Secretion Of Pulmonary Surfactant Research Articles

Liraglutide alleviates sepsis-induced acute lung injury by regulating pulmonary surfactant through inhibiting autophagy

Background Pulmonary surfactant (PS) plays an important role in the treatment of sepsis-induced acute lung injury (ALI). Liraglutide, a glucagon-like peptide-1 (GLP-1) analog, improves the secretion and function of PS in ALI, but the underlying mechanism remains unknown. This study aimed to investigate how liraglutide regulates PS secretion in ALI. Methods C57BL/6 mice were injected subcutaneously with normal saline containing different concentrations of liraglutide after the establishment of the ALI model. MLE-12 cells were treated with liraglutide after LPS stimulation. The survival rate of mice, wet/dry weight ratio, inflammatory factors in bronchoalveolar lavage fluid (BALF), pulmonary injury, and apoptosis were analyzed. Cell viability, proliferation, apoptosis, the expression of SP-A, SP-B, and expression of autophagy-related proteins in cells were measured. Results ALI mice showed reduced pulmonary injury, less apoptosis, and less inflammation compared to the controls. Liraglutide prolonged survival, decreased the wet/dry weight ratio, reduced inflammatory responses, and attenuated pulmonary edema compared with the ALI group. Moreover, LPS-induced cell damage and reduction of SP-A and SP-B expression were markedly reversed by liraglutide in MLE-12 cells. Furthermore, the protective effects of liraglutide were reversed by rapamycin. Conclusion Liraglutide alleviate sepsis-induced ALI by inhibiting autophagy and regulating PS.

Overstretching alveolar epithelial type II cells decreases surfactant secretion via actin polymerization and intracellular trafficking alteration

Pulmonary surfactant is essential for maintaining proper lung function. Alveolar epithelial type II (AE2) cells secrete surfactants via lamellar bodies (LBs). In tidal loading during each breath, the physiological cyclic stretching of AE2 cells promotes surfactant secretion. Excessive stretching inhibits surfactant secretion, which is considered to contribute to the development of lung damage. However, its precise mechanism remains unknown. This study tested whether actin polymerization and intracellular transport are required for pulmonary surfactant secretion and the association of actin polymerization and transport in identical human AE2-derived A549 cells using live-cell imaging, not in the bulk cells population. We found that overstretching approximately doubled actin polymerization into filaments (F-actin) and suppressed LB secretion by half in the fluorescent area ratio, compared with physiological stretching (F-actin: 1.495 vs 0.643 (P < 0.01); LB: 0.739 vs 0.332 (P < 0.01)). An inhibitor of actin polymerization increased LB secretion. Intracellular tracking using fluorescent particles revealed that cyclic stretching shifted the particle motion perpendicularly to the direction of stretching according to the orientation of the F-actin (proportion of perpendicular axis motion prior particle: 0h 40.12 % vs 2h 63.13 % (P < 0.01)), and particle motion was restricted over time in the cells subjected to overstretching, indicating that overstretching regulates intracellular transport dynamics (proportion of stop motion particle: 0h 1.01 % vs 2h 11.04 % (P < 0.01)). These findings suggest that overstretching changes secretion through the cytoskeleton: overstretching AE2 cells inhibits pulmonary surfactant secretion, at least through accelerating actin polymerization and decreasing intracellular trafficking, and the change in actin orientation would modulate intracellular trafficking.

The Role of Pulmonary Surfactant Phospholipids in Fibrotic Lung Diseases

Diffuse parenchymal lung diseases (DPLD) or Interstitial lung diseases (ILD) are a heterogeneous group of lung conditions with common characteristics that can progress to fibrosis. Within this group of pneumonias, idiopathic pulmonary fibrosis (IPF) is considered the most common. This disease has no known cause, is devastating and has no cure. Chronic lesion of alveolar type II (ATII) cells represents a key mechanism for the development of IPF. ATII cells are specialized in the biosynthesis and secretion of pulmonary surfactant (PS), a lipid-protein complex that reduces surface tension and minimizes breathing effort. Some differences in PS composition have been reported between patients with idiopathic pulmonary disease and healthy individuals, especially regarding some specific proteins in the PS; however, few reports have been conducted on the lipid components. This review focuses on the mechanisms by which phospholipids (PLs) could be involved in the development of the fibroproliferative response.

Association between Thyroid Function and Respiratory Distress Syndrome in Preterm Infants.

Thyroid hormones are known to influence the production and secretion of pulmonary surfactant. The objective of this study was to explore the relationship between respiratory distress syndrome (RDS) and thyroid hormones. This was a retrospective study of preterm infants at 24-33 weeks gestational age from April 2017 to February 2019. T3, free T4 (fT4), and thyroid-stimulating hormone (TSH) were measured 1, 3, and 6 weeks after birth. Multivariate logistic regression analyses were performed to determine the relationship between RDS and TSH. A total of 146 infants were enrolled. Of these, 60 had RDS, 72 had no RDS, and 14 were excluded. T3 and TSH were lower in the RDS groups (p &lt; 0.05) on the day of birth. Multivariate logistic regression analysis indicated that lower serum TSH levels immediately after birth were associated with a higher incidence of RDS (OR, 0.89; 95% CI, 0.81-0.97). The TSH level was associated with the incidence of RDS. This suggests that suppression of the hypothalamus-pituitary axis function contributes to RDS, which is the result of surfactant deficiency.

Rare-variant collapsing analyses identified risk genes for neonatal acute respiratory distress syndrome

BackgroundAcute respiratory distress syndrome (ARDS) could account for a considerable proportion of neonatal death, while the genetic etiology and pathophysiology of neonatal ARDS remain elusive. In this case-control study, 515 neonates were enrolled in the China Neonatal Genomes Project (CNGP, NCT03931707) from August 2016 to June 2021, including 196 ARDS and 319 non-ARDS matched by sex, gestational age, birth weight, perinatal asphyxia, pneumonia, sepsis, and necrotizing enterocolitis. Clinical exome sequencing was used to detect genetic variants. Collapsing analyses together with permutation tests were used to identify ARDS risk genes enriched for rare variants in ARDS samples. In silico functional interaction analysis and expression pattern studies at different stages of lung development were used to investigate the biological functions of the risk genes. ResultsCollapsing analyses identified that rare variants were significantly abundant in the genes associated with the precursor of the lamellar body and there were eight predicted risk genes with strong confidence (P < 0.01). Among them, the expression of EDNRB increased significantly in lung development and was up-regulated in ARDS (P < 0.05). In addition, 151 predicted transcriptional target proteins of EDNRB were highly enriched in the lamellar body responsible for pulmonary surfactant storage and secretion. ConclusionsIn our study, the genes associated with pulmonary surfactant storage and release were highly enriched with rare variants. A novel neonatal ARDS risk gene EDNRB may be a key gene for neonatal lung development and pulmonary surfactant homeostasis. Additional validation in independent patient populations and further exploration of underlying molecular mechanisms are warranted.

Warburg and Scars? Alveolar Type II Cell Glycolytic Reprogramming and Differential Mitochondrial Dynamics Observed in a Murine Model of Pulmonary Fibrosis

Our emerging conceptual understanding of Idiopathic Pulmonary Fibrosis (IPF) highlights the significant role of alveolar epithelial type II cell (AT2) cell dysfunction in underlying susceptibility, disease severity, and disease progression. This multifunctional cell is solely responsible for the synthesis and secretion of pulmonary surfactant, a highly metabolically taxing process. Though mutations in surfactant component genes are one of the recognized etiological causes of IPF, the relationship between the metabolic program of the AT2 cell and IPF is poorly understood. Leveraging a novel preclinical model of IPF, the IER-SP-CI73T mouse, we aimed to characterize the role of altered AT2 metabolism in IPF fibrogenesis and remodeling. Using this model, we characterized the metabolic profile of SftpcI73T AT2 cells at 3 key time points (7,14, and 28 days) post tamoxifen induction corresponding to an initiation phase (0-7 days), development of a multicellular alveolitis (7-14 days), and transition to spontaneous fibrotic remodeling (14-28 days). Endpoints included assessment of intracellular ATP levels, TCA cycle intermediates, lactate, mitochondrial copy number, mitochondrial function, and mitochondrial dynamics. Transcriptional changes underlying the acquired metabolic program were assessed via bulk AT2 RNA-sequencing with key proteins validated by immunoblotting. We identified significant alterations to AT2 metabolism and mitochondrial function beginning in the early inflammatory phase and sustained though fibrogenesis which included: (i) early and significant transcriptional changes reflective of glycolytic reprograming and alterations in PPARg/PGC1a signaling; (ii) a novel metabolic profile marked by increased cellular ATP and accumulate TCA intermediates supporting the glycolytic phenotype; (iii) genomic, biochemical, and morphological changes indicative of impaired mitochondrial biogenesis and network dynamics suggesting sustained mitochondrial dysfunction during injury and fibrotic remodeling; (iv) transcriptional and histochemical evidence of a persistent, highly proliferative AT2 phenotype. In this preclinical model of IPF we observe an AT2 hyperproliferative state supported by glycolytic reprogramming and high ATP levels with features that recapitulate the classical Warburg effect observed in tumorigenesis. Together with observations of altered mitochondrial dynamics and function, these data suggest a significant role for metabolic dysregulation of the AT2 cell in IPF pathogenesis and present novel pathways for disease intervention.

Surfactant in SARS-CoV-2 - a therapeutic option based on underlying lung cell damage?

&lt;p&gt;&lt;strong&gt;Introduction&lt;/strong&gt;: the severe acute respiratory syndrome – coronavirus 2 (SARS Cov-2), leads to a diffuse alveolar deterioration due infection of type II pneumocytes. The type II pneumocytes are involved in synthesis and secretion of pulmonary surfactant in pulmonary alveoli. &lt;strong&gt;Objective&lt;/strong&gt;: the purpose of this study is to discuss the indication of surfactant replacement as a potential adjunctive treatment modality for SARS CoV-2, similarly treatment to neonatal respiratory distress syndrome. &lt;strong&gt;Methodology&lt;/strong&gt;: we argue that SARS can be triggered by surfactant deficiency secondary to production deficiency determined by type 2 pneumocyte injuries. In this sense, we carried out a bibliographic review. &lt;strong&gt;Conclusion&lt;/strong&gt;: thus, the replacement of human surfactant could be a potential treatment modality for SARS CoV-2, in the same way that it is indicated for the treatment of neonatal respiratory distress syndrome&lt;/p&gt;

Mechanical stretch activates piezo1 in caveolae of alveolar type I cells to trigger ATP release and paracrine stimulation of surfactant secretion from alveolar type II cells.

Secretion of pulmonary surfactant in the alveoli of the lungs is essential to maintain lung function. Stretching of alveoli during lung inflation is the main trigger for surfactant secretion. Yet, the molecular mechanisms how mechanical distension of alveoli results in surfactant secretion are still elusive. The alveolar epithelium consists of alveolar epithelial type I (ATI) and surfactant secreting type II (ATII) cells. ATI, but not ATII cells, express caveolae, small plasma membrane invaginations that can respond to plasma membrane stresses and serve mechanotransductive roles. Within this study, we investigated the role of caveolae as mechanosensors in the alveolus. We generated a human caveolin-1 knockout ATI cell (hAELVicav-/- ) using CRISPR/Cas9. Wildtype (hAELViwt ) and hAELVicav-/- cells grown on flexible membranes responded to increasing stretch amplitudes with rises in intracellular Ca2+ . The response was less frequent and started at higher stretch amplitudes in hAELVicav-/- cells. Stretch-induced Ca2+ -signals depended on Ca2+ -entry via piezo1 channels, localized within caveolae in hAELViwt and primary ATI cells. Ca2+ -entry via piezo1 activated pannexin-1 hemichannels resulting in ATP release from ATI cells. ATP release was reduced in hAELVicav-/- cells. In co-cultures resembling the alveolar epithelium, released ATP stimulated Ca2+ signals and surfactant secretion from neighboring ATII cells when co-cultured with hAELViwt but not hAELVicav-/- cells. In summary, we propose that caveolae in ATI cells are mechanosensors within alveoli regulating stretch-induced surfactant secretion from ATII cells.

Stimulation of surfactant exocytosis in primary alveolar type II cells by A. fumigatus.

Aspergillus fumigatus is an opportunistic fungal pathogen with small airborne spores (conidia) that may escape clearance by upper airways and directly impact the alveolar epithelium. Consequently, innate alveolar defense mechanisms are being activated, including professional phagocytosis by alveolar macrophages, recruitment of circulating neutrophils and probably enhanced secretion of pulmonary surfactant by the alveolar type II (AT II) cells. However, no data are available in support of the latter hypothesis. We therefore used a coculture model of GFP-Aspergillus conidia with primary rat AT II cells and studied fungal growth, cellular Ca2+ homeostasis, and pulmonary surfactant exocytosis by live cell video microscopy. We observed all stages of fungal development, including reversible attachment, binding and internalization of conidia as well as conidial swelling, formation of germ tubes and outgrowth of hyphae. In contrast to resting conidia, which did not provoke immediate cellular effects, metabolically active conidia, fungal cellular extracts (CE) and fungal culture filtrates (CF) prepared from swollen conidia caused a Ca2+-independent exocytosis. Ca2+ signals of greatly varying delays, durations and amplitudes were observed by applying CE or CF obtained from hyphae of A. fumigatus, suggesting compounds secreted by filamentous A. fumigatus that severely interfere with AT II cell Ca2+ homeostasis. The mechanisms underlying the stimulatory effects, with respect to exocytosis and Ca2+ signaling, are unclear and need to be identified.

Pulmonary-Affinity Paclitaxel Polymer Micelles in Response to Biological Functions of Ambroxol Enhance Therapeutic Effect on Lung Cancer.

PurposeCancer chemotherapy effect has been largely limited by cell autophagy and little drug accumulation at the action sites. Herein, we designed an intelligent strategy involving paclitaxel (PTX) polymer micelles in response to biological functions of ambroxol (Ax). The amphiphilic polymers polyethyleneglycol-polylactic acid (PEG-PLA) and Pluronic P105 were selected as nanocarriers to encapsulate PTX to form into lung affinity PEG-PLA/P105/PTX micelles. Ax which can up-regulate the secretion of pulmonary surfactant (PS) and inhibit autophagy was hired to change the microenvironment of the lung, thereby promoting the lung accumulation and increasing cell-killing sensitivity of the micelles.MethodsThe physical and chemical properties of the micelles were characterized including size, morphology, critical micellar concentration (CMC) and in vitro drug release behavior. The therapeutic effects of the combination regimen were characterized both in vitro and in vivo including study on Ax in promoting the secretion of pulmonary surfactant, in vitro cytotoxicity, cellular uptake, Western blotting, in vivo biodistribution, in vivo pharmacokinetics and in vivo antitumor efficacy.ResultsThe PEG-PLA/P105/PTX micelles showed a particle size of 16.7 ± 0.5 nm, a nearly round shape, small CMC and sustained drug release property. Moreover, the in vitro results indicated that Ax could increase PS and LC3 protein secretion and enhance the cytotoxicity of PEG-PLA/P105/PTX micelles toward A549 cells. The in vivo results indicated that the combination therapeutic regimen could promote the micelles to distribute in lung and enhance the therapeutic effect on lung cancer.ConclusionThis multifunctional approach of modulating the tumor microenvironment to enhance drug transportation and cell-killing sensitivity in the action sites might offer a new avenue for effective lung cancer treatment.

Pulmonary surfactant protein SP‐B promotes exocytosis of lamellar bodies in alveolar type II cells

The release of pulmonary surfactant by alveolar type II (ATII) cells is essential for lowering surface tension at the respiratory air-liquid interface, stabilizing the lungs against physical forces tending to alveolar collapse. Hydrophobic surfactant protein (SP)-B ensures the proper packing of newly synthesized surfactant particles, promotes the formation of the surface active film at the alveolar air-liquid interface and maintains its proper structure along the respiratory dynamics. We report that membrane-associated SP-B efficiently induces secretion of pulmonary surfactant by ATII cells, at the same level as potent secretagogues such as ATP. The presence in the extracellular medium of lipid-protein complexes containing SP-B activates the P2Y2 purinergic signaling pathway that ultimately triggers exocytosis of lamellar bodies by ATII cells. Our data suggest that SP-B prompts Ca2+-dependent surfactant secretion via ATP release from ATII cells. This result implies that SP-B is not only an essential component for the biophysical function of surfactant but is also a central element in the alveolar homeostasis by eliciting autocrine and paracrine cell stimulation.-Martínez-Calle, M., Olmeda, B., Dietl, P., Frick, M., Pérez-Gil, J. Pulmonary surfactant protein SP-B promotes exocytosis of lamellar bodies in alveolar type II cells.

The Influence of BuqiHuoxueTongluo Formula on Histopathology and Pulmonary Function Test in Bleomycin-Induced Idiopathic Pulmonary Fibrosis in Rats.

BuqiHuoxueTongluo Formula (BHTF) is an effective herbal prescription based on traditional Chinese medicine for idiopathic pulmonary fibrosis (IPF). The aim of this study was to elucidate the influence of BHTF on induced IPF model through the aspect of histopathology and pulmonary function test. Wistar rats with bleomycin-induced IPF were given BHTF via intragastric gavage. After 14 days and 28 days of treatment, respectively, on these two time points, we first performed pulmonary function test, performed ventilation measure, and traced the Pressure-Volume Loop under anesthesia. Then, rats were sacrificed for hematoxylin-eosin and Masson's trichrome staining, immunohistochemistry staining of TGF-β1 and α-SMA, and observation through transmission electron microscope. BHTF reduced infiltration of inflammation cells, collagen deposition, and fibrosis proliferation in pulmonary mesenchyme, inhibited the expression of TGF-β1 and α-SMA, and avoided the abnormality of ultrastructure and quantities of lamellar bodies. It also ameliorated the parameters of FVC, MVV, PEF, FEF25, and Cdyn, maintained the shape of the Pressure-Volume Loop, and improved hysteresis. BHFT relieved the histopathologic changes, improved ventilation function, compliance, and work of breathing, meliorated the capacity and elasticity of the lungs, and stabilized the alveolar surface tension. Further speaking, it had a potential impact on the secretion of pulmonary surfactant.

Characteristics of surfactant proteins in tumorigenic and inflammatory lung lesions in rodents.

Surfactant proteins (SPs) are essential for the proper structure and respiratory function of the lungs. There are four subtypes of SPs: SP-A, SP-B, SP-C, and SP-D. The expectorant drug ambroxol hydrochloride is clinically used to stimulate pulmonary surfactant and airway serous secretion. In addition, previous studies showed that ambroxol regulated SP production and attenuated pulmonary inflammation, with ambroxol hydrochloride being found to suppress quartz-induced lung inflammation via stimulation of pulmonary surfactant and airway serous secretion. In this study, we investigated the expression of SP-A, SP-B, SP-C, and SP-D in neoplastic and inflammatory lung lesions in rodents, as well as their possible application as potential markers for diagnostic purposes. SP-B and SP-C showed strong expression in lung hyperplasia and adenoma, whereas SP-A and SP-D were expressed in the mucus or exudates of inflammatory alveoli. Rodent tumorigenic hyperplasic tissues induced by various carcinogens were positive for napsin A, an aspartic proteinase involved in the maturation of SP-B; this indicated a focal increase in type II pneumocytes in the lungs. Therefore, high expression of napsin A in the alveolar walls may serve as a useful marker for prediction of the tumorigenic potential of lung hyperplasia in rodents.

Effects of the expectorant drug ambroxol hydrochloride on chemically induced lung inflammatory and neoplastic lesions in rodents.

Ambroxol hydrochloride (AH) is an expectorant drug used to stimulate pulmonary surfactant and serous airway secretion. Surfactant proteins (SPs) are essential for maintaining respiratory structure and function, although SP expression has also been reported in lung inflammatory and proliferative lesions. To determine whether AH exerts modulatory effects on these lung lesions, we examined its effects on pleural thickening induced by intrathoracic administration of dipotassium titanate (TISMO) in A/JJmsSlc (A/J) mice. We also analyzed the modulatory effects of AH on neoplastic lung lesions induced by 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in A/J mice and by N-nitrosobis (2-hydroxypropyl) amine (DHPN) in F344/DuCrlCrj (F344) rats. A/J mice treated with TISMO showed decreased body weight, increased white blood cell (WBC) counts, and pleural thickening caused by pleuritis and poor general condition. However, A/J mice treated with TISMO + 120 ppm showed significant recovery of body weight and WBC counts to the same levels as those of A/J mice not treated with TISMO, although no significant differences were observed in histopathological changes including the immunohistopathological expression of IL-1β in the lung and maximum pleural thickness regardless of AH treatment. In the NNK and DHPN experiments, no significant differences in body weight, hematology, plasma biochemistry, and histopathological changes were associated with AH concentration. These results suggest that AH potentially exerts anti-inflammatory effects but does not have a direct suppressive effect on lung tumorigenesis in rodents.

ATP is stored in lamellar bodies to activate vesicular P2X4 in an autocrine fashion upon exocytosis.

Vesicular P2X4 receptors are known to facilitate secretion and activation of pulmonary surfactant in the alveoli of the lungs. P2X4 receptors are expressed in the membrane of lamellar bodies (LBs), large secretory lysosomes that store lung surfactant in alveolar type II epithelial cells, and become inserted into the plasma membrane after exocytosis. Subsequent activation of P2X4 receptors by adenosine triphosphate (ATP) results in local fusion-activated cation entry (FACE), facilitating fusion pore dilation, surfactant secretion, and surfactant activation. Despite the importance of ATP in the alveoli, and hence lung function, the origin of ATP in the alveoli is still elusive. In this study, we demonstrate that ATP is stored within LBs themselves at a concentration of ∼1.9 mM. ATP is loaded into LBs by the vesicular nucleotide transporter but does not activate P2X4 receptors because of the low intraluminal pH (5.5). However, the rise in intravesicular pH after opening of the exocytic fusion pore results in immediate activation of vesicular P2X4 by vesicular ATP. Our data suggest a new model in which agonist (ATP) and receptor (P2X4) are located in the same intracellular compartment (LB), protected from premature degradation (ATP) and activation (P2X4), and ideally placed to ensure coordinated and timely receptor activation as soon as fusion occurs to facilitate surfactant secretion.

Alveolar injury and regeneration following deletion of ABCA3.

Adaptation to air breathing after birth is dependent upon the synthesis and secretion of pulmonary surfactant by alveolar type 2 (AT2) cells. Surfactant, a complex mixture of phospholipids and proteins, is secreted into the alveolus, where it reduces collapsing forces at the air-liquid interface to maintain lung volumes during the ventilatory cycle. ABCA3, an ATP-dependent Walker domain containing transport protein, is required for surfactant synthesis and lung function at birth. Mutations in ABCA3 cause severe surfactant deficiency and respiratory failure in newborn infants. We conditionally deleted the Abca3 gene in AT2 cells in the mature mouse lung. Loss of ABCA3 caused alveolar cell injury and respiratory failure. ABCA3-related lung dysfunction was associated with surfactant deficiency, inflammation, and alveolar-capillary leak. Extensive but incomplete deletion of ABCA3 caused alveolar injury and inflammation, and it initiated proliferation of progenitor cells, restoring ABCA3 expression, lung structure, and function. M2-like macrophages were recruited to sites of AT2 cell proliferation during the regenerative process and were present in lung tissue from patients with severe lung disease caused by mutations in ABCA3. The remarkable and selective regeneration of ABCA3-sufficient AT2 progenitor cells provides plausible approaches for future correction of ABCA3 and other genetic disorders associated with surfactant deficiency and acute interstitial lung disease.

Functional roles of C/EBPα and SUMO‑modification in lung development.

CCAAT enhancer binding protein alpha (C/EBPα) is a transcription factor regulating the core aspects of cell growth and differentiation. The present study investigated the level and functional role of C/EBPα during the development of the rat lung. C/EBPα protein exhibits a dynamic expression pattern. The correlation between the expression of C/EBPα protein and the content of glycogen during lung maturation was analyzed to understand the function of C/EBPα in lung differentiation. The high expression of C/EBPα coincides with the reduction of glycogen in the fetal lung. In addition, the authors identified that changes in the level of C/EBPα are associated with the secretion of pulmonary surfactant. C/EBPα is modified by small ubiquitin-related modifier (SUMO) post-translationally. The results of double immunofluorescence staining and immunoprecipitation demonstrated that SUMO-modified C/EBPα was present in the lung. The sumoylated C/EBPα gradually decreased during lung differentiation and was negatively correlated with pulmonary surfactant secretion, thereby suggesting that the SUMO modification may participate in C/EBPα-mediated lung growth and differentiation. These results indicated that C/EBPα played a role in lung development and provided the insight into the mechanism underlying SUMO-modification.

Suppressive effects of the expectorant drug ambroxol hydrochloride on quartz-induced lung inflammation in F344 rats.

Surfactant proteins (SPs) are essential to respiratory structure and function. The expectorant drug ambroxol hydrochloride is clinically prescribed to stimulate pulmonary surfactant and airway serous secretion. Therefore, ambroxol hydrochloride may affect SP production and pulmonary inflammation. Lung toxicity of fine particles of various materials has been examined previously in our in vivo bioassay using the intratracheal (i.t.) instillation approach. In the present study, we evaluated modulatory effects of ambroxol hydrochloride on quartz-induced lung inflammation in F344 rats. Male 6-week-old F344 rats were exposed by i.t. instillation to 2 mg of quartz particles suspended in 0.2 mL of saline. Ambroxol hydrochloride was administered at 0, 12, and 120 ppm in rat basal diet for 28 days, and then formalin-fixed paraffin-embedded lung, liver, and kidney samples were prepared. No changes in general condition, body and organ weights, or food consumption upon exposure to quartz were noted. The mean ambroxol intake in rats of the 12 ppm group was comparable to the human conventional dose. Histopathology of lung lesions was evaluated, and the degree of inflammation was scored. At 120 ppm, ambroxol hydrochloride significantly decreased individual lung inflammation scores for pulmonary edema and lymph follicle proliferation around the bronchiole, as well as the total inflammation score, in quartz-treated rats. Expression of SP-C in the type II alveolar cells and macrophages was greater in inflammatory lesions than in non-inflamed areas. Ambroxol treatment did not affect expression of SP-B and SP-C. In conclusion, we demonstrated that ambroxol hydrochloride relieves quartz-induced lung inflammation.

Interfacial sensing regulates alveolar barrier function in lung epithelial monolayer

Alveolar Type II cells (AT II cells) are located in the alveoli of the lung and are in close proximity to an air-liquid-interface. An important function of AT II cells is the production and secretion of pulmonary surfactant. Pulmonary surfactant is an essential substance, which reduces the high surface tension acting at the alveolar interface. Different stimuli and forces act on this nanometer scaled gas-blood-barrier. As AT II cells are responsible for the regulation and maintenance of alveolar structures and processes, we suggest that changes of the extracellular environment lead to a fast feedback response via functional and morphological changes in the cells. In order to test this hypothesis, primary AT II cells isolated from rat lung were grown on cell culture inserts with porous membranes for longer time periods, applying different culture conditions. We found out that in contrast to many cell lines, applying culture media supplemented with different concentrations of growth factor, nutrients or corticoids had no effect on the barrier function of primary lung cells. However, we discovered that ATII cells cultured in immersed-liquid-interface (ILI) conditions show a significantly higher transepithelial electrical resistance (TER) in comparison to cells that are cultured under air-liquid-interface (ALI) conditions. These results were confirmed by testing transport capacity of different-sized (< 1 – 70kDa) dextran-conjugates from the basolateral to the apical compartment. Interestingly, the loss of intercellular tightness was not principally based on changes in tight junction protein expression. Instead, we observed dramatic and quick alterations in actin cytoskeleton formation. The TER effect between the two cultures was not observed when ALI treated cells were covered with a hyperthin layer of surfactant. Therefore, we suggest that the surface tension, which acts on the air exposed cells, induce a fast cell response via calcium influx, which leads to actin reformation followed by functional and morphological cell differentiation. We propose that this newly discovered mechanism of interfacial sensing is essential for the AT II cells for maintaining the sensitive alveolar lining fluid homeostasis during physiological and pathophysiological setting.

The protective effect of different airway humidification liquids to lung after tracheotomy in traumatic brain injury: The role of pulmonary surfactant protein-A (SP-A)

The purpose of this study was to establish a rat model of a brain injury with tracheotomy and compared the wetting effects of different airway humidification liquids, afterward, the best airway humidification liquid was selected for the clinical trial, thus providing a theoretical basis for selecting a proper airway humidification liquid in a clinical setting. Rats were divided into a sham group, group A (0.9% NaCl), group B (0.45% NaCl), group C (0.9% NaCl+ambroxol) and group D (0.9% NaCl+Pulmicort). An established rat model of traumatic brain injury with tracheotomy was used. Brain tissue samples were taken to determine water content, while lung tissue samples were taken to determine wet/dry weight ratio (W/D), histological changes and expression levels of SP-A mRNA and SP-A protein. 30 patients with brain injury and tracheotomy were selected and divided into two groups based on the airway humidification liquid instilled in the trachea tube, 0.45% NaCl and 0.9% NaCl+ambroxol. Blood was then extracted from the patients to measure the levels of SP-A, interleukin-6 (IL-6), interleukin-8 (IL-8) and tumour necrosis factor-α (TNF-α). The difference between group C and other groups in lung W/D and expression levels of SP-A mRNA and SP-A protein was significant (P<0.05). In comparison, the histological changes showed that the lung tissue damage was smallest in group C compared to the three other groups. Aspect of patients, 0.45% NaCl group and 0.9% NaCl+ambroxol group were significantly different in the levels of SP-A, IL-6, IL-8 and TNF-α (P<0.01). In the present study, 0.9% NaCl+ambroxol promote the synthesis and secretion of pulmonary surfactant, and has anti-inflammatory and antioxidant effects, which inhibit the release of inflammatory factors and cytokines, making it an ideal airway humidification liquid.