Non-invasive assessment of small airway remodelling in smokers

Revisiting Peter Macklem's old dream through the PRISm of lung volumes

In healthy asymptomatic smokers with normal FEV1/FVC, abnormal CT lung volumes that reflect small airway dysfunction and emphysema could be used as a biomarker to identify susceptible smokers at increased risk of progressing to COPD https://bit.ly/3XZDj1s.

Inflammatory parameters and pulmonary biomarkers in smokers with and without chronic obstructive pulmonary disease (COPD)

Background

We organized this study in order to investigate differences in serum inflammatory profiles and circulating serum pneumoproteins between smokers with and without chronic obstructive pulmonary disease (COPD).

Methods

Patients aged 35–70 years with COPD and a smoking history ≥10 pack-years (cases, n=38) and 38 participants with the same smoking history without COPD (controls) were included in a comparative study conducted as part of a population-based cross-sectional study with 2,388 individuals in northwestern Russia. Cases and controls were matched for age and smoking history. Airflow obstruction (AO) was defined using forced expiratory volume in 1 second (FEV1)/forced vital capacity (FVC) <0.70 and/or FEV1/FVC < lower limit of the normal cut-off values. Patients at risk for COPD were reassessed using a standardized diagnostic work-up protocol. Several parameters, among which four inflammatory biomarkers [the high-sensitivity C-reactive protein (hs-CRP), interleukin (IL)-6, IL-8, and tumor necrosis factor-α (TNF-α) levels] and two pneumoproteins [surfactant protein D (SP-D) and Clara cell secretory protein 16 (CC16)], were measured in the peripheral blood. Systemic inflammation was defined as at least 2 or more elevated biomarker levels.

Results

Out of all smokers, 57.9% with normal spirometry and 36.8% with COPD did not have systemic inflammation, whereas 44.7% of the patients with COPD and 5.3% of the patients without AO demonstrated at least two elevated biomarker levels. No difference in age, gender, and smoking history, environmental and occupational exposure was found between the non-inflamed and the inflamed smokers. Of all risk factors studied, only COPD was associated with systemic inflammation [odds ratio (OR) 11.42, 95% confidence interval (CI): 2.13–58.84].

Conclusions

Our study describes the systemic inflammatory network pattern associated with COPD and how it differs from the pattern in smokers with normal lung function. Systemic inflammation is not present in all smokers with COPD; in contrast, some non-obstructed smokers are characterized by systemic inflammation. From this perspective, smoking itself could be seen as a disease and studied accordingly.

Trial Registration

NCT02307799.

Identification of potential diagnostic and therapeutic target genes for lung squamous cell carcinoma

The purpose of this study was to identify potential molecular markers of lung squamous cell carcinoma (LUSC). Three datasets containing LUSC mRNA sequencing data were downloaded from the Gene Expression Omnibus, The Cancer Genome Atlas and the Gene Expression Profiling Interactive Analysis databases. These datasets were used to identify significantly differentially expressed genes (DEGs) in LUSC. A protein-protein interaction network of the DEGs was constructed followed by Gene Ontology, Kyoto Encyclopedia of Genes and Genomes and overall survival analyses of the DEGs. A total of 37 DEGs between LUSC and normal tissues were identified, including 26 downregulated genes and 11 upregulated genes. Biological Process enrichment analysis revealed that the DEGs were mainly enriched in ‘cell adhesion’, ‘cell-matrix adhesion’, ‘anatomical structure morphogenesis’, ‘ECM-receptor interaction’ and ‘focal adhesion’. Overall survival analysis demonstrated that transcription factor 21, α-2-macroglobulin, acyl-CoA synthetase long chain family member 5, integrin subunit β8, meiotic nuclear divisions 1 and secretoglobin family 1A member 1 were significantly associated with the occurrence and development of lung cancer, and these genes were selected as hub genes. The results obtained in the present study may aid the elucidation of the molecular mechanisms involved in the development of LUSC and may provide potential targets for LUSC treatment.

Lung development, regeneration and plasticity: From disease physiopathology to drug design using induced pluripotent stem cells

Lungs have a complex structure composed of different cell types that form approximately 17 million airway branches of gas-delivering bronchioles connected to 500 million gas-exchanging alveoli. Airways and alveoli are lined by epithelial cells that display a low rate of turnover at steady-state, but can regenerate the epithelium in response to injuries. Here, we review the key points of lung development, homeostasis and epithelial cell plasticity in response to injury and disease, because this knowledge is required to develop new lung disease treatments. Of note, canonical signaling pathways that are essential for proper lung development during embryogenesis are also involved in the pathophysiology of most chronic airway diseases. Moreover, the perfect control of these interconnected pathways is needed for the successful differentiation of induced pluripotent stem cells (iPSC) into lung cells. Indeed, differentiation of iPSC into airway epithelium and alveoli is based on the use of biomimetics of normal embryonic and fetal lung development. In vitro iPSC-based models of lung diseases can help us to better understand the impaired lung repair capacity and to identify new therapeutic targets and new approaches, such as lung cell therapy.

Biomarkers in the Management of Difficult Asthma

Difficult asthma is a heterogeneous disease of the airways including various types of bronchial inflammation and various degrees of airway remodeling. Therapeutic response of severe asthmatics can be predicted by the use of biomarkers of Type2-high or Type2-low inflammation. Based on sputum cell analysis, four inflammatory phenotypes have been described. As induced sputum is time-consuming and expensive technique, surrogate biomarkers are useful in clinical practice.

Eosinophilic phenotype is likely to reflect ongoing adaptive immunity in response to allergen. Several biomarkers of eosinophilic asthma are easily available in clinical practice (blood eosinophils, serum IgE, exhaled nitric oxyde, serum periostin). Neutrophilic asthma is thought to reflect innate immune system activation in response to pollutants or infectious agents while paucigranulocytic asthma is thought to be not inflammatory and characterized by smooth muscle dysfunction. We currently lack of user-friendly biomarkers of neutrophilic asthma and airway remodeling.

In this review, we summarize the biomarkers available for the management of difficult asthma.

CCSP G38A polymorphism environment interactions regulate CCSP levels differentially in COPD

Impaired airway homeostasis in chronic obstructive pulmonary disease (COPD) could be partly related to club cell secretory protein (CCSP) deficiency. We hypothesize that CCSP G38A polymorphism is involved and aim to examine the influence of the CCSP G38A polymorphism on CCSP transcription levels and its regulatory mechanisms. CCSP genotype and CCSP levels in serum and sputum were assessed in 66 subjects with stable COPD included in a 1-yr observational study. Forty-nine of them had an exacerbation. In an in vitro study, the impact on the CCSP promoter of 38G wild-type or 38A variant was assessed. BEAS-2B cells were transfected by either the 38G or 38A construct, in the presence/absence of cigarette smoke extract (CSE) or lipopolysaccharides (LPS). Cotransfections with modulating transcription factors, p53 and Nkx2.1, identified by in silico analysis by using ConSite and TFSEARCH were conducted. A allele carrier COPD patients had lower serum and sputum CCSP levels, especially among active smokers, and a decreased body mass index, airflow obstruction, dyspnea, and exercise capacity (BODE) score. In vitro, baseline CCSP transcription levels were similar between the wild and variant constructs. CSE decreased more profoundly the CCSP transcription level of 38A transfected cells. The opposite effect was observed with p53 cotransfection. LPS stimulation induced CCSP repression in 38A promoter transfected cells. Cotransfection with Nkx2.1 significantly activated the CCSP promoters irrespective of the polymorphism. Circulating CCSP levels are associated with smoking and the CCSP G38A polymorphism. CSE, LPS, and the Nkx2.1 and p53 transcription factors modulated the CCSP promoter efficiency. The 38A polymorphism exaggerated the CCSP repression in response to p53 and CSE.

Quantification of Pathologic Air Trapping in Lung Transplant Patients Using CT Density Mapping: Comparison with Other CT Air Trapping Measures

To determine whether density mapping (DM) is more accurate for detection and quantification of pathologic air trapping (pAT) in patients after lung transplantation compared to other CT air trapping measures. One-hundred forty-seven lung and heart-lung transplant recipients underwent CT-examinations at functional residual capacity (FRC) and total lung capacity (TLC) and PFT six months after lung transplantation. Quantification of air trapping was performed with the threshold-based method in expiration (EXP), density mapping (DM) and the expiratory to inspiratory ratio of the mean lung density (E/I-ratio MLD). A non-rigid registration of inspiration-expiration CT-data with a following voxel-to-voxel mapping was carried out for DM. Systematic variation of attenuation ranges was performed for EXP and DM and correlated with the ratio of residual volume to total lung capacity (RV/TLC) by Spearman rank correlation test. AT was considered pathologic if RV/TLC was above the 95th percentile of the predicted upper limit of normal values. Receiver operating characteristic (ROC) analysis was performed. The optimal attenuation range for the EXP method was from -790 HU to -950 HU (EXP(-790 to -950HU)) (r = 0.524, p<0.001) to detect air trapping. Within the segmented lung parenchyma, AT was best defined as voxel difference less than 80 HU between expiration and registered inspiration using the DM method. DM correlated best with RV/TLC (r = 0.663, p<0.001). DM and E/I-ratio MLD showed a larger AUC (0.78; 95% CI 0.69-0.86; 0.76, 95% CI 0.67-0.85) than EXP(-790 HU to -950 HU) (0.71, 95% CI 0.63-0.78). DM and E/I-ratio MLD showed better correlation with RV/TLC and are more suited quantitative CT-methods to detect pAT in lung transplant patients than the EXP(-790HU to -950HU).

Relationship between CT air trapping criteria and lung function in small airway impairment quantification

BACKGROUND

Small airways are regarded as the elective anatomic site of obstruction in most chronic airway diseases. Expiratory computed tomography (CT) is increasingly used to assess obstruction at this level but there is no consensus regarding the best quantification method. We aimed to evaluate software-assisted CT quantification of air trapping for assessing small airway obstruction and determine which CT criteria better predict small airway obstruction on single breath nitrogen test (SBNT).

METHODS

Eighty-nine healthy volunteers age from 60 to 90 years old, underwent spirometrically-gated inspiratory (I) and expiratory (E) CT and pulmonary function tests (PFTs) using SBNT, performed on the same day. Air trapping was estimated using dedicated software measuring on inspiratory and expiratory CT low attenuation area (LAA) lung proportion and mean lung density (MLD). CT indexes were compared to SBNT results using the Spearman correlation coefficient and hierarchical dendrogram analysis. In addition, receiver operating characteristic (ROC) curve analysis was performed to determine the optimal CT air-trapping criterion.

RESULTS

43 of 89 subjects (48,3%) had dN2 value above the threshold defining small airway obstruction (i.e. 2.5% N2/l). Expiratory to inspiratory MLD ratio (r = 0.40) and LAA for the range -850 -1024 HU (r = 0.29) and for the range -850 -910 HU (r = 0.37) were positively correlated with SBNT results. E/I MLD was the most suitable criterion for its expression. Expiratory to inspiratory MLD ratio (E/I MLD) showed the highest AUC value (0.733) for small airway obstruction assessment.

CONCLUSION

Among all CT criteria, all correlating with small airway obstruction on SBNT, E/I MLD was the most suitable criterion for its expression in asymptomatic subjects with mild small airway obstruction

TRIAL REGISTRATION

Registered at Clinicaltrials.gov, identifier: NCT01230879.

The safety of sputum induction in adults with acute exacerbation of COPD

INTRODUCTION

Induced sputum is a non-invasive method, and a useful tool to evaluate inflammatory cells and mediators in the airway lumen in the setting of acute exacerbation of chronic obstructive pulmonary disease (AECOPD). However, the inhalation of hypertonic saline solution to induce sputum may cause a bronchoconstrictive response, so it is important to evaluate the success and safety of sputum induction (SI).

OBJECTIVES

The aims of this study were to assess the safety and efficacy of SI in adults with AECOPD.

METHODS

Eighty-three AECOPD subjects and 26 healthy controls underwent a modified SI. The outcome measures included fall in lung function during induction and success of SI.

RESULTS

Adults hospitalized with AECOPD had moderate to very severe airflow obstruction. SI was successful in over 80% of subjects. The percentage decrease in forced expiratory volume in 1s (FEV1 ) from baseline by the Global initiative for Chronic Obstructive Lung Disease (GOLD) category was median 1.2(interquartile range, 0.5-3.3)(GOLD II), 2.3(1.3-3.2)(GOLD III), 5.2(3.3-8.6)(GOLD IV) and 1.4(0.5-3.2)(control), respectively. A fall in FEV1 of >20% occurred in only one subject with AECOPD who was in GOLD category III. The decrease in percentage of FEV1 from baseline was greatest in the second stage of induction, and correlated with that of the final stage (r=0.589; P=0.01). The fall in FEV1 during induction increased with GOLD category (P<0.05).

CONCLUSIONS

SI can be safely and successfully performed in patients with moderate to very severe chronic obstructive pulmonary disease who experience an exacerbation using this modified induction protocol. The early decrease in FEV1 can be used to predict the maximum fall.

RNA-Seq quantification of the human small airway epithelium transcriptome

Background

The small airway epithelium (SAE), the cell population that covers the human airway surface from the 6^th generation of airway branching to the alveoli, is the major site of lung disease caused by smoking. The focus of this study is to provide quantitative assessment of the SAE transcriptome in the resting state and in response to chronic cigarette smoking using massive parallel mRNA sequencing (RNA-Seq).

Results

The data demonstrate that 48% of SAE expressed genes are ubiquitous, shared with many tissues, with 52% enriched in this cell population. The most highly expressed gene, SCGB1A1, is characteristic of Clara cells, the cell type unique to the human SAE. Among other genes expressed by the SAE are those related to Clara cell differentiation, secretory mucosal defense, and mucociliary differentiation. The high sensitivity of RNA-Seq permitted quantification of gene expression related to infrequent cell populations such as neuroendocrine cells and epithelial stem/progenitor cells. Quantification of the absolute smoking-induced changes in SAE gene expression revealed that, compared to ubiquitous genes, more SAE-enriched genes responded to smoking with up-regulation, and those with the highest basal expression levels showed most dramatic changes. Smoking had no effect on SAE gene splicing, but was associated with a shift in molecular pattern from Clara cell-associated towards the mucus-secreting cell differentiation pathway with multiple features of cancer-associated molecular phenotype.

Conclusions

These observations provide insights into the unique biology of human SAE by providing quantit-ative assessment of the global transcriptome under physiological conditions and in response to the stress of chronic cigarette smoking.

[Importance of the distal airway in COPD]

Chronic obstructive pulmonary disease (COPD) is characterized by inflammation causing airflow obstruction. However, the initial histological lesion of COPD occurs in the respiratory bronchiole and spirometry is unable to detect involvement of this area until the disease is advanced. Major advances have been made in characterizing the inflammatory process in the small airways. However, in clinical practice, a non-invasive marker of small airways involvement, which would allow injury and the effect of treatment to be monitored, is lacking. To date, the combination of bronchodilators and inhaled corticosteroids is recommended for the most severe cases, although the effects of this therapeutic option on the small airways are not well known. New treatments that reach the distal airways and novel techniques to assess the small airways will allow a more complete approach to this disease.

Induction of the unfolded protein response by cigarette smoke is primarily an activating transcription factor 4-C/EBP homologous protein mediated process

PURPOSE

Cigarette smoke is the major risk factor associated with the development of chronic obstructive pulmonary disease (COPD). Recent studies propose a link between endoplasmic reticulum (ER) stress and emphysema, demonstrated by increased ER stress markers under smoking conditions. Here, we investigate whether cigarette smoke-induced ER stress is cell specific and correlates with acute and chronic cigarette smoke exposure.

METHODS

Gene and protein expression changes in human primary lung cell cultures following cigarette smoke extract (CSE) exposure were monitored by qPCR and Western blot analysis. Mice and guinea pigs were exposed to cigarette smoke and ER stress markers examined in whole lung homogenates. Inflammatory cells from the bronchoalveolar lavage fluid of 10 days smoke exposed mice were also examined.

RESULTS

Cigarette smoke induced a trend increase in the ER stress response through an activating transcription factor 4 (ATF4) mediated induction of C/EBP homologous protein (CHOP) in primary small airway epithelial cells. Bronchial epithelial cells and macrophages responded similarly to CSE. Wild-type mice and guinea pigs exposed to acute levels of cigarette smoke exhibited increased levels of CHOP but not at significant levels. However, after long-term chronic cigarette smoke exposure, CHOP expression was reduced. Interestingly, inflammatory cells from smoke exposed mice had a significant increase in CHOP/ATF4 expression.

CONCLUSION

A trend increase in CHOP levels appear in multiple human lung cell types following acute cigarette smoke exposure in vitro. In vivo, inflammatory cells, predominately macrophages, demonstrate significant cigarette smoke-induced ER stress. Early induction of CHOP in cigarette smoke may play a pivotal role in early induction of lung disease, however in vivo long-term cigarette smoke exposure exhibited a reduction in the ER stress response.