Airway administration of dexamethasone, 3'-5'-cyclic adenosine monophosphate, and isobutylmethylxanthine facilitates compensatory lung growth in adult mice

Drug Regimen for Patients after a Pneumonectomy

Pneumonectomy is an entire lung removal and is indicated for both malignant and benign diseases. Due to its invasiveness and postoperative complications, pneumonectomy is still associated with high mortality and morbidity. Appropriate postoperative management is crucial in pneumonectomy patients to improve quality of life and overall survival rates. Diverse drug regimens are under development to be used in adjuvant chemotherapy or to improve respiratory health after a pneumonectomy. The most common causes for a pneumonectomy are non-small cell lung cancer, malignant pleural mesothelioma, and tuberculosis; thus, an appropriate drug regimen is necessary. The uncommon incidence of pneumonectomy cases remains the major obstacle in studies of postoperative drug regimens. As the majority of current studies include post-lobectomy and post-segmentectomy patients, it is highly recommended that further research of postoperative drug regimens be focused on post-pneumonectomy patients.

Nuclear factor-kappa B influences early phase of compensatory lung growth after pneumonectomy in mice

Background

Compensatory lung growth (CLG) is a well-established lung regeneration model. However, the sequential mechanisms, including unknown molecular triggers or regulators, remain unclear. Nuclear factor- kappa B (NF-κB) is known to be essential for inflammation and tissue regeneration; therefore, we investigated the role of NF-κB in CLG.

Methods

C57BL/6 J mice underwent either a left pneumonectomy or a thoracotomy (n = 77). Gene microarray analysis was performed to detect genes that were upregulated at 12 h after pneumonectomy. NF-κB protein expression was examined by immunohistochemistry and Western blot. To investigate the influence of NF-κB on CLG, either an NF-κB inhibitor SN50 or saline was administered following pneumonectomy and the degree of CLG was evaluated in each group by measuring the lung dry weight index (LDWI) and the mean linear intercept.

Results

Gene microarray analysis identified 11 genes that were significantly but transiently increased at 12 h after pneumonectomy. Among the 11 genes, NF-κB was selected based on its reported functions. Western blot analysis showed that NF-κB protein expression after pneumonectomy was significantly higher at 12 h compared to 48 h. Additionally, NF-κB protein expression at 12 h after pneumonectomy was significantly higher than at both 12 and 48 h after thoracotomy (p < 0.029 for all). NF-κB protein expression, evaluated through immunohistochemistry, was expressed mainly in type 2 alveolar epithelial cells and was significant increased 12 h after pneumonectomy compared to 48 h after pneumonectomy and both 12 and 48 h after thoracotomy (p < 0.001 for all). SN50 administration following pneumonectomy induced a significant decrease in NF-κB expression (p = 0.004) and LDWI compared to the vehicle administration (p = 0.009).

Conclusions

This is the first report demonstrating that NF-κB signaling may play a key role in CLG. Given its pathway is crucial in tissue regeneration of various organs, NF-κB may shed light on identification of molecular triggers or clinically usable key regulators of CLG.

Therapeutic potential of recombinant thrombomodulin for lung injury after pneumonectomy via inhibition of high-mobility group box 1 in mice

BACKGROUND

Surgical acute respiratory distress syndrome (ARDS) is an extremely critical condition which may occur after major lung resection. Despite advances in minimally invasive surgical procedures and progress in the therapeutic management of this disease, prognosis remains poor. In this study, we investigated the contribution of high-mobility group box 1 (HMGB1) in a surgical ARDS model and evaluated the possible therapeutic effect of recombinant thrombomodulin (rTM) for the treatment of surgical ARDS.

METHODS

C57BL/6J mice underwent left pneumonectomy. rTM was injected at 12 hours before surgery, followed by 12 hours for 3 days after surgery. Lipopolysaccharide (LPS) was administered at 2 hours after surgery. We conducted a histologic analysis and measured HMGB1, IL-6, IL-1β, and TNF-α in bronchoalveolar lavage fluid on day 3 after pneumonectomy. Data were compared between the treatment groups.

RESULTS

On histologic analysis, left pneumonectomy followed by LPS administration induced both severe inflammatory cellular infiltration and alveolar wall congestion with hemorrhage. rTM administration rescued these histologic changes. The level of HMGB1, IL-6, IL-1β, and TNF-α in bronchoalveolar lavage fluid was significantly increased by LPS administration after pneumonectomy and significantly decreased by rTM administration with LPS and pneumonectomy (p < 0.001). Also, LPS alone showed no statistical differences in HMGB1 or proinflammatory cytokine level compared with pneumonectomy (PNX) group. In addition, the survival outcome was also improved by rTM administration.

CONCLUSIONS

LPS administration after left pneumonectomy could induce the severe lung injury. PNX and LPS have similar contribution to this model and may play a synergistic role in this process. rTM may have the potential therapeutic effect for surgical ARDS via suppression of HMGB1 and the secretion of proinflammatory cytokines induced by the administration of LPS after left pneumonectomy.

Predictors of long-term compensatory response of pulmonary function following major lung resection for non-small cell lung cancer

BACKGROUND AND OBJECTIVE

Long-term pulmonary function which might include compensatory response (CR) significantly influences quality of life of long-term survivor after major lung resection. We investigated long-term pulmonary function after major lung resection.

METHODS

A total of 137 patients who had undergone lobar resection for non-small cell lung cancer (NSCLC) from May 2013 to June 2014 had spirometry at 10-14 months after surgery. Actual post-operative forced expiratory volume in 1 s (FEV₁ ) (FEV_1apo )/predicted post-operative FEV₁ (FEV_1ppo ), actual post-operative forced vital capacity (FVC) (FVC_apo )/predicted post-operative FVC (FVC_ppo ), its relationship with clinicopathological factors and immunohistochemistry for pro-surfactant protein C (pro-SPC), thyroid transcription factor-1 (TTF-1) and vascular endothelial growth factor receptor 2 (VEGFR2) were investigated.

RESULTS

FEV_1apo /FEV_1ppo showed strong correlation with FVC_apo /FVC_ppo (r = 0.628; P < 0.001). We defined greater CR as both FEV_1apo /FEV_1ppo and FVC_apo /FVC_ppo were >120%. Greater CR was significantly associated with decreased smoking index (P < 0.001) and greater resected subsegments (P = 0.037). The never-smoker group revealed significantly greater CR compared with the smoker group in both FEV_1apo /FEV_1ppo (119.9 ± 12.5% vs 107.5 ± 14.2%; P = 0.030) and FVC_apo /FVC_ppo (117.9 ± 9.98% vs 107.2 ± 13.1%; P = 0.046) in case-matched comparison. The expression of pro-SPC, TTF-1 and VEGFR2 in the normal lung parenchyma of greater CR group was significantly higher than those of lesser CR group (P < 0.001 for each). In addition, pro-SPC, TTF-1 and VEGFR2 expressions showed a significant correlation to the degree of CR especially in the smoker group (r = 0.631, 0.705 and 0.732, respectively; P < 0.001 for each).

CONCLUSION

Our data suggest that smokers may develop lesser long-term CR after major lung resection. Decreased expression of pro-SPC, TTF-1 and VEGFR2 may indicate decreased capacity of CR, especially in patients who smoke.

Alveolar macrophage phenotype expression in airway-instilled bone marrow cells in mice

No uniform consensus has been established regarding post-pneumonectomy lung regeneration. This study was undertaken to determine whether airway-instilled lung- or bone marrow-derived cells are able to differentiate and reconstitute as lung component cells in the course of post-pneumonectomy lung growth. Bone marrow cells or lung cells obtained from C57 black (BL)/6-GFP mice were intratracheally instilled into C57BL/6 mice treated with left pneumonectomy and cell differentiation was examined. It is unclear whether intratracheally instilled lung or bone marrow cells differentiate into non-hematopoietic cells after pneumonectomy. However, regardless of whether pneumonectomy is performed, intratracheally instilled bone marrow cells display a surface antigen profile that is similar to alveolar macrophages. Furthermore, these newly differentiated macrophages function similarly to resident macrophages in terms of TNF-α production, suggesting that bone marrow stem cells acquire the same macrophage phenotype. In conclusion, intratracheally instilled bone marrow cells adapt to the surrounding microenvironment, directly differentiating into alveolar macrophages, and remain in the alveolar space for at least 3 months.

The pneumonectomy model of compensatory lung growth: insights into lung regeneration

Pneumonectomy (PNX) in experimental animals leads to a species- and age-dependent compensatory growth of the remaining lung lobes. PNX mimics the loss of functional gas exchange units observed in a number of chronic destructive lung diseases. However, unlike in disease models, this tissue loss is well defined, reproducible and lacks accompanying inflammation. Furthermore, compensatory responses to the tissue loss can be easily quantified. This makes PNX a potentially useful model for the study of the cellular and molecular events which occur during realveolarisation. It may therefore help to get a better understanding of how to manipulate these pathways, in order to promote the generation of new alveolar tissue as therapies for destructive lung diseases. This review will explore the insights that experimental PNX has provided into the physiological factors which promote compensatory lung growth as well as the importance of age and species in the rate and extent of compensation. In addition, more recent studies which are beginning to uncover the key cellular and molecular pathways involved in realveolarisation will be discussed. The potential relevance of experimental pneumonectomy to novel therapeutic strategies which aim to promote lung regeneration will also be highlighted.

Recent advances in late lung development and the pathogenesis of bronchopulmonary dysplasia

In contrast to early lung development, a process exemplified by the branching of the developing airways, the later development of the immature lung remains very poorly understood. A key event in late lung development is secondary septation, in which secondary septa arise from primary septa, creating a greater number of alveoli of a smaller size, which dramatically expands the surface area over which gas exchange can take place. Secondary septation, together with architectural changes to the vascular structure of the lung that minimize the distance between the inspired air and the blood, are the objectives of late lung development. The process of late lung development is disturbed in bronchopulmonary dysplasia (BPD), a disease of prematurely born infants in which the structural development of the alveoli is blunted as a consequence of inflammation, volutrauma, and oxygen toxicity. This review aims to highlight notable recent developments in our understanding of late lung development and the pathogenesis of BPD.

Airway administration of vascular endothelial growth factor siRNAs induces transient airspace enlargement in mice

PURPOSE

Reduction in the level of vascular endothelial growth factor (VEGF) has been implicated in the pathogenesis of pulmonary emphysema. To this end, pharmacological VEGF receptor blockade, and the Cre-lox system models have been utilized to study the effects of VEGF depletion in the lung. These models generally reproduce air space enlargement resembling clinical emphysema. Here we report a potentially more readily available model of lung targeted VEGF depletion by airway administration of VEGF small inhibitory RNA oligonucleotides (siRNAs) in mice.

METHODS

Airway administration of VEGF siRNAs were done in C57BL/6 mice. The lungs were removed for histology and protein analysis 2, and 4 days later. Airspace enlargement was evaluated by lung volume measurement, and histological analyses. VEGF levels were analyzed by western blot and immunohistochemistry.

RESULTS

Airway administration of VEGF siRNAs induced transient air space enlargement in the mouse lung morphologically resembling the previously reported models of pulmonary emphysema. VEGF expression was significantly reduced in the lung, particularly in the alveolar septal cells. We also found that in this particular model, sequential airway administration of recombinant VEGF protein attenuated this air space enlargement. Additionally, we found that airway administration of DCI, a combination of dexamethasone, 3'-5'-cyclic adenosine monophosphate, and isobutylmethylxanthine attenuated the air space enlargement in this particular model, at least in part through the recovery of lung VEGF expression.

CONCLUSIONS

The pathogenesis of pulmonary emphysema is likely to be multifaceted, but the present mouse model may be useful in dissecting the involvement of VEGF in pulmonary emphysema.

Synergistic effect of caffeine and glucocorticoids on expression of surfactant protein B (SP-B) mRNA

Administration of glucocorticoids and caffeine is a common therapeutic intervention in the neonatal period, but possible interactions between these substances are still unclear. The present study investigated the effect of caffeine and different glucocorticoids on expression of surfactant protein (SP)-B, crucial for the physiological function of pulmonary surfactant. We measured expression levels of SP-B, various SP-B transcription factors including erythroblastic leukemia viral oncogene homolog 4 (ErbB4) and thyroid transcription factor-1 (TTF-1), as well as the glucocorticoid receptor (GR) after administering different doses of glucocorticoids, caffeine, cAMP, or the phosphodiesterase-4 inhibitor rolipram in the human airway epithelial cell line NCI-H441. Administration of dexamethasone (1 µM) or caffeine (5 mM) stimulated SP-B mRNA expression with a maximal of 38.8±11.1-fold and 5.2±1.4-fold increase, respectively. Synergistic induction was achieved after co-administration of dexamethasone (1 mM) in combination with caffeine (10 mM) (206±59.7-fold increase, p<0.0001) or cAMP (1 mM) (213±111-fold increase, p = 0.0108). SP-B mRNA was synergistically induced also by administration of caffeine with hydrocortisone (87.9±39.0), prednisolone (154±66.8), and betamethasone (123±6.4). Rolipram also induced SP-B mRNA (64.9±21.0-fold increase). We detected a higher expression of ErbB4 and GR mRNA (7.0- and 1.7-fold increase, respectively), whereas TTF-1, Jun B, c-Jun, SP1, SP3, and HNF-3α mRNA expression was predominantly unchanged. In accordance with mRNA data, mature SP-B was induced significantly by dexamethasone with caffeine (13.8±9.0-fold increase, p = 0.0134). We found a synergistic upregulation of SP-B mRNA expression induced by co-administration of various glucocorticoids and caffeine, achieved by accumulation of intracellular cAMP. This effect was mediated by a caffeine-dependent phosphodiesterase inhibition and by upregulation of both ErbB4 and the GR. These results suggested that caffeine is able to induce the expression of SP-transcription factors and affects the signaling pathways of glucocorticoids, amplifying their effects. Co-administration of caffeine and corticosteroids may therefore be of benefit in surfactant homeostasis.