Oral N-acetylcysteine attenuates elastase-induced pulmonary emphysema in rats

The Role of Oxidative Stress and Antioxidants in Cardiovascular Comorbidities in COPD

Oxidative stress driven by several environmental and local airway factors associated with chronic obstructive bronchiolitis, a hallmark feature of COPD, plays a crucial role in disease pathomechanisms. Unbalance between oxidants and antioxidant defense mechanisms amplifies the local inflammatory processes, worsens cardiovascular health, and contributes to COPD-related cardiovascular dysfunctions and mortality. The current review summarizes recent developments in our understanding of different mechanisms contributing to oxidative stress and its countermeasures, with special attention to those that link local and systemic processes. Major regulatory mechanisms orchestrating these pathways are also introduced, with some suggestions for further research in the field.

Response to Intravenous N-Acetylcysteine Supplementation in Critically Ill Patients with COVID-19

Administering N-acetylcysteine (NAC) could counteract the effect of free radicals, improving the clinical evolution of patients admitted to the Intensive Care Unit (ICU). This study aimed to investigate the clinical and biochemical effects of administering NAC to critically ill patients with COVID-19. A randomized controlled clinical trial was conducted on ICU patients (n = 140) with COVID-19 and divided into two groups: patients treated with NAC (NAC-treated group) and patients without NAC treatment (control group). NAC was administered as a continuous infusion with a loading dose and a maintenance dose during the study period (from admission until the third day of ICU stay). NAC-treated patients showed higher PaO₂/FiO₂ (p ≤ 0.014) after 3 days in ICU than their control group counterparts. Moreover, C-reactive protein (p ≤ 0.001), D-dimer (p ≤ 0.042), and lactate dehydrogenase (p ≤ 0.001) levels decreased on the third day in NAC-treated patients. Glutathione concentrations decreased in both NAC-treated (p ≤ 0.004) and control (p ≤ 0.047) groups after 3 days in ICU; whereas glutathione peroxidase did not change during the ICU stay. The administration of NAC manages to improve the clinical and analytical response of seriously ill patients with COVID-19 compared to the control group. NAC is able to stop the decrease in glutathione concentrations.

Therapeutic Potential of Small Molecules Targeting Oxidative Stress in the Treatment of Chronic Obstructive Pulmonary Disease (COPD): A Comprehensive Review

Chronic obstructive pulmonary disease (COPD) is an increasing and major global health problem. COPD is also the third leading cause of death worldwide. Oxidative stress (OS) takes place when various reactive species and free radicals swamp the availability of antioxidants. Reactive nitrogen species, reactive oxygen species (ROS), and their counterpart antioxidants are important for host defense and physiological signaling pathways, and the development and progression of inflammation. During the disturbance of their normal steady states, imbalances between antioxidants and oxidants might induce pathological mechanisms that can further result in many non-respiratory and respiratory diseases including COPD. ROS might be either endogenously produced in response to various infectious pathogens including fungi, viruses, or bacteria, or exogenously generated from several inhaled particulate or gaseous agents including some occupational dust, cigarette smoke (CS), and air pollutants. Therefore, targeting systemic and local OS with therapeutic agents such as small molecules that can increase endogenous antioxidants or regulate the redox/antioxidants system can be an effective approach in treating COPD. Various thiol-based antioxidants including fudosteine, erdosteine, carbocysteine, and N-acetyl-L-cysteine have the capacity to increase thiol content in the lungs. Many synthetic molecules including inhibitors/blockers of protein carbonylation and lipid peroxidation, catalytic antioxidants including superoxide dismutase mimetics, and spin trapping agents can effectively modulate CS-induced OS and its resulting cellular alterations. Several clinical and pre-clinical studies have demonstrated that these antioxidants have the capacity to decrease OS and affect the expressions of several pro-inflammatory genes and genes that are involved with redox and glutathione biosynthesis. In this article, we have summarized the role of OS in COPD pathogenesis. Furthermore, we have particularly focused on the therapeutic potential of numerous chemicals, particularly antioxidants in the treatment of COPD.

The antioxidant N-acetylcysteine promotes immune response and inhibits epithelial-mesenchymal transition to alleviate pulmonary fibrosis in chronic obstructive pulmonary disease by suppressing the VWF/p38 MAPK axis

Background/aim

N-Acetylcysteine (NAC) demonstrates applications in the prevention of exacerbation of chronic obstructive pulmonary disease (COPD). COPD is often characterized by fibrosis of the small airways. This study aims at investigating the physiological mechanisms by which NAC might mediate the pulmonary fibrosis in COPD.

Methods

A total of 10 non-smokers without COPD and 10 smokers with COPD were recruited in this study, and COPD rat models were established. Cigarette smoke extract (CSE) cell models were constructed. The gain- or loss-of-function experiments were adopted to determine the expression of VWF and the extent of p38 MAPK phosphorylation, levels of interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and immunoglobulins (IgG, IgM and IgA) in the serum of COPD rats and supernatant of alveolar epithelial cells and to detect cell invasion and migration and the ratio of CD3⁺, CD4⁺, CD8⁺ and CD4⁺/CD8⁺T lymphocytes.

Results

Expression of VWF and the extent of p38 MAPK phosphorylation were increased in COPD. NAC inhibited p38 MAPK phosphorylation by reducing the VWF expression. NAC could inhibit cell migration and invasion, elevate E-cadherin expression, the ratio of CD3⁺, CD4⁺, CD8⁺ and CD4⁺/CD8⁺T lymphocytes, and levels of IgG, IgA, and IgM, and reduce N-cadherin expression and levels of IL-6 and TNF-α in CSE cells and serum of COPD rats. NAC promoted immune response and suppressed epithelial-mesenchymal transformation (EMT) to relieve COPD-induced pulmonary fibrosis in vitro and in vivo by inhibiting the VWF/p38 MAPK axis.

Conclusions

Collectively, NAC could ameliorate COPD-induced pulmonary fibrosis by promoting immune response and inhibiting EMT process via the VWF/p38 MAPK axis, therefore providing us with a potential therapeutic target for treating COPD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10020-021-00342-y.

N-Acetylcysteine as Adjuvant Therapy for COVID-19 - A Perspective on the Current State of the Evidence

The looming severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused a long-lasting pandemic of coronavirus disease 2019 (COVID-19) around the globe with substantial morbidity and mortality. N-acetylcysteine, being a nutraceutical precursor of an important antioxidant glutathione, can perform several biological functions in mammals and microbes. It has consequently garnered a growing interest as a potential adjunctive therapy for coronavirus disease. Here, we review evidence concerning the effects of N-acetylcysteine in respiratory viral infections based on currently available in vitro, in vivo, and human clinical investigations. The repurposing of a known drug such as N-acetylcysteine may significantly hasten the deployment of a novel approach for COVID-19. Since the drug candidate has already been translated into the clinic for several decades, its established pharmacological properties and safety and side-effect profiles expedite preclinical and clinical assessment for the treatment of COVID-19. In vitro data have depicted that N-acetylcysteine increases antioxidant capacity, interferes with virus replication, and suppresses expression of pro-inflammatory cytokines in cells infected with influenza viruses or respiratory syncytial virus. Furthermore, findings from in vivo studies have displayed that, by virtue of immune modulation and anti-inflammatory mechanism, N-acetylcysteine reduces the mortality rate in influenza-infected mice animal models. The promising in vitro and in vivo results have prompted the initiation of human subject research for the treatment of COVID-19, including severe pneumonia and acute respiratory distress syndrome. Albeit some evidence of benefits has been observed in clinical outcomes of patients, precision nanoparticle design of N-acetylcysteine may allow for greater therapeutic efficacy.

Alpha-1 antitrypsin deficiency and recombinant protein sources with focus on plant sources: Updates, challenges and perspectives

Alpha-1 antitrypsin deficiency (A1ATD) is an autosomal recessive disease characterized by low plasma levels of A1AT, a serine protease inhibitor representing the most abundant circulating antiprotease normally present at plasma levels of 1-2 g/L. The dominant clinical manifestations include predispositions to early onset emphysema due to protease/antiprotease imbalance in distal lung parenchyma and liver disease largely due to unsecreted polymerized accumulations of misfolded mutant A1AT within the endoplasmic reticulum of hepatocytes. Since 1987, the only FDA licensed specific therapy for the emphysema component has been infusions of A1AT purified from pooled human plasma at the 2020 cost of up to US $200,000/year with the risk of intermittent shortages. In the past three decades various, potentially less expensive, recombinant forms of human A1AT have reached early stages of development, one of which is just reaching the stage of human clinical trials. The focus of this review is to update strategies for the treatment of the pulmonary component of A1ATD with some focus on perspectives for therapeutic production and regulatory approval of a recombinant product from plants. We review other competitive technologies for treating the lung disease manifestations of A1ATD, highlight strategies for the generation of data potentially helpful for securing FDA Investigational New Drug (IND) approval and present challenges in the selection of clinical trial strategies required for FDA licensing of a New Drug Approval (NDA) for this disease.

An antioxidant suppressed lung cellular senescence and enhanced pulmonary function in aged mice

Oxidative stress is one of the major causes of cellular senescence in mammalian cells. The excess amount of reactive oxygen species generated by oxygen metabolism is pathogenic and facilitates tissue aging. Lung tissue is more susceptible to oxidative stress than other organs because it is directly exposed to environmental stresses. The aging of lung tissues increases the risk of chronic diseases. Senescent cells accumulate in tissues during aging and contribute to aging-associated morbidity; however, the roles of cellular senescence in lung aging and diseases have not yet been elucidated in detail. To clarify the physiological role of oxidative stress-induced cellular senescence in aging-associated declines in pulmonary function, we herein investigated the effects of the antioxidant N-acetyl-L-cysteine (NAC) on lung cellular senescence and aging in mice. The administration of NAC to 1-year-old mice reduced the expression of senescence-associated genes in lung tissue. Pulmonary function and lung morphology were partly restored in mice administered NAC. Collectively, these results suggest that oxidative stress is a major inducer of cellular senescence in vivo and that the control of oxidative stress may prevent lung aging and diseases.

Conventional and Nanotechnology Based Approaches to Combat Chronic Obstructive Pulmonary Disease: Implications for Chronic Airway Diseases

Chronic obstructive pulmonary disease (COPD) is the most prevalent obstructive lung disease worldwide characterized by decline in lung function. It is associated with airway obstruction, oxidative stress, chronic inflammation, mucus hypersecretion, and enhanced autophagy and cellular senescence. Cigarette smoke being the major risk factor, other secondary risk factors such as the exposure to air pollutants, occupational exposure to gases and fumes in developing countries, also contribute to the pathogenesis of COPD. Conventional therapeutic strategies of COPD are based on anti-oxidant and anti-inflammatory drugs. However, traditional anti-oxidant pharmacological therapies are commonly used to alleviate the impact of COPD as they have many associated repercussions such as low diffusion rate and inappropriate drug pharmacokinetics. Recent advances in nanotechnology and stem cell research have shed new light on the current treatment of chronic airway disease. This review is focused on some of the anti-oxidant therapies currently used in the treatment and management of COPD with more emphasis on the recent advances in nanotechnology-based therapeutics including stem cell and gene therapy approaches for the treatment of chronic airway disease such as COPD and asthma.

Extracellular Matrix Component Remodeling in Respiratory Diseases: What Has Been Found in Clinical and Experimental Studies?

Changes in extracellular matrix (ECM) components in the lungs are associated with the progression of respiratory diseases, such as asthma, chronic obstructive pulmonary disease (COPD), and acute respiratory distress syndrome (ARDS). Experimental and clinical studies have revealed that structural changes in ECM components occur under chronic inflammatory conditions, and these changes are associated with impaired lung function. In bronchial asthma, elastic and collagen fiber remodeling, mostly in the airway walls, is associated with an increase in mucus secretion, leading to airway hyperreactivity. In COPD, changes in collagen subtypes I and III and elastin, interfere with the mechanical properties of the lungs, and are believed to play a pivotal role in decreased lung elasticity, during emphysema progression. In ARDS, interstitial edema is often accompanied by excessive deposition of fibronectin and collagen subtypes I and III, which can lead to respiratory failure in the intensive care unit. This review uses experimental models and human studies to describe how inflammatory conditions and ECM remodeling contribute to the loss of lung function in these respiratory diseases.

Exercise-Induced Bronchoconstriction and the Air We Breathe

An association between airway dysfunction and airborne pollutant inhalation exists. Volatilized airborne fluorocarbons in ski wax rooms, particulate matter, and trichloromines in indoor environments are suspect to high prevalence of exercise-induced bronchoconstriction and new-onset asthma in athletes competing in cross-country skiing, ice rink sports, and swimming. Ozone is implicated in acute decreases in lung function and the development of new-onset asthma from exposure during exercise. Mechanisms and genetic links are proposed for pollution-related new-onset asthma. Oxidative stress from airborne pollutant inhalation is a common thread to progression of airway damage. Key pollutants and mechanisms for each are discussed.

Immune-mediated inflammation in the pathogenesis of emphysema: insights from mouse models

The cellular mechanisms that result in the initiation and progression of emphysema are clearly complex. A growing body of human data combined with discoveries from mouse models utilizing cigarette smoke exposure or protease administration have improved our understanding of emphysema development by implicating specific cell types that may be important for the pathophysiology of chronic obstructive pulmonary disease. The most important aspects of emphysematous damage appear to be oxidative or protease stress and sustained macrophage activation and infiltration of other immune cells leading to epithelial damage and cell death. Despite the identification of these associated processes and cell types in many experimental studies, the reasons why cigarette smoke and other pollutants result in unremitting damage instead of injury resolution are still uncertain. We propose an important role for macrophages in the sequence of events that lead and maintain this chronic tissue pathologic process in emphysema. This model involves chronic activation of macrophage subtypes that precludes proper healing of the lung. Further elucidation of the cross-talk between epithelial cells that release damage-associated signals and the cellular immune effectors that respond to these cues is a critical step in the development of novel therapeutics that can restore proper lung structure and function to those afflicted with emphysema.

Protective effects of N-acetylcysteine on peroxidative changes of the fetal rat lungs whose mothers were exposed to cigarette smoke

Background: This experimental study investigated the protective effects of N-acetylcysteine (NAC) on peroxidative changes in fetal lungs in the offspring of rats exposed to cigarette smoke. Methods: Thirty fetal rats used for analysis, were divided into three groups as follows: control group (n = 10), whose mothers were exposed to fresh air; group I (n=10), whose mothers were exposed to cigarette smoke; and group II (n=10), whose mothers were exposed to cigarette smoke and given 10 mg/kg per day NAC. In groups I and II, smoke exposure was started 4 weeks before the pregnancy, and continued to the 14th day of pregnancy, and in Group II, NAC was administered intraperitoneally for 14 days. The mothers and their fetuses were decapitated on the 14th day of pregnancy. Malondialdehyde (MDA) and glutathione (GSH) levels were determined in the lung tissues of fetuses to determine the oxidant-antioxidant balance. Results: While tissue MDA levels in Group I were found significantly higher than the control group (129.7±65.4 versus 63.4±15.4 nmol/100 mg protein, P <0.05), GSH levels were significantly lower (17.1±7.3 versus 45.4±8.1 nmol/mg protein, P <0.01). Furthermore, in Group II, MDA levels were significantly lower (56.9± 20.6 versus 129.7±65.4 nmol/100 mg protein, P <0.05), and GSH levels were significantly higher (34.57±10.7 versus 17.1±7.3 nmol/mg protein, P <0.0001) when compared with Group I. No statistically significant difference was found in tissue MDA and GSH levels between Group II and the control group (P >0.05). Conclusions: These results suggest that smoke exposure during pregnancy causes oxidative damage in fetal lungs. This smoke-induced damage might be prevented by NAC. Human & Experimental Toxicology (2007) 26, 99-103

Collagenase mRNA Overexpression and Decreased Extracellular Matrix Components Are Early Events in the Pathogenesis of Emphysema

To describe the progression of parenchymal remodeling and metalloproteinases gene expression in earlier stages of emphysema, mice received porcine pancreatic elastase (PPE) instillation and Control groups received saline solution. After PPE instillation (1, 3, 6 hours, 3 and 21 days) we measured the mean linear intercept, the volume proportion of types I and III collagen, elastin, fibrillin and the MMP-1, -8, -12 and -13 gene expression. We observed an initial decrease in type I (at the 3rd day) and type III collagen (from the 6th hour until the 3rd day), in posterior time points in which we detected increased gene expression for MMP-8 and -13 in PPE groups. After 21 days, the type III collagen fibers increased and the type I collagen values returned to similar values compared to control groups. The MMP-12 gene expression was increased in earlier times (3 and 6 hours) to which we detected a reduced proportion of elastin (3 days) in PPE groups, reinforcing the already established importance of MMP-12 in the breakdown of ECM. Such findings will be useful to better elucidate the alterations in ECM components and the importance of not only metalloelastase but also collagenases in earlier emphysema stages, providing new clues to novel therapeutic targets.

Oxidative stress and free radicals in COPD--implications and relevance for treatment

Oxidative stress occurs when free radicals and other reactive species overwhelm the availability of antioxidants. Reactive oxygen species (ROS), reactive nitrogen species, and their counterpart antioxidant agents are essential for physiological signaling and host defense, as well as for the evolution and persistence of inflammation. When their normal steady state is disturbed, imbalances between oxidants and antioxidants may provoke pathological reactions causing a range of nonrespiratory and respiratory diseases, particularly chronic obstructive pulmonary disease (COPD). In the respiratory system, ROS may be either exogenous from more or less inhalative gaseous or particulate agents such as air pollutants, cigarette smoke, ambient high-altitude hypoxia, and some occupational dusts, or endogenously generated in the context of defense mechanisms against such infectious pathogens as bacteria, viruses, or fungi. ROS may also damage body tissues depending on the amount and duration of exposure and may further act as triggers for enzymatically generated ROS released from respiratory, immune, and inflammatory cells. This paper focuses on the general relevance of free radicals for the development and progression of both COPD and pulmonary emphysema as well as novel perspectives on therapeutic options. Unfortunately, current treatment options do not suffice to prevent chronic airway inflammation and are not yet able to substantially alter the course of COPD. Effective therapeutic antioxidant measures are urgently needed to control and mitigate local as well as systemic oxygen bursts in COPD and other respiratory diseases. In addition to current therapeutic prospects and aspects of genomic medicine, trending research topics in COPD are presented.

Update on the pathological processes, molecular biology, and clinical utility of N-acetylcysteine in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a common and morbid disease characterized by high oxidative stress. Its pathogenesis is complex, and involves excessive oxidative stress (redox imbalance), protease/antiprotease imbalance, inflammation, apoptosis, and autoimmunity. Among these, oxidative stress has a pivotal role in the pathogenesis of COPD by initiating and mediating various redox-sensitive signal transduction pathways and gene expression. The protective physiological mechanisms of the redox balance in the human body, their role in the pathogenesis of COPD, and the clinical correlation between oxidative stress and COPD are reviewed in this paper. N-acetylcysteine (NAC) is a mucolytic agent with both antioxidant and anti-inflammatory properties. This paper also reviews the use of NAC in patients with COPD, especially the dose-dependent properties of NAC, eg, its effects on lung function and the exacerbation rate in patients with the disease. Earlier data from BRONCUS (the Bronchitis Randomized on NAC Cost-Utility Study) did not suggest that NAC was beneficial in patients with COPD, only indicating that it reduced exacerbation in an “inhaled steroid-naïve” subgroup. With regard to the dose-dependent properties of NAC, two recent randomized controlled Chinese trials suggested that high-dose NAC (1,200 mg daily) can reduce exacerbations in patients with COPD, especially in those with an earlier (moderately severe) stage of disease, and also in those who are at high risk of exacerbations. However, there was no significant effect on symptoms or quality of life in patients receiving NAC. Further studies are warranted to investigate the effect of NAC at higher doses in non-Chinese patients with COPD.

Interrelated role of cigarette smoking, oxidative stress, and immune response in COPD and corresponding treatments

Cigarette smoking (CS) can impact the immune system and induce pulmonary disorders such as chronic obstructive pulmonary disease (COPD), which is currently the fourth leading cause of chronic morbidity and mortality worldwide. Accordingly, the most significant risk factor associated with COPD is exposure to cigarette smoke. The purpose of the present study is to provide an updated overview of the literature regarding the effect of CS on the immune system and lungs, the mechanism of CS-induced COPD and oxidative stress, as well as the available and potential treatment options for CS-induced COPD. An extensive literature search was conducted on the PubMed/Medline databases to review current COPD treatment research, available in the English language, dating from 1976 to 2014. Studies have investigated the mechanism by which CS elicits detrimental effects on the immune system and pulmonary function through the use of human and animal subjects. A strong relationship among continued tobacco use, oxidative stress, and exacerbation of COPD symptoms is frequently observed in COPD subjects. In addition, therapeutic approaches emphasizing smoking cessation have been developed, incorporating counseling and nicotine replacement therapy. However, the inability to reverse COPD progression establishes the need for improved preventative and therapeutic strategies, such as a combination of intensive smoking cessation treatment and pharmaceutical therapy, focusing on immune homeostasis and redox balance. CS initiates a complex interplay between oxidative stress and the immune response in COPD. Therefore, multiple approaches such as smoking cessation, counseling, and pharmaceutical therapies targeting inflammation and oxidative stress are recommended for COPD treatment.

New drug therapies for COPD

Clinical trials with new drugs for chronic obstructive pulmonary disease (COPD) have been performed. Viruses exacerbate COPD and bacteria may play a part in severe COPD; therefore, antibiotic and antiviral approaches have a sound rationale. Antiinflammatory approaches have been studied. Advances in understanding the molecular basis of other processes have resulted in novel drugs to target reactive oxidant species, mucus, proteases, fibrosis, cachexia, and muscle wasting, and accelerated aging. Studies with monoclonal antibodies have been disappointing, highlighting the tendency for infections and malignancies during treatment. Promising future directions are lung regeneration with retinoids and stem cells.

Effects of N-acetylcysteine in ozone-induced chronic obstructive pulmonary disease model

Introduction

Chronic exposure to high levels of ozone induces emphysema and chronic inflammation in mice. We determined the recovery from ozone-induced injury and whether an antioxidant, N-acetylcysteine (NAC), could prevent or reverse the lung damage.

Methods

Mice were exposed to ozone (2.5 ppm, 3 hours/12 exposures, over 6 weeks) and studied 24 hours (24h) or 6 weeks (6W) later. Nac (100 mg/kg, intraperitoneally) was administered either before each exposure (preventive) or after completion of exposure (therapeutic) for 6 weeks.

Results

After ozone exposure, there was an increase in functional residual capacity, total lung volume, and lung compliance, and a reduction in the ratio of forced expiratory volume at 25 and 50 milliseconds to forced vital capacity (FEV₂₅/FVC, FEV₅₀/FVC). Mean linear intercept (L_m) and airway hyperresponsiveness (AHR) to acetylcholine increased, and remained unchanged at 6W after cessation of exposure. Preventive NAC reduced the number of BAL macrophages and airway smooth muscle (ASM) mass. Therapeutic NAC reversed AHR, and reduced ASM mass and apoptotic cells.

Conclusion

Emphysema and lung function changes were irreversible up to 6W after cessation of ozone exposure, and were not reversed by NAC. The beneficial effects of therapeutic NAC may be restricted to the ASM.

High-dose N-acetylcysteine in stable COPD: the 1-year, double-blind, randomized, placebo-controlled HIACE study

BACKGROUND

The mucolytic and antioxidant effects of N-acetylcysteine (NAC) may have great value in COPD treatment. However, beneficial effects have not been confirmed in clinical studies, possibly due to insufficient NAC doses and/or inadequate outcome parameters used. The objective of this study was to investigate high-dose NAC plus usual therapy in Chinese patients with stable COPD.

METHODS

The 1-year HIACE (The Effect of High Dose N-acetylcysteine on Air Trapping and Airway Resistance of Chronic Obstructive Pulmonary Disease-a Double-blinded, Randomized, Placebo-controlled Trial) double-blind trial conducted in Kwong Wah Hospital, Hong Kong, randomized eligible patients aged 50 to 80 years with stable COPD to NAC 600 mg bid or placebo after 4-week run-in. Lung function parameters, symptoms, modified Medical Research Council (mMRC) dyspnea and St. George's Respiratory Questionnaire (SGRQ) scores, 6-min walking distance (6MWD), and exacerbation and admission rates were measured at baseline and every 16 weeks for 1 year.

RESULTS

Of 133 patients screened, 120 were eligible (93.2% men; mean age, 70.8±0.74 years; %FEV1 53.9±2.0%). Baseline characteristics were similar in the two groups. At 1 year, there was a significant improvement in forced expiratory flow 25% to 75% (P=.037) and forced oscillation technique, a significant reduction in exacerbation frequency (0.96 times/y vs 1.71 times/y, P=.019), and a tendency toward reduction in admission rate (0.5 times/y vs 0.8 times/y, P=.196) with NAC vs placebo. There were no significant between-group differences in mMRC dypsnea score, SGRQ score, and 6MWD. No major adverse effects were reported.

CONCLUSION

In this study, 1-year treatment with high-dose NAC resulted in significantly improved small airways function and decreased exacerbation frequency in patients with stable COPD.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT01136239; URL: www.clinicaltrials.gov.

Antioxidant pharmacological therapies for COPD

Increased oxidative stress occurs in the lungs and systemically in COPD, which plays a role in many of the pathogenic mechanisms in COPD. Hence, targeting local lung and systemic oxidative stress with agents that modulate the antioxidants/redox system or boost endogenous antioxidants would be a useful therapeutic approach in COPD. Thiol antioxidants (N-acetyl-l-cysteine [NAC] and N-acystelyn, carbocysteine, erdosteine, and fudosteine) have been used to increase lung thiol content. Modulation of cigarette smoke (CS) induced oxidative stress and its consequent cellular changes have also been reported to be effected by synthetic molecules, such as spin traps (α-phenyl-N-tert-butyl nitrone), catalytic antioxidants (superoxide dismutase [ECSOD] mimetics), porphyrins, and lipid peroxidation and protein carbonylation blockers/inhibitors (edaravone and lazaroids/tirilazad). Preclinical and clinical trials have shown that these antioxidants can reduce oxidative stress, affect redox and glutathione biosynthesis genes, and proinflammatory gene expression. In this review the approaches to enhance lung antioxidants in COPD and the potential beneficial effects of antioxidant therapy on the course of the disease are discussed.

RETRACTED: NAD(P)H:quinone oxidoreductase 1 protects lungs from oxidant-induced emphysema in mice

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). This article has been retracted at the request of the Authors. Since learning of potential discrepancies between the raw data from the animal pulmonary physiology laboratory at Duke that were used to calculate the in vivo pulmonary mechanics and the re-exported machine-generated raw data, some studies published elsewhere have been replicated successfully. However it is not possible to replicate this study as the NQO1-deficient mice on the C57BL/6 background are no longer available from the NCI. The authors recognize that previous work to identify differences in alveolar size can vary dependent on background strain when comparing inbred mouse strains (Soutiere SE et al Resp Physiol Neurobiol 2004;140(3)183–91 doi: 10.1016/j.resp.2004.02.003). Because of the prolonged period of time required to successfully backcross NQO1-deficient animals onto C57BL/6J background and the time required to repeat studies presented in this manuscript the authors think it does not seem feasible to conduct replicate studies in a reasonable timeline. Therefore, the most appropriate course of action is to retract the report as it is the authors' goal to maintain accuracy of the scientific record to the best of their ability. The authors offer sincere apologies to the scientific community.

Neutrophil activation in severe, early-onset COPD patients versus healthy non-smoker subjects in vitro: effects of antioxidant therapy

BACKGROUND

Neutrophils and oxidative stress have been implicated in the pathogenesis of COPD. Severe, early-onset COPD is characterized by a rapid decline in the lung function at an early age; however, nothing is known about neutrophil activation in COPD patients.

OBJECTIVES

The aim of this study was to evaluate peripheral blood neutrophil activation in severe, early-onset COPD patients versus healthy non-smokers and the effect of N-acetyl-L-cysteine (NAC) on neutrophil activation in vitro.

METHODS

Neutrophils were isolated from 15 severe, early-onset COPD patients and 15 age-matched healthy subjects and stimulated with N-formyl-Met-Leu-Phe (fMLP) in the presence or absence of NAC (10 μM to 10 mM). Neutrophil chemotaxis, elastase release, reactive oxygen species (ROS), intracellular thiols and apoptosis were measured by Boyden chamber, spectrofluorometry, CMFDA and H2DCF-DA dyes and by annexin V-FITC, respectively.

RESULTS

Chemotaxis of peripheral blood neutrophils from COPD patients in response to fMLP was 30% more increased than that observed in healthy subjects. Elastase release in response to fMLP was 2-fold higher in neutrophils from COPD patients versus healthy subjects. Intracellular thiol levels were 30% lower in COPD and ROS was approximately 30% higher in COPD versus healthy neutrophils. Spontaneous apoptosis showed no differences in both groups of patients and fMLP-induced apoptosis was higher in COPD. Pre-treatment with the antioxidant NAC effectively attenuated neutrophil chemotaxis, elastase release and ROS as well as effectively increased thiol levels in COPD.

CONCLUSIONS

Neutrophils in severe, early-onset COPD patients are highly activated and this is alleviated by NAC in vitro.

Effects of allogeneic mesenchymal stem cells in experimental treatment of pulmonary emphysema

The aim of the study was to asses morphologic and morphometric lung tissue changes and peritoneal macrophages activity (MA) after allogeneic mesenchymal stem cells (MSCs) systemic transplantation in acute elastase model of pulmonary emphysema(PE) in rats. Methods: Forty Wistar rats, 3-months old, were randomized into 4 groups. Control group (1 group) was injected intratracheally 0,4 ml of normal saline, other animals (2-4 groups) received one intratracheal injection of 20 units (U) porcine pancreatic elastase in 0,4 ml of saline. Next day (3 group) and 7 day (4 group) rats were intravenously injected 2 x 106 autologous MSCs in 0,5 ml of saline. 2 group was used as emphysema control. Before euthanizing at the 21* day rats were undergone peritoneal lavage with analysis of hemi-luminescent macrophages activity in the obtained fluid. Results: the lungs of 2-4 groups had various degrees of PE. The width of alveolar ducts (VAD) in group 2 experimental emphysema increased by 231% versus the control group. The transplantation of MSCs in a day after elastase decreased VAD by an average of 50.3% compared to the control of experimental emphysema. In animals MSCs injected at the 7th day of study, this sizes decreased more greater - by 64,5%, but was higher by 40.7% compared to the first control group. Another quantitative measure of PE - alveolar index - was significantly increased by 149% in group 2 compared to control. The transplantation of MSCs at 1st and 7th day of experiment leaded to alveolar index decreasing, respectively on 163.4 and 237% . The peak Index of hemi-luminescent macrophages activity (Mv/106 cells) was 28,8+1,1 (1 group), 57,3 +1,3 (2 group), 35,8+1,6 (3 group), 31,9+1,9 (4 group). Conclusions: our study confirmed the possibility of regenerative lung tissue effect of autologous MSCs intravenous injected in experimental rat models of PE.

Pharmacological antioxidant strategies as therapeutic interventions for COPD

Cigarette/tobacco smoke/biomass fuel-induced oxidative and aldehyde/carbonyl stress are intimately associated with the progression and exacerbation of chronic obstructive pulmonary disease (COPD). Therefore, targeting systemic and local oxidative stress with antioxidants/redox modulating agents, or boosting the endogenous levels of antioxidants are likely to have beneficial effects in the treatment/management of COPD. Various antioxidant agents, such as thiol molecules (glutathione and mucolytic drugs, such as N-acetyl-L-cysteine and N-acystelyn, erdosteine, fudosteine, ergothioneine, and carbocysteine), have been reported to modulate various cellular and biochemical aspects of COPD. These antioxidants have been found to scavenge and detoxify free radicals and oxidants, regulate of glutathione biosynthesis, control nuclear factor-kappaB (NF-kappaB) activation, and hence inhibiting inflammatory gene expression. Synthetic molecules, such as specific spin traps like α-phenyl-N-tert-butyl nitrone, a catalytic antioxidant (ECSOD mimetic), porphyrins (AEOL 10150 and AEOL 10113), and a superoxide dismutase mimetic M40419, iNOS and myeloperoxidase inhibitors, lipid peroxidation inhibitors/blockers edaravone, and lazaroids/tirilazad have also been shown to have beneficial effects by inhibiting cigarette smoke-induced inflammatory responses and other carbonyl/oxidative stress-induced cellular alterations. A variety of oxidants, free radicals, and carbonyls/aldehydes are implicated in the pathogenesis of COPD, it is therefore, possible that therapeutic administration or supplementation of multiple antioxidants and/or boosting the endogenous levels of antioxidants will be beneficial in the treatment of COPD. This review discusses various novel pharmacological approaches adopted to enhance lung antioxidant levels, and various emerging beneficial and/or prophylactic effects of antioxidant therapeutics in halting or intervening the progression of COPD. This article is part of a Special Issue entitled: Antioxidants and Antioxidant Treatment in Disease.

Elastase-induced pulmonary emphysema: insights from experimental models

Several distinct stimuli can be used to reproduce histological and functional features of human emphysema, a leading cause of disability and death. Since cigarette smoke is the main cause of emphysema in humans, experimental researches have attempted to reproduce this situation. However, this is an expensive and cumbersome method of emphysema induction, and simpler, more efficacious alternatives have been sought. Among these approaches, elastolytic enzymes have been widely used to reproduce some characteristics of human cigarette smoke-induced disease, such as: augmentation of airspaces, inflammatory cell influx into the lungs, and systemic inflammation. Nevertheless, the use of elastase-induced emphysema models is still controversial, since the disease pathways involved in elastase induction may differ from those occurring in smoke-induced emphysema. This indicates that the choice of an emphysema model may impact the results of new therapies or drugs being tested. The aim of this review is to compare the mechanisms of disease induction in smoke and elastase emphysema models, to describe the differences among various elastase models, and to establish the advantages and disadvantages of elastase-induced emphysema models. More studies are required to shed light on the mechanisms of elastase-induced emphysema.

L-NAME and L-arginine differentially ameliorate cigarette smoke-induced emphysema in mice

Nitric oxide (NO) represents one of the most important intra- and extracellular mediators and takes part in both biologic and pathologic processes. This study aimed to verify the treatment with an NO inhibitor and an NO substrate in pulmonary emphysema induced by cigarette smoke (CS) in a murine model. We compared N-acetylcysteine (NAC), a precursor of glutathione, to G-nitro-L-arginine-methyl ester or L-NAME (LN), which is an NO inhibitor, and to l-arginine (LA), which is a substrate for NO formation. Mice were divided into several groups: control, CS, CS + LN, CS + LA, and CS + NAC. Control and CS groups were treated daily with a vehicle, while CS + LN, CS + LA, and CS + NAC groups were treated daily with LN (60 mg/kg), LA (120 mg/kg) and NAC (200 mg/kg), respectively. The bronchoalveolar lavage was analyzed and the lungs were removed for histological and biochemical analysis. CS increases neutrophil number. Neutrophil number was lowest in CS + LN, followed by CS + LA. The lungs of CS + LN, CS + LA and CS + NAC mice were protected compared to the lungs of CS mice, but not equal to the quality of lungs in control mice. The CS group also exhibited increased oxidative stress, which was also present in the CS + LN group and to a lesser extent in the CS + LA group. Tissue inhibitor of metalloproteinase 1 and 2 increased in the CS + LN group and to a lesser extent in the CS + LA group relative to the control group. These results suggest that LN and LA treatment protected the mouse lung from CS. However, NAC treatment was more than LN and LA. We suggest that the protection conferred by LN treatment requires a balance between proteases and antiproteases, and that protection conferred by LA treatment involves the balance between oxidants and antioxidants.

Role of nitric oxide synthases in elastase-induced emphysema

Nitric oxide (NO) in combination with superoxide produces peroxynitrites and induces protein nitration, which participates in a number of chronic degenerative diseases. NO is produced at high levels in the human emphysematous lung, but its role in this disease is unknown. The aim of this study was to determine whether the NO synthases contribute to the development of elastase-induced emphysema in mice. nNOS, iNOS, and eNOS were quantified and immunolocalized in the lung after a tracheal instillation of elastase in mice. To determine whether eNOS or iNOS had a role in the development of emphysema, mice bearing a germline deletion of the eNOS and iNOS genes and mice treated with a pharmacological iNOS inhibitor were exposed to elastase. Protein nitration was determined by immunofluorescence, protein oxidation was determined by ELISA. Inflammation and MMP activity were quantified by cell counts, RT-PCR and zymography in bronchoalveolar lavage fluid. Cell proliferation was determined by Ki67 immunostaining. Emphysema was quantified morphometrically. iNOS and eNOS were diffusely upregulated in the lung of elastase-treated mice and a 12-fold increase in the number of 3-nitrotyrosine-expressing cells was observed. Over 80% of these cells were alveolar type 2 cells. In elastase-instilled mice, iNOS inactivation reduced protein nitration and increased protein oxidation but had no effect on inflammation, MMP activity, cell proliferation or the subsequent development of emphysema. eNOS inactivation had no effect. In conclusion, in the elastase-injured lung, iNOS mediates protein nitration in alveolar type 2 cells and alleviates oxidative injury. Neither eNOS nor iNOS are required for the development of elastase-induced emphysema.

Pulmonary toxicity of chronic exposure to tobacco and biomass smoke in rats

OBJECTIVE

The objective of this study was to examine the separate and combined effects of tobacco and biomass smoke exposure on pulmonary histopathology in rats.

INTRODUCTION

In addition to smoking, indoor pollution in developing countries contributes to the development of respiratory diseases.

METHODS

Twenty-eight adult rats were divided into four groups as follows: control group (Group I, no exposure to tobacco or biomass smoke), exposed to tobacco smoke (Group II), exposed to biomass smoke (Group III), and combined exposure to tobacco and biomass smoke (Group IV). After six months the rats in all four groups were sacrificed. Lung tissue samples were examined under light microscopy. The severity of pathological changes was scored.

RESULTS

Group II differed from Group I in all histopathological alterations except intraparenchymal vascular thrombosis. There was no statistically significant difference in histopathological changes between the subjects exposed exclusively to tobacco smoke (Group II) and those with combined exposure to tobacco and biomass smoke (Group IV). The histopathological changes observed in Group IV were found to be more severe than those in subjects exposed exclusively to biomass smoke (Group III).

DISCUSSION

Chronic exposure to tobacco and biomass smoke caused an increase in severity and types of lung injury.

CONCLUSION

Exposure to cigarette smoke caused serious damage to the respiratory system, particularly with concomitant exposure to biomass smoke.

Moving towards a new generation of animal models for asthma and COPD with improved clinical relevance

Asthma and chronic obstructive pulmonary disease (COPD) are complex inflammatory airway diseases characterised by airflow obstruction that remain leading causes of hospitalization and death worldwide. Animal modelling systems that accurately reflect disease pathophysiology continue to be essential to the development of new therapies for both conditions. In this review, we describe preclinical in vivo models that recapitulate many of the features of asthma and COPD. Specifically, we discuss the pro's and con's of the standard models and highlight recently developed systems designed to more accurately reflect the complexity of both diseases. For instance, clinically relevant allergens (i.e. house dust mite) are now being used to mimic the inflammatory changes and airway remodelling that result after chronic allergen exposures. Additionally, systems are being developed to mimic steroid-resistant and viral exacerbations of allergic inflammation - aspects of asthma where there is an acute need for new therapies. Similarly, COPD models have evolved to align with the improved clinical understanding of the factors contributing to disease progression. This includes using cigarette smoke to model not only airway inflammation and remodelling, but some systemic changes (e.g. hypertension and skeletal muscle alterations) that are thought to influence disease. Further, mouse genetics are being exploited to gain insights into the genetics of COPD susceptibility. The new models of asthma and COPD described herein demonstrate that improved clinical understanding of the diseases and better preclinical models is an iterative process that will hopefully lead to therapies that can effectively manage severe asthma and COPD.

Activation of the WNT/β-catenin pathway attenuates experimental emphysema

RATIONALE

Chronic obstructive pulmonary disease (COPD) is a devastating disease, for which no causal therapy is available.

OBJECTIVES

To characterize WNT/β-catenin signaling in COPD in humans and elucidate its potential role as a preventive and therapeutic target in experimental emphysema in mice.

METHODS

The expression, localization, and activity of WNT/β-catenin signaling was assessed in 12 COPD and 12 transplant donor samples using quantitative reverse transcriptase polymerase chain reaction, immunohistochemistry, and Western blotting. The role of WNT/β-catenin signaling was assessed in elastase- and cigarette smoke-induced emphysema and therapeutic modulation thereof in elastase-induced emphysema in TOPGAL reporter and wild-type mice in vivo.

MEASUREMENTS AND MAIN RESULTS

No differences in the mRNA expression profile of the main WNT/β-catenin signaling components were observed comparing COPD and donor lung homogenates. Immunohistochemical analysis revealed reduced numbers of nuclear β-catenin-positive alveolar epithelial cells in COPD. Similarly, WNT/β-catenin signaling was down-regulated in both experimental emphysema models. Preventive and therapeutic, WNT/β-catenin activation by lithium chloride attenuated experimental emphysema, as assessed by decreased airspace enlargement, improved lung function, reduced collagen content, and elevated expression of alveolar epithelial cell markers.

CONCLUSIONS

Decreased WNT/β-catenin signaling is involved in parenchymal tissue destruction and impaired repair capacity in emphysema. These data indicate a crucial role of WNT/β-catenin signaling in lung repair mechanisms in vivo, and highlight WNT/β-catenin activation as a future therapeutic approach for emphysema.

Extracellular superoxide dismutase protects against pulmonary emphysema by attenuating oxidative fragmentation of ECM

Extracellular superoxide dismutase (ECSOD or SOD3) is highly expressed in lungs and functions as a scavenger of O(2)(*-). ECM fragmentation, which can be triggered by oxidative stress, participates in the pathogenesis of chronic obstructive pulmonary disease (COPD) through attracting inflammatory cells into the lungs. The level of SOD3 is significantly decreased in lungs of patients with COPD. However, the role of endogenous SOD3 in the development/progression of emphysema is unknown. We hypothesized that SOD3 protects against emphysema by attenuating oxidative fragmentation of ECM in mice. To test this hypothesis, SOD3-deficient, SOD3-transgenic, and WT C57BL/6J mice were exposed to cigarette smoke (CS) for 3 d (300 mg total particulate matter/m(3)) to 6 mo (100 mg/m(3) total particulate matter) or by intratracheal elastase injection. Airspace enlargement, lung inflammation, lung mechanical properties, and exercise tolerance were determined at different time points during CS exposure or after elastase administration. CS exposure and elastase administration caused airspace enlargement as well as impaired lung function and exercise capacity in SOD3-null mice, which were improved in mice overexpressing SOD3 and by pharmacological SOD mimetic. These phenomena were associated with SOD3-mediated protection against oxidative fragmentation of ECM, such as heparin sulfate and elastin, thereby attenuating lung inflammatory response. In conclusion, SOD3 attenuates emphysema and reduces oxidative fragmentation of ECM in mouse lung. Thus, pharmacological augmentation of SOD3 in the lung may have a therapeutic potential in the intervention of COPD/emphysema.

Targeted treatment in COPD: a multi-system approach for a multi-system disease

Chronic obstructive pulmonary disease is a varied condition when examined from a number of different perspectives including factors which influence disease development, pathological process and clinical features. There may be a complex interaction between the degree by which each of these processes influences the development of COPD and the subsequent clinical phenotype with which the patient presents. The varied host response and subsequent clinical phenotype has generated much interest in recent years. It is possible that failure of treatment to impact on mortality and reverse the disease process is because of the heterogeneous nature of the condition. Identification and targeted treatment of clinical and pathological phenotypes within the broad spectrum of COPD may therefore improve outcome. This article will review previous work which has attempted to phenotype COPD and identify if specific treatment for these phenotypes has been shown to be of benefit. It will examine the work on pathological processes and clinical manifestations, both pulmonary and systemic, and will focus on pharmacological therapies.

Oral N-acetylcysteine attenuates pulmonary emphysema and alveolar septal cell apoptosis in smoking-induced COPD in rats

BACKGROUND AND OBJECTIVE

The role of apoptosis in lung destruction in emphysema/COPD is increasingly being recognized. The relationship between anti-oxidants and alveolar septal cell apoptosis in COPD lungs remains to be elucidated. The aim of this study was to investigate the effects of the anti-oxidant, N-acetylcysteine (NAC), on the development of emphysema and alveolar septal cell apoptosis in smoking-induced COPD in rats.

METHODS

Sprague-Dawley rats (n = 48) were randomly assigned to normal, COPD, sham and NAC groups. The effects of treatment were assessed by measuring the levels of vascular endothelial growth factor (VEGF) in BAL fluid by ELISA, VEGF and VEGF receptor-2 (VEGFR2) protein expression by western blotting, and the apoptotic index (AI) of alveolar septal cells by terminal deoxynucleotidyl transferase dUTP nick-end labelling (TUNEL) assay. Histopathological evaluations (mean linear intercept (MLI), destructive index (DI)) and lung function measurements were performed.

RESULTS

FEV(0.3)/FVC and PEF were lower in the COPD group than in the normal group. MLI and DI were lower in the NAC-treated group than in the COPD or sham-treated groups. As confirmed by western blotting, the levels of VEGF in BAL fluid were higher in the NAC-treated group than in the COPD group. VEGFR2 protein expression was higher in the NAC-treated group than in the COPD group. The AI was significantly lower in the NAC-treated group than in the COPD group. There was an inverse correlation between levels of VEGF in BAL fluid and the AI of alveolar septal cells.

CONCLUSIONS

NAC attenuates lung damage, pulmonary emphysema and alveolar septal cell apoptosis by partly reversing the decrease in VEGF secretion and VEGFR2 protein expression in smoking-induced COPD in rats.

Exposure to ambient levels of particles emitted by traffic worsens emphysema in mice

OBJECTIVES

We investigated effects of chronic exposure (2 months) to ambient levels of particulate matter (PM) on development of protease-induced emphysema and pulmonary remodeling in mice.

METHODS

Balb/c mice received nasal drop of either papain or normal saline and were kept in two exposure chambers situated in an area with high traffic density. One of them received ambient air and the other had filters for PM.

RESULTS

mean concentration of PM10 was 2.68 +/- 0.38 and 33.86 +/- 2.09 microg/m3, respectively, in the filtered and ambient air chambers (p < 0.001). After 2 months of exposure, lungs from papain-treated mice kept in the chamber with ambient air presented greater values of mean linear intercept, an increase in density of collagen fibers in alveolar septa and in expression of 8-isoprostane (p = 0.002, p < 0.05 and p = 0.002, respectively, compared to papain-treated mice kept in the chamber with filtered air). We did not observe significant differences between these two groups in density of macrophages and in amount of cells expressing matrix metalloproteinase-12. There were no significant differences in saline-treated mice kept in the two chambers.

CONCLUSIONS

We conclude that exposure to urban levels of PM worsens protease-induced emphysema and increases pulmonary remodeling. We suggest that an increase in oxidative stress induced by PM exposure influences this response. These pulmonary effects of PM were observed only in mice with emphysema.

Improving the cadmium-induced centriacinar emphysema model in rats by concomitant anti-oxidant treatment

1. The aim of the present study was to perform an evolutionary analysis of the morphometrical, biochemical and functional parameters of centriacinar emphysema induced by cadmium chloride (CdCl2) in rats and to determine the effects of concomitant N-acetylcysteine (NAC) administration. 2. Male Wistar rats were instilled orotracheally with either CdCl2 (n = 24) or saline (n = 24). One group of rats, consisting of both CdCl2- and saline-treated rats, was fed a normal diet (n = 24), whereas the other group received NAC (n = 24). 3. Changes in inspiratory capacity (IC), lung compliance (CL), expiratory flow at 75% (F75), forced vital capacity (FVC) and hydroxyproline content were assessed 2, 8, 21 and 45 days after instillation. Polymorphonuclear cells were evaluated 2 and 8 days after instillation and the mean linear intercept (Lm) was determined at 21 and 45 days. 4. Over time, CdCl2 instillation causes several changes that are bound up with centriacinar emphysema. The concomitant administration of NAC to CdCl2-treated rats partially reversed Lm at 21 days compared with CdCl2 alone (115 +/- 2 vs 127 +/- 2, respectively; P < 0.05). However, 45 days after instillation, NAC improved lung function in CdCl2-treated rats compared with that in the saline-treated control group (IC 14.64 vs 15.25, respectively (P = 0.054); FVC 16.94 vs 16.28, respectively (P = 0.052), F75 31.41 vs 32.48, respectively (P = 0.062)). In addition, 45 days after instillation, NAC reduced lung collagen content in both the saline-treated control (100 vs 81% alone and in the presence of NAC, respectively) and CdCL2-treated groups (213 vs 161% alone and in the presence of NAC, respectively). In addition, although the results were not significant, NAC tended to reduce Lm and enhance CL in NAC + CdCl2-treated rats. 5. In conclusion, NAC partially improved emphysematous changes and reduced collagen deposition, which diminished the CdCl2-induced fibrotic component of centriacinar emphysema.

Differences in lung glutathione metabolism may account for rodent susceptibility in elastase-induced emphysema development

Syrian Golden hamsters develop more severe emphysema than Sprague-Dawley rats after intratracheal instillation of the same dose of elastase/body weight. Although species variations in antielastase defenses may largely explain these results, other variables, such as differences in lung antioxidants, cannot be overlooked since oxidative stress modulates antiprotease activity. We propose that elastase instillation might affect lung glutathione (GSH) metabolism differently in these species. Our aim was to study in hamsters and rats, lung glutathione metabolism at different times, from the stage of diffuse alveolar damage to advanced emphysema. We measured total and oxidized glutathione content as well as activity and expression of enzymes related to GSH synthesis and redox cycling: γ-glutamylcysteine synthetase, glutathione peroxidase, and glutathione reductase. Whereas rats showed no significant changes in these measurements, hamsters showed significant derangement in GSH metabolism early after elastase instillation: 25% fall in total GSH ( P < 0.05) with no increase in oxidized glutathione associated with reduced enzyme activities 24 h after elastase [60% for γ-glutamylcysteine synthetase ( P < 0.01), 30% for glutathione peroxidase ( P < 0.01), and 75% for glutathione reductase ( P < 0.001)]. GSH homeostasis was restored at the end of the first week, involving transient increased expression of these enzymes. We conclude that elastase induces significant alterations in GSH metabolism of hamster lungs and no overall change in rat lungs. Although differences in disease severity may account for our findings, the hamster becomes vulnerable to functional inhibition of α1-antitrypsin by oxidants and thus, even more susceptible to injury than it would be, considering only its low α1-antitrypsin level.

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.

Gene therapy for chronic obstructive pulmonary disease: twilight or triumph?

Chronic obstructive pulmonary disease (COPD) is a clinical syndrome presenting as progressive airflow limitation that is poorly reversible as a result of bronchitis and emphysema. The prevalence of COPD is alarming and even more so its current and projected impact on morbidity and mortality. To date, there are no effective treatments for emphysema, nor are there efficient clinical management strategies. Existing and prospective therapies, although promising, have yet to demonstrate their efficacy to slow, halt or reverse the disease. Novel approaches using gene therapy and stem cell technologies may offer new opportunities. However, this will remain almost entirely dependent on a more thorough understanding of the pathogenesis of COPD. This review is not aimed at highlighting the vast effort of studying COPD, but rather describing the state of the field in an abstract fashion to expose the focus of research efforts to date, which has primarily been limited to predisposing factors and inflammation. We would like to draw attention to other elements of the disease, such as the alveolar remodelling that characterises emphysema. Although the main cause may prove to be elusive, carefully designed clinical treatment and management may deliver the required therapeutic outcome.

Antioxidant and anti-inflammatory efficacy of NAC in the treatment of COPD: discordant in vitro and in vivo dose-effects: a review

In order to develop efficient therapeutic regimes for chronic obstructive pulmonary disease (COPD), N-acetylcysteine (NAC) has been tested as a medication which can suppress various pathogenic processes in this disease. Besides its well-known and efficient mucolytic action, NAC meets these needs by virtue of its antioxidant and anti-inflammatory modes of action. NAC is a thiol compound which by providing sulfhydryl groups, can act both as a precursor of reduced glutathione and as a direct ROS scavenger, hence regulating the redox status in the cells. In this way it can interfere with several signaling pathways that play a role in regulating apoptosis, angiogenesis, cell growth and arrest and inflammatory response. Overall, the antioxidant effects of NAC are well documented in in vivo and in vitro studies. It successfully inhibits oxidative stress at both high and low concentrations, under acute (in vitro) and chronic administration (in vivo). With regard to its anti-inflammatory action, in contrast, the effects of NAC differ in vivo and in vitro and are highly dose-dependent. In the in vitro settings anti-inflammatory effects are seen at high but not at low concentrations. On the other hand, some long-term effectiveness is reported in several in vivo studies even at low dosages. Increasing the dose seems to improve NAC bioavailability and may also consolidate some of its effects. In this way, the effects that are observed in the clinical and in vivo studies do not always reflect the success of the in vitro experiments. Furthermore, the results obtained with healthy volunteers do not always provide incontrovertible proof of its usefulness in COPD especially when number of exacerbations and changes in lung function are chosen as the primary outcomes. Despite these considerations and in view of the present lack of effective therapies to inhibit disease progression in COPD, NAC and its derivatives, because of their multiple molecular modes of action, remain promising medication once doses and route of administration are optimized.

The Effect of Cigarette Smoke-derived Oxidants on the Inflammatory Response of the Lung

The inhalation of cigarette smoke triggers a marked cellular influx in the lung and this inflammation is believed to play a central role in the development of smoke-related lung diseases such as asthma and COPD. Studies demonstrate that smoke-derived oxidants are a major factor in this inflammatory reaction to cigarette smoke. These oxidants can overwhelm the lung's antioxidant defenses and they can up regulate inflammation by a number of mechanisms. Free radicals directly stimulate the production of chemotactic compounds such as 8-isoprostane. In addition, smoke-derived oxidants can activate several intracellular signaling cascades including NF-κB, MAPK and AP-1. This transcriptional activation induces the expression of cytokines and intracellular adhesion molecules that facilitates the trafficking of neutrophils, macrophages and lymphocytes into the lung. Moreover, oxidants can promote chromatin remodeling that facilitates the expression of proinflammatory genes by stimulating the acetylation of histone residues in the nucleosome. This leads to conformational changes that enhance expression by rendering the gene more accessible to binding to transcriptional factors. Thus, the oxidant-antioxidant imbalance generated by cigarette smoke can promote inflammation which is critical to the functional decline that occurs in both asthma and COPD patients. Future research is needed to better define the effects of smoke-derived oxidants on lung inflammation and to determine the most efficacious strategies for generating significant antioxidant protection in the lung.

Quantitative characterization of airspace enlargement in emphysema

The mean linear intercept (L(m)) can be used to estimate the surface area for gas exchange in the lung. However, in recent years, it is most commonly used as an index for characterizing the enlargement of airspaces in emphysema and the associated severity of structural destruction in the lung. Specifically, an increase in L(m) is thought to result from an increase in airspace sizes. In this paper, we examined how accurately L(m) measures the linear dimensions of airspaces from histological sections and a variety of computer-generated test images. To this end, we developed an automated method for measuring linear intercepts from digitized images of tissue sections and calculate L(m) as their mean. We examined how the shape of airspaces and the variability of their sizes influence L(m) as well as the distribution of linear intercepts. We found that, for a relatively homogeneous enlargement of airspaces, L(m) was a reliable index for detecting emphysema. However, in the presence of spatial heterogeneities with a large variability of airspace sizes, L(m) did not significantly increase and sometimes even decreased compared with its value in normal tissue. We also developed an automated method for measuring the area and computed an equivalent diameter of each individual airspace that is independent of shape. Finally, we introduced new indexes based on the moments of diameter that we found to be more reliable than L(m) to characterize airspace enlargement in the presence of heterogeneities.

Focus on antioxidant enzymes and antioxidant strategies in smoking related airway diseases

Cigarette smoke causes significant oxidant stress which is further enhanced by recruitment and activation of inflammatory cells to the lung. Polymorphisms in some detoxification enzymes are thought to increase the risk of developing chronic obstructive pulmonary disease (COPD), but the ultimate role of genetic variability in antioxidant and/or detoxification enzymes in COPD remains obscure. Some antioxidant enzymes are inducted, but the extent of induction is insufficient to protect the lung/alveolar epithelium against cigarette smoke. Exogenous antioxidants such as vitamins do not seem to protect against cigarette smoke related lung injury. Glutathione related synthetic drugs such as N-acetylcysteine have shown some benefits, but they may have pro-oxidant side effects. Synthetic compounds with superoxide dismutase and catalase activities have shown promising results in animal models against a variety of oxidant exposures including cigarette smoke in the lung. These results are in agreement with studies highlighting the importance of alveolar antioxidant protection mechanisms in oxidant stress and their inducibility. These new drugs need to be tested in cigarette smoking related lung injury/inflammation since inflammation/oxidant stress can continue after discontinuation of smoking.

Defect of hepatocyte growth factor production by fibroblasts in human pulmonary emphysema

Pulmonary emphysema results from an excessive degradation of lung parenchyma associated with a failure of alveolar repair. Secretion by pulmonary fibroblasts of hepatocyte growth factor (HGF) and keratinocyte growth factor (KGF) is crucial to an effective epithelial repair after lung injury. We hypothesized that abnormal HGF or KGF secretion by pulmonary fibroblasts could play a role in the development of emphysema. We measured in vitro production of HGF and KGF by human fibroblasts cultured from emphysematous and normal lung samples. HGF and KGF production was quantified at basal state and after stimulation. Intracellular content of HGF was lower in emphysema (1.52 pg/μg, range of 0.15–7.40 pg/μg) than in control fibroblasts (14.16 pg/μg, range of 2.50–47.62 pg/μg; P = 0.047). HGF production by emphysema fibroblasts (19.3 pg/μg protein, range of 10.4–39.2 pg/μg) was lower than that of controls at baseline (57.5 pg/μg, range of 20.4–116 pg/μg; P = 0.019) and after stimulation with interleukin-1β or prostaglandin E2. Neither retinoic acids (all- trans and 9- cis) nor N-acetylcysteine could reverse this abnormality. KGF production by emphysema fibroblasts (5.3 pg/μg, range of 2.2–9.3 pg/μg) was similar to that of controls at baseline (2.6 pg/μg, range of 1–6.1 pg/μg; P = 0.14) but could not be stimulated with interleukin-1β. A decreased secretion of HGF by pulmonary fibroblasts could contribute to the insufficient alveolar repair in pulmonary emphysema.