Autoimmunity, T-cells and STAT-4 in the pathogenesis of chronic obstructive pulmonary disease

Identification of related-genes of T cells in lung tissue of chronic obstructive pulmonary disease based on bioinformatics and experimental validation

T cells are one of the main cell types shaping the immune microenvironment in chronic obstructive pulmonary disease (COPD). They persist andplay cytotoxic roles. The purpose of this study aimed to explore the potential related-genes of T cells in lung tissue of COPD. Chip data GSE38974 and single_celldata GSE196638 were downloaded from the GEO database. Difference analyses and WGCNA of GSE38974 were performed to identify DEGs and the modules most associated with the COPD phenotype. Various cell subsets were obtained by GSE196638, and DEGs of T cells were further identified. GO, GSEA and KEGG enrichment analyses were conducted to explore the biological functions and regulatory signaling pathways of the DEGs and DEGs of T cells. The intersection of the DEGs, module genes and DEGs of T cells was assessed to acquire related-genes of T cells. The mRNA and protein expression levels of related-genes ofT cells were verified in lung tissue of mouse with emphysema model. Based on GSE38974 difference analysis, 3811 DEGs were obtained. The results of WGCNA showed that the red module had the highest correlation coefficient with the COPD phenotype. GSE196638 analysis identified 124 DEGs of T cells. The GO, GSEAand KEGG enrichment analyses mainly identified genes involved in I-kappaB kinase/NF-kappaB signaling, receptor signaling pathway via STAT, regulationof CD4-positive cells, regulation of T-helper cell differentiation, chemokine signaling pathway, Toll-likereceptor signaling pathway, CD8-positive cells, alpha-beta T cell differentiation, MAPK signaling pathway and Th17 cell differentiation. The DEGs, genes of the red module and DEGs of T cells were overlapped to acquire FOXO1 and DDX17. The results of RT-qPCR and Western Blot indicate that the mRNA and protein expression levels of FOXO1 and DDX17 in lung tissue of emphysema mice were significantly higher compared with those in air-exposed mice. FOXO1 as well as DDX17 may be related-genesof T cells in lung tissue of patient with COPD, and their participation in the biological processes of different signaling pathways may inspire further COPD research.

SOCS-JAK-STAT inhibitors and SOCS mimetics as treatment options for autoimmune uveitis, psoriasis, lupus, and autoimmune encephalitis

Autoimmune diseases arise from atypical immune responses that attack self-tissue epitopes, and their development is intricately connected to the disruption of the JAK-STAT signaling pathway, where SOCS proteins play crucial roles. Conditions such as autoimmune uveitis, psoriasis, lupus, and autoimmune encephalitis exhibit immune system dysfunctions associated with JAK-STAT signaling dysregulation. Emerging therapeutic strategies utilize JAK-STAT inhibitors and SOCS mimetics to modulate immune responses and alleviate autoimmune manifestations. Although more research and clinical studies are required to assess their effectiveness, safety profiles, and potential for personalized therapeutic approaches in autoimmune conditions, JAK-STAT inhibitors and SOCS mimetics show promise as potential treatment options. This review explores the action, effectiveness, safety profiles, and future prospects of JAK inhibitors and SOCS mimetics as therapeutic agents for psoriasis, autoimmune uveitis, systemic lupus erythematosus, and autoimmune encephalitis. The findings underscore the importance of investigating these targeted therapies to advance treatment options for individuals suffering from autoimmune diseases.

Pathogenesis of COPD at the cellular and molecular level

Chronic inflammatory responses in the lung of patients with stable mild-to severe forms of COPD play a central role in the definition, comprehension and monitoring of the disease state. A better understanding of the COPD pathogenesis can't avoid a detailed knowledge of these inflammatory changes altering the functional health of the lung during the disease progression. We here summarize and discuss the role and principal functions of the inflammatory cells populating the large, small airways and lung parenchyma of patients with COPD of increasing severity in comparison with healthy control subjects: T and B lymphocytes, NK and Innate Lymphoid cells, macrophages, and neutrophils. The differential inflammatory distribution in large and small airways of patients is also discussed. Furthermore, relevant cellular mechanisms controlling the homeostasis and the "normal" balance of these inflammatory cells and of structural cells in the lung, such as autophagy, apoptosis, necroptosis and pyroptosis are as well presented and discussed in the context of the COPD severity.

Novel pharmacological strategies to treat cognitive dysfunction in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a major incurable global health burden and currently the 3rd largest cause of death in the world, with approximately 3.23 million deaths per year. Globally, the financial burden of COPD is approximately €82 billion per year and causes substantial morbidity and mortality. Importantly, much of the disease burden and health care utilisation in COPD is associated with the management of its comorbidities and viral and bacterial-induced acute exacerbations (AECOPD). Recent clinical studies have shown that cognitive dysfunction is present in up to 60% of people with COPD, with impairments in executive function, memory, and attention, impacting on important outcomes such as quality of life, hospitalisation and survival. The high prevalence of cognitive dysfunction in COPD may also help explain the insufficient adherence to therapeutic plans and strategies, thus worsening disease progression in people with COPD. However, the mechanisms underlying the impaired neuropathology and cognition in COPD remain largely unknown. In this review, we propose that the observed pulmonary oxidative burden and inflammatory response of people with COPD 'spills over' into the systemic circulation, resulting in damage to the brain and leading to cognitive dysfunction. As such, drugs targeting the lungs and comorbidities concurrently represent an exciting and unique therapeutic opportunity to treat COPD and cognitive impairments, which may lead to the production of novel targets to prevent and reverse the debilitating and life-threatening effects of cognitive dysfunction in COPD.

An immunometabolic pathomechanism for chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is an inflammatory disease characterized by limitation of expiratory airflow. Cellular and molecular pathways involved in disease pathogenesis are not completely defined. Our study reveals that metabolism and immune response cooperate in COPD pathogenesis and progression. COPD subjects with different disease stages showed progressive increase of systemic leptin, an adipose tissue-derived proinflammatory molecule, that, at high concentrations, impaired the capacity of T cells to engage in glycolysis and to generate regulatory T cells. Thus, the loss of these immunoregulatory circuits during COPD determined the hyperactivation of effector T cells that amplified inflammation, leading to progressive decline of lung function. Understanding these immunometabolic mechanisms can have important implications for monitoring COPD progression and for disease treatment.

Chronic obstructive pulmonary disease (COPD) is an inflammatory condition associated with abnormal immune responses, leading to airflow obstruction. Lungs of COPD subjects show accumulation of proinflammatory T helper (Th) 1 and Th17 cells resembling that of autoreactive immune responses. As regulatory T (T_reg) cells play a central role in the control of autoimmune responses and their generation and function are controlled by the adipocytokine leptin, we herein investigated the association among systemic leptin overproduction, reduced engagement of glycolysis in T cells, and reduced peripheral frequency of T_reg cells in different COPD stages. These phenomena were also associated with an impaired capacity to generate inducible T_reg (iT_reg) cells from conventional T (T_conv) cells. At the molecular level, we found that leptin inhibited the expression of forkhead-boxP3 (FoxP3) and its splicing variants containing the exon 2 (FoxP3-E2) that correlated inversely with inflammation and weakened lung function during COPD progression. Our data reveal that the immunometabolic pathomechanism leading to COPD progression is characterized by leptin overproduction, a decline in the expression of FoxP3 splicing forms, and an impairment in T_reg cell generation and function. These results have potential implications for better understanding the autoimmune-like nature of COPD and the pathogenic events leading to lung damage.

The Interplay Between Immune Response and Bacterial Infection in COPD: Focus Upon Non-typeable Haemophilus influenzae

Chronic obstructive pulmonary disease (COPD) is a debilitating respiratory disease and one of the leading causes of morbidity and mortality worldwide. It is characterized by persistent respiratory symptoms and airflow limitation due to abnormalities in the lower airway following consistent exposure to noxious particles or gases. Acute exacerbations of COPD (AECOPD) are characterized by increased cough, purulent sputum production, and dyspnea. The AECOPD is mostly associated with infection caused by common cold viruses or bacteria, or co-infections. Chronic and persistent infection by non-typeable Haemophilus influenzae (NTHi), a Gram-negative coccobacillus, contributes to almost half of the infective exacerbations caused by bacteria. This is supported by reports that NTHi is commonly isolated in the sputum from COPD patients during exacerbations. Persistent colonization of NTHi in the lower airway requires a plethora of phenotypic adaptation and virulent mechanisms that are developed over time to cope with changing environmental pressures in the airway such as host immuno-inflammatory response. Chronic inhalation of noxious irritants in COPD causes a changed balance in the lung microbiome, abnormal inflammatory response, and an impaired airway immune system. These conditions significantly provide an opportunistic platform for NTHi colonization and infection resulting in a "vicious circle." Episodes of large inflammation as the consequences of multiple interactions between airway immune cells and NTHi, accumulatively contribute to COPD exacerbations and may result in worsening of the clinical status. In this review, we discuss in detail the interplay and crosstalk between airway immune residents and NTHi, and their effect in AECOPD for better understanding of NTHi pathogenesis in COPD patients.

Quantitative Computed Tomography (CT) Assessment of Emphysema in Patients with Severe Chronic Obstructive Pulmonary Disease (COPD) and its Correlation with Age, Sex, Pulmonary Function Tests, BMI, Smoking, and Biomass Exposure

Background

To evaluate the role of HRCT in quantifying emphysema in severe COPD patients and to study the variations in the pattern of emphysema in relation to age, sex, FEV1, smoking index, biomass exposure, and BMI.

Material/Methods

Automatic lung segmentation of HRCT scans in 41 severe COPD patients (GOLD stage III or more) was done using an emphysema protocol. The extent of emphysema was assessed using the density mask method with a threshold of –950 HU (%LAA-950). The percentage of emphysema in each lung lobe and both lungs was correlated with 6 parameters – age, sex, BMI, smoking index, biomass exposure, and FEV₁.

Results

Smoking resulted in homogenously distributed emphysema regardless of the severity of smoking. BMI was inversely correlated with the extent of emphysema. A significant association was found between the percentage of emphysema in the right lower lobe and BMI (P=0.015), between biomass exposure and the percentage of emphysema in RUL, RLL, and both lungs (P values of 0.024, 0.016, and 0.036, respectively). The extent of emphysema was disproportionately low compared to the amount of obstruction on PFTs, indicating an airway predominant variety of COPD with significant biomass exposure.

Conclusions

Smoking is associated with a relatively homogenous distribution of emphysema with no regional predilection. Biomass exposure produces predominantly right-sided emphysema. BMI decreases with increasing levels of emphysema in the right lower lobe. These risk factors of emphysema patterns are helpful in deciding on the management, including surgical options.

COPD immunopathology

The immunopathology of chronic obstructive pulmonary disease (COPD) is based on the innate and adaptive inflammatory immune responses to the chronic inhalation of cigarette smoking. In the last quarter of the century, the analysis of specimens obtained from the lower airways of COPD patients compared with those from a control group of age-matched smokers with normal lung function has provided novel insights on the potential pathogenetic role of the different cells of the innate and acquired immune responses and their pro/anti-inflammatory mediators and intracellular signalling pathways, contributing to a better knowledge of the immunopathology of COPD both during its stable phase and during its exacerbations. This also has provided a scientific rationale for new drugs discovery and targeting to the lower airways. This review summarises and discusses the immunopathology of COPD patients, of different severity, compared with control smokers with normal lung function.

Simvastatin Suppresses Airway IL-17 and Upregulates IL-10 in Patients With Stable COPD

BACKGROUND

Statins have immunomodulatory properties that may provide beneficial effects in the treatment of COPD. We investigated whether a statin improves the IL-17/IL-10 imbalance in patients with COPD, as has previously been demonstrated in patients with asthma.

METHODS

Thirty patients with stable COPD were recruited to a double-blind, randomized, controlled, crossover trial comparing the effect of simvastatin, 20 mg po daily, with that of a matched placebo on sputum inflammatory markers and airway inflammation. Each treatment was administered for 4 weeks separated by a 4-week washout period. The primary outcome was the presence of T-helper 17 cytokines and indoleamine 2,3-dioxygenase (IDO) in induced sputum. Secondary outcomes included sputum inflammatory cells, FEV1, and symptoms using the COPD Assessment Test (CAT).

RESULTS

At 4 weeks, there was a significant reduction in sputum IL-17A, IL-22, IL-6, and CXCL8 concentrations (mean difference, -16.4 pg/mL, P = .01; -48.6 pg/mL, P < .001; -45.3 pg/mL, P = .002; and -190.9 pg/mL, P = .007, respectively), whereas IL-10 concentrations, IDO messenger RNA expression (fold change), and IDO activity (kynurenine to tryptophan ratio) were markedly increased during simvastatin treatment compared with placebo treatment periods (mean difference, 24.7 pg/mL, P < .001; 1.02, P < .001; and 0.47, P < .001, respectively). The absolute sputum macrophage count, proportion of macrophages, and CAT score were reduced after simvastatin compared with placebo (mean difference, -0.16 × 106, P = .004; -14.1%, P < .001; and -3.2, P = .02, respectively). Values for other clinical outcomes were similar between the simvastatin and placebo treatments.

CONCLUSIONS

Simvastatin reversed the IL-17A/IL-10 imbalance in the airways and reduced sputum macrophage but not neutrophil counts in patients with COPD.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT01944176; www.clinicaltrials.gov.

Upregulation of IL-17A/F from human lung tissue explants with cigarette smoke exposure: implications for COPD

Background

Chronic obstructive pulmonary disease (COPD) is an inflammatory disorder marked by relative resistance to steroids. The IL-17 superfamily, which mediates cross-talk between the adaptive and innate immune systems, has been associated with diminished responses to steroids. Increasing evidence supports elevated IL-17 expression in the lung of COPD subjects. However, whether cells of the immune system (systemic) and/or local lung cells are contributing to the elevated IL-17 remains unclear. To address this issue, we utilized a human parenchymal lung tissue explant culture system with cigarette smoke exposure to investigate the expression of IL-17 and the mechanisms involved.

Methods

Parenchymal lung tissue removed from 10 non-COPD and 8 COPD patients was sectioned and cultured with different concentrations of cigarette smoke extract (CSE) for 3 or 6 hours. Tissue viability was evaluated by LDH (lactate dehydrogenase) in culture supernatants. Western blot and real-time PCR were performed to evaluate IL-17A/F expression. To investigate the mechanisms, pharmacological inhibitors for MAPK p38, ERK1/2, NF-κB and PI3K pathways were added into the culture media.

Results

No tissue damage was observed after the cigarette smoke exposure for 3 h or 6 h compared with the control media. At the protein level, the expression of both IL-17A (2.4 ± 0.6 fold) and IL-17 F (3.7 ± 0.7 fold) in the tissue from non-COPD subjects was significantly increased by 5% of CSE at 3 h. For COPD subjects, IL-17A/F expression were significantly increased only at 6 h with 10% of CSE (IL-17A: 4.2 ± 0.8 fold; IL-17 F: 3.3 ± 0.8 fold). The increased expression of IL-17A/F is also regulated at the mRNA level. The inhibitors for NF-κB and PI3K pathways significantly inhibited CSE-induced IL-17A/F expression from lung tissue of non-COPD subjects.

Conclusions

We found the evidence that the expression of both IL-17A and IL-17 F is increased by the cigarette smoke exposure in explants from both non-COPD and COPD subjects, supporting that local lung cells contribute IL-17 production. The elevated IL-17A/F expression is dependent on NF-κB and PI3K pathways. These observations add to the growing evidence which suggests that Th17 cytokines play a significant role in COPD.

Imbalance of peripheral blood Th17 and Treg responses in patients with chronic obstructive pulmonary disease

BACKGROUND

Autoimmune responses mediated by cluster of differentiation 4(+) T cells may contribute to the development of chronic obstructive pulmonary disease (COPD). However, little is known about the frequency of peripheral blood Th17 cells and of regulatory T cells (Tregs) in Chinese patients with COPD. This study is aimed at determining the frequency of circulating Th17 and Tregs in patients with moderate and severe COPD, heavy smokers and healthy controls (HC).

METHOD

The percentages of circulating T-helper type (Th)17 cells and Tregs were determined by flow cytometry in 32 patients with moderate COPD, 33 patients with severe COPD, 35 smokers, and 31 HC. The concentrations of serum Th17- and Treg-related cytokines were measured by enzyme-linked immunosorbent assay (ELISA). The levels of retinoic acid orphan receptor (ROR)-γt and Forkhead box p3 (Foxp3) mRNA transcripts in peripheral blood mononuclear cells were determined by real-time polymerase chain reaction. The potential correlation between the percentages of Th17 Tregs, serum cytokines and lung function was evaluated.

RESULTS

In comparison with that in the smokers and HC, significantly higher frequencies of Th17 cells and higher levels of ROR-γt mRNA transcripts and serum interleukin (IL)-17A, IL-6, IL-21, IL-22 and IL-23, but lower frequency of Tregs and lower levels of Foxp3 and serum IL-10 were detected in patients with moderate and severe COPD. The increased ratios of Th17 to Tregs were negatively correlated with the values of forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1) and FEV1/FVC.

CONCLUSIONS

An imbalance of circulating Th17 cells and Tregs is associated with the deterioration of pulmonary function in patients with moderate and severe COPD.

Immunopathogenesis of chronic obstructive pulmonary disease

PURPOSE OF REVIEW

Chronic obstructive pulmonary disease (COPD) is defined by airflow obstruction and is associated with an exaggerated inflammatory response to noxious stimuli, such as cigarette smoke. Inflammation and recruitment of immune cells drives the underlying pathophysiology; however, the roles of immune cells in the pathogenesis of COPD are evolving and this review will discuss the latest advancements in this field.

RECENT FINDINGS

Leukocytes including macrophages, neutrophils and lymphocytes are increased in the airways of COPD patients. Despite the presence of increased innate immune cells, COPD airways are often colonized with bacteria suggesting an underlying defect. Macrophages from COPD patients have reduced phagocytic ability which may drive the persistence of inflammation. Differing macrophage phenotypes have been associated with disease suggesting that the surrounding pulmonary environment in COPD may generate a specific phenotype that is permanently pro-inflammatory. COPD neutrophils are also aberrant with increased survival and motility, but lack direction which could lead to more widespread destruction during migration. Finally, an element of autoimmunity, driven by Th17 cells, and alterations in the ratios of lymphocyte subsets may also be involved in disease progression.

SUMMARY

COPD pathogenesis is complex with contributions from both the innate and adaptive immune systems, and the interaction of these cells with their environment mediates inflammation.

Pathogenic mechanism of second hand smoke induced inflammation and COPD

Second hand smoke (SHS) introduces thousands of toxic chemicals into the lung, including carcinogens and oxidants, which cause direct airway epithelium tissue destruction. It can also illicit indirect damage through its effect on signaling pathways related to tissue cell repair and by the abnormal induction of inflammation into the lung. After repeated exposure to SHS, these symptoms can lead to the development of pulmonary inflammatory disorders, including chronic obstructive pulmonary disease (COPD). COPD is a severe pulmonary disease characterized by chronic inflammation and irreversible tissue destruction. There is no causal cure, as the mechanism behind the development and progression of the disease is still unknown. Recent discoveries implicate genetic predisposition associated with inflammatory response contributed to the development of COPD, linked to irregular innate and adaptive immunity, as well as a risk factor for cancer. The use of animal models for both cigarette smoke (CS) and SHS associated in vivo experiments has been crucial in elucidating the pathogenic mechanisms and genetic components involved in inflammation-related development of COPD.

Pulmonary inflammatory reaction and structural changes induced by cigarette smoke exposure in the Guinea pig

Cigarette smoke (CS) induces an inflammatory process in the lung that may underlie the development of chronic obstructive pulmonary disease (COPD). The nature and characteristics of this process have not been fully established in animal models. We aimed to evaluate the pulmonary inflammatory reaction and its involvement in structural changes in guinea pigs chronically exposed to CS. 19 Hartley guinea pigs were exposed to 7 cigarettes/day, during 3 or 6 months. 18 control guinea pigs were sham-exposed. Numbers of neutrophils, macrophages and eosinophils and lymphoid follicles were assessed in different lung structures. Airway and vessel morphometry, alveolar space size and collagen deposition were also quantified. After 6 months of exposure, CS-exposed guinea pigs showed increased numbers of neutrophils, macrophages and eosinophils in the airways, intrapulmonary vessels and alveolar septa, as well as lymphoid follicles. Increased numbers of muscularized intrapulmonary vessels were apparent at 3 months. After 6 months of exposure, the airway wall thickened and the alveolar space size increased. Collagen deposition was also apparent in airway walls and alveolar septa after 6 months' exposure. The magnitude of airway wall-thickening correlated with the number of infiltrating inflammatory cells, and the extension of collagen deposition correlated with alveolar space size. We conclude that in the guinea pig, 6 months of CS exposure induces inflammatory cell infiltrate in lung structures, at an intensity that correlates with airway remodelling. These changes resemble those observed in COPD, thus endorsing the pathogenic role of CS and the usefulness of this animal model for its study.

Increase of Th17 cells in peripheral blood of patients with chronic obstructive pulmonary disease

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is a progressive disorder characterized by an inflammatory response to cigarette smoke. A disorder in immune regulation contributing to the pathogenesis of COPD has been suggested, however, little is known about the involvement of CD4 (+) T cells. To determine the distribution of different CD4(+) T cell subsets in patients with COPD, current smokers without COPD (CS) and healthy subjects (HS), and its correlation with pulmonary function.

METHODS

Th1, Th2, Th17 and Treg, subsets, were quantified by flow cytometry in peripheral blood (PB) of 39 patients with COPD, 14 CS and 15 HS. Correlations were assessed with Spearman's rank test. The association between Th17 and lung function was evaluated with a multivariate logistic regression analysis.

RESULTS

An increase of Th17 cells (median 9.7% range 0.8-22.5%) was observed in patients with COPD compared with CS (median 2.8% range 0.8-10.6) and HS (median 0.6% range 0.4-1%, p < 0.0001). Th1 and Tregs subsets were also increased in COPD and CS compared to HS. Inverse correlations were found between Th17 with FEV(1)%p r = -0.57 and with FEV(1)/FVC r = -0.60, (p < 0.0001 for both comparison). In addition, increase of Th17 predicted the presence [OR 1.76 (CI 95% 1.25-2.49, p = 0.001)] and severity of airflow limitation [OR 1.13 (CI95% 1.02-1.25, p = 0.02)].

CONCLUSIONS

The increase of Th17 response and the lost of balance between CD4(+) T cell subsets, suggest a lack of regulation of the systemic inflammatory response that may contribute to pathogenesis in COPD patients.

Altered immune phenotype in peripheral blood cells of patients with scleroderma-associated pulmonary hypertension

Pulmonary arterial hypertension is a common and fatal complication of scleroderma that may involve inflammatory and autoimmune mechanisms. Alterations in the gene expression of peripheral blood mononuclear cells have been previously described in patients with pulmonary arterial hypertension. Our goal is to identify differentially expressed genes in peripheral blood mononuclear cells in scleroderma patients with and without pulmonary hypertension as biomarkers of disease. Gene expression analysis was performed on a Microarray Cohort of scleroderma patients with (n = 10) and without (n = 10) pulmonary hypertension. Differentially expressed genes were confirmed in the Microarray Cohort and validated in a Validation Cohort of scleroderma patients with (n = 15) and without (n = 19) pulmonary hypertension by RT-qPCR. We identified inflammatory and immune-related genes including interleukin-7 receptor (IL-7R) and chemokine receptor 7 as differentially expressed in patients with scleroderma-associated pulmonary hypertension. Flow cytometry confirmed decreased expression of IL-7R on circulating CD4+ T-cells from scleroderma patients with pulmonary hypertension. Differences exist in the expression of inflammatory and immune-related genes in peripheral blood cells from patients with scleroderma-related pulmonary hypertension compared to those with normal pulmonary artery pressures. These findings may have implications as biomarkers to screen at-risk populations for early diagnosis and provide insight into mechanisms of scleroderma-related pulmonary hypertension.

[Role of inflammation in the etiopathogenesis of COPD]

Inflammation is one of the first immune system responses to any type of aggression. As with any type of aggression, the lesion produced by inhalation of tobacco smoke prompts an innate inflammatory response. Subsequently, this lesion is stimulated by the release of various chemical factors that enhance the inflammatory response and, finally--depending on the type of aggression--acquired immunity is activated, which, mediated by lymphocyte participation, serves to establish a physical barrier against the propagation of the lesion and to aid repair of the damaged pulmonary tissue. However, the balance between inflammation and repair is not always maintained, as is the case in chronic obstructive pulmonary disease (COPD), in which marked changes appear in the architecture of the airways, alveolar spaces and pulmonary arteries, forming the structural background of the functional changes characteristic of this disease. COPD is basically a pulmonary disease but data are available on the existence of associated systemic inflammation. The origins of this systemic inflammation are unclear: some information indicates that tobacco smoke is a direct origin common to local and systemic inflammation, while other data point to primary pulmonary inflammation that secondarily produces systemic involvement. The present review describes the main mechanisms involved in both pulmonary and systemic inflammation in COPD.

Inflammatory changes in the airways of mice caused by cigarette smoke exposure are only partially reversed after smoking cessation

BACKGROUND

Tobacco smoking irritates and damages the respiratory tract and contributes to a higher risk of developing lung emphysema. At present, smoking cessation is the only effective treatment for reducing the progression of lung emphysema, however, there is hardly anything known about the effects of smoking cessation on cytokine and chemokine levels in the airways. To the best of our knowledge, this is the first reported in vivo study in which cytokine profiles were determined after cessation of cigarette smoke exposure.

METHODS

The severity of airway remodeling and inflammation was studied by analyzing alveolar enlargement, heart hypertrophy, inflammatory cells in the bronchoalveolar lavage fluid (BALF) and lung tissue and by determining the cytokine and chemokine profiles in the BALF of A/J mice exposed to cigarette smoke for 20 weeks and 8 weeks after smoking cessation.

RESULTS

The alveolar enlargement and right ventricle heart hypertrophy found in smoke-exposed mice remained unchanged after smoking cessation. Although the neutrophilic inflammation in the BALF of cigarette smoke-exposed animals was reduced after smoking cessation, a sustained inflammation in the lung tissue was observed. The elevated cytokine (IL-1 alpha and TNF-alpha) and chemokine (CCL2 and CCL3) levels in the BALF of smoke-exposed mice returned to basal levels after smoking cessation, while the increased IL-12 levels did not return to its basal level. The cigarette smoke-enhanced VEGF levels did not significantly change after smoking cessation. Moreover, IL-10 levels were reduced in the BALF of smoke-exposed mice and these levels were still significantly decreased after smoking cessation compared to the control animals.

CONCLUSION

The inflammatory changes in the airways caused by cigarette smoke exposure were only partially reversed after smoking cessation. Although smoking cessation should be the first step in reducing the progression of lung emphysema, additional medication could be provided to tackle the sustained airway inflammation.

Chronic cigarette smoke exposure primes NK cell activation in a mouse model of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a debilitating, progressive lung disease punctuated by exacerbations of symptoms. COPD exacerbations are most often associated with viral infections, and exposure to cigarette smoke (CS) followed by viral infection has been shown experimentally to enhance lung inflammation, tissue destruction, and airway fibrosis. Despite this, however, the cellular mechanisms responsible for this effect are unknown. In this study, we examined NK cell function in a mouse model of COPD given the vital role of NK cells following viral infection. Ex vivo stimulation of lung leukocytes with poly(I:C), ssRNA40, or ODN1826 enhanced production of NK cell-derived IFN-gamma in CS-exposed mice. NK cells from CS-exposed mice exhibited a novel form of priming; highly purified NK cells from CS-exposed mice, relative to NK cells from filtered air-exposed mice, produced more IFN-gamma following stimulation with IL-12, IL-18, or both. Further, NK cell priming was lost following smoking cessation. NKG2D stimulation through overexpression of Raet1 on the lung epithelium primed NK cell responsiveness to poly(I:C), ssRNA40, or ODN1826 stimulation, but not cytokine stimulation. In addition, NK cells from CS-exposed mice expressed more cell surface CD107a upon stimulation, demonstrating that the NK cell degranulation response was also primed. Together, these results reveal a novel mechanism of activation of the innate immune system and highlight NK cells as important cellular targets in controlling COPD exacerbations.

Cigarette smoke impairs clearance of apoptotic cells through oxidant-dependent activation of RhoA

RATIONALE

Cigarette smoke (CS) is the primary cause of chronic obstructive pulmonary disease (COPD), an effect that is, in part, due to intense oxidant stress. Clearance of apoptotic cells (efferocytosis) is a critical regulator of lung homeostasis, which is defective in smokers and in patients with COPD, suggesting a role in disease pathogenesis.

OBJECTIVES

We hypothesized that CS would impair efferocytosis through oxidant-dependent activation of RhoA, a known inhibitor of this process.

METHODS

We investigated the effect of CS on efferocytosis in vivo and ex vivo, using acute, subacute, and long-term mouse exposure models.

MEASUREMENTS AND MAIN RESULTS

Acute and subacute CS exposure suppressed efferocytosis by alveolar macrophages in a dose-dependent, reversible, and cell type-independent manner, whereas more intense CS exposure had an irreversible effect. In contrast, CS did not alter ingestion through the Fc gamma receptor. The inhibitory effect of CS on apoptotic cell clearance depended on oxidants, because the effect was blunted in oxidant-resistant ICR mice, and was prevented by either genetic or pharmacologic antioxidant strategies in vivo and ex vivo. CS inhibited efferocytosis through oxidant-dependent activation of the RhoA-Rho kinase pathway because (1) CS activated RhoA, (2) antioxidants prevented RhoA activation by CS, and (3) inhibitors of the RhoA-Rho kinase pathway reversed the suppressive effect of CS on apoptotic cell clearance in vivo and ex vivo.

CONCLUSIONS

These findings advance the hypothesis that impaired efferocytosis may contribute to the pathogenesis of COPD and suggest the therapeutic potential of drugs targeting the RhoA-Rho kinase pathway.

Sustained CTL activation by murine pulmonary epithelial cells promotes the development of COPD-like disease

Chronic obstructive pulmonary disease (COPD) is a lethal progressive lung disease culminating in permanent airway obstruction and alveolar enlargement. Previous studies suggest CTL involvement in COPD progression; however, their precise role remains unknown. Here, we investigated whether the CTL activation receptor NK cell group 2D (NKG2D) contributes to the development of COPD. Using primary murine lung epithelium isolated from mice chronically exposed to cigarette smoke and cultured epithelial cells exposed to cigarette smoke extract in vitro, we demonstrated induced expression of the NKG2D ligand retinoic acid early transcript 1 (RAET1) as well as NKG2D-mediated cytotoxicity. Furthermore, a genetic model of inducible RAET1 expression on mouse pulmonary epithelial cells yielded a severe emphysematous phenotype characterized by epithelial apoptosis and increased CTL activation, which was reversed by blocking NKG2D activation. We also assessed whether NKG2D ligand expression corresponded with pulmonary disease in human patients by staining airway and peripheral lung tissues from never smokers, smokers with normal lung function, and current and former smokers with COPD. NKG2D ligand expression was independent of NKG2D receptor expression in COPD patients, demonstrating that ligand expression is the limiting factor in CTL activation. These results demonstrate that aberrant, persistent NKG2D ligand expression in the pulmonary epithelium contributes to the development of COPD pathologies.

Smoking and chronic obstructive pulmonary disease (COPD). Parallel epidemics of the 21 century

One hundred million deaths were caused by tobacco in the 20(th) century, and it is estimated that there will be up to one billion deaths attributed to tobacco use in the 21(st) century. Chronic obstructive pulmonary disease (COPD) is rapidly becoming a global public health crisis with smoking being recognized as its most important causative factor. The most effective available treatment for COPD is smoking cessation. There is mounting evidence that the rate of progression of COPD can be reduced when patients at risk of developing the disease stop smoking, while lifelong smokers have a 50% probability of developing COPD during their lifetime. More significantly, there is also evidence that the risk of developing COPD falls by about half with smoking cessation. Several pharmacological interventions now exist to aid smokers in cessation; these include nicotine replacement therapy, bupropion, and varenicline. All pharmacotherapies for smoking cessation are more efficacious than placebo, with odds ratios of about 2. Pharmacologic therapy should be combined with nonpharmacologic (behavioral) therapy. Unfortunately, despite the documented efficacy of these agents, the absolute number of patients who are abstinent from smoking at 12 months of follow-up is low.

Persistence of lung CD8 T cell oligoclonal expansions upon smoking cessation in a mouse model of cigarette smoke-induced emphysema

The role of adaptive immunity in the development or progression of chronic obstructive pulmonary disease (COPD) remains undefined. Recently, the presence of autoantibodies and autoreactive T cells has been demonstrated in COPD patients. In addition, oligoclonal expansions of lung T cells have been observed in COPD patients, but the overlapping incidence of infections, tumors, and cigarette smoke exposure obscures the antigenic stimulus. We analyzed the TCR Vbeta repertoire of CD4 and CD8 T cells purified from the lungs and spleens of mice chronically exposed to cigarette smoke. In a mouse model of COPD, we demonstrate that chronic cigarette smoke exposure causes oligoclonal expansions of T cells isolated from the lungs, but not spleens. TCR Vbeta repertoire analyses revealed oligoclonal expansions predominantly occurred in lung CD8 T cells, with preferential usage of Vbeta7, Vbeta9, Vbeta13, and Vbeta14. Using nucleotide sequence analysis based on Jbeta analyses, we demonstrate selection of CDR3 amino acid motifs, which strongly suggests Ag-driven oligoclonal T cell expansion. Analysis of the lung TCR Vbeta repertoire of mice with cigarette smoke-induced emphysema, which had undergone smoking cessation for 6 mo, revealed that oligoclonal expansions persisted. This study formally demonstrates that chronic cigarette smoke exposure, alone, causes a persistent adaptive T cell immune response. These findings have important implications for therapeutic approaches in the treatment of COPD, and provide insight into potential mechanisms involved in disease pathogenesis.

Mechanisms of cigarette smoke-induced COPD: insights from animal models

Cigarette smoke-induced animal models of chronic obstructive pulmonary disease support the protease-antiprotease hypothesis of emphysema, although which cells and proteases are the crucial actors remains controversial. Inhibition of either serine or metalloproteases produces significant protection against emphysema, but inhibition is invariably accompanied by decreases in the inflammatory response to cigarette smoke, suggesting that these inhibitors do more than just prevent matrix degradation. Direct anti-inflammatory interventions are also effective against the development of emphysema, as are antioxidant strategies; the latter again decrease smoke-induced inflammation. There is increasing evidence for autoimmunity, perhaps directed against matrix components, as a driving force in emphysema. There is intriguing but controversial animal model evidence that failure to repair/failure of lung maintenance also plays a role in the pathogenesis of emphysema. Cigarette smoke produces small airway remodeling in laboratory animals, possibly by direct induction of fibrogenic growth factors in the airway wall, and also produces pulmonary hypertension, at least in part through direct upregulation of vasoactive mediators in the intrapulmonary arteries. Smoke exposure causes goblet cell metaplasia and excess mucus production in the small airways and proximal trachea, but these changes are not good models of either chronic bronchitis or acute exacerbations. Emphysema, small airway remodeling, pulmonary hypertension, and mucus production appear to be at least partially independent processes that may require different therapeutic approaches.

Current concepts in mechanisms of emphysema

Over the last 10 years, there has been a remarkable degree of progress in our understanding of the pathophysiological mechanisms involved in the genesis of emphysema. This review attempts to summarize these data.

Lung inflammation in rats following subchronic exposure to cigarette mainstream smoke

Female Sprague-Dawley rats were exposed to mainstream smoke from standard reference cigarettes and a nontobacco cellulose cigarette for 35 days. Whole smoke and smoke fractions were investigated. Lung inflammation was evaluated by differentiation of bronchoalveolar lavage cells and lymphocytes in thoracic lymph nodes. Histopathological changes in the nose and larynx were assessed. Results showed that the particulate phase of cigarette mainstream smoke is mostly responsible for inflammation in the lung (neutrophil increase up to 240-fold) and hyperplastic and metaplastic epithelial changes in the larynx, whereas irritative volatile constituents in the gas phase are mostly responsible for changes in the nose.

Relation between duration of smoking cessation and bronchial inflammation in COPD

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is associated with airway inflammation. Although smoking cessation improves symptoms and the decline in lung function in COPD, it is unknown whether bronchial inflammation in patients with established COPD varies with the duration of smoking cessation.

METHODS

114 patients (99 men) with COPD of mean (SD) age 62 (8) years, a median (IQR) smoking history of 42 (31-55) pack years, no inhaled or oral corticosteroids, all current or ex-smokers (n = 42, quit >1 month, median cessation duration 3.5 years), post-bronchodilator FEV(1) 63 (9)% predicted, and FEV(1)/IVC 48 (9)% were studied cross sectionally. The numbers of subepithelial T lymphocytes (CD3, CD4, CD8), neutrophils, macrophages, eosinophils, mast cells, and plasma cells were measured in bronchial biopsy specimens (median (IQR)/0.1 mm(2)) using fully automated image analysis.

RESULTS

Ex-smokers with COPD had higher CD3+, CD4+, and plasma cell numbers than current smokers with COPD (149 (88-225) v 108 (61-164), p = 0.036; 58 (32-90) v 40 (25-66), p = 0.023; and 9.0 (5.5-20) v 7.5 (3.1-14), p = 0.044, respectively), but no difference in other inflammatory cells. Short term ex-smokers (<3.5 years) had higher CD4+ and CD8+ cell numbers than current smokers (p = 0.017, p = 0.023; respectively). Conversely, long term ex-smokers (quit > or =3.5 years) had lower CD8+ cell numbers than short term ex-smokers (p = 0.009), lower CD8/CD3 ratios than both current smokers and short-term ex-smokers (p = 0.012, p = 0.003; respectively), and higher plasma cell numbers than current smokers (p = 0.003).

CONCLUSIONS

With longer duration of smoking cessation, CD8 cell numbers decrease and plasma cell numbers increase. This indicates that bronchial T lymphocyte and plasma cell counts, but not other inflammatory cells, are related to duration of smoking cessation in patients with COPD.

Oligoclonal CD4+ T cells in the lungs of patients with severe emphysema

RATIONALE

Within the lungs of patients with severe emphysema, inflammation continues despite smoking cessation. Foci of T lymphocytes in the small airways of patients with emphysema have been associated with disease severity. Whether these T cells play an important role in this continued inflammatory response is unknown.

OBJECTIVE

The aim of this study was to determine if T cells recruited to the lungs of subjects with severe emphysema contain oligoclonal T-cell populations, suggesting their accumulation in response to antigenic stimuli.

METHODS

Lung T-cell receptor (TCR) Vbeta repertoire from eight patients with severe emphysema and six control subjects was evaluated at the time of tissue procurement (ex vivo) and after 2 weeks of culture with interleukin 2 (in vitro). Junctional region nucleotide sequencing of expanded TCR-Vbeta subsets was performed.

RESULTS

No significantly expanded TCR-Vbeta subsets were identified in ex vivo samples. However, T cells grew from all emphysema (n = 8) but from only one of the control lung samples (n = 6) when exposed to interleukin 2 (p = 0.0013). Within the cultured cells, seven major CD4-expressing TCR-Vbeta subset expansions were identified from five of the patients with emphysema. These expansions were composed of oligoclonal populations of T cells that had already been expanded in vivo.

CONCLUSION

Severe emphysema is associated with inflammation involving T lymphocytes that are composed of oligoclonal CD4+ T cells. These T cells are accumulating in the lung secondary to conventional antigenic stimulation and are likely involved in the persistent pulmonary inflammation characteristic of severe emphysema.

The development of emphysema in cigarette smoke-exposed mice is strain dependent

Only 20% of smokers develop chronic obstructive pulmonary disease. An important determinant of susceptibility is genomic variation. We undertook this study to define strains of mice with different susceptibilities for the development of smoking-induced emphysema because they could help identify genetic factors of susceptibility. NZWLac/J, C57BL6/J, A/J, SJ/L, and AKR/J strains were exposed to cigarette smoke for 6 months. Elastance (Htis), the extent of emphysema (mean linear intercept [Lm]), and the inflammatory cell and cytokine response were measured. NZWLac/J had no change in Lm or Htis (resistant). C57BL6/J, A/J, and SJ/L increased Lm, but not Htis (mildly susceptible). AKR/J increased Lm and Htis (super-susceptible). Only AKR/J had significant inflammation comprising macrophages, neutrophils, and T cells. The AKR/J showed an upregulation of Th1 cytokines whereas in the C57BL/6/J and NZWlac/J, cytokines did not change or were downregulated. We conclude that Lm, elastance, and inflammation are features that are needed to phenotype emphysema in mice. The inflammatory cell and cytokine profile may be an important determinant of the phenotype in response to cigarette smoke exposure. The identification of resistant and susceptible strains for the development of emphysema could be useful for genomic studies of emphysema susceptibility in mice and eventually in humans.