Identification of novel NRF2-dependent genes as regulators of lead and arsenic toxicity in neural progenitor cells.

Lead (Pb) and arsenic (As) are prevalent metal contaminants in the environment. Exposures to these metals are associated with impaired neuronal functions and adverse effects on neurodevelopment in children. However, the molecular mechanisms by which Pb and As impair neuronal functions remain poorly understood. Here, we identified F2RL2, TRIM16L, and PANX2 as novel targets of Nuclear factor erythroid 2-related factor 2 (NRF2)-the master transcriptional factor for the oxidative stress response-that are commonly upregulated with both Pb and As in human neural progenitor cells (NPCs). Using a ChIP (Chromatin immunoprecipitation)-qPCR assay, we showed that NRF2 directly binds to the promoter region of F2RL2, TRIM16L, and PANX2 to regulate expression of these genes. We demonstrated that F2RL2, PANX2, and TRIM16L have differential effects on cell death, proliferation, and differentiation of NPCs in both the presence and absence of metal exposures, highlighting their roles in regulating NPC function. Furthermore, the analyses of the transcriptomic data on NPCs derived from autism spectrum disorder (ASD) patients revealed that dysregulation of F2RL2, TRIM16L, and PANX2 was associated with ASD genetic backgrounds and ASD risk genes. Our findings revealed that Pb and As induce a shared NRF2-dependent transcriptional response in NPCs and identified novel genes regulating NPC function. While further in vivo studies are warranted, this study provides a novel mechanism linking metal exposures to NPC function and identifies potential genes of interest in the context of neurodevelopment.

Building Career Paths for Ph.D., Basic and Translational Scientists in Clinical Departments in the United States: An Official American Thoracic Society Workshop Report.

Rationale: To identify barriers and opportunities for Ph.D., basic and translational scientists to be fully integrated into clinical units. Objectives: In 2022, an ad hoc committee of the American Thoracic Society developed a project proposal and workshop to identify opportunities and barriers for scientists who do not practice medicine to develop successful careers and achieve tenure-track faculty positions in clinical departments and divisions within academic medical centers (AMCs) in the United States. Methods: This document focuses on results from a survey of adult and pediatric pulmonary, critical care, and sleep medicine division chiefs as well as a survey of workshop participants, including faculty in departmental and school leadership roles in both basic science and clinical units within U.S. AMCs. Results: We conclude that full integration of non-clinically practicing basic and translational scientists into the clinical units, in addition to their traditional placements in basic science units, best serves the tripartite mission of AMCs to provide care, perform research, and educate the next generation. Evidence suggests clinical units do employ Ph.D. scientists in large numbers, but these faculty are often hired into non-tenure track positions, which do not provide the salary support, start-up funds, research independence, or space often associated with hiring in basic science units within the same institution. These barriers to success of Ph.D. faculty in clinical units are largely financial. Conclusions: Our recommendation is for AMCs to consider and explore some of our proposed strategies to accomplish the goal of integrating basic and translational scientists into clinical units in a meaningful way.

Perspective on high-throughput bioanalysis to support in vitro assays in early drug discovery.

As the desire for a shortened design/make/test/learn cycle increases in early drug discovery, the pressure to rapidly deliver drug metabolism pharmacokinetic data continues to rise. From a bioanalytical standpoint, in vitro assays are challenging because they are amenable to automation and thus capable of generating a high number of samples for analysis. To keep up with analysis demands, automated method development workflows, rapid sample analysis approaches and efficient data analysis software must be utilized. This work provides an outline of how we implemented those three aspects to provide bioanalytical support for in vitro drug metabolism pharmacokinetic assays, which include developing hundreds of mass spectrometry methods and analyzing thousands of samples per week, while delivering a median bioanalytical turnaround time of 1-2 business days.

Neonatal hypoxic ischemic encephalopathy increases acute kidney injury urinary biomarkers in a rat model.

Hypoxic ischemic encephalopathy (HIE) is associated with acute kidney injury (AKI) in neonates with birth asphyxia. This study aimed to utilize urinary biomarkers to characterize AKI in an established neonatal rat model of HIE. Day 7 Sprague-Dawley rat pups underwent HIE using the Rice-Vannucci model (unilateral carotid ligation followed by 120 mins of 8% oxygen). Controls included no surgery and sham surgery. Weights and urine for biomarkers (NGAL, osteopontin, KIM-1, albumin) were collected the day prior, daily for 3 days post-intervention, and at sacrifice day 14. Kidneys and brains were processed for histology. HIE pups displayed histological evidence of kidney injury including damage to the proximal tubules, consistent with resolving acute tubular necrosis, and had significantly elevated urinary levels of NGAL and albumin compared to sham or controls 1-day post-insult that elevated for 3 days. KIM-1 significantly increased for 2 days post-HIE. HIE did not significantly alter osteopontin levels. Seven days post-start of experiment, controls were 81.2% above starting weight compared to 52.1% in HIE pups. NGAL and albumin levels inversely correlated with body weight following HIE injury. The AKI produced by the Rice-Vannucci HIE model is detectable by urinary biomarkers, which can be used for future studies of treatments to reduce kidney injury.

Diacetyl inhalation impairs airway epithelial repair in mice infected with influenza A virus.

Bronchiolitis obliterans (BO) is a debilitating disease of the small airways that can develop following exposure to toxic chemicals as well as respiratory tract infections. BO development is strongly associated with diacetyl (DA) inhalation exposures at occupationally relevant concentrations or severe influenza A viral (IAV) infections. However, it remains unclear whether lower dose exposures or more mild IAV infections can result in similar pathology. In the current work, we combined these two common environmental exposures, DA and IAV, to test whether shorter DA exposures followed by sublethal IAV infection would result in similar airways disease. Adult mice exposed to DA vapors 1 h/day for 5 consecutive days followed by infection with the airway-tropic IAV H3N2 (HKx31) resulted in increased mortality, increased bronchoalveolar lavage (BAL) neutrophil percentage, mixed obstruction and restriction by lung function, and subsequent airway remodeling. Exposure to DA or IAV alone failed to result in significant pathology, whereas mice exposed to DA + IAV showed increased α-smooth muscle actin (αSMA) and epithelial cells coexpressing the basal cell marker keratin 5 (KRT5) with the club cell marker SCGB1A1. To test whether DA exposure impairs epithelial repair after IAV infection, mice were infected first with IAV and then exposed to DA during airway epithelial repair. Mice exposed to IAV + DA developed similar airway remodeling with increased subepithelial αSMA and epithelial cells coexpressing KRT5 and SCGB1A1. Our findings reveal an underappreciated concept that common environmental insults while seemingly harmless by themselves can have catastrophic implications on lung function and long-term respiratory health when combined.

Ataxia telangiectasia mutated is required for efficient proximal airway epithelial cell regeneration following influenza A virus infection.

Children and young adults with mutant forms of ataxia telangiectasia mutated (ATM), a kinase involved in DNA damage signaling and mitochondrial homeostasis, suffer from recurrent respiratory infections, immune deficiencies, and obstructive airways disease associated with disorganized airway epithelium. We previously showed in mice how Atm was required to mount a protective immune memory response to influenza A virus [IAV; Hong Kong/X31 (HKx31), H3N2]. Here, Atm wildtype (WT) and knockout (Atm-null) mice were used to investigate how Atm is required to regenerate the injured airway epithelium following IAV infection. When compared with WT mice, naive Atm-null mice had increased airway resistance and reduced lung compliance that worsened during infection before returning to naïve levels by 56 days postinfection (dpi). Although Atm-null lungs appeared pathologically normal before infection by histology, they developed an abnormal proximal airway epithelium after infection that contained E-cadherin+, Sox2+, and Cyp2f2+ cells lacking secretoglobin family 1 A member 1 (Scgb1a1) protein expression. Patchy and low expression of Scgb1a1 were eventually observed by 56 dpi. Genetic lineage tracing in HKx31-infected mice revealed club cells require Atm to rapidly and efficiently restore Scgb1a1 expression in proximal airways. Since Scgb1a1 is an immunomodulatory protein that protects the lung against a multitude of respiratory challenges, failure to efficiently restore its expression may contribute to the respiratory diseases seen in individuals with ataxia telangiectasia.

Neonatal Hyperoxia Activates Activating Transcription Factor 4 to Stimulate Folate Metabolism and Alveolar Epithelial Type 2 Cell Proliferation.

Oxygen supplementation in preterm infants disrupts alveolar epithelial type 2 (AT2) cell proliferation through poorly understood mechanisms. Here, newborn mice are used to understand how hyperoxia stimulates an early aberrant wave of AT2 cell proliferation that occurs between Postnatal Days (PNDs) 0 and 4. RNA-sequencing analysis of AT2 cells isolated from PND4 mice revealed hyperoxia stimulates expression of mitochondrial-specific methylenetetrahydrofolate dehydrogenase 2 and other genes involved in mitochondrial one-carbon coupled folate metabolism and serine synthesis. The same genes are induced when AT2 cells normally proliferate on PND7 and when they proliferate in response to the mitogen fibroblast growth factor 7. However, hyperoxia selectively stimulated their expression via the stress-responsive activating transcription factor 4 (ATF4). Administration of the mitochondrial superoxide scavenger mitoTEMPO during hyperoxia suppressed ATF4 and thus early AT2 cell proliferation, but it had no effect on normative AT2 cell proliferation seen on PND7. Because ATF4 and methylenetetrahydrofolate dehydrogenase are detected in hyperplastic AT2 cells of preterm infant humans and baboons with bronchopulmonary dysplasia, dampening mitochondrial oxidative stress and ATF4 activation may provide new opportunities for controlling excess AT2 cell proliferation in neonatal lung disease.

Low-dose hyperoxia primes airways for fibrosis in mice after influenza A infection.

It is well known that supplemental oxygen used to treat preterm infants in respiratory distress is associated with permanently disrupting lung development and the host response to influenza A virus (IAV). However, many infants who go home with normally functioning lungs are also at risk for hyperreactivity after a respiratory viral infection. We recently reported a new, low-dose hyperoxia mouse model (40% for 8 days; 40×8) that causes a transient change in lung function that resolves, rendering 40×8 adult animals functionally indistinguishable from room air controls. Here we report that when infected with IAV, 40×8 mice display an early transient activation of TGFß signaling and later airway hyperreactivity associated with peribronchial inflammation (profibrotic macrophages) and fibrosis compared with infected room air controls, suggesting neonatal oxygen induced hidden molecular changes that prime the lung for hyperreactive airways disease. Although searching for potential activators of TGFß signaling, we discovered that thrombospondin-1 (TSP-1) is elevated in naïve 40×8 mice compared with controls and localized to lung megakaryocytes and platelets before and during IAV infection. Elevated TSP-1 was also identified in human autopsy samples of former preterm infants with bronchopulmonary dysplasia. These findings reveal how low doses of oxygen that do not durably change lung function may prime it for hyperreactive airways disease by changing expression of genes, such as TSP-1, thus helping to explain why former preterm infants who have normal lung function are susceptible to airway obstruction and increased morbidity after viral infection.

Neonatal hyperoxia impairs adipogenesis of bone marrow-derived mesenchymal stem cells and fat accumulation in adult mice.

Preterm birth is a risk factor for growth failure and development of respiratory disease in children and young adults. Their early exposure to oxygen may contribute to lung disease because adult mice exposed to hyperoxia as neonates display reduced lung function, changes in the host response to respiratory viral infections, and develop pulmonary hypertension and heart failure that shortens their lifespan. Here, we provide new evidence that neonatal hyperoxia also impairs growth by inhibiting fat accumulation. Failure to accumulate fat may reflect a systemic defect in adipogenic potential of stem cells because bone marrow-derived mesenchymal cells (BMSCs) isolated from the mice grew slower and were more oxidized compared to controls. They also displayed reduced capacity to accumulate lipid and differentiate into adipocytes. BMSCs from adult mice exposed to neonatal hyperoxia express lower levels of peroxisome proliferator-activated receptor gamma (PPARγ), a transcription factor that drives adipocyte differentiation. The defect in adipogenesis was rescued by expressing PPARγ in these cells. These findings reveal early life exposure to high levels of oxygen may suppresses fat accumulation and impair adipogenic differentiation upstream of PPARγ signaling, thus potentially contributing to growth failure seen in people born preterm.

Neonatal hyperoxia inhibits proliferation and survival of atrial cardiomyocytes by suppressing fatty acid synthesis.

Preterm birth increases the risk for pulmonary hypertension and heart failure in adulthood. Oxygen therapy can damage the immature cardiopulmonary system and may be partially responsible for the cardiovascular disease in adults born preterm. We previously showed that exposing newborn mice to hyperoxia causes pulmonary hypertension by 1 year of age that is preceded by a poorly understood loss of pulmonary vein cardiomyocyte proliferation. We now show that hyperoxia also reduces cardiomyocyte proliferation and survival in the left atrium and causes diastolic heart failure by disrupting its filling of the left ventricle. Transcriptomic profiling showed that neonatal hyperoxia permanently suppressed fatty acid synthase (Fasn), stearoyl-CoA desaturase 1 (Scd1), and other fatty acid synthesis genes in the atria of mice, the HL-1 line of mouse atrial cardiomyocytes, and left atrial tissue explanted from human infants. Suppressing Fasn or Scd1 reduced HL-1 cell proliferation and increased cell death, while overexpressing these genes maintained their expansion in hyperoxia, suggesting that oxygen directly inhibits atrial cardiomyocyte proliferation and survival by repressing Fasn and Scd1. Pharmacologic interventions that restore Fasn, Scd1, and other fatty acid synthesis genes in atrial cardiomyocytes may, thus, provide a way of ameliorating the adverse effects of supplemental oxygen on preterm infants.

Neonatal hyperoxia enhances age-dependent expression of SARS-CoV-2 receptors in mice.

The severity of COVID-19 lung disease is higher in the elderly and people with pre-existing co-morbidities. People who were born preterm may be at greater risk for COVID-19 because their early exposure to oxygen (hyperoxia) at birth increases the severity of respiratory viral infections. Hyperoxia at birth increases the severity of influenza A virus infections in adult mice by reducing the number of alveolar epithelial type 2 (AT2) cells. Since AT2 cells express the SARS-CoV-2 receptors angiotensin converting enzyme (ACE2) and transmembrane protease/serine subfamily member 2 (TMPRSS2), their expression should decline as AT2 cells are depleted by hyperoxia. Instead, ACE2 was detected in airway Club cells and endothelial cells at birth, and then AT2 cells at one year of age. Neonatal hyperoxia stimulated expression of ACE2 in Club cells and in AT2 cells by 2 months of age. It also stimulated expression of TMPRSS2 in the lung. Increased expression of SARS-CoV-2 receptors was blocked by mitoTEMPO, a mitochondrial superoxide scavenger that reduced oxidative stress and DNA damage seen in oxygen-exposed mice. Our finding that hyperoxia enhances the age-dependent expression of SARS-CoV-2 receptors in mice helps explain why COVID-19 lung disease is greater in the elderly and people with pre-existing co-morbidities.

Lung SOD3 limits neurovascular reperfusion injury and systemic immune activation following transient global cerebral ischemia.

BACKGROUND AND OBJECTIVES: Studies implicate the lung in moderating systemic immune activation via effects on circulating leukocytes. In this study, we investigated whether targeted expression of the antioxidant extracellular superoxide dismutase (SOD3) within the lung would influence post-ischemic peripheral neutrophil activation and CNS reperfusion injury. METHODS: Adult, male mice expressing human SOD3 within type II pneumocytes were subjected to 15 min of transient global cerebral ischemia. Three days post-reperfusion, lung and brain tissue was collected and analyzed by immunohistochemistry for inflammation and injury markers. In vitro motility and neurotoxicity assays were conducted to ascertain the direct effects of hSOD3 on PMN activation. Results were compared against C57BL/6 age and sex-matched controls. RESULTS: Relative to wild-type controls, hSOD3 heterozygous mice exhibited a reduction in lung inflammation, blood-brain barrier damage, and post-ischemic neuronal injury within the hippocampus and cortex. PMNs harvested from hSOD3 mice were also resistant to LPS priming, slower-moving, and less toxic to primary neuronal cultures. CONCLUSIONS: Constitutive, focal expression of hSOD3 is neuroprotective in a model of global cerebral ischemia-reperfusion injury. The underlying mechanism of SOD3-dependent protection is attributable in part to effects on the activation state and toxic potential of circulating neutrophils. These results implicate lung-brain coupling as a determinant of cerebral ischemia-reperfusion injury and highlight post-stroke lung inflammation as a potential therapeutic target in acute ischemic cerebrovascular injuries.

Neonatal hyperoxia enhances age-dependent expression of SARS-CoV-2 receptors in mice.

The severity of COVID-19 lung disease is higher in the elderly and people with pre-existing co-morbidities. People who were born preterm may be at greater risk for COVID-19 because their early exposure to oxygen at birth increases their risk of being hospitalized when infected with RSV and other respiratory viruses. Our prior studies in mice showed how high levels of oxygen (hyperoxia) between postnatal days 0-4 increases the severity of influenza A virus infections by reducing the number of alveolar epithelial type 2 (AT2) cells. Because AT2 cells express the SARS-CoV-2 receptors angiotensin converting enzyme (ACE2) and transmembrane protease/serine subfamily member 2 (TMPRSS2), we expected their expression would decline as AT2 cells were depleted by hyperoxia. Instead, we made the surprising discovery that expression of Ace2 and Tmprss2 mRNA increases as mice age and is accelerated by exposing mice to neonatal hyperoxia. ACE2 is primarily expressed at birth by airway Club cells and becomes detectable in AT2 cells by one year of life. Neonatal hyperoxia increases ACE2 expression in Club cells and makes it detectable in 2-month-old AT2 cells. This early and increased expression of SARS-CoV-2 receptors was not seen in adult mice who had been administered the mitochondrial superoxide scavenger mitoTEMPO during hyperoxia. Our finding that early life insults such as hyperoxia enhances the age-dependent expression of SARS-CoV-2 receptors in the respiratory epithelium helps explain why COVID-19 lung disease is greater in the elderly and people with pre-existing co-morbidities.

Early Neonatal Oxygen Exposure Predicts Pulmonary Morbidity and Functional Deficits at 1 Year.

OBJECTIVE: To evaluate the predictive value of cumulative oxygen exposure thresholds over the first 2 postnatal weeks, linking them to bronchopulmonary dysplasia (BPD) and 1-year pulmonary morbidity and lung function in extremely low gestational age newborns. STUDY DESIGN: Infants (N = 704) enrolled in the Prematurity and Respiratory Outcomes Program, a multicenter prospective cohort study, that survived to discharge were followed through their neonatal intensive care unit hospitalization to 1-year corrected age. Cumulative oxygen exposure (OxygenAUC14) thresholds were derived from univariate models of BPD, stratifying infants into high-, intermediate-, and low-oxygen exposure groups. These groups were then used in multivariate logistic regressions to prospectively predict post-prematurity respiratory disease (PRD), respiratory morbidity score (RMS) in the entire cohort, and pulmonary function z scores (N = 108 subset of infants) at 1-year corrected age. RESULTS: Over the first 14 postnatal days, infants exposed to high oxygen averaged ≥33.1% oxygen, infants exposed to intermediate oxygen averaged 29.1%-33.1%, and infants exposed to low oxygen were below both cutoffs. In multivariate models, infants exposed to high oxygen showed increased PRD and RMS, whereas infants exposed to intermediate oxygen demonstrated increased moderate/severe RMS. Infants in the high/intermediate groups had decreased forced expiratory volume at 0.5 seconds/forced vital capacity ratio. CONCLUSIONS: OxygenAUC14 establishes 3 thresholds of oxygen exposure that risk stratify infants early in their neonatal course, thereby predicting short-term (BPD) and 1-year (PRD, RMS) respiratory morbidity. Infants with greater OxygenAUC14 have altered pulmonary function tests at 1 year of age, indicating early evidence of obstructive lung disease and flow limitation, which may predispose extremely low gestational age newborns to increased long-term pulmonary morbidity. TRIAL REGISTRATION: ClinicalTrials.gov: NCT01435187.

Correction to Identification of Quinoline-Based RIP2 Kinase Inhibitors with an Improved Therapeutic Index to the hERG Ion Channel.

[This corrects the article DOI: 10.1021/acsmedchemlett.8b00344.].

Understanding Pharmacokinetic Disconnect in Preclinical Species for 4-Aminoquinolines: Consequences of Low Permeability and High P-glycoprotein Efflux Ratio on Rat and Dog Oral Pharmacokinetics.

Receptor Interacting Protein 2 (RIP2) kinase inhibitors have been reported for therapeutic opportunities in inflammatory bowel diseases such as Ulcerative Colitis and Crohn's disease. During lead optimization, team identified 4-aminoquinoline series and several compounds from this series were investigated in rat and dog pharmacokinetic studies. While compounds such as GSKA and GSKB demonstrated acceptable pharmacokinetics in rat and dog, further progression of these compounds was halted due to adverse findings in advanced safety studies. Structurally similar analogues incorporating polarity at C-7 position of 4-aminoquinoline resulted in identification of GSKC - GSKF. Interestingly, following oral administration to rat at similar low dose, GSKC - GSKF demonstrated significantly low systemic drug exposure compared to GSKA and GSKB (3-17-fold difference). However, in dog, dose normalized oral systemic exposure for GSKC - GSKF was comparable to GSKA and GSKB (within 2-fold). A series of studies were conducted to understand the disconnect which highlighted that an intrinsic reduction in permeability and high P-glycoprotein (P-gp) efflux ratio for C-7 substituted analogues were driving pharmacokinetic disconnect between rat and dog. Oral absorption was minimally impacted in dog by P-gp mediated efflux compared to rat because the leakier gastrointestinal tract in dog likely overcomes this effect.

Tumor Necrosis Factor Induces Obliterative Pulmonary Vascular Disease in a Novel Model of Connective Tissue Disease-Associated Pulmonary Arterial Hypertension.

OBJECTIVE: Connective tissue disease (CTD)-associated pulmonary arterial hypertension (PAH) is the second most common etiology of PAH and carries a poor prognosis. Recently, it has been shown that female human tumor necrosis factor (TNF)-transgenic (Tg) mice die of cardiopulmonary disease by 6 months of age. This study was undertaken to characterize this pathophysiology and assess its potential as a novel model of CTD-PAH. METHODS: Histologic analysis was performed on TNF-Tg and wild-type (WT) mice to characterize pulmonary vascular and right ventricular (RV) pathology (n = 40 [4-5 mice per group per time point]). Mice underwent right-sided heart catheterization (n = 29) and micro-computed tomographic angiography (n = 8) to assess vascular disease. Bone marrow chimeric mice (n = 12), and anti-TNF-treated mice versus placebo-treated mice (n = 12), were assessed. RNA sequencing was performed on mouse lung tissue (n = 6). RESULTS: TNF-Tg mice displayed a pulmonary vasculopathy marked by collagen deposition (P < 0.001) and vascular occlusion (P < 0.001) with associated RV hypertrophy (P < 0.001) and severely increased RV systolic pressure (mean ± SD 75.1 ± 19.3 mm Hg versus 26.7 ± 1.7 mm Hg in WT animals; P < 0.0001). TNF-Tg mice had increased α-smooth muscle actin (α-SMA) staining, which corresponded to proliferation and loss of von Willebrand factor (vWF)-positive endothelial cells (P < 0.01). There was an increase in α-SMA-positive, vWF-positive cells (P < 0.01), implicating endothelial-mesenchymal transition. Bone marrow chimera experiments revealed that mesenchymal but not bone marrow-derived cells are necessary to drive this process. Treatment with anti-TNF therapy halted the progression of disease. This pathology closely mimics human CTD-PAH, in which patient lungs demonstrate increased TNF signaling and significant similarities in genomic pathway dysregulation. CONCLUSION: The TNF-Tg mouse represents a novel model of CTD-PAH, recapitulates key disease features, and can serve as a valuable tool for discovery and assessment of therapeutics.

Extended pharmacodynamic responses observed upon PROTAC-mediated degradation of RIPK2.

Proteolysis-Targeting Chimeras (PROTACs) are heterobifunctional small-molecules that can promote the rapid and selective proteasome-mediated degradation of intracellular proteins through the recruitment of E3 ligase complexes to non-native protein substrates. The catalytic mechanism of action of PROTACs represents an exciting new modality in drug discovery that offers several potential advantages over traditional small-molecule inhibitors, including the potential to deliver pharmacodynamic (PD) efficacy which extends beyond the detectable pharmacokinetic (PK) presence of the PROTAC, driven by the synthesis rate of the protein. Herein we report the identification and development of PROTACs that selectively degrade Receptor-Interacting Serine/Threonine Protein Kinase 2 (RIPK2) and demonstrate in vivo degradation of endogenous RIPK2 in rats at low doses and extended PD that persists in the absence of detectable compound. This disconnect between PK and PD, when coupled with low nanomolar potency, offers the potential for low human doses and infrequent dosing regimens with PROTAC medicines.

Pulmonary mechanics and structural lung development after neonatal hyperoxia in mice.

BACKGROUND: Supplemental oxygen exposure administered to premature infants is associated with chronic lung disease and abnormal pulmonary function. This study used mild (40%), moderate (60%), and severe (80%) oxygen to determine how hyperoxia-induced changes in lung structure impact pulmonary mechanics in mice. METHODS: C57BL/6J mice were exposed to room air or hyperoxia from birth through postnatal day 8. Baseline pulmonary function and methacholine challenge was assessed at 4 and 8 weeks of age, accompanied by immunohistochemical assessments of both airway (smooth muscle, tethering) and alveolar (simplification, elastin deposition) structure. RESULTS: Mild/moderate hyperoxia increased baseline airway resistance (40% only) and airway hyperreactivity (40 and 60%) at 4 weeks accompanied by increased airway smooth muscle deposition, which resolved at 8 weeks. Severe hyperoxia increased baseline compliance, baseline resistance, and total elastin/surface area ratio without increasing airway hyperreactivity, and was accompanied by increased alveolar simplification, decreased airway tethering, and changes in elastin distribution at both time points. CONCLUSIONS: Mild to moderate hyperoxia causes changes in airway function and airway hyperreactivity with minimal parenchymal response. Severe hyperoxia drives its functional changes through alveolar simplification, airway tethering, and elastin redistribution. These differential responses can be leveraged to further develop hyperoxia mouse models.