chorioamnionitis is a frequent cause of preterm birth and is associated with an increased risk for injury responses in the lung, gastrointestinal tract, brain, and other fetal organs. Chorioamnionitis is a polymicrobial nontraditional infectious disease because the organisms causing chorioamnionitis are generally of low virulence and colonize the amniotic fluid often for extended periods, and the host (mother and the fetus) does not have typical infection-related symptoms such as fever. In this review, we discuss the effects of chorioamnionitis in experimental animal models that mimic the human disease. Our focus is on the immune changes in multiple fetal organs and the pathogenesis of chorioamnionitis-induced injury in different fetal compartments. As chorioamnionitis disproportionately affects preterm infants, we discuss the relevant developmental context for the immune system. We also provide a clinical context for the fetal responses.

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.

Interleukin-19 in fetal systemic inflammation

OBJECTIVE

The fetal inflammatory response syndrome (FIRS) is considered the fetal counterpart of the systemic inflammatory response syndrome (SIRS), which can be caused by infection and non-infection-related insults. Although the initial response is mediated by pro-inflammatory signals, the control of this response is achieved by anti-inflammatory mediators which are essential for the successful outcome of the affected individual. Interleukin (IL)-19 is capable of stimulating the production of IL-10, a major anti-inflammatory cytokine, and is a potent inducer of the T-helper 2 (Th2) response. The aim of this study was to determine if there is a change in umbilical cord plasma IL-19 and IL-10 concentrations in preterm neonates with and without acute funisitis, the histologic counterpart of FIRS.

METHODS

A case-control study was conducted including 80 preterm neonates born after spontaneous labor. Neonates were classified according to the presence (n = 40) or absence of funisitis (n = 40), which is the pathologic hallmark of FIRS. Neonates in each group were also matched for gestational age. Umbilical cord plasma IL-19 and IL-10 concentrations were determined by ELISA.

RESULTS

1) The median umbilical cord plasma IL-19 concentration was 2.5-fold higher in neonates with funisitis than in those without funisitis (median 87 pg/mL; range 20.6-412.6 pg/mL vs. median 37 pg/mL; range 0-101.7 pg/mL; p < 0.001); 2) newborns with funisitis had a significantly higher median umbilical cord plasma IL-10 concentration than those without funisitis (median 4 pg/mL; range 0-33.5 pg/mL vs. median 2 pg/mL; range 0-13.8 pg/mL; p < 0.001); and 3) the results were similar when we included only patients with funisitis who met the definition of FIRS by umbilical cord plasma IL-6 concentrations ≥ 17.5 pg/mL (p < 0.001).

CONCLUSION

IL-19 and IL-10 are parts of the immunologic response of FIRS. A subset of fetuses with FIRS had high umbilical cord plasma IL-19 concentrations. In utero exposure to high systemic concentrations of IL-19 may reprogram the immune response.

Pulmonary and systemic inflammatory responses to intra-amniotic IL-1α in fetal sheep

Clinical and epidemiological studies implicate IL-1 as an important mediator of perinatal inflammation. We tested the hypothesis that intra-amniotic IL-1α would induce pulmonary and systemic fetal inflammatory responses. Sheep with singleton fetuses were given an intra-amniotic injection of recombinant sheep IL-1α (100 μg) and were delivered 1, 3, or 7 days later, at 124 ± 1 days gestation (n=5-8/group). A separate group of sheep were given two intra-amniotic IL-1α injections (100 μg dose each): 7 days and again 1 day prior to delivery. IL-1α induced a robust increase in monocytes, neutrophils, lymphocytes, and IL-8 protein in bronchoalveolar lavage fluid. H(2)O(2) secretion was increased in inflammatory cells isolated from lungs of IL-1α-exposed lambs upon LPS challenge in vitro compared with control monocytes. T lymphocytes were recruited to the lung. IL-1β, cyclooxygenase-1, and cyclooxygenase-2 mRNA expression increased in the lung 1 day after intra-amniotic IL-1α exposure. Lung volumes increased 7 days after intra-amniotic IL-1α exposure, with minimal anatomic changes in air space morphology. The weight of the posterior mediastinal lymph node draining the lung and the gastrointestinal tract doubled, inducible nitric oxide synthase (NOSII)-positive cells increased, and Foxp3-positive T-regulatory lymphocytes decreased in the lymph node after IL-1α exposure. In the blood, neutrophil counts and plasma haptoglobin increased after IL-1α exposure. Compared with a single exposure, exposure to intra-amniotic IL-1α 7 days and again 1 day before delivery had a variable effect (increases in some inflammatory markers, but not pulmonary cytokines). IL-1α is a potent mediator of the fetal inflammatory response syndrome.

IL-1α mediated chorioamnionitis induces depletion of FoxP3+ cells and ileal inflammation in the ovine fetal gut

Background

Endotoxin induced chorioamnionitis increases IL-1 and provokes an inflammatory response in the fetal ileum that interferes with intestinal maturation. In the present study, we tested in an ovine chorioamnionitis model whether IL-1 is a major cytokine driving the inflammatory response in the fetal ileum.

Method

Sheep bearing singleton fetuses received a single intraamniotic injection of recombinant ovine IL-1α at 7, 3 or 1 d before caesarian delivery at 125 days gestational age (term = 150 days).

Results

3 and 7 d after IL-1α administration, intestinal mRNA levels for IL-4, IL-10, IFN-γ and TNF-α were strongly elevated. Numbers of CD3+ and CD4+ T-lymphocytes and myeloidperoxidase+ cells were increased whereas FoxP3+ T-cells were detected at low frequency. This increased proinflammatory state was associated with ileal mucosal barrier loss as demonstrated by decreased levels of the intestinal fatty acid binding protein and disruption of the tight junctional protein ZO-1.

Conclusion

Intraamniotic IL-1α causes an acute detrimental inflammatory response in the ileum, suggesting that induction of IL-1 is a critical element in the pathophysiological effects of endotoxin induced chorioamnionitis. A disturbed balance between T-effector and FoxP3+ cells may contribute to this process.

Chorioamnionitis: a multiorgan disease of the fetus?

The bacterial infection of chorion and amnion is a common finding in premature delivery and is referred to as chorioamnionitis. As the mother rarely shows symptoms of a systemic inflammation, the course of chorioamnionitis is frequently asymptomatic and chronic. In contrast, the fetal inflammatory response syndrome represents a separate phenomenon, including umbilical inflammation and increased serum levels of proinflammatory cytokines in the fetus. Ascending maternal infections frequently lead to systemic fetal inflammatory reaction. Clinical studies have shown that antenatal exposure to inflammation puts the extremely immature neonates at a high risk for worsening pulmonary, neurological and other organ development. Interestingly, the presence of chorioamnionitis is associated with a lower rate of neonatal mortality in extremely immature newborns. In the following review, the pathogeneses of inflammation-associated perinatal morbidity are outlined. The concept of fetal multiorganic disease during intrauterine infection is introduced and discussed.

Pulmonary and systemic expression of monocyte chemotactic proteins in preterm sheep fetuses exposed to lipopolysaccharide-induced chorioamnionitis

Monocyte chemoattractant proteins (MCP-1 and MCP-2) mediate monocyte and T-lymphocyte chemotaxis, and IL-1 contributes to the pathogenesis of chorioamnionitis-induced lung inflammation and fetal inflammatory responses. We tested the hypothesis that IL-1 mediates the systemic and pulmonary induction of MCP-1 and MCP-2 in response to lipopolysaccharide (LPS)-induced chorioamnionitis. MCP-1 mRNA, MCP-2 mRNA, and MCP-1 protein expression were measured in two models: 1) intra-amniotic LPS and 2) intra-amniotic recombinant sheep IL-1alpha given at varying intervals before preterm delivery at 124 d GA. Intra-amniotic LPS or IL-1alpha induced MCP-1 mRNA and protein and MCP-2 mRNA in fetal lung many fold at 1-2 d. LPS induced intense MCP-1 expression in subepithelial mesenchymal cells and interstitial inflammatory cells in the lung. Inhibition of IL-1 signaling with recombinant human IL-1 receptor antagonist (rhIL-1ra) did not attenuate LPS induced increase in MCP-1 or MCP-2 expression. MCP-1 and MCP-2 were not induced in liver or chorioamnion, but MCP-1 increased in cord plasma. LPS or IL-1 can induce robust expression of MCP-1 or MCP-2 in the fetal lung. LPS induction of MCP-1 is not IL-1 dependent in fetal sheep. MCP-1 and MCP-2 may be significant contributors to fetal inflammation.

Long term consequences of oxygen therapy in the neonatal period

Preterm and term infants are frequently exposed to high concentrations of oxygen for prolonged periods. In experimental models, high and prolonged oxygen exposures cause delayed alveolar septation and a bronchopulmonary dysplasia phenotype. Often, however, the oxygen exposure is tolerated in that the infants recover without severe lung or systemic injury. Multiple exposures change oxygen sensitivity in adult and newborn animals. Examples are antenatal corticosteroids, inflammatory mediators or preconditioning with oxygen, which will increase tolerance to oxygen injury. Intrauterine growth restriction or postnatal nutritional deficits will increase oxygen injury. Different infants probably have quite variable sensitivities to oxygen injury, but there are no biomarkers available to predict the risk of oxygen injury.

Modulation of fetal inflammatory response on exposure to lipopolysaccharide by chorioamnion, lung, or gut in sheep

OBJECTIVE

We hypothesized that fetal lipopolysaccharide exposures to the chorioamnion, lung, or gut would induce distinct systemic inflammatory responses.

STUDY DESIGN

Groups of 5-7 time-mated ewes were used to surgically isolate the fetal respiratory and the gastrointestinal systems from the amniotic compartment. Outcomes were assessed at 124 days gestational age, 2 days and 7 days after lipopolysaccharide (10 mg, Escherichia coli 055:B5) or saline solution infusions into the fetal airways or amniotic fluid.

RESULTS

Lipopolysaccharide induced systemic inflammatory changes in all groups in the blood, lung, liver, and thymic lymphocytes. Changes in lymphocytes in the posterior mediastinal lymph node draining lung and gut, occurred only after direct contact of lipopolysaccharide with the fetal lung or gut.

CONCLUSION

Fetal systemic inflammatory responses occurred after chorioamnion, lung, or gut exposures to lipopolysaccharide. The organ responses differed based on route of the fetal exposure.

IL-8 signaling does not mediate intra-amniotic LPS-induced inflammation and maturation in preterm fetal lamb lung

Preterm infants exposed to chorioamnionitis and preterm sheep fetuses exposed to intra-amniotic (IA) LPS have lung inflammation, increased IL-8 levels, and lung maturation. We tested the hypothesis that IL-8 signaling mediates IA LPS-induced lung inflammation and lung maturation. Two strategies were used: 1) we tested if IA injection of recombinant sheep IL-8 (rsIL-8) induced fetal inflammation and 2) if IL-8 signaling was blocked by a novel CXCR2 receptor blocker, nicotinanilide thioglycolate methyl ester (NTME). To test effects of IL-8 in the fetus, rsIL-8 was given intravascularly (50 microg) at 124 +/- 1 day of gestation (term = 150 days). A separate group of sheep was given IA rsIL-8 (100 microg) and delivered 5 h to 7 days later at 124 +/- 1 day of gestation. After confirming efficacy of the CXCR2 inhibitor, effects of IL-8 blockade were tested by injecting fetal sheep intramuscularly with NTME (10 mg) before IA injection of Escherichia coli LPS (10 mg). Sheep fetuses were delivered 1 or 7 days after injections at 124 +/- 1 day of gestation. IA rsIL-8 induced a modest fivefold increase in bronchoalveolar lavage (BAL) monocytes and neutrophils and increased lung monocyte hydrogen peroxide generation. However, rsIL-8 did not induce lung maturation. Intravascular rsIL-8 did not change fetal cardiovascular variables, blood pH, or blood leukocyte counts. Inhibition of CXCR2 decreased IA LPS-induced increases in BAL proteins at 1 day but not at 7 days. NTME did not significantly decrease IA LPS-induced BAL leukocyte influx and lung cytokine mRNA expression. Inhibition of CXCR2 did not change IA LPS-induced lung maturation. IL-8 signaling does not mediate LPS-induced lung inflammation and lung maturation.

IL-1 mediates pulmonary and systemic inflammatory responses to chorioamnionitis induced by lipopolysaccharide

RATIONALE

Chorioamnionitis frequently associates with preterm delivery and increased amniotic fluid IL-1, and causes fetal lung and systemic inflammation. However, chorioamnionitis is also associated with a paradoxical reduction in the incidence of surfactant deficiency-related respiratory distress syndrome in preterm infants.

OBJECTIVES

To identify the role of IL-1 signaling in the mediation of pulmonary and systemic inflammation and lung maturation in a fetal sheep model of lipopolysaccharide (LPS) induced chorioamnionitis.

METHODS

After confirming the efficacy of recombinant human IL-1 receptor antagonist (rhIL-1ra), fetal sheep were exposed to intraamniotic (IA) injections of Escherichia coli LPS with or without prior IA injections of rhIL-1ra. Preterm lambs were delivered at 82% of term gestation.

MEASUREMENTS AND MAIN RESULTS

rhIL-1ra decreased IA LPS-induced lung inflammation assessed by decreased lung neutrophil and monocyte influx, inducible nitric oxide synthase expression, lung IL-6 and IL-1beta mRNA expression, and airway myeloperoxidase concentrations. rhIL-1ra inhibited IA LPS-induced fetal systemic inflammation assessed by decreased plasma IL-8, protein carbonyls, blood neutrophilia, and the expression of serum amyloid A3 mRNA in the liver. rhIL-1ra also partially blocked the lung maturational effects of IA LPS. Therefore blockade of IL-1 signaling in the amniotic compartment inhibited fetal lung and systemic inflammation and lung maturation in response to LPS-induced chorioamnionitis.

CONCLUSIONS

IL-1 plays a central role in the pathogenesis of chorioamnionitis-induced fetal inflammatory responses.

Prenatal inflammation and lung development

Prenatal exposure of very low birth weight infants to chronic indolent chorioamnionitis with organisms such as mycoplasma and ureaplasma is frequent. Chorioamnionitis is inconsistently associated with changed risks of respiratory distress syndrome (RDS) or bronchopulmonary dysplasia (BPD), probably because the diagnosis of chorioamnionitis does not quantify the extent or duration of the fetal exposures to infection and inflammation. The correlations between prenatal exposures and postnatal lung disease also are confounded by the imprecision of the diagnoses of RDS and BPD. In animal models, chorioamnionitis caused by pro-inflammatory mediators or live ureaplasma induces lung maturation, but also causes alveolar simplification and vascular injury. Intra-amniotic endotoxin administration also modulates the fetal innate immune system, resulting in maturation of monocytes to alveolar macrophages and the induction or paralysis of inflammatory responses depending on exposure history. Prenatal inflammation can have profound effects on the fetal lung and subsequent immune responses.

High and low body temperature during the initiation of ventilation for near-term lambs

AIMS

Recent literature suggests hypothermia may protect against lung injury. We evaluated body temperature as a variable in lung inflammation due to oxygenation and mechanical ventilation following delivery of near-term lambs.

METHODS

Twin fetuses were randomized prior to delivery at 140 d GA (term 150 d): unventilated controls, normothermic ventilated with room air, normothermic ventilated with 100% oxygen, low temperature ventilated (target 35 degrees C) with 100% oxygen, and high temperature (target 40 degrees C) with 100% oxygen. Lambs were intubated for gentle mechanical ventilation (tidal volume 7-8ml/kg). Temperature targeting was with radiant warmers and plastic wrap for normothermia, with heat lamps for hyperthermia, and with ice packs for hypothermia. Lambs were euthanized after 2h mechanical ventilation. Post-mortem, bronchoalveolar lavage fluid and lung tissue samples were evaluated for inflammatory responses by measuring inflammatory cell counts, protein, myeloperoxidase, protein carbonyl, and pro-inflammatory cytokine mRNA.

RESULTS

Target temperatures were achieved by 30min of age and tightly maintained for the 2h study. There were no differences in physiologic variables among groups except those directly resulting from study protocol-PaO2 from air vs. 100% oxygen and body temperature. Indicators of inflammation increased similarly in all ventilated groups compared to unventilated controls.

CONCLUSION

Moderate hyperthermia or hypothermia did not affect lung injury responses to the initiation of ventilation at birth in near-term lambs.

Photogrammetry of fetal breathing movements during the third trimester of pregnancy: observations in normal and abnormal pregnancies

OBJECTIVE

To evaluate parameters of fetal breathing movements-displacement of the fetal abdominal wall during inspiration and expiration, time of inspiration and expiration and speed of inspiration and expiration-between 30 and 36 weeks' gestation in normal pregnancies, and in those complicated by gestational diabetes or maternal hypertension.

METHODS

Three categories of pregnancy were investigated: 49 were normal, 16 had pregnancy-induced diabetes and 10 were hypertensive. According to their gestational age, the patients were divided into two groups: Group A between 30 and 32 weeks' gestation and Group B between 33 and 36 weeks. Using photogrammetry and a computer-operated algorithm, six parameters of fetal breathing movements were investigated.

RESULTS

There were significant differences in the various fetal parameters measured among the three categories of pregnant women. Up until 32 weeks of gestation, the displacements during inspiration and expiration were larger, the speeds of inspiration and expiration were higher, and the times for inspiration and expiration were shorter in the diabetic and hypertensive groups than in the normal group. In the later period, between 33 and 36 weeks, fetuses of pregnancy-induced diabetic patients showed the lowest inspiration and expiration times and the highest speeds of inspiration and expiration.

CONCLUSIONS

Photogrammetry in conjunction with a computer-operated algorithm can be used to assess fetal breathing movements. There are significant differences in fetal breathing movements between normal pregnancies and those that are complicated by gestational diabetes or hypertension.

Antenatal inflammation and lung injury: prenatal origin of neonatal disease

INTRODUCTION

Antenatal inflammation in utero may be associated with lung injury and subsequent aberrant lung development resulting in bronchopulmonary dysplasia (BPD). BPD has become a developmental disease with a uniform arrest in lung development.

STUDY DESIGN

The role of antenatal inflammation in the induction of lung injury was explored in a sheep model suitable for the study of lung development with respect to human development. Chorioamnionitis was induced by a single injection of endotoxin into the amniotic cavity under ultrasound guidance.

RESULT

Endotoxin-induced chorioamnionitis caused a cascade of lung injury, pulmonary inflammation and remodeling in the fetal lung similar to lung injury previously described in adult animal models. The structural changes in the fetal lung after chorioamnionitis showed little to no fibrosis and alveolar/microvascular simplification similar to new BPD. The identified cytokine networks and regulators may explain the absence of fibrosis and lung simplification after strictly intra-uterine inflammation.

CONCLUSION

The mechanisms of antenatal inflammation in the fetal lung were multifactorial and could be antenatally modulated. Fetal pulmonary inflammation was temporarily suppressed by maternal glucocorticoid therapy. However, pulmonary inflammation could be augmented postnatally by resuscitation, oxygen toxicity, mechanical ventilation and pulmonary and systemic infection, which opens a broad window of clinical options.

Toll-like receptors and agonist responses in the developing fetal sheep lung

Toll-like receptors (TLRs) are pattern recognition molecules that initiate innate immune responses. Intra-amniotic exposure of fetal sheep to pro-inflammatory stimuli causes pulmonary inflammation and induced lung maturation. We examined TLR ontogeny and fetal lung responsiveness to three different TLR agonists. We cloned ovine TLRs 2, 3, and 4 and found 83-88% homology between these ovine and human TLRs. Lung TLR2 and 4 mRNAs increased throughout late gestation to 50% of adult level in the term newborn lamb. Doses of 10 mg of PAMCysK4 (TLR2 agonist), poly I:C dsRNA (TLR3 agonist), or E. coli O55:B5 lipopoysaccharide (LPS) (TLR4 agonist) were given by intra-amniotic injection 2 d or 7 d before operative delivery of preterm lambs at 123 d (n = 4-7/group). The TLR4 agonist induced lung inflammation and maturation, whereas the TLR2 agonist gave less consistent responses. Intra-amniotic LPS increased TLR2 mRNA expression primarily in the inflammatory cells and TLR4 mRNA diffusely in multiple cell types. The TLR3 agonist had no effects, and TLR3 mRNA in the fetal lung did not change after LPS exposure. We conclude that TLR2 and TLR4 mRNAs increase through gestation and expression of TLR2 and TLR4 are induced by LPS in the fetal sheep lung.

Intratracheal administration of endotoxin attenuates hyperoxia-induced lung injury in neonatal rats

PURPOSE

This study was undertaken to determine the effects of intratracheal administration of endotoxin on hyperoxia-induced lung injury in neonatal rats.

MATERIALS AND METHODS

Newborn Sprague Dawley rat pups were divided into four experimental groups: normoxia control (NC), normoxia with endotoxin treatment (NE), hyperoxia control (HC), and hyperoxia with endotoxin treatment (HE) groups. In HC and HE, rat pups were subjected to 14 days of hyperoxia (> 95% oxygen) within 12 hours after birth. In endotoxin treated group (NE and HE), Escherichia coli endotoxin (0.5microg in 0.03mL of saline) was given intratracheally at the 1st, 3rd and 5th postnatal day. Radial alveolar count (RAC), mean linear intercept (MLI), RAC/MLI ratios, and degree of fibrosis were measured to assess the changes in lung morphology.

RESULTS

During the research period, survival rates in both HC and HE were notably reduced 7 days after endotoxin was administered, but body weight gain was considerably reduced only in HC. On day 14, significant arrest in alveolarization, as evidenced by the decrease of RAC and RAC/MLI ratio and increase of MLI as well as increased fibrosis, were noted in HC. Although slight but significant arrest in alveolarization and increased fibrosis score were observed in NE compared to NC, the hyperoxia-induced lung damage observed in HC was significantly improved in HE.

CONCLUSION

This study suggests that intratracheal administration of endotoxin significantly attenuated hyperoxia-induced lung injury in neonatal rats.

Foot-and-mouth disease virus infection in fetal lambs: tissue tropism and cytokine response

Foot-and-mouth disease virus (FMDV) can cause transplacental infection and death in fetal lambs. This study investigates the pathogenesis of FMDV infection in ovine fetuses using in-situ hybridization (ISH) to detect viral transcripts in tissue and real-time reverse transcriptase polymerase chain reaction (RT-PCR) assays to quantify the fetal cytokine response to infection. FMDV ribonucleic acid (RNA) was localized mainly to the heart and skeletal muscles of fetuses and was only occasionally expressed in the lingual epithelium, demonstrating that FMDV has a different tissue tropism in the fetus compared with that in adult sheep. There was early expression of genes encoding anti-viral cytokines (IFN-alpha and IFN-beta) in fetuses at 2 and 4 days post-infection (dpi), followed by a marked rise in the transcription of pro-inflammatory cytokine genes (IFN-gamma, TNF-alpha and IL-1alpha) from 7 to 18 dpi, particularly in the heart. The degree of cytokine mRNA expression correlated with fetal infection and was likely to be a factor in fetal death. In contrast, cytokine gene expression in infected neonatal lambs was much less and mainly occurred between 2 and 4 dpi. This study identifies two key factors in the pathogenicity of FMDV in fetal lambs: viral tropism for cardiac and skeletal muscles, and a marked cytokine response following infection.