Noninvasive and invasive pulmonary function in mouse models of obstructive and restrictive respiratory diseases

Retinoic acid signaling is essential for airway smooth muscle homeostasis

Airway smooth muscle (ASM) is a dynamic and complex tissue involved in regulation of bronchomotor tone, but the molecular events essential for the maintenance of ASM homeostasis are not well understood. Observational and genome-wide association studies in humans have linked airway function to the nutritional status of vitamin A and its bioactive metabolite retinoic acid (RA). Here, we provide evidence that ongoing RA signaling is critical for the regulation of adult ASM phenotype. By using dietary, pharmacologic, and genetic models in mice and humans, we show that (a) RA signaling is active in adult ASM in the normal lung, (b) RA-deficient ASM cells are hypertrophic, hypercontractile, profibrotic, but not hyperproliferative, (c) TGF-β signaling, known to cause ASM hypertrophy and airway fibrosis in human obstructive lung diseases, is hyperactivated in RA-deficient ASM, (d) pharmacologic and genetic inhibition of the TGF-β activity in ASM prevents the development of the aberrant phenotype induced by RA deficiency, and (e) the consequences of transient RA deficiency in ASM are long-lasting. These results indicate that RA signaling actively maintains adult ASM homeostasis, and disruption of RA signaling leads to aberrant ASM phenotypes similar to those seen in human chronic airway diseases such as asthma.

Design and nonlinear modeling of a sensitive sensor for the measurement of flow in mice

OBJECTIVE

While many studies rely on flow and pressure measurements in small animal models of respiratory disease, such measurements can however be inaccurate and difficult to obtain. Thus, the goal of this study was to design and implement an easy-to-manufacture and accurate sensor capable of monitoring flow.

APPROACH

We designed and 3D printed a flowmeter and utilized parametric (resistance and inertance) and nonparametric (polynomial and Volterra series) system identification to characterize the device. The sensor was tested in a closed system for apparent flow using the common mode rejection ratio (CMRR). The sensor properly measured tidal volumes and respiratory rates in spontaneously breathing mice. The device was used to evaluate a ventilator's ability to deliver a prescribed volume before and after lung injury.

MAIN RESULTS

The parametric and polynomial models provided a reasonable prediction of the independently measured flow (Adjusted coefficient of determination [Formula: see text]  =  0.9591 and 0.9147 respectively), but the Volterra series of the 1st, 2nd, and 3rd order with a memory of six time points provided better fits ([Formula: see text]  =  0.9775, 0.9787, and 0.9954, respectively). At and below the mouse breathing frequency (1-5 Hz), CMRR was higher than 40 dB. Following lung injury, the sensor revealed a significant drop in delivered tidal volume.

SIGNIFICANCE

We demonstrate that the application of nonparametric nonlinear Volterra series modeling in combination with 3D printing technology allows the inexpensive and rapid fabrication of an accurate flow sensor for continuously measuring small flows in various physiological conditions.

Cholesterol metabolism promotes B-cell positioning during immune pathogenesis of chronic obstructive pulmonary disease

The development of chronic obstructive pulmonary disease (COPD) pathogenesis remains unclear, but emerging evidence supports a crucial role for inducible bronchus-associated lymphoid tissue (iBALT) in disease progression. Mechanisms underlying iBALT generation, particularly during chronic CS exposure, remain to be defined. Oxysterol metabolism of cholesterol is crucial to immune cell localization in secondary lymphoid tissue. Here, we demonstrate that oxysterols also critically regulate iBALT generation and the immune pathogenesis of COPD In both COPD patients and cigarette smoke (CS)-exposed mice, we identified significantly upregulated CH25H and CYP7B1 expression in airway epithelial cells, regulating CS-induced B-cell migration and iBALT formation. Mice deficient in CH25H or the oxysterol receptor EBI2 exhibited decreased iBALT and subsequent CS-induced emphysema. Further, inhibition of the oxysterol pathway using clotrimazole resolved iBALT formation and attenuated CS-induced emphysema in vivo therapeutically. Collectively, our studies are the first to mechanistically interrogate oxysterol-dependent iBALT formation in the pathogenesis of COPD, and identify a novel therapeutic target for the treatment of COPD and potentially other diseases driven by the generation of tertiary lymphoid organs.

Loss of Hox5 function results in myofibroblast mislocalization and distal lung matrix defects during postnatal development

Alveologenesis is the final stage of lung development and is responsible for the formation of the principle gas exchange units called alveoli. The lung mesenchyme, in particular the alveolar myofibroblasts, are drivers of alveolar development, however, few key regulators that govern the proper distribution and behavior of these cells in the distal lung during alveologenesis have been identified. While Hox5 triple mutants (Hox5 aabbcc) exhibit neonatal lethality, four-allele, compound mutant mice (Hox5 AabbCc) are born in Mendelian ratios and are phenotypically normal at birth. However, they exhibit defects in alveologenesis characterized by a BPD-like phenotype by early postnatal stages that becomes more pronounced at adult stages. Invasive pulmonary functional analyses demonstrate significant increases in total lung volume and compliance and a decrease in elastance in Hox5 compound mutants. SMA+ myofibroblasts in the distal lung are distributed abnormally during peak stages of alveologenesis and aggregate, resulting in the formation of a disrupted elastin network. Examination of other key components of the distal lung ECM, as well as other epithelial cells and lipofibroblasts reveal no differences in distribution. Collectively, these data indicate that Hox5 genes play a critical role in alveolar development by governing the proper cellular behavior of myofibroblasts during alveologenesis.

The Role of Regulatory T Cell in Nontypeable Haemophilus influenzae-Induced Acute Exacerbation of Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is associated with irreversible persistent airflow limitation and enhanced inflammation. The episodes of acute exacerbation (AECOPD) largely depend on the colonized pathogens such as nontypeable Haemophilus influenzae (NTHi), one of the most commonly isolated bacteria. Regulatory T cells (Tregs) are critical in controlling inflammatory immune responses and maintaining tolerance; however, their role in AECOPD is poorly understood. In this study, we hypothesized a regulatory role of Tregs, as NTHi participated in the progress of COPD. Immunological pathogenesis was investigated in a murine COPD model induced by cigarette smoke (CS). NTHi was administrated through intratracheal instillation for an acute exacerbation. Weight loss and lung function decline were observed in smoke-exposed mice. Mice in experimental groups exhibited serious inflammatory responses via histological and cytokine assessment. Expression levels of Tregs and Th17 cells with specific cytokines TGF-β1 and IL-17 were detected to assess the balance of pro-/anti-inflammatory influence partially. Our findings suggested an anti-inflammatory activity of Tregs in CS-induced model. But this activity was suppressed after NTHi administration. Collectively, these data suggested that NTHi might play a necessary role in downregulating Foxp3 to impair the function of Tregs, helping development into AECOPD.

HSP27 inhibitor attenuates radiation-induced pulmonary inflammation

Radiation therapy has been used to treat over 70% of thoracic cancer; however, the method usually causes radiation pneumonitis. In the current study, we investigated the radioprotective effects of HSP27 inhibitor (J2) on radiation-induced lung inflammation in comparison to amifostine. In gross and histological findings, J2 treatment significantly inhibited immune cell infiltration in lung tissue, revealing anti-inflammatory potential of J2. Normal lung volume, evaluated by micro-CT analysis, in J2-treated mice was higher compared to that in irradiated mice. J2-treated mice reversed radiation-induced respiratory distress. However, amifostine did not show significant radioprotective effects in comparison to that of J2. In HSP27 transgenic mice, we observed increased immune cells recruitment and decreased volume of normal lung compared to wild type mice. Increased ROS production and oxidative stress after IR were down-regulated by J2 treatment, demonstrating antioxidant property of J2. The entire data of this study collectively showed that J2 may be an effective therapeutic agent for radiation-induced lung injury.

Remote ischemic preconditioning attenuates cardiopulmonary bypass-induced lung injury

The use of cardiopulmonary bypass (CPB) in cardiac surgeries is known to induce pathological changes in vital organs such as lungs. Remote ischemic preconditioning (RIPC) is a protective strategy that has shown to be able to reduce tissue damage related to ischemia-reperfusion injury (IRI). The current study seeks to evaluate the beneficial effects of limb RIPC on lung tissues and function in a rat CPB model. RIPC, which consisted of three cycles of 5-min ischemia and subsequently 5-min reperfusion, was induced in the hind limbs of the animals via a tourniquet. Bronchoalveolar lavage (BAL) fluid analysis and hematoxylin and eosin staining revealed that limb RIPC could significantly attenuate CPB-induced pulmonary injury, as evidenced by a combination of lower total BAL protein content, less severe alveolar wall thickening and reduced intra-alveolar neutrophil infiltration. Consistently, RIPC was also found to improve the proliferation capacity of the bronchioalveolar stem cells isolated from the lung tissues in rats subjected to surgical procedure with CPB. These beneficial effects translated into significantly improved lung function. Further investigation suggested that RIPC could up-regulate the serum levels of several anti-inflammatory cytokines such as interleukin (IL)-4 and 10, which might play a role in its pulmonoprotective effects. Taken together, the current study provided convincing evidence that limb RIPC could be a useful strategy for minimizing CPB-induced organ injuries in patients undergoing CPB surgery.

Loss of Vascular CD34 Results in Increased Sensitivity to Lung Injury

Survival during lung injury requires a coordinated program of damage limitation and rapid repair. CD34 is a cell surface sialomucin expressed by epithelial, vascular, and stromal cells that promotes cell adhesion, coordinates inflammatory cell recruitment, and drives angiogenesis. To test whether CD34 also orchestrates pulmonary damage and repair, we induced acute lung injury in wild-type (WT) and Cd34^-/- mice by bleomycin administration. We found that Cd34^-/- mice displayed severe weight loss and early mortality compared with WT controls. Despite equivalent early airway inflammation to WT mice, CD34-deficient animals developed interstitial edema and endothelial delamination, suggesting impaired endothelial function. Chimeric Cd34^-/- mice reconstituted with WT hematopoietic cells exhibited early mortality compared with WT mice reconstituted with Cd34^-/- cells, supporting an endothelial defect. CD34-deficient mice were also more sensitive to lung damage caused by influenza infection, showing greater weight loss and more extensive pulmonary remodeling. Together, our data suggest that CD34 plays an essential role in maintaining vascular integrity in the lung in response to chemical- and infection-induced tissue damage.

Female mice lacking Pald1 exhibit endothelial cell apoptosis and emphysema

Paladin (Pald1, mKIAA1274 or x99384) was identified in screens for vascular-specific genes and is a putative phosphatase. Paladin has also been proposed to be involved in various biological processes such as insulin signaling, innate immunity and neural crest migration. To determine the role of paladin we have now characterized the Pald1 knock-out mouse in a broad array of behavioral, physiological and biochemical tests. Here, we show that female, but not male, Pald1 heterozygous and homozygous knock-out mice display an emphysema-like histology with increased alveolar air spaces and impaired lung function with an obstructive phenotype. In contrast to many other tissues where Pald1 is restricted to the vascular compartment, Pald1 is expressed in both the epithelial and mesenchymal compartments of the postnatal lung. However, in Pald1 knock-out females, there is a specific increase in apoptosis and proliferation of endothelial cells, but not in non-endothelial cells. This results in a transient reduction of endothelial cells in the maturing lung. Our data suggests that Pald1 is required during lung vascular development and for normal function of the developing and adult lung in a sex-specific manner. To our knowledge, this is the first report of a sex-specific effect on endothelial cell apoptosis.

Effect of anti-IgE in occupational asthma caused by exposure to low molecular weight agents

BACKGROUND

The role of immunoglobulin (Ig)-E in occupational asthma (OA) due to low molecular weight (LMW) agents is not well established compared to classical atopic asthma. In this study, we evaluate whether anti-IgE monoclonal antibody (mAb) has an effect in a mouse model of OA, using persulfate salts.

METHODS

On days 1 and 8, BALB/C mice were dermally sensitized with 5% ammonium persulfate (AP) or dimethyl sulfoxide (DMSO). On days 15, 18, and 21, animals were injected intraperitoneally with anti-IgE mAb or PBS 6 hours before challenge with AP or saline. Airway hyper-responsiveness (AHR) using a methacholine test, airway inflammation in bronchoalveolar lavage (BAL) and lung tissue, and total free IgE in serum samples were analyzed 24, 48, and 96 hours after the last challenge.

RESULTS

Anti-IgE mAb treatment almost completely neutralized free serum IgE. In AP-sensitized and challenged mice, anti-IgE mAb treatment abolished AHR 24 hour and 48 hour after the last challenge and significantly reduced the total number of eosinophils and neutrophils 48 hour and 96 hour after the last AP challenge compared with nontreated mice. Levels of interleukin (IL)-13 in BAL were also significantly decreased after anti-IgE administration 24 hour and 48 hour after the last AP challenge. Histological analysis of the lung sections from anti-IgE-treated mice revealed normal inflammatory patterns similar to control groups 48 hour after the last challenge.

CONCLUSIONS

Anti-IgE-treated mice showed a significant improvement in asthma features related to the AHR and airway inflammation. Anti-IgE mAb has positive effects in OA induced by persulfate salts.

Human induced pluripotent stem cell-derived lung progenitor and alveolar epithelial cells attenuate hyperoxia-induced lung injury

BACKGROUND AIMS

Bronchopulmonary dysplasia (BPD), a chronic lung disease characterized by disrupted lung growth, is the most common complication in extreme premature infants. BPD leads to persistent pulmonary disease later in life. Alveolar epithelial type 2 cells (AEC2s), a subset of which represent distal lung progenitor cells (LPCs), promote normal lung growth and repair. AEC2 depletion may contribute to persistent lung injury in BPD. We hypothesized that induced pluripotent stem cell (iPSC)-derived AECs prevent lung damage in experimental oxygen-induced BPD.

METHODS

Mouse AECs (mAECs), miPSCs/mouse embryonic stem sells, human umbilical cord mesenchymal stromal cells (hUCMSCs), human (h)iPSCs, hiPSC-derived LPCs and hiPSC-derived AECs were delivered intratracheally to hyperoxia-exposed newborn mice. Cells were pre-labeled with a red fluorescent dye for in vivo tracking.

RESULTS

Airway delivery of primary mAECs and undifferentiated murine pluripotent cells prevented hyperoxia-induced impairment in lung function and alveolar growth in neonatal mice. Similar to hUCMSC therapy, undifferentiated hiPSCs also preserved lung function and alveolar growth in hyperoxia-exposed neonatal NOD/SCID mice. Long-term assessment of hiPSC administration revealed local teratoma formation and cellular infiltration in various organs. To develop a clinically relevant cell therapy, we used a highly efficient method to differentiate hiPSCs into a homogenous population of AEC2s. Airway delivery of hiPSC-derived AEC2s and hiPSC-derived LPCs, improved lung function and structure and resulted in long-term engraftment without evidence of tumor formation.

CONCLUSIONS

hiPSC-derived AEC2 therapy appears effective and safe in this model and warrants further exploration as a therapeutic option for BPD and other lung diseases characterized by AEC injury.

Integrative characterization of chronic cigarette smoke-induced cardiopulmonary comorbidities in a mouse model

Cigarette smoke-triggered inflammatory cascades and consequent tissue damage are the main causes of chronic obstructive pulmonary disease (COPD). There is no effective therapy and the key mediators of COPD are not identified due to the lack of translational animal models with complex characterization. This integrative chronic study investigated cardiopulmonary pathophysiological alterations and mechanisms with functional, morphological and biochemical techniques in a 6-month-long cigarette smoke exposure mouse model. Some respiratory alterations characteristic of emphysema (decreased airway resistance: Rl; end-expiratory work and pause: EEW, EEP; expiration time: Te; increased tidal mid-expiratory flow: EF50) were detected in anaesthetized C57BL/6 mice, unrestrained plethysmography did not show changes. Typical histopathological signs were peribronchial/perivascular (PB/PV) edema at month 1, neutrophil/macrophage infiltration at month 2, interstitial leukocyte accumulation at months 3-4, and emphysema/atelectasis at months 5-6 quantified by mean linear intercept measurement. Emphysema was proven by micro-CT quantification. Leukocyte number in the bronchoalveolar lavage at month 2 and lung matrix metalloproteinases-2 and 9 (MMP-2/MMP-9) activities in months 5-6 significantly increased. Smoking triggered complex cytokine profile change in the lung with one characteristic inflammatory peak of C5a, interleukin-1α and its receptor antagonist (IL-1α, IL-1ra), monokine induced by gamma interferon (MIG), macrophage colony-stimulating factor (M-CSF), tissue inhibitor of matrix metalloproteinase-1 (TIMP-1) at months 2-3, and another peak of interferon-γ (IFN-γ), IL-4, 7, 13, 17, 27 related to tissue destruction. Transient systolic and diastolic ventricular dysfunction developed after 1-2 months shown by significantly decreased ejection fraction (EF%) and deceleration time, respectively. These parameters together with the tricuspid annular plane systolic excursion (TAPSE) decreased again after 5-6 months. Soluble intercellular adhesion molecule-1 (sICAM-1) significantly increased in the heart homogenates at month 6, while other inflammatory cytokines were undetectable. This is the first study demonstrating smoking duration-dependent, complex cardiopulmonary alterations characteristic to COPD, in which inflammatory cytokine cascades and MMP-2/9 might be responsible for pulmonary destruction and sICAM-1 for heart dysfunction.

Receptor for advanced glycation end-products and World Trade Center particulate induced lung function loss: A case-cohort study and murine model of acute particulate exposure

World Trade Center-particulate matter(WTC-PM) exposure and metabolic-risk are associated with WTC-Lung Injury(WTC-LI). The receptor for advanced glycation end-products (RAGE) is most highly expressed in the lung, mediates metabolic risk, and single-nucleotide polymorphisms at the AGER-locus predict forced expiratory volume(FEV). Our objectives were to test the hypotheses that RAGE is a biomarker of WTC-LI in the FDNY-cohort and that loss of RAGE in a murine model would protect against acute PM-induced lung disease. We know from previous work that early intense exposure at the time of the WTC collapse was most predictive of WTC-LI therefore we utilized a murine model of intense acute PM-exposure to determine if loss of RAGE is protective and to identify signaling/cytokine intermediates. This study builds on a continuing effort to identify serum biomarkers that predict the development of WTC-LI. A case-cohort design was used to analyze a focused cohort of male never-smokers with normal pre-9/11 lung function. Odds of developing WTC-LI increased by 1.2, 1.8 and 1.0 in firefighters with soluble RAGE (sRAGE)≥97pg/mL, CRP≥2.4mg/L, and MMP-9≤397ng/mL, respectively, assessed in a multivariate logistic regression model (ROCAUC of 0.72). Wild type(WT) and RAGE-deficient(Ager-/-) mice were exposed to PM or PBS-control by oropharyngeal aspiration. Lung function, airway hyperreactivity, bronchoalveolar lavage, histology, transcription factors and plasma/BAL cytokines were quantified. WT-PM mice had decreased FEV and compliance, and increased airway resistance and methacholine reactivity after 24-hours. Decreased IFN-γ and increased LPA were observed in WT-PM mice; similar findings have been reported for firefighters who eventually develop WTC-LI. In the murine model, lack of RAGE was protective from loss of lung function and airway hyperreactivity and was associated with modulation of MAP kinases. We conclude that in a multivariate adjusted model increased sRAGE is associated with WTC-LI. In our murine model, absence of RAGE mitigated acute deleterious effects of PM and may be a biologically plausible mediator of PM-related lung disease.

Vitamin E isoform γ-tocotrienol protects against emphysema in cigarette smoke-induced COPD

Inflammation and oxidative stress contribute to emphysema in COPD. Although corticosteroids are the standard of care for COPD, they do not reduce oxidative stress, and a subset of patients is steroid-resistant. Vitamin E isoform γ-tocotrienol possesses both anti-inflammatory and anti-oxidative properties that may protect against emphysema. We aimed to establish the therapeutic potential of γ-tocotrienol in cigarette smoke-induced COPD models in comparison with prednisolone. BALB/c mice were exposed to cigarette smoke for 2 weeks or 2 months. γ-Tocotrienol and prednisolone were given orally. Bronchoalveolar lavage (BAL) fluid and lung tissues were assessed for inflammation, oxidative damage, and regulation of transcription factor activities. Emphysema and lung function were also evaluated. γ-Tocotrienol dose-dependently reduced cigarette smoke-induced BAL fluid neutrophil counts and levels of cytokines, chemokines and oxidative damage biomarkers, and pulmonary pro-inflammatory and pro-oxidant gene expression, but restored lung endogenous antioxidant activities. γ-Tocotrienol acted by inhibiting nuclear translocation of STAT3 and NF-κB, and up-regulating Nrf2 activation in the lungs. In mice exposed to 2-month cigarette smoke, γ-tocotrienol ameliorated bronchial epithelium thickening and destruction of alveolar sacs in lungs, and improved lung functions. In comparison with prednisolone, γ-tocotrienol demonstrated better anti-oxidative efficacy, and protection against emphysema and lung function in COPD. We revealed for the first time the anti-inflammatory and antioxidant efficacies of γ-tocotrienol in cigarette smoke-induced COPD models. In addition, γ-tocotrienol was able to attenuate emphysematous lesions and improve lung function in COPD. γ-Tocotrienol may have therapeutic potential for the treatment of COPD.

Generation of a Chronic Obstructive Pulmonary Disease Model in Mice by Repeated Ozone Exposure

Chronic obstructive pulmonary disease (COPD) is characterized by persistent airflow limitation and lung parenchymal destruction. It has a very high incidence in aging populations. The current conventional therapies for COPD focus mainly on symptom-modifying drugs; thus, the development of new therapies is urgently needed. Qualified animal models of COPD could help to characterize the underlying mechanisms and can be used for new drug screening. Current COPD models, such as lipopolysaccharide (LPS) or the porcine pancreatic elastase (PPE)-induced emphysema model, generate COPD-like lesions in the lungs and airways but do not otherwise resemble the pathogenesis of human COPD. A cigarette smoke (CS)-induced model remains one of the most popular because it not only simulates COPD-like lesions in the respiratory system, but it is also based on one of the main hazardous materials that causes COPD in humans. However, the time-consuming and labor-intensive aspects of the CS-induced model dramatically limit its application in new drug screening. In this study, we successfully generated a new COPD model by exposing mice to high levels of ozone. This model demonstrated the following: 1) decreased forced expiratory volume 25, 50, and 75/forced vital capacity (FEV25/FVC, FEV50/FVC, and FEV75/FVC), indicating the deterioration of lung function; 2) enlarged lung alveoli, with lung parenchymal destruction; 3) reduced fatigue time and distance; and 4) increased inflammation. Taken together, these data demonstrate that the ozone exposure (OE) model is a reliable animal model that is similar to humans because ozone overexposure is one of the etiological factors of COPD. Additionally, it only took 6 - 8 weeks, based on our previous work, to create an OE model, whereas it requires 3 - 12 months to induce the cigarette smoke model, indicating that the OE model might be a good choice for COPD research.

Hyperoxia treatment of TREK-1/TREK-2/TRAAK-deficient mice is associated with a reduction in surfactant proteins

We previously proposed a role for the two-pore domain potassium (K2P) channel TREK-1 in hyperoxia (HO)-induced lung injury. To determine whether redundancy among the three TREK isoforms (TREK-1, TREK-2, and TRAAK) could protect from HO-induced injury, we now examined the effect of deletion of all three TREK isoforms in a clinically relevant scenario of prolonged HO exposure and mechanical ventilation (MV). We exposed WT and TREK-1/TREK-2/TRAAK-deficient [triple knockout (KO)] mice to either room air, 72-h HO, MV [high and low tidal volume (TV)], or a combination of HO + MV and measured quasistatic lung compliance, bronchoalveolar lavage (BAL) protein concentration, histologic lung injury scores (LIS), cellular apoptosis, and cytokine levels. We determined surfactant gene and protein expression and attempted to prevent HO-induced lung injury by prophylactically administering an exogenous surfactant (Curosurf). HO treatment increased lung injury in triple KO but not WT mice, including an elevated LIS, BAL protein concentration, and markers of apoptosis, decreased lung compliance, and a more proinflammatory cytokine phenotype. MV alone had no effect on lung injury markers. Exposure to HO + MV (low TV) further decreased lung compliance in triple KO but not WT mice, and HO + MV (high TV) was lethal for triple KO mice. In triple KO mice, the HO-induced lung injury was associated with decreased surfactant protein (SP) A and SPC but not SPB and SPD expression. However, these changes could not be explained by alterations in the transcription factors nuclear factor-1 (NF-1), NKX2.1/thyroid transcription factor-1 (TTF-1) or c-jun, or lamellar body levels. Prophylactic Curosurf administration did not improve lung injury scores or compliance in triple KO mice.

Cardiorespiratory pathogenesis of sickle cell disease in a mouse model

The nature and development of cardiorespiratory impairments associated with sickle cell disease are poorly understood. Given that the mechanisms of these impairments cannot be addressed adequately in clinical studies, we characterized cardiorespiratory pathophysiology from birth to maturity in the sickle cell disease SAD mouse model. We identified two critical phases of respiratory dysfunction in SAD mice; the first prior to weaning and the second in adulthood. At postnatal day 3, 43% of SAD mice showed marked apneas, anemia, and pulmonary vascular congestion typical of acute chest syndrome; none of these mice survived to maturity. The remaining SAD mice had mild lung histological changes in room air with an altered respiratory pattern, seizures, and a high rate of death in response to hypoxia. Approximately half the SAD mice that survived to adulthood had an identifiable respiratory phenotype including baseline tachypnea at 7–8 months of age, restrictive lung disease, pulmonary hypertension, cardiac enlargement, lower total lung capacity, and pulmonary vascular congestion. All adult SAD mice demonstrated impairments in exercise capacity and response to hypoxia, with a more severe phenotype in the tachypneic mice. The model revealed distinguishable subgroups of SAD mice with cardiorespiratory pathophysiology mimicking the complications of human sickle cell disease.

An Official American Thoracic Society Workshop Report: Use of Animal Models for the Preclinical Assessment of Potential Therapies for Pulmonary Fibrosis

Numerous compounds have shown efficacy in limiting development of pulmonary fibrosis using animal models, yet few of these compounds have replicated these beneficial effects in clinical trials. Given the challenges associated with performing clinical trials in patients with idiopathic pulmonary fibrosis (IPF), it is imperative that preclinical data packages be robust in their analyses and interpretations to have the best chance of selecting promising drug candidates to advance to clinical trials. The American Thoracic Society has convened a group of experts in lung fibrosis to discuss and formalize recommendations for preclinical assessment of antifibrotic compounds. The panel considered three major themes (choice of animal, practical considerations of fibrosis modeling, and fibrotic endpoints for evaluation). Recognizing the need for practical considerations, we have taken a pragmatic approach. The consensus view is that use of the murine intratracheal bleomycin model in animals of both genders, using hydroxyproline measurements for collagen accumulation along with histologic assessments, is the best-characterized animal model available for preclinical testing. Testing of antifibrotic compounds in this model is recommended to occur after the acute inflammatory phase has subsided (generally after Day 7). Robust analyses may also include confirmatory studies in human IPF specimens and validation of results in a second system using in vivo or in vitro approaches. The panel also strongly encourages the publication of negative results to inform the lung fibrosis community. These recommendations are for preclinical therapeutic evaluation only and are not intended to dissuade development of emerging technologies to better understand IPF pathogenesis.

Automated full-range pressure-volume curves in mice and rats

Pressure-volume (PV) curves constructed over the entire lung volume range can reliably detect functional changes in mouse models of lung diseases. In the present study, we constructed full-range PV curves in healthy and elastase-treated mice using either a classic manually operated technique or an automated approach using a computer-controlled piston ventilator [flexiVent FX; Scientific Respiratory Equipment (SCIREQ), Montreal, Quebec, Canada]. On the day of the experiment, subjects were anesthetized, tracheotomized, and mechanically ventilated. Following an initial respiratory mechanics scan and degassing of the lungs with 100% O₂, full-range PV curves were constructed using either the classic or the automated technique. In control mice, superimposable curves were obtained, and statistical equivalence was attained between the two methodologies. In the elastase-treated ones, where significant changes in respiratory mechanics and lung volumes were expected, very small differences were observed between the two techniques, and the criteria for statistical equivalence were met in two out of four parameters assessed. The automated technique was adapted to rats and used to estimate the functional residual capacity (FRC) by volume subtraction. This novel approach generated FRC estimates consistent with the literature, with added accuracy relative to the existing method in diseased subjects. In conclusion, the automated technique generated full-range PV curves that were equivalent or very close to those obtained with the classic method under physiological or severe pathological conditions. The automation facilitated some technical aspects of the procedure, eased its use across species, and helped derive a more accurate estimate of FRC in preclinical models of respiratory disease.NEW & NOTEWORTHY Partial and full-range pressure-volume (PV) curves are frequently used to characterize lung disease models. Whereas automated techniques exist to construct partial PV curves, a manually operated approach is classically employed to build the full-range ones. In this study, the full-range PV curve technique was automated using a computer-controlled piston ventilator. The automation simplified the technique, facilitated its extension to other species, and inspired a novel way of estimating the functional residual capacity in laboratory rodents.

IL-13 is a central mediator of chemical-induced airway hyperreactivity in mice

BACKGROUND

While the importance of the Th2 cytokine IL-13 as a central mediator of airway hyperreactivity (AHR) has been described in allergic protein-induced asthma, this has never been investigated in chemical-induced asthma.

OBJECTIVE

We examined the importance of IL-13 in a mouse model of chemical-induced AHR, using toluene-2,4-diisocyanate (TDI).

METHODS

In a first set-up, wild type (WT) and IL-13 knockout (KO) C57Bl/6 mice were dermally treated on days 1 and 8 with 1% TDI or vehicle (acetone/olive oil) on both ears. On day 15, mice received an intranasal instillation with 0.1% TDI or vehicle. In a second set-up, WT mice sensitized with 1% TDI or vehicle, received i.v. either anti-IL-13 or control antibody prior to the intranasal challenge.

RESULTS

TDI-sensitized and TDI-challenged WT mice showed AHR to methacholine, in contrast to TDI-sensitized and TDI-challenged IL-13 KO mice, which also showed lower levels of total serum IgE. TDI-sensitized and TDI-challenged IL-13 KO mice had lower numbers of T-cells in the auricular lymph nodes. TDI-treated WT mice, receiving anti-IL-13, showed no AHR, in contrast to those receiving control antibody, despite increased levels of IgE. Anti-IL-13 treatment in TDI-treated WT mice resulted in lower levels of serum IL-13, but did not induce changes in T- and B-cell numbers, and in the cytokine production profile.

CONCLUSION AND CLINICAL RELEVANCE

We conclude that IL-13 plays a critical role in the effector phase of chemical-induced, immune-mediated AHR. This implicates that anti-IL-13 treatment could have a beneficial effect in patients with this asthma phenotype.

Sirolimus alters lung pathology and viral load following influenza A virus infection

Background

Inhibitors of mTOR, such as sirolimus, have been shown to induce thymus involution and inflammatory lung disease in mice. The latter effect supports the role of this serine/threonine kinase in ameliorating lung inflammation. Other studies have shown sirolimus reduces/delays lung disease associated with various strains of influenza A virus (IAV). Thus, the effects of mTOR inhibitors on influenza infection deserve further studies.

Methods

Here, we examined the changes in lung viral copies, pathology and pulmonary function associated with IAV (A/PR/8/34) infection in mice treated with sirolimus.

Results

Body weight loss peaked between days 6–11 post-infection and was more severe in IAV-infected mice that were administered sirolimus as compared to mice that received IAV alone (p = 0.030). Natural log viral gene copies, mean ± SD per mg lung tissue, in IAV-infected mice that were administered sirolimus were 17.31 ± 1.27 on day 4, 19.31 ± 7.46 on day 10, and 0 on day 25. The corresponding number of copies in mice that received IAV alone were 18.56 ± 0.95 on day 4 (p = 0.132), 1.52 ± 1.39 on day 10 (p = 0.008), and 0 on day 25. Lung pathology was evident on days 4, 10, and 25 post infection, with mean ± SD inflammatory score of 9.0 ± 4.5 in IAV-infected mice that were administered sirolimus, as compared to 11.5 ± 4.5 (p = 0.335) in mice received IAV alone (maximum score, 26.0). Impaired lung function was evident in IAV-infected mice on days 4 and 10, as demonstrated by increased airway resistance and decreased compliance.

Conclusions

In this model, the effects of sirolimus on influenza infection included severe weight loss and modified viral replication, respiratory function and lung inflammation. The adverse events associated with sirolimus treatment are consistent with its potent immunosuppressive activity and, thus, preclude its use in IAV infection.

Hydrogen Sulfide Prevents and Partially Reverses Ozone-Induced Features of Lung Inflammation and Emphysema in Mice

Hydrogen sulfide (H2S), a novel signaling gasotransmitter in the respiratory system, may have antiinflammatory properties in the lung. We examined the preventive and therapeutic effects of H2S on ozone-induced features of lung inflammation and emphysema. C57/BL6 mice were exposed to ozone or filtered air over 6 weeks. Sodium hydrogen sulfide (NaHS), an H2S donor, was administered to the mice either before ozone exposure (preventive effect) or after completion of 6 weeks of ozone exposure (therapeutic effect). The ozone-exposed mice developed emphysema, measured by micro-computed tomography and histology, airflow limitation, measured by the forced maneuver system, and increased lung inflammation with augmented IL-1β, IL-18, and matrix metalloproteinase-9 (MMP-9) gene expression. Ozone-induced changes were associated with increased Nod-like receptor pyrin domain containing 3 (NLRP3)-caspase-1 activation and p38 mitogen-activated protein kinase phosphorylation and decreased Akt phosphorylation. NaHS both prevented and reversed lung inflammation and emphysematous changes in alveolar space. In contrast, NaHS prevented, but did not reverse, ozone-induced airflow limitation and bronchial structural remodeling. In conclusion, NaHS administration prevented and partially reversed ozone-induced features of lung inflammation and emphysema via regulation of the NLRP3-caspase-1, p38 mitogen-activated protein kinase, and Akt pathways.

Forced expiration measurements in mouse models of obstructive and restrictive lung diseases

Background

Pulmonary function measurements are important when studying respiratory disease models. Both resistance and compliance have been used to assess lung function in mice. Yet, it is not always clear how these parameters relate to forced expiration (FE)-related parameters, most commonly used in humans. We aimed to characterize FE measurements in four well-established mouse models of lung diseases.

Method

Detailed respiratory mechanics and FE measurements were assessed concurrently in Balb/c mice, using the forced oscillation and negative pressure-driven forced expiration techniques, respectively. Measurements were performed at baseline and following increasing methacholine challenges in control Balb/c mice as well as in four disease models: bleomycin-induced fibrosis, elastase-induced emphysema, LPS-induced acute lung injury and house dust mite-induced asthma.

Results

Respiratory mechanics parameters (airway resistance, tissue damping and tissue elastance) confirmed disease-specific phenotypes either at baseline or following methacholine challenge. Similarly, lung function defects could be detected in each disease model by at least one FE-related parameter (FEV_0.1, FEF_0.1, FVC, FEV_0.1/FVC ratio and PEF) at baseline or during the methacholine provocation assay.

Conclusions

FE-derived outcomes in four mouse disease models behaved similarly to changes found in human spirometry. Routine combined lung function assessments could increase the translational utility of mouse models.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-017-0610-1) contains supplementary material, which is available to authorized users.

Effects of diesel exhaust particle exposure on a murine model of asthma due to soybean

BACKGROUND

Exposure to soybean allergens has been linked to asthma outbreaks. Exposure to diesel exhaust particles (DEP) has been associated with an increase in the risk of asthma and asthma exacerbation; however, in both cases the underlying mechanisms remain poorly understood, as does the possible interaction between the two entities.

OBJECTIVE

To investigate how the combination of soybean allergens and DEP can affect the induction or exacerbation of asthma in a murine model.

METHODS

BALB/c mice received intranasal instillations of saline, 3 or 5 mg protein/ml soybean hull extract (SHE), or a combination of one of these three solutions with DEP. Airway hyperresponsiveness (AHR), pulmonary inflammation in bronchoalveolar lavage, total serum immunoglobulin E and histological studies were assessed.

RESULTS

A 5 mg protein/ml SHE solution was able by itself to enhance AHR (p = 0.0033), increase eosinophilic inflammation (p = 0.0003), increase levels of IL-4, IL-5, IL-13, IL-17A, IL-17F and CCL20, and reduce levels of IFN-γ. The combination of 5 mg protein/ml SHE with DEP also produced an increase in AHR and eosinophilic inflammation, but presented a slightly different cytokine profile with higher levels of Th17-related cytokines. However, while the 3 mg protein/ml SHE solution did not induce asthma, co-exposure with DEP resulted in a markedly enhanced AHR (p = 0.002) and eosinophilic inflammation (p = 0.004), with increased levels of IL-5, IL-17F and CCL20 and decreased levels of IFN-γ.

CONCLUSIONS & CLINICAL RELEVANCE

The combination of soybean allergens and DEP is capable of triggering an asthmatic response through a Th17-related mechanism when the soybean allergen concentration is too low to promote a response by itself. DEP monitoring may be a useful addition to allergen monitoring in order to prevent new asthma outbreaks.

Posttreatment with Protectin DX ameliorates bleomycin-induced pulmonary fibrosis and lung dysfunction in mice

Protectin DX (10S,17S-dihydroxydocosa-4Z,7Z,11E,13Z,15E,19Z-hexaenoic acid) (PDX), generated from Ω-3 fatty docosahexaenoic acids, is believed to exert anti-inflammatory and proresolution bioactions. To date, few studies have been performed regarding its effect on pulmonary fibrosis. Herein we show that PDX exerts a potential therapeutic effect which is distinct from its anti-inflammation and pro-resolution activity on mice with pulmonary fibrosis. In the present study, we showed that bleomycin (BLM) increased inflammatory infiltration, collagen deposition, and lung dysfunction on day7 after challenged in mice. Posttreatment with PDX ameliorated BLM-induced inflammatory responses, extracellular matrix (ECM) deposition and the level of cytokines related to fibrosis as evaluated by histology analysis, transformation electron microscope (TEM), lung hydroxyproline content and cytokines test. Moreover, PDX improved lung respiratory function, remedied BLM-induced hypoxemia and prolonged life span. In addition, we found that PDX reversed epithelial–mesenchymal transition (EMT) phenotypic transformation in vivo and in vitro, reinforcing a potential mechanism of promoting fibrosis resolution. In summary, our findings showed that posttreatment with PDX could ameliorate BLM-induced pulmonary fibrosis and lung dysfunction in mice and PDX may be considered as a promising therapeutic approached to fibrotic lung diseases.

Disruption of the Hepcidin/Ferroportin Regulatory System Causes Pulmonary Iron Overload and Restrictive Lung Disease

Emerging evidence suggests that pulmonary iron accumulation is implicated in a spectrum of chronic lung diseases. However, the mechanism(s) involved in pulmonary iron deposition and its role in the in vivo pathogenesis of lung diseases remains unknown. Here we show that a point mutation in the murine ferroportin gene, which causes hereditary hemochromatosis type 4 (Slc40a1^C326S), increases iron levels in alveolar macrophages, epithelial cells lining the conducting airways and lung parenchyma, and in vascular smooth muscle cells. Pulmonary iron overload is associated with oxidative stress, restrictive lung disease with decreased total lung capacity and reduced blood oxygen saturation in homozygous Slc40a1^C326S/C326S mice compared to wild-type controls. These findings implicate iron in lung pathology, which is so far not considered a classical iron-related disorder.

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Ferroportin resistance to hepcidin binding leads to pulmonary iron overload.

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Lung iron accumulation is restricted to specific cell types.

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Iron overload causes restrictive lung disease and decreased blood oxygen saturation.

Pulmonary iron accumulation is associated with a wide spectrum of lung diseases, such as chronic obstructive pulmonary disease and cystic fibrosis. Impaired lung function was further reported in patients with thalassemia major, a disease hallmarked by transfusional iron overload. So far, the mechanism(s) leading to pulmonary iron deposition and its role in disease onset and progression are still unknown. Our study shows that in a murine disease model, in which the control of systemic iron homeostasis is disrupted, iron accumulates in the lung and correlates with oxidative stress, restrictive lung disease and decreased blood oxygen saturation. These findings implicate iron overload in lung pathology, which is not considered a classical iron-related disorder.

Effects of human umbilical cord blood mononuclear cells on respiratory system mechanics in a murine model of neonatal lung injury

BACKGROUND

Mononuclear cells (MNCs) have well-documented beneficial effects in a wide range of adult pulmonary diseases. The effects of human umbilical cord blood-derived MNCs on neonatal lung injury, highly relevant for potential autologous application in preterm newborns at risk for bronchopulmonary dysplasia (BPD), remain incompletely established. The aim of this study was to determine the long-term morphologic and functional effects of systemically delivered MNCs in a murine model of neonatal lung injury.

MATERIALS AND METHODS

MNCs from cryopreserved cord blood (1 × 10⁶ cells per pup) were given intravenously to newborn mice exposed to 90% O₂ from birth; controls received cord blood total nucleated cells (TNCs) or granular cells, or equal volume vehicle buffer (sham controls). In order to avoid immune rejection, we used SCID mice as recipients. Lung mechanics (flexiVent™), engraftment, growth, and alveolarization were evaluated eight weeks postinfusion.

RESULTS

Systemic MNC administration to hyperoxia-exposed newborn mice resulted in significant attenuation of methacholine-induced airway hyperreactivity, leading to reduction of central airway resistance to normoxic levels. These bronchial effects were associated with mild improvement of alveolarization, lung compliance, and elastance. TNCs had no effects on alveolar remodeling and were associated with worsened methacholine-induced bronchial hyperreactivity. Granular cell administration resulted in a marked morphologic and functional emphysematous phenotype, associated with high mortality. Pulmonary donor cell engraftment was sporadic in all groups.

CONCLUSIONS

These results suggest that cord blood MNCs may have a cell type-specific role in therapy of pulmonary conditions characterized by increased airway resistance, such as BPD and asthma. Future studies need to determine the active MNC subtype(s), their mechanisms of action, and optimal purification methods to minimize granular cell contamination.

Airway smooth muscle dysfunction in Pompe (Gaa-/- ) mice

Pompe disease is an autosomal recessive disorder caused by a deficiency of acid α-glucosidase (GAA), an enzyme responsible for hydrolyzing lysosomal glycogen. Deficiency of GAA leads to systemic glycogen accumulation in the lysosomes of skeletal muscle, motor neurons, and smooth muscle. Skeletal muscle and motor neuron pathology are known to contribute to respiratory insufficiency in Pompe disease, but the role of airway pathology has not been evaluated. Here we propose that GAA enzyme deficiency disrupts the function of the trachea and bronchi and this lower airway pathology contributes to respiratory insufficiency in Pompe disease. Using an established mouse model of Pompe disease, the Gaa^-/- mouse, we compared histology, pulmonary mechanics, airway smooth muscle (ASM) function, and calcium signaling between Gaa^-/- and age-matched wild-type (WT) mice. Lysosomal glycogen accumulation was observed in the smooth muscle of both the bronchi and the trachea in Gaa^-/- but not WT mice. Furthermore, Gaa^-/- mice had hyporesponsive airway resistance and bronchial ring contraction to the bronchoconstrictive agents methacholine (MCh) and potassium chloride (KCl) and to a bronchodilator (albuterol). Finally, calcium signaling during bronchiolar smooth muscle contraction was impaired in Gaa^-/- mice indicating impaired extracellular calcium influx. We conclude that GAA enzyme deficiency leads to glycogen accumulation in the trachea and bronchi and impairs the ability of lower ASM to regulate calcium and respond appropriately to bronchodilator or constrictors. Accordingly, ASM dysfunction may contribute to respiratory impairments in Pompe disease.

Standardized Herbal Formula PM014 Inhibits Radiation-Induced Pulmonary Inflammation in Mice

Radiation therapy is widely used for thoracic cancers. However, it occasionally causes radiation-induced lung injuries, including pneumonitis and fibrosis. Chung-Sang-Bo-Ha-Tang (CSBHT) has been traditionally used to treat chronic pulmonary disease in Korea. PM014, a modified herbal formula derived from CSBHT, contains medicinal herbs of seven species. In our previous studies, PM014 exhibited anti-inflammatory effects in a chronic obstructive pulmonary disease model. In this study, we have evaluated the effects of PM014 on radiation-induced lung inflammation. Mice in the treatment group were orally administered PM014 six times for 2 weeks. Effects of PM014 on radiation pneumonitis were evaluated based on histological findings and differential cell count in bronchoalveolar lavage fluid. PM014 treatment significantly inhibited immune cell recruitment and collagen deposition in lung tissue. Normal lung volume, evaluated by radiological analysis, in PM014-treated mice was higher compared to that in irradiated control mice. PM014-treated mice exhibited significant changes in inspiratory capacity, compliance and tissue damping and elastance. Additionally, PM014 treatment resulted in the downregulation of inflammatory cytokines, chemokines, and fibrosis-related genes and a reduction in the transforming growth factor-β1-positive cell population in lung tissue. Thus, PM014 is a potent therapeutic agent for radiation-induced lung fibrosis and inflammation.

Combined Effects of in Utero and Adolescent Tobacco Smoke Exposure on Lung Function in C57Bl/6J Mice

BACKGROUND

Fetal determinants of airway function, such as in utero exposure to maternal cigarette smoke (CS), may create a predisposition to adult airflow obstruction and chronic obstructive pulmonary disease (COPD) in adulthood. It has been suggested that active smoking in adolescence and preexisting airflow obstruction have synergistic deleterious effects.

OBJECTIVE

We used a mouse model to investigate whether there is a synergistic effect of exposure to CS in utero and during adolescence on lung function.

METHODS

Female C57Bl/6J mice were exposed to CS or to filtered room air during pregnancy. Exposure to CS began 2 weeks before mating and continued until delivery. After birth, the pups were not exposed to CS until day 21 (D21). Between D21 and D49, corresponding to "adolescence," litters were randomized for an additional 4 weeks of exposure to CS. Lung morphometry, lung mechanics, and the expression of genes involved in senescence were evaluated in different subsets of mice on D21 and D49.

RESULTS

In utero exposure to CS induced significant lung function impairment by D21. CS exposure between D21 and D49 induced significant functional impairment only in mice exposed to CS prenatally. On D49, no difference was observed between subgroups in terms of lung p53, p16, p21, and Bax mRNA levels.

CONCLUSIONS

Our findings suggest that prenatal and adolescent CS exposure have a synergistic effect on lung function in mice. The combined effect did not appear to be a consequence of early pulmonary senescence. Citation: Drummond D, Baravalle-Einaudi M, Lezmi G, Vibhushan S, Franco-Montoya ML, Hadchouel A, Boczkowski J, Delacourt C. 2017. Combined effects of in utero and adolescent tobacco smoke exposure on lung function in C57Bl/6J mice. Environ Health Perspect 125:392-399; http://dx.doi.org/10.1289/EHP54.

The use of mesenchymal stromal cells in treatment of lung disorders

The therapeutic use of mesenchymal stromal cells (MSCs) represents a promising alternative clinical strategy for treating acute and chronic lung disorders. Several preclinical reports demonstrated that MSCs can secrete multiple paracrine factors and that their immunomodulatory properties can support endothelial and epithelial regeneration, modulate the inflammatory cascade and protect lungs from damage. The effects of MSC transplantation into patients suffering from lung diseases should be fully evaluated through careful assessment of safety and associated risks, which is a prerequisite for translation of preclinical research into clinical practice. In this article, we summarize the current status of preclinical research and review initial MSC-based clinical trials for treating lung injuries and lung disorders.

Cellular senescence mediates fibrotic pulmonary disease

Idiopathic pulmonary fibrosis (IPF) is a fatal disease characterized by interstitial remodelling, leading to compromised lung function. Cellular senescence markers are detectable within IPF lung tissue and senescent cell deletion rejuvenates pulmonary health in aged mice. Whether and how senescent cells regulate IPF or if their removal may be an efficacious intervention strategy is unknown. Here we demonstrate elevated abundance of senescence biomarkers in IPF lung, with p16 expression increasing with disease severity. We show that the secretome of senescent fibroblasts, which are selectively killed by a senolytic cocktail, dasatinib plus quercetin (DQ), is fibrogenic. Leveraging the bleomycin-injury IPF model, we demonstrate that early-intervention suicide-gene-mediated senescent cell ablation improves pulmonary function and physical health, although lung fibrosis is visibly unaltered. DQ treatment replicates benefits of transgenic clearance. Thus, our findings establish that fibrotic lung disease is mediated, in part, by senescent cells, which can be targeted to improve health and function.

Role of IL-17A in murine models of COPD airway disease

Small airway fibrosis is a major pathological feature of chronic obstructive pulmonary disease (COPD) and is refractory to current treatments. Chronic inflammatory cells accumulate around small airways in COPD and are thought to play a major role in small airway fibrosis. Mice deficient in α/β T cells have recently been shown to be protected from both experimental airway inflammation and fibrosis. In these models, CD4+Th17 cells and secretion of IL-17A are increased. However, a pathogenic role for IL-17 in specifically mediating fibrosis around airways has not been demonstrated. Here a role for IL-17A in airway fibrosis was demonstrated using mice deficient in the IL-17 receptor A (il17ra) Il17ra-deficient mice were protected from both airway inflammation and fibrosis in two different models of airway fibrosis that employ COPD-relevant stimuli. In these models, CD4+ Th17 are a major source of IL-17A with other expressing cell types including γδ T cells, type 3 innate lymphoid cells, polymorphonuclear cells, and CD8+ T cells. Antibody neutralization of IL-17RA or IL-17A confirmed that IL-17A was the relevant pathogenic IL-17 isoform and IL-17RA was the relevant receptor in airway inflammation and fibrosis. These results demonstrate that the IL-17A/IL-17 RA axis is crucial to murine airway fibrosis. These findings suggest that IL-17 might be targeted to prevent the progression of airway fibrosis in COPD.

Cardiopulmonary and histological characterization of an acute rat lung injury model demonstrating safety of mesenchymal stromal cell infusion

BACKGROUND AIMS

In the field of cellular therapy, potential cell entrapment in the lungs following intravenous administration in a compromised or injured pulmonary system is an important concern that requires further investigation. We developed a rat model of inflammatory and fibrotic lung disease to mimic the human clinical condition of obliterative bronchiolitis (OB) and evaluate the safety of intravenous infusion of mesenchymal stromal cells (MSCs). This model was used to obtain appropriate safety information and functional characterization to support the translation of an ex vivo-generated cellular product into human clinical trials. To overcome spontaneous recovery and size limitations associated with current animal models, we used a novel multiple dose bleomycin strategy to induce lasting lung injury in rats.

METHODS

Intratracheal instillation of bleomycin was administered to rats on multiple days. MSCs were intravenously infused 7 days apart. Detailed pulmonary function tests including forced expiratory volume, total lung capacity, and invasive hemodynamic measurements were conducted to define the representative disease model and monitor cardiopulmonary hemodynamic consequences of the cell infusion. Post-euthanasia assessments included a thorough evaluation of lung morphology and histopathology.

RESULTS

The double dose bleomycin instillation regimen resulted in severe and irreversible lung injury and fibrosis. Cardiopulmonary physiological monitoring reveled that no adverse events could be attributed to the cell infusion process.

DISCUSSION

Although our study did not show the infusion of MSCs to result in an improvement in lung function or rescue of damaged tissue this study does confirm the safety of MSC infusion into damaged lungs.

X-Ray based Lung Function measurement-a sensitive technique to quantify lung function in allergic airway inflammation mouse models

In mice, along with the assessment of eosinophils, lung function measurements, most commonly carried out by plethysmography, are essential to monitor the course of allergic airway inflammation, to examine therapy efficacy and to correlate animal with patient data. To date, plethysmography techniques either use intubation and/or restraining of the mice and are thus invasive, or are limited in their sensitivity. We present a novel unrestrained lung function method based on low-dose planar cinematic x-ray imaging (X-Ray Lung Function, XLF) and demonstrate its performance in monitoring OVA induced experimental allergic airway inflammation in mice and an improved assessment of the efficacy of the common treatment dexamethasone. We further show that XLF is more sensitive than unrestrained whole body plethysmography (UWBP) and that conventional broncho-alveolar lavage and histology provide only limited information of the efficacy of a treatment when compared to XLF. Our results highlight the fact that a multi-parametric imaging approach as delivered by XLF is needed to address the combined cellular, anatomical and functional effects that occur during the course of asthma and in response to therapy.

Proton-pump inhibitor omeprazole attenuates hyperoxia induced lung injury

Background

The administration of supplemental oxygen to treat ventilatory insufficiency may lead to the formation of reactive oxygen species and subsequent tissue damage. Cytochrome P4501A1 (CYP1A1) can modulate hyperoxic lung injury by a currently unknown mechanism. Our objective was to evaluate the effect of administration of omeprazole on the induction of CYP1A1 and its influence on hyperoxic lung injury in an established preterm rabbit model.

Methods

Omeprazole was administered either (1) directly to the fetus, (2) to the mother or (3) after birth to the pups in different doses (2–10 or 20 mg/kg). Controls were injected with the same amount of saline. Pups were housed in normoxia (21 %) or hyperoxia (>95 %) for 5 days. Outcome parameters were induction of CYP1A1 measured by real-time polymerase chain reaction (RT-PCR) immediately after delivery, at day 3 and day 5 as well as lung function, morphometry and immunohistochemistry assessed at day 5 of life. Transcriptome analysis was used to define the targeted pathways.

Results

Daily neonatal injections demonstrated a dose-dependent increase in CYP1A1. Lung function tests showed a significant improvement in tissue damping, tissue elasticity, total lung capacity, static compliance and elastance. Morphometry revealed a more developed lung architecture with thinned septae in animals treated with the highest dose (20 mg/kg) of omeprazole. Surfactant protein B, vascular endothelial growth factor and its receptor were significantly increased on immunohistochemical stainings after omeprazole treatment.

Conclusions

Neonatal administration of omeprazole induces CYP1A1 in a dose-dependent matter and combined pre- and postnatal administration attenuates hyperoxic lung injury in preterm rabbits, even with the lowest dose of omeprazole without clear CYP1A1 induction.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-016-1009-3) contains supplementary material, which is available to authorized users.

Persistence of respiratory and inflammatory responses after dermal sensitization to persulfate salts in a mouse model of non-atopic asthma

Background

Exposure to ammonium persulfate (AP) has been reported to be the main cause of occupational asthma in hairdressers. The aim of this study is to assess how long the asthmatic response to AP can be induced after dermal sensitization in a mouse model.

Methods

BALB/c mice received dermal applications of AP or dimethylsulfoxide (DMSO) (control) on days 1 and 8. They then received a single nasal instillation (challenge) of AP or saline on days 15, 22, 29, 36, 45, 60 and 90. Respiratory responsiveness to methacholine was measured 24 h after the challenge using a non-specific methacholine provocation test. Pulmonary inflammation was analysed in bronchoalveolar lavage (BAL), and total serum immunoglobulin (Ig) E, IgG1 and IgG2a were measured in serum samples. Histological analysis of lung slides was performed.

Results

Mice dermally sensitized and intranasally challenged with AP showed respiratory responsiveness to methacholine as long as 45 days after initial sensitization, as well as increased percentage of neutrophils in BAL compared with the control group. At day 60, dermally sensitized mice still presented bronchial hyperresponsiveness, while the percentage of neutrophils returned to baseline levels similar to those of controls. Total serum IgE increased significantly on day 22 after dermal sensitization. Total serum IgG1 and IgG2a increased from 45 days after dermal sensitization and remained high at 90 days.

Conclusions

Both respiratory responsiveness to methacholine and airway inflammation responses decrease with increasing time between sensitization and challenge. Respiratory responsiveness to methacholine tends to persist longer than inflammation.

Neuro-immune interactions in chemical-induced airway hyperreactivity

Asthma may be induced by chemical sensitisers, via mechanisms that are still poorly understood. This type of asthma is characterised by airway hyperreactivity (AHR) and little airway inflammation. Since potent chemical sensitisers, such as toluene-2,4-diisocyanate (TDI), are also sensory irritants, it is suggested that chemical-induced asthma relies on neuro-immune mechanisms.We investigated the involvement of transient receptor potential channels (TRP) A1 and V1, major chemosensors in the airways, and mast cells, known for their ability to communicate with sensory nerves, in chemical-induced AHR.In vitro intracellular calcium imaging and patch-clamp recordings in TRPA1- and TRPV1-expressing Chinese hamster ovarian cells showed that TDI activates murine TRPA1, but not TRPV1. Using an in vivo model, in which an airway challenge with TDI induces AHR in TDI-sensitised C57Bl/6 mice, we demonstrated that AHR does not develop, despite successful sensitisation, in Trpa1 and Trpv1 knockout mice, and wild-type mice pretreated with a TRPA1 blocker or a substance P receptor antagonist. TDI-induced AHR was also abolished in mast cell deficient Kit(Wsh) (/Wsh) mice, and in wild-type mice pretreated with the mast cell stabiliser ketotifen, without changes in immunological parameters.These data demonstrate that TRPA1, TRPV1 and mast cells play an indispensable role in the development of TDI-elicited AHR.

Coactivator-Associated Arginine Methyltransferase-1 Function in Alveolar Epithelial Senescence and Elastase-Induced Emphysema Susceptibility

Chronic obstructive pulmonary disease (COPD) is characterized by an irreversible loss of lung function and is one of the most prevalent and severe diseases worldwide. A major feature of COPD is emphysema, which is the progressive loss of alveolar tissue. Coactivator-associated arginine methyltransferase-1 (CARM1) regulates histone methylation and the transcription of genes involved in senescence, proliferation, and differentiation. Complete loss of CARM1 leads to disrupted differentiation and maturation of alveolar epithelial type II (ATII) cells. We thus hypothesized that CARM1 regulates the development and progression of emphysema. To address this, we investigated the contribution of CARM1 to alveolar rarefication using the mouse model of elastase-induced emphysema in vivo and small interfering (si)RNA-mediated knockdown in ATII-like LA4 cells in vitro. We demonstrate that emphysema progression in vivo is associated with a time-dependent down-regulation of CARM1. Importantly, elastase-treated CARM1 haploinsufficient mice show significantly increased airspace enlargement (52.5 ± 9.6 μm versus 38.8 ± 5.5 μm; P < 0.01) and lung compliance (2.8 ± 0.32 μl/cm H2O versus 2.4 ± 0.4 μl/cm H2O; P < 0.04) compared with controls. The knockdown of CARM1 in LA4 cells led to decreased sirtuin 1 expression (0.034 ± 0.003 versus 0.022 ± 0.001; P < 0.05) but increased expression of p16 (0.27 ± 0.013 versus 0.31 ± 0.010; P < 0.5) and p21 (0.81 ± 0.088 versus 1.28 ± 0.063; P < 0.01) and higher β-galactosidase-positive senescent cells (50.57 ± 7.36% versus 2.21 ± 0.34%; P < 0.001) compared with scrambled siRNA. We further demonstrated that CARM1 haploinsufficiency impairs transdifferentiation and wound healing (32.18 ± 0.9512% versus 8.769 ± 1.967%; P < 0.001) of alveolar epithelial cells. Overall, these results reveal a novel function of CARM1 in regulating emphysema development and premature lung aging via alveolar senescence as well as impaired regeneration, repair, and differentiation of ATII cells.

Effects of antenatal lipopolysaccharide and postnatal hyperoxia on airway reactivity and remodeling in a neonatal mouse model

BACKGROUND

Antenatal inflammation and preterm birth are associated with the development of airway diseases such as wheezing and asthma. Utilizing a newborn mouse model, we assessed the effects of maternal inflammation and postnatal hyperoxia on the neonatal airway.

METHODS

Pregnant C57/Bl6 dams were injected with lipopolysaccharide (LPS) or saline on embryonic day 16. Offspring were placed in room air or hyperoxia (50% O2) for 7 d and then returned to normoxia. Airway mechanics, histology, and laser capture micro-dissection (LCM) were performed.

RESULTS

At postnatal day 21, maternal LPS- and 50% O2-exposed pups exhibited increased resistance and decreased compliance compared to 21% O2 pups; however their effects were not synergistic. LPS and hyperoxia each increased the thickness of airway smooth muscle (ASM), but not the airway epithelial layer. Structural changes were largely limited to the conducting airways. Upregulation of inflammatory markers in the lung was observed at birth. LCM revealed increased collagen-3, transforming growth factor β, and connective tissue growth factor expression with LPS and hyperoxia within the ASM layer.

CONCLUSION

These novel studies provide functional, structural, and molecular evidence that antenatal inflammation is detrimental to the developing airway. Exposure to moderate hyperoxia does not exacerbate LPS effects on the airway.

Plethysmography measurements of respiratory function in conscious unrestrained mice

Whole body plethysmography (WBP) is used to quantify pulmonary function in conscious, unrestrained mice. We determined currently whether time of day and environmental lighting influence day-to-day reproducibility of pulmonary function, and quantifed the necessary habituation time in the WBP chamber. Two-month-old male C57BL6 and mdx mice (n = 8/group, reverse light cycle), were examined on consecutive days using a calibrated WBP chamber and manufacturer software was used to calculate respiratory measures. Respiratory data stabilized between 5-10 min for all variables. Mice exhibited time of day respiratory differences, performing more forceful and less frequent breaths midday (11:45 a.m. and 3:00 p.m.) compared to 7:30 a.m. WBP performed in darkened conditions elicited more forceful breathing than lit conditions. Day-to-day reproducibility during controlled conditions ranged from r(2) = 0.58 to 0.62 for the functional measures. Findings indicate reproducible respiratory data are obtainable following a 15-min chamber habituation and standardization of time of day and room lighting.

Comprehensive systems biology analysis of a 7-month cigarette smoke inhalation study in C57BL/6 mice

Smoking of combustible cigarettes has a major impact on human health. Using a systems toxicology approach in a model of chronic obstructive pulmonary disease (C57BL/6 mice), we assessed the health consequences in mice of an aerosol derived from a prototype modified risk tobacco product (pMRTP) as compared to conventional cigarettes. We investigated physiological and histological endpoints in parallel with transcriptomics, lipidomics, and proteomics profiles in mice exposed to a reference cigarette (3R4F) smoke or a pMRTP aerosol for up to 7 months. We also included a cessation group and a switching-to-pMRTP group (after 2 months of 3R4F exposure) in addition to the control (fresh air-exposed) group, to understand the potential risk reduction of switching to pMRTP compared with continuous 3R4F exposure and cessation. The present manuscript describes the study design, setup, and implementation, as well as the generation, processing, and quality control analysis of the toxicology and ‘omics’ datasets that are accessible in public repositories for further analyses.

Mechanical Stimulation by Postnasal Drip Evokes Cough

Cough affects all individuals at different times, and its economic burden is substantial. Despite these widespread adverse effects, cough research relies on animal models, which hampers our understanding of the fundamental cause of cough. Postnasal drip is speculated to be one of the most frequent causes of chronic cough; however, this is a matter of debate. Here we show that mechanical stimuli by postnasal drip cause chronic cough. We distinguished human cough from sneezes and expiration reflexes by airflow patterns. Cough and sneeze exhibited one-peak and two-peak patterns, respectively, in expiratory airflow, which were also confirmed by animal models of cough and sneeze. Transgenic mice with ciliary dyskinesia coughed substantially and showed postnasal drip in the pharynx; furthermore, their cough was completely inhibited by nasal airway blockade of postnasal drip. We successfully reproduced cough observed in these mice by injecting artificial postnasal drip in wild-type mice. These results demonstrated that mechanical stimulation by postnasal drip evoked cough. The findings of our study can therefore be used to develop new antitussive drugs that prevent the root cause of cough.

Mechanical Stress and the Induction of Lung Fibrosis via the Midkine Signaling Pathway

RATIONALE

Lung-protective ventilatory strategies have been widely used in patients with acute respiratory distress syndrome (ARDS), but the ARDS mortality rate remains unacceptably high and there is no proven pharmacologic therapy.

OBJECTIVES

Mechanical ventilation can induce oxidative stress and lung fibrosis, which may contribute to high dependency on ventilator support and increased ARDS mortality. We hypothesized that the novel cytokine, midkine (MK), which can be up-regulated in oxidative stress, plays a key role in the pathogenesis of ARDS-associated lung fibrosis.

METHODS

Blood samples were collected from 17 patients with ARDS and 10 healthy donors. Human lung epithelial cells were challenged with hydrogen chloride followed by mechanical stretch for 72 hours. Wild-type and MK gene-deficient (MK(-/-)) mice received two-hit injury of acid aspiration and mechanical ventilation, and were monitored for 14 days.

MEASUREMENTS AND MAIN RESULTS

Plasma concentrations of MK were higher in patients with ARDS than in healthy volunteers. Exposure to mechanical stretch of lung epithelial cells led to an epithelial-mesenchymal transition profile associated with increased expression of angiotensin-converting enzyme, which was attenuated by silencing MK, its receptor Notch2, or NADP reduced oxidase 1. An increase in collagen deposition and hydroxyproline level and a decrease in lung tissue compliance seen in wild-type mice were largely attenuated in MK(-/-) mice.

CONCLUSIONS

Mechanical stretch can induce an epithelial-mesenchymal transition phenotype mediated by the MK-Notch2-angiotensin-converting enzyme signaling pathway, contributing to lung remodeling. The MK pathway is a potential therapeutic target in the context of ARDS-associated lung fibrosis.

Transplacental Administration of Rosiglitazone Attenuates Hyperoxic Lung Injury in a Preterm Rabbit Model

INTRODUCTION

Continuous improvements in perinatal care have allowed the survival of increasingly more prematurely born infants. The establishment of respiration in an extremely immature yet still developing lung results in chronic lung injury with significant mortality and morbidity. We experimentally evaluated a novel medical strategy to prevent hyperoxia-induced lung injury by prenatal rosiglitazone.

MATERIALS AND METHODS

Pregnant rabbits were injected with saline or rosiglitazone (3 mg/kg) 48 and 24 h prior to preterm delivery at 28 days of gestation (term = 31 days). The pups were held in normoxia (21% O2) or hyperoxia (>95% O2), and assessment was done at three different time points (1 h, 24 h and 7 days).

RESULTS

The administration of rosiglitazone resulted in a significant decrease in tissue damping (resistance) on day 7. Furthermore, significantly increased expression of vascular endothelial growth factor, fetal liver kinase 1 and surfactant protein B immediately after delivery was noted by immunohistochemistery. On day 7, there was a more mature lung parenchymal architecture in rosiglitazone-exposed pups.

DISCUSSION

In a preterm rabbit model, prenatal maternal administration of rosiglitazone attenuates neonatal hyperoxic lung injury and results in a more mature pulmonary parenchyma.