Oxidant-antioxidant balance in the blood of patients with chronic obstructive pulmonary disease after smoking cessation

New drugs under development for COPD

The characteristic features of chronic obstructive pulmonary disease (COPD) include inflammation and remodelling of the lower airways and lung parenchyma together with activation of inflammatory and immune processes. Due to the increasing habit of cigarette smoking worldwide COPD prevalence is increasing globally. Current therapies are unable to prevent COPD progression in many patients or target many of its hallmark characteristics which may reflect the lack of adequate biomarkers to detect the heterogeneous clinical and molecular nature of COPD. In this chapter we review recent molecular data that may indicate novel pathways that underpin COPD subphenotypes and indicate potential improvements in the classes of drugs currently used to treat COPD. We also highlight the evidence for new drugs or approaches to treat COPD identified using molecular and other approaches including kinase inhibitors, cytokine- and chemokine-directed biologicals and small molecules, antioxidants and redox signalling pathway inhibitors, inhaled anti-infectious agents and senolytics. It is important to consider the phenotypes/molecular endotypes of COPD patients together with specific outcome measures to target new therapies to particular COPD subtypes. This will require greater understanding of COPD molecular pathologies and a focus on biomarkers of predicting disease subsets and responder/non-responder populations.

Glutathione Peroxidase in Stable Chronic Obstructive Pulmonary Disease: A Systematic Review and Meta-analysis

Chronic obstructive pulmonary disease (COPD) is a progressive disease that is characterized by a state of persistent inflammation and oxidative stress. The presence of oxidative stress in COPD is the result of an imbalance between pro-oxidant and antioxidant mechanisms. The aim of this review was to investigate a possible association between glutathione peroxidase (GPx), a key component of antioxidant defense mechanisms, and COPD. A systematic search for relevant studies was conducted in the electronic databases PubMed, Web of Science, Scopus, and Google Scholar, from inception to June 2021. Standardized mean differences (SMDs) were used to express the differences in GPx concentrations between COPD patients and non-COPD subjects. Twenty-four studies were identified. In 15 studies assessing whole blood/erythrocytes (GPx isoform 1), the pooled results showed that GPx concentrations were significantly lower in patients with COPD (SMD = −1.91, 95% CI −2.55 to −1.28, p < 0.001; moderate certainty of evidence). By contrast, in 10 studies assessing serum/plasma (GPx isoform 3), the pooled results showed that GPx concentrations were not significantly different between the two groups (very low certainty of evidence). The concentration of GPx-1, but not GPx-3, is significantly lower in COPD patients, suggesting an impairment of antioxidant defense mechanisms in this group.

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.

Reactive Oxygen Species and Antioxidative Defense in Chronic Obstructive Pulmonary Disease

The respiratory system is continuously exposed to endogenous and exogenous oxidants. Chronic obstructive pulmonary disease (COPD) is characterized by chronic inflammation of the airways, leading to the destruction of lung parenchyma (emphysema) and declining pulmonary function. It is increasingly obvious that reactive oxygen species (ROS) and reactive nitrogen species (RNS) contribute to the progression and amplification of the inflammatory responses related to this disease. First, we described the association between cigarette smoking, the most representative exogenous oxidant, and COPD and then presented the multiple pathophysiological aspects of ROS and antioxidative defense systems in the development and progression of COPD. Second, the relationship between nitric oxide system (endothelial) dysfunction and oxidative stress has been discussed. Third, we have provided data on the use of these biomarkers in the pathogenetic mechanisms involved in COPD and its progression and presented an overview of oxidative stress biomarkers having clinical applications in respiratory medicine, including those in exhaled breath, as per recent observations. Finally, we explained the findings of recent clinical and experimental studies evaluating the efficacy of antioxidative interventions for COPD. Future breakthroughs in antioxidative therapy may provide a promising therapeutic strategy for the prevention and treatment of COPD.

Therapeutic effects of black seed oil supplementation on chronic obstructive pulmonary disease patients: A randomized controlled double blind clinical trial

This study sought to examine whether supplementation of Black Seed Oil (BSO) can improve pulmonary function tests (PFTs), inflammation, and oxidant-antioxidant markers in COPD patients. The study involved 100 patients of mild to moderate COPD divided randomly into 2 groups who were appointed to receive standard medication only (control group) or with additional Black Seed Oil (BSO group). They were assessed initially and after 3 months, 44 patients responded in control group and 47 patients in BSO group. BSO group evidenced a significant decreasing in oxidant and inflammatory markers; thiobarbituric acid reactive-substances (TBARS), protein carbonyl (PC) content, interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α), a significant increase in antioxidants; superoxide dismutase (SOD), catalase (CAT), reduced glutathione (GSH), glutathione peroxidase (GPx), vitamin C, and E, and a significant improvement in PFTs versus control group and baseline levels. Supplementation of Black Seed Oil may be an effective adjunct therapy to improve pulmonary functions, inflammation, and oxidant-antioxidant imbalance in COPD patients.

NOVEL antioxidant and oxidant biomarkers related to sarcopenia in COPD

BACKGROUND

The relation between oxidative stress (OS) and sarcopenia in COPD remains unknown.

OBJECTIVE

To analyze OS levels and its association with sarcopenia in COPD.

METHODS

Thirty-nine individuals with COPD (69±7years; 41%female) and thirty-five for the control group (69±7years; 43%female) were included. Advanced oxidation protein products (AOPP), paraoxonase-1 (PON1), superoxide dismutase activity (SOD), catalase dismutase activity (CAT), sulfhydryl group (SH), nitric oxide metabolites (NOX), total radical trapping antioxidant parameter (TRAP) were analysed. OS markers were correlated with handgrip and quadriceps strength, gait speed, skeletal muscle mass index, fat-free mass index, maximum inspiratory and expiratory pressure. European criteria were used to identify sarcopenia.

RESULTS

In COPD, antioxidant capacity was correlated with muscle mass and strength (r from 0.5 to 0.64) P<0.05 for all. TRAP≤ 850 μM/trolox and AOPP≤65 μM/l were associated with sarcopenia (OR:8.3; 95% CI: 1.4-49.6 and OR:14; 95%CI: 2.2-87.1, respectively; P<0.05 for both).

CONCLUSION

OS is associated with sarcopenia in COPD.

Reliability and Usefulness of Different Biomarkers of Oxidative Stress in Chronic Obstructive Pulmonary Disease

Introduction

Chronic obstructive pulmonary disease (COPD) is a progressive disease characterized by airflow limitation that is not fully reversible after inhaled bronchodilator use associated with an abnormal inflammatory condition. The biggest risk factor for COPD is cigarette smoking. The exposure to noxious chemicals contained within tobacco smoke is known to cause airway epithelial injury through oxidative stress, which in turn has the ability to elicit an inflammatory response. In fact, the disruption of the delicate balance between oxidant and antioxidant defenses leads to an oxidative burden that has long been held responsible to play a pivotal role in the pathogenesis of COPD. There are currently several biomarkers of oxidative stress in COPD that have been evaluated in a variety of biological samples. The aim of this review is to identify the best studied molecules by summarizing the key literature findings, thus shedding some light on the subject.

Methods

We searched for relevant case-control studies examining oxidative stress biomarkers in stable COPD, taking into account the analytical method of detection as an influence factor.

Results

Many oxidative stress biomarkers have been evaluated in several biological matrices, mostly in the blood. Some of them consistently differ between the cases and controls even when allowing different analytical methods of detection.

Conclusions

The present review provides an overview of the oxidative stress biomarkers that have been evaluated in patients with COPD, bringing focus on those molecules whose reliability has been confirmed by the use of different analytical methods.

Monitoring Antioxidant Enzyme Activity during Exacerbations of Chronic Obstructive Pulmonary Disease

Superoxide dismutases (SODs) and catalase (CAT) have been implicated as major antioxidant enzymes of the human lungs. In this study, we investigated whether activities of these enzymes are altered in the airways of patients hospitalized with acute exacerbation of chronic obstructive pulmonary disease (AECOPD). SOD and CAT activities were measured in the sputum, exhaled breath condensate, and serum of 36 COPD patients experiencing a severe exacerbation. Measurements were performed using colorimetric assays in samples collected at the time of hospital admission and at the time of hospital discharge following treatment of AECOPD. For comparison, antioxidants were also assessed in 24 stable COPD patients and 23 healthy control subjects. SOD and CAT activities in sputum were significantly increased in patients with AECOPD compared to those with stable disease (SOD: 0.142 [0.053-0.81] vs. 0.038 [0.002-0.146] U/mL, p < 0.01; CAT: 48.7 [18.7-72.6] vs. 10.2 [2.9-40.6] nmol/min/mL, p < 0.05), while treatment of exacerbation led to a decrease in enzyme activities (SOD: 0.094 [0.046-0.45] U/mL, p < 0.05; CAT: 28.0 [7.3-60.4] nmol/min/mL, p < 0.005). No changes were observed in the serum (p > 0.05). Both SOD and CAT activities significantly correlated with sputum neutrophil and lymphocyte cell counts in patients with AECOPD. Moreover, SOD and CAT values correlated with each other and also with sputum malondialdehyde, an established marker for oxidative stress. Our data demonstrate that sputum antioxidant activity is elevated during COPD exacerbation and suggest that activation of SODs and CAT is an integral part of the human defense mechanism against the increased oxidant production associated with AECOPD.

NOX4 expression and distal arteriolar remodeling correlate with pulmonary hypertension in COPD

Background

Pulmonary hypertension (PH) in chronic obstructive pulmonary disease (COPD) is suggested as the consequence of emphysematous destruction of vascular bed and hypoxia of pulmonary microenvironment, mechanisms underpinning its pathogenesis however remain elusive. The dysregulated expression of nicotinamide adenine dinucleotide phosphate (NADPH)-oxidases and superoxide generation by pulmonary vasculatures have significant implications in the hypoxia-induced PH.

Methods

In this study, the involvement of NADPH oxidase subunit 4 (NOX4) in pulmonary arteriolar remodeling of PH in COPD was investigated by ascertaining the morphological alteration of pulmonary arteries and pulmonary blood flow using cardiac magnetic resonance imaging (cMRI), and the expression and correlation of NOX4 with pulmonary vascular remodeling and pulmonary functions in COPD lungs.

Results

Results demonstrated that an augmented expression of NOX4 was correlated with the increased volume of pulmonary vascular wall in COPD lung. While the volume of distal pulmonary arteries was inversely correlated with pulmonary functions, despite it was positively associated with the main pulmonary artery distensibility, right ventricular myocardial mass end-systolic and right ventricular myocardial mass end-diastolic in COPD. In addition, an increased malondialdehyde and a decreased superoxide dismutase were observed in sera of COPD patients. Mechanistically, the abundance of NOX4 and production of reactive oxygen species (ROS) in pulmonary artery smooth muscle cells could be dynamically induced by transforming growth factor-beta (TGF-β), which in turn led pulmonary arteriolar remodeling in COPD lungs.

Conclusion

These results suggest that the NOX4-derived ROS production may play a key role in the development of PH in COPD by promoting distal pulmonary vascular remodeling.

Soluble guanylate cyclase stimulation reduces oxidative stress in experimental Chronic Obstructive Pulmonary Disease

Objective

Soluble guanylate cyclase (sGC) is a key enzyme of the nitric oxide–cyclic guanosine 3′,5′-monophosphate (NO–cGMP) signaling pathway, and its pharmacological stimulation has been shown to prevent the development of emphysema and pulmonary vascular remodeling in animal models of chronic obstructive pulmonary disease (COPD). The aim of this study was to evaluate the effects of sGC stimulation on oxidative stress in the plasma of guinea pigs chronically exposed to cigarette smoke (CS).

Methods and results

Guinea pigs were exposed to CS or sham for three months, and received either the sGC stimulator BAY 41–2272 or vehicle. Body weight was measured weekly; and markers of oxidative stress in plasma, and airspace size and inflammatory cell infiltrate in lung tissue were analyzed at the end of the study. Compared to sham-exposed guinea pigs, CS-exposed animals gained less body weight and showed higher plasma levels of nitrated tyrosine residues (3-NT), 4-hydroxynonenal (4-HNE), and 8-hydroxydeoxyguanosine (8-OHdG). Treatment with the sGC stimulator led to a body weight gain in the CS-exposed guinea pigs similar to non-exposed and attenuated the increase in 3-NT and 4-HNE. Plasma levels of 3-NT correlated with the severity of inflammatory cell infiltrate in the lung.

Conclusion

Stimulation of sGC prevents oxidative stress induced by CS exposure and is associated with an attenuated inflammatory response in the lung.

Decreased activity of butyrylcholinesterase in blood plasma of patients with chronic obstructive pulmonary disease

INTRODUCTION

Butyrylcholinesterase (BChE) is involved in the metabolism of endogenous lipids and xenobiotics, such as esters of carboxylic or phosphoric acids. Butyrylcholinesterase activity is associated with both inflammation and oxidative stress. Changes in the activity of this enzyme have been observed in various diseases such as liver cirrhosis, diabetes, neurodegenerative disease and others.

MATERIAL AND METHODS

The study involved 30 patients with chronic obstructive pulmonary disease (COPD) and 18 healthy subjects. The COPD patients were divided according to the severity of the disease by applying the classification of COPD based on GOLD standards for forced expiratory volume in 1 s (FEV₁) and the FEV₁/forced expiratory volume (FVC) ratio. The control group comprised blood samples collected from healthy subjects without concomitant diseases related to the respiratory system. Butyrylcholinesterase activity, lipid peroxidation and total antioxidant capacity (TAC) were determined in the blood plasma.

RESULTS

A significant (p < 0.05) decrease in the activity of BChE, associated with an increase in lipid peroxidation and a decrease in the total antioxidant capacity, was observed in blood plasma of patients with chronic obstructive pulmonary disease.

CONCLUSIONS

The study shows for the first time that activity of BChE in the blood plasma of patients diagnosed with chronic obstructive pulmonary disease is considerably reduced compared with healthy subjects. These changes were accompanied by a decrease of TAC and an increase of lipid peroxidation, which suggests that they may be related to the oxidative stress induced by COPD disease.

Circulating biomarkers of oxidative stress in chronic obstructive pulmonary disease: a systematic review

Chronic obstructive pulmonary disease (COPD) is a progressive condition characterized by airflow limitation associated with an abnormal inflammatory response of the lungs to noxious particles and gases, caused primarily by cigarette smoking. Increased oxidative burden plays an important role in the pathogenesis of COPD. There is a delicate balance between the toxicity of oxidants and the protective function of the intracellular and extracellular antioxidant defense systems, which is critically important for the maintenance of normal pulmonary functions. Several biomarkers of oxidative stress are available and have been evaluated in COPD. In this review, we summarize the main literature findings about circulating oxidative stress biomarkers, grouped according to their method of detection, measured in COPD subjects.

Nrf2 expression is increased in peripheral blood mononuclear cells derived from mild-moderate ex-smoker COPD patients with persistent oxidative stress

Inadequacy of antioxidant nuclear factor-E2-related factor 2 (Nrf2) and endoplasmic reticulum stress-mediated unfolded protein response has been implicated in severe chronic obstructive pulmonary disease (COPD) and cigarette smoking-induced emphysema. As evidence suggests that the ability to upregulate Nrf2 expression may influence the progression of COPD and no data exist up to now in ex-smokers with mild-moderate COPD, this study was first aimed to evaluate Nrf2 and unfolded protein response expression in peripheral blood mononuclear cells (PBMC) of mild-moderate ex-smokers with COPD compared to smoking habit-matched non-COPD subjects. Then, we tested whether oxidative stress persists after cigarette smoking cessation and whether the concentrations of oxidized phospholipids (oxidation products of the phospholipid 1-palmitoyl-2-arachidonyl-sn-glycero-3-phosphorylcholine [oxPAPC]) in the PBMC of the same subjects may have a causative role in determining the upregulation of Nrf2. The expression (mRNA and protein) of Nrf2 and of its related gene heme oxygenase-1 was significantly increased in COPD group without differences in the unfolded protein response. Plasma malondialdehyde, the circulating marker of oxidative stress, and oxPAPC in PBMC were significantly higher in COPD than in non-COPD subjects. The fact that the expression of p47phox, a subunit of NADPH oxidase, was increased in PBMC of COPD patients and that it was directly correlated with oxPAPC may indicate that oxPAPC may be one of the determinants of oxidative stress-induced Nrf2 upregulation. Finally, we also demonstrated that lung function inversely correlated with plasma malondialdehyde and with Nrf2 and heme oxygenase-1 mRNA expression in all subjects. Our results indicate that mild-moderate ex-smokers with COPD may be able to counteract oxidative stress by increasing the expression of Nrf2/antioxidant-response elements. Because Nrf2 failure significantly contributes to the development of COPD, our findings suggest that the possibility to prevent Nrf2 reduction may open a new scenario in helping to prevent the oxidative stress-associated lung function decline.

N-acetylcysteine in COPD: why, how, and when?

Oxidants have long been recognized to have an important role in the pathogenesis of COPD, and in this cigarette smoke has a strong responsibility, because it generates a conspicuous amount of oxidant radicals able to modify the structure of the respiratory tract and to enhance several mechanisms that sustain lung inflammation in COPD. In fact, oxidative stress is highly increased in COPD and natural antioxidant capacities, mainly afforded by reduced glutathione, are often overcome. Thus an exogenous supplementation of antioxidant compounds is mandatory to at least partially counteract the oxidative stress. For this purpose N-acetylcysteine has great potentialities due to its capacity of directly contrasting oxidants with its free thiols, and to the possibility it has of acting as donor of cysteine precursors aimed at glutathione restoration. Many studies in vitro and in vivo have already demonstrated the antioxidant capacity of NAC. Many clinical studies have long been performed to explore the efficacy of NAC in COPD with altern results, especially when the drug was used at very low dosage and/or for a short period of time. More recently, several trials have been conducted to verify the appropriateness of using high-dose NAC in COPD, above all to decrease the exacerbations rate. The results have been encouraging, even if some of the data come from the most widely sized trials that have been conducted in Chinese populations. Although other evidence should be necessary to confirm the results in other populations of patients, high-dose oral NAC nevertheless offers interesting perspectives as add-on therapy for COPD patients.

Oxidative stress and damage to erythrocytes in patients with chronic obstructive pulmonary disease--changes in ATPase and acetylcholinesterase activity

The study indicates, for the first time, the changes in both ATPase and AChE activities in the membrane of red blood cells of patients diagnosed with COPD. Chronic obstructive pulmonary disease (COPD) is one of the most common and severe lung disorders. We examined the impact of COPD on redox balance and properties of the membrane of red blood cells. The study involved 30 patients with COPD and 18 healthy subjects. An increase in lipid peroxidation products and a decrease in the content of -SH groups in the membrane of red blood cells in patients with COPD were observed. Moreover, an increase in the activity of glutathione peroxidase and a decrease in superoxide dismutase, but not in catalase activity, were found as well. Significant changes in activities of erythrocyte membrane enzymes in COPD patients were also evident demonstrated by a considerably lowered ATPase activity and elevated AChE activity. Changes in the structure and function of red blood cells observed in COPD patients, together with changes in the activity of the key membrane enzymes (ATPases and AChE), can result from the imbalance of redox status of these cells due to extensive oxidative stress induced by COPD disease.

Heterogeneity of Systemic Oxidative Stress Profiles in COPD: A Potential Role of Gender

Oxidative stress (OS) plays a key role in the muscle impairment and exercise capacity of COPD patients. However, the literature reveals that systemic OS markers show great heterogeneity, which may hinder the prescription of effective antioxidant supplementation. This study therefore aimed to identify OS markers imbalance of COPD patients, relative to validated normal reference values, and to investigate the possibility of systemic OS profiles. We measured systemic enzymatic/nonenzymatic antioxidant and lipid peroxidation (LP) levels in 54 stable COPD patients referred for a rehabilitation program. The main systemic antioxidant deficits in these patients concerned vitamins and trace elements. Fully 89% of the COPD patients showed a systemic antioxidant imbalance which may have caused the elevated systemic LP levels in 69% of them. Interestingly, two patient profiles (clusters 3 and 4) had a more elevated increase in LP combined with increased copper and/or decreased vitamin C, GSH, and GPx. Further analysis revealed that the systemic LP level was higher in COPD women and associated with exercise capacity. Our present data therefore support future supplementations with antioxidant vitamins and trace elements to improve exercise capacity, but COPD patients will probably show different positive responses.

Activity of α1-antitrypsin and some lysosomal enzymes in the blood serum of patients with chronic obstructive pulmonary disease after smoking cessation

The activity of α₁-antitrypsin (AAT) and the lysosomal enzymes, cathepsin D (CTS D), arylsulfatase (ASA), and acid phosphatase, (AcP) was determined in patients with COPD (GOLD category A). Moreover, the diagnostic usefulness of these parameters in blood serum was assessed along with establishing whether smoking cessation affects these parameters. The study included 70 patients with COPD who ceased smoking (study group) and two control groups of 33 subjects each: nonsmokers without COPD (control I) and patients with COPD who continued smoking (control II). In control I, blood was taken once and in control II, at the start of the experiment and after the 1st, 2nd, and 3rd months. AAT in the patients exhibited higher activity than in the healthy subjects at all time points. AAT activity in the patients before the start of the experiment was ~80% higher (P < 0.001) than in control I. No statistically significant differences in CTS D, ASA, and AcP activity were found. COPD involves increased AAT activity and unchanged activities of the assessed lysosomal enzymes. Three-month tobacco abstinence does not affect these parameters in peripheral blood. Determining the AAT levels in blood serum can be used in the diagnostics of COPD.

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.

Oxidant-antioxidant status in the blood of horses with symptomatic recurrent airway obstruction (RAO)

Background

Systemic oxidative stress in horses with recurrent airway obstruction (RAO) is poorly characterized.

Objectives

The goal of this study was to investigate whether equine RAO is associated with systemic disturbances in the oxidant‐antioxidant equilibrium.

Animals

Seven healthy horses and 7 horses with symptomatic RAO.

Methods

A prospective study. Healthy and RAO‐affected horses were exposed to a 48‐hour challenge with moldy hay and straw to induce clinical exacerbation of RAO. Venous blood was collected and the activities of the superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and glutathione reductase (GR) in equine erythrocyte lysates were measured. The concentration of thiobarbituric acid‐reactive substances (TBARSs) was assessed both in erythrocyte lysates and in plasma.

Results

A significant increase in the activities of GPx and SOD was detected in RAO‐affected horses compared with the control animals. There was no significant difference between groups in terms of the erythrocyte lysate activities of CAT, GR, or TBARs or the plasma concentration of TBARs.

Conclusion and Clinical Importance

Our results support the hypothesis that RAO in horses is associated with systemic oxidative stress. Future studies are needed to assess whether horses suffering from RAO can benefit from antioxidant supplementation.

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.