Functional variants of antioxidant genes in smokers with COPD and in those with normal lung function

Genetic and epigenetic inactivation of extracellular superoxide dismutase promotes an invasive phenotype in human lung cancer by disrupting ECM homeostasis

Extracellular superoxide dismutase (EcSOD) is an important superoxide scavenger in the lung in which its loss, sequence variation, or abnormal expression contributes to lung diseases; however, the role of EcSOD in lung cancer has yet to be studied. We hypothesized that EcSOD loss could affect malignant progression in lung, and could be either genetic or epigenetic in nature. To test this, we analyzed EcSOD expression, gene copy number, promoter methylation, and chromatin accessibility in normal lung and carcinoma cells. We found that normal airway epithelial cells expressed abundant EcSOD and had an unmethylated promoter, whereas EcSOD-negative lung cancer cells displayed aberrant promoter hypermethylation and decreased chromatin accessibility. 5-aza-dC induced EcSOD suggesting that cytosine methylation was causal, in part, to silencing. In 48/50 lung tumors, EcSOD mRNA was significantly lower as early as stage I, and the EcSOD promoter was hypermethylated in 8/10 (80%) adenocarcinomas compared with 0/5 normal lung samples. In addition, 20% of the tumors showed loss of heterozygosity (LOH) of EcSOD. Reexpression of EcSOD attenuated the malignant phenotype of lung carcinoma cells by significantly decreasing invasion and survival. Finally, EcSOD decreased heparanase and syndecan-1 mRNAs in part by reducing NF-κB. By contrast, MnSOD and CuZnSOD showed no significant changes in lung tumors and had no effect on heparanase expression. Taken together, the loss of EcSOD expression is unique among the superoxide dismutases in lung cancer and is the result of EcSOD promoter methylation and LOH, suggesting that its early loss may contribute to ECM remodeling and malignant progression.

Pathogenic triad in COPD: oxidative stress, protease-antiprotease imbalance, and inflammation

Patients with chronic obstructive pulmonary disease (COPD) exhibit dominant features of chronic bronchitis, emphysema, and/or asthma, with a common phenotype of airflow obstruction. COPD pulmonary physiology reflects the sum of pathological changes in COPD, which can occur in large central airways, small peripheral airways, and the lung parenchyma. Quantitative or high-resolution computed tomography is used as a surrogate measure for assessment of disease progression. Different biological or molecular markers have been reported that reflect the mechanistic or pathogenic triad of inflammation, proteases, and oxidants and correspond to the different aspects of COPD histopathology. Similar to the pathogenic triad markers, genetic variations or polymorphisms have also been linked to COPD-associated inflammation, protease–antiprotease imbalance, and oxidative stress. Furthermore, in recent years, there have been reports identifying aging-associated mechanistic markers as downstream consequences of the pathogenic triad in the lungs from COPD patients. For this review, the authors have limited their discussion to a review of mechanistic markers and genetic variations and their association with COPD histopathology and disease status.

Smoking and COPD increase sputum levels of extracellular superoxide dismutase

Extracellular superoxide dismutase (ECSOD) is the major superoxide-scavenging enzyme in the lung. Certain ECSOD polymorphisms are protective against COPD. We postulated that smokers and COPD subjects would have altered levels of ECSOD in the lung, airway secretions, and/or plasma. Lung tissue ECSOD was evaluated from nonsmokers, smokers, and subjects with mild to very severe COPD by Western blot, immunohistochemistry, and ELISA. ECSOD levels in plasma, bronchoalveolar lavage fluid (BALF), and induced-sputum supernatants were analyzed by ELISA and correlated with smoking history and disease status. Immunohistochemistry identified ECSOD in extracellular matrix around bronchioles, arteries, and alveolar walls, with decreases seen in the interstitium and vessels of severe COPD subjects using digital image analysis. Plasma ECSOD did not differ between COPD subjects and controls nor based on smoking status. ECSOD levels in induced sputum supernatants were elevated in current smokers and especially in COPD subjects compared to nonsmokers, whereas corresponding changes could not be seen in the BALF. ECSOD expression was reduced around vessels and bronchioles in COPD lungs. Substantial increases in sputum ECSOD in smokers and COPD is interpreted as an adaptive response to increased oxidative stress and may be a useful biomarker of disease activity in COPD.

Genetic evidence linking lung cancer and COPD: a new perspective

Epidemiological studies indicate that tobacco smoke exposure accounts for nearly 90% of cases of chronic obstructive pulmonary disease (COPD) and lung cancer. However, genetic factors may explain why 10%–30% of smokers develop these complications. This perspective reviews the evidence suggesting that COPD is closely linked to susceptibility to lung cancer and outlines the potential relevance of this observation. Epidemiological studies show that COPD is the single most important risk factor for lung cancer among smokers and predates lung cancer in up to 80% of cases. Genome-wide association studies of lung cancer, lung function, and COPD have identified a number of overlapping “susceptibility” loci. With stringent phenotyping, it has recently been shown that several of these overlapping loci are independently associated with both COPD and lung cancer. These loci implicate genes underlying pulmonary inflammation and apoptotic processes mediated by the bronchial epithelium, and link COPD with lung cancer at a molecular genetic level. It is currently possible to derive risk models for lung cancer that incorporate lung cancer-specific genetic variants, recently identified “COPD-related” genetic variants, and clinical variables. Early studies suggest that single nucleotide polymorphism-based risk stratification of smokers might help better target novel prevention and early diagnostic strategies in lung cancer.

Current concepts on oxidative/carbonyl stress, inflammation and epigenetics in pathogenesis of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a global health problem. The current therapies for COPD are poorly effective and the mainstays of pharmacotherapy are bronchodilators. A better understanding of the pathobiology of COPD is critical for the development of novel therapies. In the present review, we have discussed the roles of oxidative/aldehyde stress, inflammation/immunity, and chromatin remodeling in the pathogenesis of COPD. An imbalance of oxidants/antioxidants caused by cigarette smoke and other pollutants/biomass fuels plays an important role in the pathogenesis of COPD by regulating redox-sensitive transcription factors (e.g., NF-κB), autophagy and unfolded protein response leading to chronic lung inflammatory response. Cigarette smoke also activates canonical/alternative NF-κB pathways and their upstream kinases leading to sustained inflammatory response in lungs. Recently, epigenetic regulation has been shown to be critical for the development of COPD because the expression/activity of enzymes that regulate these epigenetic modifications have been reported to be abnormal in airways of COPD patients. Hence, the significant advances made in understanding the pathophysiology of COPD as described herein will identify novel therapeutic targets for intervention in COPD.

Update in chronic obstructive pulmonary disease: role of antioxidant and metabolizing gene polymorphisms

Chronic obstructive pulmonary disease (COPD) is characterized by systemic and local chronic inflammation and oxidative stress. The sources of the increased oxidative stress in COPD patients derive from the increased burden of inhaled oxidants such as cigarette smoke and other forms of particulate or gaseous air pollution and from the increase in reactive oxygen species (ROS) generated by several inflammatory, immune, and structural airways cells. There is increasing evidence that genetic factors may also contribute to the pathogenesis if COPD, particularly antioxidant genes, which may confer a susceptibility to environmental insults such as cigarette smoke and thereafter development of COPD. Consequently, heme oxygenase-1 (HO-1), superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), microsomal epoxide hydrolase (EPHX1), and cytochrome P450 (CYP) genetic polymorphisms may have an important role in COPD pathogenesis. In this review the authors summarized the most recent findings dealing with these antioxidant genes contributing to the free radical neutralization and xenobiotic enzymes playing a role in different phases of cell detoxification reactions related to the redox status imbalance in COPD, with an emphasis on their possible roles in disease progression.

Allele-specific effects of ecSOD on asbestos-induced fibroproliferative lung disease in mice

Previous work by others suggests that there is a strain-dependent variation in the susceptibility to inflammatory lung injury in mice. Specifically, the 129/J mice appear to be more resistant to asbestos-induced pulmonary fibrosis than the C57BL/6 strain. A separate line of evidence suggests that extracellular superoxide dismutase (ecSOD) may play an important role in protecting the lung from such injuries. We have recently reported that the 129/J strain of mice has an ecSOD genotype and phenotype distinctly different from those of the C57BL/6 mice. In order to identify ecSOD as a potential "asbestos-injury resistance" gene, we bred congenic mice, on the C57BL/6 background, carrying the wild type (sod3wt) or the 129/J (sod3129) allele for ecSOD. This allowed us to examine the role of ecSOD polymorphism in susceptibility to lung injury in an otherwise identical genetic background. Interestingly, asbestos treatment induces a significant (~40%) increase in plasma ecSOD activity in the sod3129 mice, but not in the sod3wt mice. Asbestos administration results in a loss of ecSOD activity and protein from lung tissue of both congenic strains, but the lung ecSOD activity remains significantly higher in sod3129 mice. As expected, asbestos treatment results in a significant recovery of ecSOD protein in bronchoalveolar lavage fluid (BALF). The BALF of sod3129 mice also have significantly lower levels of proteins and inflammatory cells, especially neutrophils, accompanied by a significantly lower extent of lung injury, as measured by a pathology index score or hydroxyproline content. Immunohistochemistry reveals a significant loss of ecSOD from the tips of the respiratory epithelial cells in response to asbestos treatment and that the loss of immunodetectable ecSOD is compensated for by enzyme expression by infiltrating cells, especially in the sod3wt mice. Our studies thus identify ecSOD as an important anti-inflammatory gene, responsible for most, if not all of the resistance to asbestos-induced lung injury reported for the 129/J strain of mice. The data further suggest allele-specific differences in the regulation of ecSOD expression. These congenic mice therefore represent a very useful model to study the role of this enzyme in all inflammatory diseases. Polymorphisms in human ecSOD have also been reported and it appears logical to assume that such variations may have a profound effect on disease susceptibility.

Superoxide dismutase, catalase, glutathione peroxidase and gluthatione S-transferases M1 and T1 gene polymorphisms in three Brazilian population groups

Antioxidants such as superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX1) reduce the oxidation rates in the organism. Gluthatione S-transferases (GSTs) play a vital role in phase 2 of biotransformation of many substances. Variation in the expression of these enzymes suggests individual differences for the degree of antioxidant protection and geographical differences in the distribution of these variants. We described the distribution frequency of CAT (21A/T), SOD2 (Ala9Val), GPX1 (Pro198Leu), GSTM1 and GSTT1 polymorphisms in three Brazilian population groups: Kayabi Amerindians (n = 60), Kalunga Afro-descendants (n = 72), and an urban mixed population from Federal District (n = 162). Frequencies of the variants observed in Kalunga (18% to 58%) and Federal District (33% to 63%) were similar to those observed in Euro and Afro-descendants, while in Kayabi (3% to 68%), depending on the marker, frequencies were similar to the ones found in different ethnic groups. Except for SOD2 in all population groups studied here, and for GPX1 in Kalunga, the genotypic distributions were in accordance with Hardy-Weinberg Equilibrium. These data can clarify the contribution of different ethnicities in the formation of mixed populations, such as that of Brazil. Moreover, outcomes will be valuable resources for future functional studies and for genetic studies in specific populations. If these studies are designed to comprehensively explore the role of these genetic polymorphisms in the etiology of human diseases they may help to prevent inconsistent genotype-phenotype associations in pharmacogenetic studies.

Endogenous enzymes (NOX and ECSOD) regulate smoke-induced oxidative stress

Chronic obstructive pulmonary disease (COPD) is the fourth leading cause of death in the United States and the incidence is increasing as the population ages. Cigarette smoking is the primary risk factor; however, only a minority of smokers develop the disease. Inhalation of cigarette smoke introduces an abundance of free radicals into the lungs, causing oxidative stress and inflammation. We hypothesized that after the initial burst of oxidative stress associated with cigarette smoke exposure, a sustained source of endogenous free radical production is modulated by the antioxidant enzyme extracellular superoxide dismutase (ECSOD) and the superoxide-generating complex NADPH oxidase (NOX). Primary mouse macrophages exposed to cigarette smoke extract exhibited increased oxidative stress as indicated by fluorogenic dyes and isoprostane concentration, which was suppressed in the presence of both a superoxide dismutase mimetic and a NOX inhibitor. Similarly, primary macrophages isolated from ECSOD-overexpressing mice or NOX-deficient mice showed reduced oxidative stress in response to cigarette smoke treatment. In addition, both reduced glutathione and cytokines (MIP2 and IFNγ) were increased in bronchoalveolar lavage fluid of wild-type mice exposed to cigarette smoke but not in ECSOD-overexpressing or NOX-deficient mice. These data suggest that the mechanisms underlying the host defense against cigarette smoke-induced oxidative damage and subsequent development of COPD may include endogenous oxidases and antioxidant enzymes.

Markers of anti-oxidant response in tobacco smoke exposed subjects: a data-mining review

Tobacco smoke exposure is the cause of exaggerated inflammatory responses and tissue destruction leading to chronic bronchitis and emphysema. A number of studies have used biochemical and immunological technologies to identify biomarkers of severity, risk and pharmacological target of disease. Recently, genomic and proteomic studies have been carried out to explore tobacco smoke-induced lung damage mechanisms. Eight of these studies, including 81 healthy non-smokers, 138 healthy smokers and 24 smokers with COPD, had open platform generated data available online and were reviewed in order to identify markers of smoke-induced damage by analyzing differential gene and protein expression in healthy individuals exposed to tobacco smoke in comparison with chronic obstructive pulmonary disease (COPD) smokers and healthy non-smokers. To this end the Ingenuity Pathways Analysis, a web-based application enables identifying the main biological functions and pathways, was used. The pathway most significantly associated with healthy smokers was the Nrf2-mediated Oxidative Stress Response (p-value < 0.01): out of the 22 genes/proteins identified in healthy smokers, 19 were up-regulated and three down-regulated, compared to non-smokers. Interestingly, four genes/proteins of the same pathway were differentially regulated in COPD, one up-regulated and three down-regulated, compared to healthy smokers. Moreover, in the comparison between COPD and healthy smokers, our analysis showed that the most relevant pathway was the Mitochondrial Dysfunction (p-value < 0.01) with 12 differentially regulated genes/proteins. This data-mining review supports the notion that Nrf2-regulated anti-oxidant genes play a central role in protection against tobacco smoke toxic effects and may be amenable to use as COPD risk biomarkers. Furthermore, this review suggests that mitochondrial dysfunction may be involved in the development of COPD.

Association of the superoxide dismutase (V16A) and catalase (C262T) genetic polymorphisms with the clinical outcome of patients with acute paraquat intoxication

BACKGROUND/AIMS

Many patients with acute paraquat (PQ) intoxication die even at low PQ concentrations, whereas others with similar concentrations recover. Therefore, it is possible that individual differences in antioxidant capacity are responsible for the variable clinical outcome in patients with acute PQ intoxication.

METHODS

We investigated whether there was a relationship between the genetic polymorphisms of SOD (V16A), catalase (C262T), and GPX1 (C593T) in 62 patients with acute PQ intoxication and the clinical outcomes of these patients.

RESULTS

The frequency of the Mn-SOD V/V, V/A, and A/A genotypes were 56.3, 43.5, and 0% in survivors and 86.9, 13.1, and 0% in non-survivors (p > 0.05). The GPX1 C/C, C/T, and T/T genotypes were present in 100, 0, and 0% of all subjects. The catalase C/C, C/T, and T/T genotypes were present in 100, 0, and 0% of survivors, and in 82.6, 17.4, and 0% of non-survivors. Neither erythrocyte SOD activity nor catalase activity were significantly different between survivors and non-survivors.

CONCLUSIONS

No association was found between clinical outcome of acute PQ intoxication and the genetic polymorphism of GPX1 (C593T) or the genetic polymorphisms or enzyme activity of superoxide dismutase (V16A) or catalase (C262T).

Current perspectives of oxidative stress and its measurement in chronic obstructive pulmonary disease

Cigarette smoking, the principal aetiology of chronic obstructive pulmonary disease (COPD) in the developed countries, delivers and generates oxidative stress within the lungs. This imbalance of oxidant burden and antioxidant capacity has been implicated as an important contributing factor in the pathogenesis of COPD. Oxidative processes and free radical generation orchestrate the inflammation, mucous gland hyperplasia, and apoptosis of the airway lining epithelium which characterises COPD. Pivotal oxidative stress/pro-inflammatory molecules include reactive oxygen species such as the superoxides and hydroxyl radicals, pro-inflammatory cytokines including leukotrienes, interleukins, tumour necrosis factor alpha, and activated transcriptional factors such as nuclear factor kappa-B and activator protein 1. The lung has a large reserve of antioxidant agents such as glutathione and superoxide dismutase to counter oxidants. However, smoking also causes the depletion of antioxidants, which further contributes to oxidative tissue damage. The downregulation of antioxidant pathways has also been associated with acute exacerbations of COPD. The delivery of redox-protective antioxidants may have preventative and therapeutic potential of COPD. Although these observations have yet to translate into common clinical practice, preliminary clinical trials and studies of animal models have shown that interventions to counter this oxidative imbalance may have potential to better manage COPD. There is, thus, a need for the ability to monitor such interventions and exhaled breath condensate is rapidly emerging as a novel and noninvasive approach in the sampling of airway epithelial lining fluid which could be used for repeated analysis of oxidative stress and inflammation in the lungs.

The effect of hydrogen peroxide-induced oxidative stress on leukocytes depends on age and physical training in healthy human subjects carrying the same genotypes of antioxidant enzymes' gene polymorphisms

OBJECTIVES

Reactive oxygen species account for the background levels of oxidatively damaged DNA in normal tissues. Physical exercise increases oxygen consumption and can cause oxidative stress. This stress can also involve deficient antioxidant defenses, which can be influenced by certain genetic polymorphisms. Because regular exercise is a known inducer of antioxidant enzymes, the objective of this study was to compare, by comet assay, differences in the DNA damage between apparently healthy individuals and trained aerobic sportsmen carrying the same single nucleotide polymorphisms of manganese superoxide dismutase (Val9Ala), catalase (-21A/T), glutathione peroxidase 1 (Pro198Leu), before and after exposing leukocytes from peripheral blood to hydrogen peroxide (H₂O₂).

METHODS

Athletes were compared with nonathletes after a situation that promotes reactive oxygen species increase (a race). Blood samples were submitted to genotyping and comet assay, and the athletes and nonathletes were paired according to their gender, age, and MnSOD, CAT, and GPx-1 genotypes.

RESULTS

For nonathletes, there was a positive correlation between H₂O₂ concentrations and DNA damage levels. For athletes, these correlations showed differences between sexes, indicating that running may impose higher oxidative stress on the DNA of women than of men. Significant differences appeared for nonathletes in the comparisons between younger and older age groups after treatment with H₂O₂ at 250 μM.

CONCLUSIONS

This suggests that, for individuals carrying the same genotypes of antioxidant enzymes' genes, the effect of H₂O₂-induced oxidative stress depends mainly on age and physical training. It also suggests that aerobic physical training can reduce oxidative damages to DNA, preventing related diseases in older people.

Glucocorticoid insensitivity as a future target of therapy for chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is characterized by an abnormal and chronic inflammatory response in the lung that underlies the chronic airflow obstruction of the small airways, the inexorable decline of lung function, and the severity of the disease. The control of this inflammation remains a key strategy for treating the disease; however, there are no current anti-inflammatory treatments that are effective. Although glucocorticoids (GCs) effectively control inflammation in many diseases such as asthma, they are less effective in COPD. The molecular mechanisms that contribute to the development of this relative GC-insensitive inflammation in the lung of patients with COPD remain unclear. However, recent studies have indicated novel mechanisms and possible therapeutic strategies. One of the major mechanisms proposed is an oxidant-mediated alteration in the signaling pathways in the inflammatory cells in the lung, which may result in the impairment of repressor proteins used by the GC receptor to inhibit the transcription of proinflammatory genes. Although these studies have described mechanisms and targets by which GC function can be restored in cells from patients with COPD, more work is needed to completely elucidate these and other pathways that may be involved in order to allow for more confident therapeutic targeting. Given the relative GC-insensitive nature of the inflammation in COPD, a combination of therapies in addition to a restoration of GC function, including effective alternative anti-inflammatory targets, antioxidants, and proresolving therapeutic strategies, is likely to provide better targeting and improvement in the management of the disease.

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.

The cyclooxygenase-2-765C promoter polymorphism protects against the development of chronic obstructive pulmonary disease

BACKGROUND

Susceptibility to Chronic Obstructive Pulmonary Disease (COPD) has a genetic component. We undertook a study to determine if a genetic variant of the gene encoding the cyclooxygenase-2 gene influences the likelihood of developing COPD.

METHODS

In a case control study the frequency of a single nucleotide polymorphism in the promoter region of the cyclooxygenase-2 gene (-765 G → C) was determined in 205 subjects with COPD, 171 chronic smokers with normal lung function (resistant smokers) and 95 healthy blood donors using the polymerase chain reaction and restriction enzyme fragment length polymorphism.

RESULTS

The frequency of the C allele of the -765 cyclooxygenase-2 polymorphism was higher in resistant smokers (24.6%) compared with subjects with COPD (14.4%, OR = 1.98, 95% CI = 1.28-3.06, p = 0.003) and blood donors (14.7%, OR = 1.97, 95% CI = 1.14-3.41, p = 0.03).

CONCLUSIONS

The -765C allele, which has been shown to be associated with decreased promoter activity of the cyclooxygenase-2 gene, is more common in resistant smokers. This raises the possibility that decreased activity of cyclooxygenase-2 may protect smokers against the development of COPD.

Polymorphisms in the superoxide dismutase-3 gene are associated with emphysema in COPD

Superoxide dismutase-3 (SOD3) is a major extracellular antioxidant enzyme, and previous studies have indicated a possible role of this gene in chronic obstructive pulmonary disease (COPD). We hypothesized that polymorphisms in the SOD3 gene would be associated with COPD and COPD-related phenotypes. We genotyped three SOD3 polymorphisms (rs8192287 (E1), rs8192288 (I1), and rs1799895 (R213G)) in a case-control cohort, with severe COPD cases from the National Emphysema Treatment Trial (NETT, n = 389) and smoking controls from the Normative Aging Study (NAS, n = 472). We examined whether the single nucleotide polymorphisms (SNPs) were associated with COPD status, lung function variables, and quantitative computed tomography (CT) measurements of emphysema and airway wall thickness. Furthermore, we tried to replicate our initial findings in two family-based studies, the International COPD Genetics Network (ICGN, n = 3061) and the Boston Early-Onset COPD Study (EOCOPD, n = 949). In NETT COPD cases, the minor alleles of SNPs E1 and I1 were associated with a higher percentage of emphysema (%LAA950) on chest CT scan (p = .029 and p = .0058). The association with E1 was replicated in the ICGN family study, where the minor allele was associated with more emphysema (p = .048). Airway wall thickness was positively associated with the E1 SNP in ICGN; however, this finding was not confirmed in NETT. Quantitative CT data were not available in EOCOPD. The SNPs were not associated with lung function variables or COPD status in any of the populations. In conclusion, polymorphisms in the SOD3 gene were associated with CT emphysema but not COPD susceptibility, highlighting the importance of phenotype definition in COPD genetics studies.

Overcoming reduced glucocorticoid sensitivity in airway disease: molecular mechanisms and therapeutic approaches

There is a considerable and growing unmet medical need in respiratory disease concerning effective anti-inflammatory therapies for conditions such as severe asthma, chronic obstructive pulmonary disease and cystic fibrosis. These diseases share a predominant characteristic of an enhanced and uncontrolled inflammatory response in the lungs, which contributes to disease progression, hospitalization and mortality. These diseases are poorly controlled by current anti-inflammatory therapies including glucocorticoids, which are otherwise effective in many other inflammatory conditions or in milder disease such as asthma. The exact cause of this apparent impairment of glucocorticoid function remains largely unclear; however, recent studies have now implicated a number of possible mechanisms. Central among these is an elevation of the oxidant burden in the lungs and the resulting reduction in the activity of histone deacetylase (HDAC)-2. This contributes to both the enhancement of proinflammatory mediator expression and the impaired ability of the glucocorticoid receptor (GR)-alpha to repress proinflammatory gene expression. The oxidant-mediated reduction in HDAC-2 activity is, in part, a result of an elevation in the phosphoinositol 3-kinase (PI3K) delta/Akt signalling pathway. Blockade of the PI3Kdelta pathway restores glucocortiocoid function in both in vitro and in vivo models, and in primary cells from disease. In addition, inhibition of the PI3Kdelta and PI3Kgamma isoforms is anti-inflammatory in both innate and adaptive immune responses. Consequently, selective inhibition of this pathway may provide a therapeutic strategy both as a novel anti-inflammatory and in combination therapy with glucocorticoids to restore their function. However, a number of other oxidant-related and -unrelated mechanisms, including altered kinase signalling and expression of the dominant negative GRbeta, may also play a role in the development of glucocorticoid insensitivity. Further elucidation of these mechanisms and pathways will enable novel therapeutic targeting for alternative anti-inflammatory drugs or combination therapies providing restoration for the anti-inflammatory action of glucocorticoids.

Gene polymorphisms against DNA damage induced by hydrogen peroxide in leukocytes of healthy humans through comet assay: a quasi-experimental study

BACKGROUND

Normal cellular metabolism is well established as the source of endogenous reactive oxygen species which account for the background levels of oxidative DNA damage detected in normal tissue. Hydrogen peroxide imposes an oxidative stress condition on cells that can result in DNA damage, leading to mutagenesis and cell death. Several potentially significant genetic variants related to oxidative stress have already been identified, and angiotensin I-converting enzyme (ACE) inhibitors have been reported as possible antioxidant agents that can reduce vascular oxidative stress in cardiovascular events.

METHODS

We investigate the influences of haptoglobin, manganese superoxide dismutase (MnSOD Val9Ala), catalase (CAT -21A/T), glutathione peroxidase 1 (GPx-1 Pro198Leu), ACE (I/D) and gluthatione S-transferases GSTM1 and GSTT1 gene polymorphisms against DNA damage and oxidative stress. These were induced by exposing leukocytes from peripheral blood of healthy humans (N = 135) to hydrogen peroxide (H2O2), and the effects were tested by comet assay. Blood samples were submitted to genotyping and comet assay (before and after treatment with H2O2 at 250 microM and 1 mM).

RESULTS

After treatment with H2O2 at 250 microM, the GPx-1 polymorphism significantly influenced results of comet assay and a possible association of the Pro/Leu genotype with higher DNA damage was found. The highest or lowest DNA damage also depended on interaction between GPX-1/ACE and Hp/GSTM1T1 polymorphisms when hydrogen peroxide treatment increased oxidative stress.

CONCLUSIONS

The GPx-1 polymorphism and the interactions between GPX-1/ACE and Hp/GSTM1T1 can be determining factors for DNA oxidation provoked by hydrogen peroxide, and thus for higher susceptibility to or protection against oxidative stress suffered by healthy individuals.

Smoking and atherosclerotic cardiovascular disease: Part IV: Genetic markers associated with smoking

Genes influence smoking behavior, affect the metabolism of nicotine and specific chemicals produced during combustion, and enhance (or diminish) pathomechanistic pathways associated with the atherogenic potential of smoking, including oxidative stress, its inflammatory burden or procoagulant potential. Genome-wide association studies have revolutionized the search for new functional genetic markers with ever increasing marker density and the precision in identifying new genetic loci without the need for prior knowledge of functional pathways. Nevertheless, the statistical challenge remains to identify the few true positives, the need for replication of findings and the tedious work of identifying functional genetic variants and their mode of action. Genetic variation within a gene or in areas of the genetic code that control the expression of such a gene is far from being understood. Major advances include the detection of large-scale copy-number variants in the human genome and the demonstration of the decisive role of ‘miRNA’ in controlling gene expression. The role of the genomic methylation pattern in controlling the transcription of the underlying genetic sequence and its role in interacting with environmental influences have yet to be explored in depth. Although candidate genes and their genetic variants have been associated with atherosclerosis and cigarette smoking, a major breakthrough has still to be made.

Association of tumor necrosis factor-alpha-863C/A gene polymorphism with chronic obstructive pulmonary disease

The aim of this study was to investigate genetic effects on the pathogenesis of chronic obstructive pulmonary disease (COPD). The study was conducted as a prospective case-control study in a medical center in southern Taiwan. The patient group consisted of 145 male patients with smoking-related COPD and a control group of 139 resistant smokers from July 2004 to September 2009. We compared allele and genotype frequencies of three tag single nucleotide polymorphisms (SNP) of the TNF-alpha gene promoter region at -308, -863, and -1031 in all subjects. We also analyzed the influence of each genetic variant on pulmonary function parameters, body mass index (BMI), serum TNF-alpha levels, and outcomes among heavy smokers with or without COPD. COPD patients had a significantly lower A allele frequency (9.7 vs. 15.1%, OR = 0.6, p = 0.048, false discovery rate q = 0.144) and a significantly lower A carrier genotype frequency (19.3 vs. 30.2%, OR = 0.52, p = 0.042, q = 0.135) than resistant smokers. The -863 CA genotype was associated with a better FEV(1)/FVC ratio (79 vs. 71.5%, p = 0.034), and higher BMI (24.9 vs. 23.6 kg/m(2), p = 0.048). In addition, COPD patients with the -1031 C carrier genotype had higher serum TNF-alpha levels (20.9 vs. 16.2 pg/ml, p = 0.01). BMI (hazard ratio = 0.84, 95% CI = 0.74-0.96, p = 0.008) was the only independent predictor for mortality. The TNF-alpha -863 A allele may confer a degree of resistance to the susceptibility to and muscle wasting of COPD among heavy smokers.

Chronic obstructive pulmonary disease: towards pharmacogenetics

Chronic obstructive pulmonary disease (COPD) is a common problem worldwide, and it is recognized that the term encompasses overlapping sub-phenotypes of disease. The development of a sub-phenotype may be determined in part by an individual's genetics, which in turn may determine response to treatment. A growing understanding of the genetic factors that predispose to COPD and its sub-phenotypes and the pathophysiology of the condition is now leading to the suggestion of individualized therapy based on the patients' clinical phenotype and genotype. Pharmacogenetics is the study of variations in treatment response according to genotype and is perhaps the next direction for genetic research in COPD. Here, we consider how knowledge of the pathophysiology and genetic risk factors for COPD may inform future management strategies for affected individuals.

ABCC1 polymorphisms contribute to level and decline of lung function in two population-based cohorts

OBJECTIVE

The ATP-binding cassette transporter ABCC1 [i.e. multidrug resistance-associated protein 1 (MRP1)] is a membrane-bound pump excreting a variety of xenobiotics from the cell, and thus ABCC1 may play an important role in smoking-related lung function loss and development of chronic obstructive pulmonary disease (COPD). We earlier showed that bronchial epithelium of COPD patients have lower ABCC1 expression than that of healthy controls, with even further decrements in more severe COPD stages. In line with these results, we now aimed to assess effects of ABCC1 single nucleotide polymorphisms (SNPs) on both the level and the longitudinal course of lung function in the general population.

METHODS

All 51 prevalent (minor allele frequency >5%) and noncorrelated (r<0.8) ABCC1 SNPs were analyzed in two independent, prospective, population-based cohorts, that is, Doetinchem (n = 1152) and Vlagtwedde-Vlaardingen (n = 1390) studies (three and seven median lung function measurements, respectively, per patient), using linear regression and linear mixed-effect models.

RESULTS

SNPs rs4148382 and rs212093 in the 3'-ABCC1 region were significantly associated with a higher and lower forced expiratory volume in 1 s (FEV1), respectively, in both the cohorts. Another rs35621 SNP (intron 14) was significantly associated with a highly excessive FEV1 decline in both cohorts. All replicated associations were additionally confirmed by permutation testing.

CONCLUSION

This is the first study showing a significant relationship between ABCC1 SNPs and lung function in two independent cohorts. These SNPs are therefore putative candidates for studies aiming to prevent COPD and investigating pharmacogenetics in established COPD.

Meta-analyses on suspected chronic obstructive pulmonary disease genes: a summary of 20 years' research

RATIONALE

Chronic obstructive pulmonary disease (COPD) is a complex disorder with high mortality worldwide. Studies on the role of candidate genes and their polymorphisms in COPD development have so far produced ambiguous results.

OBJECTIVES

The aim of this study was to reveal the role of COPD candidate genes using data collected in previous research.

METHODS

We performed meta-analyses on 20 polymorphisms in 12 genes, after searching the PubMed and Embase databases for publications on COPD. These genes involve three main pathways associated with COPD development: the inflammatory, protease-antiprotease balance, and antioxidant pathways.

MEASUREMENTS AND MAIN RESULTS

We obtained significant results for three TGFB1 polymorphisms, although these were based only on a few studies. The IL1RN VNTR polymorphism increases the risk for COPD (odds ratio [OR], 1.7; 95% confidence interval [CI], 1.09-2.65), whereas the TNFA -308 G/A polymorphism does so only in Asian populations (OR, 2.01; 95% CI, 1.21-3.31). The GSTP1 I105V polymorphism was protective for COPD in Asian populations only (OR, 0.69; 95% CI, 0.56-0.85).

CONCLUSIONS

These results demonstrate the importance of ethnicity in identifying specific COPD genes.

Level and course of FEV1 in relation to polymorphisms in NFE2L2 and KEAP1 in the general population

BACKGROUND

The metabolism of xenobiotics plays an essential role in smoking related lung function loss and development of Chronic Obstructive Pulmonary Disease. Nuclear Factor Erythroid 2-Like 2 (NFE2L2 or NRF2) and its cytosolic repressor Kelch-like ECH-associated protein-1 (KEAP1) regulate transcription of enzymes involved in cellular detoxification processes and Nfe2l2-deficient mice develop tobacco-induced emphysema. We assessed the impact of Single Nucleotide Polymorphisms (SNPs) in both genes on the level and longitudinal course of Forced Expiratory Volume in 1 second (FEV1) in the general population.

METHODS

Five NFE2L2 and three KEAP1 tagging SNPs were genotyped in the population-based Doetinchem cohort (n = 1,152) and the independent Vlagtwedde-Vlaardingen cohort (n = 1,390). On average 3 FEV1 measurements during 3 surveys, respectively 7 FEV1 measurements during 8 surveys were present. Linear Mixed Effect models were used to test cross-sectional and longitudinal genetic effects on repeated FEV1 measurements.

RESULTS

In the Vlagtwedde-Vlaardingen cohort SNP rs11085735 in KEAP1 was associated with a higher FEV1 level (p = 0.02 for an additive effect), and SNP rs2364723 in NFE2L2 was associated with a lower FEV1 level (p = 0.06). The associations were even more significant in the pooled cohort analysis. No significant association of KEAP1 or NFE2L2 SNPs with FEV1 decline was observed.

CONCLUSION

This is the first genetic study on variations in key antioxidant transcriptional regulators KEAP1 and NFE2L2 and lung function in a general population. It identified 2 SNPs in NFE2L2 and KEAP1 which affect the level of FEV1 in the general population. It additionally shows that NFE2L2 and KEAP1 variations are unlikely to play a role in the longitudinal course of FEV1 in the general population.

Overexpression of extracellular superoxide dismutase attenuates heparanase expression and inhibits breast carcinoma cell growth and invasion

Increased expression of heparanase stimulates the progression of various human cancers, including breast cancer. Therefore, a deeper understanding of the mechanisms involved in regulating heparanase is critical in developing effective treatments for heparanase-overexpressing cancers. In this study, we investigated the potential use of extracellular superoxide dismutase (EcSOD) to enhance the inhibitory effects of heparin/low molecular weight heparin (LMWH) in breast cancer cells. EcSOD binds to cell surfaces and the extracellular matrix through heparin-binding domain (HBD). Deleting this HBD rendered the protein a more potent inhibitor of breast cancer growth, survival, and invasion. Among the treatment combinations examined, EcSODDeltaHBD plus LMWH provided the best tumor suppressive effects in inhibiting breast cancer growth and invasion in vitro. We have further shown that overexpression of EcSOD decreased accumulation of vascular endothelial growth factor in the culture medium and increased the level of intact cell surface-associated heparan sulfate, thus implicating inhibition of heparanase expression as a potential mechanism. Overexpression of EcSOD inhibited steady-state heparanase mRNA levels by >50% as determined by quantitative reverse transcription-PCR. Moreover, heparanase promoter activation was suppressed by EcSOD as indicated by a luciferase reporter assay. These findings reveal a previously unrecognized molecular pathway showing that regulation of heparanase transcription can be mediated by oxidative stress. Our study implies that overexpression of EcSOD is a promising strategy to enhance the efficacy of heparin/LMWH by inhibiting heparanase as a novel treatment for breast cancer.

Lung cancer susceptibility model based on age, family history and genetic variants

Background

Epidemiological and pedigree studies suggest that lung cancer results from the combined effects of age, smoking, impaired lung function and genetic factors. In a case control association study of healthy smokers and lung cancer cases, we identified genetic markers associated with either susceptibility or protection to lung cancer.

Methodology/Principal Findings

We screened 157 candidate single nucleotide polymorphisms (SNP) in a discovery cohort of 439 subjects (200 controls and 239 lung cancer cases) and identified 30 SNPs associated with either the healthy smokers (protective) or lung cancer (susceptibility) phenotype. After genotyping this 30 SNP panel in a validation cohort of 491 subjects (248 controls and 207 lung cancers) and, using the same protective and susceptibility genotypes from our discovery cohort, a 20 SNP panel was selected based on replication of SNP associations in the validation cohort. Following multivariate logistic regression analyses, including the selected SNPs from runs 1 and 2, we found age and family history of lung cancer to be significantly and independently associated with lung cancer. Numeric scores were assigned to both the SNP and demographic data, and combined to form a simple algorithm of risk.

Conclusions/Significance

Significant differences in the distribution of the lung cancer susceptibility score was found between normal controls and lung cancer cases, which remained after accounting for differences in lung function. Validation in other case-control and prospective cohorts are underway to further define the potential clinical utility of this model.

Superoxide dismutase 3, extracellular (SOD3) variants and lung function

Polymorphisms in Superoxide dismutase 3, extracellular (SOD3) have been associated with reduced lung function and susceptibility to chronic obstructive pulmonary disease (COPD) in adults. Previously, we identified SOD3 as a contributing factor to altered ventilation efficiency (dead space volume/total lung capacity) in mice. Because SOD3 protects the extracellular matrix of the lung, we hypothesized that SOD3 variants also may influence postnatal lung function development. In this study, SOD3 transcript and protein localization were examined in mouse strains with differing ventilation efficiency [C3H/HeJ (high), JF1/Msf (low)] during postnatal lung development. Compared with C3H/HeJ mice, JF1/Msf mice had Sod3 promoter single nucleotide polymorphisms (SNPs) that could affect transcription factor binding sites and a decline in total lung SOD3 mRNA during postnatal development. In adult JF1/Msf mice, total lung SOD3 activity as well as SOD3 transcript and protein in airway epithelial and alveolar type II cells and the associated matrix decreased. In children (n = 1,555; age 9-11 yr), two common SOD3 SNPs, one located in the promoter region [C/T affecting a predicted aryl hydrocarbon receptor-xenobiotic response element (AhR-XRE) binding motif] and the other in exon 2 (Thr/Ala missense mutation), were associated with decreased forced expiratory volume in 1 s (FEV(1)), and the promoter SNP was associated with decreased maximal expiratory flow at 25% volume (MEF(25)). In vitro, a SOD3 promoter region-derived oligonucleotide containing the C variant was more effective in competing with the nuclear protein-binding capacity of a labeled probe than that containing the T variant. Along with the previous associated risk of lung function decline in COPD, these findings support a possible role of SOD3 variants in determining lung function in children.

Recent advances in genetic predisposition to clinical acute lung injury

It has been well established that acute lung injury (ALI), and the more severe presentation of acute respiratory distress syndrome (ARDS), constitute complex traits characterized by a multigenic and multifactorial etiology. Identification and validation of genetic variants contributing to disease susceptibility and severity has been hampered by the profound heterogeneity of the clinical phenotype and the role of environmental factors, which includes treatment, on outcome. The critical nature of ALI and ARDS, compounded by the impact of phenotypic heterogeneity, has rendered the amassing of sufficiently powered studies especially challenging. Nevertheless, progress has been made in the identification of genetic variants in select candidate genes, which has enhanced our understanding of the specific pathways involved in disease manifestation. Identification of novel candidate genes for which genetic association studies have confirmed a role in disease has been greatly aided by the powerful tool of high-throughput expression profiling. This article will review these studies to date, summarizing candidate genes associated with ALI and ARDS, acknowledging those that have been replicated in independent populations, with a special focus on the specific pathways for which candidate genes identified so far can be clustered.

Genetic variation and gene expression in antioxidant related enzymes and risk of COPD: a systematic review

BACKGROUND

Observational epidemiological studies of dietary antioxidant intake, serum antioxidant concentration and lung outcomes suggest that lower levels of antioxidant defences are associated with decreased lung function. Another approach to understanding the role of oxidant/antioxidant imbalance in the risk of chronic obstructive pulmonary disease (COPD) is to investigate the role of genetic variation in antioxidant enzymes, and indeed family based studies suggest a heritable component to lung disease. Many studies of the genes encoding antioxidant enzymes have considered COPD or COPD related outcomes, and a systematic review is needed to summarise the evidence to date, and to provide insights for further research.

METHODS

Genetic association studies of antioxidant enzymes and COPD/COPD related traits, and comparative gene expression studies with disease or smoking as the exposure were systematically identified and reviewed. Antioxidant enzymes considered included enzymes involved in glutathione metabolism, in the thioredoxin system, superoxide dismutases (SOD) and catalase.

RESULTS

A total of 29 genetic association and 15 comparative gene expression studies met the inclusion criteria. The strongest and most consistent effects were in the genes GCL, GSTM1, GSTP1 and SOD3. This review also highlights the lack of studies for genes of interest, particularly GSR, GGT and those related to TXN. There were limited opportunities to evaluate the contribution of a gene to disease risk through synthesis of results from different study designs, as the majority of studies considered either association of sequence variants with disease or effect of disease on gene expression.

CONCLUSION

Network driven approaches that consider potential interaction between and among genes, smoke exposure and antioxidant intake are needed to fully characterise the role of oxidant/antioxidant balance in pathogenesis.

National Emphysema Treatment Trial state of the art: genetics of emphysema

Although a hereditary contribution to emphysema has been long suspected, severe alpha1-antitrypsin deficiency remains the only conclusively proven genetic risk factor for chronic obstructive pulmonary disease (COPD). Recently, genome-wide linkage analysis has led to the identification of two promising candidate genes for COPD: TGFB1 and SERPINE2. Like multiple other COPD candidate gene associations, even these positionally identified genes have not been universally replicated across all studies. Differences in phenotype definition may contribute to nonreplication in genetic studies of heterogeneous disorders such as COPD. The use of precisely measured phenotypes, including emphysema quantification on high-resolution chest computed tomography scans, has aided in the discovery of additional genes for clinically relevant COPD-related traits. The use of computed tomography scans to assess emphysema and airway disease as well as newer genetic technologies, including gene expression microarrays and genome-wide association studies, has great potential to detect novel genes affecting COPD susceptibility, severity, and response to treatment.

Superoxide dismutase 3 polymorphism associated with reduced lung function in two large populations

RATIONALE

Superoxide dismutase (SOD) 3 inhibits oxidative fragmentation of lung matrix components collagen I, hyaluronan, and heparan sulfate. Inherited change in SOD3 expression or function could affect lung matrix homeostasis and influence pulmonary function.

OBJECTIVES

To identify novel SOD3 polymorphisms that are associated with lung function or chronic obstructive pulmonary disease (COPD).

METHODS

Resequencing of 182 individuals identified two novel polymorphisms, E1 (rs8192287) and I1 (rs8192288), in a conserved region of the SOD3 gene of potential relationship to lung function. We next genotyped 9,093 individuals from the Copenhagen City Heart Study for the polymorphisms and recorded spirometry, and admissions and deaths due to COPD during 26-year follow-up. Finally, we validated our findings in a cross-sectional analysis of 35,635 individuals from the Copenhagen General Population Study.

MEASUREMENTS AND MAIN RESULTS

Genotyping the Copenhagen City Heart Study identified 35 E1/I1 homozygotes, 1,050 heterozygotes, and 8,008 noncarriers (Hardy-Weinberg equilibrium: P = 0.93). Using quadruple lung function measurements, we found that E1/I1 homozygotes had 7% lower FVC % predicted (P = 0.006) and 4% lower FEV(1) % predicted (P = 0.12) compared with noncarriers. In the Copenhagen General Population Study, E1/I1 homozygotes also had lower FVC % predicted than noncarriers (P = 0.03), confirming an association between E1/I1 genotype and reduced lung function. E1/I1 homozygotes had adjusted hazard ratios for COPD hospitalization and COPD mortality of 2.5 (95% confidence interval, 1.0-5.9) and 3.7 (95% confidence interval, 0.9-15), respectively; the results were independent of influence from the R213G allele of the SOD3 gene.

CONCLUSIONS

We identified two novel polymorphisms in a conserved region of the SOD3 gene and show that individuals that are homozygous for these polymorphisms have reduced FVC % predicted in two large, population-based studies.

Smoking in moderate/severe preeclampsia worsens pregnancy outcome, but smoking cessation limits the damage

We studied phenotypic and clinical outcome data in an observational, multicenter cohort study of 1001 Western European white women and their singleton babies, with stringently defined moderate-to-severe preeclampsia. Ninety women admitted to being current smokers; 71 had stopped smoking before entry to the study. Across the categories of never-smoker, stopped, and current smoker there were significant increases in the proportion of women delivering before 34 weeks' gestation (P=0.011), delivering a baby below the third birth weight centile (P<0.001), or delivering a baby with any adverse outcome (P=0.011). By comparison with never-smokers, smoking during pregnancy was associated with a doubling of risk of being delivered before 34 weeks' (odds ratio: 1.98; 95% CI: 1.24 to 3.16; P=0.004), of delivering babies below the third centile of corrected birth weight (odds ratio: 2.20; 95% CI 1.41 to 3.44; P<0.0001), or for their babies to have any adverse outcome (odds ratio: 1.87; 95% CI: 1.19 to 2.95; P<0.006). Worryingly, the risk of developing eclampsia was increased 5-fold (odds ratio: 4.88; 95% CI: 1.44 to 16.61; P=0.005). The proportion of smokers in these preeclamptic women was lower than in our pregnant population generally. However, preeclampsia still carries significant perinatal morbidity, and cigarette smoking in preeclamptic pregnancies exacerbates this. Stopping smoking decreases the risks. Smoking in young women should be a particular target for advice by general practitioners before pregnancy, with active encouragement after conception to enroll in such trials as the current Smoking, Nicotine and Pregnancy Trial to support cessation.

Frontiers in emphysema research

Chronic obstructive pulmonary disease (COPD) is a complex inflammatory disease with a myriad of pulmonary and nonpulmonary disease manifestations. COPD is a heterogeneous disease consisting of emphysematous destruction, airway inflammation, remodeling, and obstruction. Once conceptualized as a unidimensional disease isolated to the lung, it is now recognized to have significant systemic manifestations, such as osteoporosis, cardiovascular disease, and skeletal muscle wasting. As the clinical phenotypic expressions of COPD become more precisely characterized, so does the pathogenesis of this disease. Great strides are now being made in our understanding of genetic susceptibility, airway inflammation, the immune response to cigarette smoke, and inflammatory biomarkers. This review will discuss the most recent progress on selected topics in COPD pathogenesis, inflammation, and genetics. With time, we hope to expand our current understanding to predict who will develop disease and who will not, and why some patients develop particular disease phenotypes. In addition, we hope to clarify the inflammatory mechanisms involved in order to develop novel therapies and identify disease biomarkers that will lead to better tools for monitoring disease activity. Finally, we hope to develop treatments aimed at lung regeneration and repair, to reverse lung damage that has already occurred. We are optimistic that novel therapies like gene therapy and advanced antiinflammatory agents will be in our future. Judging by the progress made in the last decade, these tools may soon become a reality.

Redox imbalance and ventilator-induced lung injury

Mechanical ventilation (MV) is an indispensable therapy in the care of critically ill patients with acute lung injury and the acute respiratory distress syndrome; however, it is also known to further lung injury in certain conditions of mechanical stress, leading to ventilator-induced lung injury (VILI). The mechanisms by which conventional MV exacerbates lung injury and inflammation are of considerable clinical significance. Redox imbalance has been postulated, among other mechanisms, to enhance/perpetuate susceptibility to VILI. A better understanding of these pathologic mechanisms will help not only in alleviating the side effects of mechanical forces but also in the development of new therapeutic strategies. Here, we review the relevance of oxidative stress in VILI from human studies as well as cellular and mouse models of mechanical stress. Potential therapeutic avenues for the treatment of VILI with exogenous administration of antioxidants also are discussed.

Framingham Heart Study genome-wide association: results for pulmonary function measures

BACKGROUND

Pulmonary function measures obtained by spirometry are used to diagnose chronic obstructive pulmonary disease (COPD) and are highly heritable. We conducted genome-wide association (GWA) analyses (Affymetrix 100K SNP GeneChip) for measures of lung function in the Framingham Heart Study.

METHODS

Ten spirometry phenotypes including percent of predicted measures, mean spirometry measures over two examinations, and rates of change based on forced expiratory volume in one second (FEV1), forced vital capacity (FVC), forced expiratory flow from the 25th to 75th percentile (FEF25-75), the FEV1/FVC ratio, and the FEF25-75/FVC ratio were examined. Percent predicted phenotypes were created using each participant's latest exam with spirometry. Predicted lung function was estimated using models defined in the set of healthy never-smokers, and standardized residuals of percent predicted measures were created adjusting for smoking status, pack-years, and body mass index (BMI). All modeling was performed stratified by sex and cohort. Mean spirometry phenotypes were created using data from two examinations and adjusting for age, BMI, height, smoking and pack-years. Change in pulmonary function over time was studied using two to four examinations with spirometry to calculate slopes, which were then adjusted for age, height, smoking and pack-years.

RESULTS

Analyses were restricted to 70,987 autosomal SNPs with minor allele frequency > or = 10%, genotype call rate > or = 80%, and Hardy-Weinberg equilibrium p-value > or = 0.001. A SNP in the interleukin 6 receptor (IL6R) on chromosome 1 was among the best results for percent predicted FEF25-75. A non-synonymous coding SNP in glutathione S-transferase omega 2 (GSTO2) on chromosome 10 had top-ranked results studying the mean FEV1 and FVC measurements from two examinations. SNPs nearby the SOD3 and vitamin D binding protein genes, candidate genes for COPD, exhibited association to percent predicted phenotypes.

CONCLUSION

GSTO2 and IL6R are credible candidate genes for association to pulmonary function identified by GWA. These and other observed associations warrant replication studies. This resource of GWA results for pulmonary function measures is publicly available at http://www.ncbi.nlm.nih.gov/projects/gap/cgi-bin/study.cgi?id=phs000007 webcite.

Candidate genes controlling pulmonary function in mice: transcript profiling and predicted protein structure

Impaired development and reduced lung capacity are risk factors of asthma and chronic obstructive pulmonary disease. Previously, our genomewide linkage analysis of C3H/HeJ (C3H) and JF1/Msf (JF1) mouse strains identified quantitative trait loci (QTLs) associated with the complex traits of dead space volume (Vd), total lung capacity (TLC), lung compliance (CL), and diffusing capacity for CO (D(CO)). We assessed positional candidate genes by comparing C3H with JF1 lung transcript levels by microarray and by comparing C3H, BALB/cByJ, C57BL/6J, A/J, PWD/PhJ, and JF1 strains, using exon sequencing to predict protein structure. Microarray identified >900 transcripts differing in C3H and JF1 lungs related to lung development, function, and remodeling. Of these, three genes localized to QTLs associated with differences in lung function. C3H and JF1 strains differed in transcript and protein levels of superoxide dismutase 3, extracellular [SOD3; mouse chromosome (mCh) 5: VD] and transcript of trefoil factor 2 (TFF2; mCh 17: TLC and D(CO)), and ectonucleotide pyrophosphatase/phosphodiesterase 2 (ENPP2; mCh 15: TLC and CL). Nucleotide sequencing of Sod3, Tff2, and previously identified Relaxin 1 (Rln1; mCh 19: CL) uncovered polymorphisms that could lead to nonsynonymous amino acid changes and altered predicted protein structure. Gene-targeted Sod3(-/-) mice had increased conducting airway volume (Vd/TLC) compared with strain-matched control Sod3(+/+) mice, consistent with the QTL on mCh 5. Two novel genes (Tff2 and Enpp2) have been identified and two suspected genes (Sod3 and Rln1) have been supported as determinants of lung function in mice. Findings with gene-targeted mice suggest that SOD3 is a contributing factor defining the complex trait of conducting airway volume.

Current thinking on genetics of chronic obstructive pulmonary disease

PURPOSE OF REVIEW

There is growing evidence that genetics plays a role in the development of chronic obstructive pulmonary disease. This review deals with the most recent findings, new methods to detect genetic susceptibility that may be helpful in this field, and how the environment may act on the genetic code of susceptible individuals and chronic obstructive pulmonary disease sufferers.

RECENT FINDINGS

Candidate gene association studies have identified genes that may have roles in the pathogenesis of chronic obstructive pulmonary disease. Not all studies that have found associations between genes and chronic obstructive pulmonary disease phenotypes have been replicated, however. The realization of this challenge in itself is a major step forward and, coupled with exciting new methods to identify susceptibility genes, may provide the impetus to move the field beyond the notion that alpha-1 antitrypsin is the only proven cause of the disease.

SUMMARY

Candidate gene studies need to be interpreted with caution because of their lack of reproducibility. Genome-wide association studies may offer the best approach to identifying susceptibility genes in chronic obstructive pulmonary disease. Epigenetics needs to be considered in concert with genetic findings.

Genetics of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a complex disease with multifactorial background, based on the interaction of environmental and genetic factors. Environmental factors are clearly related to the development of the disease. However, family and twin studies suggested genetics factors to be one of the important determinants for the development of COPD. Different approaches have been used to identify genes of interest. Genomewide linkage analysis found areas of interest on different chromosomes, with some genes located in this regions being identified and replicated as susceptibility genes. Numerous of candidate genes that could be linked to disease pathogenesis have been implicated in COPD genetics. However, the candidate gene approach is often limited by inconsistent results in other study populations. Recently, a combination of different methods is used giving more evidence for some candidate genes, including TGFbeta-1, Surfactant, SERPINE2 and microsomal epoxide hydrolase. In the future ongoing exact phenotype definition, combination of several approaches, genome-wide association studies and animal model genetics will lead to new insights into the genetics of COPD, with epigenetic factors needs to be further investigated and considered in concert with genetic findings.

Future therapeutic treatment of COPD: struggle between oxidants and cytokines

Chronic obstructive pulmonary disease (COPD) is a global health problem. Being a progressive disease characterized by inflammation and predominantly caused by tobacco smoking, it deteriorates pulmonary and skeletal muscle functioning, and reduces physical behavior, societal participation and quality of life. During the last two decades studies were focused on the airway and systemic inflammation, oxidative stress, and airway and/or parenchymal remodeling. Macrophages, neutrophils and T cells are thought to be important key players, as well as structural cells like fibroblasts, epithelial, endothelial and smooth muscle cells. Mediators and proteins including cytokines, chemokines, growth factors, proteinases, and oxidants seem to be involved differentially in its pathogenesis. Current pharmacological treatments are directed to reducing airway inflammation, boosting the endogenous levels of anti-oxidants and relieving airway contraction and sputum production. Most agents were primarily used for treating asthma. But in contrast to asthma, these treatments are not very effective in COPD. As a result, novel more specifically acting interventional drugs with less side effects are being developed to treat chronic inflammatory diseases, including COPD. This review highlights studies on novel or potential drug antioxidants such as dietary antioxidants supplementation, N-acetyl-L-cysteine, N-acystelyn, endosteine, antioxidant enzyme mimetics, and anti-inflammatory agents like antagonists of cytokines, such as tumor necrosis factor (TNF)-alpha, CXCL8, and CCL2, and inhibitors of signal transduction proteins including phosphodiesterase 4, MAPK p38, P1-3k, and NFkappaB.