Superoxide dismutases in the lung and human lung diseases

Catalytic antioxidants: a radical approach to new therapeutics

In humans, several pathologies involve the overproduction of reactive oxygen species. Metal-containing catalytic antioxidants have emerged as a novel class of potential therapeutic agents that scavenge a wide range of reactive oxygen species. There are three structural classes of manganese-containing catalytic antioxidants that have efficacy in several oxidative stress models of human disease. The classes are divided based on their in vitro selectivity towards the scavenging of superoxide. The selective catalytic antioxidants include the macrocyclics, whereas the non-selective catalytic antioxidants include the salens and porphyrins. Cardiovascular, neurodegenerative and inflammatory lung disorders are all potentially important targets for catalytic antioxidant therapy.

Particulate phase cigarette smoke increases MnSOD, NQO1, and CINC-1 in rat lungs

Loss of antioxidant/oxidant homeostasis perpetuates inflammation in the lungs and may contribute to the development of COPD and lung cancer. Cigarette smoke (CS) is a primary source of airway oxidative stress and recruits inflammatory cells into smokers' lungs. However, whether these consequences are attributable to a specific or the collective fraction of CS is unknown. We investigated whether the particulate or the gas phase of CS would alter expression of the antioxidant enzymes MnSOD and NQO1 or CINC-1. Sprague Dawley rats were exposed to sham (n = 10) or the particulate phase (PP; n = 10) or gas phase (n = 10) of a Kentucky reference cigarette (1R4F) for 2 h/d for 28 d, after which animals were sacrificed and the lower left lobe of the lung was removed. Immunoblots for SOD and NQO1 revealed that lungs exposed to PP had higher MnSOD/actin and NQO1/actin ratios than either sham-or gas phase-treated animals. In contrast, CuZnSOD remained unchanged. In PP-exposed animals, CINC-1 was 3-fold higher than in sham-exposed animals. The increases in MnSOD and NQO1 protein were associated with increases in total SOD, NQO1, and MPO activities. These data provide evidence that the PP of CS alters oxidant/antioxidant homeostasis in the lungs and participates in the pathogenesis of CS-induced lung diseases such as COPD and cancer.

alpha1-Antitrypsin deficiency . 6: new and emerging treatments for alpha1-antitrypsin deficiency

Alpha-1-antitrypsin (AAT) deficiency is a genetic condition that increases the risk of developing lung and liver disease, as well as other associated conditions. Most treatment of affected individuals is not specifically directed at AAT deficiency but focuses on the resultant disease state. The only currently available specific therapeutic agent-namely, intravenous augmentation with plasma derived AAT protein-is marketed in a limited number of countries. Treatments aimed at correcting the underlying genetic abnormality, supplementing or modifying the gene product, and halting or reversing organ injury are now beginning to emerge. These innovative approaches may prove effective at modifying or eliminating diseases association with AAT deficiency.

Amsacta moorei entomopoxvirus expresses an active superoxide dismutase

The entomopoxvirus from Amsacta moorei serves as the prototype of the group B entomopoxviruses. One of the interesting genes found in Amsacta moorei entomopoxvirus (AmEPV) is a superoxide dismutase (sod) (open reading frame AMV255). Superoxide dismutases (SODs) catalyze the conversion of superoxide radicals to hydrogen peroxide and oxygen. Many vertebrate poxviruses contain a sod gene, but to date, none have been demonstrated to be active. There are three families of SODs, characterized by their metal ion-binding partners, Fe, Mn, or Cu and Zn. Poxvirus enzymes belong to the Cu-Zn SOD family. Unlike inactive vertebrate poxvirus SODs, AMVSOD contains all the amino acids necessary for function. We expressed and purified a 6X-His-tagged version of the AMVSOD in Escherichia coli. The recombinant AMVSOD demonstrates superoxide dismutase activity both in an in situ gel assay and by stopped flow spectrophotometry. The k(cat)/K(m) for AMVSOD is 4 x 10(7) M(-1)s(-1). In infected cells, the AMVSOD protein behaves as a dimer and is catalytically active; however, disruption of the gene in AMEPV has little or no effect on growth of the virus in cell culture. An analysis of mRNA expression indicates that AMVsod is expressed late during infection of Lymantria dispar (Ld652) cells and produces a discrete nonpolydisperse transcript. Characterization of protein expression with a monoclonal antibody generated against AMVSOD confirms that the AMVSOD protein can be classified as a late, postreplicative gene. Therefore, AMVSOD is the first example of an active poxvirus SOD.

Impaired superoxide radical production by bronchoalveolar lavage cells from NO(2)-exposed rats

Production of superoxide radicals is a central property of professional phagocytes used to combat invading microorganisms. Even though the number of macrophages and neutrophils is often increased in the lungs of patients with chronic lung diseases, these patients frequently suffer from bacterially induced exacerbations. To understand the underlying mechanisms, we investigated the production of superoxide radicals by bronchoalveolar lavage (BAL) cells in a rat NO(2) exposure model (10 ppm NO(2) for 1, 3, or 20 days). We showed that cells from NO(2)-exposed animals display a significantly impaired superoxide radical release after zymosan stimulation. The use of specific inhibitors (antimycin or diphenyleneiodonium [DPI]) revealed that the major enzyme systems, NADPH oxidase and complex III of the respiratory chain, are affected. In addition, we investigated gene expression and enzyme activities of antioxidant enzymes. mRNA expression was significantly enhanced for glutathione peroxidase (GPx)-3 and CuZn-superoxide dismutase (SOD) in BAL cells from animals exposed 3 and 20 days, and GPx and SOD enzyme activities were increased in BAL cells from rats exposed 20 days. In conclusion, concomitant occurrence of reduced production and increased scavenging of superoxide radicals resulted in the drastically impaired release of these radicals from BAL cells of NO(2)-exposed rats.

Distribution of antioxidant enzymes in developing human lung, respiratory distress syndrome, and bronchopulmonary dysplasia

We studied cell-specific protein expression of all the major antioxidant enzymes (AOEs) and related proteins, such as copper-zinc superoxide dismutase (CuZnSOD), manganese SOD (MnSOD), extracellular SOD (ECSOD), catalase, the heavy and light chains of gamma-glutamylcysteine synthetase (gamma-GCS-l and gamma-GCS-h, also called glutamate cysteine ligase), the rate-limiting enzyme in glutathione synthesis, hemeoxygenase-1 (HO-1), and thioredoxin (Trx), in developing human lung, respiratory distress syndrome, and bronchopulmonary dysplasia by immunohistochemistry. Generally, after 17 weeks of gestational age, MnSOD was predominantly expressed in bronchial epithelium, alveolar epithelium, and macrophages, CuZnSOD was expressed in bronchial epithelium, ECSOD was expressed in bronchial epithelium, vascular endothelium, and the extracellular matrix, catalase was expressed in bronchial epithelium and alveolar macrophages, gamma-GCS-h was expressed in bronchial epithelium and endothelium, and gamma-GCS-l was expressed in bronchial epithelium. Trx was restricted to bronchial epithelium and to a lesser extent to alveolar macrophages, and HO-1 found in alveolar macrophages. Basically, the expression of these enzymes was similar in normal and diseased lung. It can be concluded that various AOEs and related proteins differ in their distribution and expression in lung before term, but generally it seems that infants are better adapted to high oxygen tension than might be expected.

Peroxiredoxins, a novel protein family in lung cancer

Cigarette smoke, the major risk factor for lung cancer, induces an accumulation of reactive oxygen species. These have multiple effects on cell defense, cell proliferation and cell death. Thus, compounds involved in the regulators of redox balance can be hypothesized to play a fundamental role in both carcinogenesis and tumor progression. Here, we have evaluated the expressions of all 6 peroxiredoxins (Prxs I-VI) in lung carcinomas. Prxs represent a protein family with the capability of breaking down hydrogen peroxide; thus, they can participate in cellular antioxidant defense, regulate cell proliferation and increase drug resistance of cultured cells. Altogether 92 cases were investigated by immunohistochemistry, including 32 adenocarcinomas, 45 squamous cell, 9 small cell and 6 other carcinomas. Additionally, 11 cases with adenocarcinoma or squamous cell carcinoma were studied by Western analysis and/or by RT-PCR. Prxs I, II, IV and VI were particularly elevated in lung carcinomas as assessed by immunohistochemistry and/or RT-PCR. Western analysis revealed that Prxs I and IV were significantly elevated in tumors compared to nonmalignant tissue (p = 0.04 and 0.002, respectively). There were remarkable variations in Prx expression in various tumor subtypes, the most striking being Prx IV expression, which was mainly associated with adenocarcinoma. Elevated Prx VI expression was associated with high-grade squamous cell carcinoma (p = 0.03) and Prx II expression, with advanced tumor stage (p = 0.01). Our results suggest that Prxs may have effects on the progression of lung cancer.

Antioxidant enzymes and redox regulating thiol proteins in malignancies of human lung

Oxidants are known to modulate cell proliferation and apoptosis, and induce synthesis of growth factors that play an important role in tumor growth and invasion. Antioxidant enzymes and thiol proteins regulating cellular redox state constitute the major cellular protection against oxidants. Consequently, they are also associated both with carcinogenesis and tumor progression. Superoxide dismutases, glutamate cysteine ligase, catalase, thioredoxins and peroxiredoxins, which are the most important of these enzymes, are expressed in lung malignancies, and especially in pleural mesothelioma. This has consequences not only for tumor behavior but also for resistance of tumor cells to cytotoxic drugs and radiation.

Chronic oxidative stress and radiation-induced late normal tissue injury: a review

PURPOSE

It is proposed that the development and progression of radiation-induced late effects are driven, in part, by chronic oxidative stress. This mini-review presents data to support this hypothesis and provides the foundation for antioxidant-based interventional approaches directed at modulating late normal tissue injury.

CONCLUSIONS

Although a causal link between chronic oxidative stress and radiation-induced late normal tissue injury remains to be established, a growing body of evidence appears to support the hypothesis that chronic oxidative stress might serve to drive the progression of radiation-induced late effects. The similarity between chronic tissue injury, chronic inflammation and fibrosis observed in a variety of disease states, including radiation late effects, is provocative and offers the opportunity to apply antioxidant-based therapies to mitigate and/or treat late radiation-induced normal tissue injury.

Binding of xanthine oxidase to glycosaminoglycans limits inhibition by oxypurinol

Although the binding of xanthine oxidase (XO) to glycosaminoglycans (GAGs) results in significant alterations in its catalytic properties, the consequence of XO/GAG immobilization on interactions with clinically relevant inhibitors is unknown. Thus, the inhibition kinetics of oxypurinol for XO was determined using saturating concentrations of xanthine. When XO was bound to a prototypical GAG, heparin-Sepharose 6B (HS6B-XO), the rate of inactivation for uric acid formation from xanthine was less than that for XO in solution (k(inact) = 0.24 versus 0.39 min(-1)). Additionally, the overall inhibition constant (K(i)) of oxypurinol for HS6B-XO was 2-5-fold greater than for free XO (451 versus 85 nm). Univalent electron flux (O(2)(.) formation) was diminished by the binding of XO to heparin from 28.5% for free XO to 18.7% for GAG-immobilized XO. Similar to the results obtained with HS6B-XO, the binding of XO to bovine aortic endothelial cells rendered the enzyme resistant to inhibition by oxypurinol, achieving approximately 50% inhibition. These results reveal that GAG immobilization of XO in both HS6B and cell models substantially limits oxypurinol inhibition of XO, an event that has important relevance for the use of pyrazolo inhibitors of XO in clinical situations where XO and its products may play a pathogenic role.

Response of rat alveolar type II cells and human lung tumor cells towards oxidative stress induced by hydrogen peroxide and paraquat

The expression of MDR1b coding mRNA is increased in alveolar type II cells from juvenile rat lung in culture. Hydrogen peroxide and paraquat-induced further upregulation supporting that oxidative stress mediated mechanisms are involved in the regulation of MDR1b in rat lung. The expression rates of mRNA for catalase, Cu/Zn-superoxide dismutase (Cu/Zn-SOD) and Mn-superoxide dismutase (Mn-SOD) remains constant during culture and were not modulated by hydrogen peroxide or paraquat. Thus, antioxidative enzymes in primary A II cells from rat lung are not regulated by reactive oxygen species dependent mechanisms. Primary A II cells were substantially more sensitive towards paraquat-induced cytotoxicity and lipid peroxidation than the permanent human lung tumor cell lines H322 and H358. A 100 microM hydrogen peroxide for 2h induces substantial DNA damage which is not paralleled by an increased rate of lipid peroxidation. The expression rate of mRNA coding for catalase and Mn-SOD was not changed and almost the same is true for the activity of catalase and Cu/Zn-SOD. Only 50 microM paraquat induced a significant decrease in catalase activity and an increase in Cu/Zn-SOD activity.

Manganese superoxide dismutase Ala-9Val polymorphism and risk of breast cancer in a population-based case-control study of African Americans and whites

Introduction

A polymorphism in the manganese superoxide dismutase (MnSOD) gene, Ala-9Val, has been examined in association with breast cancer risk in several epidemiologic studies. Results suggest that the Ala allele increases the risk of breast cancer and modifies the effects of environmental exposures that produce oxidative damage to DNA.

Methods

We examined the role of the MnSOD Ala-9Val polymorphism in a population-based case–control study of invasive and in situ breast cancer in North Carolina. Genotypes were evaluated for 2025 cases (760 African Americans and 1265 whites) and for 1812 controls (677 African Americans and 1135 whites).

Results

The odds ratio for MnSOD Ala/Ala versus any MnSOD Val genotypes was not elevated in African Americans (odds ratio = 0.9, 95% confidence interval = 0.7–1.2) or in whites (odds ratio = 1.0, 95% confidence interval = 0.8–1.2). Greater than additive joint effects were observed for the Ala/Ala genotype and smoking, radiation to the chest, and occupational exposure to ionizing radiation. Antagonism was observed between the Ala/Ala genotype and the use of nonsteroidal anti-inflammatory drugs.

Conclusions

The MnSOD genotype may contribute to an increased risk of breast cancer in the presence of specific environmental exposures. These results provide further evidence for the importance of reactive oxygen species and of oxidative DNA damage in the etiology of breast cancer.

Decreased arginine bioavailability and increased serum arginase activity in asthma

Recent studies suggest that a nitric oxide (NO) deficiency and elevated arginase activity may play a role in the pathogenesis of asthma. Although much attention has been directed toward measurements of exhaled NO in asthma, no studies to date have evaluated levels of plasma arginase or arginine, the substrate for NO production, in patients with asthma. This study, therefore, measured amino acid levels, arginase activity, and nitric oxide metabolites in the blood of patients with asthma, as well as NO in exhaled breath. Although levels of virtually all amino acids were reduced, patients with asthma exhibited a striking reduction in plasma arginine levels compared with normal control subjects without asthma (45 +/- 22 vs. 94 +/- 29 microM, p < 0.0001), and serum arginase activity was elevated (1.6 +/- 0.8 vs. 0.5 +/- 0.3 micromol/ml/hour, asthma vs. control, p < 0.0001). High arginase activity in patients with asthma may contribute to low circulating arginine levels, thereby limiting arginine bioavailability and creating a NO deficiency that induces hyperreactive airways. Addressing the alterations in arginine metabolism may result in new strategies for treatment of asthma.

Ultrastructural and chromosomal studies on manganese superoxide dismutase in malignant mesothelioma

Mesothelioma represents an aggressive tumor type with high resistance to all treatment modalities. Its pathogenesis is strongly associated with exposure to asbestos fibers and probably with free radicals. One of the most important free radical scavenging enzymes, mitochondrial manganese superoxide dismutase (MnSOD), has been shown to be elevated in mesothelioma (K. Kahlos et al., 1998, Am. J. Respir. Cell Mol. Biol. 18:570-580). In the present study, we could detect intense ultrastructural accumulation of MnSOD in the mitochondrial compartment of malignant mesothelioma cells. There was no association between the immunohistochemical reactivity and the most common and functional polymorphic variant of MnSOD, the Ala to Val amino acid change at 9 position (16th amino acid from the beginning of the signal sequence), in the 31 mesothelioma cases investigated. Comparative genomic hybridization and fluorescence in situ hybridization did not reveal any changes in chromosome 6, where the MnSOD gene is located. Sequencing of the MnSOD promoter region in four mesothelioma cell lines showed similar nucleotide variables in the malignant and nonmalignant cells. Therefore, the intense expression of MnSOD in the mitochondria of mesothelioma cells does not appear be associated with any major chromosomal alterations or the polymorphism of MnSOD gene. Association with oxidative/nitrosative stress in mesothelioma using nitrotyrosine immunostaining pointed to a tendency for more intense reactivity in those mesotheliomas with higher MnSOD expression (P = 0.069).

Superoxide dismutases in malignant cells and human tumors

Reactive oxygen metabolites have multifactorial effects on the regulation of cell growth and the capacity of malignant cells to invade. Overexpression of the superoxide dismutases (SODs) in vitro increases cell differentiation, decreases cell growth and proliferation, and can reverse a malignant phenotype to a nonmalignant one. The situation in vivo is more complex due to multiple interactions of tumor cells with their environment. Numerous in vivo studies show that the superoxide dismutases can be highly expressed in aggressive human solid tumors. Furthermore, high SOD has occasionally been associated with a poor prognosis and with resistance to cytotoxic drugs and radiation. Most of the apparent conflicts between the above in vitro and in vivo observations can be reconciled by considering the net redox status of tumor cells in different environments. Administering high concentrations of SOD to cells in vitro is usually associated with a non- or less malignant phenotype, whereas secondary induction of SOD in tumors in vivo can be associated with an aggressive malignant transformation probably due to the altered (oxidative) redox state in the malignant cells. This concept suggests that for many types of tumors antioxidants could be used to diminish the invasive capability of malignant cells.

Particulate air pollutants and asthma. A paradigm for the role of oxidative stress in PM-induced adverse health effects

Asthma is a chronic inflammatory disease, which involves a variety of different mediators, including reactive oxygen species. There is growing awareness that particulate pollutants act as adjuvants during allergic sensitization and can also induce acute asthma exacerbations. In this communication we review the role of oxidative stress in asthma, with an emphasis on the pro-oxidative effects of diesel exhaust particles and their chemicals in the respiratory tract. We review the biology of oxidative stress, including protective and injurious effects that explain the impact of particulate matter-induced oxidative stress in asthma.