American journal of physiology. Lung cellular and molecular physiology最新文献

Bronchopulmonary dysplasia (BPD) associated pulmonary hypertension (PH) or BPD-PH is a lung disease of infants with significant morbidity. Adrenomedullin (Adm) is an angiogenic peptide that signals through calcitonin receptor-like receptor (Calcrl) and receptor activity modifying protein 2 (RAMP2). Adm deficiency potentiates hyperoxia-induced experimental BPD-PH in mice; however, whether Adm overexpression can mitigate this lung disease is unclear. Thus, we tested the hypothesis that Adm overexpression attenuates hyperoxia (HO)-induced murine experimental BPD-PH by using a novel transgenic mouse that overexpresses Adm globally (Adm^hi/hi mice). One-day-old Adm^hi/hi mice or their wild-type littermates (Adm^+/+ mice) were exposed to HO ([Formula: see text] 70%) for 14 days and allowed to recover in normoxia (NO, [Formula: see text] 21%) for an additional 14 days. Controls were maintained in NO for 28 days. On postnatal day (P) 14, we harvested the lungs to determine the extent of Adm expression and apoptosis. On P28, we quantified alveolarization, lung vascularization, and PH. HO-exposed Adm^+/+ mice demonstrated increased lung apoptosis, decreased alveolarization and lung vascularization, and indices of PH, indicating that neonatal HO exposure causes BPD-PH. However, Adm overexpression attenuated experimental BPD-PH, as evident by the decreased extent of hyperoxia-induced lung apoptosis and inflammation, alveolar and vascular simplification, pulmonary vascular remodeling, and PH in Adm^hi/hi mice than in Adm^+/+ mice. Collectively, our results demonstrate that Adm overexpression attenuates HO-induced murine experimental BPD-PH, emphasizing the therapeutic potential of Adm for BPD-PH in preterm infants.NEW & NOTEWORTHY The deficiency of the proangiogenic peptide, adrenomedullin (Adm), exacerbates the severe infantile lung disorder, bronchopulmonary dysplasia-associated pulmonary hypertension (BPD-PH), in mice. However, whether Adm therapy can mitigate this disease is unclear. Our study, conducted with a rigorous methodology, suggests a potential solution. Using a novel mouse that overexpresses Adm to overcome the pharmacological limitations of the peptide, we demonstrate that Adm can mitigate this disorder, highlighting the therapeutic potential of Adm for human BPD-PH.

A sustained contraction of the airway smooth muscle increases its contractile capacity through a time-dependent process called force adaptation and concordantly increases the response to methacholine in healthy subjects. Whether this occurs in asthma remains to be investigated. The present study aimed at evaluating force adaptation on the methacholine response in asthmatic patients. Thirty-four very mild to mild asthmatic patients underwent a methacholine challenge on two separate visits. Although the same cumulative concentration was administered on both visits, one challenge was preceded by force adaptation induced by inhaling low concentrations of methacholine at 5-min intervals. On each visit, respiratory mechanics were monitored before and throughout the methacholine challenge by oscillometry, and the degree of inflammation was assessed by measuring the fraction of exhaled nitric oxide. The results demonstrate that the final response to methacholine was greater in the challenge with than without force adaptation. For example, whereas the average change in respiratory system reactance caused by the methacholine challenge without force adaptation was 55.4 ± 67.9%, it amounted to 118.1 ± 150.7% with force adaptation (P = 0.0069). Interestingly, force adaptation on the methacholine response was weakly but negatively correlated with the degree of inflammation. In fact, when patients were split into two groups, one with the least inflammation and one with the most inflammation, force adaptation potentiated the methacholine response in the former but not in the latter. We conclude that although force adaptation potentiates the response to methacholine in asthmatic patients, this effect is mainly driven by patients with very little inflammation.NEW & NOTEWORTHY A sustained contraction of the airway smooth muscle (ASM) increases its contractility through force adaptation, but whether this alters the methacholine response in asthma is unknown. Asthmatic patients underwent two methacholine challenges with identical cumulative concentration but one including a period of ASM preactivation. The preactivation enhanced the response in patients with little inflammation but not in more inflamed patients. This suggests that force adaptation increases the methacholine response only in patients with low inflammation.

The respiratory system is integrated to optimize efficiency. Dysfunction of one element often impacts others. For example, in chronic obstructive pulmonary disease (COPD), both obstructive sleep apnea and small airways dysfunction are associated with worse emphysema. In bronchopulmonary dysplasia (BPD), cystic lung disease and tracheobronchomalacia are often comorbid. Furthermore, childhood asthma predisposes to COPD. Although mouse models have elucidated key mechanisms in respiratory disease, to date, no models have accounted for how conducting airway dysfunction impacts alveolar structure and function. We report a novel murine partial tracheal occlusion (PTO) model and a complementary esophageal pressure monitoring technique to begin answering these questions. A 50% reduction in trachea diameter was achieved using a 19-gauge needle to prevent complete closure of a microsurgical clip on the anterior trachea. Esophageal pressure was measured by advancing a 3.5-French pressure transducing catheter 3 cm into the esophagus. In 8-10-wk-old C57BL/6 mice, PTO did not cause appreciable alteration of distal lung structure despite a 10-mmHg increase in transpulmonary pressure gradient. However, PTO after tracheal aspiration of 0.5 units of porcine pancreatic elastase (PPE) resulted in 20 µm greater (P < 0.001) mean linear intercept than PPE + sham. This model can be leveraged in mouse models of asthma, BPD, and COPD to understand how conducting airway dysfunction and increased transpulmonary pressure impacts distal lung structure. The PTO model is a relatively simple, well-tolerated model of conducting airway dysfunction that potentiates distal lung injury and expands our understanding of how mechanical forces influence pathological remodeling processes in the distal lung.NEW & NOTEWORTHY Lung diseases often involve both the conducting airways and the lung parenchyma, but we do not have tools to determine the mechanisms by which one affects the other. We developed a mouse partial tracheal occlusion model that increases the pressure required to generate a breath and also a novel way to measure this pressure. We can now test different hypotheses about how lung strain causes pathological lung remodeling.

Lung fibroblasts generate and respond to mechanical, biochemical, and matrix cues present in their microenvironment. With the advent of next-generation sequencing technologies, multiple studies describe transcriptionally unique fibroblast subpopulations in the human lung. However, limited published data suggest a loss of fibroblast native phenotypes and functions after culture ex vivo. In this study, we characterized changes in transcriptional programs of human lung mesenchyme isolated from freshly procured tissue and maintained in traditional cell culture conditions. Our results demonstrate that fibroblasts isolated and cultured in this manner adopt transcriptional programs largely distinct from those observed in vivo. To recapitulate distinct native fibroblast states in vitro, we sought to develop a screening approach to identify cues promoting native fibroblast identities. From published single-cell data, we identified unique transcriptional markers of alveolar and adventitial fibroblast subpopulations and validated the sensitivity of ELISAs for detecting changes in secreted markers of these fibroblast subpopulations. We then stimulated primary human lung fibroblasts with soluble cues known to act on fibroblasts, quantifying changes in secreted and transcriptional markers by ELISA and qPCR. Although our small pilot screen did not identify single cues capable of fully recapitulating fibroblast in vivo states, it established a system that can be expanded to broadly screen additional cues and pointed toward factors likely to be critical in developing better culture models for studying human lung fibroblast function and plasticity.NEW & NOTEWORTHY Recent studies highlight transcriptionally distinct fibroblast subpopulations in human lungs. We observed the loss of these native transcriptional programs as fresh isolated cells are maintained in traditional culture conditions. Identifying the signals defining native fibroblast identities will be pivotal to creating culture models that preserve unique subpopulations. The screening system developed here will allow the investigation of a broad selection of cues, leading to better culture models for studying human lung fibroblast function and plasticity.

The pulmonary alveolar-capillary niche is a highly specialized interface that balances gas exchange with maintenance functions and repair. Advances in single cell transcriptomics have uncovered endothelial heterogeneity, which underlies developmental angiogenesis and plastic responses to injury. Emerging evidence from a neonatal hyperoxia model highlights CAP1 to CAP2 transitions and the role of p53 in maintaining lineage fidelity. Beyond intrinsic lineage plasticity, circulating mediators such as cell-free hemoglobin drive endothelial barrier disruption through oxidative injury and lipid modification. As new signaling pathways and therapeutics targets emerge, complementary strategies are being developed at the cellular level, including adoptive transfer of mesenchymal stromal and immune cells, although mechanisms of endothelial adhesion and homing remain incompletely defined. Finally, biomechanical forces such as shear stress have become critical contextual cues for endothelial signaling, yet remain underrepresented in some experimental models. Together, these insights underscore the central role of endothelial heterogeneity, injury responses, and environmental cues in shaping pulmonary vascular health and repair, with implications for designing targeted therapies in both pediatric and adult lung disease.

Trikafta (elexacaftor/tezacaftor/ivacaftor; ETI) is approved for cystic fibrosis (CF) patients with at least one F508del mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) gene or another responsive mutation based on in vitro data. However, the pharmacological effects of ETI on F508del-CFTR remain incompletely defined in vitro. To explore the mechanisms underlying Trikafta's clinical efficacy, we used primary bronchial epithelial cells from F508del homozygous patients and CFBE41o-cells expressing F508del-CFTR. We assessed CFTR maturation, turnover, chloride transport, and thermal stability under various ETI concentrations and treatment durations at physiological temperature using electrophysiology (Ussing chamber, patch-clamp) and biochemical assays. We found that ETI efficacy on F508del-CFTR is strongly influenced by both treatment duration and concentration. Reducing ETI from standard doses, i.e., E (3 µM), T (18 µM), and I (1 µM), to 33%, 11%, 3.3%, and 1.1% decreased function and maturation, but 33% retained most of the corrective effect. After 2 h of treatment, around 50% of the CFTR-dependent current was preserved, unlike in untreated cells. Notably, replacing elexacaftor with bamocaftor further improved F508del-CFTR maturation and function compared with ETI, though it did not affect the rate of current decline over time. These findings highlight the importance of optimizing ETI dose and exposure duration, as both significantly affect F508del-CFTR stability and function. The retained efficacy at reduced concentrations suggests possible individualized dosing strategies, particularly for patients experiencing adverse effects with full-dose ETI.NEW & NOTEWORTHY Our in vitro study underscores that ETI/BTI's efficacy in improving F508del-CFTR function depends on treatment concentration and duration, impacting the protein's metabolic and thermal stability. Although ETI/BTI only partially addresses F508del-CFTR's inherent thermal instability, reduced doses retained significant effectiveness. This finding supports dose optimization as a promising strategy to sustain therapeutic benefits while minimizing side effects, offering a personalized approach to treatment for individuals with cystic fibrosis experiencing adverse effects from standard dosing.

Sex appears to modulate interactions between neural mechanisms involved in regulating pulmonary ventilation during mild hypoxic exercise. Therefore, we compared pulmonary ventilation responses elicited by isolated and combined stimulation of the carotid chemoreflex and muscle mechanoreflex between males and females. Twenty-eight healthy adults (14 females) underwent four experimental manipulations: 1) normoxic rest (no stimulation), 2) hypoxic rest (carotid chemoreflex stimulation), 3) normoxic passive movement (muscle mechanoreflex stimulation), and 4) hypoxic passive movement (reflexes costimulation). Isocapnia was maintained using a rebreathing system, and hypoxia was induced by breathing 12% oxygen. Passive movement involved 30-s bouts of unilateral knee manipulation at 300°/s, with surface electromyography confirming absence of voluntary muscle contractions. In males, the pulmonary ventilation response to passive limb movement (last 10 s change vs. rest) was greater under hypoxia than normoxia (means ± SD: hypoxia = 3.6 ± 2.0 vs. normoxia = 1.6 ± 2.4 L/min; P = 0.003), whereas no difference was observed in females (hypoxia = 1.9 ± 2.4 vs. normoxia = 2.2 ± 1.5 L/min; P = 1.000). Moreover, pulmonary ventilation remained elevated in males (hypoxia = 2.7 ± 2.4 vs. normoxia = -0.1 ± 2.2; P < 0.001) but not in females (hypoxia = 0.4 ± 3.3 vs. normoxia = 0.5 ± 1.5; P = 1.000), 30 s following passive limb movement under hypoxia. These findings support a synergistic carotid chemoreflex-muscle mechanoreflex interaction in males but not in females. The persistent ventilatory elevation poststimulation indicates that short-term potentiation contributes to this synergistic interaction in males.NEW & NOTEWORTHY Pulmonary ventilation response to passive limb movement is greater under hypoxia than normoxia in males but not in females. These results support a synergistic interaction between the carotid chemoreflex and muscle mechanoreflex in males but not in females. In addition, pulmonary ventilation remains elevated in males but not in females after the cessation of passive limb movement under hypoxia, suggesting that short-term potentiation may be a mechanism mediating this synergistic reflex interaction in males.

Intravenous bolus (ivb) injection of fentanyl triggers a vagal-mediated immediate apnea and subsequent respiratory depression in anesthetized rats. This study compared the gender-dependence of these responses in conscious rats and roles of peripheral and central opioid receptors (ORs), especially µ- and mu1 opioid receptor (µ₁-ORs) in the genesis of these responses. Cardiorespiratory responses to ivb injection of fentanyl (50 µg·kg^-1) were recorded in male and female conscious rats (study I). The same protocols were performed after: naloxone (NLX) and naloxone methiodide (NLM) to systemically and peripherally antagonize ORs, respectively (study II); D-Phe-Cys-Tyr-D-Trp-Arg-Thr-Pen-Thr-NH2 (CTAP) and methylnaltrexone (MNTX) to systemically and peripherally block opioid mu-receptors (study III); and naloxonazine (NLZ) to systemically block µ₁-ORs (study IV). ivb injection of fentanyl induced an immediate life-threatening apnea (∼1.5 min) and severe bradycardia, which was followed by cardiorespiratory depression lasting for ∼55 min with little difference between genders. NLX fully eliminated and CTAP substantially blunted all cardiorespiratory responses to fentanyl, whereas NLM and MNTX substantially minimized the immediate apnea and reduced bradycardia by ∼50% with limited impact on the subsequent cardiorespiratory depression. NLZ nearly abolished the fentanyl-evoked responses. Our results indicate that peripherally restricted OR (particularly µ₁-OR) antagonism prevents the fentanyl-induced immediate apnea, but fails to change the subsequent respiratory depression.NEW & NOTEWORTHY The cardiorespiratory responses to rapid intravenous injection of fentanyl have not been fully investigated. We demonstrate in this study that intravenous bolus injection of fentanyl triggers an immediate sustained apnea and subsequent respiratory depression without remarkable gender-difference in conscious rats. The immediate apnea is triggered by activating peripheral opioid receptors and the subsequent respiratory depression is mediated by activating central opioid receptors, in which µ1-opioid receptors play a key role.

Acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) are inflammatory conditions with substantial rates of morbidity and mortality, but no effective treatments. The lack of effective treatments and unacceptably high mortality rates for ARDS are partly due to an incomplete understanding of the mechanisms that control ALI/ARDS and subsequent vascular repair. Transforming growth factors (TGFs) are a class of growth factors that regulate the vascular response to inflammation, including migration, proliferation, and differentiation of cells comprising the lung vasculature. Here we review studies that describe the impact of the TGF family on inflammatory lung injury and subsequent vascular repair and fibrosis. We highlight gaps in understanding TGF isoform-specific roles in ALI/ARDS and outline directions for future research in the field of TGF-dependent regulation of inflammatory lung injury and vascular repair. Functional roles of the TGFs have been investigated in ALI/ARDS pathogenesis and pulmonary fibrosis, with a predominance for studies showing a proinjurious and profibrotic impact of TGF-β1. Studies have also shown that TGF-α is positively associated with inflammatory lung injury and fibrosis. However, the contributions of TGF-β2 and TGF-β3 to ALI/ARDS are unclear, and the contributions of all the TGF isoforms to vascular repair after ALI/ARDS are not well characterized. Improved understanding of the regulation of inflammatory lung injury and repair by the TGFs could lead to the development of a safe and effective treatment strategy for patients with ALI/ARDS.