Endothelial LAT1 (SLC7A5) Mediates S-Nitrosothiol Import and Modulates Respiratory Sequelae of Red Blood Cell Transfusion In Vivo.

BACKGROUND: Increased adhesivity of red blood cells (RBCs) to endothelial cells (ECs) may contribute to organ dysfunction in malaria, sickle cell disease, and diabetes. RBCs normally export nitric oxide (NO)-derived vascular signals, facilitating blood flow. S-nitrosothiols (SNOs) are thiol adducts formed in RBCs from precursor NO upon the oxygenation-linked allosteric transition in hemoglobin. RBCs export these vasoregulatory SNOs on demand, thereby regulating regional blood flow and preventing RBC-EC adhesion, and the large (system L) neutral amino acid transporter 1 (LAT1; SLC7A5) appears to mediate SNO export by RBCs. METHODS: To determine the role of LAT1-mediated SNO import by ECs generally and of LAT1-mediated SNO import by ECs in RBC SNO-dependent modulation of RBC sequestration and blood oxygenation in vivo, we engineered LAT1fl/fl; Cdh5-Cre+ mice, in which the putative SNO transporter LAT1 can be inducibly depleted (knocked down, KD) specifically in ECs ("LAT1ECKD"). RESULTS: We show that LAT1 in mouse lung ECs mediates cellular SNO uptake. ECs from LAT1ECKD mice (tamoxifen-induced LAT1fl/fl; Cdh5-Cre+) import SNOs poorly ex vivo compared with ECs from wild-type (tamoxifen-treated LAT1fl/fl; Cdh5-Cre-) mice. In vivo, endothelial depletion of LAT1 increased RBC sequestration in the lung and decreased blood oxygenation after RBC transfusion. CONCLUSION: This is the first study showing a role for SNO transport by LAT1 in ECs in a genetic mouse model. We provide the first direct evidence for the coordination of RBC SNO export with EC SNO import via LAT1. SNO flux via LAT1 modulates RBC-EC sequestration in lungs after transfusion, and its disruption impairs blood oxygenation by the lung.

2022 Year in review: Neonatal pulmonology.

This review outlines some of the major contributions to Neonatal Pulmonology published in 2022 in Pediatric Pulmonology in the areas of lung ultrasound, prevention and treatment of bronchopulmonary dysplasia, and pulmonary function outcomes of neonatal lung disease.

2020 year in review: Neonatal pulmonology.

Pediatric Pulmonology publishes original research, reviews, and case reports related to a wide range of children's respiratory disorders. This review summarizes the past year's publications in the topic area of neonatal pulmonology, in the context of selected literature from other journals relevant to the discipline.

Retraction Note: Intra-amniotic LPS amplifies hyperoxia-induced airway hyperreactivity in neonatal rats.

This paper has been retracted at the request of the authors.

2018 year in review: Part 2 of 4: Neonatal lung disease.

Pediatric Pulmonology publishes original research, reviews and case reports related to a wide range of children's respiratory disorders. This review (Part 2 of a 4-part series) summarizes the past year's publications in the topic area of neonatal lung diseases, in the context of selected literature from other journals relevant to the discipline.

2017 pediatric pulmonology year in review part 2-neonatology.

The articles published in 2017 in topic areas relevant to neonatal pulmonology are reviewed in Part 2 of the Year-in-Review.

Gestational Exposure to Air Pollution Alters Cortical Volume, Microglial Morphology, and Microglia-Neuron Interactions in a Sex-Specific Manner.

Microglia are the resident immune cells of the brain, important for normal neural development in addition to host defense in response to inflammatory stimuli. Air pollution is one of the most pervasive and harmful environmental toxicants in the modern world, and several large scale epidemiological studies have recently linked prenatal air pollution exposure with an increased risk of neurodevelopmental disorders such as autism spectrum disorder (ASD). Diesel exhaust particles (DEP) are a primary toxic component of air pollution, and markedly activate microglia in vitro and in vivo in adult rodents. We have demonstrated that prenatal exposure to DEP in mice, i.e., to the pregnant dams throughout gestation, results in a persistent vulnerability to behavioral deficits in adult offspring, especially in males, which is intriguing given the greater incidence of ASD in males to females (∼4:1). Moreover, there is a striking upregulation of toll-like receptor (TLR) 4 gene expression within the brains of the same mice, and this expression is primarily in microglia. Here we explored the impact of gestational exposure to DEP or vehicle on microglial morphology in the developing brains of male and female mice. DEP exposure increased inflammatory cytokine protein and altered the morphology of microglia, consistent with activation or a delay in maturation, only within the embryonic brains of male mice; and these effects were dependent on TLR4. DEP exposure also increased cortical volume at embryonic day (E)18, which switched to decreased volume by post-natal day (P)30 in males, suggesting an impact on the developing neural stem cell niche. Consistent with this hypothesis, we found increased microglial-neuronal interactions in male offspring that received DEP compared to all other groups. Taken together, these data suggest a mechanism by which prenatal exposure to environmental toxins may affect microglial development and long-term function, and thereby contribute to the risk of neurodevelopmental disorders.

Intermittent hypoxia during recovery from neonatal hyperoxic lung injury causes long-term impairment of alveolar development: A new rat model of BPD.

Bronchopulmonary dysplasia (BPD) is a chronic lung injury characterized by impaired alveologenesis that may persist into adulthood. Rat models of BPD using varying degrees of hyperoxia to produce injury either cause early mortality or spontaneously recover following removal of the inciting stimulus, thus limiting clinical relevance. We sought to refine an established rat model induced by exposure to 60% O2 from birth by following hyperoxia with intermittent hypoxia (IH). Rats exposed from birth to air or 60% O2 until day 14 were recovered in air with or without IH (FIO2 = 0.10 for 10 min every 6 h) until day 28 Animals exposed to 60% O2 and recovered in air had no evidence of abnormal lung morphology on day 28 or at 10-12 wk. In contrast, 60% O2-exposed animals recovered in IH had persistently increased mean chord length, more dysmorphic septal crests, and fewer peripheral arteries. Recovery in IH also increased pulmonary vascular resistance, Fulton index, and arterial wall thickness. IH-mediated abnormalities in lung structure (but not pulmonary hypertension) persisted when reexamined at 10-12 wk, accompanied by increased pulmonary vascular reactivity and decreased exercise tolerance. Increased mean chord length secondary to IH was prevented by treatment with a peroxynitrite decomposition catalyst [5,10,15,20-Tetrakis(4-sulfonatophenyl)-21H,23H-porphyrin iron (III) chloride, 30 mg/kg/day, days 14-28], an effect accompanied by fewer inflammatory cells. We conclude that IH during recovery from hyperoxia-induced injury prevents recovery of alveologenesis and leads to changes in lung and pulmonary vascular function lasting into adulthood, thus more closely mimicking contemporary BPD.

Early-Life Intranasal Colonization with Nontypeable Haemophilus influenzae Exacerbates Juvenile Airway Disease in Mice.

Accumulating evidence suggests a connection between asthma development and colonization with nontypeable Haemophilus influenzae (NTHi). Specifically, nasopharyngeal colonization of human infants with NTHi within 4 weeks of birth is associated with an increased risk of asthma development later in childhood. Monocytes derived from these infants have aberrant inflammatory responses to common upper respiratory bacterial antigens compared to those of cells derived from infants who were not colonized and do not go on to develop asthma symptoms in childhood. In this study, we hypothesized that early-life colonization with NTHi promotes immune system reprogramming and the development of atypical inflammatory responses. To address this hypothesis in a highly controlled model, we tested whether colonization of mice with NTHi on day of life 3 induced or exacerbated juvenile airway disease using an ovalbumin (OVA) allergy model of asthma. We found that animals that were colonized on day of life 3 and subjected to induction of allergy had exacerbated airway disease as juveniles, in which exacerbated airway disease was defined as increased cellular infiltration into the lung, increased amounts of inflammatory cytokines interleukin-5 (IL-5) and IL-13 in lung lavage fluid, decreased regulatory T cell-associated FOXP3 gene expression, and increased mucus production. We also found that colonization with NTHi amplified airway resistance in response to increasing doses of a bronchoconstrictor following OVA immunization and challenge. Together, the murine model provides evidence for early-life immune programming that precedes the development of juvenile airway disease and corroborates observations that have been made in human children.

Bronchopulmonary dysplasia impairs L-type amino acid transporter-1 expression in human and baboon lung.

Bronchopulmonary dysplasia (BPD) is an inflammatory lung disorder common in premature infants who undergo mechanical ventilation with supplemental oxygen. Inhaled nitric oxide (iNO) has been used to prevent experimental and clinical BPD. Earlier studies showed that NO effects in alveolar epithelial cells (AEC) are mediated by S-nitrosothiol uptake via L-type amino acid transporter-1 (LAT1). Because LAT1 expression could influence the efficacy of iNO therapy, we sought to determine whether pulmonary LAT1 expression is altered in preterm baboons with experimental BPD and in human newborns susceptible to developing BPD. Using fixed lung obtained from 125 d to 140 d gestation baboon models of BPD, LAT1 immunostaining was measured in control and BPD animals. In adult controls and in 140 d gestational controls (GC), LAT1 was expressed in both type I and type II AECs. In 140 d BPD lungs, LAT1 expression density in alveolar tissue was decreased. In 125 d GC baboons, LAT1 immunostaining was largely confined to cuboidal AECs, whereas animals given 14 d of mechanical ventilation exhibited diminished alveolar septal LAT1 Labeling. The pattern in adult human donor lung was comparable to that observed in adult baboons. LAT1 was expressed in lungs obtained from some but not all very premature newborns at autopsy. In human and baboon lung, adult and newborn, pulmonary vascular cells expressed LAT1. In summary, LAT1 is expressed in AECs and pulmonary vascular cells in baboons and humans. Experimental BPD in premature baboons decreases pulmonary LAT1 expression and alters its spatial localization. Heterogeneity of functional LAT1 could affect S-nitrosothiol importation, which could impair iNO therapy. Pediatr Pulmonol. 2016;51:1048-1056. © 2016 Wiley Periodicals, Inc.

Boronic acid-containing aminopyridine- and aminopyrimidinecarboxamide CXCR1/2 antagonists: Optimization of aqueous solubility and oral bioavailability.

The chemokine receptors CXCR1 and CXCR2 are important pharmaceutical targets due to their key roles in inflammatory diseases and cancer progression. We have previously identified 2-[5-(4-fluoro-phenylcarbamoyl)-pyridin-2-ylsulfanylmethyl]-phenylboronic acid (SX-517) and 6-(2-boronic acid-5-trifluoromethoxy-benzylsulfanyl)-N-(4-fluoro-phenyl)-nicotinamide (SX-576) as potent non-competitive boronic acid-containing CXCR1/2 antagonists. Herein we report the synthesis and evaluation of aminopyridine and aminopyrimidine analogs of SX-517 and SX-576, identifying (2-{(benzyl)[(5-boronic acid-2-pyridyl)methyl]amino}-5-pyrimidinyl)(4-fluorophenylamino)formaldehyde as a potent chemokine antagonist with improved aqueous solubility and oral bioavailability.

Boronic acid-containing CXCR1/2 antagonists: Optimization of metabolic stability, in vivo evaluation, and a proposed receptor binding model.

Blockade of undesired neutrophil migration to sites of inflammation remains an area of substantial pharmaceutical interest. To effect this blockade, a validated therapeutic target is antagonism of the chemokine receptor CXCR2. Herein we report the discovery of 6-(2-boronic acid-5-trifluoromethoxy-benzylsulfanyl)-N-(4-fluoro-phenyl)-nicotinamide 6, an antagonist with activity at both CXCR1 and CXCR2 receptors (IC50 values 31 and 21 nM, respectively). Compound 6 exhibited potent inhibition of neutrophil influx in a rat model of pulmonary inflammation, and is hypothesized to interact with a unique intracellular binding site on CXCR2. Compound 6 (SX-576) is undergoing further investigation as a potential therapy for pulmonary inflammation.

Neonatal lung function and therapeutics.

Respiratory diseases are increasingly recognized as having their origins during perinatal and early postnatal lung development, a time of significant adaptation to large changes in redox conditions as well as to mechanical forces. This Forum of the journal presents a Forum highlighting studies of the interplay between reactive oxygen/nitrogen species and the systems that have evolved to degrade them or exploit them, as well as the cellular repair processes which respond to early life redox stress in the lung. This group of authors suggests new understandings of these events that may point the way to improved therapeutic approaches.

Hyperoxia inhibits nitric oxide treatment effects in alveolar epithelial cells via effects on L-type amino acid transporter-1.

AIMS: The aims of this study were to determine hyperoxia effects on S-nitrosothiol (SNO) accumulation and L-type amino acid transporter 1 (LAT1) expression/function in alveolar epithelium and to determine whether hyperoxia impairs exogenous nitric oxide (NO) treatment effects in alveolar epithelium through effects on LAT1 expression and/or function. RESULTS: SNO accumulation in vitro and in vivo after NO treatment was dependent on the LAT1 system transport. Hyperoxia (60% or 90%) impaired NO effects on SNO accumulation and soluble guanylyl cyclase activation in proportion to the magnitude of hyperoxia and the duration of exposure, up to 12 h, in type I-like (R3/1) and type II-like (L2) rat and human (A549) alveolar epithelial cells. LAT function, determined by sodium-independent (3)H-leucine uptake, was impaired in a parallel manner. Hyperoxia impaired LAT1 expression in alveolar epithelial cells, determined by immunoblots and immunofluorescence, and in newborn rats exposed to 60% O2 for 4 days, determined by immunohistochemistry. INNOVATION: Despite significant preclinical evidence, inhaled NO has shown disappointing limitations in clinical applications. Our studies suggest an important explanation: oxidative stress, a common feature of diseases in which therapeutic NO would be considered, impairs LAT1 expression and function, blocking a major route for inhaled NO (iNO) action, that is, the uptake of S-nitrosocysteine via LAT1. CONCLUSIONS: SNO uptake after NO treatment is dependent on LAT1. Hyperoxia impairs SNO uptake and NO effects during NO exposure and impairs LAT system function and LAT1 expression. Effects on SNO formation and transport must be considered for rational optimization of NO-based therapeutics.

Prenatal air pollution exposure induces sexually dimorphic fetal programming of metabolic and neuroinflammatory outcomes in adult offspring.

Environmental chemical exposures during critical windows of development may contribute to the escalating prevalence of obesity. We tested the hypothesis that prenatal exposure to diesel exhaust particles (DEP), a primary component of air pollution, would prime microglia long-term, resulting in exacerbated metabolic and affective outcomes following exposure to a high-fat diet in adulthood. Time-mated mouse dams were intermittently exposed to respiratory instillations of either vehicle (VEH) or DEP throughout gestation. Adult male and female offspring were then fed either a low-fat diet (LFD) or high-fat diet (HFD) for 9 weeks. The male offspring of DEP-exposed dams exhibited exaggerated weight gain, insulin resistance, and anxiety-like behavior on HFD compared to the male offspring of VEH-exposed dams, whereas female offspring did not differ according to prenatal treatment. Furthermore, HFD induced evidence of macrophage infiltration of both adipose tissue and the brain in both sexes, but these cells were more activated specifically in DEP/HFD males. DEP/HFD males also expressed markedly higher levels of microglial/macrophage, but not astrocyte, activation markers in the hippocampus, whereas females exhibited only a suppression of astrocyte activation markers due to HFD. In a second experiment, DEP male offspring mounted an exaggerated peripheral IL-1ß response to an LPS challenge at postnatal day (P)30, whereas their central IL-1ß response did not differ from VEH male offspring, which is suggestive of macrophage priming due to prenatal DEP exposure. In sum, prenatal air pollution exposure "programs" offspring for increased susceptibility to diet-induced metabolic, behavioral, and neuroinflammatory changes in adulthood in a sexually dimorphic manner.

Maternal stress and effects of prenatal air pollution on offspring mental health outcomes in mice.

BACKGROUND: Low socioeconomic status is consistently associated with reduced physical and mental health, but the mechanisms remain unclear. Increased levels of urban air pollutants interacting with parental stress have been proposed to explain health disparities in respiratory disease, but the impact of such interactions on mental health is unknown. OBJECTIVES: We aimed to determine whether prenatal air pollution exposure and stress during pregnancy act synergistically on offspring to induce a neuroinflammatory response and subsequent neurocognitive disorders in adulthood. METHODS: Mouse dams were intermittently exposed via oropharyngeal aspiration to diesel exhaust particles (DEP; 50 µg × 6 doses) or vehicle throughout gestation. This exposure was combined with standard housing or nest material restriction (NR; a novel model of maternal stress) during the last third of gestation. RESULTS: Adult (postnatal day 60) offspring of dams that experienced both stressors (DEP and NR) displayed increased anxiety, but only male offspring of this group had impaired cognition. Furthermore, maternal DEP exposure increased proinflammatory interleukin (IL)-1ß levels within the brains of adult males but not females, and maternal DEP and NR both decreased anti-inflammatory IL-10 in male, but not female, brains. Similarly, only DEP/NR males showed increased expression of the innate immune recognition gene toll-like receptor 4 (Tlr4) and its downstream effector, caspase-1. CONCLUSIONS: These results show that maternal stress during late gestation increases the susceptibility of offspring-particularly males-to the deleterious effects of prenatal air pollutant exposure, which may be due to a synergism of these factors acting on innate immune recognition genes and downstream neuroinflammatory cascades within the developing brain.