Lung Fluid Absorption Research Articles

Protocol for a multicenter, double-blind, randomized, placebo-controlled phase III trial of the inhaled β2-adrenergic receptor agonist salbutamol for transient tachypnea of the newborn (the REFSAL trial).

Transient tachypnea of the newborn (TTN), which results from inadequate absorption of fetal lung fluid, is the most common cause of neonatal respiratory distress. Stimulation of β-adrenergic receptors enhances alveolar fluid absorption. Therefore, the β2-adrenergic receptor agonist salbutamol has been proposed as a treatment for TTN. This study aims to evaluate the efficacy and safety of salbutamol as supportive pharmacotherapy together with non-invasive nasal continuous positive airway pressure (NIV/nCPAP) for the prevention of persistent pulmonary hypertension of the newborn (PPHN) in infants with TTN. This multicenter, double-blind, phase III trial will include infants with a gestational age between 32 and 42 weeks who are affected by respiratory disorders and treated in eight neonatal intensive care units in Poland. A total of 608 infants within 24 h after birth will be enrolled and randomly assigned (1:1) to receive nebulized salbutamol with NIV or placebo (nebulized 0.9% NaCl) with NIV. The primary outcome is the percentage of infants with TTN who develop PPHN. The secondary outcomes are the severity of respiratory distress (assessed with the modified TTN Silverman score), frequency of need for intubation, duration of NIV and hospitalization, acid-base balance (blood pH, partial pressure of O2 and CO2, and base excess), and blood serum ionogram for Na+, K+, and Ca2+. The Respiratory Failure with Salbutamol (REFSAL) study will be the first clinical trial to evaluate the efficacy and safety of salbutamol in the prevention of persistent pulmonary hypertension in newborns with tachypnea, and will improve short term outcomes. If successful, the study will demonstrate the feasibility of early intervention with NIV/nCPAP together with nebulized salbutamol in the management of TTN. The study protocol was approved by the Bioethics Committee of the Medical University of Warsaw, Warsaw, Poland on November 16, 2020 (decision number KB/190/2020). All procedures will follow the principles of the Declaration of Helsinki. The results of the study will be submitted for knowledge translation in peer-reviewed journals and presented at national and international pediatric society conferences. It is registered at ClinicalTrials.gov NCT05527704, EudraCT 2020-003913-36; Protocol version 5.0 from 04/01/2022.

Use of lung ultrasound and and aEEG patterns to predict the need for mechanical ventilation and the readiness for extubation in neonates with respiratory distress

Objective. The aim of the study was to establish if lung ultrasound findings could anticipate the need for intubation and mechanical ventilation in neonates with respiratory distress and if lung ultrasound and aEEG criteria could be used in appreciation of the readiness for extubation of the neonatal patients resulting in a decrease of the rate of extubation failure. Material and method. There were analyzed the cases of 50 late preterm and early term neonates presenting with respiratory distress. Lung ultrasound was performed during the first 4 hours after delivery in all the neonates and then as clinically indicated in the case of ventilated patients. A lung ultrasound was performed in all the ventilated patients before extubation. 12 of the 25 ventilated patients were also monitored by aEEG. The decisions regarding the intubation and mechanical ventilation and the moment of extubation of the patients were taken by the clinicians in accordance with the local and international guidelines. The extubation failure was defined as the need to re-intubate the patient in the first 24 hours after the extubation. The lung ultrasound pattern was considered as normal if the image was consisting of A lines with rare B lines or ”double lung point” as in the case of the delayed absorption of fetal lung fluid and abnormal in the case of “white lung” appearance (coalescent B lines) or an image of consolidation. A normal aEEG was defined as the presence of a continuous normal voltage pattern with sleep-wake cycles present and an abnormal aEEG as either discontinuous normal voltage, burst-suppression, low voltage or flat background patterns. The lung ultrasound patterns in the first hours of life were compared between patients that needed intubation and those that did not need mechanical ventilation. The lung ultrasound and aEEG patterns before extubation were compared between the patients that did not need re-intubation and those with extubation failure. Results. An abnormal image on lung ultrasound was significantly associated with the risk of intubation (p < 0.001) (sensitivity 84%, specificity 100%, positive predictive value 100% and negative predictive value 86.2%) An abnormal lung ultrasound pattern before extubation was associated with a significant risk of extubation failure (p < 0.049) (sensitivity 75%, specificity 85%, positive predictive value 50%, negative predictive value 94.7%). In the case of the subset of patients in which aEEG was performed, an abnormal aEEG pattern was significantly associated with extubation failure (p < 0.034) (sensitivity 100%, specificity 88%, positive predictive value 75%, negative predictive value 100%). In the case of association of the two parameters (lung ultrasound and aEEG pattern) there was again a statistically significant association between the abnormal patterns and extubation failure. Conclusions. An abnormal lung ultrasound during the first hours of life is a strong predictor for the need of intubation and mechanical ventilation in the neonates with respiratory distress. The normal lung ultrasound pattern just before extubation is predictive of a good evolution without the need for re-intubation of the patient. A normal aEEG pattern at the same time is associated also with a decreased risk of extubation failure.

Conditioned Medium of Bone Marrow Mesenchymal Stem Cells Involved in Acute Lung Injury by Regulating Epithelial Sodium Channels via miR-34c

BackgroundOne of the characteristics of acute lung injury (ALI) is severe pulmonary edema, which is closely related to alveolar fluid clearance (AFC). Mesenchymal stem cells (MSCs) secrete a wide range of cytokines, growth factors, and microRNA (miRNAs) through paracrine action to participate in the mechanism of pulmonary inflammatory response, which increase the clearance of edema fluid and promote the repair process of ALI. The epithelial sodium channel (ENaC) is the rate-limiting step in the sodium–water transport and edema clearance in the alveolar cavity; the role of bone marrow-derived MSC-conditioned medium (BMSC-CM) in edema clearance and how miRNAs affect ENaC are still seldom known.MethodsCCK-8 cell proliferation assay was used to detect the effect of BMSC-CM on the survival of alveolar type 2 epithelial (AT2) cells. Real-time polymerase chain reaction (RT-PCR) and western blot were used to detect the expression of ENaC in AT2 cells. The effects of miR-34c on lung fluid absorption were observed in LPS-treated mice in vivo, and the transepithelial short-circuit currents in the monolayer of H441 cells were examined by the Ussing chamber setup. Dual luciferase reporter gene assay was used to detect the target gene of miR-34c.ResultsBMSC-CM could increase the viability of mouse AT2 cells. RT-PCR and western blot results showed that BMSC-CM significantly increased the expression of the γ-ENaC subunit in mouse AT2 cells. MiR-34c could restore the AFC and lung wet/dry weight ratio in the ALI animal model, and Ussing chamber assay revealed that miR-34c enhanced the amiloride-sensitive currents associated with ENaC activity in intact H441 cell monolayers. In addition, we observed a higher expression of miR-34c in mouse AT2 cells administrated with BMSC-CM, and the overexpression or inhibition of miR-34c could regulate the expression of ENaC protein and alter the function of ENaC. Finally, we detected that myristoylated alanine-rich C kinase substrate (MARCKS) may be one of the target genes of miR-34c.ConclusionOur results indicate that BMSC-CM may alleviate LPS-induced ALI through miR-34c targeting MARCKS and regulate ENaC indirectly, which further explores the benefit of paracrine effects of bone marrow-derived MSCs on edematous ALI.

Influence of Alveolar Fluid on Aquaporins and Na+/K+-ATPase and Its Possible Theoretical or Clinical Significance.

Pulmonary edema is the most common pathophysiological change in pulmonary disease. Aquaporins (AQPs) and Na+/K+-ATPase play pivotal roles in alveolar fluid clearance. This study aimed to explore the influence of increased alveolar fluid on the absorption of lung fluid. Eighty New Zealand rabbits were randomly divided into eight groups (n = 10 in each group), and models of different alveolar fluid contents were established by the infusion of different volumes of normal saline (NS) via the endotracheal tube. Five animals in each group were sacrificed immediately after infusion to determine the wet/dry ratio, while the remaining animals in each group were killed 4 hours later to determine the wet/dry ratio at 4 hours. Additionally, lung specimens were collected from each group, and quantitative real-time PCR (qRT-PCR), western blot, and immunohistochemical (IHC) analyses of AQPs and Na+/K+-ATPase were performed. The qRT-PCR analysis and western blot studies showed markedly decreased mRNA and protein levels of AQP1 and Na+/K+-ATPase when the alveolar fluid volume was ≥6 mL/kg, and the mRNA level of AQP5 was significantly reduced when the alveolar fluid volume was ≥4 mL/kg. In addition, IHC analysis showed the same results. At 4 hours, the lung wet/dry ratio was significantly increased when the alveolar fluid volume was ≥6 mL/kg; however, compared with 0 hours after NS infusion, there was still a significant absorption of alveolar fluid for a period of 4 hours. The results of this study suggest that increased alveolar fluid may induce the downregulation of the mRNA and protein expression of AQPs and Na+/K+-ATPase, which appear to affect alveolar fluid clearance in rabbit lungs. Early intervention is required to avoid excessive alveolar fluid accumulation. · The expression levels of AQPs and Na+/K+--ATPase were significantly decreased as alveolar fluid increased.. · At 4 hours, wet/dry ratio was significantly increased when infusion volume was ≥ 6 mL/kg.. · Early intervention is required to avoid excessive alveolar fluid accumulation..

The effect of inhaled salbutamol on the outcomes of transient tachypnea of the newborn

BackgroundTransient tachypnea of the newborn (TTN) is a self-limiting disease that results from a reduction in the rate of lung fluid clearance in neonates. A delay in lung fluid absorption in neonates disrupts the transition from intrauterine to extrauterine life. Use of beta-adrenergic antagonists, such as salbutamol, accelerates lung fluid clearance. The current study aimed to evaluate the effect of inhaled salbutamol on the clinical progression of TTN treatment. MethodsIn the current triple-blind clinical trial, a total of 148 inpatients diagnosed with TTN were randomly divided into 2 groups. The treatment group (n = 74) received inhaled salbutamol and the placebo group (n = 74) received inhaled normal saline. The drug administration was started 6 h after birth and continued in the case of continued respiratory distress and the need for oxygen as adjuvant therapy for up to 72 h maximum after the initiation of treatment. To evaluate the response to treatment with inhaled salbutamol, we assessed the respiratory rate (RR), heart rate (HR), fraction of inspired oxygen (FIO2) level, and O2 saturation at intervals of 30 min as well as 1 h and 4 h after drug administration. The results were compared between the groups. ResultsThe results of the current study indicated a significant difference between the treatment and placebo groups in the treatment duration, hospitalization duration, need for continuous positive airway pressure therapy (CPAP), and time of oral feeding initiation. In addition, no complication was observed during the treatment. It is noteworthy that, following the improvement of disease symptoms and reduction of hospitalization. This reduction may decrease the treatment costs and anxiety of parents, which was associated with proper mental and economic outcomes. ConclusionAlthough, in the current study, drug administration was continued for 72 h maximum, the prescription of at most 4 doses of salbutamol may have had maximum efficiency in the remediation process. To evaluate the therapeutic role of inhaled salbutamol, further studies are recommended.

The rate of neonatal respiratory distress syndrome/transient tachypnea in the newborn and the amniotic lamellar body count in twin pregnancies compared with singleton pregnancies

BackgroundWhether or not the period of fetal lung maturity differs between twin and singleton pregnancies has not been clarified. We examined whether or not fetal lung maturity and fetal lung absorption are achieved earlier in twin fetuses than in singleton fetuses. MethodsWe registered 454 singleton pregnancies and 398 twin pregnancies with no congenital abnormalities affecting the respiratory function or neonatal deaths. All patients were delivered by Caesarean section without labor between 24 and 38 gestational weeks. The amniotic fluid samples were analyzed immediately without centrifugation. A multiple logistic regression analysis was performed to explore the relationship between twin pregnancy and neonatal respiratory distress syndrome and transient tachypnea of the newborn (RDS/TTN). ResultsThe rate of RDS/TTN in infants was significantly higher and the lamellar body counts (LBCs) significantly lower in singleton pregnancies than that in twin pregnancies (P < .001). According to a multivariate logistic regression analysis, twin pregnancy (odds ratio, 0.34; 95% confidence interval, 0.22–0.55) was a significant preventive factor for neonatal RDS/TTN. ConclusionsWe showed that twin fetuses experience more rapid lung maturation and lung fluid absorption than singleton fetuses, as confirmed by the higher LBC values in twin fetuses.

Application of sustained lung inflations for neonatal resuscitation

Application of sustained lung inflation(SLI)during neonatal resuscitation can increase alveolar opening, promote lung fluid absorption and maintain the appropriate functional residual capacity (FRC) which can complete the transition from fetal phase of respiratory system to neonatal period.In recent years, SLI has also been confirmed by a large number of animal experiments and clinical studies, and it is expected to be practically applied in the resuscitation of newborns.However, more randomized controlled trials with a large number of samples is required for exploring suitable populations, methods of operation, and recent or long-term effects on newborns.Now, the application and research of SLI in neonatal resuscitation are described. Key words: Sustained lung inflation; Neonatal resuscitation; Infant, newborn; Infant, premature

Effectiveness of intratracheal salbutamol in addition to surfactant on the clinical course of newborns with respiratory distress syndrome: a clinical trial.

BackgroundIn addition to surfactant deficiency, increase of lung fluid content and secretion of fluid derived from the blood participate in the pathogenesis of RDS in newborns.We hypothesized that the administration of salbutamol (β-agonist) to increase lung fluid absorption would decrease the INSURE failure rate in newborns with respiratory distress syndrome (RDS) treated with intratracheal surfactant.MethodsDesignBlinded, randomized clinical trial study.Setting/populationLevel III NICU, premature infants with RDS requiring intratracheal Surfactant.Forty Eight newborns with RDS treated with intratracheal Surfactant were randomized into two groups as Group A, Normal saline (as control group) and Group B (intervention group), Salbutamol were administered intratracheally in addition to Surfactant. Intubation-Surfactant administration- Rapid Extubation (INSURE) failure rate as primary outcome and secondary outcome as follow: duration of the need to NCPAP, mechanical ventilation and oxygen therapy; complications (patent ductus arteriosus, pneumothorax); mortality (respiratory or prematurity related complication) and the duration of hospitalization were assessed.ResultsTwenty Four patients in each group were studied. INSURE failure was seen in16 (66.7 %) and 10 (41.7 %) of normal saline and salbutamol groups respectively (p = 0.082). The duration of NCPAP in control group was 69.5 ± 54.9 h while in Salbutamol group was 51.6 ± 48.7 h (p = 0.316). All of deaths were related to respiratory failure. No differences in mortality or complications of RDS were observed. The duration of hospitalization was longer in control group than interventional group, 28.3 ± 18.1 and 18.6 ± 8.6 days, respectively. (p = 0.047).ConclusionSalbutamol may improve the clinical course of newborns with RDS requiring Surfactant.Trial registration numberIRCT2014072714215N1

Association of SCNN1A Single Nucleotide Polymorphisms with neonatal respiratory distress syndrome.

Increasing evidence has demonstrated that lung fluid absorption disorders might be an important cause of neonatal respiratory distress syndrome (RDS) by influencing gas exchange or surfactant function. The SCNN1A gene, which encodes the α-ENaC, might predispose infants to RDS. To explore whether the single-nucleotide polymorphisms (SNPs) of SCNN1A are associated with RDS, we conducted a case-control study to investigate the RDS-associated loci in Han Chinese infants. Seven target SNPs were selected from the SCNN1A gene and were genotyped using the improved multiplex ligase detection reaction (iMLDR). In the total sample, only rs4149570 was associated with NRDS; this association was further confirmed in logistic regression analysis after adjusting for birth weight, gestational age and sex. In the subgroup of infants whose gestational age was 37 weeks and older, in addition to rs4149570, rs7956915 also showed a significant association with RDS. Interestingly, these associations were only observed in term infants. No significant association was observed between the target SNPs and the risk of RDS in preterm infants. We report for the first time that the rs4149570 and rs7956915 polymorphisms of SCNN1A might play important roles in the susceptibility to RDS, particularly in term infants.

The Effects of Inhaled Albuterol in Transient Tachypnea of the Newborn

PurposeTransient tachypnea of the newborn (TTN) is a disorder caused by the delayed clearance of fetal alveolar fluid. β-adrenergic agonists such as albuterol (salbutamol) are known to catalyze lung fluid absorption. This study examined whether inhalational salbutamol therapy could improve clinical symptoms in TTN. Additional endpoints included the diagnostic and therapeutic efficacy of salbutamol as well as its overall safety.MethodsFrom January 2010 through December 2010, we conducted a prospective study of 40 newborns hospitalized with TTN in the neonatal intensive care unit. Patients were given either inhalational salbutamol (28 patients) or placebo (12 patients), and clinical indices were compared.ResultsThe duration of tachypnea was shorter in patients receiving inhalational salbutamol therapy, although this difference was not statistically significant. The duration of supplemental oxygen therapy and the duration of empiric antibiotic treatment were significantly shorter in the salbutamol-treated group. No adverse effects were observed in either treatment group.ConclusionsInhalational salbutamol therapy reduced the duration of supplemental oxygen therapy and the duration of empiric antibiotic treatment, with no adverse effects. However, the time between salbutamol therapy and clinical improvement was too long to allow definitive conclusions to be drawn. Further studies examining a larger number of patients with strict control over dosage and frequency of salbutamol inhalations are necessary to better direct the treatment of TTN.

Mechanism and regulation of alveolar fluid transport in neonates

Alveolar fluid transport is closely associated with neonatal lung development neonatal respiratory diseases,such as wet lung,pulmonary hyaline membrane disease,pneumonia,which are related with decreased lung fluid transport.This review introduces the characteristics of neonatal pulmonary fluid balance,including lung fluid secretion and absorption equilibrium,list clinical factors which can increase pulmonary fluid,explain important lung fluid transport mechanisms and their regulations.Inhaling beta agonists or glucocorticoid is a viable therapeutic strategy. Key words: Alveolar fluid transport; Newborn infants; Mechanism and regulation

AR Highlights

The editorial office of The Anatomical Record is pleased to launch AR Highlights as new content. The purpose of AR Highlights is to draw attention to papers that are published in recent issues of the Journal. AR Highlights are written by the Journal's Science Writer, Ellen Jensen Serotonin (5-HT) has many important functions during development. Therefore, it is speculated that there is a link between 5-HT and dysfunction and neurological developmental disorders, such as autism. The mouse has proven to be a useful genetic model for the developmental role of 5-HT. Early genetic models showed that increasing amounts of 5-HT during development modulate neural circuits and affect subsequent adult behavior. However, there is conflicting evidence in recent genetic models with decreased 5-HT levels in the brain, where the brain develops normally. In this article, the authors review the existing literature on genetic hyposerotonergic models. They discuss the main strategies that have been used to obtain mice with low 5-HT levels and summarize the neurological and behavioral changes that have been observed in these models. While these models appear to have normal brain development as mentioned above, there are problems with somatic growth and physiological functions. Abnormal adult behavior is also observed. The varied sources of 5-HT during development comprise a complex system with many different serotonin receptor subtypes in which small changes in the method of 5-HT depletion or in the timing of the depletion can result in very different phenotypes. These mice models could provide important insights into the mechanisms underlying various human mental disorders, which appear in adults but are believed to originate from developmental abnormalities. The authors also discuss the need to better characterize the behavioral phenotype of hyposerotonergic mice as well as determine how the effects of developmental depletion of 5-HT relate to effects of functional 5-HT deficiency during adult life. Autism is a neurodevelopmental disorder that is characterized by impaired social interaction and communication and repetitive behavior. It is a debilitating disease with no known cure. Recent findings in autism have investigated abnormality of GABAergic neurotransmission. Since previous reports have shown the presence of autistic behavior in patients with Fragile X syndrome, and that lower levels of Fragile X mental retardation protein (FMRP) expression may cause autistic behavior, the authors decided to investigate whether FMRP levels could be lower in children and adults with autism and aimed to relate FMRP levels to GABAA receptor underexpression. Indeed, the authors found reduced FMRP levels and GABAA receptor beta 3 protein in the vermis of adults with autism. This reduction in FMRP is intriguing since none of the subjects used in their study were diagnosed with Fragile X syndrome. Another important, novel finding is that metabotropic glutamate receptor 5 (involved in a number of important functions both during brain development and in adult life) protein levels were increased in the vermis of children with autism. The results of this study provide further insight into the mechanisms of autism and provide several promising avenues of possible future treatments for autism. At the end of gestation, the direction of ion and fluid flow across the lung rapidly changes from secretion to absorption. In the lungs, Na generates the driving force for fluid absorption. Na transport by epithelial Na channels (ENaCs) requires Cl transport (i.e., the cystic fibrosis transmembrane regulator [CFTR]). The authors investigated the cellular location of Na and Cl channels during fetal lung development and after interleukin (IL)-1β (stimulates lung maturation) pretreatment in guinea pigs. Their results indicate that IL-1β may activate ENaC, which in turn leads to induced distal lung fluid absorption in fetal lungs. This suggests that the appearance of ENaC in alveolar epithelial type I cells may be responsible, in part, for the conversion of the alveolar epithelium from distal lung fluid secretion to fluid absorption. The presence of ENaC at the cell membrane is essential for removal of fetal lung fluid at birth. Additionally, the authors found that increased gestational age was associated with a relocation of ENaC subunits and CFTR Cl channels, resulting in a more mature lung. This concept provides a novel molecular model for the rapid transition from distal lung fluid secretion in fetal lungs to absorption in near-term and newborn lungs. Ultimately, the authors' findings could lead to a better understanding of the molecular mechanisms at the membrane level responsible for the very rapid transition from a fluid-secreting lung to a fluid absorbing lung at birth, and assist in development of new drugs for treatment of preterm babies suffering from respiratory distress syndrome.

Fetal Lung Epithelial Ion Channels Relocate in the Cell Membrane During Late Gestation

Near the end of gestation, the direction of ion and fluid flow across the alveolar epithelium rapidly changes from secretion to absorption. Thus, the relative cell membrane location of epithelial Na channels (ENaCs) and cystic fibrosis transmembrane regulator (CFTR) Cl channels during late fetal lung development and after maternal interleukin-1β (IL-1β) pretreatment was the focus of our study. Western blot analysis after sucrose gradient separation of caveolin-1-(Cav-1)-rich membrane regions (CRR) and Cav-1-poor membrane (non-CRR) revealed primary CRR ENaC localization at gestation day (GD) 61 in guinea pigs. Correlating with the natural induction of distal lung fluid absorption, ENaC appeared in the non-CRR cell membrane regions at GD68. Conversely, CFTR was present in the non-CRR cell membrane regions at GD61 and in the CRRs at GD68. IL-1β-induced conversion to distal lung fluid absorption at GD61 was associated with ENaC non-CRR presence and CFTR CRR presence, suggesting that relative ENaC and CFTR locations induced distal lung fluid absorption and decreased fluid secretion. Instilling fetal lungs with the CRR-disrupting agent methyl-β-cyclodextrin resulted in the conversion from lung fluid secretion to absorption and ENaC non-CRR presence at GD61. Coimmunoprecipitation of Cav-1 with α- and β-ENaC demonstrated reduced coimmunoprecipitation with increased GD and after IL-1β pretreatment. On the other hand, coimmunoprecipitation of Cav-1 with CFTR demonstrated increased coimmunoprecipitation with increasing GD and after IL-1β pretreatment. This concept may provide novel molecular mechanisms for the rapid transition from fetal distal lung fluid secretion to absorption in near-term lungs.

Newborn Respiratory Disorders

Newborn Respiratory Disorders

Lung fluid absorption is induced in preterm guinea pigs ventilated with low tidal volumes

ABSTRACTThe objective of this study was to determine if low tidal volume (Vt) ventilation was beneficial when ventilating preterm fetuses. The authors ventilated preterm guinea pig fetuses at gestation day (GD) 67, 3 days before birth, newborn, and 10-day-old (PD10) guinea pigs with low Vt (6 mL/kg body weight [bw]) and compared them to age-matched fetuses/animals ventilated with higher potentially injurious Vt (12 mL/kg bw). Lung fluid absorption was measured after intratracheal instillation of 5% albumin in 0.9% NaCl. Low Vt ventilation stimulated lung fluid absorption when compared to higher Vt in all groups. The increased lung fluid absorption in low Vt–ventilated fetuses was associated with increased α epithelial Na channel (αEnaC) mRNA. However, αENaC and βENaC protein was unchanged over the 1-hour study. Because stretch induces mitogen-activated protein (MAP) kinase expression and MAP kinases may affect lung fluid absorption, the authors investigated if MAP kinase (MAPK) expression was affected by Vt. Extracellular signal-regulated kinase (ERK) and MAPK/ERK kinase (MEK) were phosphorylated in the higher Vt–ventilated guinea pig fetuses. This suggested that a reduced activation of MAP kinases might explain the increased lung fluid absorption in the low Vt–ventilated fetuses. Thus these data suggest that low Vt ventilation increases fetal lung fluid absorption and thus may be preferential to use clinically.

Low Pulmonary Expression of Epithelial Na+ Channel and Na+, K+-ATPase in Newborn Infants with Congenital Diaphragmatic Hernia

Background: It has been suggested from several animal studies and clinical observations that congenital diaphragmatic hernia (CDH) with pulmonary hypoplasia is accompanied by a disturbed perinatal ion transport. This could lead to respiratory distress due to slower clearance of fetal lung fluid at birth. Objectives: The purpose of this study was to determine whether CDH is related to changes in the expression of three rate-limiting transporter proteins in lung epithelium at birth. Methods: Tracheal aspirate was collected from 12 newborn infants with CDH and from 8 newborn control patients. Sampling was performed at postnatal age 18 and at 43 h in the CDH group and at 18 h in the control group. The protein abundance of α-, β- and γ-epithelial Na⁺ channel (ENaC), aquaporin 5 and Na⁺, K⁺-ATPase α₁ was analyzed using semiquantitative immunoblotting. Results: The levels of β-ENaC, γ-ENaC and Na⁺, K⁺-ATPase α₁ collected at 18 h postnatally were significantly lower in CDH infants compared to control infants. In the CDH group, no significant difference in the expression of the ENaC subunits, Na⁺, K⁺-ATPase α₁ or aquaporin 5 could be detected between the two sampling time points. Conclusions: This downregulation may result in an abnormal lung fluid absorption which could be an important mechanism behind the respiratory distress seen in newborn CDH patients.

Correlation between SCNN1A gene polymorphism and the NRDS, and screening of its TagSNPs

Background: In near term/term infants with NRDS demonstrate poor efficacy of exogenous PS. Their respiratory distress may be different in pathogenesis from preterm infants-RDS. Studies have reported that barrier to lung fluid absorption in the near term/full-term infants plays an important role in the pathogenesis of NRDS. The electrolyte transport of alveolar epithelial cells through by epithelial sodium channel (a-ENaC) is the key step in epithelial lung fluid of transit. Now research shows that genetic polymorphisms between individuals contribute to the number and activity of a-ENaC. Methods: Our research will use the methods of combination by HapMap database and the haplotype, analysis all SNPs of SCNN1A which encoding a-ENaC, and selected the tagging SNPs which are closely related to RDS incidence of near-term/full-term infants. And analysis functional significance of SNPs based on the use of ELISA, qPCR, reporter gene. Study Goal: In order to provide new explanations for the pathogenesis of near term/term infants' RDS from a genetic point of view, the theoretical foundation of molecular genetics for revealling the specific mechanisms of lung fluid absorption that could lead NRDS need to be elucidated, and new markers for early warning in NRDS clinical screening need to be found.

TNF‐alpha inhibits alpha‐ENaC2 expression through oxidative stress pathway in lung epithelial cells

The α‐subunit of the epithelial sodium channel ENaC plays an important role in lung fluid absorption. In human lungs, α‐ENaC is expressed as several splice variants. The α2‐ENaC is one of the major variants and possesses channel function. Previous studies show that α1‐ENaC expression is suppressed by TNF‐α but it was unclear whether α2‐ENaC variants in human cells are similarly affected. In this study, we aim to investigate TNF‐α inhibits α2‐ENaC expression via increased reactive oxygen species. We found that TNF‐α reduces α2‐ENaC expression and antioxidants attenuate this inhibition. Our results demonstrate that 1. TNF‐α inhibits ENaC1 and ENaC2 mRNA expression and promoter activity; 2. H2O2 inhibits ENaC1 and ENaC2 mRNA expression and promoter activity; 3. Antioxidant inhibits TNF‐α suppressed ENaC2 mRNA expression but not ENaC1; 4. TNF‐α receptor‐binding domain but not lectin‐like domain mediates the inhibition of α2‐ENaC expression. These data suggest that TNF‐α suppresses α2‐ENaC expression in human lung epithelial cells through the inhibition of its core promoter, and this inhibition is dependent on TNF‐α mediated oxidative stress. This work was supported by a grant from the Department of Veterans Affairs.

IL-1β-induced cortisol stimulates lung fluid absorption in fetal guinea pigs via SGK-mediated Nedd4-2 inhibition

We tested the hypothesis that interleukin (IL)-1beta-induced cortisol synthesis stimulates distal lung fluid absorption in fetal guinea pigs via induction of serum- and glucocorticoid-regulated kinase (SGK) and inhibition of neural precursor cell expressed, developmentally downregulated protein 4-2 (Nedd4-2). IL-1beta was subcutaneously administered daily to timed-pregnant guinea pigs over 3 days. Fetuses were obtained by abdominal hysterotomy at gestation day (GD)61 and GD68 and instilled with an isosmolar 5% albumin solution into the lungs. Distal lung fluid movement was measured over 1 h from the change in distal air space protein concentration. Fetal lungs were secreting lung fluid at GD61 while absorbing lung fluid at GD68. Distal lung fluid absorption was induced at GD61 by IL-1beta but unaffected at GD68. Plasma cortisol concentrations were increased by IL-1beta at GD61 and endogenously at GD68. Distal lung fluid absorption was measured and correlated to SGK and Nedd4-2 expression and to alpha-epithelial Na channel (ENaC) expression. SGK was increased by IL-1beta and late during gestation (GD68), while Nedd4-2 was decreased by IL-1beta and late during gestation. alpha-ENaC was induced by IL-1beta at GD61 and increased late during gestation. Thus our study suggests that cortisol-stimulated fetal lung fluid absorption is mediated by increased ENaC expression and may be governed by the SGK/Nedd4-2 pathway. These observations may explain why babies delivered preterm after intrauterine inflammation have a reduced risk of developing severe respiratory distress.

RNA interference for CFTR attenuates lung fluid absorption at birth in rats

BackgroundSmall interfering RNA (siRNA) against αENaC (α-subunit of the epithelial Na channel) and CFTR (cystic fibrosis transmembrane conductance regulator) was used to explore ENaC and CTFR function in newborn rat lungs.MethodsTwenty-four hours after trans-thoracic intrapulmonary (ttip) injection of siRNA-generating plasmid DNA (pSi-0, pSi-4, or pSi-C2), we measured CFTR and ENaC expression, extravascular lung water, and mortality.ResultsαENaC and CFTR mRNA and protein decreased by ~80% and ~85%, respectively, following αENaC and CFTR silencing. Extravascular lung water and mortality increased after αENaC and CFTR-silencing. In pSi-C2-transfected isolated DLE cells there were attenuated CFTR mRNA and protein. In pSi-4-transfected DLE cells αENaC mRNA and protein were both reduced. Interestingly, CFTR-silencing also reduced αENaC mRNA and protein. αENaC silencing, on the other hand, only slightly reduced CFTR mRNA and protein.ConclusionThus, ENaC and CFTR are both involved in the fluid secretion to absorption conversion around at birth.