Recovery of bronchial epithelium on stopping smoking

The Challenge of Long-Term Cultivation of Human Precision-Cut Lung Slices

Human precision-cut lung slices (PCLS) have proven to be an invaluable tool for numerous toxicologic, pharmacologic, and immunologic studies. Although a cultivation period of <1 week is sufficient for most studies, modeling of complex disease mechanisms and investigating effects of long-term exposure to certain substances require cultivation periods that are much longer. So far, data regarding tissue integrity of long-term cultivated PCLS are incomplete. More than 1500 human PCLS from 16 different donors were cultivated under standardized, serum-free conditions for up to 28 days and the viability, tissue integrity, and the transcriptome was assessed in great detail. Even though viability of PCLS was well preserved during long-term cultivation, a continuous loss of cells was observed. Although the bronchial epithelium was well preserved throughout cultivation, the alveolar integrity was preserved for about 2 weeks, and the vasculatory system experienced significant loss of integrity within the first week. Furthermore, ciliary beat in the small airways gradually decreased after 1 week. Interestingly, keratinizing squamous metaplasia of the alveolar epithelium with significantly increasing manifestation were found over time. Transcriptome analysis revealed a significantly increased immune response and significantly decreased metabolic activity within the first 24 hours after PCLS generation. Overall, this study provides a comprehensive overview of histomorphologic and pathologic changes during long-term cultivation of PCLS.

SARS-CoV-2 infection and smoking: What is the association? A brief review

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The link between smoking and the expression of SARS-CoV-2 key entry genes is discussed.

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Smoking-related cardiac and respiratory diseases are risk factors for COVID-19.

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The impact of smoking on ACE-2 and TMPRSS2 receptors expression is controversial.

Susceptibility to severe illness from COVID-19 is anticipated to be associated with cigarette smoking as it aggravates the risk of cardiovascular and respiratory illness, including infections. This is particularly important with the advent of a new strain of coronaviruses, the severe acute respiratory syndrome coronavirus (SARS-CoV-2) that has led to the present pandemic, coronavirus disease 2019 (COVID-19). Although, the effects of smoking on COVID-19 are less described and controversial, we presume a link between smoking and COVID-19. Smoking has been shown to enhance the expression of the angiotensin-converting enzyme-2 (ACE-2) and transmembrane serine protease 2 (TMPRSS2) key entry genes utilized by SARS-CoV-2 to infect cells and induce a ‘cytokine storm’, which further increases the severity of COVID-19 clinical course. Nevertheless, the impact of smoking on ACE-2 and TMPRSS2 receptors expression remains paradoxical. Thus, further research is necessary to unravel the association between smoking and COVID-19 and to pursue the development of potential novel therapies that are able to constrain the morbidity and mortality provoked by this infectious disease. Herein we present a brief overview of the current knowledge on the correlation between smoking and the expression of SARS-CoV-2 key entry genes, clinical manifestations, and disease progression.

A Brief History of Bronchitis in England and Wales

Chronic bronchitis is associated with hypertrophy of airway submucosal glands and with mucus and squamous metaplasia of the surface epithelium. A historical review of research on these and other pathological changes is provided. Next, from annual reports of the Registrar-General's Office (and later the Office of National Statistics), death rates per unit population from acute and chronic bronchitis (a term that here includes chronic obstructive pulmonary disease [COPD]) are calculated for England and Wales from 1838 to the present. It is argued that a large increase in the death rate between 1838 and 1879, from all forms of bronchitis combined, was due primarily to increased levels of atmospheric coal smoke, whereas a decrease from 1879 to 1935 was due to progressively cleaner air. Between 1935 and the mid-1960s, mortality from chronic bronchitis among men increased dramatically, after which it has fallen, a pattern that parallels changes in cigarette smoking. Finally, a brief historical review of the treatments for chronic bronchitis is presented.

Cigarette Smoke Exposure and Inflammatory Signaling Increase the Expression of the SARS-CoV-2 Receptor ACE2 in the Respiratory Tract

The factors mediating fatal SARS-CoV-2 infections are poorly understood. Here, we show that cigarette smoke causes a dose-dependent upregulation of angiotensin converting enzyme 2 (ACE2), the SARS-CoV-2 receptor, in rodent and human lungs. Using single-cell sequencing data, we demonstrate that ACE2 is expressed in a subset of secretory cells in the respiratory tract. Chronic smoke exposure triggers the expansion of this cell population and a concomitant increase in ACE2 expression. In contrast, quitting smoking decreases the abundance of these secretory cells and reduces ACE2 levels. Finally, we demonstrate that ACE2 expression is responsive to inflammatory signaling and can be upregulated by viral infections or interferon treatment. Taken together, these results may partially explain why smokers are particularly susceptible to severe SARS-CoV-2 infections. Furthermore, our work identifies ACE2 as an interferon-stimulated gene in lung cells, suggesting that SARS-CoV-2 infections could create positive feedback loops that increase ACE2 levels and facilitate viral dissemination.

Are healthy smokers really healthy?

Cigarette smoke contains more than 4500 chemicals which have toxic, mutagenic and carcinogenic effects. Strong evidences have shown that current smokers take a significantly higher risk of cardiovascular diseases, chronic obstructive pulmonary disease (COPD) and lung cancer than nonsmokers. However, less attention has been paid to the smoking induced abnormalities in the individuals defined as healthy smokers who are normal with spirometry, radiographic images, routine physical exam and categorized as healthy control group in many researches. Actually, ‘healthy smokers’ are not healthy. This narrative review focuses on the smoking related pathophysiologic changes mainly in the respiratory system of healthy smokers, including inflammation and immune changes, genetic alterations, structural changes and pulmonary dysfunction.

Squamous Metaplasia Is Increased in the Bronchial Epithelium of Smokers with Chronic Obstructive Pulmonary Disease

Aims

To quantify the extent of squamous metaplasia in bronchial biopsies and relate it to the presence of chronic obstructive pulmonary disease (COPD), a smoking-related pathology.

Methods

Bronchial biopsies (n = 15 in each group) from smokers with COPD GOLD stage1 and GOLD stage2, smokers without COPD and healthy non-smokers were stained immunohistochemically with a panel of antibodies that facilitated the identification of pseudostratified epithelium and distinction of squamous metaplasia and squamous epithelium from tangentially cut epithelium. The percentage length of each of these epithelial phenotypes was measured as a percent of total epithelial length using computerised image analysis. Sections were also stained for carcinoembryonic antigen and p53, early markers of carcinogenesis, and Ki67, and the percentage epithelial expression measured.

Results

The extent of squamous metaplasia was significantly increased in both COPD1 and COPD2 compared to healthy smokers and healthy non-smokers. The amount of fully differentiated squamous epithelium was also increased in COPD1 and COPD2 compared to healthy non-smokers, as was the expression of carcinoembryonic antigen. These features correlated with one other.

Conclusion

In subjects with COPD there is a loss of pseudostratified epithelium accompanied by an increase in squamous metaplasia with transition into a fully squamous epithelium and expression of early markers of carcinogenesis.

Pathohistological changes of tracheal epithelium in laryngectomized patients

Total laryngectomy results in a permanent disconnection of the upper and lower airways. Thus, the upper airways are bypassed and can no longer condition, humidify, and filter the inhaled air, leading to damage of the tracheobronchial epithelium. There is little scientific information available about the effects of tracheostoma breathing and the degree of mucosal damage in laryngectomized patients. The aims of this study were to determine the histopathologic findings and investigate the potential impact of using a heat and moisture exchanger (HME) on the tracheal epithelium in long-term tracheostomy patients. Tracheal mucosal biopsies were taken from a total of 70 patients. Specimens were stained with hematoxylin and eosin and examined by a light microscope. Normal pseudostratified ciliated columnar epithelium was found in only 9 (12.9%) cases; while, 17 (24.3%) cases had some degree of basal cell hyperplasia. Squamous metaplasia was the most common finding (50%). Pre-invasive lesions (mild and moderate squamous dysplasia) were found in only one patient who used an HME, and in eight (11.4%) non-users. Although the HME cannot completely restore the physiological functions of the upper respiratory track, it delivers a better quality of air to the lower airways and has a positive effect on tracheal mucosa.

Genetic polymorphisms of phase I and phase II metabolic enzymes as modulators of lung cancer susceptibility

OBJECTIVES

Tobacco exposure remains the main etiologic factor for lung cancer (LC). Interactions between environment and individual genetic profile are particularly important for this disease. The aim of this study was to evaluate the contribution of CYP1A1*2A, CYP1A1*2C, CYP2D6*4, GSTP1, GSTM1, GSTT1 and NAT2 polymorphisms for the susceptibility to LC in a Portuguese population considering their demographic and clinical characteristics.

MATERIALS AND METHODS

A total of 200 LC and 247 controls subjects from the Centre of Portugal were studied. Clinical and demographic characteristics were collected from clinical files and by individual questionnaires. Polymorphisms of CYP1A1*2A, CYP1A1*2C, CYP2D6*4, GSTP1, GSTM1, GSTT1 and NAT2 were genotyped using PCR-RFLP, PCR multiplex, ARMS and real time.

RESULTS

Gender, family history of cancer, smoke cessation and alcohol consumption were independent risk factors (p < 0.05). Associations found between phases I and II genes and LC population reveal a sex dependent distribution. Logistic regression analysis demonstrates that enhanced activation by CYPs, associated by reduced or loss of function of phase II enzymes, can lead to a greater risk. GSTP1 and NAT2 polymorphisms studied have a significant contribution for the histological tumour types and the presence of metastases, at time of diagnosis, respectively, when males with smoking habits were considered.

CONCLUSION

Multiple interactions between environment and individual characteristics are clearly associated to this disease. Variants of the detoxification genes may act synergistically contributing to this disease and modifying the risk posed by smoking and sex. The GSTT1*0 and GSTP1 (Ile462Val) might contribute to the malignant phenotype through different mechanisms.

A panel of antibodies for identifying squamous metaplasia in endobronchial biopsies from smokers

Toxic injury can induce squamous metaplasia of respiratory epithelium, which normally is pseudostratified. Terminally differentiated squamous epithelial cells have a flattened, elongated appearance. During differentiation, they have an intermediate phenotype that is difficult to identify and distinguish from tangentially cut columnar cells in tissue sections from endobronchial biopsies, whose small size makes orientation difficult. The aim of our study was to develop a panel of antibodies that could be employed to distinguish normal epithelium from metaplastic epithelium and would be suitable for use on endobronchial biopsies. Nasal polyp tissue and tonsil tissue, which have pseudostratified and squamous epithelia, respectively, were collected from surgical cases and embedded in glycol methacrylate resin. Cut sections were stained immunohistochemically with a panel of antibodies to cytokeratins (CK), whose expression varies with epithelial type and stage of differentiation, and involucrin, a marker of terminal squamous differentiation. Squamous epithelium stained positively for CK5/6, CK13 and involucrin. In the pseudostratified epithelium, basal cells exhibited weak staining for CK13 and strong staining for CK5/6, and columnar cells exhibited strong immunoreactivity for CK7, CK8 and CK18. Application of this panel to endobronchial biopsies from smokers enabled areas of squamous metaplasia to be distinguished from tangentially sectioned epithelium.

Pulmonary fibrosis and lung carcinoma: a comparative study of metaplastic epithelia in honeycombed areas of usual interstitial pneumonia with or without lung carcinoma

Usual interstitial pneumonia (UIP), or idiopathic pulmonary fibrosis, has been considered to be associated with a high risk for lung carcinoma. To investigate this well-known but still equivocal relationship, we reviewed the clinical features of UIP autopsy cases with or without lung carcinoma (n = 32 and 38, respectively), and compared the morphology and cell kinetics of metaplastic epithelia in the honeycombed areas (n = 11, each group). Thirty-two of 70 UIP autopsy cases showed lung carcinomas. Clinically, UIP with lung carcinoma showed a male predominance (P = 0.001), a higher rate of smoking history (P = 0.001) and a later onset of UIP (P = 0.02), compared with UIP without lung carcinoma. Most of the carcinomas were peripheral in origin (90%), and 65% were topographically associated with honeycombed areas or the border between honeycombing and non-fibrotic areas. Quantitative assessment of the metaplastic epithelia in the honeycombed areas revealed that squamous metaplasia, but not cuboidal cell metaplasia or bronchial cell metaplasia, occurred more frequently in UIP with lung carcinoma than in UIP without lung carcinoma (P = 0.02). There were no significant differences between the two groups with regard to the labeling indexes of Ki-67 and p53 in the metaplastic epithelia, including squamous metaplasia. The degree of atypical squamous metaplasia was not different between the two groups. The quantitative predominance of squamous metaplasia in the honeycombed areas may not be a precursor for lung carcinoma, but might reflect a constitutional susceptibility of UIP patients to develop a lung carcinoma.

Molecular damage in the bronchial epithelium of current and former smokers

BACKGROUND

Most lung cancers are attributed to smoking. These cancers have been associated with multiple genetic alterations and with the presence of preneoplastic bronchial lesions. In view of such associations, we evaluated the status of specific chromosomal loci in histologically normal and abnormal bronchial biopsy specimens from current and former smokers and specimens from nonsmokers.

METHODS

Multiple biopsy specimens were obtained from 18 current smokers, 24 former smokers, and 21 nonsmokers. Polymerase chain reaction-based assays involving 15 polymorphic microsatellite DNA markers were used to examine eight chromosomal regions for genetic changes (loss of heterozygosity [LOH] and microsatellite alterations).

RESULTS

LOH and microsatellite alterations were observed in biopsy specimens from both current and former smokers, but no statistically significant differences were observed between the two groups. Among individuals with a history of smoking, 86% demonstrated LOH in one or more biopsy specimens, and 24% showed LOH in all biopsy specimens. About half of the histologically normal specimens from smokers showed LOH, but the frequency of LOH and the severity of histologic change did not correspond until the carcinoma in situ stage. A subset of biopsy specimens from smokers that exhibited either normal or preneoplastic histology showed LOH at multiple chromosomal sites, a phenomenon frequently observed in carcinoma in situ and invasive cancer. LOH on chromosomes 3p and 9p was more frequent than LOH on chromosomes 5q, 17p (17p13; TP53 gene), and 13q (13q14; retinoblastoma gene). Microsatellite alterations were detected in 64% of the smokers. No genetic alterations were detected in nonsmokers.

CONCLUSIONS

Genetic changes similar to those found in lung cancers can be detected in the nonmalignant bronchial epithelium of current and former smokers and may persist for many years after smoking cessation.

Association between acute inflammatory cells in lavage fluid and bronchial metaplasia

In epidemiologic studies, airway disease and parenchymal injury are known morbid outcomes of occupational exposure to asbestos. However, the relationship of inflammatory events considered to be responsible for parenchymal injury to the subsequent development of airway injury is unknown. To assess this we performed bronchoalveolar lavage (BAL) and airway biopsies on a population of subjects with exposure to asbestos in the workplace. As an index of airway injury, we employed histologic metaplasia seen in mucosal biopsy specimens. Lung BAL fluid was analyzed for two potentially relevant protein markers and for inflammatory cells recovered from the lower respiratory tract. We related metaplasia to demographic features of this study population (eg, smoking history and asbestos exposure data) and also to the protein and cellular markers recovered by BAL. We studied 50 workers and detected keratinizing metaplasia in 15 and varying lesser abnormalities in the other 28. Cigarette smoking was not associated with the presence of metaplasia (p less than 0.2). Smoking status was associated with an increase in BAL cells (p less than 0.02); however, neither the percent nor concentration of acute inflammatory cells was significantly increased. Acute inflammatory cells (percent and cells per milliliter of BAL fluid) were significantly increased among the subjects with severe metaplasia compared with other study subjects. This increase was true of both neutrophils and eosinophils and the sum of these two (p less than 0.02). Stratification of subjects by smoking status demonstrated a persistent association of inflammatory cells with metaplasia. By logistic regression analysis, polymorphonuclear leukocytes per milliliter and eosinophils per milliliter were significantly related to the presence of metaplasia in two independent models (odds ratios, 9.9 and 7.6, respectively). Cigarette smoking and other demographic or BAL variables were not significantly associated with metaplasia in these models.

Chronic obstructive pulmonary disease and asthma. General and medical management with special attention to exacerbations

The general management of patients with chronic obstructive pulmonary disease and asthma is discussed. Pathophysiological mechanisms of bronchial obstruction and inflammation are briefly described. The importance of preventive measures is emphasized. Medicine prescribed in chronic obstructive pulmonary disease and asthma, their relative place in treatment schedules and route of administration are reviewed. Finally, the importance of maximal bronchodilatation in exacerbations is stressed and the few indications for antibiotic treatment are discussed.

The effects of cigarette smoking on voice-fundamental frequency

Previous group research has shown that the mean voice-fundamental frequency (F0) for individuals who smoke is lower than that of age- and sex-matched nonsmokers. It is believed that this reduction in F0 is a result of edema of the vocal folds caused by tobacco smoke. This study investigated F0 changes during smoking and no-smoking periods. Data were collected before, during, and after a 40-hour period of no-smoking. Analysis of the voice recordings showed a rise in voice F0 for the two smoking subjects during the 40-hour no-smoking period. Age- and sex-matched control subjects did not show a rise in their F0 during the same tasks. Results suggest that the pitch-lowering effects of cigarette smoking may be reversed after as few as 40 hours of smoking cessation.

Squamous metaplasia of the subglottic space and its relation to smoking

A macroscopic staining method was used to assess the incidence and extent of squamous metaplasia of the subglottic portion of the larynx. A total of 226 postmortem specimens were studied, 105 from nonsmokers and 121 from smokers. More than half of the specimens stained showed some metaplasia, but the incidence and extent of metaplasia was greater in smokers than in nonsmokers, and women were more affected than men. The incidence of metaplasia was greater in pipe and cigar smokers than in nonsmokers, but previous smokers did not differ from nonsmokers.